During carcinogenesis, a proto-oncogene is converted to an oncogene by a chromosomal translocation that places the coding sequence under control of a highly active promoter. This mechanism is BEST exemplified by which translocation-tumor pair?

• A t(9;22) BCR-ABL in CML — fusion protein with constitutive tyrosine kinase
• B t(11;22) EWS-FLI1 in Ewing sarcoma — chimeric transcription factor
• C t(15;17) PML-RARA in APML — fusion blocking differentiation
• D t(8;14) MYC-IgH in Burkitt lymphoma — MYC overexpression ✓

Explanation

The t(8;14) in Burkitt lymphoma juxtaposes the MYC proto-oncogene to the highly active IgH enhancer, leading to constitutive overexpression of MYC without structural alteration of the protein. BCR-ABL and EWS-FLI1 produce chimeric fusion proteins with new functions, while PML-RARA blocks myeloid differentiation — these are qualitative rather than purely quantitative (overexpression) changes.

Reference: Robbins & Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

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