Chaetoceros socialis extract triggers apoptosis in oral and colorectal cancer cells through PI3K/AKT/mTOR pathway modulation

Conventional chemotherapy remains a cornerstone in cancer treatment; however, its clinical efficacy is limited by severe side effects on normal tissues. This has encouraged interest in natural compounds with selective anticancer properties and reduced toxicity. Chaetoceros socialis (C. socialis), a marine diatom microalga, exhibits antioxidant and potential antitumor activities. Given the global burden of colorectal cancer and complications associated with oral cancer treatments such as stomatitis and jaw osteonecrosis, there is a need for safer alternatives. This study aimed to investigate the anticancer potential of ethanolic extract of C. socialis against colorectal (HT-29) and oral (KB) cancer cells, focusing on cytotoxicity, apoptosis, and molecular mechanisms. The ethanolic extract of C. socialis was prepared by maceration and solvent evaporation. Anticancer effects were assessed on HT-29 and KB cells using the MTT assay for viability, Annexin V-FITC/PI staining and flow cytometry for apoptosis, and (Quantitative) qPCR for expression of apoptosis- and signaling-related genes. C. socialis extract reduced cell viability in a dose-dependent manner. After 24 h, viability was 44.06% in KB (20 µg/mL) and 44.48% in HT-29 (12.5 µg/mL), while normal HUVEC cells maintained high viability (89.44% at 20 µg/mL). Flow cytometry showed strong apoptosis induction (48.68% in KB, 21.28% in HT-29 at IC₅₀). qPCR revealed upregulation of Caspase-3, Caspase-8, Caspase-9, Bax, PTEN, P21, P53 , and FAS and downregulation of Bcl-2, AKT , and mTOR. C. socialis extract exerts selective anticancer effects through apoptosis induction and modulation of the PI3K/AKT/mTOR pathway, supporting its potential as a natural therapeutic candidate. Schematic overview of the experimental workflow illustrating the selective anticancer effects of Chaetoceros socialis ethanolic extract on colorectal (HT-29) and oral squamous carcinoma (KB) cells. The diagram highlights the extraction process, treatment of cancer cell lines, and assessment of cytotoxicity and apoptosis. Mechanistically, the extract is proposed to induce apoptosis through modulation of key regulators, including upregulation of pro-apoptotic genes ( Caspase-3, Caspase-8, Caspase-9, Bax, P53, PTEN, P21, FAS ) and downregulation of anti-apoptotic proteins (Bcl-2) as well as PI3K/AKT/mTOR signaling components ( AKT, mTOR ). Normal human umbilical vein endothelial cells (HUVECs) were included to evaluate the extract’s safety profile, demonstrating minimal cytotoxicity. This graphical summary integrates both the experimental workflow and the proposed molecular mechanisms underlying the selective anticancer activity of C. socialis extract.