Abstract A55: A role of bone morphogenetic protein signaling in pancreatic cancer

TGF-beta signaling has a crucial role in pancreatic tumorigenesis, and almost all of pancreatic cancers carry at least one genetic alteration of TGF-beta related genes, such as SMAD4, TGFBR2, SMAD3, and BMPR2. However, the role of BMP signaling in pancreatic cancer remains unclear. Previous studies reported the depletion of BMP signaling resulted in the aggressive phenotype of cancer, and some reported BMP signaling played an important role in tumor progression and metastasis.

We have already established pancreas-specific Tgbr2 knockout mice in the context of Kras activation, which clinically and histopathologically recapitulate human PDAC. With regard to PDAC, Smad4 mutation or deletion is more commonly observed, however the Smad4 knockout mice with activating Kras mutation was reported to show cystic type tumor of pancreas. Therefore, our Kras+Tgfbr2KO might be the closest approximation of the human PDAC in terms of histology. We examined the effect of BMP signaling on the tumorigenesis and progression of PDAC using this mouse model.

We performed immunohistochemistry of murine PDAC to evaluate whether BMP signaling was related to the PDAC progression. We examined the effect of Bmp4 and Bmp7 on the proliferation, invasion and adhesion using murine PDAC and PanIN cells in vitro. We have already established the murine PDAC cell lines from Pancreas-specific Kras+Tgfbr2KO mice and murine PanIN cells from Pancreas-specific activating Kras mutation mice. Bmpr2 was knocked down in PanIN cell lines using shRNA, and we examined whether the effect of BMP signaling was canceled by Bmpr2 knockdown. In vivo, we evaluated the effect of BMP signaling on tumor growth and tumor-stromal interaction using the xenograft mouse model of Bmpr2-negative PanIN cells.

The immunohistochemistry of murine pancreas tissues demonstrated that Smad1/5/8 was more strongly phosphorylated in PDAC compared to PanIN lesion. We also observed that Smad1/5/8 was phosphorylated in stromal cells surrounding tumor areas, which was likely to suggest the importance of BMP signaling in PDAC progression and tumor-stromal interaction. In vitro, both Bmp4 and Bmp7 did not affect the proliferation and invasion of PDAC and PanIN cells, but they increased the adhesion of PDAC and PanIN cells, and knockdown of Bmpr2 canceled the effect of Bmps. In vivo, we evaluated the growth of subcutaneous tumor allograft and the tumors of Bmpr2-negative PanIN cells showed slower tumor growth than tumors of the control, differently from the results in vitro. These results suggested that BMP signaling was associated with the tumor-stromal interaction and played important role in tumor progression.

In this study we evaluated the role of BMP signaling in pancreatic cancer using pancreas-specific Kras+Tgfbr2KO mice, and demonstrated that BMP signaling played important role in the adhesion and progression of pancreatic cancer, which was due to the tumor-stromal interaction.

Citation Format: Koji Miyabayashi, Hideaki Ijichi, Ryota Takahashi, Keisuke Yamamoto, Yoshinari Asaoka, Keisuke Tateishi, Yousuke Nakai, Hiroyuki Isayama, Harold L. Moses, Kazuhiko Koike. A role of bone morphogenetic protein signaling in pancreatic cancer. [abstract]. In: Proceedings of the AACR Special Conference on Pancreatic Cancer: Innovations in Research and Treatment; May 18-21, 2014; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2015;75(13 Suppl):Abstract nr A55.

Abstract P6-03-04: TGF-β receptor type III is a tumor promoter in mesenchymal-stem like triple negative breast cancer

Introduction: There is a major need to better understand the molecular basis of triple negative breast cancer (TNBC) in order to develop effective therapeutic strategies. Using gene expression data from 587 TNBC patients we previously identified six subtypes of the disease, among which a Mesenchymal-Stem Like (MSL) subtype. The MSL subtype has significantly higher expression of the transforming growth factor beta (TGF-β) pathway-associated genes relative to other subtypes, including the TGF-β receptor type III (TβRIII). We hypothesize that TβRIII is tumor promoter in mesenchymal-stem like TNBC cells.

Methods: Representative MSL cell lines SUM159, MDA-MB-231 and MDA-MB-157 were used to study the roles of TβRIII in the MSL subtype. We stably expressed short hairpin RNAs specific to TβRIII (TβRIII-KD). These cells were then used for xenograft tumor studies in vivo; and migration, invasion, proliferation and three dimensional culture studies in vitro. Furthermore, we utilized human gene expression datasets to examine TβRIII expression patterns across all TNBC subtypes.

Results: TβRIII was the most differentially expressed TGF-β signaling gene in the MSL subtype. Silencing TβRIII expression in MSL cell lines significantly decreased cell motility and invasion. In addition, when TβRIII-KD cells were grown in a three dimensional (3D) culture system or nude mice, there was a loss of invasive protrusions and a significant decrease in xenograft tumor growth, respectively. In pursuit of the mechanistic underpinnings for the observed TβRIII-dependent phenotypes, we discovered that integrin-α2 was expressed at higher level in MSL cells after TβRIII-KD. Stable knockdown of integrin-α2 in TβRIII-KD MSL cells rescued the ability of the MSL cells to migrate and invade at the same level as MSL control cells.

Conclusions: We have found that TβRIII is required for migration and invasion in vitro and xenograft growth in vivo. We also show that TβRIII-KD elevates expression of integrin-α2, which is required for the reduced migration and invasion, as determined by siRNA knockdown studies of both TβRIII and integrin-α2. Overall, our results indicate a potential mechanism in which TβRIII modulates integrin-α2 expression to effect MSL cell migration, invasion, and tumorigenicity.

Citation Format: Bojana Jovanovic, J Scott Beeler, Michael W Pickup, Anna Chytil, Agnieszka E Gorska, William J Ashby, Brian D Lehmann, Andries Zijlstra, Jennifer A Pietenpol, Harold L Moses. TGF-β receptor type III is a tumor promoter in mesenchymal-stem like triple negative breast cancer [abstract]. In: Proceedings of the Thirty-Seventh Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2014 Dec 9-13; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2015;75(9 Suppl):Abstract nr P6-03-04.

A Murine Model of K-RAS and β-Catenin Induced Renal Tumors Expresses High Levels of E2F1 and Resembles Human Wilms Tumor

PURPOSE

Wilms tumor is the most common renal neoplasm of childhood. We previously found that restricted activation of the WNT/β-catenin pathway in renal epithelium late in kidney development is sufficient to induce small primitive neoplasms with features of epithelial Wilms tumor. Metastatic disease progression required simultaneous addition of an activating mutation of the oncogene K-RAS. We sought to define the molecular pathways activated in this process and their relationship to human renal malignancies.

MATERIALS AND METHODS

Affymetrix® expression microarray data from murine kidneys with activation of K-ras and/or Ctnnb1 (β-catenin) restricted to renal epithelium were analyzed and compared to publicly available expression data on normal and neoplastic human renal tissue. Target genes were verified by immunoblot and immunohistochemistry.

RESULTS

Mouse kidney tumors with activation of K-ras and Ctnnb1, and human renal malignancies had similar mRNA expression signatures and were associated with activation of networks centered on β-catenin and TP53. Up-regulation of WNT/β-catenin targets (MYC, Survivin, FOXA2, Axin2 and Cyclin D1) was confirmed by immunoblot. K-RAS/β-catenin murine kidney tumors were more similar to human Wilms tumor than to other renal malignancies and demonstrated activation of a TP53 dependent network of genes, including the transcription factor E2F1. Up-regulation of E2F1 was confirmed in murine and human Wilms tumor samples.

CONCLUSIONS

Simultaneous activation of K-RAS and β-catenin in embryonic renal epithelium leads to neoplasms similar to human Wilms tumor and associated with activation of TP53 and up-regulation of E2F1. Further studies are warranted to evaluate the role of TP53 and E2F1 in human Wilms tumor.

Age- and pregnancy-associated DNA methylation changes in mammary epithelial cells

Postnatal mammary gland development and differentiation occur during puberty and pregnancy. To explore the role of DNA methylation in these processes, we determined the genome-wide DNA methylation and gene expression profiles of CD24(+)CD61(+)CD29(hi), CD24(+)CD61(+)CD29(lo), and CD24(+)CD61(-)CD29(lo) cell populations that were previously associated with distinct biological properties at different ages and reproductive stages. We found that pregnancy had the most significant effects on CD24(+)CD61(+)CD29(hi) and CD24(+)CD61(+)CD29(lo) cells, inducing distinct epigenetic states that were maintained through life. Integrated analysis of gene expression, DNA methylation, and histone modification profiles revealed cell-type- and reproductive-stage-specific changes. We identified p27 and TGFβ signaling as key regulators of CD24(+)CD61(+)CD29(lo) cell proliferation, based on their expression patterns and results from mammary gland explant cultures. Our results suggest that relatively minor changes in DNA methylation occur during luminal differentiation compared with the effects of pregnancy on CD24(+)CD61(+)CD29(hi) and CD24(+)CD61(+)CD29(lo) cells.

Abstract B10: Epidermal growth factor receptor inhibitor prolongs survival in pancreatic cancer by blocking gemcitabine-induced mitogen-activated protein kinase signal

Pancreatic ductal adenocarcinoma (PDAC) is the most deadly cancer worldwide. Although many regimens have been tried against PDAC, an epidermal growth factor receptor (EGFR) inhibitor erlotinib in combination with gemcitabine is the only molecular target drug superior to gemcitabine alone. However, the mechanism by which PDAC with extremely frequent KRAS-mutation benefits from EGFR inhibition remains largely unknown. In this study, we evaluated the efficacy of erlotinib in combination with gemcitabine using a murine PDAC model with transforming growth factor-beta receptor II knockout plus Kras activation and investigated the mode of action.

The mice were treated using the following drug doses and treatment schedules; erlotinib was administered from 3 weeks of age and gemcitabine was administered from 4 weeks of age. We isolated PDAC cells from the murine PDAC tissues. Effects of erlotinib on the proliferation and intracellular signaling of the murine PDAC cells or human PDAC cell lines were examined in vitro. We sacrificed the mice at 7 weeks of age, and excised the pancreatic tissues and processed for western blot analysis and immunohistochemistry. We evaluated the expression of EGFR ligands by real-time PCR and the heterodimer formation of EGFR with ErbB2 by immunoprecipitaiton after incubation with gemcitabine in vitro. We assessed whether the effect of gemcitabine on EGFR/ErbB2 activation is secondary to mitogen activated protein kinase (MAPK) signal activation after incubation with or without MEK inhibitor and gemcitabine by western blot analysis and real-time PCR.

Gemcitabine + erlotinib inhibited PDAC progression and significantly prolonged the survival of the PDAC mice compared to gemcitabine alone. Gemcitabine or erlotinib also inhibited in vitro PDAC cell proliferation. Interestingly, Gemcitabine induced MAPK signaling, which was dramatically inhibited by adding erlotinib, even in the Kras-mutant PDAC cells. The suggested mechanisms were that gemcitabine induced EGFR ligand expression and also ErbB2 activation by increasing heterodimer formation with EGFR and maintaining high ErbB2 protein level in PDAC cells. We observed that the gemcitabine-induced MAPK signaling activation was in part due to induction of Egfr ligands(Egf, Tgf-a, Amphiregulin) expression by real-time PCR and ELISA. Using a phospho-RTK antibody array, we also observed that Gem induced Erbb2 activation in PDAC cells, and validated by western blot analysis, real-time PCR, and immunohistochemistry. Erlotinib inhibited the ErbB2 activation, partly by inhibiting heterodimer formation with EGFR and also decreasing ErbB2 protein expression in PDAC cells.

We observed that gemcitabine-induced EGFR ligands up-regulation and EGFR/ErbB2 activation require intact MAPK signaling and these are secondary effects of MAPK signal activation and that gemcitabine induced the activation irrespective of KRAS status and gemcitabine sensitivity.

This model helps us to evaluate an efficacy of new drugs and to investigate mechanisms of the mode of action and chemoresistance. This study provides clinical insights into potent therapeutic strategies for this difficult cancer.

Citation Format: Koji Miyabayashi, Hideaki Ijichi, Ryota Takahashi, Dai Mohri, Keisuke Yamamoto, Yoshinari Asaoka, Tsuneo Ikenoue, Keisuke Tateishi, Harold L. Moses, Kazuhiko Koike. Epidermal growth factor receptor inhibitor prolongs survival in pancreatic cancer by blocking gemcitabine-induced mitogen-activated protein kinase signal. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B10. doi: 10.1158/1557-3125.RASONC14-B10

Attenuated transforming growth factor beta signaling promotes metastasis in a model of HER2 mammary carcinogenesis

Introduction

Transforming growth factor beta (TGFβ) plays a major role in the regulation of tumor initiation, progression, and metastasis. It is depended on the type II TGFβ receptor (TβRII) for signaling. Previously, we have shown that deletion of TβRII in mammary epithelial of MMTV-PyMT mice results in shortened tumor latency and increased lung metastases. However, active TGFβ signaling increased the number of circulating tumor cells and metastases in MMTV-Neu mice. In the current study, we describe a newly discovered connection between attenuated TGFβ signaling and human epidermal growth factor receptor 2 (HER2) signaling in mammary tumor progression.

Methods

All studies were performed on MMTV-Neu mice with and without dominant-negative TβRII (DNIIR) in mammary epithelium. Mammary tumors were analyzed by flow cytometry, immunohistochemistry, and immunofluorescence staining. The levels of secreted proteins were measured by enzyme-linked immunosorbent assay. Whole-lung mount staining was used to quantitate lung metastasis. The Cancer Genome Atlas (TCGA) datasets were used to determine the relevance of our findings to human breast cancer.

Results

Attenuated TGFβ signaling led to a delay tumor onset, but increased the number of metastases in MMTVNeu/DNIIR mice. The DNIIR tumors were characterized by increased vasculogenesis, vessel leakage, and increased expression of vascular endothelial growth factor (VEGF). During DNIIR tumor progression, both the levels of CXCL1/5 and the number of CD11b+Gr1+ cells and T cells decreased. Analysis of TCGA datasets demonstrated a significant negative correlation between TGFBR2 and VEGF genes expression. Higher VEGFA expression correlated with shorter distant metastasis-free survival only in HER2+ patients with no differences in HER2-, estrogen receptor +/- or progesterone receptor +/- breast cancer patients.

Conclusion

Our studies provide insights into a novel mechanism by which epithelial TGFβ signaling modulates the tumor microenvironment, and by which it is involved in lung metastasis in HER2+ breast cancer patients. The effects of pharmacological targeting of the TGFβ pathway in vivo during tumor progression remain controversial. The targeting of TGFβ signaling should be a viable option, but because VEGF has a protumorigenic effect on HER2+ tumors, the targeting of this protein could be considered when it is associated with attenuated TGFβ signaling.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-014-0425-7) contains supplementary material, which is available to authorized users.

Abstract 2676: Inhibition of bmp signaling suppresses metastasis in mammary cancer

Bone Morphogenetic Proteins (BMPs) are secreted cytokines/growth factors that play differing roles in cancer. BMPs are overexpressed in human breast cancers, but loss of BMP signaling in mammary carcinomas can accelerate metastasis. We show that human breast cancers display active BMP signaling, which is rarely downregulated or homozygously deleted. We hypothesized that systemic inhibition of BMP signaling in both the tumor and the surrounding microenvironment could prevent tumor progression and metastasis. To test this hypothesis, we used DMH1, a BMP antagonist in MMTV.PyVmT expressing mice. Treatment with DMH1 reduced lung metastasis and the tumors were less proliferative and more apoptotic. In the surrounding tumor microenvironment, treatment with DMH1 altered fibroblasts, lymphatic vessels and macrophages to be less tumor promoting. These results indicate that inhibition of BMP signaling may successfully target both the tumor and the surrounding microenvironment to reduce tumor burden and metastasis.

Citation Format: Philip Owens, Michael W. Pickup, Sergey V. Novitskiy, Jennifer M. Giltnane, Agnes E. Gorska, Corey R. Hopkins, Charles C. Hong, Harold L. Moses. Inhibition of bmp signaling suppresses metastasis in mammary cancer. [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 2676. doi:10.1158/1538-7445.AM2014-2676

Concerted loss of TGFβ-mediated proliferation control and E-cadherin disrupts epithelial homeostasis and causes oral squamous cell carcinoma

Although the etiology of squamous cell carcinomas of the oral mucosa is well understood, the cellular origin and the exact molecular mechanisms leading to their formation are not. Previously, we observed the coordinated loss of E-cadherin (CDH1) and transforming growth factor beta receptor II (TGFBR2) in esophageal squamous tumors. To investigate if the coordinated loss of Cdh1 and Tgfbr2 is sufficient to induce tumorigenesis in vivo, we developed two mouse models targeting ablation of both genes constitutively or inducibly in the oral-esophageal epithelium. We show that the loss of both Cdh1 and Tgfbr2 in both models is sufficient to induce squamous cell carcinomas with animals succumbing to the invasive disease by 18 months of age. Advanced tumors have the ability to invade regional lymph nodes and to establish distant pulmonary metastasis. The mouse tumors showed molecular characteristics of human tumors such as overexpression of Cyclin D1. We addressed the question whether TGFβ signaling may target known stem cell markers and thereby influence tumorigenesis. From our mouse and human models, we conclude that TGFβ signaling regulates key aspects of stemness and quiescence in vitro and in vivo. This provides a new explanation for the importance of TGFβ in mucosal homeostasis.

BMPR2 loss in fibroblasts promotes mammary carcinoma metastasis via increased inflammation

Bone Morphogenetic Protein (BMP) receptors mediate a diverse range of signals to regulate both development and disease. BMP activity has been linked to both tumor promoting and suppressive functions in both tumor cells and their surrounding microenvironment. We sought to investigate the requirement for BMPR2 in stromal fibroblasts during mammary tumor formation and metastasis. We utilized FSP1 (Fibroblast Specific Protein-1) promoter driven Cre to genetically delete BMPR2 in mice expressing the MMTV.PyVmT mammary carcinoma oncogene. We found that abrogation of stromal BMPR2 expression via FSP1 driven Cre resulted in increased tumor metastasis. Additionally, similar to epithelial BMPR2 abrogation, stromal loss of BMPR2 results in increased inflammatory cell infiltration. We proceeded to isolate and establish fibroblast cell lines without BMPR2 and found a cell autonomous increase in inflammatory cytokine secretion. Fibroblasts were co-implanted with syngeneic tumor cells and resulted in accelerated tumor growth and increased metastasis when fibroblasts lacked BMPR2. We observed that the loss of BMPR2 results in increased chemokine expression, which facilitates inflammation by a sustained increase in myeloid cells. The chemokines increased in BMPR2 deleted cells correlated with poor outcome in human breast cancer patients. We conclude that BMPR2 has tumor suppressive functions in the stroma by regulating inflammation.

Role of TGF-β signaling in generation of CD39+CD73+ myeloid cells in tumors

There is growing evidence that generation of adenosine from ATP, which is mediated by the CD39/CD73 enzyme pair, predetermines immunosuppressive and proangiogenic properties of myeloid cells. We have previously shown that the deletion of the TGF-β type II receptor gene (Tgfbr2) expression in myeloid cells is associated with decreased tumor growth, suggesting protumorigenic effect of TGF-β signaling. In this study, we tested the hypothesis that TGF-β drives differentiation of myeloid-derived suppressor cells into protumorigenic terminally differentiated myeloid mononuclear cells (TDMMCs) characterized by high levels of cell-surface CD39/CD73 expression. We found that TDMMCs represent a major cell subpopulation expressing high levels of both CD39 and CD73 in the tumor microenvironment. In tumors isolated from mice with spontaneous tumor formation of mammary gland and conditional deletion of the type II TGF-β receptor in mammary epithelium, an increased level of TGF-β protein was associated with further increase in number of CD39(+)CD73(+) TDMMCs compared with MMTV-PyMT/TGFβRII(WT) control tumors with intact TGF-β signaling. Using genetic and pharmacological approaches, we demonstrated that the TGF-β signaling mediates maturation of myeloid-derived suppressor cells into TDMMCs with high levels of cell surface CD39/CD73 expression and adenosine-generating capacity. Disruption of TGF-β signaling in myeloid cells resulted in decreased accumulation of TDMMCs, expressing CD39 and CD73, and was accompanied by increased infiltration of T lymphocytes, reduced density of blood vessels, and diminished progression of both Lewis lung carcinoma and spontaneous mammary carcinomas. We propose that TGF-β signaling can directly induce the generation of CD39(+)CD73(+) TDMMCs, thus contributing to the immunosuppressive, proangiogenic, and tumor-promoting effects of this pleiotropic effector in the tumor microenvironment.

Transforming growth factor beta receptor type III is a tumor promoter in mesenchymal-stem like triple negative breast cancer

Introduction

There is a major need to better understand the molecular basis of triple negative breast cancer (TNBC) in order to develop effective therapeutic strategies. Using gene expression data from 587 TNBC patients we previously identified six subtypes of the disease, among which a mesenchymal-stem like (MSL) subtype. The MSL subtype has significantly higher expression of the transforming growth factor beta (TGF-β) pathway-associated genes relative to other subtypes, including the TGF-β receptor type III (TβRIII). We hypothesize that TβRIII is tumor promoter in mesenchymal-stem like TNBC cells.

Methods

Representative MSL cell lines SUM159, MDA-MB-231 and MDA-MB-157 were used to study the roles of TβRIII in the MSL subtype. We stably expressed short hairpin RNAs specific to TβRIII (TβRIII-KD). These cells were then used for xenograft tumor studies in vivo; and migration, invasion, proliferation and three dimensional culture studies in vitro. Furthermore, we utilized human gene expression datasets to examine TβRIII expression patterns across all TNBC subtypes.

Results

TβRIII was the most differentially expressed TGF-β signaling gene in the MSL subtype. Silencing TβRIII expression in MSL cell lines significantly decreased cell motility and invasion. In addition, when TβRIII-KD cells were grown in a three dimensional (3D) culture system or nude mice, there was a loss of invasive protrusions and a significant decrease in xenograft tumor growth, respectively. In pursuit of the mechanistic underpinnings for the observed TβRIII-dependent phenotypes, we discovered that integrin-α2 was expressed at higher level in MSL cells after TβRIII-KD. Stable knockdown of integrin-α2 in TβRIII-KD MSL cells rescued the ability of the MSL cells to migrate and invade at the same level as MSL control cells.

Conclusions

We have found that TβRIII is required for migration and invasion in vitro and xenograft growth in vivo. We also show that TβRIII-KD elevates expression of integrin-α2, which is required for the reduced migration and invasion, as determined by siRNA knockdown studies of both TβRIII and integrin-α2. Overall, our results indicate a potential mechanism in which TβRIII modulates integrin-α2 expression to effect MSL cell migration, invasion, and tumorigenicity.

Depletion of carcinoma-associated fibroblasts and fibrosis induces immunosuppression and accelerates pancreas cancer with reduced survival

Pancreatic ductal adenocarcinoma (PDAC) is associated with marked fibrosis and stromal myofibroblasts, but their functional contribution remains unknown. Transgenic mice with the ability to delete αSMA(+) myofibroblasts in pancreatic cancer were generated. Depletion starting at either noninvasive precursor (pancreatic intraepithelial neoplasia) or the PDAC stage led to invasive, undifferentiated tumors with enhanced hypoxia, epithelial-to-mesenchymal transition, and cancer stem cells, with diminished animal survival. In PDAC patients, fewer myofibroblasts in their tumors also correlated with reduced survival. Suppressed immune surveillance with increased CD4(+)Foxp3(+) Tregs was observed in myofibroblast-depleted mouse tumors. Although myofibroblast-depleted tumors did not respond to gemcitabine, anti-CTLA4 immunotherapy reversed disease acceleration and prolonged animal survival. This study underscores the need for caution in targeting carcinoma-associated fibroblasts in PDAC.

ALCAM/CD166 is a TGF-β-responsive marker and functional regulator of prostate cancer metastasis to bone

The dissemination of prostate cancer to bone is a common, incurable aspect of advanced disease. Prevention and treatment of this terminal phase of prostate cancer requires improved molecular understanding of the process as well as markers indicative of molecular progression. Through biochemical analyses and loss-of-function in vivo studies, we demonstrate that the cell adhesion molecule, activated leukocyte cell adhesion molecule (ALCAM), is actively shed from metastatic prostate cancer cells by the sheddase ADAM17 in response to TGF-β. Not only is this posttranslational modification of ALCAM a marker of prostate cancer progression, the molecule is also required for effective metastasis to bone. Biochemical analysis of prostate cancer cell lines reveals that ALCAM expression and shedding is elevated in response to TGF-β signaling. Both in vitro and in vivo shedding is mediated by ADAM17. Longitudinal analysis of circulating ALCAM in tumor-bearing mice revealed that shedding of tumor, but not host-derived ALCAM is elevated during growth of the cancer. Gene-specific knockdown of ALCAM in bone-metastatic PC3 cells greatly diminished both skeletal dissemination and tumor growth in bone. The reduced growth of ALCAM knockdown cells corresponded to an increase in apoptosis (caspase-3) and decreased proliferation (Ki67). Together, these data demonstrate that the ALCAM is both a functional regulator as well as marker of prostate cancer progression.

The roles of TGFβ in the tumour microenvironment

The influence of the microenvironment on tumour progression is becoming clearer. In this Review we address the role of an essential signalling pathway, that of transforming growth factor-β, in the regulation of components of the tumour microenvironment and how this contributes to tumour progression.

Stromally derived lysyl oxidase promotes metastasis of transforming growth factor-β-deficient mouse mammary carcinomas

The tumor stromal environment can dictate many aspects of tumor progression. A complete understanding of factors driving stromal activation and their role in tumor metastasis is critical to furthering research with the goal of therapeutic intervention. Polyoma middle T-induced mammary carcinomas lacking the type II TGF-β receptor (PyMT(mgko)) are highly metastatic compared with control PyMT-induced carcinomas (PyMT(fl/fl)). We hypothesized that the PyMT(mgko)-activated stroma interacts with carcinoma cells to promote invasion and metastasis. We show that the extracellular matrix associated with PyMT(mgko) tumors is stiffer and has more fibrillar collagen and increased expression of the collagen crosslinking enzyme lysyl oxidase (LOX) compared with PyMT(fl/fl) mammary carcinomas. Inhibition of LOX activity in PyMT(mgko) mice had no effect on tumor latency and size, but significantly decreased tumor metastasis through inhibition of tumor cell intravasation. This phenotype was associated with a decrease in keratin 14-positive myoepithelial cells in PyMT(mgko) tumors following LOX inhibition as well as a decrease in focal adhesion formation. Interestingly, the primary source of LOX was found to be activated fibroblasts. LOX expression in these fibroblasts can be driven by myeloid cell-derived TGF-β, which is significantly linked to human breast cancer. Overall, stromal expansion in PyMT(mgko) tumors is likely caused through the modulation of immune cell infiltrates to promote fibroblast activation. This feeds back to the epithelium to promote metastasis by modulating phenotypic characteristics of basal cells. Our data indicate that epithelial induction of microenvironmental changes can play a significant role in tumorigenesis and attenuating these changes can inhibit metastasis. Cancer Res; 73(17); 5336-46. ©2013 AACR.

Bone Morphogenetic Proteins stimulate mammary fibroblasts to promote mammary carcinoma cell invasion

Bone Morphogenetic Proteins (BMPs) are secreted cytokines that are part of the Transforming Growth Factor β (TGFβ) superfamily. BMPs have been shown to be highly expressed in human breast cancers, and loss of BMP signaling in mammary carcinomas has been shown to accelerate metastases. Interestingly, other work has indicated that stimulation of dermal fibroblasts with BMP can enhance secretion of pro-tumorigenic factors. Furthermore, treatment of carcinoma-associated fibroblasts (CAFs) derived from a mouse prostate carcinoma with BMP4 was shown to stimulate angiogenesis. We sought to determine the effect of BMP treatment on mammary fibroblasts. A large number of secreted pro-inflammatory cytokines and matrix-metallo proteases (MMPs) were found to be upregulated in response to BMP4 treatment. Fibroblasts that were stimulated with BMP4 were found to enhance mammary carcinoma cell invasion, and these effects were inhibited by a BMP receptor kinase antagonist. Treatment with BMP in turn elevated pro-tumorigenic secreted factors such as IL-6 and MMP-3. These experiments demonstrate that BMP may stimulate tumor progression within the tumor microenvironment.

Bone Morphogenetic Proteins stimulate mammary fibroblasts to promote mammary carcinoma cell invasion

Bone Morphogenetic Proteins (BMPs) are secreted cytokines that are part of the Transforming Growth Factor β (TGFβ) superfamily. BMPs have been shown to be highly expressed in human breast cancers, and loss of BMP signaling in mammary carcinomas has been shown to accelerate metastases. Interestingly, other work has indicated that stimulation of dermal fibroblasts with BMP can enhance secretion of pro-tumorigenic factors. Furthermore, treatment of carcinoma-associated fibroblasts (CAFs) derived from a mouse prostate carcinoma with BMP4 was shown to stimulate angiogenesis. We sought to determine the effect of BMP treatment on mammary fibroblasts. A large number of secreted pro-inflammatory cytokines and matrix-metallo proteases (MMPs) were found to be upregulated in response to BMP4 treatment. Fibroblasts that were stimulated with BMP4 were found to enhance mammary carcinoma cell invasion, and these effects were inhibited by a BMP receptor kinase antagonist. Treatment with BMP in turn elevated pro-tumorigenic secreted factors such as IL-6 and MMP-3. These experiments demonstrate that BMP may stimulate tumor progression within the tumor microenvironment.

Abstract 2301: Myeloid cells promote fibroblast invasion and lead mammary adenocarcinoma cell invasion

Myeloid cells localize to invasive edges of solid tumors where they promote invasive tumor growth, intravasation into vasculature and metastasis of malignant cells1,2. Fibroblasts, on the other hand, lead collective cell migration3 of carcinoma cells via fostering extracellular matrix (ECM) remodeling and generating tracks of collagen fibers that act as “highways” for cell migration4,5. To identify soluble molecules mediating these juxtacrine communication mechanisms between myeloid cells and fibroblasts in potentiating metastasis, we conducted pilot studies with subsets of spleen- or tumor-derived myeloid cells, tumor-derived fibroblasts, and mammary adenocarcinoma cells. Whereas spleen-derived CD11b+Ly6ChiLy6G− monocytes promote fibroblast migration ex vivo, two populations of tumor-derived myeloid cells, e.g., CD11b+Gr1+ and CD11b+Gr1− cells possessed this capability. In ex vivo migration assays, fibroblast migration was dependent on myeloid cell-derived factors, e.g., CXCL11, CXCL15, FGF2, IGF-1 and Shh, as well as fibroblast Akt and ERK1/2 phosphorylation. Inhibition of fibroblast MEK reduced myeloid cell-induced fibroblast migration, whereas FGF-RI inhibition completely abolished this capability. These studies indicate a role for myeloid cell-fibroblast communication in fostering migration (and potentially activation) of fibroblasts that lead collective cell migration properties of mammary carcinoma cells. Ongoing studies are identifying specific subpopulations of tumor-associated myeloid cells possessing these activities, as well as the role of FGF receptor signaling pathways in facilitating metastasis.

1.

Wyckoff, J.B., et al. Direct visualization of macrophage-assisted tumor cell intravasation in mammary tumors. Cancer Res 67, 2649-2656 (2007).

2.

Qian, B.Z. & Pollard, J.W. Macrophage diversity enhances tumor progression and metastasis. Cell 141, 39-51 (2010).

3.

Friedl, P., Locker, J., Sahai, E. & Segall, J.E. Classifying collective cancer cell invasion. Nat Cell Biol 14, 777-783 (2012).

4.

Khalil, A.A. & Friedl, P. Determinants of leader cells in collective cell migration. Integr Biol (Camb) 2, 568-574 (2010).

5.

Gritsenko, P.G., Ilina, O. & Friedl, P. Interstitial guidance of cancer invasion. J Pathol 226, 185-199 (2012).

The authors acknowledge generous support from the NIH/NCI, a Dept of Defense (DoD) Breast Cancer Research Program Postdoctoral Fellowship, a DoD Era of Hope Scholar Expansion Award, Susan G. Komen Fndt, and the Breast Cancer Research Fndt.

Citation Format: Aubie K. Shaw, Sergey Novitskiy, Lisa M. Coussens, Harold L. Moses. Myeloid cells promote fibroblast invasion and lead mammary adenocarcinoma cell invasion. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 2301. doi:10.1158/1538-7445.AM2013-2301

Abstract 4698: Gene expression profiles of triple negative breast cancer epithelial and stromal cells are predictive of treatment response

Lacking human epithelial growth factor receptor 2 (HER2) amplification as well as estrogen and progesterone receptors, TNBC is a heterogeneous collection of biologically diverse cancers that likely contributes to variable clinical outcomes for patients suffering from this disease. Since TNBC lacks well-defined molecular targets, we recently performed gene expression (GE) analyses and identified six distinct molecular TNBC subtypes with unique biologies. To further decipher the contribution of tumor epithelium and its adjacent stroma to the biology of TNBC and clinical response to treatments, we performed GE analysis on biopsy material from 20 TNBC patients enrolled in a phase II clinical trial [VICC-BRE0904; a neoadjuvant study of cisplatin and paclitaxel±RAD001 (mTOR inhibitor)]. We isolated RNA from both tumor epithelial and stromal cells using laser capture microdissection. Our goal is to determine if GE from tumor epithelial and/or stromal cells is predictive of response to treatment. Our preliminary results indicate that there is differential GE in both tumor epithelial as well as stromal cells in pretreatment biopsies of responders versus non-responders. Patients with higher expression of proliferation genes such as MKI67, KIFCI, AURKB, E2F3, and DNA damage response genes TP53BP2, CHEK1, RPA1, BLM were more responsive to treatment compared to non-responders. Upon completion of the phase II clinical trial and correlative molecular analyses, we anticipate identifying biomarkers of drug sensitivity that will provide insight to novel combination therapies for the different subtypes of TNBC.

Citation Format: Bojana Jovanovic, Steven X. Chen, Brian D. Lehmann, Kimberly N. Johnson, Violeta Sanchez, Maria G. Kuba, Melinda E. Sanders, Ingrid A. Mayer, Harold L. Moses, Jennifer A. Pietenpol. Gene expression profiles of triple negative breast cancer epithelial and stromal cells are predictive of treatment response. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 4698. doi:10.1158/1538-7445.AM2013-4698

Turn off the IDO: will clinical trials be successful?

Indoleamine 2,3-dioxygenase (IDO) is overexpressed in many human cancers and is believed to play a role in tumor immune evasion, but a requirement for IDO in tumor progression has not been formally shown. The study by Smith and colleagues in this issue of Cancer Discovery provides genetic evidence for the importance of IDO in tumorigenesis, which supports the use of IDO inhibitors in clinical trials in humans.

Abstract A56: Bone morphogenetic protein antagonist DMH1 inhibits metastasis in a mouse model of breast cancer

Bone Morphogenetic Proteins (BMPs) are secreted cytokines/growth factors belonging to the Transforming Growth Factor β (TGFβ) superfamily. BMPs have recently been shown to be overexpressed in human breast cancers; however, loss of BMP signaling in mammary carcinomas has also been shown to accelerate metastases. Human breast cancers display active BMP signaling by phosphorylated Smads 1, 5 and 8 in both the tumor and the stromal microenvironment. We hypothesized that inhibiting BMP signaling in both the tumor epithelium as well as the surrounding microenvironment would prevent tumor progression. To test this hypothesis we used DMH1, which is a selective and specific antagonist of the type I BMP receptor. Mice that express the MMTV.PyVmT oncogene were either treated with DMSO vehicle or DMH1 for six weeks following initial mammary tumor palpation. Following six weeks, animals were euthanatized and evaluated for lung metastases. Whole mount staining of lungs revealed a statically significant reduction in lung metastasis in DMH1 treated animals compared to vehicle treated (p-value = 0.03). Primary tumors demonstrated reduced proliferation (BrdU incorporation) and increased apoptosis (cleaved-caspase-3) when treated with DMH1. RNA isolated from peripheral blood at the time of sacrifice indicated decreased circulating tumor cells measured by real-time PCR. Overall, the BMP pathway represents an understudied pathway that may be suitable for targeted therapy in breast cancer.

Citation Format: Philip Owens, Michael W. Pickup, Agnieszka E. Gorska, Sergey V. Novitskiy, Charles C. Hong, Harold L. Moses. Bone morphogenetic protein antagonist DMH1 inhibits metastasis in a mouse model of breast cancer. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Invasion and Metastasis; Jan 20-23, 2013; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2013;73(3 Suppl):Abstract nr A56.

Erlotinib prolongs survival in pancreatic cancer by blocking gemcitabine-induced MAPK signals

Pancreatic ductal adenocarcinoma (PDAC) is one of the most deadly cancers worldwide. Although many regimens have been used for PDAC treatment, the combination of the EGF receptor (EGFR) inhibitor erlotinib with gemcitabine has been the only molecular-targeted drug tested so far that has been superior to gemcitabine alone. The mechanism underlying this effective combinational regimen remains unknown. Here, we show that the combination is superior to gemcitabine alone in blocking progression and prolonging survival in a murine model of PDAC (Kras activation with Tgfbr2 knockout). We found that gemcitabine induced mitogen-activated protein kinase signaling, which was dramatically inhibited by erlotinib even in the Kras-activated PDAC cells in the mouse model. Mechanistic investigations suggested that gemcitabine induces EGFR ligand expression and ERBB2 activation by increasing heterodimer formation with EGFR, thereby maintaining high levels of ERBB2 protein in PDAC cells. Overall, our findings suggest a significant role of ERBB in PDAC treatment.

Therapeutic effect of c-Jun N-terminal kinase inhibition on pancreatic cancer

c-Jun N-terminal kinase (JNK) is a member of the mitogen-activated protein kinase (MAPK) family, and it is reportedly involved in the development of several cancers. However, the role of JNK in pancreatic cancer has not been elucidated. We assessed t he involvement of JNK in the development of pancreatic cancer and investigated the therapeutic effect of JNK inhibitors on this deadly cancer. Small interfering RNAs against JNK or the JNK inhibitor SP600125 were used to examine the role of JNK in cellular proliferation and the cell cycles of pancreatic cancer cell lines. Ptf1a(cre/+) ;LSL-Kras(G12D/+) ;Tgfbr2(flox/flox) mice were treated with the JNK inhibitor to examine pancreatic histology and survival. The effect of JNK inhibition on tumor angiogenesis was also assessed using cell lines and murine pancreatic cancer specimens. JNK was frequently activated in human and murine pancreatic cancer in vitro and in vivo. Growth of human pancreatic cancer cell lines was suppressed by JNK inhibition through G1 arrest in the cell cycle with decreased cyclin D1 expression. In addition, oncogenic K-ras expression led to activation of JNK in pancreatic cancer cell lines. Treatment of Ptf1a(cre/+) ;LSL-Kras(G12D/+) ;Tgfbr2(flox/flox) mice with the JNK inhibitor decreased growth of murine pancreatic cancer and prolonged survival of the mice significantly. Angiogenesis was also decreased by JNK inhibition in vitro and in vivo. In conclusion, activation of JNK promotes development of pancreatic cancer, and JNK may be a potential therapeutic target for pancreatic cancer.

Abstract A69: The novel strategy for treatment of pancreactic ductal adenocarcinoma targeting tumor microenvironment

Background and Aim: Previously, we have reported a genetically engineered mouse pancreatic ductal adenocarcinoma (PDAC) progression model which has pancreatic-specific transforming growth factor-beta receptor type II knockout in the context of Kras activation. This model shows PDAC with 100 % penetrance and recapitulates the signature of human PDAC well. Using this model, we explored novel treatment for PDAC targeting tumor microenvironment.

Materials and Methods: To investigate whether the mice model is suitable for the drug screening, the mice were treated with gemcitabine or S-1, which are the standard drug for human PDAC, To the next, for single agent treatment, mice were treated with axitinib (A) or sunitinib (S), which are multi-kinase inhibitors, or candesartan (C) or telmisartan (T), which are anigiotensin II receptor blockers (ARBs), respectively. For combined agent experiment, mice were treated with A, C, or T combined with gemcitabine or S-1. Treatment continued until 8 weeks of age. Moreover, for the survival analysis, the drug treatment was continued until the mice became distressed. In vivo anti-tumor effect and survival time were assessed. Immunostaining of tumor tissue for caspase 3, Ki67, CD31, F4/80, α-SMA, and VEGF was performed. Azan staining also performed for the assessment of fibrosis in the tumor.

Results: Gemcitabine and S-1 showed anti-proliferative effect and prolonged overall survival of these mice compared to control, as well as human cases. Median survival time of single use of A and S group was significantly longer and that of C and T group was tended to be longer than that of control group. The entire drug-treatment group showed significantly stronger anti-tumor effect in vivo compared to control. Combined treatment led to statistically significant longer survival and more anti-tumor effect than that of single agent-treated group. A and S group showed significantly higher caspase 3 staining and lower Ki67 staining than that of control, however, C and T group showed no change of these staining, compared to control. Microvessel density, F4/80, and α-SMA staining, VEGF expression, and azan staining of the entire drug-treated group was significantly lower than that of control.

Conclusion: Targeting tumor microenvironment, such as angiogenesis, immune cell infiltration and fibrosis, using multi-kinase inhibitor or ARB in addition to cytotoxic agents, such as gemcitabine or S-1, may be a promising therapeutics for PDAC.

Citation Format: Motohisa Tada, Hideaki Ijichi, Koji Miyabayashi, Yoshinari Asaoka, Dai Mohri, Tsuneo Ikenoue, Rintarou Mikata, Takeshi Ishihara, Fumihiko Kanai, Masao Omata, Harold L. Moses, Osamu Yokosuka. The novel strategy for treatment of pancreactic ductal adenocarcinoma targeting tumor microenvironment. [abstract]. In: Proceedings of the AACR Special Conference on Tumor Immunology: Multidisciplinary Science Driving Basic and Clinical Advances; Dec 2-5, 2012; Miami, FL. Philadelphia (PA): AACR; Cancer Res 2013;73(1 Suppl):Abstract nr A69.