Background: More than 80% of intestinal neoplasia is associated with the adenomatous polyposis coli (APC) mutation. Doublecortin-like kinase 1 (Dclk1), a kinase protein, is overexpressed in colorectal cancer and specifically marks tumor stem cells (TSCs) that self-renew and increased the tumor progeny in Apc ^Min/+ mice. However, the role of Dclk1 expression and its contribution to regulating pro-survival signaling for tumor progression in Apc mutant cancer is poorly understood. Methods: We analyzed DCLK1 and pro-survival signaling gene expression datasets of 329 specimens from TCGA Colon Adenocarcinoma Cancer Data. The network of DCLK1 and pro-survival signaling was analyzed utilizing the GeneMANIA database. We examined the expression levels of Dclk1 and other stem cell-associated markers, pro-survival signaling pathways, cell self-renewal in the isolated intestinal epithelial cells of Apc ^Min/+ mice with high-grade dysplasia and adenocarcinoma. To determine the functional role of Dclk1 for tumor progression, we knocked down Dclk1 and determined the pro-survival signaling pathways and stemness. We used siRNA technology to gene silence pro-survival signaling in colon cancer cells in vitro. We utilized FACS, IHC, western blot, RT-PCR, and clonogenic (self-renewal) assays. Results: We found a correlation between DCLK1 and pro-survival signaling expression. The expression of Dclk1 and stem cell-associated markers Lgr5, Bmi1, and Musashi1 were significantly higher in the intestinal epithelial cells of Apc ^Min/+ mice than in wild-type controls. Intestinal epithelial cells of Apc ^Min/+ mice showed increased expression of pro-survival signaling, pluripotency and self-renewal ability. Furthermore, the enteroids formed from the intestinal Dclk1⁺ cells of Apc ^Min/+ mice display higher pluripotency and pro-survival signaling. Dclk1 knockdown in Apc ^Min/+ mice attenuates intestinal adenomas and adenocarcinoma, and decreases pro-survival signaling and self-renewal. Knocking down RELA and NOTCH1 pro-survival signaling and DCLK1 in HT29 and DLD1 colon cancer cells in vitro reduced the tumor cells’ ability to self-renew and survive. Conclusion: Our results indicate that Dclk1 is essential in advancing intestinal tumorigenesis. Knocking down Dclk1 decreases tumor stemness and progression and is thus predicted to regulate pro-survival signaling and tumor cell pluripotency. This study provides a strong rationale to target Dclk1 as a treatment strategy for colorectal cancer.

MicroRNAs (miRNAs) offer great potential as cancer biomarkers. The importance of miRNAs profiling in tissue and body fluids in colorectal cancer (CRC) have been addressed respectively in many studies. The purpose of our study is to systematically assess the expression of miRNAs in cancer tissue and matched plasma samples and to evaluate their usefulness as minimally invasive diagnostic biomarkers for the detection of CRC. The study was divided into two phases: firstly, qRT-PCR based TaqMan Low Density MiRNA Arrays (TLDAs) was used to screen the differentially expressed miRNAs in 6 plasma samples of CRC patients and 6 healthy controls. Secondly, marker validation by stem-loop reverse transcription real-time PCR using an independent set of paired cancer tissues (n = 88) and matched plasma samples (CRC, n = 88; control, n = 40). Correlation analysis was determined by Pearson’s test. Receiver operating characteristic curve analyses were applied to obtain diagnostic utility of the differentially expressed miRNAs. Target gene prediction and signal pathway analyses were used to predict the function of miRNAs. TLDAs identified 42 miRNAs, which were differentially expressed in patients and healthy individuals. Five of them (miR-375, miR-150, miR-206, miR-125b and miR-126*) were chosen to be validated in plasma and tissue samples. The results indicated that for plasma sample, miR-375 (p < 0.0001) and miR-206 (p = 0.0002) were dysregulated and could discriminate CRC patients from healthy controls. For tissue samples, miR-375 (p < 0.0001), miR-150 (p < 0.0001), miR-125b (p = 0.0065) and miR-126*(p = 0.0009) were down-regulated. miR-375 was significantly down-regulated and positively correlated in both tissue and plasma samples (r = 0.4663, p = 0.0007). Gene ontology and signal pathway analyses showed that most of the target genes that were regulated by miR-375 were involved in some critical pathways in the development and progression of cancer. Our results indicate that the down-regulation of miR-375 in plasma and tissue is matched in CRC. Moreover, bioinformatics prediction revealed miR-375 association with some critical signal pathways in the development and progression of CRC. Therefore, plasma miR-375 holds great promise to be an alternative tissue biomarker for CRC detection.

Aberrant O‐glycosylation is frequently observed in colorectal cancer (CRC) patients, but it is unclear if it contributes intrinsically to tumorigenesis. Here, we investigated the biological consequences of aberrant O‐glycosylation in CRC. We first detected the expression profile of Tn antigen in a serial of human CRC tissues and then explored the genetic and biosynthetic mechanisms. Moreover, we used a human CRC cell line (LS174T), which express Tn antigen, to assess whether aberrant O‐glycosylation can directly promote oncogenic properties. It showed that Tn antigen was detected in around 86% human primary and metastatic CRC tissues. Bio‐functional investigations showed that T‐synthase and Cosmc were both impaired in cancer tissues. A further analysis detected an occurrence of hypermethylation of Cosmc gene, which possibly caused its loss‐of‐function and a consequent inactive T‐synthase. Transfection of LS174T cells with WT Cosmc restored mature O‐glycosylation, which subsequently down‐regulated cancer cell proliferation, migration and apoptotic‐resistant ability. Significantly, the expression of MUC2, a heavily O‐glycosylated glycoprotein that plays an essential role in intestinal function, was uniformly reduced in human CRC tissues as well as in LS174T cells. These data suggest that aberrant O‐glycosylation contributes to the development of CRC through direct induction of oncogenic properties in cancer cells.

MicroRNA-375 suppresses human colorectal cancer metastasis by targeting Frizzled 8