The expression analysis of NGAL and NGALR in clear cell renal cell carcinoma

Clear cell renal cell carcinoma (ccRCC) is the most prevalent subtype of kidney cancer. Recently, neutrophil gelatinase-associated lipocalin (NGAL) and its cell surface receptor, NGALR, have been reported to play critical roles in various tumors. However, the expression pattern and biological involvement of NGAL and NGALR in ccRCC remain unclear. In this study, we performed systematic analyses of 22 ccRCC data sets to characterize the expression patterns of NGAL and NGALR. The expression levels of NGAL and NGALR were significantly down-regulated in ccRCC samples in most of the data sets and the merged data set by meta-analysis. Furthermore, we also investigated the correlations between the expression of these two genes and their clinical associations with prognoses of ccRCC patients. Using integrated analyses of multiple ccRCC data sets, co-expression genes for NGAL and NGALR were identified. In addition, the sub-network analyses and biological pathway enrichment analyses were performed based on these co-expression genes. Finally, an activity score matrix for 23 pathways was constructed and confirmed as clinical prognostic signatures for ccRCC. Taken together, these findings determined the expression levels of NGAL and NGALR in ccRCC tumors, and provided the basis for a further examination of their biological roles.