exam 3 review

Unregulated Cell Cycle in Cancer Cells

• Cancer cells exhibit an unregulated cell cycle, leading to uncontrolled growth and division.

• A tumor may remain localized but poses a risk for infiltration into surrounding normal tissues.

  • A cancer cell can detach from the primary tumor and migrate into nearby healthy tissue.

  • This migration can lead to further division and the creation of new tumor sites.

Migration vs. Metastasis

• Migration refers to cancer cells moving a short distance from the original tumor.

• Metastasis involves the spread of cancer cells to distant locations in the body.

  • Requires entry into blood vessels or the lymphatic system.

  • Following entry, cancer cells travel through the circulatory system to colonize distant organs.

    • Example: Breast cancer cells commonly migrate to the lungs, resulting in secondary lung tumors.

    • Once in circulation, cells must exit blood vessels into surrounding tissues to form new tumors.

Role of Blood Vessels in Tumor Growth

• Angiogenesis is the process through which tumors develop new blood vessels.

  • Tumors need blood vessels to sustain growth beyond a certain size by accessing nutrients (e.g., glucose) and oxygen.

  • Cancer cells secrete growth factors that stimulate the formation of blood vessels, enabling access to these essential resources.

  • The relationship between angiogenesis and tumor growth can inadvertently enhance metastasis due to the presence of blood vessels facilitating the spread of cancer cells.

Mechanisms of Cellular Movement

• Actin polymerization contributes to cellular movement by pushing the membrane forward during migration.

• Motor proteins, such as myosin, participate in contraction at the rear end of the cell, aiding in movement.

• Cancer cells may not actively replicate while in transit; replication occurs once they successfully exit the blood/lymphatic system in a new location.

Lac Operon Overview

• The lac operon is a key regulatory mechanism in bacteria for lactose utilization.

  • Comprised of regulator genes (e.g., lacI), structural genes (e.g., lacZ, lacY), a promoter, and an operator.

  • Negative Regulation: The repressor (lacI protein) binds to the operator to inhibit transcription in the absence of lactose.

    • Lactose binding to the repressor induces a conformational change, preventing binding to the operator, thereby promoting transcription.

  • Positive Regulation: The CAP (catabolite activator protein) binds to a specific site to enhance RNA polymerase binding, contingent upon cAMP presence—indicating low glucose levels in the cell.

Phenomena of Feedback Regulation

• Negative feedback is observed through the degradation of cyclins, which are proteins that regulate the cell cycle transitions via CDK (cyclin-dependent kinase) activation.

  • Cyclin levels fluctuate throughout the cell cycle due to their synthesis and degradation, while CDK levels remain constant.

  • MPF (M-phase promoting factor) is activated through cyclin-CDK complexes, facilitating progression into mitosis.

  • Degradation of cyclins initiates the exit from mitosis.

• Differentiation between cyclins for various phases (S-phase, M-phase), each playing distinct roles in cell cycle regulation, such as chromatin condensation and spindle formation.

Conclusion

• Understanding these biological processes, including migration, metastasis, and cell cycle regulation, is crucial for comprehending cancer progression and potential therapeutic targets.