The c-myc gene is located at chromosome 8q24. It is required for progression through the cell cycle and promotes cellular proliferation. Myc null cell lines show a profound growth defect, with lengthening of both G1 and G2 phases of the cell cycle. There is a marked reduction in cyclin D1-CDK4 and D1-CDK6 complexes during entry to the S phase, with lesser reductions in Cyclin E2 -CDK2 and cyclin A-CDK2. Myc induces expression of cyclins D1 and D2.
Oncogenic expression of c-myc involves mutations on exon 2; such mutations are found in more than 50% of Burkitt's lymphomas. The typical translocation in Burkitt lymphoma is t(8;14)(q24;q23), juxtaposing the c-myc and the immunoglobulin heavy chain genes1. Variants translocations are to 2p11 or 22q11, juxtaposing the kappa or lambda light chain genes respectively. FISH can be performed with dual probes can demonstrate the IgH/c-myc translocation. Tricolour with a probe against the centromere of chromosome 8 will control of c-myc amplification or loss of the derivative chromosome 8. Dual colour break-apart probes with show splitting of the gene.
The t(8;14)(q24;q32) translocation and the c-MYC/immunoglobulin heavy-chain (IGH) fusion gene are not specific to Burkitt lymphoma but are also seen in diffuse large B-cell lymphoma2,3, blastic mantle cell lymphoma4 and transformed follicular lymphoma5.
References
1 Leoncini, L., Lazzi, S., Bellan, C. and Tosi, P. Cell kinetics and cell cycle regulation in lymphomas. J Clin Pathol 2002;55:648-55. FULL TEXT
5 Yano T, Jaffe ES, Longo DL, et al. MYC rearrangements in histologically progressed follicular lymphomas. Blood 1992; 80:758-67 FULL TEXT
Last revised 15.11.2006
©SMUHT/PW Bishop