Myelomagenesis: capturing early microenvironment changes

Assessing the frequency of CD163+ tumor-associated macrophages and CD3+ T lymphocytes between MGUS and plasma cell myeloma

Plasma cell dyscrasias (PCDs) are a heterogeneous group of diseases, and the most common is monoclonal gammopathy of undetermined significance (MGUS). This premalignant PCD consistently precedes multiple myeloma (MM), with a 1% risk of progression per year. Evading and suppressing the host immune system is an important step in the progression of MGUS to MM. This pilot study was designed to assess whether MGUS and MM have a distinct microenvironment, characterized by a unique distribution of immune cells, including tumor-associated macrophages. Evaluation of bone marrow (BM) tumor microenvironment was performed using immunohistochemical quantification of T cells (CD3), macrophages (CD68), and a macrophage subtype (CD163). The findings were compared between MGUS and MM to determine whether differences existed. The results suggest that there is a significantly lower percentage of CD3-positive, CD68-positive and CD163-positive immune effector cells in BM trephine biopsy samples from patients with MGUS than in those from patients with untreated MM (p < 0.001). Interestingly, in a patient treated for MM, the percentages of CD3+ and CD68+ cells were the same as those in other patients with untreated MM; however, the percentage of CD163+ cells reduced and correlated with low plasma cell count. Future studies are required to investigate whether the percentage of CD163+ cells is correlated with disease burden in patients with MM. If this is the case, then the level of soluble CD163 in plasma could be a potential biomarker of disease burden in patients with nonsecretory myelomas, in whom measurements of levels of paraprotein and free light chains are inconclusive.

Anti-Cancer Activity of Curcumin on Multiple Myeloma

Multiple Myeloma (MM) is the third most common and deadly hematological malignancy, which is characterized by a progressive monoclonal proliferation within the bone marrow. MM is cytogenetically heterogeneous with numerous genetic and epigenetic alterations, which lead to a wide spectrum of signaling pathways and cell cycle checkpoint aberrations. MM symptoms can be attributed to CRAB features (hyperCalcemia, Renal failure, Anemia, and Bone lesion), which profoundly affect both the Health-Related Quality of Life (HRQoL) and the life expectancy of patients. Despite all enhancement and improvement in therapeutic strategies, MM is almost incurable, and patients suffering from this disease eventually relapse. Curcumin is an active and non-toxic phenolic compound, isolated from the rhizome of Curcuma longa L. It has been widely studied and has a confirmed broad range of therapeutic properties, especially anti-cancer activity, and others, including anti-proliferation, anti-angiogenesis, antioxidant and anti-mutation activities. Curcumin induces apoptosis in cancerous cells and prevents Multidrug Resistance (MDR). Growing evidence concerning the therapeutic properties of curcumin caused a pharmacological impact on MM. It is confirmed that curcumin interferes with various signaling pathways and cell cycle checkpoints, and with oncogenes. In this paper, we summarized the anti- MM effects of curcumin.

BTK induces CAM-DR through regulation of CXCR4 degradation in multiple myeloma

Cellular adhesion-mediated drug resistance (CAM-DR) occurs frequently in patients with relapsed or refractory multiple myeloma (MM). Elucidating the mechanism underlying CAM-DR and developing the corresponding treatment may prove to be promising for the clinical management of MM. Bruton's tyrosine kinase (BTK) has been attracting attention in relation to MM progression and drug resistance. BTK was reported to be associated with cell surface CXCR4, a classic cell adhesion molecule and homing factor. However, the exact association between BTK and CAM-DR in MM remains elusive. In this study, we demonstrated that promoting BTK expression induced MM cell adherence to the extracellular matrix (ECM) and stromal cells in vitro and in vivo, and that CAM-DR could be reversed by separating MM cells from ECM or stromal cells. Enhancing BTK expression levels increased CXCR4 expression in MM cells. In addition, BTK may bind directly with CXCR4 and prevent its ubiquitination-induced degradation. Finally, a BTK inhibitor exerted synergistic therapeutic effects with bortezomib in a 5TMM3VT MM mouse model. These findings revealed a novel role of BTK in CAM-DR and may provide a promising approach to MM treatment.

Classification of Solitary Plasmacytoma, Is it more Intricate than Presently Suggested? A Commentary

A query regarding the definition and the classification of solitary plasmacytoma is apparently still pending. The clinical course, the response to treatment and the propensity to progress to plasma cell myeloma, are all a function of the classification which must be established on a firm basis. Solitary plasmacytoma should be recognized in the continuum of the plasma cell neoplasms. Moreover, whether the solitary plasmacytoma of bone and the extramedullary type of the tumor represent two distinct disease entities, exhibiting separate biological characteristics, has not been finally established. To appraise the similarities and differences between these two types of lesion, we have scrutinized recent investigations relating their classification. A commentary highlighting our conclusions follows.

CXCL12 and CXCR7 are relevant targets to reverse cell adhesion-mediated drug resistance in multiple myeloma

Cell adhesion-mediated drug resistance (CAM-DR) by the bone marrow (BM) is fundamental to multiple myeloma (MM) propagation and survival. Targeting BM protection to increase the efficacy of current anti-myeloma treatment has not been extensively pursued. To extend the understanding of CAM-DR, we hypothesized that the cytotoxic effects of novel anti-myeloma agents may be abrogated by the presence of BM stroma cells (BMSCs) and restored by addition of the CXCL12 antagonist NOX-A12 or the CXCR4 inhibitor plerixafor. Following this hypothesis, we evaluated different anti-myeloma agents alone, with BMSCs and when combined with plerixafor or NOX-A12. We verified CXCR4, CD49d (also termed ITGA4) and CD44 as essential mediators of BM adhesion on MM cells. Additionally, we show that CXCR7, the second receptor of stromal-derived-factor-1 (CXCL12), is highly expressed in active MM. Co-culture proved that co-treatment with plerixafor or NOX-A12, the latter inhibiting CXCR4 and CXCR7, functionally interfered with MM chemotaxis to the BM. This led to the resensitization of MM cells to the anti-myeloma agents vorinostat and pomalidomide and both proteasome inhibitors bortezomib and carfilzomib. Within a multicentre phase I/II study, NOX-A12 was tested in combination with bortezomib-dexamethasone, underlining the feasibility of NOX-A12 as an active add-on agent to antagonize myeloma CAM-DR.