Lower alpha diversity of Bifidobacteriaceae in HER2+ breast cancer patients treated with Trastuzumab [146]. • Probiotic supplements containing Bifidobacterium longum prevented docetaxel-induced weight gain in breast cancer patients [150]. •Bifidobacterium enriched in anti-PD-1 treated obese breast cancer mice [165]. Here, PDCD1 is linked to breast carcinoma.