Matrix-regulated integrin αvβ5 maintains α5β1-dependent desmoplastic traits prognostic of neoplastic recurrence

• Published in: eLife Vol. 6
• Main Authors: Franco-Barraza, Janusz, Francescone, Ralph, Luong, Tiffany, Shah, Neelima, Madhani, Raj, Cukierman, Gil, Dulaimi, Essel, Devarajan, Karthik, Egleston, Brian L, Nicolas, Emmanuelle, Katherine Alpaugh, R, Malik, Ruchi, Uzzo, Robert G, Hoffman, John P, Golemis, Erica A, Cukierman, Edna
• Format: Journal Article
• Language: English
• Published: Cambridge eLife Sciences Publications Ltd 31-01-2017; eLife Sciences Publications, Ltd
• Subjects: Adenocarcinoma; alpha5beta1 integrin; Cancer; Cancer Biology; cancer-associated fibroblasts; Computer applications; desmoplasia; Endosomes; Extracellular matrix; Fibroblasts; Genotype & phenotype; Human Biology and Medicine; Immunofluorescence; Laboratories; Localization; Medical prognosis; myofibroblasts; Pancreas; Pancreatic cancer; pancreatic ductal adenocarcinoma; Smad2 protein; Tumorigenesis; Tumors; Variables
• ISSN: 2050-084X; 2050-084X
• DOI: 10.7554/eLife.20600

Desmoplasia, a fibrotic mass including cancer-associated fibroblasts (CAFs) and self-sustaining extracellular matrix (D-ECM), is a puzzling feature of pancreatic ductal adenocarcinoma (PDACs). Conflicting studies have identified tumor-restricting and tumor-promoting roles of PDAC-associated desmoplasia, suggesting that individual CAF/D-ECM protein constituents have distinguishable tumorigenic and tumor-repressive functions. Using 3D culture of normal pancreatic versus PDAC-associated human fibroblasts, we identified a CAF/D-ECM phenotype that correlates with improved patient outcomes, and that includes CAFs enriched in plasma membrane-localized, active α
5
β
1
-integrin. Mechanistically, we established that TGFβ is required for D-ECM production but dispensable for D-ECM-induced naïve fibroblast-to-CAF activation, which depends on α
v
β
5
-integrin redistribution of pFAK-independent active α
5
β
1
-integrin to assorted endosomes. Importantly, the development of a simultaneous multi-channel immunofluorescence approach and new algorithms for computational batch-analysis and their application to a human PDAC panel, indicated that stromal localization and levels of active SMAD2/3 and α
5
β
1
-integrin distinguish patient-protective from patient-detrimental desmoplasia and foretell tumor recurrences, suggesting a useful new prognostic tool.
Tumors are not entirely made out of cancerous cells. They contain many other components – referred to as tumor stroma – that may either encourage or hinder the tumor’s growth. Tumor stroma includes non-cancerous cells and a framework of fibrous sugary proteins, called the extracellular matrix, which surround and signal to cells while providing physical support.
In the most common and aggressive form of pancreatic cancer, the stroma often makes up the majority of the tumor’s mass. Sometimes the stroma of these pancreatic tumors can protect the cancer cells from anti-cancer drugs. Researchers have therefore been interested in finding out exactly which aspects of the tumor stroma shield and support cancer cells, and which impede their growth and progression. Answering these questions could make it possible to develop new drugs that will change a tumor-supporting stroma into one that hinders the tumor’s growth and spread.
The most abundant cells in the stroma of pancreatic tumors are called cancer-associated fibroblasts. Healthy specialized fibroblasts – known as pancreatic stellate cells – help to build and maintain the ‘normal’ extracellular matrix and so these cells normally restrict a tumor’s development. However, cancer cells can adapt healthy fibroblasts into cancer-associated fibroblasts, which produce an altered extracellular matrix that could allow the tumor to grow.
Franco-Barraza et al. have now compared healthy and cancer-associated fibroblasts from patients’ pancreatic tumors. One of the main differences between these two cell types was the location of the activated form of a molecule called α
5
β
1
-integrin. Healthy fibroblasts, in a normal extracellular matrix, have active α
5
β
1
-integrin on the surface of the cell. However, a number of tumor-promoting signals, including some from the altered extracellular matrix, could force the active α
5
β
1
-integrins to relocate inside the fibroblasts instead. In further experiments, where the activated integrin was retained at the cell surface, the fibroblasts were able to resist the influence of the cancer-associated extracellular matrix. Then again, if the active α
5
β
1
-integrins were directed inside the cells, healthy cells turned into cancer-associated fibroblasts.
With this information in hand, Franco-Barraza et al. examined tumor samples from over a hundred pancreatic cancer patients using a new microscopy-based technique that distinguishes cancer cells from stroma cells. The analysis confirmed the pattern observed in the laboratory: those patients who appeared to produce more normal extracellular matrix and have active α
5
β
1
-integrin localized mostly to the surface of the cells survived longer without the cancer returning than those patients who lacked these stroma traits. Samples from patients with kidney cancer also showed similar results and, as before, an altered extracellular matrix was linked to a worse outcome of the disease.
Together these findings suggest that if future studies uncover ways to relocate or maintain active α
5
β
1
-integrin to the cell surface of fibroblasts they could lead to new treatments to restrict the growth of tumors in cancer patients.