FGFR1 and cancer: At 8 μg/ml, IMB-R1B inhibited MG63 cell growth by 47 %, and IMB-R1A by 30 % (Fig. 3d), indicating that the adverse effect of IMB-R1 on cancer cells was in fact due to its anti-FGFR1 activity, and not any other, non-relevant component in the sera.