Vitamin K enhancement of sorafenib-mediated HCC cell growth inhibition in vitro and in vivo

Ferritinophagy induced ferroptosis in the management of cancer

BACKGROUND

Ferroptosis, a newly form of regulated cell death (RCD), is characterized by iron dyshomeostasis and unrestricted lipid peroxidation. Emerging evidence depicts a pivotal role for ferroptosis in driving some pathological processes, especially in cancer. Triggering ferroptosis can suppress tumor growth and induce an anti-tumor immune response, denoting the therapeutic promises for targeting ferroptosis in the management of cancer. As an autophagic phenomenon, ferritinophagy is critical to induce ferroptosis by degradation of ferritin to release intracellular free iron. Recently, a great deal of effort has gone into designing and developing anti-cancer strategies based on targeting ferritinophagy to induce ferroptosis.

CONCLUSION

This review delineates the regulatory mechanism of ferritinophagy firstly and summarizes the role of ferritinophagy-induced ferroptosis in cancer. Moreover, the strategies targeting ferritinophagy to induce ferroptosis are highlighted to unveil the therapeutic value of ferritinophagy as a target to manage cancer. Finally, the future research directions on how to cope with the challenges in developing ferritinophagy promoters into clinical therapeutics are discussed.

Vitamin K: A novel cancer chemosensitizer

Cancer incidences are growing rapidly and causing millions of deaths globally. Cancer treatment is one of the most exigent challenges. Drug resistance is a natural phenomenon and is considered one of the major obstacles in the successful treatment of cancer by chemotherapy. Combination therapy by the amalgamation of various anticancer drugs has suggested modulating tumor response by targeting various signaling pathways in a synergistic or additive manner. Vitamin K is an essential nutrient and has recently been investigated as a potential anticancer agent. The combination of vitamin K analogs, such as vitamins K1, K2, K3, and K5, with other chemotherapeutic drugs have demonstrated a safe, cost-effective, and most efficient way to overcome drug resistance and improved the outcomes of prevailing chemotherapy. Published reports have shown that vitamin K in combination therapy improved the efficacy of clinical drugs by promoting apoptosis and cell cycle arrest and overcoming drug resistance by inhibiting P-glycoprotein. In this review, we discuss the mechanism, cellular targets, and possible ways to develop vitamin K subtypes into effective cancer chemosensitizers. Finally, this review will provide a scientific basis for exploiting vitamin K as a potential agent to improve the efficacy of chemotherapeutic drugs.

Vitamin K Contribution to DNA Damage—Advantage or Disadvantage? A Human Health Response

Vitamin K is the common name for a group of compounds recognized as essential for blood clotting. The group comprises phylloquinone (K1)—a 2-methyl-3-phytyl-1,4-naphthoquinone; menaquinone (K2, MK)—a group of compounds with an unsaturated side chain in position 3 of a different number of isoprene units and a 1,4-naphthoquinone group and menadione (K3, MD)—a group of synthetic, water-soluble compounds 2-methyl-1,4-naphthoquinone. However, recent epidemiological studies suggest that vitamin K has various benefits that go beyond blood coagulation processes. A dietary intake of K1 is inversely associated with the risk of pancreatic cancer, K2 has the potential to induce a differentiation in leukemia cells or apoptosis of various types of cancer cells, and K3 has a documented anti-cancer effect. A healthy diet rich in fruit and vegetables ensures an optimal supply of K1 and K2, though consumers often prefer supplements. Interestingly, the synthetic form of vitamin K—menadione—appears in the cell during the metabolism of phylloquinone and is a precursor of MK-4, a form of vitamin K2 inaccessible in food. With this in mind, the purpose of this review is to emphasize the importance of vitamin K as a micronutrient, which not only has a beneficial effect on blood clotting and the skeleton, but also reduces the risk of cancer and other pro-inflammatory diseases. A proper diet should be a basic and common preventive procedure, resulting in a healthier society and reduced burden on healthcare systems.

New insights into vitamin K biology with relevance to cancer

Phylloquinone (vitamin K1) and menaquinones (vitamin K2 family) are essential for post-translational γ-carboxylation of a small number of proteins, including clotting factors. These modified proteins have now been implicated in diverse physiological and pathological processes including cancer. Vitamin K intake has been inversely associated with cancer incidence and mortality in observational studies. Newly discovered functions of vitamin K in cancer cells include activation of the steroid and xenobiotic receptor (SXR) and regulation of oxidative stress, apoptosis, and autophagy. We provide an update of vitamin K biology, non-canonical mechanisms of vitamin K actions, the potential functions of vitamin K-dependent proteins in cancer, and observational trials on vitamin K intake and cancer.

Medicinal Prospects of Antioxidants From Algal Sources in Cancer Therapy

Though cancer therapeutics can successfully eradicate cancerous cells, the effectiveness of these medications is mostly restricted to several deleterious side effects. Therefore, to alleviate these side effects, antioxidant supplementation is often warranted, reducing reactive species levels and mitigating persistent oxidative damage. Thus, it can impede the growth of cancer cells while protecting the normal cells simultaneously. Moreover, antioxidant supplementation alone or in combination with chemotherapeutics hinders further tumor development, prevents chemoresistance by improving the response to chemotherapy drugs, and enhances cancer patients' quality of life by alleviating side effects. Preclinical and clinical studies have been revealed the efficacy of using phytochemical and dietary antioxidants from different sources in treating chemo and radiation therapy-induced toxicities and enhancing treatment effectiveness. In this context, algae, both micro and macro, can be considered as alternative natural sources of antioxidants. Algae possess antioxidants from diverse groups, which can be exploited in the pharmaceutical industry. Despite having nutritional benefits, investigation and utilization of algal antioxidants are still in their infancy. This review article summarizes the prospective anticancer effect of twenty-three antioxidants from microalgae and their potential mechanism of action in cancer cells, as well as usage in cancer therapy. In addition, antioxidants from seaweeds, especially from edible species, are outlined, as well.

Artesunate synergizes with sorafenib to induce ferroptosis in hepatocellular carcinoma

Sorafenib is the first-line medication for advanced hepatocellular carcinoma (HCC), but it can only extend limited survival. It is imperative to find a combination strategy to increase sorafenib efficacy. Artesunate is such a preferred candidate, because artesunate is clinically well-tolerated and more importantly both drugs can induce ferroptosis through different mechanisms. In this study we investigated the combined effect of sorafenib and artesunate in inducing ferroptosis of HCC and elucidated the involved molecular mechanisms. We showed that artesunate greatly enhanced the anticancer effects of low dose of sorafenib against Huh7, SNU-449, and SNU-182 HCC cell lines in vitro and against Huh7 cell xenograft model in Balb/c nude mice. The combination index method confirmed that the combined effect of sorafenib and artesunate was synergistic. Compared with the treatment with artesunate or sorafenib alone, combined treatment induced significantly exacerbated lipid peroxidation and ferroptosis, which was blocked by N-acetyl cysteine and ferroptosis inhibitors liproxstatin-1 and deferoxamine mesylate, but not by inhibitors of other types of cell death (z-VAD, necrostatin-1 and belnacasan). In Huh7 cells, we demonstrated that the combined treatment induced oxidative stress and lysosome-mediated ferritinophagy, two essential aspects of ferroptosis. Sorafenib at low dose mainly caused oxidative stress through mitochondrial impairments and SLC7A11-invovled glutathione depletion. Artesunate-induced lysosome activation synergized with sorafenib-mediated pro-oxidative effects by promoting sequential reactions including lysosomal cathepsin B/L activation, ferritin degradation, lipid peroxidation, and consequent ferroptosis. Taken together, artesunate could be repurposed to sensitize sorafenib in HCC treatment. The combined treatment can be easily translated into clinical applications.

Efficacy and safety of sorafenib plus vitamin K treatment for hepatocellular carcinoma: A phase II, randomized study

The previous retrospective study suggested that dosing vitamin K may enhance the anticancer action of sorafenib against hepatocellular carcinoma. To confirm it, we performed a phase II, randomized, open‐label study. Patients with hepatocellular carcinoma were randomly assigned to receive sorafenib + vitamin K2 (menatetrenone, 45 mg daily, orally) or sorafenib only. Between 1 May 2012 and 1 May 2016, 68 patients were screened. Forty‐four eligible patients were assigned at a 1:1 ratio to each cohort. The objective response rate in the vitamin K‐dosed group was significantly higher than that in the sorafenib only group (27.3% vs 4.5%, respectively; p = 0.039). The median time of progression‐free survival was significantly extended in the vitamin K‐dosed group compared with the sorafenib only group (4.9 months vs 2.7 months, respectively; hazard ratio (HR), 0.44; 95% confidence interval (CI): 0.21–0.89; p = 0.018). Although there was no significant difference between the two groups in the median time of overall survival, patients in the vitamin K‐dosed group with a complete response or partial response achieved a significantly extended median time of overall survival compared with the other patients in the vitamin K‐dosed group or the patients in the sorafenib only group (26.1 months vs 9.0 months; HR, 0.34; 95% CI: 0.11–0.95; p = 0.046 or 11.5 months; HR, 0.16; 95% CI: 0.034–0.70; p = 0.006, respectively). Dosing vitamin K could augment the anticancer action of sorafenib against HCC.

Sorafenib and Mesenchymal Stem Cell Therapy: A Promising Approach for Treatment of HCC

Hepatocellular carcinoma (HCC) is the fifth most commonly diagnosed cancer and the second most common cause of cancer-related death worldwide. Sorafenib (Sora) is used as a targeted therapy for HCC treatment. Mesenchymal stem cells (MSCs) are applied as a new approach to fight malignancies. Drug resistance and side effects are the major concerns with Sora administration. The effect of using the combination of sorafenib and MSCs on tumor regression in xenograft HCC models was evaluated in this study. Methods and Materials. Human hepatocellular carcinoma cell lines (HepG2) were subcutaneously implanted into the flank of 18 nude mice. The animals were randomly divided into six groups (n = 3); each received Sora (oral), MSCs (IV injection), MSCs (local injection), Sora + MSCs (IV injection), Sora + MSCs (local injection), or no treatment (the control group). Six weeks after tumor implantation, the mice were scarified and tumoral tissues were resected in their entirety. Histopathological and immunohistochemical evaluations were used to measure tumor proliferation and angiogenesis. Apoptotic cells were quantified using the TUNEL assay. Results. No significant difference was found in the tumor grade among the treatment groups. Differentiation features of the tumoral cells were histopathologically insignificant in all the groups. Tumor necrosis was highest in the hpMSC (local) + Sora group. Tumor cell proliferation was reduced in hpMSC (local) + Sora-treated and hpMSC (IV) + Sora-treated mice compared with the other groups. Apoptotic-positive cells occupied a greater proportion in the Sora, hpMSC (IV) + Sora, and hpMSC (local) + Sora groups. Conclusion. A combination of chemotherapy and MSC can yield to more favorable results in the treatment of HCC.

Vitamin K2 promotes PI3K/AKT/HIF-1α-mediated glycolysis that leads to AMPK-dependent autophagic cell death in bladder cancer cells

Vitamin K2 has been shown to exert remarkable anticancer activity. However, the detailed mechanism remains unclear. Here, our study was the first to show that Vitamin K2 significantly promoted the glycolysis in bladder cancer cells by upregulating glucose consumption and lactate production, whereas inhibited TCA cycle by reducing the amounts of Acetyl-CoA. Moreover, suppression of PI3K/AKT and HIF-1α attenuated Vitamin K2-increased glucose consumption and lactate generation, indicating that Vitamin K2 promotes PI3K/AKT and HIF-1α-mediated glycolysis in bladder cancer cells. Importantly, upon glucose limitation, Vitamin K2-upregulated glycolysis markedly induced metabolic stress, along with AMPK activation and mTORC1 pathway suppression, which subsequently triggered AMPK-dependent autophagic cell death. Intriguingly, glucose supplementation profoundly abrogated AMPK activation and rescued bladder cancer cells from Vitamin K2-triggered autophagic cell death. Furthermore, both inhibition of PI3K/AKT/HIF-1α and attenuation of glycolysis significantly blocked Vitamin K2-induced AMPK activation and subsequently prevented autophagic cell death. Collectively, these findings reveal that Vitamin K2 could induce metabolic stress and trigger AMPK-dependent autophagic cell death in bladder cancer cells by PI3K/AKT/HIF-1α-mediated glycolysis promotion.

Investigation of possible effects of apigenin, sorafenib and combined applications on apoptosis and cell cycle in hepatocellular cancer cells

Hepatocellular carcinoma (HCC) is the most common type of liver tumors. There is only one chemodrug for treatment called sorafenib that is an effective multikinase inhibitor. However, most of the patients gain resistance to sorafenib treatment in six months. Thus, there is a limitation for treatment of HCC. Apigenin is a natural flavonoid that has been used for many years as an antioxidant and anti-inflammatory agent. The aim of this study is to investigate the combined therapeutic effects of sorafenib and apigenin upon apoptosis and cell cycle on HepG2 cell line. Cytotoxic effects of sorafenib and apigenin on HepG2 cells were determined by XTT assay. Effects of single and combined treatment on cell migration, invasion and colony formation were analysed by wound healing, transwell matrigel invasion assay and colony formation assay, respectively. TUNEL assay was performed for analyse apoptosis rates. Expression changes of genes related with apoptosis and cell cycle were analysed by quantitative real-time PCR. Combined treatment of sorafenib and apigenin has more decreasing effects on cell viability than single treatment groups. Also, combination group caused significant increase of apoptotic cells. Migration and invasion capability of cells in combined treatment group are decreased. Lastly, quantitative real-time PCR results showed that combination of both drugs arrested cell cycle and increased apoptotic gene expressions more than single treatment groups. This is the first study that investigating the combined treatment of sorafenib and apigenin on HCC in vitro. By combined treatment, apigenin potentiates sorafenib cytotoxicity on HepG2 cells. Effects of combined treatment on migration, invasion, apoptosis and gene expressions showed that may sorafenib and apigenin have synergistic effect.

Vitamin K2 induces non-apoptotic cell death along with autophagosome formation in breast cancer cell lines

BACKGROUND

Vitamin K₂ (VK2) has been reported to induce apoptosis in many types of cancer cells including leukemia. However, there are no precise reports regarding the breast cancer cells. From the stand point of clinical implications of VK2 including chemoprevention, we investigated the effects of VK2 on breast cancer cell lines.

METHODS

Breast cancer cell lines were cultured with VK2, and the cytotoxicity and cell death phenotype were examined. The HL-60 leukemia cells were used as a control for VK2-induced apoptosis.

RESULTS

VK2 exhibited the cytotoxic effect, especially in triple negative breast cancer cell lines, namely, MDA-MB-231 and MDA-MB-468. However, in contrast to HL-60 cells, typical features of the cells undergoing apoptosis, such as chromatin condensation, nuclear fragments, and cleavage of caspase-3 were not detected. Transmission electron microscopy exhibited an increased number of autophagosomes/autolysosomes with plasma membrane integrity. An autophagy inhibitor, 3-methyladenine, apparently attenuated VK2-induced cytotoxicity, which indicated the involvement of autophagy-dependent cell death. Interestingly, both VK2-induced non-apoptotic cell death in MDA-MB-231 cells and VK2-induced apoptosis in HL-60 cells were suppressed in the presence of reactive oxygen species (ROS) scavengers. Therefore, ROS production by VK2 seems to be located up-stream in the molecular machinery for both the types of cell death execution.

CONCLUSION

The VK2 induced non-apoptotic cell death along with autophagy, in triple negative breast cancer cell lines. Cell death phenotype induced by VK2 appears to differ among the type of cancers. This suggests the possibility of using VK2 for the breast cancer therapy.

Complete response by vitamin K2 analog monotherapy in sorafenib-failure advanced hepatocellular carcinoma: A case report

There have been reports that a vitamin K2 (VK2) analog is beneficial for the prevention of recurrence in hepatocellular carcinoma (HCC) patients after curative therapy. However, the VK2 analogs in current use do not appear to show dramatic antitumor effects when given alone. Here, we report the case of a 67-year-old male patient with sorafenib-failure advanced HCC who achieved complete response (CR) after VK2 analog monotherapy. At the time of sorafenib failure confirmation, the patient had multiple intrahepatic tumors, multiple lung metastases, and Vp3 portal vein tumor thrombosis. He had poor liver function (Child-Pugh score of 9, Child-Pugh class B) and poor performance status (Eastern Cooperative Oncology Group performance status 2). Both serum α-fetoprotein (AFP) and des-γ-carboxy prothrombin (DCP) levels were elevated (558 900 ng/mL and 917 300 mAU/mL, respectively). Treatment with VK2 analog was initiated at 45 mg/day. Five months later, both tumor markers had decreased to normal levels (AFP 8 ng/mL and DCP 10 mAU/mL). Contrast-enhanced computed tomography showed that all intrahepatic tumors had shrunk, there was no enhancement of tumor staining in the arterial phase, and all lung metastases and portal vein tumor thromboses had disappeared. We considered that CR was achieved according to the modified Response Evaluation Criteria in Solid Tumors. Eighteen months after the start of VK2 analog administration, the patient continues to receive treatment and has remained in CR without adverse events. Here, we report a rare case of sorafenib-failure advanced HCC in which sustained CR was achieved by VK2 analog monotherapy.

Dynamic contrast enhanced perfusion CT imaging: A diagnostic biomarker tool for survival prediction of tumour response to antiangiogenetic treatment in patients with advanced HCC lesions

PURPOSE

To investigate whether perfusion-CT (p-CT) imaging could depict the inhibition of tumor neoangiogenesis induced by Sorafenib in advanced hepatocellular carcinoma (HCC), and whether it could be useful in predicting survival during treatment.

MATERIALS AND METHODS

Ninety-eight p-CT examinations were performed among 29 cirrhotic patients, with advanced HCC, before and every 2 months after Sorafenib administration, on a 256-slice MDCT scanner. Perfusion parameters were considered and statistically compared, at baseline and follow-up, between non-progressor (complete response, stable disease or partial response) and progressor (progressive disease) group. Kaplan-Meier analyses estimated the time-to-survival in overall population, after stratifying patients according to mRECIST.

RESULTS

The group that responded to Sorafenib showed a significant reduction of values in HCC target lesions after anti-angiogenic therapy (p < 0.01), in comparison with progressor group that demonstrated an increase or no significant variation. When patients were stratified into mRECIST, higher survival rate was observed in the non-progressor group compared to the progressor (48.6% vs 28.6%), and statistically significant correlation (p=0.01) was found between percentage variation of perfusion parameters, from baseline to follow-up, and overall survival rate.

CONCLUSION

Quantitative analysis of perfusion parameters, represents prognostic indicators useful in assessment of response to anti-angiogenic therapy, allowing for optimization of individualized treatment.

Strong enhancement by IGF1-R antagonists of hepatocellular carcinoma cell migration inhibition by Sorafenib and/or vitamin K1

PURPOSE

Emerging evidence indicates that combining Sorafenib with vitamin K1 (VK1) may result in a synergistic inhibition of hepatocellular carcinoma (HCC) cell migration and proliferation. Despite this synergy, its benefits may be limited due to drug resistance resulting from cross-talk with the tumor microenvironment. Insulin-like growth factor-1 (IGF1) signaling acts as an important modulator of HCC cell growth, motility and drug resistance. Therefore, we aimed to explore the effects of Sorafenib in combination with VK1 and/or IGF1-R antagonists on HCC cells.

METHODS

Scratch wound migration assays were performed to assess the motility of HCC-derived PLC/PRF/5, HLF and Hep3B cells. The synergistic, additive or antagonistic effects of Sorafenib, VK1 and IGF1-R antagonists on HCC cell motility were assessed using CompuSyn software. The effects mediated by these various compounds on HCC cytoskeleton organization were evaluated using DyLight 554 Phalloidin staining. Proliferation and migration-associated signaling pathways were analyzed in PLC/PRF/5 cells using Erk1/2 and Akt activation kits and Western blotting (Mek, JNK, Akt, Paxillin and p38), respectively.

RESULTS

The effects of the IGF1-R antagonists GSK1838705A and OSI-906 on HCC cell migration inhibition after Sorafenib and/or VK1 administration, individually or in combination, were evaluated. We found a synergistic effect in PLC/PRF/5, HLF and Hep3B cells for combinations of fixed doses of GSK1838705A or OSI-906 together with different doses of Sorafenib and/or VK1. The levels of synergy were found to be stronger at higher Sorafenib and/or VK1 concentrations and lower or absent at lower concentrations, with some variation among the different cell lines tested. In addition, we found that in PLC/PRF/5 and HLF cells IGF1-R blockage strongly enhanced the reduction and redistribution of F-actin induced by Sorafenib and/or VK1 through alterations in the phosphorylation levels of some of the principal proteins involved in the MAPK signaling cascade, which is essential for cell migration.

CONCLUSIONS

Our results indicate that modulation of the efficacy of Sorafenib through combinations with VK1 and/or IGF1-R antagonists results in synergistic inhibition of HCC cell migration.

IGF-1R tyrosine kinase inhibitors and Vitamin K1 enhance the antitumor effects of Regorafenib in HCC cell lines

The recent RESORCE trial showed that treatment with Regorafenib after Sorafenib failure provided a significant improvement in overall survival in HCC patients. Preclinical and clinical trial data showed that Regorafenib is a more potent drug than Sorafenib. In this study we aimed at improving Regorafenib actions and at reducing its toxicity, by targeting parallel pathways or by combination with Vitamins K (VKs). We investigated the effects of Regorafenib administrated at low concentrations and in combination with either VK1 and/or with GSK1838705A or OSI-906, two IGF1-R inhibitors, on HCC cell growth and motility. Our results showed that both IGF1-R inhibitors potentiated the antiproliferative and pro-apoptotic effects of Regorafenib and/or VK1 in HCC cell lines. Moreover we provide evidence that the combined treatment with IG1-R antagonists and Regorafenib (and/or VK1) also caused a significant reduction and depolymerization of actin resulting in synergistic inhibition exerted on cell migration. Thus, simultaneous blocking of MAPK and PI3K/Akt cascades with IGF1-R inhibitors plus Regorafenib could represent a more potent approach for HCC treatment.

Increased matrix stiffness promotes tumor progression of residual hepatocellular carcinoma after insufficient heat treatment

Aggravated behaviors of hepatocellular carcinoma (HCC) will occur after inadequate thermal ablation. However, its underlying mechanisms are not fully understood. Here, we assessed whether the increased matrix stiffness after thermal ablation could promote the progression of residual HCC. Heat‐treated residual HCC cells were cultured on tailorable 3D gel with different matrix stiffness, simulating the changed physical environment after thermal ablation, and then the mechanical alterations of matrix stiffness on cell phenotypes were explored. Increased stiffness was found to significantly promote the proliferation of the heat‐treated residual HCC cells when the cells were cultured on stiffer versus soft supports, which was associated with stiffness‐dependent regulation of ERK phosphorylation. Heat‐exposed HCC cells cultured on stiffer supports showed enhanced motility. More importantly, vitamin K1 reduced stiffness‐dependent residual HCC cell proliferation by inhibiting ERK phosphorylation and suppressed the in vivo tumor growth, which was further enhanced by combining with sorafenib. Increased matrix stiffness promotes the progression of heat‐treated residual HCC cells, proposing a new mechanism of an altered biomechanical environment after thermal ablation accelerates HCC development. Vitamin K1 plus sorafenib can reverse this protumor effect.

Clinical Impact of Vitamin K Dosing on Sorafenib Treatment for Hepatocellular Carcinoma

Background: Some researchers have suggested that vitamin K enhances the antitumor effect of sorafenib for hepatocellular carcinoma (HCC) in vitro and in vivo. In this study, we examined the clinical impact of vitamin K dosing for sorafenib treatment. Methods: Twenty-nine out of 65 patients treated with sorafenib for HCC were simultaneously dosed with vitamin K. We retrospectively investigated progression-free survival (PFS) and overall survival (OS) in the vitamin K-dosed group and sorafenib alone group. We also examined the changes in serum des-γ-carboxy prothrombin (DCP) levels, which vitamin K is involved with. Results: The median PFS was prolonged in the sorafenib + vitamin K group compared with the sorafenib alone group (6.0 months and 2.0 months, respectively; P<0.001, hazard ratio〔HR〕: 0.25). The median OS was also significantly extended (12.5 months vs. 10.0 months; P=0.009, HR: 0.47). Despite suppressed tumor growth, serum DCP levels had increased in cases of disease-controlled patients in the sorafenib alone group 8 weeks after the beginning of treatment, (2.28±0.91 to 2.64±1.03, P= 0.048). In contrast, the serum DCP levels of the sorafenib + vitamin K group had declined both in patients with controlled disease and in patients with progressive disease (1.97±0.57 to 1.29±0.28, P=0.002 and 2.90±1.32 to 1.78±0.53, P=0.034, respectively). Conclusions: To the best of our knowledge, this is the first clinical report showing enhanced antitumor action of sorafenib by vitamin K. Our clinical findings suggest that vitamin K may have the synergistic effect by suppressing production of DCP, a tumor growth and angiogenesis factor.

Effects of microRNA-126 on cell proliferation, apoptosis and tumor angiogenesis via the down-regulating ERK signaling pathway by targeting EGFL7 in hepatocellular carcinoma

This study intends to explore the effects of microRNA-126 (miR-126) on cell proliferation, apoptosis, and tumor angiogenesis in hepatocellular carcinoma (HCC) by regulating epidermal growth factor-like domain 7 (EGFL7) through extracellular signal-regulated kinase (ERK) signaling. HCC tissues and adjacent normal tissues were obtained from 184 HCC patients. HCC cells were separately transfected with recombinant plasmids. Western blotting and qRT-PCR were applied to detect miR-126 and EGFL7, ERK, Fas/FasL, Bcl-2, Caspase mRNA and protein levels. CCK8 and TUNEL were performed to determinate cell proliferation and apoptosis. Flow cytometry was used to analyze cell cycle distribution. Rats model of HCC was constructed, and tumor weight and the number of new blood vessels were recorded after 3 weeks of tumor transplantation. Compared with the adjacent normal tissues, HCC tissues exhibited lower miR-126 expression, and higher EGFL7, and ERK mRNA and protein levels. Overexpression of miR-126 in HCC cell lines suppressed EGFL7, ERK, Bcl-2, and P-ERK, and increased apoptotic-associated proteins Fas/FasL and Caspase-3, and it inhibited cell proliferation and induced cell apoptosis. Overexpression of miR-126 in nude mice resulted in reduced tumor weight and less new blood vessels in tumors. The inhibition of miR-126 decreased cell apoptosis, and enhanced cell proliferation and tumor angiogenesis. This study demonstrates that miR-126 might decrease cell proliferation, induce apoptosis, and inhibit tumor angiogenesis in HCC by inhibiting EGFL7 via down-regulating the ERK signaling pathway.

Vitamin K2 Induces Mitochondria-Related Apoptosis in Human Bladder Cancer Cells via ROS and JNK/p38 MAPK Signal Pathways

The effects of vitamin K2 on apoptosis in a variety of cancer cells have been well established in previous studies. However, the apoptotic effect of vitamin K2 on bladder cancer cells has not been evaluated. The aim of this study is to examine the apoptotic activity of Vitamin K2 in bladder cancer cells and investigate the underlying mechanism. In this study, Vitamin K2 induced apoptosis in bladder cancer cells through mitochondria pathway including loss of mitochondria membrane potential, cytochrome C release and caspase-3 cascade. Furthermore, the phosphorylation of c-Jun N-terminal kinase (JNK) and p38 MAPK was detected in Vitamin K2-treated cells and both SP600125 (an inhibitor of JNK) and SB203580 (an inhibitor of p38 MAPK) completely abolished the Vitamin K2-induced apoptosis and loss of mitochondria membrane potential. Moreover, the generation of reactive oxygen species (ROS) was detected in bladder cancer cells, upon treatment of vitamin K2 and the anti-oxidant N-acetyl cysteine (NAC) almost blocked the Vitamin K2-triggered apoptosis, loss of mitochondria membrane potential and activation of JNK and p38 MAPK. Taken together, these findings revealed that Vitamin K2 induces apoptosis in bladder cancer cells via ROS-mediated JNK/p38 MAPK and Mitochondrial pathways.

Vitamin K and hepatocellular carcinoma: The basic and clinic

Vitamin K (VK), which was originally identified as a cofactor involved in the production of functional coagulation factors in the liver, has been shown to be involved in various aspects of physiological and pathological events, including bone metabolism, cardiovascular diseases and tumor biology. The mechanisms and roles of VK are gradually becoming clear. Several novel enzymes involved in the VK cycle were identified and have been shown to be linked to tumorigenesis. The VKs have been shown to suppress liver cancer cell growth through multiple signaling pathways via the transcription factors and protein kinases. A VK2 analog was applied to the chemoprevention of hepatocellular carcinoma (HCC) recurrence after curative therapy and was shown to have beneficial effects, both in the suppression of HCC recurrence and in patient survival. Although a large scale randomized control study failed to demonstrate the suppression of HCC recurrence, a meta-analysis suggested a beneficial effect on the long-term survival of HCC patients. However, the beneficial effects of VK administration alone were not sufficient to prevent or treat HCC in clinical settings. Thus its combination with other anti-cancer reagents and the development of more potent novel VK derivatives are the focus of ongoing research which seeks to achieve satisfactory therapeutic effects against HCC.

Vitamin K1 exerts antiproliferative effects and induces apoptosis in three differently graded human colon cancer cell lines

Vitamin K1 has been demonstrated as having anticancer potentiality mainly in liver cancer cells. Beyond the reported mechanisms of cancer inhibition (cell cycle arrest and induction of apoptosis), a possible control by vitamin K1 on molecules affecting cell growth could be hypothesized. In the literature, few (if any) data are available on its antitumor effects on colon cancer cells. Therefore, the aims of the study were to investigate in three differently graded human colon cancer cell lines (Caco-2, HT-29, and SW480) the effects of increasing concentrations of vitamin K1 (from 10 μM to 200 μM) administered up to 72 h on (1) cell proliferation, (2) apoptosis with the possible involvement of the MAPK pathway, and (3) polyamine biosynthesis. Vitamin K1 treatment caused a significant antiproliferative effect and induced apoptosis in all the cell lines, with the involvement of the MAPK pathway. A concomitant and significant decrease in the polyamine biosynthesis occurred. This is the first study demonstrating a significant polyamine decrease in addition to the antiproliferative and proapoptotic effects following vitamin K1 administration to colon cancer cell lines. Therapeutically, combinations of vitamin K1 with polyamine inhibitors and/or analogues may represent a suitable option for chemoprevention and/or treatment in future strategies for colorectal cancer management.

ABT-263 enhances sorafenib-induced apoptosis associated with Akt activity and the expression of Bax and p21((CIP1/WAF1)) in human cancer cells

BACKGROUND AND PURPOSE

Sorafenib, a potent inhibitor that targets several kinases associated with tumourigenesis and cell survival, has been approved for clinical treatment as a single agent. However, combining sorafenib with other agents improves its anti-tumour efficacy in various preclinical tumour models. ABT-263, a second-generation BH3 mimic, binds to the anti-apoptotic family members Bcl-2, Bcl-xL and Bcl-w, and has been demonstrated to enhance TNFSF10 (TRAIL)-induced apoptosis in human hepatocarcinoma cells. Hence, we investigated the effects of ABT-263 treatment combined with sorafenib.

EXPERIMENTAL APPROACH

The effects of ABT-263 combined with sorafenib were investigated in vitro, on cell viability, clone formation and apoptosis, and the mechanism examined using western blot and flow cytometry. This combination was also evaluated in vivo, in a mouse xenograft model; tumour growth, volume and weights were measured and a TUNEL assay performed.

KEY RESULTS

ABT-263 enhanced sorafenib-induced apoptosis while sparing non-tumourigenic cells. Although ABT-263 plus sorafenib significantly stimulated intracellular reactive oxygen species production and subsequent mitochondrial depolarization, this was not sufficient to trigger cell apoptosis. ABT-263 plus sorafenib significantly decreased Akt activity, which was, at least partly, involved in its effect on apoptosis. Bax and p21 (CIP1/WAF1) were shown to play a critical role in ABT-263 plus sorafenib-induced apoptosis. Combining sorafenib with ABT-263 dramatically increased its efficacy in vivo.

CONCLUSION AND IMPLICATIONS

The anti-tumour activity of ABT-263 plus sorafenib may involve the induction of intrinsic cell apoptosis via inhibition of Akt, and reduced Bax and p21 expression. Our findings offer a novel effective therapeutic strategy for tumour treatment.

A preclinical evaluation of a novel multikinase inhibitor, SKLB-329, as a therapeutic agent against hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is a serious life-threatening malignant disease of liver. Molecular targeted therapies are considered a promising strategy for the treatment of HCC. Sorafenib is the first, and so far the only targeted drug approved by the US Food and Drug Administration (FDA) for clinical therapy of HCC. Despite being effective in some HCC patients, some demerits of sorafenib in the treatment of HCC, such as modest survival benefits, and drug resistance, have also been reported, which highlights the unmet medical need among patients with HCC. Here, we report a novel multikinase inhibitor discovered by us, SKLB-329, which potently inhibits angiogenesis-related kinases including VEGFR1/2/3, and FGFR2, and the Src kinase. SKLB-329 significantly inhibited endothelial cell growth, migration, invasion and tube formation. It showed potent anti-angiogenic activity in a transgenic zebrafish model. Moreover, SKLB-329 could efficiently restrain the proliferation of HCC cells through down-regulation of Src-mediated FAK and Stat3 activity. In vivo, oral administration of SKLB-329 considerably suppressed the tumor growth in HCC xenograft models (HepG2 and SMMC7721) in a dose-dependent manner. In all of the in vitro and in vivo assays of this investigation, sorafenib was used as a positive control, and in most assays SKLB-329 exhibited a higher potency compared with the positive control. In addition, SKLB-329 also bears favorable pharmacokinetic properties. Collectively, the results of preclinical studies presented here demonstrate that SKLB-329 is a promising drug candidate for HCC treatment.

Reversibility of regorafenib effects in hepatocellular carcinoma cells

PURPOSE

Multikinase growth inhibitors inhibit their target kinases with varying potency. Patients often require lower doses or therapy breaks due to drug toxicities. To evaluate the effects of drug withdrawal on hepatocellular carcinoma cells after incubation with growth-inhibitory concentrations of regorafenib, cell growth, migration and invasion, and signaling were examined.

METHODS

Cell proliferation, motility, and invasion were analyzed by MTT, wound healing, and invasion assays, respectively, and MAPK pathway protein markers were analyzed by Western blot.

RESULTS

After regorafenib removal, cell growth, migration, and invasion recovered. Repeated drug exposure resulted in changes in cell growth patterns. Recovery could be blocked by sub-growth-inhibitory concentrations of either doxorubicin or vitamin K1. Recovery of growth was associated with increased phospho-JNK, phospho-p38, and phospho-STAT3 levels. The recovery of growth, migration, and signaling were blocked by a JNK inhibitor.

CONCLUSIONS

Removal of regorafenib from growth-inhibited cells resulted in a JNK-dependent recovery of growth and migration.

Early prediction of response of sorafenib on hepatocellular carcinoma by CT perfusion imaging: an animal study

OBJECTIVE

This study evaluated the feasibility of CT perfusion parameters for the early efficacy prediction of sorafenib in the treatment of hepatocellular carcinoma (HCC) in rats.

METHODS

CT hepatic perfusion measurements were performed in the livers of 40 rats implanted with rat HCC. The rats in the experimental group (n = 28) were treated by oral gavage with sorafenib (20 mg per day), whereas the rats in the control group (n = 12) were treated by normal saline. Rats were classified into the responder group if the maximum diameter of their tumour had decreased 21 days after treatment, whereas the other rats were classified into the non-responder group. Data were analysed using the Pearson correlation analysis or analysis of variance.

RESULTS

CT perfusion was used to depict haemodynamic changes before and after treatment. The arterial liver perfusion was significantly decreased in the responder group on Day 11 after treatment with sorafenib (from 71.5 to 53.4 ml min(-1) 100 ml(-1)), whereas no significant changes were observed in the non-responder group (p = 0.87). The maximum diameter of the tumour was also significantly decreased in the responder group on Day 21 after treatment (p = 0.042), whereas the maximum tumour diameter was significantly increased in the control group (p = 0.001). CONCLUSION AND ADVANCES IN KNOWLEDGE: CT perfusion could be used to quantitatively analyse the haemodynamic changes in the treatment of HCC with sorafenib, which indicates that this approach may be developed for the early prediction of treatment efficacy for sorafenib.

YC-1 enhances the anti-tumor activity of sorafenib through inhibition of signal transducer and activator of transcription 3 (STAT3) in hepatocellular carcinoma

Background

Traditional systemic chemotherapy does not provide survival benefits in patients with hepatocellular carcinoma (HCC). Molecular targeted therapy shows promise for HCC treatment, however, the duration of effectiveness for targeted therapies is finite and combination therapies offer the potential for improved effectiveness.

Methods

Sorafenib, a multikinase inhibitor, and YC-1, a soluble guanylyl cyclase (sGC) activator, were tested in HCC by proliferation assay, cell cycle analysis and western blot in vitro and orthotopic and ectopic HCC models in vivo.

Results

In vitro, combination of sorafenib and YC-1 synergistically inhibited proliferation and colony formation of HepG2, BEL-7402 and HCCLM3 cells. The combination also induced S cell cycle arrest and apoptosis, as observed by activated PARP and caspase 8. Sorafenib and YC-1 respectively suppressed the expression of phosphorylated STAT3 (p-STAT3) (Y705) in a dose- and time-dependent manner. Combination of sorafenib and YC-1 significantly inhibited the expression of p-STAT3 (Y705) (S727), p-ERK1/2, cyclin D1 and survivin and SHP-1 activity compared with sorafenib or YC-1 used alone in all tested HCC cell lines. In vivo, sorafenib-YC-1 combination significantly suppressed the growth of HepG2 tumor xenografts with decreased cell proliferation and increased apoptosis observed by PCNA and PARP. Similar results were also confirmed in a HCCLM3 orthotopic model. There was a reduction in CD31-positive blood vessels and reduced VEGF expression, which suggested a combinational effect of sorafenib and YC-1 on angiogenesis. The reduced expression of p-STAT3, cyclin D1 and survivin was also observed with the combination of sorafenib and YC-1.

Conclusions

Our data show that sorafenib-YC-1 combination is a novel potent therapeutic agent that can target the STAT3 signaling pathway to inhibit HCC tumor growth.

Vitamin k2, a naturally occurring menaquinone, exerts therapeutic effects on both hormone-dependent and hormone-independent prostate cancer cells

In recent years, several studies have shown that vitamin k2 (VK2) has anticancer activity in a variety of cancer cells. The antitumor effects of VK2 in prostate cancer are currently not known. In the present study, we sought to characterize the anticancer potential of VK2 in both androgen-dependent and -independent prostate cancer cells. Our investigations show that VK2 is able to suppress viability of androgen-dependent and androgen-independent prostate cancer cells via caspase-3 and -8 dependent apoptosis. We also show that VK2 treatment reduces androgen receptor expression and PSA secretion in androgen-dependent prostate cancer cells. Our results also implicate VK2 as a potential anti-inflammatory agent, as several inflammatory genes are downregulated in prostate cancer cells following treatment with VK2. Additionally, AKT and NF-kB levels in prostate cancer cells are reduced significantly when treated with VK2. These findings correlated with the results of the Boyden chamber and angiogenesis assay, as VK2 treatment reduced cell migration and angiogenesis potential of prostate cancer cells. Finally, in a nude mice model, VK2 administration resulted in significant inhibition of both androgen-dependent and androgen-independent tumor growth. Overall, our results suggest that VK2 may be a potential therapeutic agent in the treatment of prostate cancer.

Effects of low concentrations of regorafenib and sorafenib on human HCC cell AFP, migration, invasion, and growth in vitro

Sorafenib was shown in clinical trial to enhance survival in hepatocellular carcinoma (HCC) patients, but with minimal tumor shrinkage. To correlate several indices of HCC growth at various drug concentrations, HCC cells were grown in various low concentrations of two multikinase inhibitors, regorafenib (Stivarga) and sorafenib (Nexavar) and their effects were examined on alpha-fetoprotein (AFP), cell growth, migration, and invasion. In two AFP positive human HCC cell lines, AFP was inhibited at 0.1-1 µM drug concentrations. Cell migration and invasion were also inhibited at similar low drug concentrations. However, 10-fold higher drug concentrations were required to inhibit cell growth in both AFP positive and negative cells. To investigate this concentration discrepancy of effects, cells were then grown for prolonged times and sub-cultured in low drug concentrations and then their growth was re-tested. The growth in these drug-exposed cells was found to be slower than cells without prior drug exposure and they were also more sensitive to subsequent drug challenge. Evidence was also found for changes in cell signaling pathways in these slow-growth cells. Low multikinase inhibitor concentrations thus modulate several aspects of HCC cell biology.

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

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

Fluoro-Sorafenib (Regorafenib) effects on hepatoma cells: growth inhibition, quiescence, and recovery

To evaluate the growth-inhibitory properties of the potent multi-kinase antagonist Regorafenib (Fluoro-Sorafenib), which was synthesized as a more potent Sorafenib, a Raf inhibitor and to determine whether similar mechanisms were involved, human hepatoma cell lines were grown in the presence or absence of Regorafanib and examined for growth inhibition. Western blots were performed for Raf targets, apoptosis, and autophagy. Regorafenib inhibited growth of human Hep3B, PLC/PRF/5, and HepG2 cells in a concentration- and time-dependent manner. Multiple signaling pathways were altered, including MAP kinases phospho-ERK and phospho-JNK and its target phospho-c-Jun. There was evidence for apoptosis by FACS, cleavage of caspases and increased Bax levels; as well as induction of autophagy, as judged by increased Beclin-1 and LC3 (II) levels. Prolonged drug exposure resulted in cell quiescence. Full growth recovery occurred after drug removal, unlike with doxorubicin chemotherapy. Regorafenib is a potent inhibitor of cell growth. Cells surviving Regorafenib treatment remain viable, but quiescent and capable of regrowth following drug removal. The reversibility of tumor cell growth suppression after drug removal may have clinical implications.

The monoclonal antibody CH12 enhances the sorafenib-mediated growth inhibition of hepatocellular carcinoma xenografts expressing epidermal growth factor receptor variant III

The multikinase inhibitor sorafenib is the first oral agent to show activity against human hepatocellular carcinoma (HCC). Although the clinical application of sorafenib has shown good tolerability in the studied populations, it also causes multiple human dose-limiting toxicities. Thus, there is a strong need to reduce the overall dose of sorafenib. We have reported that the epidermal growth factor receptor variant III (EGFRvIII) expression can decrease the sensitivity of HCC cells to chemotherapeutic drugs. Therefore, we sought to explore whether EGFRvIII can affect the sensitivity of HCC cells to sorafenib. In this study, we observed that EGFRvIII expression significantly decreased the sensitivity of HCC cells to sorafenib. To enhance the antitumor effect and reduce the overall dose of sorafenib, we evaluated the combined effects of CH12, a monoclonal antibody against EGFRvIII, and sorafenib on the growth of HCC cells expressing EGFRvIII in vitro and in vivo. The results showed that, when CH12 was combined with sorafenib, the tumor growth suppression effect was significantly increased, and the concentration of sorafenib required for growth inhibition was substantially reduced. Mechanistically, the combination could more noticeably downregulate the phosphorylation of constitutively active extracellular signal-regulated kinase (ERK), Akt (Thr308), and signal transducer and activator of transcription 3 (STAT3) than sorafenib alone. Collectively, these findings demonstrate that CH12 interacts additively with sorafenib to strongly inhibit the tumor growth of HCC xenografts expressing EGFRvIII by enhancing the sorafenib-mediated inhibition of the MEK/ERK, phosphoinositide 3-kinase/AKT, and STAT3 pathways.

Synergistic growth inhibition by sorafenib and vitamin K2 in human hepatocellular carcinoma cells

OBJECTIVE

Sorafenib is an oral multikinase inhibitor that has been proven effective as a single-agent therapy in hepatocellular carcinoma, and there is a strong rationale for investigating its use in combination with other agents. Vitamin K2 is nearly non-toxic to humans and has been shown to inhibit the growth of hepatocellular carcinoma. In this study, we evaluated the effects of a combination of sorafenib and vitamin K2 on the growth of hepatocellular carcinoma cells.

METHODS

Flow cytometry, 3-(4,5-dimethyl-2-thiazolyl-2,5-diphenyl-2H-tetrazolium bromide) and nude mouse xenograft assays were used to examine the effects of sorafenib and vitamin K2 on the growth of hepatocellular carcinoma cells. Western blotting was used to elucidate the possible mechanisms underlying these effects.

RESULTS

Assays for 3-(4,5-dimethyl-2-thiazolyl-2,5-diphenyl-2H-tetrazolium bromide) revealed a strong synergistic growth-inhibitory effect between sorafenib and vitamin K2. Flow cytometry showed an increase in cell cycle arrest and apoptosis after treatment with a combination of these two drugs at low concentrations. Sorafenib-mediated inhibition of extracellular signal-regulated kinase phosphorylation was promoted by vitamin K2, and downregulation of Mcl-1, which is required for sorafenib-induced apoptosis, was observed after combined treatment. Vitamin K2 also attenuated the downregulation of p21 expression induced by sorafenib, which may represent the mechanism by which vitamin K2 promotes the inhibitory effects of sorafenib on cell proliferation. Moreover, the combination of sorafenib and vitamin K2 significantly inhibited the growth of hepatocellular carcinoma xenografts in nude mice.

CONCLUSIONS

Our results determined that combined treatment with sorafenib and vitamin K2 can work synergistically to inhibit the growth of hepatocellular carcinoma cells. This finding raises the possibility that this combined treatment strategy might be promising as a new therapy against hepatocellular carcinoma, especially for patients with poor liver tolerance.

Sorafenib decreases proliferation and induces apoptosis of prostate cancer cells by inhibition of the androgen receptor and Akt signaling pathways

Antihormonal and chemotherapy are standard treatments for nonorgan-confined prostate cancer. The effectivity of these therapies is limited and the development of alternative approaches is necessary. In the present study, we report on the use of the multikinase inhibitor sorafenib in a panel of prostate cancer cell lines and their derivatives which mimic endocrine and chemotherapy resistance. (3)H-thymidine incorporation assays revealed that sorafenib causes a dose-dependent inhibition of proliferation of all cell lines associated with downregulation of cyclin-dependent kinase 2 and cyclin D1 expression. Apoptosis was induced at 2  μM of sorafenib in androgen-sensitive cells, whereas a higher dose of the drug was needed in castration-resistant cell lines. Sorafenib stimulated apoptosis in prostate cancer cell lines through downregulation of myeloid cell leukemia-1 (MCL-1) expression and Akt phosphorylation. Although concentrations of sorafenib required for the antitumor effect in therapy-resistant sublines were higher than those needed in parental cells, the drug showed efficacy in cells which became resistant to bicalutamide and docetaxel respectively. Most interestingly, we show that sorafenib has an inhibitory effect on androgen receptor (AR) and prostate-specific antigen expression. In cells in which AR expression was downregulated by short interfering RNA, the treatment with sorafenib increased apoptosis in an additive manner. In summary, the results of the present study indicate that there is a potential to use sorafenib in prostate cancers as an adjuvant therapy option to current androgen ablation treatments, but also in progressed prostate cancers that become unresponsive to standard therapies.

The role of PKC isoforms in the inhibition of NF-κB activation by vitamin K2 in human hepatocellular carcinoma cells

Vitamin K (VK) has diverse protective effects against osteoporosis, atherosclerosis and carcinogenesis. We recently reported that menatetrenone, a VK2 analogue, suppressed nuclear factor (NF)-κB activation in human hepatoma cells. Although NF-κB is regulated by isoforms of protein kinase C (PKC), the involvement of PKCs in VK2-mediated NF-κB inhibition remains unknown. Therefore, the effects of VK2 on the activation and the kinase activity of each PKC isoform were investigated. The human hepatoma Huh7 cells were treated with PKC isoform-specific inhibitors and/or siRNAs against each PKC isoform with or without 12-O-tetradecanoylphorbol-13-acetate (TPA). VK2 inhibited the TPA-induced NF-κB activation in Huh7 cells. NF-κB activity was inhibited by the pan-PKC inhibitor Ro-31-8425, but not by the PKCα-specific inhibitor Gö6976. The knockdown of individual PKC isoforms including PKCα, δ and ɛ showed only marginal effects on the NF-κB activity. However, the knockdown of both PKCδ and PKCɛ, together with treatment with a PKCα-specific inhibitor, depressed the NF-κB activity. VK2 suppressed the PKCα kinase activity and the phosphorylation of PKCɛ after TPA treatment, but neither the activation nor the enzyme activity of PKCδ was affected. The knockdown of PKCɛ abolished the TPA-induced phosphorylation of PKD1, and the effects of PKD1 knockdown on NF-κB activation were similar to those of PKCɛ knockdown. Collectively, all of the PKCs, including α, δ and ɛ, and PKD1 are involved in the TPA-mediated activation of NF-κB. VK2 inhibited the NF-κB activation through the inhibition of PKCα and ɛ kinase activities, as well as subsequent inhibition of PKD1 activation.

Sorafenib: complexities of Raf-dependent and Raf-independent signaling are now unveiled

Hepatocellular carcinoma (HCC) is the most common primary cancer worldwide. The only current drug available for clinical treatment of HCC is sorafenib, which inhibits multiple signaling kinases including Raf family members, platelet-derived growth factor receptor, vascular endothelial growth factor receptors 1 and 2, c-Kit, and Fms-like tyrosine kinase 3. Many studies have revealed that the mechanism underlying the antitumor effect of sorafenib is complex. Because sorafenib inhibits C-Raf more potently than B-Raf, the therapeutic efficacy of sorafenib is strongly influenced by the relative expression and activity of B-Raf and C-Raf and the complex interactions between these factors. Moreover, Rafindependent signaling mechanisms have recently emerged as important pathways of sorafenib-induced cell death. Basic research studies have suggested that using sorafenib as part of a combination therapy may improve its effect, although this has yet to be confirmed by clinical evidence. Further studies of the functional mechanism of sorafenib are required to advance the development of targeted therapy for HCC. To aid future work on sorafenib, we here review the current literature pertaining to sorafenib signaling and its clinical efficacy in both monotherapy and combination therapy.

Differential effects of vitamin K1 on AFP and DCP levels in patients with unresectable HCC and in HCC cell lines

PURPOSE

DCP is a useful HCC tumor marker, which reflects a defect in vitamin K metabolism. We tested the hypothesis that vitamin K treatment of HCC patients might suppress this marker and possibly AFP also.

EXPERIMENTAL DESIGN

HCC patients who had both elevated AFP and DCP were included. A phase I cohort was treated with escalating vitamin K1 intravenous weekly doses and a 27-patient phase II cohort was then treated with a fixed oral daily dose.

RESULTS

A maximum tolerated dose was not reached up to 100-fold the normal vitamin K1 dose. No toxicities were found up to 1,000 mg/infusion. In the phase II cohort, 93% of patients had tumor marker responses by decreased DCP levels, but only 22% had responses by decreased AFP levels. CT scans showed 11% of patients had PRs, 59% had stable tumors and 29.6% had tumor progression. Mechanism studies showed that vitamin K1 induced phosphorylation of JNK and c-Jun and caspase-mediated apoptosis.

CONCLUSIONS

Vitamin K1 was non-toxic at high doses, strongly inhibited plasma DCP levels, but weakly suppressed AFP levels. The results provide evidence that the two tumor markers are not directly linked and that DCP levels may not reflect HCC cell growth, as DCP levels were decreased in patients without AFP change, and were suppressed in vitro at 1% of the vitamin K1 concentration needed to inhibit AFP.