To modify YC-1, an inhibitor of hypoxia-inducible factor-1α (HIF-1α) into nanoparticles and explore its effect on reversing chemoresistance of colorectal cancer cells.

Nano-inhibitor mPEG₃₅₀-YC-1 (MYC-1) was prepared by the carboxyl condensation reaction of the active functional group hydroxyl (-OH) in the YC-1 molecule with methoxy polyethylene glycol carboxylic acid, and was verified by ¹H nuclear magnetic resonance (¹H-NMR). Its morphology was analyzed by transmission electron microscope (TEM), and its particle size distribution was analyzed by dynamic light scattering (DLS). By interacting FITC-labeled MYC-1 (FYC-1) with HCT15 cells, the uptake ability of FYC-1 by the cells was observed using laser confocal microscopy. The cytotoxicity of MYC-1 was measured with CCK-8 assay. The sensitization effect of MYC-1 on the chemotherapy drug 5-Fu was detected through toxicity tests of resistant HCT15 cells (resistant HCT15, R-HCT15) and live/dead cell staining. The mechanism of MYC-1 reversing drug resistance was determined with immunofluorescence staining of HIF-1α and western blotting. Finally, a subcutaneous transplanted tumor model of R-HCT15 cells was constructed. The tumor bearing mice were randomly divided into PBS, 5-Fu, MYC-1, and MYF groups, with 3 mice in each group. The tumor volume and weight were observed after treatment in each group to evaluate the ability of MYC-1 to reverse 5-Fu resistance in colorectal cancer.

The nano-inhibitor MYC-1 was successfully prepared. TEM and DLS showed that MYC-1 could self-assemble into nanoparticles with a diameter of approximately 19.96±2.97 nm in aqueous solution. FYC-1 was also successfully prepared. When FYC-1 was interacted with HCT15 cells, FYC-1 could be better taken up by the cells, indicating that the amphiphilic MYC-1 could be better endocytosed into the cells to exert its function. When MYC-1 and 5-Fu acted in combination in colon cancer R-HCT15 cells, the resistance index (RI) was decreased from 7.99 to 1.55, and the relative reversal rate (RRR) of RI was 80.6%. Live (green)/dead (red) cell staining revealed that MYC-1 increased the toxicity of 5-Fu to R-HCT15 cells. Immunofluorescence staining (P<0.01) and Western blotting indicated that MYC-1 effectively inhibited the intracellular expression of HIF-1α. The combined action of MYC-1 and 5-Fu on mice with R-HCT15 subcutaneous transplanted tumors had the best therapeutic effect when compared with PBS (P<0.001), 5-Fu (P<0.01), and MYC-1 (P<0.01). Immunofluorescence staining of HIF-1α in tumor tissues displayed that the expression of HIF-1α was decreased in the MYC-1 and MYF groups. HE staining showed that there was no obvious damage to the important organs in each treatment group.

Nano-inhibitor MYC-1 can reverse the drug resistance of colorectal cancer to 5-Fu chemotherapy by reducing the expression of HIF-1α protein in colorectal cancer cells, thereby effectively improving the therapeutic effect of 5-Fu.