▁Because ▁A PE 1 ▁performs ▁an ▁essential ▁function ▁in ▁DNA ▁base - ex c ision ▁repair ▁path way , ▁it ▁has ▁become ▁a ▁target ▁for ▁research ers ▁looking ▁for ▁means ▁to ▁prevent ▁cancer ▁cells ▁from ▁surv iving ▁chem other apy . ▁Not ▁only ▁is ▁A PE 1 ▁needed ▁in ▁and ▁of ▁itself ▁to ▁create ▁the ▁nick ▁in ▁the ▁DNA ▁back bone ▁so ▁that ▁the ▁en zym es ▁involved ▁later ▁in ▁the ▁B ER ▁path way ▁can ▁recognize ▁the ▁AP - site , ▁it ▁also ▁has ▁a ▁re do x ▁function ▁that ▁helps ▁activ ate ▁other ▁en zym es ▁involved ▁in ▁DNA ▁repair . ▁As ▁such , ▁knock ing ▁down ▁A PE 1 ▁could ▁lead ▁to ▁tum or ▁cell ▁sens itivity , ▁thus ▁prevent ing ▁cancer ▁cells ▁from ▁pers isting ▁after ▁chem other apy . ▁ ▁A PE 2 ▁en zym e ▁activity ▁A PE 2 ▁has ▁much ▁we aker ▁AP ▁end on uc lease ▁activity ▁than ▁A PE 1 , ▁but ▁its ▁ 3 '- 5 ' ▁ex on uc lease ▁activity ▁is ▁strong ▁compared ▁with ▁A PE 1 ▁and ▁it ▁has ▁a ▁fairly ▁strong ▁ 3 '- ph osph odi ester ase ▁activity . ▁ ▁The ▁A PE 2 ▁ 3 ' ▁– 5 ' ▁ex on uc lease ▁activity ▁has ▁the ▁ability ▁to ▁hydro ly ze ▁bl unt - ended ▁du plex ▁DNA , ▁partial ▁DNA ▁du ple xes ▁with ▁a ▁re cess ed ▁ 3 ' ▁- ter minus ▁or ▁a ▁single ▁nucle ot ide ▁gap ▁containing ▁heter odu plex