Abstract 3001: Dysregulation of the mitotic spindle checkpoint contributes to the development of human genital tract leiomyosarcoma

Abstract

Abstract Genes involved in maintaining chromosomal stability are often aberrantly expressed in human cancers and have now emerged as potential therapeutic targets. Using cDNA microarrays, we found that 26 of the 50 most overexpressed genes in human uterine leiomyosarcoma (ULMS) regulate centrosome structure and function. Using qPCR and Western blot, we confirmed that CDC20, TTK, TPX2, UBE2C, CENPA, and Aurora A and B kinases were markedly overexpressed when specimens of human uterine leiomyosarcoma (ULMS) (n = 8) were compared to normal myometrium (n = 8) or benign uterine leiomyomas. Consistent with increased levels of Aurora A kinase activity, we found increased levels of phospho-Aurora A when specimens of uterine leiomyosarcoma were probed immunohistochemically. Functionally, we found that targeting Aurora A kinase expression by siRNA significantly inhibits the proliferation of an established leiomyosarcoma cell line SK-LMS as well as three cell strains (285, 505, 987) derived from metastatic human leiomyosarcomas. Similar to other cell types, inhibition of Aurora A activity resulted in a G2-M cell cycle arrest and the induction of apoptosis as measured by Caspase 3/7 expression. We also used MK5108, a novel small molecule inhibitor highly specific for Aurora kinase A, to treat leiomyosarcoma cell lines and found that increasing concentration both inhibited proliferation and induced apoptosis. Combining MK5108 with gemcitabine, docetaxel and cisplatin, cytotoxic agents currently used to clinically manage human uterine leiomyosarcoma (ULMS), significantly potentiated the ability of each chemotherapy to decrease proliferation and induce cell death. To better explore the role of Aurora kinase expression in vivo, mice were xenografted by intraperitoneally injecting 2 × 106 SK-LMS cells. We found that the oral administration of MK5108 at both 30mg/kg (n=4) and 60 mg/kg (n=4) significantly decreased the number of total implants as well as the mean size of the 5 largest intraperitoneal implants when compared to sham-treated animals (n=4). A trend toward decreased total tumor burden was also observed at both MK5108 dose levels, although no statistical difference was observed. Treatment with MK5108 was accompanied by increased intratumoral apoptosis as indexed by TUNEL assay as well as decreased proliferation as indicated by Ki-67 expression. These results are the first to demonstrate that defects in centrosomal maturation and spindle assembly could play an important role in the etiology of human genital tract leiomyosarcoma. In particular, Aurora A activity seems to be central to the development of human genital tract leiomyosarcoma. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3001. doi:10.1158/1538-7445.AM2011-3001