Cancer 2a Flashcards
Cancer
uncontrolled proliferation of cells that serves no physiologic fxn
neoplasm
any new growth
benign
encapsulated and well-differentiated
malignant
invasive and dedifferentiated
tumor
reserved for malignant cancers
metastasis
spread of cancer to other areas of the body-est. of secondary tumors
tumor marker
specific biochem marker (hormone, enzyme,gene,antibody) present in or on tumor cells, or in body fluids
Benign cells charcteristics
-grow slowly
-well-defined border
-not invasive
-well-differentiated: looks like cells which they arose from
-dividing cells are rare
-does not metastasize
Malignant cells characteristic
-grow rapidly
-does not have a border
-invade local structure and tissues
-poorly differentiated, may not be able to determine tissue or origin
-many dividing cells
-can spread distantly through blood and lymph vessels
Normal cells
-differentiate
-follow specific instructions
-fulfill roles of cell type
-populations controlled by balance of apoptosis and growth
Cancer cells
-break all the rules
-dedifferentiate: cells lose organization and order
-become anaplastic (without form) and pleiomorphic (many shapes, sizes)
-no longer fulfill specified role
-hijack the body’s mechanisms to promote their own survival.
Hallmarks of cancer cells (8 biological capabilities)
- sustaining proliferative signaling
- evading growth suppressors
- Enabling replicative immortality
- Resisting cell death
- Inducing and accessing vasculature
- activating invasion and metastasis
- avoiding immune destruction
- deregulating cell metabolism
Hallmarks of cancer cells -2 enablers of change
- Genome instability and mutation
- Tumor-promoting inflammation
Mutations characteristics
-5-6 different pathways are required to transform normal cells to cancer cells
-accumulate with age
Genetic changes (mutations)
-DNA changes
-Epigenetic changes
-microRNA expression
Types of genes prone to mutations
-oncogenes
-tumor suppressor genes
-caretaker genes
Point mutation
change of single nucleotide
nucleotide insertions/deletion
changes way that the gene is “read”
-think adding a random letter to a word
chromosomal rearrangement
may lead to the production of new or altered protein
gene amplification
increases copy number of genes and hence gene effects
gene silencing
turns off a gene’s effect
exogenous sequence
from virus, can alter fxn
Oncogenes
normally signal proliferation-signal cell to divide
-common ex. RAS
RAS
a “molecular switch” that initiates proliferation
-point mutation turn the switch on permanently
Chronic myeloid leukemia (CML)
result of novel protein that promotes uncontrolled growth
Chromosomal translocation
2 chromosomes fuse together in the middle of 2 different genes
ex. bcr on chromosome 9
abl on chromosome 22
resulting protein –> promotes myeloid cell proliferation
N-myc
-a normal oncogene
-fetal brain development
-( in neurblastma cells?)
Gene amplification
leads to hundreds of copies of
gene–>exaggerated proliferation signal
Tumor-suppressor genes
normally halt proliferation- tell the cell to stop dividing
-mutation makes these genes inactive.
Tumor-suppressor gene types
-RB1(retinoblastoma)
-p53
-APC
-BRCA1 (breast cancer)
requires ___mutation because we have __alleles for each gene
2, 2
RB1 (retinoblastoma gene)
-normally strongly inhibits division
-inactivation leads to uncontrolled proliferation (point mutation)
-requires 2 mutations to inactivate both copies of genes
p53 gene
-normally guardian of the genome
-activated by cell stress
-when a cell is damages, p53 tells it to repair or die.
-mutated p53 gene found in nearly every human cancer ever studied
-activated caretaker gene
Caretaker genes
-normally maintain genomic integrity
-conducts DNA repair; repair mismatched not, signal-strand breaks, dbl-strand breaks.
-mistakes during replication or exposure to radiation/chemicals
-loss of fxn leads to incr mutation rates
-MANY of the genes implicated in cancer
epigenetic changes
-alter expression of genes without mutating sequence
Meythlation
addition of methyl molecules to DNA blocks transcription
-STOP signal-no transcription
-DNA can be directly methylated, silencing tumor-suppressor genes or activation oncogenes
methylation of _____promotes cancer
tumor suppressor genes
demethylation of _____ promotes cancer
oncogene
Acetylation
-allows gene expression
-alters histones and chromatin
-GO signal
microRNA (miRNA)
-short sequences 22 nt that bind to mRNA
-Inhibiting translation into protein
-changes in miRNA abundance can change expression of genes
Oncomirs
miRNAs that stimulate progression of cancer
- Sustaining proliferative signaling
-induced angiogenesis
-lots of proliferation =lots of blood flow and nutrients needed
-tumor cells release growth factors
Growth factors
released by tumor cells:
-Vascular endothelial growth factor (VEGF)
-Platelet-derived growth factor (PDGF)
-Basic fibroblast growth factor (bFGF)
- Evading growth suppression
-contact inhibition
-anchorage dependence
-due to loss of cadherin and integrin expression
Contact inhibition
- in normal stop dividing after forming a complete monolayer bc of contact
-in cancer cells that will keep dividing and pile on each other
Anchorage dependence
-Non-cancerous cells only proliferate when attached to a surface. they cannot divide in soft agar bc they cannot attach
-cancer cells are anchorage-independent can proliferate in soft agar
telomeres
-are repeated sequences at the ends of chromosomes
-maintain chromosome stability during replication
-normal cells can only divide a finite amount of times –> Hayflick limit–>senescence (stops dividing)