Cytogenetic analysis of a tumor from the jaw of a 14-year-old boy shows a balanced reciprocal translocation between chromosomes 8 and 14. Molecular analysis confirms juxtaposition of MYC downstream of an immunoglobulin gene regulatory element. Which functional consequence of this arrangement drives the neoplasm?
- A MYC coding sequence acquires activating point mutations within its kinase domain
- B Constitutive MYC expression driven by the immunoglobulin heavy chain enhancer, independent of normal growth signals ✓
- C Formation of a chimeric tyrosine kinase with constitutive activity
- D Loss of MYC expression leading to uncontrolled apoptosis evasion
Correct answer: B. Constitutive MYC expression driven by the immunoglobulin heavy chain enhancer, independent of normal growth signals
Explanation
In endemic Burkitt lymphoma, t(8;14)(q24;q32) places the intact MYC proto-oncogene adjacent to the immunoglobulin heavy chain locus on chromosome 14. The powerful IgH enhancer drives constitutive MYC transcription, uncoupling MYC expression from normal mitogenic signaling and promoting unchecked cell growth. MYC is a transcription factor with no kinase domain, so option A is false, and the coding sequence itself remains structurally normal, unlike BCR-ABL fusion kinases.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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