Oxaliplatin is a first-line chemotherapeutic agent for colorectal carcinoma (CRC). However, its therapeutic efficacy is often curtailed due to severe side effects and development of drug resistance. Norcantharidin (NCTD) has shown antitumor activity in preclinical studies of colorectal cancer and other malignancies. It also has been utilized as a chemosensitizer in studies of various cancer cell lines in vitro. However, its clinical efficacy in patients with CRC, particularly in combination with oxaliplatin, has not been established.

Both of oxaliplatin and NCTD could enhance the reactive oxygen species (ROS) levels in tumor cells. Yet, it remains unclear whether NCTD can augment the sensitivity of CRC cells to oxaliplatin via ROS generation. Given that macrophage polarization is closely associated with tumor cell death and tumor progression, the effects of NCTD and oxaliplatin-induced cell death on macrophage polarization was studied as well.

This study used CCK8 assays to investigate the synergistic effects of oxaliplatin and NCTD in CRC cells. ROS and immunofluorescence staining was applied to detect ROS levels and DNA damage levels in CRC cells when treated by oxaliplatin and NCTD. Western blotting and ELISA were applied to determine the levels of proteins in CRC cells. The conditioned media were collected from CRC cell cultures and were used to treat the macrophage cell line RAW264.7 to explore its polarization. Finally, a subcutaneous tumor model was applied to study the effects of oxaliplatin and NCTD on CRC cells in vivo.

The in vitro experiments demonstrated the synergistic lethal effects of NCTD and oxaliplatin on CRC cells. Mechanistic investigations revealed that the combination of NCTD and oxaliplatin enhanced reactive oxygen species (ROS) levels, which in turn triggered CRC cell death resembling pyroptosis, which was associated with DNA damage/caspase-3/GSDME. More importantly, the pyroptosis-like cell death (PLCD) in CRC cells induced by the combination of NCTD and oxaliplatin conspicuously shifted M1 polarization of macrophages, which might contribute to the hindrance of tumor progression. The results of animal experiments corroborated those of experiments in vitro.

Our data indicate synergistic effects of NCTD and oxaliplatin in CRC models, warranting additional research to characterize the underlying mechanisms and evaluate its translational potential.