In fact, the CA IX activity level is higher in cancer types with a high number of CTCs; the quantity of exosomal CA IX is increased in hypoxia response; the release of the exosomal gangliocyte is correlated to the exosomal CA IX expression increase; the circulating CA IX is associated to tumors of urogenital origin; CA IX disrupts cell-cell and cell-matrix interactions by triggering tumour acidification. Here, CA9 is linked to cancer.