Vol. 296, Issue 3, 712-715, March 2001

Both Extraneuronal Monoamine Transporter and O⁶-Methylguanine-DNA Methyltransferase Expression Influence the Antitumor Efficacy of 2-Chloroethyl-3-sarcosinamide- 1-nitrosourea in Human Tumor Xenografts

Zhong-Ping Chen, Zhi-Min Wang, Christopher A. Carter, Michael C. Alley, Gérard Mohr and Lawrence C. Panasci

Lady Davis Institute for Medical Research, Sir Mortimer B. Davis-Jewish General Hospital, McGill University, Montreal, Quebec, Canada (Z.P.C., Z.M.W., G.M., L.C.P.); Cancer Center, Sun Yat-sen University of Medical Sciences, Guangzhou, China (Z.P.C.); Bayer Corp, West Haven, Connecticut (C.A.C.); and Developmental Therapeutics Program, Division of Cancer Treatment, Diagnosis, and Centers, National Cancer Institute, Frederick Cancer Research and Development Center, Frederick, Maryland (M.C.A.)

We previously have found that 2-chloroethyl-3-sarcosinamide-1-nitrosourea (SarCNU) is a selective cytotoxin that enters cells via the extraneuronal transporter for monoamine transmitters (EMT). Both in vitro and in vivo studies demonstrated that SarCNU was more effective than BCNU against human gliomas. To clarify whether EMT expression correlates with antitumor efficacy of SarCNU, we determined human EMT (EMTh) and O⁶-methylguanine-DNA methyltransferase (MGMT) expression in nine human xenograft models using semiquantitative reverse-transcription polymerase chain reaction. These results were compared with the antitumor effects of SarCNU and the standard chloroethylnitrosourea antitumor agent 1,3-bis(2-chloroethyl)-1-nitrosourea (BCNU). There was no significant correlation between EMTh expression and antitumor efficacy of SarCNU or BCNU. Also, there was no significant correlation between MGMT expression and SarCNU efficacy. However, a significant correlation was found between MGMT expression and BCNU antitumor efficacy. Interestingly, multiple regression analysis demonstrated a significant correlation between SarCNU efficacy and EMTh plus MGMT expression, whereas there was no correlation between BCNU efficacy and MGMT plus EMTh expression. Thus, the absence of a linear correlation between SarCNU efficacy and EMTh expression appears to be due, at least in part, to the presence of DNA repair, specifically, MGMT, in these xenograft models. These studies suggest that MGMT expression alone correlates with BCNU activity, whereas both EMTh and MGMT expression are important determinants of SarCNU activity against human tumor xenograft models. SarCNU is in clinical trials and these results may have important clinical implications.