Transcriptomic analysis of laser-capture microdissected tumors reveals RAD51AP1 as a tumor-specific marker associated progression from pancreatic intraepithelial neoplasia to invasive pancreatic cancer.

BACKGROUND: Pancreatic ductal adenocarcinoma (PDAC) has a poor prognosis and most patients are diagnosed at a stage where the disease is unresectable, locally advanced, or has already metastasized. Invasive pancreatic cancer is believed to arise through a progression of noninvasive ductal lesions referred to as pancreatic intraepithelial neoplasia (PanIN). The mechanisms driving the transition from PanIN, to invasive PDAC are not fully understood. Moreover, extensive stromal involvement of pancreatic cancer tissue complicates bulk analysis, hindering precise tumor-specific molecular data. METHODS: This issue was addressed through a comprehensive in-silico analysis of laser-capture microdissected (LCM) pure tumor epithelial cells from transcriptomic PDAC cohort datasets, with survival outcomes further validated using TCGA. We employed LCM to evaluate mRNA expression in PanIN lesions, tumor epithelial, and stromal cells, using RT-qPCR in 20 PDAC patients. Immunohistochemistry (IHC) on 353 PDAC patients, including 73 PanIN lesions and 280 tumor tissues on tissue microarray (TMA) slides, provided further confirmation. RESULTS: Based on in-silico analysis, RAD51AP1 was identified as a tumor-specific marker associated with aggressive tumor behavior in captured PDAC samples. RT-qPCR validation demonstrated significantly elevated RAD51AP1 expression in tumor epithelial cells compared to tumor stromal cells, PanIN lesions, and adjacent normal tissues. Consistently, IHC findings for nucleus, cytoplasm, and membrane localization revealed higher RAD51AP1 protein expression in tumor tissues compared to PanIN lesions and normal tissues. This increased expression was correlated with tumor progression and aggressiveness in PDAC patients, as well as reduced survival and poor prognosis in patients with PanIN lesions. CONCLUSIONS: RAD51AP1 is a tumor-specific molecule that associated with more aggressive behavior, advanced disease, and a worse survival rate.