Question

In a recent study, the expression profiles for 6900 genes in normal and malignant breast tissues from rats were compared. RNA was extracted using the following tissues:

a. breast tissue from virgin rats

b. breast tissue from pregnant rats

c. breast tissue from lactating rats

d. breast carcinomas induced by the meat-derived carcinogen, PhIP

e. breast carcinomas induced by the experimental carcinogen, DMBA

Tissues a, b, c were grouped together as normal and tissues d, e were grouped as carcinoma samples. Genes that were either induced (more than 2-fold increase in expression) or repressed (more than 2-fold decrease in expression) in both carcinomas were determined compared to normal samples. A partial listing of differentially expressed genes is below:

Induced:

Cell growth and cell cycle related genes

-platelet derived growth factor A (PDGF-A)

-cyclin dependent kinase 4 (CDK4)

-cyclin D

Signal transduction and transcription related genes

-FOS

-MYC

-Rho-A

Repressed:

Extracellular matrix genes

-alpha 1 type v collagen

-actin

-fibronectin

Signal transduction and transcription related genes

-p53

QUESTION: What specific characteristic of cancer might be stimulated by the 1) overexpression of Rho-A? 2) the repression of extracellular matrix genes?

Answer 1

ans- 1) overexpression of Rho-A , its activity like actin organisation, cell motility, cytokinesis etc. will be increased resulting in growth of cancer. 2)ECM deposited by cancer cells is important for the growth and proliferation of cancer cells as it has ezymes and chaperon proteins which help in growth of cancer cells so the repression of ECM genes will suppress the growth of cancer.