Tumour Photosensitizers Approaches to Enhance the Selectivity

8/10/2019 Tumour Photosensitizers Approaches to Enhance the Selectivity

1/7

~ e f

AND

~ f J G Y

E L S E V I E R Journal of Photochemistryand PhotobiologyB: Biology36 (1996) 87-93

Tum our photosensit izers approaches to enhance the selec t iv i ty and

efficiency of photodynam ic therapy

G i u l i o J o r i

Department o f Biology, University of Pa dova, via Trieste 75. 35121 P adova. Italy

Abs t r ac t

While Photofrin, the photosensitizer currently in clinical use for photndynaraic therapy (P DT ) of tumours, has been show n to be both

efficacious and safe in the treatm ent of a variety of huma n ~:ancers, ts chem ical heterogeneity and low absorbance in the phototherape utically

useful wavelt:ngth range (600-850 nm) make the developlrtent of new pho tosensitizers with improve d characteristics desirable. A suitable

manipulation of the molecular structure of porphyrins offers several interesting possibilities for controlling the optical and photophysical

properties of the photosensitizer, as well as its bindistribution between tumour and pe ri tu ~ ra l tissues or at the subtissular and subcellular

level. The achievem ent of these goals m ay also be facilitated by the association of the photoseasitizer w ith selected delivery systems, opening

the way to a qualitative and quantitative improvement of PD T.

Keywords: Tumourphotosensitizers;Photofrin

1 I n t r o d u c t i o n

The r ecen t r egu la to ry app rova l o f Pho to f r in as a tumour -

pho to sens i t i z ing agen t fo r the pho todynam ic therapy (PD T)

o f lung , oesophagea l and b ladder cancer opens new cha l -

lenges to bo th c l in ic ians and bas ic inves t iga to r s s ince t ime

now seems r ipe fo r a qua l i t a t ive improvemen t o f the tech -

n ique a long d i f f e r en t gu ide l ines , such as : ( a ) def in i t ion o f

PD T p ro toco ls w h ich y ie ld op t imal r esu l t s w i th sp ec i f ic turn-

ou r types ( e .g . tu rnou ts a t d i f f e r en t ana tomica l s i t es , o r hav -

ing d i f f e r en t th ickness , h i s to log ica l f ea tu res , deg ree o f

vascu la r iza t ion , e tc . ) and assessme n t o f the po ten t ia l o f PDT

to com pete w i th ex is t ing therap ies fo r the same tumour s ; ( b )

e n h a n c e m e n t o f t h e e f f i c a c y o f P D T ( e . g . i n c r e as e d s e l e ct i v -

i ty o f tumour ta rge t ing p oss ib ly th rough con juga t ion o f the

pho to sens i t i ze r to tumour - spec i f ic de l ivery sy s tems ; in t r a -

opera to r ia l app l ica t ion o f PDT fo r the s te r i l i za t ion o f the

tumour bed a f te r su rg ica l r esec t ion ) ; and ( c ) expans ion o f

the scope o f PD T to t r ea t cond i t ions o ther t it an m al ignanc ies ,

inc lud ing a theromas , r es tenos is o f a r te r ies a f te r ang iop las ty ,

pso r ias i s and sex ua l ly t r an smi t ted d i seases , v i r a l o r microb ia l

in f ec t ions and b loo d bank ing [ 1 ] .

Mo s t p r e - c l in ica l and c l in ica l s tud tes have been per fo rme d

so f a r w i th Pho to f r in I I , a chem ica l ly p r epared der iva t ive o f

haematopo rphy r in , and an impress ive body o f in fo rmat ion

has been co l le c ted on the in v i t r o / in v ivo behav iou r o f th i s

d rug [2 - 4 ] in sp i te o f it s in tr in s ic l imi ta t ions , such as the

la rge deg ree o f chemica l he te rogene i ty and the low mo lar

1011-1344/96/$15.00 1996 Else vierScienceS.A. All ngMs reserved

P i l S I O I I - 1344 (96 )0735 2 -6

ex t inc t ion coef f ic ien t in the r ed spec t r a l r eg ion [5 ] . T hese

da ta were u sed as a bas i s to deve lop and tes t a l a rge number

o f second genera t ion tum our - loca l ize r s and -pho to sens i t i ze r s ,

f rom wh ich a hand fu l o f pho to therapeu t ic agen ts has been

se lec ted ~ ,d p r esen t ly a r e in phase I / I I c l in ica l t r i a l s ( see

Tab le 1 ) . Un l ike Pho to f r in , a l l newly proposed PDT agen ts

a r e charac te r ized by a h igh deg ree o f chemica l pu r i ty and a

h i g h m o l a r e x t i n c ti o n c o e f f i c i e n t a t t h e a b s o r p t i o n m a x i m u m

in the r ed spec t r a l r eg ion , wh ich i s l a rger by one o r two o ther s

o f magn i tude than tha t typ ica l o f Pho to f r in a t 630 nm. Th is

a r t ic le r ev iew s the com mo n f ea tu res and spec i f ic p roper t ies

o f such pho to sens i t i ze r s in an a t temp t to d r aw som e conc lu -

s ions of genera l in terest .

2 . G e n e r a l p r o p e r t i e s o f a p h o t o d y n a m l c t u m o u r

s e n s i t i z e r

Some proper t ies wh ich have been iden t i f ied as typ ica l o f

an e f f ic ien t pho todynamic tu rnou t sens i t i ze r a r e l i s ted in

Tab le 2 . Such proper t ies can be opera t iona l ly subd iv ided in to

pbys ico -cbem ica l , pho tophys ica l , pharm aco log ica l and pho -

to therapeu t ic . I t i s obv ious f rom Ta b le 2 tha t the success o f

a PD T t r ea tmen t r equ i r es an op t im al in te rp lay am ong a num-

ber o f severa l d i f f e r en t pa ramete r s and none o f the p r esen t ly

ava i lab le tumour pho to sens i t i ze r s mee ts a l l r equ i r emen ts to

a sa t i s f ac tory ex ten t . How ever , po rphy r in s and th e i r ana logs

(ch lo r in s , ph tha locyan ines , naph tha locvan ines , po rphyce-

nes ) a r e endowed w i th two f av 'mrab le tea tu res :


2/7

~8 G. Jor i /Jo urn al o f Photochemis try and Photobio logy B: Bio logy 36 (1996) 87- 93

"' able I

"l'amourphotosensitizerspresently used in clinical rials for PDT of tumoars

'1 oto~ nsitiz er Remarks Absorption maximum Molar Reference

in the red absorptivity ~

n m ) M -

Is cm-~)

Phot. )frin contains main lycovalentHp oligomers,plu s 630 3 200 ~' [41

Hp, Pp and HVD

Benz~,,~orphyrinderivativ e requires lipid-baseddelivery ystems 690 43 000 [6]

Mono.~spartyl-chlorine6 fast clearanc e rom umo ur/skin 675 47 000 17]

m-Tetrahydroxypbenyl-chlorin to be administered n alkaline solutionsor 35 000 [ 8]

water/DMSO mixtures

$n ( IV -etioparpurin requires lipid-baseddelivery ystems 660 28 000 [9 ]

Zn( il)-phthalocya nine requires lipid-baseddelive ry ystems 675 243 000 {10]

Hp = haematoporphyrin; Pp = pm toporphyrin; HVD = hydroxyethyl-vinyl-deatemporphyrin

a Da ta for n,,onomericcompounds, with he exceptionof Photofrin

t, App roximatevaluedue to inhomogeneityof the preparalion and scarse reproducibilityof monomer.oligomer quilibria

1 . The po ;s ib i l i ty to m od i fy the chem ica l s t ruc tu re a t d i f -

f e r en t loc i and w i th var ious leve ls o f complex i ty , inc lud ing

the s ize ~ f the ma crocyc le and the ex tens ion o f the a romat ic

e lec t ron c loud , the coo rd ina t ion o f meta l ions w i th the fou r

central n i trogen ,~toms, and the nature of the per ipheral sub-

s t i tuen ts and /o r , ax ia l i igands ( see F ig . 1 ) . Th is a l lows a

r emarkab le f lex ib i l i ty in the des ign o f the pho to sens i t i z ing

agen t , so tha t d if fe r< .;nt l eve ls o f hyd ro - / l ip o -ph i l ic i ty , t en -

dency to unde rgo agg rega t ion , sub t i s su la r o r subce l lu la r d i s -

t r ibu tion , spec t ro scop k ' and pho toph ys ica l p roper t ies can be

impar ted to the pho to se l : s i t i ze r mo lecu le [ I 1 ] .

Thus , the in se r t ion o f two p o la r subs ti tuen ts ( e .g . ca rbox -

y la te , su lphona te o r hyd roxy l g roup s ) on two ad jacen t r ings

o f t h e m a c r o c y c l e a n d t h e c o n s e q u e n t p r e s e n c e o f a h y d r o -

p h o b i c m a t r i x o n t h e o p p o s i t ~ s i d e o f t h e m o l e c u l e ( t w o

unsubs t i tu ted r ings ) makes the pho to sens i t i ze r an amph i -

ph i l ic spe c ies ; in th i s way , the po rphy r in a ch ieves a su f fic ien t

wate r - so lub i l i ty , to a l low i t s sy s temic in jec t ion in v ivo , wh i le

i t r e ta in s a h igh tendency to c ro ss the l ip id bar r ie r o f the

c y t o p l a s m i c m e m b r a n e o f t u m o u r c e l l s a n d l o c a l i z e a t e n d o-

ce l lu la r s i t es [ 12 ] . I n par t icu la r , a p r e le r en t ia l t a rge t ing o f

ly sosom es has been propose d to occu r [ 13 ] fo r amph iph i l ie

d isu lphona ted ph tha iocyan ines . Even in the case o f deep ly

hyd roph ob ic p o rphy r ino id s , such as those ha 'Ang one o r no

po la r subs t i tuen ts , sy s tem ic in jec t ion in to the b loods t r eam i s

poss ib le , p rov ided the pho to sens i t i ze r s a r e p r e - il , co rpo ra ted

in to su itab le de l ivery sy s tems (Ta b le 3 ) .

A t the sam e t ime , the p r esence o f e lec t r ica l ly charged func-

t iona l g roups p ro t rud ing f rom the p y r ro le r ings o r bulk) " ax ia l

i igands perp end icu la r to the p lane o f the po rphy r in mo le~.ule

genera tes e lec t ro s ta t ic r epu ls ion and s te r ic h ind rance , the reby

preven t ing the fo rm at ion o f agg rega tes [ 17 ] wh ich w ou ld

d ras t ica l ly inh ib i t the pho to sens i t i z ing ac t iv i ty [18 ,19 ] .

A c t u a l l y , a l t ho u g h t h e o l i g o m e r i c c o m p o n e n t s o f P h o t o fr i n

are known to g ive the main con t r ibu t ion to the tumour - loca i -

iz ing proper t ies , i t is now genera l ly accep ted tha t on ly mon-

omer ic po rphy r ino id s ac t as e f f ic ien t pho to sens i t i ze r s o f

b io log ica l sy s tem s , espe c ia l ly in d i f fu s ion -con t ro l led pho to -

processes [20 ] .

Typica l ly , in neu t ra l aqueo us so lu t ions a t 10 p ,M conc en -

t r a t ions , on ly abou t 50% o f d ica rboxy l ic haematopo rphy r in

and deu te ropo rphy r in ex is t in a monomer ic s ta te , compared

wi th 100% m onom er iza t ion fo r the oc tad icarboxy l ic u ropo r -

p h y r in [ 1 7 ] . S i m i l a rl y , A l ( I I I ) - p h t h a l o c y a n i n e s s h o w a

much smal le r t endency to agg rega te than the co r r espond ing

Z n ( I I ) - d e r i v a t i v e s o w i n g t o t h e p r e s e n c e o f a n a d d i t i o n a l

o r thogona l l igand ( e .g . ch lo r ine) fo r the AI ion [21 ] . An

ana logous inh ib i t ion o f agg rega t ion was ob ta ined by fu s ion

o f ou t -o f -p lane cyc l ic hyd rocarbon s t ruc tu res w i th the i so in -

do le r ings , o f ph tha locyan ine , such as in Zn ( I I ) - te t r ab enz o -

d ibar r e leno -oc tabu toxy -ph tha locyan ine [ 22 ] .

2 . The pr esence o f ab so rp t ion bands in the 600 -850 nm

wavelen g th reg ion , co r r esponds w i th ma x im al l igh t pene t r a -

t ion in to mam mal ian t i s sues [23 ] . F o r ligh t ly p igm en ted

tumour s the t r an smiss ion o f inc iden t l igh t inc reases up to

a b o u t 7 0 0 n m , w h i l e i n t h e p r e s e n c e o f a n e x t e n s i v e p i g m e n -

t a ti o n ( s u c h a s i n m e l a n o t ic m e l a n o m a ) o n l y a t w a v e l e n g th s

longer than 780 nm i s some t i s su la r t r an sparency i s observed

[ 23 ] : a s a consequen ce , p igm en ted me lanom a i s in sens i t ive

to PDT wi th Pho to f r in and undergoes an impor tan t pho to -

damage on ly in the p r esence o f naph tha locyan ines wh ich

d i s p l a y a n in t e n se a b s o rb a n c e ( E a b o u t 5 0 0 0 0 0 M - ~ c m - ~ )

a t 780 nm, thereby e f f ic ien t ly compet ing wi th melan in fo r

l igh t ab so rp t ion [24 ] .

In genera l , the u se o f pho to sens i t i ze rs w i th a h igh ex t inc-

t ion coef f ic ien t o f f e r s the p oss ib i l i ty to in jec t sm al le r d rug

doses , wh ich g ives fu r ther advan tages over Pho to f r in and

o ther haematopo rphy r in - r e la ted po rphy r in s wh ich exh ib i t a

w e a k a b s o r b a nc e a b o v e 6 0 0 n m ( T a b l e 1 ) . A n i n g e n i ou s

man ipu la t ion o f the chemica l s t ruc tu re o f the pho to sens i t i ze r

o f ten a l lows one to enhance the mo lar ab so rp t iv i ty , as wel l

as to sh i ft the abso rp t ion bands in o rder to ob ta in an op t im al

match ing to the op t ica l charac te r i s ti cs o f any g iven tumour .

Typica l examp les a r e summ ar ized in Tab le 4 . C lear ly , the

a , ld i t ion o f one o r two benzene mo ie t ies to each py r ro le o r

the in se r tion o f add it iona l doub le bonds in to the 18 z - e lec t ro n

c loud o f the po rphy r in m acroc yc le r esu l ts in a r ed sh i f t o f the

a b s o ~ t i o n m a x i m u m a n d h y p e r c h ro m i c i t y . A " f i n e t u n i n g "


3/7

G. Jori /Journal of Phowchemistry and Photobiology B: Biology 36 1996) 87-93

Table 2

Main features of an efficient photodynamic agent for tun,ours

Property Related structural and biological features

Physico-chemical

High chemical purity

Large mo lar extinction coefficient in the red

Low tendency to aggregation in an aqueous m ilieu

Photophysical

Long triplet lifetime

High yield of nO2 generation an d/or electron transfer to substrate molecules

Pharmacological

Efficient and selective targeting of the tumou r tissue

Fast clearance from serum and healthy tissues

Low system ic toxicity

Phototherapeutic

Efficient and preferential killing of m alignant cells

Lack o f side effects

Lack of mutagenic potential

Purification may be especially laborious in the p resence of two or more

peripheral substituents and/or chiral centers

Extensive conjug ation of 'x electrons alon g the n~.acrocycle

Presence of electrically charged perip heral substituents or bulky axial

ligands to the central metal ion

Extensive monomerization ( favoured by distribution in apolar regioos of

membranous systems )

Easy accessibility by m olecular oxygen or close p roximity to substrates with

suitable redox potential

Hydmphobic or amphiphilic properties; association with suitable delivery

systems

High affinity for serum proteios responsible for transport of dyes from

peripheral tissues to liver

Lethal dost: (LD-50) higher than ca. 300 mg k g- t body weight

Large concentration difference between tumourlpentumoural tissues and/o r

fast healing of any p butodemag~l healthy tissue

Minimal accumulation in skin to avoid cutaneous p hotosensitivity

No photoeffect on D NA

o f t h e a b s o r p t i o n p r o p e r t i e s c a n b e a l s o a c h i e v e d : t h u s , p a r t i al

h y d r o g e n a t i o n o f o n e o r t w o p y r r o l e r i n g s c o n v e r ts p o r p h i n e s

t o c h l o r i n s a n d , r e s p e c t i v e l y , b a c t e r i o c h i o r i n s w i t h a s i m u l -

t a n e o u s b a t h o c .h r o m i c s h i f t o f 5 0 - 1 5 0 n m [ 2 6 ] ; h o w e v e r , t h e

i n t r o d u c t i o n o f e i g h t a l k o x y s u b s t i t u e n t s i n t h e / 3 p o s i t i o n o f

t h e p h e n y l r i n g o f t h e p h t h a l o c y a n i n e i s o i n d o l e s , a s w e l l a s

t h e r e p l a c e m e n t o f t h e ce n t r a l G e ( I V ) i o n by P d ( l I ) , a l l o w s

o n e t o s h i f t t h e a b s o r p t i o n b a n d t o s e le c t e d w a v e l e n g t h s i n

t h e 7 0 0 - 8 0 0 n m i n t e r va l [ 2 7 ] .

I n a n y c a s e , n o a p p r e c i a b l e c y t o t o x i c i t y i s s h o w n b y t h e

p h o t o s e n s i t i z e r o r l i g h t a l o n e , a t l e a s t a t t h e p h o t o t h e r a p e u b

i c a l l y a c t i v e d r u g d o s e s a n d f l u e n c e r a t e s : o n l y t h e c o m b i -

n a t i o n o f t h e t w o a g e n t s c a u s e s t u m o u r d a m a g e [ 2 , 2 5 ] .

A c t u a l l y , L D - 5 0 v a l u e s f o r m o s t p o r p h y r i n o i d s r a n g e

b e t w e e n 2 0 0 - 5 0 0 m g k g - t b o d y w e i g h t a s c o m p a r e d w i t h

i n j e c te d d o s e s l o w e r t h a n 5 , an d s o m e t i m e s I m g k g - t w h i c h

a r e r e c o m m e n d e d i n c u r r e n t P D T p r o t o c o ls . M o r e o v e r , n o

f u n c t i o n a l o r m o r p h o l o g i c a l a l t e ra t i o n s h a v e b e e n f o u n d i n

p o r p h y r i n - l o a d e d t i ss u e s [ 2 8 ] ; o n e p o s s i b le e x c e p t i o n i s

r e p r e s e n t e d b y m e s o - t e t r a ( 4 - s u l p h o n a t o p h e n y l ) p o r p h i n e

( T P P S 4 ) , f o r w h i c h k i d n e y a n d n e u r a l t o x i c i t y h a s b e e n

c l a i m e d [ 2 9 ] . A t t h e s a m e t i m e , i r r a d i a t i o n o f t i s s u e s w i t h

l i g h t w a v e l e n g t h s l o n g e r t h a n 6 0 0 n m c a u s e s n o d e t e c ta b l e

e f f e c t s , p r o v i d e d t h e f l u e n c e r a t e i s k e p t b e l o w a b o u t

1 5 0 m W c m - 2 i n o r d e r t o a v o i d h e a t d e p o s it i o n i n t h e t i s su e

a n d t h e c o n s e q u e n t o n s e t o f t h e r m a l d a m a g e .

I n t h e n e x t p a r a g r a p h s t h e p h a r m a c o k i n c t i c a n d p h o t o -

b i o l o g i c al p a r a m e t e r s w h i c h c o n t r o l t h e e f fi c a cy o f t h e P D T

t r e a t m e n t w i l l b e d i s c u s s e d .

3 , S e l e ct i v it y o f P D T a c t i o n o n t h e t u m o u r t i s s u e

T h e e s s e n t ia l g o a l o f P D T i s to i n d u c e a n e f f i c i en t p h o t o -

s e n s i ti z e d n e c r o s i s o f t h e t u m o u r m a s s w h i l e m i n i m i z i n g t h e

d a m a g e o f t h e p e r i t u m o u r a l t i s s ue s .

A f i rs t c r i t e r i o n t o a s s e s s t h e p o t e n t i a l s e l e c t i v i t y o f P D T

t r e a t m e n t i s t h e r a ti o b e t w e e n t h e p h o t o s e n s i t i z e r c o n c e n t ra -

t i o n i n t h e t u r n o u t a n d t h e t i s s u e f r o m w h i c h t h e t u r n o u t

o r i g i n a t e s o r i n t o w h i c h t h e t u m o u r g r o w s . T h i s r a t i o i s h a r d l y

p r e d i c t ab l e s i n c e t h e d e t e r m i n a n t s o f p o r p h y r i n u p t a k e a n d

c l e a r a n c e b y t u r n o u t s a r e p o o r l y u n d e r s t o o d a n d i t i s l i k e l y

t h a t t h e o v e r a l l p r o c e s s i s t h e r e s u l t a n t o f v a r i o u s p r o p e r t i e s

t y p i c a l o f m o s t n e o p l a s t i c t i s s u e s , i n c l u d i n g t h e l e a k y v a s -

c u l a t u r e , h i g h c e l l p r o l i f e r a t i o n r a t e , l o w e r p H v a l u e , a n d

i n e f f i c i e n t l y m p h a t i c d r a i n a g e [ 4 ] . F o r P h o t o f r i n , re p o r t e d

r a t io s v a ry f r o m 1 - 1 . 5 ( s k i n t u r n o u t s ) t o a b o v e 1 0 ( b r a i n

t u m o u r s , a s o n e w o u l d e x p e c t o w i n g t o t h e i n a b il i t y o f p o r -

p h y r i n d e r i v a t i v e s t o c r o s s t h e i n t a c t b l o o d - b r a i n b a r r i e r )

[ 5 , 1 4 ] . I n g e n e r a l , t h e s e l e c t i v i t y o f m m o u r t a r g e t i n g i s

e n h a n c e d u p o n i n c r e a s i n g t h e d e g r e e o f h y d r o p h o b i c i t y o f

t h e p h o t o s e n s i t iz e r o r b y i m p a r t i n g a m p h i p h i l i c p r o p e r t i e s t o

i t s m o l e c u l e [ 1 2 ] . I n o r d e r t o i n d u c e a m o r e s p e c i f i c l o c a l i -

z a t i o n o f t h e i n j e c t e d p h o t o s e n s i t i z e r i n t h e t u r n o u t t i s s u e ,

o n e c a n t a k e a d v a n t a g e o f t h e i n t r i n s ic f e a t u r e s o f t h e m a l i g -

n a n t c e ll s ( T a b l e 5 ) . W h i l e t h e p o t en t i a l o f t h e s e a p p r o a c h e s

h a s n o t b e e n f u ll y e x p l o it e d , e n c o u r a g i n g r e s u l ts h a v e b e e n

o b t a i n e d i n s e v e r a l c e ll a n d a n i m a l s t u d i e s [ 1 6 , 3 0 ] , s o t h a t

f u r t h e r i n v e s t i g a t i o n s a l o n g t h e s e d i r e c t i o n s a r e c e r t a i n l y w a r -

r a n t e d . I n p a r t i c u l a r, t h e r e a r e i n d i c a t i o n s [ 1 4 - 1 6 ] t h a t t h e

a s s o c i at i o n o f th e p o r p h y r i n o i d c o m p o u n d s w i t h m o n o c l o n a l


4/7

90 G. Jori /Jo urn al o f Photochemistry and Photokio logy B: Biology 36 (1996) 87- 93

Porphycene

Naphthalocyanine

I-2

M = m etal ion

R : p eripheral substttuent

L : axial hgand

Fig . I . a ) Basic chemica l s t ructure o f porphyd ns and re la ted compounds

wi th enhanced ahsorbance a t wave lengths longer than 600 nm. b) Scheme

of the ~hemical structure o f a me~allo-phthalocyanine ndicating possible

peripheral substituents (R ) and axial ligands (L) to the metal ion.

Table 3

a n t i b o d i es o r L D L m a r k e d l y r e d u c e s t h e s k i n l e v el s c f p h o -

t o s e n si t iz e r , t h u s p r e v e n t i n g t h e d e v e l o p m e n t o f g e n e r a l i z e d

c u t a n e o u s p h o t o s e n s i ti v i ty , w h i c h o f t e n r e p r e s e n t s a n u n d e -

s i r ed s i de e f f ec t o f P D T [ 3 ] .

H o w e v e r , e v e n f o r r e l a ti v e ly I o w - t u m o u r / h e a l t h y t i ss u e

r a t io s o f p h o t o s e n s i t iz e r c o n c e n t r a t i o n , t h e s e l e c ti v i t y o f P D T

a c t i o n c a n s t i l l b e a c h i e v e d p r o v i d e d t h e p e r i t u m o u r a l c o m -

p a r t m e n t s a r e l e s s r e s p o n s i v e t o r e d l i g h t - i r r a d i a t i o n o r h e a l

m o r e r a p i d l y f r o m p h o t o d a m a g e a s c o m p a r e d w i t h t u m o u r

t i s s u e s [ 3 1 ] . A g a i n , n o g e n e r a l p r e d i c t i o n i s p o s s i b l e a t t h e

p r e s e n t s t a g e o f o u r r e s e a r c h i n t h i s f i e l d , s i n c e t h e p h o t o -

c h e m i c a l b e h a v i o u r o f a t i s s u e i s s t r i c t l y d e p e n d e n t o n i t s

b i o c h e m i c a l c o m p o s i t i o n a n d p h y s i o l o g i c a l p r o p e r t i e s [ 3 2 ] ;

f o r e x a m p l e , s i n c e p h o t o d y n a m i c a c t i o n o c c u r s v i a p h o t o o x -

i d a t i v e s t e p s , th e l o c a l c o n c e n t r a t i o n o f a n t i o x i d a n t s p l a y s a

m a j o r r o l e [ 3 , 1 4 ] . I t m u s t b e a l s o e m p h a s i z e d t h a t t h e m a i n

c e l l u l a r c o n s t i t u e n t s , s u c h a s p r o t e i n s , s a t u r a t e d o r u n s a t u -

r a t e d l i p i d s , n u c l e i c a c i d s a n d c a r b o h y d r a t e s d i s p l a y a v e r y

d i f f e r e n t s u s c e p t i b i l i t y t o p h o t o s e n s i t i z e d o x i d a t i o n [ 3 2 ] . A

v e r y i n t e r e s t in g s t a r t in t h i s d i re c t i o n w a s p e r f o r m e d b y B o w n

a n d c o w o r k e r s w h o u n d e r t o o k a s y s t e m a t i c s t u d y o n t h e

r e s p o n s i v e n e s s o f n o r m a l t i s s u e s , s u c h a s l i v e r , p a n c r e a s o r

c o l o n , to P D T [ 3 1 , 3 3 ] .

4 E f fi ci en c y o f t h e p h o t o t h e r a p e u t i c tr e a t m e n t

S e v e r al a u t h o r s i n d e p e n d e n t l y r e p o r t e d [ 3 5 , 3 6 ] t h a t t h e

e x t e n t o f P D T - i n d u c e d t u m o u r n e c r o s i s i s r e l a t ed t o t h e c o n -

c e n t r a t i o n o f t h e p h o t o s e n s i t i z e r i n t h e n e o p l a s t i c t i s s u e . O n l y

f o r re l a ti v e l y h i g h i n t r a t u m o u r a l a c c u m u l a t i o n o f t h e p h o t o -

s e n s i t i z e r, m a y a d e c r e a s e i n t h e e f f ic i e n c y o f t u m o u r p b o -

t o r e s p o n s e o c c u r d u e t o t h e l i g h t - f i l t e r i n g a c t i o n e x e r t e d b y

t h e d y e m o l e c u l e s p r e s e n t i n t h e s u p e r f i c i a l l a y e r s o f t h e

t i s s u e . I n t h i s c o n n e c t i o n , i t h a s b e e n o b s e r v e d t h a t h y d r o -

p h o b i c p o r p h y r i n d e r i v a t i v e s a r e a c c u m u l a t e d i n l a r g e r

a m o u n t s a n d r e t a i n e d f o r lo n g e r p e r i o d s o f t i m e b y a v a r i et y

o f e x p e r i m e n t a l t u r n o u t s [ 4 , 2 5 ] . A n i m p o r t a n t c o n t r i b u t i o n

t o t hi s e n h a n c e d u p t a k e c o u l d b e g i v e n b y t h e a s s o c ia t i o n o f

s u c h p h o t o s e n s i t i z e r s w i t h l i p i d - t y p e d e l i v e r y s y s t e m s

Delivery systems used for the in vivo administration of tumour photosensitizers (see ref. 14-16 for a more detailed discussion)

Delivery system Photosensitizer Observed hehaviour of the photosensitizer

Liposomes made by

DPPC Hp, ZnPc, SnET2

DMPC ZnPc, SnET2

POPC, OOPC ZnPc

Cremophor EL emulsion SnET2, ZnPc

LDL Hp, ZnPc, BPD

Albumin Photofrin

Epidermal growth factor (EG F) Hp

Antibodies Hp. chlorin e6, BPD

Highly preferential delivery to lipopmteins in the serum

Delivery to both lipopmteins and albumin

Selective release to lipop roteins

Preferential delivery to serum LDL as compared to liposome-delivered dyes

Fast redistribution among all members of the lipoprotein family: targeting of malignant cells

in the turnout tissue

Exchange with lipoproteins in serum: large amou nts recovered in the vascular stroma

Efficient binding to EG F cell receptor

Highly selective targeting of turnout cells (most enco uraging results in cell cultures )

Abbreviations: DPPC , dipalmitoyl-phosphatidylcholine, DM PC, dimiristoyl-phosphatidylcholine; POPC, monopalmitoyl-monooleyl-pbosphatidylcholine;

OOi"S. dioleyl-pho sphatidylserine, LDL, low-density lipoproteins; Hp, haematop orphyrin:ZnPc. Zn(ll)-phthalocyanine; SnET2. Sn(IV)-etiopurporin; BPD.

benzoporphyrin derivative.


5/7

G. Jori / Journa o f Phowchemistry and Photobiology B: Biology 36 (1996) 87-9 3 91

Table 4

Modulation of the absorption propetliesof porp byrinoid compounds hrough a manipulation of the ir chemicalstructu~ (data for nmnomericdyes). See Ref.

[25] for further details.

Photosensitizerclass Absorption maximum n the red Extinctioncofficivm

nm)

(M - I cm - t )

Hematoporhyrin ( 18 or) 630 2 800

26 r - porphyrin 780 0 000

34 r - porphyrin 760 370 000

AI( ll)-phthalocyanine 675 228 000

Si( IV -naphthalocyanine 773 557 000

THP-porphine 646 4 000

THP-chiorin 650 22 000

THP-bactefiechlorin 735 910 00

Ge ( IV -phthalocyanine 678 205 000

Ge 1V -octabutoxyp hthalocyanine 761 233 0Q0

Pd (11) octabutoxyp hthalocyanine 732 51 000

828 279 000

THP = meso-tetra-hydroxy-phenyl

(Tab les 1 and 3 ) an d /o r the i r p r e f e r en tia l tr an spo rt in the

b loods t r eam by l ipopro te in s (T ab le 5 ) . How ever , th i s ru le

has som e im por tan t excep t ion , s ince a f ew pho to sens i t ize r s ,

such as mono-asp ar ty l - ch lo r in e6 [7 ] and TPPS4 [2 9 ] , w h ich

are endowed wi th a good wate r - so lub i l i ty , a r e exce l len t

tumo ur loca l ize r s .

T h e e f f i ci e n c y o f t u m o u r t r e a t m e n t b y P D T i s a l s o h e a v i ly

in f luenced by the sub t i s su la r and subce l lu la r d i s t r ibu t ion o f

the pho to sens i t i ze r . Th is pa ram ete r i s aga in dependen t on the

chem ica l s t ruc tu re o f the dye [37 ] . Pho to f r in , p robab ly

because o f i t s he te rogeneous compos i t ion , i s pa r t i t ioned

amo ng severa l d i f f e r en t compar tmen ts o f the tumour . As a

consequence , upon pho toexc i ta t ion , th i s po rphy r in induces

the mod i f ica t ion o f var ious s i t es , inc lud ing the b lood vesse l s ,

mal igna n t ce l l s and non -vascu la r s t roma [ 3 ] . I n many cases ,

vascu la r dam age appear s 1o pr edom ina te [ 13 ] .

An ex tens ion o f these me chan is t ic s tud ies to po rphy r ino id s

wi th d i f f e r en t phys ic o -chem ica l p roper t ies s t rong ly sugges t s

[38 ] tha t a lbumin -car r ied dyes a r e main ly depos i ted in the

ex t r ace l lu la r mat r ix , hence they cause an ea r ly impa i rmen t o f

b lood c i r cu la t ion . More hyd rop hob ic dyes , wh ich a r e la rge ly

t r anspo r ted by l ipopro te in s , a r e r e leased in s ide tumour ce l l s

(Tab le 5 ) , wh ich s t rong ly f avou r s a d i r ec t ea r ly pho toda-

ma ge o f such ce l l s [ 3 ,25 ] . R ecen t ly , the ro le o f macrop hages

in the overa l l pho toprocess has been r e - eva lua ted [ 39 ] ; mac-

rophages can e f f ic ien t ly accum ula te h igh ly agg rega ted mate -

Table 5

r ia l , a s i t i s p r esen t in Pho to f r in , as wel l as l ipo some- o r

C remophor -de l ivered po rphy r ino id s .

In any case , i t appear s tha t m os t po rphy r in - type pho to sen -

s i t ize r s loca l ize in the ce l l m emb ranes [ 14 ,25 ] ; the re fo re ,

pho to induced ce l l dea th i s u sua l ly a consequence o f

m e m b r a n e d a m a g e : m i t o c h o nd r i a, r o u g h e n d o p l a s m i c r e t i c -

a l u m , l y s o s o m e s a n d p l a s m a m e m b r a n e h a v e b e e n i n v o k e d

as p r imary ta rge ts o f the pho toprocess [ 2 ,3 ,39 ] , the i r r e la t ive

impor tance p robab ly depend ing on the d i s t r ibu t ion o f the

spec i f ic pho to sens i ti ze r . I t i s a l so poss ib le tha t the lo ss o f ce l l

su rv iva l r e f lec ts a co -opera t ive e f f ec t a r i s ing f rom th e s imu l -

taneous imp ai rmen t o f m u l t ip le s i t es , r a ther than be ing de te r -

mined by the i r r ever s ib le mod i f ica t ion o f o ne c r i t i ca l t a rge t .

T o o b t a in m o r e p r e c i s e i n f o r m a t io n o n t h i s t o p i c i t m a y b e

impor tan t to u se pho to sens i t i ze r s wh ich a r c o r ien ta ted toward

a spec i f ic ce l l si t e . Th is ap proach i s exemp l i f ied in r ecen t

a r t ic les showing the p oss ib i l i ty to ob ta in spec i f ic t a rge t ing o f

ly sosom es by assoc ia t ion o f the po rphy f in w i th a ly sosomo -

t rop ic agen t [40 ] o r to se lec t ive ly labe l the ou te r o r inner

m i t o c h o n d r i a l m e m b r a n e b y a n a p p r o p r i a t e c h o i c e o f t h e

l i p o s o m e c a r r i e r [ 4 1 ] .

5 . C o n c l u s i o n s

In sp i te o f pe r s i s t ing uncer ta in t ies abou t de ta i led mecha-

n isms lead ing to po rphy r in -pho to sens i t i zed ce l l and t i s sue

Approaches o enhance h e selectivityof tumoor argeting by porphyrin-typephotosensitizer

App roa ch Rationale Specific example

Incorporationof photosensitizer nto serum LDL Several ypes of neoplastic cellsexpress a large HI), ZnP c [ 14]

number of LDL receiaors

Covalentbinding of photosensitizers o m onoclonalantibod ies Antib odies re directedagainst antigens specifically Hp, chlorin e6 [ 15,16]

present at the surface of tumonrcells

Use of cationicphotosensitizers Mitechoodriaof tumonr ceils have an unu sua lly Triphenylmethaneerivatives [ 34]

high affinity or cationiccompounds

Hp = haem atoporphyrin;ZnPc= Zn (ll ) -phthalocyanine


6/7

92

G. Jori /Jo ur nal o f Photochemistry a nd Photobiology B: B iology 36 (I 996) 87-93

necrosis, it is well ascertained that nuclear damage is a late

event and ha s a minor influence on the photoprocess. This

would rule out any risk of a mutagenic effect of PDT, whic h

is especially i mportant i f the phototherapeutic treatment is to

be repeated at relatively short time intervals or is used in

combination with other therapeutic modalities. At the same

time, the steadily accumulating information on the factors

which modulate the pharmacokinetic behaviour and the cell/

tissue distribution of photosensitizers, as well as the effi-

ciency of tumour photosensitization makes it feasible to

explore two potentially innovative developments of the

technique:

i) The use of a combination of photosensitizers with dif-

ferent intracellular and intratissular localization patterns

which act in a synergistic m anne r to improve the efficacy of

PDT. In particular, it is import ant to assess the possibility to

stimulate ap optosis of at least som e types of neoplastic cells

by PDT treatment, as it is suggested by recent findings [42] .

it) The definition of a variety of integrated PDT systems

(photosensitizer, delivery system, irradiation modalities)

which are tailored to the treatment of neoplastic cells with

specific properties, such as the mitotic index, metastatic

potential, invasiveness of the extracellular matrix, degree of

pigmentati on, etc. As ment ioned earlier, there are now several

possibilities for introducing predetermined physico-chemi-

cal, biological, photobiol ogical and optical properties into the

photosensitizer molecule by chemical synthesis.

Acknowledgements

This work received financial support from EU in the frame-

work of the program Hu ma n Mobility Capital , contract

No. ERB CHRXC T930178 (PDT Network).

e f e r e n c e s

[ I ] A. M. Richter, R.K. Chowdhary, L. Ratkay, AK. Jain, A.J. Canaan,

H. Meadows, M. Obochi, D. Waterfield and J.G. Levy, Nononcologic

potentials for photodynamic herapy,

Proc. SPIE, 2078 (1994)

293-

304.

[2] C.J. Gomer, Photodynamic herapy in the treatment of malignancies,

Sere. Hematol ., 26 (19 89) 27-34.

[3] C. Zhou, Meci~anisms of tumor necrosis induced by photodynamic

therapy, J.

Photochem. Photobiol., B:BioL 3 [

1989) 299-318.

[4] T.J. Dougherty, Photosansitizers: herapy and detection of malignant

tumors,Photochem. Photobiol . , 45 (1987 ) 879-889.

[51 D.A. Bellnier and B.W. Henderson, Determinants for photodynamic

tissue destruction, in B.W. Henderson and T.J. Dougherly (eds.),

Photod ynam ic Therapy. B asic Princip les and Cl in ical Appl icat ions,

MarceI-Dekker, New York, 1992, pp. 117-128.

[6] J.G. Levy, E. Waterfield, A.M. Richter, C. Smith, H. Lui, L. Hroza,

R.R. Anderson and V. Salvatori, Photodynamic therapy of

malignancies with benzoporphyrinderivative monoaeidring A, Proc.

S PIE , 2 0 7 8 (1 9 9 4 ) 91-101.

[7] J.S. Nelson, W.G. Roberts and MW. Berus, In vivo studies on the

utilization of mono-L-aspartyl-chlorine6 for photodynamic herapy,

Ca n cer Res. , 4 7 (1 9 8 7 ) 4681-4685.

[8] H.B. Ris, H.J. Altermatt, R Inderbitzi, R. Hess, B. Nacbbur, J.C.M.

Stewart, Q. Wang, C.K. Lira. R. Bonnett, M.C. Berenbaum and U.

AIthans, Photodynamic therapy with chlorins for diffuse malignant

mesothelioma: initial clinical results,Br. J. Cancer, 64 ( 1991 ) I 116-

1120.

[9] S.H. Selman, G.M. Garbo, R.W. Keck, M. Kroimer-Bimbaumand

A.R. Morgan, A dose response analysis of purpurin derivatives used

as photosensitizers for the photodynamie reatment of transplantable

urothelial tumours, . Urol . . 137 (1987) 1255-1257.

[ 10] K. Schieweck, H.-G. Capraro, U. Isele, P. van Hoogevest,M. Ochsner,

T. Manrer and E. Batt, CGP 55 847, liposome-delivered zinc(ll)-

phthaloe.yanine as a phototherapeutic agent for tumors,Proc. SPIE,

2 0 7 8 (1 9 9 4 ) 107-118.

[ I I ] G. Jori and E. Reddi. Second generation photosensitizers for the

photodynamic therapy of tumours, in R.H. Douglas. J. Moan and G.

Rontb (eds.), Light in Biology and M edi t ia e , Vol. 2, Plenum, London,

1991, pp. 253-266.

[12] D. Kessel, Determinants of hematoporphyrin-catalyzed photo-

sensitization,Photochem. P hotobiol. , 36 (19 82) 99-101.

[13] J. Moan, K. Berg, H.B. Steen, T. Warloe and K. Madslien,

Fluorescence and photodynamie effects of phthalocyanines and

porphyrins in cells, in B.W. Henderson and T.J. Dougherty (eds.),

Phow dynam ic Therapy. Ba sic Princip les a t td Chnica l Applications,

MarceI-Dekker, New York, 1992, pp. 19-36.

[14] G. Jori, Low density lipoproteins-liposome delivery systems for

turnout photosensitizers in vivo, in B.W. Henderson and T.J.

Dougherty (eds.),

Photodynamic Therapy. Basic Principles an d

ClinicalApplications, MarceI-Dekker, New York, 1992, pp. 173-186.

I151 D. Mew, C.K. Wat , G.H.N. Towers and J.G. Levy, Photo-

immanotherapy: reatmant of animal turnouts wi th tumor-specific

monoclonal antibody-hematoporphyrinconjugates,

J. Immunol., 130

(1983) 1473-1477.

[ 16 ] T. Hasan, Photosensitizerdelivery mediated by macromolecularcarrier

systems, n B.W. Hendersonand TJ. Dougherty ( eds. ),

Photodynamic

Thernpy. Basic Principles an d Clinical Applications, MarceI-Dekker,

New York, 1992, pp. 187-200.

[ 171 G. Jori and J.D. Spikes, Photobiochemistry of porphyrins, in K.C.

Smith ted.),

Topics in P Itotomedicine,

Plenum, New York, 1983, pp.

183-319.

[ 18] E. Reddi and G. Jori, Steady-state and time-resolved spectroscopic

studies of photodynamic sensitizers: porphyrinsand phthalocyanines,

Rev. Chem. In term., I0 (1988) 241-268.

[19] G. Jor i, Molecular and cellular mechanisms in photomedicine:

porphyrins in microheterogeneousenvironments, n R.V. Bansasson,

G. Jori, E. Land and T.G. Troscott (ed~,.),Primary Photoprocesses in

Biology and Medicine, Plenum Press, New York, 1985, pp. 349-355.

1201 J.D. Spikes, Phthalocyanines as photosensitizers n biological systems

and for the photodynamic herapy of tumours,

Phow chem . Photobiol. ,

4 3 (1 9 8 6 ) 691-699.

[21] E. Ben-Hut, Photochemistry and photobiology of phthalocyanines:

new sensitizers for photodynamic therapy of cancer, in A. Favre, R

Tyrrell and J. Cadet (eds.), From Photophysics to Pho wbiolo gy,

Elsevier Science Publisher, New York. 1987, pp. 407-420.

[ 22 ] B.D. Rihter, M.D. Bohorquez,M.AJ. Rodgersozld M.E. Kanney,Two

new sterically hindered phthalocyanines: synthetic and photodynamic

aspects,Photochem. PhotobioL. 55 (1992) 677-680.

[23] L.O. Svaasand. E. MartineUi, C.J. Gomer and A.E. Prufio, Optical

characteristics of intraocular urnouts n the visible and near-infrared.,

Proc. SPIE. 1203 (1990) 2-21.

[24] R. Biolo, G. Jori, M. Sancta, R. Pratesi, U. Vanni, B. Rihter, M.E.

Kanney and M.A.J. Rodgers, Photodynamic herapy of B 16 pigmented

melanoma with liposome-delivered Si(IV)-naphthalocyanine,

Photochem. Photobiol . . 59 (1 994) 362-365.

[25] G. Jor i, Far-red absorbing photosensitizars: their use in the

photodynamic herapy of urnouts,J. Photochem. Photobiol., A :Chem.,

6 2 ( 1 9 9 2 )

371-378.


7/7

G. Jori /Jou rna l o f Photochemistry and Photnbiology B: Biology 36 (1996) 87-93

9 3

[26 ] R . Benn ett and M. Berenbanm , Porphy rins us photosensitizers, in G.

Beck and S . Hamet t ( eds . )

Photosensitizing Compounds their

Chemistry, Biology and Clinical Use (Ciba Foundation Syml,~sium

146), J. Wiley , Chichester, 1989, pp. 40-59 .

[271 B.D. Rihter, M.E, Kenney. W.E. Ford an d M.A.L Rodgers,

Photodynamic react ions involv ing Pd( l l ) -octabu toxy-na phtha lo-

cyan ine and molecu lar oxygen , J .

Am . C hem. Soc.. 115 ( 1992, )

8 1 4 6 -

8152.

[28] G. Jori and E. Reddi, Photochemotherapy of turnouts: mole cula r and

biop hysi cal bases., in R. Pratesi (ed.)

Optronic Techniques in

Diagnostic and Therapeutic Medicine,

Plenum, N ew York, 1991, pp.

227-236 .

[29] J .W. Wink elman . Quant i ta, ive s tudies o n tctraphanylporphine-

sulfonate and hematopoq3hyrin der ivative, in D, Kessel ted . )

Methods

in Porphyrin Photnsensitizatian,

Vol. 1 93, Plenum, N ew York, 1985,

pp. 91-102.

[301 G, Jor i , Factm~ co otm ll ing the select ivi ty and eff iciency of turnout

damage in photodynamic therapy,

Lasers Mad. Sei., 5 (1990)

115-

120.

[311 S.G. Bown, Photodynamic therapy to scien t is ts and cl inicians : one

wor ld o r two? , J .

Photochem. P hotobiol.. B:BioL.

6 (1990) 1-12.

[32] B.C, Wilso n and M .S. Pat terson, Physics of photodynamic therapy.

Phys. Med. Biol., 31 (1986)

327-360.

[33] H. Ban . N. Krasner, P.B. Bou les, P. Chatlani and S.G. Bown,

Photodynamic thera py for colorectal cancer: a quantitative p ilot study,

Br. J. Surg., 77 (1990)

93-96 .

[341 A.R. Oseroff, C ation ic sensitizers, comb ination therapies, and new

methodologies, in B.W, Henderson and T.J. Dougherty ( ads .),

Photodynamic Therapy. Basic Principles and Clinical Applications,

Ma rceI-De kker Inc. , Ne w York, 1992, pp. 79-96.

[ 351 C.J. Tralau, H. Bart. A.J. MacR obert an d S.G, Bow n, Relative m erits

of porphyrin and phthalocyanine sensitize.lion for photodyaamic

therapy, in D. Kessel ted. ) .

Photodynamic Therapy of Neoplastic

Disease,

Vol. , CRC, Boca Ralon, 1990, pp. 263-278.

1361 A.J . MaeRohon, S.G . Bown and D . P hi l l i l~, Wha t are the ideal

photoproperties for a sensitizer. '?, in G. Bec k and S. Hametlt reds .)

Photoser~itizing Compounds: their Chemistry. Biology and Clinical

Use (Ciba Foundanon Symposium 1461,

J. Wile y, Chichester, 1989,

pp. 4--16.

[37 ] G. Jori. Photodynamic therapy: a nove l approach t o the treatment of

tumours.Bull. Mol. Biol. Mad.. 15 t

1990) 73-83.

[38] D, Kessel. HPD:

s m l c t u m

and d eterminan ts of Iocalizalion, in D.

Kessei (ed. )

Photod.vanmic Therapy of Neoplastic Disease,

CRC,

Boc a Raton, 1990. pp. 1-14,

[391 M . Kot'holik, G. IG 'osl and D.J. Chaplin, Photofrin u pla kc by murine

macmphages,

Cancer Res.. 51 (

1991 ) 22 51-2255 .

[40] C. Candide, P. Modi~re~ J,C. Maziere, S. G oldsle in, R. Santus, L.

Dubertmt, I.P. Reyflt~lann and J. PolnowskL In vitro interaction o f t ~

photoact ive ant ican~.er po ~h yrin der ivat iv e Phatofr in I1 with low

dens i ty l i popmte insand i ts del ivery o cul tured f ibroblas ts ,

FEBSLett. .

207

(1986) 133-138.

[411 F. R icchelli, S. Gobb~, G. Jori, G. lvloreno, F. V inzen s an d C, Salet,

Photosensitization of nutochoodria by liposome-houod porpbyrins,

Photochera. Photobiol., 58

t 1993 ) 53-58.

[421 L.C. Penning, J.W,M. Lagethorg, J,H. VanDierendonck, C.J.

Com elisse, T.M.A.R, Dubbelman and J , Van Steveninck, T he role of

DNA damage and inh ib i tion of po ly tA DP- r ibos y l ) a t ion in los s o f

clonogenici ty of ma rine L929 f ibroblasts , caused by ph otedyna mical ly

induced oxid ative stress, Cancer Res.. 54 (1994) 5561-5567 .

Tumour Photosensitizers Approaches to Enhance the Selectivity

Documents

Transcript of Tumour Photosensitizers Approaches to Enhance the Selectivity