22A 6-Gene pSTAT3 Transcriptomic Score Identifies an Immunosuppressive, Chemotherapy-Resistant Phenotype and Predicts Poor Survival in Biliary Tract Cancer

Background

Phosphorylated STAT3 (pSTAT3) signaling promotes tumor progression and immune evasion in various solid malignancies. However, its specific prognostic role and association with the tumor microenvironment (TME) in biliary tract cancer (BTC) remain poorly defined. We sought to develop a robust transcriptomic pSTAT3 activity score to stratify BTC patients and elucidate the biological drivers of therapeutic resistance.

Methods

We analyzed transcriptomic data from 198 BTC patients at MD Anderson Cancer Center and utilized The Cancer Genome Atlas (TCGA-CHOL, n = 30 matched samples) for validation. A pSTAT3 activity score was constructed as the geometric mean of six canonical downstream targets (SOCS3, BCL2, MYC, MMP9, HGF, IL6) using the formula:

1 6 ∑ i = 1 6 log 2   ( E x p r e s s i o n + i 1 )

We correlated this score with proteomic data (RPPA), clinical outcomes (mPFS, mOS), and 29 established immune gene signatures to characterize the TME (Bagaev, Cancer Cell 2021).

Results

The 6-gene mRNA score demonstrated a positive correlation with proteomic pSTAT3 levels in TCGA, validating its biological relevance. In the MD Anderson cohort, High pSTAT3 status was a significant negative prognostic factor across all stages. High pSTAT3 patients exhibited significantly shorter median progression-free survival (2.3 vs. 6.9 months, p < 0.0001) and overall survival (7.5 vs. 15.4 months, p < 0.0001) compared to the Low pSTAT3 group. TME deconvolution revealed that High pSTAT3 tumors are characterized by a distinct immunosuppressive phenotype, significantly enriched for Treg and Th2 signatures, angiogenesis, and inflammation (PTGS2/COX-2), while showing downregulation of the gemcitabine transporter SLC29A1. Notably, first-line immunotherapy did not confer a survival benefit in the High pSTAT3 subgroup.

Conclusions

The proposed 6-gene pSTAT3 score robustly identifies a high-risk BTC subclass characterized by primary chemotherapy resistance and a Treg-enriched immunosuppressive TME. These findings suggest standard chemo-immunotherapy is ineffective for this subgroup, highlighting the need for novel targeted strategies to reverse this aggressive phenotype.