To ascertain whether BRD4 inhibition, resulting in transcriptional suppression of CtIP and RAD51, specifically curtailed tumor growth in the absence of PARP1 in vivo, we xenografted colorectal carcinoma cells, including HCT116 and isogenic parp1 KO cells, into fertilized zebrafish embryos. The gene discussed is PARP1; the disease is colorectal carcinoma.