Cancer - 1 - Etiology of Cancer

Cancer is a group of diseases characterized by uncontrolled cell proliferation, invasion of surrounding tissues, and metastasis. The development of cancer is a multifactorial process involving genetic, environmental, chemical, physical, and biological factors.

🔬 Etiology of Cancer
1. Genetic Factors

✔️ Activation of Proto-oncogenes → Oncogenes (gain of function)

Examples:

RAS gene
MYC gene
HER2/neu gene

✔️ Inactivation of Tumor Suppressor Genes (loss of function)

Examples:

TP53 (p53) – "Guardian of the Genome"
RB gene (Retinoblastoma gene)
APC gene

✔️ Defects in DNA repair genes

Examples:

BRCA1 and BRCA2 mutations
Lynch syndrome (Mismatch repair defect)
2. Chemical Carcinogens

Chemicals that induce mutations and malignant transformation.

Examples:

✔️ Tobacco smoke (benzopyrene, nitrosamines)
✔️ Aflatoxin B1 (hepatocellular carcinoma)
✔️ Aromatic amines (bladder cancer)
✔️ Asbestos (mesothelioma)

3. Physical Carcinogens

✔️ Ultraviolet (UV) radiation

Causes pyrimidine dimers
Associated with skin cancers

✔️ Ionizing radiation

X-rays
Gamma rays
Radioactive exposure

Associated with leukemia, thyroid cancer, etc.

4. Biological Carcinogens
Oncogenic Viruses

✔️ Human Papillomavirus (HPV) → Cervical cancer
✔️ Epstein-Barr Virus (EBV) → Burkitt lymphoma, nasopharyngeal carcinoma
✔️ Hepatitis B & C viruses → Hepatocellular carcinoma
✔️ HTLV-1 → Adult T-cell leukemia

Bacteria

✔️ Helicobacter pylori → Gastric carcinoma

5. Lifestyle and Environmental Factors

✔️ Smoking
✔️ Alcohol consumption
✔️ Obesity
✔️ High-fat, low-fiber diet
✔️ Physical inactivity
✔️ Environmental pollution

6. Hormonal Factors

✔️ Estrogen exposure → Breast and endometrial cancers
✔️ Androgens → Prostate cancer

🧬 Molecular Basis

Cancer develops through:

✔️ Activation of oncogenes
✔️ Loss of tumor suppressor genes
✔️ Defective apoptosis
✔️ Impaired DNA repair
✔️ Accumulation of multiple mutations

🎯 High-Yield Exam Points

🔹 Cancer is a multifactorial disease.
🔹 p53 is called the "Guardian of the Genome."
🔹 Tobacco smoking is the most important preventable cause of cancer.
🔹 HPV is strongly associated with cervical cancer.
🔹 BRCA mutations increase breast and ovarian cancer risk.
🔹 DNA repair defects predispose to malignancy.

📚 Quick Summary

Etiology of Cancer = Genetic Factors + Chemical Carcinogens + Physical Carcinogens + Biological Agents + Lifestyle Factors + Hormonal Influences

📚 Useful for:
MBBS | BDS | Nursing | Allied Health Sciences | PG Aspirants

#Cancer #EtiologyOfCancer #Carcinogenesis #MolecularBiology #Biochemistry #MBBS #MedicalEducation

Видео Cancer - 1 - Etiology of Cancer канала Dr. Ashish Anjankar