Background: Breast cancer is the most common malignancy in women worldwide. P2X7 is a transmembrane receptor expressed in breast cancer and activated by the ATP tumor microenvironment, driving cell proliferation, angiogenesis, and metastasis via different signaling pathways. The role of the P2X7 receptor, hypoxia, and autophagy in regulating tumor progression is controversial. The multikinase inhibitor regorafenib prevents the activation of numerous kinases involved in angiogenesis, proliferation, and metastasis. The present study aimed to evaluate the modulatory effect of regorafenib on the hypoxia/angiogenesis/P2X7R/autophagy axis on the MCF7 breast cancer cell line and its impact on different signaling pathways involved in breast cancer pathogenesis. Methods: The levels of VEGF, VEGFR, PI3K, NF-κB, HIF-1α, and LC3-II were analyzed using ELISA, and caspase-3 activity was also assessed colorimetrically. Phosphorylated (p)-p38 MAPK and purinergic ligand-gated ion channel 7 (P2X7) receptor protein expression levels were analyzed via Western blotting. Reverse transcription-quantitative PCR was used to determine the mRNA expression levels of Beclin 1 (BECN1), LC3-II, and sequestosome 1 (p62). Results: Regorafenib reduced MCF7 cell viability in a dose-dependent manner. Furthermore, regorafenib significantly reduced levels of PI3K, NF-κB, VEGF, VEGFR, P2X7 receptor, and p-p38 MAPK protein expression, and markedly reduced p62 mRNA expression levels. However, regorafenib significantly increased caspase-3 activity, as well as BECN1 and LC3-II mRNA expression levels. Conclusions: Regorafenib was demonstrated to possibly exhibit antitumor activity on the breast cancer cell line via modulation of the P2X7/HIF-1α/VEGF, P2X7/P38, P2X7/ERK/NF-κB, and P2X7/beclin 1 pathways.

Background: Doxorubicin-induced cardiotoxicity (DIC) is a major limitation of anthracycline chemotherapy and is characterized by oxidative stress, apoptosis, and myocardial remodeling. Dysregulation of AMP-activated protein kinase (AMPK) and its downstream effector sirtuin-1 (SIRT1) has been implicated in the molecular pathogenesis of DIC. Vardenafil (Var), a selective phosphodiesterase-5 inhibitor, has shown cardiovascular benefits; however, its impact on AMPK/SIRT1 signaling during DIC remains unclear. Methods: DIC was induced in rats by cumulative doxorubicin administration. Cardiac function, serum injury biomarkers, oxidative stress indices, histopathological alterations, apoptosis, fibrosis, and molecular markers associated with the AMPK/SIRT1 pathway were evaluated. In addition, molecular docking was performed to assess the potential interaction of Var with AMPK. Results: Var significantly improved cardiac function and reduced serum levels of lactate dehydrogenase, creatine kinase, and blood urea nitrogen. Treatment attenuated myocardial oxidative stress, restored glutathione content, reduced lipid peroxidation, and alleviated histopathological damage. Furthermore, Var suppressed caspase-3 and TGF-β1 expression while enhancing HO-1 levels. Var treatment was associated with restoration of cardiac phosphorylated AMPK (p-AMPK) expression and increased SIRT1, Nrf2, and PPARγ levels in doxorubicin-treated rats, consistent with modulation of an AMPK/SIRT1-associated cytoprotective network. Molecular docking demonstrated favorable interactions between Var and AMPK, providing supportive in silico evidence for the observed molecular findings. Conclusions: These findings demonstrate that Var attenuates doxorubicin-induced cardiotoxicity, and its cardioprotective effects are associated with restoration of the p-AMPK/SIRT1/Nrf2/PPARγ signaling pathway, together with reductions in oxidative stress, apoptosis, and fibrosis. Collectively, these findings suggest that Var attenuates early Dox-induced cardiac injury, potentially through modulation of the AMPK/SIRT1 signaling pathway, warranting further validation in long-term and dose–response studies.