Photodynamic therapy augments oxaliplatin-induced immunogenic cell death in colorectal cancer.

Colorectal cancer is one of the most frequently diagnosed cancers. Immunotherapy has been proven to be a potential treatment option for colorectal cancer. Colorectal cancer maintains immune escape by expressing low immunogenicity and following the tolerogenic cell death pathway. There is also emerging evidence that oxaliplatin and photodynamic therapy (PDT) can promote anti-tumor immunity. However, the effect of PDT combined with oxaliplatin on colorectal cancer remains elusive. Here, we analyzed the viability of HCT116 and DLD-1 cell lines after treatment with the combination of PDT and oxaliplatin. We found that the viability decreased significantly after the combination treatment. Meanwhile, we also detected that sinoporphyrin sodium (DVDMS)-derived PDT could amplify oxaliplatin-induced immunogenic cell death (ICD) in different colorectal cancer cell lines. More importantly, the combination of DVDMS-derived PDT and oxaliplatin presented strong immunogenic potential in immunocompetent BALB/c mice in the vaccination assay. Taken together, our data demonstrated that the combination of DVDMS-derived PDT and oxaliplatin is a potential novel therapy for colorectal cancer.