Application of RNA Sequencing to identify transcriptome modification by DCLK1 in Colorectal Cancer Cells

Doublecortin like kinase 1 (DCLK1) is a cancer stem cell marker for the colorectal cancer (CRC). It plays critical roles in the oncogenesis, progression and metastasis of CRC. DCLK1 can be an intriguing therapeutic target for CRC treatment. However, the molecular mechanism of how DCLK1 functions is unclear currently. In our research, we aim to apply RNA-Sequencing (RNA Seq) technology, a high throughput massively Next Generation Sequencing approach, to monitor transcriptome changes due to DCLK1 over-expression in the CRC cells. In order to achieve our goal, RNA from quadruplicate samples from two clones of isogenic DCLK1 stable over-expression cells and the parental wild type HCT116 cells was sent for RNA Seq on the Illumina NextSeq500 platform. Differentially expressed (DE) genes were evaluated by t-test (P <0.05 and fold-change ±1.5 or greater) using two methods: (1) FWER; and (2) Benjamani and Hochberg FDR (false discovery rate) which corrects for multiple comparisons. Gene networks and functional analysis were evaluated using Ingenuity Pathways Analysis (IPA). We identified 1463 DE genes common for both DCLK1 overexpression clone A and clone B cells. IPA results indicated that 72 canonical pathways were significantly modified by DCLK1 over-expression (P<0.05), among which 9 out of the top 10 pathways are involved in the cell cycle regulation, indicating that DCLK1 might play its tumorigenesis role via activation of pathways facilitating cell proliferation, repression of pathways inhibiting cells proliferation and function against pathways facilitating cell apoptosis. Cell cycle analysis results confirmed the IPA findings, which demonstrated that DCLK1 over-expression cells had much less G0/G1 cells but much more S and G2/M cells (P<0.05). In conclusion, DCLK1 over-expression significantly modified transcriptome profile of CRC cancer cells. Control of the cell cycle regulation might be one of the critical mechanism for DCLK1 function. Our findings provide more direct evidence for the development of DCLK1 as a therapeutic target for CRC treatment, and will be of great benefit for the discovery of novel therapeutic target within the DCLK1 molecular network for the treatment of colorectal cancer patients.