ABSTRACT
Long non-coding RNAs (lncRNAs) are aberrantly expressed in many disease conditions, including cancer. Accumulating evidence indicates that some lncRNAs may play critical roles in cancer progression and metastasis. Here, we identify a set of lncRNAs that are upregulated in metastatic subpopulations isolated from colon cancer HCT116 cells in vivo and show that one of these lncRNAs, which we name CALIC, is required for the metastatic activity of colon cancer cells. We show that CALIC associates with the RNA-binding protein hnRNP-L and imparts specificity to hnRNP-L-mediated gene expression. Furthermore, we demonstrate that the CALIC/hnRNP-L complex upregulates the tyrosine kinase receptor AXL and that knockdown of CALIC or AXL using shRNA in colon cancer cells attenuates their ability to form metastases in mice. These results suggest that the CALIC/hnRNP-L complex enhances the metastatic potential of colon cancer cells.
Subject(s)
Colonic Neoplasms/genetics , Gene Expression Regulation, Neoplastic , Liver Neoplasms/genetics , Proto-Oncogene Proteins/genetics , RNA, Long Noncoding/genetics , Receptor Protein-Tyrosine Kinases/genetics , Ribonucleoproteins/genetics , Animals , Cell Proliferation , Colonic Neoplasms/metabolism , Colonic Neoplasms/mortality , Colonic Neoplasms/pathology , Disease Progression , Female , HCT116 Cells , Humans , Liver Neoplasms/metabolism , Liver Neoplasms/mortality , Liver Neoplasms/secondary , Lymphatic Metastasis , Mice , Mice, Inbred BALB C , Mice, Nude , Protein Binding , Proto-Oncogene Proteins/antagonists & inhibitors , Proto-Oncogene Proteins/metabolism , RNA, Long Noncoding/antagonists & inhibitors , RNA, Long Noncoding/metabolism , RNA, Small Interfering/genetics , RNA, Small Interfering/metabolism , Receptor Protein-Tyrosine Kinases/antagonists & inhibitors , Receptor Protein-Tyrosine Kinases/metabolism , Ribonucleoproteins/metabolism , Signal Transduction , Survival Analysis , Xenograft Model Antitumor Assays , Axl Receptor Tyrosine KinaseABSTRACT
Aberrant activation of Wnt/ß-catenin signaling is a major driving force in colon cancer. Wnt/ß-catenin signaling induces the expression of the transcription factor c-Myc, leading to cell proliferation and tumorigenesis. c-Myc regulates multiple biological processes through its ability to directly modulate gene expression. Here, we identify a direct target of c-Myc, termed MYU, and show that MYU is upregulated in most colon cancers and required for the tumorigenicity of colon cancer cells. Furthermore, we demonstrate that MYU associates with the RNA binding protein hnRNP-K to stabilize CDK6 expression and thereby promotes the G1-S transition of the cell cycle. These results suggest that the MYU/hnRNP-K/CDK6 pathway functions downstream of Wnt/c-Myc signaling and plays a critical role in the proliferation and tumorigenicity of colon cancer cells.
Subject(s)
Cell Cycle , Cyclin-Dependent Kinase 6/metabolism , Proto-Oncogene Proteins c-myc/metabolism , RNA, Long Noncoding/metabolism , Wnt Signaling Pathway , Animals , Base Sequence , Carcinogenesis/genetics , Carcinogenesis/pathology , Cell Line, Tumor , Cell Proliferation , Clone Cells , Colonic Neoplasms/genetics , Colonic Neoplasms/pathology , Heterogeneous-Nuclear Ribonucleoprotein K/metabolism , Humans , Mice, Nude , RNA, Long Noncoding/genetics , Up-Regulation/geneticsABSTRACT
The transcription factor GATA6 is a critical regulator of cell proliferation and development in the gastrointestinal tract. We have recently reported that GATA6 induces the expression of the intestinal stem cell marker LGR5 and enhances the clonogenicity and tumorigenicity of colon cancer cells, but not the growth of these cells cultured under adherent conditions. Here we show that REG4, a member of the regenerating islet-derived (REG) family, is also a target of GATA6. We further demonstrate that REG4 is downregulated by overexpression of miR-363, which suppresses GATA6 expression. Moreover, we show that GATA6-mediated activation of REG4 enhances the growth of colon cancer cells under adherent conditions and is required for their tumorigenicity. Taken together, our findings demonstrate that GATA6 simultaneously induces the expression of genes essential for the growth of colon cancer cells under adherent conditions (REG4) and genes required for their clonogenicity (LGR5), and that the miR-363-GATA6-REG4/LGR5 signaling cascade promotes the tumorigenicity of colon cancer cells.
