Design, synthesis, and antitumor activity of novel thioheterocyclic nucleoside derivatives by suppressing the c-MYC pathway

Eightly-four novel thioheterocyclic nucleoside derivatives were designed, synthesized, and evaluated for antitumor activity <i>in vitro</i> and <i>in vivo</i>. Most of the compounds inhibited the growth of HCT116 and HeLa cancer cells <i>in vitro</i>, among them <b>33a</b> and <b>36b</b> exhibited potent activity against HCT116 cells (IC₅₀ = 0.27 and 0.49 μmol/L, respectively). Both compounds <b>33a</b> and <b>36b</b> inhibited cell metastasis, arrested the cell cycle in the G₂/M phase, and induced apoptosis <i>in vitro</i>. Mechanistic studies revealed that <b>33a</b> and <b>36b</b> increased ROS levels, led to DNA damage, ER stress, and mitochondrial dysfunction, and inhibited autophagy in HCT116 cells. Biological information analysis, RNA-sequencing, Gene Set Enrichment Analysis (GSEA), drug affinity responsive target stability (DARTS) assay, cellular thermal shift assay (CETSA), and SPR experiments identified that compounds <b>33a</b> and <b>36b</b> showed antitumor activity by suppressing the c-MYC pathway. <i>c-MYC</i> silencing assays indicated that c-MYC proteins participated in <b>33a</b>-mediated anticancer activities in HCT116 cells. More importantly, compound <b>33a</b> presented favorable pharmacokinetic properties in mice (<i>T</i> _1/2 = 6.8 h) and showed significant antitumor efficacy <i>in vivo</i> without obvious toxicity, showing promising potential for further clinical development.