LECTURE 15. CANCER: DEVELOPMENTAL MECHANISMS AND ONCOGENESIS
Optional reading: Alberts et al., Molecular Biology of the Cell. Chapter 23.
1. Oncogenesis-The process whereby normal cells become cancer cells.
2. Tumor - a population of cells that result from the localized, unregulated growth and division of a single cell. Occurs in the face of normal restraints on growth. Also called a neoplasm.
3. Metastasis - the migration of cells from a tumor and their invasion of other tissues. Only
when tumors metastasize are they considered malignant or cancerous.
1. Approximately 0.6 million US citizens will die of cancer this year.
2. About 1.4 million new cases will be reported in this country this year.
3. Collectively, cancers are the #2 killer of Americans (behind cardiovascular disease) and account for almost 25% of all deaths.
4. Roughly 50% of all cancers are of the lung, intestine and breast. Nearly 150,000 women will develop breast cancer this year.
C. THE NATURE OF CANCER:
As has become appreciated over the years, cancer is not a single disease, but a whole collection of disorders that constitute at least 300 different histological types. These types can be grouped into a series of classes, based largely on the embryological origin of the initial tumor cells. Carcinomas are epithelial in origin (ectodermal and endodermal); sarcomas are derived from connective tissue (mesodermal); leukemias are from blood-forming cells; melanomas derive from pigment cells (melanocytes); and teratomas arise from germ cells or gonadal tissue.
Tumors are the result of localized, unregulated, cell growth. For a tumor to become malignant, cells must begin to metastasize (move), and invade, other tissues. The original tumor is called a primary tumor. and all the cells derive from single aberrant cell. As tumors metastasize the new...