Understanding Mitosis and Cancer Treatment

Oct 19, 2024

Lecture on Mitosis and Cell Cycle

Introduction

  • Discussion centered around cell cycle focusing on mitosis.
  • Importance of cyclins and CDKs in cell cycle progression.
  • CDKs 4 and 6 are vital in G1 to S phase transition.
  • CDK inhibitors are used in treating negative breast cancer.

Mitosis Basics

  • Mitosis involves nuclear division (chromosomes divided) and cytokinesis (cytoplasmic division).
  • Occurs in somatic (body) cells, which are always diploid (46 chromosomes in humans).
  • Mitosis results in two genetically identical diploid daughter cells.

Mitosis vs. Cell Types

  • Somatic Cells: Body cells, always diploid, undergo mitosis.
  • Mitosis: Divides the nucleus (chromosomes), followed by cytokinesis (cytoplasm).
  • In humans, body cells have 46 chromosomes which remain diploid post-mitosis.

Stages of Mitosis

  • Prophase:
    • Nuclear membrane breaks down.
    • Nucleolus disappears.
    • Spindle fibers form from microtubule organizing centers (centrioles).
  • Metaphase:
  • Chromosomes line up at the metaphase plate.
  • Spindle fully forms and attaches to chromosomes' centromeres via kinetochores.
  • Anaphase:
    • Sister chromatids are pulled apart as cohesin protein dissolves.
  • Telophase:
    • Chromosomes reach poles.
    • Nuclear membrane reforms.
    • Spindle fibers disassemble.
  • Cytokinesis:
    • Animal cells: Cytoplasm divides outside-in using microfilament ring.
    • Plant cells: Cytoplasm divides inside-out due to rigid cell wall.

Cell Cycle Overview

  • Interphase (G1, S, G2) not part of division; prepares for mitosis.
  • Chromosomes replicate during S phase to prepare for division.

Chromosome Number and Division

  • Diploidy: 2n = 46 in humans, remains constant through mitosis.
  • Replicated Unreplicated Chromosomes: Post-anaphase chromosomes are unreplicated.

Factors Affecting Cell Division

  • Growth factors and anchorage dependence crucial for mitosis.
  • Density Dependence: Cells stop dividing when touching each other.

Cancer Cells

  • Lack proper regulation, ignore density dependence, can metastasize.

  • Mutation in genes like p53 affects tumor development.

  • Master tumor suppressor gene; crucial for DNA damage response.

    • Loss of function can lead to cancer.

  • Cancer Development:

    • Involves multiple mutations over time.
    • Tumors can be benign or malignant.

Cancer and Treatment

  • p53 Function: Tumor suppressor gene halts cell cycle for DNA repair or cell death.
  • Telomerase: Enzyme associated with aging and immortalizing cancer cells.
    • Its activity decreases with age.
  • Treatments:
    • Radiation: Disrupts cell repair mechanisms.
    • Chemotherapy: Targets dividing cells but affects healthy dividing cells too.
    • Immunotherapy: Boosts immune response but effectiveness varies.

Apoptosis

  • Programmed cell death for removing damaged cells.
  • Important for damage control, e.g., in sunburned skin.

Conclusion

  • Mitosis ensures genetic consistency for growth and repair.
  • Advances in understanding cell division have led to improved treatments for diseases like cancer.

The lecture wraps up with a note on the importance of continued research in cancer treatments and the impact of genetic understanding on medical advancements.