The role of the focal adhesion protein PINCH1 for the radiosensitivity of adhesion and suspension cell cultures

Mesenchymal stem cells reversibly de-differentiate myofibroblasts to fibroblast-like cells by inhibiting the TGF-β-SMAD2/3 pathway

BACKGROUND

Myofibroblasts (MFB), one of the major effectors of pathologic fibrosis, mainly derived from the activation of fibroblast to myofibroblast transition (FMT). Although MFBs were historically considered terminally differentiated cells, their potential for de-differentiation was recently recognized and implied with therapeutic value in treating fibrotic diseases, for instance, idiopathic pulmonary fibrosis (IPF) and post allogeneic hematopoietic stem cell transplantation bronchiolitis obliterans (BO). During the past decade, several methods were reported to block or reverse MFB differentiation, among which mesenchymal stem cells (MSC) have demonstrated potential but undetermined therapeutic values. However, the MSC-mediated regulation of FMT and underlying mechanisms remained largely undefined.

METHOD

By identifying TGF-β1 hypertension as the pivotal landmark during the pro-fibrotic FMT, TGF-β1-induced MFB and MSC co-culture models were established and utilized to investigate regulations by MSC on FMT in vitro. Methods including RNA sequencing (RNA-seq), Western blot, qPCR and flow cytometry were used.

RESULT

Our data revealed that TGF-β1 readily induced invasive signatures identified in fibrotic tissues and initiated MFB differentiation in normal FB. MSC reversibly de-differentiated MFB into a group of FB-like cells by selectively inhibiting the TGF-β-SMAD2/3 signaling. Importantly, these proliferation-boosted FB-like cells remained sensitive to TGF-β1 and could be re-induced into MFB.

CONCLUSION

Our findings highlighted the reversibility of MSC-mediated de-differentiation of MFB through TGF-β-SMAD2/3 signaling, which may explain MSC's inconsistent clinical efficacies in treating BO and other fibrotic diseases. These de-differentiated FB-like cells are still sensitive to TGF-β1 and may further deteriorate MFB phenotypes unless the pro-fibrotic microenvironment is corrected.

PINCH1 knockout aggravates myocardial infarction in mice via mediating the NF-κB signaling pathway

Myocardial infarction (MI), the leading cause of death among patients with cardiovascular diseases, is characterized by acute cardiac muscle injury due to severe impairment of the coronary blood supply, which may lead to cardiogenic shock and cardiac arrest. Particularly interesting new cysteine histidine rich 1 (PINCH1) protein, a key component of the integrin signaling pathway, interacts with several proteins and serves a vital role in numerous cellular processes, including cytoskeleton remodeling, cell proliferation and cell migration. To investigate the role of PINCH1 in heart injury in the present study, PINCH1 was knocked out in the myocardial tissue of mice (age, 18 weeks) to induce MI. In addition, cell viability, migration and apoptosis, as well as the expression levels of NF-κB-associated proteins were determined in murine HL1 cardiomyocytes with a conditional PINCH1 shRNA using Cell Counting Kit-8, Transwell, flow cytometry and western blot assays, respectively. Furthermore, the cardiac expansion and myocardial fibrosis in PINCH1 knockout mice was investigated in vivo by performing morphological and histological examinations. Additionally, the murine ventricular myocardial ultrastructure was evaluated using an electron microscope, and the cardiomyocyte apoptotic rate and expression levels of NF-κB-related proteins were determined using TUNEL and western blot assays, respectively. The results showed that the apoptotic rate in the in vivo PINCH1 knockdown group was significantly increased. In addition, the protein expression levels of NF-κB signaling pathway-related proteins, including NF-κB, myeloid differentiation factor 88, TNF-α and caspase-3, were significantly increased in the in vivo PINCH1 knockdown group compared with the wild-type group, but the protein expression of MMP2 and MMP9 were the opposite. Overall, the in vitro and in vivo results revealed that PINCH1 knockout in mice significantly aggravated MI via the NF-κB signaling pathway.

Transcriptome-wide Profiling of Cerebral Cavernous Malformations Patients Reveal Important Long noncoding RNA molecular signatures

Cerebral cavernous malformations (CCMs) are low-flow vascular malformations in the brain associated with recurrent hemorrhage and seizures. The current treatment of CCMs relies solely on surgical intervention. Henceforth, alternative non-invasive therapies are urgently needed to help prevent subsequent hemorrhagic episodes. Long non-coding RNAs (lncRNAs) belong to the class of non-coding RNAs and are known to regulate gene transcription and involved in chromatin remodeling via various mechanism. Despite accumulating evidence demonstrating the role of lncRNAs in cerebrovascular disorders, their identification in CCMs pathology remains unknown. The objective of the current study was to identify lncRNAs associated with CCMs pathogenesis using patient cohorts having 10 CCM patients and 4 controls from brain. Executing next generation sequencing, we performed whole transcriptome sequencing (RNA-seq) analysis and identified 1,967 lncRNAs and 4,928 protein coding genes (PCGs) to be differentially expressed in CCMs patients. Among these, we selected top 6 differentially expressed lncRNAs each having significant correlative expression with more than 100 differentially expressed PCGs. The differential expression status of the top lncRNAs, SMIM25 and LBX2-AS1 in CCMs was further confirmed by qRT-PCR analysis. Additionally, gene set enrichment analysis of correlated PCGs revealed critical pathways related to vascular signaling and important biological processes relevant to CCMs pathophysiology. Here, by transcriptome-wide approach we demonstrate that lncRNAs are prevalent in CCMs disease and are likely to play critical roles in regulating important signaling pathways involved in the disease progression. We believe, that detailed future investigations on this set of identified lncRNAs can provide useful insights into the biology and, ultimately, contribute in preventing this debilitating disease.

The cancer cell adhesion resistome: mechanisms, targeting and translational approaches

Cell adhesion-mediated resistance limits the success of cancer therapies and is a great obstacle to overcome in the clinic. Since the 1990s, where it became clear that adhesion of tumor cells to the extracellular matrix is an important mediator of therapy resistance, a lot of work has been conducted to understand the fundamental underlying mechanisms and two paradigms were deduced: cell adhesion-mediated radioresistance (CAM-RR) and cell adhesion-mediated drug resistance (CAM-DR). Preclinical work has evidently demonstrated that targeting of integrins, adapter proteins and associated kinases comprising the cell adhesion resistome is a promising strategy to sensitize cancer cells to both radiotherapy and chemotherapy. Moreover, the cell adhesion resistome fundamentally contributes to adaptation mechanisms induced by radiochemotherapy as well as molecular drugs to secure a balanced homeostasis of cancer cells for survival and growth. Intriguingly, this phenomenon provides a basis for synthetic lethal targeted therapies simultaneously administered to standard radiochemotherapy. In this review, we summarize current knowledge about the cell adhesion resistome and highlight targeting strategies to override CAM-RR and CAM-DR.

Direct evidence for cell adhesion-mediated radioresistance (CAM-RR) on the level of individual integrin β1 clusters

The cellular interaction with the extracellular matrix (ECM) modulates many key processes such as proliferation, migration, differentiation and survival. In addition, cells cultured under 3D conditions in presence of an ECM display a marked radioresistance towards ionizing radiation (IR) in comparison to conventionally 2D cultured cells. This process, also known as "cell-adhesion-mediated-radio-resistance" (CAM-RR), has been linked to the chromatin structure that differs between cells cultured on stiff surfaces versus cell grown on soft planar supports or in 3D environments. As integrins are the key mediators of cell adhesion and mechanosensing, they originate the molecular signalling towards chromatin remodelling in response to a cell's microenvironment. We aimed to investigate this molecular origin that leads to CAM-RR by investigating the distribution of integrins at the single molecule level and show that cells cultured in 2D keep a lower fraction of integrin β1 in clusters and maintain a less defined cluster status than 3D cultured cells. Upon X-irradiation this nanoscale distribution of integrin β1 is disturbed at much lower dosages in 2D versus 3D cultured cells. Radioresistance is thus linked to the ability to maintain a well defined organization of integrins in clusters, making integrin distribution a potential drug target for radiosensitization.

Signaling via PINCH: Functions, binding partners and implications in human diseases

Particularly interesting new cysteine-histidine-rich protein (PINCH) is a LIM-domain-only adaptor that plays important roles in cytoskeletal organization and extracellular matrix adhesion, migration, proliferation and survival. Mammalian cells have two functional PINCH proteins, PINCH1 and PINCH2. PINCH not only binds to Nck2 and engages in the signaling of growth factor receptors, but also forms a ternary complex with ILK and parvin (IPP complex). Normally, the IPP complex locates to focal adhesions participating in the signaling of integrins and mediating the interaction of cytoskeleton and extracellular matrix (ECM). Accumulative evidence indicates that abnormalities in PINCH signaling are involved in the pathogenesis of important diseases, such as cancers, renal diseases, cardiomyopathy, and HIV. Therefore, clarifying the functions of PINCH and its interactions with key factors is important for better understanding of signaling events both in health and disease.

ILKAP, ILK and PINCH1 control cell survival of p53-wildtype glioblastoma cells after irradiation

The prognosis is generally poor for patients suffering from glioblastoma multiforme (GBM) due to radiation and drug resistance. Prosurvival signaling originating from focal adhesion hubs essentially contributes to therapy resistance and tumor aggressiveness. As the underlying molecular mechanisms remain largely elusive, we addressed whether targeting of the focal adhesion proteins particularly interesting new cysteine-histidine-rich 1 (PINCH1), integrin-linked kinase (ILK) and ILK associated phosphatase (ILKAP) modulates GBM cell radioresistance. Intriguingly, PINCH1, ILK and ILKAP depletion sensitized p53-wildtype, but not p53-mutant, GBM cells to radiotherapy. Concomitantly, these cells showed inactivated Glycogen synthase kinase-3β (GSK3β) and reduced proliferation. For PINCH1 and ILKAP knockdown, elevated levels of radiation-induced γH2AX/53BP1-positive foci, as a marker for DNA double strand breaks, were observed. Mechanistically, we identified radiation-induced phosphorylation of DNA protein kinase (DNAPK), an important DNA repair protein, to be dependent on ILKAP. This interaction was fundamental to radiation survival of p53-wildtype GBM cells. Conclusively, our data suggest an essential role of PINCH1, ILK and ILKAP for the radioresistance of p53-wildtype GBM cells and provide evidence for DNAPK functioning as a central mediator of ILKAP signaling. Strategies for targeting focal adhesion proteins in combination with radiotherapy might be a promising approach for patients with GBM.

Molecular Targeting of Integrins and Integrin-Associated Signaling Networks in Radiation Oncology

Radiation and chemotherapy are the main pillars of the current multimodal treatment concept for cancer patients. However, tumor recurrences and resistances still hamper treatment success regardless of advances in radiation beam application, particle radiotherapy, and optimized chemotherapeutics. To specifically intervene at key recurrence- and resistance-promoting molecular processes, the development of potent and specific molecular-targeted agents is demanded for an efficient, safe, and simultaneous integration into current standard of care regimens. Potential targets for such an approach are integrins conferring structural and biochemical communication between cells and their microenvironment. Integrin binding to extracellular matrix activates intracellular signaling for regulating essential cellular functions such as survival, proliferation, differentiation, adhesion, and cell motility. Tumor-associated characteristics such as invasion, metastasis, and radiochemoresistance also highly depend on integrin function. Owing to their dual functionality and their overexpression in the majority of human malignancies, integrins present ideal and accessible targets for cancer therapy. In the following chapter, the current knowledge on aspects of the tumor microenvironment, the molecular regulation of integrin-dependent radiochemoresistance and current approaches to integrin targeting are summarized.

LIM-only protein FHL2 critically determines survival and radioresistance of pancreatic cancer cells

Numerous factors determine the current poor prognosis of pancreatic ductal adenocarcinoma (PDAC). One of the greatest challenges to overcome is treatment resistance. Among a large repertoire of intrinsic resistance mechanisms, integrin-mediated cell adhesion to extracellular matrix (ECM) has been identified to be fundamental. Coalesced in focal adhesion complexes, integrins, receptor tyrosine kinases, protein kinases and adapter proteins mediate prosurvival signaling. Four and a half LIM domains protein 2 (FHL2) is one of these adapter proteins, which operates through protein-protein interactions and shows tumor-specific expression. Based on this, we investigated FHL2 expression in PDAC specimens and three-dimensionally grown cell lines and how FHL2 mechanistically contributes to cell survival, cell cycling and radiation resistance. PDAC exhibited a significantly increased and heterogeneous FHL2 expression. Upon FHL2 depletion, pancreatic cancer cell lines showed significantly decreased cell survival, proliferation and radioresistance as well as enhanced apoptosis and MEK/ERK signaling and cyclin D1, E, A and B1 expression were strongly induced. Targeting of FHL2 and MEK1 was similarly effective than FHL2 depletion alone, suggesting MEK1 as a downstream signaling mediator of FHL2. Taken together, our results provide evidence for the importance of the focal adhesion protein FHL2 in pancreatic cancer cell survival, proliferation and radiosensitivity.

Actin cytoskeleton organization, cell surface modification and invasion rate of 5 glioblastoma cell lines differing in PTEN and p53 status

Glioblastoma cells exhibit highly invasive behavior whose mechanisms are not yet fully understood. The present study explores the relationship between the invasion capacity of 5 glioblastoma cell lines differing in p53 and PTEN status, expression of mTOR and several other marker proteins involved in cell invasion, actin cytoskeleton organization and cell morphology. We found that two glioblastoma lines mutated in both p53 and PTEN genes (U373-MG and SNB19) exhibited the highest invasion rates through the Matrigel or collagen matrix. In DK-MG (p53wt/PTENwt) and GaMG (p53mut/PTENwt) cells, F-actin mainly occurred in the numerous stress fibers spanning the cytoplasm, whereas U87-MG (p53wt/PTENmut), U373-MG and SNB19 (both p53mut/PTENmut) cells preferentially expressed F-actin in filopodia and lamellipodia. Scanning electron microscopy confirmed the abundant filopodia and lamellipodia in the PTEN mutated cell lines. Interestingly, the gene profiling analysis revealed two clusters of cell lines, corresponding to the most (U373-MG and SNB19, i.e. p53 and PTEN mutated cells) and less invasive phenotypes. The results of this study might shed new light on the mechanisms of glioblastoma invasion.

Focal adhesion signaling and therapy resistance in cancer

Interlocking gene mutations, epigenetic alterations and microenvironmental features perpetuate tumor development, growth, infiltration and spread. Consequently, intrinsic and acquired therapy resistance arises and presents one of the major goals to solve in oncologic research today. Among the myriad of microenvironmental factors impacting on cancer cell resistance, cell adhesion to the extracellular matrix (ECM) has recently been identified as key determinant. Despite the differentiation between cell adhesion-mediated drug resistance (CAMDR) and cell adhesion-mediated radioresistance (CAMRR), the underlying mechanisms share great overlap in integrin and focal adhesion hub signaling and differ further downstream in the complexity of signaling networks between tumor entities. Intriguingly, cell adhesion to ECM is per se also essential for cancer cells similar to their normal counterparts. However, based on the overexpression of focal adhesion hub signaling receptors and proteins and a distinct addiction to particular integrin receptors, targeting of focal adhesion proteins has been shown to potently sensitize cancer cells to different treatment regimes including radiotherapy, chemotherapy and novel molecular therapeutics. In this review, we will give insight into the role of integrins in carcinogenesis, tumor progression and metastasis. Additionally, literature and data about the function of focal adhesion molecules including integrins, integrin-associated proteins and growth factor receptors in tumor cell resistance to radio- and chemotherapy will be elucidated and discussed.

PINCH expression in relation to radiation response in co-cultured colon cancer cells and in rectal cancer patients

Particularly interesting new cysteine-histidine rich protein (PINCH), involved in cell spreading, motility and proliferation, has been shown to enhance radioresistance in colon cancer cell lines. The expression of PINCH in relation to radiation was studied in co-cultured colon cancer cells. Furthermore, the clinical significance between PINCH and radiotherapy (RT) was analyzed in rectal cancer patients with or without RT. The relative PINCH expression in colon cancer (KM12C) cells cultured separately and in co-culture was examined by western blotting and real-time PCR, and was analyzed over a period of 8 and 24 h after radiation. PINCH expression was immunohistochemically examined in 137 primary rectal tumors for which 65 cases did not receive RT and 72 cases received RT. PINCH expression tended to decrease from that in the separately cultured KM12C cells without radiation to that in cells with radiation at 8 h (P=0.060); while in the co-cultured cells, no significant difference was found (P=0.446). In patients with RT, strong PINCH expression was related to worse survival, when compared to patients with weak expression, independent of TNM stage, degree of differentiation, age and p53 status (P=0.029, RR 4.03, 95% CI 1.34‑12.1). No survival relationship for the patients without RT was observed (P=0.287). A statistical interaction analysis between PINCH, RT and survival showed a trend towards significance (P=0.057). In conclusion, PINCH predicts survival in rectal cancer patients with RT, but not in patients without RT. The expression of PINCH may be regulated by radiation and by environmental factors surrounding the cells.

Hsp90 inhibition by NVP-AUY922 and NVP-BEP800 decreases migration and invasion of irradiated normoxic and hypoxic tumor cell lines

This study explores the impact of Hsp90 inhibitors NVP-AUY922 and NVP-BEP800 in combination with ionizing radiation (IR) on the migration and invasion of lung carcinoma A549 and glioblastoma SNB19 cells, under normoxia or hypoxia. Independent of oxygen concentration, both drugs decreased the migration and invasion rates of non-irradiated tumor cells. Combined drug-IR treatment under hypoxia inhibited cell invasion to a greater extent than did each treatment alone. Decreased migration of cells correlated with altered expression of several matrix-associated proteins (FAK/p-FAK, Erk2, RhoA) and impaired F-actin modulation. The anti-metastatic efficacy of the Hsp90 inhibitors could be useful in combinational therapies of cancer.

Focal adhesion-chromatin linkage controls tumor cell resistance to radio- and chemotherapy

Cancer resistance to therapy presents an ongoing and unsolved obstacle, which has clear impact on patient's survival. In order to address this problem, novel in vitro models have been established and are currently developed that enable data generation in a more physiological context. For example, extracellular-matrix- (ECM-) based scaffolds lead to the identification of integrins and integrin-associated signaling molecules as key promoters of cancer cell resistance to radio- and chemotherapy as well as modern molecular agents. In this paper, we discuss the dynamic nature of the interplay between ECM, integrins, cytoskeleton, nuclear matrix, and chromatin organization and how this affects the response of tumor cells to various kinds of cytotoxic anticancer agents.

PINCH is an independent prognostic factor in rectal cancer patients without preoperative radiotherapy--a study in a Swedish rectal cancer trial of preoperative radiotherapy

Background

The clinical significance between particularly interesting new cysteine-histidine rich protein (PINCH) expression and radiotherapy (RT) in tumours is not known. In this study, the expression of PINCH and its relationship to RT, clinical, pathological and biological factors were studied in rectal cancer patients.

Methods

PINCH expression determined by immunohistochemistry was analysed at the invasive margin and inner tumour area in 137 primary rectal adenocarcinomas (72 cases without RT and 65 cases with RT). PINCH expression in colon fibroblast cell line (CCD-18 Co) was determined by western blot.

Results

In patients without RT, strong PINCH expression at the invasive margin of primary tumours was related to worse survival, compared to patients with weak expression, independent of TNM stage and differentiation (P = 0.03). No survival relationship in patients with RT was observed (P = 0.64). Comparing the non-RT with RT subgroup, there was no difference in PINCH expression in primary tumours (invasive margin (P = 0.68)/inner tumour area (P = 0.49). In patients with RT, strong PINCH expression was related to a higher grade of LVD (lymphatic vessel density) (P = 0.01)

Conclusions

PINCH expression at the invasive margin was an independent prognostic factor in patients without RT. RT does not seem to directly affect the PINCH expression.

PINCH-1 promotes Bcl-2-dependent survival signalling and inhibits JNK-mediated apoptosis in the primitive endoderm

The focal adhesion (FA) protein PINCH-1 is required for the survival of primitive endoderm (PrE) cells. How PINCH-1 regulates this fundamental process is not known. Here, we use embryoid bodies (EBs) and isolated EB-derived PrE cells to investigate the mechanisms by which PINCH-1 promotes PrE survival. We report that loss of PINCH-1 in PrE cells leads to a sustained activity of JNK and the pro-apoptotic factor Bax. Mechanistically, the sustained JNK activation was due to diminished levels of the JNK inhibitory factor Ras suppressor protein-1 (RSU-1), whose stability was severely reduced upon loss of PINCH-1. Chemical inhibition of JNK attenuated apoptosis of PrE cells but failed to reduce Bax activity. The increased Bax activity was associated with reduced integrin signalling and diminished Bcl-2 levels, which were shown to inhibit Bax. Altogether our findings show that PINCH-1 is a pro-survival factor that prevents apoptosis of PrE cells by modulating two independent signalling pathways; PINCH-1 inhibits JNK-mediated apoptosis by stabilizing the PINCH-1 binding protein RSU-1, and promotes Bcl-2-dependent pro-survival signalling downstream of integrins.

Dual targeting of EGFR and focal adhesion kinase in 3D grown HNSCC cell cultures

PURPOSE

Epidermal growth factor receptor (EGFR) and focal adhesion kinase (FAK) show frequent overexpression and hyperactivity in various human malignancies including head and neck squamous cell carcinomas (HNSCC). To examine effects of dual EGFR/FAK inhibition on cellular radiosensitivity of HNSCC cells in a more physiological environment, we employed a previously established laminin-rich extracellular matrix (lrECM) based three-dimensional (3D) cell culture model.

MATERIALS AND METHODS

UTSCC15 and SAS HNSCC cell lines stably transfected with EGFR-CFP or CFP were used. Single or combined EGFR (Cetuximab, siRNA) and FAK (TAE226, siRNA) inhibition were accomplished prior to measuring clonogenic survival and protein expression and phosphorylation. Immunofluorescence enabled visualization of EGFR-CFP and FAK.

RESULTS

Cetuximab resulted in higher radiosensitization in EGFR-CFP overexpressing cell lines than CFP controls. Single EGFR or FAK inhibition mediated radiosensitization, while dual EGFR/FAK targeting further augmented this effect. Despite signaling alterations upon Cetuximab and siRNA knockdown, analysis of protein expression and phosphorylation indicates EGFR and FAK signaling coexistence without obvious overlap.

CONCLUSIONS

Combined EGFR/FAK targeting yielded stronger radiosensitization than either approach alone, which might be based on non-overlapping downstream signaling. Whether dual targeting of EGFR and FAK can reasonably be combined with radiotherapy and chemotherapy needs clarification.