Correlation of comprehensive molecular mapping of pancreatic ductal adenocarcinoma with XPO1 mRNA expression levels to potential clinical targets.
Authors: Seeber Andreas , Gruber Rebecca , Kocher Florian , Zimmer Kai , Puccini Alberto , Krause Harris Benjamin , Neureiter Daniel , Klieser Eckhard , Salcher Stefan , Martowicz Agnieszka , Lou Emil , El-Deiry Wafik S. , Fontana Elisa , Gulhati Pat , Khushman Moh'd M. , Fong Dominic , Lenz Heinz-Josef , Wolf Domink , Oberley Matthew James , Sokolova Viktorija 
Published: June 2023

4144 Background: Encouraging pre-clinical efficacy targeting Exportin-1 (XPO1) - a master regulator of tumor suppressor protein export - has been reported in pancreatic ductal adenocarcinoma (PDAC) and clinical trials are currently ongoing. However, limited data is available regarding expression and function of XPO1 in PDAC. Thus, we investigated XPO1 mRNA expression and its clinical and immune correlates in PDAC. Methods: 5,488 PDACs were tested at Caris Life Sciences (Phoenix, AZ) with NGS of DNA (WES) and RNA (WTS) . TMB-H was defined as ≥10 mutations/MB. The cohort was stratified in quartiles according to XPO1 mRNA expression status, and XPO1-high ( XPO1H) and XPO1-low ( XPO1L) expression were defined as ≥top and <bottom quartile of transcripts per million (TPM). Immune cell fraction was calculated by QuantiSeq method. Gene expression profiles were analyzed for transcriptomic signatures predictive of response to immune checkpoint inhibitors (T cell-inflamed score) and MAPK pathway activation (MPA). The Mann-Whitney U and X2 tests were applied as appropriate, with p-values adjusted for multiple comparisons. Real-world overall survival (OS) data was obtained from insurance claims. TGCA data were used to validate molecular, biological and immunological findings. Single-cell RNA analyses on a publicly available dataset were performed to elaborate cellular localization of XPO1. Results: Increased XPO1 mRNA expression was observed in metastatic lesions compared to primary tumors (p<0.001). Copy number amplification and mutation prevalence was comparable between XPO1H and XPO1L samples (p>0.05), along with similar rates of MSI-H/dMMR (1.3 vs 0.9%) and TMB-H (2.0 vs 1.3%; p>0.05). XPO1H PDACs were associated with a significant higher prevalence of T cell-inflamed tumors compared to XPO1L cases (58 vs 5%; p<0.05), consistent with higher immune cell infiltration in the XPO1H quartile as compared to XPO1L (p<0.05), except for immunosuppressive regulatory T cells and monocytes (p>0.05). XPO1H was associated with a higher MPA score as compared to XPO1L (2.4 vs -2.1 Arbitrary Units; p<0.05). XPO1H was associated with shorter OS (HR 1.09 [1.1-1.4], p=0.048). Validation studies using TCGA datasets corroborate our findings and confirmed increased immune cell infiltration as a function of XPO1. Moreover, single cell data revealed predominant and high expression of XPO1 in the tumor cell compartment. Conclusions: This is the first study comprehensively mapping XPO1 mRNA expression and immune-correlates in PDAC. We found that high XPO1 is linked to increased immune cell infiltration with a T cell-inflamed pattern. Our data provided a potential rationale to combine immune checkpoint therapy (+/- XPO1 inhibitors) in XPO1H PDACs.