Downregulating hypoxia-inducible factor-2α improves the efficacy of doxorubicin in the treatment of hepatocellular carcinoma

SerpinB3: A Multifaceted Player in Health and Disease-Review and Future Perspectives

SerpinB3, a member of the serine-protease inhibitor family, has emerged as a crucial player in various physiological and pathological processes. Initially identified as an oncogenic factor in squamous cell carcinomas, SerpinB3's intricate involvement extends from fibrosis progression and cancer to cell protection in acute oxidative stress conditions. This review explores the multifaceted roles of SerpinB3, focusing on its implications in fibrosis, metabolic syndrome, carcinogenesis and immune system impairment. Furthermore, its involvement in tissue protection from oxidative stress and wound healing underscores its potential as diagnostic and therapeutic tool. Recent studies have described the therapeutic potential of targeting SerpinB3 through its upstream regulators, offering novel strategies for cancer treatment development. Overall, this review underscores the importance of further research to fully elucidate the mechanisms of action of SerpinB3 and to exploit its therapeutic potential across various medical conditions.

Hypoxia-Induced Signaling in Gut and Liver Pathobiology

Oxygen (O2) is essential for cellular metabolism and biochemical reactions. When the demand for O2 exceeds the supply, hypoxia occurs. Hypoxia-inducible factors (HIFs) are essential to activate adaptive and survival responses following hypoxic stress. In the gut (intestines) and liver, the presence of oxygen gradients or physiologic hypoxia is necessary to maintain normal homeostasis. While physiologic hypoxia is beneficial and aids in normal functions, pathological hypoxia is harmful as it exacerbates inflammatory responses and tissue dysfunction and is a hallmark of many cancers. In this review, we discuss the role of gut and liver hypoxia-induced signaling, primarily focusing on HIFs, in the physiology and pathobiology of gut and liver diseases. Additionally, we examine the function of HIFs in various cell types during gut and liver diseases, beyond intestinal epithelial and hepatocyte HIFs. This review highlights the importance of understanding hypoxia-induced signaling in the pathogenesis of gut and liver diseases and emphasizes the potential of HIFs as therapeutic targets.

Novel Molecular Targets for Immune Surveillance of Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is a common and aggressive cancer with a high mortality rate. The incidence of HCC is increasing worldwide, and the lack of effective screening programs often results in delayed diagnosis, making it a challenging disease to manage. Immunotherapy has emerged as a promising treatment option for different kinds of cancers, with the potential to stimulate the immune system to target cancer cells. However, the current immunotherapeutic approaches for HCC have shown limited efficacy. Since HCC arises within a complex tumour microenvironment (TME) characterized by the presence of various immune and stromal cell types, the understanding of this interaction is crucial for the identification of effective therapy. In this review, we highlight recent advances in our understanding of the TME of HCC and the immune cells involved in anti-tumour responses, including the identification of new possible targets for immunotherapy. We illustrate a possible classification of HCC based on the tumour immune infiltration and give evidence about the role of SerpinB3, a serine protease inhibitor involved in the regulation of the immune response in different cancers.

Inflammatory processes involved in NASH-related hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fourth leading cause of cancer-related death worldwide. In the recent years nonalcoholic fatty liver disease (NAFLD) is becoming a growing cause of HCCs and the incidence of NAFLD-related HCCs is expected to further dramatically increase by the next decade. Chronic inflammation is regarded as the driving force of NAFLD progression and a key factor in hepatic carcinogenesis. Hepatic inflammation in NAFLD results from the persistent stimulation of innate immunity in response to hepatocellular injury and gut dysbiosis as well as by the activation of adaptive immunity. However, the relative roles of innate and adaptive immunity in the processes leading to HCC are still incompletely characterized. This is due to the complex interplay between different liver cell populations, which is also strongly influenced by gut-derived bacterial products, metabolic/nutritional signals. Furthermore, carcinogenic mechanisms in NAFLD/NASH appear to involve the activation of signals mediated by hypoxia inducible factors. This review discusses recent data regarding the contribution of different inflammatory cells to NAFLD-related HCC and their possible impact on patient response to current treatments.

Regulation of epithelial-mesenchymal transition by tumor microenvironmental signals and its implication in cancer therapeutics

Epithelial-mesenchymal transition (EMT) has been implicated in various aspects of tumor development, including tumor invasion and metastasis, cancer stemness, and therapy resistance. Diverse stroma cell types along with biochemical and biophysical factors in the tumor microenvironment impinge on the EMT program to impact tumor progression. Here we provide an in-depth review of various tumor microenvironmental signals that regulate EMT in cancer. We discuss the molecular mechanisms underlying the role of EMT in therapy resistance and highlight new therapeutic approaches targeting the tumor microenvironment to impact EMT and tumor progression.

Effects of Sensitized Sorafenib with a Paeoniflorin and Geniposide Mixture on Liver Cancer via the NF-κB-HIF-2α-SerpinB3 Pathway

Purpose

This study focused on determining the anticancer effect of paeoniflorin and geniposide mixture (PFGS) combined with sorafenib (Sor) in hepatocellular carcinoma (HCC) and, in particular, whether PFGS increases the antitumor effect of Sor by modulating the NF-κB/HIF-2α/SerpinB3 pathway.

Methods

The H22 hepatoma tumor-bearing mouse model was treated with PFGS, Sor, and a combination of the two drugs for 12 days. The effects of PFGS combined with Sor on tumor growth and apoptosis and the expression of NF-κB, HIF-2α, and SerpinB3 in tumor tissue were assessed. In addition, Sor-resistant hepatoma cells were treated with PFGS, Sor, and the combination of the two drugs in vitro. The effects of PFGS combined with Sor on cell proliferation and invasion and the protein expression of NF-κB p65, HIF-2α, and SerpinB3 were investigated.

Results

PFGS combined with Sor treatment synergistically inhibited tumor growth in HCC tumor-bearing mice. Immunostaining showed that PFGS combined with Sor treatment significantly decreased the expression of Ki-67 and obviously induced apoptosis in the tumor compared with a single treatment. Similarly, PFGS combined with Sor treatment significantly downregulated the expression of NF-κB, HIF-2α, and SerpinB3 in the tumor compared with a single treatment. Additionally, PFGS combined with Sor markedly inhibited cell proliferation and invasion and activation of the NF-κB/HIF-2α/SerpinB3 pathway in Sor-resistant hepatoma cells compared with a single treatment.

Conclusion

Our study demonstrated that PFGS synergistically increased the antiliver cancer effects of Sor by lowering activation of the NF-κB/HIF-2α/SerpinB3 pathway. These findings provided a scientific foundation for clinical studies using PFGS and Sor to treat liver cancer.

HIF-2α-targeted interventional chemoembolization multifunctional microspheres for effective elimination of hepatocellular carcinoma

Transcatheter arterial chemoembolization (TACE) is widely used for the treatment of advanced hepatocellular carcinoma (HCC). However, the long-term hypoxic microenvironment caused by TACE seriously affects the therapeutic effect of TACE. HIF-2α plays a crucial role on the chronic hypoxia process, which might be an ideal target for TACE therapy. Herein, a multifunctional polyvinyl alcohol (PVA)/hyaluronic acid (HA)-based microsphere (PT/DOX-MS) co-loaded with doxorubicin (DOX) and PT-2385, an effective HIF-2α inhibitor, was developed for enhanced TACE treatment efficacy. In vitro and in vivo studies revealed that PT/DOX-MS had a superior ability to treat HCC by blocking the tumor cells in G2/M phase, prompting cell apoptosis, and inhibiting tumor angiogenesis. The antitumor mechanisms of PT/DOX-MS were possibly due to that the introduction of PT-2385 could effectively inhibit the expression level of HIF-2α in hypoxic HCC cells, thereby down-regulating the expression levels of Cyclin D1, VEGF and TGF-α. In addition, the combination of DOX and PT-2385 could jointly inhibit VEGF expression, which was another reason accounting for the combined anti-cancer effect of PT/DOX-MS. Overall, our study demonstrated that PT/DOX-MS is a promising embolic agent for enhanced HCC treatment via the combined effect of hypoxia microenvironment improvement, chemotherapy, and embolization.

Hepatocyte-Specific Deletion of HIF2α Prevents NASH-Related Liver Carcinogenesis by Decreasing Cancer Cell Proliferation

BACKGROUND & AIMS

Hypoxia and hypoxia-inducible factors (HIFs) are involved in chronic liver disease progression. We previously showed that hepatocyte HIF-2α activation contributed significantly to nonalcoholic fatty liver disease progression in experimental animals and human patients. In this study, using an appropriate genetic murine model, we mechanistically investigated the involvement of hepatocyte HIF-2α in experimental nonalcoholic steatohepatitis (NASH)-related carcinogenesis.

METHODS

The role of HIF-2α was investigated by morphologic, cellular, and molecular biology approaches in the following: (1) mice carrying hepatocyte-specific deletion of HIF-2α (HIF-2α^-/- mice) undergoing a NASH-related protocol of hepatocarcinogenesis; (2) HepG2 cells stably transfected to overexpress HIF-2α; and (3) liver specimens from NASH patients with hepatocellular carcinoma.

RESULTS

Mice carrying hepatocyte-specific deletion of HIF-2α (hHIF-2α^-/-) showed a significant decrease in the volume and number of liver tumors compared with wild-type littermates. These effects did not involve HIF-1α changes and were associated with a decrease of cell proliferation markers proliferating cell nuclear antigen and Ki67. In both human and rodent nonalcoholic fatty liver disease-related tumors, HIF-2α levels were strictly associated with hepatocyte production of SerpinB3, a mediator previously shown to stimulate liver cancer cell proliferation through the Hippo/Yes-associated protein (YAP)/c-Myc pathway. Consistently, we observed positive correlations between the transcripts of HIF-2α, YAP, and c-Myc in individual hepatocellular carcinoma tumor masses, while HIF-2α deletion down-modulated c-Myc and YAP expression without affecting extracellular signal-regulated kinase 1/2, c-Jun N-terminal kinase, and AKT-dependent signaling. In vitro data confirmed that HIF-2α overexpression induced HepG2 cell proliferation through YAP-mediated mechanisms.

CONCLUSIONS

These results indicate that the activation of HIF-2α in hepatocytes has a critical role in liver carcinogenesis during NASH progression, suggesting that HIF-2α-blocking agents may serve as novel putative therapeutic tools.

Mild chronic hypoxia-induced HIF-2α interacts with c-MYC through competition with HIF-1α to induce hepatocellular carcinoma cell proliferation

PURPOSE

Hepatocellular carcinoma (HCC) has emerged as a leading cause of cancer-related deaths globally, in which hypoxia and activated hypoxia-inducible factors (HIFs) play important roles. The sibling rivalry between HIF-1α and HIF-2α in hypoxic tumor growth and progression still remains to be resolved, including in HCC. In this study, we aimed to analyze the mechanism by which HIF-1α and HIF-2α balance the proliferative response of HCC cells to hypoxia.

METHODS

The expression of HIF-1α, HIF-2α, c-MYC, Rictor and Raptor in corresponding tumor and non-tumor tissues from twenty-six patients with HCC was analyzed. The relationships between HIF-1α and HIF-2α and their respective effects were evaluated further in vitro in hypoxic HCC cells using co-immunoprecipitation, chromatin immunoprecipitation, in situ proximity ligation, annexin V-FITC/PI staining apoptosis and MTT assay. In addition, short hairpin RNA (shRNA) transfections targeting HIF-1α/2α and Rictor and Western blotting were applied in HCC cells to study the underlying mechanism.

RESULTS

We found that HIF-2α expression showed a positive correlation with c-MYC expression in tumor tissues, whereas HIF-1α did not. In vitro, increased HCC cell proliferation and an increased interaction between HIF-2α and c-MYC were observed under mild chronic hypoxic conditions. Although mild hypoxia led to HIF-1α, HIF-2α and c-MYC up-regulation, we found that mTORC2-regulated HIF-2α competed with HIF-1α to bind to c-MYC. Moreover, we found that HIF-2α knockdown decreased the expression of downstream c-MYC, suppressed hypoxic cell proliferation, and induced HCC cell apoptosis, whereas HIF-1α knockdown did not. Additionally, we found that the PI3K inhibitor apitolisib counteracted the effect of HIF-2α, thereby inducing HCC cell apoptosis.

CONCLUSIONS

Our data highlight a role of HIF-2α in activating and binding c-MYC, thereby inducing HCC cell proliferation during mild chronic hypoxia. The PI3K/mTORC2/HIF-2α/c-MYC axis may play a key role in this process. The PI3K inhibitor apitolisib may serve as a potential treatment option for patients suffering from HCC, especially in cases with rapidly growing tumors under mild chronic hypoxic conditions.

Role of long noncoding RNA-mediated competing endogenous RNA regulatory network in hepatocellular carcinoma

Long noncoding RNAs (lncRNAs) and microRNAs (miRNAs) are noncoding RNAs (ncRNAs) that occupy over 90% of the human genome, and their main function is to directly or indirectly regulate messenger RNA (mRNA) expression and participate in the tumorigenesis and progression of malignances. In particular, some lncRNAs can interact with miRNAs as competing endogenous RNAs (ceRNAs) to modulate mRNA expression. Accordingly, these RNA molecules are interrelated and coordinate to form a dynamic lncRNA-mediated ceRNA regulatory network. Mounting evidence has revealed that lncRNAs that act as ceRNAs are closely related to tumorigenesis. To date, numerous studies have established many different regulatory networks in hepatocellular carcinoma (HCC), and perturbations in these ceRNA interactions may result in the initiation and progression of HCC. Herein, we emphasize recent advances concerning the biological function of lncRNAs as ceRNAs in HCC, with the aim of elucidating the molecular mechanism underlying these HCC-related RNA molecules and providing novel insights into the diagnosis and treatment of HCC.

HIF2A overexpression reduces cisplatin sensitivity in cervical cancer by inducing excessive autophagy

Background

Hypoxia-induced autophagy is a crucial factor that induces chemotherapy resistance in tumor cells. As a key regulator facilitating the adaptation of solid tumors to hypoxia, the role of hypoxia-inducible factors (HIFs) in regulating hypoxia-induced chemotherapy resistance and autophagy has been extensively studied. However, the majority of studies have mainly focused on HIF-1. Direct evidence concerning the role of HIF2A in cisplatin resistance is sparse, and its underlying mechanism is not yet known.

Methods

Animal models were constructed by subcutaneously injecting cervical cancer cells stably overexpressing HIF2A (LV-HIF2A) with or without intraperitoneal injection of cisplatin. Tumor size and weight were evaluated to determine tumor growth. Apoptosis was detected by TUNEL assay and protein expression by western blotting.

Results

Nude mice injected with cells overexpressing HIF2A showed larger and heavier tumors than those in mice injected with negative control lentivirus (LV-NC)-infected cells, with or without cisplatin. Fewer apoptotic cells were noted in tumor tissues from the LV-HIF2A group than from the LV-NC group, with or without cisplatin. Additionally, expression of the anti-apoptotic protein, B-cell lymphoma 2 (BCL2), and autophagy-related proteins, beclin 1 and autophagy related 5 (ATG5), were found to be higher in the LV-HIF2A group than in the LV-NC group, regardless of cisplatin treatment. Moreover, expression of the pro-apoptotic protein, BCL2-associated X (BAX), was lower in tumor tissues from the LV-HIF2A group than from the LV-NC group. Effect of HIF2A overexpression on cisplatin sensitivity was found to be alleviated in vivo by the autophagy inhibitor, 3-methyladenine (3-MA).

Conclusions

HIF2A overexpression promoted tumor growth and autophagy but suppressed apoptosis in vivo, with or without cisplatin. The HIF2A overexpression-affected cisplatin sensitivity was alleviated by 3-MA. Therefore, we suggest that HIF2A overexpression reduces cisplatin sensitivity in cervical cancer by inducing excessive autophagy.

PTEN in Colorectal Cancer: Shedding Light on Its Role as Predictor and Target

Molecular assessment of colorectal cancer (CRC) is receiving growing attention, beyond RAS and BRAF, because of its influence on prognosis and prediction in cancer treatment. PTEN (phosphatase and tensin homologue), a tumor suppressor, regulating cell division and apoptosis, has been explored, and significant evidence suggests a role in cetuximab and panitumumab resistance linked to the epidermal growth factor receptor (EGFR) signal transduction pathway. Factors influencing PTEN activity should be analyzed to develop strategies to maximize the tumor suppressor role and to improve tumor response to cancer treatment. Therefore, an in-depth knowledge of the PI3K-Akt pathway—one of the major cancer survival pathways—and the role of PTEN—a major brake of this pathway—is essential in the era of precision medicine. The purpose of this literature review is to summarize the role of PTEN as a predictive factor and possible therapeutic target in CRC, focusing on ongoing studies and the possible implications in clinical practice.

Endovascular Ion Exchange Chemofiltration Device Reduces Off-Target Doxorubicin Exposure in a Hepatic Intra-arterial Chemotherapy Model

Purpose

To determine if endovascular chemofiltration with an ionic device (ChemoFilter [CF]) can be used to reduce systemic exposure and off-target biodistribution of doxorubicin (DOX) during hepatic intra-arterial chemotherapy (IAC) in a preclinical model.

Materials and Methods

Hepatic IAC infusions were performed in six pigs with normal livers. Animals underwent two 10-minute intra-arterial infusions of DOX (200 mg) into the common hepatic artery. Both the treatment group and the control group received initial IAC at 0 minutes and a second dose at 200 minutes. Prior to the second dose, CF devices were deployed in and adjacent to the hepatic venous outflow tract of treatment animals. Systemic exposure to DOX was monitored via blood samples taken during IAC procedures. After euthanasia, organ tissue DOX concentrations were analyzed. Alterations in systemic DOX exposure and biodistribution were compared by using one-tailed t tests.

Results

CF devices were well tolerated, and no hemodynamic, thrombotic, or immunologic complications were observed. Animals treated with a CF device had a significant reduction in systemic exposure when compared with systemic exposure in the control group (P <.009). Treatment with a CF device caused a significant decrease in peak DOX concentration (31%, P <.01) and increased the time to maximum concentration (P <.03). Tissue analysis was used to confirm significant reduction in DOX accumulation in the heart and kidneys (P <.001 and P <.022, respectively). Mean tissue concentrations in the heart, kidneys, and liver of animals treated with CF compared with those in control animals were 14.2 μg/g ± 1.9 (standard deviation) versus 26.0 μg/g ± 1.8, 46.4 μg/g ± 4.6 versus 172.6 μg/g ± 40.2, and 217.0 μg/g ± 5.1 versus 236.8 μg/g ± 9.0, respectively. Fluorescence imaging was used to confirm in vivo DOX binding to CF devices.

Conclusion

Reduced systemic exposure and heart bioaccumulation of DOX during local-regional chemotherapy to the liver can be achieved through in situ adsorption by minimally invasive image-guided CF devices.© RSNA, 2019.

Combination therapy of hepatocellular carcinoma by DNA shuffling-based VEGF vaccine and doxorubicin

Antiangiogenic therapy can enhance the efficacy of chemotherapy against solid tumors. This study was to determine whether TT46, a potential VEGF vaccine from DNA shuffling with a helper T-cell epitope of tetanus toxin B subunit, could enhance the efficacy of doxorubicin to combat hepatocellular carcinoma (HCC). Compared with monotherapy, the combination with TT46 vaccination and doxorubicin could significantly reduce microvessel counts and inhibit tumor angiogenesis. Enhanced immunization with TT46 for total six doses could induce long-term response maintenance with high anti-VEGF antibody titers in body. As a result, the combination with enhanced TT46 vaccination and doxorubicin significantly inhibited the HCC growth, and improved the survival rate of HCC-bearing mice in both of subcutaneous tumor model and lung metastasis model. In conclusion, the combined therapy with TT46 vaccination and doxorubicin has antitumor effects in both a prophylactic and therapeutic setting in a mouse model of H22 hepatocellular carcinoma.

Hypoxia inducible factors in hepatocellular carcinoma

Hepatocellular carcinoma is one of the most prevalent and lethal cancers with limited therapeutic options. Pathogenesis of this disease involves tumor hypoxia and the activation of hypoxia inducible factors. In this review, we describe the current understanding of hypoxia signaling pathway and summarize the expression, function and target genes of hypoxia inducible factors in hepatocellular carcinoma. We also highlight the recent progress in hypoxia-targeted therapeutic strategies in hepatocellular carcinoma and discuss further the future efforts for the study of hypoxia and/or hypoxia inducible factors in this deadly disease.

Downregulation and pro-apoptotic effect of hypoxia-inducible factor 2 alpha in hepatocellular carcinoma

The role of HIF-2α in hepatocellular carcinoma (HCC) is unclear. The aim of the present study was to investigate the expression pattern and role of HIF-2α in HCC patients. Immunohistochemical staining and western blotting analyses were applied to detect the protein level of HIF-2α in 206 paired HCC and peritumoral tissues. Kaplan-Meier survival and Cox proportional hazard regression analyses were performed to identify risk factors for overall survival and recurrence-free survival in these patients. The function of HIF-2α was studied in HCC cells and in vivo models. We found that the protein levels of HIF-2α in HCC tissues were lower than in peritumoral tissues, and were negatively correlated with tumor size (P < 0.05). Kaplan-Meier survival and univariate analysis revealed that HCC patients with high HIF-2α protein levels had longer overall survival (P < 0.05). Over-expression of HIF-2α induced apoptosis in HCC cells and increased the levels of pro-apoptotic proteins, Bak, ZBP-89 and PDCD4, whereas the inhibition of HIF-2α expression achieved opposite results. The findings were confirmed in a mouse HCC xenograft model. In conclusion, our study revealed that HIF-2α was decreased and played an anti-tumorigenic role in HCC.

New insights into sorafenib resistance in hepatocellular carcinoma: Responsible mechanisms and promising strategies

It is disappointing that only a few patients with hepatocellular carcinoma (HCC) obtain a significant survival benefit from the sorafenib treatment, which is currently regarded as a first-line chemotherapeutic therapy in patients with advanced HCC. Most patients are highly refractory to this therapy. Therefore, it is necessary to identify resistant factors and explore potential protocols that can be used to overcome the resistance or substitute sorafenib once the resistance is formed. In fact, a growing body of studies has been focusing on the resistance mechanisms or the method to overcome it. The limitation of sorafenib efficacy has been partially but not fully elucidated. Moreover, some protocols have shown encouraging outcomes but still need to be further verified in clinical trials. In this review, we summarize the recent findings on the potential mechanisms that contribute to sorafenib resistance and discuss strategies that can be used to improve the treatment outcome.

Poly((D,L)lactic-glycolic)acid-star glucose nanoparticles for glucose transporter and hypoglycemia-mediated tumor targeting

Poly((D,L)lactic-glycolic)acid-star glucose (PLGA-Glc) polymer-based nanoparticles (NPs) were fabricated for tumor-targeted delivery of docetaxel (DCT). NPs with an approximate mean diameter of 241 nm, narrow size distribution, negative zeta potential, and spherical shape were prepared. A sustained drug release pattern from the developed NPs was observed for 13 days. Moreover, drug release from PLGA-Glc NPs at acidic pH (endocytic compartments and tumor regions) was significantly improved compared with that observed at physiological pH (normal tissues and organs). DCT-loaded PLGA-Glc NPs (DCT/PLGA-Glc NPs) exhibited an enhanced antiproliferation efficiency rather than DCT-loaded PLGA NPs (DCT/PLGA NPs) in Hep-2 cells, which can be regarded as glucose transporters (GLUTs)-positive cells, at ≥50 ng/mL DCT concentration range. Under glucose-deprived (hypoglycemic) conditions, the cellular uptake efficiency of the PLGA-Glc NPs was higher in Hep-2 cells compared to that observed in PLGA NPs. Cy5.5-loaded NPs were prepared and injected into a Hep-2 tumor-xenografted mouse model for in vivo near-infrared fluorescence imaging. The PLGA-Glc NPs group exhibited higher fluorescence intensity in the tumor region than the PLGA NPs group. These results imply that the PLGA-Glc NPs have active tumor targeting abilities based on interactions with GLUTs and the hypoglycemic conditions in the tumor region. Therefore, the developed PLGA-Glc NPs may represent a promising tumor-targeted delivery system for anticancer drugs.

Liposomal curcumin and its application in cancer

Curcumin (CUR) is a yellow polyphenolic compound derived from the plant turmeric. It is widely used to treat many types of diseases, including cancers such as those of lung, cervices, prostate, breast, bone and liver. However, its effectiveness has been limited due to poor aqueous solubility, low bioavailability and rapid metabolism and systemic elimination. To solve these problems, researchers have tried to explore novel drug delivery systems such as liposomes, solid dispersion, microemulsion, micelles, nanogels and dendrimers. Among these, liposomes have been the most extensively studied. Liposomal CUR formulation has greater growth inhibitory and pro-apoptotic effects on cancer cells. This review mainly focuses on the preparation of liposomes containing CUR and its use in cancer therapy.

Overexpression and correlation of HIF-2α, VEGFA and EphA2 in residual hepatocellular carcinoma following high-intensity focused ultrasound treatment: Implications for tumor recurrence and progression

Rapid growth of residual tumors can occur as a result of their recurrence and progression. The present study aimed to investigate the expression of hypoxia inducible factor-2 subunit α (HIF-2α), vascular endothelial growth factor A (VEGFA), erythropoietin-producing hepatocellular A2 (EphA2) and angiogenesis in residual hepatocellular carcinoma (HCC), following treatment with high-intensity focused ultrasound (HIFU) ablation, in order to investigate the association between protein expression and tumor recurrence and growth. Athymic BALB/c (nu/nu) mice were subcutaneously inoculated with the HCC cell line HepG2, in order to create xenograft tumors. Approximately 30 days post-inoculation, eight mice were treated with HIFU, whereas eight mice received no treatment and acted as the control group. Residual tumor tissues were obtained from the experimental groups after one month. Levels of HIF-2α, VEGFA, EphA2 and cluster of differentiation 31 (CD31) expression was measured by immunohistochemical staining. CD31-positive vascular endothelial cells were counted to calculate microvascular density (MVD), and western blot analysis was performed to determine levels of HIF-2α, VEGFA, and EphA2 protein. It was found that the expression levels of HIF-2α, VEGFA, EphA2, and MVD proteins in residual HCC tissues were significantly higher than in the control group tissues (P<0.05). Tumor MVD was strongly correlated with VEGFA (R=0.957, P<0.01) and EphA2 (R=0.993, P<0.01) protein expression levels. Furthermore, there was a significant positive correlation between HIF-2α and EphA2 expression (R=0.991, P<0.01). The correlation between VEGFA and EphA2 expression was also positive (R=0.985, P<0.01). These data suggest that overexpression of HIF-2α, VEGFA and EphA2 is related to angiogenesis in residual HCC following HIFU ablation, potentially via their association with key mediators of recurrence.

Dehydroascorbic Acids-modified Polymer Micelles Target Cancer Cells to Enhance Anti-tumor Efficacy of Paclitaxel

Paclitaxel (PTX), especially albumin-bound PTX in clinical, has displayed significant inhibition of tumor growth in patients. But the systemic distribution and poor water solubility of PTX often lead to severe side effects, consequently limiting the anti-tumor efficacy. In this study, we developed a novel PTX-loaded polymeric micelle drug delivery system. These self-assembled polymeric micelles from core to outside consisted of poly L-phenylalanine (pPhe), DTSSP linked poly L-lysine (pLys), poly ethylene glycol (PEG) and dehydroascorbic acids (DHA). pPhe formed the hydrophobic core to encapsulate PTX; DTSSPs on pLys covalently cross-linked and formed disulfide bond to stabilize PTX from loss in blood circulation; PEG improved solubility to lower toxicity of PTX for its high hydrophilicity; DHA targeted tumors by specifically recognizing GLUT1 mainly expressed on tumor cells. Thus, PTX would be precisely released into tumor cells with high dose of glutathione to break disulfide bond. Moreover, these PTX-loaded polymer micelles significantly suppressed tumor cell viability, proliferation, and migration in vitro, and also greatly inhibited tumor growth and prolonged survival in tumor-bearing mice without detectable side effects. Therefore, the new drug delivery system could reduce severe side effects and enhance anti-tumor efficacy of PTX via peripheral stabilization, low toxicity and tumor targeting.

Oxidative Stress Promotes Doxorubicin-Induced Pgp and BCRP Expression in Colon Cancer Cells Under Hypoxic Conditions

P-glycoprotein (Pgp) and breast cancer resistance protein (BCRP) are ATP binding cassette (ABC) transporters that are overexpressed in different drug-resistant cancer cell lines. In this study, we investigated whether doxorubicin promotes Pgp and/or BCRP expression to induce drug resistance in colon cancer cells under hypoxic conditions. We analyzed HIF-1α activity via ELISA, Pgp, and BCRP expression by qRT-PCR and the relationship between doxorubicin uptake and ABC transporter expression via confocal microscopy in HT-29WT and HT-29 doxorubicin-resistant colon cancer cells (HT-29DxR). These cells were treated with doxorubicin and/or CoCl₂ (chemical hypoxia), and reactive oxygen species inductors. We found that the combination of chemically induced hypoxia and doxorubicin promoted Pgp mRNA expression within 24 h in HT-29WT and HT-29DxR cells. Both doxorubicin and CoCl₂ alone or in combination induced Pgp and BCRP expression, as demonstrated via confocal microscopy in each of the above two cell lines. Thus, we surmised that Pgp and BCRP expression may result from synergistic effects exerted by the combination of doxorubicin-induced ROS production and HIF-1α activity under hypoxic conditions. However, HIF-1α activity disruption via the administration of E3330, an APE-1 inhibitor, downregulated Pgp expression and increased doxorubicin delivery to HT-29 cells, where it served as a substrate for Pgp, indicating the existence of an indirect relationship between Pgp expression and doxorubicin accumulation. Thus, we concluded that Pgp and BCRP expression can be regulated via cross-talk between doxorubicin and hypoxia, promoting drug resistance in HT-29 WT, and HT-29DxR cells and that this process may be ROS dependent. J. Cell. Biochem. 118: 1868-1878, 2017. © 2017 Wiley Periodicals, Inc.

Advances in Hypoxia-Mediated Mechanisms in Hepatocellular Carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common and the third most deadly malignant tumor worldwide. Hypoxia and related oxidative stress are heavily involved in the process of HCC development and its therapies. However, direct and accurate measurement of oxygen concentration and evaluation of hypoxic effects in HCC prove difficult. Moreover, the hypoxia-mediated mechanisms in HCC remain elusive. Here, we summarize recent major evidence of hypoxia in HCC lesions shown by measuring partial pressure of oxygen (pO₂), the clinical importance of hypoxic markers in HCC, and recent advances in hypoxia-related mechanisms and therapies in HCC. For the mechanisms, we focus mainly on the roles of oxygen-sensing proteins (i.e., hypoxia-inducible factor and neuroglobin) and hypoxia-induced signaling proteins (e.g., matrix metalloproteinases, high mobility group box 1, Beclin 1, glucose metabolism enzymes, and vascular endothelial growth factor). With respect to therapies, we discuss mainly YQ23, sorafenib, 2-methoxyestradiol, and celastrol. This review focuses primarily on the results of clinical and animal studies.

Stable knockdown of CREB, HIF-1 and HIF-2 by replication-competent retroviruses abrogates the responses to hypoxia in hepatocellular carcinoma

The fast proliferation of tumor cells develops faster than the vasculature, resulting, in most malignant tumors, in generation of hypoxic regions. Hypoxia renders solid tumors resistant to radiation and chemotherapeutics while providing opportunities for tumor-selective therapies targeting tumor hypoxia. Here we exploit two properties of tumors: propagation of tumor cells and ongoing generation of hypoxic regions to construct a system that preferentially leads to the death of tumor cells and thus hinders tumor growth. We constructed murine leukemia virus replication-competent (RCR) viruses that infect only propagating cells. These viruses express small hairpin RNAs (shRNAs) targeting cyclic AMP-response-element binding protein (CREB), hypoxia-inducible factors 1 (HIF)-1 or HIF-2 individually or all three together (X3). These viruses efficiently infected in vitro human hepatocellular carcinoma (HepG2 and FLC4) cells and established persistence of the virus and knocked down the expression of the regulators of the hypoxia-responding genes. Knockdown of either HIF-1 or CREB or both in hypoxia reduced the expression of hypoxia-response elements- and CRE-mediated gene expression, diminished cell proliferation and increased caspase-3 activity. We did not detect any significant effect of the efficiently knocked down HIF-2 on any of the functions tested in vitro. Moreover, severe combined immunodeficiency mice implanted subcutaneously with HepG2 stably infected with recombinant RCRs showed reduction of tumor growth and vascular endothelial growth factor expression, and no hypoxia-guided neovascularization. Combined treatment (RCRs+doxorubicin) improved efficacy in the context of in vitro hypoxia and in vivo (with either vACE-CREB or vACE-X3). This synergistic effect may lead to an improved efficacy and safety profile of the treatment that may result in fewer side effects.

Therapeutic targeting of hypoxia and hypoxia-inducible factors in cancer

Insufficient tissue oxygenation, or hypoxia, contributes to tumor aggressiveness and has a profound impact on clinical outcomes in cancer patients. At decreased oxygen tensions, hypoxia-inducible factors (HIFs) 1 and 2 are stabilized and mediate a hypoxic response, primarily by acting as transcription factors. HIFs exert differential effects on tumor growth and affect important cancer hallmarks including cell proliferation, apoptosis, differentiation, vascularization/angiogenesis, genetic instability, tumor metabolism, tumor immune responses, and invasion and metastasis. As a consequence, HIFs mediate resistance to chemo- and radiotherapy and are associated with poor prognosis in cancer patients. Intriguingly, perivascular tumor cells can also express HIF-2α, thereby forming a "pseudohypoxic" phenotype that further contributes to tumor aggressiveness. Therefore, therapeutic targeting of HIFs in cancer has the potential to improve treatment efficacy. Different strategies to target hypoxic cancer cells and/or HIFs include hypoxia-activated prodrugs and inhibition of HIF dimerization, mRNA or protein expression, DNA binding capacity, and transcriptional activity. Here we review the functions of HIFs in the progression and treatment of malignant solid tumors. We also highlight how HIFs may be targeted to improve the management of patients with therapy-resistant and metastatic cancer.

Glucose transporter isoform 1 expression enhances metastasis of malignant melanoma cells

The glucose transporter isoform 1 (GLUT1; SLC2A1) is a key rate-limiting factor in the transport of glucose into cancer cells. Enhanced GLUT1 expression and accelerated glycolysis have been found to promote aggressive growth in a range of tumor entities. However, it was unknown whether GLUT1 directly impacts metastasis. Here, we aimed at analyzing the expression and function of GLUT1 in malignant melanoma. Immunohistochemical analysis of 78 primary human melanomas on a tissue micro array showed that GLUT1 expression significantly correlated with the mitotic activity and a poor survival. To determine the functional role of GLUT1 in melanoma, we stably suppressed GLUT1 in the murine melanoma cell line B16 with shRNA. GLUT1 suppressed melanoma cells revealed significantly reduced proliferation, apoptosis resistance, migratory activity and matrix metalloproteinase 2 (MMP2) expression. In a syngeneic murine model of hepatic metastasis, GLUT1-suppressed cells formed significantly less metastases and showed increased apoptosis compared to metastases formed by control cells. Treatment of four different human melanoma cell lines with a pharmacological GLUT1 inhibitor caused a dose-dependent reduction of proliferation, apoptosis resistance, migratory activity and MMP2 expression. Analysis of MAPK signal pathways showed that GLUT1 inhibition significantly decreased JNK activation, which regulates a wide range of targets in the metastatic cascade. In summary, our study provides functional evidence that enhanced GLUT1 expression in melanoma cells favors their metastatic behavior. These findings specify GLUT1 as an attractive therapeutic target and prognostic marker for this highly aggressive tumor.

Downregulation of Kinesin spindle protein inhibits proliferation, induces apoptosis and increases chemosensitivity in hepatocellular carcinoma cells

Background: Kinesin spindle protein (KSP) plays a critical role in mitosis. Inhibition of KSP function leads to cell cycle arrest at mitosis and ultimately to cell death. The aim of this study was to suppress KSP expression by specific small-interfering RNA (siRNA) in Hep3B cells and evaluate its anti-tumor activity. Methods: Three siRNA targeting KSP (KSP-siRNA #1-3) and one mismatched-siRNA (Cont-siRNA) were transfected into cells. Subsequently, KSP mRNA and protein levels, cell proliferation, and apoptosis were examined in both Hep3B cells and THLE-3 cells. In addition, the chemosensitivity of KSP-siRNA-treated Hep3B cells with doxorubicin was also investigated using cell proliferation and clonogenic survival assays. Results: The expression of endogenous KSP at both mRNA and protein levels in Hep3B cells was higher than in THLE-3 cells. In Hep3B cells, KSP-siRNA #2 showed a further downregulation of KSP as compared to KSP-siRNA #1 or KSP-siRNA #3. It also exhibited greater suppression of cell proliferation and induction of apoptosis than KSP-siRNA #1 or KSP-siRNA #3; this could be explained by the significant downregulation of cyclin D1, Bcl-2, and survivin. In contrast, KSP-siRNAs had no or lower effects on KSP expression, cell proliferation and apoptosis in THLE-3 cells. We also noticed that KSP-siRNA transfection could increase chemosensitivity to doxorubicin in Hep3B cells, even at low doses compared to control. Conclusion: Reducing the expression level of KSP, combined with drug treatment, yields promising results for eradicating hepatocellular carcinoma (HCC) cells in vitro. This study opens a new direction for liver cancer treatment.

Bufalin Reverses Resistance to Sorafenib by Inhibiting Akt Activation in Hepatocellular Carcinoma: The Role of Endoplasmic Reticulum Stress

Sorafenib is the standard first-line therapeutic treatment for patients with advanced hepatocellular carcinoma (HCC), but its use is hampered by the development of drug resistance. The activation of Akt by sorafenib is thought to be responsible for this resistance. Bufalin is the major active ingredient of the traditional Chinese medicine Chan su, which inhibits Akt activation; therefore, Chan su is currently used in the clinic to treat cancer. The present study aimed to investigate the ability of bufalin to reverse both inherent and acquired resistance to sorafenib. Bufalin synergized with sorafenib to inhibit tumor cell proliferation and induce apoptosis. This effect was at least partially due to the ability of bufalin to inhibit Akt activation by sorafenib. Moreover, the ability of bufalin to inactivate Akt depended on endoplasmic reticulum (ER) stress mediated by inositol-requiring enzyme 1 (IRE1). Silencing IRE1 with siRNA blocked the bufalin-induced Akt inactivation, but silencing eukaryotic initiation factor 2 (eIF2) or C/EBP-homologous protein (CHOP) did not have the same effect. Additionally, silencing Akt did not influence IRE1, CHOP or phosphorylated eIF2α expression. Two sorafenib-resistant HCC cell lines, which were established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition but were sensitive to bufalin. Thus, Bufalin reversed acquired resistance to sorafenib by downregulating phosphorylated Akt in an ER-stress-dependent manner via the IRE1 pathway. These findings warrant further studies to examine the utility of bufalin alone or in combination with sorafenib as a first- or second-line treatment after sorafenib failure for advanced HCC.

Targeting hypoxia-inducible factor-2α enhances sorafenib antitumor activity via β-catenin/C-Myc-dependent pathways in hepatocellular carcinoma

Sorafenib is a type of multikinase inhibitor that exhibits antiangiogenic and antiproliferative effects; in addition, sorafenib is a unique first-line drug recommended for the treatment of advanced hepatocellular carcinoma (HCC). However, the effectiveness of HCC treatment remains poor due to acquired drug resistance. It has been suggested that hypoxia, induced as a results of the antiangiogenic effects of sustained sorafenib treatment, may be an important factor in sorafenib resistance. The transcription factor hypoxia-inducible factor (HIF)-2α has been reported to be associated with cell proliferation under hypoxic conditions; therefore, it was hypothesized that hypoxia may enhance tumor cell proliferation via this mechanism. The present study aimed to evaluate whether the knock-down of HIF-2α was able to enhance the therapeutic efficacy of sorafenib in order to effectively treat HCC. The results demonstrated that hypoxia protected HCC cells against sorafenib; however, short hairpin RNA-HIF-2α transfection in combination with sorafenib treatment exhibited a significantly synergistic effect against HCC cell proliferation. In addition, HCC cells acquired increased β-catenin/C-Myc expression, which enhanced proliferation under hypoxic conditions; however, targeted knock-down of HIF-2α or C-Myc markedly decreased cell proliferation in HCC cells. In conclusion, the results of the present study indicated that the targeted knock-down of HIF-2α in combination with sorafenib may be a promising strategy for the treatment of HCC.

Dual-targeting and pH/redox-responsive multi-layered nanocomplexes for smart co-delivery of doxorubicin and siRNA

Multi-layered nanocomplexes (MLNs) were designed here to provide smart co-delivery of doxorubicin (DOX) and vascular endothelial growth factor (VEGF) siRNA. The electrostatically self-assembled MLNs were constructed by TAT peptide modified mesoporous silica nanoparticles (TAT-MSN) as the cationic core for DOX loading, poly(allylamine hydrochloride)-citraconic anhydride (PAH-Cit) as the anionic inner layer, and galactose-modified trimethyl chitosan-cysteine (GTC) conjugate as the cationic outer layer to encapsulate siRNA. Their strong stability at pH 7.4 and 6.5 protected siRNA from degradation in the blood and tumor microenvironment. Galactose ligands on the GTC outer layers effectively facilitated the internalization of MLNs through receptor-mediated endocytosis. Afterwards, the endosomal/lysosomal acidity (pH 5.0) triggered the charge reversal of PAH-Cit, thereby inducing the disassembly of MLNs and their escape to the cytosol. Cytoplasmic glutathione further accelerated siRNA release through cleaving disulfide bonds in GTC layers, leading to high silencing efficiencies. Meanwhile, the exposed DOX-loaded cores were transported into the nuclei by virtue of TAT peptide and exhibited sustained release thereafter. As a result, potent antitumor efficacies of MLNs were noted following intravenous injection at a low dose with no apparent toxicity detected. Therefore, MLNs served as an effective and safe vector to maximize synergistic effect of chemodrugs and therapeutic genes.

The emerging role of hypoxia-inducible factor-2 involved in chemo/radioresistance in solid tumors

The hypoxic condition is a common feature that negatively impacts the efficacy of radio- and chemotherapy in solid tumors. Hypoxia-inducible factors (HIF-1, 2, 3) predominantly regulate the adaptation to hypoxia at the cellular or organismal level. HIF-2 is one of the three known alpha subunits of HIF transcription factors. Previous studies have shown that HIF-1 is associated with chemotherapy failure. Accumulating evidence in recent years suggests that HIF-2 also contributes to chemo/radioresistance in solid tumors. Despite sharing similar structures, HIF-1α and HIF-2α had highly divergent and even opposing roles in solid tumors under hypoxic conditions. Recent studies have also implied that HIF-2α had a role in chemo/radioresistance through different mechanisms, at least partly, compared to HIF-1α. The present paper summarizes the function of HIF-2 in chemo/radioresistance in solid tumors as well as some of its novel mechanisms that contributed to this pathological process.

HIF-2alpha-dependent PAI-1 induction contributes to angiogenesis in hepatocellular carcinoma

Hypoxia promotes progression of hepatocellular carcinoma (HCC), not only affecting tumor cell proliferation and invasion, but also angiogenesis and thus, increasing the risk of metastasis. Hypoxia inducible factors (HIF)-1α and -2α cause adaptation of tumors to hypoxia, still with uncertainties towards the angiogenic switch. We created a stable knockdown of HIF-1α and HIF-2α in HepG2 cells and generated cocultures of HepG2 spheroids with embryonic bodies as an in vitro tumor model mimicking the cancer microenvironment. The naturally occuring oxygen and nutrient gradients within the cocultures allow us to question the role of distinct HIF isoforms in regulating HCC angiogenesis. In cocultures with a HIF-2α knockdown, angiogenesis was attenuated, while the knockdown of HIF-1α was without effect. Microarray analysis identified plasminogen activator inhibitor 1 (PAI-1) as a HIF-2α target gene in HepG2 cells. The knockdown of PAI-1 in HepG2 cells also lowered angiogenesis. Blocking plasmin, the downstream target of PAI-1, with aprotinin in HIF-2α knockdown (k/d) cells proved a cause-effect relation and restored angiogenesis, with no effect on control cocultures. Suggestively, HIF-2α increases PAI-1 to lower concentrations of active plasmin, thereby supporting angiogenesis. We conclude that the HIF-2α target gene PAI-1 favors the angiogenic switch in HCC.

Combined Antiangiogenic and Mammalian Target of Rapamycin Inhibitor Targeted Therapy in Metaplastic Breast Cancer Harboring a PIK3CA Mutation

Metaplastic breast cancer (MpBC) is an extremely rare breast cancer subtype, characterized by a heterogeneous phenotype. MpBC aggressive biology is attributed to its stem cell-like characteristics. Since these tumors are largely chemoresistant, novel targeted therapies should be explored. Herein, we report the clinical course of a 59-year-old African American woman with MpBC with a PIK3CA mutation in codon 545, exon 10 (GAG to AAG; p.Glu545Lys) and a TP53 mutation in codon 286, exon 8 (GAA to AAA; p.Glu286Lys). The same mutations were observed in the primary and secondary sites. The patient was treated with a molecularly matched therapy using a combined antiangiogenic and mammalian target of rapamycin kinase inhibitor strategy that included liposomal doxorubicin, bevacizumab, and temsirolimus. Partial remission was achieved. In this report, the scientific rationale underlying the activity of this combination was explored. In conclusion, patients may benefit from being offered molecular profiling early during the course of the disease to receive a therapy guided accordingly.

2-Methoxyestradiol synergizes with sorafenib to suppress hepatocellular carcinoma by simultaneously dysregulating hypoxia-inducible factor-1 and -2

Sorafenib is the approved systemic drug of choice for advanced hepatocellular carcinoma (HCC), but has demonstrated limited benefits because of drug resistance. 2-Methoxyestradiol (2ME2) has been shown to be a promising anticancer drug against various types of cancers and acts by dysregulating hypoxia-inducible factor (HIF)-1. Hypoxic cancer cells are extremely resistant to therapies since they elicit strong survival ability due to the cellular adaptive response to hypoxia, which is controlled by HIF-1 and HIF-2. The present study has demonstrated that sorafenib downregulated the expression of HIF-1α, making the hypoxic response switch from HIF-1α- to HIF-2α-dependent pathways, resulting in upregulation of HIF-2α, which contributes to the insensitivity of hypoxic HCC cells to sorafenib. HIF-2α played a dominant role in regulating VEGF, thus sorafenib in turn increased the expression of VEGF (a downstream molecule of both HIF-1 and HIF-2) and cyclin D1 (a downstream molecule of HIF-2), but reduced the expression of LDHA (a downstream molecule of HIF-1), in hypoxic HCC cells. 2ME2 significantly reduced the expression of both HIF-1α and HIF-2α, and their downstream molecules, VEGF, LDHA and cyclin D1, rendering hypoxic HCC cells to increased sensitivity to 2ME2. 2ME2 also inhibited the nuclear translocation of HIF-1α and HIF-2α proteins, but had no effect on their mRNA expression. 2M2 synergized with sorafenib to suppress the proliferation and induction of apoptosis of HCC cells in vitro and in vivo, and inhibited tumoral angiogenesis. These results indicate that 2ME2 given in combination with sorafenib acts synergistically for treating HCC.

Downregulating sCLU enhances the sensitivity of hepatocellular carcinoma cells to gemcitabine by activating the intrinsic apoptosis pathway

PURPOSE

The purpose of this study was to investigate whether the therapeutic activity of gemcitabine (GCB) in hepatocellular carcinoma (HCC) could be increased by the down-regulation of secretory clusterin (sCLU), a glycoprotein that is considered to play a cytoprotective role in the resistance to chemotherapy.

METHODS

The expression of sCLU was detected in HCC tumor tissues and cell lines. A cell viability and apoptosis assay were performed in parental HCC cells or the same cells transfected with sCLU shRNA and treated with or without GCB. The potential downstream pathways were investigated using the Human Apoptosis RT(2) Profiler™ PCR Array.

RESULTS

The expression levels of sCLU in HCC tissues were significantly higher than in adjacent non-tumor liver tissues and were associated with the histological grade and transarterial chemoembolization. sCLU overexpression was also found in three HCC cell lines and hepatocytes. The depletion of sCLU synergistically increased GCB sensitivity in Bel7402 and SMMC7721 cells and induced cell apoptosis. Based on the PCR array analysis, sCLU depletion also resulted in the up-regulation of BNIP1, GADD45A, TNFRSF10A, and TRADD and down-regulation of AKT1 in Bel7402 and SMMC7721 cells compared with the parental controls. These results were further supported by a Western blot analysis, which showed increased GADD45a protein expression and the decreased expression of phosphorylated AKT. GADD45a overexpression also increased the sensitivity to GCB in the Bel7402 and SMMC7721 cells.

CONCLUSION

Targeting sCLU may be a useful method to enhance the cytotoxic effect of GCB in hepatocellular carcinoma.

Inhibition of Akt reverses the acquired resistance to sorafenib by switching protective autophagy to autophagic cell death in hepatocellular carcinoma

Sorafenib is the standard first-line systemic drug for advanced hepatocellular carcinoma (HCC), but the acquired resistance to sorafenib results in limited benefits. Activation of Akt is thought to be responsible for mediating the acquired resistance to sorafenib. The present study aims to examine the underlying mechanism and seek potential strategies to reverse this resistance. Two sorafenib-resistant HCC cell lines, which had been established from human HCC HepG2 and Huh7 cells, were refractory to sorafenib-induced growth inhibition and apoptosis in vitro and in vivo. Sustained exposure to sorafenib activated Akt via the feedback loop of mTOR but independent of protein phosphatase 2A in HCC cells. Autophagy participated in the resistance to sorafenib as inhibition of autophagy reduced the sensitivity of sorafenib-resistant HCC cells to sorafenib, whereas activation of autophagy by rapamycin had the opposite effect. However, rapamycin did not show a synergistic effect with sorafenib to inhibit cell proliferation, while it also activated Akt via a feedback mechanism in sorafenib-resistant HCC cells. Inhibition of Akt reversed the acquired resistance to sorafenib by switching autophagy from a cytoprotective role to a death-promoting mechanism in the sorafenib-resistant HCC cells. Akt inhibition by GDC0068 synergized with sorafenib to suppress the growth of sorafenib-resistant HCC tumors that possessed the sorafenib-resistant feature in vivo. The results have provided evidence for clinical investigation of GDC0068, a novel ATP-competitive pan-Akt inhibitor, as the second-line treatment after the failure of sorafenib-medicated molecular targeted therapy for advanced HCC.

Meloxicam executes its antitumor effects against hepatocellular carcinoma in COX-2- dependent and -independent pathways

BACKGROUND

Cyclooxygenase (COX)-2 is overexpressed in many types of cancers including hepatocellular carcinoma (HCC). Meloxicam, a selective COX-2 inhibitor, has shown potential therapeutic effects against HCC, but the mechanisms accounting for its anti-cancer activities remain unclear.

METHODS AND FINDINGS

Meloxicam inhibited the ability of human HCC cells expressing higher levels of COX-2 to migrate, invade, adhere and form colonies through upregulating the expression of E-cadherin and downregulating the expression of matrix metalloproteinase (MMP) -2. Meloxicam induced cell apoptosis by upregulating pro-apoptotic proteins including Bax and Fas-L, and downregulating anti-apoptotic proteins including survivin and myeloid cell leukemia-1 (Mcl-1), through inhibiting phosphorylation of AKT. Addition of prostaglandin E2 (PGE2), the major product of COX-2, could abrogate the effects of meloxicam on the expression of survivin and myeloid cell leukemia-1 (Mcl-1), but not Bax and Fas-L, indicating that meloxicam induces cell apoptosis via both COX-2-dependent and -independent pathways. Meloxicam also induced cell autophagy by upregulating Beclin 1 and light chain 3-II. Specific inhibition of autophagy by 3-methyladenine and chloroquine had little effect on cell apoptosis but could enhance the pro-apoptotic effects of meloxicam by further upregulating the expression of Bax.

CONCLUSIONS

Meloxicam executes its antitumor effects by targeting the COX-2/MMP-2/E-cadherin, AKT, apoptotic and autophagic pathways in COX-2-dependent and -independent pathways, and inhibition of cell autophagy could help to overcome the resistance to meloxicam-induced apoptosis in HCC.

Meloxicam executes its antitumor effects against hepatocellular carcinoma in COX-2- dependent and -independent pathways

Background

Cyclooxygenase (COX)-2 is overexpressed in many types of cancers including hepatocellular carcinoma (HCC). Meloxicam, a selective COX-2 inhibitor, has shown potential therapeutic effects against HCC, but the mechanisms accounting for its anti-cancer activities remain unclear.

Methods and Findings

Meloxicam inhibited the ability of human HCC cells expressing higher levels of COX-2 to migrate, invade, adhere and form colonies through upregulating the expression of E-cadherin and downregulating the expression of matrix metalloproteinase (MMP) -2. Meloxicam induced cell apoptosis by upregulating pro-apoptotic proteins including Bax and Fas-L, and downregulating anti-apoptotic proteins including survivin and myeloid cell leukemia-1 (Mcl-1), through inhibiting phosphorylation of AKT. Addition of prostaglandin E2 (PGE2), the major product of COX-2, could abrogate the effects of meloxicam on the expression of survivin and myeloid cell leukemia-1 (Mcl-1), but not Bax and Fas-L, indicating that meloxicam induces cell apoptosis via both COX-2-dependent and -independent pathways. Meloxicam also induced cell autophagy by upregulating Beclin 1 and light chain 3-II. Specific inhibition of autophagy by 3-methyladenine and chloroquine had little effect on cell apoptosis but could enhance the pro-apoptotic effects of meloxicam by further upregulating the expression of Bax.

Conclusions

Meloxicam executes its antitumor effects by targeting the COX-2/MMP-2/E-cadherin, AKT, apoptotic and autophagic pathways in COX-2-dependent and -independent pathways, and inhibition of cell autophagy could help to overcome the resistance to meloxicam-induced apoptosis in HCC.

HIF-1α and HIF-2α: siblings in promoting angiogenesis of residual hepatocellular carcinoma after high-intensity focused ultrasound ablation

Background

High-intensity focused ultrasound (HIFU) is a widely applied to treatment for unresectable hepatocellular carcinoma. However, insufficient HIFU can result in rapid progression of the residual tumor. The mechanism of such rapid growth of the residual tumor after HIFU ablation is poorly understood.

Objective

The aim of this study was to investigate the dynamic angiogenesis of residual tumor, and the temporal effect and mechanism of the HIF-1, 2α in the residual tumor angiogenesis.

Methods

Xenograft tumors of HepG2 cells were created by subcutaneously inoculating nude mice (athymic BALB/c nu/nu mice) with hepatoma cells. About thirty days after inoculation, all mice (except control group) were treated by HIFU and assigned randomly to 7 groups according to various time intervals (1st, 3rd, 5th day (d) and 1st, 2nd, 3rd, 4th week (w)). The residual tumor tissues were obtained from the experimental groups at various time points. Protein levels of HIF-1α, HIF-2α, VEGF-A, and EphA2 were quantified by immunohistochemistry analysis and Western Blot assays, and mRNA levels measured by Q-PCR. Microvascular density was calculated with counting of CD31 positive vascular endothelial cells by immunohistochemical staining.

Results

Compared with the control group, protein and mRNA levels of HIF-1α reached their highest levels on the 3rd day (P<0.01), then decreased (P<0.05). HIF-2α expression reached its highest level on the 2nd week compared with control group (P<0.01), then decreased (2w–4w) (P<0.05). The protein and mRNA levels of VEGF-A and EphA2 in the residual tumor tissues group that received HIFU were significantly decreased until 1 week compared with the control group (P<0.01). However, the levels increased compared to controls in 2–4 weeks (P<0.05). Similar results were obtained for MVD expression (P<0.05).

Conclusion

Insufficient HIFU ablation promotes the angiogenesis in residual carcinoma tissue over time. The data indicate that the HIF-1, 2α/VEGFA/EphA2 pathway is involved.

Upregulation of HIF-2α induced by sorafenib contributes to the resistance by activating the TGF-α/EGFR pathway in hepatocellular carcinoma cells

Sorafenib, the first-line systemic drug for advanced hepatocellular carcinoma (HCC), has demonstrated limited benefits with very low response rates. Thus it is essential to investigate the underlying mechanisms for the resistance to sorafenib and seek potential strategy to enhance its efficacy. Hypoxic cells inside solid tumors are extremely resistant to therapies as their survival ability is increased due to the cellular adaptive response to hypoxia, which is controlled by hypoxia-inducible factor (HIF)-1 and HIF-2. Sorafenib inhibits HIF-1α synthesis, making the hypoxic response switch from HIF-1α- to HIF-2α-dependent pathways and providing a mechanism for more aggressive growth of tumors. The present study has demonstrated that upregulation of HIF-2α induced by sorafenib contributes to the resistance of hypoxic HCC cells by activating the transforming growth factor (TGF)-α/epidermal growth factor receptor (EGFR) pathway. Blocking the TGF-α/EGFR pathway by gefitinib, a specific EGFR inhibitor, reduced the activation of STAT (signal transducer and activator of transcription) 3, AKT and ERK (extracellular signal-regulated kinase), and synergized with sorafenib to inhibit proliferation and induce apoptosis of hypoxic HCC cells. Transfection of HIF-2α siRNA into HCC cells downregulated the expression of VEGF (vascular endothelial growth factor), cyclin D1, HIF-2α and TGF-α, and inhibited the activation of EGFR. HIF-2α siRNA inhibited the proliferation and promoted the apoptosis of HCC cells in vitro, and synergized with sorafenib to suppress the growth of HCC tumors in vivo. The results indicate that targeting HIF-2α-mediated activation of the TGF-α/EGFR pathway warrants further investigation as a potential strategy to enhance the efficacy of sorafenib for treating HCC.

Matrine inhibits proliferation and induces apoptosis of human colon cancer LoVo cells by inactivating Akt pathway

The present study has investigated the anti-tumor activity and the underlying mechanisms of matrine on human colon cancer LoVo cells. Matrine inhibited the proliferation of the cells in dose- and time-dependent manners. The concentration required for 50 % inhibition (IC50) was 1.15, 0.738, and 0.414 mg/ml, when cell were incubated with matrine for 24, 48, and 72 h, respectively. Matrine induced cell cycle arrest at G1 phase by downregulating cyclin D1 and upregulating p27 and p21. Matrine induced cell apoptosis by reducing the ratio of Bcl-2/Bax and increasing the activation of caspase-9 in a dose-dependent manner. Matrine displayed its anti-tumor activity by inactivating Akt, the upstream factor of the above proteins. Matrine significantly reduced the protein levels of pAkt, and increased the protein levels of other downstream factors, pBad and pGSK-3β. Specific inhibition of pAkt induced cell apoptosis, and synergized with matrine to inhibit the proliferation of LoVo cells; whereas activation of Akt neutralized the inhibitory effect of matrine on cell proliferation. The present study has demonstrated that matrine inhibits proliferation and induces apoptosis of human colon cancer LoVo cells by inactivating Akt pathway, indicating matrine may be a potential anti-cancer agent for colon cancer.

Up-regulation of survivin by AKT and hypoxia-inducible factor 1α contributes to cisplatin resistance in gastric cancer

This study investigated the contribution of survivin and its upstream regulators, AKT and hypoxia-inducible factor 1α (HIF-1α), to the resistance of gastric cancer cells to cisplatin (CDDP). We found that over-expression of survivin increased the resistance of SGC7901 and BGC823 gastric cancer cells to CDDP. Its over-expression abrogated CDDP-induced inhibition of cell proliferation and CDDP-induced cell apoptosis. In contrast, down-regulation of survivin expression using small hairpin RNA (shRNA) vectors and the small-molecule inhibitor YM155, or inhibition of survivin function using a recombinant cell-permeable dominant-negative survivin protein (dNSur9), promoted CDDP-induced apoptosis. CDDP-resistant sub-lines generated from the parental SGC7901 and BGC823 cells by exposure to increasing concentrations of CDDP expressed higher levels of HIF-1α and survivin in response to hypoxia, and higher levels of phosphorylated AKT (pAKT). Specific inhibition of AKT reduced the expression of HIF-1α and survivin, whereas specific inhibition or depletion of HIF-1α reduced survivin expression but had no effect on the expression of phosphorylated AKT. The expression levels of survivin affected the therapeutic efficacy of CDDP in treating gastric tumors in mice. Specific inhibition of survivin, AKT and HIF-1α enhanced the sensitivity of CDDP-resistant cells to CDDP. Specific inhibition of survivin, AKT and HIF-1α synergized with CDDP to suppress the growth of gastric tumors that had been engineered to overexpress survivin. In summary, the results provide evidence that up-regulation of survivin by AKT and HIF-1α contributes to CDDP resistance, indicating that inhibition of these pathways may be a potential strategy for overcoming CDDP resistance in the treatment of gastric cancer.

Mechanisms of resistance to sorafenib and the corresponding strategies in hepatocellular carcinoma

Sorafenib, the unique drug as first-line treatment for advanced hepatocellular carcinoma (HCC), has opened a window of hope after searching for effective agents to combat HCC for decades. However, the overall outcomes are far from satisfactory. One of the explanations is the genetic heterogeneity of HCC, which has led to identifying predictive biomarkers for primary resistance to sorafenib, and then applying the concept of personalized medicine, or seeking therapeutic strategies such as combining sorafenib with other anticancer agents. Some of the combinations have demonstrated a better effectiveness than sorafenib alone, with good tolerance. The acquired resistance to sorafenib has also drawn attention. As a multikinase inhibitor, sorafenib targets several cellular signaling pathways but simultaneously or sequentially the addiction switches and compensatory pathways are activated. Several mechanisms are involved in the acquired resistance to sorafenib, such as crosstalks involving PI3K/Akt and JAK-STAT pathways, hypoxia-inducible pathways, epithelial-mesenchymal transition, etc. Based on the investigated mechanisms, some other molecular targeted drugs have been applied as second-line treatment for treat HCC after the failure of sorafenib therapy and more are under evaluation in clinical trials. However, the exact mechanisms accounting for sorafenib resistance remains unclear. Further investigation on the crosstalk and relationship of associated pathways will better our understanding of the mechanisms and help to find effective strategies for overcoming sorafenib resistance in HCC.

Hypoxia inducible factor 2 alpha inhibits hepatocellular carcinoma growth through the transcription factor dimerization partner 3/ E2F transcription factor 1-dependent apoptotic pathway

Hypoxia inducible factors (HIFs) are activated in many tumors and show either promoter or suppressor activity, depending on tumor cell biology and background. However, the role of HIF member HIF-2α remains unclear in hepatocellular carcinoma (HCC). Here, HIF-2α expression was measured in HCC and paired peritumoral tissues by quantitative real-time polymerase chain reaction, western blotting, and immunofluorescence assays, and the clinical significance was explored in 246 HCC patients. In cell culture, HIF-2α levels were up-regulated or down-regulated by use of expression or short hairpin RNA recombinant plasmid, respectively. Cells were analyzed by immunoblotting, chromatin immunoprecipitation coupled with microarray, coimmunoprecipitation, and immunohistochemical staining. In vivo tumor growth was analyzed in nude mice. We found that the average expression of HIF-2α was relatively low in HCC tissues, and the decreased level was associated with lower overall survival (P=0.006). High HIF-2α expression in HCC cells induced higher levels of apoptosis and expression of proapoptotic proteins and inhibited cell and tumor growth. Furthermore, HIF-2α inhibited expression of the novel target gene, transcription factor dimerization partner 3 (TFDP3). TFDP3 protein was found to bind with E2F transcription factor 1 (E2F1) and inhibit its transcriptional activity through both p53-dependent and -independent pathways. Reintroduction of TFDP3 expression reversed HIF-2α-induced apoptosis.

CONCLUSIONS

Data gathered from cell lines, tumorigenicity studies, and primary HCC samples demonstrate a negative role of HIF-2α in tumors, which is mediated by the TFDP3/E2F1 pathway. Our study provides evidence supporting a possible tumor-suppressor role for HIF-2α and has uncovered a mechanism that links HIF-2α to a fundamental biological regulator, E2F1.

Secretory clusterin contributes to oxaliplatin resistance by activating Akt pathway in hepatocellular carcinoma

Secretory clusterin (sCLU) is expressed in numerous cancers and is associated with the resistance to chemotherapy. However, the role of sCLU in the resistance of hepatocellular carcinoma (HCC) to oxaliplatin (OXA), a recently used third-generation platinum agent, remains unclear. The stable transfectants that are depleted of or overexpress sCLU and OXA-resistant cells were generated using human HCC cells. Overexpression of sCLU abrogated OXA-induced inhibition of cell growth and cell apoptosis, but depletion of sCLU synergized with OXA to inhibit cell growth and enhance cell apoptosis, by regulating proteins involved in mitochondrial apoptosis pathways, such as Bcl-2, Bax, Bcl-xL and caspase-9, and affecting phosphorylation of Akt and GSK-3β. Overexpression of sCLU in either OXA-resistant cells or stable transfectants that overexpress sCLU significantly increased phosphorylated Akt. However, specific inhibition of Akt enhanced sensitivity of sCLU-overexpressing cells to OXA, but had no effect on sCLU expression, suggesting that the regulatory effects between sCLU and pAkt may be in a one-way manner in HCC cells. The expression levels of sCLU affected the therapeutic efficacy of OXA to treat HCC tumors established in immunodeficiency mice. The results have demonstrated that sCLU contributes to OXA resistance by activating Akt pathway, indicating that sCLU may be a novel molecular target for overcoming OXA resistance in HCC.