Background:
The wnt signaling pathway has been implicated in colon and other cancers. nevertheless, few or no mutations of ctnnb1 (beta-catenin) have so far been described in brain cancer. we therefore examined the prevalence of constitutive activation of the wnt signaling pathway in brain cancer specimens as well as cancer cell lines.
Method:
We used polymerase chain reaction pcr and direct sequencing methods to investigate whether mutations in the ctnnb1 phosphorylation sites s33, s37, s41 and t45 were present in 68 brain tumours, including meningioma, astrocytoma, pituitary adenoma, neuroblastoma, metastasis to the brain, and cell lines.
Findings:
Ctnnb1 gene mutations were not found in either the original brain tumour specimens or the cell lines. however, a missense mutation of ctnnb1 was identified at residue 33, tct (ser) --> tgt (cys) in a patient with lung metastasis to brain. in addition, in vitro functional assay showed that the s33c mutant of beta-catenin did affect transcriptional activity in a tcf-4-luciferase reporter construct.
Conclusions:
These results indicate that the mutation of exon 3 of the ctnnb1 gene in brain tumours may be a rare event and yet may be required for a small subset of human metastatic brain tumours.