<i>BRCA1/Trp53</i> heterozygosity and replication stress drive esophageal cancer development in a mouse model.

Abstract

<i>BRCA1</i> germline mutations are associated with an increased risk of breast and ovarian cancer. Recent findings of others suggest that <i>BRCA1</i> mutation carriers also bear an increased risk of esophageal and gastric cancer. Here, we employ a <i>Brca1/Trp53</i> mouse model to show that unresolved replication stress (RS) in <i>BRCA1</i> heterozygous cells drives esophageal tumorigenesis in a model of the human equivalent. This model employs 4-nitroquinoline-1-oxide (4NQO) as an RS-inducing agent. Upon drinking 4NQO-containing water, <i>Brca1</i> heterozygous mice formed squamous cell carcinomas of the distal esophagus and forestomach at a much higher frequency and speed (∼90 to 120 d) than did wild-type (WT) mice, which remained largely tumor free. Their esophageal tissue, but not that of WT control mice, revealed evidence of overt RS as reflected by intracellular CHK1 phosphorylation and 53BP1 staining. These <i>Brca1</i> mutant tumors also revealed higher genome mutation rates than those of control animals; the mutational signature SBS4, which is associated with tobacco-induced tumorigenesis; and a loss of <i>Brca1</i> heterozygosity (LOH). This uniquely accelerated <i>Brca1</i> tumor model is also relevant to human esophageal squamous cell carcinoma, an often lethal tumor.