Cathepsin L in human meningiomas

Abstract

Background. Although meningiomas are considered as benign tumours, about 10% comprise a subgroup of atypical meningiomas, classified as WHO grade II, with greater likelihood of recurrences and/or aggressive behaviour, including the possibility of brain tissue invasion. The lysosomal cysteine endopeptidase cathepsin L plays a role in tumour cell invasion and malignant progression of cancer, and has been suggested as a prognostic marker for certain types of tumours.

Results. In our study, we compared the expression of cathepsin L in 30 meningiomas with their clinical invasiveness. Cathepsin L was determined by immunohistochemical analysis, quantitative real-time RT-PCR and Northern blot. We showed that expression of cathepsin L protein was significantly higher (p=0.019) in 9 atypical than in 21 benign meningiomas. Within the group of benign meningiomas, expression of cathepsin L was significantly lower in the transitional histological subtype. We measured the levels of cathepsin L A type of RNA splicing variants: LA, LAI and LAII, but not LAIII and not the LB variant, the latter being several times lower than the L A type. In contrast to protein levels, the levels of cathepsin L A, AI, AII RNA variants did not differ between histological subtypes or between benign and atypical meningiomas. The expression of total measured cathepsin L A, AI, AII RNA variants in the samples, taken from the centre and the periphery of the tumours, also showed no statistically significant differences.

Conclusions. These results indicate that cathepsin L protein over-expression may contribute to the development of the aggressive and possibly invasive character of atypical meningiomas and that it may be up regulated at the translational level.