Question

Of the four tissue types (epithelial, connective, muscle and nervous), which one is the MOST likely to develop into cancerous tissue and WHY? Explain how cancer could develop in this tissue by SPECIFYINGwhich genes (what do the genes control/code for?) within the cells are likely to be mutated that would cause this tissue to grow uncontrollably.

Answer 1

Out of the above-mentioned tissues, the epithelial tissue has the maximum chances to give rise to cancer tissues. The most important reason for this is that the epithelial cells reproduce and divide more rapidly as compared to other tissues. The rapid dividing phenomenon is physiologically relevant because, in case of injury, these tissues are capable of dividing much faster so as to heal the wound. Other tissues such as the muscle or the neurons do not divide once they get mature. Thus the chances of these tissues turning cancerous are very unlikely.

Mainly there are two types of genes which are involved in the initiation of cancer:

1. Tumor suppressor genes

2. Oncogenes

1.Tumor suppressor genes: A tumor suppressor gene is a gene that protects a cell from getting transformed into a cancer cell. When this gene gets mutates and loses its function which is basically to suppress tumor formation, the cells become cancerous. Popular examples in this category are retinoblastoma protein (pRb),  p53 tumor-suppressor protein encoded by the TP53 gene, PTEN, JAK2, NOTCH1, and IL2.

2. Oncogenes: These are certain genes in our cells which are in the inactive form (proto-oncogenes) and are needed for the cell growth and division. When these genes are expressed normally, the cells grow and divide at a normal rate and rest of the time these genes are switched off and the cells do not divide. However, when they get mutated they remain permanently active and the cells continuously divided in an uncontrolled manner. Popular examples in this category are RAS (K Ras), MYC (c-MYC), WNT, ERK, and TRK (receptor tyrosine kinase).