CTGF/CCN2 stimulation contributes to HC11 cell proliferation. (A) HC11-TRE and HC11-TRE-CTGF cells were seeded in 96-well microtiter plates in serum-free media with EGF (10 ng/ml). (B) HC11 cells were seeded in serum-free media with EGF (10 ng/ml) plus serum-free conditioned media from HC11-TRE or HC11-TRE-CTGF (1:1 ratio). Cell proliferation was determined at 24, 48, 72, and 96 hours post addition of EGF using the MTT assay. The results are reported as the mean + S.D. of four determinations. *, p < 0.005.