Plaunotol and geranylgeraniol induce caspase-mediated apoptosis in colon cancer.

BACKGROUND: Plaunotol, a kind of isoprenoid extracted from a Thai medical plant, plau-noi, is structurally similar to geranylgeraniol (GGOH), another isoprenoid reported to exert strong anticancer effects. Recently, we have reported on its inhibitory effects on tumor angiogenesis and direct effects on gastric cancer cells. Here, we aimed to test whether plaunotol could have some therapeutic effect on colon cancer. MATERIALS AND METHODS: Human colon cancer cell line DLD1 was used. Tumor cells were cultured in the presence of plaunotol or GGOH, and their proliferation was measured by MTS assay. Apoptosis was evaluated by Annexin V and propidium iodide double-staining or terminal-deoxynucleotidyl assay. The activation of caspase-3, -8, and -9 was analyzed by flow cytometry and Western blot analysis for PRRP cleavage. RESULTS: Plaunotol and GGOH strongly inhibited the proliferative activity of DLD1, dependent on induction of apoptosis. The induction of apoptosis by either plaunotol or GGOH was dependent on the activation of both caspase-8 and caspase-9 pathways. CONCLUSIONS: Plaunotol would be a potential anticancer agent against colon cancer, and since it is already available in Japan and Thailand for clinical use as an anti-ulcer/antigastritis agent, clinical trials will be designed to confirm the present findings.

Pilot study of anti-angiogenic vaccine using fixed whole endothelium in patients with progressive malignancy after failure of conventional therapy.

Vaccines targeting tumour angiogenesis were recently shown to inhibit tumour growth in animal models. However, there is still a lack of information about the clinical utility of anti-angiogenic vaccination. Therefore, here, we aimed to test the clinical effects of a vaccine using glutaraldehyde-fixed human umbilical vein endothelial cells (HUVECs). Six patients with recurrent malignant brain tumours and three patients with metastatic colorectal cancer received intradermal injections of 5x10(7) HUVECs/dose (in total 230 vaccinations). ELISA and flow cytometry revealed immunoglobulin response against HUVECs' membrane antigens. ELISPOT and chromium-release cytotoxicity assay revealed a specific cellular immune response against HUVECs, which were lysed in an effectors:targets ratio-dependent manner. Gadolinium-contrasted MRI showed partial or complete tumour responses in three malignant brain tumour patients. Except for a DTH-like skin reaction at the injection site, no adverse effect of vaccination could be observed. Our results suggest that the endothelial vaccine can overcome peripheral tolerance of self-angiogenic antigens in clinical settings, and therefore should be useful for adjuvant immunotherapy of cancer.

Plaunotol induces apoptosis of gastric cancer cells.

Although some isoprenoids, such as taxans and geranylgeraniol (GGOH), have been reported to have strong anticancer activities, the effect of plaunotol, the isoprenoid extracted from the leaves of Plau-noi, on cancer has not yet been evaluated. Here, we aimed to investigate the effect of plaunotol on gastric cancer cell lines. Three gastric cancer cell lines, namely MKN-45, MKN-74 and AZ-521 were used. Plaunotol was tested at 10, 20, 30 and 40 micromol/L. Plaunotol dose-dependently inhibited the growth of all gastric cancer cells, dependent on the induction of apoptosis. Caspases-8, -9 and -3, were found to be activated in the apoptotic cells. The expression of Bax protein was increased, but Bcl-2 and Bcl-xL protein expressions were not significantly affected. Plaunotol should be a promising new antitumor agent, and since it is already available for clinical use in Japan, its anticancer properties should be confirmed in clinical trials.