Oncogenes

Oncogenes

arise from mutation or overexpression of proto-oncogenes; introduced by a virus, mutations in tumor suppressor genes, mutations in DNA repair genes

Proto-oncogenes

normal genes that code for proteins that promote cell growth and the cell cycle, or prevent cell death (growth factors, GTPases, transcription factors, etc)

Tumor suppressor genes

prevent DNA damage or persistence of mutations, generally act to slow down cell division so DNA repair can take place

Gene p53

a tumor suppressor gene that encodes a protein that can detect DNA damage, stops the cell cycle to promote DNA repair, or induce apoptosis if there is too much DNA to repair (more than half of all cell cancers have a mutation in p53)

Causes of cancer

loss of tumor suppressor genes or gain of oncogenes

Virus-induced cancers

many viruses have oncogenes which may result in the transformation of an infected cell into a cancerous cell, or develops as a result of secondary effects

Examples of Virus induced cancers

Rous sarcoma virus (RSV), Epstein-Barr virus (herpes virus), Hepatitis B, Human papillomavirus

BRCA1 and BRCA2

genes that encode for proteins called breast cancer type 1 and type 2 susceptibility proteins

Philadelphia chromosome

an abnormality of chromosome 22 where part of chromosome 9 is transferred to it making an abnromal BRC-ABL fusion gene (an oncogene)

Hormones

naturally promote cell growth in target tissues, can contribute to the proliferation in some cancers, implicated in links between obesity and cancer

Apoptosis

genetically controlled cell death, important to development and addition to removal of unwanted or damaged cells

Signals that induce apoptosis

following DNA damage or other cell damage, lack of survival signals like growth factors or cell-cell contact, infected by a virus, end of functional cell life

Capases

enzymes that break down cell components and organelles during apoptosis

Telomeres

extra DNA at the ends of chromosomes that protect chromosomes

Telomerase

an enzyme which adds DNA repeat units to telomeres, which makes cells “immortal”, turned back on in cancer cells

HeLa Cells

cells that were removed from Henrietta Lacks and used in research since 1951