Previous studies have demonstrated that mesenchymal stem cells from multiple myeloma (MM) patients (MM-hMSCs) display a distinctive gene expression profile, an enhanced production of cytokines and an impaired osteogenic differentiation ability compared to normal donors (ND-hMSCs). However, the underlying molecular mechanisms are unclear. In the present study, we observed that MM-hMSCs exhibited an abnormal upregulation of miR-135b, showing meanwhile an impaired osteogenic differentiation and a decrease of SMAD5 expression, which is the target of miR-135b involved in osteogenesis. By gain and loss of function studies we confirmed that miR-135b negatively regulated hMSCs osteogenesis. We also found that MM cell-produced factors stimulated ND-hMSCs to upregulate the expression of miR-135b. Importantly, treatment with a miR-135b inhibitor promoted osteogenic differentiation in MM-hMSCs. Finally, we observed that MM cell-derived soluble factors could induce an upregulation of miR-135b expression in ND-hMSCs in an indirect coculture system and the miR-135b expression turned to normal level after the removal of MM cells. Collectively, we provide evidence that miR-135b is involved in the impaired osteogenic differentiation of MSCs derived from MM patients and might therefore be a promising target for controlling bone disease.
Radioimmunotherapy (RIT) is a cancer treatment that combines radiation therapy with tumor-directed monoclonal antibodies (Abs). Although RIT had been introduced for the treatment of CD20 positive non-Hodgkin lymphoma decades ago, it never found a broad clinical application. In recent years, researchers have developed theranostic agents based on Ab fragments or small Ab mimetics such as peptides, affibodies or single-chain Abs with improved tumor-targeting capacities. Theranostics combine diagnostic and therapeutic capabilities into a single pharmaceutical agent; this dual application can be easily achieved after conjugation to radionuclides. The past decade has seen a trend to increased specificity, fastened pharmacokinetics, and personalized medicine. In this review, we discuss the different strategies introduced for the noninvasive detection and treatment of hematological malignancies by radiopharmaceuticals. We also discuss the future applications of these radiotheranostic agents.
Hypersialylation of cancer cells induces an immunosuppressive microenvironment. The binding of sialic acid by siglec receptors expressed on immune cells initiates a downstream response via immunoreceptor tyrosine-based inhibitory motif (ITIM) signalling. Cancer associated fibroblasts (CAFs) in the colorectal cancer (CRC) microenvironment are highly immunosuppressive and associated with poor survival. The role of sialyation in stromal cell-mediated immunosuppression, however, is unknown. Here, we investigated if sialylation of CAFs contributed to their potent immunosuppressive properties.
Methods
Tumour cell secretome (TCS) from multiple CRC cell lines was used to condition primary human and mouse bone marrow-derived stromal cells, as CAF precursors. Normal and CAFs were isolated from colon tumour resections. Stromal cells were cultured with stimulated splenocytes (mouse) or PBMCs (human) and their immunosuppressive properties were assessed by flow cytometry. An in vivo mouse model of CT26 CRC was used to assess the role of highly sialylated stromal cells in tumour development. Mice were injected subcutaneously with CT26 cells alone, or co-injected with TCS-conditioned stromal cells, either control or de-sialylated. 14 days post induction, tumous, draining lymph nodes and spleen were assessed for frequency and expression of T cell activation markers.
Results
Tumour conditioning resulted in significantly higher expression of both α2,6-linked sialic acid and specific Siglec ligands on stromal cells. CAFs were significantly more sialylated than stromal cells isolated from adjacent normal associated tissue (NAFs) (figure 1). Following co-culture, CAFs induced significantly higher levels of CD8+ T cells with an exhausted phenotype as determined by TIM-3 and PD-1 expression. Siglec-7 and -9 receptors were induced by CAFs on CD8 T cells. Furthermore, de-sialylation of CAFs, specifically, prior to co-culture resulted in a significant reduction in exhausted CD8+ T cells and attenuation of their immunosuppressive ability (figure 2). 14d post tumour induction in vivo, mice with TCS-conditioned, stromal-dense tumours had significantly fewer activated CD4+ and CD8+ CD25-expressing T cells, both intra-tumourally and distally in the draining lymph nodes and spleen. They also had low levels of cytotoxic granzyme B-expressing CD8+ T cells. Interestingly, this suppression was sialylation-dependent. De-sialylation of TCS-conditioned stromal cells led to restoration of activated T cell levels in tumours and peripheral lymphoid tissues, as well as a marked increase in cytotoxic T cells (figure 3).
Conclusions
These results demonstrate, for the first time, that tumour stromal cells suppress activated T cells through sialic acid dependent interactions. We show that targeting stromal cell sialylation may represent a novel immune checkpoint to reactivate anti-tumour immunity.
Ethics Approval
The animal study was approved by the Animals Care Research Ethics Committee of the National University of Ireland, Galway (NUIG) and conducted under individual and project authorisation licenses from the Health Products Regulatory Authority (HPRA) of Ireland (AE19125/P077). The study using human samples was approved by University Hospital Galway Ethics committee under an ethically approved protocol (Clinical Research Ethics Committee, Ref: C.A. 2074).
Abstract Diffuse large B cell lymphoma (DLBCL) and mantle cell lymphoma (MCL) are among the most aggressive B cell non-Hodgkin lymphomas. Maternal embryonic leucine zipper kinase (MELK) plays a role in cancer cell cycle progression and is associated with poor prognosis in several cancer cell types. In this study, the role of MELK in DLBCL and MCL and the therapeutic potential of MELK targeting is evaluated. MELK is highly expressed in DLBCL and MCL patient samples, correlating with a worse clinical outcome in DLBCL. Targeting MELK, using the small molecule OTSSP167, impaired cell growth and survival and induced caspase-mediated apoptosis in the lymphoma cells. Western blot analysis revealed that MELK targeting decreased the phosphorylation of FOXM1 and the protein levels of EZH2 and several mitotic regulators, such as Cdc25B, cyclin B1, Plk-1, and Aurora kinases. In addition, OTSSP167 also sensitized the lymphoma cells to the clinically relevant Bcl-2 inhibitor venetoclax by strongly reducing Mcl1 levels. Finally, OTSSP167 treatment of A20-inoculated mice resulted in a significant prolonged survival. In conclusion, targeting MELK with OTSSP167 induced strong anti-lymphoma activity both in vitro and in vivo. These findings suggest that MELK could be a potential new target in these aggressive B cell malignancies.
Abstract Immuno‐oncology has been at the forefront of cancer treatment in recent decades. In particular immune checkpoint and chimeric antigen receptor (CAR)‐T cell therapy have achieved spectacular results. Over the years, CAR‐T cell development has followed a steady evolutionary path, focusing on increasing T cell potency and sustainability, which has given rise to different CAR generations. However, there was less focus on the mode of interaction between the CAR‐T cell and the cancer cell; more specifically on the targeting moiety used in the CAR and its specific properties. Recently, the importance of optimizing this domain has been recognized and the possibilities have been exploited. Over the last 10 years—in addition to the classical scFv‐based CARs—single domain CARs, natural receptor‐ligand CARs, universal CARs and CARs targeting more than one antigen have emerged. In addition, the specific parameters of the targeting domain and their influence on T cell activation are being examined. In this review, we concisely present the history of CAR‐T cell therapy, and then expand on various developments in the CAR ectodomain. We discuss different formats, each with their own advantages and disadvantages, as well as the developments in affinity tuning, avidity effects, epitope location, and influence of the extracellular spacer.
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