IntroductionMultiple myeloma appears to arise from initiating chromosomal translocations and duplications in postgerminal center plasma cells with subsequent secondary mutations contributing to disease progression. 1,2 Six unique myeloma variants can be identified by gene expression profiling with 3 of the 6 groups anchored by an initiating chromosome translocation. It is noteworthy that a unifying event of cyclin D dysregulation is identified in all subgroups. 1,2 One of the initiating chromosomal abnormalities in myeloma involves members of the Maf family of oncogenes. 1 Maf proteins are basic leucine zipper transcription factors in the AP1 family and regulate gene transcription by binding DNA sequences known as MAF responsive elements (MAREs). 3,4 Of the Maf family, c-maf was the first endogenous member identified and is probably the best characterized with respect to function. 5 Genes up-regulated by c-maf include cyclin D2, ␤-integrin 7, ARK 5 and CCR1, all of which are important in the pathogenesis of multiple myeloma. [6][7][8] c-maf is dysregulated in multiple myeloma. For example, approximately 25% of myeloma cell lines have a t(14;16) translocation. 6 In patients with myeloma, approximately 6% have a t(14;16) or t(14;20), translocations that juxtapose IgH with c-maf and its homolog mafB, respectively. 9,10 The frequency of c-maf overexpression in patients who lack the t(14;16) has varied from study to study, depending on the method to assess its overexpression and ranges from 5% to 50%. 6,11,12 In malignant cell lines, including multiple myeloma, overexpression of c-maf augments cell proliferation and increases tumor formation in xenograft models. 6,7 Conversely, inhibition of c-maf with dominant-negative constructs decreases cell proliferation, impairs adhesion to marrow stroma, and delays tumor growth. 6 Overexpression of c-maf is also clinically relevant in that patients with myeloma and the t(14;16) c-maf translocation have a shorter overall survival. 13 Although the functional importance of c-maf has been described, the mechanisms that govern its regulation have not been fully elucidated. Therefore, molecules that decrease c-maf and subsequently its downstream targets, particularly cyclin D2, could further our understanding of the regulation of c-maf. Improved understanding of c-maf will help develop therapies that target this protein.To this end, we developed a high-throughput chemical genomics screen to identify compounds that inhibit c-maf-dependent transactivation of the cyclin D2 promoter. With this assay, we screened libraries of off-patent drugs and chemicals and were surprised to identify glucocorticoids as inhibitors of c-mafdependent cyclin D2 transactivation. Subsequent studies demonstrated that glucocorticoids decrease c-maf protein by promoting its ubiquitination through the up-regulation of ubiquitin C mRNA. Thus, this chemical biology approach has provided insights into a novel mechanism of c-maf regulation. The publication costs of this article were defrayed in part by page charge ...

Knockout and transgenic studies in mice demonstrate that normal somatic tissues redundantly express 3 cyclin D proteins, whereas tumor cells seem dependent on a single overexpressed cyclin D. Thus, selective suppression of the individual cyclin D deregulated in a tumor represents a biologically valid approach to targeted cancer therapy. In multiple myeloma, overexpression of 1 of the cyclin D proteins is a ubiquitous feature, unifying at least 7 different initiating genetic events. We demonstrate here that RNAi of genes encoding cyclin D1 and cyclin D2 (CCND1 and CCND2, respectively) inhibits proliferation and is progressively cytotoxic in human myeloma cells. By screening a chemical library using a cell-based assay for inhibition of CCND2 trans-activation, we identified the plant cytokinin kinetin riboside as an inhibitor of CCND2 trans-activation. Kinetin riboside induced marked suppression of CCND2 transcription and rapidly suppressed cyclin D1 and D2 protein expression in primary myeloma cells and tumor lines, causing cell-cycle arrest, tumor cell-selective apoptosis, and inhibition of myeloma growth in xenografted mice. Mechanistically, kinetin riboside upregulated expression of transcription repressor isoforms of cAMP-response element modulator (CREM) and blocked both trans-activation of CCND2 by various myeloma oncogenes and cis-activation of translocated CCND1, suggesting induction of an overriding repressor activity that blocks multiple oncogenic pathways targeting cyclin D genes. These data support targeted repression of cyclin D genes as a therapeutic strategy for human malignancies. IntroductionMultiple myeloma (MM) is a postgerminal center B cell malignancy characterized by clonal plasma cell expansion. The disease manifests clinically with anemia, monoclonal immunoglobulin, renal insufficiency, and lytic bone lesions and currently affects 63,000 people in the United States alone (1); moreover, as it is currently incurable, MM causes a disproportionate 2% of all cancer deaths.Although myeloma tumors present with complex karyotypes and an assortment of structural and numerical chromosomal abnormalities, these tumors are unified in their ubiquitous targeting of cyclin D genes for overexpression. Of MM tumors, 54% overexpress cyclin D1 (CCND1), 48% overexpress cyclin D2 (CCND2), 3% overexpress cyclin D3 (CCND3), and 8% overexpress both CCND1 and CCND2 (2). Deregulated expression of single CCND genes in MM occurs as the result of selective cyclin D gene trans-activation by deregulated transcription factors or from translocation of a single

Hacs1, a SH3 and SAM domain-containing adaptor protein, is up-regulated by IL-4 in activated B cells and strongly expressed in dendritic cells. To elucidate the function of Hacs1 in immune regulation, we generated Hacs1(-/-) mice by deletion of the SH3 and SAM domains. Hacs1(-/-) mice were viable and fertile and had normal bone marrow B-cell development and normal splenic T- and B-cell populations. However, adult Hacs1(-/-) mice had increased peritoneal B1a cells (IgM(+)CD5(+)). On immunization with T-cell-independent antigen TNP-Ficoll, Hacs1(-/-) mice had increased production of anti-TNP IgM and IgG3. Purified splenic B cells from Hacs1(-/-) mice showed increased cell proliferation on BCR (B-cell receptor) stimulation. We further demonstrate that the Hacs1(-/-) B cells had increased global tyrosine phosphorylation, including tyrosine kinases Lyn and Akt. Both T-helper type 1 (T(h)1) and T-helper type 2 (T(h)2) humoral responses were enhanced in Hacs1(-/-) mice. In vitro bone marrow-derived Hacs1(-/-) dendritic cells showed increased IL-12 production on stimulation with ovalbumin (OVA). This study suggests that Hacs1 is an immunoinhibitory adaptor that might be a useful target for immune suppression therapy.-Wang, D., Stewart, A. K., Zhuang, L., Zhu, Y., Wang, Y., Shi, C., Keating, A., Slutsky, A., Zhang, H., Wen, X.-Y. Enhanced adaptive immunity in mice lacking the immunoinhibitory adaptor Hacs1.

Although immunomodulatory drugs (IMiDs), such as thalidomide, lenalidomide, and pomalidomide, are widely used in the treatment of multiple myeloma (MM), the molecular mechanism of IMiDs' action is largely unknown. In this review, we will summarize recent advances in the application of IMiDs in MM cancer treatment as well as their effects on immunomodulatory activities, anti-angiogenic activities, intervention of cell surface adhesion molecules between myeloma cells and bone marrow stromal cells, anti-inflammatory activities, anti-proliferation, pro-apoptotic effects, cell cycle arrest, and inhibition of cell migration and metastasis. In addition, the potential IMiDs' target protein, IMiDs' target protein's functional role, and the potential molecular mechanisms of IMiDs resistance will be discussed. We wish, by presentation of our naive discussion, that this review article will facilitate further investigation in these fields.

Although chemotherapeutic agents and molecular medicine are pillars of successful treatment of cancer, the recent clinical development of immunotherapies shows compelling promise in the treatment of many tumor types. In hematologic malignancies, immunotherapies centered upon cytolytic T lymphocytes as drugs, such as chimeric antigen receptor (CAR)-T cells and bispecific T-cell engagers (BiTE) or antibodies (BsAb), are central among these advances. BiTEs and BsAbs are "offthe-shelf" drug therapies that circumvent the need for timeconsuming and expensive ex vivo manipulation of patient cells. These agents often consist of monoclonal antibodies or singlechain variable fragments in the case of BiTEs, engineered with one binding site directed toward a tumor-specific antigen and another against the T-lymphocyte activating receptor CD3epsilon. BsAbs redirect T cells to kill tumors by bringing them into physical contact and activating secretion of cytotoxic molecules (1). Due to their novel mode of action, BsAb therapeutics may provide an effective option for all patients, including those with cytogenetically high-risk or heavily pretreated disease that renders them more resistant to standard-of-care therapy.