The American Cancer Society's most recent estimates showed that there were 43,140 new cases of pancreatic ductal adenocarcinoma (PDAC) and 36,800 deaths from PDAC in 2010. This dismal prognosis results from the fact that pancreatic cancer is not only aggressive but also a highly chemo-resistant malignancy. Specifically, the pronounced fibrotic reaction present in both the primary tumor and distant metastases limits the delivery and efficacy of chemotherapy. PDAC tumors demonstrate increased expression of the collagenase membrane type 1-matrix metalloproteinase (MT1-MMP, MMP-14) and high mobility group A2 (HMGA2), an architectural DNA-binding protein involved in regulating chromatin structure. The objective of this application is thus to de- lineate the mechanisms by which the fibrotic reaction contributes to chemotherapy resistance. Our central hy- pothesis is that the collagen microenvironment promotes chemo-resistance by inducing euchromatin formation and facilitating DNA repair. We further hypothesize that targeting MT1-MMP in vivo will consequently increase chemo-sensitivity not only through altering the chromatin structure but also by attenuating fibrosis progression itself. This hypothesis is based on our preliminary data demonstrating that PDAC cels grown in 3D collagen gels have increased histone H3 acetylation;decreased expression of heterochromatin protein 11 (HP11);and are protected from gemcitabine-induced checkpoint arrest. Our preliminary data also show that collagen in- creases HMGA2 and MT1-MMP in PDAC cells, and decreasing HMGA2 or MT1-MMP levels with siRNA at- tenuates the gemcitabine resistance seen in the collagen microenvironment. Surprisingly, expression of human MT1-MMP in transgenic and xenograft mouse models of pancreatic cancer paradoxically results in pronounced fibrosis associated with stellate cell activation. Experiments proposed in Aim 1 have been designed to deter- mine the mechanism by which 3D collagen induces euchromatin to promote chemo-resistance. Specifically, we will examine the role of HMGA2 in enhancing euchromatin in 3D collagen and in facilitating DNA repair. Ex- periments proposed in Aim 2 have been designed to test the hypothesis that targeting MT1-MMP will increase chemo-sensitivity by inducing heterochromatin and reducing DNA repair. MT1-MMP will be targeted with func- tion blocking antibody and gold nanoparticles functionalized with MT1-MMP-specific siRNA. Experiments in Aim 3 have been designed to test the hypothesis that targeting MT1-MMP will also attenuate fibrosis in addi- tion to enhancing chemo-sensitivity. The approach is innovative because it will utilize in vitro organotypic and in vivo orthotopic and transgenic mouse models of pancreatic cancer, together with gold nanoparticles functional- ized with siRNA, to demonstrate that targeting MT1-MMP sensitizes PDAC cells to the effects of chemother- apy. The proposed research is significant because it is a critical first step in the continuum of research that will not only address how the pronounced fibrotic reaction contributes to chemo-resistance but will also lead to identification of MT1-MMP as a therapeutic target to increase chemotherapy response of PDAC tumors.
The proposed research is relevant to the health of veterans because characterizing the mechanisms through which the collagen-rich fibrotic reaction contributes to chemotherapy resistance is ultimately expected to identify novel targets and approaches for the treatment of pancreatic cancer. Accordingly, the proposed research is relevant to the VA's mission because it will develop fundamental knowledge required to reduce the substantial morbidity and mortality caused by pancreatic cancer, as well as other malignancies characterized by a pronounced fibrotic reactions.
