TLR4 and non-small cell lung carcinoma: Similarly, the inducible expression of PD-L1 by TLR4 could explain the correlated expression of PD-L1 and TLR4 in NSCLC in the present study, and this could be one potential mechanism of PD-L1 overexpression in TILs negative tumor microenvironment except for the genetic alternations in intrinsic immune resistance.