Abstract 1767: Anthracenyl isoxazole amides (AIMs) as novel agents for brain tumors
Authors: Alison K. Kearns, Mariusz P. Gajewski, Nicholas R. Natale, Howard D. Beall
Journal: Cancer Research (2012)

Abstract In the United States, the average survival rate for malignant brain tumors is approximately one year. Despite recent advancements in treatment, there remains a need for the development of new therapeutic agents to target and treat malignant brain tumors to increase survival and quality of life. Due to its pivotal role in cancer cell proliferation, telomerase has become an attractive target in the development of new anticancer agents. The enzymatic activity of telomerase is responsible for telomere maintenance and adds the guanine-rich DNA sequence repeats to the 3′ end of DNA strands in the telomere regions. Human telomeric DNA has the potential to adopt G-quartet conformations, which in turn can stack in various arrangements to form G quadruplexes (G4). To this end, molecules that bind telomeric G4 DNA and inhibit telomerase have substantial anticancer potential. The objective of this study was to evaluate the cytotoxicity of a novel series of anthracenyl isoxazole amides (AIMs), capable of selectively binding to G4 telomeric DNA, and determine the ability of the AIMs to penetrate cell membranes and enter the nuclei of cancer cells. These AIMs have demonstrated significant activity against brain tumor cell lines in the DTP NCI-60 cell line panel, and COMPARE analysis indicated that these molecules exerted their cytotoxicity via a unique mechanism. Two AIMs, referred to here as AIM-dimer and AIM-double tail (AIM-dt), showed single digit micromolar IC50 values (4.75 +/− 0.27 and 3.13 +/− 0.45, respectively) by MTT assay when tested in the human glioblastoma cell line SNB-19. As a followup to the cytotoxicity studies, apoptosis was evaluated by flow cytometry (Annexin V). The results indicated that both AIMs induced apoptosis in SNB-19 cells at higher levels than untreated cells after a four-hour treatment. Since the AIMs are known to autofluoresce, confocal microscopy was performed to determine if they were able to penetrate cell membranes of the SNB-19 cells. Contrary to bioavailability calculations made with Symyx Draw v3.1, which suggested that only the AIM-dt had acceptable properties for cell penetration, both compounds were found to enter the cells. Perhaps more intriguing, however, are the results from the laser scanning cytometry (iCys) studies. SNB-19 cells were co-treated with either AIM-dimer or AIM-dt and the nuclear stain propidium iodide. Images taken of each AIM clearly indicated co-localization of the AIM at the nucleus, suggesting that these AIMs are able to penetrate cell membranes and reach the nuclei and therefore have potential to bind DNA. Further studies will be focused on elucidating the mechanism of action of the AIMs as well as confirming their interactions at the level of G4 telomeric DNA. Supported by NIH Grant P20RR017670 (HDB). 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 1767. doi:1538-7445.AM2012-1767