IntroductionMultiple myeloma (MM), a malignancy hallmarked by accumulation of malignant plasma cells in the bone marrow, remains largely incurable despite the use of conventional and novel therapies. 1 The bone marrow (BM) microenvironment promotes tumor cell growth, survival, and confers drug resistance against conventional agents. 2 Although currently available anti-MM strategies have been effective in targeting the bulk of tumor cells, it has been postulated that a tumor-initiating subpopulation or cancer stem cell persists, which may be responsible for eventual relapses. 3 Side population (SP) cells are an enriched source of cancer-initiating cells with stem cell properties, which have been identified in solid tumors, as well as in hematopoietic malignancies. [4][5][6][7][8] The SP cells show a distinct ''low-staining pattern" with the Hoechst 33342 dye. 9 Importantly, SP cells possess the ability to generate non-SP cells both in vitro and in vivo, and are associated with chemoresistance and tumorigenicity in vivo. 4,10 The prevalence and biologic function of SP cells in MM are not fully defined.In the late 1990s, thalidomide was introduced to the treatment of relapsed/refractory MM; however, its effect in patients is associated with dose-and duration-dependent side effects. 11,12 Since then, more potent immunomodulatory drugs (IMiDs), such as lenalidomide, have been introduced. Lenalidomide has been approved for the treatment of both myelodysplasia with deletion of chromosome 5q and for relapsed MM, specifically in combination with dexamethasone. 12,13 Although IMiDs act directly on tumor cells, block adherence to bone marrow stromal cells (BMSCs), modulate angiogenesis and cytokines, and up-regulate host antitumor immunity, the molecular mechanism for their action remains largely undefined, and it is unclear whether they target SP cells in MM. [14][15][16][17][18] In this study, we identified SP cells in MM cell lines as well as in primary MM tumor cells by flow cytometry-based Hoechst 33342 staining, and showed heterogeneity in the percentage of SP cells, as well as the lack of strict correlation between SP fraction and CD138 Ϫ status. SP cells exhibited clonogenic and tumorigenic potential; and importantly, lenalidomide significantly decreased the percentage and clonogenicity of SP cells at clinically relevant concentrations. Moreover, lenalidomide only slightly altered expression of drug-resistant transporter ABCG2 with no effect on functional activity of BCRP1 efflux pump. Modulation of diverse signaling cascades in SP cells by lenalidomide, including changes in Akt, GSK-3␣/␤, MEK1, c-Jun, p53, and p70S6K phosphorylation was observed. Adherence to BMSCs increased the percentage, viability, and proliferation potential of SP cells. Interestingly, both lenalidomide and thalidomide attenuated this stimulatory effect of BMSCs by significantly decreasing SP cell percentages. Therefore, our studies provide insight toward developing novel strategies Submitted February 5, 2010; accepted October 10, 2010. Prepub...

Background: Elucidating the molecular mechanisms by which tumors become resistant to Herceptin is critical for the treatment of Her2-overexpressed metastatic breast cancer.

Specific niches within the tumor bone marrow (BM) microenvironment afford a sanctuary for multiple myeloma (MM) clones due to stromal cell-tumor cell interactions, which confer survival advantage and drug resistance. Defining the sequelae of tumor cell interactions within the MM niches on an individualized basis may provide the rationale for personalized therapies. To mimic the MM niche, we here describe a new 3D co-culture ex-vivo model in which primary MM patient BM cells are co-cultured with mesenchymal stem cells (MSC) in a hydrogel 3D system. In the 3D model, MSC with conserved phenotype (CD73+CD90+CD105+) formed compact clusters with active fibrous connections, and retained lineage differentiation capacity. Extracellular matrix molecules, integrins, and niche related molecules including N-cadherin and CXCL12 are expressed in 3D MSC model. Furthermore, activation of osteogenesis (MMP13, SPP1, ADAMTS4, and MGP genes) and osteoblastogenic differentiation was confirmed in 3D MSC model. Co-culture of patient-derived BM mononuclear cells with either autologous or allogeneic MSC in 3D model increased proliferation of MM cells, CXCR4 expression, and SP cells. We carried out immune profiling to show that distribution of immune cell subsets was similar in 3D and 2D MSC model systems. Importantly, resistance to novel agents (IMiDs, bortezomib, carfilzomib) and conventional agents (doxorubicin, dexamethasone, melphalan) was observed in 3D MSC system, reflective of clinical resistance. This 3D MSC model may therefore allow for studies of MM pathogenesis and drug resistance within the BM niche. Importantly, ongoing prospective trials are evaluating its utility to inform personalized targeted and immune therapy in MM.

Red blood cell distribution width (RDW) is a parameter reported in complete blood cell count tests, and has been reported as an inflammatory biomarker. Multiple myeloma (MM) is known to be associated with inflammatory microenvironments. However, the importance of RDW has been seldom studied in MM. For this study, 146 symptomatic myeloma patients with available RDW at diagnosis were retrospectively reviewed, and their characteristics were compared between two groups, those with high (>14.5%) and normal (≤14.5%) RDW. RDW was correlated to hemoglobin, MM stage, β2-microglobulin, M-protein, bone marrow plasma cells, and cellularity (P < 0.001). During induction, overall response rates of the two groups were similar (P = 0.195); however, complete response rate was higher in the normal-RDW group than it was in the high-RDW group (P = 0.005). With a median follow-up of 47 months, the normal-RDW group showed better progression-free survival (PFS) (24.2 versus 17.0 months, P = 0.029) compared to the high-RDW group. Overall survival was not different according to the RDW level (P = 0.236). In multivariate analysis, elevated RDW at diagnosis was a poor prognostic factor for PFS (HR 3.21, 95% CI 1.24–8.32) after adjustment with other myeloma-related prognostic factors. RDW would be a simple and immediately available biomarker of symptomatic MM, reflecting the systemic inflammation.