Abstract P3-05-09: The role of TGF-beta receptor type 3 in breast cancer progression

Breast cancer is a diverse group of diseases. Gene expression profiling has identified luminal A, luminal B, Her2-like, Normal breast-like and Basal-like as major classifications of breast cancer diseases. These correlate to the overall patient survival with the basal-like subtype, clinically termed as triple-negative breast cancers (TNBC), demonstrating the poorest overall outcome. The poor patient outcome is primarily due to absence of hormonal receptor targets ER, PR and HER2 which are the major drug-targets for currently available therapies. Considering that TNBC lacks well-defined molecular targets, our group pursued extensive genomic molecular and biological analysis of over 500 tumor tissues from TNBC patients. Ultimately, this led to the discovery of six, TNBC subtypes; among which are Mesenchymal-Stem Like (MSL) and Mesechymal (M). These two subtypes share a unique biological driver, the TGF-beta pathway.

To gain insight into the role of the TGF-β pathway signaling in TNBC we have performed gene expression analysis on all six TNBC subtypes. A major finding was that among all TGF-β pathway-associated genes, TGF-beta receptor type 3 (TBR3) is most differentially expressed in MSL and M tumor subtypes of TNBC. Based on these findings, we are hypothesizing that TBR3 is required for maintenance of tumorigenicity in MSL and M subtypes of the triple-negative breast cancer.

In order to test our hypothesis we have screened 15 TNBC cell lines for both RNA and protein levels of TBR3 and validated that TBR3 is differentially expressed in M and MSL subtypes. Furthermore, we have manipulated TBR3 expression in M and MSL TNBC cell lines and tested their ‘biologies’ using both an in vitro and in vivo model systems. Preliminary results indicate that upon silencing TBR3 expression, cell motility as well as ability to cluster together in 3D culture system is significantly changed. In addition, our xenograft mouse model also demonstrated a significant change in tumor onset and growth.

We are interested in validating the prognostic and functional contribution of TBR3 to the breast cancer progression. The results of this study will provide insight into the potential use of the TGF-β signaling axis for prognostic or therapeutic utility in breast cancer patients.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P3-05-09.

TGF-β receptor II loss promotes mammary carcinoma progression by Th17 dependent mechanisms

We report that IL-17 significantly increases the secretion of CXCL1 and CXCL5 from mammary carcinoma cells, which is downregulated by TGF-β through the type II TGF-β receptor (TβRII). Carcinoma cells with conditional knockout of TβRII (Tgfbr2(KO)) have enhanced sensitivity to IL-17a in the stimulation of chemokine secretion. During polyoma middle T (PyMT) induced tumor progression, levels of Th17 inducing cytokines TGF-β, IL-6, IL-23 were increased in PyMT/Tgfbr2(KO) tumors, which was associated with an increased number of Th17 cells. IL-17 increased the suppressive function of MDSCs on T cells through the upregulation of Arg, IDO, and COX2. Treatment of PyMT/Tgfbr2(KO) mice with anti-IL-17 Ab decreased carcinoma growth and metastatic burden. Analysis of human breast cancer transcriptome databases showed a strong association between IL-17 gene expression and poor outcome in lymph node positive, estrogen receptor negative or luminal B subtypes suggesting potential therapeutic approaches.

Abstract B71: Potential role of hemoglobin in colorectal cancer initiation in inflammatory bowel disease setting

Background: Inflammatory bowel disease (IBD) is a recognized high risk condition to develop colorectal cancer (CRC) and other intestinal cancers. Several risk factors have been described, allowing preventive strategies to focus on these patients: extensive long-standing disease, severity of inflammation, family history of CRC and primary sclerosing cholangitis (PSC).

Aims: While using MALDI MS tissue profiling, we found a unique spectral peak at mass-to-charge ratio (m/z) 5045 to be more intense in inflamed colon samples from IBD patients compared to adjacent normal tissue and/ or diverticulosis (DV). We investigated this signal as a possible transforming factor in CRC initiation, in the setting of IBD.

Methods: We profiled colonic mucosal and submucosal layers of 99 IBD patients for biomarkers that differentiated ulcerative colitis (UC) from Crohn's colitis (CC). We determined these unique differentiating proteins by histology-directed proteomic profiling using MALDI MS; protein identification utilized LC/MS/MS. We tested DNA damage by exposing an identified protein to a normal colonic epithelial cell-line (NCM 356). DNA damage was tested by comet assay.

Results: LC-MS/MS identified m/z 5045 in CC/UC subjects as triply charged free hemoglobin ion chain (Hb). Validation studies used protein extracts and tissues from full thickness samples from UC, CC, and diverticulosis (DV, controls) subjects. Both CC and UC mucosal and submucosal samples were strongly positive for Hb-α. However, DV staining was restricted to erythrocytes found in submucosal capillaries. There was no significant difference in Hb-α level between UC and CC; however UC and CC levels were significantly higher than those in DV samples (p< 0.006 and p< 0.0001, respectively). When normal colonocytes (1x105 cells/ml) were exposed to Hb (300μM for 4 hours), there was clear DNA damage analyzed by comet assay. We noted macrophage erythrophagocytosis of extravasated erythrocytes.

Conclusion: Free Hb was found in UC/CC but not DV mucosa/submucosa tissue. Free Hb resulted from extravasated macrophage erythrophagocytosis. Hb significantly induced DNA-damage of normal epithelial colonocytes (NCM356). DNA-damage could potentially increase risks for CRC transformation. Further elucidative studies are underway.

Citation Format: Laura A. Franklin, Joan C. Smith, Billy R. Ballard, Erin H. Seeley, Mary K. Washington, Jeremy L. Norris, Kevin L. Schey, Harold L. Moses, Richard M. Caprioli, Samuel E. Adunyah, Amosy E. M'Koma. Potential role of hemoglobin in colorectal cancer initiation in inflammatory bowel disease setting. [abstract]. In: Proceedings of the Fifth AACR Conference on the Science of Cancer Health Disparities in Racial/Ethnic Minorities and the Medically Underserved; 2012 Oct 27-30; San Diego, CA. Philadelphia (PA): AACR; Cancer Epidemiol Biomarkers Prev 2012;21(10 Suppl):Abstract nr B71.

Lack of transforming growth factor-β signaling promotes collective cancer cell invasion through tumor-stromal crosstalk

INTRODUCTION

Transforming growth factor beta (TGF-β) has a dual role during tumor progression, initially as a suppressor and then as a promoter. Epithelial TGF-β signaling regulates fibroblast recruitment and activation. Concurrently, TGF-β signaling in stromal fibroblasts suppresses tumorigenesis in adjacent epithelia, while its ablation potentiates tumor formation. Much is known about the contribution of TGF-β signaling to tumorigenesis, yet the role of TGF-β in epithelial-stromal migration during tumor progression is poorly understood. We hypothesize that TGF-β is a critical regulator of tumor-stromal interactions that promote mammary tumor cell migration and invasion.

METHODS

Fluorescently labeled murine mammary carcinoma cells, isolated from either MMTV-PyVmT transforming growth factor-beta receptor II knockout (TβRII KO) or TβRIIfl/fl control mice, were combined with mammary fibroblasts and xenografted onto the chicken embryo chorioallantoic membrane. These combinatorial xenografts were used as a model to study epithelial-stromal crosstalk. Intravital imaging of migration was monitored ex ovo, and metastasis was investigated in ovo. Epithelial RNA from in ovo tumors was isolated by laser capture microdissection and analyzed to identify gene expression changes in response to TGF-β signaling loss.

RESULTS

Intravital microscopy of xenografts revealed that mammary fibroblasts promoted two migratory phenotypes dependent on epithelial TGF-β signaling: single cell/strand migration or collective migration. At epithelial-stromal boundaries, single cell/strand migration of TβRIIfl/fl carcinoma cells was characterized by expression of α-smooth muscle actin and vimentin, while collective migration of TβRII KO carcinoma cells was identified by E-cadherin+/p120+/β-catenin+ clusters. TβRII KO tumors also exhibited a twofold greater metastasis than TβRIIfl/fl tumors, attributed to enhanced extravasation ability. In TβRII KO tumor epithelium compared with TβRIIfl/fl epithelium, Igfbp4 and Tspan13 expression was upregulated while Col1α2, Bmp7, Gng11, Vcan, Tmeff1, and Dsc2 expression was downregulated. Immunoblotting and quantitative PCR analyses on cultured cells validated these targets and correlated Tmeff1 expression with disease progression of TGF-β-insensitive mammary cancer.

CONCLUSION

Fibroblast-stimulated carcinoma cells utilize TGF-β signaling to drive single cell/strand migration but migrate collectively in the absence of TGF-β signaling. These migration patterns involve the signaling regulation of several epithelial-to-mesenchymal transition pathways. Our findings concerning TGF-β signaling in epithelial-stromal interactions are important in identifying migratory mechanisms that can be targeted as recourse for breast cancer treatment.

Pathway analyses identify TGFBR2 as potential breast cancer susceptibility gene: results from a consortium study among Asians

BACKGROUND

The TGF-β signaling pathway plays a significant role in the carcinogenic process of breast cancer.

METHODS

We systematically evaluated associations of common variants in TGF-β signaling pathway genes with breast cancer risk using a multistage, case-control study among Asian women.

RESULTS

In the first stage, 341 single-nucleotide polymorphisms with minor allele frequencies ≥ 0.05 across 11 genes were evaluated among 2,926 cases and 2,380 controls recruited as a part of the Shanghai Breast Cancer Genetics Study (SBCGS). In the second stage, 20 SNPs with promising associations were evaluated among an additional 1,890 cases and 2,000 controls from the SBCGS. One variant, TGFBR2 rs1078985, had highly consistent and significant associations with breast cancer risk among participants in both study stages, as well as promising results from in silico analysis. Additional genotyping was carried out among 2,475 cases and 2,343 controls from the SBCGS, as well as among 5,077 cases and 5,384 controls from six studies in the Asian Breast Cancer Consortium (stage III). Pooled analysis of all data indicated that minor allele homozygotes (GG) of TGFBR2 rs1078985 had a 24% reduced risk of breast cancer compared with major allele carriers (AG or AA; OR, 0.76; 95% CI, 0.65-0.89; P = 8.42 × 10(-4)).

CONCLUSION

These findings support a role for common genetic variation in TGF-β signaling pathway genes, specifically in TGFBR2, in breast cancer susceptibility.

IMPACT

These findings may provide new insights into the etiology of breast cancer as well as future potential therapeutic targets.

Deletion of TGF-β signaling in myeloid cells enhances their anti-tumorigenic properties

By crossing LysM-Cre and TGF-β type II receptor (Tgfbr2) floxed mice we achieved specific deletion of Tgfbr2 in myeloid cells (Tgfbr2(MyeKO) mice). S.c.-injected (LLC, EL4-OVA) and implanted (MMTV-PyMT) carcinoma cells grow slower in Tgfbr2(MyeKO) mice. The number of CD45(+) cells in the tumor tissue was the same in both genotypes of mice, but upon analysis, the percentage of T cells (CD45(+)CD3(+)) in the KO mice was increased. By flow cytometry analysis, we did not detect any differences in the number and phenotype of TAMs, CD11b(+)Gr1(+), and DCs in Tgfbr2(MyeKO) compared with Tgfbr2(MyeWT) mice. ELISA and qRT-PCR data showed differences in myeloid cell functions. In Tgfbr2(MyeKO) TAMs, TNF-α secretion was increased, basal IL-6 secretion was down-regulated, TGF-β did not induce any VEGF response, and there was decreased MMP9 and increased MMP2 and iNOS expression. TGF-β did not have any effect on CD11b(+)Gr1(+) cells isolated from Tgfbr2(MyeKO) mice in the regulation of Arg, iNOS, VEGF, and CXCR4, and moreover, these cells have decreased suppressive activity relative to T cell proliferation. Also, we found that DCs from tumor tissue of Tgfbr2(MyeKO) mice have increased antigen-presented properties and an enhanced ability to stimulate antigen-specific T cell proliferation. We conclude that Tgfbr2 in myeloid cells has a negative role in the regulation of anti-tumorigenic functions of these cells, and deletion of this receptor decreases the suppressive function of CD11b(+)Gr1(+) cells and increases antigen-presenting properties of DCs and anti-tumorigenic properties of TAMs.

Abstract A39: The exploration of novel strategy for treatment of pancreactic ductal adenocarcinoma targeting tumor microenvironment with multi-kinase inhibitors

Background and Aim: Pancreatic ductal adenocarcinoma (PDAC) is an almost uniformly lethal disease in humans. Previously, we have reported a genetically engineered mouse PDAC progression model which has pancreatic-specific transforming growth factor-beta receptor type II knockout in the context of Kras activation (Ijichi H, et al 2006). This model shows PDAC with 100% penetrance and recapitulates the signature of human PDAC well. Using this model, we explored novel treatment for PDAC.

Materials and Methods: At first, to investigate whether the mice model is suitable for the drug screening, the mice were treated with gemcitabine (12.5 mg/kg) by intraperitoneal (i.p.) injection or S-1 (8.4 mg/kg) per oral, which are the standard drug for human PDAC. To the next, for single agent treatment, mice were treated orally 6 times a week with vehicle (0.5 % carboxymethyl cellulose, CMC), sunitinib (40 mg/kg), and axitinib (30mg/kg), both of which are multikinase inhibitors targeting vascular endothelial growth factor receptor (VEGFR) and platelet derived growth factor receptor (PDGFR) from the 3 weeks of age. For combined agent experiment, mice were treated orally with vehicle (0.5 % CMC) or axitinib from the 3 weeks of age and also treated with saline or gemcitabine, i.p. twice a week from the 4 weeks of age. Treatment continued until 8 weeks of age. Moreover, for the survival analysis, the drug treatment was continued until the mice became distressed according to the same schedule stated above. In vivo anti-tumor effect and survival time were assessed. Immunostaining of tumor tissue for caspase 3, Ki67, CD31, F4/80 and VEGF was performed. Azan staining also performed for the assessment of fibrosis in the tumor.

Results: Gemcitabine and S-1 showed antiproliferative effect and prolonged overall survival of these mice compared to control, as well as human cases. Median survival time of single use of axtinib and sunitinib group was significantly longer (p <0.01) than that of control group. Axitinib and sunitinib group showed significantly stronger anti-tumor effect in vivo (p <0.01). In the combined treatment experiment, gemcitabine plus axitinib-treated group showed statistically significant longer survival and more anti-tumor effect than that of gemcitabine or axtinib alone-treated group (p <0.01). Axitinib and sunitinib group showed significantly higher caspase 3 stainng and lower Ki67 staining than that of control (p <0.01). Microvessel density (CD 31 staining) of axitinib and sunitinib group was significantly lower than that of control (p <0.01). F4/80 staining was significantly lower in axitinib and sunitinib-treated group than that of control (p <0.05). VEGF expression of axitinib and sunitinib group was significantly lower than that of control a (p <0.001). Azan staining showed significantly lower fibrosis in axitinib and sunitinib-treated group compared to control (p <0.01).

Conclusion: Targeting not only cancer cells but also tumor microenvironment, such as angiogenesis, infiltration of immune cells, and fibrosis, with the use of multikinase inhibitors in addition to gemcitabine, may be a promising therapeutics for PDAC.

Abstract 2058: Colorectal cancer in the setting of inflammatory bowel disease: role of hemoglobin

Colorectal carcinoma (CRC) is a serious complication of inflammatory bowel disease (IBD) and accounts for approximately 15% of all IBD-associated deaths. The likelihood of IBD-related carcinoma is greater than that of sporadic CRC. Over one half are diagnosed at stage III or IV. During the last few years we have worked on mining colon mucosal and submucosal layers for discovery of biomarkers that differentiate ulcerative colitis (UC) from Crohn's colitis (CC). Using LC-MS/MS, we examined signals found to be significantly different between CC and UC samples. We found a signal at m/z 5045 which was more intense in UC samples. The MALDI spectrum did not identify an intact protein entity but did identify hemoglobin chains. Macrophages are highly versatile phagocytes active in multiple roles in the immune system and key players in the inflammatory response. The microenvironment of most inflammation is filled with a large population of macrophages. In IBD, studies have found that macrophages can count for more than 50% of the exudative mass. Their presence within the inflammatory microenvironment, in some cases, has been proven to increase transformation, angiogenesis, and immunosuppression. In hemorrhagic situations (as in UC) macrophages engulf erythrocytes and as a result release free heme iron (heFe). Earlier studies observed that heFe has cellular proliferation effects on colon cancer cells. Recently, the potential carcinogenic effects of heFe were documented when it was shown that heFe increases the number of aberrant crypt foci in colon mucosa. In the colon, iron is expected to increase the production of reactive oxygen (O2) species (ROS) from peroxides via the Fenton reaction, which may be the cause of cellular toxicity and even pro-mutagenic lesions. Intracellular reactions with active O2 can result in the initiation and progression of carcinogenesis by induction of gene mutations, chromosomal damage and cytotoxic effects. We hypothesize that elevated expression of mucosal free heFe would be associated with an increased risk of UC-associated CRC. To validate this will require investigating whether hemoglobin could be classified as a proliferative or transforming agent for colon cancer cells by causing reactive oxygen species release. For this purpose, we plan to study the cellular viability of differentiated colon cell line (cancer: CCL 224, CCL 227 and normal: NCM 356 and NCM 460) after administration of hemoglobin at different concentrations. ROS production will be investigated in each step. Additionally, we intend to examine the potential cytotoxicity of hemoglobin. Supported: MMC-VICC Cancer Partnership Grant # 3U54CA091408-09S 1 (SEA & HLM); MeTRC grant # 5U54RR026140-03 (SEA), and Vanderbilt SPORE in GI Cancer Grant # P50CA095103

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2058. doi:1538-7445.AM2012-2058

Abstract 1500: Bone morphogenetic proteins stimulate mammary fibroblasts to promote mammary tumorigenesis

Bone Morphogenetic Proteins (BMPs) are secreted cytokines/growth factors belonging to the Transforming Growth Factor ≤ (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. Stimulation of dermal fibroblasts with BMP4 can enhance pro-tumorigenic factors uniquely from the epidermal response. Additionally, treatment of carcinoma-associated fibroblasts (CAFs) derived from a mouse prostate carcinoma with BMP have been reported to stimulate tumor-associated angiogenesis. We sought to determine the effect of BMP treatment on mammary fibroblasts and determine their response during mammary tumor progression. We first identified secreted pro-inflammatory cytokines and matrix-metalloproteinases (MMPs) upregulated in response to BMP4 treatment. We found that fibroblasts stimulated with BMP4 could enhance tumor invasion, which was inhibited by a BMP receptor kinase antagonist. We next demonstrated that BMP signaling was specifically absent in the stroma of human ductal and lobular carcinoma in situ (DCIS & LCIS). Yet after progression to invasion, breast tumors of many distinct subtypes contained a stroma active for BMP signaling. We further extended these observations with human normal mammary fibroblasts and compared them to human fibroblasts from breast cancer and found that BMP was capable of inducing MMP3 and IL-6 secretion in normal fibroblasts. However carcinoma associated fibroblasts had constitutively elevated levels of MMP3 and IL-6 that corresponded to enhanced BMP signaling in addition to loss of secreted BMP antagonists. These experiments demonstrate that BMP may play important tumor promoting functions within the tumor microenvironment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 1500. doi:1538-7445.AM2012-1500

Abstract LB-495: Myeloid-derived suppressor cells promote cancer-associated fibroblast migration and carcinoma cell invasion

Metastasis the most devastating part of cancer, yet we know very little about the earliest steps of metastasis. Myeloid-Derived Suppressor Cells (MDSC) are CD11b+, Gr-1+ bone marrow-derived cells that have been shown to promote tumor development by suppressing T cells. In addition to immune suppression, MDSC can promote metastasis. MDSC localize to the invasive edges of primary tumors and promote breast cancer lung metastasis. Localized invasion of cancer cells is the earliest step of metastasis and fibroblasts are required for breast cancer cell invasion. Fibroblasts remodel the ECM and leave tracks for collective migration of carcinoma cells. These studies seek to identify the mechanism of MDSC promotion of metastasis by determining if MDSC can stimulate fibroblast migration and lead localized carcinoma invasion. Freshly isolated MDSC from a mammary tumor-bearing mouse increase fibroblast migration. TGFβRII-/- fibroblasts demonstrate a further increase in migration in response to MDSC, suggesting that TGFβ signaling is not required for MDSC promotion of fibroblast migration. MDSC secretions act directly on fibroblasts since conditioned medium from MDSC increases fibroblast migration to the same extent as live MDSC. Antibody array analysis identified several MDSC secreted proteins, including CXCL11, CXCL15, FGF2, IGF-I, IL-4 and Shh. MDSC increase carcinoma cell invasion through Matrigel, but only when fibroblasts are present. MDSC treatment of fibroblasts stimulates Akt and ERK1/2 phosphorylation and loss of secreted proteins, including SDF-1, TIMP-1, TNFα and VEGF. Analysis of subsets of MDSC identified that monocytic MDSC (CD11b+, Ly6Chi, Ly6G-) increase fibroblast migration more than other myeloid cell populations. Tumor-derived MDSC promote fibroblast migration more that splenic MDSC. These studies show that MDSC can lead fibroblasts to stimulate carcinoma invasion and suggest that perivascular MDSC may be the earliest stimulus for localized invasion during metastasis.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr LB-495. doi:1538-7445.AM2012-LB-495

p120-catenin is essential for terminal end bud function and mammary morphogenesis

Although p120-catenin (p120) is crucial for E-cadherin function, ablation experiments in epithelial tissues from different organ systems reveal markedly different effects. Here, we examine for the first time the consequences of p120 knockout during mouse mammary gland development. An MMTV-Cre driver was used to target knockout to the epithelium at the onset of puberty. p120 ablation was detected in approximately one-quarter of the nascent epithelium at the forth week post-partum. However, p120 null cells were essentially nonadherent, excluded from the process of terminal end bud (TEB) morphogenesis and lost altogether by week six. This elimination process caused a delay in TEB outgrowth, after which the gland developed normally from cells that had retained p120. Mechanistic studies in vitro indicate that TEB dysfunction is likely to stem from striking E-cadherin loss, failure of cell-cell adhesion and near total exclusion from the collective migration process. Our findings reveal an essential role for p120 in mammary morphogenesis.

Altered prostate epithelial development in mice lacking the androgen receptor in stromal fibroblasts

BACKGROUND

Androgens and the androgen receptor (AR) play important roles in the development of male urogenital organs. We previously found that mice with total AR knockout (ARKO) and epithelial ARKO failed to develop normal prostate with loss of differentiation. We have recently knocked out AR gene in smooth muscle cells and found the reduced luminal infolding and IGF-1 production in the mouse prostate. However, AR roles of stromal fibroblasts in prostate development remain unclear.

METHODS

To further probe the stromal fibroblast AR roles in prostate development, we generated tissue-selective knockout mice with the AR gene deleted in stromal fibroblasts (FSP-ARKO). We also used primary culture stromal cells to confirm the in vivo data and investigate mechanisms related to prostate development.

RESULTS

The results showed cellular alterations in the FSP-ARKO mouse prostate with decreased epithelial proliferation, increased apoptosis, and decreased collagen composition. Further mechanistic studies demonstrated that FSP-ARKO mice have defects in the expression of prostate stromal growth factors. To further confirm these in vivo findings, we prepared primary cultured mouse prostate stromal cells and found knocking down the stromal AR could result in growth retardation of prostate stromal cells and co-cultured prostate epithelial cells, as well as decrease of some stromal growth factors.

CONCLUSIONS

Our FSP-ARKO mice not only provide the first in vivo evidence in Cre-loxP knockout system for the requirement of stromal fibroblast AR to maintain the normal development of the prostate, but may also suggest the selective knockdown of stromal AR might become a potential therapeutic approach to battle prostate hyperplasia and cancer.

β-Catenin and K-RAS synergize to form primitive renal epithelial tumors with features of epithelial Wilms' tumors

Wilms' tumor (WT) is the most common childhood renal cancer. Although mutations in known tumor-associated genes (WT1, WTX, and CATNB) occur only in a third of tumors, many tumors show evidence of activated β-catenin-dependent Wnt signaling, but the molecular mechanism by which this occurs is unknown. A key obstacle to understanding the pathogenesis of WT is the paucity of mouse models that recapitulate its features in humans. Herein, we describe a transgenic mouse model of primitive renal epithelial neoplasms that have high penetrance and mimic the epithelial component of human WT. Introduction of a stabilizing β-catenin mutation restricted to the kidney is sufficient to induce primitive renal epithelial tumors; however, when compounded with activation of K-RAS, the mice develop large, bilateral, metastatic, multifocal primitive renal epithelial tumors that have the histologic and staining characteristics of the epithelial component of human WT. These highly malignant tumors have increased activation of the phosphatidylinositol 3-kinase-AKT and extracellular signal-regulated kinase pathways, increased expression of total and nuclear β-catenin, and increased downstream targets of this pathway, such as c-Myc and survivin. Thus, we developed a novel mouse model in which activated K-RAS synergizes with canonical Wnt/β-catenin signaling to form metastatic primitive renal epithelial tumors that mimic the epithelial component of human WT.

Inhibiting Cxcr2 disrupts tumor-stromal interactions and improves survival in a mouse model of pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), one of the most lethal neoplasms, is characterized by an expanded stroma with marked fibrosis (desmoplasia). We previously generated pancreas epithelium-specific TGF-β receptor type II (Tgfbr2) knockout mice in the context of Kras activation (mice referred to herein as Kras+Tgfbr2KO mice) and found that they developed aggressive PDAC that recapitulated the histological manifestations of the human disease. The mouse PDAC tissue showed strong expression of connective tissue growth factor (Ctgf), a profibrotic and tumor-promoting factor, especially in the tumor-stromal border area, suggesting an active tumor-stromal interaction. Here we show that the PDAC cells in Kras+Tgfbr2KO mice secreted much higher levels of several Cxc chemokines compared with mouse pancreatic intraepithelial neoplasia cells, which are preinvasive. The Cxc chemokines induced Ctgf expression in the pancreatic stromal fibroblasts, not in the PDAC cells themselves. Subcutaneous grafting studies revealed that the fibroblasts enhanced growth of PDAC cell allografts, which was attenuated by Cxcr2 inhibition. Moreover, treating the Kras+Tgfbr2KO mice with the CXCR2 inhibitor reduced tumor progression. The decreased tumor progression correlated with reduced Ctgf expression and angiogenesis and increased overall survival. Taken together, our data indicate that tumor-stromal interactions via a Cxcr2-dependent chemokine and Ctgf axis can regulate PDAC progression. Further, our results suggest that inhibiting tumor-stromal interactions might be a promising therapeutic strategy for PDAC.

Abstract A45: Molecular targets in early detection and differentiation of inflammatory bowel disease-associated colon-rectal-anal cancer disparities

The inflammatory bowel disease (IBD), Crohn's (CC) and ulcerative colitis (UC), affect approximately 1–2 of every 1000 people in developed countries. These chronic inflammatory diseases result in significant morbidity and mortality. All IBD-associated colorectal-anal cancers (CRAC) occurred in segments of colitis and are frequently diagnosed at an advanced stage. This presentation is a continuation of our work that investigates potential molecules that could define a unique classifier between CC and UC and early detection of CRAC.

There are multiple challenges to identifying protein classifiers suggesting outcome prediction and differentiation for patients with IBD and/or IBD-CRAC from molecular interpretation standpoints is complex. While there are technical approach advances, the goal is clear however: to produce scientific evidence which can provide personalized expert care to patients.

We have developed an amenable proteomic methodology that supports the diagnostic feasibility to discriminate molecularly, different inflammatory colitis. The histologic layers of colectomy samples from patients with confirmed UC and CC tissues were analyzed using matrix-assisted laser de-sorption/ionization mass spectrometry (MALDI MS) for proteomic profiling.

Our previous findings (1) prompted further sample collection resulting in an increased sample size that would allow a more robust analysis. The samples from colon tissues collected in 2008 and samples collected in 2010 were re-randomized into training and independent test sets in order to avoid systematic differences between new and old data sets, typical for MALD-ToF spectra acquired in situ from tissue at different times. MALDI-ToF spectra were included in the analysis only for samples containing more than 3 unique spectra. Our studies have successfully identified 11 highly significant mass-to-charge ratio (m/z) signals (m/z 5045, 6139, 9245, 8413, 3666, 3595, 4122, 8774, 2778, 9232 and 9519) that distinguish CC from UC. These features are independent of the tissue of origin and represent disease specific markers. Some of these signatures were only found in the colonic mucosa (m/z 8413, 3666 & 3595) or submucosa (m/z 4122, 8774, 2778, 9232 & 9519) while others were found in both two layers (m/z 5045, 6139 & 9245). This information may provide new avenues for the development of novel diagnostic, prognostic and therapeutic targets. We will analyze CRAC in IBD segments2,3 to look for these proteins that may help in studying their biological mechanisms in cancer transformation.

Support: 3U54CA091408-09S1 (to MMC-VICC Partnership: SE Adunyah & HL Moses)

References:

1. M'Koma AE, Seely EH, Washington MK, Schwartz DA, Muldoon RL, Herline AJ, Wise PE, Caprioli RM Proteomic Profiling of Mucosal and Submucosal Colonic Tissues Yields Protein Signatures that Differentiate the Inflammatory Colitides. Inflamm Bowel Dis 2011;17:875-83.

2. M'Koma AE, Moses HL, Adunyah SE. Inflammatory bowel disease-associated colorectal cancer: proctocolectomy andmucosectomy does not necessarily eliminate pouch related cancer incidences. Int J colorect Dis 2011;26:533-52.

3. Um JW, M'Koma AE. Pouch-related dysplasia and adenocarcinoma following restorative proctocolectomy for ulcerative colitis. Tech coloproctol 2011;15:7-16.

Citation Information: Cancer Epidemiol Biomarkers Prev 2011;20(10 Suppl):A45.

Inflammatory bowel disease-associated colorectal cancer: proctocolectomy and mucosectomy do not necessarily eliminate pouch-related cancer incidences

BACKGROUND

Colorectal cancer (CRC), the most lethal long-term complication of inflammatory bowel disease (IBD), is the culmination of a complex sequence of molecular and histologic derangements of the colon epithelium that are initiated and at least partially sustained by prolonged chronic inflammation. Dysplasia, the earliest histologic manifestation of this process, plays an important role in cancer prevention by providing the first clinical alert that this sequence is under way and by serving as an endpoint in colonoscopic surveillance of patients at high risk for CRC. Restorative proctocolectomy (RPC) is indicated for patients with IBD, specifically for ulcerative colitis that is refractory to medical treatment, emergency conditions, and/or in case of neoplastic transformation. Even after RPC with mucosectomy, pouch-related carcinomas have recently been reported with increasing frequency since the first report in 1984. We review IBD-associated CRC and pouch-related neoplasia prevalence, adverse events, risk factors, and surveillances.

METHODS

Literature of IBD-associated CRC patients and those undergoing RPC surgeries through 2010 were prospectively reviewed.

RESULTS

We found 12 studies from retrospective series and 15 case reports. To date, there are 43 reported cases of pouch-related cancers. Thirty-two patients had cancer in the anal transit zone (ATZ); of these, 28 patients had mucosectomy. Eleven patients had cancer found in the pouch body.

CONCLUSION

RPC with mucosectomy does not necessarily eliminate risks. There is little evidence to support routine surveillance of pouch mucosa and the ATZ except for patients associated with histological type C changes, sclerosing cholangitis, and unremitting pouchitis.

Abstract 2845: Dominant-negative TGFβRII (DNIIR) in c-neu-induced mammary carcinoma cells increases metastasis by disturbing vasculogenesis and pericyte balance

In a mouse model with knockout of the type II TGF-β receptor (Tgfbr2) in mammary carcinoma cells (MMTV-PyMT), we have shown that TGF-β suppresses the expression of chemokines from tumor cells that are responsible for the expansion and recruitment of MDSCs in tumor bearing mice and these cells play a key role in tumor growth and metastasis. With the combination of the MMTV-c-neu oncogene and MMTV-DNIIR, tumors developed with a median latency of 41 weeks, 7 weeks later than mice expressing the MMTV-c-neu transgene alone. This indicates that c-neu signaling may cooperate to some degree with TGF-β signaling to induce tumor formation. This is different from the results with Tgfbr2 KO in combination with the PyMT transgene where the median latency was much shorter than with the MMTV-PyMT transgene alone. Significantly, expression of the DNIIR along with c-neu increases pulmonary metastases four fold similar to the effect of knockout of Tgfbr2 in the PyMT model. This model is important, because expression of the DNIIR transgene increases latency of mammary tumor formation in parallel with increases pulmonary metastases.

Because of the long latency in the c-neu model, we used of established c-neu and c-neu/DNIIR (cDNIIR) cell lines in collagen plugs orthotopically implanted in syngeneic mice. We found that cDNIIR implants have a longer latency than the c-neu cells, similar to that observed with the spontaneous tumors. However, by 11 weeks, the cDNIIR tumors are the same size as the c-neu tumors. Importantly, the cDNIIR tumors metastasize more readily to the lung than the c-neu tumors similar to the spontaneous model. We found that cDNIIR carcinoma cells, unlike the PyMT-Tgfbr2 KO cells, actually express less CXCL1/5 in parallel with less abundance of myeloid cells in tumor tissue. Protein analysis showed that cDNIIR cells express significantly more MCP-1, IL-6 and VEGF than c-neu cells. Also, we found that TGF-β has a very strong effect for up-regulation of VEGF secretion from cDNIIR cells compared with c-neu, which we expect is the primary mechanism for increased metastasis. It has been shown by other investigators that TGF-β plays an important role in pericytes and activation of this signaling pathway in these cells is necessary to support angio-and vasculogenesis. We hypothesize that increased binding of TGF-β to cDNIIR will lead to diminished TGF-β in tumor microenvironment and result in a decreased number of pericytes. By immunofluorescent staining of tumor tissue for blood vessels (CD31) and pericytes (desmin, NG2) we found fewer vessels wrapped by pericytes in cDNIIR mice.

We conclude that the tumor microenvironment of mammary carcinomas expressing DNIIR have increased vasculogenesis by up-regulation of VEGF in tumor cells and reduced pericytes. As a result these mice have more metastasis by increased permeability and leakage of tumor vessels.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2845. doi:10.1158/1538-7445.AM2011-2845

Abstract 544: Blockade of CXC chemokines/CXCR2 axis in the tumor microenvironment as a potent therapeutic strategy for pancreatic ductal adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC), one of the most lethal neoplasms, is characterized histologically by expanded stromal components with marked fibrosis, which suggests that tumor-stromal interaction might play an important role in PDAC progression.

We have established pancreas epithelium-specific transforming growth factor-ß receptor type II (Tgfbr2) knockout mice in the context of active Kras (KrasG12D) expression (Kras+Tgfbr2KO), which developed differentiated PDAC with 100% penetrance and recapitulated histology of human PDAC described above.

In the AACR annual meetings 2009-10, we have reported that tumor-stromal interaction in the PDAC model promoted tumor progression and blockade of CXC chemokines/CXCR2 axis inhibited tumor growth and extended survival of the mice.

We further examined the underlying mechanisms of tumor-stromal interaction. The CXC chemokines secreted from the PDAC cells did not change autocrine PDAC cell proliferation nor that of stromal fibroblasts, but induced CTGF expression in the stromal fibroblasts and promoted tumor angiogenesis, which resulted in promotion of tumor growth. Expression of the CXC chemokines was downregulated by TGF-β signaling, whereas, NF-κB signaling was required for the expression. Subcutaneous xenografts coinjected with the PDAC cells and fibroblasts grew faster than those with PDAC cells alone, which suggested tumor-promoting tumor-stromal interaction. We further examined the xenograft growth of CXCR2-knocked down (KD) PDAC cells and CXCR2-intact firbroblasts, compared with that of CXCR2-intact PDAC cells and CXCR2-KD fibroblasts. Results suggested that intact CXCR2 in the stromal fibroblasts was required for the tumor-promoting CXC chemokines/CXCR2 axis. In conclusion, blockade of the CXC chemokines/CXCR2 axis might have a key role in modulating the tumor microenvironment and for development of more effective therapeutic strategy for PDAC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 544. doi:10.1158/1538-7445.AM2011-544

Abstract LB-463: Proteomic patterns of colonic submucosa delineates the inflammatory colitides. This could aid understand IBD-related colorectal malignancy

Purpose: Differentiating Crohn's colitis (CC) and ulcerative colitis (UC) can be challenging even in combination of clinical, endoscopic, radiologic and histopathology examination. Biomarker studies have thus far been unsuccessful for disease delineation. We aim to use unique tissue proteomic methods to evaluate colonic tissue layers for potential biomarkers to identify CC vs. UC. Methods: Fresh-frozen colon specimens from resections for IBD and/or colorectal cancer were retrospectively retrieved. Colitis diagnoses were histologically re-confirmed by a blinded gastrointestinal pathologist. Three sample groups (n=5 each group) were examined: normal colon from CRC specimens (control), UC & CC. MALDI-MS was used to profile mucosal and submucosal compartments individually. Frozen tissues were sectioned at ∼10–15 μm for mounting onto either metal or conductive glass target plates (the glass plates allowing for histologic and MALDI-MS analysis on the same section). Sinapinic acid (20 mg/mL in 50:50 acetonitrile: 0.1% TFA in water) was used to give the best combination of uniform crystal coverage and signal quality for direct tissue protein analysis. Results: MALDI-MS achieved high mass accuracy (±0.01 Daltons) in the lower mass range (<15 kDa). There was distinguishable isotopic resolution of mass-to-charge ratio (m/z) values between normal vs the IBD and more strikingly between CC vs. UC (p< 0.0009) of SAM and FDR tests. There were 5 statistically significant discriminative m/z peaks observed in CC vs UC submucosa. The mucosa did not yield such distinctive peaks. Both the mucosa and submucosa provided signatures that differentiated IBD (CC or UC)) from control tissues (p< 0.001). Conclusions: MALDI-MS tissue profiling as described distinguished the colitides. The methodology revealed 5 m/z peaks of interest. Analyses are underway to identify these IBD discriminative proteins. We hypothesize that these biomarker candidates that distinguish UC from CC will allow delineation of indeterminate colitis into UC or CC. Whether these protein fingerprints play a role in colonic carcinogenesis remains to be elucidated.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-463. doi:10.1158/1538-7445.AM2011-LB-463

Abstract LB-428: Upregulation of serum amyloid A1 (SAA 1) gene is associated with ulcerative colitis-related colon cancer

Purpose: Ulcerative colitis (UC)-associated colon cancer is frequently diagnosed in an advanced stage. SAA1 is a secreted protein made in the liver and circulates in low levels in blood. SAA1 gene is expressed in colon carcinomas and is a chemoattractant with induction of migration, adhesion, and tissue infiltration of monocytes and Polymorphnuclear-leucocytes (PMN-L).

Methods: Laser capture microdissection of colonic submucosa from UC (n=8), Crohn's colitis (CC) (n=8)), and normal (NL, n=8) samples was performed. The submucosal mRNA was extracted using the PicoPure(TM) RNA Isolation Kit. Comprehensive gene expression analysis of the pooled mRNA from each group was then performed using the Affymetrix GeneChip® Gene 1.0 ST Array System. Statistical comparisons of UC vs. CC and NL as well as CC versus UC and NL were performed (Wilcoxon Rank Test). To detect changes for UC, we compared UC to CC and UC to NL; and for CC, we compared CC to UC and CC to NL.

Results: Analysis of all UC vs. CC and NL controls showed 28,869 genes which were represented on the array by 26 probes spread across the full length of each gene. When compared UC vs. CC and NL SAA1 remained the most upregulated gene showing a 56.8-folds and 91.3-folds (p< 0.0001) over expression.

Conclusion: Microarray assessments show significantly overexpression of SAA1 in UC specimens. SAA1 has a role in local inflammation in the microenvironment of malignant tissue and is expressed in colon carcinomas. Our finding may potentially facilitate and validate the SAA1 as a new early predictive clinical marker and a unique target for designing novel selective inhibitors for therapeutic intervention of UC-associated CRC.

Acknowledgement: 3U54CA091408–09S1 (MMC-VICC partnership)

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr LB-428. doi:10.1158/1538-7445.AM2011-LB-428

Abstract 3292: The exploration of novel strategy for treatment of pancreactic cancer using genetically engineered mice

(Background and Aim) Pancreatic ductal adenocarcinoma (PDAC) is an almost uniformly lethal disease in human. Previously, we have reported a genetically engineered mouse PDAC progression model which has pancreatic-specific transforming growth factor-beta receptor type II knockout in the context of Kras activation (Ijichi H, et al 2006). This model shows PDAC with 100 % penetrance and recapitulates the signature of human PDAC well. Using this model, we explored novel treatment for PDAC.

(Materials and Methods) For single agent treatment, mice were treated orally 6 times per week with vehicle (0.5 % carboxymethyl cellulose, CMC), sunitinib, axitinib, 5 kinds of anigiotensin II receptor blockers (ARBs), such as candesartan, telmisartan, losartan, valsartan, or olmesartan, respectively from the 3 wk of age. For combined agent experiment, mice were treated orally with vehicle (0.5 % CMC), axitinib or candesartan from the 3 wk of age and also treated with saline or gemcitabine, i.p. twice a week, from the 4 wk of age. Treatment continued until the mice became distressed, and then they were dissected. In vivo anti-tumor effect and survival time were assessed. Immunostaining of tumor tissue for caspase 3, Ki67, CD31, and VEGF was performed.

(Results)Median survival time of single use of axtinib and sunitinib group was statistically longer and that of candesartan and telmisartan group was tended to be longer than that of control group. Axtinib, sunitinib, candesartan, and telmisartan group showed significant anti-tumor effect in vivo. In the combined treatment experiment, using gemcitabine showed statistically significant longer survival and more anti-tumor effect than that of single agent treatment group. Axitinib and sunitinib group showed significantly higher caspase 3 score and lower Ki67 score than that of control, however, candesartan and telimisartan group showed no change of these scores, compared to control. Microvessel density of axtinib, sunitinib, candesartan, and telmisartan group was significantly lower than that of control and other ARBs. VEGF expression of candesartan and telmisartan group was significantly lower than that of control and other ARBs.

(Conclusion)Targeting angiogenesis with multikinase inhibitor or ARB in addition to gemcitabine may be a promising therapeutics for PDAC.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 3292. doi:10.1158/1538-7445.AM2011-3292

Abstract 2381: Preclinical molecular targeting therapy of pancreatic cancer using a genetically engineered mouse model

Patients with pancreatic ductal adenocarcinoma have a poor prognosis. New therapeutic approaches to improve the prognosis are expected. We generated pancreas-specific Tgfbr2 knockout mice in the context of Kras activation, which recapitulated clinical and histopathological manifestations of human pancreatic cancer. Using this model we investigated the anti-tumor effects of gemcitabine and molecular targeted drugs.

We treated the mice with EGFR inhibitor elrotinib or VEGFR inhibitor axitinib in combination with gemcitabine. Median survival times were 45, 60, 77, and 74 days for control, gemcitabine alone, gemcitabine + axitinib, and gemcitabine + erlotinib, respectively.

In vitro assays, elrotinib inhibited phosphorylation of EGFR and both drugs also inhibited proliferation of human pancreatic cancer cell lines in vitro.This mouse model also recapitulated chemosensitivity of human pancreatic cancer and suggested erlotinib and axitinib in combination with gemcitabine can be superior to gemcitabine alone. This mouse model helps us to investigate the mechanism of the action of drugs and chemoresistance.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 2381. doi:10.1158/1538-7445.AM2011-2381

Abstract 922: Disruption of bone morphogenetic protein receptor 2 accelerates mammary carcinoma metastasis to the lung

Bone Morphogenetic Proteins (BMPs) are members of the Transforming Growth Factor β (TGFβ) superfamily of signaling molecules. BMPs can elicit a wide range of effects in many cell types and have previously been shown to induce growth inhibition in cancers as well as normal epithelia. Recently, it has been demonstrated that BMP4 and BMP7 are overexpressed in human breast cancers and may have both tumor suppressive and promoting effects. We sought to determine whether disruption of the Bone Morphogenetic Protein Receptor 2 (BMPR2) would alter mammary tumor progression in mice that express the Polyoma middle T antigen (PyVmT). Mice expressing PyVmT under the mammary specific MMTV promoter were combined with mice that have Doxycycline inducible expression of a dominant negative (DN) BMPR2. We did not observe any differences in tumor latency. However, when we measured pulmonary metastases, we found that mice expressing the BMPR2-DN had a five fold increase in lung metastases. We characterized several cell autonomous changes and found that BMPR2-DN expressing tumor cells had higher rates of proliferation and epithelial to mesenchymal transition (EMT). We also identified unique changes in the tumor microenvironment, which included inflammatory cells and secreted chemokines/ cytokines that accompanied BMPR2-DN expressing tumors. We identified several molecules including ccl-9 (MIP1γ), which was elevated in BMPR2-DN expressing tumors. Ccl-9 has recently been shown to be an important chemokine in the recruitment of myeloid cells that promote metastatic progression. We discovered that tumor cells treated exogenously with BMP4 ligand repressed ccl-9 mRNA and that this repression was limited in cells expressing BMPR2-DN. We conclude that BMPR2 has tumor suppressive function in mammary epithelia and that disruption can accelerate mammary carcinoma metastases via paracrine stimulation of myeloid cells in the tumor microenvironment.

Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 922. doi:10.1158/1538-7445.AM2011-922

Loss of one Tgfbr2 allele in fibroblasts promotes metastasis in MMTV: polyoma middle T transgenic and transplant mouse models of mammary tumor progression

Accumulation of fibroblasts is a phenomenon that significantly correlates with formation of aggressive cancers. While studies have shown that the TGF-β signaling pathway is an important regulator of fibroblast activation, the functional contribution of TGF-β signaling in fibroblasts during multi-step tumor progression remains largely unclear. In previous studies, we used a sub-renal capsule transplantation model to demonstrate that homozygous knockout of the Tgfbr2 gene (Tgbr2(FspKO)) enhanced mammary tumor growth and metastasis. Here, we show for the first time a significant role for loss of one Tgfbr2 allele during multi-step mammary tumor progression. Heterozygous deletion of Tgfbr2 in stromal cells in MMTV-PyVmT transgenic mice (PyVmT/Tgfbr2(hetFspKO) mice) resulted in earlier tumor formation and increased stromal cell accumulation. In contrast to previous studies of Tgbr2(FspKO) fibroblasts, Tgfbr2(hetFspKO) fibroblasts did not significantly increase tumor growth, but enhanced lung metastasis in PyVmT transgenic mice and in co-transplantation studies with PyVmT mammary carcinoma cells. Furthermore, Tgfbr2(hetFspKO) fibroblasts enhanced mammary carcinoma cell invasiveness associated with expression of inflammatory cytokines including CXCL12 and CCL2. Analyses of Tgbr2(FspKO) and Tgfbr2(hetFspKO) fibroblasts revealed differences in the expression of factors associated with metastatic spread, indicating potential differences in the mechanism of action between homozygous and heterozygous deletion of Tgfbr2 in stromal cells. In summary, these studies demonstrate for the first time that loss of one Tgfbr2 allele in fibroblasts enhances mammary metastases in a multi-step model of tumor progression, and demonstrate the importance of clarifying the functional contribution of genetic alterations in stromal cells in breast cancer progression.