The aim of the study was to investigate the correlation between claudin (CLDN) protein expression and clinicopathological parameters as well as survival in histological subtypes of non-small cell lung cancer. Archived surgical resection specimens of 137 pathologic stage I primary bronchial cancers including 49 adenocarcinomas of non-lepidic variants (ADC), 46 adenocarcinomas of lepidic variants (L-ADC), and 42 squamous cell carcinomas (SCC) were examined. Immunohistochemistry (IHC) using antibodies against CLDN1,-2,-3,-4,-7 proteins as well as semiquantitative estimation (IHC scores 0-5) were performed. Claudin IHC scores of L-ADC differed significantly from ADC (CLDN1: p = 0.009, CLDN2: p = 0.005, CLDN3: p = 0.004, CLDN4: p = 0.001, CLDN7: p < 0.001, respectively) and SCC (CLDN1: p < 0.001, CLDN3: p < 0.001, CLDN7: p < 0.001, respectively). Highly significant CLDN3-CLDN4 parallel expression could be demonstrated in ADC and L-ADC (p < 0.001 in both), which was not observed in SCC (p = 0.131). ADC and SCC showed no correlation with smoking, whereas in case of L-ADC heavier smoking correlated with higher CLDN3 expression (p = 0.020). Regarding claudin expression and survival, in SCC significant correlation could be demonstrated between CLDN1 IHC positivity and better survival (p = 0.038). In NSCLC as a whole, high CLDN2 expression proved to be a better prognostic factor when compared with cases where CLDN2 IHC score was 0-1 vs. 2-5 (p = 0.009), however, when analyzed separately, none of the histological subgroups showed correlation between CLDN2 expression and overall survival. The claudin expression pattern was significantly different not only between the SCC-ADC and SCC-L-ADC but also between the L-ADC and ADC histological subgroups, which strongly underlines that L-ADC represents a distinct entity within the ADC group. CLDN1 overexpression is a good prognostic factor in NSCLC, but only in the SCC subgroup.
Keywords: Claudin; Immunohistochemistry; Lung cancer; Survival.