In our previous study, we showed that prexasertib, a checkpoint kinase 1 (Chk1) inhibitor, enhances the effects of standard drugs for pancreatic cancer, including gemcitabine (GEM), S-1, and the combination of GEM and S-1 (GS). The combination of prexasertib and GS has a strong antitumor effect and induces apoptosis in pancreatic cancer cells by downregulating anti-apoptotic protein Bcl-2. In the present study, we investigated the combined effect of GEM, S-1, and prexasertib with a selective Bcl-2 inhibitor (venetoclax) and a non-selective Bcl-2 inhibitor (navitoclax) in SUIT-2 pancreatic cancer cells. An MTT assay revealed that the combination of prexasertib with navitoclax showed a synergistic effect but the combination with venetoclax did not. Investigation of the pancreatic cancer cell lines SUIT-2, MIA PaCa-2, and BxPC-3 revealed that BxPC-3 also showed a high synergistic effect when combined with prexasertib and navitoclax but not venetoclax. Mechanistic analysis of the combined effect showed that apoptosis was induced. Bcl-2 knockdown with siRNA and prexasertib treatment did not induce apoptosis, whereas Bcl-xL knockdown with siRNA and prexasertib treatment resulted in strong induction of apoptosis. In addition, among the three cell lines, the combined effect of prexasertib and navitoclax resulted in increased apoptotic cell death because the protein expression levels of Bcl-xL and Chk1 were higher. Our results demonstrate that the combination of prexasertib and navitoclax has a strong antitumor effect and induces apoptosis in pancreatic cancer cells by downregulating Bcl-xL. Simultaneous inhibition of Chk1 and Bcl-xL could be a new strategy for treating pancreatic cancer.

在我们以前的研究中，我们显示了检查点激酶1（Chk1）抑制剂prexasertib可以增强胰腺癌标准药物的作用，包括吉西他滨（GEM），S-1以及GEM和S-1（GS）的组合）。prexasertib和GS的组合具有很强的抗肿瘤作用，并通过下调抗凋亡蛋白Bcl-2诱导胰腺癌细胞凋亡。在本研究中，我们研究了在SUIT-2胰腺癌细胞中GEM，S-1和prexasertib与选择性Bcl-2抑制剂（venetoclax）和非选择性Bcl-2抑制剂（navitoclax）的联合作用。MTT分析显示，普雷沙塞替尼与navitoclax的组合显示出协同作用，而与venetoclax的组合则没有协同作用。胰腺癌细胞系SUIT-2，MIA PaCa-2，BxPC-3和BxPC-3揭示，当与prexasertib和navitoclax组合但与venetoclax组合时，BxPC-3也显示出高协同作用。联合作用的机理分析表明诱导了细胞凋亡。siRNA和prexasertib处理的Bcl-2基因敲低没有诱导细胞凋亡，而siRNA和prexasertib处理的Bcl-xL基因敲除导致强烈的细胞凋亡诱导。此外，在这三种细胞系中，由于Bcl-xL和Chk1的蛋白质表达水平较高，因此prexasertib和navitoclax的联合作用导致凋亡细胞死亡增加。我们的结果表明，prexasertib和navitoclax的组合具有很强的抗肿瘤作用，并通过下调Bcl-xL诱导胰腺癌细胞凋亡。