Simultaneous inhibition of Chk1 and Bcl-xL induces apoptosis in vitro and represses tumour growth in an in vivo xenograft model

We previously showed that prexasertib, a checkpoint kinase 1 (Chk1) inhibitor, and navitoclax, a Bcl-2 and Bcl-xL inhibitor, induced a synergistic inhibitory effect on cell proliferation in vitro. Here, we investigated the effect of the simultaneous knockdown of Chk1 and each antiapoptotic protein of the Bcl-2 family (Bcl-2, Bcl-xL, or Mcl-1) with small interfering RNAs on apoptosis in three pancreatic cancer cell lines. Only simultaneous knockdown of Chk1 and Bcl-xL induced significant apoptosis compared with single knockdown in all three cell lines. We evaluated the anti-tumour effects of combined prexasertib and navitoclax treatment in a mouse xenograft model. Treatment to control volume ratios were calculated as 63.2% for prexasertib, 79.4% for navitoclax, and 36.8% for prexasertib and navitoclax. These findings suggest that the simultaneous inhibition of Chk1 and Bcl-xL may be an effective treatment for pancreatic cancer.