PLAGL2 and POFUT1 are regulated by an evolutionarily conserved bidirectional promoter and are collaboratively involved in colorectal cancer by maintaining stemness.

BACKGROUND: Our previous study revealed that PLAGL2 or POFUT1 can promote tumorigenesis and maintain significant positive correlations in colorectal cancer (CRC). However, the mechanism leading to the co-expression and the underlying functional and biological implications remain unclear. METHODS: Clinical tumor tissues and TCGA dataset were utilized to analyze the co-expression of PLAGL2 and POFUT1. Luciferase reporter assays, specially made bidirectional promoter vectors and ectopic expression of 3'UTR were employed to study the mechanisms of co-expression. In vitro and in vivo assays were performed to further confirm the oncogenic function of both. The sphere formation assay, immunofluorescence, Western blot and qRT-PCR were performed to investigate the effect of both genes in colorectal cancer stem cells (CSCs). FINDINGS: PLAGL2 and POFUT1 maintained co-expression in CRC (r = 0.91, p < .0001). An evolutionarily conserved bidirectional promoter, rather than post-transcriptional regulation by competing endogenous RNAs, caused the co-expression of PLAGL2 and POFUT1 in CRC. The bidirectional gene pair PLAGL2/POFUT1 was subverted in CRC and acted synergistically to promote colorectal tumorigenesis by maintaining stemness of colorectal cancer stem cells through the Wnt and Notch pathways. Finally, PLAGL2 and POFUT1 share transcription factor binding sites, and introducing mutations into promoter regions with shared transcription regulatory elements led to a decrease in the PLAGL2/POFUT1 promoter activity in both directions. INTERPRETATION: Our team identified for the first time a bidirectional promoter pair oncogene, PLAGL2-POFUT1, in CRC. The two genes synergistically promote the progression of CRC and affect the characteristics of CSCs, which can offer promising intervention targets for clinicians and researchers. FUND: National Nature Science Foundation of China, the Hunan province projects of Postgraduate Independent Exploration and Innovation of Central South University.

DEAD-box helicase 27 plays a tumor-promoter role by regulating the stem cell-like activity of human colorectal cancer cells.

BACKGROUND: Cancer stem cells (CSCs) are responsible for all important characteristics of tumors. DEAD-box helicase 27 (DDX27) is a member of the DEAD-box RNA helicase family, and there have been only a few studies on DDX27 function in cancer cells. This study is aimed at exploring whether DDX27 has any relation to tumorigenesis of colorectal cancer (CRC) and elucidating the potential mechanism. METHODS: Data from Catalog Of Somatic Mutations In Cancer, Gene Expression Omnibus, and The Cancer Genome Atlas databases reveal that DDX27 is overexpressed in CRC tissues. qRT-PCR and Western blots were used to evaluate the expression level of DDX27 in 40 paired clinical CRC samples. DDX27 was knockdown in HT29 and HCT116 cell line with shRNA. Then CCK-8, colony formation assay and flow cytometry assay were performed to examine proliferative ability, cell cycle and sensitivity to 5-fluorouracil. Sphere-formation assay and in vivo subcutaneous tumor-formation assay were used to assess self-renewal in vitro and vivo as well as the tumor-initiating potential. RESULTS: DDX27 is upregulated in CRC tissues and downregulation of DDX27 inhibits proliferation of colorectal cancer cell and promotes sensitivity to 5-fluorouracil. Downregulation of DDX27 can downregulate the gene expression of known CSC markers in CRC cells, inhibit sphere-formation ability, and promote colonosphere differentiation. Downregulation of DDX27 in CSCs can decrease the tumor-initiating ability of CRC cells in vivo. CONCLUSION: DDX27 may play a tumorpromoter role of CRC by regulating the stem cell-like activity of CRC cells.

Overexpression of NELFCD promotes colorectal cancer cells proliferation, migration, and invasion.

PURPOSE: Negative elongation factor complex member C/D (NELFCD), mapped to chromosome 20q13.32, has been found to be significantly overexpressed in colorectal cancer (CRC) by our previous research. However, whether its overexpression contributes to CRC development is unknown. We aimed to explore the biological and clinical roles of NELFCD in CRC. MATERIALS AND METHODS: The expression of NELFCD was detected by qRT-PCR and Western blot. The biological function of NELFCD on CRC cell proliferation, migration, invasion, and apoptosis was detected by cell counting kit-8, plate colony formation assay, transwell migration and invasion assays, and flow cytometry in vitro and by murine xenograft tumor growth in vivo. Moreover, we evaluated the correction between its expression level and clinicopathologic parameters. RESULTS: We found NELFCD was overexpressed in 50 pairs of CRC tissues in comparison to the adjacent nontumor tissues (P<0.05). Knockdown of NELFCD significantly impaired cell proliferation, migration and invasion abilities, facilitated cell apoptosis in vitro, and inhibited tumorigenesis of CRC cells in vivo. NELFCD levels were remarkably connected with tumor location in CRC patients. CONCLUSION: NELFCD is overexpressed and plays an oncogenic role in CRC. Targeting NELFCD may provide a potential therapeutic option for NELFCD-amplified tumors.