To investigate whether the tumor suppressor miR-34a can regulate miR-21 through CD24/Src signalling, and to elucidate a possible role for AP-1 family members in such a regulation, co-transfection experiments were performed either with PM-34a, an expression construct for constitutively active Src (A-Src), or with a combination of both. The gene discussed is SRC; the disease is neoplasm.