Abstract 1115: A discrete tuning of α5β1 integrin activity sustains the tumor-ECM induced fibroblastic activation in pancreatic cancer stroma
Authors: Franco-Barraza Janusz , Luong Tiffany , Shah Neelima , Madhani Raj , Alpaugh Katherine , Hoffman John , Cukierman Edna 
Published: May 2015

Pancreatic adenocarcinoma (PDAC) presents one of the highest mortality rates amongst all neoplasias. The desmoplastic microenvironment characteristic of PDAC plays a pivotal role in this aggressive cancer progression. Using an in vivo-mimetic 3D human stroma system, we have shown that quiescent fibroblasts become activated, undergoing a desmoplastic (i.e., myofibroblastic) phenotypic switch in response to tumor-associated (TA) but not to normal fibroblast-derived extracellular matrix (ECM). Nevertheless, the molecular mechanisms responsible for this process remain unclear.

Using syngeneic human fibroblasts harvested from patient-matched normal and tumor samples, we produced a human 3D pancreatic stromal system. The system was used to investigate the role of integrins during the TA-ECM-induced phenotypic switch, focusing on two integrins associated with myofibroblastic differentiation, αvβ5 and α5β1. We evaluated the role of well-known integrin signaling effectors, i.e., non-receptor tyrosine kinases FAK and Src family kinases (SFK), in the observed TA-ECM-induced phenotypic switch. Approaches included the use of specific inhibitors or activators of integrins and SFK or FAK chemical or genetic inhibitors. Our data strongly suggest a αvβ5/α5β1-integrin cross-talk necessary to maintain the TA-ECM-induced phenotypic switch. This fine-tuned integrin cross-talk participates in the TA-ECM-induced overexpression and stress fiber localization of desmoplastic stroma marker, α-smooth muscle actin (α-SMA).

Our findings correlate with clustering of α5β1-integrin at TA-ECM-altered 3D adhesion structures, together with differences in α5β1 activation. Interestingly, we uncovered a mechanism whereby αvβ5-integrin activity, in a SFK/FAK-dependent manner, inhibits a FAK-independent α5β1-integrin activity, preventing it from inhibiting the TA-ECM-induced phenotypic switch. Finally, using patient samples, we verified our in vitro generated hypothesis, while results suggested that αvβ5-integrin inhibition may constitute a valid inhibitory PDAC-associated stroma clinical treatment/approach. Likewise, this work also concluded that the TA-ECM-regulated mechanism studied may comprise a clinically relevant occurrence, suggestive of a noteworthy value in assessing stromal activity in PDAC patients.

Funding provided by The Commonwealth of Pennsylvania, The Bucks County Chapter Board of Associates and NCI/NIH grants CA113451 and CA06927

Citation Format: Janusz Franco-Barraza, Tiffany Luong, Neelima Shah, Raj Madhani, Katherine Alpaugh, John Hoffman, Edna Cukierman. A discrete tuning of α5β1 integrin activity sustains the tumor-ECM induced fibroblastic activation in pancreatic cancer stroma. [abstract]. In: Proceedings of the 105th Annual Meeting of the American Association for Cancer Research; 2014 Apr 5-9; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2014;74(19 Suppl):Abstract nr 1115. doi:10.1158/1538-7445.AM2014-1115