Kindlin-2 induced by TGF-β signaling promotes pancreatic ductal adenocarcinoma progression through downregulation of transcriptional factor HOXB9

Cold atmospheric plasma enhances SLC7A11-mediated ferroptosis in non-small cell lung cancer by regulating PCAF mediated HOXB9 acetylation

Lung cancer is a leading cause of cancer death worldwide, with high incidence and poor survival rates. Cold atmospheric plasma (CAP) technology has emerged as a promising therapeutic approach for cancer treatment, inducing oxidative stress in malignant tissues without causing thermal damage. However, the role of CAP in regulating lung cancer cell ferroptosis remains unclear. Here, we observed that CAP effectively suppressed the growth and migration abilities of lung cancer cells, with significantly increased ferroptotic cell death, lipid peroxidation, and decreased mitochondrial membrane potential. Mechanistically, CAP regulates SLC7A11-mediated cell ferroptosis by modulating HOXB9. SLC7A11, a potent ferroptosis suppressor, was markedly reduced by HOXB9 knockdown, while it was enhanced by overexpressing HOXB9. The luciferase and ChIP assays confirmed that HOXB9 can directly target SLC7A11 and regulate its gene transcription. Additionally, CAP enhanced the acetylation modification level of HOXB9 by promoting its interaction with acetyltransferase p300/CBP-associated factor (PCAF). Acetylated HOXB9 affects its protein ubiquitination modification level, which in turn affects its protein stability. Notably, the upregulation of SLC7A11 and HOXB9 mitigated the suppressive effects of CAP on ferroptosis status, cell proliferation, invasion, and migration in lung cancer cells. Furthermore, animal models have also confirmed that CAP can inhibit the progression of lung cancer in vivo. Overall, this study highlights the significance of the downregulation of the HOXB9/SLC7A11 axis by CAP treatment in inhibiting lung cancer, offering novel insights into the potential mechanisms and therapeutic strategies of CAP for lung cancer.

Engineered extracellular vesicles for targeted reprogramming of cancer-associated fibroblasts to potentiate therapy of pancreatic cancer

Pancreatic cancer is one of the deadly malignancies with a significant mortality rate and there are currently few therapeutic options for it. The tumor microenvironment (TME) in pancreatic cancer, distinguished by fibrosis and the existence of cancer-associated fibroblasts (CAFs), exerts a pivotal influence on both tumor advancement and resistance to therapy. Recent advancements in the field of engineered extracellular vesicles (EVs) offer novel avenues for targeted therapy in pancreatic cancer. This study aimed to develop engineered EVs for the targeted reprogramming of CAFs and modulating the TME in pancreatic cancer. EVs obtained from bone marrow mesenchymal stem cells (BMSCs) were loaded with miR-138-5p and the anti-fibrotic agent pirfenidone (PFD) and subjected to surface modification with integrin α5-targeting peptides (named IEVs-PFD/138) to reprogram CAFs and suppress their pro-tumorigenic effects. Integrin α5-targeting peptide modification enhanced the CAF-targeting ability of EVs. miR-138-5p directly inhibited the formation of the FERMT2-TGFBR1 complex, inhibiting TGF-β signaling pathway activation. In addition, miR-138-5p inhibited proline-mediated collagen synthesis by directly targeting the FERMT2-PYCR1 complex. The combination of miR-138-5p and PFD in EVs synergistically promoted CAF reprogramming and suppressed the pro-cancer effects of CAFs. Preclinical experiments using the orthotopic stroma-rich and patient-derived xenograft mouse models yielded promising results. In particular, IEVs-PFD/138 effectively reprogrammed CAFs and remodeled TME, which resulted in decreased tumor pressure, enhanced gemcitabine perfusion, tumor hypoxia amelioration, and greater sensitivity of cancer cells to chemotherapy. Thus, the strategy developed in this study can improve chemotherapy outcomes. Utilizing IEVs-PFD/138 as a targeted therapeutic agent to modulate CAFs and the TME represents a promising therapeutic approach for pancreatic cancer.

MFG-E8 induces epithelial-mesenchymal transition and anoikis resistance to promote the metastasis of pancreatic cancer cells

Pancreatic cancer is an extremely malignant tumor, and only a few clinical treatment options exist. MFG-E8 and kindlin-2 all play an important role in cancer progression. However, the specific mechanism occurring between MFG-E8, kindlin-2 and the migration and invasion of pancreatic cancer cells remains unelucidated. To unravel the specific mechanism, this study assessed the potential association between MFG-E8 and kindlin-2 as well as the involvement of MFG-E8 in pancreatic cancer using two pancreatic cancer cell lines (MiaPaCa-2 and PANC-1). Pancreatic cancer cells were treated with 0, 250, and 500 ng/ml MFG-E8, and the effects of MFG-E8 on the migration, invasion, and anoikis of pancreatic cancer cells were observed. To investigate the role of kindlin-2 in pancreatic cancer, kindlin-2-shRNAi was transfected to knock down its expression level in the two pancreatic cancer cell lines. Furthermore, cilengitide, a receptor blocker of MFG-E8, was used to explore the relationship between MFG-E8, kindlin-2, and pancreatic cancer progression. Our findings demonstrated that MFG-E8 promotes the migration and invasion of pancreatic cancer cells and induces cell anoikis resistance in a dose-dependent manner, which was effectively counteracted by cilengitide, a receptor blocker. Additionally, the knockdown of kindlin-2 expression nullified the effect of MFG-E8 on the migration and invasion of pancreatic cancer cells. Consequently, this study provides insights into the specific mechanism underlying the interplay between MFG-E8 and kindlin-2 in the progression of pancreatic cancer cells.

Kindlin-2 Regulates the Oncogenic Activities of Integrins and TGF-β In Triple Negative Breast Cancer Progression and Metastasis

Background

Kindlin-2, an adaptor protein, is dysregulated in various human cancers, including triple negative breast cancer (TNBC), where it drives tumor progression and metastasis by influencing several cancer hallmarks. One well-established role of Kindlin-2 involves the regulation of integrin signaling, achieved by directly binding to the cytoplasmic tail of the integrin β subunit. In this study, we present novel insights into Kindlin-2's involvement in stabilizing the β1-Integrin:TGF-β type 1 receptor (TβRI) complexes, acting as a physical bridge that links β1-Integrin to TβRI. The loss of Kindlin-2 results in the degradation of this protein complex, leading to the inhibition of downstream oncogenic pathways.

Methods

Our methodology encompassed a diverse range of in vitro assays, including CRISPR/Cas9 gene editing, cell migration, 3D tumorsphere formation and invasion, solid binding, co-immunoprecipitation, cell adhesion and spreading assays, as well as western blot and flow cytometry analyses, utilizing MDA-MB-231 and 4T1 TNBC cell lines. Additionally, preclinical in vivo mouse models of TNBC tumor progression and metastasis were employed to substantiate our findings.

Results

The investigation revealed that the direct interaction between Kindlin-2 and β1-Integrin is mediated through the C-terminal F3 domain of Kindlin-2, while the interaction between Kindlin-2 and TβRI is facilitated through the F2 domain of Kindlin-2. Disruption of this bridge, achieved via CRISPR/Cas9-mediated knockout of Kindlin-2, led to the degradation of β1-Integrin and TβRI, resulting in the inhibition of oncogenic pathways downstream of both proteins, subsequently hindering tumor growth and metastasis. Treatment of Kindlin-2-deficient cells with the proteasome inhibitor MG-132 restored the expression of both β1-Integrin and TβRI. Furthermore, the rescue of Kindlin-2 expression reinstated their oncogenic activities both in vitro and in vivo.

Conclusions

This study identifies a novel function of Kindlin-2 in stabilizing the β1-Integrin:TβR1 complexes and regulating their downstream oncogenic signaling. The translational implications of these findings are substantial, potentially unveiling new therapeutically targeted pathways crucial for the treatment of TNBC tumors.

FRMD8 targets both CDK4 activation and RB degradation to suppress colon cancer growth

Cyclin-dependent kinase 4 (CDK4) and retinoblastoma protein (RB) are both important cell-cycle regulators that function in different scenarios. Here, we report that FERM domain-containing 8 (FRMD8) inhibits CDK4 activation and stabilizes RB, thereby causing cell-cycle arrest and inhibiting colorectal cancer (CRC) cell growth. FRMD8 interacts separately with CDK7 and CDK4, and it disrupts the interaction of CDK7 with CDK4, subsequently inhibiting CDK4 activation. FRMD8 competes with MDM2 to bind RB and attenuates MDM2-mediated RB degradation. Frmd8 deficiency in mice accelerates azoxymethane/dextran-sodium-sulfate-induced colorectal adenoma formation. The FRMD8 promoter is hypermethylated, and low expression of FRMD8 predicts poor prognosis in CRC patients. Further, we identify an LKCHE-containing FRMD8 peptide that blocks MDM2 binding to RB and stabilizes RB. Combined application of the CDK4 inhibitor and FRMD8 peptide leads to marked suppression of CRC cell growth. Therefore, using an LKCHE-containing peptide to interfere with the MDM2-RB interaction may have therapeutic value in CDK4/6 inhibitor-resistant patients.

Identification of HOXB9 to predict prognosis of endometrial cancer based on comprehensive bioinformatics analysis

BACKGROUND

The HOXB9 gene, which plays a key role in embryonic development, is also involved in the regulation of various human cancers. However, the potential relationship between HOXB9 and endometrial cancer (EC) has not yet been comprehensively analyzed and fully understood.

METHODS

We used multiple bioinformatics tools to explore the role of HOXB9 in EC.

RESULTS

The expression of HOXB9 was significantly upregulated in pan-cancer, including EC (P < 0.05). Quantitative real time polymerase chain reaction (qRT-PCR) experiment confirmed the high expression of HOXB9 in EC from clinical samples (P < 0.001). Double validated by Enrichr and Metascape, HOXB9 showed a strong correlation with HOX family, suggesting that HOX family may also involve in the development of EC (P < 0.05). Enrichment analysis revealed HOXB9 is mainly associated with cellular process, developmental process, P53 signaling pathway, etc. At the single-cell level, the clusters of cells ranked were glandular and luminal cells c-24, glandular and luminal cells c-9, endothelial cells c-15, compared with the other cells. At the genetic level, promoter methylation levels of HOXB9 were significantly higher in tumors than in normal tissues. Furthermore, variations of HOXB9 were closely associated with overall survival (OS) and recurrence free survival (RFS) in EC patients (P < 0.05). The agreement between univariate and multivariate Cox regression indicated that the results were more reliable. Stages III and IV, G2 and G3, tumor invasion ≥ 50%, mixed or serous histological type, age > 60 years, and high expression of HOXB9 were risk factors strongly associated with OS in EC patients (P < 0.05). Therefore, six factors were incorporated to construct a nomogram for survival prediction. Finally, we used the Kaplan-Meier (KM) curve, receiver operating characteristic (ROC) curve, and time-dependent ROC to assess predictive power of HOXB9. KM curve showed EC patients overexpressing HOXB9 had a worse OS. AUC of diagnostic ROC was 0.880. AUCs of time-dependent ROC were 0.602, 0.591, and 0.706 for 1-year, 5-year, and 10-year survival probabilities (P < 0.001).

CONCLUSIONS

Our study provids new insights into the diagnosis and prognosis of HOXB9 in EC and constructs a model that can accurately predict the prognosis of EC.

[Kindlin-2 regulates endometrium development via mTOR and Hippo signaling pathways in mice]

OBJECTIVE

To investigate the effects and mechanisms of Kindlin-2 on uterus development and reproductive capacity in female mice.

METHODS

Cdh16-Cre tool mice and Kindlin-2^flox/flox mice were used to construct the mouse model of uterus specific knockout of Kindlin-2, and the effects of Kindlin-2 deletion on uterine development and reproduction capacity of female mice were observed. High expression and knockdown of Kindlin-2 in endometrial cancer cell lines HEC-1 and Ish were used to detect the regulation of mammalian target of rapamycin (mTOR) signaling pathway. In addition, uterine proteins of the female mice with specific knockout of Kindlin-2 and female mice in the control group were extracted to detect the protein levels of key molecules of mTOR signaling pathway and Hippo signaling pathway.

RESULTS

The mouse model of uterine specific knockout of Kindlin-2 was successfully constructed. The knockout efficiency of Kindlin-2 in mouse uterus was identified and verified by mouse tail polymerase chain reaction (PCR), Western blot protein identification, immunohistochemical staining (IHC) and other methods. Compared with the control group, the female mice with uterus specific deletion of Kindlin-2 lost weight, seriously impaired reproductive ability, and the number of newborn mice decreased, but the proportion of the female mice and male mice in the newborn mice did not change. Hematoxylin eosin staining (HE) experiment showed that the endometrium of Kindlin-2 knockout group was incomplete and the thickness of uterine wall became thinner. In terms of mechanism, the deletion of Kindlin-2 in endo-metrial cancer cell lines HEC-1 and Ish could downregulate the protein levels of mTOR, phosphorylated mTOR, adenosine monophosphate-activated protein kinase (AMPK), phosphorylated AMPK and phosphorylated ribosomal protein S6 (S6), and the mTOR signal pathway was inhibited. It was found that the specific deletion of Kindlin-2 could upregulate the protein levels of Mps one binding 1 (MOB1) and phosphorylated Yes-associated protein (YAP) in the uterus of the female mice, and the Hippo signal pathway was activated.

CONCLUSION

Kindlin-2 inhibits the development of uterus by inhibiting mTOR signal pathway and activating Hippo signal pathway, thereby inhibiting the fertility of female mice.

Homeobox B9 Promotes the Progression of Hepatocellular Carcinoma via TGF-β1/Smad and ERK1/2 Signaling Pathways

Objectives

Homeobox B9 (HOXB9), a homeodomain-containing transcription factor, may play a role in hepatocellular carcinoma (HCC) progression. However, the exact mechanisms underlying its action remain unclear. Materials and methods. Immunohistochemistry was used to investigate the expression of HOBX9 and its prognostic values in HCC patients. HCC cells were transfected with pBabe-HOXB9 and shHOXB9 plasmids, and MTT assay, Transwell assays, and xenograft mouse models were employed to determine the effects of HOXB9 on HCC cell proliferation, migration, and invasion in vitro and in vivo. The biological mechanisms involved in the role of HOXB9 were determined with Western blot and RT-qPCR methods.

Results

HOXB9 expression was significantly increased in HCC tissues and cell lines. Patients with higher HOXB9 levels were associated with poor prognosis. Overexpression of HOXB9 in BEL-7405 cells promoted proliferation, migration, and invasion, whereas knockdown of HOXB9 in HepG2 cells significantly reduced cell proliferation, migration, and invasion abilities. Mechanically, a positive correlation was found between HOXB9 expression and transforming growth factor-β1 (TGF-β1) and extracellular signal-regulated kinase (ERK)1/2 pathway in HCC tissues. HOXB9 overexpression stimulated TGF-β1/Smads signaling pathway in BEL-7405 cells. In contrast, HOXB9 knockdown inhibited the TGF-β1/Smads signaling pathway in HepG2 cells. In addition, the treatment with TGF-β1 inhibitor, LY364947, significantly reserved HOXB9 overexpression-induced cell proliferation, migration, and invasion abilities.

Conclusions

These findings validated that HOXB9 promoted proliferation, migration, and invasion in HCC cells by stimulating the TGF-β1/Smads and ERK1/2 signaling pathway. HOXB9 could be a promising prognostic biomarker and a potential therapeutic target in HCC.

The Role of Feedback Loops in Targeted Therapy for Pancreatic Cancer

Pancreatic cancer is the leading cause of cancer-related deaths worldwide, with limited treatment options and low long-term survival rates. The complex and variable signal regulation networks are one of the important reasons why it is difficult for pancreatic cancer to develop precise targeted therapy drugs. Numerous studies have associated feedback loop regulation with the development and therapeutic response of cancers including pancreatic cancer. Therefore, we review researches on the role of feedback loops in the progression of pancreatic cancer, and summarize the connection between feedback loops and several signaling pathways in pancreatic cancer, as well as recent advances in the intervention of feedback loops in pancreatic cancer treatment, highlighting the potential of capitalizing on feedback loops modulation in targeted therapy for pancreatic cancer.

HOXB9 blocks cell cycle progression to inhibit pancreatic cancer cell proliferation through the DNMT1/RBL2/c-Myc axis

Homeobox B9 (HOXB9) is involved in the occurrence and development of malignant tumors. However, the functions and underlying molecular mechanisms of HOXB9 in pancreatic cancer have yet to be identified. In this study, we find that both HOXB9 mRNA and protein levels are down-regulated in pancreatic cancer tissues and cell lines. Kaplan-Meier survival plots of 150 pancreatic cancer cases show that higher expression of HOXB9 in pancreatic cancer patients is associated with higher survival rates. We also find that over-expression of HOXB9 inhibits pancreatic cancer cell proliferation both in cell lines and the nude mouse xenograft as well as PDX models. Applying cell cycle PCR array analysis, Flow CytoMetry, ChIP-qPCR, and luciferase experiments, we observe that HOXB9 blocks cell cycle progression in the G0/G1 phase via up-regulating RBL2 and inhibiting c-Myc, and we further find that DNMT1 inhibits the expression of HOXB9 in pancreatic cancer by promoting the methylation of its promoter. Our findings highlight a novel mechanism of the DNMT1/HOXB9/RBL2/c-Myc pathway in regulating the cell cycle and proliferation of pancreatic cancer cells and provide a research basis for the prognosis and therapeutic application of HOXB9 in pancreatic cancer.

Targeted Deletion of Kindlin-2 in Mouse Mammary Glands Inhibits Tumor Growth, Invasion, and Metastasis Downstream of a TGF-β/EGF Oncogenic Signaling Pathway

Breast cancer (BC) is one of the leading causes of cancer-related deaths due in part to its invasive and metastatic properties. Kindlin-2 (FERMT2) is associated with the pathogenesis of several cancers. Although the role of Kindlin-2 in regulating the invasion-metastasis cascade in BC is widely documented, its function in BC initiation and progression remains to be fully elucidated. Accordingly, we generated a floxed mouse strain by targeting the Fermt2 (K2^lox/lox) locus, followed by tissue-specific deletion of Kindlin-2 in the myoepithelial compartment of the mammary glands by crossing the K2^lox/lox mice with K14-Cre mice. Loss of Kindlin-2 in mammary epithelial cells (MECs) showed no deleterious effects on mammary gland development, fertility, and lactation in mice bearing Kindlin-2-deletion. However, in a syngeneic mouse model of BC, mammary gland, specific knockout of Kindlin-2 inhibited the growth and metastasis of murine E0771 BC cells inoculated into the mammary fat pads. However, injecting the E0771 cells into the lateral tail vein of Kindlin-2-deleted mice had no effect on tumor colonization in the lungs, thereby establishing a critical role of MEC Kindlin-2 in supporting BC tumor growth and metastasis. Mechanistically, we found the MEC Kindlin-2-mediated inhibition of tumor growth and metastasis is accomplished through its regulation of the TGF-β/ERK MAP kinase signaling axis. Thus, Kindlin-2 within the mammary gland microenvironment facilitates the progression and metastasis of BC.

Single-cell RNA transcriptome reveals the intra-tumoral heterogeneity and regulators underlying tumor progression in metastatic pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) is the most frequent and aggressive pancreatic tumor characterized by high metastatic risk and special tumor microenvironment. To comprehensively delineate the complex intra-tumoral heterogeneity and the underlying mechanism during metastatic lesions malignant progression, single-cell RNA sequencing (scRNA-seq) was employed. PCA and TSNE were used for dimensionality reduction analysis and cell clustering. Find All Markers function was used to calculate differential genes in each cluster, and Do Heatmap function was used to plot the distribution of differential genes in each cluster. GSVA was employed to assign pathway activity estimates to individual cells. Lineage trajectory progression was inferred by monocle. CNV status was inferred to compare the heterogeneity among patients and subtypes by infercnv. Ligand-receptor interactions were identified by CellPhoneDB, and regulons network of cells was analyzed by SCENIC. Through RNA-sequencing of 6236 individual cells from 5 liver metastatic PDAC lesions, 10 major cell clusters are identified by using unbiased clustering analysis of expression profiling and well-known cell markers. Cells with high CNV level were considered as malignant cells and pathway analyses were carried out to highlight intratumor heterogeneity in PDAC. Pseudotime trajectory analysis revealed that components of multiple tumor-related pathways and transcription factors (TFs) were differentially expressed along PDAC progression. The complex cellular communication suggested potential immunotherapeutic targets in PDAC. Regulon network identified multiple candidates for promising cell-specific transcriptional factors. Finally, metastatic-related genes expression levels and signaling pathways were validated in bulk RNA Sequencing data. This study contributed a comprehensive single-cell transcriptome atlas and contributed into novel insight of intratumor heterogeneity and molecular mechanism in metastatic PDAC.

Kindlin-2 promoted the progression of keloids through the Smad pathway and Fas/FasL pathway

Keloids are benign skin tumors characterized by aggressive growth. To date, there is no exact treatment because little is known about its pathological mechanism. Therefore, it is important to investigate the mechanism of its occurrence and development to identify therapeutic targets. In this study, the expression of Kindlin-2 was higher in keloid fibroblasts (KFs) than in normal skin fibroblasts (NFs). In vitro experiments showed that knocking down Kindlin-2 in KFs could promote cell apoptosis and inhibit cell proliferation, cell migration and invasion, and contractile capability. Western blot results showed that the phosphorylation of Smad3 in KFs was inhibited after knocking down Kindlin-2, inhibiting the activation of the Smad pathway. Moreover, knocking down Kindlin-2 increased the expression of Fas and FasL in KFs, which demonstrated that knocking down Kindlin-2 promoted the activation of the exogenous apoptotic pathway of KFs and then facilitated apoptosis. The above results revealed that knocking down Kindlin-2 in KFs can inhibit the activation of the Smad pathway and promote the activation of the Fas/FasL exogenous apoptosis pathway, thereby altering the cytological function of KFs. Therefore, Kindlin-2 might play an important role in the occurrence and development of keloids and could become a new target to treat keloids.

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.

Integrin β1 Promotes Pancreatic Tumor Growth by Upregulating Kindlin-2 and TGF-β Receptor-2

The tumor microenvironment plays a critical role in defining the growth and malignancy of solid tumors. Extracellular matrix (ECM) proteins such as collagen, vitronectin, and fibronectin are major components of the tumor microenvironment. Tumor growth-promoting reciprocal interaction between ECM and cytoplasmic proteins is regulated by the cell surface receptors called integrins. This study investigated the mechanism by which integrin β1 promotes pancreatic tumor growth. In MIA PaCa-2 pancreatic cancer cell line, the loss of integrin β1 protein reduced the ability of cells to proliferate in a 3D matrix and compromised the ability to form a focal adhesion complex. Decreased expression of integrin α5 was observed in KO cells, which resulted in impaired cell spreading and adhesion on vitronectin and fibronectin. Reduced expression of the integrin-associated protein, kindlin-2 was also recorded. The downregulation of kindlin-2 decreased the phosphorylation of Smad2/3 by reducing the expression of TGF-β receptor 2. These results unravel a new mechanism of integrin β1 in tumor growth by modifying the expression of kindlin-2 and TGF-β receptor 2 signaling.

Phenotypic Plasticity Conferred by the Metastatic Microenvironment of the Brain Strengthens the Intracranial Tumorigenicity of Lung Tumor Cells

Lung cancer is the leading cause of cancer-related deaths and is the primary source of brain metastases. Despite great advances in the study of the genetics and etiology of lung cancer in previous decades, the identification of the factors and mechanisms underlying the brain metastasis of lung tumors is still an open question. In this study, the results of bioinformatic conjoint analysis revealed that the metastatic microenvironment in the brain conferred lung tumor cell phenotypic plasticity, characterized by neural cell-like and embryonic–stem cell-like features. Meanwhile, the metabolic phenotype of the educated tumor cells underwent transition characterized by oxygen-related metabolism. The results of the experiments demonstrated that the downregulation of HOXB9 weakened the tumorigenicity of lung tumor cells. Bioinformatic prediction analysis also determined that many cell cycle-associated factors were potentially transcribed by HOXB9. Collectively, the results of this study suggested that under the influence of the metastatic environment of the brain, lung tumor cells seemed to acquire phenotypic plasticity characterized by neural cell-like features, and this transition may be associated with the aberrant upregulation of HOXB9.

Kindlin-2 Mediates Mechanical Activation of Cardiac Myofibroblasts

We identify the focal adhesion protein kindlin-2 as player in a novel mechanotransduction pathway that controls profibrotic cardiac fibroblast to myofibroblast activation. Kindlin-2 is co-upregulated with the myofibroblast marker α-smooth muscle actin (α-SMA) in fibrotic rat hearts and in human cardiac fibroblasts exposed to fibrosis-stiff culture substrates and pro-fibrotic TGF-β1. Stressing fibroblasts using ferromagnetic microbeads, stretchable silicone membranes, and cell contraction agonists all result in kindlin-2 translocation to the nucleus. Overexpression of full-length kindlin-2 but not of kindlin-2 missing a putative nuclear localization sequence (∆NLS kindlin-2) results in increased α-SMA promoter activity. Downregulating kindlin-2 with siRNA leads to decreased myofibroblast contraction and reduced α-SMA expression, which is dependent on CC(A/T)-rich GG(CArG) box elements in the α-SMA promoter. Lost myofibroblast features under kindlin-2 knockdown are rescued with wild-type but not ∆NLS kindlin-2, indicating that myofibroblast control by kindlin-2 requires its nuclear translocation. Because kindlin-2 can act as a mechanotransducer regulating the transcription of α-SMA, it is a potential target to interfere with myofibroblast activation in tissue fibrosis.

Kindlin-2 Inhibits the Hippo Signaling Pathway by Promoting Degradation of MOB1

The Hippo signaling pathway plays a key role in development and cancer progression. However, molecules that intrinsically inhibit this pathway are less well known. Here, we report that the focal adhesion molecule Kindlin-2 inhibits Hippo signaling by interacting with and degrading MOB1 and promoting the interaction between MOB1 and the E3 ligase praja2. Kindlin-2 thus inhibits the phosphorylation of LATS1 and YAP and promotes YAP translocation into the nucleus, where it activates downstream Hippo target gene transcription. Kindlin-2 depletion activates Hippo/YAP signaling and alleviates renal fibrosis in Kindlin-2 knockout mice with unilateral ureteral occlusion (UUO). Moreover, Kindlin-2 levels are negatively correlated with MOB1 and phosphorylated (p) YAP in samples from patients with renal fibrosis. Altogether, these results demonstrate that Kindlin-2 inhibits Hippo signaling through degradation of MOB1. A specific long-lasting siRNA against Kindlin-2 effectively alleviated UUO-induced renal fibrosis and could be a potential therapy for renal fibrosis.

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.

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

HIF-1α interacts with Kindlin-2 and influences breast cancer elasticity: A study based on shear wave elastography imaging

Breast cancer was the most frequent and the second most deadly cancer in women in 2018 in China; thus, early diagnosis of breast cancer is important. Studies have reported that tissue stiffness promotes cancer progression through increased collagen or fibrosis. Shear wave elastography (SWE) is a technique for measuring tissue stiffness. However, the mechanisms underlying cancer tissue stiffness or fibrosis are not entirely clear. Hypoxia‐inducible factor 1 (HIF‐1α) is expressed in response to hypoxia and contributes to tumor progression and metastasis. Kindlin‐2 is an important co‐activator of integrin. We have reported that Kindlin‐2 influences breast cancer stiffness and metastasis. In this study, SWE was used to determine the maximum elasticity (E_max) of patients before operation or core needle biopsy. The specimens were used for staining. Knockdown, overexpression, co‐immunoprecipitation, and immunofluorescence assays were used to explore the relationship between HIF‐1α and Kindlin‐2. We found that HIF‐1α and Kindlin‐2 were highly expressed in invasive breast cancer and that the expression levels of HIF‐1α and Kindlin‐2 were correlated with E_max. HIF‐1α interacts with Kindlin‐2. Besides, HIF‐1α and Kindlin‐2 influence the expression of P4HA1, an important protein in collagen biogenesis through the integrin/FAK pathway. Our study first identified a new mechanism of invasive breast cancer stiffness by linking HIF‐1α and Kindlin‐2 to collagen biogenesis. Therefore, based on SWE, E_max could be a physical biomarker of invasive breast cancer for early, noninvasive diagnosis, and HIF‐1α and Kindlin‐2 could be pathological markers for early diagnosis and targeted therapy.

Tumor-associated macrophages regulate gastric cancer cell invasion and metastasis through TGFβ2/NF-κB/Kindlin-2 axis

Objective

Recent studies have shown that tumor-associated macrophages (TAMs) play an important role in cancer invasion and metastasis. Our previous studies have reported that TAMs promote the invasion and metastasis of gastric cancer (GC) cells through the Kindlin-2 pathway. However, the mechanism needs to be clarified.

Methods

THP-1 monocytes were induced by PMA/interleukin (IL)-4/IL-13 to establish an efficient TAM model in vitro and M2 macrophages were isolated via flow cytometry. A dual luciferase reporter system and chromatin immunoprecipitation (ChIP) assay were used to investigate the mechanism of transforming growth factor β2 (TGFβ2) regulating Kindlin-2 expression. Immunohistochemistry was used to study the relationships among TAM infiltration in human GC tissues, Kindlin-2 protein expression, clinicopathological parameters and prognosis in human GC tissues. A nude mouse oncogenesis model was used to verify the invasion and metastasis mechanisms in vivo.

Results

We found that Kindlin-2 expression was upregulated at both mRNA and protein levels in GC cells cocultured with TAMs, associated with higher invasion rate. Kindlin-2 knockdown reduced the invasion rate of GC cells under coculture condition. TGFβ2 secreted by TAMs regulated the expression of Kindlin-2 through the transcription factor NF-кB. TAMs thus participated in the progression of GC through the TGFβ2/NF-κB/Kindlin-2 axis. Kindlin-2 expression and TAM infiltration were significantly positively correlated with TNM stage, and patients with high Kindlin-2 expression had significantly poorer overall survival than patients with low Kindlin-2 expression. Furthermore, Kindlin-2 promoted the invasion of GC cells in vivo.

Conclusions

This study elucidates the mechanism of TAMs participating in GC cell invasion and metastasis through the TGFβ2/NF-κB/Kindlin-2 axis, providing a possibility for new treatment options and approaches.

HOX family transcription factors: Related signaling pathways and post-translational modifications in cancer

HOX family transcription factors belong to a highly conserved subgroup of the homeobox superfamily that determines cellular fates in embryonic morphogenesis and the maintenance of adult tissue architecture. HOX family transcription factors play key roles in numerous cellular processes including cell growth, differentiation, apoptosis, motility, and angiogenesis. As tumor promoters or suppressors HOX family members have been reported to be closely related with a variety of cancers. They closely regulate tumor initiation and growth, invasion and metastasis, angiogenesis, anti-cancer drug resistance and stem cell origin. Here, we firstly described the pivotal roles of HOX transcription factors in tumorigenesis. Then, we summarized the main signaling pathways regulated by HOX transcription factors, including Wnt/β-catenin, transforming growth factor β, mitogen-activated protein kinase, phosphoinositide 3-kinase/Akt, and nuclear factor-κB signalings. Finally, we outlined the important post-translational modifications of HOX transcription factors and their regulation in cancers. Future research directions on the HOX transcription factors are also discussed.

Wnt-11 Expression Promotes Invasiveness and Correlates with Survival in Human Pancreatic Ductal Adeno Carcinoma

Pancreatic ductal adenocarcinoma (PDAC) is one of the deadliest forms of cancer, proving difficult to manage clinically. Wnt-11, a developmentally regulated gene producing a secreted protein, has been associated with various carcinomas but has not previously been studied in PDAC. The present study aimed to elucidate these aspects first in vitro and then in a clinical setting in vivo. Molecular analyses of Wnt-11 expression as well as other biomarkers involved qRT-PCR, RNA-seq and siRNA. Proliferation was measured by MTT; invasiveness was quantified by Boyden chamber (Matrigel) assay. Wnt-11 mRNA was present in three different human PDAC cell lines. Wnt-11 loss affected epithelial-mesenchymal transition and expression of neuronal and stemness biomarkers associated with metastasis. Indeed, silencing Wnt-11 in Panc-1 cells significantly inhibited their Matrigel invasiveness without affecting their proliferative activity. Consistently with the in vitro data, human biopsies of PDAC showed significantly higher Wnt-11 mRNA levels compared with matched adjacent tissues. Expression was significantly upregulated during PDAC progression (TNM stage I to II) and maintained (TNM stages III and IV). Wnt-11 is expressed in PDAC in vitro and in vivo and plays a significant role in the pathophysiology of the disease; this evidence leads to the conclusion that Wnt-11 could serve as a novel, functional biomarker PDAC.

Elevated kindlin-2 promotes tumour progression and angiogenesis through the mTOR/VEGFA pathway in melanoma

Background: In our previous study, kindlin-2 promoted skin wound healing and decreased the permeability of neovascularization during angiogenesis. Herein, we explored the biological function and underlying mechanism of kindlin-2 in cutaneous melanoma.

Methods and Results: Through a series of in vitro assays, we found that high levels of kindlin-2 promoted migration and invasion of melanoma cells without influencing cell proliferation. Quantitative real-time polymerase chain reaction (qRT-PCR) and western blot analyses showed that upregulated kindlin-2 promoted the cellular epithelial-mesenchymal transition (EMT). Importantly, we found that melanoma cells overexpressing kindlin-2 promoted angiogenesis and VEGFA secretion in vitro and facilitated tumour growth and lung metastasis in vivo. To unveil the underlying mechanism, we conducted Next-generation sequencing (NGS) and differential expression analyses. Kyoto Encyclopedia of Genes and Genomes (KEGG) analysis showed that overlapping differentially expressed genes (DEGs) were primarily enriched in the TGF-β, mTOR and VEGF signalling pathways. Then, we confirmed that the mTOR/VEGFA pathway was activated during the process of kindlin-2-induced melanoma progression and angiogenesis. Moreover, we demonstrated that kindlin-2 was significantly overexpressed in clinical melanoma samples and that a high level of kindlin-2 predicted a poor prognosis.

Conclusions: Taken together, these findings showed that kindlin-2 promotes angiogenesis and tumour progression via the mTOR/VEGFA pathway.

HOXB13 networking with ABCG1/EZH2/Slug mediates metastasis and confers resistance to cisplatin in lung adenocarcinoma patients

Rationale: Distant metastasis and chemoresistance are the major causes of short survival after initial chemotherapy in lung adenocarcinoma patients. However, the underlying mechanisms remain elusive. Our pilot study identified high expression of the homeodomain transcription factor HOXB13 in chemoresistant lung adenocarcinomas. We aimed to investigate the role of HOXB13 in mediating lung adenocarcinoma chemoresistance.

Methods: Immunohistochemistry assays were employed to assess HOXB13 protein levels in 148 non-small cell lung cancer patients. The role of HOXB13 in lung adenocarcinoma progression and resistance to cisplatin therapy was analyzed in cells, xenografted mice, and patient-derived xenografts. Needle biopsies from 15 lung adenocarcinoma patients who were resistant to cisplatin and paclitaxel therapies were analyzed for HOXB13 and EZH2 protein levels using immunohistochemistry.

Results: High expression of HOXB13 observed in 17.8% of the lung adenocarcinoma patients in this study promoted cancer progression and predicted poor prognosis. HOXB13 upregulated an array of metastasis- and drug-resistance-related genes, including ABCG1, EZH2, and Slug, by directly binding to their promoters. Cisplatin induced HOXB13 expression in lung adenocarcinoma cells, and patient-derived xenografts and depletion of ABCG1 enhanced the sensitivity of lung adenocarcinoma cells to cisplatin therapy. Our results suggest that determining the combined expression of HOXB13 and its target genes can predict patient outcomes.

Conclusions: A cisplatin-HOXB13-ABCG1/EZH2/Slug network may account for a novel mechanism underlying cisplatin resistance and metastasis after chemotherapy. Determining the levels of HOXB13 and its target genes from needle biopsy specimens may help predict the sensitivity of lung adenocarcinoma patients to platinum-based chemotherapy and patient outcomes.

Distinct expression profiles and functions of Kindlins in breast cancer

Background

Kindlin-1, − 2, and − 3 are the three members of the Kindlin family. They are best known as regulators of integrin functions, contributing to fundamental biological processes such as cell survival, adhesion and migration. Their deregulation leads to diverse pathologies including a broad range of cancers in which both, tumor-promoting and tumor-inhibiting functions have been described.

Methods

To better characterize Kindlins implication in breast cancer, in vitro experiments were performed in a series of cancer cell lines. We first assessed their expression profiles and subcellular distributions. Then, their involvement in breast cancer cell morphology, migration and invasion was verified by examining phenotypic changes induced by the depletion of either isoforms using RNA interference. An expression study was performed in a series of breast cancer patient derived xenografts (n = 58) to define the epithelial and stromal contribution of each Kindlin. Finally, we analyzed the expression levels of the three Kindlins in a large series of human breast tumors, at the RNA (n = 438) and protein (n = 129) levels and we evaluated their correlation with the clinical outcome.

Results

We determined that Kindlin-1 and Kindlin-2, but not Kindlin-3, were expressed in breast tumor cells. We uncovered the compensatory roles of Kindlin-1 and -2 in focal adhesion dynamics and cell motility. Remarkably, Kindlin-2 had a predominant effect on cell spreading and Kindlin-1 on cell invasion. In line with these experimental observations, Kindlin-1 overexpression was associated with a worse patients’ outcome. Notably, Kindlin-3, expressed by tumor infiltrating leukocytes, also correlated with a poor prognosis of breast cancer patients.

Conclusion

This study demonstrates that each one of the Kindlin family members has a different expression profile emphasizing their redundant and complementary roles in breast tumor cells. We highlight the specific link between Kindlin-1 and breast cancer progression. In addition, Kindlin-3 overexpression in the tumor microenvironment is associated with more aggressive breast tumors.

These results suggest that Kindlins play distinctive roles in breast cancer. Kindlins may be useful in identifying breast cancer patients with a worst prognosis and may offer new avenues for therapeutic intervention against cancer progression.

Electronic supplementary material

The online version of this article (10.1186/s13046-018-0955-4) contains supplementary material, which is available to authorized users.

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.

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.

A hydrophobic residue in the TALE homeodomain of PBX1 promotes epithelial-to-mesenchymal transition of gastric carcinoma

Pre-B-cell leukemia homeobox 1 (PBX1) was originally identified as a proto-oncogene in human leukemia. Although this protein has been shown to contribute to cellular development and tumorigenesis, the role of PBX1 in gastric carcinoma (GC) remains unclear. In this study, we observed increased expression of PBX1 in GC tissues compared with adjacent normal tissues. This increase in PBX1 expression levels negatively correlated with HOXB9 mRNA expression and was also associated with malignancy and metastasis. PBX1 promoted proliferation and metastasis of GC cells both in vitro and in vivo. These phenomena were also accompanied by epithelial-to-mesenchymal transition (EMT). Additionally, we observed that PBX1 promotes the expression of tumor growth and angiogenic factors. A structural model of the PBX1-HOX complex revealed that hydrophobic binding between PBX1 and the hexapeptide motif might be required for EMT induction. This analysis also demonstrated that the Phe²⁵² residue in the first helix of the TALE homeodomain is involved in the latter hydrophobic binding reaction. In vitro data from PBX1 mutants suggest that PBX1 cannot promote tumorigenesis of GC cells via EMT induction when Phe²⁵² residues lose hydrophobicity. It is likely that the presence of this residue is essential in facilitating hydrophobic binding with the hexapeptide motif. These findings suggest that PBX1 may be a potential target for GC treatment and this study provides a platform to elucidate the molecular mechanisms that underpin the role of PBX1 in GC tumorigenesis.

HOXB9 acetylation at K27 is responsible for its suppression of colon cancer progression

We previously reported that HOXB9 is overexpressed in colon cancer and predicts a favourable patient outcome, which is opposite to the tumour-promoting role of HOXB9 in other cancers. We hypothesized that HOXB9 acetylation may account for its inhibitory role in colon cancer. We aim to examine the role of acetylated HOXB9 in colon cancer cells and patients. The AcK27-HOXB9 levels in colon cancer cells and patients were analysed by Western blot analysis and immunohistochemistry separately. Correlation between AcK27-HOXB9 expression and patient survival was assessed by Kaplan-Meier analysis. HOXB9 target gene EZH2 was determined by luciferase assay in HOXB9-transfected colon cancer cells. Nucleocytoplasmic translocation of HOXB9 was detected by subcellular fractionation and immunofluorescence. The AcK27-HOXB9 level was decreased in colon cancer patients and predicted better outcome. HOXB9 upregulated oncogenic EZH2 expression, whereas AcK27-HOXB9 suppressed it by translocating HOXB9 from nuclei into cytoplasm. We demonstrated that AcK27-HOXB9 inhibits while non-acetylated HOXB9 promotes EZH2 expression and colon cancer progression. Thus, AcK27-HOXB9 underlies the tumour suppressive role of HOXB9. Detection of the ratio between AcK27-HOXB9 and HOXB9 is of differential diagnostic value for colon 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 could influence breast nodule elasticity and improve lymph node metastasis in invasive breast cancer

This study investigated the relationship between quantitative parameters of shear wave elastography (SWE, maximum elasticity [Emax], minimum elasticity [Emin], mean elasticity [Emean]), collagen intensity and Kindlin-2 expression in benign and malignant breast nodules, and if Kindlin-2 expression is related with lymph node metastasis. A total of 102 breast nodules from 102 patients were included in our study who underwent ultrasound elastography before surgery or core needle biopsy. There was a significant difference between benign and malignant breast nodules in Emax, Emean, collagen intensity and Kindlin-2 expression, but it had no difference in Emin. Collagen intensity and Kindlin-2 expression both correlated positively with Emax, but not with Emean. Among 38 malignant breast nodules, the average Emax of the metastasis group was higher than that of the non-metastasis group, but it had no statistical significance. Compared with the non-metastasis group, Kindlin-2 expression was considerably higher in the metastasis group. However, there was no difference in collagen intensity between the metastasis group and the non-metastasis group. In conclusion, Kindlin-2 and collagen might contribute to breast nodule elasticity through molecular mechanisms. In breast cancer, overexpression of Kindlin-2 might be a risk factor for lymph node metastasis.

Differential expression of Kindlin-1 and Kindlin-2 correlates with esophageal cancer progression and epidemiology

Esophageal cancer (EC) is one of the most lethal malignancies in China, but the etiology and risk factors remain unclear. The integrin-interacting proteins Kindlin-1 and Kindlin-2 are focal adhesion molecules that activate transmembrane receptor integrins and regulate tumor cell growth, invasion, and metastasis. Here, we report that Kindlin-1 and Kindlin-2 are differentially expressed among Chinese EC patients. For this, Kindlin-1 and Kindlin-2 expression was evaluated in 220 EC patients by immunohistochemistry (IHC) and found to be correlated with the EC progression, along with a variety of epidemiologic parameters, including smoking, family EC history, and EC invasion status. Moreover, data downloaded from the Oncomine database revealed that both Kindlin-1 and Kindlin-2 were upregulated in ECs compared with normal esophageal tissues; although Kindlin-1 was highly expressed in well-differentiated tumors, whereas Kindlin-2 was more prevalent in poorly differentiated tumors. Collectively, these data suggest that Kindlin-1 may inhibit, while Kindlin-2 may promote, EC progression. This study, for the first time, linked the expression of Kindlin-1 and Kindlin-2 with EC family genetic background and living habits, which may help further our understanding of the various causes of EC.

Inflammation and Epithelial-Mesenchymal Transition in Pancreatic Ductal Adenocarcinoma: Fighting Against Multiple Opponents

Pancreatic ductal adenocarcinoma (PDAC) is the most common type of pancreatic cancer and one of the most lethal human cancers. Inflammation is a critical component in PDAC initiation and progression. Inflammation also contributes to the aggressiveness of PDAC indirectly via induction of epithelial-mesenchymal transition (EMT), altogether leading to enhanced resistance to chemotherapy and poor survival rates. This review gives an overview of the key pro-inflammatory signaling pathways involved in PDAC pathogenesis and discusses the role of inflammation in induction of EMT and development of chemoresistance in patients with PDAC.

Kindlin-2 in pancreatic stellate cells promotes the progression of pancreatic cancer

Pancreatic stellate cells (PSCs) play a pivotal role in pancreatic fibrosis associated with pancreatic ductal adenocarcinoma (PDAC). Kindlin-2 is a focal adhesion protein that regulates the activation of integrins. This study aimed to clarify the role of kindlin-2 in PSCs in pancreatic cancer. Kindlin-2 expression in 79 resected pancreatic cancer tissues was examined by immunohistochemical staining. Kindlin-2-knockdown immortalized human PSCs were established using small interfering RNA. Pancreatic cancer cells were treated with conditioned media of PSCs, and the cell proliferation and migration were examined. SUIT-2 pancreatic cancer cells were subcutaneously injected into nude mice alone or with PSCs and the size of the tumors was monitored. Kindlin-2 expression was observed in PDAC and the peritumoral stroma. Stromal kindlin-2 expression was associated with shorter recurrence-free survival time after R0 resection. Knockdown of kindlin-2 resulted in decreased proliferation, migration, and cytokine expression in PSCs. The PSC-induced proliferation and migration of pancreatic cancer cells were suppressed by kindlin-2 knockdown in PSCs. In vivo, co-injection of PSCs increased the size of the tumors, but this effect was abolished by kindlin-2 knockdown in PSCs. In conclusion, kindlin-2 in PSCs promoted the progression of pancreatic cancer.

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.

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.

PCAF-mediated acetylation of transcriptional factor HOXB9 suppresses lung adenocarcinoma progression by targeting oncogenic protein JMJD6

HOXB9 is a homeobox domain-containing transcription factor, playing an important role in embryonic development and cancer progression. However, the precise post-translational modifications (PTMs) of HOXB9 and the corresponding roles are unclear. Here, we report that acetyltransferase p300/CBP-associated factor (PCAF) interacts with and acetylates HOXB9 both in vivo and in vitro Conversely, the acetylation of HOXB9 can be reversed by deacetylase SIRT1. Furthermore, we found that HOXB9 is acetylated at lysine 27 (AcK27). Functionally, in contrast to the wild type HOXB9, AcK27-HOXB9 decreased its capacity in promoting lung cancer cell migration and tumor growth in mice. Mechanistically, AcK27-HOXB9 suppresses the transcription of its target gene Jumonji domain-containing protein 6 (JMJD6) by direct occupying the promoter of JMJD6 gene. For clinical relevance, elevated HOXB9 acetylation at K27 predicts a better prognosis in lung adenocarcinoma patients. Taken together, we identified the first PTM of HOXB9 by demonstrating that HOXB9 can be acetylated and AcK27-HOXB9 counteracts the role of the wild-type HOXB9 in regulating lung adenocarcinoma progression.

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.

Kindlin-2 interacts with and stabilizes EGFR and is required for EGF-induced breast cancer cell migration

Epidermal growth factor receptor (EGFR) mediates multiple signaling pathways that regulate cell proliferation, migration and tumor invasion. Kindlin-2 has been known as a focal adhesion molecule that binds to integrin to control cell migration and invasion. However, molecular mechanisms underlying the role of Kindlin-2 in breast cancer progression remain elusive. Here we report that Kindlin-2 interacts with EGFR and mediates EGF-induced breast cancer cell migration. We found that EGF treatment dramatically increases Kindlin-2 expression at both mRNA and protein levels in a variety of cancer cells. Inhibitors specific for EGFR or PI3K blocked Kindlin-2 induction by EGF. Importantly, Kindlin-2 interacted with EGFR kinase domain, which was independent of Kindlin-2 binding to integrin cytoplasmic domain. Intriguingly, Kindlin-2 stabilized EGFR protein by blocking its ubiquitination and degradation. Depletion of Kindlin-2 impaired EGF-induced cell migration. Our results demonstrated that Kindlin-2 participates in EGFR signaling and regulates breast cancer progression.