Primary myelofibrosis (PMF) is a myeloproliferative neoplasm which is a precursor to myeloid leukemia. Dysmegakaryopoiesis and extramedullary hematopoiesis characterize PMF, which is also associated with bone marrow (BM) stromal alterations marked by fibrosis, neoangiogenesis and osteomyelosclerosis. In particular, contributions to PMF from mesenchymal stromal cells (MSC) have been suggested by mouse studies, but evidence in humans remains lacking. In this study, we show that BM MSC from PMF patients exhibit unique molecular and functional abnormalities distinct from other myeloproliferative neoplasms and these abnormalities are maintained stably ex vivo in the absence of leukemic cells. PMF-MSC overexpressed heparin-binding cytokines, including pro-inflammatory TGF-β1 and osteogenic BMP-2, as well as glycosaminoglycans such as heparan sulfate and chondroitin sulfate. Transcriptome and functional analyses revealed alterations in MSC differentiation characterized by an increased osteogenic potential and a TGF-β1 signaling signature. Accordingly, phospho-Smad2 levels were intrinsically increased in PMF-MSC along with enhanced expression of the master bone regulator RUNX2, while inhibiting the endogenous TGF-β1 receptor TGFβR1 impaired osteogenic differentiation in these MSC. Taken together, our results define the source of a critical osteogenic function in PMF that supports its pathophysiology, suggesting that combined targeting of both the hematopoietic and stromal cell compartments in PMF patients may heighten therapeutic efficacy.

Activation of Notch signaling in hematopoietic cells by tumors contributes to immune escape. T-cell defects in tumors can be reversed by treating tumor-bearing mice with multivalent forms of the Notch receptor ligand DLL-1, but the immunologic correlates of this effect have not been elucidated. Here, we report mechanistic insights along with the efficacy of combinational treatments of multivalent DLL-1 with oncoprotein targeting drugs in preclinical mouse models of lung cancer. Systemic DLL-1 administration increased T-cell infiltration into tumors and elevated numbers of CD44+CD62L+CD8+ memory T cells while decreasing the number of regulatory T cells and limiting tumor vascularization. This treatment was associated with upregulation of Notch and its ligands in tumor-infiltrating T cells enhanced expression of T-bet and phosphorylation of Stat1/2. Adoptive transfer of T cells from DLL1-treated tumor-bearing immunocompetent hosts into tumor-bearing SCID-NOD immunocompromised mice attenuated tumor growth and extended tumor-free survival in the recipients. When combined with the EGFR-targeted drug erlotinib, DLL-1 significantly improved progression-free survival by inducing robust tumor-specific T-cell immunity. In tissue culture, DLL1 induced proliferation of human peripheral T cells, but lacked proliferative or clonogenic effects on lung cancer cells. Our findings offer preclinical mechanistic support for the development of multivalent DLL1 to stimulate antitumor immunity. Cancer Res; 75(22); 1–14. ©2015 AACR.

Activation of Notch signaling in hematopoietic cells by tumors contributes to immune escape. T cell defects in tumors can be reversed by treating tumor-bearing mice with multivalent forms of the Notch receptor ligand DLL-1, but the immunologic correlates of this effect have not been elucidated. Here we report mechanistic insights along with the efficacy of combinational treatments of multivalent DLL-1 with oncoprotein targeting drugs in preclinical mouse models of lung cancer. Systemic DLL-1 administration increased T cell infiltration into tumors and elevated numbers of CD44+CD62L+CD8+ memory T cells, while decreasing the number of regulatory T cells and limiting tumor vascularization. This treatment was associated with upregulation of Notch and its ligands in tumor-infiltrating T cells, enhanced expression of T-bet and phosphorylation of Stat1/2. Adoptive transfer of T cells from DLL1-treated tumor-bearing immunocompetent hosts into tumor-bearing SCID-NOD immunocompromised mice attenuated tumor growth and extended tumor-free survival in the recipients. When combined with the EGFR-targeted drug erlotinib, DLL-1 significantly improved progression-free survival by inducing robust tumor-specific T cell immunity. In tissue culture, DLL1 induced proliferation of human peripheral T cells but lacked proliferative or clonogenic effects on lung cancer cells. Our findings offer preclinical mechanistic support for the development of multivalent DLL1 to stimulate antitumor immunity.

Pancreatic ductal adenocarcinoma (PDAC) offers an optimal model for discovering “druggable” molecular pathways that participate in inflammation-associated cancer development. Chronic pancreatitis, a common prolonged inflammatory disease, behaves as a well-known premalignant condition that contributes to PDAC development. Although the mechanisms underlying the pancreatitis-to-cancer transition remain to be fully elucidated, emerging evidence supports the hypothesis that the actions of proinflammatory mediators on cells harboring Kras mutations promote neoplastic transformation. Recent elegant studies demonstrated that the IL17 pathway mediates this phenomenon and can be targeted with antibodies, but the downstream mechanisms by which IL17 functions during this transition are currently unclear. In this study, we demonstrate that IL17 induces the expression of REG3β, a well-known mediator of pancreatitis, during acinar-to-ductal metaplasia and in early pancreatic intraepithelial neoplasia (PanIN) lesions. Furthermore, we found that REG3β promotes cell growth and decreases sensitivity to cell death through activation of the gp130-JAK2-STAT3-dependent pathway. Genetic inactivation of REG3β in the context of oncogenic Kras-driven PDAC resulted in reduced PanIN formation, an effect that could be rescued by administration of exogenous REG3β. Taken together, our findings provide mechanistic insight into the pathways underlying inflammation-associated pancreatic cancer, revealing a dual and contextual pathophysiologic role for REG3β during pancreatitis and PDAC initiation. Cancer Res; 75(22); 1–11. ©2015 AACR.

Pancreatic ductal adenocarcinoma (PDAC) offers an optimal model for discovering “druggable” molecular pathways that participate in inflammation-associated cancer development. Chronic pancreatitis, a common prolonged inflammatory disease, behaves as a well-known premalignant condition that contributes to PDAC development. Although the mechanisms underlying the pancreatitis-to-cancer transition remain to be fully elucidated, emerging evidence supports the hypothesis that the actions of proinflammatory mediators on cells harboring Kras mutations promote neoplastic transformation. Recent elegant studies demonstrated that the IL-17 pathway mediates this phenomenon and can be targeted with antibodies, but the downstream mechanisms by which IL-17 functions during this transition are currently unclear. In this study, we demonstrate that IL-17 induces the expression of REG3β, a well-known mediator of pancreatitis, during acinar-to-ductal metaplasia and in early PanIN lesions. Furthermore, we found that REG3β promotes cell growth and decreases sensitivity to cell death through activation of the gp130-JAK2-STAT3-dependent pathway. Genetic inactivation of REG3β in the context of oncogenic Kras-driven PDAC resulted in reduced PanIN formation, an effect that could be rescued by administration of exogenous REG3β. Taken together, our findings provide mechanistic insight into the pathways underlying inflammation-associated pancreatic cancer, revealing a dual and contextual pathophysiological role for REG3β during pancreatitis and PDAC initiation.