Enhancement of myeloma development mediated though myeloma cell-Th2 cell interactions after microbial antigen presentation by myeloma cells and DCs

Microbial agents are regarded as a potential cause of tumors, but their direct effects on tumors, such as myeloma, are not well studied. Our studies demonstrated that expression of HLA-DR and CD40 on the myeloma cell membrane surface is upregulated by interferon-γ and/or microbial antigens (Ags). Unlike prior studies, our study showed that Th2 cells cannot promote myeloma growth directly. However, Bacillus Calmette–Guerin Vaccine (BCGV)-specific Th2 cells stimulated by BCGV-loaded dendritic cells (DCs) promoted myeloma clonogenicity directly when the myeloma cells expressed major histocompatibility complex Class-II molecules (MHC-II) and took up BCGV Ag. B-cell lymphoma 6 (Bcl-6) protein expression and the proportion of HLA-DR+ or CD40+ cells were higher in colonies of Th2 cell-stimulated myeloma cells. Furthermore, anti-HLA-DR or neutralizing CD40 antibody could prevent this increase in Bcl-6 expression and colony number. These results indicate that microbes and microbial Ag-specific Th2 cells may directly impact the biology of myeloma and contribute to tumor progression. Activation may be limited to MHC-II+ myeloma cells that retain B cell and stem cell characteristics. Taken together, our data suggest that factors involved in microbial Ag presentation, such as DCs, Th2 cells and so on, are potential targets for myeloma therapeutic intervention

Dysregulated Recruitment of the Histone Methyltransferase EZH2 to the Class II Transactivator (CIITA) Promoter IV in Breast Cancer Cells

One mechanism frequently utilized by tumor cells to escape immune system recognition and elimination is suppression of cell surface expression of Major Histocompatibility Class II (MHC II) molecules. Expression of MHC II is regulated primarily at the level of transcription by the Class II Transactivator, CIITA, and decreased CIITA expression is observed in multiple tumor types. We investigate here contributions of epigenetic modifications to transcriptional silencing of CIITA in variants of the human breast cancer cell line MDA MB 435. Significant increases in histone H3 lysine 27 trimethylation upon IFN-γ stimulation correlate with reductions in transcription factor recruitment to the interferon-γ inducible CIITA promoter, CIITApIV, and with significantly increased CIITApIV occupancy by the histone methyltransferase enhancer of zeste homolog 2 (EZH2). Most compelling is evidence that decreased expression of EZH2 in MDA MB 435 variants results in significant increases in CIITA and HLA-DRA mRNA expression, even in the absence of interferon-γ stimulation, as well as increased cell surface expression of MHC II. Together, these data add mechanistic insight to prior observations of increased EZH2 expression and decreased CIITA expression in multiple tumor types

Establishment of a murine graft-versus-myeloma model using allogeneic stem cell transplantation

Background: Multiple myeloma (MM) is a malignant plasma cell disorder with poor long-term survival and high recurrence rates. Despite evidence of graft-versus-myeloma (GvM) effects, the use of allogeneic hematopoietic stem cell transplantation (allo-SCT) has remained controversial in MM. In the current study, we investigated the anti-myeloma effects of allo-SCT from B10.D2 mice into MHC-matched myeloma-bearing Balb/cJ mice (previously injected with the MOPC315.BM myeloma cell line), based on a chronic graft-versus-host disease (GvHD) murine model. Methods and results: Balb/cJ mice were injected intravenously with luciferase-transfected MOPC315.BM cells, and received 30 days later an allogeneic (B10.D2 donor) or autologous (Balb/cJ donor) transplantation by intravenous administration of bone marrow cells and splenocytes. We observed a graft-versus-myeloma effect in 94% of the allogeneic transplanted mice, as luciferase signal completely disappeared after transplantation, whereas all the autologous transplanted mice showed myeloma evolution. Lower serum paraprotein levels and myeloma infiltration in bone marrow and spleen in the allogeneic setting confirmed the observed GvM effect, while allogeneic mice also displayed chronic GvHD symptoms. In vivo and in vitro data suggest the involvement of effector memory CD4 and CD8 T cells in the GvM effect. The essential role of CD8 T cells was demonstrated in vivo where CD8 T-cell depletion of the graft resulted in reduced GvM effects. Finally, TCR V spectratyping analysis identified V families within CD4 and CD8 T cells which were associated with both GvM effects and GVHD, whereas other V families within CD4 T cells were associated exclusively with either GvM or GvHD responses. Conclusions: We successfully established an immunocompetent murine model of graft-versus-myeloma. This is the first immunocompetent murine model which is based on a MM model closely resembling human MM disease (bone marrow tropism, ...) and using allo-SCT after the disease establishment, as a curative treatmen