Expression of lumican in bone metastatic A549/luc cells. (A) The A549 human lung cancer cell line transfected with the luciferase gene (A549/luc) was injected into the left ventricle of a NOD-SCID mouse. After 40 days (D40), the luciferase activity was observed in the femurs of mice by the IVIS imaging system. The bone marrow cells of mice with bone metastasis were collected and cultured in vitro to establish the bone metastatic cell line, A549/luc BM 1st. The BM 1st cells were injected again into a different mouse and the luciferase activity was detected on D28. The bone marrow cells of this mouse were collected and cultured in vitro to establish a highly bone metastatic cell line, A549/luc BM 2nd. The expression of lumican in the parental A549/luc (P), A549/luc BM 1st, and A549/luc BM 2nd cells was determined by quantitative-real-time PCR (B) and Western blot analysis (C). The level of lumican expression in each cell line was individually normalized to the internal control (actin), and the numbers in (C) indicate the level of lumican expression in bone metastatic A549/luc cells as compared to the parental A549/luc cells (level set to 1).