CANCER: A LOSS OF CONTROL OF CELL CYCLE CONTROL

Cellular replication, or the cell cycle, is controlled and highly regulated by internal and external chemical signals. Occasionally cells arise that no longer recognize or respond to these regulatory signals. The cells that ignore chemical messages and divide uncontrollably are referred to as being transformed. Transformed cells specialize in replication but do not differentiate into the appropriate cell type for the organ in which they are proliferating.   When growing, transformed cells pile on top of one another and ignore signals from adjacent cells. This loss of contact inhibition is an important characteristic of a transformed cell. Most transformed cells are located and destroyed by the immune system. If a transformed cell is not destroyed, it will continue to replicate uncontrollably and eventually form a solid mass, or tumor. Tumor cells actively encourage blood vessels in the local area to grow and vascularize, thereby providing the tumor with its own supply of food and oxygen. Tumors that grow rapidly and invade surrounding tissue are described as malignant, whereas tumors that are self-contained and noninvasive are described as benign. Malignant tumors overwhelm normal cells as they overgrow and displace normal tissues. If untreated, these tumors will ultimately cause loss of organ function and eventual death of the host due to a depletion of tissue nutrients as well as the inability of the transformed cell to carry out normal tissue or organ function. The group of diseases characterized by malignant tumors is referred to collectively as cancer.

ACTIVITY

In this activity you will access various sites including University of Pennsylvania's Oncolink site. These sites contain information about cancer types, diagnoses, and therapies.  In this activity you will learn the basic facts about cancer. 

Use these sites or others to answer these questions:

American Cancer Society         Cancer. gov        U of P Cancer "Oncolink"

1. Describe three characteristics that differentiate a benign tumor from a malignant tumor.

2. What is the "multiple hit hypothesis" (as it relates to cancer)?

3. Describe the role of the P53 gene in carcinogenesis.

4. What is the difference between carcinoma and sarcoma?

5.  Do you know someone who had cancer?  What kind did they have?  How were they treated?  Did they survive?

6.  What are the survival rates for the different cancer types?

7.  What are all the things you can do to reduce your risk of the different cancer types?