Association of PAK4 expression with overall survival in patients with non-small cell lung cancer (NSCLC).

Abstract

e21149 Background: P21-activated kinase 4 (PAK4) is a crucial effector of the Rho GTPases. It acts as a regulatory switch that controls a wide range of cellular functions and plays a pivotal role in cancer progression and metastasis. Very little is known about the expression and prognostic value of PAK4 in NSCLC. Methods: 17,689 NSCLC tumor samples were analyzed using next-generation sequencing (NextSeq, 592 Genes, or WES NovaSeq), immunohistochemistry (IHC), and whole transcriptome sequencing (NovaSeq) (Caris Life Sciences, Phoenix, AZ). PD-L1 expression was analyzed by IHC (Dako 22c3; PD-L1 positive: TPS >1%). TMB was measured by counting all somatic mutations found per tumor (TMB-high: >10 mutations/MB). Tumors with PAK4-high (H) and PAK4-low (L) expression were classified as those in top quartile and bottom 3 quartiles, respectively. Immune cell infiltrates were calculated by Quantiseq. Significance was determined using chi-square and Wilcoxon rank sum test and adjusted for multiple comparisons (q-value < 0.05). Survival was extracted from insurance claims data and calculated from the time of tissue collection to the last contact using Kaplan-Meier estimates. Results: There was no difference in median age, gender, smoking status, and histologic distribution between PAK-H and PAK-L tumors. Compared to PAK4-L, the PAK4-H was associated with higher frequency of co-mutations in TP53 (76.3% vs 63.9%, p < 0.0001) and RB1 (13.6% vs 8.1%, p < 0.0001). PAK4-H tumors were associated with greater genomic loss of heterozygosity (24.1% vs 16.4%, p < 0.0001), and expression of immune checkpoint genes ( LAG3, PDCD1, PDCD1LG2, CD274, IDO1, CTLA4, CD80, HAVCR2; p < 0.05). KRAS (including KRAS G12C) , BRAF, STK11, and EGFR mutations, and ALK and ROS1 fusions were less frequent in PAK4-H tumors (p < 0.001). A greater proportion of PAK4-H tumors were TMB-H (40.3% vs 33.3%, p < 0.0001) and PD-L1 negative (48.2% vs 40.8%, p < 0.001). PAK4-H tumors had lower infiltration of B cells, M1/M2 macrophages, CD8+ T-cells, and Tregs (p < 0.001). Overall survival (OS) was inferior among patients with PAK4-H tumors (median, 14.9 vs 21.5 months, HR = 1.28, 95% CI, 1.21-1.36, p < 0.001), which was driven by adenocarcinoma histology. Survival with immunotherapy was also inferior in patients with PAK4-H adenocarcinoma (median, 23.6 vs 30.3 months, HR = 1.23, 95% CI, 1.02-1.48, p = 0.03), but not squamous cell carcinoma. A similar trend in survival was noted in patients who received EGFR- and ALK inhibitors. Conclusions: PAK4-H expression in NSCLC is associated with a higher frequency of alterations predisposing to genomic instability, differentially modulated immune phenotype, and a lower frequency of actionable genomic alterations. Patients with PAK4-H adenocarcinoma have inferior OS, and survival with immunotherapy and targeted therapy. PAK4-H expression defines a subgroup of patients with un unmet need for novel treatment strategies.