Pentoxifylline Inhibits WNT Signalling in β-Cateninhigh Patient-Derived Melanoma Cell Populations

Tumor-Infiltrating iNKT Cells Activated through c-Kit/Sca-1 Are Induced by Pentoxifylline, Norcantharidin, and Their Mixtures for Killing Murine Melanoma Cells

The involvement of NK and other cytotoxic cells is considered the first defense line against cancer. However, a significant lack of information prevails on the possible roles played by factors considered characteristic of primitive cells, such as c-kit and Sca-1, in activating these cells, particularly in melanoma models subjected to treatments with substances under investigation, such as the case of norcantharidin. In this study, B16F1 murine melanoma cells were used to induce tumors in DBA/2 mice, estimating the proportions of NK and iNKT cells; the presence of activation (CD107a+) and primitive/activation (c-kit+/Lya6A+) markers and some tumor parameters, such as the presence of mitotic bodies, nuclear factor area, NK and iNKT cell infiltration in the tumor, infiltrated tumor area, and infiltrating lymphocyte count at 10x and 40x in specimens treated with pentoxifylline, norcantharidin, and the combination of both drugs. Possible correlations were estimated with Pearson's correlation analysis. It should be noted that, despite having demonstrated multiple correlations, immaturity/activation markers were related to these cells' activation. At the tumor site, iNKT cells are the ones that exert the cytotoxic potential on tumor cells, but they are confined to specific sites in the tumor. Due to the higher number of interactions of natural killer cells with tumor cells, it is concluded that the most effective treatment was PTX at 60 mg/kg + NCTD at 0.75 mg/kg.

Nucleolin Targeting by N6L Inhibits Wnt/β-Catenin Pathway Activation in Pancreatic Ductal Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and resistant cancer with no available effective therapy. We have previously demonstrated that nucleolin targeting by N6L impairs tumor growth and normalizes tumor vessels in PDAC mouse models. Here, we investigated new pathways that are regulated by nucleolin in PDAC. We found that N6L and nucleolin interact with β-catenin. We found that the Wnt/β-catenin pathway is activated in PDAC and is necessary for tumor-derived 3D growth. N6L and nucleolin loss of function induced by siRNA inhibited Wnt pathway activation by preventing β-catenin stabilization in PDAC cells. N6L also inhibited the growth and the activation of the Wnt/β-catenin pathway in vivo in mice and in 3D cultures derived from MIA PaCa2 tumors. On the other hand, nucleolin overexpression increased β-catenin stabilization. In conclusion, in this study, we identified β-catenin as a new nucleolin interactor and suggest that the Wnt/β-catenin pathway could be a new target of the nucleolin antagonist N6L in PDAC.

Enzymatic Activity of CD73 Modulates Invasion of Gliomas via Epithelial-Mesenchymal Transition-Like Reprogramming

Glioblastoma (GBM) is the most aggressive malignant primary brain tumour in adulthood. Despite strong research efforts current treatment options have a limited impact on glioma stem-like cells (GSCs) which contribute to GBM formation, progression and chemoresistance. Invasive growth of GSCs is in part associated with epithelial-mesenchymal-like transition (EMT), a mechanism associated with CD73 in several cancers. Here, we show that CD73 regulates the EMT activator SNAIL1 and further investigate the role of enzymatic and non-enzymatic CD73 activity in GBM progression. Reduction of CD73 protein resulted in significant suppression of GSC viability, proliferation and clonogenicity, whereas CD73 enzymatic activity exhibited negative effects only on GSC invasion involving impaired downstream adenosine (ADO) signalling. Furthermore, application of phosphodiesterase inhibitor pentoxifylline, a potent immunomodulator, effectively inhibited ZEB1 and CD73 expression and significantly decreased viability, clonogenicity, and invasion of GSC in vitro cultures. Given the involvement of adenosine and A3 adenosine receptor in GSC invasion, we investigated the effect of the pharmacological inhibition of A3AR on GSC maintenance. Direct A3AR inhibition promoted apoptotic cell death and impaired the clonogenicity of GSC cultures. Taken together, our data indicate that CD73 is an exciting novel target in GBM therapy. Moreover, pharmacological interference, resulting in disturbed ADO signalling, provides new opportunities to innovate GBM therapy.

WNT Signaling in Melanoma

WNT-signaling controls important cellular processes throughout embryonic development and adult life, so any deregulation of this signaling can result in a wide range of pathologies, including cancer. WNT-signaling is classified into two categories: β-catenin-dependent signaling (canonical pathway) and β-catenin-independent signaling (non-canonical pathway), the latter can be further divided into WNT/planar cell polarity (PCP) and calcium pathways. WNT ligands are considered as unique directional growth factors that contribute to both cell proliferation and polarity. Origin of cancer can be diverse and therefore tissue-specific differences can be found in WNT-signaling between cancers, including specific mutations contributing to cancer development. This review focuses on the role of the WNT-signaling pathway in melanoma. The current view on the role of WNT-signaling in cancer immunity as well as a short summary of WNT pathway-related drugs under investigation are also provided.

17-Aminogeldanamycin selectively diminishes IRE1α-XBP1s pathway activity and cooperatively induces apoptosis with MEK1/2 and BRAFV600E inhibitors in melanoma cells of different genetic subtypes

Outcomes of melanoma patient treatment remain unsatisfactory despite accessibility of oncoprotein-targeting drugs and immunotherapy. Here, we reported that 17-aminogeldanamycin more potently activated caspase-3/7 in BRAF^V600E melanoma cells than geldanamycin, another inhibitor of heat shock protein 90 (HSP90). 17-aminogeldanamycin alleviated self-triggered compensatory increase in HSP70 mRNA level and induced endoplasmic reticulum (ER) stress, which was followed by selective diminution of cytoprotective IRE1α-XBP1s pathway activity of unfolded protein response (UPR), inhibition of ERK1/2 activity and induction of apoptosis. Concomitantly, ATF6/p50 level and expression of PERK-dependent genes, CHOP and BIM, remained unaltered. This might result from an inframe deletion in EIF2AK3 leading to a PERK^L21del variant revealed by whole-exome sequencing in melanoma cell lines. 17-aminogeldanamycin exhibited similar activity in NRAS^Q61R melanoma cells that harbored a heterozygous inactivating variant of NAD(P)H:quinone oxidoreductase 1 (NQO1^P187S). In addition, 17-aminogeldanamycin acted cooperatively with trametinib (an inhibitor of MEK1/2) and vemurafenib (an inhibitor of BRAF^V600E) in induction of apoptosis in melanoma cell lines as evidenced by in-cell caspase-3/7 activation and PARP cleavage that occurred earlier compared with either drug used alone. As trametinib and vemurafenib did not significantly affect HSP70 and GRP78 transcript levels, cooperation of MEK/BRAF^V600E inhibitors and 17-aminogeldanamycin might result from a concurrent inhibition of the RAS/RAF/MEK/ERK cascade and IRE1α-dependent signaling, and cell-intrinsic ER homeostasis can determine the extent of the drug cooperation. Our study indicates that 17-aminogeldanamycin takes several advantages compared with other HSP90-targeting compounds, and can complement activity of BRAF/MEK inhibitors in melanoma cells of different genetic subtypes.

Pentoxifylline alleviated cardiac injury via modulating the cardiac expression of lncRNA-00654-miR-133a-SOX5 mRNA in the rat model of ischemia-reperfusion

Pentoxifylline (PTX) protects from many cardiovascular complications. It plays a critical role in stem cell proliferation and differentiation. Here, the effect of PTX administration on cardiac ischemia and dysfunction was explored. PTX in 3 doses (20, 30, and 40 mg/kg), was administered in vivo 5 min before a 45 min occlusion of the left anterior descending artery, followed by a 120 min reperfusion in male Wistar rats. The left ventricular end-diastolic pressure and dP/dt_max were assessed. Blood and cardiac tissue samples were collected for measuring the levels of cardiac enzymes and the expression of lncRNA-00654-miR-133a-SOX5. Samples of left ventricles were collected and processed for light microscopic, immunohistochemical staining for c-kit (a marker for cardiac progenitor cells) and transmission electron microscopic examination. PTX administration showed improvements in cardiac function tests, enzymes, and myocytes. Microscopic features showed minimal cardiac edema, hemorrhage, cellular inflammatory infiltration and fibrosis in addition to increased c-kit + cells in cardiac tissue samples. Notably, this treatment also produced a dose-dependent decrease in lncRNA-00654 with an increase in SOX5 mRNA and miRNA-133a-3p expressions. In conclusion, PTX has the potential to alleviate cardiac injury and increase the number of c-kit + cells following ischemia-reperfusion in the rat model via modulation of lncRNA-00654 and miR-133a-SOX5 mRNA expressions.

Thymoquinone and pentoxifylline enhance the chemotherapeutic effect of cisplatin by targeting Notch signaling pathway in mice

AIMS

Notch signaling is highly implicated in several cancers and chemoresistance. Therefore, Notch-targeted therapies might be beneficial in enhancing chemotherapeutic effect and cancer regression. This study aimed to investigate implication of Notch in development and progression of solid Ehrlich carcinoma (SEC) and enhancement of anticancer effect of cisplatin (CIS) by addition of thymoquinone (TQ) and pentoxifylline (PTX) through modulation of Notch.

MAIN METHODS

SEC was induced in mice as model for mammary carcinoma by s.c. injection of 1 × 10⁶ Ehrlich cells into back of the mice. On 12^th day, solid tumor was developed and mice were divided into seven groups; tumor control, early CIS (ECIS), ECIS + ETQ, ECIS + ETQ + EPTX, late CIS (LCIS), LCIS + LTQ, and LCIS + LTQ + LPTX. Early treatment was started on 12^th day, whereas late treatment was begun on 19^th day from tumor inoculation. At the endpoint, samples were collected for detection of Notch1, Hes1, Jagged1, β-catenin, TNF-α, IL-6, IFN-γ, IL-2, VEGF, apoptosis, CD4, and CD8.

KEY FINDINGS

Adding PTX and TQ to CIS significantly reduced Notch1, Hes1, Jagged1, β-catenin, TNF-α, IL-6, IFN-γ, and VEGF with increment in IL-2, CD4, CD8, and apoptotic cells. Moreover, early treated groups showed remarkable attenuation in tumor growth and the relevant parameters compared to their counterpart later groups.

SIGNIFICANCE

Addition of PTX with TQ to CIS showed a synergistic chemotherapeutic action and induced better oncostatic effect mainly through Notch suppression. Consequently, shutting Notch could be of great interest in promoting chemosensetivity and cancer control.

Vascular Endothelium in Neonatal Sepsis: Basic Mechanisms and Translational Opportunities

Neonatal sepsis remains a major health issue worldwide, especially for low-birth weight and premature infants, with a high risk of death and devastating sequelae. Apart from antibiotics and supportive care, there is an unmet need for adjunctive treatments to improve the outcomes of neonatal sepsis. Strong and long-standing research on adult patients has shown that vascular endothelium is a key player in the pathophysiology of sepsis and sepsis-associated organ failure, through a direct interaction with pathogens, leukocytes, platelets, and the effect of soluble circulating mediators, in part produced by endothelial cells themselves. Despite abundant evidence that the neonatal immune response to sepsis is distinct from that of adults, comparable knowledge on neonatal vascular endothelium is much more limited. Neonatal endothelial cells express lower amounts of adhesion molecules compared to adult ones, and present a reduced capacity to neutralize reactive oxygen species. Conversely, available evidence on biomarkers of endothelial damage in neonates is not as robust as in adult patients, and endothelium-targeted therapeutic opportunities for neonatal sepsis are almost unexplored. Here, we summarize current knowledge on the structure of neonatal vascular endothelium, its interactions with neonatal immune system and possible endothelium-targeted diagnostic and therapeutic tools for neonatal sepsis. Furthermore, we outline areas of basic and translational research worthy of further study, to shed light on the role of vascular endothelium in the context of neonatal sepsis.

Inhibitory effects of pentoxifylline on inflammation-related tumorigenesis in rat colon

Chronic inflammation in the colorectum increases the risk of colorectal cancer development. Pentoxifylline, a medicine used for improving the circulation, has been reported to inhibit TNF-α production and to ameliorate inflammatory bowel disease and non-alcoholic steatohepatitis. In this study, we investigated the effects of pentoxifylline on inflammation-related colon tumorigenesis in a rodent model using Kyoto APC delta rats, which have APC mutation and are susceptible to colon carcinogenesis. Male Kyoto APC delta rats were treated with azoxymethane and dextran sodium sulfate, and were subsequently administered water, with or without pentoxifylline. At the end of the experiment, the development of colorectal tumor was significantly inhibited in the pentoxifylline group. The pentoxifylline treatment also lowered the levels of oxidative stress markers and mRNAs of pro-inflammatory cytokines, including TNF-α and IL-6, in the colon mucosa. The PCNA labeling index and the inflammation score were also decreased in the colon of rats in the pentoxifylline -treated group. We also used an endoscopy to observe the tumor progression and inflammation in the colon of rats, revealing that inflammation grade was significantly lower in pentoxifylline-treated group at several points during the experiment. These findings suggest that pentoxifylline treatment might be useful for chemoprevention of inflammation-related colon cancer.

Exogenous growth factors bFGF, EGF and HGF do not influence viability and phenotype of V600EBRAF melanoma cells and their response to vemurafenib and trametinib in vitro

It has been shown that the response of ^V600EBRAF melanoma cells to targeted therapeutics is affected by growth factors. We have investigated the influence of three different growth factors, bFGF, EGF and HGF used either alone or in combination, on the response of ^V600EBRAF melanoma cell populations established from surgical specimens to vemurafenib and trametinib, targeting ^V600EBRAF and MEK1/2, respectively.

We report that proliferation and phenotype of ^V600EBRAF melanoma cell populations were not detectably influenced by exogenous growth factors. Neither cell distribution in cell cycle and CCND1 expression nor activity of signaling pathways crucial for melanoma development and maintenance, including the RAF/MEK/ERK pathway, WNT/β-catenin pathway and NF-κB signaling, were affected by the presence of different growth factors. We furthermore show that vemurafenib and trametinib abrogated the activity of ERK1/2, arrested cells in G₀/G₁ cell cycle phase, triggered apoptosis, induced changes in the expression of CXCL8, CCND1 and CTGF and the frequency of Ki-67^high and CD271^high cells. These effects were, however, similar in the presence of different growth factors. Interestingly, comparable results were also obtained for melanoma cells grown without exogenous growth factors bFGF, EGF and HGF for a period as long as 4 months prior the drug treatment.

We conclude that the composition or lack of exogenous growth factors bFGF, EGF and HGF do not markedly influence viability and phenotype of ^V600EBRAF melanoma cells and their response to vemurafenib and trametinib in vitro. Our results question the necessity of these growth factors in the medium that is used for culturing ^V600EBRAF melanoma cells.

Vemurafenib and trametinib reduce expression of CTGF and IL-8 in V600EBRAF melanoma cells

Clinical evidence has revealed that while RAS/RAF/MEK/ERK pathway is a crucial component of melanomagenesis, other signaling pathways can also contribute to the malignant growth and development of resistance to targeted therapies. We explored the response of ^V600EBRAF melanoma cells derived from surgical specimens and grown in stem cell medium to vemurafenib and trametinib, drugs targeting the activity of ^V600EBRAF and MEK1/2, respectively. Cell growth and apoptosis were monitored by real-time imaging system, immunophenotype and cell cycle by flow cytometry, gene expression by quantitative real-time PCR, immunoblotting and enzyme-linked immunosorbent assay. The ^V600EBRAF melanoma cell populations were diverse. Differences in morphology, pigmentation, cell cycle profiles, and immunophenotype were observed. At the molecular level, melanoma cells differed in the phosphorylation of ERK1/2, NF-κB, and β-catenin, and expression of several relevant genes, including MITF-M, DKK1, CCND1, BRAF, CXCL8, and CTGF. Despite having different characteristics, melanoma cells responded similarly to vemurafenib and trametinib. Both drugs reduced ERK1/2 phosphorylation and percentages of cells expressing Ki-67 at high level, inhibited expression of CCND1 and induced cell cycle arrest in the G_o/G₁ phase. These expected cytostatic effects were accompanied by increased CD271 expression, a marker of stem-like cells. NF-κB activity was reduced by both drugs, however, not completely abolished, whereas the level of active β-catenin was increased by drugs in three out of six cell populations. Interestingly, expression of IL-8 and CTGF was significantly reduced by treatment with vemurafenib and trametinib. Simultaneous inhibition of NF-κB activity and induction of ERK1/2 phosphorylation revealed that CTGF expression depends on ERK1/2 activity but not on NF-κB activity. Both, the positive effects of treatment with vemurafenib and trametinib such as the newly identified CTGF suppression and undesired effects such as increased CD271 expression suggesting selection of melanoma stem-like cells should be considered in the development of combination treatment for melanoma patients.