A tissue microarray representing 248 clinically annotated stage I-II NSCLC cases was stained using immunohistochemistry (IHC) and scored for HHSP proteins namely, SHH, PTCH1, SMO, GLI1, and GLI2; as well as, ALDH1A1, a putative cancer stem cell marker. Data was analyzed for correlation between IHC staining, EGFR and KRAS mutations, and clinical characteristics including relapse-free survival (RFS) and overall survival (OS).
In adenocarcinoma, there were significant correlations of IHC expression between SHH and downstream HHSP receptor SMO (p = 0.017) and transcription factor GLI1 (p = 0.001), while SMO correlated with GLI1 (p = 0.007). In squamous cell carcinoma, SHH significantly correlated with GLI2 protein expression (p = 0.003). After multiple testing correction, there was no significant correlation between any of the six markers and RFS or OS.
Key downstream components of the HHSP show correlation with sonic hedgehog ligand (SHH) expression, suggesting that ligand-dependent signaling is more prevalent in primary NSCLC tumors. Surprisingly, in early-stage NSCLC, there were no significant correlations between HHSP proteins or ALDH1A1 and RFS or OS.