Regulation mechanism of lung fibroblast proliferation remains unknown. To elucidate the key molecules in it, we here established mortal and immortal non-transformed lung fibroblast cell line/strains with elongated lifespan by telomerase reversetranscriptase gene transfection. Comparing the expression profiles of them, 51 genes were explored to be the candidates responsible for regulation of cellular proliferation of lung fibroblasts. This set of fibrobrast strains of same origin with different proliferative capacities may become useful model cells for research on lung fibroblast growth regulation and the candidate genes explored in this study may provide biomarkers or therapeutic targets of pulmonary fibrosis.