Prostate cancer remains one of the most prevalent cancers in aging men. Active surveillance subpopulation of patients with prostate cancer includes men with varying cancer risk categories of precancerous disease due to prostatic intraepithelial neoplasia (PIN) heterogeneity. Identifying molecular alterations associated with PIN can provide preventable measures through finding novel pharmacologic targets for cancer interception. Targeted nutritional interception may prove to be the most appropriate chemoprevention for intermediate- and high-risk active surveillance patients. Here, we have generated two prostate-specific transgenic mouse models, one overexpressing MTA1 (R26MTA1) and the other overexpressing MTA1 on the background of Pten heterozygosity (R26MTA1; Pten+/f), in which we examined the potential chemopreventive efficacy of dietary pterostilbene. We show that MTA1 promotes neoplastic transformation of prostate epithelial cells by activating cell proliferation and survival, leading to PIN development. Moreover, MTA1 cooperates with PTEN deficiency to accelerate PIN development by increasing cell proliferation and MTA1-associated signaling. Further, we show that mice fed with a pterostilbene-supplemented diet exhibited more favorable histopathology with decreased severity and number of PIN foci accompanied by reduced proliferation, angiogenesis, and inflammation concomitant to reduction in MTA1 and MTA1-associated CyclinD1, Notch2, and oncogenic miR-34a and miR-22 levels. Prevention Relevance: Developing novel interceptive strategies for prostate cancer chemoprevention is a paramount goal in clinical oncology. We offer preclinical evidence for the potential of pterostilbene as a promising natural agent for MTA1-targeted interceptive strategy in future cancer prevention trials towards protecting select patients with prostate cancer under active surveillance from developing cancer.

<p>Supplementary Figure 1: A, transgene integration and genotyping scheme of MTA1 transgenic animals. B, genotyping of MTA1 founder 870#2. Supplementary Figure 2: A, average body weight of mice fed different diets during 22 weeks (monitored weekly). B, effect of PTER-Diet on food intake (g). Supplementary Table 1: Nutritional composition of diets. Supplementary Table 2: Primers for genotyping used in this study. Supplementary Table 3: Antibodies for immunoblots and IHC used in this study. Supplementary Table 4: Primers for qRT-PCR used in this study.</p>

Metastasis-associated protein 1 (MTA1) plays role in prostate cancer progression and metastasis. We have previously reported on the MTA1-targeted chemopreventive and therapeutic efficacy of pterostilbene (Pter) in the prostate-specific Pten heterozygous (Pten+/f; Pb-Cre+) and Pten null (Ptenf/f; Pb-Cre+) mice. To investigate the exact role of MTA1 in prostate cancer tumorigenesis and its early stages, we developed appropriate mouse models, namely prostate-specific MTA1-knocked in (MTA1-tg) and MTA1-tg on the background of prostate-specific Pten heterozygosity (MTA+/+, Pten+/f; Pb-Cre+). In the current project, we asked three major questions: 1) whether prostate MTA1 overexpression in the context of Pten loss promotes an earlier onset, greater total incidence and accelerated PIN or tumor growth rate; 2) what MTA1-associated molecules are involved in prostate cancer progression; and 3) whether Pter supplemented diet can provide beneficial effects. Identified from our ChIP-Seq data MTA1-associated molecules included CyclinD1, Notch2, and two neuroendocrine markers, namely CHGA and SYP. Using two prostate cancer cell lines, DU145 and PC3M and their corresponding MTA1 knockdown (shMTA1) clones, we validated the direct link between MTA1 and these markers on mRNA and protein levels. Further, we generated 28 prostate-specific MTA1+/+; Pten+/f; Pb-Cre+ mice and randomized them into two major groups: 1) mice on control diet (Ctrl-Diet) and 2) mice on Pter-Diet. After 5 months of feeding with corresponding diets (AIN-76A phytoestrogen free diets supplemented or not with Pter at 100 mg/kg/diet), mice were sacrificed and prostate tissues were isolated for histological, immunochemical and molecular analysis. Results demonstrated the contribution of MTA1 in more aggressive histological phenotype (Ki67, PCNA, p27, SMA, CK8), increased levels of oncogenic MTA1-guided molecules (CyclinD1, Notch2, CHGA, SYP, AR) and the potential for Pter in prostate cancer chemoprevention. Citation Format: Rutu Hemani, Ninad Inamdar, Avinash Kumar, Virginia Donovan, Anait S. Levenson. Novel prostate cancer mouse models for testing targeted chemopreventive potential of pterostilbene [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 1144.

<p>Supplementary Figure 1: A, transgene integration and genotyping scheme of MTA1 transgenic animals. B, genotyping of MTA1 founder 870#2. Supplementary Figure 2: A, average body weight of mice fed different diets during 22 weeks (monitored weekly). B, effect of PTER-Diet on food intake (g). Supplementary Table 1: Nutritional composition of diets. Supplementary Table 2: Primers for genotyping used in this study. Supplementary Table 3: Antibodies for immunoblots and IHC used in this study. Supplementary Table 4: Primers for qRT-PCR used in this study.</p>