Expression of the chemokine receptor CCR1 promotes the dissemination of multiple myeloma plasma cells in vivo

Multiple myeloma (MM) disease progression is dependent on the ability of MM plasma cells (PC) to egress from the bone marrow (BM), enter the circulation and disseminate to distal BM sites. Expression of the chemokine CXCL12 by BM stromal cells is crucial for MM PC retention within the BM. However, the mechanisms which overcome CXCL12-mediated retention to enable dissemination are poorly understood. We have previously identified that treatment with the CCR1 ligand CCL3 inhibits the response to CXCL12 in MM cell lines, suggesting that CCL3/CCR1 signaling may enable egress of MM PC from the BM. Here, we demonstrated that CCR1 expression was an independent prognostic indicator in newly diagnosed MM patients. Furthermore, we showed that CCR1 is a crucial driver of dissemination in vivo, with CCR1 expression in the murine MM cell line 5TGM1 being associated with an increased incidence of bone and splenic disseminated tumors in C57BL/KaLwRij mice. Furthermore, we demonstrated that CCR1 knockout in the human myeloma cell line OPM2 resulted in a >95% reduction in circulating MM PC numbers and BM and splenic tumor dissemination following intratibial injection in NSG mice. Therapeutic targeting of CCR1 with the inhibitor CCX9588 significantly reduced OPM2 or RPMI-8226 dissemination in intratibial xenograft models. Collectively, our findings suggest a novel role for CCR1 as a critical driver of BM egress of MM PC during tumor dissemination. Furthermore, these data suggest that CCR1 may represent a potential therapeutic target for the prevention of MM tumor dissemination.Mara N. Zeissig, Duncan R. Hewett, Vasilios Panagopoulos, Krzysztof M. Mrozik, L. Bik To, Peter I. Croucher, Andrew C.W. Zannettino, and Kate Vandyk

Targeted disruption of bone marrow stromal cell-derived Gremlin1 limits multiple myeloma disease progression in vivo

In most instances, multiple myeloma (MM) plasma cells (PCs) are reliant on factors made by cells of the bone marrow (BM) stroma for their survival and growth. To date, the nature and cellular composition of the BM tumor microenvironment and the critical factors which drive tumor progression remain imprecisely defined. Our studies show that Gremlin1 (Grem1), a highly conserved protein, which is abundantly secreted by a subset of BM mesenchymal stromal cells, plays a critical role in MM disease development. Analysis of human and mouse BM stromal samples by quantitative PCR showed that GREM1/Grem1 expression was significantly higher in the MM tumor-bearing cohorts compared to healthy controls (p < 0.05, Mann-Whitney test). Additionally, BM-stromal cells cultured with 5TGM1 MM PC line expressed significantly higher levels of Grem1, compared to stromal cells alone (p < 0.01, t-test), suggesting that MM PCs promote increased Grem1 expression in stromal cells. Furthermore, the proliferation of 5TGM1 MM PCs was found to be significantly increased when co-cultured with Grem1-overexpressing stromal cells (p < 0.01, t-test). To examine the role of Grem1 in MM disease in vivo, we utilized the 5TGM1/KaLwRij mouse model of MM. Our studies showed that, compared to immunoglobulin G (IgG) control antibody-treated mice, mice treated with an anti-Grem1 neutralizing antibody had a decrease in MM tumor burden of up to 81.2% (p < 0.05, two-way ANOVA). The studies presented here demonstrate, for the first time, a novel positive feedback loop between MM PCs and BM stroma, and that inhibiting this vicious cycle with a neutralizing antibody can dramatically reduce tumor burden in a preclinical mouse model of MM.Kimberley C. Clark, Duncan R. Hewett, Vasilios Panagopoulos, Natalya Plakhova, Khatora S. Opperman, Alanah L. Bradey, Krzysztof M. Mrozik, Kate Vandyke, Siddhartha Mukherjee, Gareth C.G. Davies, Daniel L. Worthley, and Andrew C.W. Zannettin

Mesenchymal stromal cell senescence in haematological malignancies

OnlinePublAcute myeloid leukaemia (AML), chronic lymphocytic leukaemia (CLL), and multiple myeloma (MM) are age-related haematological malignancies with defned precursor states termed myelodysplastic syndrome (MDS), monoclonal B-cell lymphocytosis (MBL), and monoclonal gammopathy of undetermined signifcance (MGUS), respectively. While the progression from asymptomatic precursor states to malignancy is widely considered to be mediated by the accumulation of genetic mutations in neoplastic haematopoietic cell clones, recent studies suggest that intrinsic genetic changes, alone, may be insuffcient to drive the progression to overt malignancy. Notably, studies suggest that extrinsic, microenvironmental changes in the bone marrow (BM) may also promote the transition from these precursor states to active disease. There is now enhanced focus on extrinsic, age-related changes in the BM microenvironment that accompany the development of AML, CLL, and MM. One of the most prominent changes associated with ageing is the accumulation of senescent mesenchymal stromal cells within tissues and organs. In comparison with proliferating cells, senescent cells display an altered profle of secreted factors (secretome), termed the senescence-associated-secretory phenotype (SASP), comprising proteases, infammatory cytokines, and growth factors that may render the local microenvironment favourable for cancer growth. It is well established that BM mesenchymal stromal cells (BM-MSCs) are key regulators of haematopoietic stem cell maintenance and fate determination. Moreover, there is emerging evidence that BM-MSC senescence may contribute to age-related haematopoietic decline and cancer development. This review explores the association between BM-MSC senescence and the development of haematological malignancies, and the functional role of senescent BM-MSCs in the development of these cancers.Natalya Plakhova, Vasilios Panagopoulos, Kate Vandyke, Andrew C. W. Zannettino, Krzysztof M. Mrozi

Muscles of the neck, and boundaries of the triangles

Engraved by Butterworth and Heath from a drawing by H.V. Carter.Anatomical diagram of the muscles of the neck, lateral view.Title from caption

Sympathetic nerve

Engraved by Butterworth and Heath from a drawing by H.V. Carter.Anatomical diagram of the sympathetic nervous system shown in a cross-section of the head and torso.Title from caption

Muscles of the chest and front of the arm, superficial view

Engraved by Butterworth and Heath from a drawing by H.V. Carter.Anatomical diagram of the muscles of the chest, shoulder, and upper arm, anterior view.Title from caption

Muscles of the back, deep layers

Engraved by Butterworth and Heath from a drawing by H.V. Carter.Anatomical diagram of the back muscles, posterior view.Title from caption

Bones of the right foot, plantar surface

Engraved by Butterworth and Heath from a drawing by H.V. Carter.Anatomical diagram of the bones of the right foot, plantar surface.Title from caption

Posterior surface of fore-arm, superficial muscles

Engraved by Butterworth and Heath from a drawing by H.V. Carter.Anatomical diagram of the muscles of the forearm, anterior view.Title from caption