Cell Division and Cancer

Cell Signaling and Cancer

• Receptor proteins receive signals for cell division, activating ras, which leads to gene activation and cell division.
• Mutations in ras cause permanent activation, leading to constitutive activation of the cell cycle.

Tumor Suppressor Genes

• Over 30 genes are classified as tumor suppressors, involved in DNA repair, apoptosis, and preventing abnormal cell division.
• Loss-of-function mutations in tumor suppressor genes contribute to cancer progression.
• Examples include BRCA1, which is involved in DNA repair, and inherited mutations increase the risk of breast cancer.

Characteristics of Cancer Cells

• Cancer cells are resistant to apoptosis and have uncontrolled ability to divide.
• They are insensitive to antigrowth factors and can invade neighboring tissues.
• They can form new tumors (metastases) at distant sites and secrete chemical signals for angiogenesis.

Tumorigenesis

• Genetic changes in tumorigenesis involve gain of function (oncogenes) and loss of function (tumor suppressor genes).
• Non-lethal genetic damage is central to carcinogenesis.

Cancer Genes

• There are two types of cancer genes: tumor suppressor genes and oncogenes.
• Approximately 400 somatic "cancer genes" have been identified, with many more to be discovered.

Oncogenes

• Oncogenes are genes that promote cell growth and division in a controlled manner.
• Examples include ras, which acts as a switch in signal transduction pathways, regulating cell division.

External Causes of Cancer

• Ultraviolet radiation and tobacco smoke and diet are external causes of cancer.

Chronic Myelogenous Leukemia (CML)

• CML is a cancer of white blood cells, characterized by a consistent chromosome translocation (t(9:22)(q34;q11)) known as the Philadelphia chromosome (Ph+).
• This mutation leads to unregulated expression of a gene and its kinase product, causing activation of intracellular signaling pathways and uncontrolled proliferation of CML cells.