Increased expression of kindlin-2 is correlated with hematogenous metastasis and poor prognosis in patients with clear cell renal cell carcinoma

YBX1 knockdown induces renal cell carcinoma cell apoptosis via Kindlin-2

Among urological tumors, renal cell carcinoma (RCC) is the third-highest mortality rate tumor, and 20%-30% of RCC patients present with metastases at the time of diagnosis. While the treatment of RCC has been improved over the last few years, its mortality stays high. Y-box binding protein 1 (YBX1) is a well-known oncoprotein that has tumor-promoting functions. YBX1 is widely considered to be an attractive therapeutic target in cancer. To develop novel therapeutics to target YBX1, it is of great importance to understand how YBX1 is finely regulated in cancer. Our previous studies showed that YBX1 in RCC cells significantly promoted cell adhesion, migration, and invasion. However, the role of YBX1 in RCC cells apoptosis has not been reported. In this study, we investigated the effect of YBX1 on cell apoptosis and elucidated the mechanisms involved. Results showed that YBX1 regulated RCC cells apoptosis and reactive oxygen species (ROS) generation via Kindlin-2. These findings indicated that YBX1 inhibited RCC cells apoptosis and may serve as a candidate RCC prognostic marker and a potential therapeutic target. Abbreviations: RCC: Renal cell carcinoma; YBX1: Y-box binding protein 1; ROS: Reactive oxygen species; ccRCC: Clear cell renal cell carcinoma; mccRCC: Metastatic clear cell renal cell carcinoma; G3BP1: Ras-GTPase activating protein SH3 domain-binding proteins 1; SPP1: Secreted phosphoprotein 1; NF-κB: Nuclear factor kappa beta; ECM: Extracellular matrix; EMT: Epithelial-mesenchymal transition; PYCR1: Pyrroline-5-carboxylate reductase 1; MEM: Eagle's Minimum Essential Medium; DMEM: Dulbecco's modified Eagle medium; FBS: Fetal bovine serum; PCR: Polymerase chain reaction; shRNA: Short hairpin RNA; siRNA: Small interfering RNA; BSA: Bovine serum albumin; DCFH-DA: 2,7-Dichlorodihydrofluorescein diacetate; FITC: Fluorescein isothiocyanate; PI: Propidium iodide.

Comprehensive analysis of prognostic value and immune infiltration of kindlin family members in non-small cell lung cancer

BACKGROUND

Kindlin Family Members have been reported to be aberrantly expressed in various human cancer types and involved in tumorigenesis, tumor progression, and chemoresistance. However, their roles in non-small cell lung cancer (NSCLC) remain poorly elucidated.

METHODS

We analyzed the prognostic value and immune infiltration of Kindlins in NSCLC through Oncomine, GEPIA, UALCAN, CCLE, Kaplan‑Meier plotter, cBioPortal, TIMER, GeneMANIA, STRING, and DAVID database. Additionally, the mRNA expression levels of Kindlins were verified in 30 paired NSCLC tissues and NSCLC cell lines by real-time PCR.

RESULTS

The expression level of FERMT1 was remarkably increased in NSCLC tissues and NSCLC cell lines, while FERMT2 and FERMT3 were reduced. Kindlins expressions were associated with individual cancer stages and nodal metastasis. We also found that higher expression level of FERMT1 was obviously correlated with worse overall survival (OS) in patients with NSCLC, while higher FERMT2 was strongly associated with better overall survival (OS) and first progression (FP). Additionally, the expression of FERMT2 and FERMT3 were obviously correlated with the immune infiltration of diverse immune cells. Functional enrichment analysis has shown that Kindlins may be significantly correlated with intracellular signal transduction, ATP binding and the PI3K-Akt signaling pathway in NSCLC.

CONCLUSIONS

The research provides a new perspective on the distinct roles of Kindlins in NSCLC and likely has important implications for future novel biomarkers and therapeutic targets in NSCLC.

Kindlins as modulators of breast cancer progression

Kindlin-1 (K1, FERMT1), Kindlin-2 (K2, FERMT2), and Kindlin-3 (K3, FERMT3) are the three members of the kindlin family of adapter proteins found in mammals. One or more kindlins are found in most cell types, K1 primarily in epithelial cells, K3 in primarily hematopoietic cells and also endothelial cells, and K2 is very broadly distributed. The kindlins consist primarily of a 4.1-erzin-radixin-moiesin (FERM) domain, which is transected by a lipid-binding plextrin-homology (PH) domain. Deficiencies of each kindlin in mice and/ or humans have profound pathogenic consequences. The most well-established function of kindlins depends on their ability to participate in the activat integrin adhesion receptors. This function depends on the binding of each kindlin to the beta subunit of integrins where it cooperates with talin to enhance avidity of interactions with cognate extracellular matrix ligands. Deficiencies of many different integrins are lethal, are critical for normal development of mammary tissue, and excessive expression and/or activation of certain integrins are associated with progression and metastasis of breast cancer. However, via its interaction with many other intracellular proteins, kindlins can influence numerous cellular responses. Changes in expression of each of the three kindlins have been reported in association with breast cancer, with several studies indicating that kindlins are among the most upregulated genes in breast cancer. The association of abnormal functions of K2 with breast cancer is particularly extensive with many reports indicating that it is a major driver of breast cancer via its promotion of cancer cell proliferation, survival, adhesion, migration, invasion, the epithelial-to-mesenchymal transition and its influence on macrophage recruitment and phenotype. These associations suggest that the kindlins and their functions represent an intriguing therapeutic target for exploration of breast cancer therapy.

Role of Kindlin-2 in cancer progression and metastasis

Cancer metastasis is a complex and multistep process whereby cancer cells escape the confines of the primary site to establish a new residency at distant sites. This multistep process is also known as the invasion-metastasis cascade. The biological and molecular mechanisms that control the invasion-metastasis cascade, which ultimately leads to the spread of cancer cells into distant sites, remain poorly understood. Kindlin-2 (K2) belongs to the 4.1-ezrin-ridixin-moesin (FERM) domain family of proteins, which interact with the cytoplasmic tails of β-integrin subunits, leading to the activation of extensive biological functions. These biological functions include cell migration, differentiation, cancer initiation, development, and invasion. In this review, we will discuss the various molecular signaling pathways that are regulated by K2 during the invasion-metastasis cascade of cancer tumors. These signaling pathways include TGFβ, Wnt/β-Catenin, Hedgehog, p53 and senescence, and cancer stem cell (CSC) maintenance. We will also discuss the molecular signaling pathways that regulate K2 function both at the transcriptional and the posttranslational levels. Finally, we will consider molecular mechanisms to specifically target K2 as novel therapeutic options for cancer treatment.

Effects of Kindlin-2 on proliferation and migration of VSMC and integrinβ1 andβ3 activity via FAK-PI3K signaling pathway

Vascular hyperplasia after vascular trauma is one of the difficult problems in clinical treatment. Nowadays, there is no effective treatment for vascular hyperplasia. Previous studies have shown that integrinβ1 andβ3 activity play an important role in vascular hyperplasia. Kindlin-2 has been shown to modulate integrinβ1 andβ3 activity in cancer. Therefore, in this study, we hope to explore the relationship between Kindlin-2 and vascular hyperplasia. We overexpressed or knocked down Kindlin-2 by adenovirus. The results showed that Kindlin-2 overexpression could regulate integrinβ1 andβ3 activity through FAK-PIK3 signaling pathways ex vivo and in vivo, thereby affecting the proliferation and migration of VSMC, and then it causes the consequences of vascular hyperplasia. Therefore, Our results show that Kindlin-2 may be a potential target for the treatment of vascular hyperplasia.

GIV•Kindlin Interaction Is Required for Kindlin-Mediated Integrin Recognition and Activation

Cells perceive and respond to the extracellular matrix via integrin receptors; their dysregulation has been implicated in inflammation and cancer metastasis. Here we show that a guanine nucleotide-exchange modulator of trimeric-GTPase Gαi, GIV (a.k.a Girdin), directly binds the integrin adaptor Kindlin-2. A non-canonical short linear motif within the C terminus of GIV binds Kindlin-2-FERM3 domain at a site that is distinct from the binding site for the canonical NPxY motif on the -integrin tail. Binding of GIV to Kindlin-2 allosterically enhances Kindlin-2's affinity for β1-integrin. Consequently, integrin activation and clustering are maximized, which augments cell adhesion, spreading, and invasion. Findings elucidate how the GIV•Kindlin-2 complex has a 2-fold impact: it allosterically synergizes integrin activation and enables β1-integrins to indirectly access and modulate trimeric GTPases via the complex. Furthermore, Cox proportional-hazard models on tumor transcriptomics provide trans-scale evidence of synergistic interactions between GIV•Kindlin-2•β1-integrin on time to progression to metastasis.

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GIV and Kindlin (K2), two integrin adaptors that promote metastasis, bind each other

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Binding of GIV or integrin to K2 allosterically enhances GIV•K2•integrin complexes

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Binding is required for the maximal recruitment of GIV and K2 to active integrins

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Binding facilitates integrin clustering, activation, tumor cell adhesion, invasion

GRIM-19 deficiency promotes clear cell renal cell carcinoma progression and is associated with high TNM stage and Fuhrman grade

Clear cell renal cell carcinoma (ccRCC) exhibits the highest mortality among all urological malignancies. The investigation of the potential disease progression markers can improve ccRCC diagnosis and treatment. Gene associated with retinoid-interferon-induced mortality-19 (GRIM-19) is involved in carcinogenesis and cancer progression in a variety of cancer types including RCC. While, its role in ccRCC remains unclear, this cancer type is considered the most aggressive RCC subtype. In the present study, RT-qPCR, western blotting and immunohistochemical (IHC) assays demonstrated that GRIM-19 protein and mRNA levels were downregulated in ccRCC tumor tissues compared with the corresponding levels noted in paracancerous non-tumor tissues. The deficiency of this protein contributed in relaxed and/or collapsed structures of the kidney tubules and collecting duct noted in tumor tissues. Moreover, the reduction in GRIM-19 expression was associated with high tumor, lymph nodes and metastasis (TNM) stage and Fuhrman grade of ccRCC tumors. The data suggested that GRIM-19 acted as a tumor suppressor and that its deficiency promoted ccRCC development and progression. GRIM-19 can be considered a potential tumor marker for ccRCC.

Prognostic value of Kindlin-2 expression in patients with solid tumors: a meta-analysis

Background

Kindlin-2 is one of the Kindlin family members which are evolutionarily conserved focal adhesion proteins with integrin β-binding affinity. Recently, accumulative studies have suggested that Kindlin-2 plays important roles in tumor biology. However, the prognostic significance of Kindlin-2 in patients with solid tumors remains controversial. Therefore, this study aimed to clarify the prognostic value of Kindlin-2 in solid tumors via meta-analysis.

Methods

A comprehensive search was performed in PubMed, Embase, Web of Science and EBSCO for all relevant studies reporting the prognostic significance of Kindlin-2 expression in solid cancer patients. The summary hazard ratio (HR) and corresponding 95% confidence interval (CI) were calculated to estimate the association between Kindlin-2 expression with survival of solid cancer patients.

Results

We included 14 eligible studies containing 1869 patients in our meta-analysis. The pooled results indicated that high Kindlin-2 expression was significantly associated with poor overall survival (OS) (pooled HR 1.66, 95% CI 1.44–1.92, P < 0.0001), disease-free survival (DFS)/recurrence-free survival (RFS)/progression-free survival (PFS) (pooled HR 1.73, 95% CI 1.16–2.57, P = 0.0067). For certain tumor types, high Kindlin-2 expression was significantly correlated with a poor outcome in patients with solid tumors, including pancreatic ductal adenocarcinoma (DFS/RFS/PFS), esophageal squamous cell carcinoma (OS, DFS/RFS/PFS), hepatocellular carcinoma (OS), clear cell renal cell carcinoma (OS), bladder cancer (OS, DFS/RFS/PFS), chondrosarcoma (OS), osteosarcoma (OS), gastric cancer (DFS/RFS/PFS), and glioma (OS).

Conclusions

Our meta-analysis demonstrated that high Kindlin-2 expression might indicate poor outcome in patients with solid tumors and could serve as a prognostic biomarker for solid cancer patients.

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 promotes hepatocellular carcinoma invasion and metastasis by increasing Wnt/β-catenin signaling

Background

Kindlin-2 is a member of the focal adhesion protein family that regulates invasion and metastasis in multiple malignancies; however, little is known about the role of Kindlin-2 in hepatocellular carcinoma (HCC) progression.

Methods

Immunohistochemistry was used to investigate Kindlin-2 expression in 177 pairs of human HCC and adjacent liver tissue samples. The role of Kindlin-2 in the in vitro invasion and migration of HCC cell lines was evaluated in MHCC97H, LM3 and SMMC7721 cells. Microarray expression analysis was applied to explore the molecular mechanism through which Kindlin-2 promoted HCC progression. Quantitative real-time PCR and Western blotting were performed to verify the microarray results.

Results

High Kindlin-2 expression was found to significantly correlate with aggressive HCC clinicopathological features including tumor encapsulation, microvascular invasion, extrahepatic metastasis and poor prognosis. In vitro, Kindlin-2 knockout or knockdown inhibited HCC cell adhesion, migration and invasion, while ectopic Kindlin-2 expression promoted these processes. Importantly, Kindlin-2 activated Wnt/β-catenin signaling and increased β-catenin expression, especially levels of non-phosphorylated β-catenin, as well as two Wnt/β-catenin signaling pathway targets, Axin2 and MMP7. Kindlin-2 also induced a change in the expression profile of HCC cells, suggesting the cells underwent epithelial-mesenchymal transition. For example, the expression of the epithelial marker E-cadherin was downregulated, while the mesenchymal markers Vimentin, N-cadherin and Snail were upregulated.

Conclusion

Kindlin-2 promotes HCC invasion, metastasis and epithelial-mesenchymal transition through Wnt/β-catenin signaling.

Kindlin-2 Modulates the Survival, Differentiation, and Migration of Induced Pluripotent Cell-Derived Mesenchymal Stromal Cells

Kindlin-2 is a multidomain intracellular protein that can be recruited to β-integrin domains to activate signaling, initiate transcriptional programs, and bind to E-cadherin. To explore its involvement in cell fate decisions in mesenchymal cells, we studied the effects of Kindlin-2 modification (overexpression/knockdown) in induced pluripotent cell-derived mesenchymal stromal cells (iPSC-MSCs). Kindlin-2 overexpression resulted in increased proliferation and reduced apoptosis of iPSC-MSCs, as well as inhibition of their differentiation towards osteocytes, adipocytes, and chondrocytes. In contrast, siRNA-mediated Kindlin-2 knockdown induced increased apoptosis and increased differentiation response in iPSC-MSCs. The ability of iPSC-MSCs to adhere to VCAM-1/SDF-1α under shear stress and to migrate in a wound scratch assay was significantly increased after Kindlin-2 overexpression. In contrast, inhibition of mixed lymphocyte reaction (MLR) was generally independent of Kindlin-2 modulation in iPSC-MSCs, except for decreased production of interleukin-2 (IL-2) after Kindlin-2 overexpression in iPS-MSCs. Thus, Kindlin-2 upregulates survival, proliferation, stemness, and migration potential in iPSC-MSCs and may therefore be beneficial in optimizing performance of iPSC-MSC in therapies.

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.