Cancer Biology Quiz

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Questions and Answers

Which chemical is converted to an active form by hydroxylation to cause lung and bladder cancer?

Aromatic amines

Nitrosamines

Aflatoxins

3,4-Benzpyrene (correct)

What type of cancer is associated with exposure to asbestos?

Mesothelioma (correct)

Lung cancer

Skin cancer

Bladder cancer

Which virus is primarily associated with causing hepatocellular carcinoma?

Epstein Barr virus

HIV

Hepatitis B virus (correct)

Human papilloma virus

What is the role of DNA repair genes in cancer?

They help in the repair of DNA damage. Signup and view all the answers

What is the main outcome of chronic exposure to nitrosamines from dietary sources?

Gastrointestinal cancer Signup and view all the answers

Which type of cancer is associated with the presence of schistosoma infection?

Bladder cancer Signup and view all the answers

What alteration is primarily associated with oncogenes in cancer development?

Point mutation Signup and view all the answers

What is a common characteristic of proto-oncogenes found in normal cells?

They are involved in the normal regulation of cell growth. Signup and view all the answers

What is the role of oncogenes in cancer development?

They encode proteins that promote cell growth. Signup and view all the answers

Which gene is primarily associated with retinoblastoma?

Retinoblastoma gene Signup and view all the answers

What percentage of cancers are associated with mutations in the p53 gene?

Over 50% Signup and view all the answers

What is the primary function of DNA repair genes?

To accurately copy each strand of DNA during cell division. Signup and view all the answers

Which condition is primarily associated with BRCA1 and BRCA2 genes?

Breast cancer Signup and view all the answers

What describes the process of carcinogenesis?

It involves the accumulation of genetic alterations over time. Signup and view all the answers

What is the significance of the guardian of the genome?

It prevents uncontrolled cell growth. Signup and view all the answers

How does mutation of DNA repair genes affect cancer risk?

It leads to an increased risk of cancer due to accumulated mutations. Signup and view all the answers

Which of the following is an example of an inherited condition linked to an increased risk of developing tumors?

Xeroderma pigmentosum Signup and view all the answers

Which oncogene is associated with the promotion of cancer due to its role in cell growth signaling?

ras Signup and view all the answers

What is the primary factor that contributes to extrinsic factors causing cancer?

Carcinogenic chemicals Signup and view all the answers

Which stage of carcinogenesis involves the irreversible genetic change leading to mutant cells?

Initiation Signup and view all the answers

Which of the following is NOT an agent implicated in tumor development?

Vitamin C Signup and view all the answers

What is the common pathway through which tumor suppressor genes (TSG) and oncogenes affect cancer development?

They regulate cell cycle and growth. Signup and view all the answers

Which of the following medical conditions is associated with an increased risk of malignancy?

Hashimoto’s thyroiditis Signup and view all the answers

What factor is NOT an intrinsic factor contributing to tumor development?

Environmental exposure Signup and view all the answers

Which defect is characterized by sensitivity to ultraviolet light due to a failure in DNA repair mechanisms?

Retinitis pigmentosa Signup and view all the answers

What is the consequence of an initial exposure to a carcinogen during the initiation phase of chemical carcinogenesis?

It causes a permanent mutation in the DNA. Signup and view all the answers

Which of the following syndromes is linked to a mutation in the p53 gene?

Li Fraumeni syndrome Signup and view all the answers

What type of DNA damage is most commonly associated with high doses of radiation?

Double stranded breaks Signup and view all the answers

Which genetic alteration is linked to Familial breast/ovarian cancer?

BRCA1 mutation Signup and view all the answers

What mechanism involves the conversion of polycyclic hydrocarbons to their active forms in the body?

Metabolic enzymatic conversion Signup and view all the answers

Which of the following is NOT considered an extrinsic factor contributing to DNA damage?

Genetic mutations Signup and view all the answers

What is the role of promoters in the tumor formation process?

They enhance tumor development in already initiated cells. Signup and view all the answers

Study Notes

Tumour Development

Tumours develop due to alterations or mutations in the genetic code.
Tumour development can be influenced by both intrinsic (inherited, internal) and extrinsic (external) factors.

Intrinsic Factors

Inheritance: Inherited conditions can predispose to tumour development related to DNA repair. Inherited susceptibility to a range of tumors can occur due to alterations in one or multiple genes.
Host factors: Factors like age, immune status, and hormones also play a role.
- Age: Cancer incidence increases with age.
- Cumulative exposure to carcinogens: Repeated exposure affects risk
- Latency: Time between exposure and manifestation
- Accumulating genetic lesions
- Innate defence
- Immune factors
- Hormones: Affect vulnerability to some cancers.

Extrinsic Factors

Radiation: Exposure to radiation can lead to DNA damage, increasing cancer risk
- Evidence: Skin cancer in radiologists, increased lung cancer risk in unprotected miners, and increased thyroid cancer risk in children receiving radiotherapy for head and neck (H&N) problems. Hiroshima survivors—early cases like leukemia, lymphoma; later cases like breast and thyroid cancers.
- Mechanisms: Diverse DNA damage including single and double-stranded breaks and base damage. Dose and quality of radiation impact the outcome. Low dose: genomic instability. High dose: DNA breaks, translocation, less frequent point mutations.
Chemicals: Carcinogenic chemicals interact with DNA, causing specific base damage and single-strand breaks. Damage may not be fully repaired, leading to mutations. Certain chemicals require metabolic conversion to become carcinogenic.
- Types: Polycyclic aromatic hydrocarbons (e.g., coal tar, cigarette smoke, 3,4-Benzbyrene important in conversion to active form -aryl hydrocarbon hydroxylase), aromatic amines (B-naphthalamines hydroxylated to inactive form in bladder) and nitrosamines (from dietary nitrates/nitrites). Examples: lung cancer, bladder cancer, skin cancer, and gastrointestinal cancer.
Viruses: Some viruses (e.g., Epstein Barr, Hepatitis B, Human papilloma) can cause cancer through viral oncogenes and altered DNA processes.
- Examples: Hepatitis B and hepatocellular carcinoma; Epstein Barr and Burkitt's and Nasopharyngeal cancers; Human Papillomavirus (HPV) and cervical cancer.
Other factors: Several other factors are involved e.g. asbestos (mesothelioma), aflatoxins (liver cancer), parasites (bladder and gastric cancers), and aspects of diet or lifestyle

Mechanisms in Carcinogenesis

Time lag between exposure and clinical cancer.
Stages: initiation, promotion, progression
Initiating stimulus effects influenced by genetic factors and DNA repair.
Promotion relies on local tissue responses and immune functions.
Progression involves changes in gene activity and numbers leading to tumor development.
Tumour progression is not a single alteration to one gene. It's the accumulation of alterations influenced by several factors.

Hallmarks of Cancer

Self-sufficiency in growth signals
Evading apoptosis
Insensitivity to anti-growth signals
Sustained angiogenesis
Limitless replicative potential
Tissue invasion and metastasis

Molecular Bases of Cancer

Cancer is a genetic disease, characterized by altered DNA with point mutations, deletions, and translocations
Cancer cells evade natural defense mechanisms, including DNA damage repair and apoptosis (programmed cell death).

Genes Involved

Oncogenes: Altered proto-oncogenes present in normal cells that accelerate growth. Examples: c-myc (amplified in breast cancer and neuroblastoma), Ras (intracellular signalling mutation in colon and lung cancers), c-erbB-2 (HER-2; amplification in breast cancers).
Tumor suppressor genes: Genes that normally restrain growth; loss of function leads to uncontrolled growth. Examples include RB gene (Retinoblastoma) and p53 (p53 mutated in >50% of cancers).
DNA repair genes: Critical for accurate DNA replication during cell division. Defects in these genes increase the risk of accumulating mutations. Examples include BRACA1 and BRACA2 (breast cancer), and mismatch repair genes.

Objectives

Understand inherited susceptibility to tumors.
Understand the inheritance of certain tumors (e.g., familial adenomatous polyposis, breast cancer, retinoblastoma, ataxia telangiectasia, xeroderma pigmentosum).
Understand the functions of oncogenes (and their alterations) and tumor suppressor genes (and their alterations). The importance of DNA repair genes
Stages in carcinogenesis (Initiation, Promotion, Progression).
Agents causing tumors (radiation, chemicals, viruses, hormones, parasites, etc).
Occupations associated with tumor development.
Medical conditions increasing tumor risk.
Geographic variations in malignant tumor incidence.
Host factors affecting the development of tumours.

Important Concepts:

DNA repair mechanisms
Genetic alterations resulting in tumor development
Role of intrinsic and extrinsic factors in tumor development
Mechanisms driving cancer progression.

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Description

Test your knowledge on the biological mechanisms behind cancer development. This quiz covers various aspects such as the role of genes, environmental factors, and specific types of cancer associated with certain exposures. Challenge yourself to see how well you understand the complexities of cancer biology.