SC-2001 overcomes STAT3-mediated sorafenib resistance through RFX-1/SHP-1 activation in hepatocellular carcinoma

Regulatory factor X1 promotes sorafenib-induced ferroptosis in hepatocellular carcinoma by transcriptional regulation of BECN1

BACKGROUND

Sorafenib is a commonly used first-line kinase-targeted drug for advanced hepatocellular carcinoma (HCC) patients suffering from limited efficacy. Emerging evidence indicates that sorafenib exerts anti-cancer activity through the induction of ferroptosis in HCC cells, but the underlying mechanism is still unclear.

METHODS

The whole transcriptome sequencing and bioinformatics analysis were used to screen for target genes. The expression and subcellular localization of regulatory factor X1 (RFX1) were determined through immunohistochemistry, immunofluorescence, PCR and western blot analyses. The impact of RFX1 on HCC cell growth was assessed using CCK8, colony formation assays, cell death assays, and animal experiments. Glutathione measurement, iron assay and lipid peroxidation detection assays were performed to investigate ferroptosis of HCC cells. The regulatory mechanism of RFX1 in HCC was investigated by sgRFX1, co-IP, ChIP and luciferase experiments. Immunohistochemical and survival analyses were performed to examine the prognostic significance of RFX1 in HCC.

RESULTS

In this study, we found that RFX1 promote ferroptosis in HCC cells. Further, we showed that sorafenib induces cell death through RFX1-mediated ferroptosis in HCC cells. The enhancing effect of RFX1 on HCC cell ferroptosis is largely dependent on inhibition of cystine/glutamate antiporter (system Xc-) activity through the BECN-SLC7A11 axis, where RFX1 directly binds to the promoter region of BECN1 and upregulates BECN1 expression. In addition, a STAT3-RFX1-BECN1 signalling loop was found to promote RFX1 expression in HCC cells.

CONCLUSIONS

Our study reveals a novel mechanism underlying sorafenib-induced HCC cell death.

RXR agonist, Bexarotene, effectively reduces drug resistance via regulation of RFX1 in embryonic carcinoma cells

Aberrant expression of multidrug resistance (MDR) proteins is one of the features of cancer stem cells (CSCs) that make them escape chemotherapy. A well-orchestrated regulation of multiple MDRs by different transcription factors in cancer cells confers this drug resistance. An in silico analysis of the major MDR genes revealed a possible regulation by RFX1 and Nrf2. Previous reports also noted that Nrf2 is a positive regulator of MDR genes in NT2 cells. But we, for the first time, report that Regulatory factor X1 (RFX1), a pleiotropic transcription factor, negatively regulates the major MDR genes, Abcg2, Abcb1, Abcc1, and Abcc2, in NT2 cells. The levels of RFX1 in undifferentiated NT2 cells were found to be very low, which significantly increased upon RA-induced differentiation. Ectopic expression of RFX1 reduced the levels of transcripts corresponding to MDRs and stemness-associated genes. Interestingly, Bexarotene, an RXR agonist that acts as an inhibitor of Nrf2-ARE signaling, could increase the transcription of RFX1. Further analysis revealed that the RFX1 promoter has binding sites for RXRα, and upon Bexarotene exposure RXRα could bind and activate the RFX1 promoter. Bexarotene, alone or in combination with Cisplatin, could inhibit many cancer/CSC-associated properties in NT2 cells. Also, it significantly reduced the expression of drug resistance proteins and made the cells sensitive towards Cisplatin. Our study proves that RFX1 could be a potent molecule to target MDRs, and Bexarotene can induce RXRα-mediated RFX1 expression, therefore, would be a better chemo-assisting drug during therapy.

Hypoxia-induced exosomes facilitate lung pre-metastatic niche formation in hepatocellular carcinoma through the miR-4508-RFX1-IL17A-p38 MAPK-NF-κB pathway

Background: Hypoxia plays an important role in the lung metastasis of hepatocellular carcinoma (HCC). However, the process by which hypoxia promotes the formation of a pre-metastatic niche (PMN) and its underlying mechanism remain unclear. Methods: Exosomes derived from normoxic and hypoxic HCC cells were collected to induce fibroblast activation in vitro and PMN formation in vivo. The micro RNA (miR) profiles of the exosomes were sequenced to identify differentially expressed miRNAs. Gain- and loss-of-function analyses were performed to investigate miR-4508 function. Dual-luciferase, western blotting, and real-time reverse transcription-PCR analyses were used to identify the direct targets of miR-4508 and its downstream signaling pathways. To demonstrate the roles of hypoxic tumor-derived exosomes (H-TDEs) and miR-4508 in the lung metastasis of liver cancer, H22 tumor cells were injected through the tail vein of mice. Blood plasma-derived exosomes from patients with HCC who underwent transarterial chemoembolization (TACE) were applied to determine clinical correlations. Results: We demonstrated that H-TDEs activated lung fibroblasts and facilitated PMN formation, thereby promoting lung metastasis in mice. Screening for upregulated exosomal miRNAs revealed that miR-4508 and its target, regulatory factor X1 (RFX1), were involved in H-TDE-induced lung PMN formation. Moreover, miR-4508 was significantly upregulated in plasma exosomes derived from patients with HCC after TACE. We confirmed that the p38 MAPK-NF-κB signaling pathway is involved in RFX1 knockdown-induced fibroblast activation and PMN formation. In addition, IL17A, a downstream target of RFX1, was identified as a link between RFX1 knockdown and p38 MAPK activation in fibroblasts. Conclusion: Hypoxia enhances the release of TDEs enriched with miR-4508, thereby promoting lung PMN formation by targeting the RFX1-IL17A-p38 MAPK-NF-κB pathway. These findings highlight a novel mechanism underlying hypoxia-induced pulmonary metastasis of HCC.

Deciphering STAT3 signaling potential in hepatocellular carcinoma: tumorigenesis, treatment resistance, and pharmacological significance

Hepatocellular carcinoma (HCC) is considered one of the greatest challenges to human life and is the most common form of liver cancer. Treatment of HCC depends on chemotherapy, radiotherapy, surgery, and immunotherapy, all of which have their own drawbacks, and patients may develop resistance to these therapies due to the aggressive behavior of HCC cells. New and effective therapies for HCC can be developed by targeting molecular signaling pathways. The expression of signal transducer and activator of transcription 3 (STAT3) in human cancer cells changes, and during cancer progression, the expression tends to increase. After induction of STAT3 signaling by growth factors and cytokines, STAT3 is phosphorylated and translocated to the nucleus to regulate cancer progression. The concept of the current review revolves around the expression and phosphorylation status of STAT3 in HCC, and studies show that the expression of STAT3 is high during the progression of HCC. This review addresses the function of STAT3 as an oncogenic factor in HCC, as STAT3 is able to prevent apoptosis and thus promote the progression of HCC. Moreover, STAT3 regulates both survival- and death-inducing autophagy in HCC and promotes cancer metastasis by inducing the epithelial-mesenchymal transition (EMT). In addition, upregulation of STAT3 is associated with the occurrence of chemoresistance and radioresistance in HCC. Specifically, non-protein-coding transcripts regulate STAT3 signaling in HCC, and their inhibition by antitumor agents may affect tumor progression. In this review, all these topics are discussed in detail to provide further insight into the role of STAT3 in tumorigenesis, treatment resistance, and pharmacological regulation of HCC.

Potential Treatment Strategies for Hepatocellular Carcinoma Cell Sensitization to Sorafenib

Liver cancer is highly malignant, has a low sensitivity to chemotherapy, and is associated with poor patient prognosis. The last 3 years have seen the emergence of promising targeted therapies for the treatment of hepatocellular carcinoma (HCC). For over 10 years, before the discovery of lenvatinib, sorafenib was only first-line therapeutic agent available for the treatment of advanced HCC. However, several clinical studies have shown that a considerable proportion liver cancer patients are insensitive to sorafenib. Very few patients actually substantially benefit from treatment with sorafenib, and the overall efficacy of the drug has not been satisfactory; therefore, sorafenib has attracted considerable research attention. This study, which is based on previous studies and reports, reviews the potential mechanisms underlying sorafenib resistance and summarizes combination therapies and potential drugs that can be used to sensitize HCC cells to sorafenib.

Niclosamide Revitalizes Sorafenib through Insulin-like Growth Factor 1 Receptor (IGF-1R)/Stemness and Metabolic Changes in Hepatocellular Carcinoma

Sorafenib is the first approved systemic targeting agent for advanced HCC; however, when used alone, drug resistance can result in considerably reduced efficacy. Here, we demonstrate that niclosamide, an antihelminthic agent approved by the US Food and Drug Administration, can be repurposed to increase sorafenib sensitivity in sorafenib-resistant HCC cells. We generated sorafenib-resistant HCC cell lines (HepG2215_R and Hep3B_R) with elevated IGF-1R levels and strong properties in terms of stemness and epithelial-mesenchymal transition. Niclosamide was found to increase sorafenib sensitivity effectively in both cell lines and their organoids. The underlying mechanism involves the modulation of cancer stemness, IGF-1R/p-IGF1R/OCT4, and metabolic changes. The combination of sorafenib and niclosamide, but not linsitinib, effectively suppressed the IGF-1R/OCT4 expressions, yielded a synergistic combination index (CI), and attenuated stemness-related properties such as secondary tumor sphere formation and cell migration in sorafenib-resistant HCC cells. Notably, niclosamide significantly suppressed the sorafenib-induced IGF-1R phosphorylation prompted by IGF-1 treatment. Niclosamide effectively downregulated the sorafenib-induced gene expression associated with glycolysis (GLUT1, HK2, LDHA, and PEPCK), stemness (OCT4), and drug resistance (ABCG2) and enhanced the ability of sorafenib to reduce the mitochondrial membrane potential in vitro. The synergistic effect of a combination of niclosamide and sorafenib in vivo was further demonstrated by the decreased tumor size and tumor volume resulting from apoptosis regulation. Our results suggest that niclosamide can enhance sorafenib sensitivity in sorafenib-resistant HCC cells through IGF-1R/stemness regulation and metabolic changes. Our findings highlight a practical clinical strategy for enhancing sorafenib sensitivity in HCC.

HMGCS2 Mediation of Ketone Levels Affects Sorafenib Treatment Efficacy in Liver Cancer Cells

Primary liver cancer is the fifth leading death of cancers in men, and hepatocellular carcinoma (HCC) accounts for approximately 90% of all primary liver cancer cases. Sorafenib is a first-line drug for advanced-stage HCC patients. Sorafenib is a multi-target kinase inhibitor that blocks tumor cell proliferation and angiogenesis. Despite sorafenib treatment extending survival, some patients experience side effects, and sorafenib resistance does occur. 3-Hydroxymethyl glutaryl-CoA synthase 2 (HMGCS2) is the rate-limiting enzyme for ketogenesis, which synthesizes the ketone bodies, β-hydroxybutyrate (β-HB) and acetoacetate (AcAc). β-HB is the most abundant ketone body which is present in a 4:1 ratio compared to AcAc. Recently, ketone body treatment was found to have therapeutic effects against many cancers by causing metabolic alternations and cancer cell apoptosis. Our previous publication showed that HMGCS2 downregulation-mediated ketone body reduction promoted HCC clinicopathological progression through regulating c-Myc/cyclin D1 and caspase-dependent signaling. However, whether HMGCS2-regulated ketone body production alters the sensitivity of human HCC to sorafenib treatment remains unclear. In this study, we showed that HMGCS2 downregulation enhanced the proliferative ability and attenuated the cytotoxic effects of sorafenib by activating expressions of phosphorylated (p)-extracellular signal-regulated kinase (ERK), p-P38, and p-AKT. In contrast, HMGCS2 overexpression decreased cell proliferation and enhanced the cytotoxic effects of sorafenib in HCC cells by inhibiting ERK activation. Furthermore, we showed that knockdown HMGCS2 exhibited the potential migratory ability, as well as decreasing zonula occludens protein (ZO)-1 and increasing c-Myc expression in both sorafenib-treated Huh7 and HepG2 cells. Although HMGCS2 overexpression did not alter the migratory effect, expressions of ZO-1, c-Myc, and N-cadherin decreased in sorafenib-treated HMGCS2-overexpressing HCC cells. Finally, we investigated whether ketone treatment influences sorafenib sensitivity. We showed that β-HB pretreatment decreased cell proliferation and enhanced antiproliferative effect of sorafenib in both Huh7 and HepG2 cells. In conclusion, this study defined the impacts of HMGCS2 expression and ketone body treatment on influencing the sorafenib sensitivity of liver cancer cells.

Small Molecule Inhibitors for Hepatocellular Carcinoma: Advances and Challenges

According to data provided by World Health Organization, hepatocellular carcinoma (HCC) is the sixth most common cause of deaths due to cancer worldwide. Tremendous progress has been achieved over the last 10 years developing novel agents for HCC treatment, including small-molecule kinase inhibitors. Several small molecule inhibitors currently form the core of HCC treatment due to their versatility since they would be more easily absorbed and have higher oral bioavailability, thus easier to formulate and administer to patients. In addition, they can be altered structurally to have greater volumes of distribution, allowing them to block extravascular molecular targets and to accumulate in a high concentration in the tumor microenvironment. Moreover, they can be designed to have shortened half-lives to control for immune-related adverse events. Most importantly, they would spare patients, healthcare institutions, and society as a whole from the burden of high drug costs. The present review provides an overview of the pharmaceutical compounds that are licensed for HCC treatment and other emerging compounds that are still investigated in preclinical and clinical trials. These molecules are targeting different molecular targets and pathways that are proven to be involved in the pathogenesis of the disease.

STAT3 pathway in cancers: Past, present, and future

Signal transducer and activator of transcription 3 (STAT3), a member of the STAT family, discovered in the cytoplasm of almost all types of mammalian cells, plays a significant role in biological functions. The duration of STAT3 activation in normal tissues is a transient event and is strictly regulated. However, in cancer tissues, STAT3 is activated in an aberrant manner and is induced by certain cytokines. The continuous activation of STAT3 regulates the expression of downstream proteins associated with the formation, progression, and metastasis of cancers. Thus, elucidating the mechanisms of STAT3 regulation and designing inhibitors targeting the STAT3 pathway are considered promising strategies for cancer treatment. This review aims to introduce the history, research advances, and prospects concerning the STAT3 pathway in cancer. We review the mechanisms of STAT3 pathway regulation and the consequent cancer hallmarks associated with tumor biology that are induced by the STAT3 pathway. Moreover, we summarize the emerging development of inhibitors that target the STAT3 pathway and novel drug delivery systems for delivering these inhibitors. The barriers against targeting the STAT3 pathway, the focus of future research on promising targets in the STAT3 pathway, and our perspective on the overall utility of STAT3 pathway inhibitors in cancer treatment are also discussed.

Therapeutic effects of TM4SF5-targeting chimeric and humanized monoclonal antibodies in hepatocellular and colon cancer models

The transmembrane 4 L six family member 5 (TM4SF5) is aberrantly expressed in hepatocellular and colorectal cancers, and has been implicated in tumor progression, suggesting that it could serve as a novel therapeutic target. Previously, we screened a murine antibody phage-display library to generate a novel monoclonal antibody, Ab27, that is specific to the extracellular loop 2 of TM4SF5. In this study, we evaluated the effects of chimeric Ab27 using cancer cells expressing endogenous TM4SF5 or stably overexpressing TM4SF5 in vivo and in vitro. Monotherapy with Ab27 significantly decreased tumor growth in liver and colon cancer xenograft models, including a sorafenib-resistant model, and decreased the phosphorylation of focal adhesion kinase (FAK), p27^Kip1, and signal transducer and activator of transcription 3 (STAT3). No general Ab27 toxicity was observed in vivo. Combination treatment with Ab27 and sorafenib or doxorubicin exerted higher antitumor activity than monotherapy. In addition, we humanized the Ab27 sequence by the complementarity-determining region (CDR) grafting method. The humanized antibody Ab27-hz9 had reduced immunogenicity but exhibited target recognition and antitumor activity comparable with those of Ab27. Both Ab27 and Ab27-hz9 efficiently targeted tumor cells expressing TM4SF5 in vivo. These observations strongly support the further development of Ab27-hz9 as a novel therapeutic agent against liver and colorectal cancers.

Upregulation of USP22 and ABCC1 during Sorafenib Treatment of Hepatocellular Carcinoma Contribute to Development of Resistance

Sorafenib is a small molecule that blocks tumor proliferation by targeting the activity of multi-kinases for the treatment of advanced hepatocellular carcinoma (HCC). Increasing sorafenib resistance following long-term treatment is frequently encountered. Mechanisms underlying sorafenib resistance remain not completely clear. To further understand the mechanism of sorafenib resistance in HCC, we established sorafenib-resistant cell lines by slowly increasing sorafenib concentration in cell culture medium. Upregulation of USP22 and ABCC1 were found in Sorafenib-resistant cells. Sorafenib-resistant cells treated with USP22 siRNA showed significant reduction in endogenous mRNA and protein levels of ABCC1. During sorafenib treatment, upregulation of USP22 increases ABCC1 expression and subsequently contributes to sorafenib resistance in HCC cells. Immunohistochemical analysis revealed a positive correlation between USP22 and ABCC1 expression in tissue samples from sorafenib-resistant patients (Pearson’s correlation = 0.59, p = 0.03). Our findings indicate that upregulation of USP22 and ABCC1 expression during treatment contribute to sorafenib resistance in HCC cells and that USP22 has strong potential as a therapeutic target for overcoming sorafenib resistance in HCC patients.

Crocetin imparts antiproliferative activity via inhibiting STAT3 signaling in hepatocellular carcinoma

STAT3 is a key oncogenic transcription factor, often overactivated in several human cancers including hepatocellular carcinoma (HCC). STAT3 modulates the expression of genes that are connected with cell proliferation, antiapoptosis, metastasis, angiogenesis, and immune evasion in tumor cells. In this study, we investigated the effect of crocetin on the growth of HCC cells and dissected its underlying molecular mechanism in imparting a cytotoxic effect. Crocetin suppressed proliferation, promoted apoptosis, and counteracted the invasive capacity of HCC cells. Besides, crocetin downregulated the constitutive/inducible STAT3 activation (STAT3^Y705 ), nuclear accumulation of STAT3 along with suppression of its DNA binding activity in HCC cells with no effect on STAT5 activation. Crocetin suppressed the activity of upstream kinases such as Src, JAK1, and JAK2. Sodium pervanadate treatment terminated the crocetin-propelled STAT3 inhibition suggesting the involvement of tyrosine phosphatases. Crocetin increased the expression of SHP-1 and siRNA-mediated SHP-1 silencing resulted in the negation of crocetin-driven STAT3 inhibition. Further investigation revealed that crocetin treatment inhibited the expression of STAT3 regulated genes (Bcl-2, Bcl-xL, cyclin D1, survivin, VEGF, COX-2, and MMP-9). Taken together, this report presents crocetin as a novel abrogator of the STAT3 pathway in HCC cell lines.

A Yes-Associated Protein (YAP) and Insulin-Like Growth Factor 1 Receptor (IGF-1R) Signaling Loop Is Involved in Sorafenib Resistance in Hepatocellular Carcinoma

The role of a YAP-IGF-1R signaling loop in HCC resistance to sorafenib remains unknown.

METHOD

Sorafenib-resistant cells were generated by treating naïve cells (HepG2215 and Hep3B) with sorafenib. Different cancer cell lines from databases were analyzed through the ONCOMINE web server. BIOSTORM-LIHC patient tissues (46 nonresponders and 21 responders to sorafenib) were used to compare YAP mRNA levels. The HepG2215_R-derived xenograft in SCID mice was used as an in vivo model. HCC tissues from a patient with sorafenib failure were used to examine differences in YAP and IGF-R signaling.

RESULTS

Positive associations exist among the levels of YAP, IGF-1R, and EMT markers in HCC tissues and the levels of these proteins increased with sorafenib failure, with a trend of tumor-margin distribution in vivo. Blocking YAP downregulated IGF-1R signaling-related proteins, while IGF-1/2 treatment enhanced the nuclear translocation of YAP in HCC cells through PI3K-mTOR regulation. The combination of YAP-specific inhibitor verteporfin (VP) and sorafenib effectively decreased cell viability in a synergistic manner, evidenced by the combination index (CI).

CONCLUSION

A YAP-IGF-1R signaling loop may play a role in HCC sorafenib resistance and could provide novel potential targets for combination therapy with sorafenib to overcome drug resistance in HCC.

The phosphatase Shp1 interacts with and dephosphorylates cortactin to inhibit invadopodia function

BACKGROUND

Invadopodia are actin-based cell-membrane protrusions associated with the extracellular matrix degradation accompanying cancer invasion. The elucidation of the molecular mechanisms leading to invadopodia formation and activity is central for the prevention of tumor spreading and growth. Protein tyrosine kinases such as Src are known to regulate invadopodia assembly, little is however known on the role of protein tyrosine phosphatases in this process. Among these enzymes, we have selected the tyrosine phosphatase Shp1 to investigate its potential role in invadopodia assembly, due to its involvement in cancer development.

METHODS

Co-immunoprecipitation and immunofluorescence studies were employed to identify novel substrate/s of Shp1AQ controlling invadopodia activity. The phosphorylation level of cortactin, the Shp1 substrate identified in this study, was assessed by immunoprecipitation, in vitro phosphatase and western blot assays. Short interference RNA and a catalytically-dead mutant of Shp1 expressed in A375MM melanoma cells were used to evaluate the role of the specific Shp1-mediated dephosphorylation of cortactin. The anti-invasive proprieties of glycerophosphoinositol, that directly binds and regulates Shp1, were investigated by extracellular matrix degradation assays and in vivo mouse model of metastasis.

RESULTS

The data show that Shp1 was recruited to invadopodia and promoted the dephosphorylation of cortactin at tyrosine 421, leading to an attenuated capacity of melanoma cancer cells to degrade the extracellular matrix. Controls included the use of short interference RNA and catalytically-dead mutant that prevented the dephosphorylation of cortactin and hence the decrease the extracellular matrix degradation by melanoma cells. In addition, the phosphoinositide metabolite glycerophosphoinositol facilitated the localization of Shp1 at invadopodia hence promoting cortactin dephosphorylation. This impaired invadopodia function and tumor dissemination both in vitro and in an in vivo model of melanomas.

CONCLUSION

The main finding here reported is that cortactin is a specific substrate of the tyrosine phosphatase Shp1 and that its phosphorylation/dephosphorylation affects invadopodia formation and, as a consequence, the ability of melanoma cells to invade the extracellular matrix. Shp1 can thus be considered as a regulator of melanoma cell invasiveness and a potential target for antimetastatic drugs. Video abstract.

RFX1: a promising therapeutic arsenal against cancer

Regulatory factor X1 (RFX1) is an evolutionary conserved transcriptional factor that influences a wide range of cellular processes such as cell cycle, cell proliferation, differentiation, and apoptosis, by regulating a number of target genes that are involved in such processes. On a closer look, these target genes also play a key role in tumorigenesis and associated events. Such observations paved the way for further studies evaluating the role of RFX1 in cancer. These studies were indispensable due to the failure of conventional chemotherapeutic drugs to target key cellular hallmarks such as cancer stemness, cellular plasticity, enhanced drug efflux, de-regulated DNA repair machinery, and altered pathways evading apoptosis. In this review, we compile significant evidence for the tumor-suppressive activities of RFX1 while also analyzing its oncogenic potential in some cancers. RFX1 induction decreased cellular proliferation, modulated the immune system, induced apoptosis, reduced chemoresistance, and sensitized cancer stem cells for chemotherapy. Thus, our review discusses the pleiotropic function of RFX1 in multitudinous gene regulations, decisive protein–protein interactions, and also its role in regulating key cell signaling events in cancer. Elucidation of these regulatory mechanisms can be further utilized for RFX1 targeted therapy.

Sorafenib and CuB exert synergistic antitumor effects against hepatocellular carcinoma cells via inhibition of STAT3 phosphorylation

Sorafenib, the first‐line agent for treatment of advanced hepatocellular carcinoma (HCC), improves median overall survival by approximately 3 months. In the present study, we investigated whether sorafenib combined with cucurbitacin B (CuB), a natural tetracyclic triterpenoid isolated from Cucurbitaceae, exerts enhanced antitumor effects against HCC. Cell viability and colony formation ability were detected by cell‐counting kit‐8 and colony formation assays. Cell cycle and apoptosis were analyzed by flow cytometry. Protein expression was detected by western blotting. HepG2 xenografts in nude mice were used to evaluate in vivo antitumor effects. We report that sorafenib and CuB exhibited synergistic effects on cellular proliferation inhibition and cell apoptosis induction, but not on cell cycle arrest. Furthermore, combination treatment enhanced levels of cleaved caspase 3 and cleaved caspase 9, but suppressed phosphorylation of STAT3. Epidermal growth factor, a potent stimulator of signal transducer and activator of transcription‐3 (STAT3), promoted cell viability and colony formation ability, whereas combination treatment exerted inhibitory effects on epidermal growth factor‐induced STAT3 phosphorylation. Finally, HepG2 xenograft mice cotreated with sorafenib and CuB exhibited reduced tumor progression without notable weight loss. In conclusion, sorafenib and CuB exert synergistic antitumor effects through a pathway that may involve STAT3 phosphorylation, and this may represent a promising therapeutic approach for treatment of HCC.

STAT3 transcription factor as target for anti-cancer therapy

STATs constitute a large family of transcription activators and transducers of signals that have an important role in many cell functions as regulation of proliferation and differentiation of the cell also regulation of apoptosis and angiogenesis. STAT3 as a member of that family, recently was discovered to have a vital role in progression of different types of cancers. The activation of STAT3 was observed to regulate multiple gene functions during cancer-like cell proliferation, differentiation, apoptosis, metastasis, inflammation, immunity, cell survival, and angiogenesis. The inhibition of STAT3 activation has been an important target for cancer therapy. Inhibitors of STAT3 have been used for a long time for treatment of many types of cancers like leukemia, melanoma, colon, and renal cancer. In this review article, we summarize and discuss different drugs inhibiting the action of STAT3 and used in treatment of different types of cancer.

Long Noncoding RNA RMRP Suppresses the Tumorigenesis of Hepatocellular Carcinoma Through Targeting microRNA-766

PURPOSE

This study aimed to explore the regulatory effect of long noncoding RNA (lncRNA) ribonuclease mitochondrial RNA processing gene (RMRP) on hepatocellular carcinoma (HCC).

METHODS

The expression of RMRP in HCC tissues and cell lines was assessed by qRT-PCR. Kaplan-Meier method was utilized to analyze the correlation between RMRP expression and the survival of HCC patients. MHCC97H and HuH7 cells were transfected with pcDNA3.1-RMRP or pcDNA3.1, respectively. MTT and flow cytometry assays were conducted to examine the proliferation and apoptosis of HCC cells, respectively. The migration and invasion of HCC cells were assessed using wound healing and transwell assays, respectively. StarBase3.0 and dual-luciferase reporter gene assay were used to identify the target relationship between miR-766 and RMRP. A xenografted tumor model was established in rats to evaluate the effect of RMRP in vivo.

RESULTS

RMRP was down-regulated in HCC tissues and cells. Low expression of RMRP was correlated with poor survival of HCC patients. The A495 value and colony number were significantly decreased in pcDNA3.1-RMRP-transfected MHCC97H and HuH7 cells. The apoptosis rate was significantly increased in pcDNA3.1-RMRP-transfected MHCC97H and HuH7 cells. The migration rate and the number of invasive cells were significantly decreased in pcDNA3.1-RMRP-transfected MHCC97H and HuH7 cells. MiR-766 was a target of RMRP and eliminated the anti-tumor effect of RMRP on MHCC97H cells. The up-regulation of RMRP suppressed the growth of xenograft tumors in rats.

CONCLUSION

Overexpression of RMRP suppressed the tumorigenesis of HCC by targeting miR-766.

Treatment with a new benzimidazole derivative bearing a pyrrolidine side chain overcomes sorafenib resistance in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a major cause of cancer-related death worldwide. Currently, sorafenib is the standard first-line drug for patients with advanced HCC. However, long-term exposure to sorafenib often results in reduced sensitivity of tumour cells to the drug, leading to acquired resistance. Therefore, developing new compounds to treat sorafenib resistance is urgently needed. Although benzimidazole and its derivatives have been reported to exert antimicrobial and antitumour effects, the anti-drug resistance potential of these molecules is still unknown. In this study, we established sorafenib-resistant (SR) cell lines and an acquired sorafenib resistance xenograft model. We showed that treatment with a benzimidazole derivative bearing a pyrrolidine side chain (compound 9a) inhibited the proliferation of SR cells by blocking the phosphorylation of AKT, p70S6 and the downstream molecule RPS6. In addition, caspase 3/PARP-dependent apoptotic signals were induced in 9a-treated cells. Regarding epithelial-mesenchymal transition (EMT) activities, 9a treatment significantly suppressed the migration of SR cells. In particular, the levels of EMT-related transcription factors (snail, slug and twist) and mesenchymal markers (vimentin and N-cadherin) were downregulated. In the acquired sorafenib resistance xenograft model, compound 9a administration decreased the growth of tumours with acquired sorafenib resistance and the expression of the HCC markers α-fetoprotein, glypican 3 and survivin. In conclusion, treatment with this compound may be a novel therapeutic strategy for patients with sorafenib resistance.

Regorafenib reverses HGF-induced sorafenib resistance by inhibiting epithelial-mesenchymal transition in hepatocellular carcinoma

Sorafenib resistance is one of the major obstacles towards achieving a better outcome in patients with advanced hepatocellular carcinoma (HCC), in which aberrant activation of the hepatocyte growth factor (HGF)/mesenchymal‐epithelial transition pathway is frequently observed. Here, we report that HCC cells develop sorafenib resistance following HGF stimulation. Furthermore, HGF activates the downstream extracellular signal‐related kinase (ERK) and signal transducer and activator of transcription 3 (STAT3) pathway and induces epithelial–mesenchymal transition (EMT) by up‐regulating Snail in HCC cells. Inhibition of ERK and STAT3 abolished the rescue effect of HGF by down‐regulating Snail and EMT. Moreover, phosphoinositide 3‐kinase/Akt was also activated in HGF‐treated HCC cells, although it had no effect on Snail expression. Notably, we also found that regorafenib reversed HGF‐induced sorafenib resistance by inhibiting ERK and STAT3, and subsequently down‐regulating Snail and EMT. Taken together, our results indicate that HGF induces sorafenib resistance by activating phosporylated (P)‐ERK/Snail/EMT and P‐STAT3/Snail/EMT pathways. Inhibition of P‐ERK and P‐STAT3 by regorafenib can block HGF‐induced EMT, thereby reversing HGF‐induced sorafenib resistance.

Kinome-Wide siRNA Screening Identifies Src-Enhanced Resistance of Chemotherapeutic Drugs in Triple-Negative Breast Cancer Cells

Background: Chemotherapy is the main treatment for triple-negative breast cancer (TNBC), which lack molecular markers for diagnosis and therapy. Cancer cells activate chemoresistant pathways and lead to therapeutic failure for patients with TNBC. Several kinases have been identified as chemoresistant genes. However, the involvement of kinases in the chemoresistance in TNBC cells is not fully understood.

Methods: We employed a kinome siRNA library to screen whether targeting any kinases could increase the chemosensitivity of TNBC cell lines. The effects of kinase on cell viability in various breast cancer cells were validated with ATP level and colony formation. Protein expression and phosphorylation were determined by immunoblotting. The Cancer Genome Atlas (TCGA) dataset was collected to analyze the correlation of Src expression with prognosis of TNBC patients.

Results: Primary screening and validation for the initial hits showed that Src kinase was a potential doxorubicin-resistant kinase in the TNBC cell lines MDA-MB-231 and Hs578T. Both siRNA against Src and the Src inhibitor dasatinib enhanced the cytotoxic effects of doxorubicin in TNBC cells. Moreover, phosphorylation of AKT and signal transducer and activator of transcription 3 (STAT3), downstream effectors of Src, were accordingly decreased in Src-silenced or -inhibited TNBC cells. Additionally, TCGA data analysis indicated that Src expression levels in tumor tissues were higher than those in tumor-adjacent normal tissues in patients with TNBC. High co-expression level of Src and STAT3 was also significantly correlated with poor prognosis in patients.

Conclusion: Our results showed that Src-STAT3 axis might be involved in chemoresistance of TNBC cells.

Antrodia cinnamomea boosts the anti-tumor activity of sorafenib in xenograft models of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) has been recognized worldwide as one of the major causes of cancer death. The medicinal fungus Antrodia cinnamomea (A. cinnamomea) has been served as a functional food for liver protection. The aim of the present study was to investigate the potential activity of A. cinnamomea extracts as a safe booster for the anticancer activity of sorafenib, a multi-kinase inhibitor approved for the treatment of HCC. The biologically active triterpenoids in the ethanolic extracts of A. cinnamomea (EAC) were initially identified by HPLC/LC/MS then the different extracts and sorafenib were assessed in vitro and in vivo. EAC could effectively sensitize HCC cells to low doses of sorafenib, which was perceived via the ability of the combination to repress cell viability and to induce cell cycle arrest and apoptosis in HCC cells. The ability of EAC to enhance sorafenib activity was mediated through targeting mitogen-activated protein (MAP) kinases, modulating cyclin proteins expression and inhibiting cancer cell invasion. Moreover, the proposed combination significantly suppressed ectopic tumor growth in mice with high safety margins compared to single-agent treatment. Thus, this study highlights the advantage of combining EAC with sorafenib as a potential adjuvant therapeutic strategy against HCC.

SHP-1 Acts as a Tumor Suppressor in Hepatocarcinogenesis and HCC Progression

Src homology region 2 (SH2) domain-containing phosphatase 1 (SHP-1, also known as PTPN6) is a nonreceptor protein tyrosine phosphatase that acts as a negative regulator of inflammation. Emerging evidence indicates that SHP-1 plays a role in inhibiting the progression of hepatocellular carcinoma (HCC). However, the role of SHP-1 in hepatocarcinogenesis remains unknown. Here, we find that levels of SHP-1 are significantly downregulated in human HCC tissues compared with those in noncancerous tissues (P < 0.001) and inversely correlate with tumor diameters (r = -0.4130, P = 0.0002) and serum α-fetoprotein levels (P = 0.047). Reduced SHP-1 expression was associated with shorter overall survival of patients with HCC with HBV infection. Overexpression of SHP-1 suppressed proliferation, migration, invasion, and tumorigenicity of HCC cells, whereas knockdown of SHP-1 enhanced the malignant phenotype. Moreover, knockout of Ptpn6 in hepatocytes (Ptpn6^HKO ) enhanced hepatocarcinogenesis induced by diethylnitrosamine (DEN) as well as metastasis of primary liver cancer in mice. Furthermore, systemic delivery of SHP-1 by an adenovirus expression vector exerted a therapeutic effect in an orthotopic model of HCC in NOD/SCID mice and DEN-induced primary liver cancers in Ptpn6^HKO mice. In addition, SHP-1 inhibited the activation of JAK/STAT, NF-κB, and AKT signaling pathways, but not the MAPK pathway in primary hepatocytes from DEN-treated mice and human HCC cells. Together, our data implicate SHP-1 as a tumor suppressor of hepatocarcinogenesis and HCC progression and propose it as a novel prognostic biomarker and therapeutic target of HCC.Significance: The nonreceptor protein tyrosine phosphatase SHP-1 acts as a tumor suppressor in hepatocellular carcinoma. Cancer Res; 78(16); 4680-91. ©2018 AACR.

Chemical and genetic inhibition of STAT3 sensitizes hepatocellular carcinoma cells to sorafenib induced cell death

Hepatocellular carcinoma (HCC) has become the second leading cause of cancer related death, with an increasing death rate in recent years. For advanced HCC, sorafenib is the first-line FDA approved drug, with no more than 3 months' overall survival advantage. Recently, a novel strategy has been proposed to improve sorafenib efficacy through enhancing the ability of sorafenib to induce cell death. STAT3 plays a key role in cancer development and recurrence by promoting cell proliferation, survival and immune evasion through its well-established function as a transcription factor in cancer. Notably, STAT3 transcription activity, indicated by its phosphorylation on Y705 is heterogeneous in different liver cancer cell lines. And sorafenib attenuates STAT3 phosphorylation on Y705. However, the role of STAT3 in sorafenib induced cell death is still largely unknown. Here, we show that liver cancer cells also exhibit heterogeneous sensitivities to sorafenib induced cell death, which co-relates with the STAT3-Y705 phosphorylation levels and JAK1/2 expression levels in Hep3B, Huh7 and HepG2 cells. Furthermore, overexpression or knockdown of STAT3 could switch HCC cells between resistant and sensitive to sorafenib induced cell death, which could be partially due to its regulation on Mcl-1, an anti-apoptotic protein. Finally, both inhibitors of STAT3 SH2 domain (S3i-201) or STAT3 upstream kinases JAKs (JAK inhibitor I) could synergistically enhance sorafenib induced cell death. Taken together, these data strongly suggest that STAT3 is not only a downstream effector of sorafenib, but also a key regulator of cellular sensitivity to sorafenib induced cell death, which provide support for the notion to develop STAT3-targeting drugs to improve clinical efficacy of sorafenib in liver cancer.

Use of a MCL-1 inhibitor alone to de-bulk melanoma and in combination to kill melanoma initiating cells

MCL-1 (BCL-2 family anti-apoptotic protein) is responsible for melanoma's resistance to therapy. Cancer initiating cells also contribute to resistance and relapse from treatments. Here we examined the effects of the MCL-1 inhibitor SC-2001 in killing non melanoma-initiating-cells (bulk of melanoma), and melanoma-initiating-cells (MICs). By itself, SC-2001 significantly kills melanoma cells under monolayer conditions in vitro and in a conventional mouse xenograft model. However, even at high doses (10μM), SC-2001 does not effectively eliminate MICs. In contrast, the combination of SC-2001 with ABT-737 (a BCL-2/BCL-XL/BCL-W inhibitor) significantly decreases ALDH+ cells, disrupts primary spheres, and inhibits the self-renewability of MICs. These results were observed in multiple melanomas, including short term cultures of relapsed tumors from current treatments, independent of the mutation status of BRAF or NRAS. Using a low-cell-number mouse xenograft model, we examined the effects of these treatments on the tumor initiating ability of MIC-enriched cultures. The combination therapy reduces tumor formation significantly compared to either drug alone. Mechanistic studies using shRNA and the CRISPR-Cas9 technology demonstrated that the upregulation of pro-apoptotic proteins NOXA and BIM contribute to the combination-induced cell death. These results indicate that the MCL-1 inhibitor SC-2001 combined with ABT-737 is a promising treatment strategy for targeting melanoma.

Synergistic antitumor effects of tanshinone IIA and sorafenib or its derivative SC-1 in hepatocellular carcinoma cells

Introduction

Hepatocellular carcinoma (HCC) is the most common form of hepatic malignancy in the world. We aimed to determine the effect of tanshinone IIA (Tan-IIA) in combination with sorafenib or its derivative SC-1 on cytotoxicity, apoptosis, and metastasis in human HCC cells.

Materials and methods

Cytotoxicity was detected by MTT assay. Apoptosis and sub-G1 populations were analyzed by flow cytometry. Cell migration and invasion were evaluated by Transwell assay. Protein expression was detected by Western blot.

Results

Tan-IIA combined with sorafenib or SC-1 exerted synergistic cytotoxicity in HCC cells. Elevated proportions of sub-G1 and caspase activation were observed in the combinative treatments; in addition, marked inhibition of cell migration and invasion, which could be mediated by the modulation of epithelial–mesenchymal transition was observed. pSTAT3 levels were significantly reduced as well.

Conclusion

A combination therapy using Tan-IIA and sorafenib or SC-1 could be a promising approach to target HCC, and further preclinical investigations are warranted to establish their synergetic advantage.

The Roles of Protein Tyrosine Phosphatases in Hepatocellular Carcinoma

The protein tyrosine phosphatase (PTP) family is involved in multiple cellular functions and plays an important role in various pathological and physiological processes. In many chronic diseases, for example cancer, PTP is a potential therapeutic target for cancer treatment. In the last two decades, dozens of PTP inhibitors which specifically target individual PTP molecules were developed as therapeutic agents. Hepatocellular carcinoma (HCC) is one of the most common malignant tumors and is the second most lethal cancer worldwide due to a lack of effective therapies. Recent studies have unveiled both oncogenic and tumor suppressive functions of PTP in HCC. Here, we review the current knowledge on the involvement of PTP in HCC and further discuss the possibility of targeting PTP in HCC.

Increasing AR by HIF-2α inhibitor (PT-2385) overcomes the side-effects of sorafenib by suppressing hepatocellular carcinoma invasion via alteration of pSTAT3, pAKT and pERK signals

Although sorafenib is currently used as a standard treatment for advanced hepatocellular carcinoma, low response rate, transient and limited efficacy, primary and acquired resistance and negative side-effects gain increasing attentions, suggesting the need for better efficacious combination therapy. Here, we demonstrated that the sorafenib-induced or hypoxia-induced hypoxia inducible factor (HIF)-2α could bind to an hypoxia responsive element within 500 bp region of androgen receptor (AR) promoter and thus transcriptionally suppress AR. Importantly, In vitro and In vivo studies suggested a specific and potent HIF-2α inhibitor, PT-2385, could significantly enhance sorafenib efficacy by suppressing HIF-2α, increasing AR and suppressing downstream pSTAT3/pAKT/pERK pathways. Clinical samples further confirmed the role of HIF-2α and AR. It is promising that PT-2385 could alleviate the undesirable side-effects of sorafenib treatment by sorafenib-PT-2385 combination therapy, which may shed light for late-stage HCC patients.

Secreted GRP78 activates EGFR-SRC-STAT3 signaling and confers the resistance to sorafeinib in HCC cells

Acquired resistance is a common phenomenon for HCC patients who undergone sorafenib treatment, however the mechanism by which acquired resistance develops remains elusive. In this study, we found that GRP78 could be detected in the serum samples of HCC patients and the conditional medium of multiple HCC cell lines, suggesting that GRP78 is secreted by HCC cells. Further studies showed that secreted GRP78 facilitated the proliferation and inhibited the apoptosis induced by sorafenib both in HCC cell lines and in tumor xenografts. We further found that secreted GRP78 could interact physically with EGFR, therefore activates EGFR signaling pathway. knockdown of EGFR decreased secreted GRP78 induced phosphorylation of SRC and STAT3. By contrast, overexpression of EGFR further enhanced the phosphorylation of SRC and STAT3 induced by secreted GRP78, suggesting the critical role of EGFR in secreted GRP78 conferred resistance to sorafeinib. Moreover, inhibition of SRC by PP2 antagonized the resistance to sorafenib and inhibited the activation of STAT3 conferred by secreted GRP78. Taken together, our results showed that secreted GRP78 could interact with EGFR, activate EGFR-SRC-STAT3 signaling, conferring the resistance to sorafenib.

Gankyrin induces STAT3 activation in tumor microenvironment and sorafenib resistance in hepatocellular carcinoma

Most hepatocellular carcinomas (HCC) develop as a result of chronic liver inflammation. We have shown that the oncoprotein gankyrin is critical for inflammation‐induced tumorigenesis in the colon. Although the in vitro function of gankyrin is well known, its role in vivo remains to be elucidated. We investigated the effect of gankyrin in the tumor microenvironment of mice with liver parenchymal cell‐specific gankyrin ablation (Alb‐Cre;gankyrin^f/f) and gankyrin deletion both in liver parenchymal and non‐parenchymal cells (Mx1‐Cre;gankyrin^f/f). Gankyrin upregulates vascular endothelial growth factor expression in tumor cells. Gankyrin binds to Src homology 2 domain‐containing protein tyrosine phosphatase‐1 (SHP‐1), mainly expressed in liver non‐parenchymal cells, resulting in phosphorylation and activation of signal transducer and activator of transcription 3 (STAT3). Gankyrin deficiency in non‐parenchymal cells, but not in parenchymal cells, reduced STAT3 activity, interleukin (IL)‐6 production, and cancer stem cell marker (Bmi1 and epithelial cell adhesion molecule [EpCAM]) expression, leading to attenuated tumorigenic potential. Chronic inflammation enhances gankyrin expression in the human liver. Gankyrin expression in the tumor microenvironment is negatively correlated with progression‐free survival in patients undergoing sorafenib treatment for HCC. Thus, gankyrin appears to play a critical oncogenic function in tumor microenvironment and may be a potential target for developing therapeutic and preventive strategies against HCC.

The tyrosine kinase inhibitor nintedanib activates SHP-1 and induces apoptosis in triple-negative breast cancer cells

Triple-negative breast cancer (TNBC) remains difficult to treat and urgently needs new therapeutic options. Nintedanib, a multikinase inhibitor, has exhibited efficacy in early clinical trials for HER2-negative breast cancer. In this study, we examined a new molecular mechanism of nintedanib in TNBC. The results demonstrated that nintedanib enhanced TNBC cell apoptosis, which was accompanied by a reduction of p-STAT3 and its downstream proteins. STAT3 overexpression suppressed nintedanib-mediated apoptosis and further increased the activity of purified SHP-1 protein. Moreover, treatment with either a specific inhibitor of SHP-1 or SHP-1-targeted siRNA reduced the apoptotic effects of nintedanib, which validates the role of SHP-1 in nintedanib-mediated apoptosis. Furthermore, nintedanib-induced apoptosis was attenuated in TNBC cells expressing SHP-1 mutants with constantly open conformations, suggesting that the autoinhibitory mechanism of SHP-1 attenuated the effects of nintedanib. Importantly, nintedanib significantly inhibited tumor growth via the SHP-1/p-STAT3 pathway. Clinically, SHP-1 levels were downregulated, whereas p-STAT3 was upregulated in tumor tissues, and SHP-1 transcripts were associated with improved disease-free survival in TNBC patients. Our findings revealed that nintedanib induces TNBC apoptosis by acting as a SHP-1 agonist, suggesting that targeting STAT3 by enhancing SHP-1 expression could be a viable therapeutic strategy against TNBC.

Alteration of SHP-1/p-STAT3 Signaling: A Potential Target for Anticancer Therapy

The Src homology 2 (SH2) domain-containing protein tyrosine phosphatase 1 (SHP-1), a non-receptor protein tyrosine phosphatase, has been reported as a negative regulator of phosphorylated signal transducer and activator of transcription 3 (STAT3) and linked to tumor development. In this present review, we will discuss the importance and function of SHP-1/p-STAT3 signaling in nonmalignant conditions as well as malignancies, its cross-talk with other pathways, the current clinical development and the potential role of inhibitors of this pathway in anticancer therapy and clinical relevance of SHP-1/p-STAT3 in cancers. Lastly, we will summarize and highlight work involving novel drugs/compounds targeting SHP-1/p-STAT3 signaling and combined strategies that were/are discovered in our and our colleagues’ laboratories.

Sorafenib analogue SC-60 induces apoptosis through the SHP-1/STAT3 pathway and enhances docetaxel cytotoxicity in triple-negative breast cancer cells

Recurrent triple-negative breast cancer (TNBC) needs new therapeutic targets. Src homology region 2 domain-containing phosphatase-1 (SHP-1) can act as a tumor suppressor by dephosphorylating oncogenic kinases. One major target of SHP-1 is STAT3, which is highly activated in TNBC. In this study, we tested a sorafenib analogue SC-60, which lacks angiokinase inhibition activity, but acts as a SHP-1 agonist, in TNBC cells. SC-60 inhibited proliferation and induced apoptosis by dephosphorylating STAT3 in both a dose- and time-dependent manner in TNBC cells (MDA-MB-231, MDA-MB-468, and HCC1937). By contrast, ectopic expression of STAT3 rescued the anticancer effect induced by SC-60. SC-60 also increased the SHP-1 activity, but this effect was inhibited when the N-SH2 domain (DN1) was deleted or with SHP-1 point mutation (D61A), implying that SHP-1 is the major target of SC-60 in TNBC. The use of SC-60 in combination with docetaxel synergized the anticancer effect induced by SC-60 through the SHP-1/STAT3 pathway in TNBC cells. Importantly, SC-60 also displayed a significant antitumor effect in an MDA-MB-468 xenograft model by modulating the SHP-1/STAT3 axis, indicating the anticancer potential of SC-60 in TNBC treatment. Targeting SHP-1/p-STAT3 and the potential combination of SHP-1 agonist with chemotherapeutic docetaxel is a feasible therapeutic strategy for TNBC.

Activating JAK1 mutation may predict the sensitivity of JAK-STAT inhibition in hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common type of cancers worldwide. However, current therapeutic approaches for this epidemic disease are limited, and its 5-year survival rate hasn't been improved in the past decades. Patient-derived xenograft (PDX) tumor models have become an excellent in vivo system for understanding of disease biology and drug discovery. In order to identify new therapeutic targets for HCC, whole-exome sequencing (WES) was performed on more than 60 HCC PDX models. Among them, four models exhibited protein-altering mutations in JAK1 (Janus Kinase 1) gene. To explore the transforming capability, these mutations were then introduced into HEK293FT and Ba/F3 cells. The results demonstrated that JAK1^S703I mutation was able to activate JAK-STAT (Signal Transducer and Activator of Transcription) signaling pathway and drive cell proliferation in the absence of cytokine stimulation in vitro. Furthermore, the sensitivity to the treatment of a JAK1/2 inhibitor, ruxolitinib, was observed in JAK1^S703I mutant PDX model, but not in other non-activating mutant or wild type models. Pharmacodynamic analysis showed that phosphorylation of STAT3 in the Ruxolitinib-treated tumor tissues was significantly suppressed. Collectively, our results suggested that JAK1^S703I is an activating mutation for JAK-STAT signaling pathway in vitro and in vivo, and JAK-STAT pathway might represent a new therapeutic approach for HCC treatment. Monotherapy using a more potent and specific JAK1 inhibitor and combinatory therapy should be further explored in JAK1 mutant PDX models.

Sorafenib with ASC-J9® synergistically suppresses the HCC progression via altering the pSTAT3-CCL2/Bcl2 signals

Sorafenib is currently used as a standard treatment to suppress the progression of hepatocellular carcinoma (HCC), especially in advanced stages. However, patients who receive Sorafenib treatment eventually develop resistance without clear mechanisms. There is a great need for better efficacy of Sorafenib treatment in combination with other therapies. Here, we demonstrated that the treatment combining Sorafenib with ASC‐J9^® could synergistically suppress HCC progression via altering cell‐cycle regulation, apoptosis and invasion. Mechanism dissection suggests that while Sorafenib impacts little or even slightly increases the activated/phosphorylated STAT3 (p‐STAT3), a key stimulator to promote the HCC progression, adding ASC‐J9^® significantly suppresses the p‐STAT3 expression and its downstream genes including CCL2 and Bcl2. Interrupting these signals via constitutively active STAT3 partially reverses the synergistic suppression of Sorafenib‐ASC‐J9^® combination on HCC progression. In vivo studies further confirmed the synergistic effect of Sorafenib‐ASC‐J9^® combination. Together, these results suggest the newly developed Sorafenib‐ASC‐J9^® combination is a novel therapy to better suppress HCC progression.

What's new?

Sorafenib is currently a standard treatment to suppress the progression of hepatocellular carcinoma (HCC). STAT3 activation may however play a role in the development of Sorafenib resistance. Following earlier studies suggesting that ASC‐J9^® may alter activated p‐STAT3 signals to suppress prostate cancer metastasis, here the authors found that combining Sorafenib with ASC‐J9^® may synergistically suppress HCC progression. Sorafenib had little impact on p‐STAT3, whereas ASC‐J9^® significantly suppressed p‐STAT3 expression and its downstream genes, including CCL2 and Bcl2. Clinical studies using human HCC samples also demonstrated that higher expression of p‐STAT3 might be linked to the lower response to Sorafenib treatment.

microRNA-539 suppresses tumor growth and tumorigenesis and overcomes arsenic trioxide resistance in hepatocellular carcinoma

AIMS

Dysregulation of microRNAs (miRNAs) plays a critical role in tumor growth and progression. In this study, we sought to explore the expression and biological roles of miR-539 in hepatocellular carcinoma (HCC).

MAIN METHODS

The expression of miR-539 in human HCC tissues and cell lines was examined. The effects of miR-539 overexpression on cell growth, tumorigenicity, arsenic trioxide resistance of HCC cells were determined. The signaling pathways involved in the action of miR-539 in HCC were also investigated.

KEY FINDINGS

miR-539 was downregulated in HCC tissues and cells, relative to corresponding controls. Overexpression of miR-539 inhibited HCC cell viability and colony formation in vitro and impaired tumorigenesis of HCC cells in vivo. Transfection with miR-539 mimic significantly induced apoptosis in HepG2 cells, which was coupled with reduced expression of anti-apoptotic proteins Bcl-2 and Bcl-xL and decreased phosphorylation of Stat3. Overexpression of a constitutively active form of Stat3 partially blocked miR-539-mediated apoptosis. Enforced expression of miR-539 resensitized arsenic trioxide-resistant HCC cells to arsenic trioxide. Intratumoral delivery of miR-539 mimic significantly retarded the growth of xenograft tumors from arsenic trioxide-resistant HCC cells by about 35%, compared to delivery of control miRNA (P<0.05). In combination with arsenic trioxide, miR-539 mimic yielded about 80% decrease in tumor burden.

SIGNIFICANCE

miR-539 functions as a tumor suppressor in HCC and reexpression of this miRNA offers a potential therapeutic strategy for this disease.

Elevated hepatocyte growth factor expression as an autocrine c-Met activation mechanism in acquired resistance to sorafenib in hepatocellular carcinoma cells

Hepatocellular carcinoma (HCC) is the most common type of primary liver cancer and the third leading cause of cancer‐related deaths worldwide. Limitations in HCC treatment result due to poor prognosis and resistance against traditional radiotherapy and chemotherapies. The multikinase inhibitor sorafenib is the only FDA approved drug available for advanced HCC patients, and development of second‐line treatment options for patients who cannot tolerate or develop resistance to sorafenib is an urgent medical need. In this study, we established sorafenib‐resistant cells from Huh7 and Mahlavu cell lines by long‐term sorafenib exposure. Sorafenib‐resistant HCC cells acquired spindle‐shape morphology, upregulated mesenchymal markers, and showed significant increase in both migration and invasion abilities compared to their parental counterparts. Moreover, after long‐term sorafenib treatment, HCC cells showed induction of hepatocyte growth factor (HGF) synthesis and secretion along with increased levels of c‐Met kinase and its active phosphorylated form, indicating autocrine activation of HGF/c‐Met signaling. Importantly, the combined treatment of the resistant cells with c‐Met kinase inhibitor SU11274 and HGF neutralizing antibody significantly reversed the increased invasion ability of the cells. The combined treatment also significantly augmented sorafenib‐induced apoptosis, suggesting restoration of sorafenib sensitivity. These results describe, for the first time, compensatory upregulation of HGF synthesis leading to autocrine activation of HGF/c‐Met signaling as a novel cellular strategy in the acquisition of sorafenib resistance. Therefore, we suggest that combinatorial therapeutic strategies with HGF and c‐Met inhibitors comprise promising candidates for overcoming sorafenib resistance.

The STAT3 pathway as a therapeutic target in head and neck cancer: Barriers and innovations

Proteins of the signal transducer and activator of transcription (STAT) family mediate cellular responses to cytokines and growth factors. Aberrant regulation of the STAT3 oncogene contributes to tumor formation and progression in many cancers, including head and neck squamous cell carcinoma (HNSCC), where hyperactivation of STAT3 is implicated in both treatment resistance and immune escape. There are no oncogenic gain-of-function mutations in HNSCC. Rather, aberrant STAT3 signaling is primarily driven by upstream growth factor receptors, such as Janus kinase (JAK) and epidermal growth factor receptor (EGFR). Moreover, genomic silencing of select protein tyrosine phosphatase receptors (PTPRs), tumor suppressors that dephosphorylate STAT3, may lead to prolonged phosphorylation and activation of STAT3. This review will summarize current knowledge of the STAT3 pathway and its contribution to HNSCC growth, survival, and resistance to standard therapies, and discuss STAT3-targeting agents in various phases of clinical development.

Long noncoding RNAs in hepatocellular carcinoma: Novel insights into their mechanism

Hepatocellular carcinoma (HCC) is the predominant subject of liver malignancies which arouse global concern. Advanced studies have found that long noncoding RNAs (lncRNAs) are differentially expressed in HCC and implicate they may play distinct roles in the pathogenesis and metastasis of HCC. However, the underlying mechanisms remain largely unclear. In this review, we summarized the functions and mechanisms of those known aberrantly expressed lncRNAs identified in human HCC tissues. We hope to enlighten more comprehensive researches on the detailed mechanisms of lncRNAs and their application in clinic, such as being used as diagnostic and prognostic biomarkers and the targets for potential therapy. Although studies on lncRNAs in HCC are still deficient, an improved understanding of the roles played by lncRNAs in HCC will lead to a much more effective utilization of those lncRNAs as novel candidates in early detection, diagnosis, prevention and treatment of HCC.

A long noncoding RNA perturbs the circadian rhythm of hepatoma cells to facilitate hepatocarcinogenesis

Clock circadian regulator (CLOCK)/brain and muscle arnt-like protein-1 (BMAL1) complex governs the regulation of circadian rhythm through triggering periodic alterations of gene expression. However, the underlying mechanism of circadian clock disruption in hepatocellular carcinoma (HCC) remains unclear. Here, we report that a long noncoding RNA (lncRNA), highly upregulated in liver cancer (HULC), contributes to the perturbations in circadian rhythm of hepatoma cells. Our observations showed that HULC was able to heighten the expression levels of CLOCK and its downstream circadian oscillators, such as period circadian clock 1 and cryptochrome circadian clock 1, in hepatoma cells. Strikingly, HULC altered the expression pattern and prolonged the periodic expression of CLOCK in hepatoma cells. Mechanistically, the complementary base pairing between HULC and the 5' untranslated region of CLOCK mRNA underlay the HULC-modulated expression of CLOCK, and the mutants in the complementary region failed to achieve the event. Moreover, immunohistochemistry staining and quantitative real-time polymerase chain reaction validated that the levels of CLOCK were elevated in HCC tissues, and the expression levels of HULC were positively associated with those of CLOCK in clinical HCC samples. In functional experiments, our data exhibited that CLOCK was implicated in the HULC-accelerated proliferation of hepatoma cells in vitro and in vivo. Taken together, our data show that an lncRNA, HULC, is responsible for the perturbations in circadian rhythm through upregulating circadian oscillator CLOCK in hepatoma cells, resulting in the promotion of hepatocarcinogenesis. Thus, our finding provides new insights into the mechanism by which lncRNA accelerates hepatocarcinogenesis through disturbing circadian rhythm of HCC.

Investigational therapies targeting signal transducer and activator of transcription 3 for the treatment of cancer

INTRODUCTION

Signal transducer and activator of transcription 3 (STAT3) mediates the expression of a variety of genes in response to cell stimuli and thus plays a key role in several cellular processes such as cell growth and apoptosis. Deregulation of the STAT3 activity has been shown in many malignancies, including breast, head and neck, prostate, pancreas, ovarian and brain cancers and melanoma. Thus, STAT3 may represent an ideal target for cancer therapy.

AREAS COVERED

The authors review recent data on the role of STAT3 in tumor initiation and progression, as well as the ongoing clinical trials in cancer patients. The content includes information derived from trial databases, regulatory authorities and scientific literature.

EXPERT OPINION

Targeting STAT3 activation leads to the inhibition of tumor growth and metastasis both in vitro and in vivo without affecting normal cells; this suggests that STAT3 could be a valid molecular target for cancer therapy. Extensive clinical research is trying to find anti-STAT3 agents with high single-agent activity. The identification and development of novel drugs that can target deregulated STAT3 activation effectively is both a scientific and clinical challenge that needs to be addressed in the near future.