Effects of Pubertal Exposure to Butyl Benzyl Phthalate, Perfluorooctanoic Acid, and Zeranol on Mammary Gland Development and Tumorigenesis in Rats.

Endocrine-disrupting chemicals (EDCs)-including butyl benzyl phthalate (BBP), perfluorooctanoic acid (PFOA), and zeranol (α-ZAL, referred to as ZAL hereafter)-can interfere with the endocrine system and produce adverse effects. It remains unclear whether pubertal exposure to low doses of BBP, PFOA, and ZAL has an impact on breast development and tumorigenesis. We exposed female Sprague Dawley rats to BBP, PFOA, or ZAL through gavage for 21 days, starting on day 21, and analyzed their endocrine organs, serum hormones, mammary glands, and transcriptomic profiles of the mammary glands at days 50 and 100. We also conducted a tumorigenesis study for rats treated with PFOA and ZAL using a 7,12-dimethylbenz[a]anthracene (DMBA) model. Our results demonstrated that pubertal exposure to BBP, PFOA, and ZAL affected endocrine organs and serum hormones, and induced phenotypic and transcriptomic changes. The exposure to PFOA + ZAL induced the most phenotypic and transcriptomic changes in the mammary gland. PFOA + ZAL downregulated the expression of genes related to development at day 50, whereas it upregulated genes associated with tumorigenesis at day 100. PFOA + ZAL exposure also decreased rat mammary tumor latency, reduced the overall survival of rats after DMBA challenge, and affected the histopathology of mammary tumors. Therefore, our study suggests that exposure to low doses of EDCs during the pubertal period could induce changes in the endocrine system and mammary gland development in rats. The inhibition of mammary gland development by PFOA + ZAL might increase the risk of developing mammary tumors through activation of signaling pathways associated with tumorigenesis.

Combined Inhibition of AKT and KIT Restores Expression of Programmed Cell Death 4 (PDCD4) in Gastrointestinal Stromal Tumor.

The majority of gastrointestinal stromal tumor (GIST) patients develop resistance to the first-line KIT inhibitor, imatinib mesylate (IM), through acquisition of secondary mutations in KIT or bypass signaling pathway activation. In addition to KIT, AKT is a relevant target for inhibition, since the PI3K/AKT pathway is crucial for IM-resistant GIST survival. We evaluated the activity of a novel pan-AKT inhibitor, MK-4440 (formerly ARQ 751), as monotherapy and in combination with IM in GIST cell lines and preclinical models with varying IM sensitivities. Dual inhibition of KIT and AKT demonstrated synergistic effects in IM-sensitive and -resistant GIST cell lines. Proteomic analyses revealed upregulation of the tumor suppressor, PDCD4, in combination treated cells. Enhanced PDCD4 expression correlated to increased cell death. In vivo studies revealed superior efficacy of MK-4440/IM combination in an IM-sensitive preclinical model of GIST compared with either single agent. The combination demonstrated limited efficacy in two IM-resistant models, including a GIST patient-derived xenograft model possessing an exon 9 KIT mutation. These studies provide strong rationale for further use of AKT inhibition in combination with IM in primary GIST; however, alternative agents will need to be tested in combination with AKT inhibition in the resistant setting.