Periostin- and podoplanin-positive cancer-associated fibroblast subtypes cooperate to shape the inflamed tumor microenvironment in aggressive pancreatic adenocarcinoma.

Cancer-associated fibroblasts (CAFs) are orchestrators of the pancreatic ductal adenocarcinoma (PDAC) microenvironment. Previously we described four CAF subtypes with specific molecular and functional features. Here, we have refined our CAF subtype signatures using RNAseq and immunostaining with the goal of defining bioinformatically the phenotypic stromal and tumor epithelial states associated with CAF diversity. We used primary CAF cultures grown from patient PDAC tumors, human data sets (in-house and public, including single-cell analyses), genetically engineered mouse PDAC tissues, and patient-derived xenografts (PDX) grown in mice. We found that CAF subtype RNAseq signatures correlated with immunostaining. Tumors rich in periostin-positive CAFs were significantly associated with shorter overall survival of patients. Periostin-positive CAFs were characterized by high proliferation and protein synthesis rates and low α-smooth muscle actin expression and were found in peri-/pre-tumoral areas. They were associated with highly cellular tumors and with macrophage infiltrates. Podoplanin-positive CAFs were associated with immune-related signatures and recruitment of dendritic cells. Importantly, we showed that the combination of periostin-positive CAFs and podoplanin-positive CAFs was associated with specific tumor microenvironment features in terms of stromal abundance and immune cell infiltrates. Podoplanin-positive CAFs identified an inflammatory CAF (iCAF)-like subset, whereas periostin-positive CAFs were not correlated with the published myofibroblastic CAF (myCAF)/iCAF classification. Taken together, these results suggest that a periostin-positive CAF is an early, activated CAF, associated with aggressive tumors, whereas a podoplanin-positive CAF is associated with an immune-related phenotype. These two subpopulations cooperate to define specific tumor microenvironment and patient prognosis and are of putative interest for future therapeutic stratification of patients. © 2022 The Authors. The Journal of Pathology published by John Wiley & Sons Ltd on behalf of The Pathological Society of Great Britain and Ireland.

Promising in vivo efficacy of the BET bromodomain inhibitor OTX015/MK-8628 in malignant pleural mesothelioma xenografts.

It has recently been reported that a large proportion of human malignant pleural mesothelioma (MPM) cell lines and patient tissue samples present high expression of the c-MYC oncogene. This gene drives several tumorigenic processes and is overexpressed in many cancers. Although c-MYC is a strategic target to restrain cancer processes, no drugs acting as c-MYC inhibitors are available. The novel thienotriazolodiazepine small-molecule bromodomain inhibitor OTX015/MK-8628 has shown potent antiproliferative activity accompanied by c-MYC downregulation in several tumor types. This study was designed to evaluate the growth inhibitory effect of OTX015 on patient-derived MPM473, MPM487 and MPM60 mesothelioma cell lines and its antitumor activity in three patient-derived xenograft models, MPM473, MPM487 and MPM484, comparing it with cisplatin, gemcitabine and pemetrexed, three agents which are currently used to treat MPM in the clinic. OTX015 caused a significant delay in cell growth both in vitro and in vivo. It was the most effective drug in MPM473 xenografts and showed a similar level of activity as the most efficient treatment in the other two MPM models (gemcitabine in MPM487 and cisplatin in MPM484). In vitro studies showed that OTX015 downregulated c-MYC protein levels in both MPM473 and MPM487 cell lines. Our findings represent the first evidence of promising therapeutic activity of OTX015 in mesothelioma.

OTX015 (MK-8628), a novel BET inhibitor, displays in vitro and in vivo antitumor effects alone and in combination with conventional therapies in glioblastoma models.

Bromodomain and extraterminal (BET) bromodomain (BRD) proteins are epigenetic readers that bind to acetylated lysine residues on chromatin, acting as co-activators or co-repressors of gene expression. BRD2 and BRD4, members of the BET family, are significantly increased in glioblastoma multiforme (GBM), the most common primary adult brain cancer. OTX015 (MK-8628), a novel BRD2/3/4 inhibitor, is under evaluation in dose-finding studies in solid tumors, including GBM. We investigated the pharmacologic characteristics of OTX015 as a single agent and combined with targeted therapy or conventional chemotherapies in glioblastoma cell lines. OTX015 displayed higher antiproliferative effects compared to its analog JQ1, with GI50 values of approximately 0.2 µM. In addition, C-MYC and CDKN1A mRNA levels increased transiently after 4 h-exposure to OTX015, while BRD2, SESN3, HEXIM-1, HIST2H2BE, and HIST1H2BK were rapidly upregulated and sustained after 24 h. Studies in three additional GBM cell lines supported the antiproliferative effects of OTX015. In U87MG cells, OTX015 showed synergistic to additive activity when administered concomitant to or before SN38, temozolomide or everolimus. Single agent oral OTX015 significantly increased survival in mice bearing orthotopic or heterotopic U87MG xenografts. OTX015 combined simultaneously with temozolomide improved mice survival over either single agent. The passage of OTX015 across the blood-brain barrier was demonstrated with OTX015 tumor levels 7 to 15-fold higher than in normal tissues, along with preferential binding of OTX015 to tumor tissue. The significant antitumor effects seen with OTX015 in GBM xenograft models highlight its therapeutic potential in GBM patients, alone or combined with conventional chemotherapies.

Polycationic calixarene PTX013, a potent cytotoxic agent against tumors and drug resistant cancer.

Previously, we reported on the anti-tumor activities of two designed calix[4]arene-based topomimetics (PTX008 and PTX009) of the amphipathic, angiostatic peptide Anginex. Here, we chemically modified the hydrophobic and hydrophilic faces of PTX008 and PTX009, and discovered new calixarene compounds that are more potent, cytotoxic anti-tumor agents. One of them, PTX013, is particularly effective at inhibiting the growth of several human cancer cell lines, as well as drug resistant cancer cells. Mechanistically, PTX013 induces cell cycle arrest in sub-G1 and G0/G1 phases of e.g. SQ20B cells, a radio-resistant human head and neck carcinoma model. In the syngeneic B16F10 melanoma tumor mouse model, PTX013 (0.5 mg/Kg) inhibits tumor growth by about 50-fold better than parent PTX008. A preliminary pharmacodynamics study strongly suggests that PTX013 exhibits good in vivo exposure and a relatively long half-life. Overall, this research contributes to the discovery of novel therapeutics as potentially useful agents against cancer in the clinic.

Microbiome and pancreatic ductal adenocarcinoma.

Pancreatic ductal adenocarcinoma (PDAC) incidence and related-deaths are increasing worldwide. PDAC is characterized by poor prognosis due to late diagnosis, high metastatic capacity and resistance to therapy. This is partially due to its specific microenvironment, where the stroma is prominent over tumor cells. Besides the oral and gut microbiota, the intratumor microbiome, i.e. the bacterial and fungal microorganisms present within the tumor, was recently introduced as a new partner of the tumor microenvironment of PDAC modulating pancreatic carcinogenesis, intratumor immune infiltrates, and response to chemotherapy. In this review, we propose an overview of current knowledge about the roles of bacteria and fungi in PDAC development and biology, and discuss potential therapeutic implications.

Macrophages in the microenvironment of head and neck cancer: potential targets for cancer therapy.

The microenvironment of solid tumors has become a promising target for future therapies modulating immune cells. Patients with advanced head and neck cancer, which still portends a poor outcome, are particularly in need of innovative approaches. In oral squamous cell carcinoma, high density of tumor-associated macrophages (TAMs) appears consistently associated with poor prognosis, whereas data are currently limited for other head and neck sites. Several approaches to block TAMs have been investigated, including TAMs inactivation by means of the colony stimulating factor 1 (CSF-1)/CSF-1 receptor (CSF-1R) inhibitors or strategies to reprogram TAMs from M2 protumoral phenotype toward M1 antitumoral phenotype. This review focuses on both prognostic and therapeutic aspects related to TAMs in head and neck carcinomas.

The bromodomain inhibitor OTX015 (MK-8628) exerts anti-tumor activity in triple-negative breast cancer models as single agent and in combination with everolimus.

Triple-negative breast cancer (TNBC) is an aggressive and heterogeneous subgroup of breast tumors clinically defined by the lack of estrogen, progesterone and HER2 receptors, limiting the use of the targeted therapies employed in other breast malignancies. Recent evidence indicates that c-MYC is a key driver of TNBC. The BET-bromodomain inhibitor OTX015 (MK-8628) has potent antiproliferative activity accompanied by c-MYC down-regulation in several tumor types, and has demonstrated synergism with the mTOR inhibitor everolimus in different models. The aim of this study was to evaluate the anti-tumor activity of OTX015 as single agent and in combination with everolimus in TNBC models. OTX015 was assayed in three human TNBC-derived cell lines, HCC1937, MDA-MB-231 and MDA-MB-468, all showing antiproliferative activity after 72 h (GI50 = 75-650 nM). This was accompanied by cell cycle arrest and decreased expression of cancer stem cells markers. However, c-MYC protein and mRNA levels were only down-regulated in MDA-MB-468 cells. Gene set enrichment analysis showed up-regulation of genes involved in epigenetic control of transcription, chromatin and the cell cycle, and down-regulation of stemness-related genes. In vitro, combination with everolimus was additive in HCC1937 and MDA-MB-231 cells, but antagonistic in MDA-MB-468 cells. In MDA-MB-231 murine xenografts, tumor mass was significantly (p < 0.05) reduced by OTX015 with respect to vehicle-treated animals (best T/C = 40.7%). Although everolimus alone was not active, the combination was more effective than OTX015 alone (best T/C = 20.7%). This work supports current clinical trials with OTX015 in TNBC (NCT02259114).

OTX015 (MK-8628), a novel BET inhibitor, exhibits antitumor activity in non-small cell and small cell lung cancer models harboring different oncogenic mutations.

Inhibitors targeting epigenetic control points of oncogenes offer a potential mean of blocking tumor progression in small cell and non-small cell lung carcinomas (SCLC, NSCLC). OTX015 (MK-8628) is a BET inhibitor selectively blocking BRD2/3/4. OTX015 was evaluated in a panel of NSCLC or SCLC models harboring different oncogenic mutations. Cell proliferation inhibition and cell cycle arrest were seen in sensitive NSCLC cells. MYC and MYCN were downregulated at both the mRNA and protein levels. In addition, OTX015-treatment significantly downregulated various stemness cell markers, including NANOG, Musashi-1, CD113 and EpCAM in H3122-tumors in vivo. Conversely, in SCLC models, weak antitumor activity was observed with OTX015, both in vitro and in vivo. No predictive biomarkers of OTX015 activity were identified in a large panel of candidate genes known to be affected by BET inhibition. In NSCLC models, OTX015 was equally active in both EML4-ALK positive and negative cell lines, whereas in SCLC models the presence of functional RB1 protein, which controls cell progression at G1, may be related to the final biological outcome of OTX015. Gene expression profiling in NSCLC and SCLC cell lines showed that OTX015 affects important genes and pathways with a very high overlapping between both sensitive and resistant cell lines. These data support the rationale for the OTX015 Phase Ib (NCT02259114) in solid tumors, where NSCLC patients with rearranged ALK gene or KRAS-positive mutations are currently being treated.

Targeting MYCN-Driven Transcription By BET-Bromodomain Inhibition.

PURPOSE: Targeting BET proteins was previously shown to have specific antitumoral efficacy against MYCN-amplified neuroblastoma. We here assess the therapeutic efficacy of the BET inhibitor, OTX015, in preclinical neuroblastoma models and extend the knowledge on the role of BRD4 in MYCN-driven neuroblastoma. EXPERIMENTAL DESIGN: The efficacy of OTX015 was assessed in in vitro and in vivo models of human and murine MYCN-driven neuroblastoma. To study the effects of BET inhibition in the context of high MYCN levels, MYCN was ectopically expressed in human and murine cells. The effect of OTX015 on BRD4-regulated transcriptional pause release was analyzed using BRD4 and H3K27Ac chromatin immunoprecipitation coupled with DNA sequencing (ChIP-Seq) and gene expression analysis in neuroblastoma cells treated with OTX015 compared with vehicle control. RESULTS: OTX015 showed therapeutic efficacy against preclinical MYCN-driven neuroblastoma models. Similar to previously described BET inhibitors, concurrent MYCN repression was observed in OTX015-treated samples. Ectopic MYCN expression, however, did not abrogate effects of OTX015, indicating that MYCN repression is not the only target of BET proteins in neuroblastoma. When MYCN was ectopically expressed, BET inhibition still disrupted MYCN target gene transcription without affecting MYCN expression. We found that BRD4 binds to super-enhancers and MYCN target genes, and that OTX015 specifically disrupts BRD4 binding and transcription of these genes. CONCLUSIONS: We show that OTX015 is effective against mouse and human MYCN-driven tumor models and that BRD4 not only targets MYCN, but specifically occupies MYCN target gene enhancers as well as other genes associated with super-enhancers. Clin Cancer Res; 22(10); 2470-81. ©2015 AACR.

Fsn0503h antibody-mediated blockade of cathepsin S as a potential therapeutic strategy for the treatment of solid tumors.

Degradation of extracellular matrix components is a key step in tumor progression, facilitating invasion, angiogenesis, and metastasis. The lysosomal cysteine protease cathepsin S (Cat-S) is a prominent player in this process. We evaluated the antitumor activity of Fsn0503h, the first Cat-S-antagonistic humanized monoclonal antibody, in a panel of cancer cell lines and in human colon carcinoma xenografts. Cat-S was expressed in 11 out of 36 solid tumor-derived cell lines. Fsn0503h significantly reduced the invasive capacity of all Cat-S-expressing cell lines in vitro. This was confirmed by the Cat-S small-molecule inhibitor Z-FL-COCHO, validating the importance of this protease in tumor cell invasiveness. Interestingly, Fsn0503h displayed antiproliferative effects in Cat-S positive and some Cat-S-negative cell lines. We provide the first demonstration of in vivo activity of Fsn0503h against a colorectal tumor xenograft model, with a 10 mg/kg three times a week intravenous schedule being optimal. In conclusion, Fsn0503h not only inhibited the invasiveness of cancer cells in vitro, but also exerted antitumor effects both in vitro and in vivo. These findings validate Cat-S as a therapeutic target, and support the development of Fsn0503h for the therapy of solid tumors.

Unraveling galectin-1 as a novel therapeutic target for cancer.

Galectins belong to a family of carbohydrate-binding proteins with an affinity for ß-galactosides. Galectin-1 is differentially expressed by various normal and pathologic tissues and displays a wide range of biological activities. In oncology, galectin-1 plays a pivotal role in tumor growth and in the multistep process of invasion, angiogenesis, and metastasis. Evidence indicates that galectin-1 exerts a variety of functions at different steps of tumor progression. Moreover, it has been demonstrated that galectin-1 cellular localization and galectin-1 binding partners depend on tumor localization and stage. Recently, galectin-1 overexpression has been extensively documented in several tumor types and/or in the stroma of cancer cells. Its expression is thought to reflect tumor aggressiveness in several tumor types. Galectin-1 has been identified as a promising drug target using synthetic and natural inhibitors. Preclinical data suggest that galectin-1 inhibition may lead to direct antiproliferative effects in cancer cells as well as antiangiogenic effects in tumors. We provide an up-to-date overview of available data on the role of galectin-1 in different molecular and biochemical pathways involved in human malignancies. One of the major challenges faced in targeting galectin-1 is the translation of current knowledge into the design and development of effective galectin-1 inhibitors in cancer therapy.

OTX008, a selective small-molecule inhibitor of galectin-1, downregulates cancer cell proliferation, invasion and tumour angiogenesis.

BACKGROUND: Galectin-1 (Gal1), a carbohydrate-binding protein is implicated in cancer cell proliferation, invasion and tumour angiogenesis. Several Gal1-targeting compounds have recently emerged. OTX008 is a calixarene derivative designed to bind the Gal1 amphipathic ß-sheet conformation. Our study contributes to the current understanding of the role of Gal1 in cancer progression, providing mechanistic insights into the anti-tumoural activity of a novel small molecule Gal1-inhibitor. METHODS: We evaluated in vitro OTX008 effects in a panel of human cancer cell lines. For in vivo studies, an ovarian xenograft model was employed to analyse the antitumour activity. Finally, combination studies were performed to analyse potential synergistic effects of OTX008. RESULTS: In cultured cancer cells, OTX008 inhibited proliferation and invasion at micromolar concentrations. Antiproliferative effects correlated with Gal1 expression across a large panel of cell lines. Furthermore, cell lines expressing epithelial differentiation markers were more sensitive than mesenchymal cells to OTX008. In SQ20B and A2780-1A9 cells, OTX008 inhibited Gal1 expression and ERK1/2 and AKT-dependent survival pathways, and induced G2/M cell cycle arrest through CDK1. OTX008 enhanced the antiproliferative effects of Semaphorin-3A (Sema3A) in SQ20B cells and reversed invasion induced by exogenous Gal1. In vivo, OTX008 inhibited growth of A2780-1A9 xenografts. OTX008 treatment was associated with downregulation of Gal1 and Ki67 in treated tumours, as well as decreased microvessel density and VEGFR2 expression. Finally, combination studies showed OTX008 synergy with several cytotoxic and targeted therapies, principally when OTX008 was administered first. CONCLUSION: This study provides insights into the role of Gal1 in cancer progression as well as OTX008 mechanism of action, and supports its further development as an anticancer agent.

Antitumor agent calixarene 0118 targets human galectin-1 as an allosteric inhibitor of carbohydrate binding.

Calix[4]arene compound 0118 is an angiostatic agent that inhibits tumor growth in mice. Although 0118 is a topomimetic of galectin-1-targeting angiostatic amphipathic peptide Anginex, we had yet to prove that 0118 targets galectin-1. Galectin-1 is involved in pathological disorders like tumor endothelial cell adhesion and migration and therefore presents a relevant target for therapeutic intervention against cancer. Here, (15)N-(1)H HSQC NMR spectroscopy demonstrates that 0118 indeed targets galectin-1 at a site away from the lectin's carbohydrate binding site and thereby attenuates lactose binding to the lectin. Flow cytometry and agglutination assays show that 0118 attenuates binding of galectin-1 to cell surface glycans, and the inhibition of cell proliferation by 0118 is found to be correlated with the cellular expression of the lectin. In general, our data indicate that 0118 targets galectin-1 as an allosteric inhibitor of glycan/carbohydrate binding. This work contributes to the clinical development of antitumor calixarene compound 0118.

Epithelial-to-mesenchymal transition and oncogenic Ras expression in resistance to the protein kinase Cbeta inhibitor enzastaurin in colon cancer cells.

Identifying molecular factors of sensitivity and resistance of cancer cells to enzastaurin, a drug inhibiting protein kinase C (PKC) beta, remains a major challenge to improve its clinical development. Investigating the cellular effects of enzastaurin in a panel of 20 human cancer cell lines, we found that most cells displaying oncogenic K-Ras mutations also display resistance to enzastaurin. Wild-type (WT) K-Ras cancer cells displaying high sensitivity to enzastaurin also expressed high mRNA levels of epithelial markers, such as E-cadherin (CDH1), and low mRNA expressions of mesenchymal markers, such as vimentin, N-cadherin (CDH2), and other genes frequently expressed in mesenchymal transition such as ZEB1, TWIST, SLUG, SNAIL, and TGFbeta. WT K-Ras enzastaurin-resistant cells also expressed high levels of mesenchymal markers. Based on this observation, the effects of enzastaurin were investigated in epithelial colon COLO205-S cells that expressed WT Ras/Raf and its derived COLO205-R mesenchymal counterpart selected for resistance to most PKC modulators and displaying oncogenic K-Ras (G13D/exon 2). In COLO205-S cells, inhibition of phosphorylated PKCbeta led to the inactivation of AKT and glycogen synthase kinase 3beta and was associated with apoptosis without significant effect on cell cycle progression. In COLO205-R cells, enzastaurin induced mainly necrosis at high concentrations. In COLO205-R cells, a strong activation of extracellular signal-regulated kinase 1/2 possibly due to oncogenic K-Ras was predominantly associated with transcription of potent antiapoptotic genes, such as BCL2, GADD45B, and CDKN1A, as well as the multidrug resistance gene ABCB1. From this study, colon cancer cells undergoing apoptosis under enzastaurin exposure seem to frequently express a WT Ras and an epithelial phenotype.

Epithelial-to-mesenchymal transition and resistance to ingenol 3-angelate, a novel protein kinase C modulator, in colon cancer cells.

Acquired resistance to protein kinase C (PKC) modulators may explain the failure of clinical trials in patients with cancer. Herein, we established a human colon cancer cell line resistant to PEP005, a drug that inhibits PKCalpha and activates PKCdelta. Colo205-R cells, selected by stepwise exposure to PEP005, were >300-fold more resistant to PEP005 than parental Colo205-S cells and were cross-resistant to phorbol 12-myristate 13-acetate, bryostatin, bistratene A, and staurosporine. No PKCalpha or PKCdelta mutation was detected in Colo205-S and Colo205-R cells. Changes in Colo205-R cells were reminiscent of the epithelial-to-mesenchymal transition (EMT) phenotype. Accordingly, Colo205-R cells were more invasive than Colo205-S in Matrigel assays and in mouse xenografts. We also found an increased mRNA expression of several EMT genes, such as those encoding for transforming growth factor-beta and vimentin, along with a decreased mRNA expression of genes involved in epithelial differentiation, such as CDH1 (E-cadherin), CLDN4 (claudin 4), S100A4, and MUC1, in Colo205-R compared with Colo205-S cells in vitro and in vivo. Interestingly, high expression of ET-1 was shown in Colo205-R cells and correlated with low sensitivity to PEP005 and staurosporine in a panel of 10 human cancer cell lines. Inhibition of the ET-1 receptor ETR-A with bosentan restored the antiproliferative effects of PEP005 in Colo205-R cells and decreased the invasive properties of this cell line. Exogenous exposure to ET-1 and silencing ET-1 expression using small interfering RNA modulated cell signaling in Colo205-S and Colo205-R. In summary, acquired resistance to PEP005 was associated with expression of EMT markers and activates the ET-1/ETR-A cell signaling.