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. The gene discussed is GREM1; the disease is small intestine neoplasm.