The Identification of New c-FLIP Inhibitors for Restoring Apoptosis in TRAIL-Resistant Cancer Cells.

The catalytically inactive caspase-8-homologous protein, c-FLIP, is a potent antiapoptotic protein highly expressed in various types of cancers. c-FLIP competes with caspase-8 for binding to the adaptor protein FADD (Fas-Associated Death Domain) following death receptors' (DRs) activation via the ligands of the TNF-R family. As a consequence, the extrinsic apoptotic signaling pathway involving DRs is inhibited. The inhibition of c-FLIP activity in tumor cells might enhance DR-mediated apoptosis and overcome immune and anticancer drug resistance. Based on an in silico approach, the aim of this work was to identify new small inhibitory molecules able to bind selectively to c-FLIP and block its anti-apoptotic activity. Using a homology 3D model of c-FLIP, an in silico screening of 1880 compounds from the NCI database (National Cancer Institute) was performed. Nine molecules were selected for in vitro assays, based on their binding affinity to c-FLIP and their high selectivity compared to caspase-8. These molecules selectively bind to the Death Effector Domain 2 (DED2) of c-FLIP. We have tested in vitro the inhibitory effect of these nine molecules using the human lung cancer cell line H1703, overexpressing c-FLIP. Our results showed that six of these newly identified compounds efficiently prevent FADD/c-FLIP interactions in a molecular pull-down assay, as well as in a DISC immunoprecipitation assay. The overexpression of c-FLIP in H1703 prevents TRAIL-mediated apoptosis; however, a combination of TRAIL with these selected molecules significantly restored TRAIL-induced cell death by rescuing caspase cleavage and activation. Altogether, our findings indicate that new inhibitory chemical molecules efficiently prevent c-FLIP recruitment into the DISC complex, thus restoring the caspase-8-dependent apoptotic cascade. These results pave the way to design new c-FLIP inhibitory molecules that may serve as anticancer agents in tumors overexpressing c-FLIP.

Radiosensitizing Fe-Au nanocapsules (hybridosomes®) increase survival of GL261 brain tumor-bearing mice treated by radiotherapy.

Glioblastoma remains a cancer for which the effectiveness of treatments has shown little improvement over the last decades. For this pathology, multiple therapies combining resection, chemotherapy and radiotherapy remain the norm. In this context, the use of high-Z nanoparticles such as gold or hafnium to potentiate radiotherapy is attracting more and more attention. Here, we evaluate the potentiating effect of hollow shells made of gold and iron oxide nanoparticles (hybridosomes®) on the radiotherapy of glioblastoma, using murine GL261-Luc+ brain tumor model. While iron oxide seems to have no beneficial effect for radiotherapy, we observe a real effect of gold nanoparticles-despite their low amount-with a median survival increase of almost 20% compared to radiotherapy only and even 33% compared to the control group. Cellular and in vivo studies show that a molecule of interest nano-precipitated in the core of the hybridosomes® is released and internalized by the surrounding brain cells. Finally, in vivo studies show that hybridosomes® injected intra-tumorally are still present in the vicinity of the brain tumor more than 5 days after injection (duration of the Stupp protocol's radiation treatment). Interestingly, one mouse treated with radiotherapy in the presence of gold-containing hybridosomes® survived 78 days. Monitoring of the tumoral growth of this long-term survivor using both MRI and bioluminescence revealed a decrease of the tumor size after treatment. These very encouraging results are a proof-of-concept that hybridosomes® are really effective tools for the development of combined therapies (chemo-radiotherapy).

Orthotopic model of lung cancer: isolation of bone micro-metastases after tumor escape from Osimertinib treatment.

BACKGROUND: Osimertinib is a third generation tyrosine kinase inhibitor (TKI) that targets the epidermal growth factor receptor (EGFR) in lung cancer. However, although this molecule is not subject to some of the resistance mechanisms observed in response to first generation TKIs, ultimately, patients relapse because of unknown resistance mechanisms. New relevant non-small cell lung cancer (NSCLC) mice models are therefore required to allow the analysis of these resistance mechanisms and to evaluate the efficacy of new therapeutic strategies. METHODS: Briefly, PC-9 cells, previously modified for luciferase expression, were injected into the tail vein of mice. Tumor implantation and longitudinal growth, almost exclusively localized in the lung, were evaluated by bioluminescence. Once established, the tumor was treated with osimertinib until tumor escape and development of bone metastases. RESULTS: Micro-metastases were detected by bioluminescence and collected for further analysis. CONCLUSION: We describe an orthotopic model of NSCLC protocol that led to lung primary tumor nesting and, after osimertinib treatment, by metastases dissemination, and that allow the isolation of these small osimertinib-resistant micro-metastases. This model provides new biological tools to study tumor progression from the establishment of a lung tumor to the generation of drug-resistant micro-metastases, mimicking the natural course of the disease in human NSCLC patients.

Human ex vivo prostate tissue model system identifies ING3 as an oncoprotein.

BACKGROUND: Although the founding members of the INhibitor of Growth (ING) family of histone mark readers, ING1 and ING2, were defined as tumour suppressors in animal models, the role of other ING proteins in cellular proliferation and cancer progression is unclear. METHODS: We transduced ex vivo benign prostate hyperplasia tissues with inducible lentiviral particles to express ING proteins. Proliferation was assessed by H3S10phos immunohistochemistry (IHC). The expression of ING3 was assessed by IHC on a human prostate cancer tissue microarray (TMA). Gene expression was measured by DNA microarray and validated by real-time qPCR. RESULTS: We found that ING3 stimulates cellular proliferation in ex vivo tissues, suggesting that ING3 could be oncogenic. Indeed, ING3 overexpression transformed normal human dermal fibroblasts. We observed elevated levels of ING3 in prostate cancer samples, which correlated with poorer patient survival. Consistent with an oncogenic role, gene-silencing experiments revealed that ING3 is required for the proliferation of breast, ovarian, and prostate cancer cells. Finally, ING3 controls the expression of an intricate network of cell cycle genes by associating with chromatin modifiers and the H3K4me3 mark at transcriptional start sites. CONCLUSIONS: Our investigations create a shift in the prevailing view that ING proteins are tumour suppressors and redefine ING3 as an oncoprotein.

Brief Report: Proteasomal Indoleamine 2,3-Dioxygenase Degradation Reduces the Immunosuppressive Potential of Clinical Grade-Mesenchymal Stromal Cells Undergoing Replicative Senescence.

Owing to their immunosuppressive properties, mesenchymal stromal cells (MSCs) obtained from bone marrow (BM-MSCs) or adipose tissue (ASCs) are considered a promising tool for cell therapy. However, important issues should be considered to ensure the reproducible production of efficient and safe clinical-grade MSCs. In particular, high expansion rate, associated with progressive senescence, was recently proposed as one of the parameters that could alter MSC functionality. In this study, we directly address the consequences of replicative senescence on BM-MSC and ASC immunomodulatory properties. We demonstrate that MSCs produced according to GMP procedures inhibit less efficiently T-cell, but not Natural Killer (NK)- and B-cell, proliferation after reaching senescence. Senescence-related loss-of-function is associated with a decreased indoleamine 2,3-dioxygenase (IDO) activity in response to inflammatory stimuli. In particular, although STAT-1-dependent IDO expression is transcriptionally induced at a similar level in senescent and nonsenescent MSCs, IDO protein is specifically degraded by the proteasome in senescent ASCs and BM-MSCs, a process that could be reversed by the MG132 proteasome inhibitor. These data encourage the use of appropriate quality controls focusing on immunosuppressive mechanisms before translating clinical-grade MSCs in the clinic. Stem Cells 2017;35:1431-1436.

tert-Butylphenolic Derivatives from Paenibacillus odorifer-A Case of Bioconversion.

Two compounds (1) and (2) containing tert-butylphenol groups were, for the first time, produced during the culture of Paenibacillus odorifer, a bacterial strain associated with the crustose lichen, Rhizocarpon geographicum. Their entire structures were identified by one-dimensional (1D) and two-dimensional (2D) NMR and high-resolution electrospray ionisation mass spectrometry (HRESIMS) spectroscopic analyses. Among them, Compound 1 exhibited significant cytotoxicity against B16 murine melanoma and HaCaT human keratinocyte cell lines with micromolar half maximal inhibitory concentration (IC50) values. Furthermore, after supplementation studies, a putative biosynthesis pathway was proposed for Compound 1 throughout a bioconversion by this bacterial strain of butylated hydroxyanisole (BHA), an antioxidant polymer additive.

Hypoxia Differentially Modulates the Genomic Stability of Clinical-Grade ADSCs and BM-MSCs in Long-Term Culture.

Long-term cultures under hypoxic conditions have been demonstrated to maintain the phenotype of mesenchymal stromal/stem cells (MSCs) and to prevent the emergence of senescence. According to several studies, hypoxia has frequently been reported to drive genomic instability in cancer cells and in MSCs by hindering the DNA damage response and DNA repair. Thus, we evaluated the occurrence of DNA damage and repair events during the ex vivo expansion of clinical-grade adipose-derived stromal cells (ADSCs) and bone marrow (BM)-derived MSCs cultured with platelet lysate under 21% (normoxia) or 1% (hypoxia) O2 conditions. Hypoxia did not impair cell survival after DNA damage, regardless of MSC origin. However, ADSCs, unlike BM-MSCs, displayed altered γH2AX signaling and increased ubiquitylated γH2AX levels under hypoxic conditions, indicating an impaired resolution of DNA damage-induced foci. Moreover, hypoxia specifically promoted BM-MSC DNA integrity, with increased Ku80, TP53BP1, BRCA1, and RAD51 expression levels and more efficient nonhomologous end joining and homologous recombination repair. We further observed that hypoxia favored mtDNA stability and maintenance of differentiation potential after genotoxic stress. We conclude that long-term cultures under 1% O2 were more suitable for BM-MSCs as suggested by improved genomic stability compared with ADSCs.

SUMOylation of the ING1b tumor suppressor regulates gene transcription.

The INhibitor of Growth (ING) proteins are encoded as multiple isoforms in five ING genes (ING1 -5) and act as type II tumor suppressors. They are growth inhibitory when overexpressed and are frequently mislocalized or downregulated in several forms of cancer. ING1 and ING2 are stoichiometric members of histone deacetylase complexes, whereas ING3-5 are stoichiometric components of different histone acetyltransferase complexes. The INGs target these complexes to histone marks, thus acting as epigenetic regulators. ING proteins affect angiogenesis, apoptosis, DNA repair, metastasis and senescence, but how the proteins themselves are regulated is not yet clear. Here, we find a small ubiquitin-like modification (SUMOylation) of the ING1b protein and identify lysine 193 (K193) as the preferred ING1b SUMO acceptor site. We also show that PIAS4 is the E3 SUMO ligase responsible for ING1b SUMOylation on K193. Sequence alignment reveals that the SUMO consensus site on ING1b contains a phosphorylation-dependent SUMOylation motif (PDSM) and our data indicate that the SUMOylation on K193 is enhanced by the S199D phosphomimic mutant. Using an ING1b protein mutated at the major SUMOylation site (ING1b E195A), we further demonstrate that ING1b SUMOylation regulates the binding of ING1b to the ISG15 and DGCR8 promoters, consequently regulating ISG15 and DGCR8 transcription. These results suggest a role for ING1b SUMOylation in the regulation of gene transcription.

ING1 and ING2: multifaceted tumor suppressor genes.

Inhibitor of Growth 1 (ING1) was identified and characterized as a "candidate" tumor suppressor gene in 1996. Subsequently, four more genes, also characterized as "candidate" tumor suppressor genes, were identified by homology search: ING2, ING3, ING4, and ING5. The ING proteins are characterized by a high homology in their C-terminal domain, which contains a Nuclear Localization Sequence and a Plant HomeoDomain (PHD), which has a high affinity to Histone 3 tri-methylated on lysine 4 (H3K4Me3). The ING proteins have been involved in the control of cell growth, senescence, apoptosis, chromatin remodeling, and DNA repair. Within the ING family, ING1 and ING2 form a subgroup since they are evolutionarily and functionally close. In yeast, only one gene, Pho23, is related to ING1 and ING2 and possesses also a PHD. Recently, the ING1 and ING2 tumor suppressor status has been fully established since several studies have described the loss of ING1 and ING2 protein expression in human tumors and both ING1 and ING2 knockout mice were reported to have spontaneously developed tumors, B cell lymphomas, and soft tissue sarcomas, respectively. In this review, we will describe for the first time what is known about the ING1 and ING2 genes, proteins, their regulations in both human and mice, and their status in human tumors. Furthermore, we explore the current knowledge about identified functions involving ING1 and ING2 in tumor suppression pathways especially in the control of cell cycle and in genome stability.

Simple elaboration of drug-SPION nanocapsules (hybridosomes®) by solvent shifting: Effect of the drug molecular structure and concentration.

Drug nanocapsules coated with iron oxide nanoparticles (SPION) were elaborated by the simultaneous nanoprecipitation of the drug and the nanoparticles, through solvent shifting. We examined four drugs: sorafenib, sorafenib tosylate, α-tocopherol and paclitaxel, to cover the cases of molecular solids, ionic solids, and molecular liquids. We first investigated the formation of the drug core in the final mixture of solvents at different concentrations. A Surfactant-Free Micro-Emulsion domain (SFME, thermodynamically stable) was observed at low drug concentration and an Ouzo domain (metastable) at high drug concentration, except for the case of paclitaxel which crystallizes at high concentration without forming an Ouzo domain. When co-nanoprecipitated with the molecular drugs in the Ouzo domain (sorafenib or α-tocopherol), the SPION limited the coalescence of the drug particles to less than 100 nm, forming capsules with a drug encapsulation efficiency of ca 80 %. In contrast, larger capsules were formed from the SFME or when using the ionic form (sorafenib tosylate). Finally, the sorafenib-SPION capsules exhibit a similar chemotherapeutic effect as the free drug on the hepatocellular carcinoma in vitro.

Afatinib or Bevacizumab in combination with Osimertinib efficiently control tumor development in orthotopic murine models of non-small lung cancer.

Lung cancer is one of the most common and deadliest cancers. Preclinical models are essential to study new therapies and combinations taking tumor genetics into account. We have established cell lines expressing the luciferase gene from lines with varied genetic backgrounds, commonly encountered in patients with pulmonary adenocarcinoma. We have characterized these lines by testing their response to multiple drugs. Thus, we have developed orthotopic preclinical mouse models of NSCLC with very high engraftment efficiency. These models allow the easy monitoring of tumor growth, particularly in response to treatment, and of tumor cells dissemination in the body. We show that concomitant treatment with osimertinib (3rd generation tyrosine kinase inhibitor targeting mutated EGFR) and bevacizumab (anti-angiogenic targeting VEGF) can have a beneficial therapeutic effect on EGFR-mutated tumors. We also show that the addition of afatinib to osimertinib-treated tumors in escape leads to tumor growth inhibition. No such effect is observed with selumetinib or simvastatin. These preclinical mouse models therefore make it possible to test innovative therapeutic combinations and are also a tool of choice for studying resistance mechanisms.

Newly identified tumor suppressor functions of ING proteins.

The INhibitor of Growth (ING) proteins (ING1, ING2, ING3, ING4 and ING5) are a family of epigenetic regulators. Their decreased expression in numerous cancers led to identifying the ING proteins as gatekeeper tumor suppressors as they regulate cell cycle progression, apoptosis and senescence. Subsequently, they were also described as caretaker tumor suppressors through their involvement in DNA replication and the DNA damage response (DDR). Recent studies have identified new interactions of the ING proteins with proteins or pathways implicated in cell proliferation, the maintenance of stem cells pluripotency or the DDR. Furthermore, the ING proteins have been identified as regulators of ribosomal RNA synthesis and of mRNA stability and as regulators of mitochondrial DNA transcription resulting in the regulation of metabolism. These new findings highlight new antitumorigenic activities of the ING proteins that are potential targets for cancer treatment.

Genomic characteristics and clinical significance of CD56+ circulating tumor cells in small cell lung cancer.

Circulating tumor cells (CTC) have been studied in various solid tumors but clinical utility of CTC in small cell lung cancer (SCLC) remains unclear. The aim of the CTC-CPC study was to develop an EpCAM-independent CTC isolation method allowing isolation of a broader range of living CTC from SCLC and decipher their genomic and biological characteristics. CTC-CPC is a monocentric prospective non-interventional study including treatment-naïve newly diagnosed SCLC. CD56+ CTC were isolated from whole blood samples, at diagnosis and relapse after first-line treatment and submitted to whole-exome-sequencing (WES). Phenotypic study confirms tumor lineage and tumorigenic properties of isolated cells for the 4 patients analyzed with WES. WES of CD56+ CTC and matched tumor biopsy reveal genomic alteration frequently impaired in SCLC. At diagnosis CD56+ CTC were characterized by a high mutation load, a distinct mutational profile and a unique genomic signature, compared to match tumors biopsies. In addition to classical pathways altered in SCLC, we found new biological processes specifically affected in CD56+ CTC at diagnosis. High numeration of CD56+ CTC (> 7/ml) at diagnosis was associated with ES-SCLC. Comparing CD56+ CTC isolated at diagnosis and relapse, we identify differentially altered oncogenic pathways (e.g. DLL3 or MAPK pathway). We report a versatile method of CD56+ CTC detection in SCLC. Numeration of CD56+ CTC at diagnosis is correlated with disease extension. Isolated CD56+ CTC are tumorigenic and show a distinct mutational profile. We report a minimal gene set as a unique signature of CD56+ CTC and identify new affected biological pathways enriched in EpCAM-independent isolated CTC in SCLC.

GLI1, a novel target of the ER stress regulator p97/VCP, promotes ATF6f-mediated activation of XBP1.

Upon accumulation of improperly folded proteins in the Endoplasmic Reticulum (ER), the Unfolded Protein Response (UPR) is triggered to restore ER homeostasis. The induction of stress genes is a sine qua non condition for effective adaptive UPR. Although this requirement has been extensively described, the mechanisms underlying this process remain in part uncharacterized. Here, we show that p97/VCP, an AAA+ ATPase known to contribute to ER stress-induced gene expression, regulates the transcription factor GLI1, a primary effector of Hedgehog (Hh) signaling. Under basal (non-ER stress) conditions, GLI1 is repressed by a p97/VCP-HDAC1 complex while upon ER stress GLI1 is induced through a mechanism requiring both USF2 binding and increase histone acetylation at its promoter. Interestingly, the induction of GLI1 was independent of ligand-regulated Hh signaling. Further analysis showed that GLI1 cooperates with ATF6f to induce promoter activity and expression of XBP1, a key transcription factor driving UPR. Overall, our work demonstrates a novel role for GLI1 in the regulation of ER stress gene expression and defines the interplay between p97/VCP, HDAC1 and USF2 as essential players in this process.

Preclinical Models for Acquired Resistance to Third-Generation EGFR Inhibitors in NSCLC: Functional Studies and Drug Combinations Used to Overcome Resistance.

Epidermal growth factor receptor (EGFR)-tyrosine kinase inhibitors (TKIs) are currently recommended as first-line treatment for advanced non-small-cell lung cancer (NSCLC) with EGFR-activating mutations. Third-generation (3rd G) EGFR-TKIs, including osimertinib, offer an effective treatment option for patients with NSCLC resistant 1st and 2nd EGFR-TKIs. However, the efficacy of 3rd G EGFR-TKIs is limited by acquired resistance that has become a growing clinical challenge. Several clinical and preclinical studies are being carried out to better understand the mechanisms of resistance to 3rd G EGFR-TKIs and have revealed various genetic aberrations associated with molecular heterogeneity of cancer cells. Studies focusing on epigenetic events are limited despite several indications of their involvement in the development of resistance. Preclinical models, established in most cases in a similar manner, have shown different prevalence of resistance mechanisms from clinical samples. Clinically identified mechanisms include EGFR mutations that were not identified in preclinical models. Thus, NRAS genetic alterations were not observed in patients but have been described in cell lines resistant to 3rd G EGFR-TKI. Mainly, resistance to 3rd G EGFR-TKI in preclinical models is related to the activation of alternative signaling pathways through tyrosine kinase receptor (TKR) activation or to histological and phenotypic transformations. Yet, preclinical models have provided some insight into the complex network between dominant drivers and associated events that lead to the emergence of resistance and consequently have identified new therapeutic targets. This review provides an overview of preclinical studies developed to investigate the mechanisms of acquired resistance to 3rd G EGFR-TKIs, including osimertinib and rociletinib, across all lines of therapy. In fact, some of the models described were first generated to be resistant to first- and second-generation EGFR-TKIs and often carried the T790M mutation, while others had never been exposed to TKIs. The review further describes the therapeutic opportunities to overcome resistance, based on preclinical studies.

Characterization of the Peri-Membrane Fluorescence Phenomenon Allowing the Detection of Urothelial Tumor Cells in Urine.

Urine cytology is non-invasive, easy to collect, with medium sensitivity and a high specificity. It is an effective way to detect high-grade bladder cancer (BC), but it is less effective on low-grade BC because the rate of equivocal results is much higher. Recently, the fluorescent properties of plasma membranes of urothelial tumor cells (UTC) found in urine cytology have been shown to be useful in improving the early detection of BC. This phenomenon is called peri-membrane fluorescence (PMF). Based on previous studies that have identified the PMF on UTCs, the main objective was to characterize this phenomenon. For this study, a software was specially created to quantify the PMF of all tested cells and different treatments performed. PMF was not found to be a morphological and discriminating feature of UTCs, all cells in shape and not from urine show PMF. We were able to highlight the crucial role of plasma membrane integrity in the maintenance of PMF. Finally, it was found that the induction of a strong cellular stress induced a decrease in PMF, mimicking what was observed in non-tumor cells collected from urine. These results suggest that PMF is found in cells able to resist this stress, such as tumor cells.

Stress-induced tyrosine phosphorylation of RtcB modulates IRE1 activity and signaling outputs.

ER stress is mediated by three sensors and the most evolutionary conserved IRE1α signals through its cytosolic kinase and endoribonuclease (RNase) activities. IRE1α RNase activity can either catalyze the initial step of XBP1 mRNA unconventional splicing or degrade a number of RNAs through regulated IRE1-dependent decay. Until now, the biochemical and biological outputs of IRE1α RNase activity have been well documented; however, the precise mechanisms controlling whether IRE1α signaling is adaptive or pro-death (terminal) remain unclear. We investigated those mechanisms and hypothesized that XBP1 mRNA splicing and regulated IRE1-dependent decay activity could be co-regulated by the IRE1α RNase regulatory network. We identified that RtcB, the tRNA ligase responsible for XBP1 mRNA splicing, is tyrosine-phosphorylated by c-Abl and dephosphorylated by PTP1B. Moreover, we show that the phosphorylation of RtcB at Y306 perturbs RtcB interaction with IRE1α, thereby attenuating XBP1 mRNA splicing. Our results demonstrate that the IRE1α RNase regulatory network is dynamically fine-tuned by tyrosine kinases and phosphatases upon various stresses and that the extent of RtcB tyrosine phosphorylation determines cell adaptive or death outputs.