Inhibited Cancer Invasion Research Articles

Aberrant E-cadherin and γ-catenin expression in malignant mesothelioma and its diagnostic and biological relevance

Cadherins and their associated cytoplasmic proteins, catenins, are critical to the maintenance of normal tissue integrity and the suppression of cancer invasion. The cadherin profile in malignant mesothelioma (MM) is not well defined and the role of the cadherin–catenin system in the pathogenesis of MM remains to be determined. By means of Western blot analysis and immunohistochemistry the expression of E (epithelial)-, N (neural)-, P (placental)-cadherin, and α-, β- and γ-catenins was studied in nine human MM cell lines and five human mesothelial cell lines. Mesothelial cells consistently expressed only N-cadherin and α- and β-catenins. All but one MM cell line were N-cadherin-positive and all of them were also positive for α- and β-catenins. E-cadherin was found in six (66.7%) and γ-catenin in seven (77.8%) MM cell lines. Five of these E-cadherin-positive lines co-expressed N-cadherin and the remaining one was also P-cadherin-positive. Double immunofluorescence staining revealed the plasma membrane co-localisation of both cadherin types in MM cell lines that co-expressed E- and N-cadherin or E- and P-cadherin, respectively. Immunoprecipitation showed complexes of β-catenin with both cadherin types when co-expressed. The results point to upregulation of E-cadherin and γ-catenin in most MM cases and demonstrate that cadherin expression is more heterogeneous and less mutually exclusive in MM compared with the mesothelium, although the biological significance of this finding remains unclear.

Adhesion-independent mechanism for suppression of tumor cell invasion by E-cadherin.

Loss of E-cadherin expression or function in tumors leads to a more invasive phenotype. In this study, we investigated whether the invasion suppressor activity of E-cadherin is mediated directly by tighter physical cell adhesion, indirectly by sequestering β-catenin and thus antagonizing β-catenin/T cell factor (TCF) signaling, or by other signaling pathways. To distinguish mechanisms, we expressed wild-type E-cadherin and various E-cadherin mutants in invasive E-cadherin–negative human breast (MDA-MB-231) and prostate (TSU-Pr1) epithelial carcinoma cell lines using a tetracycline-inducible system. Our data confirm that E-cadherin inhibits human mammary and prostate tumor cell invasion. We find that adhesion is neither necessary nor sufficient for suppressing cancer invasion. Rather, the invasion suppressor signal is mediated through the β-catenin–binding domain of the E-cadherin cytoplasmic tail but not through the p120ctn-binding domain. β-catenin depletion also results in invasion suppression. However, alteration in the β-catenin/TCF transcriptional regulation of target genes is not required for the invasion suppressor activity of E-cadherin, suggesting the involvement of other β-catenin–binding proteins.

Expression of e-cadherin and catenins in early gastric cancer.

E-cadherin and its associated cytoplasmic proteins including alpha-, beta-, and gamma-catenin play a pivotal role in the maintenance of normal tissue architecture and the suppression of cancer invasion. The purpose of this study was to evaluate the expression of E-cadherin and alpha-, beta-, and gamma-catenin in a larger sample of early gastric cancer, and to examine the relation between these expressions and various clinicopathologic variables. The expression of E-cadherin and alpha-, beta-, and gamma-catenin was investigated using immunohistochemical technique with formalin-fixed, paraffin-embedded tissue specimens obtained from 108 patients who underwent surgery for early gastric cancer. In the gastric mucosa of noncancerous areas, epithelial cells showed equally strong membranous expression of E-cadherin and alpha-, beta-, and gamma-catenin proteins at the cell-cell boundaries. Reduced expression of E-cadherin and alpha-, beta-, and gamma-catenin was demonstrated in 43.5%, 39.8%, 42.6%, and 50% of cancer tissues, respectively. Whereas 34 tumors (31.5%) displayed preserved expression of all four E-cadherin-catenin complex components, 21 tumors (19.4%) displayed reduced expression of all components of this complex. Reduced expression of E-cadherin and alpha- and gamma-catenin occurred more frequently in diffuse than in intestinal types of cancer, and decreased expression of E-cadherin and alpha-, beta-, and gamma-catenin correlated with poor differentiation. The expression of E-cadherin and beta- and gamma-catenin did not correlate with the patient's age, gender, tumor size, location, macroscopic type, depth of invasion, or lymph node metastasis. Only reduced expression of alpha-catenin correlated with lymph node metastasis. Reduced expression of all four E-cadherin-catenin complex components correlated with poorly differentiated and diffuse-type cancers, but not with the patient's age, gender, tumor size, location, macroscopic type, depth of invasion, or lymph node metastasis. These results suggest that dysfunction of the E-cadherin-catenin complex occurs in an early stage of carcinogenesis, playing a crucial role in disruption of tissue architecture and loss of differentiation in early gastric cancer.

A quinolinone derivative, vesnarinone (OPC-8212), significantly inhibits the in vitro and in vivo growth of human pancreatic cancer cell lines.

A quinolinone derivative, vesnarinone, has been used as a cardiotonic agent. Previous studies have demonstrated that vesnarinone has potent antitumor activity. The present study was designed to assess the antitumor effects of vesnarinone on human pancreatic cancer cell lines in vitro and in vivo. The in vitro effects of vesnarinone on the human pancreatic cancer cell lines (PANC-1, MIA PaCa-2 and BxPC-3) were assessed by the MTT assay, the Trypan blue dye exclusion test and the Matrigel invasion chamber assay. The inhibition of in vivo tumor growth was evaluated on two human pancreatic cancer xenografts (BxPC-3 and SPa-1) transplanted s.c. into nude mice. The dose of vesnarinone for 50% inhibition of cell growth in a 7 day culture ranged between 10 and 20 micrograms/ml as verified by the Trypan blue dye exclusion test. The dose for 50% cytotoxicity after a 3 day culture in the MTT assay was 32 micrograms/ml for PANC-1 and 30 micrograms/ml for BxPC-3, but 50% cytotoxicity for MIA PaCa-2 was not achieved by the maximal dose of vesnarinone (50 micrograms/ml). Nomalsky optic microscopy and acridine orange staining demonstrated the vacuolization and crater-like changes in the cell nucleus after vesnarinone treatment. Moreover, staining of an apoptosis marker (Le(y) protein) and nick end-labeling increased. Vesnarinone also inhibited cancer invasion in the Matrigel invasion chamber assay. In vivo, BxPC-3 and SPa-1 were s.c. transplanted into the nude mice, and vesnarinone (5 or 50 mg/kg) was daily administered orally for 21 days. In both lines, vesnarinone at 50 mg/kg achieved significant inhibition. The present study suggests that vesnarinone may be a new therapeutic agent for pancreatic cancer.

Inhibition of osteolytic bone metastasis of breast cancer by combined treatment with the bisphosphonate ibandronate and tissue inhibitor of the matrix metalloproteinase-2.

Multiple steps are involved in the metastasis of cancer cells from primary sites to distant organs. These steps should be considered in the design of pharmacologic approaches to prevent or inhibit the metastatic process. In the present study, we have compared the effects of inhibiting several steps involved in the bone metastatic process individually with inhibition of both together. The steps we chose were matrix metalloproteinase (MMP) secretion, likely involved in tumor cell invasion, and osteoclastic bone resorption, the final step in the process. We used an experimental model in which inoculation of human estrogen-independent breast cancer MDA-231 cells into the left cardiac ventricle of female nude mice causes osteolytic lesions in bone. To inhibit cancer invasiveness, the tissue inhibitor of the MMP-2 (TIMP-2), which is a natural inhibitor of MMPs, was overexpressed in MDA-231 cells. To inhibit bone resorption, a potent bisphosphonate, ibandronate (4 microg/mouse) was daily administered subcutaneously. Nude mice received either; (a) nontransfected MDA-231 cells; (b) nontransfected MDA231 cells and ibandronate; (c) TIMP-2-transfected MDA-231 cells; or (d) TIMP-2-transfected MDA-231 cells and ibandronate. In mice from group a, radiographs revealed multiple osteolytic lesions. However, in mice from group b or group c, osteolytic lesions were markedly decreased. Of particular note, in animals from group d receiving both ibandronate and TIMP-2-transfected MDA-231 cells, there were no radiologically detectable osteolytic lesions. Survival rate was increased in mice of groups c and d. There was no difference in local enlargement in the mammary fat pad between nontransfected and TIMP-2-transfected MDA-231 cells. These results suggest that inhibition of both MMPs and osteoclastic bone resorption are more efficacious treatment for prevention of osteolytic lesions than either alone, and suggest that when therapies are designed based on the uniqueness of the bone microenvironment and combined with several common steps in the metastatic process, osteolytic bone metastases can be more efficiently and selectively inhibited.

U-77,863: a novel cinnanamide isolated from Streptomyces griseoluteus that inhibits cancer invasion and metastasis.

Several cinnamoyl compounds have been shown to have antitumor activities, but not specifically anti-invasive or antimetastatic effects. U-77,863 (o-methyl cinnanamide) was originally isolated from a fermentation beer of Streptomyces griseoluteus and recently synthesized (Harper, DE and Welch DR. Journal of Antibiotics, in press). Based upon some differential activities of cinnanamides, in general, and U-77,863, specifically, we tested the hypothesis that U-77,863 could inhibit invasion and metastasis of human malignant melanoma cell lines C8161 and A375M. Pretreatment of melanoma cells in vitro with nontoxic doses of U-77,863 caused a dose-, and time-dependent, reversible reduction (IC50 = 12.5 micrograms/ml) of invasion through Matrigel-coated polycarbonate filters in the Membrane Invasion Culture System (MICS). Likewise, lung colonization was significantly (P < 0.05) inhibited when tumor cells were pretreated in vitro with U-77,863 prior to intravenous injection. Structure-activity analysis revealed that the acrylamide side-chain alone and cinnanamide were only slightly less potent than U-77,863, whereas cinnamic acid analogs did not inhibit tumor cell invasion at doses < or = 100 micrograms/ml. U-77,863 inhibits invasion and metastasis without decreasing growth rates or clonogenic potential. Adhesion to endothelial monolayers or extracellular matrices (Matrigel) is not affected by exposure to U-77,863. U-77,863 presumably inhibits metastasis by inhibiting tumor cell extravasation (invasion). U-77,863 is a lead compound for developing a novel class of anti-invasive/anti-metastatic drugs.