Long-term response to maintenance treatment with rituximab in CD20+multiple myeloma

Is rheumatoid arthritis a B-cell haematological disease with a predilection for the joints? Following the B cell thread to its logical conclusion

B-cell depleting therapy (BCDT) is effective in suppressing synovitis and erosions in rheumatoid arthritis suggesting that a cell of the B-lymphocyte lineage is critical in the pathogenesis of this disease. Non-Hodgkins lymphoma (NHL) also responds to BCDT but multiple myeloma (MM), does not as cells have differentiated beyond the CD20-bearing stage. However, there are similarities between B-NHL, MM and RA that suggest all 3 conditions could be initiated and perpetuated by the same cellular players. Numerous plasma cells and B cells are present within rheumatoid synovial membrane, and subarticular bone where they contribute to osteitis. On MRI scans this appears as bone oedema, which has been demonstrated to precede the development of bone erosions. Plasma cell clonality has been detected within RA synovial membrane and bone marrow. It is proposed that RA could represent a "forme fruste" of a B cell neoplastic condition, with production of autoantibodies that target a self-antigen within the joint. The activation of rheumatoid bone osteoclasts by anticitrullinated protein antibodies supports this theory. The erosions of RA would have parallels with the lytic lesions of MM but autoantigen targeting dictates that erosions occur at joint margins. This theory is discussed from rheumatologic and haematologic perspectives.

Is CD20 positive plasma cell myeloma a unique clinicopathological entity? A study of 40 cases and review of the literature

AIMS

A number of clinicopathological features have been attributed to the CD20 positive subset of plasma cell myeloma (PCM). CD20 is an appealing therapeutic target given the success with monoclonal antibody regimens in a spectrum of B cell lymphomas. To date, a small number of reports have described CD20 PCM as a unique subset, and these are not conclusive, especially taking into consideration reporting bias. This study aims to further identify the clinicopathological features of CD20 PCM.

METHODS

A retrospective analysis of all newly diagnosed PCM between 2003 and 2010 was undertaken. Trephine material was retrieved and reviewed for CD20, and for positive cases an extended immunohistochemical (IHC) panel including cyclin D1 was subsequently performed.

RESULTS

The review of our 40 cases and those described in the literature demonstrated that these are heterogeneous with regard to clinical features, morphology, biochemical features, immunophenotype, and cytogenetics.

CONCLUSION

Based on our study and review of the literature, CD20 PCM cases represent a heterogeneous disease and not a unique clinicopathological entity.

Screening of multiple myeloma by polyclonal rabbit anti-human plasmacytoma cell immunoglobulin

Antibody-based immunotherapy has been effectively used for tumor treatment. However, to date, only a few tumor-associated antigens (TAAs) or therapeutic targets have been identified. Identification of more immunogenic antigens is essential for improvements in multiple myeloma (MM) diagnosis and therapy. In this study, we synthesized a polyclonal antibody (PAb) by immunizing rabbits with whole human plasmacytoma ARH-77 cells and identified MM-associated antigens, including enlonase, adipophilin, and HSP90s, among others, via proteomic technologies. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay showed that 200 µg/mL PAb inhibits the proliferation of ARH-77 cells by over 50% within 48 h. Flow cytometric assay indicated that PAb treatment significantly increases the number of apoptotic cells compared with other treatments (52.1% vs. NS, 7.3% or control rabbit IgG, 9.9%). In vivo, PAb delayed tumor growth and prolonged the lifespan of mice. Terminal deoxynucleotidyl transferase dUTP nick end labeling assay showed that PAb also induces statistically significant changes in apoptosis compared with other treatments (P<0.05). We therefore conclude that PAb could be used for the effective screening and identification of TAA. PAb may have certain anti-tumor functions in vitro and in vivo. As such, its combination with proteomic technologies could be a promising approach for sieving TAA for the diagnosis and therapy of MM.