Klotho endows hepatoma cells with resistance to anoikis via VEGFR2/PAK1 activation in hepatocellular carcinoma

The multikinase inhibitor axitinib in the treatment of advanced hepatocellular carcinoma: the current clinical applications and the molecular mechanisms

Advanced hepatocellular carcinoma (HCC) is a formidable public health problem with limited curable treatment options. Axitinib, an oral tyrosine kinase inhibitor, is a potent and selective second-generation inhibitor of vascular endothelial growth factor receptor (VEGFR) 1, 2, and 3. This anti-angiogenic drug was found to have promising activity in various solid tumors, including advanced HCC. At present, however, there is no relevant review article that summarizes the exact roles of axitinib in advanced HCC. In this review, 24 eligible studies (seven studies in the ClinicalTrials, eight experimental studies, and nine clinical trials) were included for further evaluation. The included randomized or single-arm phase II trials indicated that axitinib could not prolong the overall survival compared to the placebo for the treatment of advanced HCC, but improvements in progression free survival and time to tumor progression were observed. Experimental studies showed that the biochemical effects of axitinib in HCC might be regulated by its associated genes and affected signaling cascades (e.g. VEGFR2/PAK1, CYP1A2, CaMKII/ERK, Akt/mTor, and miR-509-3p/PDGFRA). FDA approved sorafenib combined with nivolumab (an inhibitor of PD-1/PD-L1) as the first line regimen for the treatment of advanced HCC. Since both axitinib and sorafenib are tyrosine kinase inhibitors as well as the VEGFR inhibitors, axitinib combined with anti-PDL-1/PD-1 antibodies may also exhibit tremendous potential in anti-tumoral effects for advanced HCC. The present review highlights the current clinical applications and the molecular mechanisms of axitinib in advanced HCC. To move toward clinical applications by combining axitinib and other treatments in advanced HCC, more studies are still warranted in the near future.

P-21 Activated Kinases in Liver Disorders

The p21 Activated Kinases (PAKs) are serine threonine kinases and play important roles in many biological processes, including cell growth, survival, cytoskeletal organization, migration, and morphology. Recently, PAKs have emerged in the process of liver disorders, including liver cancer, hepatic ischemia-reperfusion injury, hepatitis, and liver fibrosis, owing to their effects in multiple signaling pathways in various cell types. Activation of PAKs promotes liver cancer growth and metastasis and contributes to the resistance of liver cancer to radiotherapy and chemotherapy, leading to poor survival of patients. PAKs also play important roles in the development and progression of hepatitis and other pathological processes of the liver such as fibrosis and ischemia-reperfusion injury. In this review, we have summarized the currently available studies about the role of PAKs in liver disorders and the mechanisms involved, and further explored the potential therapeutic application of PAK inhibitors in liver disorders, with the aim to provide a comprehensive overview on current progress and perspectives of PAKs in liver disorders.

VEGFR2 insufficiency enhances phosphotoxicity and undermines Klotho's protection against peritubular capillary rarefaction and kidney fibrosis

Vascular endothelial growth factor (VEGF) and its cognate receptor (VEGFR2) system are crucial for cell functions associated with angiogenesis and vasculogenesis. Klotho contributes to vascular health maintenance in the kidney and other organs in mammals, but it is unknown whether renoprotection by Klotho is dependent on VEGF/VEGFR2 signaling. We used heterozygous VEGFR2-haploinsufficient (VEGFR2+/-) mice resulting from heterozygous knockin of green fluorescent protein in the locus of fetal liver kinase 1 encoding VEGFR2 to test the interplay of Klotho, phosphate, and VEGFR2 in kidney function, the vasculature, and fibrosis. VEGFR2+/- mice displayed downregulated VEGF/VEGFR2 signaling in the kidney, lower density of peritubular capillaries, and accelerated kidney fibrosis, all of which were also found in the homozygous Klotho hypomorphic mice. High dietary phosphate induced higher plasma phosphate, greater peritubular capillary rarefaction, and more kidney fibrosis in VEGFR2+/- mice compared with wild-type mice. Genetic overexpression of Klotho significantly attenuated the elevated plasma phosphate, kidney dysfunction, peritubular capillary rarefaction, and kidney fibrosis induced by a high-phosphate diet in wild-type mice but only modestly ameliorated these changes in the VEGFR2+/- background. In cultured endothelial cells, VEGFR2 inhibition reduced free VEGFR2 but enhanced its costaining of an endothelial marker (CD31) and exacerbated phosphotoxicity. Klotho protein maintained VEGFR2 expression and attenuated high phosphate-induced cell injury, which was reduced by VEGFR2 inhibition. In conclusion, normal VEGFR2 function is required for vascular integrity and for Klotho to exert vascular protective and antifibrotic actions in the kidney partially through the regulation of VEGFR2 function.NEW & NOTEWORTHY This research paper studied the interplay of vascular endothelial growth factor receptor type 2 (VEGFR2), high dietary phosphate, and Klotho, an antiaging protein, in peritubular structure and kidney fibrosis. Klotho protein was shown to maintain VEGFR2 expression in the kidney and reduce high phosphate-induced cell injury. However, Klotho cytoprotection was attenuated by VEGFR2 inhibition. Thus, normal VEGFR2 function is required for vascular integrity and Klotho to exert vascular protective and antifibrotic actions in the kidney.

Investigation of the Role of Induced Overexpression of the Isolated Secreted Klotho on the A-172 Human Glioblastoma Cells

Klotho gene, identified in 1997 as an anti-aging gene, can manufacture two protein products: transmembrane and secreted forms. The later research revealed the involvement of klotho in carcinogenesis. However, little is known about the action of different Klotho forms on antitumor effects is still. The purpose of this article is to evaluate the effect of isolated secreted Klotho overexpression on the growth features of human glioblastoma cell line A-172.A-172 was transfected by a plasmid vector incorporating secreted Klotho sequence by the liposomal method. Overexpression assay was carried out quantitatively on both mRNA and protein using RT-qPCR and ELISA, correspondingly. It was shown that the relative expression of secreted Klotho in the experimental group was significantly higher than in the untransfected group by both methods (p < 0.001). At the same time, the growth curves and MTT proliferation assay demonstrated significantly decreased values under induced overexpression (p < 0.01). The increased amount of cells with activated caspases and annexin V (p < 0.001) corresponded with the expression of secreted Klotho. This mechanism, as suggested, maybe causative of the observed effects.

Clinicopathological and Prognostic Significance of Klotho and Estrogen Receptors Expression in Human Hepatocellular Carcinoma

BACKGROUND

Hepatocellular carcinoma (HCC) is male-predominant cancer, but the underlying mechanism remains unclear. This study aimed to investigate the expression of the age-suppressing gene klotho and estrogen receptors (ERs) in HCC patients and analyze their association with clinicopathological variables and their effects on prognosis.

METHODS

The expression patterns of klotho, ERα, and ERβ were determined by tissue microarray and immunohistochemical technique, and their correlations with clinicopathological characteristics were investigated using univariate and multivariate analysis.

RESULTS

Klotho expression was significantly lower in HCC than in the adjacent noncancerous tissues (52.7% (49/93) vs. 90.8% (79/87), P = .000), and its protein level in HCC tissue was negatively correlated with clinical staging, histological grade, and stage of the primary tumor (T) (P < .05). Whereas the expression of nuclear ERα and ERβ was higher in HCC than their corresponding non-neoplastic tissues (55.9% (52/93) vs. 35.6% (31/87), P = .006; 59.1% (55/93) vs. 43.7% (38/87), P = .038), and the level of nuclear ERα and ERβ in HCC tissue was inversely correlated with T stage, tumor size, and clinical staging (P < .05). Correlation analysis showed the expression level of klotho, which is positively correlated with that of nuclear ERα (r = 0.243, P = .019). Patients with klotho-positive tumors had longer survival than those with klotho-negative tumors (P = .002). Cox proportional hazards model analysis demonstrated that positive expression of klotho was an important factor indicating good prognosis (P = .003).

CONCLUSION

Klotho, partially regulated by ERα-mediated estrogen pathway, acts as a tumor suppressor and might be a novel biomarker candidate for predicting progression and prognosis in HCC patients.

Metabolic Spectrum of Liver Failure in Type 2 Diabetes and Obesity: From NAFLD to NASH to HCC

Liver disease is the spectrum of liver damage ranging from simple steatosis called as nonalcoholic fatty liver disease (NAFLD) to hepatocellular carcinoma (HCC). Clinically, NAFLD and type 2 diabetes coexist. Type 2 diabetes contributes to biological processes driving the severity of NAFLD, the primary cause for development of chronic liver diseases. In the last 20 years, the rate of non-viral NAFLD/NASH-derived HCC has been increasing rapidly. As there are currently no suitable drugs for treatment of NAFLD and NASH, a class of thiazolidinediones (TZDs) drugs for the treatment of type 2 diabetes is sometimes used to improve liver failure despite the risk of side effects. Therefore, diagnosis, prevention, and treatment of the development and progression of NAFLD and NASH are important issues. In this review, we will discuss the pathogenesis of NAFLD/NASH and NAFLD/NASH-derived HCC and the current promising pharmacological therapies of NAFLD/NASH. Further, we will provide insights into "adipose-derived adipokines" and "liver-derived hepatokines" as diagnostic and therapeutic targets from NAFLD to HCC.

Role of Fibroblast Growth Factor 23 (FGF23) and αKlotho in Cancer

Together with fibroblast growth factors (FGFs) 19 and 21, FGF23 is an endocrine member of the family of FGFs. Mainly secreted by bone cells, FGF23 acts as a hormone on the kidney, stimulating phosphate excretion and suppressing formation of 1,25(OH)₂D₃, active vitamin D. These effects are dependent on transmembrane protein αKlotho, which enhances the binding affinity of FGF23 for FGF receptors (FGFR). Locally produced FGF23 in other tissues including liver or heart exerts further paracrine effects without involvement of αKlotho. Soluble Klotho (sKL) is an endocrine factor that is cleaved off of transmembrane Klotho or generated by alternative splicing and regulates membrane channels, transporters, and intracellular signaling including insulin growth factor 1 (IGF-1) and Wnt pathways, signaling cascades highly relevant for tumor progression. In mice, lack of FGF23 or αKlotho results in derangement of phosphate metabolism and a syndrome of rapid aging with abnormalities affecting most organs and a very short life span. Conversely, overexpression of anti-aging factor αKlotho results in a profound elongation of life span. Accumulating evidence suggests a major role of αKlotho as a tumor suppressor, at least in part by inhibiting IGF-1 and Wnt/β-catenin signaling. Hence, in many malignancies, higher αKlotho expression or activity is associated with a more favorable outcome. Moreover, also FGF23 and phosphate have been revealed to be factors relevant in cancer. FGF23 is particularly significant for those forms of cancer primarily affecting bone (e.g., multiple myeloma) or characterized by bone metastasis. This review summarizes the current knowledge of the significance of FGF23 and αKlotho for tumor cell signaling, biology, and clinically relevant parameters in different forms of cancer.

Soluble α-Klotho in Liver Cirrhosis and Alcoholism

AIMS AND BACKGROUND

Alpha Klotho is a transmembrane protein that serves as co-receptor for FGF23. Ectodomain of membrane bound α Klotho may be shed by membrane bound proteases (activated, among other factors, by tumor necrosis factor (TNF)-α) generating the soluble form of the protein (sKl) that functions as a hormone by itself. It modulates calcium influx into cells, blunts IGF-1/Insulin signaling, promotes synthesis of antioxidants, generally slows down tumor progression, delays cell senescence, is neuroprotective and promotes oligodendrocyte maturation and myelin synthesis, and muscle rejuvenation. It may be involved in inflammation and exerts antifibrogenic effects. Some of these pathways may become altered in alcoholism or liver cirrhosis, but data are scattered and scarce and an update is required.

METHOD

Literature survey.

RESULTS AND CONCLUSIONS

Alcohol consumption in non-alcoholics is inversely related to sKl, but alcoholic cirrhotics showed higher-than-normal sKl values in association with liver function derangement. In hepatoma cells, the intensity of Klotho staining was related to faster tumor progression and a shortened life span. Among severe alcoholic cirrhotics sKl is directly related to serum TNF-α levels, and, inversely, to brain atrophy. Given the antioxidant, anti-inflammatory, and antifibrogenic effects of Klotho, perhaps the increase in cirrhosis (and in other inflammatory conditions, such as sepsis or cancer) reflects an attempt to regulate increased inflammation, but clinical and experimental research is urgently needed in this field.

Klotho, vitamin D and homocysteine levels during acute episode and remission periods in schizophrenia patients

AIM

Neurodegenerative processes are effective in schizophrenia. However, the underlying causes of the symptoms and associated factors have not yet been fully elucidated. Recent research has focused on the relationship between neurodegeneration and vitamin D, Klotho and homocysteine levels. In this study, we aimed to investigate this relationship in schizophrenia.

METHOD

This study included 30 schizophrenic inpatients, 30 schizophrenic outpatients in remission and 28 healthy volunteers as the control group. The psychiatric diagnoses of our patients were evaluated according to DSM-IV criteria. The Positive and Negative Syndrome Scale (PANSS), the Global Assessment of Functioning (GAF) scale and the Clinical Global Impression (CGI) scale were used for clinical measurements. Serum Klotho, homocysteine, vitamin D, vitamin B12 and folic acid levels were analyzed using ELISA and compared with clinical properties.

RESULTS

The PANSS scores and CGI scores were higher in schizophrenic inpatients than outpatients, and the GAF scores were lower (p < 0.05). Three groups were compared for Klotho, homocysteine and vitamin D serum levels; Klotho levels were elevated but the difference was not statistically significant (p > 0.05). However, vitamin B12, folic acid and homocysteine levels were higher in schizophrenic patients than the control group (p < 0.05).

CONCLUSIONS

Higher levels of homocysteine with concomitant higher levels of vitamin B12 and folic acid suggest a relationship of this pathway with schizophrenia. Differences in Klotho levels were elevated but it was not significant. Replication studies to investigate probable associations with larger samples are needed.

Soluble Klotho and Brain Atrophy in Alcoholism

Aim

Fibroblast growth factor (FGF-23) and α-Klotho (Klotho) levels may be altered in inflammatory conditions, possibly as compensatory mechanisms. Klotho exerts a protective effect on neurodegeneration and improves learning and cognition. No data exist about the association of Klotho and FGF-23 levels with brain atrophy observed in alcoholics. The aim of this study is to explore these relationships.

Short summary

FGF-23 and Klotho levels are altered in inflammation, possibly as compensatory mechanisms. Klotho enhances learning, but its role in ethanol-mediated brain atrophy is unknown. We found higher FGF-23 and lower Klotho levels in 131 alcoholics compared with 41 controls. Among cirrhotics, Klotho was higher and inversely related to brain atrophy.

Methods

The study was performed on 131 alcoholic patients (54 cirrhotics) and 41 age- and sex-matched controls, in whom a brain computed tomography (CT) was performed and several indices were calculated.

Results

Marked brain atrophy was observed among patients when compared with controls. Patients also showed higher FGF-23 and lower Klotho values. However, among cirrhotics, Klotho values were higher. Klotho was inversely related to brain atrophy (for instance, ventricular index (ρ = -0.23, P = 0.008)), especially in cirrhotics. Klotho was also directly related to tumor necrosis factor (TNF) alpha (ρ = 0.22; P = 0.026) and inversely to transforming growth factor (TGF)-β (ρ = -0.34; P = 0.002), but not to C-reactive protein (CRP) or malondialdehyde levels. FGF-23 was also higher among cirrhotics but showed no association with CT indices.

Conclusions

Klotho showed higher values among cirrhotics, and was inversely related to brain atrophy. FGF-23, although high among patients, especially cirrhotics, did not show any association with brain atrophy. Some inflammatory markers or cytokines, such as CRP or TGF-β were related to brain atrophy.

Effect of PAK1 gene silencing on proliferation and apoptosis in hepatocellular carcinoma cell lines MHCC97-H and HepG2 and cells in xenograft tumor

This study intends to explore the effect of the PAK1 gene silencing on apoptosis and proliferation of hepatocellular carcinoma (HCC) MHCC97-H and HepG2 cells and cells in xenograft tumor. MHCC97-H and HepG2 cells and mice with xenograft tumor in vivo were randomly divided into control, empty vector and PAK1 shRNA groups. Morphology and the expression of green fluorescent protein of MHCC97-H and HepG2 cells and cells in xenograft tumor were observed. MTT assay and flow cytometry were used to detect proliferation, cell cycle and apoptosis of MHCC97-H and HepG2 cells and cells in xenograft tumor. The expressions of PAK1, PCNA, Ki67, Cyclin E, CDK2, p21, p53, Bax and Bcl-2 were measured using the quantitative reverse transcription polymerase chain reaction and western blotting. Compared with the control and empty vector groups, number of adherent cells of MHCC97-H and HepG2 cells and cells in xenograft tumor was reduced, and green fluorescent cells became round and reduced in the PAK1 shRNA group. Cell proliferation, the cells at S phase, the mRNA and protein expressions of PAK1, PCNA, Ki67, Cyclin E, CDK2 and Bcl-2 of MHCC97-H and HepG2 cells and cells in xenograft tumor were decreased, while the cells at G1 phase, apoptosis rate, the mRNA and protein expressions of p21, p53 and Bax of MHCC97-H and HepG2 cells and cells in xenograft tumor were increased in the PAK1 shRNA group. PAK1 gene silencing decreases proliferation of MHCC97-H cells, HepG2 cells and cells in xenograft tumor through the p53/p21 pathway.

Zerumbone suppresses the potential of growth and metastasis in hepatoma HepG2 cells via the MAPK signaling pathway

Zerumbone is an active component of Zingiber zerumbet (L.) Smith and can perform a diverse range of antitumor activities. However, the underlying molecular mechanisms of zerumbone action have not yet been elucidated. The aim of the present study was to investigate the antitumor effects, and the associated molecular mechanisms, of zerumbone in hepatoma HepG2 cells. Treatment with zerumbone markedly induced apoptosis in hepatoma HepG2 cells and suppressed their invasion and metastasis in a dose-dependent manner. Further investigation revealed that treatment with zerumbone led to the dose-dependent induction of apoptosis and cell cycle arrest at G₂/M phase in cancer cells. Zerumbone treatment led to the increased expression of p27, cytochrome c, caspase-3 and-9, and Bcl-2-associated X expression, but the decreased expression of cyclin-dependent kinase 1, cyclin B1, B-cell lymphoma-2, focal adhesion kinase, Ras homolog gene family, member A, Rho-associated protein kinase-1, and matrix metalloproteinase-2 and-9 in HepG2 cells. In addition, the phosphorylation of p38 mitogen-activated protein kinase and extracellular signal-regulated kinase 1/2, but not C-Jun N-terminal kinase 1/2, was regulated in a dose-dependent manner in response to zerumbone treatment. The results of the current study indicate that zerumbone could be used as potential anticancer agent in for the treatment of hepatoma in the future.

Concentrations of fetuin-A, osteoprotegerin and α-Klotho in patients with alcoholic liver cirrhosis

The aim of the present study was to evaluate the concentrations of fetuin-A, osteoprotegerin (OPG) and α-Klotho protein in patients with alcoholic cirrhosis at different stages of the disease, and to demonstrate that fetuin-A, osteoprotegin and α-Klotho may be used as markers of the severity of cirrhosis. A total of 54 patients with alcoholic liver cirrhosis treated in various hospitals in the Lublin region of Poland were randomly enrolled. The control group consisted of 18 healthy individuals without liver disease, who did not drink alcohol. Serum levels of fetuin-A, OPG and α-Klotho were measured by ELISA kits. Levels of fetuin-A were significantly reduced in patients with alcoholic liver cirrhosis compared with the control group. OPG levels were higher in patients with alcoholic liver cirrhosis than in the controls, whereas the levels of α-Klotho were comparable in the cirrhosis and control groups. No statistically significant differences in the concentrations of fetuin-A, OPG and α-Klotho protein were demonstrated according to type of liver cirrhosis. The findings of the present study revealed a significant negative correlation between the level of α-Klotho protein and C-reactive protein in the patients with alcoholic liver cirrhosis. Concentrations of fetuin-A were lower, whereas those of OPG were higher, in the alcoholic liver cirrhosis group compared with the control group. Fetuin-A, OPG and α-Klotho may not be good indicators of liver cirrhosis severity. In conclusion, fetuin-A and OPG may be used in the diagnosis of liver cirrhosis.

Klotho plays a critical role in clear cell renal cell carcinoma progression and clinical outcome

Klotho functions as a tumor suppressor predominantly expressed in renal tubular cells, the origin of clear cell renal cell carcinoma (ccRCC). Altered expression and/or activity of growth factor receptor have been implicated in ccRCC development. Although Klotho suppresses a tumor progression through growth factor receptor signaling including insulin-like growth factor-1 receptor (IGF-1R), the role of Klotho acting on IGF-1R in ccRCC and its clinical relevance remains obscure. Here, we show that Klotho is favorable prognostic factor for ccRCC and exerts tumor suppressive role for ccRCC through inhibiting IGF-1R signaling. Our data shows the following key findings. First, in tumor tissues, the level of Klotho and IGF-1R expression are low or high, respectively, compared to that of adjacent non-neoplastic parenchyma. Second, the Klotho expression is clearly low in higher grade of ccRCC and is closely associated with clinical outcomes in tumor progression. Third, Klotho suppresses IGF-1-stimulated cell proliferation and migration by inhibiting PI3K/Akt pathway. These results provide compelling evidence supporting that Klotho acting on IGF-1R signaling functions as tumor suppressor in ccRCC and suggest that Klotho is a potential carcinostatis substance for ccRCC.

BET Bromodomain Suppression Inhibits VEGF-induced Angiogenesis and Vascular Permeability by Blocking VEGFR2-mediated Activation of PAK1 and eNOS

The tyrosine kinase receptor vascular endothelial growth factor receptor 2 (VEGFR2) is a critical modulator of angiogenesis. Increasing evidence indicate the important role of bromodomain and extra-terminal domain (BET) of chromatin adaptors in regulating tumor growth and inflammatory response. However, whether BET proteins have a role in angiogenesis and endothelial permeability is unclear. In this study, we observed that treatment with JQ1, a specific BET inhibitor, suppressed in vitro tube formation of human umbilical vein endothelial cells (HUVECs) and in vivo angiogenesis in a Matrigel plug and oxygen-induced retinopathy neovascularization. JQ1 attenuated the VEGF-induced decrease in TEER in HUVECs and prevented Evans blue dye leakage in the VEGF-induced Miles assay in athymic Balb/c nude mice. BET inhibition with JQ1 or shRNA for Brd2 or Brd4 suppressed VEGF-induced migration, proliferation, and stress fiber formation of HUVECs. Furthermore, BET inhibition suppressed phosphorylation of VEGFR2 and PAK1, as well as eNOS activation in VEGF-stimulated HUVECs. Inhibition with VEGFR2 and PAK1 also reduced migration and proliferation, and attenuated the VEGF-induced decrease in TEER. Thus, our observations suggest the important role of BET bromodomain in regulating VEGF-induced angiogenesis. Strategies that target the BET bromodomain may provide a new therapeutic approach for angiogenesis-related diseases.

PAKs in Human Cancer Progression: From Inception to Cancer Therapeutic to Future Oncobiology

Since the initial recognition of a mechanistic role of p21-activated kinase 1 (PAK1) in breast cancer invasion, PAK1 has emerged as one of the widely overexpressed or hyperactivated kinases in human cancer at-large, allowing the PAK family to make in-roads in cancer biology, tumorigenesis, and cancer therapeutics. Much of our current understanding of the PAK family in cancer progression relates to a central role of the PAK family in the integration of cancer-promoting signals from cell membrane receptors as well as function as a key nexus-modifier of complex, cytoplasmic signaling network. Another core aspect of PAK signaling that highlights its importance in cancer progression is through PAK's central role in the cross talk with signaling and interacting proteins, as well as PAK's position as a key player in the phosphorylation of effector substrates to engage downstream components that ultimately leads to the development cancerous phenotypes. Here we provide a comprehensive review of the recent advances in PAK cancer research and its downstream substrates in the context of invasion, nuclear signaling and localization, gene expression, and DNA damage response. We discuss how a deeper understanding of PAK1's pathobiology over the years has widened research interest to the PAK family and human cancer, and positioning the PAK family as a promising cancer therapeutic target either alone or in combination with other therapies. With many landmark findings and leaps in the progress of PAK cancer research since the infancy of this field nearly 20 years ago, we also discuss postulated advances in the coming decade as the PAK family continues to shape the future of oncobiology.

Klotho: a tumor suppressor and modulator of the Wnt/β-catenin pathway in human hepatocellular carcinoma

Klotho, an anti-aging gene, has recently been shown to contribute to human hepatic tumorigenesis. In addition, it is known that Wnt signaling is antagonized by the protein klotho. Because augmented Wnt signaling has an important role in tumorigenesis of human hepatocellular carcinoma (HCC), we studied the relationship of klotho expression and activity to the Wnt pathway in this malignancy. Immunohistochemical analysis performed on tissue arrays revealed that klotho expression levels were significantly lower in HCC than in adjacent noncancerous tissues, while klotho staining was inversely correlated with clinical stage and histologic grade. Patients with klotho-expressing tumors had longer survival periods than did those with klotho-negative tumors. Overexpression of klotho as well as treatment with soluble klotho protein reduced hepatoma cell growth in vitro and in vivo, whereas klotho silencing enhanced cellular proliferation. Moreover, forced expression of klotho inhibited Wnt/β-catenin signaling, as confirmed by reduced expression of β-catenin, inhibition of translocation of β-catenin from the cytoplasm to the nucleus, and reduced expression of c-myc and cyclin D1, two known target genes of the Wnt/β-catenin pathway. In contrast, activation of the Wnt/β-catenin pathway was enhanced when klotho was silenced by inhibitory RNAs. Furthermore, serum levels of soluble klotho in patients with malignant tumors were studied, and results suggested a significant increase in these levels in HCC patients. These data suggest that klotho acts as a tumor suppressor and an inhibitor of the Wnt/β-catenin pathway in HCC, and moreover, that soluble klotho is a potential serum biomarker for HCC.

Sorafenib-based combined molecule targeting in treatment of hepatocellular carcinoma

Sorafenib is the only and standard systematic chemotherapy drug for treatment of advanced hepatocellular carcinoma (HCC) at the current stage. Although sorafenib showed survival benefits in large randomized phase III studies, its clinical benefits remain modest and most often consist of temporary tumor stabilization, indicating that more effective first-line treatment regimens or second-line salvage therapies are required. The molecular pathogenesis of HCC is very complex, involving hyperactivated signal transduction pathways such as RAS/RAF/MEK/ERK and PI3K/AKT/mTOR and aberrant expression of molecules such as receptor tyrosine kinases and histone deacetylases. Simultaneous or sequential abrogation of these critical pathways or the functions of these key molecules involved in angiogenesis, proliferation, and apoptosis may yield major improvements in the management of HCC. In this review, we summarize the emerging sorafenib-based combined molecule targeting for HCC treatment and analyze the rationales of these combinations.

Klotho inhibits human follicular thyroid cancer cell growth and promotes apoptosis through regulation of the expression of stanniocalcin-1

The new anti-aging gene Klotho has been identified as a multi-functional humoral factor which influences multiple biological processes, including tumor progression. Although ample evidence indicates that Klotho plays important roles in cervical, lung and breast cancer, the role and mechanism of Klotho in thyroid cancer are still unclear. The present study aimed to investigate the effects and mechanisms of Klotho in human thyroid cancer cell lines FTC133 and FTC238. Klotho overexpression markedly reduced thyroid cancer FTC133 and FTC238 cell proliferation and enhanced apoptosis, whereas, Klotho silencing in the FTC133 and FTC238 cells increased cell growth. Moreover, soluble human KL1 (sKL) and Klotho overexpression had a similar effect on FTC133 and FTC238 cell growth. A high level of Klotho was also found to be associated with a low level of stanniocalcin 1 (STC1) in both the FTC133 and FTC238 cell lines. STC1 silencing significantly inhibited thyroid cancer cell proliferation, whereas recombinant human STC1 (hSTC1) markedly enhanced cell proliferation. In addition, our study demonstrated that hSTC1 treatment attenuated Klotho-induced inhibition of cell proliferation and promotion of apoptosis. Our data revealed the existence of a moderating effect between Klotho and STC1, where Klotho may inhibit thyroid tumor progression by inhibiting the tumor marker level of STC1.

α-Klotho Expression in Human Tissues

CONTEXT

α-Klotho has emerged as a powerful regulator of the aging process. To date, the expression profile of α-Klotho in human tissues is unknown, and its existence in some human tissue types is subject to much controversy.

OBJECTIVE

This is the first study to characterize systemwide tissue expression of transmembrane α-Klotho in humans. We have employed next-generation targeted proteomic analysis using parallel reaction monitoring in parallel with conventional antibody-based methods to determine the expression and spatial distribution of human α-Klotho expression in health.

RESULTS

The distribution of α-Klotho in human tissues from various organ systems, including arterial, epithelial, endocrine, reproductive, and neuronal tissues, was first identified by immunohistochemistry. Kidney tissues showed strong α-Klotho expression, whereas liver did not reveal a detectable signal. These results were next confirmed by Western blotting of both whole tissues and primary cells. To validate our antibody-based results, α-Klotho-expressing tissues were subjected to parallel reaction monitoring mass spectrometry (data deposited at ProteomeXchange, PXD002775) identifying peptides specific for the full-length, transmembrane α-Klotho isoform.

CONCLUSIONS

The data presented confirm α-Klotho expression in the kidney tubule and in the artery and provide evidence of α-Klotho expression across organ systems and cell types that has not previously been described in humans.

p21-activated kinase 1 determines stem-like phenotype and sunitinib resistance via NF-κB/IL-6 activation in renal cell carcinoma

The p21-activated kinase 1 (PAK1), a serine/threonine kinase that orchestrates cytoskeletal remodeling and cell motility, has been shown to function as downstream node for various oncogenic signaling pathways to promote cell proliferation, regulate apoptosis and accelerate mitotic abnormalities, resulting in tumor formation and invasiveness. Although alterations in PAK1 expression and activity have been detected in various human malignancies, its potential biological and clinical significance in renal cell carcinoma (RCC) remains obscure. In this study, we found increased PAK1 and phosphorylated PAK1 levels in tumor tissues according to TNM stage progression. Elevated phosphorylated PAK1 levels associated with progressive features and indicated unfavorable overall survival (OS) as an independent adverse prognosticator for patients with RCC. Moreover, PAK1 kinase activation with constitutive active PAK1 mutant T423E promoted growth, colony formation, migration, invasion and stem-like phenotype of RCC cells, and vice versa, in PAK1 inhibition by PAK1 kinase inactivation with specific PAK1 shRNA, dead kinase PAK1 mutant K299R or allosteric inhibitor IPA3. Stem-like phenotype due to sunitinib administration via increased PAK1 kinase activation could be ameliorated by PAK1 shRNA, PAK1 mutant K299R and IPA3. Furthermore, nuclear factor-κB (NF-κB)/interleukin-6 (IL-6) activation was found to be responsible for PAK1-mediated stem-like phenotype following sunitinib treatment. Both IL-6 neutralizing antibody and IPA3 administration enhanced tumor growth inhibition effect of sunitinib treatment on RCC cells in vitro and in vivo. Our results unraveled that oncogenic activation of PAK1 defines an important mechanism for maintaining stem-like phenotype and sunitinib resistance through NF-κB/IL-6 activation in RCC, lending PAK1-mediated NF-κB/IL-6 activation considerable appeal as novel pharmacological therapeutic targets against sunitinib resistance.

Clinical observation of liver cancer patients treated with axitinib and cabozantinib after failed sorafenib treatment: a case report and literature review

Hepatocellular carcinoma (HCC) is a major pathological type of primary liver cancer. Sorafenib has demonstrated definite efficacy in targeted therapy for HCC. However, when treatment with sorafenib fails, suitable drugs must be found for further treatment. This article reports a case of an HCC patient who was treated with angiogenesis inhibitor axitinib and c-Met inhibitor cabozantinib following treatment with sorafenib. The report focuses on clinical treatment and toxicity. Rational application of targeted therapy is also explored.

Targeting fibroblast growth factor 19 in liver disease: a potential biomarker and therapeutic target

INTRODUCTION

Fibroblast growth factor 19 (FGF19) is a member of the hormone-like FGF family and has activity as an ileum-derived postprandial hormone. It shares high binding affinity with β-Klotho and together with the FGF receptor (FGFR) 4, is predominantly targeted to the liver. The main function of FGF19 in metabolism is the negative control of bile acid synthesis, promotion of glycogen synthesis, lipid metabolism and protein synthesis.

AREAS COVERED

Drawing on in vitro and in vivo studies, this review discusses FGF19 and some underlying mechanisms of action of FGF19 as an endocrine hormone in several liver diseases. The molecular pathway of the FGF19-FGFR4 axis in non-alcoholic liver disease and hepatocellular carcinoma are discussed. Furthermore, definition of function and pharmacological effects of FGF19 for liver disease are also presented.

EXPERT OPINION

A series of studies have highlighted a crucial role of FGF19 in liver disease. However, the conclusions of these studies are partly paradoxical and controversial. An understanding of the underlying biological mechanisms which may explain inconsistent findings is especially important for consideration of potential biomarker strategies and an exploration of the putative therapeutic efficacy of FGF19 for human liver disease.

Republished: tracing PAKs from GI inflammation to cancer

P-21 activated kinases (PAKs) are effectors of Rac1/Cdc42 which coordinate signals from the cell membrane to the nucleus. Activation of PAKs drive important signalling pathways including mitogen activated protein kinase, phospoinositide 3-kinase (PI3K/AKT), NF-κB and Wnt/β-catenin. Intestinal PAK1 expression increases with inflammation and malignant transformation, although the biological relevance of PAKs in the development and progression of GI disease is only incompletely understood. This review highlights the importance of altered PAK activation within GI inflammation, emphasises its effect on oncogenic signalling and discusses PAKs as therapeutic targets of chemoprevention.

Klotho: a novel biomarker for cancer

BACKGROUND

The Klotho gene was originally identified as an anti-aging gene in 1997. Recent studies have demonstrated aberrant expression of Klotho in a number of cancers, including breast cancer, lung cancer, hepatocellular carcinoma (HCC), and so on.

METHODS

A literature search focusing on dysregulation of Klotho and its possible mechanisms in cancer was performed.

RESULTS AND CONCLUSIONS

Downregulation of Klotho was found in several cancers, such as pancreatic cancer, HCC, and other tumors. Epigenetic modulation, such as promoter methylation and histone deacetylation, also contributed to the dysregulation of Klotho in cancers. Downregulation of Klotho resulted in promoted proliferation and reduced apoptosis of cancer cells. The relevant mechanisms include the fibroblast growth factor signaling, the insulin-like growth factor 1 receptor pathway, and the Wnt/β-catenin signaling pathway. Furthermore, the Klotho protein hopefully provides new insights into cancer target treatment.

The role of p21-activated kinases in hepatocellular carcinoma metastasis

The p21-activated kinases (PAKs) are downstream effectors of the Rho family small GTPases as well as a wide variety of mitogenic factors and have been implicated in cancer formation, development and metastasis. PAKs phosphorylate a wide spectrum of substrates to mediate extracellular signals and regulate cytoskeletal remodeling, cell motility and survival. In this review, we aim to summarize the findings regarding the oncogenic role and the underlying mechanisms of PAKs signaling in various cancers, and in particular highlight the prime importance of PAKs in hepatocellular carcinoma (HCC) progression and metastasis. Recent studies exploring the potential therapeutic application of PAK inhibitors will also be discussed.

Tracing PAKs from GI inflammation to cancer

P-21 activated kinases (PAKs) are effectors of Rac1/Cdc42 which coordinate signals from the cell membrane to the nucleus. Activation of PAKs drive important signalling pathways including mitogen activated protein kinase, phospoinositide 3-kinase (PI3K/AKT), NF-κB and Wnt/β-catenin. Intestinal PAK1 expression increases with inflammation and malignant transformation, although the biological relevance of PAKs in the development and progression of GI disease is only incompletely understood. This review highlights the importance of altered PAK activation within GI inflammation, emphasises its effect on oncogenic signalling and discusses PAKs as therapeutic targets of chemoprevention.

Klotho suppresses growth and invasion of colon cancer cells through inhibition of IGF1R-mediated PI3K/AKT pathway

Klotho (KL) was originally characterized as an aging suppressor gene, and has been identified as a tumor suppressor gene in a variety of cancers including colon cancer. However, the potential role and molecular events for KL in colon cancer remain unclear. The present study aimed to investigate the expression of KL in human colon cancer by immunohistochemistry, and to analyze the correlation between KL expression and clinicopathological characteristics of patients with colon cancer. Functional analysis after lentivirus-mediated gain of KL expression was used to assess the tumor growth and invasion in colon cancer cells in vitro and in vivo. The rate of KL expression was significantly decreased in cancer tissues compared with that in adjacent non-cancer tissues (ANCT) (60.3 vs.77.9%, P=0.022), and KL expression was negatively associated with Dukes staging (P=0.034) and depth of tumor invasion (P=0.008). Overexpression of KL in vitro inhibited cell proliferative activities and invasive potential in colon cancer cells, companied with decreased expression of p-IGF1R, p-PI3K, p-AKT, PCNA and MMP-2. In addition, the tumor volumes in the HT-29 subcutaneous tumor model treated with lentivirus‑mediated KL vector (Lv-KL) was significantly smaller than those of the negative control (NC) group (P<0.01). Taken together, our findings indicate that the expression of KL is downregulated in human colon caner and correlates with tumor invasion and Dukes staging, while overexpression of KL suppresses growth and invasion through inhibition of IGF1R-mediated PI3K/AKT pathway in colon cancer cells, suggesting that KL may serve as a potential therapeutic target for the treatment of colon cancer.

p21-Activated protein kinases and their emerging roles in glucose homeostasis

p21-Activated protein kinases (PAKs) are centrally involved in a plethora of cellular processes and functions. Their function as effectors of small GTPases Rac1 and Cdc42 has been extensively studied during the past two decades, particularly in the realms of cell proliferation, apoptosis, and hence tumorigenesis, as well as cytoskeletal remodeling and related cellular events in health and disease. In recent years, a large number of studies have shed light onto the fundamental role of group I PAKs, most notably PAK1, in metabolic homeostasis. In skeletal muscle, PAK1 was shown to mediate the function of insulin on stimulating GLUT4 translocation and glucose uptake, while in pancreatic β-cells, PAK1 participates in insulin granule localization and vesicle release. Furthermore, we demonstrated that PAK1 mediates the cross talk between insulin and Wnt/β-catenin signaling pathways and hence regulates gut proglucagon gene expression and the production of the incretin hormone glucagon-like peptide-1 (GLP-1). The utilization of chemical inhibitors of PAK and the characterization of Pak1(-/-) mice enabled us to gain mechanistic insights as well as to assess the overall contribution of PAKs in metabolic homeostasis. This review summarizes our current understanding of PAKs, with an emphasis on the emerging roles of PAK1 in glucose homeostasis.

Significance of the anti-aging protein Klotho

The Klotho gene was identified as an 'aging suppressor' in mice. Overexpression of the Klotho gene extends lifespan and defective Klotho results in rapid aging and early death. Both the membrane and secreted forms of Klotho have biological activity that include regulatory effects on general metabolism and a more specific effect on mineral metabolism that correlates with its effect on aging. Klotho serves as a co-receptor for fibroblast growth factor (FGF), but it also functions as a humoral factor that regulates cell survival and proliferation, vitamin D metabolism, and calcium and phosphate homeostasis and may serve as a potential tumor suppressor. Moreover, Klotho protects against several pathogenic processes in a FGF23-independent manner. These processes include cancer metastasis, vascular calcification, and renal fibrosis. This review covers the recent advances in Klotho research and discusses novel Klotho-dependent mechanisms that are clinically relevant in aging and age-related diseases.

Association between Serum Atypical Fibroblast Growth Factors 21 and 19 and Pediatric Nonalcoholic Fatty Liver Disease

Atypical fibroblast growth factors (FGF) 21 and 19 play a central role in energy metabolism through the mediation of Klotho coreceptor. Contradictory findings are available about the association of FGF21 and FGF19 with nonalcoholic fatty liver disease (NAFLD) in humans. We investigated the association of serum FGF21, FGF19 and liver Klotho coreceptor with non-alcoholic steatohepatitis (NASH) and fibrosis in children with NAFLD. Serum FGF21 and FGF19 were measured in 84 children with biopsy-proven NAFLD and 23 controls (CTRL). The hepatic expression of Klotho coreceptor was measured in 7 CTRL, 9 patients with NASH (NASH+) and 11 patients without NASH (NASH−). FGF21 and FGF19 showed a tendency to decrease from CTRL (median FGF21 = 196 pg/mL; median FGF19 = 201 pg/mL) to NASH− (FGF21 = 89 pg/mL; FGF19 = 81 pg/mL) to NASH+ patients (FGF21 = 54 pg/mL; FGF19 = 41 pg/mL) (p<0.001 for all comparisons) and were inversely associated with the probability of NASH and fibrosis in children with NAFLD. The hepatic expression of Klotho coreceptor was inversely associated with NASH (R² = 0.87, p<0.0001) and directly associated with serum FGF21 (R² = 0.57, p<0.0001) and FGF19 (R² = 0.67, p<0.0001). In conclusion, serum FGF19 and FGF21 and hepatic Klotho expression are inversely associated with hepatic damage in children with NAFLD and these findings may have important implications for understanding the mechanisms of NAFLD progression.