Pulsatilla Decoction Combined with 5-Fluorouracil Triggers Immunogenic Cell Death in the Colorectal Cancer Cells.

Background: Our research is designed to explore the role of co-treatment of 5-FU and Pulsatilla decoction (PD) in the modulation of Immunogenic cell death (ICD) of Colorectal cancer (CRC). Materials and Methods: Cell viability was evaluated by 3-(4,5)-dimethylthiahiazo (-z-y1)-3,5-di-phenytetrazoliumromide assays. Cell apoptosis was assessed using flow cytometry. The phosphorylation of STAT3 and expression of Mcl-1 and Bcl-xl were measured by western blot assays. The levels of ATP and HMGB1 in the supernatants of the culture medium were analyzed by ATP assays and the HMGB1 enzyme linked immunosorbent assay kit. The cell surface levels of CRT were measured by immunofluorescence assays. The tumor growth was analyzed in mice. Results: PD increased 5-FU-induced ICD in CRC cells, as demonstrated by the extracellular levels of adenosine triphosphate (ATP) and high-mobility group box 1 (HMGB1), and the surface levels of calreticulin (CRT). Our mechanism study showed that PD promoted 5-FU-induced ICD by inactivating signal transducer and activator of transcription 3 (STAT3). Furthermore, the co-treatment of 5-FU and PD further promoted 5-FU-induced CRT expression and T cell infiltration in vivo. Tumorigenicity analysis revealed that 5-FU combined with PD notably reduced tumor growth. Conclusion: This study indicated that PD enhances 5-FU-induced ICD and anti-tumor effect in CRC by inactivating STAT3. The combined application of 5-FU with PD may improve the anti-tumor activity of 5-FU in CRC.