Synergistic Effects of 125I Seed Implantation Brachytherapy and Gemcitabine in Pancreatic Tumors

Background: Monotherapy consisting of radiotherapy or chemotherapy has limited efficacy in pancreatic tumors. This study aims to investigate whether the combination of I-125 brachytherapy and gemcitabine (GEM) chemotherapy has a synergistic effect on pancreatic cancer (PC). Methods: In vitro, PANC-1 cells in the exponential phase were treated with I-125 radioactive seeds (6 Gy) and GEM (30 nM). Cell proliferation, apoptosis, and mitochondrial membrane potential were measured using the Cell Counting Kit-8 (CCK-8) assay, Terminal deoxynucleotidyl transferase dUTP nick end labeling (TUNEL) staining, and flow cytometry, respectively. In vivo, we examined the inhibitory effect of three different treatment regimens on tumor growth in mice when combined with I-125 brachytherapy and GEM. Next, we investigated the effects of the optimal scheme among the three on the tumor microenvironment, tumor tissue morphology, tumor cell apoptosis, systemic inflammatory response, and levels of apoptosis-related proteins in the tumor. Changes in the tumor microenvironment and levels of apoptosis-related proteins were measured by Western blot. The extent of damage to tumor tissue morphology was assessed by Hematoxylin and Eosin (HE) staining. Tumor cell apoptosis was measured by TUNEL staining. Changes in inflammation-related factors were determined by Enzyme-Linked Immunosorbent Assay (ELISA). Results: The results of in vitro cell experiments demonstrated that the combination of I-125 radioactive seeds (6 Gy) and GEM (30 nM) had a stronger inhibitory effect on PANC-1 cells than either alone (p < 0.05). In vivo, data showed that the GEM (after 3 d) + I-125 treatment group had the strongest tumor inhibition effect on PC (p < 0.05). Western blot analysis showed that the combined treatment of I-125 brachytherapy and GEM caused changes in the expression of collagen and connexin in the tumor microenvironment, promoted tumor cell apoptosis, upregulated the expression of pro-apoptotic proteins, and helped to restore pancreatic function (p < 0.01). Conclusion: Our research results suggest that the strategy of I-125 seed implantation surgery in mice after 3 days of GEM treatment has a more pronounced synergistic effect on the treatment of PC.