Antoine Galmiche

Iron-dependent cell death of hepatocellular carcinoma cells exposed to sorafenib

The multikinase inhibitor sorafenib is currently the treatment of reference for advanced hepatocellular carcinoma (HCC). In our report, we examined the cytotoxic effects of sorafenib on HCC cells. We report that the depletion of the intracellular iron stores achieved by using the iron chelator deferoxamine (DFX) strikingly protects HCC cells from the cytotoxic effects of sorafenib. The protective effect of the depletion of intracellular iron stores could not be explained by an interference with conventional forms of programmed cell death, such as apoptosis or autophagic cell death. We also found that DFX did not prevent sorafenib from reaching its intracellular target kinases. Instead, the depletion of intracellular iron stores prevented sorafenib from inducing oxidative stress in HCC cells. We examined the possibility that sorafenib might exert a cytotoxic effect that resembles ferroptosis, a form of cell death in which iron‐dependent oxidative mechanisms play a pivotal role. In agreement with this possibility, we found that pharmacological inhibitors (ferrostatin‐1) and genetic procedures (RNA interference against IREB‐2) previously reported to modulate ferroptosis, readily block the cytotoxic effects of sorafenib in HCC cells. Collectively, our findings identify ferroptosis as an effective mechanism for the induction of cell death in HCC. Ferroptosis could potentially become a goal for the medical treatment of HCC, thus opening new avenues for the optimization of the use of sorafenib in these tumors.

The retinoblastoma (Rb) protein regulates ferroptosis induced by sorafenib in human hepatocellular carcinoma cells

Sorafenib is the treatment of reference for advanced hepatocellular carcinoma (HCC), the most frequent form of primary liver tumour. The loss of function of the retinoblastoma (Rb) protein is an important event during liver carcinogenesis, but it is unclear whether the Rb status modulates the response of HCC cells to sorafenib. Here, we examined this question in HCC cells with reduced levels of Rb achieved through stable RNA interference. We show that HCC cells with reduced levels of Rb exhibit a two- to threefold increase in cell death induction upon exposure to sorafenib compared with controls. Sorafenib treatment of Balb/c nude mice that received tumour xenografts derived from HCC cells with reduced Rb levels resulted in complete tumour regression in 50% of the animals treated, compared with tumour stabilization in mice that received control cells. We show that, upon exposure to sorafenib, the Rb-negative status of HCC cells promotes the occurrence of ferroptosis, a form of oxidative necrosis. The findings highlight the role of Rb in the response of HCC cells to sorafenib and the regulation of ferroptosis.

New biological perspectives for the improvement of the efficacy of sorafenib in hepatocellular carcinoma.

Sorafenib, an orally-available kinase inhibitor, is the only medical treatment with a proven efficacy against Hepatocellular Carcinoma (HCC). Although the overall clinical efficacy of sorafenib is modest, recent experimental results have uncovered new potential strategies that may increase its clinical benefits. The potential implication of Receptor Tyrosine Kinases (RTKs), such as the Epidermal Growth Factor Receptor (EGFR), in the development of resistance to sorafenib highlights the importance of the RAF kinase pathway. Various strategies aiming to optimize the control exerted over this pathway by combining sorafenib with other targeted molecules (such as anti-EGFR, anti-MEK) are under investigation. Increasing the cytotoxicity of sorafenib in HCC, either through apoptosis or through new forms of non-apoptotic cell death, such as ferroptosis, may also promote more sustained tumour regression. Finally, the heterogeneity of individual responses to sorafenib is increasingly recognised, even though clinically-applicable biomarkers remain to be identified. Here, we discuss how molecular genetics and complementary approaches such as short term culture of tumour samples could help to personalize the use of sorafenib.

Upregulation of BAD, a pro-apoptotic protein of the BCL2 family, in vascular smooth muscle cells exposed to uremic conditions.

Chronic kidney disease (CKD) has recently emerged as a major risk factor for cardiovascular pathology. CKD patients display accelerated atherosclerotic process, leading to circulatory complications. However, it is currently not clear how uremic conditions accelerate atherosclerosis. Apoptosis is an important homeostatic regulator of vascular smooth cells under pathological conditions. In the present study, we explored the regulation of apoptosis in cells of the vascular wall in the uremic context. We analysed the expression and regulation of the proteins of the BCL2 family that play an essential role in apoptosis. Our results, obtained in mice and primary human smooth muscle cells exposed to two uremic toxins, point to the existence of an alteration in expression and function of one pro-apoptotic member of this family, the protein BAD. We explore the regulation of BAD by uremic toxins and report the sensitization of vascular smooth muscle cells to apoptosis upon BAD induction.

The kinase-inhibitor sorafenib inhibits multiple steps of the Hepatitis C Virus infectious cycle in vitro.

Hepatitis C Virus (HCV) chronic infection is a major cause of hepatocellular carcinoma. Sorafenib is the only medical treatment that has been approved for the treatment of this cancer. It is a multikinase inhibitor with anti-tumor activity against a wide variety of cancers. Sorafenib blocks angiogenesis and tumor cell proliferation through inhibition of kinases, such as VEGFR2, PDGFR, or the serine/threonine kinases RAF. Previous studies have reported an anti-HCV effect of sorafenib in vitro, but various mechanisms of action have been described. The aim of this study was to clarify the action of sorafenib on the complete HCV infectious cycle. In order to examine the action of sorafenib on all steps of the HCV infectious cycle, we used a combination of validated cell culture models, based on the HuH-7 reference cell line and primary human hepatocytes. We found that sorafenib blocks HCV infection by altering the viral entry step and the production of viral particles. Moreover, we observed that treatment with sorafenib lead to a modification of Claudin-1 expression and localization, which could partly be responsible for the anti-HCV effect. Collectively, our findings confirm the anti-HCV effect of sorafenib in vitro, while highlighting the complexity of the action of sorafenib on the HCV infectious cycle.

Metallothionein-1 as a biomarker of altered redox metabolism in hepatocellular carcinoma cells exposed to sorafenib

BackgroundSorafenib, a kinase inhibitor active against various solid tumours, induces oxidative stress and ferroptosis, a new form of oxidative necrosis, in some cancer cells. Clinically-applicable biomarkers that reflect the impact of sorafenib on the redox metabolism of cancer cells are lacking.MethodsWe used gene expression microarrays, real-time PCR, immunoblot, protein-specific ELISA, and gene reporter constructs encoding the enzyme luciferase to study the response of a panel of cancer cells to sorafenib. Tumour explants prepared from surgical hepatocellular carcinoma (HCC) samples and serum samples obtained from HCC patients receiving sorafenib were also used.ResultsWe observed that genes of the metallothionein-1 (MT1) family are induced in the HCC cell line Huh7 exposed to sorafenib. Sorafenib increased the expression of MT1G mRNA in a panel of human cancer cells, an effect that was not observed with eight other clinically-approved kinase inhibitors. We identified the minimal region of the MT1G promoter that confers inducibility by sorafenib to a 133 base pair region containing an Anti-oxidant Response Element (ARE) and showed the essential role of the transcription factor NRF2 (Nuclear factor erythroid 2-Related Factor 2). We examined the clinical relevance of our findings by analysing the regulation of MT1G in five tumour explants prepared from surgical HCC samples. Finally, we showed that the protein levels of MT1 increase in the serum of some HCC patients receiving sorafenib, and found an association with reduced overall survival.ConclusionThese findings indicate that MT1 constitute a biomarker adapted for exploring the impact of sorafenib on the redox metabolism of cancer cells.

Farnesyltransferase inhibitor R115777 protects against vascular disease in uremic mice.

BACKGROUND Atherosclerosis and vascular calcification are major contributors to cardiovascular morbidity and mortality among chronic kidney disease patients. The mevalonate pathway may play a role in this vascular pathology. Farnesyltransferase inhibitors such as R115777 block one branch of mevalonate pathway. We studied the effects of farnesyltransferase inhibitor R115777 on vascular disease in apolipoprotein E deficient mice with chronic renal failure and on mineral deposition in vitro. METHODS AND RESULTS Female uremic and non-uremic apolipoprotein E deficient mice were randomly assigned to four groups and treated with either farnesyltransferase inhibitor R115777 or vehicle. Farnesyltransferase inhibitor R115777 inhibited protein prenylation in mice with chronic renal failure. It decreased aortic atheromatous lesion area and calcification in these animals, and reduced vascular nitrotyrosine expression and total collagen as well as collagen type I content. Proteomic analysis revealed that farnesyltransferase inhibitor corrected the chronic renal failure-associated increase in serum apolipoprotein IV and α globin, and the chronic renal failure-associated decrease in serum fetuin A. Farnesyltransferase inhibitor further inhibited type I collagen synthesis and reduced mineral deposition in vascular smooth muscle cells in vitro, probably involving Ras-Raf pathway. CONCLUSIONS We show for the first time that farnesyltransferase inhibition slows vascular disease progression in chronic renal failure by both indirect systemic and direct local actions. This beneficial effect was mediated via a reduction in oxidative stress and favorable changes in vasoprotective peptides.

Alpha-fetoprotein is a biomarker of unfolded protein response and altered proteostasis in hepatocellular carcinoma cells exposed to sorafenib

Sorafenib is the treatment of reference for advanced hepatocellular carcinoma (HCC). A decrease in the serum levels of Alpha-fetoprotein (AFP) is reported to be the biological parameter that is best associated with disease control by sorafenib. In order to provide a biological rationale for the variations of AFP, we analyzed the various steps of AFP production in human HCC cell lines exposed to sorafenib. Sorafenib dramatically reduced the levels of AFP produced by HCC cells independently of its effect on cell viability. The mRNA levels of AFP decreased upon sorafenib treatment, while the AFP protein remained localized in the Golgi apparatus. Sorafenib activated the Regulated Inositol-Requiring Enzyme-1α (IRE-1α) and the PKR-like ER Kinase (PERK)-dependent arms of the Unfolded Protein Response (UPR). The inhibition of IRE-1α partially restored the mRNA levels of AFP upon treatment with sorafenib. The inhibition of both pathways partially prevented the drop in the production of AFP induced by sorafenib. The findings provide new insights on the regulation of AFP, and identify it as a biomarker suitable for the exploration of HCC cell proteostasis in the context of therapeutic targeting.

Neurotensin regulation induces overexpression and activation of EGFR in HCC and restores response to erlotinib and sorafenib

Hepatocellular carcinoma (HCC) is the third leading cause of death from cancer due to the combination of late diagnosis and a lack of curative treatments. The identification of factors which promote tumor aggressiveness, and those that predict treatment responses, are a means to optimize the management of HCC patients. The complex of Neurotensin (NTS) and its high affinity receptor (NTSR1) has been shown to induce tumor growth and metastasis process in various cancers. In this paper, we propose that NTS and NTSR1 can assist in the management of HCC. Concomitant expression of NTS/NTSR1 was correlated with poor prognosis and found in 50% of HCC patients. We show that NTSR1 expression was positively correlated with the alteration of the Wnt/β-catenin pathway. Its activation creates EGFR driver activation which consequently enhances tumor progression, and sensitizes HCC tumor cells to TKI, such as sorafenib. The NTS/NTSR1 complex is a potential drug target for HCC, because it is an upstream regulator in the chain of cellular events involved in HCC progression. It could also be used as a theranostic biomarker for sorafenib to improve the HCC patient management.

Probing Tumour Proteostasis and the UPR with Serum Markers

Tumour proteostasis and the unfolded protein response (UPR) are emerging drivers of tumour progression and important determinants of clinical efficacy of cancer therapy. Recent findings indicate that they also regulate the production of protein tumour markers. Here, we discuss how this new knowledge opens up new perspectives for cancer therapeutics.