Cyclin D1 gene activation in human myeloma cells is independent of DNA hypomethylation or histone hyperacetylation

Objective. Overexpression of cyclin D1 is a common event in solid and hematological cancers. In multiple myeloma (MM), a B-cell hemopathy, one mechanism responsible for cyclin D1 expression is the translocation t(11;14)(q13;q32). But this translocation does not account for cyclin D1 gene activation in all MM. We have hypothesized that epigenetic events could regulate cyclin D1 gene transcription. Methods. Using 6 MM cell lines representative of different cyclin D1 expression levels and exhibiting various chromosome 11 abnormalities, as well as normal B cells, we studied DNA methylation and histone acetylation of the cyclin D1 promoter. Results. With the bisullite sequencing technique, we have studied the DNA methylation status of the core minimal cyclin D1 promoter containing Sp1- and CRE-binding sites. Our results show that this region is not methylated in 6 human MM cell lines as well as in normal B lymphocytes, independently of cyclin D1 expression. Treatment with the DNA methyltransferase inhibitor 5-aza-deoxycytidine (5-Aza) had no effect on cyclin D1 gene transcription. Chromatin immunoprecipitation (ChIP) experiments indicated that acetylated histones H4 are located at both the active and inactive cyclin D1 promoter. Treatment with a histone deacetylase inhibitor, trichostatin A (TSA), had no effect on gene transcription, nor had combined TSA plus 5-Aza treatment. Conclusion. The cyclin D1 gene is silenced within the B lineage by a mechanism different from DNA methylation or histone deacetylation. (c) 2005 International Society for Experimental Hematology. Published by Elsevier Inc.