TGF-beta1 up-regulates paxillin protein expression in malignant astrocytoma cells: requirement for a fibronectin substrate

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.

TGF-β1 Facilitates TAp63α Protein Lysosomal Degradation to Promote Pancreatic Cancer Cell Migration

TGF-β signaling plays a pivotal role in promoting tumor cell migration and cancer metastasis. ΔNp63α and TAp63α are two major isoforms of p53-related p63 protein. Our recent study has shown that TGF-β1 promotes ΔNp63α protein degradation to facilitate cancer metastasis. However, whether TAp63α is involved in TGF-β1-induced cancer metastasis remains unclear. In this study, we show that, in human pancreatic cancer MIA PaCa-2 cells harboring p53-R248W allele, TGF-β1 can significantly inhibit TAp63α protein stability in a Smad pathway-independent manner. Lysosome inhibitor, chloroquine, but not proteasome inhibitor MG132, can rescue TGF-β1-induced downregulation of TAp63α protein. In addition, we show that either TGF-β1 treatment or silencing of TAp63α can dramatically increase migration of MIA PaCa-2 cells. Importantly, the restored expression of TAp63α can effectively block TGF-β1-induced migration of MIA PaCa-2 cells. Mechanistically, we show that TGF-β1 promotes TAp63α protein degradation, leading to upregulation of p53-R248W protein expression, and consequently resulting in elevated MIA PaCa-2 cell migration. Together, this study indicates that lysosomal degradation is an important way for regulating TAp63α protein fate and highlights that TGF-β1-TAp63α-mutant p53 axis is critically important in pancreatic cancer metastasis.

Insights on the Pathogenesis of Aneurysm through the Study of Hereditary Aortopathies

Thoracic aortic aneurysms (TAA) are permanent and localized dilations of the aorta that predispose patients to a life-threatening risk of aortic dissection or rupture. The identification of pathogenic variants that cause hereditary forms of TAA has delineated fundamental molecular processes required to maintain aortic homeostasis. Vascular smooth muscle cells (VSMCs) elaborate and remodel the extracellular matrix (ECM) in response to mechanical and biochemical cues from their environment. Causal variants for hereditary forms of aneurysm compromise the function of gene products involved in the transmission or interpretation of these signals, initiating processes that eventually lead to degeneration and mechanical failure of the vessel. These include mutations that interfere with transduction of stimuli from the matrix to the actin-myosin cytoskeleton through integrins, and those that impair signaling pathways activated by transforming growth factor-β (TGF-β). In this review, we summarize the features of the healthy aortic wall, the major pathways involved in the modulation of VSMC phenotypes, and the basic molecular functions impaired by TAA-associated mutations. We also discuss how the heterogeneity and balance of adaptive and maladaptive responses to the initial genetic insult might contribute to disease.

Amniotic membrane promotes focal adhesion remodeling to stimulate cell migration

During wound healing, the migration of keratinocytes onto newly restored extracellular matrix aims to reestablish continuity of the epidermis. The application of amniotic membrane (AM) to chronic, deep traumatic, non-healing wounds has proven successful at stimulating re-epithelialization. When applied on epithelial cell cultures, AM activates extracellular signal-regulated kinases 1/2 (ERK1/2) and c-Jun N-terminal kinases 1/2 (JNK1/2), with the overexpression and phosphorylation of c-Jun along the wound edge. The effect of AM on the migration of cells was investigated by studying critical proteins involved in the focal adhesions turn-over: Focal Adhesion Kinase (FAK), Paxillin and Vinculin. In Mv1Lu and HaCaT cells, validated models for cell migration and wound healing, AM affected the expression and activation of Paxillin, but did not affect Vinculin expression, both factors which integrate into focal adhesions. Moreover, AM regulation also affected FAK activity through phosphorylation. Finally, we have determined that AM regulation of focal adhesions involves both JNK and MEK MAP kinase signaling pathways. This data provides a molecular background to understand how AM regulates critical cell and molecular aspects of cell migration, organizing and directing the movement of cells by the continuous formation, maturation, and turnover of focal adhesion structures at the migration leading edge.

Overexpression of Paxillin Correlates with Tumor Progression and Predicts Poor Survival in Glioblastoma

AIMS

To explore the prognostic and clinicopathological features of glioma with Paxillin (PXN) expression based on a large number of samples.

METHODS

RNA sequencing data of 325 glioma samples from Chinese Glioma Genome Atlas (CGGA) database were obtained as discovery set. Three additional datasets were further obtained as validation sets. The protein expression pattern of PXN in glioma was measured by IHC. Kaplan-Meier survival and multivariate Cox analysis were used to estimate the survival distributions. Moreover, the functional annotation of PXN was also analyzed.

RESULTS

In the discovery set, PXN overexpression was significantly associated with high-grade glioma as well as the higher mortality in survival analysis (log-rank test, P < 0.01). The results of the other validation datasets showed similar findings. PXN also served as an independent prognostic biomarker in glioblastoma patients. Functional assays showed that PXN contributed to glioma cell proliferation and invasion.

CONCLUSION

PXN plays as an oncogene in glioma progression and suggests a new potential biotarget for therapy.

S100A4 promotes pancreatic cancer progression through a dual signaling pathway mediated by Src and focal adhesion kinase

S100A4 expression is associated with poor clinical outcomes of patients with pancreatic cancer. The effects of loss or gain of S100A4 were examined in pancreatic cancer cell lines. S100A4 downregulation remarkably reduces cell migration and invasion, inhibits proliferation, and induces apoptosis in pancreatic tumor cells. S100A4 downregulation results in significant cell growth inhibition and apoptosis in response to TGF-β1, supporting a non-canonical role of S100A4 in pancreatic cancer. The role of S100A4 in tumor progression was studied by using an orthotopic human pancreatic cancer xenograft mouse model. Tumor mass is remarkably decreased in animals injected with S100A4-deficient pancreatic tumor cells. P27^Kip1 expression and cleaved caspase-3 are increased, while cyclin E expression is decreased, in S100A4-deficient pancreatic tumors in vivo. S100A4-deficient tumors have lower expression of vascular endothelial growth factor, suggesting reduced angiogenesis. Biochemical assays revealed that S100A4 activates Src and focal adhesion kinase (FAK) signaling events, and inhibition of both kinases is required to maximally block the tumorigenic potential of pancreatic cancer cells. These findings support that S100A4 plays an important role in pancreatic cancer progression in vivo and S100A4 promotes tumorigenic phenotypes of pancreatic cancer cells through the Src-FAK mediated dual signaling pathway.

Expression of PRMT5 correlates with malignant grade in gliomas and plays a pivotal role in tumor growth in vitro

Protein arginine methyltransferase 5 (PRMT5) catalyzes the formation of ω-NG,N'G-symmetric dimethylarginine residues on histones as well as other proteins. These modifications play an important role in cell differentiation and tumor cell growth. However, the role of PRMT5 in human glioma cells has not been characterized. In this study, we assessed protein expression profiles of PRMT5 in control brain, WHO grade II astrocytomas, anaplastic astrocytomas, and glioblastoma multiforme (GBM) by immunohistochemistry. PRMT5 was low in glial cells in control brain tissues and low grade astrocytomas. Its expression increased in parallel with malignant progression, and was highly expressed in GBM. Knockdown of PRMT5 by small hairpin RNA caused alterations of p-ERK1/2 and significantly repressed the clonogenic potential and viability of glioma cells. These findings indicate that PRMT5 is a marker of malignant progression in glioma tumors and plays a pivotal role in tumor growth.

Calumenin-15 facilitates filopodia formation by promoting TGF-β superfamily cytokine GDF-15 transcription

Filopodia, which are actin-rich finger-like membrane protrusions, have an important role in cell migration and tumor metastasis. Here we identify 13 novel calumenin (Calu) isoforms (Calu 3-15) produced by alternative splicing, and find that Calu-15 promotes filopodia formation and cell migration. Calu-15 shuttles between the nucleus and cytoplasm through interacting with importin α, Ran GTPase, and Crm1. The phosphorylation of the threonine at position 73 (Thr-73) by casein kinase 2 (CK2) is essential for the nuclear import of Calu-15, and either Thr-73 mutation or inhibition of CK2 interrupts its nuclear localization. In the nucleus, Calu-15 increases the transcription of growth differentiation factor-15 (GDF-15), a member of the transforming growth factor-β (TGF-β) superfamily, via binding to its promoter region. Furthermore, Calu-15 induces filopodia formation mediated by GDF-15. Together, we identify that Calu-15, a novel isoform of Calu with phosphorylation-dependent nuclear localization, has a critical role in promoting filopodia formation and cell migration by upregulating the GDF-15 transcription.

Zyxin is a transforming growth factor-β (TGF-β)/Smad3 target gene that regulates lung cancer cell motility via integrin α5β1

Although TGF-β acts as a tumor suppressor in normal tissues and in early carcinogenesis, these tumor suppressor effects are lost in advanced malignancies. Single cell migration and epithelial-mesenchymal transition (EMT), both of which are regulated by TGF-β, are critical steps in mediating cancer progression. Here, we sought to identify novel direct targets of TGF-β signaling in lung cancer cells and have indentified the zyxin gene as a target of Smad3-mediated TGF-β1 signaling. Zyxin concentrates at focal adhesions and along the actin cytoskeleton; as such, we hypothesized that cytoskeletal organization, motility, and EMT in response to TGF-β1 might be regulated by zyxin expression. We show that TGF-β1 treatment of lung cancer cells caused rapid phospho-Smad3-dependent expression of zyxin. Zyxin expression was critical for the formation and integrity of cell adherens junctions. Silencing of zyxin decreased expression of the focal adhesion protein vasodilator-activated phospho-protein (VASP), although the formation and morphology of focal adhesions remained unchanged. Zyxin-depleted cells displayed significantly increased integrin α5β1 levels, accompanied by enhanced adhesion to fibronectin and acquisition of a mesenchymal phenotype in response to TGF-β1. Zyxin silencing led to elevated integrin α5β1-dependent single cell motility. Importantly, these features are mirrored in the K-ras-driven mouse model of lung cancer. Here, lung tumors revealed decreased levels of both zyxin and phospho-Smad3 when compared with normal tissues. Our data thus demonstrate that zyxin is a novel functional target and effector of TGF-β signaling in lung cancer. By regulating cell-cell junctions, integrin α5β1 expression, and cell-extracellular matrix adhesion, zyxin may regulate cancer cell motility and EMT during lung cancer development and progression.

Scram1 is a modifier of spinal cord resistance for astrocytoma on mouse Chr 5

Tumor location can profoundly affect morbidity and patient prognosis, even for the same tumor type. Very little is known about whether tumor location is determined stochastically or whether genetic risk factors can affect where tumors arise within an organ system. We have taken advantage of the Nf1-/+;Trp53-/+cis mouse model of astrocytoma/glioblastoma to map genetic loci affecting whether astrocytomas are found in the spinal cord. We identify a locus on distal Chr 5, termed Scram1 for spinal cord resistance to astrocytoma modifier 1, with a LOD score of 5.0 and a genome-wide significance of P < 0.004. Mice heterozygous for C57BL/6J×129S4/SvJae at this locus show less astrocytoma in the spinal cord compared to 129S4/SvJae homozygous mice, although we have shown previously that 129S4/SvJae mice are more resistant to astrocytoma than C57BL/6J. Furthermore, the astrocytomas that are found in the spinal cord of Scram1 heterozygous mice arise in older mice. Because spinal cord astrocytomas are very rare and difficult to treat, a better understanding of the genetic factors that govern astrocytoma in the spine may lead to new targets of therapy or prevention.

Neutrophil granulocytes promote the migratory activity of MDA-MB-468 human breast carcinoma cells via ICAM-1

Tumor infiltrating neutrophil granulocytes do not only exhibit tumor eliminating functions but also promote tumor progression. We have recently shown that neutrophil granulocytes can serve as linking cells for the adhesion of MDA-MB-468 breast carcinoma cells to pulmonary endothelium. Neutrophil granulocytes but not MDA-MB-468 cells express beta(2)-integrins, the ligands of the intercellular adhesion molecule (ICAM)-1, whereas ICAM-1 is strongly expressed on MDA-MB-468 cells. Consequently, the herein presented study was performed to investigate if this interaction has also an influence on the migratory activity of the tumor cells and whether ICAM-1 signaling plays a role in this process, too. We found that the continuous release of interleukin-8 (IL-8) and GRO-alpha by MDA-MB-468 cells increases the migratory activity of neutrophil granulocytes and attracts these cells towards the tumor cells which enables direct cell-cell interactions. These interactions in turn increase the migratory activity of the tumor cells in an ICAM-1 clustering-dependent mechanism since transfection of the tumor cells with specific siRNA against ICAM-1 abolished the effect. Moreover, ICAM-1 cross-linking on tumor cells induces the phosphorylation of focal adhesion components such as focal adhesion kinase and paxillin via src kinase as well as the activation of the p38 MAPK pathway via Rho kinase in a time-dependent manner. Our results provide evidence that ICAM-1 is coupled to intracellular signaling pathways involved in tumor cell migration. Thus, neutrophil granulocytes can act as modulators of the metastatic capability of tumor cells by ligation of ICAM-1.

Transforming growth factor-beta (TGF-beta) and brain tumours

Since its discovery in the late 1970s considerable research has linked transforming growth factor-beta (TGF-beta) to several human diseases such as fibrosis, auto-immunity and cancer. TGF-beta acts initially as a growth inhibitory factor in early stages of tumour development. In contrast, as tumours evolve, they develop mechanisms to evade the growth-regulatory effects of TGF-beta, resulting in greater tumour invasiveness, increased metastatic potential and inhibition of surrounding immune responses. However, although extensively studied, the molecular mechanisms that trigger tumour cells to "switch" from TGF-beta-inhibited to TGF-beta-promoted are still not fully understood. Contradictory studies that demonstrate opposite cellular effects mediated by TGF-beta are abundant throughout the literature. This review summarizes the current molecular mechanisms involved in the tumour suppressive and tumour progressive characteristics of TGF-beta in brain tumours. Potential therapeutic agents that target TGF-beta and related proteins being evaluated against brain tumours is also discussed.

Streptococcal modulation of cellular invasion via TGF-beta1 signaling

Group A Streptococcus (GAS) and other bacterial pathogens are known to interact with integrins as an initial step in a complex pathway of bacterial ingestion by host cells. Efficient GAS invasion depends on the interaction of bound fibronectin (Fn) with integrins and activation of integrin signaling. TGF-beta1 regulates expression of integrins, Fn, and other extracellular matrix proteins, and positively controls the integrin signaling pathway. Therefore, we postulated that TGF-beta1 levels could influence streptococcal invasion of mammalian cells. Pretreatment of HEp-2 cells with TGF-beta1 increased their capacity to ingest GAS when the bacteria expressed fibronectin-binding proteins (M1 or PrtF1). Western blots revealed significant induction of alpha5 integrin and Fn expression by HEp-2 cells in response to TGF-beta1. Increased ingestion of streptococci by these cells was blocked by a specific inhibitor of the TGF-beta1 receptor I and antibodies directed against alpha5 integrin and Fn, indicating that increased invasion depends on TGF-beta1 up-regulation of both the alpha5 integrin and Fn. The capacity of TGF-beta1 to up-regulate integrin expression and intracellular invasion by GAS was reproduced in primary human tonsil fibroblasts, which could be a source of TGF-beta1 in chronically infected tonsils. The relationship between TGF-beta1 and GAS invasion was strengthened by the observation that TGF-beta1 production was stimulated in GAS-infected primary human tonsil fibroblasts. These findings suggest a mechanism by which GAS induce a cascade of changes in mammalian tissue leading to elevated expression of the alpha5beta1 receptor, enhanced invasion, and increased opportunity for survival and persistence in their human host.

Regulation of paxillin family members during epithelial-mesenchymal transformation: a putative role for paxillin delta

Epithelial-mesenchymal transformation (EMT) and the resulting induction of cell motility are essential components of tissue remodeling during embryonic development and wound repair, as well as tumor progression to an invasive metastatic phenotype. Paxillin, a multi-domain adaptor and phosphoprotein has previously been implicated in integrin signaling and cell motility. In this report we characterize a novel paxillin gene product, paxillin delta, generated from an evolutionarily conserved internal translation initiation site within the full-length paxillin mRNA. Paxillin delta, which lacks the key phosphorylation sites Y31 and Y118 as well as the ILK and actopaxin binding LD1 motif, exhibits a restricted distribution to epithelial cell types and is downregulated during TGF-beta1-induced EMT of normal murine mammary gland (NMuMG) epithelial cells. Interestingly, Hic-5, a paxillin superfamily member, exhibits a reciprocal protein expression profile to paxillin delta. In addition, paxillin delta expression is maintained following NMuMG differentiation in a 3D collagen I gel while other focal adhesion components are downregulated. Paxillin delta protein expression coincided with reduced paxillin tyrosine phosphorylation in NMuMG cells and paxillin delta overexpression in CHO.K1 cells inhibited adhesion-mediated tyrosine phosphorylation of paxillin. Forced expression of paxillin delta in NMuMG cells suppressed cell migration whereas Hic-5 overexpression stimulated motility. Together our data support a role for paxillin delta as a naturally occurring functional antagonist of paxillin signaling potentially through suppression of a Crk-mediated pathway during processes associated with cell migration.

Effect of enamel matrix derivative on periodontal ligament cells in vitro is diminished by Porphyromonas gingivalis

BACKGROUND

Enamel matrix derivative (EMD) has been shown to possess a mitogenic effect to induce effective periodontal regeneration, however, it is unclear whether periodontal pathogens can modulate the effect of EMD. The present study examined the influence of Porphyromonas gingivalis on EMD-stimulated periodontal ligament (PDL) cells.

METHODS

P. gingivalis ATCC33277 and its mutants deficient in fimbriae (delta fimA) or gingipains (delta rgpA delta rgpB, delta kgp, and delta rgpA delta rgpB delta kgp) were employed. PDL cells were grown on EMD-coated dishes and infected with P. gingivalis wild strain or a mutant. Cell migration and proliferation were then evaluated with an in vitro wound healing assay. The expression of transforming growth factor-beta1 (TGF-beta1) and insulin-like growth factor I (IGF-I) mRNA by PDL cells was examined. Further, the degradation and phosphorylation of extracellular signal-regulated kinase 1 and 2 (ERK1/2) as well as paxillin in infected PDL cells were estimated using Western blot analysis.

RESULTS

P. gingivalis ATCC33277 inhibited the migration and proliferation of PDL cells on EMD-coated dishes, and the mutants delta fimA, delta rgpA delta rgpB, and delta kgp showed the same effects. Further, each of these organisms diminished the expression of TGF-beta1 and IGF-I mRNA, as well as the phosphorylation of ERK1/2 from EMD-stimulated PDL cells. In addition, total paxillin protein was markedly degraded by both the wild-type strain and each of the mutants except for delta rgpA delta rgpB delta kgp, which showed a negligible effect in all of the assays with EMD-stimulated PDL cells.

CONCLUSION

These results suggest that P. gingivalis diminishes the effect of EMD on PDL cells in vitro through a cooperative action of gingipains.

Postgenomic global analysis of translational control induced by oncogenic signaling

It is commonly assumed that developmental and oncogenic signaling achieve their phenotypic effects primarily by directly regulating the transcriptional profile of cells. However, there is growing evidence that the direct effect on transcription may be overshadowed by differential effects on the translational efficiency of specific existing mRNA species. Global analysis of this effect using microarrays indicates that this mechanism of controlling protein production provides a highly specific, robust, and rapid response to oncogenic and developmental stimuli. The mRNAs so affected encode proteins involved in cell-cell interaction, signal transduction, and growth control. Furthermore, a large number of transcription factors capable of secondarily rearranging the transcriptional profile of the cell are controlled at this level as well. To what degree this translational control is either necessary or sufficient for tumor formation or maintenance remains to be determined.

The pattern of enhancement of Src kinase activity on platelet-derived growth factor stimulation of glioblastoma cells is affected by the integrin engaged

Enhanced expression of both integrin alpha v beta 3 and platelet-derived growth factor receptor (PDGFr) has been described in glioblastoma tumors. We therefore explored the possibility that integrin alpha v beta 3 cooperates with PDGFr to promote cell migration in glioblastoma cells, and extended the study to identify the Src family members that are activated on PDGF stimulation. Glioblastoma cells utilize integrins alpha v beta 3 and alpha v beta 5 to mediate vitronectin attachment. We found that physiologic PDGF stimulation (83 pm, 10 min) of vitronectin-adherent cells promoted the specific recruitment of integrin alpha v beta 3-containing focal adhesions to the cell cortex and alpha v beta 3-mediated cell motility. Analysis of PDGFr immunoprecipitates indicated an association of the PDGFr beta with integrin alpha v beta 3, but not integrin alpha v beta 5. Cells plated onto collagen or laminin, which engage different integrins, exhibited significantly less migration on PDGF stimulation, indicating a cooperation of alpha v beta 3 and the PDGFr beta in glioblastoma cells that promotes migration. Further analysis of the cells plated onto vitronectin indicated that PDGF stimulation caused an increase in Src kinase activity, which was associated with integrin alpha v beta 3. In the vitronectin-adherent cells, Lyn was associated preferentially with alpha v beta 3 both in the presence and absence of PDGF stimulation. In contrast, Fyn was associated with both alpha v beta 3 and alpha v beta 5. Moreover, PDGF stimulation increased the activity of Lyn, but not Fyn, in vitronectin-adherent cells, and the activity of Fyn, but not Lyn, in laminin-adherent cells. Using cells attached to mAb anti-alpha v beta 3 or mAb anti-integrin alpha 6, we confirmed the activation of specific members of the Src kinase family with PDGF stimulation. Down-regulation of Lyn expression by siRNA significantly inhibited the cell migration mediated by integrin alpha v beta 3 in PDGF-stimulated cells, demonstrating the PDGFr beta cooperates with integrin alpha v beta 3 in promoting the motility of vitronectin-adherent glioblastoma cells through a Lyn kinase-mediated pathway. Notably, the data indicate that engagement of different integrins alters the identity of the Src family members that are activated on stimulation with PDGF.

Cell interactions with three-dimensional matrices

Signaling and other cellular functions differ in three-dimensional compared with two-dimensional systems. Cell adhesion structures can evolve in vitro towards in-vivo-like adhesions with distinct biological activities. In this review, we examine recent advances in studies of interactions of fibroblasts with collagen gels and fibronectin-containing matrices that mimic in vivo three-dimensional microenvironments. These three-dimensional systems are illuminating mechanisms of cell-matrix interactions in living organisms.