2 ) ▁occurrence ▁of ▁foc al ▁ad hes ion ▁with ▁the ▁invol vement ▁of ▁integr ins ▁ β 1 ▁and ▁ β 3 ▁at ▁the ▁contact ▁site ▁between ▁the ▁ext rac ell ular ▁matrix ▁and ▁the ▁cell ; ▁ 3 ) ▁assembly ▁of ▁foc al ▁contacts , ▁which ▁is ▁based ▁on ▁integr in - medi ated ▁interactions , ▁and ▁activation ▁of ▁prote ol yt ic ▁en zym es ▁( matrix ▁metal lo prote in ases , ▁ser ine ▁and ▁thre on ine ▁prote ases , ▁cat he ps ins ) ▁at ▁the ▁“ cell - matrix ” ▁interface ▁that ▁leads ▁to ▁the ▁destruction ▁and ▁rem od eling ▁of ▁the ▁surrounding ▁ext rac ell ular ▁matrix ; ▁ 4 ) ▁a ▁change ▁in ▁the ▁act in ▁c yt os ke leton ▁polar ization ▁under ▁my os in ▁II - medi ated ▁control , ▁the ▁occurrence ▁of ▁cell ▁body ▁contra ctions ; ▁and ▁ 5 ) ▁“ pull ing ” ▁the ▁trailing ▁edge ▁toward ▁movement ▁through ▁the ▁newly ▁formed ▁defect s ▁in ▁the ▁matrix ▁structure . ▁Since ▁the ▁cells ▁which ▁use ▁the ▁fib ro blast - like ▁mechanism ▁of ▁invasion ▁follow ▁the ▁described ▁migration ▁steps , ▁their ▁speed ▁of ▁movement ▁is ▁low : ▁about ▁ 0 . 1 – ▁ μ m / min . <0x09> ▁ <0x09> ▁The ▁possibility ▁of ▁prote ol ysis ▁and ▁rem od eling ▁of ▁t issue ▁structures ▁explains ▁the ▁fact ▁that ▁mes en ch ym al ▁movement ▁of ▁a ▁tum or ▁cell ▁is ▁accompanied ▁by ▁minor ▁changes , ▁compared ▁to