▁As ▁already ▁mentioned , ▁this ▁bi ological ▁phenomen on ▁was ▁first ▁described ▁by ▁E . D . ▁Hay ▁in ▁ 1 9 9 5 . ▁Today , ▁the ▁existence ▁of ▁the ▁phenomen on ▁is ▁supported ▁by ▁the ▁results ▁of ▁a ▁large ▁number ▁of ▁studies ▁that ▁have ▁investig ated ▁the ▁mechan isms ▁of ▁invasion ▁and ▁met ast asis ▁of ▁m align ant ▁tum ors . ▁The ▁mes en ch ym al ▁mechanism ▁of ▁invasion ▁is ▁believed ▁to ▁be ▁the ▁consequence ▁of ▁E MT , ▁when ▁active ▁ded iffer enti ation ▁of ▁a ▁m align ant ▁ep ith el ial ▁tum or ▁occurs , ▁and ▁mult ic ell ular ▁groups ▁start ▁to ▁divide ▁into ▁single ▁tum or ▁cells , ▁gain ing ▁a ▁mes en ch ym al ▁phen ot ype . <0x09> ▁ <0x09> ▁A ▁number ▁of ▁research ers ▁have ▁str essed ▁that ▁tum or ▁cells ▁during ▁the ▁mes en ch ym al ▁type ▁of ▁migration ▁go ▁through ▁a ▁number ▁of ▁specific ▁sequ ential ▁steps ▁that ▁const itute ▁a ▁five - stage ▁model ▁of ▁migration . ▁This ▁cycle ▁includes ▁the ▁following ▁changes : ▁ 1 ) ▁formation ▁of ▁a ▁pro tr usion ▁on ▁one ▁of ▁the ▁cell ▁pol es ▁– ▁a ▁l am el lip odia ▁or ▁a ▁fil op odia ▁produced ▁by ▁contra ctions ▁of ▁the ▁act in ▁c yt os ke leton ▁under ▁the ▁control ▁of ▁small ▁G TP ases ▁R ac 1 ▁and ▁C dc 4 2 ▁with ▁rapid ▁invol vement ▁of ▁integr ins ▁of ▁the ▁ β 1 ▁family ; ▁