CTLA4 and cancer: The development of immune checkpoint inhibitors (ICI) targeting cytotoxic T lymphocyteantigen 4 (CTLA-4), programmed cell death protein 1 (PD-1), or their ligands (PD-L1) is amilestone in cancer therapy,1 andgrowing evidence suggests that they induce durable treatment responses and prolong survivalacross multiple types of cancer.2-4 Recently, the clinical application of anti-lymphocyte activation gene3 (LAG-3) therapy has been approved by FDA, providing new options for cancerpatients.5 Nevertheless, manypatients may eventually discontinue ICI therapy because of disease progression.