Question

Burkitt's lymphoma is due to a chromosomal translocation in which the c-myc gene on chromosome 8 is placed adjacent to an immunoglobulin heavy chain gene promoter/enhancer on chromosome 11 leading to the overproduction of c-myc protein. What is the direct target of the overexpressed c-myc protein that triggers aberrant lymphocyte proliferation?

A. Increased Jun & c-fos gene expression.

B. Increased cyclin D gene expression.

C. Increased E2F gene expression.

D. Increased BCR-ABL gene expression.

E. Increased p21CIP gene expression.

Answer 1

In Burkitt's lymphoma, the overexpressed c-myc protein targets and upregulates cyclin D gene expression, leading to uncontrolled cell division and tumor formation. The correct option is B.

Step-by-step explanation:

Burkitt's Lymphoma and the C-myc oncogene:

The overexpression of the c-myc protein in Burkitt's lymphoma leads to aberrant lymphocyte proliferation. After the c-myc gene on chromosome 8 is relocated next to an immunoglobulin heavy chain gene promoter/enhancer on chromosome 11 due to chromosomal translocation, it becomes overactive. As a transcription factor, the c-myc protein directly targets cyclin D gene expression, leading to the progression of the cell cycle and uncontrolled cell division. Cyclins, such as cyclin D, regulate the activity of cyclin-dependent kinases (CDKs), which are crucial in cell cycle progression. Therefore, when cyclin D levels are elevated due to increased expression, CDKs are activated, and the cell is pushed from the G1 phase into the S phase, leading to DNA replication and cell division.

In Burkitt's Lymphoma, this dysregulation in the cell cycle is a key component of oncogenesis, as the B cells proliferate without the normal checks and balances. This ultimately contributes to the formation of solid tumors, often with significant clinical implications, such as tumors in the jaw or oral cavity that interfere with eating. Thus, the answer to the question asked is B. Increased cyclin D gene expression.