Paxillin expression and amplification in early lung lesions of high-risk patients, lung adenocarcinoma and metastatic disease

A feedback loop between Paxillin and Yorkie sustains Drosophila intestinal homeostasis and regeneration

Balanced self-renewal and differentiation of stem cells are crucial for maintaining tissue homeostasis, but the underlying mechanisms of this process remain poorly understood. Here, from an RNA interference (RNAi) screen in adult Drosophila intestinal stem cells (ISCs), we identify a factor, Pax, which is orthologous to mammalian PXN, coordinates the proliferation and differentiation of ISCs during both normal homeostasis and injury-induced midgut regeneration in Drosophila. Loss of Pax promotes ISC proliferation while suppressing its differentiation into absorptive enterocytes (ECs). Mechanistically, our findings demonstrate that Pax is a conserved target gene of the Hippo signaling pathway in both Drosophila and mammals. Subsequent investigations have revealed Pax interacts with Yki and enhances its cytoplasmic localization, thereby establishing a feedback regulatory mechanism that attenuates Yki activity and ultimately inhibits ISCs proliferation. Additionally, Pax induces the differentiation of ISCs into ECs by activating Notch expression, thus facilitating the differentiation process. Overall, our study highlights Pax as a pivotal component of the Hippo and Notch pathways in regulating midgut homeostasis, shedding light on this growth-related pathway in tissue maintenance and intestinal function.

Evaluation of Paxillin Expression in Epithelial Dysplasia, Oral Squamous Cell Carcinoma, Lichen Planus with and without Dysplasia, and Hyperkeratosis: A Retrospective Cross-Sectional Study

BACKGROUND

Paxillin is a cytoskeletal protein involved in the pathogenesis of several types of cancers. However, the roles of paxillin in epithelial dysplasia (ED), oral squamous cell carcinoma (OSCC), oral lichen planus with dysplasia (OLPD), hyperkeratosis (HK), and oral lichen planus (OLP) have remained unnoticed in the literature. This study aimed to evaluate its attainable functions in the pathogenesis and malignant transformation of potentially malignant oral epithelium and benign lesions.

METHODS

In this retrospective cross-sectional study, paxillin expression was investigated in 99 tissue samples, including 18 cases of OSCC, 21 ED, 23 OLP, 21 OLPD, and 16 cases of HK. The tissue sections also underwent immunohistochemical paxillin staining using 3,3-diaminobenzidine (DAB) chromogen. The intensity, location, and percentage of staining were examined across all groups. Data were analyzed using the Shapiro-Wilk test, ANOVA, Pearson chi-square, Kruskal-Wallis, and Dunn's post hoc test.

RESULTS

The cytoplasmic percentage and intensity staining of Paxillin expression were evident in the central/suprabasal and basal/peripheral layers of all the obtained samples. The final staining score was significantly higher in OSCC and dysplasia compared to HK and OLP (p = 0.004). It was found that paxillin expression is associated with the grade of dysplastic samples (p < 0.001).

CONCLUSION

The present study provides evidence that paxillin may be involved in the pathogenesis of OSCC and the development and progression of dysplastic tissue, since the paxillin expression was higher than that of HK and OLP.

The Role of Paxillin Aberrant Expression in Cancer and Its Potential as a Target for Cancer Therapy

Paxillin is a multi-domain adaptor protein. As an important member of focal adhesion (FA) and a participant in regulating cell movement, paxillin plays an important role in physiological processes such as nervous system development, embryonic development, and vascular development. However, increasing evidence suggests that paxillin is aberrantly expressed in many cancers. Many scholars have also recognized that the abnormal expression of paxillin is related to the prognosis, metastases, invasion, survival, angiogenesis, and other aspects of malignant tumors, suggesting that paxillin may be a potential cancer therapeutic target. Therefore, the study of how aberrant paxillin expression affects the process of tumorigenesis and metastasis will help to develop more efficacious antitumor drugs. Herein, we review the structure of paxillin and its function and expression in tumors, paying special attention to the multifaceted effects of paxillin on tumors, the mechanism of tumorigenesis and progression, and its potential role in tumor therapy. We also hope to provide a reference for the clinical prognosis and development of new tumor therapeutic targets.

Lack of Paxillin phosphorylation promotes single-cell migration in vivo

Focal adhesions are structures that physically link the cell to the extracellular matrix for cell migration. Although cell culture studies have provided a wealth of information regarding focal adhesion biology, it is critical to understand how focal adhesions are dynamically regulated in their native environment. We developed a zebrafish system to visualize focal adhesion structures during single-cell migration in vivo. We find that a key site of phosphoregulation (Y118) on Paxillin exhibits reduced phosphorylation in migrating cells in vivo compared to in vitro. Furthermore, expression of a non-phosphorylatable version of Y118-Paxillin increases focal adhesion disassembly and promotes cell migration in vivo, despite inhibiting cell migration in vitro. Using a mouse model, we further find that the upstream kinase, focal adhesion kinase, is downregulated in cells in vivo, and cells expressing non-phosphorylatable Y118-Paxillin exhibit increased activation of the CRKII-DOCK180/RacGEF pathway. Our findings provide significant new insight into the intrinsic regulation of focal adhesions in cells migrating in their native environment.

A Systems Biology Approach for Addressing Cisplatin Resistance in Non-Small Cell Lung Cancer

Translational research in medicine, defined as the transfer of knowledge and discovery from the basic sciences to the clinic, is typically achieved through interactions between members across scientific disciplines to overcome the traditional silos within the community. Thus, translational medicine underscores 'Team Medicine', the partnership between basic science researchers and clinicians focused on addressing a specific goal in medicine. Here, we highlight this concept from a City of Hope perspective. Using cisplatin resistance in non-small cell lung cancer (NSCLC) as a paradigm, we describe how basic research scientists, clinical research scientists, and medical oncologists, in true 'Team Science' spirit, addressed cisplatin resistance in NSCLC and identified a previously approved compound that is able to alleviate cisplatin resistance in NSCLC. Furthermore, we discuss how a 'Team Medicine' approach can help to elucidate the mechanisms of innate and acquired resistance in NSCLC and develop alternative strategies to overcome drug resistance.

Immunohistochemical expression of paxillin in potentially malignant disorders and squamous cell carcinoma patients

Background

Cell adhesion molecules are essential to maintain the integrity of stratified squamous epithelium but their expression has to be dynamic to aid the mobility and turnover of cells. Paxillin is one such multi-domain protein which integrates numerous signals from cell surface receptors, integrins and growth factors. It thus functions as a regulator of various physiological and pathological processes including tissue remodeling, cell motility, gene expression, matrix organization, cell proliferation, metastasis and survival. Hence, the assessment of paxillin expression in normal control, potentially malignant disorders and oral squamous cell carcinoma patients was carried out.

Material and Methods

The present retrospective study comprised of 20 each clinically and histologically confirmed case of normal control, potentially malignant disorders, and oral squamous cell carcinomas. All the slides were stained immunohistochemically using Paxillin antibody.

Results

The localization, staining intensity and percentage of positivity for paxillin expression was statistically significant among normal control and potentially malignant disorders, whereas oral squamous cell carcinoma showed a non-significant difference. Upon comparison of histopathological grading of potentially malignant disorders, mild versus severe and moderate versus severe epithelial dysplasia showed a statistical significant difference among all the parameters of paxillin expression. However, WDSCC & MDSCC a statistically significant difference among localization and staining intensity of paxillin.

Conclusion

Paxillin may play an important role in pathogenesis of oral squamous cell carcinoma by altering the adhesive properties of the tumor cells interacting with the extracellular matrix which in turn affects their invasive behavior and histologic differentiation.

Accessory proteins of the RAS-MAPK pathway: moving from the side line to the front line

Health and disease are directly related to the RTK-RAS-MAPK signalling cascade. After more than three decades of intensive research, understanding its spatiotemporal features is afflicted with major conceptual shortcomings. Here we consider how the compilation of a vast array of accessory proteins may resolve some parts of the puzzles in this field, as they safeguard the strength, efficiency and specificity of signal transduction. Targeting such modulators, rather than the constituent components of the RTK-RAS-MAPK signalling cascade may attenuate rather than inhibit disease-relevant signalling pathways.

The hidden role of paxillin: localization to nucleus promotes tumor angiogenesis

Paxillin (PXN), a key component of the focal adhesion complex, has been associated with cancer progression, but the underlying mechanisms are poorly understood. The purpose of this study was to elucidate mechanisms by which PXN affects cancer growth and progression, which we addressed using cancer patient data, cell lines, and orthotopic mouse models. We demonstrated a previously unrecognized mechanism whereby nuclear PXN enhances angiogenesis by transcriptionally regulating SRC expression. SRC, in turn, increases PLAT expression through NF-ĸB activation; PLAT promotes angiogenesis via LRP1 in endothelial cells. PXN silencing in ovarian cancer mouse models reduced angiogenesis, tumor growth, and metastasis. These findings provide a new understanding of the role of PXN in regulating tumor angiogenesis and growth.

A Non-genetic Mechanism Involving the Integrin β4/Paxillin Axis Contributes to Chemoresistance in Lung Cancer

Tumor heterogeneity and cisplatin resistance are major causes of tumor relapse and poor survival. Here, we show that in lung cancer, interaction between paxillin (PXN) and integrin β4 (ITGB4), components of the focal adhesion (FA) complex, contributes to cisplatin resistance. Knocking down PXN and ITGB4 attenuated cell growth and improved cisplatin sensitivity, both in 2D and 3D cultures. PXN and ITGB4 independently regulated expression of several genes. In addition, they also regulated expression of common genes including USP1 and VDAC1, which are required for maintaining genomic stability and mitochondrial function, respectively. Mathematical modeling suggested that bistability could lead to stochastic phenotypic switching between cisplatin-sensitive and resistant states in these cells. Consistently, purified subpopulations of sensitive and resistant cells re-created the mixed parental population when cultured separately. Altogether, these data point to an unexpected role of the FA complex in cisplatin resistance and highlight a novel non-genetic mechanism.

FAK, paxillin, and PI3K in ameloblastoma and adenomatoid odontogenic tumor

OBJECTIVE

Integrins function to bind cells to extracellular matrix in tissues, which triggers downstream signaling cascades that are important in cell survival, proliferation, cytokine activation, and cytoskeleton reorganization. These processes also play significant roles in neoplasms. This work aimed to investigate the pattern of expression of FAK, paxillin, and PI3K in ameloblastoma and adenomatoid odontogenic tumor (AOT).

MATERIALS AND METHODS

Immunohistochemistry was used to study FAK, paxillin, and PI3K in 45 ameloblastomas (32 conventional, 12 unicystic, and 1 peripheral types), 7 AOTs, and two developing human teeth.

RESULTS

Weak expression of FAK was seen in all AOT cases, while ameloblastoma had varying expression patterns, mostly strong to weak. The pattern of expression of paxillin and PI3K was relatively similar in both tumor types. In the dental germ, FAK and paxillin stained all the enamel organ components, while PI3K stained strongly the inner enamel epithelium. Stromal expression of FAK was not found to be useful in differentiating between tumors or tumor classes.

CONCLUSION

The expression of the proteins in the enamel organ suggests that their signaling may be important in odontogenesis. While some ameloblastomas strongly expressed FAK, all cases of AOT had weak signals suggesting low presence and phosphorylating activity of FAK in the latter.

CLINICAL RELEVANCE

A subset of FAK-positive ameloblastoma (as well as their malignant or metastasizing counterparts) which may have relatively aggressive behavior may be candidates for drug targeting of FAK as an additional management option.

Rationale for Lung Adenocarcinoma Prevention and Drug Development Based on Molecular Biology During Carcinogenesis

Lung adenocarcinoma (LUAD) is the most common and aggressive subtype of lung cancer with the greatest heterogeneity and aggression. Inspite of recent years’ achievements in understanding the pathogenesis of this disease, as well as the development of new therapeutic approaches, our knowledge on crucial early molecular events during its development is still rudimentary. Recent classification and grading of LUAD has postulated that LUAD does not arise spontaneously, but through a stepwise process from lung adenomatous premalignancy atypical adenomatous hyperplasia to adenocarcinoma in situ, minimally invasive adenocarcinoma, and eventually frankly invasive predominant adenocarcinoma. In this review, we discuss the molecular processes that drive the evolutionary process that results in the formation of LUAD. We also describe how to handle lung premalignancy in clinical settings based on the most recent advances in genomic biology and our own understanding of lung cancer prevention.

Paxillin regulated genomic networks in prostate cancer

Paxillin is extensively involved in focal adhesion signaling and kinase signaling throughout the plasma membrane and cytoplasm. However, recent studies in prostate cancer suggest that paxillin also plays a critical role in regulating gene expression within the nucleus, serving as a liaison between cytoplasmic and nuclear MAPK and Androgen Receptor (AR) signaling. Here we used RNA-seq to examine the paxillin-regulated transcriptome in several human prostate cancer cell lines. First, we examined paxillin effects on androgen-mediated transcription in control or paxillin-depleted AR-positive LNCaP and C4-2 human prostate cancer cells. In androgen-dependent LNCaP cells, we found over 1000 paxillin-dependent androgen-responsive genes, some of which are involved in endocrine therapy resistance. Most paxillin-dependent AR-mediated genes in LNCaP cells were no longer paxillin-dependent in androgen-sensitive, castration-resistant C4-2 cells, suggesting that castration-resistance may markedly alter paxillin effects on genomic AR signaling. To examine the paxillin-regulated transcriptome in the absence of androgen signaling, we performed RNA-seq in AR-negative PC3 human prostate cancer cells. Paxillin enhanced several pro-proliferative pathways, including the CyclinD/Rb/E2F and DNA replication/repair pathways. Additionally, paxillin suppressed pro-apoptotic genes, including CASP1 and TNFSF10. Quantitative PCR confirmed that these pathways are similarly regulated by paxillin in LNCaP and C4-2 cells. Functional studies showed that, while paxillin stimulated cell proliferation, it had minimum effect on apoptosis. Thus, paxillin appears to be an important transcriptional regulator in prostate cancer, and analysis of its transcriptome might lead to novel approaches toward the diagnosis and treatment of this important disease.

Regulators of the RAS-ERK pathway as therapeutic targets in thyroid cancer

Thyroid cancer is mostly an ERK-driven carcinoma, as up to 70% of thyroid carcinomas are caused by mutations that activate the RAS/ERK mitogenic signaling pathway. The incidence of thyroid cancer has been steadily increasing for the last four decades; yet, there is still no effective treatment for advanced thyroid carcinomas. Current research efforts are focused on impairing ERK signaling with small-molecule inhibitors, mainly at the level of BRAF and MEK. However, despite initial promising results in animal models, the clinical success of these inhibitors has been limited by the emergence of tumor resistance and relapse. The RAS/ERK pathway is an extremely complex signaling cascade with multiple points of control, offering many potential therapeutic targets: from the modulatory proteins regulating the activation state of RAS proteins to the scaffolding proteins of the pathway that provide spatial specificity to the signals, and finally, the negative feedbacks and phosphatases responsible for inactivating the pathway. The aim of this review is to give an overview of the biology of RAS/ERK regulators in human cancer highlighting relevant information on thyroid cancer and future areas of research.

Hic-5 expression is a major indicator of cancer cell morphology, migration, and plasticity in three-dimensional matrices

The focal adhesion proteins Hic-5 and paxillin have been previously identified as key regulators of MDA-MB-231 breast cancer cell migration and morphologic mesenchymal-amoeboid plasticity in three-dimensional (3D) extracellular matrices (ECMs). However, their respective roles in other cancer cell types have not been evaluated. Herein, utilizing 3D cell-derived matrices and fibronectin-coated one-dimensional substrates, we show that across a variety of cancer cell lines, the level of Hic-5 expression serves as the major indicator of the cells primary morphology, plasticity, and in vitro invasiveness. Domain mapping studies reveal sites critical to the functions of both Hic-5 and paxillin in regulating phenotype, while ectopic expression of Hic-5 in cell lines with low endogenous levels of the protein is sufficient to induce a Rac1-dependent mesenchymal phenotype and, in turn, increase amoeboid-mesenchymal plasticity and invasion. We show that the activity of vinculin, when coupled to the expression of Hic-5 is required for the mesenchymal morphology in the 3D ECM. Taken together, our results identify Hic-5 as a critical modulator of tumor cell phenotype that could be utilized in predicting tumor cell migratory and invasive behavior in vivo.

Increased Paxillin expression in prostate cancer is associated with advanced pathological features, lymph node metastases and biochemical recurrence

Purpose Paxillin regulates cell-cell adhesion, and altered Paxillin expression has been associated with human carcinogenesis. This study analyzed the association between Paxillin expression in prostate cancer (PCa) tissues with clinicopathological features, lymph node metastasis and biochemical PCa recurrence.

Methods A total of 386 tissue specimens from PCa patients who received radical prostatectomy and 60 tissue specimens from benign prostatic hyperplasia (BPH) cases were collected to construct tissue microarrays, which were subsequently immunostained for Paxillin expression. Thirty positive lymph node tissue specimens and 10 healthy prostate tissue specimens were randomly selected for Paxillin immunostaining.

Results The association between Paxillin expression, lymph node metastasis and biochemical PCa recurrence was analyzed. Paxillin expression was significantly higher in PCa than both normal and BPH tissues (P<0.001) and was correlated with preoperative prostate-specific antigen level, Gleason score, clinical tumor stage, lymph node metastasis, positive surgical margin, extracapsular extension and seminal vesicle invasion (P<0.05 for all). Logistic regression analysis showed that Paxillin and Gleason score were independent risk factors for PCa lymph node metastasis (P<0.05). The receiver operating characteristic (ROC) curve indicated that Paxillin expression (AUC=0.723) more accurately predicted PCa lymph node metastasis than Gleason score (AUC=0.692). Kaplan-Meier curve analysis showed that increased Paxillin expression was associated with shortened biochemical-free survival (BFS) after radical prostatectomy (P<0.001).

Conclusion Paxillin was significantly upregulated in PCa compared with BPH and normal tissues and associated with lymph node metastasis and shortened BFS of PCa. Further study will investigate the underlying molecular mechanism and the role of Paxillin in PCa.

FAK and paxillin, two potential targets in pancreatic cancer

Pancreatic ductal adenocarcinoma (PDAC) is a devastating cancer in large part due to late diagnosis and a lack of effective screening tests. In spite of recent progress in imaging, surgery and new therapeutic options for pancreatic cancer, the overall five-year survival still remains unacceptably low. Numerous studies have shown that focal adhesion kinase (FAK) is activated in many cancers including PDAC and promotes cancer progression and metastasis. Paxillin, an intracellular adaptor protein that plays a key role in cytoskeletal organization, connects integrins to FAK and plays a key role in assembly and disassembly of focal adhesions. Here, we have reviewed evidence in support of FAK as a potential therapeutic target and summarized related combinatorial therapies.

Contextual tumor suppressor function of T cell death-associated gene 8 (TDAG8) in hematological malignancies

Background

Extracellular acidosis is a condition found within the tumor microenvironment due to inadequate blood perfusion, hypoxia, and altered tumor cell metabolism. Acidosis has pleiotropic effects on malignant progression; therefore it is essential to understand how acidosis exerts its diverse effects. TDAG8 is a proton-sensing G-protein-coupled receptor that can be activated by extracellular acidosis.

Methods

TDAG8 gene expression was analyzed by bioinformatic analyses and quantitative RT-PCR in human hematological malignancies. Retroviral transduction was used to restore TDAG8 expression in U937, Ramos and other blood cancer cells. Multiple in vitro and in vivo tumorigenesis and metastasis assays were employed to evaluate the effects of TDAG8 expression on blood cancer progression. Western blotting, immunohistochemistry and biochemical approaches were applied to elucidate the underlying mechanisms associated with the TDAG8 receptor pathway.

Results

TDAG8 expression is significantly reduced in human blood cancers in comparison to normal blood cells. Severe acidosis, pH 6.4, inhibited U937 cancer cell proliferation while mild acidosis, pH 6.9, stimulated its proliferation. However, restoring TDAG8 gene expression modulated the U937 cell response to mild extracellular acidosis and physiological pH by reducing cell proliferation. Tumor xenograft experiments further revealed that restoring TDAG8 expression in U937 and Ramos cancer cells reduced tumor growth. It was also shown U937 cells with restored TDAG8 expression attached less to Matrigel, migrated slower toward a chemoattractant, and metastasized less in severe combined immunodeficient mice. These effects correlated with a reduction in c-myc oncogene expression. The mechanistic investigation indicated that Gα13/Rho signaling arbitrated the TDAG8-mediated c-myc oncogene repression in response to acidosis.

Conclusions

This study provides data to support the concept that TDAG8 functions as a contextual tumor suppressor down-regulated in hematological malignancies and potentiation of the TDAG8 receptor pathway may be explored as a potential anti-tumorigenic approach in blood cancers.

Electronic supplementary material

The online version of this article (doi:10.1186/s12967-017-1305-6) contains supplementary material, which is available to authorized users.

Evaluation of paxillin expression in patients with oral squamous cell carcinoma: An immunohistochemical study

Background:

Oral squamous cell carcinoma (OSCC) is the tenth most common cancer in the world. The diagnosis of OSCC remains problematic, especially in advanced-stage tumors.

Aims:

The present study was conducted to understand the pattern of expression of paxillin in varying grades of carcinomas and also to ascertain whether its expression has an association with increasing grades.

Methods:

A total of ninety formalin-fixed paraffin-embedded tissues of OSCC were included in the study comprising thirty cases of each of well-differentiated squamous cell carcinomas, moderately differentiated squamous cell carcinomas (MDSCCs) and poorly differentiated squamous cell carcinomas (PDSCCs). The tissue sections were subjected to immunohistochemical staining of paxillin using super polymer-sensitive polymer 3,3’ diaminobenzidine detection kit. All the three groups were analyzed on various parameters including staining intensity, location and percentage of staining. SPSS 19.0 was used to analyze the data.

Results:

Paxillin stain positivity was observed in 95.5% of the cases. Predominant intense paxillin staining was demonstrated in 17 (56.6%) cases of well-differentiated squamous cell carcinoma, 28 (93.3%) cases of moderately differentiated squamous squamous cell carcinoma and 15 (50%) cases of PDSCC. A predominant cytoplasmic staining was observed in 21 (70%) cases of PDSCC and cytoplasmic plus membrane staining in 14 (46.6%) cases of MDSCC.

Conclusion:

The present study provides evidence that paxillin may be involved in the development and progression of OSCC. Thus, paxillin could be considered a useful biomarker for patient management and prognosis.

Paxillin functions as an oncogene in human gliomas by promoting cell migration and invasion

Background

Paxillin is implicated in tumorigenesis, progression and aggressive phenotypes of various malignancies, highlighting its functions in cellular adhesion, migration and survival. However, the roles of paxillin in human gliomas remain unclear. The aim of this study was to evaluate the clinical implication of paxillin expression in patients with gliomas and its biological function in glioma cells.

Patients and methods

Expression levels of paxillin gene and protein, respectively, were detected by quantitative real-time reverse transcription polymerase chain reaction, Western blot and immunohistochemistry analyses in 120 pairs of glioma and matched nontumorous brain tissues. The associations between paxillin expression and various histopathological features of glioma patients were also statistically evaluated. Then, the functions of paxillin in cell migration and invasion of glioma cell lines were determined by transwell assays in vitro.

Results

The expression levels of both paxillin gene and protein in glioma tissues were markedly higher than those in matched nontumorous brain tissues. Notably, paxillin overexpression was significantly associated with the grade of malignancy (P<0.05). Moreover, the enforced expression of paxillin promoted the migration and invasion of glioma cells, while the loss of paxillin expression efficiently suppressed cell migration and invasion of glioma cell lines.

Conclusion

Our data suggest that paxillin may function as an oncogene and its overexpression may be closely correlated with tumor progression of human gliomas by modulating tumor cell motility, implying the potential of paxillin as a new therapeutic target for glioma intervention.

ERK Signals: Scaffolding Scaffolds?

ERK1/2 MAP Kinases become activated in response to multiple intra- and extra-cellular stimuli through a signaling module composed of sequential tiers of cytoplasmic kinases. Scaffold proteins regulate ERK signals by connecting the different components of the module into a multi-enzymatic complex by which signal amplitude and duration are fine-tuned, and also provide signal fidelity by isolating this complex from external interferences. In addition, scaffold proteins play a central role as spatial regulators of ERKs signals. In this respect, depending on the subcellular localization from which the activating signals emanate, defined scaffolds specify which substrates are amenable to be phosphorylated. Recent evidence has unveiled direct interactions among different scaffold protein species. These scaffold-scaffold macro-complexes could constitute an additional level of regulation for ERK signals and may serve as nodes for the integration of incoming signals and the subsequent diversification of the outgoing signals with respect to substrate engagement.

Expression of paxillin in laryngeal squamous cell carcinoma and its prognostic value

Paxillin (PXN) gene has been reported to act as an oncogene in many malignancies and play important roles in the development of human carcinomas. However, the relationship between the expression of PXN and clinicopathological characteristics in human laryngeal carcinoma remains unclear. This study aimed to examine the expression of PXN, and to evaluate the clinical significance of its expression in human laryngeal squamous cell carcinoma (LSCC). Real-time quantitative PCR (qRT-PCR), Western blotting and immunohistochemistry were performed to analyze the expression of PXN in LSCC tissues and corresponding paracancerous normal tissues. Kaplan-Meier survival and Cox regression analyses were performed to evaluate the prognosis of patients with LSCC. The expression of PXN was significantly higher in LSCC than in matched paracancerous normal tissues. Immunohistochemical analysis was performed in human LSCC samples and the data were correlated with clinicopathologic features. Levels of PXN in LSCC were related to histopathological grade (P = 0.016), Lymph node metastasis (P = 0.029) and TNM stage (P < 0.001). Kaplan-Meier analysis revealed that survival curves of the overall survival of patients with high PXN expression was significantly worse than that of low PXN expression (P = 0.035). Cox regression analysis revealed that PXN expression level was an independent prognostic factor of the overall survival rate of patients with LSCC (P = 0.002). These findings suggest that PXN expression has potential use as a novel biomarker of LSCC patients and may serve as an independent predictive factor for prognosis of LSCC patients.

Expression of Paxillin is Correlated with Clinical Prognosis in Colorectal Cancer Patients

Background

The aim of this study was to investigate the expression of Paxillin in colorectal carcinoma and its significance in clinical prognosis.

Material/Methods

Tissue specimens from 242 colorectal cancer patients who underwent radical resection were collected in Shaanxi Provincial People’s Hospital from 2010 to 2014. The mRNA levels of Paxillin in colorectal cancer tissue and tissue adjacent to carcinoma of 62 patients were measured by quantitative real-time PCR. Immunohistochemistry staining was used to detect the expression of Paxillin in 242 samples of paraffin-embedded tissues.

Results

The mRNA and protein level of Paxillin in colorectal cancer tissues were significantly higher than those in the tissue adjacent to carcinoma (P<0.001 and P=0.003, respectively). The expression of Paxillin was significantly correlated to tumor histological grade (P<0.001), tumor size (P=0.01), serum CA199 level (P<0.001), the clinical TNM stage (P<0.001), and distant metastasis (P<0.001). Survival analysis showed that the prognosis of the patients with high expression of Paxillin was poorer than those with low expression of Paxillin (P=0.03). Cox proportional hazards model with stepwise selection showed that age, Paxillin expression level, and the clinical TNM stage were independent prognostic factors influencing survival for patients (P=0.01, P=0.004 and P<0.001, respectively).

Conclusions

Paxillin was expressed at significantly higher levels in colorectal cancer tissues and might serve as a potential prognostic indicator in patients with colorectal cancer.

MEKK2 regulates paxillin ubiquitylation and localization in MDA-MB 231 breast cancer cells

The intracellular kinase MEKK2 (mitogen-activated protein kinase/extracellular-signal-regulated kinase kinase kinase 2) is an upstream regulator of JNK (c-Jun N-terminal kinase), but additional functions for MEKK2 have not been well defined. Silencing MEKK2 expression in invasive breast tumour cells markedly inhibits xenograft metastasis, indicating that MEKK2 controls tumour cell function required for tumour progression. In our previous investigation of MEKK2 function, we discovered that tumour cell attachment to fibronectin recruits MEKK2 to focal adhesion complexes, and that MEKK2 knockdown is associated with stabilized focal adhesions and significant inhibition of tumour cell migration. In the present study we investigate MEKK2 function in focal adhesions and we report that MEKK2 physically associates with the LD1 motif of the focal adhesion protein paxillin. We reveal that MEKK2 induces paxillin ubiquitylation, and that this function requires both the paxillin LD1 motif and MEKK2 kinase activity. Finally, we demonstrate that MEKK2 promotes paxillin redistribution from focal adhesions into the cytoplasm, but does not promote paxillin degradation. Taken together, our results reveal a novel function for MEKK2 as a regulator of ubiquitylation-dependent paxillin redistribution in breast tumour cells.

Tobacco smoke induces epithelial barrier dysfunction via receptor EphA2 signaling

Erythropoietin-producing human hepatocellular carcinoma (Eph) receptors are the largest family of receptor tyrosine kinases (RTKs) that mediate various cellular and developmental processes. The degrees of expression of these key molecules control the cell-cell interactions. Although the role of Eph receptors and their ligand Ephrins is well studied in developmental processes, their function in tobacco smoke (TS)-induced epithelial barrier dysfunction is unknown. We hypothesized that TS may induce permeability in bronchial airway epithelial cell (BAEpC) monolayer by modulating receptor EphA2 expression, actin cytoskeleton, adherens junction, and focal adhesion proteins. Here we report that in BAEpCs, acute TS exposure significantly upregulated EphA2 and EphrinA1 expression, disrupted the actin filaments, decreased E-cadherin expression, and increased protein permeability, whereas the focal adhesion protein paxillin was unaffected. Silencing the receptor EphA2 expression with silencing interference RNA (siRNA) significantly attenuated TS-induced hyperpermeability in BAEpCs. In addition, when BAEpC monolayer was transfected with EphA2-expressing plasmid and treated with recombinant EphrinA1, the transepithelial electrical resistance decreased significantly. Furthermore, TS downregulated E-cadherin expression and induced hyperpermeability across BAEpC monolayer in a Erk1/Erk2, p38, and JNK MAPK-dependent manner. TS induced hyperpermeability in BAEpC monolayer by targeting cell-cell adhesions, and interestingly cell-matrix adhesions were unaffected. The present data suggest that TS causes significant damage to the BAEpCs via induction of EphA2 and downregulation of E-cadherin. Induction of EphA2 in the BAEpCs exposed to TS may be an important signaling event in the pathogenesis of TS-induced epithelial injury.

Paxillin controls endothelial cell migration and tumor angiogenesis by altering neuropilin 2 expression

Although a number of growth factors and receptors are known to control tumor angiogenesis, relatively little is known about the mechanism by which these factors influence the directional endothelial cell migration required for cancer microvessel formation. Recently, it has been shown that the focal adhesion protein paxillin is required for directional migration of fibroblasts in vitro. Here, we show that paxillin knockdown enhances endothelial cell migration in vitro and stimulates angiogenesis during normal development and in response to tumor angiogenic factors in vivo. Paxillin produces these effects by decreasing expression of neuropilin 2 (NRP2). Moreover, soluble factors secreted by tumors that stimulate vascular ingrowth, including vascular endothelial growth factor (VEGF), also decrease endothelial cell expression of paxillin and NRP2, and overexpression of NRP2 reverses these effects. These results suggest that the VEGF-paxillin-NRP2 pathway could represent a new therapeutic target for cancer and other angiogenesis-related diseases.

Paxillin expression is closely linked to the pathogenesis, progression and prognosis of gastric carcinomas

Paxillin encodes a focal adhesion-associated protein and is involved in the progression and aggressive phenotypes of malignancies through its interactions with the actin cytoskeleton and key signal transduction oncogenes. The present study aimed to investigate the clinicopathological and prognostic significance of paxillin in gastric cancer. The expression of paxillin was evaluated using tissue microarrays of gastric adjacent non-cancerous mucosa, adenoma and carcinoma specimens by immunohistochemistry. Paxillin expression was compared against clinicopathological parameters and the survival time of the patients. Paxillin was highly expressed in gastric adenoma compared with that in non-neoplastic mucosa and carcinoma (P<0.05). Paxillin expression was lower in the younger carcinoma patients compared with that in the elder carcinoma patients (P<0.05). Paxillin expression was negatively correlated with tumor size, depth of invasion and lymph node metastasis, but not with patient gender, lymphatic or venous invasion, or TNM staging (P>0.05). Higher paxillin expression was observed in intestinal-type compared with diffuse-type carcinoma (P<0.05). Kaplan-Meier analysis indicated a positive association between paxillin expression and cumulative survival rate in all, advanced and intestinal-type carcinoma patients (P<0.05). Multivariate analysis using the Cox proportional hazards model indicated that patient age, depth of invasion, lymphatic invasion, lymph node metastasis, TNM staging and Lauren classification were independent prognostic factors for all gastric carcinomas (P<0.05). Aberrant paxillin expression may be involved in the growth, invasion, metastasis and differentiation of gastric carcinoma. Altered paxillin expression may, therefore, be employed as an indicator of pathobiological behaviors and prognosis of gastric carcinomas.

Abnormal expression of paxillin correlates with tumor progression and poor survival in patients with gastric cancer

Background

Paxillin (PXN) has been found to be aberrantly regulated in various malignancies and involved in tumor growth and invasion. The clinicopathological and prognostic significance of PXN in gastric cancer is still unclear.

Methods

The expression of PXN was determined in paired gastric cancer tissues and adjacent normal tissues by Western blotting and real-time PCR. Immunohistochemistry was performed to detect the expression of PXN in 239 gastric cancer patients. Statistical analysis was applied to investigate the correlation between PXN expression and clinicopathological characteristics and prognosis in patients. Additionally, the effects of PXN on gastric cancer cell proliferation and migration were also evaluated.

Results

PXN was up-regulated in gastric cancer tissues and cell lines as compared with adjacent normal tissues and normal gastric epithelial cell line GES-1. Overexpression of PXN was correlated with distant metastasis (P = 0.001) and advanced tumor stage (P = 0.021) in gastric cancer patients. Patients with high PXN expression tended to have poor prognosis compared with patients with low PXN expression (P < 0.001). Multivariate analysis demonstrated that PXN expression was an independent prognostic factor (P = 0.020). Moreover, ectopic expression of PXN promotes cell proliferation and migration in AGS cells whereas knockdown of PXN inhibits cell proliferation and migration in SGC7901 cells.

Conclusions

PXN plays an important role in tumor progression and may be used as a potential prognostic indicator in gastric cancer.

Oral administration of transforming growth factor-β1 (TGF-β1) protects the immature gut from injury via Smad protein-dependent suppression of epithelial nuclear factor κB (NF-κB) signaling and proinflammatory cytokine production

Inflammatory immune responses play an important role in mucosal homeostasis and gut diseases. Nuclear factor κB (NF-κB), central to the proinflammatory cascade, is activated in necrotizing enterocolitis (NEC), a devastating condition of intestinal injury with extensive inflammation in premature infants. TGF-β is a strong immune suppressor and a factor in breast milk, which has been shown to be protective against NEC. In an NEC animal model, oral administration of the isoform TGF-β1 activated the downstream effector Smad2 in intestine and significantly reduced NEC incidence. In addition, TGF-β1 suppressed NF-κB activation, maintained levels of the NF-κB inhibitor IκBα in the intestinal epithelium, and systemically decreased serum levels of IL-6 and IFN-γ. The immature human fetal intestinal epithelial cell line H4 was used as a reductionistic model of the immature enterocyte to investigate mechanism. TGF-β1 pretreatment inhibited the TNF-α-induced IκBα phosphorylation that targets the IκBα protein for degradation and inhibited NF-κB activation. Chromatin immunoprecipitation (ChIP) assays demonstrated decreased NF-κB binding to the promoters of IL-6, IL-8, and IκBα in response to TNF-α with TGF-β1 pretreatment. These TGF-β1 effects appear to be mediated through the canonical Smad pathway as silencing of the TGF-β central mediator Smad4 resulted in loss of the TGF-β1 effects. Thus, TGF-β1 is capable of eliciting anti-inflammatory effects by inhibiting NF-κB specifically in the intestinal epithelium as well as by decreasing systemic IL-6 and IFN-γ levels. Oral administration of TGF-β1 therefore can potentially be used to protect against gastrointestinal diseases.

Very low levels of surface CD45 reflect CLL cell fragility, are inversely correlated with trisomy 12 and are associated with increased treatment-free survival

It has recently been suggested that the percentage of smudge cells on blood smears from patients with chronic lymphocytic leukemia (CLL) could predict overall survival. However, smudge cells are a cytological artifact influenced by multiple physical factors not related to CLL. To identify simple parameters reflecting CLL cell fragility, we studied CD45 expression in a series of 66 patients with Binet stage A CLL. Decreased CD45 expression was specific for CLL cells when compared to 44 patients with a leukemic phase of B-cell non Hodgkin lymphoma and 42 control B-cells. CD45 expression was markedly decreased for all patients with CLL with high percentages of smudge cells. CLL cells with the lowest CD45 expression were the most sensitive to osmotic shock. Very low levels of CD45 expression were significantly associated with lack of CD38 expression, absence of trisomy 12, and with increased treatment free survival time. Altogether, these results demonstrate that low levels of CD45 expression are specific to CLL cells and reflect cell fragility, suggesting that this is an important intrinsic biological feature that determines disease course.

Erythropoietin protects epithelial cells from excessive autophagy and apoptosis in experimental neonatal necrotizing enterocolitis

Neonatal necrotizing enterocolitis (NEC) is a devastating gastrointestinal disease of preterm infants. Increased intestinal epithelium permeability is an early event in NEC pathogenesis. Autophagy and apoptosis are induced by multiple stress pathways which may impact the intestinal barrier, and they have been associated with pathogenesis of diverse gastrointestinal diseases including inflammatory bowel disease. Using both in vitro and in vivo models, this study investigates autophagy and apoptosis under experimental NEC stresses. Furthermore this study evaluates the effect of erythropoietin (Epo), a component of breast milk previously shown to decrease the incidence of NEC and to preserve intestinal barrier function, on intestinal autophagy and apoptosis. It was found that autophagy and apoptosis are both rapidly up regulated in NEC in vivo as indicated by increased expression of the autophagy markers Beclin 1 and LC3II, and by evidence of apoptosis by TUNEL and cleaved caspase-3 staining. In the rat NEC experimental model, autophagy preceded the onset of apoptosis in intestine. In vitro studies suggested that Epo supplementation significantly decreased both autophagy and apoptosis via the Akt/mTOR signaling pathway and the MAPK/ERK pathway respectively. These results suggest that Epo protects intestinal epithelium from excessive autophagy and apoptosis in experimental NEC.

ERK2 but not ERK1 mediates HGF-induced motility in non-small cell lung carcinoma cell lines

Aberrant signalling of receptor tyrosine kinases (RTKs), such as c-Met, the receptor for hepatocyte growth factor (HGF), has been implicated in the oncogenesis of various tumours including non-small cell lung carcinoma (NSCLC). Through its pro-migratory properties, c-Met has been implicated specifically in the process of tumour metastasis, demanding a better understanding of the underlying signalling pathways. Various players downstream of c-Met have been well characterised, including the extracellular-signal-regulated kinases (ERKs) 1 and 2. In a small interfering RNA (siRNA)-based high-throughput wound healing screen performed in A549 lung carcinoma cells, we identified ERK2 but not ERK1 as a strong mediator of HGF-induced motility. This finding was confirmed in several NSCLC cell lines as well as in HeLa cells. One known substrate for ERK kinases in cell migration, the focal adhesion protein paxillin, was also one of the hits identified in the screen. We demonstrate that HGF stimulation results in a time-dependent phosphorylation of paxillin on serine 126, a process that can be blocked by inhibition of the ERK1/2 upstream kinase mitogen-activated protein kinase/ERK kinase 1 (MEK1) or inhibition of glycogen synthase kinase 3 (GSK3). Further, we show that paxillin turnover at focal adhesions is increased upon stimulation by HGF, an effect that is dependent on serine residues 126 (GSK3 site) and 130 (ERK site) within paxillin. In line with the isoform-specific requirement of ERK2 for HGF-mediated migration in lung tumour cell models, ERK2 but not ERK1 is shown to be responsible for paxillin serine 126 phosphorylation and its increased turnover at focal adhesions.

Paxillin mutations affect focal adhesions and lead to altered mitochondrial dynamics: relevance to lung cancer

Cytoskeletal and focal adhesion abnormalities are observed in several types of cancer, including lung cancer. We have previously reported that paxillin (PXN) was mutated, amplified, and overexpressed in a significant number of lung cancer patient samples, that PXN protein was upregulated in more advanced stages of lung cancer compared with lower stages, and that the PXN gene was also amplified in some pre-neoplastic lung lesions. Among the mutations investigated, we previously found that PXN variant A127T in lung cancer cells enhanced cell proliferation and focal adhesion formation and colocalized with the anti-apoptotic protein B Cell Lymphoma 2 (BCL-2), which is known to localize to the mitochondria, among other sites. To further explore the effects of activating mutations of PXN on mitochondrial function, we cloned and expressed wild-type PXN and variants containing the most commonly occurring PXN mutations (P46S, P52L, G105D, A127T, P233L, T255I, D399N, E423K, P487L, and K506R) in a GFP-tagged vector using HEK-293 human embryonic kidney cells. Utilizing live-cell imaging to systematically study the effects of wild-type PXN vs. mutants, we created a model that recapitulates the salient features of the measured dynamics and conclude that compared with wild-type, some mutant clones confer enhanced focal adhesion and lamellipodia formation (A127T, P233L, and P487L) and some confer increased association with BCL-2, Dynamin-related Protein-1 (DRP-1), and Mitofusion-2 (MFN-2) proteins (P233L and D399N). Further, PXN mutants, through their interactions with BCL-2 and DRP-1, could regulate cisplatin drug resistance in human lung cancer cells. The data reported herein suggest that mutant PXN variants play a prominent role in mitochondrial dynamics with direct implications on lung cancer progression and hence, deserve further exploration as therapeutic targets.

Synergistic protection of combined probiotic conditioned media against neonatal necrotizing enterocolitis-like intestinal injury

Balance among the complex interactions of the gut microbial community is important for intestinal health. Probiotic bacteria can improve bacterial balance and have been used to treat gastrointestinal diseases. Neonatal necrotizing enterocolitis (NEC) is a life-threatening inflammatory bowel disorder primarily affecting premature infants. NEC is associated with extensive inflammatory NF-κB signaling activation as well as intestinal barrier disruption. Clinical studies have shown that probiotic administration may protect against NEC, however there are safety concerns associated with the ingestion of large bacterial loads in preterm infants. Bacteria-free conditioned media (CM) from certain probiotic organisms have been shown to retain bioactivity including anti-inflammatory and cytoprotective properties without the risks of live organisms. We hypothesized that the CM from Lactobacillus acidophilus (La), Bifidobacterium infantis (Bi), and Lactobacillus plantarum (Lp), used separately or together would protect against NEC. A rodent model with intestinal injury similar to NEC was used to study the effect of CM from Lp, La/Bi, and La/Bi/Lp on the pathophysiology of NEC. All the CM suppressed NF-κB activation via preserved IκBα expression and this protected IκBα was associated with decreased liver activity of the proteasome, which is the degrading machinery for IκBα. These CM effects also caused decreases in intestinal production of the pro-inflammatory cytokine TNF-α, a downstream target of the NF-κB pathway. Combined La/Bi and La/Bi/Lp CM in addition protected intestinal barrier function by maintaining tight junction protein ZO-1 levels and localization at the tight junction. Double combined La/Bi CM significantly reduced intestinal injury incidence from 43% to 28% and triple combined La/Bi/Lp CM further reduced intestinal injury incidence to 20%. Thus, this study demonstrates different protective mechanisms and synergistic bioactivity of the CM from different organisms in ameliorating NEC-like intestinal injury in an animal model.

Overexpression of paxillin induced by miR-137 suppression promotes tumor progression and metastasis in colorectal cancer

The deregulation of paxillin (PXN) has been involved in the progression and metastasis of different malignancies including colorectal cancer (CRC). miR-137 is frequently suppressed in CRC. PXN is predicted to be a direct target of miR-137 in CRC cells. On this basis, we hypothesized that overexpression of PXN induced by suppression of miR-137 may promote tumor progression and metastasis and predicts poor prognosis. We detected the expression of PXN and miR-137 in clinical tumor tissues by immunohistochemical analysis and real-time PCR, positive PXN staining was observed in 198 of the 247 (80.1%) cases, whereas no or weak PXN staining was observed in the adjacent non-cancerous area. Higher level of PXN messenger RNA (mRNA) and lower level of miR-137 was observed in cancer tissues than adjacent non-cancerous tissues. High expression of PXN and low expression of miR-137 was associated with aggressive tumor phenotype and adverse prognosis. Moreover, the expression of PXN was negatively correlated with miR-137 expression. A dual-luciferase reporter gene assay validated that PXN was a direct target of miR-137. The use of miR-137 mimics or inhibitor could decrease or increase PXN mRNA and protein levels in CRC cell lines. Knockdown of PXN or ectopic expression of miR-137 could markedly inhibit cell proliferation, migration and invasion in vitro and repress tumor growth and metastasis in vivo. Taken together, these results demonstrated that overexpression of PXN induced by suppression of miR-137 promotes tumor progression and metastasis and could serve as an independent prognostic indicator in CRC patients.

Diverse roles for the paxillin family of proteins in cancer

The paxillin family of intracellular scaffold proteins includes paxillin, Hic-5, and leupaxin, and all have been identified as key regulators of the cellular migration machinery in both 2- and 3-dimensional microenvironments. Herein, we provide insight into the roles of these proteins during tumorigenesis and metastasis, highlighting their functions in cancer initiation as well as tumor cell dissemination and survival. Furthermore, we speculate on the potential of paxillin family proteins as both future prognostic and therapeutic targets.

Fascin-1, ezrin and paxillin contribute to the malignant progression and are predictors of clinical prognosis in laryngeal squamous cell carcinoma

Aims

Fascin-1, ezrin and paxillin, cytoskeleton-associated proteins, have been implicated in several human cancers, but their role in laryngeal squamous cell carcinoma (LSCC) is unknown. We investigated the association of their expression and clinicopathologic factors and their prognostic value in LSCC.

Materials and Methods

Quantitative RT-PCR and western blot analyses were used to examine mRNA and protein levels in 10 fresh LSCC specimens and 10 corresponding adjacent normal margin (ANM) tissues from patients undergoing surgery in 2012. We used immunohistochemistry to retrospectively study 216 paraffin blocks of LSCC samples from patients (193 men) who had undergone surgery between 2000 and 2006 and had not received special treatment before the diagnosis. Univariate analysis of patient survival involved the Kaplan–Meier method. Multivariate analyses involved the Cox proportional hazards model.

Results

The relative mRNA and protein levels of fascin-1, ezrin and paxillin were significantly greater in LSCC than ANM tissue (P<0.05). The high expression of fascin-1, ezrin or paxillin was positively correlated with poor tumor differentiation, cervical lymph node metastasis (N+), and advanced clinical stage (III+IV) (P<0.05) but not sex or metastasis. In addition, a high expression of fascin-1 (P = 0.007) or ezrin (P = 0.047) was associated with advanced tumor stage (T3+T4). The expression of fascin-1 was higher in smokers than non-smokers (P = 0.019). A high expression of fascin-1, ezrin or paxillin was associated with poor prognosis.

Conclusions

Fascin-1, ezrin and paxillin may be prognostic of poor outcome with LSCC after surgery. Our study may lead to establishing new molecular therapeutic targets and/or prognostic biomarkers in LSCC.

Sphingosine kinase 1 is required for mesothelioma cell proliferation: role of histone acetylation

Background

Malignant pleural mesothelioma (MPM) is a devastating disease with an overall poor prognosis. Despite the recent advances in targeted molecular therapies, there is a clear and urgent need for the identification of novel mesothelioma targets for the development of highly efficacious therapeutics.

Methodology/Principal Findings

In this study, we report that the expression of Sphingosine Kinase 1 (SphK1) protein was preferentially elevated in MPM tumor tissues (49 epithelioid and 13 sarcomatoid) compared to normal tissue (n = 13). In addition, we also observed significantly elevated levels of SphK1 and SphK2 mRNA and SphK1 protein expression in MPM cell lines such as H2691, H513 and H2461 compared to the non-malignant mesothelial Met5 cells. The underlying mechanism appears to be mediated by SphK1 induced upregulation of select gene transcription programs such as that of CBP/p300 and PCAF, two histone acetyl transferases (HAT), and the down regulation of cell cycle dependent kinase inhibitor genes such as p27Kip1 and p21Cip1. In addition, using immunoprecipitates of anti-acetylated histone antibody from SphK inhibitor, SphK-I2 treated Met5A and H2691 cell lysates, we also showed activation of other cell proliferation related genes, such as Top2A (DNA replication), AKB (chromosome remodeling and mitotic spindle formation), and suppression of p21 CIP1 and p27KIP1. The CDK2, HAT1 and MYST2 were, however, unaffected in the above study. Using SphK inhibitor and specific siRNA targeting either SphK1 or SphK2, we also unequivocally established that SphK1, but not SphK2, promotes H2691 mesothelioma cell proliferation. Using a multi-walled carbon nanotubes induced peritoneal mesothelioma mouse model, we showed that the SphK1−/− null mice exhibited significantly less inflammation and granulamatous nodules compared to their wild type counterparts.

Conclusions/Significance

The lipid kinase SphK1 plays a positive and essential role in the growth and development of malignant mesothelioma and is therefore a likely therapeutic target.

Paxillin mediates extranuclear and intranuclear signaling in prostate cancer proliferation

In prostate cancer, the signals that drive cell proliferation change as tumors progress from castration-sensitive (androgen-dominant) to castration-resistant states. While the mechanisms underlying this change remain uncertain, characterization of common signaling components that regulate both stages of prostate cancer proliferation is important for developing effective treatment strategies. Here, we demonstrate that paxillin, a known cytoplasmic adaptor protein, regulates both androgen- and EGF-induced nuclear signaling. We show that androgen and EGF promoted MAPK-dependent phosphorylation of paxillin, resulting in nuclear translocation of paxillin. We found nuclear paxillin could then associate with androgen-stimulated androgen receptor (AR). This complex bound AR-sensitive promoters, retaining AR within the nucleus and regulating AR-mediated transcription. Nuclear paxillin also complexed with ERK and ELK1, mediating c-FOS and cyclin D1 expression; this was followed by proliferation. Thus, paxillin is a liaison between extranuclear MAPK signaling and nuclear transcription in response to androgens and growth factors, making it a potential regulator of both castration-sensitive and castration-resistant prostate cancer. Accordingly, paxillin was required for normal growth of human prostate cancer cell xenografts, and its expression was elevated in human prostate cancer tissue microarrays. Paxillin is therefore a potential biomarker for prostate cancer proliferation and a possible therapeutic target for prostate cancer treatment.