Role of Cancer-Associated Fibroblasts in Cholangiocarcinoma

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Intrahepatic cholangiocarcinoma (ICC) is an aggressive liver tumor with limited therapeutic options and 5-­year  survival rates of less than 10%. ICC is characterized by its highly desmoplastic nature, with abundance of cancer-­ associated  fibroblasts  (CAF)  and  extracellular  matrix  (ECM).  The  role  of  CAF  and  ECM  in  ICC  remain  controversial due to the paucity of functional in vivo studies. While the majority of ICC in vitro studies support a  cancer-­promoting role of CAF, recent studies in endogenously arising pancreatic cancer, a highly desmoplastic  tumor with many similarities to ICC, have shown that CAF restrain cancer growth. Here, we seek to answer the  question  whether  CAF  promote  or  restrain  ICC,  using  a  number  of  novel  and  cell-­specific  tools  to  manipulate  CAF and tumor cells and their crosstalk in endogenously arising ICC in vivo. We hypothesize that CAF and ECM  provide a niche that promotes ICC growth and survival, and that detailed characterization of ICC-­CAF crosstalk  will  identify  novel  therapeutic  targets  within  the  tumor  microenvironment.  In  Aim  1,  we  will  determine  the  role  CAF using novel tools to determine how genetic CAF inhibition or early and late CAF ablation affect ICC growth,  proliferative and anti-­apoptotic signaling pathways, and mouse survival. In Aim 2, we will investigate pathways  that  mediate  the  recruitment,  proliferation  and  activation  of  CAF  in  ICC  focusing  on  the  hypothesis  that  tumor  cells hijack normal fibrogenic mechanism in the liver via tumor-­derived TGFb and PDGF isoforms and TGFb-­ activating integrins, resulting in accumulation and activation of CAF. In addition to detailed mechanistic studies  in knockout mice and in vitro co-­cultures, we will determine whether pharmacologic inhibition of CAF activation  by FDA-­approved drug Nintedanib or integrin-­blocking antibodies inhibit ICC growth and prolong mouse survival.  In Aim 3, we will determine pathways through which CAF modulate ICC growth, focusing on the hypothesis that CAF-derived ECM activates tumor-promoting signals in the tumor cell compartment. To test this hypothesis, we will investigate ICC development in mice with CAF-specific knockout of Col1a1, or tumor-selective knockout of collagen-sensing receptor discoidin domain receptor 1 (DDR1). In addition, we will determine whether ECM- mediated stiffness and subsequent activation of mechanosensitive signaling in tumor cells promote ICC development. We will measure tumor stiffness, activation of mechanosensitive signaling pathways and DDR1 expression in human CCA samples and correlate these to clinical outcomes. The role of stiffness and DDR1 in ICC growth and CAF-ICC crosstalk will be investigated in more detail in vitro through modulation of stiffness and by co-culturing CAF and ICC cells that lack Col1a1 or DDR1, respectively. In summary, the proposed studies  will employ novel tools to answer a long-­standing question in the field and may provide a basis for targeting ICC-­ CAF crosstalk as novel therapeutic strategy for this devastating malignancy.