Prognostic impact of CD68 and kallikrein 6 in human glioma.

AIMS To evaluate the expression of CD68 and kallikrein 6 in human gliomas, and investigate their prognostic significance for survival of brain cancer patients in comparison to some known prognostic markers. PATIENTS AND METHODS Histological sections of 51 primary astrocytic tumours (11 benign, 40 malignant) were immunohistochemically stained for CD68, cathepsin B, kallikrein 6 and Ki-67. CD68 and kallikrein 6 expressions were also analyzed by real-time PCR in nine brain tumour biopsies. RESULTS Both microglia and tumour cells expressed CD68. High CD68 and cathepsin B staining scores were significantly, more frequent in the malignant than in the benign tumours (p=0.036 and p=0.014, respectively). In contrast, the benign group presented a stronger immunoreactivity for kallikrein 6 compared with the malignant tumours (p=0.013). A CD68 staining score of tumour cells higher than 3 was a significant predictor of shorter overall survival (p<0.01) in all patients and of borderline significance in the malignant group (p=0.057). Strong CD68 staining was of greater predictive value in the subgroup of anaplastic astrocytomas (p=0.021). Furthermore, as expected on the basis of our previous studies, prognostic significance was confirmed for cathepsin B, but not for any of the other markers under evaluation. CONCLUSION Kallikrein 6 was down-regulated in malignant glioma, but this differential expression did not have an impact on patient prognosis. In contrast, immunostaining of glioma tissue for CD68 and for cathepsin B may be used for prognosis of survival in these patients. This finding suggests that besides the known role of cathepsin B in invasion and angiogenesis, CD68 may be also associated with glioma progression.