Table 1.

Classification and function of nine protein tyrosine kinase (PTK) inhibitors used in this study.

Drugs	Molecular Weight (g/mol)	Target PTKs
Ponatinib	532.56	BCR-ABL, VEGFR, PDGFR, FGFR, EpH kinase, SRC-family protein-tyrosine kinases, and Kit, RET, TIE2, Flt-3 kinase inhibitor
Sunitinib	398.47	PDGFRα, PDGFRβ, VEGFR1, VEGFR2, VEGFR3, c-KIT, Flt-3, CSF-1R, RET tyrosine kinase inhibitor
Sorafenib	464.83	KIT, Flt-3, VEGFR-2, VEGFR-3, PDGFR-β tyrosine kinase, C-Raf, B-Raf and mutant B-Raf kinase inhibitor. Unique in targeting the Raf/Mek/Erk pathway.
Dasatinib	488.01	SRC family (SRC, LCK, YES, FYN) tyrosine kinase, BCR-ABL, c-Kit, EpHA2, PDGFRβ kinase inhibitor
Pazopanib	437.52	VEGFR1, VEGFR2, VEGFR3, PDGFRα, PDGFRβ, c-kit tyrosine kinase inhibitor
Bosutinib	530.45	Src-family (Src, Lyn, Hck) tyrosine kinases, BCR-ABL kinase inhibitor
Gefitinib	446.90	EGFR/Her1/ErbB-1 tyrosine kinase inhibitor
Afatinib	485.94	EGFR (ErbB1)/HER2 (ErbB2)/ HER4 (ErbB4) tyrosine kinase inhibitor
Midostaurin	570.64	PKCα/β/γ, Syk, Flk-1, Akt, PKA, c-Kit, c-Fgr, c-Src, Flt-3, PDFRβ and VEGFR1/2 tyrosine kinase inhibitor

The following criteria were used to select drugs for the study: (1) inhibitors that strongly inhibit some cells but not too many; (2) inhibitors that inhibit a significant number of cells at higher concentration, but the spectrum of cells are not too broad. An automatic screen was set up based on these two criteria. If an inhibitor inhibited more than one cell line but fewer than 20 cell lines with IC₅₀ below 0.01 nM, the inhibitor scored one point. If a drug inhibited between two and 20 cell lines with IC₅₀ below 0.1 nM, it scored one point. With the six-point screen, the scores were tallied. If a drug scored four or above, the inhibitor was automatically chosen. With these considerations, the nine PTK inhibitors in the table were chosen. The targeted PTKs of these inhibitors can be found in the two websites (http://www.drugbank.ca and http://www.rxlist.com).