gression ▁was ▁shown ▁in ▁vit ro ▁using ▁specific ▁tum or ▁lines ▁as ▁well ▁as ▁experimental ▁models ; ▁however , ▁establishment ▁of ▁the ▁E MT ▁development ▁and ▁identification ▁of ▁tum or ▁cells ▁and ▁their ▁main ▁characteristics ▁under ▁in ▁v ivo ▁conditions ▁is ▁a ▁complex ▁task . <0x09> ▁ <0x09> ▁E MT ▁is ▁the ▁basis ▁of ▁many ▁processes ▁of ▁morph ogen esis . ▁It ▁is ▁believed ▁that ▁under ▁normal ▁conditions ▁( d uring ▁emb ry ogen esis ) ▁E MT ▁can ▁be ▁induced ▁by ▁the ▁H G F ▁( he pat ocy te ▁growth ▁factor ) ▁secret ed ▁by ▁fib ro bl asts . ▁H G F ▁bind s ▁to ▁specific ▁c - Met ▁re cept ors ▁located ▁on ▁the ▁memb rane ▁of ▁ep ith el ial ▁cells . ▁The ▁binding ▁to ▁re cept ors ▁activ ates ▁a ▁signal ing ▁path way ▁involving ▁some ▁prote ins ▁of ▁the ▁small ▁G TP ase ▁system ▁( C dc 4 2 , ▁R ac , ▁R ho A , ▁R ho C ) ▁that ▁reg ulate ▁the ▁intensity ▁of ▁act in ▁micro fil ament ▁polym er ization ▁and ▁the ▁contract ility ▁of ▁act in - my os in ▁fil aments , ▁which ▁determ ines ▁the ▁intensity ▁of ▁l am el lip odia ▁formation ▁and ▁t ension ▁of ▁the ▁matrix - att ached ▁cell . ▁In ▁this ▁case , ▁there ▁is ▁significant ▁re arr ang ement ▁of ▁the ▁whole ▁act in - my os in ▁c yt os ke leton ▁and ▁loss ▁of ▁E - c ad her in