Netrin-1 blockade inhibits tumour growth and EMT features in endometrial cancer.

Netrin-1 is upregulated in cancers as a protumoural mechanism1. Here we describe netrin-1 upregulation in a majority of human endometrial carcinomas (ECs) and demonstrate that netrin-1 blockade, using an anti-netrin-1 antibody (NP137), is effective in reduction of tumour progression in an EC mouse model. We next examined the efficacy of NP137, as a first-in-class single agent, in a Phase I trial comprising 14 patients with advanced EC. As best response we observed 8 stable disease (8 out of 14, 57.1%) and 1 objective response as RECIST v.1.1 (partial response, 1 out of 14 (7.1%), 51.16% reduction in target lesions at 6 weeks and up to 54.65% reduction during the following 6 months). To evaluate the NP137 mechanism of action, mouse tumour gene profiling was performed, and we observed, in addition to cell death induction, that NP137 inhibited epithelial-to-mesenchymal transition (EMT). By performing bulk RNA sequencing (RNA-seq), spatial transcriptomics and single-cell RNA-seq on paired pre- and on-treatment biopsies from patients with EC from the NP137 trial, we noted a net reduction in tumour EMT. This was associated with changes in immune infiltrate and increased interactions between cancer cells and the tumour microenvironment. Given the importance of EMT in resistance to current standards of care2, we show in the EC mouse model that a combination of NP137 with carboplatin-paclitaxel outperformed carboplatin-paclitaxel alone. Our results identify netrin-1 blockade as a clinical strategy triggering both tumour debulking and EMT inhibition, thus potentially alleviating resistance to standard treatments.

Cutting Edge: mTORC1 Inhibition in Metastatic Breast Cancer Patients Negatively Affects Peripheral NK Cell Maturation and Number.

NK cells are cytotoxic lymphocytes displaying strong antimetastatic activity. Mouse models and in vitro studies suggest a prominent role of the mechanistic target of rapamycin (mTOR) kinase in the control of NK cell homeostasis and antitumor functions. However, mTOR inhibitors are used as chemotherapies in several cancer settings. The impact of such treatments on patients' NK cells is unknown. We thus performed immunophenotyping of circulating NK cells from metastatic breast cancer patients treated with the mTOR inhibitor everolimus over a three-month period. Everolimus treatment resulted in inhibition of mTORC1 activity in peripheral NK cells, whereas mTORC2 activity was preserved. NK cell homeostasis was profoundly altered with a contraction of the NK cell pool and an overall decrease in their maturation. Phenotype and function of the remaining NK cell population was less affected. This is, to our knowledge, the first in vivo characterization of the role of mTOR in human NK cells.

Xevinapant Combined with Pembrolizumab in Patients with Advanced, Pretreated, Colorectal and Pancreatic Cancer: Results of the Phase Ib/II CATRIPCA Trial.

PURPOSE: Xevinapant is an orally available inhibitor of apoptosis proteins (IAP) inhibitor. Preclinical data suggest that IAP antagonism may synergize with immune checkpoint blockers by modulating the NFκB pathway in immune cells. PATIENTS AND METHODS: Adult patients with non-high microsatellite instability advanced/metastatic pancreatic ductal adenocarcinoma (PDAC) or colorectal cancer were enrolled in this phase Ib/II study and received pembrolizumab 200 mg every 3 weeks intravenously, and ascending doses of oral xevinapant (100, 150, and 200 mg daily for 14 days on/7 days off). Dose escalation followed a 3+3 design with a 21-day dose-limiting toxicity (DLT) evaluation period. Following the determination of the recommended phase II dose (RP2D), 14 patients with PDAC and 14 patients with colorectal cancer were enrolled in expansion cohorts to assess preliminary efficacy. RESULTS: Forty-one patients (26 males) with a median age of 64 years were enrolled: 13 in the dose escalation and 28 in the two expansion cohorts. No DLT was observed during dose escalation. The RP2D was identified as xevinapant 200 mg/day + pembrolizumab 200 mg every 3 weeks. The most common adverse events (AE) were fatigue (37%), gastrointestinal AE (decreased appetite in 37%, nausea in 24%, stomatitis in 12%, and diarrhea and vomiting in 10% each), and cutaneous AE (pruritus, dry skin, and rash seen in 20%, 15%, and 15% of patients, respectively). The best overall response according to RECIST1.1 was partial response (confirmed) in 1 (3%), stable disease in 4 (10%), and progressive disease in 35 (88%). CONCLUSIONS: Xevinapant combined with pembrolizumab was well tolerated with no unexpected AEs. However, antitumor activity was low.

Pembrolizumab in Lymphopenic Metastatic Breast Cancer Patients Treated with Metronomic Cyclophosphamide: A Clinical and Translational Prospective Study.

Purpose: Metastatic endocrine-resistant breast cancer (MBC) is a disease with poor prognosis and few treatment options. Low lymphocyte count is associated with limited overall survival. In a prospective cohort of lymphopenic patients with HER-2 negative MBC, we assessed the clinical and biological impact of pembrolizumab combined with metronomic cyclophosphamide. Experimental Design: This multicenter Phase II study evaluated the safety and clinical activity of pembrolizumab (intravenous (IV), 200mg, every 3 weeks) combined with metronomic cyclophosphamide (50mg/day, per os) in lymphopenic adult patients with HER2-negative MBC previously treated by at least one line of chemotherapy in this setting according to a Simon's minimax two-stage design. Blood and tumor samples were collected to assess the impact of the combined treatment on circulating immune cells and the tumor immune microenvironment through multiparametric flow cytometry and multiplex immunofluorescence analyses. Primary endpoint was the clinical benefit rate at 6 months of treatment (CBR-6M). Secondary endpoints were objective response rate (ORR), duration of response, progression free survival (PFS), and overall survival (OS). Results: Two out of the twenty treated patients presented clinical benefit (one Tumor Mutational Burden (TMB)-high patient with complete response (CR) and one patient with objective response (OR) per Response Evaluation Criteria in Solid Tumors version 1.1 (RECIST V1.1) associated with a strong increase of cytokine-producing and proliferating CD4+ T cells and higher CD8+ T cells to macrophage ratios in the tumor. This impact on CD4+ and CD8+ T cell polyfunctionality was still observed more than one year for the patient with CR. A decreased in their absolute number of CD4+ and CD8+ memory T cells was observed in other patients. Conclusion: Pembrolizumab combined with metronomic cyclophosphamide was well tolerated, and displayed limited anti-tumoral activity in lymphopenic MBC. Correlative translational data of our trial advocates for additional studies with other chemotherapy combinations.

MEVITEM-a phase I/II trial of vismodegib + temozolomide vs temozolomide in patients with recurrent/refractory medulloblastoma with Sonic Hedgehog pathway activation.

BACKGROUND: Vismodegib specifically inhibits Sonic Hedgehog (SHH). We report results of a phase I/II evaluating vismodegib + temozolomide (TMZ) in immunohistochemically defined SHH recurrent/refractory adult medulloblastoma. METHODS: TMZ-naïve patients were randomized 2:1 to receive vismodegib + TMZ (arm A) or TMZ (arm B). Patients previously treated with TMZ were enrolled in an exploratory cohort of vismodegib (arm C). If the safety run showed no excessive toxicity, a Simon's 2-stage phase II design was planned to explore the 6-month progression-free survival (PFS-6). Stage II was to proceed if arm A PFS-6 was ≥3/9 at the end of stage I. RESULTS: A total of 24 patients were included: arm A (10), arm B (5), and arm C (9). Safety analysis showed no excessive toxicity. At the end of stage I, the PFS-6 of arm A was 20% (2/10 patients, 95% unilateral lower confidence limit: 3.7%) and the study was prematurely terminated. The overall response rates (ORR) were 40% (95% CI, 12.2-73.8) and 20% (95% CI, 0.5-71.6) in arm A and B, respectively. In arm C, PFS-6 was 37.5% (95% CI, 8.8-75.5) and ORR was 22.2% (95% CI, 2.8-60.0). Among 11 patients with an expected sensitivity according to new generation sequencing (NGS), 3 had partial response (PR), 4 remained stable disease (SD) while out of 7 potentially resistant patients, 1 had PR and 1 SD. CONCLUSION: The addition of vismodegib to TMZ did not add toxicity but failed to improve PFS-6 in SHH recurrent/refractory medulloblastoma. Prediction of sensitivity to vismodegib needs further refinements.

Flow antagonizes TNF-alpha signaling in endothelial cells by inhibiting caspase-dependent PKC zeta processing.

Unidirectional laminar flow is atheroprotective, in part by inhibiting cytokine-mediated endothelial cell (EC) inflammation and apoptosis. Previously, we showed that flow inhibited TNF-alpha signaling by preventing activation of JNK. Recently, PKCzeta was identified as the PKC isoform most strongly regulated by flow pattern, with increased PKCzeta activity in regions of disturbed flow versus unidirectional flow. Interestingly, PKCzeta is cleaved by caspases after TNF-alpha stimulation to generate a 50-kDa truncated form (CATzeta, catalytic domain of PKCzeta) with a higher kinase activity than the full-length protein. We hypothesized that flow would inhibit TNF-alpha-mediated PKCzeta cleavage and thereby CATzeta formation. We found that PKCzeta activity was required for TNF-alpha-mediated JNK and caspase-3 activation in ECs. PKCzeta was rapidly cleaved to generate CATzeta in cultured bovine and human aortic ECs and in intact rabbit vessels stimulated with TNF-alpha. This truncated form of PKCzeta enhanced JNK and caspase-3 activation. Interestingly, PKCzeta cleavage was prevented by inhibitors of PKCzeta, JNK, and caspase activities, suggesting that these enzymes, via regulating CATzeta formation, modulate caspase-3 activity in ECs. Finally, we found that flow reduced caspase-dependent processing of PKCzeta and caspase-3 activation. These results define a novel role for PKCzeta as a shared signaling mediator for flow and TNF-alpha, and important for flow-mediated inhibition of proinflammatory and apoptotic events in ECs.

BMK1/ERK5 is a novel regulator of angiogenesis by destabilizing hypoxia inducible factor 1alpha.

Big MAP kinase 1 (BMK1 or ERK5) is a key mediator of endothelial cell (EC) function as shown by impaired embryonic angiogenesis and vascular collapse in BMK1 knockout mice. Hypoxia inducible factor 1alpha (HIF1alpha), a potent mediator of angiogenesis, is positively regulated by the MAP kinases, ERK1/2. Because BMK1 deficiency is associated with impaired angiogenesis we hypothesized that BMK1 might regulate HIF1alpha. To test this hypothesis, bovine lung microvascular ECs (BLMECs) were transfected with HIF1alpha and BMK1 cDNAs, and stimulated by hypoxia. HIF1alpha activity was measured by a reporter gene assay in which luciferase expression was driven by HIF1alpha activation. Hypoxia (1% O2, 24 hours) stimulated HIF1alpha activity by 5.1+/-0.6 fold. In the presence of dominant negative (DN)-BMK1, which inhibited BMK1 activity, hypoxia induced HIF1alpha activity was enhanced significantly to 6.4+/-0.4 fold. BMK1 activation by constitutively active (CA)-MEK5 inhibited HIF1alpha activity by 46+/-4%, suggesting BMK1 functions as a negative regulator of HIF1alpha activation. Activation of BMK1 reduced HIF1alpha protein levels. Ubiquitination inhibitors (30 micromol/L ALLN, 2 micromol/L lactacystin, or 100 nmol/L MG132) reduced the BMK1-mediated effect on HIF1alpha expression by >80%, suggesting that BMK1 stimulated HIF1alpha proteolysis. The negative effect of BMK1 on HIF1alpha was functionally important because transfection with CA-MEK5 significantly decreased EC migration by 68+/-10%, and inhibited angiogenesis (in vitro Matrigel assay) by 76+/-7%. In summary, BMK1 is a novel negative regulator of HIF1alpha and angiogenesis by increasing HIF1alpha ubiquitination and inhibiting HIF1alpha activity in endothelial cells.

Flow-mediated signaling modulates endothelial cell phenotype.

The focal development of atherosclerosis in the vascular tree may be explained in part by the local nature of blood flow. Bifurcations and branching points, prone to early atherogenesis, experience disturbed and oscillatory flow, whereas straight vascular regions, resistant to atherosclerosis, are exposed to steady laminar flow. A large number of studies suggest that the antiatherosclerotic effects of laminar flow are in part due to the ability of flow to modulate endothelial cell phenotype. Under steady laminar flow, endothelial cells generate molecules that promote a vasoactive, anticoagulant, anti-inflammatory, and growth-inhibitory surface. In contrast, disturbed flow induces a proliferative, prothrombotic, and adhesive phenotype. Endothelial cells are able to sense the variations of flow via mechanosensitive cell surface proteins and to transduce these signals via intracellular pathways to transcription factors in the nucleus leading to phenotypic changes. This review summarizes the "outside-in" signaling events initiated by flow that modulate endothelial cell phenotype.

Vascular shear stress and activation of inflammatory genes.

Atherosclerotic lesions form preferentially at distinct sites in the arterial tree, especially at or near branch points, bifurcations, and curvatures where there is disturbed or oscillatory blood flow. In contrast, straight regions of the vasculature exhibit uniform laminar shear stress, which is atheroprotective. The ability of laminar flow to exert an anti-inflammatory effect on the endothelial cell lining of the blood vessel is revealed by preventing monocyte adhesion, proliferation, and apoptosis. Changes in endothelial cell gene expression in response to laminar shear stress reflect these changes in cell physiology with the demonstration that physiologic flow inhibits the expression of inflammatory genes. Thus, shear stress is critically important in regulating vascular physiology and pathobiology of the vessel wall via the modulation of endothelial cell gene expression.

6A3-5/Osa2 is an early activated gene implicated in the control of vascular smooth muscle cell functions.

Vascular smooth muscle cells (VSMC) growth plays a key role in the pathophysiology of vascular diseases. However, the molecular mechanisms controlling gene transcription in VSMC remain poorly understood. We previously identified, by differential display, a new gene (6A3-5) overexpressed in proliferating rat VSMC. In this study, we have cloned the full-length cDNA by screening a rat foetal brain cDNA library and investigated its functions. The 6A3-5 protein shows 4 putative conserved functional motifs: a DNA binding domain called ARID (AT-rich interaction domain), two recently described motifs (Osa Homology Domain), and a nuclear localization signal. The deduced protein sequence was observed to be 85% identical to the recently described human Osa2 gene. Immunolabelling, using an anti-6A3-5/Osa2 monoclonal antibody, showed a nuclear localization of the 6A3-5/Osa2 protein. In addition, PDGF upregulated 6A3-5/Osa2 expression at both the transcript and protein levels in a dose and time-dependent fashion. The pattern of upregulation by PDGF was reminiscent of the early responsive gene c-fos. The PDGF-induced upregulation of 6A3-5/Osa2 and proliferation of VSMC were significantly inhibited in a dose and sequence-dependent fashion by an antisense, but not by sense, scrambled or mismatched oligonucleotides directed against 6A3-5/Osa2. In VSMC of aortas derived from hypertensive (LH) rats, 6A3-5/Osa2 is overexpressed as compared to that in normotensive (LL) rats. The 6A3-5/Osa2-gene expression is downregulated by an ACE inhibitor and upregulated by exogenous AngiotensinII in LH rats. In summary, these results indicate that 6A3-5/Osa2 is an early activated gene that belongs to a new family of proteins involved in the control of VSMC growth.

Identification, structural, and functional characterization of a new early gene (6A3-5, 7 kb): implication in the proliferation and differentiation of smooth muscle cells.

Arterial smooth muscle cells (SMCs) play a major role in atherosclerosis and restenosis. Differential display was used to compare transcription profiles of synthetic SMCs to proliferating rat cultured SMC line. An isolated cDNA band (6A3-5) was shown by northern (7 kb) to be upregulated in the proliferating cell line. A rat tissue northern showed differential expression of this gene in different tissues. Using 5' RACE and screening of a rat brain library, part of the cDNA was cloned and sequenced (5.4 kb). Sequence searches showed important similarities with a new family of transcription factors, bearing ARID motifs. A polyclonal antibody was raised and showed a protein band of 175 kd, which is localized intracellularly. We also showed that 6A3-5 is upregulated in dedifferentiated SMC (P9) in comparison to contractile SMC ex vivo (P0). This work describes cloning, structural, and functional characterization of a new early gene involved in SMC phenotype modulation.

Ischemia induces early expression of a new transcription factor (6A3-5) in kidney vascular smooth muscle cells: studies in rat and human renal pathology.

Acute renal failure, characterized by rapid decline in glomerular filtration rate, is a major cause of morbidity and mortality. During the evolution of renal diseases chronic ischemia develops. Indeed, acute or chronic renal failure may occur as a result of renal ischemia, which induces cells to dedifferentiate, proliferate, or become apoptotic. In this study, we have investigated the expression of a newly identified transcription factor, 6A3-5, under in vitro and in vivo conditions. Proliferating vascular smooth muscle were investigated in response to different mitogenic agents. The 6A3-5 expression was then studied in ischemic rat kidney, induced by renal pedicle clamping, followed, or not, by reperfusion. Subsequently human renal biopsies from early kidney grafts and chronic renal diseases were also investigated for 6A3-5 protein expression by immunohistochemistry. In vitro study shows an over-expression of 6A3-5 following 2 to 4 hours stimulation by serum or Angiotensin II, of rat proliferating aortic smooth muscle cell. Moreover, in vivo study shows that this new protein is over expressed in rat kidney submitted to 45 minutes ischemia. An anti-6A3-5 antibody shows the protein to be expressed in smooth muscle cells of the arterioles and intermediate size arteries, in mesangial cells and interstitial myofibroblasts. In human biopsies of early kidney grafts and renal disease, the same up-regulation of 6A3-5, as in acute ischemic situation, is observed. This 6A3-5 expression is intimately associated with alpha-smooth muscle cell actin expression in mesangial cells, arteriolar smooth muscle cells as well as interstitial myofibroblasts. Transcription factor 6A3-5 could potentially be a novel early vascular marker of acute and chronic renal ischemic stress implicated in tissue remodeling.