Interstitial flow in and around tumor tissue affects the mechanical microenvironment to modulate tumor cell growth and metastasis. We investigated the roles of flow-induced shear stress in modulating cell cycle distribution in four tumor cell lines and the underlying mechanisms. In all four cell lines, incubation under static conditions for 24 or 48 h led to G0/G1 arrest; in contrast, shear stress (12 dynes/cm 2 ) induced G2/M arrest. The molecular basis of the shear effect was analyzed, and the presentation on molecular mechanism is focused on human MG63 osteosarcoma cells. Shear stress induced increased expressions of cyclin B1 and p21 CIP1 and decreased expressions of cyclins A, D1, and E, cyclin-dependent protein kinases (Cdk)-1, -2, -4, and -6, and p27 KIP1 as well as a decrease in Cdk1 activity. Using specific antibodies and small interfering RNA, we found that the shear-induced G2/M arrest and corresponding changes in G2/M regulatory protein expression and activity were mediated by ␣v␤3 and ␤1 integrins through bone morphogenetic protein receptor type IA-specific Smad1 and Smad5. Shear stress also down-regulated runt-related transcription factor 2 (Runx2) binding activity and osteocalcin and alkaline phosphatase expressions in MG63 cells; these responses were mediated by ␣v␤3 and ␤1 integrins through Smad5. Our findings provide insights into the mechanism by which shear stress induces G2/M arrest in tumor cells and inhibits cell differentiation and demonstrate the importance of mechanical microenvironment in modulating molecular signaling, gene expression, cell cycle, and functions in tumor cells.M echanical microenvironment plays important roles in modulating tissue development, maintenance, and remodeling and in cellular responses and functions (1). Interstitial fluid flow in and around tissue affects the mechanical microenvironment, including the shear stress and pressure force acting on the cell surface and the tethering force acting on cell-matrix connections (2). These interstitial flow-induced forces can modulate tumor metastasis and invasion as well as anticancer drug delivery (3).Although the influence of interstitial fluid flow on tumor pathobiology and drug delivery has been studied, the effect of the flow-induced shear force on tumor cells has not been much explored. Compressive forces have been shown to inhibit tumor cell growth (4) and up-regulate adhesion molecules (5). A recent study reported that tumor cell proliferation is affected by intratumoral pressure and that activation of mitogen-activated protein kinases and nuclear antigen Ki-67 is involved in this mechanical modulation (6). Although these results show that mechanical forces can modulate tumor cell responses, the detailed mechanisms by which mechanical stimuli are transduced into cellular signaling to regulate tumor cell gene expression and functions remain unclear.Integrins have been implicated as mechanosensors in many types of cells seeded on extracellular matrix (ECM) (7), but their role in modulating mechanical responses of...

Metastasis is the major factor affecting patient survival in ovarian cancer. However, its molecular mechanisms remain unclear. Our study used isogenic pairs of low-and high-invasive ovarian cancer cell lines to demonstrate the downregulation of miRNA-138 in the highly invasive cells, and its functioning as an inhibitor of cell migration and invasion. An orthotopic xenograft mouse model further demonstrated that the expression of miRNA-138 inhibited ovarian cancer metastasis to other organs. Results indicated that miR-138 directly targeted SRY-related high mobility group box 4 (SOX4) and hypoxia-inducible factor-1a (HIF-1a), and overexpression of SOX4 and HIF-1a effectively reversed the miR-138-mediated suppression of cell invasion. Epidermal growth factor receptor acted as the downstream molecule of SOX4 by way of direct transcriptional control, whereas Slug was the downstream molecule of HIF-1a by way of proteasome-mediated degradation. Analysis of human ovarian tumors further revealed downregulation of miR-138 and upregulation of SOX4 in late-stage tumors. Patients with miR-138 low / SOX high signature are predominant in late stage and tend to have malignant phenotypes including lymph nodes metastasis, larger ascites volume and higher tumor grade. Our study demonstrates the role and clinical relevance of miR-138 in ovarian cancer cell invasion and metastasis, providing a potential therapeutic strategy for suppression of ovarian cancer metastasis by targeting SOX4 and HIF-1a pathways.Metastatic ovarian cancer is the deadliest among gynecologic malignancies, with an estimated 15,500 deaths in the United States in 2012, as reported by the National Cancer Institute. The overall 5-year survival rate is 33% when diagnosed at advanced stages; it is about 90% while the cancer is still confined to the ovary (stage I). 1 At late stages, tumor cells spread beyond the pelvic cavity and commonly undergo metastasis to the mesentery, omentum and diaphragm. 2 Metastasis to the pelvic and para-aortic lymph nodes may also occur. Elucidating the mechanisms underlying cancer metastasis will, thus, make significant contributions toward combating this disease. MicroRNAs (miRNAs), a family of small noncoding single-stranded RNAs, have recently been shown to play essential roles in cancer cell invasion and metastasis. 3 One miRNA can suppress multiple gene expressions by interacting with the 3 0 nontranslated regions (3 0 UTRs) of its target mRNAs and promoting their degradation or translational suppression resulting in the modulation of those genes' expressions and functions.A couple of recent studies have reported the role of miRNAs in modulating ovarian cancer cell invasion and metastasis. Cowden Dahl et al. showed that epidermal growth factor receptor (EGFR)-responsive miR-125a induced a mesenchymalto-epithelial transition (MET) in ovarian cancer cells. MiR125a directly targets ARID3B, which is overexpressed in serous ovarian cancer. 4 Corney et al. reported that p53-transactivated miR-34 was decreased in metastatic ovarian cance...

Glucocorticoids are widely used in conjunction with chemotherapy for ovarian cancer to prevent hypersensitivity reactions. Here we reveal a novel role for glucocorticoids in the inhibition of ovarian cancer metastasis. Glucocorticoid treatments induce the expression of miR-708, leading to the suppression of Rap1B, which result in the reduction of integrin-mediated focal adhesion formation, inhibition of ovarian cancer cell migration/invasion and impaired abdominal metastasis in an orthotopic xenograft mouse model. Restoring Rap1B expression reverts glucocorticoid-miR-708 cascade-mediated suppression of ovarian cancer cell invasion and metastasis. Clinically, low miR-708 and high Rap1B are found in late-state ovarian tumours, as compared with normal, and patients with high miR-708 show significantly better survival. Overall, our findings reveal an opportunity for glucocorticoids and their downstream mediators, miR-708 or Rap1B, as therapeutic modalities against metastatic ovarian epithelial cancer.

Background and Aims: The diagnostic accuracy of a novel serological panel (BioFibroScore