MOD 9: Cancer & Genetics Flashcards
Where are variations observed in the regulation of the cell cycle?
- Overall length of the cell cycle
- Relative length of time spent in the various phases
- How closely mitosis and cytokinesis are coupled
This protein kinase plays a role in the signaling network that controls cell size and coordinates with cell cycle progression
Target of rapamycin (TOR)
What processes do the target of rapamycin (TOR) promote?
- Translation
- Ribosome biosynthesis
- Stability of high affinity amino acid permeases
What processes do the target of rapamycin (TOR) inhibit?
- Autophagy
- Starvation-induced gene transcription
- Stability of general amino acid permeases
What conditions must the control of the cell cycle consider?
- Ensure that events of each phase are carried out in the correct order + at the appropriate time
- Ensure that each phase is completed before the next one begins
- Respond to external conditions
What factors influence the restriction point (start)?
- Growth factors
- Nutrients
- Cell size
- DNA damage
What factors influence the G2-M transition point?
- Cell size
- DNA damage
- DNA replication
What factor influences the metaphase-anaphase transition point?
Chromosome attachments to spindle
Where does the first control point occur?
In the late G1: G1 —> S progression
The G1 —> S progression point is called __________ in yeast and __________ in animal cells
Start; restriction point
Cells that successfully pass the restriction point are committed to what phase?
The S phase
At what transition point is the restriction point observed?
G2-M transition
At what transition point is the commitment made to enter mitosis?
G2-M transition
This transition point ensures that the DNA replicated is correct
G2-M transition point
In most cells, the G1 arrest is the more prevalent type of control. What type of cells consider the G2 arrest to be more important?
Frog eggs
At what transition point is the commitment made to move the two sets of chromosomes into the new cells?
Metaphase-anaphase transition
What will happen to the cell if a problem occurs in the third transition point — metaphase-anaphase transition?
The cells may stay in that state or result to apoptosis
In MEIOSIS, errors in the metaphase-anaphase transition may result to two possible conditions. What are they?
- Nondisjunction
- Aneuploidy
This condition occurs when there are errors in the metaphase-anaphase transition phase in MEIOSIS:
Spindle fibers do not allow sister chromatids to properly segregate
Nondisjunction
This condition occurs when there are errors in the metaphase-anaphase transition phase in MEIOSIS:
Different levels of ploidy in the receiving cells
Aneuploidy
TRUE OR FALSE: Mutations in genes directly lead to cancer
FALSE; It does not
Is cancer caused by a single gene or an accumulation of genes?
Cancer is caused by an accumulation of different mutations
What are the three classes of genes that are frequently mutated in cancer?
- Proto-oncogenes
- Tumor suppressor genes
- Mutator genes
These are genes that behave normally and have their own function
Proto-oncogenes
When these genes are affected by cancer-causing agents, they are the ones that will lead to oncogene
Proto-oncogenes
These are genes that may acquire dangerous functions and lead to unregulated cell division
Proto-oncogenes
What cellular oncogene is responsible for signaling tyrosine kinase?
abl
What cellular oncogene is responsible for receptor tyrosine kinase?
erb B-2 (her/neu)
What cellular oncogene is responsible for G protein?
ras
What cellular oncogene is responsible for transcription factor?
myc
What cellular oncogene is responsible for transcription regulator?
jun/fos
What cellular oncogene is responsible for signaling tyrosine kinase?
src
What cellular oncogene is responsible for signaling lipid kinase?
pi3k
What cellular oncogene potentially leads to chronic myelogenous leukemia?
abl
What cellular oncogene potentially leads to carcinoma of breast and ovary; neuroblastoma?
erb B-2 (her/neu)
What cellular oncogene potentially leads to carcinoma of colon, lung, and thyroid; melanoma?
ras
What cellular oncogene potentially leads to Burkitt’s lymphoma; carcinoma of breast and ovary
myc
What cellular oncogene potentially leads to carcinoma of breast and lung?
jun/fos
What two cellular oncogenes potentially lead to carcinoma of colon?
src and pi3k
What process is prevalent in kinases and can either disrupt, kill, or inactivate a protein?
Phosphorylation
What are the genes of interest for colorectal carcinoma?
- KRAS
- BRAF
- NRAS
- PIK3CA
- TP53
What are the genes of interest for breast carcinoma?
- PIK3CA
- TP53
- BRAF
- PTEN
- PTEN LOH by micro-satellite analysis
What are the genes of interest for prostate carcinoma?
- PTEN
- BRAF
- TMPRSS2-ERG fusion by FISH
- PTEN LOH by micro-satellite analysis
What are the genes of interest for lung carcinoma?
- EGFR
- KRAS
- BRAF
- ALK rearrangement by FISH
What are the genes of interest for ovarian carcinoma?
- TP53
- PTEN
- PIK3CA
- BRAF
- PTEN LOH by micro-satellite analysis
What are the genes of interest for malignant melanoma?
- BRAF
- KIT
- NRAS
- PIK3CA
TRUE OR FALSE: Only one gene is involved in order to lead to a particular type of cancer.
FALSE; There are many genes involved leading to a particular type of cancer
These are genes that help regulate the growth and division of cells
Tumor suppressor genes
These genes ensure that cells do not proliferate uncontrollably and act like a preventive measure
Tumor suppressor genes
These are genes that increase the mutation rate of other genes within the gene
Mutator genes
When these are altered/defective, they lead to an increase in mutation frequency of the DNA
Mutator genes
These monitor the DNA for damage and halt the cell cycle at various points
DNA damage checkpoints
How do DNA damage checkpoints halt the cell cycle at various points?
By inhibiting different Cdk-cyclin complexes
This is referred to as the guardian of the genome and it plays a central role in these checkpoint pathways
p53 protein
This gene is known to be mutated in many cancers
P53 gene
What are the 5 brief steps in how p53 works?
- Cellular stress recognition
- Activation of p53
- Cell cycle regulation
- DNA repair
- Apoptosis induction
What activates the p53 gene?
Stress, such as DNA damage or hypoxia
What factors trigger the stress that activates the p53 gene?
Radiation, chemicals, or DNA replication errors
Once the p53 gene is activated, it acts as a __________, meaning it regulates the expression of specific genes
Transcription factor
The p53 gene helps to prevent the damaged cell from dividing by inducing a temporary cell cycle arrest at what phase?
Usually at the G1 phase
What is a key protein that is a p53 unregulated modulator of apoptosis?
Puma
Puma inactivates __________, an apoptosis inhibitor
Bcl-2
What occurs when Bcl-2 is activated?
Phosphorylation
What occurs when Bcl-2 is deactivated?
Cell cycle arrest or apoptosis
Who was the first to demonstrate that cancer can be caused by a virus?
Peyton Rous (1911)
This is the cancer of the connective tissue
Sarcomas
What was shown to be caused by the Epstein-Barr virus?
Burkitt’s lymphoma
This virus was not just inherited and can be caused by an enzyme
Epstein-Barr virus (EBV)
What are the symptoms of Burkitt’s Lymphoma?
- Abdominal swelling
- Distortion of facial bones
- Night sweats
- Intestinal obstruction
- Enlarged thyroid and tonsils
What type of cancer does Hepatitis B and C lead to?
Liver cancers
What type of cancer does Human T-cell Lymphotropic Virus-1 (HTLV-1) lead to?
Adult T-cell leukemia
What type of cancer does Human papillomavirus (HPV) lead to?
Uterine and cervical cancers
What oncogenic infectious agent may cause stomach cancer?
Bacterium Heliobacter pylori (H. pylori)
This antibiotic is associated with stomach ulcers, helping to prevent stomach cancer
H. pylori
What oncogenic infectious agent causes bladder and bile duct cancer?
Flatworm infections
What are the two main classes of DNA mutations?
Oncogenes and tumor supressor genes
What are the two main classes of DNA mutations?
Oncogenes and tumor supressor genes
This is referred to as the gene whose presence can trigger cancer
Oncogene
What was the first oncogene discovered?
Rous sarcoma virus
Viruses with defects in the _________ can infect cells but don’t cause cancer
src gene
This is the uptake of foreign DNA into cells and incorporation into chromosomes
Transfection
__________ are not sufficient to cancer
Single oncogenes
__________ are not sufficient to cancer
Single oncogenes
__________ are converted into oncogenes by several distinct mechanisms
Proto-oncogenes
When proto-oncogenes’ structure or activity is disrupted by mutation, the mutant form of the gene can cause cancer:
- Point mutations
- Gene amplification
- Chromosome translocation
- Local DNA rearrangements
- Insertional mutagenesis
This is the simplest mechanism that converts a proto-oncogene into an oncogene
Point mutation
This increases the number of proto-oncogene copies, causing the protein product to be produced in-excess
Gene amplification
This gene encodes growth factor receptors and encodes for the receptor tyrosine-protein kinase erbB-2 and will lead to cancer
ERBB2 gene
In this process, a part of one chromosome is joined to another chromosome
Chromosome translocation
What are the chromosomes involved in Burkitt’s lymphoma?
Chromosomes 8 and 14
Protein formation leads to the expression of the __________
Myc protein
This is a transcription factor that has target genes which are involved in self-proliferation
Myc protein
This is a translocation chromosome that involves chromosomes 9 and 22
Philadelphia chromosome
What are the two chromosomes involved in philadelphia chromosome?
Chromosomes 9 and 22
This refers to proliferation control failure in blood
Chronic myelogenous leukemia (CML)
Translocation creates an oncogene called __________
BCR-ABL
Local rearrangements alter base sequences of __________.
Proto-oncogenes
How are proto-oncogenes’ base sequences altered through local rearrangements?
- Deletions
- Insertions
- Ineversions
- Transpositions
What is the resulting gene that fuses the tyrosine kinase part of the receptor (NTRK1) to a region of the tropomyosin molecule?
TRK oncogene
TRUE OR FALSE: Retroviruses can sometimes cause cancer by integrating their own genes into a host chromosome in a region where a proto-oncogene is located.
TRUE
What do you call the phenomenon in which the proto-oncogene is converted into an oncogene by causing it to be overexpressed?
Insertional mutagenesis
TRUE OR FALSE: The loss or inactivation of tumor suppressor does not lead to cancer.
FALSE: It may lead to cancer
YES OR NO: Is it possible to fuse cells?
Yes
YES OR NO: Is it possible to fuse cells?
Yes
How many copies of the tumor suppressor gene is mutated in hereditary cancers?
Only one copy
If the parent gametes are not mutated, when will the hereditary cancer appear?
Only after cell division
This is referred to as a rare hereditary eye cancer that develops in young children.
Heretidary retinoblastoma
Children with hereditary retinoblastoma inherit a deletion in what part of the chromosome?
Chromosome 13
TRUE OR FALSE: A deletion in chromosome 13 immediately leads to cancer.
FALSE: A deletion alone does not cause cancer
What phase progression does the Rb protein control?
The G1 to S phase progression
TRUE OR FALSE: Mutations in the Rb gene are only detected in hereditary cancers.
FALSE: They are also detected in nonhereditary cancers
This is referred to as one of the most important tumor suppressor genes in humans.
p53 gene (TP53 in humans)
What happens when p53 is inactivated?
Apoptosis, allowing defective cells to divide continuously
This is referred to as an inherited condition caused by a defective copy of the p53 gene.
Li-Fraumeni syndrome
This syndrome is characterized by the development of various types of cancers by early adulthood.
Li-Fraumeni syndrome
The Li-Fraumeni syndrome is caused by mutations in what copy of the p53 gene?
The second copy of the p53 gene
This refers to the fact that mutation rates in cancer cells are thousands of times higher than normal
Genetic instability
Most hereditary forms of breast cancer arise in women who inherit a mutant copy of either __________ or __________
BRCA1 or BRCA2 (breast cancer gene 1 and 2)
BRCA1 has a mutation in what chromosome number?
Chromosome 17
BRCA2 has a mutation in what chromosome number?
Chromosome 13
Both of these genes code for proteins involved in repair of double-strand DNA breaks
BRCA1 and BRCA2
Both of these genes code for proteins involved in repair of double-strand DNA breaks
BRCA1 and BRCA2
Breast and ovarian cells with these mutations exhibit chromosomal __________
Rearrangements
Women inheriting BRCA mutations exhibit a __________ lifetime risk for breast cancer and a __________ risk for ovarian cancer
40-80%; 15-65%
Genetic instability can be traced to mutations in __________
DNA repair genes
What pathway is defective in most cancer cells? This removes an important protective mechanism against genetic instability
p53 pathway
At which checkpoint can defects be found in cancer cells?
Mitotic spindle checkpoint
Loss of the mitotic spindle checkpoint due to mutations in the genes that regulate it can lead to __________
Chromosome mis-segregation
What are the genes and proteins involved in the mitotic spindle checkpoint?
Mad and Bub
These genes and proteins are involved in making sure that the spindle fibers are attached to the centromeres
Mad and Bub
The loss of these genes directly opens gates to excessive proliferation and formation of tumors
Gatekeepers
What are examples of gatekeepers?
Tumor suppressor genes, such as APC, RB, and p53 genes
These are genes involved in DNA repair and chromosome sorting because they maintain genetic stability. They are not, however, directly involved in controlling proliferation.
Caretakers
What will happen if the caretaker cannot repair, but the gatekeeper does not let it proceed?
Nothing…
Enumerate the 7 examples of gatekeeper genes.
- APC
- CDKN2A
- PTEN
- RB
- SMAD4
- TGFB receptor
- p53
Enumerate examples of caretaker genes.
- BRCA1, BRCA2
- MSH2, MSH3, MSH4, MSH5, MSH6, PMS1, PMS2, MLH1
- XPA, XPB, XPC, XPD, XPE, XPF, XPG
- XPV (POLn)
This tumor suppressor gene affects the Wnt signaling pathway. Is it a gatekeeper or caretaker?
APC gene; gatekeeper
This tumor suppressor gene affects the Rb and p53 signaling pathways. Is it a gatekeeper or caretaker?
CDKN2A gene; gatekeeper
This tumor suppressor gene affects the PI3K-Akt signaling pathway. Is it a gatekeeper or caretaker?
PTEN gene; gatekeeper
This tumor suppressor gene affects the restriction point control pathway. Is it a gatekeeper or caretaker?
RB gene; gatekeeper
These tumor suppressor genes affect the TGFB-Smad signal pathway. Are they gatekeepers or caretakers?
SMAD4 gene and TGFB receptor gene; gatekeeper
This tumor suppressor gene affects the DNA damage response pathway. Is it a gatekeeper or caretaker?
p53 gene; gatekeeper
What tumor suppressor genes affect DNA double-strand break repair? Are they gatekeeper or caretaker genes?
BRCA1 and BRCA2; caretaker
What tumor suppressor genes affect DNA mismatch repair? Are they gatekeeper or caretaker genes?
MSH2, MSH3, MSH4, MSH5, MSH6, PMS1, PMS2, MLH1; caretaker
What tumor suppressor genes affect DNA excision repair? Are they gatekeeper or caretaker genes?
XPA, XPB, XPC, XPD, XPE, XPF, XPG; caretaker
What tumor suppressor genes affect DNA translesion synthesis? Are they gatekeeper or caretaker genes?
XPV (POLn) gene; caretaker
What tumor suppressor genes affect DNA translesion synthesis? Are they gatekeeper or caretaker genes?
XPV (POLn) gene; caretaker
The common mutations in cancers involve the inactivation of __________ genes and the conversion of __________ to __________
Tumor suppressor genes; proto-oncogenes; oncogenes
What is the most common pattern detected in colon cancer?
- Active KRAS oncogene
- Mutation in tumor suppressor genes APC, SMAD4, and p53
In what manner does colon cancer occur?
Stepwise manner involving a lot of genes
Mutations in KRAS and SMAD4 are seen when __________ grow larger
Polyps
TRUE OR FALSE: Mutations in p53 accompany the development of cancer
TRUE
This pathway is frequently disrupted in colon cancer, inhibiting epithelial cell proliferation
TGFB-SMAD Pathway
TRUE OR FALSE: Epigenetic changes alter both a gene’s expression and its sequence
FALSE; They alter a gene’s expression only, not its sequence
What is the function of MLH1 gene-on chromosome 3?
DNA mismatch repair
What are the 6 hallmarks of carciogenesis?
- Self-sufficiency in growth signals
- Insensitivity to antigrowth signals
- Evasion of apoptosis
- Limitless replicative potential
- Sustained angiogenesis
- Tissue invasion and metastasis
This is referred to as the formation of blood vessels.
Angiogenesis