We next evaluated whether TGFBRi treatment could also prevent estrogen-induced tumorigenesis in ACI rats, which, when implanted with slow-release estradiol (E2) pellets after puberty (at 9 weeks of age) to avoid interference with pubertal development, develop ER + mammary tumors with a latency of about 6 months16. The gene discussed is ESR1; the disease is breast cancer.