The confirmation of a paradoxical effect of FGF2 on cancer cell growth was evident in these results, which manifested as a promotion of proliferation in ER + breast cancer cell lines without FGFR1 amplification (MCF7, T47D) and an inhibition of proliferation in those with FGFR1 amplification (CAMA1, MDA-MB-134). Here, FGFR1 is linked to breast cancer.