MicroRNA-224 is associated with colorectal cancer progression and response to 5-fluorouracil-based chemotherapy by KRAS-dependent and -independent mechanisms.
BACKGROUND
Colorectal cancers arise from benign adenomas, although not all adenomas progress to cancer and there are marked interpatient differences in disease progression. We have previously associated KRAS mutations with disease progression and reduced survival in colorectal cancer patients.


METHODS
We used TaqMan low-density array (TLDA) qRT-PCR analysis to identify miRNAs differentially expressed in normal colorectal mucosa, adenomas and cancers and in isogeneic KRAS WT and mutant HCT116 cells, and used a variety of phenotypic assays to assess the influence of miRNA expression on KRAS activity, chemosensitivity, proliferation and invasion.


RESULTS
MicroRNA-224 was differentially expressed in dysplastic colorectal disease and in isogeneic KRAS WT and mutant HCT116 cells. Antagomir-mediated miR-224 silencing in HCT116 KRAS WT cells phenocopied KRAS mutation, increased KRAS activity and ERK and AKT phosphorylation. 5-FU chemosensitivity was significantly increased in miR-224 knockdown cells, and in NIH3T3 cells expressing KRAS and BRAF mutant proteins. Bioinformatics analysis of predicted miR-224 target genes predicted altered cell proliferation, invasion and epithelial-mesenchymal transition (EMT) phenotypes that were experimentally confirmed in miR-224 knockdown cells.


CONCLUSIONS
We describe a novel mechanism of KRAS regulation, and highlight the clinical utility of colorectal cancer-specific miRNAs as disease progression or clinical response biomarkers.
Division of Cancer Research, Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
E B
EB
Amankwatia
Bioinformatics and Biostatistics Service, Cancer Research UK, 44 Lincolns Inn Fields, London WC2A 3PX, UK.
P
P
Chakravarty
Department of Pathology, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
F A
FA
Carey
Division of Cancer Research, Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
S
S
Weidlich
Division of Cancer Research, Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
R J C
RJ
Steele
Division of Cancer Research, Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
A J
AJ
Munro
1] Division of Cancer Research, Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK [2] CRUK Molecular Pharmacology Unit, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
C R
CR
Wolf
Division of Cancer Research, Medical Research Institute, University of Dundee, Ninewells Hospital and Medical School, Dundee DD1 9SY, UK.
G
G
Smith
D000236:Adenoma / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D000818:Animals; D000964:Antimetabolites, Antineoplastic / Q000494:pharmacology; D017209:Apoptosis / Q000187:drug effects; D049109:Cell Proliferation / Q000187:drug effects; D015179:Colorectal Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000473:pathology*; D018450:Disease Progression; D019008:Drug Resistance, Neoplasm / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay; D005472:Fluorouracil / Q000494:pharmacology*; D015972:Gene Expression Regulation, Neoplastic; D006801:Humans; D008113:Liver Neoplasms / Q000188:drug therapy / Q000235:genetics / Q000556:secondary*; D008207:Lymphatic Metastasis; D051379:Mice; D035683:MicroRNAs / Q000235:genetics*; D009154:Mutation / Q000235:genetics; D041681:NIH 3T3 Cells; D009361:Neoplasm Invasiveness; D009367:Neoplasm Staging; D011379:Prognosis; D011518:Proto-Oncogene Proteins / Q000235:genetics*; D016283:Proto-Oncogene Proteins p21(ras); D012333:RNA, Messenger / Q000235:genetics; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction; D014407:Tumor Cells, Cultured; D018631:ras Proteins / Q000235:genetics*
D000964:Antimetabolites, Antineoplastic; C117307:KRAS protein, human; C546140:MIRN224 microRNA, human; D035683:MicroRNAs; D011518:Proto-Oncogene Proteins; D012333:RNA, Messenger; D016283:Proto-Oncogene Proteins p21(ras); D018631:ras Proteins; D005472:Fluorouracil