MTSS1 and cancer: MTSS1 (metastasis suppressor-1), also known as MIM (Missing-In-Metastasis), MIM-B, BEG4 (Basal cell carcinoma-enriched gene 4) or KIAA0429, was first identified as a potential metastasis suppressor gene missing in metastatic bladder carcinoma cell lines [2] and subsequently investigated in some types of cancer.