The functional and prognostic relevance of PD1- or CTLA4-expressing tumor cells is controversial [12,41]: some groups have suggested that PD1-expressing tumor cells enhance tumor growth (by increasing the level of effector molecules responsible for cellular proliferation), whereas others showed a correlation between PD1-expressing lung cancer and inhibited proliferation (mediated by downregulated AKT and ERK1/2 phosphorylation). The gene discussed is CTLA4; the disease is lung cancer.