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Background & Objective:MicroRNAs (miRNAs) are small noncoding RNAs of 20-23 nucleotides in length that regulate expression of target mRNA at post-transcriptional level. A-ccumulating evidence suggests that miRNAs play an important role in cancer i-nvolving tumori-genesis, invasiving and durg-resistance. However, research on GIST (gastrointestinal stromal tumor) is very limited. In our study, we used the miRNA microarray to screen the differentially expressed miRNA in GIST amo-ng the imatinib-resisted group, ma-lignant group and borderline group. Then we verified the results of miRNA microar-ray by real-time PCR. Meanwhile, we applied bioinformatics methods to predict the target genes of the differentially expressed miRNAs. Finally we summarized the rela-tionship between miRNAs and GIST. We also describe the potential mechanism of miRNAs affecting the tumorgenesis, progession and drug-resistance in GIST. The re-sult of our study suggests that miRNAs may prove to be a key position of the devel-opment and drug-resistance in GISTs.Methods:10 GIST samples divided into imatinib-resisted group (n=4), malignant group (n=3), borderline group (n=3) were collected according to the clinical and pathologi-cal characters. After extracting the total RNA from these 10 samples, miRNA micro-array was applied to screen the differentially espressed miRNA. The most signifi-cantly expressed 7 miRNAs were chosen for further validation by qRT-PCR in 30 additional GISTs. Then the 7 miRNAs were evaluated for target genes using Miranda, TargetScan and PicTar database.The known and predicted target genes were mapped to signaling pathway of tumorigenesis, progession and drug-resistance using KEGG database.Results:1. Results from miRNA microarrays:The direct comparsion of imatinib-resisted group versus malignant group revealed 13 significantly differentially expressed miRNAs with p<0.05 and a fold change<0.5/>2. Five miRNAs (miR-15a, miR-16, miR-195, miR-335, miR-151-5p) were up-regulated and eight miRNAs (miR-1280, miR-140-5p, miR-320a, miR-135b, miR-664*, miR-483-5p, miR-140-3p, miR-574-3p) were down-regulated in imatinib-resisted group. Three miRNAs (miR-15a, miR-1280, miR-320a) were most significantly differentially expressed be-tween two groups; the direct comparsion of malignant group versus borderline group revealed 14 significantly differentially expressed miRNAs with p<0.05 and a fold change<0.5/>2. Five miRNAs (miR-720, miR-221, miR-130b, miR-10b, miR-135b) were up-regulated and nine miRNAs (miR-326, miR-24-1*, miR-145, miR-488, miR-218, miR-34a, miR-675*, miR-335, miR-505) were down-regulated in malignant group. Four miRNAs (miR-221, miR-135b, miR-675*, miR-218) were most signifi-cantly differentially expressed between two groups.2. Results from qRT-PCR:The expression of 3 miRNAs (miR-320a, miR-221, miR-675) were confirmed with good concordance between qRT-PCR and miRNA micro array.3. Results from bio informatics study:Differential expression of miR-15a, miR-221, miR-1280, miR-218, miR-675 may contribute to the malignant progression in GISTs. Their target genes included:KIT, PDGFRA, CD34, EGFR, PTEN, CCND, CDKN etc; Differential expression of miR-15a、miR-320a、miR-675 probably con-tribute to the imatinib-resistance in GISTs. Their target genes included:ABCA、ABCC, bcl-2 etc.Conclusions:1. Differential miRNAs expression profile between three different groups was de-tected using miRNA microarray.2. Three differentially expressed miRNAs (miR-320a, miR-221, miR-675) were confirmed in the qRT-PCR analysis.3. Some miRNAs may correlate to the tumorgenesis, development and imati-nib-resistance in GISTs.
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