Abstract A243: Identification of a target for collismycin A, a cytotoxic microbial product, by proteomic profiling.

Background: Collismycin A, a microbial product, has antiproliferative activity against tumor cells, the mechanism of which yet remains unknown. Recently, we reported an indirect drug target identification approach, termed “ChemProteoBase," which is based on specific changes in the intracellular proteome induced by chemical manipulations. Here, we report on the identification of a molecular target for collismycin A by using ChemProteoBase. Materials and Methods: HeLa cells were treated with collismycin A for 18 h, and the resulting cell lysates were subjected to two-dimensional fluorescence differential gel electrophoresis (2D-DIGE). The gel images were linked to our database containing images that were generated by 134 well-characterized small molecule drugs and probes. The 296 spots that matched on all gel images were quantified, and then hierarchical cluster analysis and similarity ranking analysis were performed. Results: Collismycin A inhibited cell growth of various human tumor cells with IC 50 values ranging from 100 to 400 nM. Flow cytometry and western blot analyses showed that collismycin A arrested cell cycle at G1 phase with the marked decrease of cyclin D1. To predict the mechanism of action of collismycin A, we performed ChemProteoBase profiling. As a result, collismycin A was clustered with Dp44mT, an iron chelator, and Dp44mT was also ranked in the highest position of a similarity ranking among 134 compounds contained in the ChemProteoBase. HR-ESI-MS analysis revealed that collismycin A forms 2 : 1 chelator-iron complex. In addition, the antiproliferative activity of collismycin A was completely abolished by the addition of excessive amounts of Fe(II) or Fe(III) ion but not other metal ions including Cu(II), Zn(II), Mn(II) and Mg(II). Conclusions: These results strongly suggest that collismycin A acts as an iron chelator, resulting in the inhibition of tumor cell growth. Recent studies have shown that iron contributes to tumor initiation, growth and metastasis, and several iron chelators are under preclinical or early clinical investigation as anticancer therapeutics. Therefore, a new iron chelator, collismycin A, might be useful for the treatment of cancers in which iron has been strongly implicated. Citation Information: Mol Cancer Ther 2013;12(11 Suppl):A243. Citation Format: Makoto Kawatani, Gyo Inoue, Makoto Muroi, Yushi Futamura, Harumi Aono, Masakazu Uramoto, Yayoi Hongo, Hiroyuki Koshino, Yasuhiro Igarashi, Naoko Takahashi-Ando, Hiroyuki Osada. Identification of a target for collismycin A, a cytotoxic microbial product, by proteomic profiling. [abstract]. In: Proceedings of the AACR-NCI-EORTC International Conference: Molecular Targets and Cancer Therapeutics; 2013 Oct 19-23; Boston, MA. Philadelphia (PA): AACR; Mol Cancer Ther 2013;12(11 Suppl):Abstract nr A243.