CD9 and breast cancer: The population levels of activated T cells were comparable for breast cancer cells treated by BP-αCD3-αEGFR-ARC Exos, αCD3-αEGFR Exos, CD9-CD38/αCD3-αEGFR Exos, and a mixture (1:1) of BP-ARC Exos and αCD3-αEGFR Exos.