ONC206, an imipridone derivative, demonstrates anti-colorectal cancer activity against stem/progenitor cells in 3D cell cultures and in patient-derived organoids.

Background: Colorectal cancer (CRC) remains one of the most frequently diagnosed and life-threatening malignancies worldwide. CRC's high recurrence rates and drug resistance have been correlated with a subpopulation of dormant slowly dividing cells termed CRC stem cells (CCSCs). Consequently, there is a pressing need to identify novel therapeutics that can effectively and specifically target CCSCs. Imipridones are promising structurally related anticancer molecules that showed efficacy in several solid and hematological preclinical models and phase I/II/III clinical trials. This study mainly aimed to assess the potential anticancer effects of ONC206, an imipridone derivative, on CRC three-dimensional in vitro culture systems using HCT116 and HT29 cells. Importantly, the study aimed at using CRC patient-derived organoids (PDOs) to test the potential therapeutic effect of ONC206.

Methods: Two-dimensional cell proliferation, viability, migration, and invasion assays were used to assess the effects of ONC206 on two colorectal cancer cell lines, HCT116 and HT29, in vitro. Immunofluorescence imaging, flow cytometry, and western blot analysis were also performed to investigate the mechanism of action of this drug. Sphere formation assay and CRC PDOs were employed to evaluate the effect of ONC206 on CRC cells in a 3D setting and specifically its potency in targeting the CRC stem/progenitor subpopulation of cells.

Results: Our results showed that ONC206 was more potent than its parental molecule ONC201 in inhibiting the proliferation and viability of HCT116 and HT29 cells. Moreover, ONC206 significantly reduced the migration and invasion indices of CRC cells. These effects were accompanied by an increase in reactive oxygen species (ROS) production, sub-G1 phase accumulation, and apoptosis in HCT116 and HT29 cells. Furthermore, ONC206 significantly inhibited the 3D colonospheres growth and self-renewal ability of CCSCs more potently than ONC201, which was associated with a decrease in the expression of CSC-related markers. Lastly, ONC206 significantly reduced the growth of organoids derived from CRC patients.

Conclusion: Collectively, our findings demonstrate that ONC206 is an effective anticancer molecule capable of targeting CCSCs, which may represent a novel therapeutic strategy that can overcome CRC resistance and recurrence.