Question

3.-9. Explain the conditions in which the following oncogene protein products may be oncogenic. 3. The growth factor EGF 5. The growth factor receptor PDGFR 6. The intracellular signal transducing molecule Ras 7. The Cak-activating protein cyclin D 9. The tumor suppressor protein p53

Answer 1

3. The growth factor EGF.

Epidermal growth factors (EGF) are involved in the development and proliferation of the cell. they function by activating the EGF receptors bound to the cell surface. When there is a high-level expression of EGFR in the presence of EGF, the cell divide at an abnormally higher rate which causes epithelial cancer. The continued activation and overexpression of EGFR are caused by point mutations of the EGFR gene.

5. The growth factor receptor PDGFR

Platelet-derived growth factor receptor (PDGFR) signaling pathway is involved in the regulation of cell growth. The dysfunction of PDGFR is observed in various cancer types. The deletion mutation and aberration in the copy number of PDGFR gene result in its high expression which leads to uncontrolled cell growth called cancer. The PDGFR dysregulation is observed in many types cancers such as lung, ovarian, colorectal and so on.

6. The intracellular signal transducing molecule Ras.

Ras proteins are GTPases involved in the various signalling pathways linked to cellular differentiation, proliferation and survival. When there is a mutation in the Ras gene, it is overexpressed and there will be more binding of the GTP which activates the signalling pathway continuously. Some of the tumors associated with the Ras mutations are adenocarcinoma, Non-small cell lung carcinoma, and colorectal carcinoma.

7. The Cdk-activating protein Cyclin D.

Cyclin D proteins activate the cyclin-dependent kinase (Cdk) during the cell proliferation process. It is involved in the transition step of the cell from G1 to S phase of the cell cycle. If the degradation of cyclin protein is not regulated properly, it may lead to cancer. Thus, when there is a mutation in this protein, it continuously activates the Cdk protein which allows the cell to bypass the checkpoint during the cell cycle and thus results in the uncontrolled proliferation of cells causing certain types of cancers such as breast cancer, lung, and bladder cancer.

9. The tumor suppressor protein p53.

This gene is involved in the regulation of the cell cycle. It binds to the DNA to induce the production of p21 protein. This protein forms complex with Cdk2 protein, so that cell cannot transit to the next stage of the cell cycle, thus producing the stop signal for cell proliferation. When the p53 gene is mutated, the stop signal cannot be produced and the cell divides continuously and forms cancerous cells. Some of the cancers caused due to the mutated p53 are breast cancer, brain tumor, colorectal, liver, lung cancer and so on.