Klotho is a novel biomarker for good survival in resected large cell neuroendocrine carcinoma of the lung

Protein interaction networks characterizing the A549 cells Klotho transfected are associated with activated pro-apoptotic Bim and suppressed Wnt/β-catenin signaling pathway

Invasive assays and lung tumor-bearing mice models using a human lung adenocarcinoma cell line A549 cells transfected with the Klotho (KL) gene, A549/KL cells, have confirmed that KL suppresses invasive/metastatic potential. This study aimed to identify the co-expression protein networks and proteomic profiles associated with A549/KL cells to understand how Klotho protein expression affects molecular networks associated with lung carcinoma malignancy. A two-step application of a weighted network correlation analysis to the cells' quantitative proteome datasets of a total of 6,994 proteins, identified by mass spectrometry-based proteomic analysis with data-independent acquisition (DIA), identified one network module as most significantly associated with the A549/KL trait. Upstream analyses, confirmed by western blot, implicated the pro-apoptotic Bim (Bcl-2-like protein 11) as a master regulator of molecular networks affected by Klotho. GeneMANIA interaction networks and quantitative proteome data implicated that Klotho interacts with two signaling axes: negatively with the Wnt/β-catenin axis, and positively by activating Bim. Our findings might contribute to the development of future therapeutic strategies.

The role of α-klotho in human cancer: molecular and clinical aspects

Klotho is a well-established longevity hormone. Its most prominent function is the regulation of phosphate homeostasis. However, klotho possesses multiple pleiotropic activities, including inhibition of major signaling pathways, reducing oxidative stress and suppressing inflammation. These activities are tightly associated with cancer, and klotho was discovered as a universal tumor suppressor. We review here novel molecular aspects of klotho activity in cancer, focusing on its structure-function relationships and clinical aspects regarding its expression, blood levels, clinical risk, and prognostic value in the clinical setting. In addition, the potential benefit of klotho treatment combined with chemotherapy, biological therapy, or immunotherapy, are discussed. Finally, as klotho was shown in preclinical models to inhibit cancer development and growth, we discuss various approaches to developing klotho-based therapies.

Undetected αKlotho in serum is associated with the most aggressive phenotype of breast cancer

Klotho, a cellular anti-senescence protein, is related to antitumor actions, growth regulation, proliferation and invasiveness in several types of tumor, including breast cancer. The present study aimed to analyze the serum levels of αKlotho in patients with breast cancer according to histopathological and immunohistochemical variables. A total of 74 patients and 60 healthy controls were recruited. Peripheral blood samples were collected and serum levels were assessed by sandwich ELISA. Clinical and diagnostic data were obtained from medical records and databases of the Clinical Hospital of the Federal University of Uberlândia (Uberlândia, Brazil). The results indicated no difference in the levels of αKlotho between patients and controls (P=0.068); however, the number of patients with breast cancer with undetectable αKlotho was high (n=52). Thus, the variables that were associated with the lowest survival rates were analyzed, relating them to undetectable αKlotho. Among cases of metastatic tumors or tumors with poor differentiation, positive lymph node status and triple-negative status, patients with undetectable αKlotho predominated and had unfavorable overall survival. Due to the significant results obtained in triple-negative patients, an in vitro analysis was performed to determine whether estrogen receptors (ERs) have a role in αKlotho production. Treatment of MCF-7 cells with ER agonists, estradiol (E2) and diarylpropionitrile (DPN), resulted in increases in αKlotho expression and supernatant levels of both agonists, demonstrating a direct association between the ER and Klotho production; of note, the ERβ-specific agonist DPN tripled αKlotho expression when compared to E2 (P=0.078). These data suggested that undetectable αKlotho in the serum of patients with breast cancer is related to unfavorable histopathological variables and poor prognosis and ERs possibly have an important role in maintaining adequate quantities of αKlotho.

Antiaging gene Klotho regulates epithelial-mesenchymal transition and increases sensitivity to pemetrexed by inducing lipocalin-2 expression

Epithelial-mesenchymal transition (EMT) is considered to serve an important role in the metastatic/invasive ability of cancer cells, in the acquisition of drug resistance, and in metabolic reprogramming. In the present study, it was hypothesized that the Klotho gene is involved in the metastatic/invasive ability of lung cancer. We previously reported an association between Klotho expression and overall survival in patients with small cell lung cancer and large cell neuroendocrine cancer. We also found that Klotho expression was associated with EMT-related molecules in lung squamous cell carcinoma. The present study aimed to analyze the function of the Klotho gene and to elucidate its relevance to the regulation of the EMT. For this purpose, GFP-Klotho plasmids were transfected into lung adenocarcinoma cells (A549) and cell lines with stable expression (A549/KL-1 and A549/KL-2) were established. A549/KL-1 cells expressed higher levels of Klotho protein by western blot analysis compared with A549/KL-2 cells. In western blotting of A549 and A549/KL-1 cells, the expression of the mesenchymal marker N-cadherin was found to be completely inhibited in A549/KL-1 cells suggesting that Klotho expression may regulate the EMT in cancer cells via the inhibition of N-cadherin. The results of the sensitivity tests demonstrated that A549/KL-1 cells were significantly more sensitive to pemetrexed compared with A549 cells (IC₅₀ A549/KL-1 vs. A549 cells, 0.1 µM vs. 0.7 µM). The results of the microarray analysis demonstrated that a very high level of lipocalin-2 (LCN2) expression was induced in the A549/KL-1 cells. Klotho overexpression completely suppressed the expression of mesenchymal markers, such as N-cadherin and Snail1 (Snail). The results of the present study suggested that there may be a new mechanism of action for the antitumor effects of pemetrexed, namely, LCN2-mediated modulation of N-cadherin expression. Klotho expression during cancer treatment has great potential as a predictor for efficacy of pemetrexed and as a factor in the selection of personalized medicine for postoperative adjuvant chemotherapy.

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.

Klotho gene polymorphism, brain structure and cognition in early-life development

Variation in the klotho gene is linked to differences in health outcomes: klotho allele KL-VS heterozygosity is associated with longevity, better cognition and greater right frontal grey matter volume in late life. Contradicting reports, however, suggest that KL-VS’s effect on health might be age-dependent. Here we examine the relationship between KL-VS genotype, cognition and brain structure in childhood and adolescence. We hypothesized that KL-VS has early influences on cognitive and brain development. We investigated the associations of KL-VS carrier status with cognition and brain morphology in a cohort of 1387 children and adolescents aged 3–21 years, examining main effects and interactions between age, sex and socioeconomic circumstance. KL-VS had no main effect on either cognition or brain structure, though there was a significant KL-VS × age interaction for cognition (specifically executive function, attention, episodic memory, and general cognition), total grey matter and total brain volume. KL-VS heterozygotes had better cognition than non-carriers before age 11, but lower cognition after age 11. Heterozygotes had smaller brains than non-carriers did in early childhood. Sex moderated the association between KL-VS and white matter volume. Among girls, KL-VS heterozygotes had smaller white matter volumes than non-carriers. Among boys, heterozygotes had greater white matter volumes than non-carriers. However, a replication in a cohort of 2306 children aged 6–12 years showed no significant associations. In contrast to findings in late life, these results show that KL-VS does not have a main effect on cognition and brain structure. Furthermore, KL-VS’s influence may depend on age and sex.

α-Klotho Expression in Mouse Tissues Following Acute Exhaustive Exercise

α-Klotho, a multifunctional protein, has been demonstrated to protect tissues from injury via anti-oxidation and anti-inflammatory effects. The expression of α-klotho is regulated by several physiological and pathological factors, including acute inflammatory stress, oxidative stress, hypertension, and chronic renal failure. Exhaustive exercise has been reported to result in tissue damage, which is induced by inflammation, oxidative stress, and energy metabolism disturbance. However, little is known about the effects of exhaustive exercise on the expression of α-klotho in various tissues. To determine the effects, the treadmill exhaustion test in mice was performed and the mice were sacrificed at different time points following exhaustive exercise. Our results confirmed that the full-length (130 kDa) and shorter-form (65 kDa) α-klotho were primarily expressed in the kidneys. Moreover, we found that, except for the kidneys and brain, other tissues primarily expressed the shorter-form α-klotho, including liver, which was in contrast to previous reports. Furthermore, the shorter-form α-klotho was decreased immediately following the acute exhaustive exercise and was then restored to the pre-exercise level or even higher levels in the next few days. Our results indicate that α-klotho may play a key role in the body exhaustion and recovery following exhaustive exercise.

Overview of microRNA-199a Regulation in Cancer

microRNAs (miRNAs) are a class of endogenous short, non-coding RNAs that regulate a multitude of genes at the post-transcriptional level. miR-199, which is a highly conserved miRNA family, consists of miR-199a and miR-199b. Researchers mainly focused on miR-199a over the past few years. Functional studies have demonstrated that mature miR-199a is a key player in the maintenance of normal homeostasis and in the regulation of disease pathogenesis. Here, we summarize the biological functions of miR-199a and review recent research on its roles in the physiological processes of cancer cells, such as proliferation, migration, invasion, apoptosis, autophagy and glycometabolism.

Rab8 GTPase regulates Klotho-mediated inhibition of cell growth and progression by directly modulating its surface expression in human non-small cell lung cancer

BACKGROUND

The klotho (KL) gene is an anti-aging gene that has recently been shown to also function as a general tumor suppressor. However, there is currently only limited information regarding the potential molecular signals for regulation of Klotho without identifying precise molecular mechanisms or interactions.

METHODS

We performed a mass spectrometry (MS) assay to screen candidate proteins complexed with Klotho derived from immunoprecipitation in human non-small cell lung cancer (NSCLC) cells, and identified Rab8 to be the protein that most prominently interacts with Klotho. We further investigated whether Rab8 can regulate trafficking of Klotho and which process it would modulate using surface biotinylation assay, immunofluorescence and fluorescence ratio microscopy. Furthermore, we explored whether Rab8 is involved in Klotho-mediated function in NSCLC, and verified the results which we found in vivo using xenograft mouse model.

FINDINGS

We report discovery of Rab8 as a Klotho-interacting protein that acts as a critical modulator of Klotho surface expression in human NSCLC. In particular, we report that Rab8 is co-localized and associated with Klotho, and Klotho trafficking is regulated by Rab8. Moreover, we found that Rab8 modulates surface levels of Klotho via a post-biosynthetic pathway, as opposed to an endocytic pathway. Furthermore, we demonstrate that Rab8 is involved in Klotho-mediated regulation of cell proliferation, migration, invasiveness, epithelial-mesenchymal transition (EMT), and Wnt-β-catenin signaling in NSCLC. Additionally, Rab8 overexpression was also found to increase Klotho-mediated inhibition of NSCLC tumorigenesis in vivo.

INTERPRETATION

Overall, our findings suggest that Rab8 GTPase can regulate Klotho-mediated inhibition of Wnt signaling activity by modulating translocation of Klotho onto the cell surface, which in turn affects Klotho-mediated inhibition of cell proliferation, migration and invasiveness in NSCLC. These results have important implications for the development of new therapeutic targets, Klotho-related research in the context of NSCLC as well as other areas, and provide a working model for Rab8 function in the context of cancer and cancer biology.

Klotho expression and nodal involvement as predictive factors for large cell lung carcinoma

INTRODUCTION

Klotho has been recently described as a carcinogenesis suppressor. Large cell neuroendocrine lung carcinoma (LCNEC) is a rare, highly malignant neoplasm. In the light of increasing incidence of neuroendocrine tumours, biomarkers predicting survival are needed. We consider that Klotho might be one.

MATERIAL AND METHODS

We analysed records of all patients diagnosed with LCNEC, atypical carcinoid and typical carcinoid operated on in our institution between 2007 and 2015. Initially, we found 134 cases. Forty-six specimens were unattainable and thus excluded from research. All patients diagnosed with LCNEC according to the WHO classification were included in the study. Immunohistochemical staining for Klotho was performed. We retrospectively reviewed patient charts and analysed multiple variables.

RESULTS

Positive staining for Klotho was present in 36 tissue specimens, while 12 patients were Klotho-negative. Survival length was significantly higher in Klotho-positive cases (p = 0.024), while advanced nodal status (N1 and N2) represented a marker of poor outcome (p = 0.011). In multivariate analysis, both Klotho presence (p = 0.015; HR = 0.37; 95% CI: 0.17-0.86) and nodal involvement (p = 0.007; HR = 3.04; 95% CI: 1.37-6.82) were independent prognostic factors. Tumour vessel invasion and visceral pleura infiltration were not associated with worse treatment results. Klotho presence predicted a favourable prognosis in these groups (p = 0.018; p = 0.007).

CONCLUSIONS

Our results suggest that Klotho might be a positive factor for predicting survival in LCNEC and nodal involvement a negative one. Thus, these two markers may assist in the selection of subjects with unfavourable prognosis and to personalise therapy regimens.

Assessment of the circulating klotho protein in lung cancer patients

The anti-aging factor, klotho has been identified as a tumor suppressor in various human cancers, including lung cancer. In vitro studies provided evidence that klotho expression influences the characteristics of lung cancer cells, however, in vivo results are lacking. The aim of our study was to evaluate whether circulating klotho protein might serve as a potential biomarker of lung cancer. Blood samples were taken from 45 newly diagnosed lung cancer patients (31 NSCLC, 14 SCLC) and 43 control subjects. Plasma klotho concentration was measured using ELISA. No difference in plasma klotho values was detected between patients and control subjects (366.3 (257.9-486.8) vs. 383.5 (304.6-489.7) pg/ml respectively (median (IQR)); p > 0.05). Plasma klotho levels in patients with distant metastasis did not differ from less advanced stage disease (354.2 (306.9-433.3 vs. 328.5 (242.5-419.7) pg/ml, p > 0.05). In contrast, analyzed with one-way ANOVA, significant difference (p = 0.04) was found between the examined histological types of lung cancer: adenocarcinoma (353 (329.4-438.5) pg/ml), squamous cell carcinoma (308 (209.6-348.1) pg/ml) and small cell lung cancer (388.8 (289.9-495.4) pg/ml). However, Tukey's post hoc test did not reveal significant difference between any pairs of histological groups. There was no difference between any histological subtype and health either. Our results suggest that circulating klotho protein cannot be considered as a biomarker for lung cancer. Further studies are warranted in order to examine the relationship between klotho expression in lung tissue and circulating levels of the protein, and to explore its mechanism of action in lung cancer.

Association between klotho expression and malignancies risk and progression: A meta-analysis

BACKGROUND

We assessed the association between tissue klotho protein expression and the risk and progression of malignancies.

METHODS

We searched the electronic databases for the studies regarding the relationship between tissue klotho protein expression and risk/progression of malignancies through January 2018. We calculated the pooled odds ratios (ORs) and corresponding 95% confidence intervals (CIs) to evaluate the impact of tissue klotho protein expression on malignancies. A fixed-effect model, or in the presence of heterogeneity, random- effect model was applied to calculate the combined ORs.

RESULTS

Eighteen studies were recruited in our pooled-analysis. Overall malignancies including liver cancer, pancreatic ductal adenocarcinoma (PDAC), ovarian cancer, esophageal squamous cell carcinoma (ESCC), neuroendocrine cancer, oral cancer and bladder cancer demonstrated significantly lower ORs than those in controls (p < 0.05). Malignancies with tissue klotho protein expression showed a pooled hazard ratio (95% CI 0.784-2.479). Malignancies with tissue klotho protein expression showed a similar OR (95% CI 0.732-1.335) of male/total to cases without tissue klotho protein expression. Malignancies with tissue klotho protein expression showed a markedly lower OR (95% CI 0.454-0.941) of metastasis compared with those without tissue klotho protein expression. Malignancies with tissue klotho protein expression showed a markedly higher OR (95% CI 1.041-1.800) of stage I-II/III-IVcompared with those without tissue klotho protein expression. Malignancies with tissue klotho protein expression showed a similar OR (95% CI 0.948-3.407) of differentiation to cases without tissue klotho protein expression. Sensitivity analysis did not change the overall results significantly. No marked publication bias was noted.

CONCLUSIONS

Tissue klotho protein expression was associated with a lower risk and progression of malignancies. Klotho may be a protective factor against malignancies risk/progression.

Effects of Klotho on fibrosis and cancer: A renal focus on mechanisms and therapeutic strategies

Klotho is a membrane-bound protein predominantly expressed in the kidney, where it acts as a permissive co-receptor for Fibroblast Growth Factor 23. In its shed form, Klotho exerts anti-fibrotic effects in several tissues. Klotho-deficient mice spontaneously develop fibrosis and Klotho deficiency exacerbates the disease progression in fibrotic animal models. Furthermore, Klotho overexpression or supplementation protects against fibrosis in various models of renal and cardiac fibrotic disease. These effects are mediated at least partially by the direct inhibitory effects of soluble Klotho on TGFβ1 signaling, Wnt signaling, and FGF2 signaling. Soluble Klotho, as present in the circulation, appears to be the primary mediator of anti-fibrotic effects. Similarly, through inhibition of the TGFβ1, Wnt, FGF2, and IGF1 signaling pathways, Klotho also inhibits tumorigenesis. The Klotho promoter gene is generally hypermethylated in cancer, and overexpression or supplementation of Klotho has been found to inhibit tumor growth in various animal models. This review focuses on the protective effects of soluble Klotho in inhibiting renal fibrosis and fibrosis in distant organs secondary to renal Klotho deficiency. We also discuss the structure-function relationships of Klotho domains and biological effects in the context of potential targeted treatment strategies.

WNT signaling - lung cancer is no exception

Since the initial discovery of the oncogenic activity of WNT ligands our understanding of the complex roles for WNT signaling pathways in lung cancers has increased substantially. In the current review, the various effects of activation and inhibition of the WNT signaling pathways are summarized in the context of lung carcinogenesis. Recent evidence regarding WNT ligand transport mechanisms, the role of WNT signaling in lung cancer angiogenesis and drug transporter regulation and the importance of microRNA and posttranscriptional regulation of WNT signaling are also reviewed.

Klotho expression is correlated to molecules associated with epithelial-mesenchymal transition in lung squamous cell carcinoma

Klotho is known as an anti-aging gene. We previously reported that the expression of Klotho is a postoperative prognostic factor for patients with lung large cell neuroendocrine carcinoma and lung small cell carcinoma. Recently, Klotho was shown to suppress the epithelial-mesenchymal transition (EMT). In the present study, we examined the association between the expression of Klotho and the regulation of EMT in lung squamous cell carcinoma. We immunohistochemically examined the expression of Klotho in patients with lung squamous cell carcinoma who had undergone surgical resection or photodynamic therapy. The immunohistochemical analysis showed that Klotho expression was observed not only in normal bronchial epithelial cells, but also in centrally located early lung cancers, which were all carcinomas in situ and were treated using PDT. However, in lung cancer patients with invasive and or advanced squamous cell carcinoma who had undergone a complete surgical resection, Klotho expression was observed in only 4 patients (13%). To elucidate the associations between the expression of Klotho and the expressions of EMT-related proteins, such as E-cadherin, N-cadherin, vimentin, and Snail, we transiently transfected GFP-Klotho plasmid DNA into the human squamous lung cancer cell line SQ5 and examined the expressions of these proteins of GFP-positive cells after sorting using flow cytometry. In SQ5 cells overexpressing GFP-Klotho, the expression of N-cadherin, which is a mesenchymal marker, was completely inhibited, compared with that in SQ5 cells transfected with the GFP vector. The overexpression of Klotho did not affect the regulation of either other mesenchymal markers (such as vimentin and Snail) or the regulation of an epithelial marker (E-cadherin). We concluded that the expression of Klotho was related to the degree of cancer invasiveness and that Klotho inhibits the expression of N-cadherin and regulates the EMT in lung cancer.

Tissue expression and source of circulating αKlotho

αKlotho (Klotho), a type I transmembrane protein and a coreceptor for Fibroblast Growth Factor-23, was initially thought to be expressed only in a limited number of tissues, most importantly the kidney, parathyroid gland and choroid plexus. Emerging data may suggest a more ubiquitous Klotho expression pattern which has prompted reevaluation of the restricted Klotho paradigm. Herein we systematically review the evidence for Klotho expression in various tissues and cell types in humans and other mammals, and discuss potential reasons behind existing conflicting data. Based on current literature and tissue expression atlases, we propose a classification of tissues into high, intermediate and low/absent Klotho expression. The functional relevance of Klotho in organs with low expression levels remain uncertain and there is currently limited data on a role for membrane-bound Klotho outside the kidney. Finally, we review the evidence for the tissue source of soluble Klotho, and conclude that the kidney is likely to be the principal source of circulating Klotho in physiology.

Klotho suppresses tumor progression via inhibiting IGF-1R signaling in T‑cell lymphoma

Klotho is a transmembrane protein and acts as an upstream modulator of insulin-like growth factor-1 receptor (IGF-1R) signaling, which was indicated to be involved in the pathogenesis of solid cancer and hematological malignancies, including T‑cell lymphoma. Although Klotho was recently identified as a tumor suppressor in several types of human malignancies, the potential role of Klotho in T‑cell lymphoma has not been reported. In the present study, we investigated the expression level and the molecular events of Klotho in T‑cell lymphoma. Significantly lower expression of Klotho was observed in T‑cell lymphoma patient samples compared to normal lymph nodes. Functional analysis after Klotho overexpression revealed significantly inhibited tumor cell viability in T‑cell lymphoma. Moreover, apoptosis of T‑cell lymphoma cells were induced after transfected with Klotho-overexpressing vectors. Forced expression of Klotho resulted in decline of activation of IGF-1R signaling, accompanied by decreased phosphorylation of its downstream targets, including AKT and ERK1/2. These data indicated that Klotho acts as a tumor suppressor via inhibiting IGF-1R signaling, thus suppressing the viability and promoting apoptosis in T‑cell lymphoma. Taken together, Klotho may serve as a potential target for the therapeutic intervention of T‑cell lymphoma.

The Role of Alpha-Klotho as a Universal Tumor Suppressor

The klotho gene is implicated in many physiological activities, among them aging, glucose metabolism, and phosphate and calcium metabolism. Many cellular activities of klotho were implicated in promoting these activities. Two of them, inhibition of the insulin-like growth factor-1 pathway and of the Wnt signaling pathway, are also major pathways associated with cancer development and progression. These discoveries prompted a surge of research aiming to elucidate the role of klotho in cancer. Studies show that klotho is universally silenced in a wide array of malignancies, including breast, pancreatic, ovarian, lung, colorectal, and melanoma, and that klotho's expression can serve as an invaluable prognostic marker. Epigenetic mechanisms, ie, promoter hypermethylation and histone deacetylation, are mainly associated with klotho's silencing; however, different micro-RNAs were also demonstrated to be involved in the process. The activity of klotho on cancer cells growth was also widely investigated, and accumulating data suggest that klotho forced expression or treatment with the soluble protein can inhibit cancer development and progression. Moreover, studies now aim to reveal the specific region in klotho protein that underlies this anticancer activity in order to develop efficient and safe klotho-based medications.

Reduced expression and growth inhibitory activity of the aging suppressor klotho in epithelial ovarian cancer

Klotho is an anti-aging transmembrane protein, which can be shed and function as a hormone. Accumulating data indicate klotho as a tumor suppressor in a wide array of malignancies, and we identified klotho as an inhibitor of the insulin-like growth factor (IGF-1) pathway in cancer cells. As this pathway is significant in the development of epithelial ovarian cancer (EOC) we studied klotho expression and activity in this tumor. Klotho mRNA levels were reduced in 16 of 19 EOC cell lines and immunohistochemistry analysis revealed high expression in normal ovaries, and reduced expression in 100 of 241 high grade papillary-serous adenocarcinoma of the ovaries, fallopian tubes and peritoneum. Reduced expression was associated with wild-type BRCA status. Klotho reduced EOC cell viability, enhanced cisplatin sensitivity, and reduced expression of mesenchymal markers. Finally, klotho inhibited IGF-1 pathway activation and inhibited transcriptional activity of the estrogen receptor. In conclusion, klotho is silenced in a substantial subset of the tumors and restoring its expression slows growth of EOC cells and inhibits major signaling pathways. As klotho is a hormone, treatment with klotho may serve as a novel treatment for EOC.

[Effect of PI3K/AKT pathway on cisplatin resistance in non-small cell lung cancer]

Accumulating evidences indicate that aberrant activation of PI3K/AKT pathway in non-small cell lung cancer plays a vital role in tumor cell proliferation,apoptosis, and survival including drug resistance. Cisplatin as first-line chemotherapy are in widespread clinical use in patients with non-small cell lung cancer, however, the development of cisplatin resistance significantly impedes its clinic efficacy. Cisplatin resistance is a complicated process that various mechanisms participating in to interact, of which PI3K/AKT pathway keeping sustained activated is one of the most important reasons. This article reviewed the progress of research on the relationship between PI3K/AKT pathway and cisplatin resistance.

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.

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.

Up-regulated miR-199a-5p in gastric cancer functions as an oncogene and targets klotho

Background

Recent studies have shown that miR-199a-5p plays opposite roles in cancer initiation and progression of different cancer types, acting as oncogene for some cancer types but as tumor suppressor gene for others. However, the role and molecular mechanism of miR-199a-5p in gastric cancer are largely unknown.

Methods

In this study, miR-199a-5p expression level in gastric cancer was first analyzed by qPCRand then validated in 103 gastric cancer patients by in situ hybridization (ISH). Gastric cancer cell lines were transfected with miR-199a-5p inhibitor and mimic, and underwent in vitro transwell assays. Target genes (klotho) were identified using Luciferase reporter assay. Immunohistochemical staining was also used to investigate on how miR-199a-5p regulates the tumour-suppressive effects of klotho in gastric cancer.

Results

In our present study, we found that miR-199a-5p level was significantly increased in gastric cancer tissues compared to paired normal tissues. We observed that miR-199a-5p could promote migration and invasion of gastric cancer cells. In situ hybridization of miR-199a-5p also confirmed that higher miR-199a-5p expression level was associated with increased likelihood of lymph node metastasis and later TNM stage. Luciferase reporter assay and immunohistochemistry revealed that klotho might be the downstream target of miR-199a-5p.

Conclusions

Our present study suggests that miR-199a-5p acts as an oncogene in gastric cancer and functions by targeting klotho.

Klotho acts as a tumor suppressor in cancers

The klotho gene is a classical "aging suppressor" gene. Its roles in the pathology of chronic kidney diseases have been well documented. However, the role of Klotho in tumorigenesis, cancer progression, and prognosis is attracting more and more attention. Recent studies have shown that Klotho participates in the progression of several types of human cancers. Klotho functions as a tumor suppressor by inhibiting insulin/IGF1, p53/p21, and Wnt signaling. Silencing klotho gene expression is mainly mediated through promoter hypermethylation and histone deacetylation in cancer. Klotho has been proposed to take part in cell proliferation, survival, autophagy, and resistance to anti-cancer therapies.

Diagnostic and prognostic significance of the alternatively spliced ACTN4 variant in high-grade neuroendocrine pulmonary tumours

BACKGROUND

High-grade neuroendocrine tumours (HGNTs) of the lung manifest a wide spectrum of clinical behaviour, but no method for predicting their outcome has been established.

MATERIALS AND METHODS

We newly established a monoclonal antibody specifically recognizing the product of the alternatively spliced ACTN4 transcript (namely, variant actinin-4), and used it to examine the expression of variant actinin-4 immunohistochemically in a total of 609 surgical specimens of various histological subtypes of lung cancer.

RESULTS

Variant actinin-4 was expressed in 55% (96/176) of HGNTs, but in only 0.8% (3/378) of non-neuroendocrine (NE) lung cancers. The expression of variant actinin-4 was significantly associated with poorer overall survival in HGNT patients (P=0.00021, log-rank test). Multivariate analysis using the Cox proportional hazards model showed that the expression of variant actinin-4 was the most significant independent negative predictor of survival in HGNT patients (hazard ratio (HR), 2.15; P=0.00113) after the presence of lymph node metastasis (HR, 2.25; P=0.00023).

CONCLUSIONS

The expression of variant actinin-4 is an independent prognostic factor for patients with HGNTs. This protein has a high affinity for filamentous actin polymers and likely promotes aggressive behaviour of cancer cells. The present clinical findings clearly support this notion.

Klotho predicts good clinical outcome in patients with limited-disease small cell lung cancer who received surgery

BACKGROUND

The important role of surgery in early-stage small cell lung cancer (SCLC) has been recognized, and curative surgical resection is recommended. However, the role of adjuvant chemotherapy for stage I SCLC has not yet been evaluated, and novel approaches focusing on the specific genomic characteristics of SCLC may be invaluable for customized therapy. In this study, we focused on the Klotho gene, which is an anti-aging gene known to be a potential tumor suppressor. We investigated whether the expression of Klotho, assessed by immunohistochemistry, can predict survival in patients with resected SCLC.

METHODS

The medical records of patients diagnosed as having limited-disease (LD) SCLC and treated by surgical resection (n=30) at Tokyo Medical University Hospital were retrospectively reviewed. The expression status of Klotho, and of the ATP-binding cassette (ABC) transporters MRP1, MDR and breast cancer resistant protein (BCRP), which can cause resistance to anticancer drugs, including irinotecan, was assessed by immunohistochemical analysis in resected surgical specimens of patients with early-stage SCLC.

RESULTS

Of the 30 patients, Klotho expression was seen in the specimens from 18 patients (60.0%), but not in those of the remaining 12 patients (40.0%). The immunostaining for Klotho was mostly localized in the cytoplasm. The expression of Klotho was significantly associated with the overall survival (OS) (ratio 0.088; 95% confidence interval 0.019-0.409; P=0.002). The administration of perioperative chemotherapy had no significant effect in improving the survival, as assessed by the Kaplan-Meier method. However, the patients showing Klotho expression in the resected specimens in p-stage I and II, may have benefited from perioperative chemotherapy. A multivariate analysis revealed no significant association between the expression status of MRP1, MDR or BCRP and the OS.

CONCLUSION

Expression of Klotho was predictive of a favorable outcome following resection in limited-disease SCLC patients, and the Klotho expression status may serve as a new biomarker for the need of additional therapies to be developed in the future.