MicroRNAs are short regulatory RNAs that negatively modulate gene expression at 
the post-transcriptional level, and are deeply involved in the pathogenesis of 
several types of cancers. To investigate whether specific miRNAs and their 
target genes participate in the molecular pathogenesis of laryngeal carcinoma, 
oligonucleotide microarrays were used to assess the differential expression 
profiles of microRNAs and mRNAs in laryngeal carcinoma tissues compared with 
normal tissues. The oncogenic miRNA, microRNA-21 (miR-21), was found to be 
upregulated in laryngeal carcinoma tissues. Knockdown of miR-21 by specific 
antisense oligonucleotides inhibited the proliferation potential of HEp-2 cells, 
whereas overexpression of miR-21 elevated growth activity of the cells, as 
detected by the colony formation assay. The cell number reduction caused by 
miR-21 inhibition was due to the loss of control of the G1-S phase transition, 
instead of a noticeable increase in apoptosis. Subsequently, a new target gene 
of miR-21, BTG2, was found to be downregulated in laryngeal carcinoma tissues. 
BTG2 is known to act as a pan-cell cycle regulator and tumor suppressor. These 
findings indicate that aberrant expression of miR-21 may contribute to the 
malignant phenotype of laryngeal carcinoma by maintaining a low level of BTG2. 
The identification of the oncogenic miR-21 and its target gene, BTG2, in 
laryngeal carcinoma is potentially valuable for cancer diagnosis and therapy.