Abstract #1822: Mechanistic studies of a novel small molecule anticancer drug, LOR-253, on cell cycle arrest and angiogenesis

LOR-253 is an anticancer drug candidate in late stage preclinical development that is advancing to clinical studies based on the results of recently completed IND-enabling GLP toxicology studies. Previously we reported that chelation of intracellular labile zinc by LOR-253 results in Kruppel like factor 4 (KLF4) induction leading to cyclin D1 repression and cell cycle arrest in HT-29 colon carcinoma cells. Cyclin D1 is a downstream target of \#946;-catenin, whose transcription is regulated by KLF4; therefore we investigated the involvement of the Wnt/\#946;-catenin signaling pathway in the mode of action of LOR-253. \#914;-catenin gene expression was analyzed by RT-PCR in samples extracted from HT-29 colon cancer cells treated with LOR-253 in vitro, and from HT-29 xenograft tumors from treated CD-1 nude mice. These studies demonstrated that LOR-253 mediated induction of KLF4 led to a decrease in \#946;-catenin expression, resulting in reduction of cyclin D1. Similar results were obtained with the NSCLC cell line NCI-H226, suggesting a role of this pathway in the down stream signaling mechanism produced by the zinc-dependent induction of KLF4. We also examined the potential anti-angiogenic activity of LOR-253, based on the results of our studies that demonstrated the down-regulation of the metal transcription factor 1 (MTF-1) gene expression in cancer cells treated with LOR-253. MTF-1 is an intracellular zinc sensor that regulates the transcription of zinc-sensitive genes involved in zinc homeostasis. It has been reported that MTF-1 regulates hypoxia-inducible factor-1\#945; (HIF-1\#945;), which plays important roles in angiogenesis pathways by regulating matrix metalloproteinases (MMPs). In addition, LOR-253 has been shown to induce KLF2 expression, which may alter the expression of vascular endothelial growth factor receptor (VEGFR) in endothelial cells. We found that LOR-253 was able to inhibit HUVEC cell mitogenesis and capillary formation in vitro. Immunohistochemical analyses of tumors isolated from LOR-253 treated mice showed reduced microvessel density, indicating inhibition of tumor angiogenesis. LOR-253 mediated down-regulation of MTF-1, HIF-1\#945;, and MMP2 was observed 24 hr after drug treatment in an H226 xenograft mouse model. Furthermore, up-regulated KLF2 and reduced VEGFR2 expression was demonstrated 24 hr after LOR-253 treatment in HUVEC cells. Taken together, the data support the potential anti-angiogenic activity of LOR-253. Citation Information: In: Proc Am Assoc Cancer Res; 2009 Apr 18-22; Denver, CO. Philadelphia (PA): AACR; 2009. Abstract nr 1822.