Novel p97/VCP inhibitor induces endoplasmic reticulum stress and apoptosis in both bortezomib‐sensitive and ‐resistant multiple myeloma cells

摘要

p97/VCP is an endoplasmic reticulum (ER)‐associated protein that belongs to the AAA (ATPases associated with diverse cellular activities) ATPase family. It has a variety of cellular functions including ER‐associated protein degradation, autophagy, and aggresome formation. Recent studies have shown emerging roles of p97/VCP and its potential as a therapeutic target in several cancer subtypes including multiple myeloma (MM). We conducted a cell‐based compound screen to exploit novel small compounds that have cytotoxic activity in myeloma cells. Among approximately 2000 compounds, OSSL_325096 showed relatively strong antiproliferative activity in MM cell lines (IC 50, 100‐500 nmol/L). OSSL_325096 induced apoptosis in myeloma cell lines, including a bortezomib‐resistant cell line and primary myeloma cells purified from patients. Accumulation of poly‐ubiquitinated proteins, PERK, CHOP, and IREα, was observed in MM cell lines treated with style="fixed-case">OSSL_325096, suggesting that it induces style="fixed-case">ER stress in style="fixed-case">MM cells. style="fixed-case">OSSL_325096 has a similar chemical structure to style="fixed-case">DBeQ, a known p97/ style="fixed-case">VCP inhibitor. Knockdown of the gene encoding p97/ style="fixed-case">VCP induced apoptosis in myeloma cells, accompanied by accumulation of poly‐ubiquitinated protein. style="fixed-case">IC 50 of style="fixed-case">OSSL_325096 to myeloma cell lines were found to be lower (0.1‐0.8 μmol/L) than those of style="fixed-case">DBeQ (2‐5 μmol/L). In silico protein–drug‐binding simulation suggested possible binding of style="fixed-case">OSSL_325096 to the style="fixed-case">ATP binding site in the D2 domain of p97/ style="fixed-case">VCP. In cell‐free style="fixed-case">ATPase assays, style="fixed-case">OSSL_325096 showed dose‐dependent inhibition of p97/ style="fixed-case">VCP ATPase activity. Finally, style="fixed-case">OSSL_325096 inhibited the growth of subcutaneous myeloma cell tumors in vivo. The present data suggest that style="fixed-case">OSSL_325096 exerts anti‐myeloma activity, at least in part through p97/ style="fixed-case">VCP inhibition.