Sitagliptin Potentiates the Anticancer Activity of Doxorubicin Through ROS-Driven Apoptosis and MMP/TIMP Regulation in HeLa Cells

Background/Objectives: Cervical cancer remains a major global health challenge, and treatment resistance limits the long-term success of chemotherapy. Drug repurposing strategies offer new opportunities for improving therapeutic outcomes by combining existing agents with established chemotherapeutics. Sitagliptin, a DPP-4 inhibitor commonly used in type 2 diabetes, has recently gained attention for its potential anticancer effects. This study aimed to investigate the cytotoxic, apoptotic, and anti-metastatic effects of sitagliptin and doxorubicin, individually and in combination, on human cervical cancer cells (HeLa), and to determine whether their combined use exerts a synergistic anticancer effect. Methods: HeLa cells were treated for 48 h with increasing concentrations of sitagliptin, doxorubicin, or their combination. Cell viability was assessed using the MTT assay. Apoptosis was evaluated by Annexin V-FITC/PI staining and caspase-8/9 activity assays. Synergy was quantified using the Chou–Talalay method, and Combination Index (CI) values were used to determine synergistic interactions. Intracellular ROS levels were measured using the DCFDA assay. Migration and invasion capacities were analyzed using wound healing and Transwell assays. MMP-1, MMP-2, TIMP-1, and TIMP-2 levels were quantified via ELISA with normalization to viable cell counts. Gene expression levels of PI3K/Akt and MAPK/ERK pathway components were measured by qRT-PCR. Bioinformatic analyses (STRING, GeneMANIA, GO, KEGG) were performed to identify common molecular targets and enriched pathways affected by both agents. Results: The combination of sitagliptin and doxorubicin significantly reduced cell viability and demonstrated a synergistic interaction (CI < 1). Combined treatment induced a marked increase in ROS production and significantly elevated apoptosis rates compared to monotherapies. Caspase-8 and caspase-9 activities were also higher in the combination group. Migration and invasion assays revealed substantial suppression of cell motility and invasive capacity. After normalization to viable cell numbers, MMP and TIMP reductions remained significant, confirming true biological inhibition rather than cell-death–related artifacts. qRT-PCR analyses showed downregulation of Akt and ERK expression, indicating suppression of key survival and proliferation pathways. Bioinformatic analyses supported these findings by highlighting enrichment in apoptotic, oxidative stress, and metastasis-related pathways. Conclusions: Sitagliptin enhances the anticancer efficacy of doxorubicin by amplifying ROS-mediated apoptosis, inhibiting migration and invasion, and modulating PI3K/Akt and MAPK/ERK signaling in cervical cancer cells. The combination exhibits a clear synergistic effect and demonstrates strong potential as a supportive therapeutic strategy. These findings warrant further in vivo and clinical-level investigations to evaluate the translational applicability of sitagliptin in cervical cancer therapy.