FADD is amplified and overexpressed in laryngeal carcinomas, and overexpression is correlated with the presence of lymph node metastasis

Proc Amer Assoc Cancer Res, Volume 47, 2006 2566 The FADD (Fas-associated death domain) gene functions as an adaptor protein in Fas-mediated apoptosis. Recently, FADD was also reported to be involved in cell cycle progression. Phosphorylation of FADD at ser194 resulted in a nuclear localization and cell cycle arrest at G2/M. Interestingly, in normal prostate epithelium only nuclear staining of FADD phosphorylated at ser194 (p-FADD) was observed, whereas in prostate cancer non-phosphorylated FADD (np-FADD) was most prominent. This suggests that the regulatory effect of FADD on cell cycle progression seems to depend on the ratio of p-FADD and np-FADD. The question remains how the balance between p-FADD and np-FADD in tumor cells is regulated. Possibilities are decreasing serine kinase activity, increasing phosphotase activity or the relative increase of the non-phosphorylated protein. FADD is located within the chromosome 11q13 region that is amplified in 36% of head and neck carcinomas. We performed high-resolution 11q13-specific array CGH to determine the copy number and structure of the 11q13 amplicon. Within the 11q13 amplicon, only FADD was amplified in 29 out of 30 laryngeal/pharyngeal carcinomas, whereas other genes were only amplified in 28 or less cases. Quantitative Taqman RT-PCR of the 15 other genes within the 11q13 amplicon revealed that FADD showed the highest correlation in a Mann-Whitney test (p<0,0001) between an increased gene copy number and expression. Immunohistochemical staining with antibodies against FADD also showed a good correlation between amplification and expression (p=0,0023). Remarkably, the p-FADD levels were not or only at very low levels detectable. To validate the clinical significance, we immunostained 168 primary laryngeal carcinomas for expression of FADD. Overexpression correlated with regional lymph node metastasis (p=0.053). The odds ratio (OR) for FADD to predict lymph node-positive laryngeal carcinomas (1.997) was larger than that of cyclin D1 (1.304) and cortactin (1.427), two established marker genes within the 11q13 core amplicon. Our results suggest that overexpression of FADD might be a mechanism to enhance progression through the G2/M and thus implicate that FADD is a good candidate gene within the 11q13 amplicon responsible for the biological behaviour of carcinomas with 11q13 amplification.