Nucleolar TAAP1/C22orf46 confers pro-survival signaling in non-small cell lung cancer

Tumor cells subvert immune surveillance by harnessing inhibitory signals to acquire immune resistance. Bispecific antibodies have been developed to direct cytotoxic T lymphocytes to the tumor site and foster their activities to reduce tumor immune resistance. Although applied with success, bispecific antibodies are not universally effective partially due to the expression of pro-survival factors by tumor cells. Here, we report a CRISPR/Cas9 screen in human non-small cell lung cancer for genes that confer tumors with increased resistance to T lymphocyte mediated killing. We show that lung carcinoma cells devoid of expression of the gene C22orf46 exhibit increased susceptibility to T cell induced apoptosis and genotoxic stress mediated by chemotherapeutic agents. We present data showing that C22orf46, previously annotated as a non-coding gene, encodes an expressed nucleolar protein with remote homologies to the BH domain-containing Bcl-2 family and propose to name this protein Tumor Apoptosis Associated Protein 1 (TAAP1). Collectively, our findings establish TAAP1/C22orf46 as a pro-survival oncogene with possible implications to therapy RNA-seq transcriptome profiling of wild-type and C22orf46-knockout NCI-H1975 cells, with both genotypes cultured and sequenced in triplicates.

肿瘤细胞通过利用抑制性信号逃避免疫监视，进而获得免疫抵抗能力。双特异性抗体（bispecific antibodies）已被开发用于引导细胞毒性T淋巴细胞迁移至肿瘤部位，并增强其抗肿瘤活性以削弱肿瘤的免疫抵抗能力。尽管双特异性抗体已取得成功的临床应用，但并非所有患者均可获益，其部分原因在于肿瘤细胞会表达促生存因子。本研究通过在人非小细胞肺癌（human non-small cell lung cancer）中开展CRISPR/Cas9筛选，鉴定出可使肿瘤获得更强T淋巴细胞介导杀伤抵抗能力的基因。研究发现，缺失C22orf46基因表达的肺癌细胞，对T细胞诱导的凋亡以及化疗药物介导的基因毒性应激的敏感性显著升高。我们的数据显示，此前被注释为非编码基因的C22orf46，实则编码一种定位于核仁的蛋白质；该蛋白与含BH结构域的Bcl-2家族蛋白存在远缘同源性，我们提议将该蛋白命名为肿瘤凋亡相关蛋白1（Tumor Apoptosis Associated Protein 1，TAAP1）。综上，本研究证实TAAP1/C22orf46是一种促生存致癌基因，具有潜在的治疗应用价值。本研究对野生型及C22orf46敲除的NCI-H1975细胞开展了RNA测序转录组分析，两种基因型的细胞均进行了三次生物学重复的培养与测序。