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GOBBLERS 2023 > Angela's Genetics > Flashcards

Angela's Genetics Flashcards

1
Q

What is the most common cause of a germline mutation?

A

Loss of heterozygosity

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2
Q

What are common hereditary tumor suppressor proteins in endometrial cancer?

A

LYNCH
MLH1 (3p22)
MSH2 (2p21)
MSH6 (2p16)
PMS2 (7p22)
EPCAM (2p21)

COWDEN
PTEN (10q23)

(Updated from Chi table)

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3
Q

What are common sporadic tumor suppressor proteins in endometrial cancer?

A

PTEN (10q24), p53 (17p13)

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4
Q

What is the translocation in Burkitts?
Which protein is overexpressed?

A

[t(8;14)]
myc protein

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5
Q

What is the translocation in CML?
Which protein is overexpressed?

A

[t(9;22)]
Abl

The Philadelphia chromosome is a reciprocal translocation involving chromosomes 9 and 22 that is commonly identified in chronic myelogenous leukemia (CML). The break points of the translocation create a fusion of two genes: ABL1 on chromosome 9 and BCR on chromosome 22.

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6
Q

Where is Rb gene located?

A

13q14

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7
Q

What is the chromosomal abnormality associated with etoposide-induced AML?

A

Rearrangements at 11q23

it’s a stretch, but: 32pos1de-1nduced AML

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8
Q

What are tumor suppressor genes?

A

Genes that normally inhibit cell proliferation, loss of heterozygosity

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9
Q

What are common hereditary tumor suppressor proteins affected in ovarian cancer?

A

BRCA1 / 2, MSH2

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10
Q

What are common sporadic tumor suppressor proteins affected in ovarian cancer?

A

p53 (encoded by TP53 on 17p13), p16 (encoded by CDKN2A)

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11
Q

What is the most common epigenetic step responsible for deactivating the second tumor-suppressor gene in the process of carcinogenesis?

A

Hypermethylation of CpG islands in the promoter region
Hypermethylation silences the promoter thus inhibiting transcription of the protein

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12
Q

What epigenetic step is critical to deactivating many tumor-suppressor genes?

A

Methylation of CpG islands in promoter regions

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13
Q

Which of the following are not associated with hereditary cancer susceptibility?
A) RB
B) P53
C) MSH
D) BRCA 1
E) Her 2 neu

A

E) Her 2 neu

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14
Q

What does the HPV protein E6 bind to?

A

P53

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15
Q

What is the most commonly inactivated gene described for human cancers?

A

P53

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16
Q

What is the gene locus of p53?

A

17p13

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17
Q

What is the most common mutation found in p53?

A

Single nucleotide missense mutation in the middle third (exons 5-8) of the gene leading to inactivation of any remaining normal P53 in the nucleus.
Mutation of one copy of the gene is accompanied by deletion of the other copy of the gene leading the cancer cell with only mutant P53 protein.

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18
Q

What is the function of p53?

A

“Guardian of the genome”
It activates genes involved in DNA damage repair pathways at G1-S and G2-M checkpoints to prevent replication and mitosis in damaged cells by inducing apoptosis

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19
Q

Where is p53 located in the cell?

A

Intranuclear

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20
Q

How does p53 stall the cell cycle?

A

Cellular damage –> induces p53 –> induces CIP/WAF/p21
–>prevents CDK phosphorylation –> prevents Rb phosphorylation
–> stops cell cycle –> eventually leading to apoptosis

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21
Q

What occurs with a mutation in P53?

A

Mutated p53 protein accumulates in nucleus and cannot bind to DNA, interfering with wild type p53 function

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22
Q

What is the most common mutation in UPSC?

A

p53

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23
Q

What is the gene defect in LiFraumeni?

A

p53

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24
Q

LiFraumeni is associated with increased risk of what cancers?

A

Sarcoma, breast, brain, leukemia, melanoma, GI
*important for us to know sarcoma, breast

LiFraumeni is also known as SBLA Syndrome (Sarcoma, Brain, Breast, Leukemia, Adrenal cortical)

Mnemonic: Could think of BLABS: breast, leukemia, adrenal cortical, brain, sarcoma

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25
Q

Which diagnostic criteria must be fulfilled for Li Fraumeni?

A
  • Sarcoma < 45yo
  • First-degree relative with any cancer <45
  • Another 1 or 2 degree relative with any young cancer or any sarcoma
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26
Q

What is the location of PTEN?

A

10q23

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27
Q

Is PTEN a Tumor suppressor or Oncogene?

A

Tumor suppressor

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28
Q

What does PTEN encode?

A

A tyrosine phosphatase that inhibits FAK, ERK, MAPK

ERKs (extracellular-signal-regulated kinases)
focal adhesion kinase (FAK)
mitogen-activated protein kinase (MAPK)

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29
Q

When PTEN is mutated and nonfunctional, which pathway is allowed to proceed?

A

PI3K/AKT pathway

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30
Q

What is the most common mutation in endometrial cancer?

A

PTEN

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31
Q

Which ovarian cancer histology exhibits higher levels of PTEN mutation?

A

Endometrioid OVCA

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32
Q

What mutations is associated with Cowden’s Syndrome?

A

PTEN

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33
Q

What cancers are associated with Cowden’s Syndrome?

A

Breast, endometrial, thyroid, and hamartomas

Mnemonic: “Pettin’ my cow Beth”
PTN - COWden - Breast/Endometrial/Thyroid/Hamartoma

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34
Q

How is Cowden’s inherited?

A

Autosomal dominant

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35
Q

What is Bannayan/Zonana?

A

Similar to Cowden’s
Caused by PTEN mutation

Bannayan-Zonana syndrome is a rare hamartomatous disorder, characterized by macrocephaly, multiple lipomas, and hemangiomas. Inheritance is by autosomal dominant transmission with few reported sporadic cases. Male predominance is also reported.

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36
Q

What are the roles of BAD BAX and BID?

A

All pro-apoptosis.

Proteins of the Bcl-2 family

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37
Q

What does downregulation of BAD, BAX or BID cause?

A

Decreased apoptosis, increased tumorogenesis

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38
Q

What are the genetic mutations associated with Lynch?

A

MSH2, MLH1, MSH6, PMS2

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39
Q

What chromosome is MLH1 located on?

A

3p22.2

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40
Q

What chromosome is MSH2 located on?

A

2p21-16

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41
Q

What does the MSH2 protein interact with?

A

MSH6

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42
Q

What is the heritability of Lynch syndrome?

A

Autosomal dominant

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43
Q

Are MLH1, MSH2 tumor suppressor genes or a proto-oncogene?

A

Tumor suppressor genes

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44
Q

What is the mechanism of instability initiated by a mutation in MLH1 and MSH2?

A

Mismatch repair causes microsatellite instability

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45
Q

What screening is recommended for patients with Lynch?

A

Annual colonoscopy at age 20-25, annual EMB at age 35

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46
Q

Where are colon cancers associated with Lynch likely to originate?

A

Proximal to the splenic flexure

*Lynch Syndrome is also known as hereditary non-polyposis colorectal cancer (HNPCC)

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47
Q

At what age is Hysterectomy recommended for patients with HNPCC (Lynch)?

A

NCCN: At completion of childbearing. May consider annual endometrial biopsy starting between age 30 and age 35

ASCO and ESMO say 35
SGO and ACOG say 40-45

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48
Q

Where in the colon do Lynch cancers occur?

A

Proximal colon

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49
Q

What gene is implicated in Colon syndrome?
What tumors is it associated with?

A

MLH1 (like lynch)
Colon, leukemia, Childhood colon cancer

50
Q

What chromosome is affected in Turcot syndrome?
What tumors is it associated with?

A

Turcot’s syndrome is characterized by familial polyposis of the colon, together with malignant brain tumors. This disorder can be caused by mutations in the adenomatous polyposis coli gene (APC, on chromosome 5q21) or in the mismatch repair genes MLH1 (chromosome 3) or PMS2 (chromosome 7).

51
Q

What is the MOST COMMON issue in patients with sporadic cancers that have MMR deficiency?

A

Hypermethylation of MLH 1 promoter

52
Q

What is the mechanism of BRCA?

A

Homologous Recombination (repair of dsDNA Breaks)
Once phosphorylated, BRCA becomes part of several complexes that relocate to damaged DNA and coordinate cell cycle checkpoints to execute DNA repair

53
Q

How does PARP work in BRCA mutated cells?

A

PARP is an enzyme that repairs ssDNA breaks via the base excision repair (BER) pathway. It is the salvage repair pathway in cells that have lost HR. Without either pathway cells can not live.

54
Q

Where is the chromosomal abnormality in BRCA1?

A

17 q 21

55
Q

Where is the BRCA2 gene located in the chromosome?

A

13 q 12

56
Q

Are BRCA 1/2 tumor suppressor genes or a proto-oncogenes?

A

Tumor suppressor genes

57
Q

What proteins does BRCA1 interact with to alter HR?

A

RAD51 and BARD1

58
Q

What proteins does BRCA2 interact with?

A

RAD51 and PALB 2

59
Q

In what syndrome are both BRCA2 copies mutated?

A

Fanconi’s anemia

60
Q

When both BRCA 2 copies are mutated, how does this clinically manifest?

A

As Fanconi’s anemia, with Bone marrow suppression, increased leukemia and tumor risk, and short stature with skeletal anomalies

61
Q

What is the most common mechanism (mutation) causing loss of heterozygosity in BRCA?

A

Nonsense mutation and frameshift alterations resulting in premature stop codons and protein truncation

62
Q

What is the incidence of ovarian cancer in BRCA1? At what age?
What is the incidence of breast cancer?

A

48%, age >40yo
Breast: 55%–72%

63
Q

What is the incidence of ovarian cancer in BRCA2? At what age?
What is the incidence of breast cancer?

A

20%, age >50
Breast: 45%–69%
***Also associated with male breast cancer

64
Q

What is Peutz-Jeghers syndrome?

A

A syndrome caused by germline mutation of STK11

65
Q

What is the heritability of Peutz-Jeghers syndrome?

A

Autosomal dominant

66
Q

What GYN cancers are associated with Peutz-Jeghers?

A

Sex cord tumors with annular tubules (SCAT), adenoma malignum, Granulosa-thecoma

67
Q

What phenotype may a patient with Peutz-Jeghers syndrome exhibit?

A

Mucocutaneous melanotic pigmentation

68
Q

What is ataxia telangiectasia? What gene is associated with it?

A

Ataxia Telangiectasia is a rare inherited childhood neurological disorder that affects the part of the brain that controls motor movement and speech.

ATM gene

69
Q

What is the function of ATM?
What is the result of mutated ATM?

A

ATM checks cells for DNA damage during meiosis/mitosis and coordinates DNA repair by activating enzymes.

Mutations in ATM prevent cells from responding correctly to DNA damage, which allows accumulation of damaged DNA and can lead to cancer.

70
Q

What is the role of ATM in Ataxia telangiectasia?

A

Mutations in ATM reduce or eliminate the function of ATM, causing cells to become unstable and die. Cells in the part of the brain involved in coordinating movements (the cerebellum) are particularly affected by loss of the ATM protein.

71
Q

What gene is affected in Turcot syndrome?

A

Turcot syndrome can arise from mutations in the MMR genes (MLH1, PMS2 = type I, associated with HNPCC) or the APC genes (type II, associated with FAP). Mutations of either gene can result in colorectal cancer and brain tumors; most commonly, glioblastomas and medulloblastomas.

72
Q

What tumors are associated with Turcot syndrome?

A

CNS tumors and colorectal cancer

73
Q

What is an oncogene?

A

Precursor: proto-oncogene –> undergoes mutation to become an oncogene

They regulate cell proliferation, growth, and differentiation, as well as control of the cell cycle and apoptosis. The products of oncogenes include growth factors, growth factor receptors, signal transducers, transcription factors, and apoptosis regulators, as well as chromatin remodelers.

74
Q

What are common oncogenes?

A

EGFR family, KRAS, MYC, FOS, JUN, FJS, Bcl-2

75
Q

What are common oncogenes in ovarian cancer?

A

HER-2/NEU,

PIK3CA,
AKT2,
C-MYC
K-RAS,

H PACK

76
Q

What are common oncogenes in endometrial cancer?

A

C-FMS, HER-2/NEU, K-RAS, C-MYC, β-Catenin

77
Q

What is the most common mechanism of oncogene activation?
A) Amplification (HER2)
B) Chromosomal rearrangement
C) Point mutation (RAS)
D) Translocation (BCR/ABL)
E) Promoter hypermethylation
F) Increased survival of cells carrying mutated genes

A

Amplification (HER2)

Verified in Chi: “amplification of members of the MYC family have most often been implicated in the development of human cancers”

78
Q

What are the three main ways to activate a proto-oncogene?

A

Mutation (RAS)
Increased expression (Her2)
Translocation (Myc)

79
Q

What is RAS?

A

A family of G proteins with GTPase activity

80
Q

What does RAS activate?

A

MAP kinase systems

81
Q

What does MAP kinase activation cause?

A

Activation of protein synthesis machinery, transcription factors, cytoskeleton

82
Q

Where is the RAS protein located in the cell?

A

Tethered to the cell membrane

83
Q

Which histologies of ovarian cancer are associated with KRAS mutations?

A

Mucinous OVCA

84
Q

Which syndrome is associated with KRAS mutation?

A

Noonan’s syndrome
Genetically inherited disorder with heterogeneous phenotypic manifestations. Most consistent features are wide-set eyes, low-set ears, short stature, and pulmonic stenosis. Inherited in an autosomal dominant manner.

85
Q

What is the result of a BRAF mutation?

A

Change a valine residue to glutamic acid, which results in an active protein that stimulates MAP kinase, deregulates genes involved in cell proliferation, differentiation, and survival

86
Q

What are fos/jun, and myc responsible for?

A

DNA replication

87
Q

What is the action of myc protein?

A

Transcription factor

88
Q

Where in the cell is the myc protein found?

A

NUCLEUS

89
Q

Which chromosome is myc on?

A

chromosome 8

90
Q

Which translocation is common in burkitts lymphoma (myc)?

A

[t(8,14)]

91
Q

What are the common nuclear proto-oncogene transcription factors?

A

FOS, JUN, MYC

92
Q

What is the role of BCL-2?

A

Inhibits apoptosis

93
Q

What tissue is BCL-2 strongly expressed in?

A

Normal endometrium

94
Q

Does Her-2 represent a heritable cancer susceptibility?

A

No

95
Q

What does her-2-neu encode for?

A

A cell-surface protein tyrosine kinase

96
Q

Her-2 is encoded by which gene? On which chromosome?

A

ERBB2 on chromosome 17

Same chromosome as BRCA1, TP53

97
Q

Which therapy is Her-2 directed? What is it’s MOA?

A

Herceptin (Traztuzumab), Monoclonal antibody to Her-2 receptor

98
Q

What percent of breast cancers have HER-2 amplification?

A

20%

99
Q

Which test should be used to confirm number of DNA gene copies of ERBB2 prior to initiating treatment?

A

FISH

100
Q

Which is not associated with increased risk of breast cancer?
A) LiFraumeni
B) Cowden
C) Heterozygous ataxia telengectasia
D) MEN

A

D) MEN

101
Q

What are Olliers disease and Maffucci syndrome? What GYN tumor is associated with these?

A

disorder that causes benign growths of cartilage in the bones (enchondromas)
Associated with juvenile granulosa cell tumors

102
Q

What does FMS encode? What is the role of MCSF?

A

A tyrosine kinase that serves as a receptor for MCSF
Serves as a chemoattractant for macrophages

103
Q

What is the gene for the CSF receptor?

*CSF: colony stimulating factor

A

FMS

104
Q

What is FMS gene often damaged in?

A

High-grade endometrial cancers

105
Q

Which two echondromatosis (cartlidge cysts that form in the bone) conditions are associated with juvenile granulosa cell tumors?

A

Olliers and Maffucci

106
Q

Who has highest risk of colon CA (Lynch not included)?
A) Family h/o colon CA
B) Personal history of EMCA
C) Grandmother with BRCA postmenopausal
D) Inflammatory bowel disease
E) Familial adenomatous polyposis

A

E) Familial adenomatous polyposis

107
Q

Which is BRCA2 least associated with?
A) Small bowel
B) Pancreatic
C) Melanoma
D) Prostate
E) Male breast cancer

A

Small bowel

108
Q

How is the ER and PR characterized?

A

High affinity and low capacity

109
Q

Which tumor marker may be elevated in mucinous ovarian tumors?

A

CEA

110
Q

Which IHC markers are elevated in mucinous ovarian tumors?

A

P16, CK7,CK20, CDX

111
Q

What oncogenes are abnormal in mucinous ovarian tumors?

A

KRAS occurs in 50-75% of mucinous ovarian cancer
(Also BRAF, but less common)

*NIH:
The KRAS gene (Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) is an oncogene that encodes a small GTPase transductor protein called KRAS.

112
Q

What oncogenes are overexpressed in Borderline or low grade serous tumors?

A

KRAS (25-50%) and BRAF (20%)

*per NIH:
The KRAS gene (Ki-ras2 Kirsten rat sarcoma viral oncogene homolog) is an oncogene that encodes a small GTPase transductor protein called KRAS.

113
Q

What Tumor suppressor proteins are commonly altered in high grade serous tumors?

A

BRCA and TP53

114
Q

What Tumor suppressor proteins are commonly altered in endometrioid ovarian cancers?

A

PTEN, P53

115
Q

What oncogenes are commonly activated in endometrioid ovarian cancers?

A

KRAS, PI3KCAr, B-catenin (grade 1)

116
Q

What is the most commonly sporadically altered tumor-suppressor gene in type 2 endometrial CA?

A

P53

117
Q

What is the most common sporadic oncogene amplified in type 2 endometrial CA?

A

HER-2/neu

118
Q

Which sporadic oncogenes are most commonly altered in type 1 endometrial cancer?

A

B-catenin, PIK3CA, KRAS (FGFR2)

119
Q

Which sporadic tumor suppressor gene is most commonly altered in type I endometrial cancer?

A

PTEN, followed by MLH1

120
Q

Which hereditary tumor suppressor genes are most commonly altered in endometrial ca?

A

MSH 2, MLH1, PMS1, 2, and MSH 6

121
Q

Does ATM mutation increase the risk of breast cancer?

A

Yes - up to 40% lifetime risk of breast cancer (risk of early and bilateral)

GOBBLERS 2023 (28 decks)

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