Three Distinct Stroma Types in Human Pancreatic Cancer Identified by Image Analysis of Fibroblast Subpopulations and Collagen

Abstract

Purpose: Cancer-associated fibroblasts have emerged to be highly heterogenous and can play multifaceted roles in dictating pancreatic ductal adenocarcinoma (PDAC) progression, immunosuppression, and therapeutic response, highlighting the need for a deeper understanding of stromal heterogeneity between patients and even within a single tumor. We hypothesized that image analysis of fibroblast subpopulations and collagen in PDAC tissues might guide stroma-based patient stratification to predict clinical outcomes and tumor characteristics. Experimental Design: A novel multiplex IHC-based image analysis system was established to digitally differentiate fibroblast subpopulations. Using whole-tissue slides from 215 treatment-naïve PDACs, we performed concurrent quantification of principal fibroblast subpopulations and collagen and defined three stroma types: collagen-rich stroma, fibroblast activation protein α (FAP)-dominant fibroblast-rich stroma, and α smooth muscle actin (ACTA2)-dominant fibroblast-rich stroma. These stroma types were assessed for the associations with cancer-specific survival by multivariable Cox regression analyses and with clinicopathologic factors, including CD8+ cell density. Results: FAP-dominant fibroblasts and ACTA2-dominant fibroblasts represented the principal distinct fibroblast subpopulations in tumor stroma. Stroma types were associated with patient survival, SMAD4 status, and transcriptome signatures. Compared with FAP-dominant fibroblast-rich stroma, collagen-rich stroma correlated with prolonged survival [HR, 0.57; 95% confidence interval (CI), 0.33–0.99], while ACTA2-dominant fibroblast-rich stroma exhibited poorer prognosis (HR, 1.65; 95% CI, 1.06–2.58). FAP-dominant fibroblast-rich stroma was additionally characterized by restricted CD8+ cell infiltrates and intense neutrophil infiltration. Conclusions: This study identified three distinct stroma types differentially associated with survival, immunity, and molecular features, thereby underscoring the importance of stromal heterogeneity in subtyping pancreatic cancers and supporting the development of antistromal therapies.

Cancer-Associated Fibroblast Subgroups Showing Differential Promoting Effect on HNSCC Progression

“…Although collagen was conventionally considered as a passive barrier to resist tumor cells [33], it is now evident that collagen is also actively involved in promoting tumor progression [32]. However, according to the recent results of Ogawa et al regarding the distinct stroma types based on stromal heterogeneity, patients with collagenrich cancer stroma showed decreased MMP gene expression levels with longer survival compared with other patients with cancer stroma highly expressing CAF markers such as α-SMA or FAP [20]. We observed that the fibroblast CAF-D group appeared to act as a physical barrier that tightly surrounds the cancer cells and protects from them expanding to the surrounding.…”

“…Considering this viewpoint, it is extremely interesting that breast cancer cell migration is dependent on collagen type I fibril alignment rather than stiffness [18] and that the collagen fibril diameter regulates cell morphology and invasiveness [19]. Interestingly, recent data have suggested that multiplex immunohistochemical (IHC) analyses of human pancreatic cancer stroma revealed a wide spectrum of phenotypical CAF variations in terms of protein expression levels of known fibroblastic markers such as α-SMA and fibroblast activation protein (FAP) [20]. In addition, they showed that welldifferentiated tumor ducts were tightly surrounded by α-SMA-dominant CAFs with thick collagen bands.…”

“…In addition, they showed that welldifferentiated tumor ducts were tightly surrounded by α-SMA-dominant CAFs with thick collagen bands. Furthermore, collagen-rich stroma was associated with prolonged cancerspecific survival compared with α-SMAor FAP-rich stroma [20]. Brisson et al showed that type III collagen (COL3) in the tumor microenvironment suppresses procarcinogenic collagen and myofibroblasts by regulating stromal organization [21].…”

[68Ga]Ga-DOTA-FAPI-04 and [18F]FDG PET/CT in the Assessment of Pancreatic Tumors: A Comparison Study

“…It is worth noting that the whole pancreas showed diffuse signi cant uptake in some patients, which covered the tumors. As we all know, desmoplasia and in ammation are two major hallmarks of pancreatic cancer [24,25]. In this circumstance, the combination with other examinations or close follow-up is of great importance for the accurate diagnosis.…”

Spatially confined sub-tumor microenvironments orchestrate pancreatic cancer pathobiology

“…Yet, tissue-based studies suggest that collagen- and ECM-rich stroma yields a better prognosis (Bolm et al, 2017; Erkan et al, 2008). Similarly, despite the wealth of functional studies showing that CAFs can promote PDAC progression and chemoresistance (Ligorio et al, 2019; Ogawa et al, 2021), higher stromal content can yield a better prognosis (Knudsen et al, 2017; Torphy et al, 2018) and the depletion of CAFs can result in more aggressive tumors in mice (Özdemir et al, 2015; Rhim et al, 2014). Thus, interactions between PDAC and stromal cells are likely not uniformly tumor promoting or inhibitory and the underlying intricate nuances have remained poorly understood.…”