Kindlin-2 controls sensitivity of prostate cancer cells to cisplatin-induced cell death

Kindlin-2 maintains liver homeostasis by regulating GSTP1-OPN-mediated oxidative stress and inflammation in mice

Hepatocyte plays a principal role in preserving integrity of the liver homeostasis. Our recent study demonstrated that Kindlin-2, a focal adhesion protein that activates integrins and regulates cell-extracellular matrix interactions, plays an important role in regulation of liver homeostasis by inhibiting inflammation pathway; however, the molecular mechanism of how Kindlin-2 KO activates inflammation is unknown. Here, we show that Kindlin-2 loss largely downregulates the antioxidant glutathione-S-transferase P1 in hepatocytes by promoting its ubiquitination and degradation via a mechanism involving protein-protein interaction. This causes overproduction of intracellular reactive oxygen species and excessive oxidative stress in hepatocytes. Kindlin-2 loss upregulates osteopontin in hepatocytes partially because of upregulation of reactive oxygen species and consequently stimulates overproduction of inflammatory cytokines and infiltration in liver. The molecular and histological deteriorations caused by Kindlin-2 deficiency are markedly reversed by systemic administration of an antioxidant N-acetylcysteine in mice. Taken together, Kindlin-2 plays a pivotal role in preserving integrity of liver function.

The Role of ARHGAP1 in Rho GTPase Inactivation during Metastasizing of Breast Cancer Cell Line MCF-7 after Treatment with Doxorubicin

Breast cancer is the most prevalent cancer type in women worldwide. It proliferates rapidly and can metastasize into farther tissues at any stage due to the gradual invasiveness and motility of the tumor cells. These crucial properties are the outcome of the weakened intercellular adhesion, regulated by small guanosine triphosphatases (GTPases), which hydrolyze to the guanosine diphosphate (GDP)-bound conformation. We investigated the inactivating effect of ARHGAP1 on Rho GTPases involved signaling pathways after treatment with a high dose of doxorubicin. Label-free quantitative proteomic analysis of the proteome isolated from the MCF-7 breast cancer cell line, treated with 1 μM of doxorubicin, identified RAC1, CDC42, and RHOA GTPases that were inactivated by the ARHGAP1 protein. Upregulation of the GTPases involved in the transforming growth factor-beta (TGF-beta) signaling pathway initiated epithelial-mesenchymal transitions. These findings demonstrate a key role of the ARHGAP1 protein in the disruption of the cell adhesion and simultaneously allow for a better understanding of the molecular mechanism of the reduced cell adhesion leading to the subsequent metastasis. The conclusions of this study corroborate the hypothesis that chemotherapy with doxorubicin may increase the risk of metastases in drug-resistant breast cancer cells.

Kindlin-2 promotes Src-mediated tyrosine phosphorylation of androgen receptor and contributes to breast cancer progression

Androgen receptor (AR) signaling plays important roles in breast cancer progression. We show here that Kindlin-2, a focal adhesion protein, is critically involved in the promotion of AR signaling and breast cancer progression. Kindlin-2 physically associates with AR and Src through its two neighboring domains, namely F1 and F0 domains, resulting in formation of a Kindlin-2-AR-Src supramolecular complex and consequently facilitating Src-mediated AR Tyr-534 phosphorylation and signaling. Depletion of Kindlin-2 was sufficient to suppress Src-mediated AR Tyr-534 phosphorylation and signaling, resulting in diminished breast cancer cell proliferation and migration. Re-expression of wild-type Kindlin-2, but not AR-binding-defective or Src-binding-defective mutant forms of Kindlin-2, in Kindlin-2-deficient cells restored AR Tyr-534 phosphorylation, signaling, breast cancer cell proliferation and migration. Furthermore, re-introduction of phosphor-mimic mutant AR-Y534D, but not wild-type AR reversed Kindlin-2 deficiency-induced inhibition of AR signaling and breast cancer progression. Finally, using a genetic knockout strategy, we show that ablation of Kindlin-2 from mammary tumors in mouse significantly reduced AR Tyr-534 phosphorylation, breast tumor progression and metastasis in vivo. Our results suggest a critical role of Kindlin-2 in promoting breast cancer progression and shed light on the molecular mechanism through which it functions in this process.

Research on the Enhancement Mechanism of Dihydromyricetin on the Inhibitory Role of Cisplatin Towards Breast Cancer Cell Activity

Objective: The purpose of our study was to evaluate Enhancement Mechanism of Dihydromyricetin (DMY) on the Inhibitory Role of Cisplatin Towards Breast Cancer Cell Activity. Materials and Methods: The MCF-7 were divided into NC, DMY, Cis and DMY+Cis groups. Using relative methods (MTT, TUNEL, Transwell, flow cytometry and wound healing) to evaluate MCF-7 cell biological activities including cell viability, apoptosis, invasion cell number and wound healing rate. The relative proteins expressions including FOXO-1, Noxa, Bim, Cyto C, Caspase-3, Caspase-9 and Apaf-1 were evaluated by WB assay. Results: MCF-7 cell viability, invasion cell number and wound healing rates were significantly depressed and apoptosis rate were significantly increased in DMY, Cis and DMY+Cis groups (P < 0.01, respectively). Compared with Cis group, cell viability, invasion cell number and wound healing rates were significantly depressed and apoptosis rate were significantly increased in DMY+Cis group (P < 0.05, respectively). Conclusion: Dihydromyricetin can effectively enhance the inhibitory effect of cisplatin on breast cancer cells.

Kindlin-2 in Sertoli cells is essential for testis development and male fertility in mice

Kindlin-2 is known to play important roles in the development of mesoderm-derived tissues including myocardium, smooth muscle, cartilage and blood vessels. However, nothing is known for the role of Kindlin-2 in mesoderm-derived reproductive organs. Here, we report that loss of Kindlin-2 in Sertoli cells caused severe testis hypoplasia, abnormal germ cell development and complete infertility in male mice. Functionally, loss of Kindlin-2 inhibits proliferation, increases apoptosis, impairs phagocytosis in Sertoli cells and destroyed the integration of blood-testis barrier structure in testes. Mechanistically, Kindlin-2 interacts with LATS1 and YAP, the key components of Hippo pathway. Kindlin-2 impedes LATS1 interaction with YAP, and depletion of Kindlin-2 enhances LATS1 interaction with YAP, increases YAP phosphorylation and decreases its nuclear translocation. For clinical relevance, lower Kindlin-2 expression and decreased nucleus localization of YAP was found in SCOS patients. Collectively, we demonstrated that Kindlin-2 in Sertoli cells is essential for sperm development and male reproduction.

Kindlin-2 deficiency induces fatal intestinal obstruction in mice

Rationale: Smooth muscle-motility disorders are mainly characterized by impaired contractility and functional intestinal obstruction. Some of these cases are caused by genetic mutations of smooth muscle genes ACTA2, ACTG2, MYH11, MYLK and LMOD1. Still the etiology is complex and multifactorial and the underlying pathology is poorly understood. Integrin interaction protein Kindlin-2 is widely expressed in striated and smooth muscle cells (SMC). However, the function of Kindlin-2 in the smooth muscle remains elusive.

Methods: We generated two mouse models using different cre promoter transgenic mice, Kindlin-2^fl/fl SM22α-cre+ (cKO mice) and Kindlin-2^fl/fl; MYH-cre+ (iKO mice). Embryos and adult tissues were prepared for hematoxylin and eosin (H&E) staining, immunohistochemistry (IHC) and terminal deoxynucleotidyl transferase dUTP nick-end labeling (TUNEL) apoptosis assay. We investigated ultrastructure changes of mouse smooth muscle using transmission electron microscopy (TEM) and measured smooth muscle contractile force in mounting aortic and intestinal rings using the multiwire myograph system (DMT 620M). In addition, cell traction force microscopy (CTFM) was applied to observe the functional change of primary SMC after Kindlin-2 depletion by RNAi.

Results: Depletion of Kindlin-2 encoding gene Fermt2 in embryonic smooth muscles leads to apoptosis, downregulates the key components of SMC, impairs smooth muscle development, and finally causes embryonic death at E14.5. Tamoxifen-induced Kindlin-2-specific knockout in adult mouse smooth muscle showed decreased blood pressure, intestinal hypoperistalsis, and eventually died of intestinal obstruction. Kindlin-2 depletion also leads to downregulated Myh11, α-SMA, and CNN, shortened myofilament, broken myofibrils, and impaired contractility of the smooth muscles in iKO mice. Mechanistically, loss of Kindlin-2 decreases Ca2⁺ influx in primary vascular smooth muscle cells (PVSMC) by downregulating the expression of calcium-binding protein S100A14 and STIM1.

Conclusion: We demonstrated that Kindlin-2 is essential for maintaining the normal structure and function of smooth muscles. Loss of Kindlin-2 impairs smooth muscle formation during embryonic development by inducing apoptosis and jeopardizes the contraction of adult smooth muscle by blocking Ca²⁺ influx that leads to intestinal obstruction. Mice with Kindlin-2 depletion in adult smooth muscle could be a potent animal model of intestinal obstruction for disease research, drug treatment and prognosis.

Cisplatin: The first metal based anticancer drug

Cisplatin or (SP-4-2)-diamminedichloridoplatinum(II) is one of the most potential and widely used drugs for the treatment of various solid cancers such as testicular, ovarian, head and neck, bladder, lung, cervical cancer, melanoma, lymphomas and several others. Cisplatin exerts anticancer activity via multiple mechanisms but its most acceptable mechanism involves generation of DNA lesions by interacting with purine bases on DNA followed by activation of several signal transduction pathways which finally lead to apoptosis. However, side effects and drug resistance are the two inherent challenges of cisplatin which limit its application and effectiveness. Reduction of drug accumulation inside cancer cells, inactivation of drug by reacting with glutathione and metallothioneins and faster repairing of DNA lesions are responsible for cisplatin resistance. To minimize cisplatin side effects and resistance, combination therapies are used and have proven more effective to defect cancers. This article highlights a systematic description on cisplatin which includes a brief history, synthesis, action mechanism, resistance, uses, side effects and modulation of side effects. It also briefly describes development of platinum drugs from very small cisplatin complex to very large next generation nanocarriers conjugated platinum complexes.

Kindlin-2 regulates hepatic stellate cells activation and liver fibrogenesis

Liver fibrosis, the common response associated with chronic liver diseases, ultimately leads to cirrhosis, a major public health problem worldwide. Activation of hepatic stellate cells (HSCs) by transforming growth factor (TGF)-β1 is a key step in liver fibrosis. Here we report that Kindlin-2 expression is elevated in the livers of mice with experimental liver fibrosis and also in the livers of patients with liver fibrosis. TGF-β1 increases Kindlin-2 expression in cultured HSCs in a p38 and ERK mitogen-activated protein kinase (MAPK)-dependent manner, partly. More importantly, Kindlin-2 deficiency significantly attenuated mouse liver fibrosis and HSC activation. Mechanistically, Kindlin-2 promotes TGF-β signaling through upregulation of Smad2 and Smad3 phosphorylation. Our work demonstrates an important role for Kindlin-2 in liver fibrosis, and inhibiting Kindlin-2 in the livers may represent a novel strategy to treat liver fibrosis.

Kindlins: Roles in development and cancer progression

The Kindlins are FERM domain proteins comprising three members (Kindlin-1, -2 and -3) which are evolutionarily conserved. Kindlins bind with β-integrin cytoplasmic tails and execute broad biological functions including directed cell migration, proliferation, differentiation and survival. In light of more and more evidence point to the importance of Kindlin family members in normal development and human diseases especially in cancers, we aim to portrait the profile of Kindlins in the regulation of embryonic development and cancer progression. We first summarize all the known binding proteins for individual member of Kindlin family. We then outline the Kindlin-regulated signaling pathways including Wnt/β-catenin, TGFβ, EGFR, and Hedgehog signalings. Furthermore, we descript the pivotal role of Kindlins in embryonic development in detail with notions that Kindlin-1 is highly expressed in endo/ectodermal originated tissues, Kindlin-2 is highly expressed in mesoderm-derived tissues and Kindlin-3 is highly expressed in mesoderm- and ectoderm-derived tissues. Deregulation of Kindlins is generally reported in cancers from different organs. We also briefly descript the role of Kindlins in other diseases. Finally, we update the recent understanding of how Kindlins are regulated and modified as well as the degradation mechanism of Kindlins, respectively.

Kindlin-2 Regulates the Growth of Breast Cancer Tumors by Activating CSF-1-Mediated Macrophage Infiltration

Interplay between tumor cells and host cells in the tumor microenvironment dictates the development of all cancers. In breast cancer, malignant cells educate host macrophages to adopt a protumorigenic phenotype. In this study, we show how the integrin-regulatory protein kindlin-2 (FERMT2) promotes metastatic progression of breast cancer through the recruitment and subversion of host macrophages. Kindlin-2 expression was elevated in breast cancer biopsy tissues where its levels correlated with reduced patient survival. On the basis of these observations, we used CRISPR/Cas9 technology to ablate Kindlin-2 expression in human MDA-MB-231 and murine 4T1 breast cancer cells. Kindlin-2 deficiency inhibited invasive and migratory properties in vitro without affecting proliferation rates. However, in vivo tumor outgrowth was inhibited by >80% in a manner associated with reduced macrophage infiltration and secretion of the macrophage attractant and growth factor colony-stimulating factor-1 (CSF-1). The observed loss of CSF-1 appeared to be caused by a more proximal deficiency in TGFβ-dependent signaling in Kindlin-2-deficient cells. Collectively, our results illuminate a Kindlin-2/TGFβ/CSF-1 signaling axis employed by breast cancer cells to capture host macrophage functions that drive tumor progression. Cancer Res; 77(18); 5129-41. ©2017 AACR.

Prognostic implications of Kindlin proteins in human osteosarcoma

The Kindlin protein family, comprising Kindlin-1, Kindlin-2 and Kindlin-3, play important roles in various human cancers. Here, to explore the clinical significance of Kindlins in human osteosarcomas, quantitative real-time PCR and Western blot analyses were performed to detect the expression of Kindlin-1, Kindlin-2 and Kindlin-3 mRNAs and proteins in 20 self-pairs of osteosarcoma and adjacent noncancerous tissues. Then, immunohistochemistry was performed to examine subcellular localizations and expression patterns of Kindlin proteins in 100 osteosarcoma and matched adjacent noncancerous tissues. Kindlin-1, Kindlin-2 and Kindlin-3 protein immunostainings were localized in the cytoplasm, nucleus and cytoplasm, respectively, of tumor cells in primary osteosarcoma tissues. Statistically, the expression levels of Kindlin-1 and Kindlin-2 mRNAs and proteins in osteosarcoma tissues were all significantly higher (both P<0.01), but those of Kindlin-3 mRNA and protein were both dramatically lower (both P<0.05), than in matched adjacent noncancerous tissues. In addition, the overexpressions of Kindlin-1 and Kindlin-2 proteins were both significantly associated with high tumor grade (both P=0.01), presence of metastasis (both P=0.006), recurrence (both P=0.006) and poor response to chemotherapy (both P=0.02). Moreover, Kindlin-1 and Kindlin-2 expressions were both identified as independent prognostic factors for overall (both P=0.01) and disease-free (P=0.02 and 0.01, respectively) survivals of osteosarcoma patients. However, no associations were observed between Kindlin-3 expression and various clinicopathologic features and patients’ prognosis. In conclusion, aberrant expression of Kindlin-1 and Kindlin-2 may function as reliable markers for progression and prognosis in osteosarcoma patients, especially for tumor recurrence.

The kindlin family: functions, signaling properties and implications for human disease

The kindlin (or fermitin) family of proteins comprises three members (kindlin-1,-2 and -3) of evolutionarily conserved focal adhesion (FA) proteins, whose best-known task is to increase integrin affinity for a ligand (also referred as integrin activation) through binding of β-integrin tails. The consequence of kindlin-mediated integrin activation and integrin-ligand binding is cell adhesion, spreading and migration, assembly of the extracellular matrix (ECM), cell survival, proliferation and differentiation. Another hallmark of kindlins is their involvement in disease. Mutations in the KINDLIN-1 (also known as FERMT1) gene cause Kindler syndrome (KS)--in which mainly skin and intestine are affected, whereas mutations in the KINDLIN-3 (also known as FERMT3) gene cause leukocyte adhesion deficiency type III (LAD III), which is characterized by impaired extravasation of blood effector cells and severe, spontaneous bleedings. Also, aberrant expression of kindlins in various forms of cancer and in tissue fibrosis has been reported. Although the malfunctioning of integrins represent a major cause leading to kindlin-associated diseases, increasing evidence also point to integrin-independent functions of kindlins that play an important role in the pathogenesis of certain disease aspects. Furthermore, isoform-specific kindlin functions have been discovered, explaining, for example, why loss of kindlins differentially affects tissue stem cell homeostasis or tumor development. This Commentary focuses on new and isoform-specific kindlin functions in different tissues and discusses their potential role in disease development and progression.

Molecular mechanisms of synergistic induction of apoptosis by the combination therapy with hyperthermia and cisplatin in prostate cancer cells

Prostate Cancer has become the second leading cause of male cancer-related incidence and mortality in United States. Hyperthermia (HT) is known to serve as a powerful tool in treatment of prostate cancer in clinical. The combination treatment with HT and cisplatin has a synergistic effect to inhibit prostate cancer progression and demonstrates better clinical effectiveness than HT or chemotherapy alone. But molecular mechanisms of this phenomenon have not been illuminated clearly. In this study, we used MTS assay to examine cell viabilities of PC-3, LNCaP, DU-145 and RM-1 cells after treated by HT and cisplatin. Then colony formation of PC-3 and DU-145 cells after treated with HT and cisplatin were photographed. To investigate whether the combination therapy would enhance apoptosis of PC-3 and DU-145 cells, we used Western blot analysis to detect expression level of proteins on apoptosis-regulated signaling pathway in PC-3 and DU-145 cells. Our results showed that the combination treatment decreased cell viabilities and colony formation of prostate cancer cells in a dose-dependent manner and this combination therapy enhanced apoptosis of PC-3 and DU-145 cells via activation of Caspase-3 and cleavage of PARP. We also found that the combination therapy could down-regulate the anti-apoptotic Bcl-2 and IAP family proteins. At last, the combination therapy activated AMPKα-JNK signaling pathway and inhibited Akt-mTOR-p70s6k signaling pathway to promote apoptosis of PC-3 and DU-145 cells. In conclusion, this study clearly elucidated how the combination therapy with HT and cisplatin promoted apoptosis of prostate cancer cells in synergy.

Of Kindlins and Cancer

Kindlins are 4.1-ezrin-ridixin-moesin (FERM) domain containing proteins. There are three kindlins in mammals, which share high sequence identity. Kindlin-1 is expressed primarily in epithelial cells, kindlin-2 is widely distributed and is particularly abundant in adherent cells, and kindlin-3 is expressed primarily in hematopoietic cells. These distributions are not exclusive; some cells express multiple kindlins, and transformed cells often exhibit aberrant expression, both in the isoforms and the levels of kindlins. Great interest in the kindlins has emerged from the recognition that they play major roles in controlling integrin function. In vitro studies, in vivo studies of mice deficient in kindlins, and studies of patients with genetic deficiencies of kindlins have clearly established that they regulate the capacity of integrins to mediate their functions. Kindlins are adaptor proteins; their function emanate from their interaction with binding partners, including the cytoplasmic tails of integrins and components of the actin cytoskeleton. The purpose of this review is to provide a brief overview of kindlin structure and function, a consideration of their binding partners, and then to focus on the relationship of each kindlin family member with cancer. In view of many correlations of kindlin expression levels and neoplasia and the known association of integrins with tumor progression and metastasis, we consider whether regulation of kindlins or their function would be attractive targets for treatment of cancer.

miR-138-Mediated Regulation of KINDLIN-2 Expression Modulates Sensitivity to Chemotherapeutics

Prostate cancer is the second leading cause of cancer-related death in men, second only to lung cancer, mainly due to disease reoccurrence as a result to lack of response to androgen deprivation therapies (ADT) after castration. Patients with metastatic castration-resistant prostate cancer (mCRPC) have very limited treatment options, with docetaxel as the first-line standard of care, for which resistance to this chemotherapeutic ultimately develops. Therefore, finding ways to sensitize tumors to chemotherapies and to limit chemoresistance provides a viable strategy to extend the survival of mCRPC patients. This study investigated the role of Kindlin-2 (FERMT2/K2), a member of the Kindlin family of FERM domain proteins and key regulators of the adhesive functions mediated by integrin, in the sensitization of mCRPC to chemotherapeutics. Loss of K2, which is overexpressed in prostate cancer cells derived from mCRPC tumors, compared with those cells derived from androgen-dependent tumors, significantly enhanced apoptosis and cell death of docetaxel-treated PC3 cells. Furthermore, it was determined that K2-mediated sensitization to docetaxel treatment is the result of inhibition of β1-integrin signaling. Finally, miR-138 specifically targeted K2 and inhibited its expression, thereby regulating a miR-138/K2/β1-integrin signaling axis in mCRPC that is critical for the modulation of sensitivity to chemotherapeutics. Thus, these data identify a novel signaling axis where K2 in combination with chemotherapeutics provides a new target for the treatment of mCRPC.

IMPLICATIONS

Targeted inhibition of Kindlin-2 in combination with chemotherapy represents an effective treatment option for mCRPC.

A three-protein signature and clinical outcome in esophageal squamous cell carcinoma

Current staging is inadequate to precisely predict clinical outcome of esophageal squamous cell carcinoma (ESCC) and determine treatment choices, which vary from operation alone to intensive multimodal regimens. The purpose of this study is to investigate the prognostic values of an immunohistochemistry-based three-protein signature model in patients with ESCC. We determined the protein expression of Annexin II, cofilin 1, ezrin, fascin, kindlin-2, moesin, MTSS1, myosin-9, profilin-1, Rac1, radixin, ROCK2, talin, tensin and villin 1 in a test cohort including 110 formalin-fixed, paraffin-embedded esophageal curative resection specimens by tissue microarrays (TMAs). A three-protein signature elicited from the protein cluster, Annexin II, kindlin-2, and myosin-9, was validated by TMAs on an independent cohort of 147 specimens. The expression of three-protein signature was highly predictive of ESCC overall survival (OS) and disease-free survival (DFS) in both generation and validation datasets. Regression analysis shows that this three-protein signature is an independent predictor for OS and DFS. Furthermore, the predictive ability of these 3 biomarkers in combination is more robust than that of each individual biomarker. This study demonstrates a clinically applicable prognostic model that accurately predicts ESCC patient survival and/or tumor recurrence, and thus could serve as a complement to current risk stratification approaches.

DNA fragmentation, caspase 3 and prostate-specific antigen genes expression induced by arsenic, cadmium, and chromium on nontumorigenic human prostate cells

Prostate cancer is one of the most common cancers and the second cause of cancer-related deaths among men. Metals are recognized as chemical carcinogens where chronic exposures to such metals are implicated in the development of cancer, including prostate cancer. This in vitro study demonstrates the relative death sensitivity of prostatic (RWPE-1) cells to arsenic (As), cadmium (Cd), and chromium (Cr) as environmental pollutants through its apoptotic effects and the effect of these chemicals on prostate-specific antigen (PSA) gene expression as a marker for their carcinogecity. RWPE-1 cells were divided into three groups that were treated with As, Cd, and Cr in three replicates, at three different concentrations for each metal for 48 h. A control group consisted of untreated RWPE1 cells was used. Apoptosis was assessed using comet assay and caspase 3 gene expression; meanwhile, PSA gene expression was evaluated by semiqualitative real-time PCR (RT-PCR). One of the novel findings of this study is that arsenic and cadmium at low concentrations decreased apoptosis of RWPE-1 cells in a concentration-dependent manner while chromium induced significant concentration-dependent increase in apoptosis. Yet, at the highest concentrations, apoptosis was relatively more induced by all chemicals. Arsenic was the most chemical inhibiting apoptosis in RWPE-1 cells at low concentration. While at the moderate and highest concentrations, cadmium was the most inhibiting chemical of RWPE-1 cells' apoptosis. No distinct differences between treated and untreated cells for PSA gene expression were observed. It can be concluded that As and Cd, at low concentrations, can reduce apoptosis of prostatic cells in a concentration-dependent manner while chromium induced it; however, all metal salts used in this study did not induce PSA gene expression.

Kindlin-2: a novel prognostic biomarker for patients with hepatocellular carcinoma

The association of aberrant expression of Kindlin-2 with tumor progression has been reported in recent years. The purpose of this study was to investigate the expression of Kindlin-2 in hepatocellular carcinoma (HCC), and to evaluate its clinical and prognostic significance. The mRNA and protein levels of Kindlin-2 in HCC and adjacent non-cancerous tissues were examined by real-time PCR and western blotting. The relationships between Kindlin-2 expression, clinicopathological features and postoperative survival of HCC patients were also evaluated. Kindlin-2 expression was higher in HCC tissues as compared to adjacent non-cancerous tissues at both mRNA and protein levels (P<0.05, respectively). Positive expression of Kindlin-2 was significantly correlated with larger tumor size (P=0.034), capsular invasion (P=0.009), microvascular invasion (P=0.028) and poor prognosis of HCC patients (P<0.001). Moreover, multivariate survival analysis identified Kindlin-2 as an independent prognostic factor for overall and disease-free survival of HCC patients (P=0.018 and 0.001, respectively). Taken together, our findings suggested that Kindlin-2 was highly expressed in HCC tissues and was closely related to clinical progression. Therefore, Kindlin-2 protein could be a potential biomarker for predicting poor prognosis of HCC patients after surgery.

Mig-2 attenuates cisplatin-induced apoptosis of human glioma cells in vitro through AKT/JNK and AKT/p38 signaling pathways

AIM

Mig-2 (also known as Kindlin-2 and FERMT2) is an important regulator of integrin activation and cell-extracellular matrix adhesion, and involved in carcinogenesis and tumor progression. The aim of this study was to investigate the role of mig-2 in cisplatin-induced apoptosis of human glioma cells in vitro.

METHODS

The expression of mig-2 was modulated in human glioma H4, HS 683 and U-87 MG cells by transfection with a plasmid carrying mig-2 or mig-2 siRNA. Cisplatin-induced apoptosis was detected using Annexin V/PI staining and flow cytometry, as well as MTS analyses. The expression of apoptosis-related or signaling proteins was examined using Western blotting analysis. H4 cells were transfected with plasmids carrying mig-2 mutants to determine the functional domain of mig-2.

RESULTS

In the 3 glioma cell lines tested, overexpression of mig-2 significantly attenuated cisplatin-induced apoptosis, whereas knock-down of mig-2 potentiated the apoptosis. The mechanisms of action of mig-2 were further addressed in H4 cells: overexpression of mig-2 markedly reduced cleaved caspase-9, caspase-8, caspase-3 and PARP, as well as p-JNK and p-p38, and increased p-AKT in cisplatin-treated H4 cells, whereas mig-2 siRNA reversely changed these apoptosis-related and signaling proteins. Furthermore, pretreatment with JNK inhibitor SP600125 and p38 inhibitor SB203580, or with AKT inhibitor LY294002 abolished the effects of mig-2 on cisplaxtin-induced apoptosis. In H4 cells, GFP-mig-2 F3 plasmid that contained only the F3 subdomain showed the same efficiency in attenuating cisplatin-induced apoptosis, as the mig-2 wild-type vector did, whereas GFP-mig-2 (1-541) plasmid that lacked the F3 subdomain was inactive.

CONCLUSION

Mig-2 significantly attenuates the antitumor action of cisplatin against human glioma cells in vitro through AKT/JNK and AKT/p38 signaling pathways. The F3 subdomain of mig-2 is necessary and sufficient for this effect.

Increased expression of kindlin 2 in luteinized granulosa cells correlates with androgen receptor level in patients with polycystic ovary syndrome having hyperandrogenemia

Hyperandrogenemia is the leading defect in patients with polycystic ovary syndrome (PCOS) and considered to be involved in the ovulation dysfunction of PCOS. During the process of ovulation, granulosa cells (GCs) undergo epithelial-mesenchymal transition (EMT), and integrin-interacting protein kindlin 2 is a well-known regulator in EMT. Therefore, our objective here was to compare the expression levels of kindlin 2 in luteinized GCs between patients with PCOS and control women and the relationship between kindlin 2 and PCOS pathogenesis. In this study, kindlin 2 expression was significantly increased in luteinized GCs from patients with PCOS, and kindlin 2 could be induced by testosterone both in vitro and in vivo. Meanwhile, kindlin 2 was positively correlated with androgen receptor (AR) in PCOS GCs. Taken together, kindlin 2 may play a role in luteinized GCs, especially in the case of excess androgen. Further studies are required to assess the specific role of kindlin 2 in follicular development and PCOS pathogenesis.

Novel focal adhesion protein kindlin-2 promotes the invasion of gastric cancer cells through phosphorylation of integrin β1 and β3

BACKGROUND

We have found that the expression of the novel focal adhesion protein kindlin-2 had a significant positive correlation with poor survival in gastric cancer. However, the mechanism by which kindlin-2 acts in gastric cancer warrants further evaluation.

METHODS

Kindlin-2 mRNA expression in gastric cancer cell lines was measured by realtime RT-PCR under normal and hypoxic conditions. Cell proliferation, apoptosis, cell cycle, tumor adhesion, cell invasion ability, and phosphorylation of integrin β1 and β3 proteins were measured to assess the influence of kindlin-2 on the malignant behavior of gastric cancer cells.

RESULTS

Kindlin-2 mRNA expression was highest in the distant metastasis gastric cancer cell line Hs-746T. Cell proliferation, adhesion with endothelium and collagen IV, invasion rate, and angiogenesis genes expression, as well as phosphorylation of integrin β1 and β3 in Hs-746T, were decreased significantly after kindlin-2 downregulation, but there was no change in apoptosis and cell cycle.

CONCLUSIONS

Kindlin-2 might promote the invasion of gastric cancer cells through enhancing proliferation and adhesion by the phosphorylation of integrin β1 and β3.

Kindlin-2 mediates activation of TGF-β/Smad signaling and renal fibrosis

Activation of TGF-β/Smad signaling plays a central role in the pathogenesis of tubulointerstitial fibrosis, but the mechanisms underlying the initial interaction of the TGF-β receptor with Smads, leading to their activation, remain unclear. Here, we found that Kindlin-2, an integrin-binding protein, physically mediated the interaction of the TGF-β type I receptor (TβRI) with Smad3 in human kidney tubular epithelial cells. Kindlin-2 bound to TβRI through its FERM domain and to Smad3 through its N terminus. Overexpression of Kindlin-2 increased TGF-β-induced Smad3 activation. Knockdown of Kindlin-2 significantly suppressed the engagement of TβRI with Smad3 and inhibited TGF-β-induced Smad3 activation, as well as the expression of its target genes. Neither transfection of a Kindlin-2 mutant incapable of binding to β1 integrin nor knockdown of β1 integrin influenced the effect of Kindlin-2 on TGF-β1-induced Smad3 activation, indicating that this effect is independent of integrin. Kindlin-2 expression was markedly increased, predominantly in renal tubular epithelial cells, both in the unilateral ureteral obstruction model of kidney fibrosis and in human tissue exhibiting tubulointerstitial fibrosis. Furthermore, in the unilateral ureteral obstruction model, knocking down Kindlin-2 significantly inhibited activation of TGF-β/Smad signaling, decreased the expression of matrix genes, and ameliorated fibrosis. In summary, Kindlin-2 physically interacts with both TβRI and Smad3, promoting the activation of TGF-β/Smad signaling and contributing to the pathogenesis of tubulointerstitial fibrosis. Blockade of Kindlin-2 might be a rational therapeutic strategy for the treatment of fibrotic kidney diseases.

Kindlin-2 expression in peritumoral stroma is associated with poor prognosis in pancreatic ductal adenocarcinoma

OBJECTIVES

Kindlin-2 is a novel focal adhesion protein reported to be expressed in breast, lung, and gastric cancers. This study aimed to investigate the significance of kindlin-2 expression in pancreatic ductal adenocarcinomas (PDACs).

METHODS

We performed immunohistochemical analysis on kindlin-2 on PDAC samples from 95 patients. We investigated the association between kindlin-2 expression and clinicopathological parameters of PDAC and the survival time of patients with PDAC who underwent pancreatectomy.

RESULTS

Kindlin-2 was highly expressed in the peritumoral stroma of PDACs. Stromal kindlin-2 expression was related to nodal metastasis (P = 0.03). Univariate analysis showed that patients with positive kindlin-2 expression had significantly shorter survival times than those with negative kindlin-2 expression (P = 0.01). In addition, multivariate analysis revealed that kindlin-2 expression was an independent factor of poor prognosis in patients with PDAC after R0 resection (RR = 2.15; P = 0.04).

CONCLUSIONS

Kindlin-2 expression in stromal components is significantly associated with poor prognosis of patients with PDAC, suggesting that kindlin-2 is a prognostic marker for patients with PDAC.

Kindlin 2 promotes breast cancer invasion via epigenetic silencing of the microRNA200 gene family

Kindlin 2, as a focal adhesion protein, controls integrin activation and regulates Wnt signaling in an integrin-binding independent manner. However, the association of Kindlin 2 with cancer-related microRNAs is unknown. Here, we report that Kindlin 2 markedly downregulates the expression of miR-200 family by inducing CpG island hypermethylation. Mechanistically, Kindlin 2 forms a complex with DNMT3A in the cell nucleus and the two proteins co-occupy the promoter of miRNA-200b. Functionally, repression of miR-200b is required for Kindlin 2-induced breast cancer cell invasion and tumor formation. Our data indicate that Kindlin 2 plays a novel role in epigenetic repression of miR-200 family, a mechanism that promotes breast cancer invasion.

A feedback regulation between Kindlin-2 and GLI1 in prostate cancer cells

Kindlin-2 is engaged in tumor progression. However, the mechanism accounting for Kindlin-2 regulation in tumor cells remained largely unknown. Here, we report a regulatory loop between Kindlin-2 and GLI1, an effector of Hedgehog signaling pathway. We show that Kindlin-2 is transcriptionally downregulated via GLI1 occupancy on the Kindlin-2 promoter. Adversely, we found that Kindlin-2 promotes GLI1 expression through a mechanism involving GSK3β inactivation and is independent of Smoothened. Functionally, knockdown of Kindlin-2 cooperates with cyclopamine, a Smoothened antagonist, to decrease the viability of prostate cancer cells. Taken together, targeting the Kindlin-2-GLI1 feedback loop may facilitate the killing of prostate cancer cells.

Opposite role of Kindlin-1 and Kindlin-2 in lung cancers

Lung cancer is highly heterogenous and is composed of various subtypes that are in diverse differential stages. The newly identified integrin-interacting proteins Kindlin-1 and Kindlin-2 are the activators of transmembrane receptor integrins that play important roles in cancer progression. In this report we present the expression profiles of Kindlin-1 and Kindlin-2 in lung cancers using patient specimens and established their correlation with lung cancer progression. We found that Kindlin-1 was expressed in epithelia-derived non-small-cell lung cancer, especially in squamous cell lung cancer but expressed at low levels in poorly differentiated large cell lung cancer. However, Kindlin-2 was highly expressed in large cell lung cancer. Both Kindlin-1 and Kindlin-2 were found not expressed or expressed at very low levels in neuroendocrine-derived small cell lung cancer. Importantly, the Kindlin-1 expression level was positively correlated with the differentiation of squamous cell lung cancer. Surprisingly, we found that the very homologous Kindlin family proteins, Kindlin-1 and Kindlin-2, displayed counteracting functional roles in lung cancer cells. Ectopic expression of Kindlin-1 in non-small-cell lung cancer cells inhibited in vitro cell migration and in vivo tumor growth, while Kindlin-2 promoted these functions. Mechanistically, Kindlin-1 prohibited epithelail to mesenchymal transition in non-small-cell lung cancer cells, while Kindlin-2 enhanced epithelail to mesenchymal transition in these cells. Taken together, we demonstrated that Kindlin-1 and Kindlin-2 differentially regulate lung cancer cell progression. Further, the expression levels of Kindlin-1 might be potentially used as a marker for lung cancer differentiation and targeting Kindlin-2 might block the invasive growth of large cell lung cancer.

The novel focal adhesion gene kindlin-2 promotes the invasion of gastric cancer cells mediated by tumor-associated macrophages

Kindlin-2 is a novel focal adhesion gene mediating the cell-extracellular matrix (ECM) adhesion. Tumor-associated macrophages (TAMs) play an important role in linking chronic inflammation to cancer progression. Both kindlin-2 and TAMs have been found to promote the invasion of gastric cancer cells in our previous studies. However, the correlation between kindlin-2 and TAMs remains unclear. Real-time RT-PCR was used to investigate kindlin-2 expression in the AGS, NCI and Hs-746T gastric cancer cell lines co-cultured with TAMs under normal or hypoxic conditions. IL8, IL10, IL11, IL17b, IL18, IL22 and IL24 expressions were measured by real-time RT-PCR in the gastric cancer lines with varying levels of kindlin-2 expression, as well as after downregulation of kindlin-2 mRNA expression by the siRNA method. We found that kindlin-2 was upregulated in all three gastric cancer cell lines when co-cultured with TAMs under normal conditions. Under hypoxic conditions, the induction of kindlin-2 expression induced by macrophages was significantly downregulated in the Hs-746T cell line. IL8, IL11, IL17b, IL22 and IL24 expression was significantly higher in gastric cell lines with high kindlin-2 expression. Downregulation of kindlin-2 mRNA decreased IL10, IL11, IL17b, IL22 and IL24 expression but IL8 and IL18 expression was upregulated. Therefore, the novel focal adhesion gene kindlin-2 may play an important role in promoting the invasion of gastric cancer cells mediated by TAMs through regulating interleukin expression.

Migfilin sensitizes cisplatin-induced apoptosis in human glioma cells in vitro

AIM

Filamin binding LIM protein 1, also known as migfilin, is a skeleton organization protein that binds to mitogen-inducible gene 2 at cell-extracellular matrix adhesions. The aim of this study was to investigate the role of migfilin in cisplatin-induced apoptosis in human glioma cells, to determine the functional domains of migfilin, and to elucidate the molecular mechanisms underlying the regulation of cisplatin-related chemosensitivity.

METHODS

The human glioma cell lines Hs683, H4, and U-87 MG were transfected with pEGFP-C2-migfilin to elevate the expression level of migfilin. RNA interference was used to reduce the expression of migfilin. To determine the functional domains of migfilin, U-87 MG cells were transfected with plasmids of migfilin deletion mutants. After treatment with cisplatin (40 μmol/L) for 24 h, the cell viability was assessed using the MTS assay, and the cell apoptotic was examined using the DAPI staining assay and TUNEL analysis. Expression levels of apoptosis-related proteins were detected by Western blot analysis.

RESULTS

Overexpression of migfilin significantly enhanced cisplatin-induced apoptosis in Hs683, H4, and U-87 MG cells, whereas downregulation of migfilin expression inhibited the chemosensitivity of these cell lines. The N-terminal region of migfilin alone was able to enhance the cisplatin-induced apoptosis. However, despite the existence of the N-terminal region, mutants of migfilin with any one of three LIM domains deleted led to a function loss. Furthermore, apoptotic proteins (PARP and caspase-3) and the anti-apoptotic protein Bcl-xL were modulated by the expression level of migfilin in combination with cisplatin.

CONCLUSION

The LIM1-3 domains of migfilin play a key role in sensitizing glioma cells to cisplatin-induced apoptosis through regulation of apoptosis-related proteins.

Kindlin 2 forms a transcriptional complex with β-catenin and TCF4 to enhance Wnt signalling

Kindlin 2, as a focal adhesion protein, controls integrin activation. However, the association of Kindlin 2 with cancer-related signalling pathways is unknown. Here we identified a new direct interaction between Kindlin 2 and the active β-catenin. Importantly, Kindlin 2 forms a tripartite complex with β-catenin and TCF4. Mechanistically, Kindlin 2 selectively strengthens the occupancy of β-catenin on the Wnt target gene Axin2 and enhances Axin2 gene expression. Functionally, the β-catenin-Axin2-Snail cascade is required for Kindlin 2-induced tumour cell invasion. Our data indicate that Kindlin 2 is a new regulator of Wnt signalling, providing a mechanistic insight into the role of Kindlin 2 in cancer progression.

[Application of capillary electrophoresis in analysis of disease specific proteins]

One of the most urgent things in life science is to find out special proteins related to human diseases. Capillary electrophoresis (CE) shows many advantages in protein analysis, such as high separation efficiency, high speed, low cost, etc. Furthermore, there are many different separation modes and multifarious detectors can be chosen in CE for the analysis of different samples. In this paper, the applications of CE in the analysis of specific proteins, which might associate with some serious diseases, such as tumor, neurodegenerative disease and transfusion transmitted infections, are summarized.