Dysregulation of apoptotic pathways in chordoma involving FAS and FASL: implications on notochord regression in zebrafish model

Chordoma is a rare malignant bone tumor arising from notochord remnants, characterized by local invasiveness and variable tendency for recurrency. Given the implication of apoptosis in notochord regression, we studied the expression of 8 proapoptotic genes mapping in 1p36 region by RT-PCR in 32 tumours showing loss of heterozigosity (LOH) in 83% of cases. None of the analyzed tumour expression profiles overlaps with that of the control and the absence of 1p36 LOH has been correlated to a better prognosis. As the apoptotic pathway mediated by FAS-FASL was found to be involved in notochord regression, we studied their expression in 34 chordomas and observed that most of them express FAS, but not FASL. To verify a possible implication of FAS/FASL pathway dysfunction during tumorigenesis, we started in vivo studies on zebrafish. We investigated zfas/zfasl expression in embryos’ total RNA during different developmental stages and observed that, while zfas has maternal and ubiquitous zygotic expression, zfasl has maternal and specific developmental stages expression. Notochordal cells were then sorted by FACS, following the injection of a GFP construct activated by a specific physaliphorous cell promoter, to study zfas/zfasl expression. While zfas expression was detected at both 24hpf and 48hpf, zfasl was not found expressed; further developmental stages will be studied to define the zfas/zfasl expression profiles. Further analyses are in progress to address functional studies aimed at opportunely silencing zfas/zfasl. Aberrant phenotypes during development will be analyzed verifying whether the reactivation of zfas/zfasl pathway might rescue normal phenotype.