Cell Cycle, Apoptosis, And Cancer

Question 1

What happens in S phase

Answer 1

DNA synthesis/replication
Histone syntheisis
Centrosome formed
Chromosome duplication

Question 2

What happens in M Phase

Answer 2

Mitosis (PMAT)

• chromosome duplication/segregation
• cytokinesis

Question 3

What happens in G1 phase of interphase ?

Answer 3

RNA and protein synthesis needed for DNA replication

*no cell division

Question 4

What happens in G2 phase of interphase ?

Answer 4

DNA stability is checked

*prep for mitosis

Question 5

What happens in G0 stage of the cell cycle?

Answer 5

Nothing. No division occurs.

Question 6

What drives cell proliferation in cell signaling networks

Answer 6

Myc-TF

Myc is a gene regulatory protein

Question 7

Myc increases _________ levels in the cell to drive proliferation

Answer 7

G1-Cyclin-dependent kinase (CDK) levels

Question 8

CDK phosphorylates what in cell cycle that drives cell proliferation

Answer 8

Retinoblastoma (Rb)

Question 9

Phospho-Rb (created from CDK) releases what in cell signaling that drives cell proliferation

Answer 9

Releases sequestered E2F (elongation factor)

*phophorylated RB is “inactive”. It releases the E2F protein to go on in its active form

Question 10

Binding of Cyclin to CDK only causes partial activation of CDK. What is needed for full activation of CDK?

Answer 10

CDK-activating kinase (CAK)

*adds phosphate to T-loop “cave site”

Question 11

What are the CDK inhibitors (CKI) that inhibit cyclin-CDK complex?

Answer 11

WEE1
- phosphorylate CDK complex inactive by added phosphate to the “roof site”

P27 (KIP1)
-bind to attached CDK complex (both the cyclin and CDK) and make it inactive

Question 12

What opposes WEE1 inhibition of the CDK complex ?

Answer 12

CDC25 phosphatase

• removes the phosphate attached by WEE1 kinase to make it active again
• dephosphorylates the “roof site”

Question 13

APC/C is activated by binding to _____

Answer 13

CDC20

*starts ubiquitination pathway

Question 14

The Activated APC/C poly-ubiquitinates it substrates. What are two proteins ubiquitnated by APC/C in the cell cycle? And why does this proteins need to be down regulated?

Answer 14

S- and M- cyclin proteins

**cyclin-S and cyclin-M activity must be inhibited to move the cell into anaphase. Without the cyclins the CDK is inactivated.

**both S- and M- proteins are sent to proteasome to get degraded

Question 15

What E3 ubiquitin ligase keeps P53 inactive though degradation in quiescent cells ?

Answer 15

MDM2

Question 16

DNA damage (increases or decreases) protein kinase activity?

Answer 16

Increases

*protein kinase phosphorylates P53 to make it active

Question 17

Activation of P53 leads to (increased or decreased) transcription of specific CKI (P21).

What is the effect on the cell cycle?

Answer 17

Increased

*binding and inactivation of cyclin-CDK by P21 causes cell cycle arrest

Question 18

What hyperphosphorylates RB to make it inactive to release active E2F?

Answer 18

CyclinD-CDK 4 and 6 complex’s

*which helps the cells pass though the restriction point in G1

Question 19

Briefly describe the extrinsic pathway of cell apoptosis.

Answer 19

*mitochondrial-independent pathway

1. A Fas ligand and TNFa binds to Fas receptor and TNFa receptor on the outside of the cell
2. FADD complex will activate production of Procaspase-8
3. TRADD complex will stimulate activiation of procaspase-8 to caspase-8
4. Caspase-8 will activate procaspase 3,6,7 to caspase 3,6,7.
5. Active caspase 3,6,7 will initiate apoptosis

Question 20

Briefly describe the intrinsic pathway of apoptosis.

Answer 20

*mitochondrial dependent because relied on cytochrome C

1. DNA damage activates P53
2. Active Caspase 8 will convert Bid to tBid and activate BAX and BAK
3. P53, BAX, BAK stimulate release of cytochrome C from the mitochondria
4. APAf-1 adds cytochrome C to an apoptosome
5. The Apoptosome activate procaspase 9 to caspase 9
6. Caspase 9 activates procaspase 3, 6, 7 to caspase 3, 6,7
7. Caspase 3, 6,7 signal apoptosis

**BCL-2 inhibits release of cytochrome C from mitochondria and the function of APAF-1

Question 21

What are the key regulators of the intrinsic pathway of cell apoptosis ? And what do they do ?

Answer 21

BAX and BCL-2

BAX
- stimulates release of Cyt C from the mitochondria and therefore stimulate the intrinsic apoptosis pathway

BLC-2

• inhibits the release of Cyt C from the mitochondria
• inhibits APAF-1 function of adding cyt C to apoptosome
• therefore inhibits the intrinsic pathway of apoptosis

Question 22

What are the two major classes of caspases ?

Answer 22

1. Initiators
   - caspase 8 and 9
   - activate many other caspases
2. Executioners
   - caspase 3
   - destroys the target by apoptosis

Question 23

Apaf1 (in the intrinsic apoptosis pathway) is activated by what? What results in what?

Answer 23

• Activated by the cytochrome C and hydrolysis of ATP
• creates the CARD domain which helps assemble the apoptosome (cyt c/apaf1 complex) by the exchange of ADP for ATP
• CARD domain and the apoptosome help activate procaspase 9
• caspase 9 activates executioner procaspases

Question 24

HER2 receptor is a common proto-oncogene in the body. What is the oncogene associated with this RTK Proto-oncogene? And what is the disease associated with the mutation?

Answer 24

HER2 receptor (RTK)
-point mutation changes valine to glutamine
*becomes NEU
-dimerizes RTK and tyrosine kinase activity turned on without ligand.
=BREAST CANCER

Question 25

EGF receptor is a common proto-oncogene in the body. What is the oncogene associated with this RTK Proto-oncogene? And what disease is associated with this mutation?

Answer 25

``` EGF receptor (RTK) -deletion occurs *EGFRvIII is created -receptor tyrosine kinase activity is constantly active = GLIOBLASTOMA ```

Question 26

Chromosome 9 and 22 are common proto-oncogenes in the body. Translocation of these acrocentric genes causes formation of what oncogenes? What is the disease associated with this mutation?

Answer 26

Chr 9 (with ABL gene) and Chr 22 (with BCR gene) - translocation occurs * der(9) and der(22) is created - both BCR and ABL gene are now on der(22) *expression of der(22) causes BCR-ABL fusion protein which causes CHRONIC MYELOGENOUS LEUKEMIA (CML)

Question 27

Point mutation of the RAS proto-oncogene changes what two amino acids and results in a RAS oncogene that is perpetually active and cause 25% of all cancers

Answer 27

Changes glycine to valine

Question 28

Gene amplification of N-MYC proto-oncogene results in what oncogene function? And causes what type of cancer?

Answer 28

Results in elevated levels of N-MYC transcription factor -seen in Neuroblastoma

Question 29

A chromosomal translocation in the proto-oncogene c-MYC (between chr 8 and 14) results in what? And causes what type of cancer?

Answer 29

Causes MYC transcription factor to be over expressed -seen in Burkitt Lymphoma

Question 30

Mutation or deletion of one copy of RB1 (gene that encodes Rb) predisposes the cell to be cancerous. The heterozygous RB1 is passed on to the child. A second “hit” by somatic mutation causes the cell to become cancerous and form tumors in highly proliferative tissues. This is what form of retinoblastoma cancer?

Answer 30

Hereditary form of Rb - causes cancer in both eyes and proliferative tissues - Rb is a tumor suppressor so mutation causes constant transition from G1 to S which causes cancer

Question 31

Retinoblastoma is a proto-oncogene. In some forms of Rb cancer, both copies of the RB1 genes are mutated by two independent mutations. This is what form of Rb cancer?

Answer 31

Sporadic form of Rb, Non-hereditary and non-cancerous cells are fine. Therefore can have the cancer in just one eye. *hereditary have it in both eyes

Question 32

Decreased DNA repair inactivates tumor suppressor function and promotes activation of oncogenes. Therefore ______ function to promote DNA repair proteins

Answer 32

Tumor suppressors

Question 33

What tumor suppressor has a mutation related to 70% of prostate cancer?

Answer 33

PTEN-Phosphatase and tensin homolog

Question 34

What tumor suppressor has a mutation associated with colon cancer ?

Answer 34

APC- Adenomatous polyposis Coli *chr 5 mutation

Question 35

What chromosome is associated with the tumor suppressors P53, BRCA, and NF-1 gene and has a mutation that is associated with more than 50% of all human tumors, breast cancer, and neurofibromatosis ?

Answer 35

Chromosome 17

Question 36

What is the normal function of the tumor suppressor NF-1 gene?

Answer 36

- encodes a GTP-ase activating protein (GAP) which turns off activated RAS protein * neurofibromatosis

Question 37

What chromosome is associated with the tumor suppressor RB gene?

Answer 37

Chromosome 13 *mutuation seen in retinoblastoma

Question 38

What chromosome is associated with the tumor suppressor APC and a mutation that causes colon cancer ?

Answer 38

Chromosome 5

Question 39

Hallmark traits of both benign and malignant tumors

Answer 39

1. Self sufficiency in growth signals 2. Evading growth suppressors (stop growth inhibition and promote growth ) 3. Enabling replicative immortality (enabling telomerase activity which prevents telomere shortening and death of cell) 4. Inducible angiogenesis ( develop new blood vessels) 5. Resist cell death (defect intrinsic and extrinsic apoptosis pathways) 6. Deregulate cellular energetics (have high rates of glycolysis by upregulating GLUT1) 7. Avoiding immune destruction (invisible to T and B lymphocytes) 8. Tumor-promoting inflammation (reactive oxygen may accelerate mutagenesis of cancer cells) 9. Genome instability and mutation (promote further mutation by epigenetics)

Question 40

Integrated HPV affects E6 and E7 which causes degradation/effects of what tumor suppressors?

Answer 40

E6 -causes P53 degradation -increased telomerase expression E7 - unbindss E2F from Rb (and keeps Rb bound to it) which allows proliferation of DNA - inhibits P21 which increases CyclinD-CDK4 activity (which also promotes E2F to move through and synthesize DNA

Question 41

EBV is a DNA virus implicated in what type of cancer

Answer 41

- Burkitt lymphoma | - Nasopharyngeal carcinoma

Question 42

Kapoi sarcoma associated herpesvirus (KSHV) is an RNA virus implicated in what type of cancer

Answer 42

Kapoi sarcoma | *seen in those infected with HIV

Question 43

What are some types of chemotherapeutic agents

Answer 43

- alkylating agents - antimetabolites - topoisomerases 1/2 Inhibitors - cytotoxic antibiotics - mitosis inhibitors

Question 44

In targeted inhibition of oncoproteins, what inhibits the HER2 receptor and the mutated NEU receptor?

Answer 44

Herceptin | Trastuzumab

Question 45

In targeted inhibition of oncoproteins, what inhibits the EGF receptor (and consequently the ERBB mutated receptor)?

Answer 45

Erbitux | Cetuximab

Question 46

In targeted inhibition of oncoproteins, what inhibits the formation of the BCR-ABL fusion protein?

Answer 46

Gleevec | Imatinib mesylate

Question 47

Herceptin (the HER2 inhibitor) has what mechanism of action?

Answer 47

1. The antigen binding region of trastuzumab blocks cleavage and dimerization of HER2 (which blocks phosphorylation of second messenger) 2. The humanized region of it bings to the immune effector cell which activates the anti-body dependent cell-mediated cytotoxicity 3. Leads to tumor-cell lysis 4. Leads to HER2 degradation *INHIBITS HER2 CLEAVAGE AND DIMERIZATION

Question 48

What is the mechanism of action for gleevec inhibition of BCR-ABL fusion protein formation?

Answer 48

ATP is normally needed for the BCR-ABL enzyme to phosphorylate the target protein and cause CML * gleevec inhibits the binding of ATP to the BCR-ABL fusion protein therefore stopping the phosphorylation of the target protein and stopping CML * INHIBITS ATP BINDING OF THE ENZYME

Question 49

What is the mechanism of action for the cetuximab inhibition of EGF receptor?

Answer 49

Erbitux inhibits the ligand binding to the EGF receptor. The tyrosine kinase is not phosphorylated and there is no activiation of the signal transduction pathway. *INHIBITS LIGAND BINDING TO RECEPTOR

Question 50

Which strand of HPV causes cervical cancer and manifestations in the mouth ?

Answer 50

16 and 18