Engagement of integrinβ1 induces resistance of bladder cancer cells to mitomycin-C

Shielding and nurturing: Fibronectin as a modulator of cancer drug resistance

Resistance to chemotherapy and targeted therapies constitute a common hallmark of most cancers and represent a dominant factor fostering tumor relapse and metastasis. Fibronectin, an abundant extracellular matrix glycoprotein, has long been proposed to play an important role in the pathobiology of cancer. Recent research has unraveled the role of Fibronectin in the onset of chemoresistance against a variety of antineoplastic drugs including DNA-damaging agents, hormone receptor antagonists, tyrosine kinase inhibitors, microtubule destabilizing agents, etc. The current review summarizes the role played by Fibronectin in mediating drug resistance against diverse anticancer drugs. We have also discussed how the aberrant expression of Fibronectin drives the oncogenic signaling pathways ultimately leading to drug resistance through the inhibition of apoptosis, promotion of cancer cell growth and proliferation.

Pharmaceutical Evaluation of Honokiol and Magnolol on Apoptosis and Migration Inhibition in Human Bladder Cancer Cells

Among herbal medicines, magnolia bark extract, particularly its components honokiol (Hono) and magnolol (Mag), has been widely documented to have antineoplastic properties. The present study aimed to evaluate the synergism of Hono and Mag in bladder cancer therapy both in vitro and in vivo. Treatment with Mag alone at concentrations up to 80 μM failed to have an antiproliferative effect. In contrast, the combination of Hono and Mag at 40 μM decreased viability, caused cell cycle arrest and enhanced the proportion of Annexin V/7AAD-positive cells. Moreover, Mag with Hono at 40 μM induced caspase 3-dependent apoptosis and autophagy. Neither Hono nor Mag alone had an anti-migratory effect on bladder cancer cells. In contrast, Hono and Mag at 20 μM inhibited the motility of TSGH8301 and T24 cells in wound-healing and Transwell assays. The above phenomena were further confirmed by decreased phosphorylated focal adhesion kinase (p-FAK), p-paxillin, integrin β1, and integrin β3 protein levels. In a nude mouse xenograft model, Mag/Hono administration preferentially retarded T24 tumor progression, which was consistent with the results of cellular experiments. Current findings suggest Hono and Mag treatment as a potential anticancer therapy for both low- and high-grade urothelial carcinoma.

MicroRNA-31 functions as a tumor suppressor and increases sensitivity to mitomycin-C in urothelial bladder cancer by targeting integrin α5

Urothelial bladder cancer (UBC) is a common genitourinary malignancy. MiR-31, a well-identified miRNA, exhibits diverse properties in different cancers. However, the specific functions and mechanisms of miR-31 in UBC have not been investigated. In this study, tumor samples, especially invasive UBC, showed significantly reduced level of miR-31, as compared with normal urothelium. Prognostic analysis using the EORTC model showed that down-regulation of miR-31 correlated with higher risks of recurrence and progression in noninvasive UBC cases. Remarkably, overexpression of miR-31 mimics in UBC cell lines inhibited cell proliferation, migration and invasion. Integrin α5 (ITGA5), an integrin family member, was subsequently identified as a direct target of miR-31 in UBC cells. When treated with mitomycin-C (MMC), miR-31-expressing UBC cells displayed lower survival and higher apoptotic rates, and deactivated Akt and ERK. These effects arising from miR-31 overexpression were abrogated by ITGA5 restoration. Furthermore, miR-31 markedly inhibited tumor growth and increased the effectiveness of MMC in UBC xenografts. In summary, our data suggest that miR-31 is a prognostic predictor and can serve as a potential therapeutic target of UBC.

Blocking integrin β1 decreases adhesion in chemoresistant urothelial cancer cell lines

Treatment failure in metastatic bladder cancer is commonly caused by acquisition of resistance to chemotherapy in association with tumor progression. Since alterations of integrins can influence the adhesive and invasive behaviors of urothelial bladder cancer cell lines, the present study aimed to evaluate the role of integrins in bladder cancer cells with acquired resistance to standard first-line chemotherapy with gemcitabine, and cisplatin. Therefore, four gemcitabine- and four cisplatin-resistant sublines out of a panel of four parental urothelial bladder cancer cell lines (TCC-SUP, HT1376, T24, and 5637) were used. Expression of integrin subunits α3, α5, α6, β1, β3, and β4 was detected using flow cytometry. Adhesion and chemotaxis were analyzed. For functional assays, integrin β1 was attenuated with a blocking antibody. In untreated cells, chemotaxis was upregulated in 3/4 gemcitabine-resistant sublines. In cisplatin-resistant cells, chemotaxis was enhanced in 2/4 cell lines. Acquired chemoresistance induced the upregulation of integrin β1 in all four tested gemcitabine-resistant sublines, as well as an upregulation in 3/4 cisplatin-resistant sublines compared with parental cell lines. Following the inhibition of integrin β1, adhesion to extracellular matrix components was downregulated in 3/4 gemcitabine-resistant sublines and in all four tested cisplatin-resistant sublines. Since integrin β1 is frequently upregulated in chemoresistant urothelial cancer cell lines and inhibition of integrin β1 may influence adhesion, further studies are warranted to evaluate integrin β1 as a potential therapeutic target for bladder cancer in vivo.

Targeting of CCN2 suppresses tumor progression and improves chemo-sensitivity in urothelial bladder cancer

Urothelial bladder cancer (UBC) is the most common urinary neoplasm in China. CCN family protein 2 (CCN2), a cysteine-rich matricellular protein, is abnormally expressed in several cancer types and involved in tumor progression or chemo-resistance. However, detailed expression patterns and effects of CCN2 in UBC still remain unknown. We found that down-regulation of CCN2 suppressed proliferation, migration and invasion of UBC cells in vitro and targeting of CCN2 decelerated xenograft growth in vivo. When treated with mitomycin C (MMC), CCN2-scilencing UBC cells showed lower survival and higher apoptotic rates and these effects were probably mediated via inactivation of Akt and Erk pathways. We also demonstrated the clinical significance of CCN2 expression, which was higher in UBC tissues and associated with advanced tumor stage and high pathologic grade. Taken together, our data suggest that CCN2 is an oncogene in UBC and might serve as a matricellular target for improving chemotherapeutic efficacy.

The difference in Ezrin-pAkt signaling axis between lepidic and papillary predominant invasive adenocarcinomas of the lung

PURPOSE

Histologic classification of invasive lung adenocarcinomas by predominant subtype has prognostic value. Papillary predominant adenocarcinoma (PPA) reportedly shows poorer prognosis than lepidic predominant adenocarcinoma (LPA); however, biological differences between PPA and LPA are unclear. The purpose of this study was to clarify biological differences between PPA and LPA.

METHODS

Clinicopathological characteristics of invasive 62 PPAs and 117 LPAs smaller than 30 mm were investigated. Furthermore, we compared immunochemical staining scores of 9 molecular markers (E-cadherin, S100A4, fibronectin, integrinβ1, ezrin, GLUT1, ALDH1, SOX2 and Nanog) between PPA and LPA. We performed Western blot analysis using ezrin shRNA-knockdown lung adenocarcinoma cell lines to examine whether molecules that are highly expressed in PPA, such as ezrin, affect pAkt. Finally, we performed immunochemical staining to compare pAkt expression level in PPA and LPA.

RESULTS

Lymphovascular and pleural invasion and lymph node metastasis were significantly more often detected in PPA than in LPA (lymphatic permeation: 31 vs 3 %, vascular invasion: 35 vs 3 %, pleural invasion: 29 vs 5 %, lymph node metastasis: 18 vs 1 %; all P < 0.01). Immunohistochemical (IHC) study revealed that expression score of ezrin was significantly higher in PPA than in LPA (38.3 vs 15.0; P < 0.01). The level of pAkt decreased in shEzrin-induced PC-9 and A549 cancer cells. Moreover, the IHC staining score of pAkt was significantly higher in PPA than in LPA (13.3 vs 0.0; P < 0.01).

CONCLUSIONS

Our results show that the activation of the ezrin-pAkt signaling axis is associated with the more aggressive clinicopathological features of PPA compared with LPA.

[Tumour-stroma interactions in urothelial cancer]

BACKGROUND

The histopathological structure of malignant tumours involves two essential compartments - the tumour parenchyma with the actual transformed cells, and the supportive tumour stroma. The latter consists of specialized mesenchymal cells, such as fibroblasts, macrophages, lymphocytes and vascular cells, as well as of their secreted products, including components of the extracellular matrix, matrix modifying enzymes and numerous regulatory growth factors and cytokines. In consequence, the tumour stroma has the ability to influence virtually all aspects of tumour development and progression, including therapeutic response.

AIM

In this article we review the current knowledge of tumor stroma interactions in urothelial carcinoma and present various experimental systems that are currently in use to unravel the biological basis of these heterotypic cell interactions.

RESULTS

For urothelial carcinoma, an extensive tumour stroma is quite typical and markers of activated fibroblasts correlate significantly with clinical parameters of advanced disease. Another clinically important variable is provided by the stromal expression of syndecan-1.

CONCLUSION

Integration of markers of activated stroma into clinical risk evaluation could aid to better stratification of urothelial bladder carcinoma patients. Elucidation of biological mechanisms underlying tumour-stroma interactions could provide new therapeutical targets.

α-Lipoic acid suppresses migration and invasion via downregulation of cell surface β1-integrin expression in bladder cancer cells

Our previous study showed α-lipoic acid (LA) downregulated cell surface β1-integrin expression of v-H-ras-transformed derivative of rat fibroblast with amelioration of their malignant phenotype. Here, we evaluated the ameliorating effect of LA on the malignant characters in H-ras-transformed bladder cancer cells. H-ras mutated bladder cancer line, T24 cells were incubated with LA to evaluate the inhibitory effect on proliferation, migration, invasion and β1-integrin expression. Fluorescence staining of F-actin and western blotting analyses of the related signaling pathways were also performed. LA inhibited the proliferation of T24 cells. Cell adhesion to collagen IV and fibronectin was strikingly inhibited by LA treatment accompanied by downregulation of cell surface but not whole cell β1-integrin expression. LA clearly inhibited cell migration and invasion of T24 cells, which were mimicked by extracellular signal-regulated kinase (ERK) and Akt pathway inhibition. Actually, LA significantly downregulated the phosphorylated ERK and Akt levels. Moreover, LA downregulated phosphorylated focal adhesion kinase level with disappearance of stress fiber formation. Finally, although LA induced the internalization of cell surface β1-integrin, disruption of the raft did not affect the action of LA. Taken together, LA is a promising agent to improve malignant character of bladder cancer cells through regulation of cellular β1-integrin localization.

HDAC inhibition suppresses bladder cancer cell adhesion to collagen under flow conditions

The influence of the histone deacetylase (HDAC)-inhibitor, valproic acid (VPA), on bladder cancer cell adhesion in vitro was investigated in this paper. TCCSUP and RT-112 bladder cancer cells were treated with VPA (0.5 or 1 mM) twice or thrice weekly for 14 days. Controls remained untreated. Tumour cell interaction with immobilized collagen was evaluated by a flow-based adhesion assay using a shear force of 2 or 4 dyne/cm(2). The effects of VPA on the integrin adhesion receptors α3, α5, β1, β3 and β4 were assessed by flow cytometry to determine integrin surface expression and by western blotting to determine the cytoplasmic integrin level. VPA of 0.5 mM and 1 mM significantly prevented binding of both RT-112 and TCCSUP cells to collagen, compared with the untreated controls. Adhesion was reduced to a higher extent when RT-112 (subjected to 2 dyne/cm(2)) or TCCSUP (subjected to 2 or 4 dyne/cm(2)) tumour cells were treated with VPA three times a week, compared to the two times a week protocol. VPA caused a significant up-regulation of the integrin α3, α5, β1, β3 and β4 subtypes on the TCCSUP cell surface membrane. In RT-112 cells, only integrin α5 was elevated on the cell surface following VPA exposure. Western blotting revealed an up-regulation of α3, α5, β3 and β4 integrins and down-regulation of the integrin β1 protein by VPA in TCCSUP. VPA also up-regulated α5 and down-regulated β1 integrin in RT-112 cells, but also reduced α3 and β3 in TCCSUP. VPA exerted adhesion-blocking properties on bladder cancer cells under physiologic flow conditions. The effects were accompanied by distinct modifications of the integrin expression profile, which differ depending on the cell lines used. Application of VPA might be an innovative option to prevent bladder cancer dissemination.