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Specific targeting of MTAP-deleted tumors with a combination of 2'-fluoroadenine and 5'-methylthioadenosine
Cancer Res. 2018 Aug 1;78(15) :4386-4395
PMID: 29844120 PMCID: PMC6072572 URL: https://www.ncbi.nlm.nih.gov/pubmed/29844120
AbstractHomozygous deletion of the methylthioadenosine phosphorylase (MTAP) gene is a frequent event in a wide variety of human cancers and is a possible molecular target for therapy. One potential therapeutic strategy to target MTAP-deleted tumors involves combining toxic purine analogs such as 6'-thioguanine (6TG) or 2'-fluoroadenine (2FA) with the MTAP substrate 5'-deoxy-5'-methylthioadenosine (MTA). The rationale is that excess MTA will protect normal MTAP+ cells from purine analog toxicity because MTAP catalyzes the conversion of MTA to adenine, which then inhibits the conversion of purine base analogs into nucleotides. However, in MTAP- tumor cells, no protection takes place because adenine is not formed. Here, we examine the effects of 6TG and 2FA in combination with MTA in vitro and in vivo. In vitro, MTA protected against both 6TG and 2FA toxicity in an MTAP-dependent manner, shifting the IC50 concentration by one to three orders of magnitude. However, in mice, MTA protected against toxicity from 2FA but failed to protect against 6TG. Addition of 100 mg/kg MTA to 20 mg/kg 2FA entirely reversed the toxicity of 2FA in a variety of tissues and the treatment was well tolerated by mice. The 2FA+MTA combination inhibited tumor growth of four different MTAP- human tumor cell lines in mouse xenograft models. Our results suggest that 2FA+MTA may be a promising combination for treating MTAP-deleted tumors.
Notes1538-7445 Tang, Baiqing Lee, Hyung-Ok An, Serim S Cai, Kathy Q Kruger, Warren D Journal Article P30 CA006927/CA/NCI NIH HHS/ Research Support, N.I.H., Extramural Cancer Res. 2018 Aug 1;78(15):4386-4395. doi: 10.1158/0008-5472.CAN-18-0814. Epub 2018 May 29.