Spatially resolved analysis of TGF/BMP signalling in pancreatic ductal adenocarcinoma by digital pathology identifies patient subgroups with adverse outcome.

BACKGROUND: Transforming Growth Factor (TGF) and Bone Morphogenetic Protein (BMP) signalling critically influence pancreatic ductal adenocarcinoma (PDAC) progression, with TGF-B paradoxically exerting both tumour-promoting and -suppressive effects. Parallel to this observation, the specific context-dependent, spatial dynamics of these pathways and their interaction with the tumour microenvironment (TME) remain poorly understood. METHODS: We performed a spatially resolved analysis of PDAC on a multi-region tissue microarray cohort of 117 curatively resected PDAC specimens consisting of tumour centre (TC), tumour front (TF), and stromal(-predominant) tissue cores each. Protein (ID1, pSMAD2) and mRNA (TGF-A, TGF-B1/2, BMP4, GREM1) expression were assessed in each tissue compartment by immunohistochemistry and in situ hybridization, respectively, quantified by digital image analysis, and correlated with clinicopathologic features. RESULTS: ID1 was significantly overexpressed in PDAC cells compared to associated stroma (p < 0.01), while pSMAD2 was largely absent in PDAC cells, but preserved among associated stroma compartments, particularly in TF cores (p = 0.04). Higher stromal GREM1 signal correlated with reduced overall tumoural ID1 protein expression (p = 0.02), and TGF-B2(high)/TGF-A(low) stroma was significantly associated with worse survival (p < 0.01). Intratumoural TGF-B2 was inversely correlated with stromal pSMAD2 expression (p = 0.03) and was associated with lymph node involvement (p = 0.02). FOXP3(+) regulatory T-cells were significantly reduced in TGF-B2(high) tumours (p = 0.04), while higher tumoural TGF-B1 exhibited a trend towards increased FOXP3(+) cells (p = 0.08). CONCLUSIONS: Our spatial analysis reveals intratumoural heterogeneity of TGF/BMP signalling and its significance for PDAC progression. Notably, stromal TGF-B2 emerges as a prognostic biomarker, while TGF-B1 and ID1 are implicated in adverse clinical and pathologic features. These findings highlight the importance of TGF/BMP signalling niches in the TME with implications for PDAC biology and can inform the development of future therapeutic strategies.