Role In Cancer Cell Migration Research Articles

A role for VICKZ proteins in the progression of colorectal carcinomas: regulating lamellipodia formation

VICKZ proteins are a highly conserved family of RNA binding proteins, implicated in RNA regulatory processes such as intracellular RNA localization, RNA stability, and translational control. During embryogenesis, VICKZ proteins are required for neural crest migration and in adults, the proteins are overexpressed primarily in different cancers. We hypothesized that VICKZ proteins may play a role in cancer cell migration. In patients, VICKZ expression varies with tumour type, with over 60% of colon, lung, and ovarian tumours showing strong expression. In colorectal carcinomas (CRCs), expression is detected at early stages, and the frequency and intensity of staining increase with progression of the disease to lymph node metastases, of which 97% express the protein at high levels. Indeed, in stage II CRC, the level of VICKZ expression in the primary lesion correlates with the degree of lymph node metastasis. In culture, VICKZ proteins rapidly accumulate in processes at the leading edge of PMA-stimulated SW480 CRC cells, where they co-localize with beta-actin mRNA. Two distinct cocktails of shRNAs, each targeting all three VICKZ paralogues, cause a dramatic drop in lamellipodia and ruffle formation in stimulated cells. Thus, VICKZ proteins help to facilitate the dynamic cell surface morphology required for cell motility. We propose that these proteins play an important role in CRC metastasis by shuttling requisite RNAs to the lamellipodia of migrating cells.

Anti apoptotic role of CCR9 in prostate cancer

Limited treatment choices are available for the PCa patients with hormone refractory and metastatic disease. One of the better choices for treating hormone refractory metastatic disease is chemotherapy. Unfortunately better efficacy of these therapeutic modalities cannot be achieved due to the indolent nature of PCa with a very low rate of apoptosis and proliferation. We have recently shown that PCa cells (PC3, LNCaP and C4‐2b) express CCR9 and play significant role in cancer cell migration and invasion in vitro. Here we show that, CCR9‐mediated activation of PI3K/AKT pathway, which inhibits the activation of caspase‐3 and ‐9. Apoptosis induced by Etoposide or Doxorubicin in PCa cells was significantly inhibited after CCL25 treatment and further achieved after blocking CCR9‐CCL25 interaction with anti‐CCR9 monoclonal antibody. These results suggest that CCR9‐mediated cell signals provide protection against drug‐induced apoptosis. Therefore, inhibition of this axis will increase the efficacy of therapeutics for prostate cancer.

TARGETING THE α 1 SUBUNIT OF THE SODIUM PUMP TO COMBAT GLIOBLASTOMA CELLS

Ion transporters play pivotal roles in cancer cell migration in general and in glioblastomas (GBMs) in particular. However, the specific role of Na/K-ATPase (the sodium pump) and, in particular, its alpha1 subunit, has remained unexplored in GBMs. The expression of Na+/K+ -ATPase alpha1 in GBM clinical samples, normal brain tissue, and a human GBM cell line has been investigated. Using the novel cardenolide UNBS1450 (Unibioscreen, Brussels, Belgium), which is a ligand of the sodium pump, we have characterized the effects of inhibiting Na+/K+ -ATPase alpha1 in human GBM cells with respect to cell proliferation; morphology; impact on intracellular Na+, Ca2+, and adenosine triphosphate; and changes in the actin cytoskeleton. We have investigated the mechanism by which UNBS1450 overcomes the apoptosis resistance of GBMs and determined its anti-tumor effects in comparative studies in vitro in GBM cell viability assays and in vivo using an orthotopic human GBM xenograft model. Overall, the alpha1 subunit of Na+/K+ -ATPase is highly expressed in a majority of glioblastomas compared with normal brain tissues, and by binding to this subunit in human U373-MG GBM cells, UNBS1450 impairs cell proliferation and migration via an intracellular adenosine triphosphate decrease-mediated disorganization of the actin cytoskeleton and cytotoxic proautophagic effects. UNBS1450 also significantly increases the in vivo survival of mice orthotopically grafted with U373-MG GBM cells. Inhibition of the Na+/K+ -ATPase alpha1 subunit in human GBM cells impairs both cell migration and cell proliferation.

Colorectal cancer cells express functional cell surface‐bound TGFβ

Disruptions to the TGFbeta signaling pathway have been implicated in most human adenocarcinomas. In addition to its role in cancer cell migration and metastasis, TGFbeta has been implicated in tumor-mediated immunosuppression. Membrane-bound TGFbeta has previously been reported to be expressed on a subset of regulatory T cells and was shown to be critical to their immune suppressive function. In the present study, we document expression of a signaling competent, endogenously derived form of cell surface-bound TGFbeta on colorectal cancer cells. While antibodies against only the mature form of TGFbeta failed to label cells, surface-bound TGFbeta was clearly detected by antibodies specific for both the latent and mature forms of the cytokine. Confirming the notion that the surface TGFbeta was in latent form, brief acid pulsing of the cells increased the amount of detectable membrane-associated TGFbeta. In coculture assays, this cell-bound TGFbeta could be activated and utilized in a paracrine fashion both by other cancer cells and by CD8+ intraepithelial lymphocytes. This effect was abrogated by the use of a furin inhibitor which decreased the membranous expression of TGFbeta on the tumor cells. Signaling competent membrane-bound TGFbeta on cancer cells is thus likely to be a key player in regulating tumor cell interactions with each other as well as with other cells in their microenvironment.

P53 Target Gene SMAR1 Is Dysregulated in Breast Cancer: Its Role in Cancer Cell Migration and Invasion

Tumor suppressor SMAR1 interacts and stabilizes p53 through phosphorylation at its serine-15 residue. We show that SMAR1 transcription is regulated by p53 through its response element present in the SMAR1 promoter. Upon Doxorubicin induced DNA damage, acetylated p53 is recruited on SMAR1 promoter that allows activation of its transcription. Once SMAR1 is induced, cell cycle arrest is observed that is correlated to increased phospho-ser-15-p53 and decreased p53 acetylation. Further we demonstrate that SMAR1 expression is drastically reduced during advancement of human breast cancer. This was correlated with defective p53 expression in breast cancer where acetylated p53 is sequestered into the heterochromatin region and become inaccessible to activate SMAR1 promoter. In a recent report we have shown that SMAR1 represses Cyclin D1 transcription through recruitment of HDAC1 dependent repressor complex at the MAR site of Cyclin D1 promoter. Here we show that downmodulation of SMAR1 in high grade breast carcinoma is correlated with upregulated Cyclin D1 expression. We also established that SMAR1 inhibits tumor cell migration and metastases through inhibition of TGFβ signaling and its downstream target genes including cutl1 and various focal adhesion molecules. Thus, we report that SMAR1 plays a central role in coordinating p53 and TGFβ pathways in human breast cancer.

Overexpression of phosphatase of regenerating liver-3 in breast cancer: association with a poor clinical outcome

Increasing evidence has suggested that phosphatase of regenerating liver-3 (PRL-3) plays an important role in cancer cell migration, invasion and metastasis. However, the correlation between the PRL-3 expression and clinical outcome in breast cancer has not been investigated. Using a PRL-3-specific monoclonal antibody 3B6, PRL-3 expression was assessed by immunohistochemistry in tumor tissues from 382 breast cancer patients with a median follow-up of 65 months. We found that 34.8% patients expressed a high level of PRL-3 protein in their tumors. Patients with a high level of PRL-3 in the tumor had a worse disease-specific survival (DSS) rate than those with a low level of PRL-3 (74.0% versus 84.9%, P = 0.011), and PRL-3 remained an independent prognostic marker for DSS (HR 1.8, 95% CI 1.1-2.9, P = 0.019) in multivariate analysis. More importantly, in 219 node-negative patients, PRL-3 showed a significant correlation with DSS in univariate analysis (P = 0.014) and retained a borderline significance (HR 2.65, 95% CI 0.92-7.64, P = 0.071) in multivariate analysis. Our results suggest that PRL-3 may serve as an unfavorable prognostic marker in breast cancer, especially for patients with node-negative diseases. Thus, our findings may provide useful information for individualized therapy in the clinical setting.

Down-regulation of uPAR and Cathepsin B retards cofilin dephosphorylation

Cathepsin B and uPAR play key roles in cancer cell migration and invasion. Here, we demonstrate that the simultaneous, siRNA-mediated down-regulation of uPAR and cathepsin B inhibits glioma cell migration and is accompanied by cytoskeletal condensation. We show that the dephosphorylation of cofilin is inhibited by the down-regulation of uPAR alone and, to a lesser extent, by the down-regulation of cathepsin B alone, and that the effect was much higher with the down-regulation of both molecules by pUC. Using FACS analysis and western blotting for the alphaVbeta3 integrin heterodimer, we determined that down-regulating uPAR subsequently causes the down-regulation of the alphaVbeta3 integrin heterodimer. As evidenced by western blot analysis of ERK1/2, pERK1/2, p38MAPK, p-p38MAPK, AKT, pAKT and PI3-k, the MEK and PI3-k pathways are inhibited. From cytoskeleton studies, we observed that the down-regulation of uPAR caused cytoskeletal condensation and that the simultaneous down-regulation of uPAR and cathepsin B was even more effective at inducing cytoskeletal condensation than uPAR alone. Our results demonstrate the relevance of uPAR in cytoskeletal dynamics and the potential of uPAR and cathepsin B as targets in the treatment of malignant gliomas.

The HGF/SF-Induced Phosphorylation of Paxillin, Matrix Adhesion, and Invasion of Prostate Cancer Cells Were Suppressed by NK4, an HGF/SF Variant

Hepatocyte growth factor/scatter factor (HGF/SF) plays a crucial role in cancer cell migration, matrix adhesion, invasion, and angiogenesis, via the phosphorylation of the c-met tyrosine kinase. This study examined the ability of NK4, a recently discovered HGF/SF variant, to inhibit the influence of HGF/SF on cell–matrix interaction, paxillin phosphorylation, and invasion of prostate cancer cells. HGF/SF was shown to dramatically enhance tumour cell motility, invasion, cell–matrix adhesion, together with an increase in the degree of paxillin phosphorylation and formation of focal adhesion complexes. However, these HGF/SF-induced effects were suppressed by the presence of NK4. NK4 effectively inhibited the degree of HGF/SF-induced paxillin phosphorylation and matrix adhesion. As a consequence, the matrix invasion of these prostate cancer cells was also suppressed by NK4. In conclusion, this study shows that these HGF/SF-enhanced events, which are critical steps in metastasis, can be inhibited through the addition of NK4, thus warranting further in vivo studies on the implication of NK4 as a potential antimetastasis agent in prostate cancer.

Ras Oncoprotein Induces CD44 Cleavage through Phosphoinositide 3-OH Kinase and the Rho Family of Small G Proteins

CD44 is a cell surface adhesion molecule for several extracellular matrix components. We previously showed that CD44 expressed in cancer cells is proteolytically cleaved at the ectodomain through membrane-anchored metalloproteases and that CD44 cleavage plays a critical role in cancer cell migration. Therefore, cellular signals that promote the migration and metastatic activity of cancer cells may regulate the CD44 ectodomain cleavage. Here, we demonstrate that the expression of the dominant active mutant of Ha-Ras (Ha-Ras(Val-12)) induces redistribution of CD44 to the newly generated membrane ruffling area and CD44 ectodomain cleavage. The migration assay revealed that the CD44 cleavage contributes to the Ha-Ras(Val-12)-induced migration of NIH3T3 cells on hyaluronate substrate. Treatment with LY294002, an inhibitor for phosphoinositide 3-OH kinase (PI3K), significantly inhibits Ha-Ras(Val-12)-induced CD44 cleavage, whereas that with PD98059, an inhibitor for MEK, does not. The active mutant p110 subunit of PI3K has also been shown to enhance the CD44 cleavage, suggesting that PI3K mediates the Ras-induced CD44 cleavage. Moreover, the expression of dominant negative mutants of Cdc42 and Rac1 inhibits the Ha-Ras(Val-12)-induced CD44 cleavage. These results suggest that Ras > PI3K > Cdc42/Rac1 pathway plays an important role in CD44 cleavage and may provide a novel molecular basis to explain how the activated Ras facilitates cancer cell migration.