Question

For each of the following terms related to regulation of the cell cycle, briefly describe how that term functions in normal cells. Then, describe how that term may be disrupted in the context of cancer cells. a. density-dependent inhibition i. normal cells – ii. cancer cells – b. anchorage dependence in. normal cells – ii. cancer cells – c. growth factors i. normal cells – ii. cancer cells

Answer 1

Answer:

- Density-dependent inhibition refers to the mechanism by which cells limit their density due to cell-cell contacts. Cancer cells may not undergo density-dependent inhibition, while normal cells exhibit density-dependent inhibition.

- Anchorage dependence refers to the mechanism by which cell stop their division after they form a single layer on a substrate. Cancer cells may not undergo anchorage dependence and therefore they continue to divide, while normal cells undergo apoptosis (programmed cell death)

- Growth factors are signaling molecules (often proteins and peptides) that promote cell division. Overexpression of these factors may lead to carcinogenesis (i.e., the proliferation of cancer cells), while the expression of these factors is normal in normal cells.

Explanation:

Density-dependent inhibition is the mechanism exhibited by normal cells which stops cell division once a threshold density value is reached. In general, cancer cells lost the density-dependent inhibition of growth and therefore they continue dividing. Anchorage dependence refers to the increase in the proliferation of cells that are attached to a solid surface. Most normal cells display anchorage dependence and therefore they need contact with a solid surface to proliferate, while cancer cells are independent of this attachment, proliferating and invading tissues (metastasis). Finally, growth factors are molecules capable of stimulating cell proliferation and cellular differentiation. In consequence, overexpression of growth factors may lead to cancer due to the uncontrolled division of cancer cells. Some examples of growth factors are Epidermal growth factor (EGF), Fibroblast growth factors (FGF) and Vascular Endothelial Growth Factor (VEGF).