Intra-tumor heterogeneity of cancer stem cell-related genes and their potential regulatory microRNAs in metastasizing colorectal carcinoma

Intra-tumor heterogeneity (ITH) is related to cancer progression, therapy resistance and recurrences, and is one of the challenging fields in cancerogenesis research. Cancer stem cells (CSC) are thought to be crucially involved in the pathogenesis of several cancer types, including colorectal carcinoma (CRC), and associated with ITH. In the present study, the expression gradient of four genes related to CSC (L1TD1, SLITRK6, ST6GALNAC1 and TCEA3) and their potential regulatory microRNAs (miRNAs) were investigated in the central part and invasive front of the primary tumor, as well as in lymph node and liver metastases. In total, 63 formalin-fixed paraffin-embedded biopsy samples of primary tumor (central part, invasive tumor front), as well as lymph node and liver metastases from 19 patients with CRC, were analyzed. The expression of selected genes (L1TD1, SLITRK6, ST6GALNAC1 and TCEA3) and miRNAs (miR-199a-3p, miR-425-5p, miR-1225-3p, miR-1233-3p and miR-1303) was evaluated using reverse transcription-quantitative PCR. Significant differences in expression were identified for all investigated genes in lymph node metastasis, but not in the liver metastases. All investigated miRNAs were significantly differentially expressed in lymph node metastasis, and miR-199a-3p, miR-425-5p and miR-1233-3p in liver metastasis. Furthermore, a negative correlation between the expression of miR-199a-3p and expression of its potential target gene SLITRK6 was confirmed. The present results provide further evidence that expression of CSC-related genes and their potential regulatory miRNAs contribute to ITH in CRC, lymph node and liver metastasis. The SLITRK6 gene and its regulatory miRNA miR-199a-3p are promising for further validation in functional studies to deepen the present understanding of the regulation of CSC-related genes in CRC.