Molecular studies of pulmonary carcinoids

Thirtyeight pulmonary carcinoids, 30 typicals (TPCs) and 8 atypical (APCs) were analyzed for membrane, cytoplasmic and/or nuclear immunohistochemical expression of Menin, -catenin, E-cadherin and p53 proteins using a Tissue Microarrays technique combined with mutational analysis. Statistical data were done by the Spearman’s Rho correlation and the SPSS (version 15.0) program was used for statistical analysis. Staining for cytoplasmic Menin was observed in 19/30 TPCs and 7/8 APCs. Membrane β-catenin expression was detected in 11/30 TPCs and 3/8 APCs, cytoplasmic expression in 8/30 TPCs and 4/8 APCs. Nuclear p53 staining was observed in only 2/38 PCs. Moreover, 24/30 TPCs and 8/8 APCs displayed membrane expression of E-cadherin. Cytoplasmic expression of Menin resulted positively associated with the cytoplasmic expression of β-catenin (P = 0.008), whereas β-catenin membrane staining showed positive correlations with cytoplasmic β-catenin (P = 0.022) and E-cadherin (P = 0.040) expressions. The DHPLC and direct sequencing of MEN1 (entire coding sequence), TP53 (exons 5-8) and CTNNB1 (exon 3) genes allowed to characterize several nucleotide variants. MEN1 gene variants were identified in 9/30 TPCs and in 5/8 APCs and included a frameshift mutation, 4 missense variants and 4 synonymous variants. Moreover, we found a novel intronic variant that is not predicted to have any effect on splicing. PCs with MEN1 variants presented an average higher level of cytoplasmic Menin stained cells compared with cases without MEN1 variants (P = 0.023). Analysis of TP53 allowed to identify 3 variants, one of which is associated with a high nuclear expression of p53. Mutational study of the CTNNB1 gene resulted negative and no nucleotide variants were detected. In conclusion, the study support a role of Menin and of theβ-catenin-Ecadherin complex in PCs, while the role of p53 results more limited.