Abstract
4201 Background: HTI-286 (HTI) is a synthetic tubulin inhibitor and a hemiasterlin analogue. It is a potent inhibitor of cell growth with an additional advantage of circumventing the P-glycoprotein-mediated resistance, which hampers efficacy of several antimicrotubule agents. Aim of our study was to investigate in-vitro antiproliferative effect of HTI in several hepatic cancer cell lines (Morris hepatoma (MH), Hep G2 and Hep 3B) and on primary human hepatocytes. Furthermore tumor growth inhibition was analyzed in a rat in-vivo study. Methods: MTT assay was done to determine the doubling time of each cell line. Exponentially growing cells were seeded with different concentrations of HTI for several doubling times. We determined the cytotoxicity and IC(50) by the MTT method. Microtubule structure was visualized by alpha-tubulin-immunofluoresence (aTIF). All animal experiments were approved by the local ethic commission. MH were implanted into American cancer institute rats (ACI) and tumor growth was pursued with MR-imaging (MR). HTI was administered via tail injection at several time points. The tumor growth was followed for over a period of one month. Results: In MH, HepG2 and Hep3B cells HTI has shown an antiproliferative effect already after one doubling time (22, 48 and 55 hours). IC(50) in MH cells was around 1 nM. Cytotoxic effect of HTI rose with increasing concentration. Proliferation of primary human hepatocytes was not affected by the HTI-treatment. aTIF showed a significant difference in HTI-treated compared to non-treated cells. The in-vivo study revealed significant growth inhibition in HTI treated group compared to a saline solution treated group. Conclusions: Our in-vitro data show that HTI inhibits proliferation of hepatic tumor cells in-vitro and tumor growth in-vivo. aTIF confirmed disrupture of microtubule organization. Furthermore primary human hepatocytes do not seem to be affected by the HTI treatment. The data suggest HTI to be considered as a potent promising cytotoxic and antiproliferative drug in liver oncology especially as it circumvents the P-glycoprotein-mediated drug resistance, being responsible for resistance to taxanes and vinca alkaloids. No significant financial relationships to disclose.
Published Version
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