Explore the vast range of titles available.

Background Mesenchymal stem cells (MSCs) activate the endogenous immune regulatory system, inducing a therapeutic effect in recipients. MSCs have demonstrated the ability to modulate the differentiation of myeloid cells toward a phagocytic and anti-inflammatory profile. Allogeneic, adipose-derived MSCs (ASCs) have been investigated for the management of complex perianal fistula, with darvadstrocel being the first ASC therapy approved in Europe in March 2018. Additionally, ASCs are being explored as a potential treatment in other indications. Yet, despite these clinical advances, their mechanism of action is only partially understood. Methods Freshly isolated human monocytes from the peripheral blood were differentiated in vitro toward M0 non-polarized macrophages (Mphs), M1 pro-inflammatory Mphs, M2 anti-inflammatory Mphs, or mature dendritic cells (mDCs) in the presence or absence of ASCs, in non-contact conditions. The phenotype and function of the differentiated myeloid populations were determined by flow cytometry, and their secretome was analyzed by OLINK technology. We also investigated the capacity of ASCs to modulate the phenotype and function of terminally differentiated M1 Mphs. The role of soluble factors interleukin (IL)-6 and prostaglandin E2 (PGE2) on the ability of ASCs to modulate myeloid cells was assessed using neutralization assays, CRISPR/Cas9 knock-down of cyclooxygenase 2 (COX-2), and ASC-conditioned medium assays using pro-inflammatory stimulus. Results Co-culture of monocytes in the presence of ASCs resulted in the polarization of Mphs and mDCs toward an anti-inflammatory and phagocytic phenotype. This was characterized by an increase in phagocytic receptors on the cell surface of Mphs (M0, M1, and M2) and mDCs, as well as modulation of chemokine receptors and reduced expression of pro-inflammatory, co-stimulatory molecules. ASCs also modulated the secretome of Mphs and mDCs, demonstrated by reduced expression of pro-inflammatory factors and increased expression of anti-inflammatory and reparative factors. Chemical inhibition of PGE2 with indomethacin abolished this modulatory effect, whereas treatment with a neutralizing anti-IL-6 antibody resulted in a partial abolishment. The knock-down of COX-2 in ASCs and the use of IL-1β-activated ASC-conditioned media confirmed the key role of PGE2 in ASC-mediated myeloid modulation. In our in vitro experimental settings, ASCs failed to modulate the phenotype and function of terminally polarized M1 Mphs. Conclusions The results demonstrate that ASCs are able to modulate the in vitro differentiation of myeloid cells toward an anti-inflammatory and reparative profile. This modulatory effect was mediated mainly by PGE2 and, to a lesser extent, IL-6.

Emerging evidence points to aberrant regulation of translation as a driver of cell transformation in cancer. Given the direct control of translation by tRNA modifications, tRNA modifying enzymes may function as regulators of cancer progression. Here, we show that a tRNA methyltransferase 9‐like ( hTRM9L/KIAA1456 ) mRNA is down‐regulated in breast, bladder, colorectal, cervix and testicular carcinomas. In the aggressive SW620 and HCT116 colon carcinoma cell lines, hTRM9L is silenced and its re‐expression and methyltransferase activity dramatically suppressed tumour growth in vivo . This growth inhibition was linked to decreased proliferation, senescence‐like G0/G1‐arrest and up‐regulation of the RB interacting protein LIN9. Additionally, SW620 cells re‐expressing hTRM9L did not respond to hypoxia via HIF1‐α‐dependent induction of GLUT1. Importantly, hTRM9L ‐negative tumours were highly sensitive to aminoglycoside antibiotics and this was associated with altered tRNA modification levels compared to antibiotic resistant hTRM9L ‐expressing SW620 cells. Our study links hTRM9L and tRNA modifications to inhibition of tumour growth via LIN9 and HIF1‐α‐dependent mechanisms. It also suggests that aminoglycoside antibiotics may be useful to treat hTRM9L‐deficient tumours. Graphical Abstract The human tRNA methyltransferase 9‐like (hTRM9L) gene is turned off in many cancers and hTRM9‐ deficient cells are susceptible to killing by aminoglycoside antibiotics, suggesting that these drugs could be re‐purposed to treat late stage cancers.

Two related papers show that cells disseminated from malignant lesions at early time points during tumorigenesis can contribute to metastases at distant organs and provide insights into the molecular basis of dissemination. A potential mechanism for metastases The origin of metastases in cancer remains an open question. In a pair of linked papers, Christoph Klein, Julio Aguirre-Ghiso and colleagues now show in mouse models that cells disseminated from tumours early in tumorigenesis can contribute to metastases at distant organs at such early time points. Both papers also provide insights into the molecular basis of dissemination, which may be useful as targets to prevent metastasis. Metastasis is the leading cause of cancer-related deaths; metastatic lesions develop from disseminated cancer cells (DCCs) that can remain dormant 1 . Metastasis-initiating cells are thought to originate from a subpopulation present in progressed, invasive tumours 2 . However, DCCs detected in patients before the manifestation of breast-cancer metastasis contain fewer genetic abnormalities than primary tumours or than DCCs from patients with metastases 3 , 4 , 5 . These findings, and those in pancreatic cancer 6 and melanoma 7 models, indicate that dissemination might occur during the early stages of tumour evolution 3 , 8 , 9 . However, the mechanisms that might allow early disseminated cancer cells (eDCCs) to complete all steps of metastasis are unknown 8 . Here we show that, in early lesions in mice and before any apparent primary tumour masses are detected, there is a sub-population of Her2 + p-p38 lo p-Atf2 lo Twist1 hi E-cad lo early cancer cells that is invasive and can spread to target organs. Intra-vital imaging and organoid studies of early lesions showed that Her2 + eDCC precursors invaded locally, intravasated and lodged in target organs. Her2 + eDCCs activated a Wnt-dependent epithelial–mesenchymal transition (EMT)-like dissemination program but without complete loss of the epithelial phenotype, which was reversed by Her2 or Wnt inhibition. Notably, although the majority of eDCCs were Twist1 hi E-cad lo and dormant, they eventually initiated metastasis. Our work identifies a mechanism for early dissemination in which Her2 aberrantly activates a program similar to mammary ductal branching that generates eDCCs that are capable of forming metastasis after a dormancy phase.

Breast cancers can recur after removal of the primary tumor and treatment to eliminate remaining tumor cells. Recurrence may occur after long periods of time during which there are no clinical symptoms. Tumor cell dormancy may explain these prolonged periods of asymptomatic residual disease and treatment resistance. We generated a dormancy gene signature from published experimental models and applied it to both breast cancer cell line expression data as well as four published clinical studies of primary breast cancers. We found that estrogen receptor (ER) positive breast cell lines and primary tumors have significantly higher dormancy signature scores (P<0.0000001) than ER- cell lines and tumors. In addition, a stratified analysis combining all ER+ tumors in four studies indicated 2.1 times higher hazard of recurrence among patients whose tumors had low dormancy scores (LDS) compared to those whose tumors had high dormancy scores (HDS) (p<0.000005). The trend was shown in all four individual studies. Suppression of two dormancy genes, BHLHE41 and NR2F1, resulted in increased in vivo growth of ER positive MCF7 cells. The patient data analysis suggests that disseminated ER positive tumor cells carrying a dormancy signature are more likely to undergo prolonged dormancy before resuming metastatic growth. Furthermore, genes identified with this approach might provide insight into the mechanisms of dormancy onset and maintenance as well as dormancy models using human breast cancer cell lines.

Background The production of human mesenchymal stromal cells (hMSC) for therapeutic use requires scalable, efficient and standardized manufacturing processes that could further benefit from shortening manufacturing time, automate and simplify operations with closed systems. This study aimed to develop an industry-ready process for the expansion and integrated downstream processing of human adipose tissue-derived MSC (ASC) using xeno-free medium and microcarriers in stirred-tank bioreactors. The proposed workflow provides controlled culture conditions and is compatible with closed and large-scale cell production. Methods ASC were directly inoculated after thawing in stirred-tank bioreactors without the need for a seed train. Microcarrier type (Plastic vs. Synthemax II-coated) in combination with xeno-free medium and stirring profile during cell attachment (intermittent vs. continuous) were optimized in 0.2 L bioreactors and subsequently scaled-up to 2 L bioreactors using power input per volume as scale-up criteria. Focusing on further process scale-up, two strategies were evaluated: (1) bead-to-bead transfer, enabling cell migration from colonized to fresh microcarriers, and (2) enzymatic detachment followed by re-inoculation as single cells. A closed downstream process, using counterflow centrifugation was integrated as an alternative to conventional open centrifugation. Results Synthemax II-coated microcarriers supported efficient cell attachment without a seed train, even under continuous stirring. Two strategies were deemed feasible for process scale-up (cell migration via bead-to-bead transfer and cell detachment and re-attachment to microcarriers as single cells) in stirred-tank bioreactors. Counterflow centrifugation achieved cell recovery yields comparable to standard centrifugation (67% vs. 75%, respectively). High cell viability (> 96%), expression of MSC characteristic surface markers (> 95%) and immunomodulatory function were preserved. Conclusions This work presents a fully integrated and scalable ASC manufacturing platform from inoculation to harvest, without requiring seed train. The process supports an efficient (up to 4-5 × 10 5 cell/mL) and robust cell expansion (regardless of donor variability, similar cells yields are obtained), enables closed downstream processing (integrating filtration and counterflow centrifugation), and shortens overall production timelines. This approach achieves a volumetric productivity, after microcarrier filtration and counterflow centrifugation, of approximately 3–4 × 10 8 cell/ L, corresponding to cell numbers that could support early-phase clinical trials. Additionally, glucose and lactate concentrations directly correlate with cell density, allowing these metabolites to be used as predictive parameters for defining harvesting day. These findings contribute to the development of a clinically- and industrially-relevant bioprocess for large-scale MSC production.

Adipose mesenchymal stem cells (ASC) are considered minimally immunogenic. This is due to the low expression of human leukocyte antigens I (HLA-I), lack of HLA-II expression and low expression of co-stimulatory molecules such as CD40 and CD80. The low rate of observed immunological rejection as well as the immunomodulatory qualities, position ASC as a promising cell-based therapy for the treatment of a variety of inflammatory indications. Yet, few studies have addressed relevant aspects of immunogenicity such as ASC donor-to-patient HLA histocompatibility or assessment of immune response triggered by ASC administration, particularly in the cases of presensitization. The present study aims to assess allo-immune responses in a cohort of Crohn's disease patients administered with allogeneic ASC (darvadstrocel formerly Cx601) for the treatment of complex perianal fistulas. We identified donor-specific antibodies (DSA) generation in a proportion of patients and observed that patients showing preexisting immunity were prone to generating DSA after allogeneic therapy. Noteworthy, naïve patients generating DSA at week 12 (W12) showed a significant reduction in DSA titer at week 52 (W52), whereas DSA titer was reduced in pre-sensitized patients only with no specificities against the donor administered. Remarkably, we did not observe any correlation of DSA generation with ASC therapeutic efficacy. complement-dependent cytotoxicity (CDC) studies have revealed limited cytotoxic levels based upon HLA-I expression and binding capacity even in pro-inflammatory conditions. We sought to identify CDC coping mechanisms contributing to the limited cytotoxic killing observed in ASC . We found that ASC express membrane-bound complement regulatory proteins (mCRPs) CD55, CD46, and CD59 at basal levels, with CD46 more actively expressed in pro-inflammatory conditions. We demonstrated that CD46 is a main driver of CDC signaling; its depletion significantly enhances sensitivity of ASC to CDC. In summary, despite relatively high clearance, DSA generation may represent a major challenge for allogeneic cell therapy management. Sensitization may be a significant concern when evaluating re-treatment or multi-donor trials. It is still unknown whether DSA generation could potentially be the consequence of donor-to-patient interaction and, therefore, subsequently link to efficacy or biological activity. Lastly, we propose that CDC modulators such as CD46 could be used to ultimately link CDC specificity with allogeneic cell therapy efficacy.

Head and neck squamous carcinoma (HNSCC) tumors carry dismal long-term prognosis and the role of tumor initiating cells (TICs) in this cancer is unclear. We investigated in HNSCC xenografts whether specific tumor subpopulations contributed to tumor growth. We used a CFSE-based label retentions assay, CD49f (α6-integrin) surface levels and aldehyde dehydrogenase (ALDH) activity to profile HNSCC subpopulations. The tumorigenic potential of marker-positive and -negative subpopulations was tested in nude (Balb/c nu/nu) and NSG (NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl)/SzJ) mice and chicken embryo chorioallantoic membrane (CAM) assays. Here we identified in HEp3, SQ20b and FaDu HNSCC xenografts a subpopulation of G0/G1-arrested slow-cycling CD49f(high)/ALDH1A1(high)/H3K4/K27me3(low) subpopulation (CD49f+) of tumor cells. A strikingly similar CD49f(high)/H3K27me3(low) subpopulation is also present in primary human HNSCC tumors and metastases. While only sorted CD49f(high)/ALDH(high), label retaining cells (LRC) proliferated immediately in vivo, with time the CD49f(low)/ALDH(low), non-LRC (NLRC) tumor cell subpopulations were also able to regain tumorigenic capacity; this was linked to restoration of CD49f(high)/ALDH(high), label retaining cells. In addition, CD49f is required for HEp3 cell tumorigenicity and to maintain low levels of H3K4/K27me3. CD49f+ cells also displayed reduced expression of the histone-lysine N-methyltransferase EZH2 and ERK1/2 phosphorylation. This suggests that although transiently quiescent, their unique chromatin structure is poised for rapid transcriptional activation. CD49f- cells can \"reprogram\" and also achieve this state eventually. We propose that in HNSCC tumors, epigenetic mechanisms likely driven by CD49f signaling dynamically regulate HNSCC xenograft phenotypic heterogeneity. This allows multiple tumor cell subpopulations to drive tumor growth suggesting that their dynamic nature renders them a \"moving target\" and their eradication might require more persistent strategies.

Hypoxia is a poor-prognosis microenvironmental hallmark of solid tumours, but it is unclear how it influences the fate of disseminated tumour cells (DTCs) in target organs. Here we report that hypoxic HNSCC and breast primary tumour microenvironments displayed upregulation of key dormancy (NR2F1, DEC2, p27) and hypoxia (GLUT1, HIF1α) genes. Analysis of solitary DTCs in PDX and transgenic mice revealed that post-hypoxic DTCs were frequently NR2F1 hi /DEC2 hi /p27 hi /TGFβ2 hi and dormant. NR2F1 and HIF1α were required for p27 induction in post-hypoxic dormant DTCs, but these DTCs did not display GLUT1 hi expression. Post-hypoxic DTCs evaded chemotherapy and, unlike ER − breast cancer cells, post-hypoxic ER + breast cancer cells were more prone to enter NR2F1-dependent dormancy. We propose that primary tumour hypoxic microenvironments give rise to a subpopulation of dormant DTCs that evade therapy. These post-hypoxic dormant DTCs may be the source of disease relapse and poor prognosis associated with hypoxia. Aguirre-Ghiso and colleagues report that hypoxia in the primary tumour microenvironment leads to upregulation of a dormancy signature in the tumour cells that persists after their dissemination to distant sites, permitting them to evade therapy.

This corrects the article DOI: 10.1038/nature20609.