► Bisphenol A as a metabolic disrupter in human HepG2 hepatoma cells at low doses. ► Induction of mitochondrial dysfunction with reactive oxygen species, lipoperoxidation, ΔΨM hyperpolarization. ► ...Process associated with lipid accumulation and pro-inflammatory cytokines secretion. ► Bisphenol A would act as a pro-steatotic compound in hepatic cells in vitro.
Bisphenol A (BPA) is an endocrine-disrupting chemical that leaches from polycarbonate plastics that consequently leads to low-dose human exposure. In addition to its known xenoendocrine action, BPA exerts a wide variety of metabolic effects, but no data are available on its actions on the functions of liver mitochondrial. To assess these effects, HepG2 cells were exposed to BPA (10−4–10−12M) and physiological parameters were measured by flow cytometry. We demonstrated a significant mitochondrial dysfunction including ROS production, ΔΨM hyperpolarization, lipid accumulation, lipoperoxidation and the release of pro-inflammatory cytokines. In conclusion, we showed that low concentrations of BPA promote lipid accumulation in hepatic cells triggered by disturbances in mitochondrial function, alterations in lipid metabolism and by inflammation that can therefore contribute to steatosis.
Chronic exposure to inorganic arsenic, a widely distributed environmental contaminant, can lead to toxic effects, including immunosuppression. Owing to the established roles of human macrophages in ...immune defense, we determined, in the present study, whether inorganic arsenic can affect these major immune cells. Our results demonstrate that noncytotoxic concentrations of arsenic trioxide (As2O3), an inorganic trivalent form, markedly impair differentiated features of human blood monocyte-derived macrophages. First, treatment of macrophages with 1 microM As2O3 induced a rapid cell rounding and a subsequent loss of adhesion. These morphologic alterations were associated with a marked reorganization of actin cytoskeleton, which includes retraction of peripheral actin extensions and formation of a cortical actin ring. In addition, As2O3 reduced expression of various macrophagic surface markers, enhanced that of the monocytic marker CD14, and altered both endocytosis and phagocytosis; unexpectedly, exposure of macrophages to the metalloid also strongly potentiated expression of TNFalpha and IL-8 induced by LPS. Finally, like monocytes, As2O3-treated macrophages can be differentiated into dendritic-like cells. Impairment of macrophage function by As2O3 mainly resulted from activation of a RhoA/Rho-associated kinase pathway; indeed, pretreatment of macrophages with the Rho-associated kinase inhibitor Y-27632 prevented metalloid effects on cytoskeleton and phagocytosis. Moreover, As2O3 was found to increase level of the active GTP-bound form of RhoA and that of phosphorylated-Moesin, a major cytoskeleton adaptor protein involved in RhoA regulation. Taken together, our results demonstrated that human macrophages constitute sensitive targets of inorganic arsenic, which may contribute to immunotoxicity of this environmental contaminant.
Glioblastomas (GBM) are brain tumors with a poor prognosis despite treatment that combines surgical resection and radio-chemotherapy. These tumors are characterized by abundant vascularization and ...significant cellular heterogeneity including GBM stem-like cells (GSC) which contribute to tumor aggressiveness, resistance, and recurrence. Recent data has demonstrated that GSC are directly involved in the formation of new vessels via their transdifferentiation into Tumor Derived Endothelial Cells (TDEC). We postulate that cellular stress such as ionizing radiation (IR) could enhance the transdifferentiation of GSC into TDEC. GSC neurospheres isolated from 3 different patients were irradiated or not and were then transdifferentiated into TDEC. In fact, TDEC obtained from irradiated GSC (TDEC IR+) migrate more towards VEGF, form more pseudotubes in Matrigel
in vitro and develop more functional blood vessels in Matrigel
plugs implanted in Nude mice than TDEC obtained from non-irradiated GSC. Transcriptomic analysis allows us to highlight an overexpression of Tie2 in TDEC IR+. All IR-induced effects on TDEC were abolished by using a Tie2 kinase inhibitor, which confirms the role of the Tie2 signaling pathway in this process. Finally, by analyzing Tie2 expression in patient GBMs by immunohistochemistry, we demonstrated that the number of Tie2+ vessels increases in recurrent GBM compared with matched untreated tumors. In conclusion, we demonstrate that IR potentiates proangiogenic features of TDEC through the Tie2 signaling pathway, which indicates a new pathway of treatment-induced tumor adaptation. New therapeutic strategies that associate standard treatment and a Tie2 signaling pathway inhibitor should be considered for future trials.
The Rho GTPase family can be classified into classic and atypical members. Classic members cycle between an inactive Guanosine DiPhosphate -bound state and an active Guanosine TriPhosphate-bound ...state. Atypical Rho GTPases, such as RND1, are predominantly in an active GTP-bound conformation. The role of classic members in oncogenesis has been the subject of numerous studies, while that of atypical members has been less explored. Besides the roles of RND1 in healthy tissues, recent data suggest that RND1 is involved in oncogenesis and response to cancer therapeutics. Here, we present the current knowledge on RND1 expression, subcellular localization, and functions in healthy tissues. Then, we review data showing that RND1 expression is dysregulated in tumors, the molecular mechanisms involved in this deregulation, and the role of RND1 in oncogenesis. For several aggressive tumors, RND1 presents the features of a tumor suppressor gene. In these tumors, low expression of
is associated with a bad prognosis for the patients. Finally, we highlight that
expression is induced by anticancer agents and modulates their response. Of note,
mRNA levels in tumors could be used as a predictive marker of both patient prognosis and response to anticancer agents.
Respiratory chain complex II has been extensively studied but little is known about its assembly and the role of its heme group. Mutations in the phylogenetically conserved histidine 127 of the SDHC ...subunit have been shown to abrogate heme binding in yeast and bacteria without impairing complex II assembly or enzymatic activities. Here we show that in mammalian cells these mutations lead to a complete reduction of SDHC in mitochondria, a destabilisation of SDHD and SDHB, and to an abrogation of complex II enzymatic activities, suggesting that in mammalian cells complex II assembly is more complex than in lower organisms.
Unlike other Rho GTPases, RhoB is rapidly induced by DNA damage, and its expression level decreases during cancer progression. Because inefficient repair of DNA double-strand breaks (DSBs) can lead ...to cancer, we investigated whether camptothecin, an anticancer drug that produces DSBs, induces RhoB expression and examined its role in the camptothecin-induced DNA damage response. We show that in camptothecin-treated cells, DSBs induce RhoB expression by a mechanism that depends notably on Chk2 and its substrate HuR, which binds to RhoB mRNA and protects it against degradation. RhoB-deficient cells fail to dephosphorylate γH2AX following camptothecin removal and show reduced efficiency of DSB repair by homologous recombination. These cells also show decreased activity of protein phosphatase 2A (PP2A), a phosphatase for γH2AX and other DNA damage and repair proteins. Thus, we propose that DSBs activate a Chk2-HuR-RhoB pathway that promotes PP2A-mediated dephosphorylation of γH2AX and DSB repair. Finally, we show that RhoB-deficient cells accumulate endogenous γH2AX and chromosomal abnormalities, suggesting that RhoB loss increases DSB-mediated genomic instability and tumor progression.
Despite maximally safe resection of the magnetic resonance imaging (MRI)–defined contrast-enhanced (CE) central tumor area and chemoradiotherapy, most patients with glioblastoma (GBM) relapse within ...a year in peritumoral FLAIR regions. Magnetic resonance spectroscopy imaging (MRSI) can discriminate metabolic tumor areas with higher recurrence potential as CNI+ regions (choline/
N
-acetyl-aspartate index >2) can predict relapse sites. As relapses are mainly imputed to glioblastoma stem-like cells (GSCs), CNI+ areas might be GSC enriched. In this prospective trial, 16 patients with GBM underwent MRSI/MRI before surgery/chemoradiotherapy to investigate GSC content in CNI−/+ biopsies from CE/FLAIR. Biopsy and derived-GSC characterization revealed a FLAIR/CNI+ sample enrichment in GSC and in gene signatures related to stemness, DNA repair, adhesion/migration, and mitochondrial bioenergetics. FLAIR/CNI+ samples generate GSC-enriched neurospheres faster than FLAIR/CNI−. Parameters assessing biopsy GSC content and time-to-neurosphere formation in FLAIR/CNI+ were associated with worse patient outcome. Preoperative MRI/MRSI would certainly allow better resection and targeting of FLAIR/CNI+ areas, as their GSC enrichment can predict worse outcomes.
Preoperative magnetic resonance spectroscopy imaging can detect GSC-enriched tumor areas in patients with Glioblastoma.
High-grade gliomas, glioblastomas (GB), are refractory to conventional treatment combining surgery, chemotherapy, mainly temozolomide, and radiotherapy. This highlights an urgent need to develop ...novel therapies and increase the efficacy of radio/chemotherapy for these very aggressive and malignant brain tumors. Recently, tumor metabolism became an interesting potential therapeutic target in various cancers. Accordingly, combining drugs targeting cell metabolism with appropriate chemotherapeutic agents or radiotherapy has become attractive. In light of these perspectives, we were particularly interested in the anti-cancer properties of a biguanide molecule used for type 2 diabetes treatment, metformin. In our present work, we demonstrate that metformin decreases mitochondrial-dependent ATP production and oxygen consumption and increases lactate and glycolytic ATP production. We show that metformin induces decreased proliferation, cell cycle arrest, autophagy, apoptosis and cell death in vitro with a concomitant activation of AMPK, Redd1 and inhibition of the mTOR pathway. Cell sensitivity to metformin also depends on the genetic and mutational backgrounds of the different GB cells used in this study, particularly their PTEN status. Interestingly, knockdown of AMPK and Redd1 with siRNA partially, but incompletely, abrogates the induction of apoptosis by metformin suggesting both AMPK/Redd1-dependent and -independent effects. However, the primary determinant of the effect of metformin on cell growth is the genetic and mutational backgrounds of the glioma cells. We further demonstrate that metformin treatment in combination with temozolomide and/or irradiation induces a synergistic anti-tumoral response in glioma cell lines. Xenografts performed in nude mice demonstrate in vivo that metformin delays tumor growth. As current treatments for GB commonly fail to cure, the need for more effective therapeutic options is overwhelming. Based on these results, metformin could represent a potential enhancer of the cytotoxic effects of temozolomide and/or radiotherapy.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
Glioblastomas are malignant brain tumors with dismal prognosis despite standard treatment with surgery and radio/chemotherapy. These tumors are defined by an important cellular heterogeneity and ...notably contain a particular subpopulation of Glioblastoma-initiating cells, which recapitulate the heterogeneity of the original Glioblastoma. In order to classify these heterogeneous tumors, genomic profiling has also been undertaken to classify these heterogeneous tumors into several subtypes. Current research focuses on developing therapies, which could take into account this cellular and genomic heterogeneity. Among these targets, integrins are the subject of numerous studies since these extracellular matrix transmembrane receptors notably controls tumor invasion and progression. Moreover, some of these integrins are considered as membrane markers for the Glioblastoma-initiating cells subpopulation. We reviewed here integrin expression according to glioblastoma molecular subtypes and cell heterogeneity. We discussed their roles in glioblastoma invasion, angiogenesis, therapeutic resistance, stemness and microenvironment modulations, and provide an overview of clinical trials investigating integrins in glioblastomas. This review highlights that specific integrins could be identified as selective glioblastoma cells markers and that their targeting represents new diagnostic and/or therapeutic strategies.
Glioblastomas (GB) are malignant brain tumors with poor prognosis despite treatment with surgery and radio/chemotherapy. These tumors are defined by an important cellular heterogeneity and notably ...contain a subpopulation of GB-initiating cells (GIC), which contribute to tumor aggressiveness, resistance, and recurrence. Some integrins are specifically expressed by GICs and could be actionable targets to improve GB treatment. Here, integrin β8 (ITGB8) was identified as a potential selective target in this highly tumorigenic GIC subpopulation. Using several patient-derived primocultures, it was demonstrated that ITGB8 is overexpressed in GICs compared with their differentiated progeny. Furthermore, ITGB8 is also overexpressed in GB, and its overexpression is correlated with poor prognosis and with the expression of several other classic stem cell markers. Moreover, inhibiting ITGB8 diminished several main GIC characteristics and features, including self-renewal ability, stemness, migration potential, and tumor formation capacity. Blockade of ITGB8 significantly impaired GIC cell viability via apoptosis induction. Finally, the combination of radiotherapy and ITGB8 targeting radiosensitized GICs through postmitotic cell death. IMPLICATIONS: This study identifies ITGB8 as a new selective marker for GICs and as a promising therapeutic target in combination with chemo/radiotherapy for the treatment of highly aggressive brain tumors.
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