肿瘤再增殖是指放化疗后残存的肿瘤细胞生长并形成新的肿瘤的过程，是导致放化疗失败的重要原因。课题组前期研究发现放化疗所致肿瘤细胞凋亡是一把双刃剑，凋亡细胞可通过Caspase-3/iPLA2/AA/PGE2通路刺激残存肿瘤细胞增殖。申请人前期研究发现放疗所致凋亡细胞亦可通过Caspase-3/PKCδ/Akt/VEGF-A通路刺激残存肿瘤细胞增殖。此外，申请人近期研究初步证实Caspase-3还可切割激活PKCε和PKCμ促进肿瘤再增殖。因此，申请人提出利用CRISPR/Cas9技术敲除PKCε或PKCμ基因，深入研究PKCε和PKCμ在凋亡细胞诱导的肿瘤再增殖中的作用机制；并通过定点突变构建PKCδ、PKCε或PKCμ的显性负性突变体（Caspase-3特异性切割位点失活），探索可否通过竞争性抑制PKCδ、PKCε或PKCμ的激活阻断放疗后肿瘤再增殖，为临床开发新的放疗增敏剂提供实验证据。

Tumor repopulation refers to the growth of residual tumor cells and the formation of new tumor after radiotherapy or chemotherapy, which is the major cause of radiotherapy and chemotherapy failure. Our previous studies had found that tumor cell apoptosis induced by radiotherapy or chemotherapy was a double-edged sword. Apoptotic cells could stimulate the proliferation of residual tumor cells through the Caspase-3/iPLA2/AA/PGE2 pathway. My previous study had showed that apoptotic cells induced by radiotherapy could also stimulate the proliferation of residual tumor cells through the Caspase-3/PKCδ/Akt/VEGF-A pathway. In addition, my recent study preliminarily validated that Caspase-3 could also activate PKCε and PKCμ to promote tumor repopulation. Therefore, I intend to utilize CRISPR/Cas9 technology to knock out the PKCε or PKCμ gene, to investigate the role of PKCε and PKCμ in apoptotic cell-induced tumor repopulation, and construct dominant negative mutants (Caspase-3 specific cleavage site inactivation) of PKCδ, PKCε or PKCμ by site-directed mutagenesis, to explore whether competitively inactivating PKCδ, PKCε or PKCμ can block tumor repopulation after radiotherapy. This study could provide experimental evidence for clinical application of new radiosensitizers.