Abstract
Hormone receptor-positive Breast Cancer (BC) driven by PI3K/Akt/mTOR signaling remains a major therapeutic challenge, particularly in settings where conventional chemotherapy causes severe systemic and reproductive toxicity. This study evaluated the antitumor and chemopreventive efficacy of Pleurotus ostreatus ethanolic extract (PoEE), compared with vincristine, a standard anticancer drug, in a 7,12-dimethylbenz(α)anthracene (DMBA) and N-methyl Urea (NMU) BC model using female Sprague-Dawley rats (n = 64). Animals were divided into eight groups receiving olive oil (control), DMBA-NMU (80 mg/kg-10 mg/kg), PoEE (600 mg/kg), vincristine (0.0005 mg/kg), and various combinations. After 25 weeks, mammary tissues were analyzed for antioxidant status, hormonal profiles, histopathology, and PI3K/Akt/mTOR pathway modulation using immunohistochemistry. ImageJ (NIH) and GraphPad Prism 8.0 were employed for image quantification and statistical analysis using one-way analysis of variance (ANOVA), respectively. DMBA-NMU administration induced aggressive hormone receptor-positive BC, elevating ER (∼26-fold) and PR (∼12-fold), with strong upregulation of PI3K (+21-fold), Akt (+9-fold), mTOR (+7-fold), Ras (+34-fold), MAPK (+45-fold), MDM2 (+13-fold), and PDK1 (+39-fold). Concurrently, tumor suppressors PTEN, GSK3β, and FOXO were significantly reduced by 81%, 95%, and 96%, respectively. This dysregulation was accompanied by decreased antioxidant enzyme activity (SOD -26.7%, CAT -27.2%) and hormonal imbalance (estradiol -23.9%, progesterone -11.3%). PoEE treatment markedly reversed these oncogenic alterations. Pre-PoEE treatment suppressed PI3K (-82%), Akt (-29%), mTOR (-17%), Ras (-93%), and MAPK (-83%), while restoring PTEN (+19-fold), GSK3β (+29-fold), and FOXO (+3-fold). PoEE enhanced estradiol (+60.9%) and progesterone (+78.9%) levels, increased SOD (+5%) and CAT (+63.6%) activities, and restored GST to 76% of control values. Post-treatment PoEE further reduced PI3K (-69%), Akt (-58%), and mTOR (-73%), while increasing PTEN (+10-fold), GSK3β (+7-fold), and FOXO (+27-fold), reflecting robust therapeutic potential. Vincristine moderately suppressed PI3K (-56%) and PDK1 (-88%) but elevated Akt (+19-fold) and MDM2 (+19-fold). PoEE and vincristine combination therapy showed selective synergy, suppressing ER (-91%), PR (-94%), Akt (-92%), and MDM2 (-94%), while increasing mTOR (+62%) and Ras (+98%). Conclusively, PoEE exerted potent anticancer effects through multi-target modulation of the PI3K/Akt/mTOR signaling axis. These underscore PoEE's promise as a low-toxicity natural therapeutic or adjuvant for hormone receptor-positive and pathway-driven breast cancers.