Proliferation and cell cycle progression in huLM^2ME, huLM-COMT^KI, huLM-COMT^KD and huLM^W.

<p>(A) Proliferation of huLM cells expressing different levels of COMT or treated with 2ME (500 nM) in absence of estrogen. The cells were cultured in phenol red-free medium containing 10% of charcoal-stripped fetal calf serum. MTT assay was used to determine the E2-independent proliferation rates of huLM^W, huLM-COMT^KD; huLM ^2ME, and huLM-COMT^KI cells. Cells (1,000/well) were seeded in 96-well microplates. After 24, 48, 72 and 96 hr, the number of viable cells was determined by reading the optical density at a wavelength of 595 nm with a reference wavelength of 650 nm. Data are representative of 3 independent experiments. *a, significantly (P<0.05) lower compared with huLM^W. *b, significantly (P<0.05) lower compared with huLM^W. (B) E₂-induced proliferation of huLM cells expressing different levels of COMT or treated with 2ME (500 nM). Data are representative of 3 independent experiments. *a, significantly (P<0.05) higher compared with huLM^W. *b, significantly (P<0.05) lower compared with huLM^W. (C) Effects of COMT expression level or treatment with 2ME (500 nM) on E₂-provoked huLM cell cycle progression. Flow cytometry using Propidium Iodide labeling of nuclei was done to determine percentage of cells in S-phase of the cell cycle. Data are representative of 3 independent experiments. *a, significantly (P<0.05) lower compared with huLM^W. *b, significantly (P<0.05) higher compared with huLM^W.