STK11 loss leads to YAP1-mediated transcriptional activation in human KRAS-driven lung adenocarcinoma cell lines.

Serine Threonine Kinase 11 (STK11) loss of function (LoF) correlates with anti-PD-1 therapy resistance in patients with KRAS-driven lung adenocarcinoma (LUAD). The molecular mechanisms governing this observation remain unclear and represent a critical outstanding question in the field of lung oncology. As an initial approach to understand this phenomenon, we knocked-out (KO) STK11 in multiple KRAS-driven, STK11-competent human LUAD cell lines and performed whole transcriptome analyses to identify STK11-loss-dependent differential gene expression. Subsequent pathway enrichment studies highlighted activation of the HIPPO/YAP1 signaling axis, along with the induction of numerous tumor-intrinsic cytokines. To validate that YAP1-mediated transcriptional activation occurs in response to STK11 loss, we pursued YAP1 perturbation as a strategy to restore an STK11-competent gene expression profile in STK11-KO LUAD cell lines. Together, our data link STK11 loss with YAP1-mediated transcriptional activation, including the upregulation of immune-evasion promoting cytokines IL-6, CXCL8 and CXCL2. Further, our results raise the intriguing possibility that YAP1 antagonism may represent a therapeutic approach to counter anti-PD-1 therapy resistance in STK11-null, KRAS-driven LUADs by modulating tumor-intrinsic gene expression to promote a "hot" tumor immune microenvironment.

Functional assessment of somatic STK11 variants identified in primary human non-small cell lung cancers.

Serine/Threonine Kinase 11 (STK11) encodes an important tumor suppressor that is frequently mutated in lung adenocarcinoma. Clinical studies have shown that mutations in STK11 resulting in loss of function correlate with resistance to anti-PD-1 monoclonal antibody therapy in KRAS-driven non-small cell lung cancer (NSCLC), but the molecular mechanisms responsible remain unclear. Despite this uncertainty, STK11 functional status is emerging as a reliable biomarker for predicting non-response to anti-PD-1 therapy in NSCLC patients. The clinical utility of this biomarker ultimately depends upon accurate classification of STK11 variants. For nonsense variants occurring early in the STK11 coding region, this assessment is straightforward. However, rigorously demonstrating the functional impact of missense variants remains an unmet challenge. Here we present data characterizing four STK11 splice-site variants by analyzing tumor mRNA, and 28 STK11 missense variants using an in vitro kinase assay combined with a cell-based p53-dependent luciferase reporter assay. The variants we report were identified in primary human NSCLC biopsies in collaboration with the University of Vermont Genomic Medicine group. Additionally, we compare our experimental results with data from 22 in silico predictive algorithms. Our work highlights the power, utility and necessity of functional variant assessment and will aid STK11 variant curation, provide a platform to assess novel STK11 variants and help guide anti-PD-1 therapy utilization in KRAS-driven NSCLCs.