A new insight into cancer stem cell markers: Could local and circulating cancer stem cell markers correlate in colorectal cancer?

Cancer stem cell (CSC) markers could serve as potential prognostic procedure. This study is aimed to investigate the local expression of doublecortin-like kinase 1 (DCLK1) and Lgr5 in colorectal cancer tissues (CRC) at both protein and messenger RNA (mRNA) level, followed by providing a comparison of the local and circulating expression pattern of these markers, based on our present and previous study. The mRNA expression level of DCLK1 and Lgr5 was evaluated using comparative real-time PCR method applying 58 fresh tumor tissues and their correspondent normal margins. Immunohistochemistry was applied to analyze the protein expression level of DCLK1 and Lgr5 in paraffin-embedded CRC tissues. The correlation of DCLK1 and Lgr5 expression pattern with clinicopathological characteristics was assessed. A higher mRNA expression level of DCLK1 (3.28-fold change, p < 0.001) and Lgr5 (2.29-fold change, p < 0.001) was observed in CRC fresh tissues compared to the normal adjacent margins, and the expression level was higher in patients with higher grade and stages of disease and patients who underwent neoadjuvant chemoradiotherapy (CRT). The protein expression level of DCLK1 and Lgr5 was also increased significantly in tumor tissues compared to normal colon tissues which were positively correlated to tumor stage and grade and neoadjuvant CRT. Taken together, the results of protein analysis were in accordance with mRNA assessment. The local expression pattern of DCLK1 and Lgr5 was also in accordance with their expression level in circulation. However, some minor inconsistencies were observed which may be attributed to several factors including the possible effect of CRT on CSC reprogramming.

Upregulation of circulating cancer stem cell marker, DCLK1 but not Lgr5, in chemoradiotherapy-treated colorectal cancer patients.

Cancer stem cell (CSC) markers have attracted considerable attention in tumor diagnostic, prognostic, and therapeutic implications. Detection of cancer stem cells in circulating blood using cancer stem cell markers has received remarkable attention recently. In this study, we aimed to investigate the messenger RNA (mRNA) expression level of Lgr5 and DCLK1 as most proposed colorectal CSC markers in blood circulation also determine the subsequent association to patients' clinical and pathological findings. Peripheral blood mononuclear cells (PBMCs) of 58 patients with colorectal cancer at stage I-IV with 33 out of 58 patients undergoing preoperative chemoradiotherapy (CRT), as well as 58 healthy controls have been isolated and the extracted RNAs were analyzed using real-time PCR. The mRNA expression pattern of CSC markers of patients and controls was compared using ΔΔCt method. The expression level of Lgr5 was significantly higher in colorectal cancer (CRC) patients comparing to healthy group (4.8-fold change, p < 0.001). Also there was a significant increase in expression level of Lgr5 in patients at stages III and IV comparing to stages I and II (p = 0.031) and higher grades (p = 0.039) of CRC. The expression of DCLK1 was also elevated in patients significantly (2.7-fold change, p < 0.001) and the related expression was increased by increasing disease stage (p = 0.025). Combination of DCLK1 and Lgr5 markers was analyzed by logistic regression and proved to be a slightly better marker compared to each marker alone. Interestingly the DCLK1 expression level was significantly higher in patients undergoing preoperative CRT (p = 0.041); however, no association to neoadjuvant CRT was observed for Lgr5. Considering the over-expression of DCLK1 and Lgr5 in circulating blood of CRC patients comparing to controls, our results might emphasize on the presence of CSCs in blood of these patients which might be attributed to their clinical and pathological characteristics and may lead to apply in future clinical implications. Moreover, the higher expression level of DCLK1 in patients undergoing CRT can propose it as a more relevant candidate among CSC markers comparing to Lgr5 for CRC patients.