Curcumin Suppresses the Progression of Colorectal Cancer by Improving Immunogenic Cell Death Caused by Irinotecan

<b><i>Background:</i></b> Irinotecan (IRI) is a common chemotherapeutic drug for colorectal cancer; however, the mechanism underlying its immunomodulatory effect remains unclear. Curcumin (CUR), an adjuvant drug with anti-inflammatory and antitumor effects, has been studied extensively, although its synergistic antitumor effect remains unclear. <b><i>Methods:</i></b> The effects of CUR and IRI on oxidative stress and their antitumor effects were detected by flow cytometry. Endoplasmic reticulum stress-related proteins including CHOP and BiP, and immunogenic cell death (ICD) proteins including calreticulin (CALR) and high mobility group box 1 (HMGB1), were detected by Western blotting. IFN-γ and TNF-α levels in the serum of mice were detected by ELISA. <b><i>Results:</i></b> IRI in combination with CUR had synergistic antitumor effects in CT-26 colon carcinoma cells. Combination treatment with IRI and CUR was more effective than IRI or CUR alone. IRI and CUR combination treatment significantly upregulated ICD-related proteins including CALR and HMGB1 and had a greater antitumor effect than IRI or CUR single treatment in vivo. CUR may synergistically improve the antitumor effect of IRI by promoting the ICD effect. <b><i>Conclusion:</i></b> Combination therapy with IRI and CUR may be an option for first-line chemotherapy in some patients with advanced colorectal cancer.