1) in vitro. Collectively, robust PHGDH knockdown did not affect non-transformed breast cells, ER+ breast cancer cells and ER− breast cancer cells with low coordinate expression of PHGDH pathway components. Therefore, PHGDH knockdown selectively affects the growth of ER− breast cancer cells with PHGDH high-expression. The gene discussed is PHGDH; the disease is breast cancer.