t-0070907 and Neoplasm-Metastasis

Peroxisome proliferator-activated receptor gamma (PPARgamma) is a ligand-activated transcription factor that has been implicated in the carcinogenesis and progression of various solid tumors, including pancreatic carcinomas. We aimed to clarify the role of this receptor in pancreatic cell motility in vitro and in metastasis in vivo. Cell motility was examined by assaying transwell migration and wound filling in Capan-1 and Panc-1 pancreatic cancer cells, with or without the PPARgamma-specific inhibitor T0070907. A severe combined immunodeficiency xenograft metastasis model was used to examine the in vivo effect of PPARgamma inhibition on pancreatic cancer metastasis. In both transwell-migration and wound-filling assays, inhibition of PPARgamma activity suppressed pancreatic cell motility without affecting in vitro cell proliferation. Inhibition of PPARgamma also suppressed liver metastasis in vivo in metastatic mice. In PPARgamma-inhibited cells, p120 catenin accumulation was induced predominantly in cell membranes, and the Ras-homologous GTPases Rac1 and Cdc42 were inactive. Inhibition of PPARgamma in pancreatic cancer cells decreased cell motility by altering p120ctn localization and by suppressing the activity of the Ras-homologous GTPases Rac1 and Cdc42. Based on these findings, PPARgamma could function as a novel target for the therapeutic control of cancer cell invasion or metastasis.

Topics: Animals; Benzamides; Catenins; cdc42 GTP-Binding Protein; Cell Adhesion Molecules; Cell Line, Tumor; Cell Movement; Delta Catenin; Humans; Ligands; Mice; Mice, SCID; Neoplasm Metastasis; Pancreatic Neoplasms; Phosphoproteins; PPAR gamma; Pyridines; rac1 GTP-Binding Protein; RNA, Small Interfering; Rosiglitazone; Thiazolidinediones; Xenograft Model Antitumor Assays

The nuclear transcription factor peroxisome proliferator-activated receptor-gamma (PPARgamma) has been identified as an important therapeutic target in murine models of colorectal cancer (CRC). To examine whether PPARgamma inhibition has therapeutic effects in late-stage CRC, the effects of PPARgamma inhibitors on CRC cell survival were examined in CRC cell lines and a murine CRC model. Low doses (0.1-1 microM) of PPARgamma inhibitors (T0070907, GW9662 and BADGE) did not affect cell survival, while higher doses (10-100 microM) of all 3 PPARgamma inhibitors caused caspase-dependent apoptosis in HT-29, Caco-2 and LoVo CRC cell lines. Apoptosis was preceded by altered cell morphology, and this alteration was not prevented by caspase inhibition. PPARgamma inhibitors also caused dual G and M cell cycle arrest, which was not required for apoptosis or for morphologic alterations. Furthermore, PPARgamma inhibitors triggered loss of the microtubule network. Notably, unlike other standard antimicrotubule agents, PPARgamma inhibitors caused microtubule loss by regulating tubulin post-transcriptionally rather than by altering microtubule polymerization or dynamics. Proteasome inhibition by epoxomicin was unable to prevent tubulin loss. siRNA-mediated reduction of PPARgamma and PPARdelta proteins did not replicate the effects of PPARgamma inhibitors or interfere with the inhibitors' effects on apoptosis, cell cycle or tubulin. PPARgamma inhibitors also reduced CRC cell migration and invasion in assays in vitro and reduced both the number and size of metastases in a HT-29/SCID xenograft metastatic model of CRC. These results suggest that PPARgamma inhibitors are a novel potential antimicrotubule therapy for CRC that acts by directly reducing microtubule precursors.

Topics: Amino Acid Chloromethyl Ketones; Anilides; Animals; Apoptosis; Benzamides; Benzhydryl Compounds; Caco-2 Cells; Caspase Inhibitors; Caspases; Cell Cycle; Cell Line, Tumor; Cell Movement; Cell Shape; Colorectal Neoplasms; Dose-Response Relationship, Drug; Epoxy Compounds; HT29 Cells; Humans; Male; Mice; Mice, SCID; Neoplasm Metastasis; PPAR delta; PPAR gamma; Proteasome Endopeptidase Complex; Pyridines; Tubulin; Xenograft Model Antitumor Assays