NSUN5 Mediates Resistance to Doxorubicin via Upregulation of DNA Damage Repair Proteins BRCA2 and BRIP1 in Colorectal Cancer

Despite advancements in diagnosis and therapy, chemotherapy resistance and metastasis remain significant challenges for colorectal cancer (CRC) patients. Addressing resistance to cell death is crucial for improving cancer treatment outcomes. NOP2/Sun RNA methyltransferase 5 (NSUN5) has been implicated in cancers, but its role in chemotherapy resistance of CRC remains unclear. Herein we reveal that NSUN5 is highly expressed in CRC through bioinformatics analysis and validation using human and mice CRC tissues. High expression of NSUN5 predicted poorer disease-free survival in CRC patients. Nsun5-deficient mice exhibited reduced tumor incidence and malignancy in an AOM/DSS-induced CRC model. NSUN5 knockdown or knockout showed diminished proliferation and migration in CRC cell lines, which was reversed by NSUN5 overexpression or reintroduction. Intriguingly, overexpression of NSUN5 conferred resistance to doxorubicin, an effective chemotherapeutic agent leads to DNA damage, whereas NSUN5 deficiency increased CRC cells' sensitivity to the drug, both in vitro and in vivo. Mechanistically, NSUN5 upregulated BRCA2 and BRCA1-interacting helicase 1 (BRIP1) expression and interacted with these proteins to prevent cell death in response to DNA damage. Analysis of our local cohort and public data sets showed a positive correlation between NSUN5, BRCA2, and BRIP1 in CRC patients. Collectively, we uncover the role of NSUN5 in CRC progression from the perspective of chemotherapy resistance, potentially offering innovative insight on the clinical therapy and prognosis of CRC. Stable NSUN5-overexpressing HCT15 cell lines were generated via lentiviral transduction, and empty vector-transfected cells served as controls, RNA-seq was employed.

尽管结直肠癌（colorectal cancer, CRC）患者的诊疗手段已取得长足进步，但化疗耐药与转移仍是亟待解决的重大临床难题。破解肿瘤细胞死亡抵抗机制，对改善癌症治疗效果至关重要。NOP2/Sun RNA甲基转移酶5（NOP2/Sun RNA methyltransferase 5, NSUN5）虽已被证实与多种肿瘤相关，但其在结直肠癌化疗耐药中的具体作用仍未明确。本研究通过生物信息学分析，并结合人类与小鼠结直肠癌组织样本进行验证，证实NSUN5在结直肠癌组织中呈高表达状态。NSUN5高表达可预示结直肠癌患者更差的无病生存率。在偶氮甲烷/葡聚糖硫酸钠（AOM/DSS）诱导的结直肠癌模型中，Nsun5基因敲除小鼠的肿瘤发生率与恶性程度均显著降低。在结直肠癌细胞系中，敲低或敲除NSUN5可显著抑制细胞增殖与迁移能力，而过表达或回补NSUN5则可逆转这一表型。值得注意的是，无论是体外还是体内实验中，NSUN5过表达可使结直肠癌细胞对多柔比星（doxorubicin）产生耐药性——多柔比星是一类可引发DNA损伤的有效化疗药物；而NSUN5缺陷则会增强结直肠癌细胞对该药物的敏感性。从分子机制来看，NSUN5可上调BRCA2与BRCA1互作解旋酶1（BRCA1-interacting helicase 1, BRIP1）的表达，并与这两种蛋白相互结合，从而在DNA损伤应激下抑制细胞死亡。对本研究本地队列及公共数据集的分析结果显示，结直肠癌患者体内NSUN5、BRCA2与BRIP1的表达水平呈正相关。综上，本研究从化疗耐药的视角揭示了NSUN5在结直肠癌进展中的作用，有望为结直肠癌的临床治疗与预后评估提供全新的研究思路。本研究通过慢病毒转染技术构建了稳定过表达NSUN5的HCT15细胞系，以空载体转染的细胞作为对照，并采用RNA测序（RNA-seq）技术开展相关检测。