Cancer

By: Aujan M., Zach J., Aditya P.

*Overview

*Genetic disease that results in uncontrolled growth.*Mutation in genetic code results in failure

of cell division control.*~90% of time, cancer mutation due to

external environmental factors. Cancer due to inherited mutations ~10% of time.

*Overview

*Deletion or duplication of nucleotides in genetic sequence can lead to mutation.*Once cell’s life cycle is disrupted,

cancerous cells begin to grow at rapid rate, forming a neoplasm.

*Genetic Basis

*Cell undergoes cell division before cell is fully mature. Since they divide at a rapid rate, successive cancer cells will be immature and dysfunctional.*Mutations occur after birth, not a

hereditary disease.

*Genetic Basis

*Genes that inhibit cell division are proto-oncogenes. These can mutate and become oncogenes.*Oncogenes – mutations causes constant

production of proteins/enzymes stimulating unrestrained cytokinesis.

*Causes of Cancer

*Majority of genetic mutations occur during S phase.* Result of 3 major mechanisms:*1.) Carcinogens – cancer causing agents that cause

mutation to cell’s DNA (anti-oncogenes). i.e.- chemicals and radiation.*2.) Viruses – viruses insert their fragment of DNA

into genetic material of cells they infect. DNA can compromise proto-oncogenes of cell.*3.) Replicative Mutations – during replication,

mutations can affect proto-oncogenes turning them into oncogenes.

*Types of Mutations:

Point Mutations

*Changes to a specific portion of a gene.*May be transmitted to offspring, allowing

it to be found in successive generations.

*Types of Mutations:

Substitutions

*Base Pair Substitution – replacement of one nucleotide and complimentary base with another complimentary pair.*Missense Mutation – altered codon still

codes for amino acid, but amino acid doesn’t make sense with function of protein.*Nonsense Mutation – causes production of

stop codon.

*Substitution

*Types of Mutations:

Insertions/Deletions

*Adding/Losing Nucleotide Pairs – more harmful than substitutions because mRNA coded in series of triplets. Loss/gain causes entire sequence to shift over, resulting in shift in reading frame.*Frameshift Mutation – nucleotides

inserted/deleted don’t come in multiple of three. Alters reading frame. Produces useless protein.

*Insertion/Deletion

*Types of Neoplasms:

Benign

*Benign Neoplasm – mass of cells whose cellular compositions is same as cells of surrounding tissues.*Surrounded by connective tissue, so

metastasis doesn’t occur.*Nuclear fission similar to that of normal

cells.*Since rate of division slightly higher than

that of normal cells, tumor will grow slowly.

*Types of Neoplasms:

Malignant

*Neoplasms whose DNA has mutated. Different from surrounding tissues.*Resemble immature and undifferentiated cells.*Growth is greatly accelerated and can become

detrimental to surrounding tissue.*Neoplasm then breaks out of connective tissue

capsule and can metastasize.*Usually contain degraded chromosomes joined

incorrectly to another gene.

*Benign (top) and Malignant (bottom)

Tumors

*How do cells avoid death?

*Apoptosis- programmed cell death*Inhibit the expression of Apaf-1*Secrete elevated levels of decoy soluble

molecule that binds to Fas-L*Utilization of human proto-oncogene Bcl-2

*Tumor Suppressor Genes

*Inhibit cell division*Contains p53 gene which binds DNA and

stops it from allowing damaged DNA to divide

*Proto-Oncogene

*Stimulates the cell cycle *Ras is a gene turns on other genes

through the signal transduction cascade which tells the cell cycle to go

*Why do cancer cells grow

uncontrollably?

*Divisions determined by telomeres *Cancer cells turn on telomerase*Cancer cells now divide without any limits

*Processing Nutrients

*Cancer cells need nutrients*Blood vessels nourish the tumor*angiogenesis

*Invading Tissues

*Invading tissues and disrupting functions*metastasizing

*Treatments

*There are no cures for cancer but treatment options do exist. *Chemotherapy- poison cancer cells*Radiation- uses x-rays and radio isotopes

to destroy cancer causing cells*Surgery- removes neoplasm and

surrounding tissues