The expression of GLTSCR2, a candidate tumor suppressor, is reduced in seborrheic keratosis compared to normal skin

Glioma tumor-suppressor candidate region gene 2 (GLTSCR2) is a recently identified nuclear protein that interacts with the tumor suppressor PTEN. GLTSCR2 regulates the stability of PTEN, and is therefore believed to have a tumor suppressive function. In a recent study, we demonstrated that GLTSCR2 often exhibits genetic alterations and down-regulation in glioblastoma specimens. However, GLTSCR2 expression levels in human tumors and its mechanism of tumor suppression remain largely unknown. We performed an immunohistochemical examination of GLTSCR2 expression in samples of seborrheic keratosis (SK, n=69), a common benign skin tumor, and normal skin (n=23), and assessed the relationship between GLTSCR2 expression and the patients' clinicopathologic factors. Our results showed that GLTSCR2 expression in SK was significantly lower than in normal skin (p<0.001), and this decreased expression of GLTSCR2 was associated with patient age (p=0.045). Using in situ hybridization analysis, we found that mRNA expression of GLTSCR2 was reduced in tumor cells compared to normal skin. This is the first study analyzing the expression of GLTSCR2, a putative tumor suppressor, in SK and normal skin. Our results show a down-regulation of this protein in SK, indicating that GLTSCR2 may have a protective effect on the development of SK.