TRAIL receptors are expressed in both malignant and stromal cells in pancreatic ductal adenocarcinoma

Abstract

This study assesses the expression of all TNF-related apoptosis-inducing ligand (TRAIL) receptors in pancreatic ductal adenocarcinoma (PDAC) tumor tissue. We aimed to include TRAIL receptor expression as an inclusion parameter in a future clinical study using a TRAIL-based therapy approach for PDAC patients. Considering the emerging influence of PDAC desmoplastic stroma on the efficacy of anti-PDAC therapies, this analysis was extended to tumor stromal cells. Additionally, we performed PDAC stroma characterization. Our retrospective cohort study (N=50) included patients with histologically confirmed PDAC who underwent surgery. The expression of TRAIL receptors (DR4, DR5, DcR1, DcR2, and OPG) in tumor and stromal cells was evaluated by immunohistochemistry (IHC). The amount of tumor stroma was assessed by anti-vimentin IHC and Mallory's trichrome staining. The prognostic impact was determined by the univariate Cox proportional hazards regression model. An extensive expression of functional receptors DR4 and DR5 and a variable expression of decoy receptors were detected in PDAC tumor and stromal cells. Functional receptors were detected also in metastatic tumor and stromal cells. A poor prognosis was associated with low or absent expression of decoy receptors in tumor cells of primary PDAC. After assessing that almost 80% of tumor mass was composed of stroma, we correlated a cellular-dense stroma in primary PDAC with reduced relapse-free survival. We demonstrated that TRAIL functional receptors are widely expressed in PDAC, representing a promising target for TRAIL-based therapies. Further, we demonstrated that a low expression of DcR1 and the absence of OPG in tumor cells, as well as a cellular-dense tumor stroma, could negatively impact the prognosis of PDAC patients.

Keywords: TRAIL receptors; pancreatic adenocarcinoma; stroma characterization.

Figure 1

TRAIL receptor expression in PDAC tumor cells. A. Representative photomicrographs of TRAIL receptor expression (DR4, DR5, DcR1, DcR2, and OPG) in PDAC tumor cells by immunohistochemistry. The score (S) is indicated on each image. Magnification 200×, scale bar 100 µm. B. Quantitative analysis of TRAIL receptor immunohistochemistry by scoring system (N=50).

Figure 2

TRAIL receptor localization in tumor cells of PDAC patients. A. Representative microphotographs of TRAIL receptor localization by immunohistochemistry. C, cytoplasmic distribution of the receptor; M+C, membrane and cytoplasmic distribution. I and II, magnification 200×; III and IV, magnification 400×. Scale bar 100 µm. B. Percentages of distribution of TRAIL receptors in tumor cells of PDAC samples.

Figure 3

TRAIL receptor expression in PDAC stroma. A. Representative photomicrographs of TRAIL receptor expression (DR4, DR5, DcR1, DcR2, and OPG) in PDAC stromal cells by immunohistochemistry. Black arrows indicate tumor cells, and asterisks indicate stromal areas. I, negative staining for DR4; II, positive staining for DR4; III, positive staining for DR5; IV, positive staining for DcR1; V, positive staining for DcR2; VI, negative staining for OPG; VII, positive staining for OPG. Magnification 200×, scale bar 100 µm. B. Quantitative analysis of TRAIL receptor expression in tumor stroma (N=50).

Figure 4

TRAIL functional receptor expression in PDAC metastases. A. Representative photomicrographs of TRAIL functional receptor expression (DR4 and DR5) in tumor and stromal cells of liver metastases from PDAC by immunohistochemistry. Black arrows indicate representative tumor cells, and asterisks indicate stromal areas. Magnification 200×, scale bar 100 µm. B. Quantitative analysis of TRAIL functional receptor expression in tumor cells and stromal cells of liver metastases from PDAC (N=8).

Figure 5

PDAC stroma characterization and quantification. A. Representative images of the normal surrounding pancreatic and tumor stromal architecture in PDAC samples. Hematoxylin and eosin staining (H&E, I-III), anti-vimentin IHC (IV-VI) staining, and Mallory’s trichrome (VII-IX) staining are shown. Magnification 100×, scale bar 200 µm. B. Vimentin and Collagen quantification (N=50). Each circle represents the mean percentage of positive pixels in a sample. The dashed line indicates the total mean value.

Figure 6

Statistical correlations. Kaplan-Meier curves of PDAC patients according to DcR1 expression in tumor cells, OPG expression in tumor cells and stromal cellular density. OS, Overall survival; RFS, Relapse-free survival.