To functionally dissect the potential role of tumor-intrinsic BTLA in tumor cells, we knocked down endogenous BTLA using two short hairpin RNAs (shRNAs) that target the distinct sequences in NCI-H1299 and A549 cells (Supplementary Figure S3A), which led to a significant increase in cell proliferation and colony formation compared to the control, respectively (Figure 2A–C). Here, BTLA is linked to neoplasm.