In tumoroids the loss of Mir34a conferred resistance to 5-FU which was mediated by Csf1r. This study provides genetic evidence for a requirement of Mir34a-mediated Csf1r suppression for intestinal stem/secretory cell homeostasis and tumor suppression, and suggests that therapeutic targeting of CSF1R may be effective for the treatment of CRCs with defects in the p53/miR-34a pathway. The gene discussed is MIR34A; the disease is neoplasm.