IDO1 and breast cancer: Chemotherapy effectiveness in TNBC and Her2 breast cancer can be augmented through the involvement of the immune system.[37] IDO inhibition has been shown to synergize with various chemotherapeutic agents, improving efficacy in chemotherapy‐refractory breast cancer.[38] Our study demonstrated that lacidipine, especially at clinically used doses (0.5 mg kg−1 and 1 mg kg−1), significantly enhanced the antitumor effects of the chemotherapeutic agents DOX or cisplatin.