Lecture 17: Hereditary Cancer and Oncoviruses Flashcards
how many hereditary cancers are known?
50 forms
about 1-2%
Ras proto-oncogene
- Ras gene family include some of the most frequently mutated genes in human tumors
- encode signal transduction molecules associated with cell membrane
- regulate cell growth and division
kinases
enzymes that are responsible for phosphorylation
how many exons does the RET proto-oncogene?
21
what happens when RET behaves like other receptor tyrosine kinases?
-then binding to ligand causes dimerization and activation of the receptor
what does it mean by saying RET is a proto-oncogene?
a single activating mutation on only one allele should be sufficient to cause neoplastic transformation
what happens when there is a mutation of codon 634?
-constitutively (always on) activate the tyrosine kinase receptor by causing receptor monomers to dimerize, mimicking the effect caused by binding of a ligand to a receptor
what processes is RET signaling involved in?
- proliferation
- migration survival
- differentiation
what can happen if constant signaling by RET is in the wrong place at the wrong time?
cell proliferation
neoplasia
the formation of a cell mass (benign or malignant)
oncoviruses
viruses that contribute to the formation of cancer
what percentage of global cancer incidence is linked to an infectious agent?
18%
what percentage of Epstein-Barr virus accounts for what percentage of all virus associated cancer?
1%
what viruses cause most cancer?
RNA retoviruses
how do pathogens infect cells?
when they gain access to the cell’s interior
-pathogens target certain cell types and not others
what makes once cell type different from another?
- heterochromatin v euchromatin
- TF collection in nucleus
- cell surface markers
- cytoplasmic proteins
about 18% of human cancers are caused by infections, what are viruses that account for 12% of that?
EBV, HPV, HepB, HepC, HTLV-1, KSHV, and MCV
what are the DNA cancer causing viruses?
EBV, HPV, HCV, PHV16, KSHV
what are the RNA cancer causing viruses?
HTLV-1, HIV-1
Retroviruses
- RNA viruses
- animal viruses that cause cancer
- reverse transcriptase copies RNA to DNA
- DNA copy enters into the nucleus
- retroviruses integrate into host genome as a provirus
provirus
replicated with host’s DNA during normal cell cycle
acute transforming retroviruses
- carry cell-derived oncogenes
- infect and transform cells into cancer cells
what are the three ways retroviruses can cause cancer?
- ) proviral DNA may integrate near protooncogenes, which stimulates high rates of transcription
- ) acute transforming retroviruses
- ) normal retrovirus with normal viral gene products can stimulate inappropriate cell growth
