Differences and overlap in plasma protein expression during colorectal cancer progression

Abstract Background Colorectal cancer (CRC) is the third most common cancer worldwide, and its incidence is expected to increase to over 2.2 million new cases in 2030. Stage II CRC is classified as localized disease, while stage III CRC has spread to regional lymph nodes. The 5-year survival rate is over 80% for patients with stage II CRC, but less than 60% for patients with stage III CRC. Proteins, especially plasma proteins that are detectable in easily obtained blood samples, that differ between stage II and III CRC could be useful for predicting and monitoring disease progression. CRC displays differences depending on primary tumor location (right colon, left colon, or rectum), and how plasma protein expression changes during CRC progression from stage II to III depending on primary tumor location is not well-characterized. Methods In this study, we have used Ultra Performance Liquid Chromatography-Ultra Definition Mass Spectrometry (UPLC-UDMSE)-based proteomics to analyze plasma samples from 83 patients with stage II or III CRC, followed by statistical and pathway analysis (data are available via ProteomeXchange). The patients were divided into groups according to tumor stage (II or III) and changes in plasma protein expression between stage II and III (localized and regional disease) samples were studied both regardless of primary tumor location and also within each primary tumor location (right colon, left colon, rectum). Results We discovered differences in plasma protein expression within all groups analyzed and identified proteins whose levels changed in one, two, or all three primary tumor locations between stage II and III CRC. Proteins were identified that could separate the groups compared and pathway analysis by IPA discovered altered pathways involved in lipid metabolism and inflammation, among others. Conclusions Plasma protein expression changes significantly as CRC progresses from stage II to III. While the levels of certain plasma proteins changed during cancer progression in only one or two primary tumor locations, the levels of 13 proteins changed in all primary tumor locations and are therefore common to CRC progression.