Low-dose photodynamic therapy-induced increase in the metastatic potential of pancreatic tumor cells and its blockade by simvastatin

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Pancreatic tumor are a deadly malignancy with high aggressiveness, and photodynamic therapy (PDT) is a prospective remedy. Nevertheless, the cells in the peripheral tissues of large tumors are often subjected to low-dose illumination and tend to survive after sublethal PDT exposure. Thus, it is of critical importance to determine the metastatic influence of PDT on pancreatic neoplasms. (17R, 18R)-2-(1-Hexyloxyethyl)-2-devinyl chlorine E6 trisodium salt (YLG-1) is a novel chlorine derivative photosensitizer, and we previously demonstrated potent growth inhibition of pancreatic neoplasms by YLG-1-mediated PDT (YLG-1-PDT). In this study, we assessed the metastatic effect of low-dose PDT with YLG-1 on pancreatic tumors and its combination with simvastatin. We found that sublethal YLG-1-PDT promoted MMP-2/9 expression in residual pancreatic tumor cells as well as tumor cell motility/invasion and liver metastasis. Since simvastatin was reported to improve the survival of patients with pancreatic tumors at an early stage and suppress the metastasis of most cancers, we utilized it during YLG-1-PDT and discovered alleviated migration/invasion, metastasis and MMP-2/9 expression. Collectively, our study results raise the concern that PDT could also be a Janus-like treatment owing to its prometastatic potential provoked by a low dosage. Concomitant use of simvastatin during PDT might be an effective method to attenuate such adverse reactions.