LC-MS/MS-based Proteomic Analysis of Locally Advanced Rectal Tumors to Identify Biomarkers for Predicting Tumor Response to Neoadjuvant Chemoradiotherapy

: Neoadjuvant chemoradiotherapy (nCRT) is a standard therapy used for locally advanced rectal cancer prior to sur-gery, which can more effectively reduce the locoregional recurrence rate and radiation toxicity compared to postoperative chemoradiotherapy. The response of patients to nCRT varies, and thus, robust biomarkers for predicting a pathological complete response are necessary. This study aimed to identify possible biomarkers involved in the complete response/non-response of rec-tal cancer patients to nCRT. Comparative proteomic analysis was performed on rectal tissue samples before and after nCRT. Pro -teins were extracted for label-free proteomic analysis. Western blot and real-time PCR were performed using rectal cancer cell line SNU-503 and radiation-resistant rectal cancer cell line SNU-503R80Gy. A total of 135 up-and 93 down-regulated proteins were identified in the complete response group. Six possible biomarkers were selected to evaluate the expression of proteins and mRNA in SNU-503 and SNU-503R80Gy cell lines. Lyso-phosphatidylcholine acyltransferase 2, annexin A13, aldo-ketose reductase family 1 member B1, and cathelicidin antimicrobial peptide appeared to be potential biomarkers for predicting a pathological complete response to nCRT. This study identified differentially expressed proteins and some potential biomarkers in the complete response group, which would be further validated in future studies.

Automated summary

This study aimed to identify possible biomarkers for predicting the response of rectal cancer patients to neoadjuvant chemoradiotherapy (nCRT). Comparative proteomic analysis was performed on rectal tissue samples before and after nCRT, and several potential biomarkers were identified, including lyso-phosphatidylcholine acyltransferase 2, annexin A13, aldo-ketose reductase family 1 member B1, and cathelicidin antimicrobial peptide.