Przewaquinone A regulates cell cycle and autophagy through the SrC/STAT3 signaling pathway to inhibit colorectal cancer progression.

Przewaquinone A (PrA), a natural active substance extracted from Salvia przewalskii Maxim, has been shown to have antitumor activity and can act as a STAT3 inhibitor to modulate the Src/STAT3 pathway. However, its role in colorectal cancer (CRC), along with its related mechanisms, has not yet been clarified. This study aims to explore whether PrA inhibits the malignant advancement of CRC via the Src/STAT3 pathway, and to provide new drug candidates and molecular targets for CRC clinical treatment. The toxic effects of PrA on normal cells NCM460 and on CRC cells (SW480, HCT116, etc.) were explored by Cell Counting Kit-8 (CCK-8) assay. The malignant phenotype, cell cycle distribution, and apoptosis rate were analyzed with the help of Transwell assay, clone formation assay, and flow cytometry. The impact of PrA on autophagic flow in CRC cells was analyzed by GFP-RFP-LC3 dual fluorescent labeling. Plasmid transfection was used to modulate Src expression to verify whether PrA acts through the Src/STAT3 pathway. Finally, subcutaneous graft tumor and carcinoma in situ models were constructed in nude mice, and cell proliferation and apoptosis were detected by pathological staining, and the expression of indicator proteins and Src/STAT3 pathway-related proteins were evaluated via western blot. PrA at 1 ~ 4 µM did not markedly impact NCM460 cell viability, but it dose-dependently reduced CRC cell viability. PrA also diminished the migration and invasion ability of CRC cells, induced G0/G1 phase cycle block, apoptosis, and autophagy, and inhibited Src/STAT3 pathway activation and nuclear translocation of STAT3. Furthermore, overexpression of Src reversed the regulatory impacts of PrA described above. In vivo, PrA treatment hindered tumor growth in nude mice, inhibited cell proliferation, and promoted apoptosis, whereas Src overexpression attenuated the tumor-suppressive effects of PrA. By suppressing the Src/STAT3 pathway, PrA regulates cell cycle and autophagy in CRC cells, thereby inhibiting CRC malignant progression.