Pancreatic cancer (PC) is a highly lethal malignancy regarding digestive system, which is the fourth leading factor of cancer-related mortalities in the globe. Prognosis is poor due to diagnosis at advanced disease stage, low rates of surgical resection, and resistance to traditional radiotherapy and chemotherapy. In order to develop novel therapeutic strategies, further elucidation of the molecular mechanisms underlying PC chemoresistance is required. Ribosomal RNA biogenesis has been implicated in tumorigenesis. Small nucleolar RNAs (snoRNAs) is responsible for post-transcriptional modifications of ribosomal RNAs during biogenesis, which have been identified as potential markers of various cancers. Here, we investigate the U3 snoRNA-associated protein RRP9/U3-55 K along with its role in the development of PC and gemcitabine resistance. qRT-PCR, western blot and immunohistochemical staining assays were employed to detect RRP9 expression in human PC tissue samples and cell lines. RRP9-overexpression and siRNA-RRP9 plasmids were constructed to test the effects of RRP9 overexpression and knockdown on cell viability investigated by MTT assay, colony formation, and apoptosis measured by FACS and western blot assays. Immunoprecipitation and immunofluorescence staining were utilized to demonstrate a relationship between RRP9 and IGF2BP1. A subcutaneous xenograft tumor model was elucidated in BALB/c nude mice to examine the RRP9 role in PC in vivo. Significantly elevated RRP9 expression was observed in PC tissues than normal tissues, which was negatively correlated with patient prognosis. We found that RRP9 promoted gemcitabine resistance in PC in vivo and in vitro. Mechanistically, RRP9 activated AKT signaling pathway through interacting with DNA binding region of IGF2BP1 in PC cells, thereby promoting PC progression, and inducing gemcitabine resistance through a reduction in DNA damage and inhibition of apoptosis. Treatment with a combination of the AKT inhibitor MK-2206 and gemcitabine significantly inhibited tumor proliferation induced by overexpression of RRP9 in vitro and in vivo. Our data reveal that RRP9 has a critical function to induce gemcitabine chemoresistance in PC through the IGF2BP1/AKT signaling pathway activation, which might be a candidate to sensitize PC cells to gemcitabine.

中文翻译：

---

RRP9通过激活AKT信号通路促进胰腺癌吉西他滨耐药


胰腺癌（PC）是一种高致死率的消化系统恶性肿瘤，是全球癌症相关死亡的第四大杀手。由于诊断时处于晚期疾病、手术切除率低以及对传统放疗和化疗的抵抗，预后较差。为了开发新的治疗策略，需要进一步阐明 PC 化学耐药性的分子机制。核糖体 RNA 生物发生与肿瘤发生有关。小核仁 RNA (snoRNA) 负责生物发生过程中核糖体 RNA 的转录后修饰，已被确定为各种癌症的潜在标志物。在这里，我们研究了 U3 snoRNA 相关蛋白 RRP9/U3-55 K 及其在 PC 和吉西他滨耐药性发展中的作用。采用 qRT-PCR、蛋白质印迹和免疫组织化学染色法检测人 PC 组织样本和细胞系中的 RRP9 表达。构建 RRP9 过表达和 siRNA-RRP9 质粒，以测试 RRP9 过表达和敲低对通过 MTT 测定研究的细胞活力、通过 FACS 和蛋白质印迹测定测量的集落形成和细胞凋亡的影响。利用免疫沉淀和免疫荧光染色来证明 RRP9 和 IGF2BP1 之间的关系。在 BALB/c 裸鼠中阐明了皮下异种移植肿瘤模型，以检查 RRP9 在体内 PC 中的作用。 PC组织中RRP9表达显着高于正常组织，与患者预后呈负相关。我们发现RRP9在体内和体外促进PC中吉西他滨的耐药性。 从机制上讲，RRP9通过与PC细胞中IGF2BP1的DNA结合区相互作用激活AKT信号通路，从而促进PC的进展，并通过减少DNA损伤和抑制细胞凋亡来诱导吉西他滨耐药。 AKT 抑制剂 MK-2206 和吉西他滨联合治疗可在体外和体内显着抑制 RRP9 过度表达诱导的肿瘤增殖。我们的数据表明，RRP9 在通过 IGF2BP1/AKT 信号通路激活诱导 PC 中吉西他滨化疗耐药方面具有关键功能，这可能是使 PC 细胞对吉西他滨敏感的候选者。