PARP1 and colonic neoplasm: Recently, we showed that PARP inhibitor-based metronomic therapy (sub-IC50 concentrations or doses at repeated intervals) or gene heterozygosity, which does not interfere with DNA repair or induce the STING pathway, blocks the suppressive function of myeloid-derived suppressor cells (MDSCs), allowing CD8+ T cells to attack tumors and synergize with anti-PD-1 immunotherapy in colon cancer models [7].