In particular, to increase the coverage of low abundant tissue derived proteins, N-glycosylated peptides were selectively enriched by SPEG and analysed after de-glycosylation by PNGase F. The results of this multi-cancer comparison revealed that localized tumours display “specific biomarkers” for each individual cancer type as well as “common biomarkers” which derive from a systemic response to cancer. This evidence concerns the gene NGLY1 and cancer.