Mmp expression is required for the tumour invasion since blocking its activity through the expression of Timp (Tissue inhibitor of metalloproteases) restrained scrib- + RasACT tumour cells from fusing with and invading the brain lobes but did not abrogate tumour overgrowth or restore pupal development [our unpublished observations, [16,18]]. The gene discussed is TIMP1; the disease is neoplasm.