CD274 and obesity due to melanocortin 4 receptor deficiency: MDSCs can suppress T cell activity through many mechanisms, one of which is expressing PD-L1 to induce T cell exhaustion.49 50 In a preclinical study, inhibiting PD-L1 on MDSCs decreased their ability to suppress T cell activity, suggesting that obesity could also accelerate tumour progression by promoting the expression of PD-L1 on MDSCs.51 Finally, a preclinical study in a breast cancer model showed that although obesity accelerated tumour progression, anti-PD-1 treatment significantly reduced tumour burden by reshaping the local TME landscape.52