FGFR1 and carcinosarcoma: In contrast, in carcinosarcoma PDX tumors with moderate or no copy number gain in FGFR1 and lower protein expression, AZD4547 did not cause a significant reduction in tumor growth The lack of significant growth inhibition seen in AB739 showing lower level FGFR1 copy number gain (5 copies) and lower FGFR1 protein expression than AB740 indicate that significant oncogenic FGFR1 activation (presumably through self-dimerization) may require a higher level of protein expression.