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