A study by Cao et al. suggested that M.tb might repress Th1 immune response and promote lung cancer metastasis through the programmed cell death protein 1 (PD-1)/programmed death ligand 1 (PD-L1) signaling pathway, while in the opinion of Holla et al. the inhibition of TNF-α-mediated apoptosis via downregulation of the expression of tumor suppressor p53 could be a possible mechanism of mycobacteria-assisted tumorigenicity in type II epithelial cells [92,93]. This evidence concerns the gene PDCD1 and lung carcinoma.