Final Exam (new) Flashcards
characteristics of cancer cells
no contact inhibition of growth low growth factor requirements no anchorage dependence no cell cycle checkpoints abnormal karyotypic profile indefinite life span
what does lack of contact inhibition mean?
cancer cells do not stop dividing when they are in contact with other cells, results in cancer cells growing on top of each other
what does it mean that cancer cells are anchorage independent?
they do not attach to the substrate and appear rounded instead of spread out like normal cells
how do tumors stimulate angiogenesis?
they secrete VEGF which stimulates formation of new blood vessels (angiogenesis) and promotes survival/growth
what’s the Warburg effect?
cancer cells may switch from mostly using oxidative phosphorylation to using mostly glycolysis. this results in available carbon atoms (building blocks from incompletely oxidized glucose) to be used for synthesis of proteins, nucleic acids, and lipids needed for growth
how do cancer cells exhibit genetic instability?
DNA replication and repair are more prone to error and mutations. DNA repair proteins are mutated and overall mutation rate increases
philadelphia chromosome
an altered chromosome 22 used as identifier of leukemia. translocation means Ber gene fuses with Abl and results in constitutively active signaling pathway leading to increased cell survival, growth, and proliferation
cancer cells are defined by excessive proliferation and invasion of other tissues. how does this explain benign and malignant tumors?
when cells do not have the invasiveness property they are benign. Once a tumor spreads to other cells and invades tissues it become malignant.
metastases are
secondary tumors created when a primary tumor cell migrates to another tissue and invades. stages of metastasis vary in difficulty such that escaping parent tissue is difficult but travel through circulation is easy, then colonization of the new site is difficult
what is intravasation and extravasation?
tumor cells leave the primary tumor and enter the vascular system by intravasation. tumor cells establish secondary tumors in other tissues through extravasation and invasion
what percent of the human genome is cancer-critical?
1%
two classes of cancer-critical genes
oncogenes: encode proteins having gain-of-function mutations, leads to overactive genes
tumor suppressor genes: encode proteins that normally prevent excessive cell survival and proliferation
how many copies of mutation are needed to cause cancer in the two types of cancer-critical genes?
oncogenes: proto-oncogenes only need one mutated copy of gene to become overactive oncogenes
tumor suppressor genes: both copies must be mutated to lose tumor prevention functionality
how can the Wnt signaling pathway lead to colorectal cancer?
APC protein keeps the Wnt signaling pathway inactive in absence of Wnt protein. APC causes degradation of beta-catenin which prevents activation of gene transcription.
mutation of APC leads to accumulation of beta-catenin and drives transcription, leading to proliferation of stem cells and potentially cancer
how many mutations are needed in the same cell before tumor state is reached?
4-6 different mutations
three common pathways that are disrupted and cause cancer
- RTK/Ras/PI3K pathway
- Rb pathway
- p53 pathway
RTK/Ras/PI3K pathway mutations
pathway is normally activated by 2 signals, in cancer cells the pathway is activated without signals. leads to hyperactive Was that increases transcription and movement through cell cycle
Rb pathway mutations
retinoblastoma protein (pRb) is a universal regulator of the cell cycle. it binds to transcription factor E2F and inactivates it, stopping cell division. mutation causes abnormal cell proliferation. the transcription factor Myc can cause hyperactive pRb if it is constitutively active
p53 pathway mutations
p53 is activated at the G1/S transition where DNA integrity is checked before S phase. p53 stops damaged DNA from replicating, and so is called guardian angel gene. p53 is stabilized by phosphorylation which makes sure it only works when it should
why does chance of getting cancer skyrocket with age?
it takes time to accumulate numerous mutations in the same cells
how can obesity lead to cancer?
fat cells make extra hormones and growth factors which tell cells to divide more often. this increases the chance of cancer cells being produced
