Liver kinase B1 expression is associated with improved prognosis and tumor immune microenvironment features in small cell lung cancer

Alessandro Dal Maso ¹ Federica Ferrarini ² Giovanni Esposito ³ Sonia Anna Minuzzo ⁴ Anna Maria Puggia ⁵ Federica Pezzuto ⁶ Elisabetta Zulato ² Loc Carlo Bao ^1,4 Mattia De Nuzzo ^1,4 Alessandra Ferro ¹ Stefano Frega ¹ Giulia Pasello ^1,4 Fiorella Calabrese ⁶ Matteo Fassan ^7,8 Federico Rea ⁶ Valentina Guarneri ^1,4 Stefano Indraccolo ^2,4* Laura Bonanno ^1,4

• ¹ Medical Oncology 2, Veneto Institute of Oncology IOV - IRCCS, Padova, Italy
• ² Basic and Translational Oncology, Veneto Institute of Oncology IOV - IRCCS, Padova, Italy
• ³ Immunology and Molecular Oncology Diagnostics, Veneto Institute of Oncology IOV - IRCCS, Padova, Italy
• ⁴ Department of Surgery, Oncology and Gastroenterology, Università degli Studi di Padova, Padova, Italy
• ⁵ Anatomy and Pathological Histology, Veneto Institute of Oncology IOV - IRCCS, Castelfranco Veneto, Italy
• ⁶ Department of Cardiac, Toracic, Vascular Sciences and Public Health, University of Padova, Padova, Italy
• ⁷ Department of Medicine, University of Padova, Padova, Italy
• ⁸ Veneto Institute of Oncology IOV - IRCCS, Padova, Italy

Background Small cell lung cancer (SCLC) is characterized by early metastatic potential and poor prognosis. Liver kinase B1 (LKB1) is a tumor suppressor and a cell metabolism regulator. LKB1 downregulation has been associated with a cold tumor immune microenvironment (TIME). We aimed to analyze the role of LKB1 in SCLC in relation to its association with overall survival (OS) and TIME components.We retrospectively evaluated SCLC patients consecutively treated at our Institution from 1996 to 2020 with available tissue. LKB1, PD-L1 on tumor cells and on tumor immune-infiltrating cells, CD8 and FOXP3 were evaluated by immunohistochemistry (IHC), categorized according to predefined cut-offs. Primary endpoint was the description of LKB1 expression, secondary endpoints the association with prognosis and TIME features.Results Tissue samples of 138 out of 481 SCLCs were adequate for molecular analyses. Eighty patients had limited stage (LS) at diagnosis and 58 extended stage (ES). Median LKB1 IHC score was 4. Patients with IHC score > 4 (n = 67) were classified as LKB1-positive. The probability of LKB1 positivity was higher in LS (odds ratio 2.78, 95% confidence interval [95%CI] 1. 18-7.14). At data cut-off (January 2, 2024), 123 patients died. Median OS (mOS) was 14.0 months . mOS was significantly longer in patients with LKB1 positive expression (32.4 months ] vs 11.2 [95%CI 8.7-14.7]; p < 0.001). At multivariate analysis, positive LKB1 expression, LS and no weight loss at diagnosis were confirmed as independent positive prognostic factors. TIME features were evaluated in 70 patients. Unexpectedly, LKB1-negative samples were more likely to show CD8+ tumor infiltrating lymphocytes (TILs; p = 0.013). No association with PD-L1 expression nor the presence of FOXP3+ TILs was found.Conclusion LKB1 expression is a potential positive prognostic marker in SCLC. In this series, LKB1 expression was negatively associated with the presence of CD8+ TILs.