Absence of herpesvirus DNA sequences in the 5T murine model of human multiple myeloma

Novel Protein Disulfide Isomerase Inhibitor with Anticancer Activity in Multiple Myeloma

Multiple myeloma cells secrete more disulfide bond-rich proteins than any other mammalian cell. Thus, inhibition of protein disulfide isomerases (PDI) required for protein folding in the endoplasmic reticulum (ER) should increase ER stress beyond repair in this incurable cancer. Here, we report the mechanistically unbiased discovery of a novel PDI-inhibiting compound with antimyeloma activity. We screened a 30,355 small-molecule library using a multilayered multiple myeloma cell-based cytotoxicity assay that modeled disease niche, normal liver, kidney, and bone marrow. CCF642, a bone marrow-sparing compound, exhibited a submicromolar IC50 in 10 of 10 multiple myeloma cell lines. An active biotinylated analog of CCF642 defined binding to the PDI isoenzymes A1, A3, and A4 in MM cells. In vitro, CCF642 inhibited PDI reductase activity about 100-fold more potently than the structurally distinct established inhibitors PACMA 31 and LOC14. Computational modeling suggested a novel covalent binding mode in active-site CGHCK motifs. Remarkably, without any further chemistry optimization, CCF642 displayed potent efficacy in an aggressive syngeneic mouse model of multiple myeloma and prolonged the lifespan of C57BL/KaLwRij mice engrafted with 5TGM1-luc myeloma, an effect comparable to the first-line multiple myeloma therapeutic bortezomib. Consistent with PDI inhibition, CCF642 caused acute ER stress in multiple myeloma cells accompanied by apoptosis-inducing calcium release. Overall, our results provide an illustration of the utility of simple in vivo simulations as part of a drug discovery effort, along with a sound preclinical rationale to develop a new small-molecule therapeutic to treat multiple myeloma. Cancer Res; 76(11); 3340-50. ©2016 AACR.

Mouse models of human myeloma

Multiple myeloma (MM) remains incurable despite high-dose chemotherapy with stem cell support. There is need, therefore, for continuous efforts directed toward the development of novel rational-based therapeutics for MM, which requires a detailed knowledge of the mutations driving this malignancy. In improving the success rate of effective drug development, it is equally imperative that biologic systems be developed to better validate these target genes. Here we review the recent developments in the generation of mouse models of MM and their impact as preclinical models for designing and assessing target-based therapeutic approaches.

Evaluation of human herpesvirus type 8 infection in childhood langerhans cell histiocytosis

The etiology of Langerhans cell histiocytosis (LCH) is unknown. Viral causes, including human herpesvirus type 6 (HHV6), have been suggested but remain unproved. The recently discovered human herpesvirus type 8 (HHV8), the cause of Kaposi's sarcoma, infects dendritic cells in the bone marrow associated with multiple myeloma. Evidence for an association of HHV8 infection with LCH in children was studied by two approaches: indirectly by HHV8-specific serologic assays and directly by detection of HHV8 sequences using polymerase chain reaction in affected bone marrow samples. Using three different assays specific for HHV8 antibodies, 3 of 10 (30%) children with LCH had detectable HHV8 antibodies, which was not different from the prevalence of 5 of 30 (17%) in healthy controls of similar age (P = 0.65). Of bone marrow samples from three additional children with LCH, all had amplifiable DNA but were negative for HHV8 sequences. These studies of a small number of patients do not demonstrate an increased prevalence of HHV8 infection in children with LCH, and they do not suggest a causal role for HHV8 in the etiology of LCH.