Pancreatic ductal adenocarcinoma (PDAC) is characterized by a strong desmoplastic reaction where the stromal compartment often accounts for more than half of the tumor volume. Pancreatic stellate cells (PSC) are a central mediator of desmoplasia. There is increasing evidence that desmoplasia is contributing to the poor therapeutic response of PDAC. We show that PSCs promote radioprotection and stimulate proliferation in pancreatic cancer cells (PCC) in direct coculture. Our in vivo studies show PSC-dependent radioprotection in response to a single dose and to fractionated radiation. Abrogating b1-integrin signaling abolishes the PSCmediated radioprotection in PCCs. Furthermore, this effect is independent of PI3K (phosphoinositide 3-kinase) but dependent on FAK. Taken together, we show for the first time that PSCs promote radioprotection of PCCs in a b1-integrin-dependent manner. Cancer Res; 71(10); 3453-8. Ó2011 AACR.

The combination of nelfinavir and chemoradiotherapy showed acceptable toxicity and promising activity in patients with pancreatic cancer.