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The treatment landscape in multiple myeloma (MM) is shifting from genotoxic drugs to immunotherapies. Monoclonal antibodies, immunoconjugates, T-cell engaging antibodies and CART cells have been incorporated into routine treatment algorithms, resulting in improved response rates. Nevertheless, patients continue to relapse and the underlying mechanisms of resistance remain poorly understood. While Impaired death receptor signaling has been reported to mediate resistance to CART in acute lymphoblastic leukemia, this mechanism yet remains to be elucidated in context of novel immunotherapies for MM. Here, we describe impaired death receptor signaling as a novel mechanism of resistance to T-cell mediated immunotherapies in MM. This resistance seems exclusive to novel immunotherapies while sensitivity to conventional anti-tumor therapies being preserved in vitro. As a proof of concept, we present a confirmatory clinical case indicating that the FADD/BID axis is required for meaningful responses to novel immunotherapies thus we report impaired death receptor signaling as a novel resistance mechanism to T-cell mediated immunotherapy in MM.
Background
While multiple in vitro studies examined mesenchymal stromal cells (MSCs) derived from bone marrow or hyaline cartilage, there is little to no data about the presence of MSCs in the joint capsule or the ligamentum capitis femoris (LCF) of the hip joint. Therefore, this in vitro study examined the presence and differentiation potential of MSCs isolated from the bone marrow, arthritic hyaline cartilage, the LCF and full-thickness samples of the anterior joint capsule of the hip joint.
Methods
MSCs were isolated and multiplied in adherent monolayer cell cultures. Osteogenesis and adipogenesis were induced in monolayer cell cultures for 21 days using a differentiation medium containing specific growth factors, while chondrogenesis in the presence of TGF-ss1 was performed using pellet-culture for 27 days. Control cultures were maintained for comparison over the same duration of time. The differentiation process was analyzed using histological and immunohistochemical stainings as well as semiquantitative RT-PCR for measuring the mean expression levels of tissue-specific genes.
Results
This in vitro research showed that the isolated cells from all four donor tissues grew plastic-adherent and showed similar adipogenic and osteogenic differentiation capacity as proven by the histological detection of lipid droplets or deposits of extracellular calcium and collagen type I. After 27 days of chondrogenesis proteoglycans accumulated in the differentiated MSC-pellets from all donor tissues. Immunohistochemical staining revealed vast amounts of collagen type II in all differentiated MSC-pellets, except for those from the LCF. Interestingly, all differentiated MSCs still showed a clear increase in mean expression of adipogenic, osteogenic and chondrogenic marker genes. In addition, the examination of an exemplary selected donor sample revealed that cells from all four donor tissues were clearly positive for the surface markers CD44, CD73, CD90 and CD105 by flow cytometric analysis.
Conclusions
This study proved the presence of MSC-like cells in all four examined donor tissues of the hip joint. No significant differences were observed during osteogenic or adipogenic differentiation depending on the source of MSCs used. Further research is necessary to fully determine the tripotent differentiation potential of cells isolated from the LCF and capsule tissue of the hip joint.
Utilizing 18F-fluorodeoxyglucose (18F-FDG) positron emission tomography (PET)/computed tomography (CT), we performed this pilot study to evaluate the link between cytogenetic/genomic markers and imaging patterns in relapsed/refractory (RR) multiple myeloma (MM). We retrospectively analyzed data of 24 patients with RRMM who were treated at our institution between November 2018 and February 2020. At the last relapse/progression, patients had been treated with a median of three (range 1–10) lines of therapy. Six (25%) patients showed FDG avid extramedullary disease without adjacency to bone. We observed significantly higher maximum standardized uptake values (SUV\(_{max}\)) in patients harboring del(17p) compared with those without del(17p) (p = 0.025). Moreover, a high SUV\(_{max}\) of >15 indicated significantly shortened progression-free survival (PFS) (p = 0.01) and overall survival (OS) (p = 0.0002). One female patient exhibited biallelic TP53 alteration, i.e., deletion and mutation, in whom an extremely high SUV\(_{max}\) of 37.88 was observed. In summary, this pilot study suggested a link between del(17p)/TP53 alteration and high SUV\(_{max}\) on 18F-FDG PET/CT in RRMM patients. Further investigations are highly warranted at this point.