TWIST1 and neoplasm: In accordance to the proteins levels (Figure 7B), the expressions of mRNA of uPA, twist, CD44, MMP-2, MMP-9, Bcl-2 and Survivin were decreased most significantly on the cells in PELA-PBAE-PTX group, suggesting again the elevated inhibition on tumor migration and invasion by the pH responsive poly(β-amino ester) copolymers.