Cisplatin at sub-toxic levels mediates integrin switch in lung cancer cells

BACKGROUND

Resistance to chemotherapeutic agents, as well as enhanced metastasis, have been frequently reported in lung cancer.

MATERIALS AND METHODS

Cytotoxicity and proliferative effects of cisplatin on H460 lung cancer cells were evaluated by the MTT assay. Migration capacity was evaluated by the wound healing assay. The number of filopodia per cell were detected by rhodamine-phalloidin staining assay. The changes of protein levels of integrins, and migration-related proteins in response to cisplatin at sub-toxic concentrations were determined by western blotting.

RESULTS

Herein we demonstrate for the first time that exposure to low concentrations of cisplatin results in increase of cell motility with the alteration of integrin expression. Cisplatin-treated cells exhibited a significant increase in the number of filopodia per cell in correlation with enhanced migration. Migration regulatory proteins, namely activated forms of focal-adhesion kinase (FAK) and ATP-dependent tyrosine kinase (AKT), were found to significantly be up-regulated in cisplatin-treated cells in comparison to those of the non-treated control. Active Rho A-GTP and Rac-GTP were found to be increased in accordance with activation of FAK/AKT signals. Furthermore, we found that such migration enhancement may be in part due to the integrin switch mediated by cisplatin treatment. Cisplatin induced a dramatic alteration in the integrin expression pattern by up-regulating integrin α4, αv, β1, and β5 which were previously reported to increase cell motility, while it had no effect on integrin α5, and β3.

CONCLUSION

As the integrin switch is a hallmark of highly aggressive cancer, these findings may provide insights for better understanding of cancer cell adaptation after exposure to cisplatin.

Differential expression and signaling activation of insulin receptor isoforms A and B: A link between breast cancer and diabetes

We showed that when insulin-like growth factor II (IGF-II) is highly expressed in breast tissues and cell lines, the IGF-I receptor signaling pathway is highly activated. Since IGF-II activates the insulin receptor (INSR), we propose that the INSR signaling is also activated in this system. We examined the expression of both INSR isoforms, insulin receptor A (INSR-A) and insulin receptor B (INSR-B), and the downstream signaling pathways in breast cancer (BC) cells and in paired (normal/tumor) breast tissues from 100 patients. Analysis was performed by real-time PCR, Western blot, immunohistochemistry, and phospho-ELISA techniques. Tumor tissues and cell lines from African-American patients expressed higher levels of INSR-A, but lower levels of INSR-B. Accordingly, insulin receptor substrate 1 and focal adhesion kinase activation were significantly increased in these women. We conclude that higher INSR-A and lower INSR-B contribute to higher proliferation and lower metabolic response. Thus, differential expression of INSR isoforms represents a potential biological link between BC and diabetes.

Survivin expression induced by endothelin-1 promotes myofibroblast resistance to apoptosis

Fibrosis of the lungs and other organs is characterized by the accumulation of myofibroblasts, effectors of wound-repair that are responsible for the deposition and organization of new extracellular matrix (ECM) in response to tissue injury. During the resolution phase of normal wound repair, myofibroblast apoptosis limits the continued deposition of ECM. Mounting evidence suggests that myofibroblasts from fibrotic wounds acquire resistance to apoptosis, but the mechanisms regulating this resistance have not been fully elucidated. Endothelin-1 (ET-1), a soluble peptide strongly associated with fibrogenesis, decreases myofibroblast susceptibility to apoptosis through activation of phosphatidylinositol 3'-OH kinase (PI3K)/AKT. Focal adhesion kinase (FAK) also promotes myofibroblast resistance to apoptosis through PI3K/AKT-dependent and -independent mechanisms, although the role of FAK in ET-1 mediated resistance to apoptosis has not been explored. The goal of this study was to investigate whether FAK contributes to ET-1 mediated myofibroblast resistance to apoptosis and to examine potential mechanisms downstream of FAK and PI3K/AKT by which ET-1 regulates myofibroblast survival. Here, we show that ET-1 regulates myofibroblast survival by Rho/ROCK-dependent activation of FAK. The anti-apoptotic actions of FAK are, in turn, dependent on activation of PI3K/AKT and the subsequent increased expression of Survivin, a member of the inhibitor of apoptosis protein (IAP) family. Collectively, these studies define a novel mechanism by which ET-1 promotes myofibroblast resistance to apoptosis through upregulation of Survivin.

Impairment of human keratinocyte mobility and proliferation by advanced glycation end products-modified BSA

The migration and proliferation of keratinocytes is critical to wound re-epithelialization and defects in this function are associated with the clinical phenomenon of chronic non-healing wounds. Advanced glycation end products (AGEs) occur through non-enzymatic glycation of long-lived proteins in diabetes and play important roles in diabetic complications. However, specific roles for AGEs in keratinocyte migration and proliferation, and the underlying molecular mechanisms, have not been fully established. The aim of the current study was to elucidate the interaction between AGE-modified bovine serum albumin (AGE-BSA) and keratinocytes. As a result, we found that AGE-BSA had no effect on the viability of keratinocytes for up to 48 h of incubation with 50 μg/ml of AGE-BSA. AGE-BSA (but not non-glycated BSA) exerted a concentration-dependent suppression of keratinocyte migration at a range of concentrations. The expression of matrix metalloproteinase-9 (MMP-9) was significantly up-regulated in keratinocytes incubated with increasing AGE-BSA, but tissue inhibitor of metalloproteinases-1 (TIMP-1) expression was down-regulated. AGE-BSA also profoundly depressed phospho-focal adhesion kinase-Tyr397 (p-FAK) and α2β1 integrin expression, while total-FAK expression levels remained constant, in keratinocytes. The proliferative capacity of keratinocytes was diminished after 72 h AGE-BSA incubation. Taken together, these findings suggested that in the presence of AGE-BSA, keratinocytes lose their migratory and proliferation abilities. These data also indicated that, in the context of the chronic hyperglycemia in diabetes, the effects of AGE-BSA on keratinocyte migration might be mediated through MMP-9/TIMP-1, p-FAK and α2β1 integrin.

Wilms' tumor 1 protein and focal adhesion kinase mediate keratinocyte growth factor signaling in breast cancer cells

BACKGROUND

Keratinocyte growth factor (KGF) has been shown to induce breast cancer metastasis in animal models. cDNA microarrays have revealed that KGF increased Wilms tumor 1 (WT1) and focal adhesion kinase (FAK) expression in breast cancer cells. The role of WT1 and FAK in KGF signaling was investigated.

MATERIALS AND METHODS

A cell culture wounding model was used to study the effects of WT1 and FAK down-regulation on KGF-induced proliferation and motility in breast cancer cells.

RESULTS

WT1 down-regulation inhibited KGF-mediated proliferation and motility of breast cancer cells, while FAK down-regulation inhibited proliferation, but had no significant effect on cell motility. WT1 down-regulation, but not FAK down-regulation, led to Erk1,2 inactivation.

CONCLUSION

KGF-mediated signaling employs WT1 and FAK to regulate breast cancer cell proliferation and motility and may represent therapeutic targets for the prevention of breast cancer progression.

Osteonectin downregulates E-cadherin, induces osteopontin and focal adhesion kinase activity stimulating an invasive melanoma phenotype

Osteonectin is recognised as a marker of metastasis progression in melanoma and has been implicated in the transition from radial to vertical growth phase. A Tetracycline-inducible system was used to regulate Osteonectin protein levels in melanoma cell lines to examine the morphological, biochemical and invasive changes that accompany its altered expression. Assay of protein and phosphorylation changes showed a downregulation of E-cadherin, upregulation of Osteopontin and a corresponding increase in phosphorylation of Focal Adhesion Kinase on Tyr(397) and Tyr(576) concomitant with Osteonectin induction. Melanoma cells overexpressing Osteonectin displayed increased invasive potential, whereas ablation of Osteonectin gene transcription using siRNA suppressed the invasive potential of these cells and resulted in the upregulation of E-cadherin. The recently described interaction of Osteonectin with Integrin Linked Kinase leading to modulation of its activity suggests a mechanism relevant to the loss of E-cadherin and cell adhesion that occurs during melanoma progression. These results indicate a central role for Osteonectin in the regulation of gene expression changes driving the progression of melanoma toward metastasis.

Eps8 facilitates cellular growth and motility of colon cancer cells by increasing the expression and activity of focal adhesion kinase

In an attempt to study the role of Eps8 in human carcinogenesis, we observe that ectopic overexpression of Eps8 in SW480 cells (low Eps8 expression) increases cell proliferation. By contrast, expressing eps8 small interference RNA in SW620 and WiDr cells (high Eps8 expression) reduces their proliferation rate. Interestingly, attenuation of Eps8 decreases Src Pi-Tyr-416, Shc Pi-Tyr-317, and serum-induced FAK Pi-Tyr-397 and Pi-Tyr-861. Remarkably, by virtue of mammalian target of rapamycin/STAT3 Pi-Ser-727, Eps8 modulates FAK expression required for cell proliferation. Within 62% of colorectal tumor specimens examined, >2-fold enhancement of Eps8 as compared with their normal counterparts is observed, especially for those from the advanced stage. In agreement with the modulation of FAK by Eps8, the concomitant expression of these two proteins in tumor specimens is observed. Notably, Eps8 attenuation also impedes the motility of SW620 and WiDr cells, which can be rescued by ectopically expressed FAK. This finding discloses the indispensability of Eps8 and FAK in cell locomotion. These results provide a novel mechanism for Eps8-mediated FAK expression and activation in colon cancer cells.

Nitric oxide inhibits enterocyte migration through activation of RhoA-GTPase in a SHP-2-dependent manner

Diseases of intestinal inflammation like necrotizing enterocolitis (NEC) are associated with impaired epithelial barrier integrity and the sustained release of intestinal nitric oxide (NO). NO modifies the cytoskeletal regulator RhoA-GTPase, suggesting that NO could affect barrier healing by inhibiting intestinal restitution. We now hypothesize that NO inhibits enterocyte migration through RhoA-GTPase and sought to determine the pathways involved. The induction of NEC was associated with increased enterocyte NO release and impaired migration of bromodeoxyuridine-labeled enterocytes from terminal ileal crypts to villus tips. In IEC-6 enterocytes, NO significantly inhibited enterocyte migration and activated RhoA-GTPase while increasing the formation of stress fibers. In parallel, exposure of IEC-6 cells to NO increased the phosphorylation of focal adhesion kinase (pFAK) and caused a striking increase in cell-matrix adhesiveness, suggesting a mechanism by which NO could impair enterocyte migration. NEC was associated with increased expression of pFAK in the terminal ileal mucosa of wild-type mice and a corresponding increase in disease severity compared with inducible NO synthase knockout mice, confirming the dependence of NO for FAK phosphorylation in vivo and its role in the pathogenesis of NEC. Strikingly, inhibition of the protein tyrosine phosphatase SHP-2 in IEC-6 cells prevented the activation of RhoA by NO, restored focal adhesions, and reversed the inhibitory effects of NO on enterocyte migration. These data indicate that NO impairs mucosal healing by inhibiting enterocyte migration through activation of RhoA in a SHP-2-dependent manner and support a possible role for SHP-2 as a therapeutic target in diseases of intestinal inflammation like NEC.

Role of tumor necrosis factor-alpha, interleukin-8, and dexamethasone in the focal adhesion kinase expression by human nucleus pulposus cells

STUDY DESIGN

Human nucleus pulposus cells from intervertebral disc specimens were cultured to study the effects of tumor necrosis factor (TNF)-alpha and interleukin (IL)-8 on the focal adhesion kinase (FAK) expression by these cells. The effect of co-stimulation with dexamethasone on the FAK expression by nucleus pulposus cells was also studied.

OBJECTIVES

To evaluate the possible role of activated FAK expressed by the human nucleus pulposus cells and its correlation with inflammatory cytokines (TNF-alpha, IL-8) and dexamethasone.

SUMMARY OF BACKGROUND DATA

There have been no reported studies showing the correlation between the activated FAK expression by human nucleus pulposus cells with inflammatory cytokines and dexamethasone.

METHODS

The FAK expression in cultured human nucleus pulposus cells was studied, and Western blot and immunofluorescence analysis were performed to assess its relation to TNF-alpha, IL-8, and dexamethasone.

RESULTS

Treatments of TNF-alpha and IL-8 up-regulated the activated FAK expression. Dexamethasone attenuated the cytokine-induced FAK expression. The effects of inflammatory cytokines on the FAK expression were found to be concentration dependent, with greater correlation shown by IL-8 than TNF-alpha.

CONCLUSION

TNF-alpha and IL-8 stimulation up-regulated the FAK expression of human nucleus pulposus cells, and the coadministration of dexamethasone attenuated it.

Up-regulation of focal adhesion kinase in non-small cell lung cancer

Focal adhesion kinase (FAK) is a non-receptor tyrosine kinase linked to the integrin and growth factor receptor-signalling pathways that regulates a number of the biological processes involved in neoplastic transformation, invasion and metastases, such as cell adhesion, migration and apoptosis. Its up-regulation might play a role in the tumourigenesis of invasive tumours, but its involvement in human lung cancer tissues has not yet been determined. We immunohistochemically compared FAK expression and localisation in 60 formalin-fixed and paraffin-embedded non-small cell lung cancer (NSCLC) tissues with that in the surrounding non-neoplastic tissue and in a further five microscopically normal lungs. FAK mRNA levels were quantitatively determined by real-time RT-PCR in frozen tissue specimens of all of the tumours and 21 matched non-neoplastic lung parenchymas, and protein expression in 16 homogenates of the matched neoplastic/non-neoplastic specimens was evaluated by Western blotting. The three different techniques showed that FAK is weakly expressed in non-neoplastic lung parenchyma and up-regulated in NSCLCs. Moreover, Western blotting and real-time RT-PCR indicated a statistically significant correlation between FAK up-regulation and higher disease stages (I+II versus III+IV, p=0.019 and 0.028, respectively). Our results provide evidence that FAK is up-regulated in NSCLCs, and suggest its potential involvement in lung cancer progression.

Reduced expression of focal adhesion kinase disrupts insulin action in skeletal muscle cells

Integrins mediate interactions between cells and extracellular matrix proteins that modulate growth factor signaling. Focal adhesion kinase (FAK) is a key multifunctional integrin pathway protein. We recently reported that disruption of FAK impairs insulin-mediated glycogen synthesis in hepatocytes. To test the hypothesis that FAK regulates skeletal muscle insulin action, we reduced FAK expression in L6 myotubes using FAK antisense. In untransfected myotubes, insulin stimulated both FAK tyrosine phosphorylation and kinase activity. Cells treated with antisense FAK showed 78 and 53% reductions in FAK mRNA and FAK protein, respectively, whereas insulin receptor substrate 1/2 and paxillin abundance were unaffected. Insulin-stimulated U-(14)C-glucose incorporation into glycogen was abolished by FAK antisense, and 2-deoxy-glucose uptake and glucose transporter 4 (GLUT4) translocation were both markedly attenuated. Antisense FAK did not alter GLUT1 or GLUT3 protein abundance. Immunofluorescence staining showed decreased FAK Tyr(397) phosphorylation and reduced actin stress fibers. Thus, in skeletal myotubes, FAK regulates the insulin-mediated cytoskeletal rearrangement essential for normal glucose transport and glycogen synthesis. Integrin signaling may play an important regulatory role in muscle insulin action.

Heat shock-induced cardioprotection activates cytoskeletal-based cell survival pathways

To define better the subcellular mechanism of heat shock (HS)-induced cardioprotection, we examined the effect of HS, as well as selective expression of individual HS proteins (HSPs), on cell injury in neonatal rat ventricular myocytes (NRVM). HS was induced in NRVM by a rapid elevation of temperature to 42 degrees C for 20 min followed by 20-24 h of recovery at 37 degrees C. Other NRVM were infected with a replication-deficient adenovirus encoding HSP27 or HSP70. On the same day, all groups were subjected to metabolic inhibition (MI). Cell injury was assayed by measurement of the percentage of total lactate dehydrogenase released, the percentage of cells staining with trypan blue, or TdT-mediated dUTP nick-end labeling, whereas cell signaling was assayed by immunoblot analysis and coimmunoprecipitation. Before MI, the viability of all treated groups did not differ significantly from control NRVM. HS resulted in a significant increase in HSP70 and HSP27 expression. Infection with either virus caused a significant increase in selective HSP content compared with control NRVM. HS protected NRVM from injury. Selective expression of HSP27 or HSP70 alone was not protective in NRVM, but dual infection with both viral vectors (HSP27 + HSP70) was protective. HS and HSP27 + HSP70 expression caused increased paxillin localization in the membrane fraction, which persisted in response to MI, compared with control NRVM. HS increased the integrin-paxillin-focal adhesion kinase interaction, whereas targeted inhibition of focal adhesion kinase activity abolished the integrin-paxillin association and resulted in an increase in cell death. HS and HSP27 + HSP70 expression increased the association of members of the focal adhesion complex and protected NRVM against irreversible injury. Cytoskeletal-based signaling pathways at focal adhesion junctions may represent a unique pathway of cardioprotection.

Effect of focal adhesion kinase (FAK) downregulation with FAK antisense oligonucleotides and 5-fluorouracil on the viability of melanoma cell lines

Inhibition of focal adhesion kinase (FAK), a non-receptor tyrosine kinase linked to tumour cell survival, causes cell rounding, loss of adhesion and apoptosis in human cancer cell lines. In this study, we tested antisense oligonucleotide inhibitors of FAK, in combination with 5-fluorouracil (5-FU), to increase its sensitivity in human melanoma cell lines. Antisense oligonucleotides directed to the 5' mRNA sequence of FAK and missense control oligonucleotides were used. In BL melanoma cells, treatment with FAK antisense oligonucleotide was associated with a 2.5-fold increase in cell death compared with treatment with control oligonucleotide (33+/-2% vs. 13+/-3%, P<0.0001). 5-FU alone had no effect on BL cells (4.4% cell death, P=0.15). The addition of 5-FU after antisense oligonucleotide resulted in a significant synergistic increase in cell death equal to 69+/-2% compared with treatments with antisense oligonucleotide alone, 5-FU alone and control oligonucleotide (P<0.0001). Similar results were found in the C8161 melanoma cell line. In both cell lines, reduction in cell viability was accompanied by an increased loss of adhesion and increased apoptosis that was proportional to the decrease in viability. Treatment with antisense oligonucleotide plus 5-FU resulted in significantly decreased p125FAK expression in both C8161 and BL melanoma cell lines, demonstrated by Western blot analyses. These data show that the downregulation of FAK by antisense oligonucleotide combined with 5-FU chemotherapy results in a greater loss of adhesion and greater apoptosis in melanoma cells than treatment with either agent alone, suggesting that the combination may be a potential therapeutic agent for human melanoma in vivo.

[Regulatory effect of integrin alpha5 and beta1 on proliferation inhibition of K562 cells induced by interferon alpha-2b]

BACKGROUND & OBJECTIVE

Integrin beta1 can inhibit the proliferation of chronic myelocytic leukemia (CML) ph+ cells. The dysfunction of integrin beta1 might accelerate the growth of CML ph+ cells. This study was to explore the effects of integrin alpha5 and beta1 on the proliferation inhibition of K562 cells induced by IFNalpha-2b.

METHODS

The expression indexes of integrin alpha5 and beta1 on K562 cells, the binding capability of K562 cells to fibronectin (FN), and K562 cell-FN binding blocking induced by integrin alpha5 and beta1 antibodies were evaluated by flow cytometry (FCM). The viability of K562 cells, treated with IFNalpha-2b (10,000 u/ml), was observed by MTT assay. The mRNA level of focal adhesion kinase (FAK) in K562 cells was detected by reverse transcription-polymerase chain reaction (RT-PCR) 48 h after treatment of interferon alpha-2b (IFNalpha-2b).

RESULTS

The positive rates of integrin alpha5 and beta1 were significantly higher on K562 cells than on bone marrow mononuclear cells from healthy donors [(97.59+/-1.04)% vs. (64.05+/-2.38)%, (99.24+/-0.52)% vs. (72.40+/-3.56)%, P<0.05). IFNalpha-2b could not change the expression of integrin alpha5 and beta1 on K562 cells, but improved the binding capability of K562 cells to FN, which could be blocked by anti-alpha5 and/or anti-beta1 antibodies. IFNalpha-2b enhanced the expression of FAK gene, and inhibited the proliferation of K562 cells. The anti-alpha5 and anti-beta1 antibodies improved the inhibitory effect of IFNalpha-2b on the proliferation of K562 cells, and blocked IFNalpha-2b-induced increase of FAK gene expression.

CONCLUSION

IFNalpha-2b could inhibit the proliferation of K562 cells through restoring the function of integrin alpha5 and beta1, enhancing binding capability of integrin alpha5 and beta1 to FN, and up-regulating FAK gene expression.

Characterization of the focal adhesion complex in human non-small cell lung cancer cell lines

BACKGROUND

The important metastatic potential of lung cancers is directly correlated with cell adhesion. Cell-extracellular matrix interactions occur in specialized structures termed focal adhesion (FA) complexes. Our aims were to investigate: (i) the expression of the major FA components in three lung cancer cell lines (non metastatic: A549, or metastatic: Calu-1 and H460), (ii) the modifications of the FA complex occurring when apoptosis was induced by Vinorelbine in the A549 cells.

MATERIALS AND METHODS

The FA complex was characterized by flow cytometry, immunocytochemical staining and Western blot.

RESULTS

The expressions of alpha3, betsaP, paxillin, p-paxillin and Grb2 varied depending on the histological type of the tumor. In apoptotic cells, the expressions of the PYK2, p-p38, PI3K and Grb2 adhesion proteins were increased.

CONCLUSION

Our data suggest that these adhesion proteins may be implicated in the transduction of death signals.

High focal adhesion kinase expression in invasive breast carcinomas is associated with an aggressive phenotype

Focal adhesion kinase (FAK) is a protein tyrosine kinase expressed in invasive breast cancer that regulates antiapoptotic signaling. We have examined FAK expression by immunohistochemistry using anti-FAK 4.47 in breast tumor samples from a large population-based, case-control study of women participating in the University of North Carolina Breast Specialized Programs of Research Excellence (SPORE), Carolina Breast Cancer Study. In this population, 629 formalin-fixed, paraffin-embedded tissue sections were stained for FAK and scored as high (3+ or 4+ intensity and > or = 90% positive cells) or otherwise. High FAK expression was associated with poor prognostic indicators including high mitotic index (>10 mitoses per 10 consecutive high-power fields), nuclear grade 3, architectural grade 3, estrogen and progesterone receptor negative, and HER-2/neu overexpressed using CB11 antibody. The association of high FAK expression with HER-2/neu overexpression lends further support that HER-2/neu and FAK collaborate to promote tumorigenesis. The presence of strong FAK expression in many high grade, estrogen- and progesterone-negative breast carcinomas indicates that FAK may be an attractive target for therapeutic intervention.

Effect of cigarette smoke extract on the proliferation of human airway epithelial cells and expression and activation of FAK

The effect of cigarette smoke extract (CSE) on the proliferation of human airway epithelial cells and the possible mechanism was studied. After airway epithelial cells were treated with different concentrations of CSE for 24 h, the cell proliferation was measured by MTT and the distribution of different cell cycles by flow cytometry. The FAK expression level was detected by Western blot and the degree of tyrosine phosphorylation by immunoprecipitation. The results showed that CSE could inhibit the proliferation of human airway epithelial cells, arrest the epithelial cells in G1 phase of cell cycle, dramatically decrease the number of epithelial cells in S and G2 phases; Meanwhile CSE could decrease the expression level of FAK and the degree of its tyrosine phosphorylation. The above effects of CSE were concentration-dependent. The expression of FAK and the degree of its phosphorylation was positively correlated to the increased number of epithelial cells in G1 phase, and negatively to the number of epithelial cells in S and G2 phases. It was concluded that the mechanism by which CSE could inhibit the proliferation of human epithelial cells was contributed to the increased expression and activation of FAK.