Abstract 837: Reproducibility of efficacy results for chemopreventive agents in the methylnitrosourea-induced rat mammary cancer model

Abstract

Abstract Perhaps the greatest question in biological science is: Can results be reproduced? This problem is of particular concern for a group whose primary mission is to screen for potentially effective agents and rank results by activity. The reproducibility of testing specific agents for chemopreventive activity, testing the same agent in various protocols, and testing multiple agents of a given mechanistic class in the MNU-induced model of ER+ breast cancer in Sprague-Dawley rats is presented. The model employs female virgin Sprague-Dawley rats on a standard 4% Teklad diet which develop ER+ mammary cancers (adenocarcinomas) following MNU injection at 50 days of age (DOA). Preventive agents were given by gavage or diet starting at 55 DOA, and animals monitored for tumor development until approximately 170 DOA. Seven agents which we had previously studied and which were strongly positive [tamoxifen, vorozole (an aromatase inhibitor), Targretin, gefitinib] or strongly negative (naproxen, Lipitor, metformin) were examined in the assays presented. These study results confirmed our previous data. We next tested these same agents in animals given a Western diet (high fat, low calcium) and again obtained the same results. We had thought that the altered physiology and potentially altered pharmacokinetics of rats on a Western diet might alter the observed chemopreventive efficacy. These studies show that the direct repetition of clearly positive and negative agents can be achieved and, in fact, repeated with a significant variation in diet. Importantly, in terms of reproducibility, we find that multiple agents of the same mechanistic class give similar results. Thus, various SERMs (tamoxifen, toremifene, Arzoxifene), RXR agonists (targretin, UAB-30, 4Me-UAB-30), EGFR inhibitors (gefitinib, Erlotinib, lapatinib) are all highly positive (70-95% reduction of cancer multiplicity). In contrast, the negative classes COX inhibitors (naproxen, sulindac, aspirin) or statins (atorvastatin or simvastatin) have been consistently negative (<20% reduction). Therefore, reproducibility of efficacy results appears to be quite solid in our chemoprevention agent development program for rat mammary cancer testing, and we can, with significant certainty, trust our results. Citation Format: Vernon E. Steele, Ronald A. Lubet, Clinton J. Grubbs. Reproducibility of efficacy results for chemopreventive agents in the methylnitrosourea-induced rat mammary cancer model. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 837.