PRF1 and squamous cell lung carcinoma: Consistent with the immunohistochemistry results, in both lung adenocarcinoma and lung squamous cell carcinomas harboring HLA LOH, we identified a significantly elevated cytolytic activity score, which measures the levels of two genes upregulated upon CD8+ T cell activation, granzyme A (GZMA) and perforin (PRF1) (Rooney et al., 2015) (Figure 5C).