Abstract 2306: Pre-clinical development of 4′-thio-2′-deoxycytidine (TdCyd) as a DNA-demethylating agent for use in treating solid tissue tumors

Targeting cancer epigenetic control of cell growth via DNA methylation has been successful in treating hematologic diseases, such as Decitabine (DAC) and Azacitidine for Myelodysplastic Syndrome including Acute Myelomonocytic Leukemia. This success has not extended to solid tissue tumors. The Division of Cancer Treatment and Diagnositcs of NCI has initiated pre-clinical development of TdCyd as an agent for treating solid tumors after promising early results in a lung adenocarcinoma xenograft model (NCI-H23). IP dosing at 5MKG (0.56 MTD) in nu/nu mice on a Q5D x 3 cycle schedule resulted in tumor stasis with no accompanying weight loss in the mice. A DAC-treated control arm treated at MTD resulted in tumor growth delay but not stasis, and a 10% weight loss was noted. Intratumoral levels of DNMT1 were reduced to undetectable levels in xenografts post administration of TdCyd by ELISA and Western Blot assays, but were unaffected by DAC treatment. Mass Spectrometry analysis demonstrated incorporation of both TdCyd and thiothymidine (TdThd) into H23 DNA. In vitro experiments on a selected panel of cancer cell lines confirmed the conversion of TdCyd to the triphosphate and re-expression of tumor suppressor proteins p15 and p16. Funded by NCI Contract No. HHSN261200800001E. Citation Format: Robert J. Kinders, Melinda Hollingshead, Jaideep Thottassery, William B. Parker, Thomas D. Pfister, Lawrence W. Anderson, Joseph E. Tomaszewski, Jerry M. Collins, James H. Doroshow. Pre-clinical development of 4′-thio-2′-deoxycytidine (TdCyd) as a DNA-demethylating agent for use in treating solid tissue tumors. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 2306. doi:10.1158/1538-7445.AM2014-2306