Previous research by the Sponsor has identified that a protein called JAM-A regulates the levels of another protein called HER-2 in breast cancer cells. Both these proteins go up in breast cancer patients, and are associated with aggressive tumours that spread to other organs. Various anti-breast cancer drugs target HER-2, but these drugs often stop working in patients for reasons which are not fully understood. If we can create alternative drugs that attack HER-2 by inhibiting JAM-A signalling, we can help to stop or slow cancer growth and potentially tackle the drug resistance problem. In a previous HRB award to the Sponsor, a new inhibitor was designed to interfere with JAM-A signalling in breast cancer cells. In this summer research project, we will chemically modify this inhibitor to make it a better drug. I will then test the ability of the modified drug to stop breast cancer cell growth (in comparison to the original drug) in a variety of laboratory experimental approaches. This research will be important in expanding a growing body of evidence that JAM-A is a good target for new anti-cancer drugs; and has the long-term goal of improving the outlook for breast cancer patients in whom the anti-HER-2 drugs stop working.