Department of Radiation Biology, Oslo University Hospital, Oslo, Norway.
Department of Pathology, Oslo University Hospital, Oslo, Norway.
Neoplasia. 2019 Apr;21(4):353-362. doi: 10.1016/j.neo.2019.01.002. Epub 2019 Mar 8.
CDK regulatory subunit 2 (CKS2) has a nuclear function that promotes cell division and is a candidate biomarker of chemoradioresistance in cervical cancer. The underlying mechanisms are, however, not completely understood. We investigated whether CKS2 also has a mitochondrial function that augments tumor aggressiveness. Based on global gene expression data of two cervical cancer cohorts of 150 and 135 patients, we identified a set of genes correlated with CKS2 expression. Gene set enrichment analysis showed enrichment of mitochondrial cellular compartments, and the hallmarks oxidative phosphorylation (OXPHOS) and targets of the MYC oncogene in the gene set. By in situ proximity ligation assay, we showed that CKS2 formed complex with the positively correlated MYC target, mitochondrial single-stranded DNA binding protein SSBP1, in the mitochondrion of cervix tumor samples and HeLa and SiHa cervical cancer cell lines, indicating a role in mitochondrial DNA (mtDNA) replication and thereby OXPHOS. CDK1 was found to be part of the complex. Flow cytometry analyses of HeLa cells showed cell cycle regulation of the CKS2-SSBP1 complex consistent with mtDNA replication activity. Moreover, repression of mtDNA replication and OXPHOS by acute hypoxia decreased CKS2-SSBP1 complex abundance and expression of MYC targets. By immunohistochemistry, cytoplasmic CKS2 expression was found to add to the prognostic impact of nuclear CKS2 expression in patients, suggesting that the mitochondrial function promotes tumor aggressiveness. Our study uncovers a novel link between regulation of cell division by nuclear pathways and OXPHOS in the mitochondrion that involves CKS2 and promotes chemoradioresistance of cervical cancer.
细胞周期蛋白依赖性激酶调节亚基 2(CKS2)具有促进细胞分裂的核功能,是宫颈癌化学放射抵抗的候选生物标志物。然而,其潜在机制尚不完全清楚。我们研究了 CKS2 是否还具有增强肿瘤侵袭性的线粒体功能。基于两个包含 150 例和 135 例患者的宫颈癌队列的全基因表达数据,我们鉴定了一组与 CKS2 表达相关的基因。基因集富集分析显示,基因集中存在与线粒体细胞区室、氧化磷酸化(OXPHOS)标志和 MYC 癌基因靶点相关的富集。通过原位邻近连接测定,我们表明 CKS2 与在宫颈肿瘤样本和 HeLa 和 SiHa 宫颈癌细胞系中线粒体中与 CKS2 表达呈正相关的 MYC 靶标,线粒体单链 DNA 结合蛋白 SSBP1 形成复合物,表明其在线粒体 DNA(mtDNA)复制和因此 OXPHOS 中发挥作用。CDK1 被发现是复合物的一部分。HeLa 细胞的流式细胞术分析显示 CKS2-SSBP1 复合物的细胞周期调节与 mtDNA 复制活性一致。此外,急性缺氧对 mtDNA 复制和 OXPHOS 的抑制降低了 CKS2-SSBP1 复合物丰度和 MYC 靶标的表达。通过免疫组织化学,细胞质 CKS2 表达被发现增加了核 CKS2 表达在患者中的预后影响,表明线粒体功能促进了肿瘤的侵袭性。我们的研究揭示了核途径调节细胞分裂与线粒体中涉及 CKS2 的 OXPHOS 之间的新联系,促进了宫颈癌的化学放射抵抗。