Common Fragile Site Gene FRA16D WWOX (WW domain containing oxidoreductase) Is Frequently Altered in Plasma Cells of Multiple Myeloma and MGUS, Possibly Related to Disease Development

Abstract 4646

The common fragile sites (CFSs) are regions of profound genomic instability, and hot-spots for deletions and other alterations in cancer cells. We have previously shown that promoter of FHIT is frequently methylated in multiple myeloma (MM) and correlated with worse prognosis. WWOX is located at a CFS region on chromosome 16q23.3, this gene is also a target of alterations in multiple cancers. The objective of current study is to find if this tumor suppressor gene is altered in MM and MGUS. Six myeloma cell lines, bone marrow mononuclear cells (BMMNC) of 165 MM and 25 MGUS patients were subjected to this study after obtaining informed consent. Isolated CD138 positive plasma cells (PC) of 24 MM were examined to see if the alteration occurred really in myeloma cells. Using methylation specific PCR, WWOX promoter methylation was detected in 2 of 6 cell lines, 35% of MM patients and 8% of MGUS patients (p=0.01). The overall survival of the MM patients with methylated WWOX tended to be worse than with unmethylated WWOX (p=0.2). Using nested RT-PCR, aberrant short transcripts of WWOX lacking exons coding SDR domain were detected in 4 cell lines, 68% of MM and 60% of MGUS (p=0.51) In isolated PC, aberrant transcripts of WWOX were detected in 58% of MM and 25% of MGUS (p=0.02). Real time PCR demonstrated higher WWOX expression in isolated PC of MM and MGUS than of BMMNC other than plasma cells (p=0.0001), and those higher WWOX were aberrant type (p=0.001). As aberrant WWOX is known to function as dominant negative for wild type, our results imply that this aberrant WWOX is an oncogene as well as losing tumor suppressor function. Since WWOX is demonstrated to regulate beta-catenin and NF-kB pathway, high frequency of aberrant WWOX expression indicates an important role in myeloma development.