Lecture 23: Cancer Flashcards
The incident of cancer now is _____
increasing
carcinomas arise from _____ and comprise ______
-epithelial cells of specific origin (ex. gut or skin)
-90% of human cancers
Sarcomas arise from _____
connective tissue
leukemias/lymphomas arise from _____
immune cells
Sarcomas and leukemias/lymphomas: arise from cells of _____
mesodermal origin including muscle, bone, blood vessels, fibroblasts, and circulating cells of the blood and lymph
Tumors are further characterized by ______
the tissue of origin (e.g. lung carcinoma or colon carcinoma)
Oncogene (def.)
gene capable of inducing cell transformation (cause cancer)
Benign Tumor is defined by _______
-abnormal cell proliferation confined to its normal
location
-Cannot invade surrounding tissues or spread to other organs. (e.g. wart)
Malignant Tumor is defined by _______
-abnormal cell proliferation that is both invasive and metastatic
-can invade and destroy adjacent normal tissue
as well as spreading to distant sites through the circulatory system
________ synonymous with cancer
Malignant Tumor
normal cell division + normal apoptosis = _____
homeostasis
increased cell division + normal apoptosis = _____
tumor
normal cell division + decreased apoptosis = _____
tumor
Benign tumors ______ whereas malignant tumors
______ and move _______
-remain at their site of origin
-destroy integrity of structure
-to distal sites (metastasis)
differences between benign tumor and malignant tumor
-malignant tumor metastasizes (spread from original location)
-benign tumor doesn’t affect normal tissue function
-malignant tumor affect normal tissue function
malignant tumor is result of ______
-accumulating mutations in genome
cancer typically happens later in life because ______
you need to accumulate mutations to the genome
Normal cells vs cancer cells: Density dependent growth inhibition/contact inhibition
-normal cells: yes
-cancer cells: no
Normal cells vs cancer cells: Growth factor requirement
-normal cells: High
-cancer cells: Low (bypass the check & balance)
Normal cells vs cancer cells: Anchorage dependence
-normal cells: Yes
-cancer cells: No
Normal cells vs cancer cells: Proliferative life span
-normal cells: Finite
-cancer cells: Infinite
Normal cells vs cancer cells: Adhesiveness
-normal cells: High
-cancer cells: Low
Normal cells vs cancer cells: Morphology
-normal cells: Flat
-cancer cells: Rounded
in normal cells, high density ____ but this doesn’t occur in cancer cells
inhibits growth
increase growth = quality of ______
division is compromised
Tumor cells have a _____ morphology from normal cells
different
Tumor cells often have _____ ratio (a characteristic of rapidly growing cells) because cell division is ______ and normal function ______
-high nucleus to cytoplasm
-dependent on nuclear material
-in the cytoplasm is not important
in tumor cells, _____ and ____ is lost
-contact inhibition and polarity
Studying cancer cells takes advantage of the fact that ____
transformed cells have different morphology & growth characteristics (can easily identify them)
Studying oncogenes goal
Find gene(s) in tumor cells that when expressed in non-transformed cells—result in loss of contact inhibition
Studying oncogenes method
1) DNA from human tumor cells -> transfected mouse NIH3T3s cells
2) culture for 2 weeks
3) extract DNA from transformed NIH3T3 cells growing among untransformed cells -> loss of contact inhibition
4) Transform new mouse cells (2nd cycle) for enrichment for oncogene DNA
5) Phage library is made from DNA isolated from secondary transfectants
6) Plate phage on E.coli which kills E-coli and create hole in plate of E-coli
7) Each plaque (hole) has human DNA from the cancer
8) Replica on filter paper + add Alu probe (Alu is unique to human so it’s used to identify human DNA)
9) Identify phage from library that has oncogene (human DNA)
mouse NIH3T3s cells are ______ so they _____
immortal but not transformed (cancer) so they exhibit contact inhibition
Creating phage library method
1) Genomic DNA (from transformed mouse cells that contain human tumor DNA)
2) Shear DNA
3) Ligate genomic DNA into phage
4) Recombinant phage has mouse and human DNA
In the human genome, _____ are much more prevalent than genes
Alu sequences (~300 base pairs)
If a human DNA fragment contains a gene, chances are that _____
it contains one or more Alu sequences
Using the phage library was used to identify _____
the human gen that produces a mutant Ras (the first human oncogene identified)
point mutation (def.)
a single nucleotide change
Oncogenic activation of Ras is the result of a ______
point mutation that keeps Ras in the GTP bound form (activated form)
Ras mutation
Gly12 >Val 12 (GGC codon to GTC)
Mutated ras oncogenes are found in _____
a lot of cancers , especially the deadliest ones
Mutated Ras can cause cause because _______
it induces the transcription of many genes that contribute to the metastatic phenotype (cell cycle progression, survival, growth, migration)
Many cancer cells target proteins in _____
Ras signaling pathways (like RTK, Ras, Raf 1, Mek)
Drugs ending in “mab” are ______. They target ____
monoclonal antibodies
RTK receptors on the cell surface
Oncogenes act _______to increase rates of cancer so ____
synergistically
mutations in multiple oncogenes = increase rate of cancer
_____is a transcription factor that regulates ______. Uncontrolled expression (______) associated with _____
- C-myc
-cellular proliferation
-gene amplification or mutations
-many tumors
Cancer is a _____ process in which cells acquire the ______ through a ______
-complex multi-step
-full malignant phenotype
- progressive accumulation of alterations
Normal cell to malignant tumor steps
normal cell –> (initiation/<—–DNA repair ) initiated cell —> (promotion) preneoplastic cell –> (progression) neoplastic cell –> (metastasis) malignant tumor
Two basic categories of oncogenic mutations
1) Gain of function mutations
2) Loss of function mutations
Gain of function mutations (def.)
result in conversion of proto-oncogenes to oncogenes
Loss of function mutations (def.)
mutations in gene that encodes proteins (tumor suppressors) that inhibition proliferation
proto-oncogene (def.)
the normal cellular gene from which an oncogene originates (gene that is the precursor of a given oncogene); promote cell survival or proliferation
tumor suppressors normal function
inhabits cell survival or proliferation
caretaker genes normal function
repair or prevent DNA damage
Genetic properties of mutant gene: proto-oncogenes
mutations are genetically dominant (only needs one mutant copy of gene)
Genetic properties of mutant gene: tumor-suppressor genes
mutations are genetically recessive (needs two mutant copies of gene)
Genetic properties of mutant gene: caretaker genes
mutations are genetically recessive (needs two mutant copies of gene)
Scenarios leading to Gain of Function Mutants
1) Point mutations or deletions-resulting in gene encoding constitutively active protein (dominant)
ex. RasD, Her2, ErbB mutants
2) Chromosomal translocation-resulting in hybrid gene encoding protein with altered activity (dominant)
ex. Trk oncoprotein
3) Chromosomal translocation-resulting in growth regulatory gene becoming under control of different promoter (dominant)
ex.c-myc/Burkitt’s lymphoma
4)Amplification (abnormal DNA replication)-of proto-oncogene region leading to overproduction of protein
ex. n-myc/neuroblastoma
Her2 receptor and EGF receptor are _____
RTK (when constitutively active, its leads to uncontrolled signaling for cell proliferation)
Point mutations or deletions lead to genes encoding RTKs _______ and
-that are constitutively active in the absence of ligand
-uncontrolled signaling leading
to cell proliferation
Anti-Her2 (monoclonal) has been developed as ______
new treatment for breast cancer
Trk receptor mutation that leads to cancer
-chromosomal translocation resulting in hybrid gene (tropomyosin + Trk receptor)
-tropomyosin region mediates ligand-independent dimerization and activation of kinase domains in Trk region»_space; uncontrolled signaling
The proto-oncogene _____is amplified in certain tumors
Myc
Scenarios leading to Tumorigenic Loss of Function Mutants
Loss or mutations of genes that encode proteins that:
*Promote apoptosis»inability to induce cell death
*Repair DNA»rapid accumulation of mutations in cells
*Function as receptors or signal transducing proteins that are required for pathways that inhibit growth»inability to respond to appropriate signals
*Regulate cell cycle check-points» inability arrest the cell cycle following DNA damage or chromosomal abnormalities
Loss of function mutants are usually _____
recessive»_space;Both copies of genes have to be lost or mutated in order for tumorigenic phenotype to develop
Risk of developing cancer can be mitigated _____
through lifestyle and diet
Most cancers development is not due to _____
family history
Immune-braking system (def.)
Programmed death-ligand 1 (PD-L1) on cells binds to its receptor (PD-1) on activated T-cells and inhibits their ability kill target cells.
PD-L1 in tumor cells is _____
highly expressed on many tumor cells»evade anti-tumor immunity
Blocking _____ allows T cell to kill tumor cell
PD-L1 or PD-1
overactive T-cell can be _____
cancer like (cause cancer)
CAR T-cell therapy (“living drugs”)
1) Remove blood from patient to get T-cells
2) Make CAR T cells in lab (insert gene for CAR) –> displays CAR (chimeric antigen receptor)
3) Grow millions of CAR T cells
4) Infuse CAR T cells into patient
5) CAR T cells bind to cancer and kill them
