Caspase-8 silenced N-type invasive NB cell lines LAN-1 and IMR-32 were investigated for their sensitivity to dox, and compared to S-type noninvasive SH-EP NB cells expressing caspase-8.
A missense mutation was detected at codon 96, GCT (Alanine) to GTT (Valine), of the caspase 8 gene in one of the NB cell lines lacking caspase 8 expression.
A missense SNP in exon 10 of the CASP8 gene SNP D302H was associated with worse overall and event-free survival in patients with MYCN-amplified neuroblastoma tumors.
Among the five individual genes, only CASP8 methylation had a significant association with poor overall survival both in Japanese (hazard ratio = 3.1; 95% confidence interval = 1.5-6.4; P = 0.002) and German (hazard ratio = 4.8; 95% confidence interval = 2.1-11; P = 0.0002) neuroblastomas.
As frequent methylation of the CASP8 gene has also been reported in neuroblastoma, we investigated whether RASSF1A and CASP8 methylation were independent or related events.
By revealing no correlation between caspase-8 expression and MYCN amplification or other established variables of aggressive disease, our findings in a large cohort of neuroblastoma patients show that inactivation of caspase-8 is not a characteristic feature of aggressive neuroblastoma.
Contrarily, the presence of the -652 6N Del or the CASP8 302His variant was reported to be an unfavorable prognostic factor in colorectal cancer or neuroblastoma.
DNA derived from 70 neuroblastomas was amplified by PCR after bisulfate modification and subjected to analysis on a self-made oligoarray that utilized a polycarbodiimide-coated slide to detect methylation of six intragenic CpG islands of caspase 8.
Epigenetic alterations have been described as well: caspase-8 (CASP8) and RAS-association domain family 1 isoform A (RASSF1A) DNA-methylation are important events for the development and progression of neuroblastoma.
Exogenous interferon-γ upregulated expression of caspase-8 in 3 of 4 neuroblastoma cell lines and increased the contribution of TRAIL to NK cytotoxicity against 2 of the 3 lines; however, relatively little inhibition of cytotoxicity was observed when activated NK cells were treated with an anti-interferon-γ neutralizing antibody.
Furthermore, gemcitabine-induced apoptosis was observed irrespective of the caspase-8 status of neuroblastoma cells, which indicates that apoptosis depends on the mitochondrial pathway.
Furthermore, the methylation pattern of 14.3.3sigma, RASSF1A and of an intragenic segment of CASP8 was significantly different between MYCN amplified and single copy neuroblastoma suggesting a specific role of epigenetic alterations in aggressive neuroblastoma.
Here we show that four different retinoic acid (RA) derivatives also increase caspase-8 protein expression in neuroblastoma, medulloblastoma and small cell lung carcinoma cell lines.
However, approximately 20% of the neuroblastoma cell lines with methylated CASP8 alleles are also highly resistant to staurosporine (STS)- and radiation-induced cell death, presumably because cytochrome c is not released from mitochondria.
Our results show that restoration of active caspase-8 expression in a caspase-8-deficient NB cell line is necessary and sufficient to fully restore TRAIL sensitivity.
Re-expression of caspase-8 in neuroblastoma cells lacking endogenous caspase-8 expression was found to promote cell adhesion to extracellular matrix and to activate adhesion-dependent signaling pathways, such as the Erk kinase cascade.