LRIG1-3 in gliomas: LRIG1 protein expression decreased in higher grade gliomas.

The LRIG gene family consists of LRIG1-3. While LRIG2 has been described as a tumor promoter, LRIG1 and LRIG3 have been identified as tumor suppressors in previous literature. Because of these contrasting roles, the expression of LRIG1-3 was examined across different grades of glioma, between primary and secondary glioblastoma and with focus on chemotherapy treatment. Human tumor tissue samples were extracted during neurosurgery and grouped among the WHO classification valid at the time of surgery. Quantitative western blot analysis, qPCR and immunofluorescence staining were performed. LRIG1 was less expressed in glioma compared to peritumoral tissue with additional decrease with ascending tumors grade. Further, secondary glioblastoma expressed more LRIG1 protein than primary. On mRNA level, the same was seen for LRIG2, were low grade glioma expressed significantly more LRIG2 than high grade glioma. And on protein level, secondary glioblastoma showed higher expression than primary. LRIG3 mRNA expression, in contrast, was significantly higher in grade II gliomas compared to surrounding control tissue, whereas chemotherapy did not significantly affect expression levels in glioblastoma. Our results reinforce suggestions that LRIG1-3 could function as diagnostic markers and therapeutic targets in the treatment of gliomas.