Podcast
Questions and Answers
Which mechanism exemplifies how a chromosome translocation can lead to oncogenesis by altering gene expression?
Which mechanism exemplifies how a chromosome translocation can lead to oncogenesis by altering gene expression?
- The fusion of two gene fragments to create a novel protein with altered function.
- A point mutation within the coding region of a tumor suppressor gene.
- The deletion of a microRNA gene, leading to reduced post-transcriptional regulation of target mRNAs.
- The translocation of an oncogene to a chromosomal region with high transcriptional activity, resulting in its overexpression. (correct)
A researcher observes that a cancer cell line exhibits resistance to apoptosis despite the presence of DNA damage. Further investigation reveals increased expression of BCL-2. How does BCL-2 contribute to this resistance?
A researcher observes that a cancer cell line exhibits resistance to apoptosis despite the presence of DNA damage. Further investigation reveals increased expression of BCL-2. How does BCL-2 contribute to this resistance?
- By directly stimulating cell proliferation through activation of growth factor signaling pathways.
- By inhibiting the release of cytochrome c from mitochondria, preventing the activation of caspases. (correct)
- By downregulating the expression of pro-apoptotic proteins, shifting the balance towards cell survival.
- By promoting DNA repair mechanisms, thereby correcting the DNA damage and preventing apoptosis.
How do homogeneously staining regions (HSRs) contribute to cancer development, and what is their origin?
How do homogeneously staining regions (HSRs) contribute to cancer development, and what is their origin?
- HSRs represent sites of active DNA repair, preventing genomic instability and cancer progression.
- HSRs are formed through epigenetic silencing of repetitive DNA sequences, altering chromatin structure.
- HSRs originate from integrated double-minute chromosomes (DMs), leading to stable amplification of oncogenes. (correct)
- HSRs arise from the initial deletion of tumor suppressor genes and promote loss of heterozygosity.
A scientist discovers a novel mutation in a gene that regulates tumor-immune interactions. Which of the following mechanisms is MOST likely to be affected by this mutation?
A scientist discovers a novel mutation in a gene that regulates tumor-immune interactions. Which of the following mechanisms is MOST likely to be affected by this mutation?
What is the primary distinction between driver mutations and mutations in apoptosis regulator genes in the context of cancer development?
What is the primary distinction between driver mutations and mutations in apoptosis regulator genes in the context of cancer development?
Following exposure to a mutagen, a cell exhibits increased activity in the PI3K-AKT and JAK-STAT pathways. How might this alteration contribute to cancer development?
Following exposure to a mutagen, a cell exhibits increased activity in the PI3K-AKT and JAK-STAT pathways. How might this alteration contribute to cancer development?
In the context of cancer genetics, what is the significance of epigenetic modifications, and how do they differ from genetic mutations?
In the context of cancer genetics, what is the significance of epigenetic modifications, and how do they differ from genetic mutations?
A researcher is investigating a new cancer therapy that aims to reactivate tumor suppressor genes silenced by DNA methylation. Which of the following mechanisms would BEST describe the action of this therapy?
A researcher is investigating a new cancer therapy that aims to reactivate tumor suppressor genes silenced by DNA methylation. Which of the following mechanisms would BEST describe the action of this therapy?
A patient is diagnosed with Chronic Myeloid Leukemia (CML) characterized by the presence of the Philadelphia chromosome. How does the BCR-ABL fusion protein contribute to the pathogenesis of CML?
A patient is diagnosed with Chronic Myeloid Leukemia (CML) characterized by the presence of the Philadelphia chromosome. How does the BCR-ABL fusion protein contribute to the pathogenesis of CML?
When considering mutations in cancer, what is the significance of the 'two-hit hypothesis' in the context of tumor suppressor genes?
When considering mutations in cancer, what is the significance of the 'two-hit hypothesis' in the context of tumor suppressor genes?
Flashcards
Neoplasia
Neoplasia
Mutations in genes that regulate cell behavior, leading to uncontrolled cell growth and tumor formation.
Proto-oncogenes
Proto-oncogenes
Normal genes that regulate cell growth; can become oncogenes if mutated or overexpressed.
Tumor Suppressor Genes
Tumor Suppressor Genes
Genes that normally prevent uncontrolled cell growth; inactivation leads to cancer progression.
Driver Mutations
Driver Mutations
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Point Mutations
Point Mutations
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Chromosomal Rearrangements (in cancer)
Chromosomal Rearrangements (in cancer)
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Gene Amplifications (in cancer)
Gene Amplifications (in cancer)
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Philadelphia Chromosome
Philadelphia Chromosome
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Aneuploidy in Cancer
Aneuploidy in Cancer
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Epigenetic Changes in Cancer
Epigenetic Changes in Cancer
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Study Notes
- Neoplasia stems from mutations altering genes regulating normal cell behavior.
- Genes frequently mutated or dysregulated in cancer are known as cancer genes, numbering around 200.
- Cancer genes are classified into oncogenes, tumor suppressor genes, apoptosis regulator genes, and interaction regulator genes.
Oncogenes
- Proto-oncogenes are the normal cellular counterparts of oncogenes.
- Oncogenes promote increased cell growth when overexpressed or mutated.
- They typically encode transcription factors or signaling molecules in pro-growth pathways.
- Oncogenes are dominant, meaning a single allele mutation can produce a pro-oncogenic effect.
Tumor Suppressor Genes
- Tumor suppressor genes normally prevent uncontrolled growth.
- Their function is lost in neoplasms via disruptive mutations, epigenetic silencing, or gene repression.
- Both alleles of a tumor suppressor gene must typically be lost for unregulated cell growth to occur.
Apoptosis Regulator Genes
- Apoptosis regulator genes primarily enhance cell survival rather than stimulating proliferation.
- Genes protecting against apoptosis are often overexpressed in cancer, while those promoting it are underexpressed.
- The overall effect is increased cell survival.
Interaction Regulator Genes
- Genes that regulate interactions between tumor cells and host cells are frequently mutated in cancers.
- Genes enhancing or inhibiting tumor cell recognition by the host immune system are particularly important.
Driver Mutations
- Driver mutations promote cancer development or progression.
- Most driver mutations affect protein-coding genes, but genes encoding regulatory RNAs, like microRNA, can also be affected.
Point Mutations
- Point mutations involve single nucleotide substitutions or small insertions and deletions.
- They can either activate an oncogene or inactivate a tumor suppressor gene, depending on their location and timing.
Large Deletions
- Large deletions remove an entire gene or several genes.
- The genes removed often have tumor suppression functions.
Chromosome Rearrangements
- Chromosome rearrangements frequently appear as translocations, causing significant changes in chromosome structure.
- In some cases, the rearrangement places a strong regulatory element near an oncogene, leading to overexpression of a normal protein.
Fusion Proteins
- Chromosome rearrangement can lead to the creation of a chimeric gene which encodes an oncogenic fusion protein composed of portions of two different proteins.
- These rearrangements are common in blood cancers and sarcomas.
MYC Gene
- Balanced translocation involving chromosomes 8 and 14 places the MYC gene near strong regulatory elements of the immunoglobulin heavy chain gene, leading to MYC overexpression.
- MYC is an oncogenic transcription factor.
Chronic Myeloid Leukemia
- In chronic myeloid leukemia, a balanced translocation involving chromosomes 9 and 22 creates a chimeric gene containing BCR and ABL gene pieces.
- This encodes a chimeric BCR-ABL fusion protein with constitutively active tyrosine kinase activity.
Gene Amplifications
- Gene amplifications produce extra copies of one or more oncogenes.
- This is another way to increase the level of protein with oncogenic activity.
- Amplified genes can be carried in extra-chromosomal DNA fragments, known as double-minute chromosomes.
- They can be present within a chromosome, appearing as an abnormal, homogeneous staining region.
NYC Gene
- NYC gene amplification in human neuroblastoma is an example of gene amplification
- The NYC gene, normally on chromosome 2p, becomes amplified.
- It appears either as extra-chromosomal double minutes or as a chromosomally integrated homogeneous staining region.
- NYC is structurally related to MYC and is an oncogenic transcription factor.
Aneuploidy
- Aneuploidy is defined as gains or losses of whole chromosomes or large portions thereof.
- How this causes cancer is incompletely understood.
- It is believed to involve changes in the expression of cancer genes in affected chromosomal regions.
Epigenetic Changes
- Epigenetic changes are heritable alterations in gene expression without mutation of the gene.
- Gene expression is regulated by post-translational histone modifications and DNA methylation.
- Both are frequently altered in cancer cells compared to normal cells.
- The contribution of epigenetic alterations is not fully understood but is likely significant in most instances of cancer.
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