PD-L1 expression predicts efficacy in the phase II SPiReL trial with MVP-S, pembrolizumab, and low-dose CPA in R/R DLBCL.

BACKGROUND: Patients with relapsed/refractory diffuse large B-cell lymphoma (R/R DLBCL) have limited treatment options. METHODS: R/R DLBCL patients, who were mostly ineligible for ASCT due to age or comorbidities, were treated with maveropepimut-S (MVP-S, previously DPX-Survivac) a survivin directed T cell educating therapy, pembrolizumab, and intermittent low-dose cyclophosphamide. FINDINGS: We identified, using univariate analysis, a subset of patients with enhanced ORR, PFS and DOR. Patients with baseline CD20+/PD-L1 expression had an ORR of 46% (6/13) and the disease control rate was 10/13 (77%). The PFS and OS of the positive CD20+/PD-L1 patients were 7.1 months and 17.4 months, whereas in the intent-to-treat (ITT) population of 25 enrolled patients, the ORR was 28% (7/25), median PFS and OS were 4.2 months and 10.1 months respectively. A total of 6/7 clinical responders occurred in CD20+/PD-L1 patients. The regimen was well-tolerated, requiring only minor dose modifications and one discontinuation. Grade 1 or 2 injection site reactions occurred in 14/25, (56%). Statistically significant associations were also seen between PFS and; injection site reactions; and ELISpot response to survivin peptides, both identifying the mechanistic importance of specific immune responses to survivin. INTERPRETATION: This immunotherapy combination was found to be active and safe in this clinically challenging patient population.

A Lower Frequency of Spliceosome Mutations Distinguishes Clonal Cytopenias of Undetermined Significance From Low-Risk Myelodysplastic Syndromes, Despite Inherent Similarities in Genomic, Laboratory, and Clinical Features.

Clonal cytopenias of undetermined significance (CCUS) are associated with an increased risk of developing a myelodysplastic syndrome (MDS); however, the mechanism and factors associated with evolution remain unclear. We propose that next-generation sequencing (NGS) of cytopenic cases with equivocal morphologic dysplasia will improve patient clinical care and that serial sequencing of such equivocal cases could identify the factors that predict evolution to MDS. We performed targeted NGS of samples from 193 individuals with confirmed or suspected MDS or MDS/myeloproliferative neoplasm, including sequential investigation for 28 individuals at the time of diagnosis and during follow-up. NGS facilitated the diagnosis of all suspicious cases as myeloid neoplasm (21%), CCUS (34%), or idiopathic cytopenias of undetermined significance (45%) when no variants were detected. We found that there was no significant difference in most measured clinical features or clonal phenotypes, such as cell counts, number of variants, variant allele frequencies, and overall survival, between CCUS and International Prognostic Scoring System-Revised-defined low-risk MDS. However, there was a significant difference in the types of variants between CCUS and low-risk MDS, with a significantly lower number of splicing factor mutations in CCUS cases (P < .001). Moreover, we observed an increased probability of evolution to MDS of individuals with CCUS compared with that in those with idiopathic cytopenias of undetermined significance over the first 5 years (P = .045). Our analyses revealed no conclusive pattern associating clonal expansion or the number of variants with the evolution of CCUS to MDS, perhaps further supporting the similarity of these diseases and the clinical importance of recognizing and formally defining CCUS as a category of precursor myeloid disease state in the next revision of the World Health Organization guidelines.

Differential Immunomodulatory Effects of Human Bone Marrow-Derived Mesenchymal Stromal Cells on Natural Killer Cells.

Mesenchymal stromal cells (MSCs) modulate immune responses through cell contact-dependent or paracrine mechanisms and are themselves known to have low immunogenicity. Given the increasing use of both natural killer (NK) cells and MSCs in cell-based therapies, we investigated the interaction between the two cell types using the NK cell lines, KHYG-1 and NK-92, and human bone marrow-derived MSCs. NK lines were cocultured with MSCs, either directly or in a transwell system, and the effects on proliferation, interferon-gamma (IFN-γ) production, and cytolytic activity of NK cells were analyzed. Cytotoxicity was measured in a 4 h chromium release assay. MSCs did not affect the proliferation of NK cell lines but reduced IFN-γ production by KHYG-1, but not NK-92, when cocultured directly at 10:1 NK:MSC ratio. MSCs suppressed K562 lysis by both KHYG-1 and NK-92 cells in contact-free transwell cocultures but only reduced cytotoxicity of KHYG-1 and not NK-92 cells when cells were in direct contact in coculture. Immunosuppressive effects of MSCs were mediated by indoleamine-2,3-dioxygenase (IDO) and prostaglandin E2 (PGE2) secreted by MSCs and were abrogated in the presence of IDO and PGE2 inhibitors. In the presence of MSCs, granule polarization was suppressed and induced respectively, in KHYG-1 and NK-92. Consistent with this, MSCs were susceptible to lysis by NK-92 but not KHYG-1. These studies indicate the differential crosstalk between MSCs and two highly cytotoxic NK lines and may be important when designing future cell therapy protocols with these two cell types.

Concise Review: TLR Pathway-miRNA Interplay in Mesenchymal Stromal Cells: Regulatory Roles and Therapeutic Directions.

Mesenchymal stromal cells (MSCs) deploy Toll-like receptors (TLRs) to respond to exogenous and endogenous signals. Activation of TLR pathways in MSCs alters their inflammatory profile and immunomodulatory effects on cells from both the innate and adaptive immune systems. Micro-RNAs (miRNAs), whose expression is modulated by TLR activation, can regulate inflammatory responses by targeting components of the TLR signaling pathways either in MSCs or in the cells with which they interact. Here, we review how the miRNA-TLR pathway axis can regulate the immunomodulatory functions of MSCs, including their interactions with monocytes/macrophages and natural killer cells, and discuss the therapeutic implications for MSC-based therapies. Stem Cells 2018;36:1655-1662.

Human mesenchymal stromal cells do not promote recurrence of soft tissue sarcomas in mouse xenografts after radiation and surgery.

BACKGROUND: Mesenchymal stromal cells (MSCs) promote wound healing, including after radiotherapy (RT) and surgery. The use of MSCs in regenerative medicine in the context of malignancy, such as to enhance wound healing post-RT/surgery in patients with soft tissue sarcomas (STSs), requires safety validation. The aim of this study was to determine the effects of human MSCs on STS growth in vitro and local recurrence and metastasis in vivo. METHODS: Human primary STS and HT-1080 fibrosarcoma lines were transduced to express luciferase/eGFP (enhanced green fluorescent protein). Sarcoma cells were co-cultured or co-injected with bone marrow-derived MSCs for growth studies. Xenograft tumor models were established with STS lines in NOD/SCID/γcnull mice. To emulate a clinical scenario, subcutaneous tumors were treated with RT/surgery prior to MSC injection into the tumor bed. Local and distant tumor recurrence was studied using histology and bioluminescence imaging. RESULTS: MSCs did not promote STS proliferation upon co-culture in vitro, which was consistent among MSCs from different donors. Co-injection of MSCs with sarcoma cells in mice exhibited no significant tumor-stimulating effect, compared with control mice injected with sarcoma cells alone. MSC administration after RT/surgery had no effect on local recurrence or metastasis of STS. DISCUSSION: These studies are important for the establishment of a safety profile for MSC administration in patients with STS. Our data suggest that MSCs are safe in STS management after standard of care RT/surgery, which can be further investigated in early-phase clinical trials to also determine the efficacy of MSCs in reducing morbidity and to mitigate wound complications in these patients.

Collagen scaffold enhances the regenerative properties of mesenchymal stromal cells.

MSCs are widely applied to regenerate heart tissue in myocardial diseases but when grown in standard two-dimensional (2D) cultures exhibit limited potential for cardiac repair and develop fibrogenic features with increasing culture time. MSCs can undergo partial cardiomyogenic differentiation, which improves their cardiac repair capacity. When applied to collagen patches they may improve cardiac tissue regeneration but the mechanisms remain elusive. Here, we investigated the regenerative properties of MSCs grown in a collagen scaffold as a three-dimensional (3D) culture system, and performed functional analysis using an engineered heart tissue (EHT) model. We showed that the expression of cardiomyocyte-specific proteins by MSCs co-cultured with rat neonatal cardiomyocytes was increased in collagen patches versus conventional cultures. MSCs in 3D collagen patches were less fibrogenic, secreted more cardiotrophic factors, retained anti-apoptotic and immunomodulatory function, and responded less to TLR4 ligand lipopolysaccharide (LPS) stimulation. EHT analysis showed no effects by MSCs on cardiomyocyte function, whereas control dermal fibroblasts abrogated the beating of cardiac tissue constructs. We conclude that 3D collagen scaffold improves the cardioprotective effects of MSCs by enhancing the production of trophic factors and modifying their immune modulatory and fibrogenic phenotype. The improvement in myocardial function by MSCs after acquisition of a partial cardiac cell-like phenotype is not due to enhanced MSC contractility. A better understanding of the mechanisms of MSC-mediated tissue repair will help to further enhance the therapeutic potency of MSCs.

Immunomodulatory Properties of Coriolus versicolor: The Role of Polysaccharopeptide.

Traditional uses of herbal medicine have depended mostly on anecdotal evidence for much of history. The increasing application of scientific rigor to the study some of these traditional therapies in recent years has revealed potent bioactivity, notably demonstrated by the 2015 Nobel Prize for the discovery of an antimalarial compound from traditional Chinese herbs. Given the recent successes of immunotherapy and checkpoint blockade, there is a renewed interest in identifying new drugs with immunomodulatory effects. As an estimated 45-60% of cancer patients worldwide are reported to use complementary alternative medicine alongside traditional therapy, this review will highlight the literature on the immunomodulatory effects of one of these compounds. We report on the induction of a largely pro-inflammatory cytokine profile by the polysaccharopeptide (PSP) isolated from the Coriolus versicolor (Yun zhi) mushroom, as well as its effects on various immune subsets, and the clinical data that have led to its widespread adoption as an adjunct cancer therapeutic in many Eastern cultures. Particular focus is given to the potential mechanisms underlying the bioactivity of PSP and reports of its ability to promote antitumor immunity by helping overcome tolerogenic tumor microenvironments.

TLR3 or TLR4 Activation Enhances Mesenchymal Stromal Cell-Mediated Treg Induction via Notch Signaling.

Mesenchymal stromal cells (MSCs) are the subject of numerous clinical trials, largely due to their immunomodulatory and tissue regenerative properties. Toll-like receptors (TLRs), especially TLR3 and TLR4, are highly expressed on MSCs and their activation can significantly modulate the immunosuppressive and anti-inflammatory functions of MSCs. While MSCs can recruit and promote the generation of regulatory T cells (Tregs), the effect of TLR activation on MSC-mediated Treg induction is unknown. In this study, we investigated the effect of ligand-mediated activation of TLR3 and TLR4 on Treg induction by human MSCs. We found that generation of Tregs in human CD4(+) lymphocyte and MSC cocultures was enhanced by either TLR3 or TLR4 activation of MSCs and that the increase was abolished by TLR3 and TLR4 gene-silencing. Augmented Treg induction by TLR-activated MSCs was cell contact-dependent and associated with increased gene expression of the Notch ligand, Delta-like 1. Moreover, inhibition of Notch signaling abrogated the augmented Treg levels in the MSC cocultures. Our data show that TLR3 or TLR4 activation of MSCs increases Treg induction via the Notch pathway and suggest new means to enhance the potency of MSCs for treating disorders with an underlying immune dysfunction, including steroid resistant acute graft-versus-host disease. Stem Cells 2017;35:265-275.

Cell adhesion molecules and their relation to (cancer) cell stemness.

Despite decades of search for anticancer drugs targeting solid tumors, this group of diseases remains largely incurable, especially if in advanced, metastatic stage. In this review, we draw comparison between reprogramming and carcinogenesis, as well as between stem cells (SCs) and cancer stem cells (CSCs), focusing on changing garniture of adhesion molecules. Furthermore, we elaborate on the role of adhesion molecules in the regulation of (cancer) SCs division (symmetric or asymmetric), and in evolving interactions between CSCs and extracellular matrix. Among other aspects, we analyze the role and changes of expression of key adhesion molecules as cancer progresses and metastases develop. Here, the role of cadherins, integrins, as well as selected transcription factors like Twist and Snail is highlighted, not only in the regulation of epithelial-to-mesenchymal transition but also in the avoidance of anoikis. Finally, we briefly discuss recent developments and new strategies targeting CSCs, which focus on adhesion molecules or targeting tumor vasculature.

Apoptin, a tumor-selective killer.

Apoptin, a small protein from chicken anemia virus, has attracted great attention, because it specifically kills tumor cells while leaving normal cells unharmed. The subcellular localization of apoptin appears to be crucial for this tumor-selective activity. In normal cells, apoptin resides in the cytoplasm, whereas in cancerous cells it translocates into the nucleus. The nuclear translocation of apoptin is largely controlled by its phosphorylation. In tumor cells, apoptin causes the nuclear accumulation of survival kinases including Akt and is phosphorylated by CDK2. Thereby, apoptin redirects survival signals into cell death responses. Apoptin also binds as a multimeric complex to DNA and interacts with several nuclear targets, such as the anaphase-promoting complex, resulting in a G2/M phase arrest. The proapoptotic signal of apoptin is then transduced from the nucleus to cytoplasm by Nur77, which triggers a p53-independent mitochondrial death pathway. In this review, we summarize recent discoveries of apoptin's mechanism of action that might provide intriguing insights for the development of novel tumor-selective anticancer drugs.

Adult stem cells and their trans-differentiation potential--perspectives and therapeutic applications.

Stem cells are self-renewing multipotent progenitors with the broadest developmental potential in a given tissue at a given time. Normal stem cells in the adult organism are responsible for renewal and repair of aged or damaged tissue. Adult stem cells are present in virtually all tissues and during most stages of development. In this review, we introduce the reader to the basic information about the field. We describe selected stem cell isolation techniques and stem cell markers for various stem cell populations. These include makers for endothelial progenitor cells (CD146/MCAM/MUC18/S-endo-1, CD34, CD133/prominin, Tie-2, Flk1/KD/VEGFR2), hematopoietic stem cells (CD34, CD117/c-Kit, Sca1), mesenchymal stem cells (CD146/MCAM/MUC18/S-endo-1, STRO-1, Thy-1), neural stem cells (CD133/prominin, nestin, NCAM), mammary stem cells (CD24, CD29, Sca1), and intestinal stem cells (NCAM, CD34, Thy-1, CD117/c-Kit, Flt-3). Separate section provides a concise summary of recent clinical trials involving stem cells directed towards improvement of a damaged myocardium. In the last part of the review, we reflect on the field and on future developments.

S100A8/A9 at low concentration promotes tumor cell growth via RAGE ligation and MAP kinase-dependent pathway.

The complex formed by two members of the S100 calcium-binding protein family, S100A8/A9, exerts apoptosis-inducing activity against various cells, especially tumor cells. Here, we present evidence that S100A8/A9 also has cell growth-promoting activity at low concentrations. Receptor of advanced glycation end product (RAGE) gene silencing and cotreatment with a RAGE-specific blocking antibody revealed that this activity was mediated via RAGE ligation. To investigate the signaling pathways, MAPK phosphorylation and NF-kappaB activation were characterized in S100A8/A9-treated cells. S100A8/A9 caused a significant increase in p38 MAPK and p44/42 kinase phosphorylation, and the status of stress-activated protein kinase/JNK phosphorylation remained unchanged. Treatment of cells with S100A8/A9 also enhanced NF-kappaB activation. RAGE small interfering RNA pretreatment abrogated the S100A8/A9-induced NF-kappaB activation. Our data indicate that S100A8/A9-promoted cell growth occurs through RAGE signaling and activation of NF-kappaB.

Autoimmunity and apoptosis--therapeutic implications.

Acquisition of a complex immune system during evolution provided organisms with the most effective defense mechanism against "foreign" or "non-self" invaders. This efficient protection against pathogens, however, has been achieved at the expense of a higher risk for "self"-directed reaction or autoimmunity. Establishment of self-tolerance and homeostasis in the immune system is regulated at different physiological stages of immune cells development. The breakdown in discrimination between "self" and "non-self" causes an aberrant immune response against autoantigens that promote damage to the "self" cells and tissue(s), resulting in various autoimmune phenotypes. Whereas activation and clonal proliferation of autoreactive T- and B- lymphocytes underlies the pathogenesis of autoimmune diseases, the mechanism by which self-tolerance is lost and autoimmune responses are induced is not clear yet. Autoimmunity is a multi-step process that occurs as a consequence of complex interaction between genetic susceptibility and non-genetic factors. Programmed cell death, as a key mechanism to regulate immune system function, has a crucial influence on both the selection process of immune cells and the maintenance of this immune tolerance in peripheral repertoire. Thus, defects in apoptotic death pathways may contribute to the development of autoimmune response in susceptible individuals in certain conditions.