NR4A1 and breast carcinoma: Interestingly, the role for TYRO3 in breast cancer appears to be limited to hormone receptor positive (HR+) tumors, as siRNA-mediated TYRO3 inhibition reduced cell density in cultures of estrogen receptor or HER2 positive cell lines, both in the presence and absence of hormone stimulation, but had no significant impact on expansion of triple negative cell lines [37].