Salivary MicroRNA in Pancreatic Cancer Patients

Background
Pancreatic cancer is the fourth leading cause of cancer death in Western countries, with the lowest 1-year survival rate among commonly diagnosed cancers. Reliable biomarkers for pancreatic cancer diagnosis are lacking and are urgently needed to allow for curative surgery. As microRNA (miRNA) recently emerged as candidate biomarkers for this disease, we explored in the present pilot study the differences in salivary microRNA profiles between patients with pancreatic tumors that are not eligible for surgery, precancerous lesions, inflammatory disease or cancer-free patients as a potential early diagnostic tool.
Methods
Whole saliva samples from patients with pancreatic cancer (n = 7), pancreatitis (n = 4), IPMN (n = 2), or healthy controls (n = 4) were obtained during endoscopic examination. After total RNA isolation, expression of 94 candidate miRNAs was screened by q(RT)PCR using Biomark Fluidgm. Human-derived pancreatic cancer cells were xenografted in athymic mice as an experimental model of pancreatic cancer.
Results
We identified hsa-miR-21, hsa-miR-23a, hsa-miR-23b and miR-29c as being significantly upregulated in saliva of pancreatic cancer patients compared to control, showing sensitivities of 71.4%, 85.7%, 85,7% and 57%, respectively and excellent specificity (100%). Interestingly, hsa-miR-23a and hsa-miR23b are overexpressed in the saliva of patients with pancreatic cancer precursor lesions. We found that hsa-miR-210 and let-7c are overexpressed in the saliva of patients with pancreatitis as compared to the control group, with sensitivity of 100% and 75%, and specificity of 100% and 80%, respectively. Last hsa-miR-216 was upregulated in cancer patients as compared to patients diagnosed with pancreatitis, with sensitivity of 50% and specificity of 100%. In experimental models of PDAC, salivary microRNA detection precedes systemic detection of cancer cells markers.
Conclusions
Our novel findings indicate that salivary miRNA are discriminatory in pancreatic cancer patients that are not eligible for surgery. In addition, we demonstrate in experimental models that salivary miRNA detection precedes systemic detection of cancer cells markers. This study stems for the use of salivary miRNA as biomarker for the early diagnosis of patients with unresectable pancreatic cancer.

Background
胰腺癌是西方国家癌症相关死亡的第四大病因，在常见确诊癌症中1年生存率最低。目前胰腺癌诊断尚缺乏可靠的生物标志物，亟需开发相关标志物以实现根治性手术。随着microRNA(miRNA)成为该疾病的候选生物标志物，本预实验探索了不可手术胰腺肿瘤患者、癌前病变患者、炎症性疾病患者以及无癌人群的唾液microRNA表达谱差异，以期作为潜在的早期诊断工具。

Methods
本研究收集了内镜检查时获取的全唾液样本，受试者包括胰腺癌患者（n=7）、胰腺炎患者（n=4）、胰腺导管内乳头状黏液瘤（Intraductal Papillary Mucinous Neoplasm，IPMN）患者（n=2）及健康对照者（n=4）。完成总RNA提取后，采用Biomark Fluidigm平台通过q(RT)PCR筛选94个候选miRNA的表达水平。将人源胰腺癌细胞异种移植至无胸腺小鼠体内，构建胰腺癌实验模型。

Results
相较于对照组，胰腺癌患者唾液中hsa-miR-21、hsa-miR-23a、hsa-miR-23b及miR-29c显著上调，其灵敏度分别为71.4%、85.7%、85.7%及57%，且特异性均达100%。值得注意的是，hsa-miR-23a与hsa-miR-23b在胰腺癌癌前病变患者的唾液中呈过表达状态。相较于对照组，胰腺炎患者唾液中hsa-miR-210与let-7c过表达，灵敏度分别为100%与75%，特异性分别为100%与80%。最后，相较于胰腺炎患者，胰腺癌患者唾液中hsa-miR-216上调，其灵敏度为50%，特异性为100%。在胰腺导管腺癌（Pancreatic Ductal Adenocarcinoma，PDAC）实验模型中，唾液microRNA检测早于癌细胞标志物的系统检测。

Conclusions
本研究的新发现表明，唾液miRNA可有效区分不可手术的胰腺癌患者。此外，本研究在实验模型中证实，唾液microRNA检测早于癌细胞标志物的系统检测。本研究支持将唾液miRNA作为不可切除胰腺癌患者早期诊断的生物标志物。