CD82 and Familial prostate cancer: By genetic screening, KAI1 (CD82, kangai, or C33), one tetraspanin particularly relevant to tumor metastasis [2, 3], has first been identified in prostate cancer and later, also in other tumor entities, including those of the stomach, colon, cervix, skin, bladder, lung, pancreas, liver, thyroid, ovary, and breast [4-7].