Cancer 2 Flashcards
How does human colon cancer evolve?
1) Cancer begins as a a benign polyp.
2) The benign polyp grows and becomes benign adenoma.
3) Later the adenoma turns into a carcinoma.
What does the multi-hit model for cancer induction (III) prove?
It proves that cancer happens due to the progression of lesions (injury) in the development of cells.
Does the exact combination of mutations and even genes altered in a given type of cancer differ from one individual to another?
Yes.
Do cancers have the same malignant potential? How is it determined?
No, they have different malignant potential despite being histologically indistinguishable. Microarray analysis is now being used to study gene expression patterns (signatures) in cancers.
What does gain-of-function to?
Gain-of-function mutations that increase the activity of proto oncogenes such as growth promoting signaling molecules, receptors, intracellular signal transduction pathways are associated with cancer.
What does loss-of-function do?
Loss-of-function mutations in tumor suppressor genes (e.g. cell cycle control proteins) can cause cancer.
Compare between loss-of-function and gain-of-function according to apoptotic property.
Gain-of-function mutations is anti-apoptotic genes and loss-of-function mutations is pro-apoptotic genes.
Where are oncogenes generated from?
They’re generated from proto-oncogenes through gain-of-function mutations.
What active protein does gain-of-function mutation create?
They create oncoprotein.
What is the result of chromosomal translocations?
They can create unregulated chimeric oncoproteins or place a proto-oncogene under the control of uncontrolled promoter.
How does inherited mutations occur?
The patient inherits one non-functional copy of a tumor-suppressor gene.
Sporadic form or retinoblastoma requires two somatic mutations (T/F)
True.
What does loss-of-function in APC and BRCA genes do?
APC leads to the development of colon cancer while BRCA genes lead to the development of breast cancer as BRCA is important in DNA repair.
What are causes of cancer?
1) Inherited mutations in tumor-suppressor genes. (e.g. retinoblastoma)
2) Oncogenic mutations in receptors (e.g. Her2 receptors)
3) Viral activators of receptors. (e.g. gp55 protein produced by spleen focus-forming virus which binds to erythropoietin (Epo) receptors in erythroid progenitor cells causing erythroleukemia. Human papillomavirus)
4) Oncogenic signal transduction proteins. (e.g. GTPase activity ineractions with GAP, Raf kinase, GAP v-Src, viral tyrosine kinase)
5) Chromosomal translocation (e.g. Chronic myelogenous leukemia which is caused due to translocation producing Philadelphia chromosome which produces BCR-ABL fusion protein and can be cured by imatinib, Burkitt’s lymphoma)
