Colorectal cancer (CRC) ranks as the second leading cause of cancer-related fatalities and is the third most commonly diagnosed cancer in Lithuania and worldwide [1]. The first sign of colorectal cancer is the formation of hyperplastic polyps on the lining of the intestine. As a result of new mutations and changes in genome methylation patterns, traditional adenomas or serrated lesions can develop and later become adenocarcinomas – a type of cancer [2]. Currently, cancer risk is assessed based on lesion size and histological features, thus distinguishing serrated adenomas from other lesions is challenging. However, recent research suggests that the pathways leading to colorectal cancer may vary between genders [3]. Adenocarcinoma development is 1.5 times higher in males than females due to different sex hormones and microbiota. Also, genome-wide methylation analysis revealed the different methylation patterns in colon tissue between males and females [4]. However, the differences in LINE-1 promoter expression in colon cancer and adenomas between genders are unclear.
The present study aimed to assess LINE-1 promoter ORF1 and ORF2 expression in tubular adenomas, adenocarcinomas, and serrated lesions, analyzing male and female cohorts separately. Adenocarcinoma samples (9 male, 11 female), tubular adenoma samples (18 male, 13 female), and serrated adenoma samples (7 male, 9 female) were collected (NCI). Quantitative analysis of LINE-1 promoter ORF1 and ORF2 expression was conducted using qPCR, the data was analyzed using Mann-Whitney and Kruskal-Wallis tests with GraphPad v.9.
The LINE-1 expression analysis results reveal statistically significant differences in ORF2 expression levels between males and females in serrated adenoma tissue samples. Also, LINE-1 ORF-2 expression in serrated adenoma was significantly lower than in tubular adenoma and adenocarcinoma in the male cohort. Receiver operating characteristic (ROC) curves for methylation levels of serrated and tubular adenoma displayed that LINE-1 ORF2 expression had reliable predictive accuracy across the test cohort, with AUC values of 0.84. The AUC value for the methylation level of serrated adenoma and adenocarcinoma also was 0.84. These results indicated that LINE-1 ORF2 expression could serve as a potential biomarker to differentiate serrated adenoma from tubular adenoma and adenocarcinoma in the male cohort.