Finally, cluster 4 showed enrichment for SP7 and OLIG1, which has been previously shown to have prognostic value in NSCLC [77], as well as TP63, the master regulator of squamous differentiation [43] that correlates with COL4A6 expression in this cluster (Additional file 1: Fig. S1D). This evidence concerns the gene COL4A6 and non-small cell lung carcinoma.