Unexpectedly, before an obvious difference in tumor size was observed, the serum levels of αPD-L1 from the MC38 Rab27a−/− tumor-bearing mice were sharply lower than those from the MC38 tumor-bearing mice (Fig. 3f), probably due to the increased binding of circulating αPD-L1 to tumor PD-L1 during tumor development. The gene discussed is CD274; the disease is neoplasm.