Periductal stromal collagen topology of pancreatic ductal adenocarcinoma differs from that of normal and chronic pancreatitis

Abstract

Pancreatic ductal adenocarcinoma continues to be one of the most difficult diseases to manage with one of the highest cancer mortality rates. This is due to several factors including nonspecific symptomatology and subsequent diagnosis at an advanced stage, aggressive metastatic behavior that is incompletely understood, and limited response to current therapeutic regimens. As in other cancers, there is great interest in studying the role of the tumor microenvironment in pancreatic ductal adenocarcinoma and whether components of this environment could serve as research and therapeutic targets. In particular, attention has turned toward the desmoplastic collagen-rich pancreatic ductal adenocarcinoma stroma for both biological and clinical insight. In this study, we used quantitative second harmonic generation microscopy to investigate stromal collagen organization and structure in human pancreatic ductal adenocarcinoma pathology tissues compared with non-neoplastic tissues. Collagen topology was characterized in whole-tissue microarray cores and at specific pathology-annotated epithelial-stroma interfaces representing 241 and 117 patients, respectively. We quantitatively demonstrate that a unique collagen topology exists in the periductal pancreatic ductal adenocarcinoma stroma. Specifically, collagen around malignant ducts shows increased alignment, length, and width compared with normal ducts and benign ducts in a chronic pancreatitis background. These findings indicate that second harmonic generation imaging can provide quantitative information about fibrosis that complements traditional histopathologic insights and can serve as a rich field for investigation into pathogenic and clinical implications of reorganized collagen as a pancreatic ductal adenocarcinoma disease marker. Pancreatic ductal adenocarcinoma is one of the most devastating human malignancies. It is currently the fourth leading cause of cancer death and projects to become the second leading cause by 2030. 1 The 5-year relative survival rate has remained in the single digits for decades. Pancreatic ductal adenocarcinoma is notoriously difficult to detect before an advanced, inoperable stage is reached due to nonspecific symptomatology and the retroperitoneal location of the pancreas, which makes palpation or routine biopsy of suspicious masses difficult. Recent advances in the sensitivity and specificity of preoperative imaging modalities such as computer tomography, magnetic resonance imaging, positron emission tomography, endoscopic ultrasonography, and endoscopic retrograde cholangiopancreatography have played an important role in enhancing pancreatic ductal adenocarcinoma diagnosis, detailing the relationship of lesions to nearby anatomical structures, and determining the course of management. 2 Despite these advances, only 10-15% of patients are diagnosed at a localized disease stage when surgical resection is possible as a potential curative therapy. However, postsurgical recurrence rates are high with 5-year survival rate of

Comparison of Picrosirius Red Staining With Second Harmonic Generation Imaging for the Quantification of Clinically Relevant Collagen Fiber Features in Histopathology Samples

“…31 In addition, in the context of the tumor microenvironment, an extreme collagen-rich stromal response is a hallmark of pancreatic cancer and can account for up to 90% of the tumor mass. 32 Furthermore, characteristic changes in collagen alignment have been documented, 12 and other stromal cues have been correlated to patient prognosis. 33 Consistent with previous SHG trends, 12 we found that key collagen properties, such as alignment, were computed to be higher in pancreatic cancer tissues compared with normal adjacent tissues using picrosirius red stain with standard polarization microscopy (PSR-POL).…”

“…32 Furthermore, characteristic changes in collagen alignment have been documented, 12 and other stromal cues have been correlated to patient prognosis. 33 Consistent with previous SHG trends, 12 we found that key collagen properties, such as alignment, were computed to be higher in pancreatic cancer tissues compared with normal adjacent tissues using picrosirius red stain with standard polarization microscopy (PSR-POL). Interestingly, all of the collagen measurements that we considered were computed to be significantly higher in the PSR-POL images relative to SHG images.…”

“…Undoubtedly, SHG has great advantages in terms of imaging depth and higher-order information, but for most of the reported histopathological studies done with standard 5-µm-thick pathology sections, these advantages are not of primary interest. [11][12][13]29 In addition, SHG is not readily accessible in the clinical setting due to high cost, lack of clinical interfaces, and relatively slow acquisition workflows.…”

“…Toward clinical translation, it has already been shown that the detection of TACS in routine histopathological evaluation of breast cancer can serve as an optical biomarker and be predictive of disease recurrence and patient survival. 11 The clinical importance of collagen organization has also been investigated in pancreatic, 12 esophageal, 13 and ovarian cancers.…”

Pancreatic cancer: a mechanobiology approach

“…This also involves integrin mechanosignalling that amplifies epidermal growth factor receptor (EGFR) dependent PI3 kinase (PI3K) signalling [16]. Furthermore, the periductal collagen in PDAC exhibits architectural and structural differences in terms of linearization, alignment, and thickness, which can serve as an independent prognostic factor but might also facilitate cancer invasion through topographical contact guidance [27,28]. New imaging modalities such as second harmonic generation (SHG) imaging and elastography enable visualisation of cell-matrix interactions in 3D environments (in vitro) [29] and assessment of mechanical properties of tissues (in vivo) [30] and will help advance our understanding how structural, topographical, and mechanical changes of the microenviron ment can impact cancer cell behaviour.…”