Collective cancer invasion forms an integrin-dependent radioresistant niche

Cancer fatalities result from metastatic dissemination and therapy resistance, both processes that depend on signals from the tumor microenvironment. To identify how invasion and resistance programs cooperate, we used intravital microscopy of orthotopic sarcoma and melanoma xenografts. We demonstrate that these tumors invade collectively and that, specifically, cells within the invasion zone acquire increased resistance to radiotherapy, rapidly normalize DNA damage, and preferentially survive. Using a candidate-based approach to identify effectors of invasion-associated resistance, we targeted beta 1 and alpha V beta 3/beta 5 integrins, essential extracellular matrix receptors in mesenchymal tumors, which mediate cancer progression and resistance. Combining radiotherapy with beta 1 or alpha V integrin monotargeting in invading tumors led to relapse and metastasis in 40-60% of the cohort, in line with recently failed clinical trials individually targeting integrins. However, when combined, anti-beta 1/alpha V integrin dual targeting achieved relapse-free radiosensitization and prevented metastatic escape. Collectively, invading cancer cells thus withstand radiotherapy and DNA damage by beta 1/alpha V beta 3/beta 5 integrin cross-talk, but efficient radiosensitization can be achieved by multiple integrin targeting

MCT4 blockade increases the efficacy of immune checkpoint blockade

Background & Aims Intratumoral lactate accumulation and acidosis impair T-cell function and antitumor immunity. Interestingly, expression of the lactate transporter monocarboxylate transporter (MCT) 4, but not MCT1, turned out to be prognostic for the survival of patients with rectal cancer, indicating that single MCT4 blockade might be a promising strategy to overcome glycolysis-related therapy resistance. Methods To determine whether blockade of MCT4 alone is sufficient to improve the efficacy of immune checkpoint blockade (ICB) therapy, we examined the effects of the selective MCT1 inhibitor AZD3965 and a novel MCT4 inhibitor in a colorectal carcinoma (CRC) tumor spheroid model co-cultured with blood leukocytes in vitro and the MC38 murine CRC model in vivo in combination with an antibody against programmed cell death ligand-1(PD-L1). Results Inhibition of MCT4 was sufficient to reduce lactate efflux in three-dimensional (3D) CRC spheroids but not in two-dimensional cell-cultures. Co-administration of the MCT4 inhibitor and ICB augmented immune cell infiltration, T-cell function and decreased CRC spheroid viability in a 3D co-culture model of human CRC spheroids with blood leukocytes. Accordingly, combination of MCT4 and ICB increased intratumoral pH, improved leukocyte infiltration and T-cell activation, delayed tumor growth, and prolonged survival in vivo. MCT1 inhibition exerted no further beneficial impact. Conclusions These findings demonstrate that single MCT4 inhibition represents a novel therapeutic approach to reverse lactic-acid driven immunosuppression and might be suitable to improve ICB efficacy

RORγt+ IL-22-producing NKp46+ cells protect from hepatic ischemia reperfusion injury in mice

Background & Aims: NKp46(+) cells are major effector cells in the pathogenesis of hepatic ischemia reperfusion injury (IRI). Nevertheless, the precise role of unconventional subsets like the IL-22-producing NKp46(+) cells (NK22) remains unknown. The purpose of this study was to examine the role of NK22 cells in IRI in transplantation, particularly with respect to regulation by the transcription factor ROR-gamma-t (ROR gamma t). Methods: To explore the role of NK22 cells in IRI in the absence of adaptive immunity, B6.ROR gamma t-(gfp/wt)-reporter and B6.ROR gamma t-(gfp/gfp)-knockout (KO) mice on a Rag KO background underwent 90 min partial warm ischemia, followed by 24 h of reperfusion. Results: Rag KO mice that possess fully functional NKp46(+) cells, and Rag-common-gamma-chain-double-KO (Rag-gamma c-DKO) mice that lack T, B and NKp46(+) cells, were used as controls. We found that Rag-gamma c-DKO mice lacking NK22 cells show more severe levels of hepatocellular damage (GPT, histological injury) when compared to both Rag-ROR gamma t-reporter and Rag KO mice that possess NK22 cells. Importantly, Rag-ROR gamma t-reporter and Rag KO mice undergoing IRI expressed high protein levels of both IL-22 and GFP (ROR gamma t), suggesting a protective role for ROR gamma t(+) NK22 cells in IRI. Therefore, we tested the hypothesis that ROR gamma t critically protects from IRI through the induction of hepatic NK22 cells by studying Rag-Ror gamma t-DKO mice under IRI conditions. We found that the lack of ROR gamma t(+) NK22 cells in Rag-Ror gamma t-DKO mice significantly enhanced IR-induced hepatocellular injury, a phenotype that could be reversed upon adoptive transfer of Rag-Ror gamma t-reporter NK22 cells into DKO mice. Conclusions: ROR gamma t+ NK22 cells play an important protective role in IRI in mice. (C) 2015 European Association for the Study of the Liver. Published by Elsevier B.V. All rights reserved

Defibrotide: an endothelium protecting and stabilizing drug, has an anti-angiogenic potential in vitro and in vivo

Defibrotide (DF) is a polydisperse mixture of 90% single-stranded oligonucleotides with anti-thrombotic and anti-apoptotic functions. DF is used in the treatment of endothelial complications in the course of allogeneic stem cell transplantation. Recent preclinical evidence suggests that DF might also have anti-neoplastic properties. In the present study we hypothesized that DF might inhibit tumors via an anti-angiogenic effect. The anti-angiogenic potential of DF was tested in vitro using human microvascular endothelial cells forming vessel structures across a layer of dermal fibroblasts. Our results show that pharmacologic DF concentrations (100 mug/ml) significantly reduced vessel formation in this assay. Similarly, DF blocked sprouting from cultured rat aortic rings. In vivo, angiogenesis in a human gastric tumor (TMK1) implanted in dorsal skin-fold chambers (in nude mice) was inhibited by i.v. application of 450 mg/kg DF. Notably, due to its short half-life, DF was most effective when given on a daily basis. Although the precise mechanism of DF remains to be elucidated, initial Western blots show that DF reduces phosphorylation-activation of p70S6 kinase, which is a key target in the PI3K/Akt/mTOR signaling pathway linked to endothelial cell and pericyte proliferation and activation. However, in vitro data suggest that DF acts independently of vascular endothelial growth factor. Taken together, our data suggest that while DF is known for its endothelium-protecting function in SCT, it also inhibits formation of new blood vessels, and thus should be considered for further testing as an adjuvant anti-cancer agent, either alone, or in combination with other drugs

In question: the scientific value of preclinical safety pharmacology and toxicology studies with cell-based therapies

A new cell-based medicinal product containing human regulatory macrophages, known as Mreg_UKR, has been developed and conforms to expectations of a therapeutic drug. Here, Mreg_UKR was subjected to pharmacokinetic, safety pharmacology, and toxicological testing, which identified no adverse reactions. These results would normally be interpreted as evidence of the probable clinical safety of Mreg_UKR; however, we contend that, owing to their uncertain biological relevance, our data do not fully support this conclusion. This leads us to question whether there is adequate scientific justification for preclinical safety testing of similar novel cell-based medicinal products using animal models. In earlier work, two patients were treated with regulatory macrophages prior to kidney transplantation. In our opinion, the absence of acute or chronic adverse effects in these cases is the most convincing available evidence of the likely safety of Mreg_UKR in future recipients. On this basis, we consider that safety information from previous clinical investigations of related cell products should carry greater weight than preclinical data when evaluating the safety profile of novel cell-based medicinal products. By extension, we argue that omitting extensive preclinical safety studies before conducting small-scale exploratory clinical investigations of novel cell-based medicinal products data may be justifiable in some instances