The EMT transcription factor ZEB1 blocks osteoblastic differentiation in bone development and osteosarcoma.

Osteosarcoma is an often-fatal mesenchyme-derived malignancy in children and young adults. Overexpression of EMT-transcription factors (EMT-TFs) has been associated with poor clinical outcome. Here, we demonstrated that the EMT-TF ZEB1 is able to block osteoblastic differentiation in normal bone development as well as in osteosarcoma cells. Consequently, overexpression of ZEB1 in osteosarcoma characterizes poorly differentiated, highly metastatic subgroups and its depletion induces differentiation of osteosarcoma cells. Overexpression of ZEB1 in osteosarcoma is frequently associated with silencing of the imprinted DLK-DIO3 locus, which encodes for microRNAs targeting ZEB1. Epigenetic reactivation of this locus in osteosarcoma cells reduces ZEB1 expression, induces differentiation, and sensitizes to standard treatment, thus indicating therapeutic options for ZEB1-driven osteosarcomas. © 2021 The Authors. The Journal of Pathology published by John Wiley & Sons, Ltd. on behalf of The Pathological Society of Great Britain and Ireland.

Feasibility and Safety of Personalized, Multi-Target, Adoptive Cell Therapy (IMA101): First-in-Human Clinical Trial in Patients with Advanced Metastatic Cancer.

IMA101 is an actively personalized, multi-targeted adoptive cell therapy (ACT), whereby autologous T cells are directed against multiple novel defined peptide-HLA (pHLA) cancer targets. HLA-A*02:01-positive patients with relapsed/refractory solid tumors expressing ≥1 of 8 predefined targets underwent leukapheresis. Endogenous T cells specific for up to 4 targets were primed and expanded in vitro. Patients received lymphodepletion (fludarabine, cyclophosphamide), followed by T-cell infusion and low-dose IL2 (Cohort 1). Patients in Cohort 2 received atezolizumab for up to 1 year (NCT02876510). Overall, 214 patients were screened, 15 received lymphodepletion (13 women, 2 men; median age, 44 years), and 14 were treated with T-cell products. IMA101 treatment was feasible and well tolerated. The most common adverse events were cytokine release syndrome (Grade 1, n = 6; Grade 2, n = 4) and expected cytopenias. No patient died during the first 100 days after T-cell therapy. No neurotoxicity was observed. No objective responses were noted. Prolonged disease stabilization was noted in three patients lasting for 13.7, 12.9, and 7.3 months. High frequencies of target-specific T cells (up to 78.7% of CD8+ cells) were detected in the blood of treated patients, persisted for >1 year, and were detectable in posttreatment tumor tissue. Individual T-cell receptors (TCR) contained in T-cell products exhibited broad variation in TCR avidity, with the majority being low avidity. High-avidity TCRs were identified in some patients' products. This study demonstrates the feasibility and tolerability of an actively personalized ACT directed to multiple defined pHLA cancer targets. Results warrant further evaluation of multi-target ACT approaches using potent high-avidity TCRs. See related Spotlight by Uslu and June, p. 865.

Human mesenchymal stromal cells express CD14 cross-reactive epitopes.

Mesenchymal stromal cells (MSCs) do not express a unique definite epitope or marker gene. As such, minimal criteria were recently established for defining multipotent MSC. These criteria include expression of CD73, CD90, CD105, and a lack of hematopoietic marker expression. However, we detected binding of a CD14 antibody on bone marrow- and placenta-derived MSC and investigated the staining of CD14 antibodies on these MSC in more detail. The MSC were isolated from human bone marrow and placenta tissue, expanded, characterized by quantitative RT-PCR, flow cytometry, and immunocytochemistry and differentiated to generate osteoblasts, chondrocytes, and adipocytes. The CD14-cross-reactive MSCs were enriched by cell sorting. Human peripheral blood mononuclear cells, fibroblasts, and hematopoietic cell lines served as controls. Utilizing four different clones of CD14 monoclonal antibodies, we found that three CD14 reagents stained the MSC. Two CD14 antibodies (HCD14 and M5E2) clearly marked the CD90(+) MSC population with distinct intensities, clone 134 620 generated a shift in flow cytometry histograms, but clone MΦP9 did not stain MSC. Transcripts encoding CD14 or the CD14 protein were not detected in MSC. We confirm that bone marrow- and placenta-derived MSC do not express CD14 and that the CD14 antibody MΦP9 discriminates between monocytes and MSC more efficiently than the other antibodies employed here. This investigation does not contradict previous work but provides a more accurate characterization of MSC.

Human Placenta-Derived CD146-Positive Mesenchymal Stromal Cells Display a Distinct Osteogenic Differentiation Potential.

Mesenchymal stromal cells (MSCs) are multipotent cells that can be differentiated in vitro into a variety of cell types, including adipocytes or osteoblasts. Our recent studies indicated that a high expression of CD146 on MSCs from bone marrow correlates with their robust osteogenic differentiation potential. We therefore investigated if expression of CD146 on MSCs from the placenta correlates with a similar osteogenic differentiation potential. The MSCs were isolated specifically from the endometrial and fetal parts of human term placenta and expanded in separate cultures and compared with MSCs from bone marrow as controls. The expression of cell surface antigens was investigated by flow cytometry. Differentiation of MSCs was documented by cytochemistry and analysis of typical lineage marker genes. CD146-positive MSCs were separated from CD146-negative cells by magnet-assisted cell sorts (MACS). We report that the expression of CD146 is associated with a higher osteogenic differentiation potential in human placenta-derived MSCs (pMSCs) and the CD146(pos) pMSCs generated a mineralized extracellular matrix, whereas the CD146(neg) pMSCs failed to do so. In contrast, adipogenic and chondrogenic differentiation of pMSCs was not different in CD146(pos) compared with CD146(neg) pMSCs. Upon enrichment of pMSCs by MACS, the CD146(neg) and CD146(pos) populations maintained their expression levels for this antigen for several passages in vitro. We conclude that CD146(pos) pMSCs either respond to osteogenic stimuli more vividly or, alternatively, CD146(pos) pMSCs present a pMSC subset that is predetermined to differentiate into osteoblasts.

ZEB1-associated drug resistance in cancer cells is reversed by the class I HDAC inhibitor mocetinostat.

Therapy resistance is a major clinical problem in cancer medicine and crucial for disease relapse and progression. Therefore, the clinical need to overcome it, particularly for aggressive tumors such as pancreatic cancer, is very high. Aberrant activation of an epithelial-mesenchymal transition (EMT) and an associated cancer stem cell phenotype are considered a major cause of therapy resistance. Particularly, the EMT-activator ZEB1 was shown to confer stemness and resistance. We applied a systematic, stepwise strategy to interfere with ZEB1 function, aiming to overcome drug resistance. This led to the identification of both its target gene miR-203 as a major drug sensitizer and subsequently the class I HDAC inhibitor mocetinostat as epigenetic drug to interfere with ZEB1 function, restore miR-203 expression, repress stemness properties, and induce sensitivity against chemotherapy. Thereby, mocetinostat turned out to be more effective than other HDAC inhibitors, such as SAHA, indicating the relevance of the screening strategy. Our data encourage the application of mechanism-based combinations of selected epigenetic drugs with standard chemotherapy for the rational treatment of aggressive solid tumors, such as pancreatic cancer.

Human term placenta-derived mesenchymal stromal cells are less prone to osteogenic differentiation than bone marrow-derived mesenchymal stromal cells.

Mesenchymal stromal cells (MSC) can be isolated from different tissues. They are capable of differentiating in vitro, for example, to osteoblasts, chondrocytes, or adipocytes. In contrast to CD34 for hematopoietic stem cells, a distinct MSC-defining antibody is not available. Further, for hematopoietic cells lineage-defining antigens such as CD3 or CD20 are known. In contrast, for MSC-derived cells lineage-associated cell surface markers are far from being established. We therefore investigated expression of cell surface antigens on human term placenta-derived MSC (pMSC) in more detail and correlated expression pattern to the osteogenic differentiation capacity of the MSC. We report that pMSC expressed the typical cell surface antigens at levels comparable to bone marrow-derived MSC (bmMSC), including CD73, CD90, and CD105, but did not express CD11b, CD34, and CD45. Further, CD164, TNAP, and the W5C5 antigens were detected on pMSC, whereas CD349 was not observed. Some pMSC expressed CD146 at low or moderate levels, and their osteogenic differentiation potential was weak. In contrast, bmMSC expressed CD146 at high levels, expression of alkaline phosphatase was significantly higher, and they presented a pronounced osteogenic differentiation potential. We conclude that MSC from different sources differ in their expression of distinct markers, and that this may correlate in part with their lineage determination. Thus, a higher percentage of bmMSC expressed CD146 at prominent levels and such cells may be better suited for bone repair. In contrast, many pMSC expressed CD146 at low or moderate levels. They, therefore, may be suitable for applications in which osteogenic differentiation is undesirable.