We further demonstrate the ability of media formulations containing bacterially-derived R-spondin 1 and Gremlin 1 to sustain the growth of organoids derived from a number of tissue types such as murine colon, mammary gland and APCmin/− small intestinal tumours and human colon epithelial and colon adenocarcinoma biopsies. Here, GREM1 is linked to colon adenocarcinoma.