US researchers have identified a protein that affects vitamin E?s retention in prostate cells and helps the vitamin slow cancer growth. Called alpha tocopherol associated protein, or TAP, the binding protein is known to perform important cellular functions, such as regulating the synthesis of cholesterol in the liver. But for the first time, a team at the University of Rochester has found it also disrupts an important signaling pathway in prostate cancer cells and suppresses growth of the cancer. Further, the protein appears to regulate retention of vitamin E in prostate cancer cells and increases the effect of vitamin E in limiting the proliferation of cancer cells, according to the team led by ShuYuan Yeh, assistant professor of urology and pathology. Their findings suggest that TAP facilitates the transport of vitamin E into prostate tissue and helps retain high concentrations of the vitamin in the cells. The scientific team also found that TAP increases vitamin E?s capacity to control the rapid growth of the cancer cells.