Abstract 149: Antitumor effect of itraconazole on hematological malignant cells by suppression of Hedgehog signal transduction via inhibition of lipid raft formation

Abstract

Abstract [Introduction and aim] Itraconazole (ITCZ) is one of the antifungal agents that inhibits fungal cell membrane ergosterol synthesis. ITCZ has been widely used for the treatment of fungal infections with high efficiency. Recently, anti-tumor effect of ITCZ was reported for solid tumors (Kim J et al. Cancer Cell 2010;17:388-399). During the treatment of hematological malignancies, ITCZ has been quite often used for invasive fungal infections; however, there has been no report for the effect of ITCZ on hematological malignancies. Therefore, we aimed to investigate the anti-tumor effect of ITCZ on hematological malignancies in the present study. [Methods] DAUDI, Jurkat, K562, Karpas299 cell lines were used as a model of hematological malignancies in the present study. At first, MTT assays were performed by treating the cells to determine if ITCZ possessed anti-tumor effect on the cell growth. Then, comprehensive analysis of intracellular signal transductions was performed utilizing reporter assay system. To evaluate the involvement of lipid raft formation by ITCZ, Gli1 expression concerning the Hedgehog signal transduction was determined by real-time PCR and western blotting, and fluorescent staining of the cells using lipid raft marker was also performed. [Results] ITCZ inhibited the cell growth by 40 to 60% determined by MTT assays in all four cell lines tested in the present study. Comprehensive analysis of intracellular signal transductions utilizing reporter assay system in Karpas299 cells showed the strong decrease of Gli1 transcription, implying the inhibition of Hedgehog signal transduction. Concerning Hedgehog signal pathway, Gli1 protein has been reported to be overexpressed in tumor cells and considered to be involved in the tumor growth, and Gli1 has also been reported to localize in lipid raft. Therefore, we hypothesized that ITCZ might influenced on the lipid raft of cell membrane and then Gli1 expression was suppressed, leading to the weakened Hedgehog signal transduction and cell growth inhibition. Fluorescent staining of Jurkat cells using lipid raft marker showed that the presence of ITCZ apparently inhibited the formation of lipid raft on cell membrane. This finding was quite similar compared to that observed when lipid raft inhibitor was added to cell culture medium. [Conclusions] ITCZ has an inhibitory effect on the cell growth in the cultured cell lines derived from hematological malignancies as same as the previous finding observed in solid tumors. Our results further indicated that ITCZ inhibited the formation of lipid raft on cell membrane, and then Hedgehog signal transduction should be weakened, finally leading to the cell growth inhibition. Taken together, the tumor inhibition by ITCZ should be favorable effect and may enhance the efficacy of the treatment of various hematological malignancies. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 149. doi:1538-7445.AM2012-149