Cancer Genetics Notes

Introduction to Cancer Genetics

  • Cancer is a leading cause of mortality worldwide, ranking as the second leading cause of death.
  • In 2018, there were approximately 9.6 million deaths attributed to cancer.
    • Common types of cancer by number of cases:
      • Lung cancer: 2.09 million cases
      • Breast cancer: 2.09 million cases
      • Colorectal cancer: 1.80 million cases
      • Prostate cancer: 1.28 million cases
      • Skin cancer (non-melanoma): 1.04 million cases
      • Stomach cancer: 1.03 million cases

Statistics on Death Rates

  • In 2021, estimated annual deaths by cause were:

    • Cardiovascular diseases: 9.89 million
    • Cancers: 7.89 million
    • COVID-19: 4.41 million
    • Chronic respiratory diseases: 2.52 million
    • Diabetes: 1.66 million

  • Annual death rates per 100,000 people from all causes must account for age standardization for comparisons across demographics.

Cancer Incidence and Mortality (2022 Estimates)

  • Female cancers:

    • Breast: Highest incidence and mortality rate
    • Corpus uteri, melanoma skin, and trachea/bronchus & lung cancers also significant.

  • Male cancers:

    • Prostate: Highest incidence and mortality rate
    • Lung, colorectal, and bladder cancers are also notable.

Pathophysiology of Cancer

  • Cancer is a heterogeneous group of disorders where cell proliferation is unchecked.
  • Cancer cells bypass normal regulatory signals for growth, leading to continuous division and the formation of tumors.
    • Tumors can be benign (non-invasive) or malignant (invasive and metastatic).
  • Tumor progression includes:
    • Initiation: Mutation of a normal cell.
    • Promotion: Growth of initiated cells, leading to hyperplasia and dysplasia.
    • Progression: Malignant transformation and metastatic spread.

Genetic Factors in Cancer

  • Most cancers stem from genetic mutations affecting cell division regulation.
  • Common gene alterations include:
    • Proto-oncogenes: Normal genes that, when mutated, become oncogenes promoting uncontrolled cell division.
    • Tumor-suppressor genes: Normal genes that inhibit cell growth; their mutation leads to loss of growth control.
  • The p53 gene is a crucial tumor-suppressor gene; mutations in p53 are implicated in about 50% of human cancers.

Oncogenes and Tumor Suppressor Genes

  • The role of oncogenes and tumor suppressor genes is fundamental in the cancerous transformation of cells.

    • Oncogenes: Mutated proto-oncogenes leading to excessive stimulation of cell growth.
    • Tumor-suppressor genes: Genes that restrict cell division; mutations can result in loss of growth inhibition.

  • Cancer risk can increase due to inherited mutations affecting these genetic controls.

Conclusion

  • Understanding the genetic basis of cancer is vital for developing effective treatments and prevention strategies.