Biopsy of a rapidly enlarging maxillary mass in a 7-year-old boy shows sheets of intermediate-sized lymphoid cells with apoptotic bodies phagocytosed by macrophages. Cytogenetic analysis detects t(8;14)(q24;q32). By what mechanism does this translocation promote tumorigenesis?
- A It creates a chimeric gene encoding a constitutively active tyrosine kinase
- B It deletes the normal allele of a tumor suppressor gene on chromosome 13
- C It places the MYC proto-oncogene adjacent to the immunoglobulin heavy chain regulatory elements, driving its constitutive overexpression ✓
- D It disrupts the coding sequence of MYC, generating a dominant-negative protein
Correct answer: C. It places the MYC proto-oncogene adjacent to the immunoglobulin heavy chain regulatory elements, driving its constitutive overexpression
Explanation
In Burkitt lymphoma the breakpoint on chromosome 8 lies upstream of MYC while the breakpoint on 14 falls within the immunoglobulin heavy chain locus, so MYC comes under control of the active immunoglobulin promoter and enhancer. The result is inappropriate constitutive MYC expression in C cells, driving proliferation, rather than any change in MYC structure. This differs mechanistically from Philadelphia chromosome-type fusions, where a novel fusion protein is created.
Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.