cancer

CANCER

Understanding Cancer

  • Hundreds of genes involved: Genes and the proteins produced by them regulate DNA replication and cell division.

  • Tight regulation: DNA replication and cell division are closely monitored processes.

  • Mutation implications: If a mutation occurs in genes that manage these processes, it can lead to serious cellular problems.

Uncontrolled Cell Division

  • Definition: Uncontrolled cell division results in a mass of unspecialized cells, often referred to as a tumor.

    • Tumors:

    • Benign Tumor:

      • Characteristics: Non-cancerous, does not invade neighboring tissues.

    • Malignant Tumor:

      • Characteristics: Cancerous, exhibits continuous growth, undergoes angiogenesis (formation of new blood vessels), and can metastasize, thus impairing organ function.

Characteristics of Cancer Cells

  • Key Features:

    • Uncontrolled cell division: Cells divide without regulation.

    • Deranged metabolism: Cancer cells often exhibit abnormal metabolic pathways.

    • Loss of attachment: Cancer cells may lose their ability to adhere to neighboring cells.

    • Chromosomal changes: Abnormalities in chromosome structure and number.

    • Example: Chronic Myeloid Leukemia (CML).

Mechanisms for Cancer

  • Normal defense: The immune system typically recognizes and destroys cancer cells.

  • Evasion of immune response: Some cancer cells develop mechanisms to evade detection.

  • Role of p53 Protein:

    • Function: Stops the cell cycle and activates DNA repair mechanisms.

    • If repairs fail: P53 triggers apoptosis (programmed cell death).

  • Mutations impact:

    • Defective mutations can impair DNA repair pathways and control of mitosis, leading to cancer.

The Cell Cycle and Cancer

  • Cell Cycle Checkpoints: Ensure accurate cell division by regulating a cell’s progress through the cell cycle.

    • If checkpoints identify problems (e.g., DNA damage), they prevent progression to further stages (G₁, S, G₂, Mitosis).

  • Apoptosis in response to damage: Cells with irreparable damage undergo apoptosis to prevent the proliferation of damaged cells.

Gene Mutations in Cancer

  • Proto-oncogenes: These promote mitosis ("GO" signals).

    • Mutation can result in overactivity, leading to excessive cell division (oncogene).

  • Tumor suppressor genes: These stop cell division ("STOP" signals).

    • Mutation can inactivate these genes, removing the inhibitory mechanism on cell division.

  • Component of cancer development: An accumulation of multiple mutations is necessary for cancer development.

Examples of Mutations and Their Effects

  • Proto-oncogenes vs oncogenes:

    • Normal proto-oncogenes respond to growth signals, while mutated oncogenes promote division regardless of external signals.

  • Tumor suppressor genes: Normal functions include recognizing damage and pausing the cycle; mutations lead to unregulated division.

  • Example: Effect of BRCA1/BRCA2 mutations on cancer predisposition.

Inherited vs Acquired Mutations

  • Inherited Mutations: Associated with higher risks of specific cancers, such as breast and ovarian cancers via BRCA gene mutations.

    • Genetic testing can identify high-risk mutations.

  • Acquired Mutations:

    • Causes: Chemicals (carcinogens), radiation (UV light, x-rays), and viruses (e.g., HPV).

    • Example: UV radiation leads to DNA bonding errors that can initiate mutations.

  • Data on risk factors: Acquired mutations contribute significantly to cancer risk due to environmental exposure and lifestyle choices.

Cancer Screening Recommendations

  • Breast Screenings: Mammograms recommended every two years starting at age 40.

  • Cervical Screenings: Pap smears recommended every three years for women aged 21-30 and every five years for ages 30-65.

  • Prostate Screenings: First prostate exam by age 50.

  • Colon Screenings: Begin at age 45, recommended every ten years.

Cancer Treatments

  • Categories of Treatments:

    • Surgery: Removal of tumors or at-risk tissues.

    • Chemotherapy: Destroys rapidly dividing cells throughout the body.

    • Radiation Therapy: Kills cells by damaging DNA in targeted areas.

    • Targeted Therapy: Specifically attacks cancer cells by exploiting their specific weaknesses (e.g., PARP inhibitors).

    • Immunotherapy: Enhances the immune system's ability to recognize and destroy cancer cells.

Targeted Therapy Example: CML

  • Targeting Specific Mutations: Imatinib is used to inhibit the BCR-ABL tyrosine kinase activity in CML, preventing cancer cell division.

Cancer Survival Statistics (1977-2013)

  • Five-Year Survival Rates: Varies by cancer type; for example:

    • Prostate cancer: 80% survival rate.

    • Lung cancer: low survival rate.

Preventive Strategies for Reducing Cancer Risk

  • Lifestyle Modifications:

    • Avoid tobacco: Reduces risk of multiple cancers.

    • Healthy diet and exercise: Maintain a balanced diet, manage weight to reduce cancer risk.

    • Screen regularly: Early detection through screenings improves treatment outcomes.

    • Vaccination: Protect against cancers caused by viral infections (e.g., HPV).

    • Genetic testing: For individuals with family histories of cancer, plan ahead with screening and potentially prophylactic surgery.