CD28 and non-small cell lung carcinoma: Importantly, we found that the serum levels of 25(OH)D3 and 1α,25(OH)2D3 in patients with NSCLC were negatively correlated with PD-1, TIGIT, and Tim-3, but positively correlated with the CD28 level on cytotoxic T cells (figure 1A, B, and online supplemental figure S3A, B).