Table 4 summarises RNA-seq data sets retrieved from 17 different cancer types, and HTRA1 is expressed in all cancers examined with the highest levels detected in glioma, breast and pancreatic cancer. HTRA1 is broadly downregulated in cancer (Table 5), consist with a previous review [91]. In general, a reduced expression of HtrA1, and in some instances a complete absence of HtrA1, is associated with poor prognosis of many cancers such as ovarian, metastatic melanoma, breast carcinoma, prostate and lung tumours (Table 5) [92,93,94,95,96,97]. This evidence concerns the gene HTRA1 and central nervous system cancer.