Abstract 4137: Loss of LKB1 mediates an immune inert phenotype in human lung adenocarcinoma
Authors: Denning Warren L. , Skoulidis Ferdinandos , Shen Li , Papadimitrakopoulou Vassiliki , Diao Lixia , Lou Yanyan , Byers Lauren A. , Wang Jing , Canales Jaime R. , Wistuba Ignacio I. , Weinstein John , Gibbons Don L. , Heymach John V. 
Published: July 2016

Abstract
Background: We recently have reported that co-mutations within KRAS-mutated lung adenocarcinoma (LUAD) define a distinct biological phenotype and may offer insights into therapeutic targeting using this classification system. The analysis revealed striking differences in checkpoint ligand expression and T cell infiltration between TP53 and STK11 (LKB1) co-mutated KRAS LUAD. We, therefore, hypothesized that loss of LKB1promotes an immune-suppressed phenotype in KRAS LUAD. To test this, we analyzed 100 immune-related genes from The Cancer Genome Atlas datasets, as well as three other sets of resected tumors from NSLC patients from MD Anderson Cancer Center.
Results: Our results revealed that tumors lacking LKB1 (LKB1-loss), as defined by mutation or gene-expression signature, resulted in a down regulation of: tumor associated immunosuppressive ligands, PD-L1, PD-L2, B7-H3, B7-H4, HVEM; T cell associated immunosuppressive ligands PD-1, CTLA-4, BTLA; co-stimulation ligands such as CD80, -86, -40L, and -40. We further examined if this loss of immunosuppression and co-stimulation resulted in changes in markers of T cell phenotypes. Indeed, tumors lacking LKB1-loss tumors demonstrated a distinct lack absence of several T cell markers including CD3, -4, & -8, but also RORC, T-bet, GATA-3, and FoxP3. To determine if myeloid cell populations, known mediators of immune suppression, were also diminished in LKB1-loss tumors, we analyzed expression of CD11c, -103, -11b, -68, and CD33. Consistent with T cell makers and suppressive ligand markers, myeloid markers were down regulated in LKB1-loss tumors. Because common immune suppression markers were lost, we then examined the expression of antigen presentation (HLA-I, HLA-II) and amino acid transporters as possible alternative methods for immune suppression. In LKB1-loss tumors, both HLA-I and HLA-II markers were down regulated, compared to tumors with intact LKB1 expression. Furthermore, genes associated with the antigen presentation complex, LMP2, TAP1&2, and B2M were also down regulated. In contrast to the immune markers described above, cationic transporters (SLC7A2), anionic transporters (SLC7A11), and neutral transporters (SLC3A2) were universally upregulated in LKB1-loss tumors.
Conclusions: LKB1 loss is associated with an inert immune phenotype. Our data suggests that reduced antigen presentation and amino acid depletion, but not checkpoint factors or MDSCs, are likely mediator of this phenotype.
Citation Format: Warren L. Denning, Ferdinandos Skoulidis, Li Shen, Vassiliki Papadimitrakopoulou, Lixia Diao, Yanyan Lou, Lauren A. Byers, Jing Wang, Jaime R. Canales, Ignacio I. Wistuba, John Weinstein, Don L. Gibbons, John V. Heymach. Loss of LKB1 mediates an immune inert phenotype in human lung adenocarcinoma. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 4137.