Loss of heterozygosity of MIR15A/MIR16-1, negative regulators of the antiapoptotic gene BCL2, is not common in odontogenic keratocysts

Objectives. The odontogenic keratocyst (OKC) is an aggressive odontogenic cyst that has a high recurrence rate. Apart from PTCH1 mutations, few molecular alterations are described in OKCs. Low expression of microRNAs (miRNAs) miR-15a and/or miR-16-1 in association with increased expression of their target, Bcl-2, have been previously found in OKC. In humans, MIR15A and MIR16-1 are clustered at chromosome position 13 q14, and loss of heterozygosity (LOH) at this locus occurs in different tumors. We aimed to determine whether deletion at 13 q14 is a potential mechanism leading to miR-15a/16-1 aberrant expression in OKC. Methods. Genomic DNA was extracted from 15 formalin-fixed, paraffin-embedded microdissected OKC cases. The polymorphic DNA markers D13S272 and D13S273 on chromosome 13 q14.3, around MIR15A/MIR16-1, were amplified by polymerase chain reaction. LOH was examined by capillary electrophoresis DNA-fragment analysis. Results. The D13S272 marker had no LOH in 12 informative cases, whereas 2 out of 9 informative cases (22%) had LOH at the D13S273 marker. Conclusions. An LOH event at MIR15A/MIR16-1 locus is not common in OKC. The mechanism underlying the regulation of miR-15a and miR-16-1 expression in OKC remains to be determined.