Sallie S. Schneider

Activation of Host Wound Responses in Breast Cancer Microenvironment

Purpose: Cancer progression is mediated by processes that are also important in wound repair. As a result, cancers have been conceptualized as overhealing wounds or wounds that do not heal, and gene expression signatures reflective of wound repair have shown value as predictors of breast cancer survival. Despite the widespread acknowledgment of commonalities between host responses to wounds and host responses to cancer, the gene expression responses of normal tissue adjacent to cancers have not been well characterized. Experimental Design: Using RNA extracted from histologically normal breast tissue from 107 patients, including 60 reduction mammoplasty patients and 47 cancer patients, we measured whole genome expression profiles and identified a gene expression signature that is induced in response to breast cancer. Results: This signature represents an in vivo wound response signature that is differentially expressed in the normal tissue of breast cancer patients compared with those without disease and is highly accurate (at least 92 sensitivity and 98 specificity) in distinguishing diseased and nondiseased. The in vivo wound response signature is highly prognostic of breast cancer survival, and there is a strong association between the groups identified by this signature and those identified using serum-treated fibroblasts and other microenvironment-derived or microenvironment-related signatures. Conclusions: The prevalence of the wound response signature in histologically normal tissue adjacent to breast cancer suggests that microenvironment response is an important variable in breast cancer progression and may be an important target for clinical interventions. (Clin Cancer Res 2009;15(22):70208)

Mitochondrial Dysfunction Impairs Tumor Suppressor p53 Expression/Function

Recently, mitochondria have been suggested to act in tumor suppression. However, the underlying mechanisms by which mitochondria suppress tumorigenesis are far from being clear. In this study, we have investigated the link between mitochondrial dysfunction and the tumor suppressor protein p53 using a set of respiration-deficient (Res−) mammalian cell mutants with impaired assembly of the oxidative phosphorylation machinery. Our data suggest that normal mitochondrial function is required for γ-irradiation (γIR)-induced cell death, which is mainly a p53-dependent process. The Res− cells are protected against γIR-induced cell death due to impaired p53 expression/function. We find that the loss of complex I biogenesis in the absence of the MWFE subunit reduces the steady-state level of the p53 protein, although there is no effect on the p53 protein level in the absence of the ESSS subunit that is also essential for complex I assembly. The p53 protein level was also reduced to undetectable levels in Res− cells with severely impaired mitochondrial protein synthesis. This suggests that p53 protein expression is differentially regulated depending upon the type of electron transport chain/respiratory chain deficiency. Moreover, irrespective of the differences in the p53 protein expression profile, γIR-induced p53 activity is compromised in all Res− cells. Using two different conditional systems for complex I assembly, we also show that the effect of mitochondrial dysfunction on p53 expression/function is a reversible phenomenon. We believe that these findings will have major implications in the understanding of cancer development and therapy.

Down-regulation of sfrp1 in a mammary epithelial cell line promotes the development of a cd44high/cd24low population which is invasive and resistant to anoikis.

BackgroundThe Wnt family of secreted proteins is implicated in the regulation of cell fate during development, as well as in cell proliferation, morphology, and migration. Aberrant activation of the Wnt/β-catenin signaling pathway leads to the development of several human cancers, including breast cancer. Secreted frizzled-related protein 1 (SFRP1) antagonizes this pathway by competing with the Frizzled receptor for Wnt ligands resulting in an attenuation of the signal transduction cascade. Loss of SFRP1 expression is observed in breast cancer, along with several other cancers, and is associated with poor patient prognosis. However, it is not clear whether the loss of SFRP1 expression predisposes the mammary gland to tumorigenesis.ResultsWhen SFRP1 is knocked down in a non-malignant immortalized mammary epithelial cell line (76 N TERT), nuclear levels of β-catenin rise and the Wnt pathway is stimulated. The SFRP1 knockdown cells exhibit increased expression of the pro-proliferative Cyclin D1 gene and increased cellular proliferation, undergo a partial epithelial-mesenchymal transition (EMT), are resistant to anchorage-independent cell death, exhibit increased migration, are significantly more invasive, and exhibit a CD24low/CD44high cell surface marker expression pattern.ConclusionOur study suggests that loss of SFRP1 allows non-malignant cells to acquire characteristics associated with breast cancer cells.

Estrogen and progesterone regulate radiation-induced p53 activity in mammary epithelium through TGF-beta-dependent pathways

DNA damage normally induces p53 activity, but responses to ionizing radiation in the mammary epithelium vary among developmental stages. The following studies examined the hormones and growth factors that regulate radiation-responsiveness of p53 in mouse mammary epithelium. Immunoreactive p21/WAF1 and TUNEL staining were used as indicators of p53 activity following exposure to ionizing radiation. In ovariectomized mice, radiation-induced accumulation of p21/WAF1 was minimal in the mammary epithelial cells (<1%). Systemic injections of estrogen and progesterone (E+P) for 72 h were necessary to recover maximal expression of p21/WAF1 following ionizing radiation (55%). The effects of E+P on radiation-induced p21/WAF1 were p53-dependent as responses were absent in Trp53−/− mice. Though hormonal treatments stimulated increases in the proportion of cycling cells (PCNA-positive), this was not directly correlated with p53 activity. Whole organ cultures were used to determine whether E+P act directly upon the mammary gland. Treatment with E+P was sufficient to render p53 responsive to radiation, but TGF-β-neutralizing antibodies blocked responsiveness. In the absence of E+P, TGF-β1 alone did not alter p53 activity. These results demonstrate that estrogen and progesterone together with TGF-β signaling are necessary for maintenance of p53 activity in the mammary epithelium.

Mice deficient in Sfrp1 exhibit increased adiposity, dysregulated glucose metabolism, and enhanced macrophage infiltration.

The molecular mechanisms involved in the development of obesity and related complications remain unclear. Wnt signaling plays an important role in preadipocyte differentiation and adipogenesis. The expression of a Wnt antagonist, secreted frizzled related protein 1 (SFRP1), is increased in response to initial weight gain, then levels are reduced under conditions of extreme obesity in both humans and animals. Here we report that loss of Sfrp1 exacerbates weight gain, glucose homeostasis and inflammation in mice in response to diet induced obesity (DIO). Sfrp1-/- mice fed a high fat diet (HFD) exhibited an increase in body mass accompanied by increases in body fat percentage, visceral white adipose tissue (WAT) mass, and adipocyte size. Moreover, Sfrp1 deficiency increases the mRNA levels of key de novo lipid synthesis genes (Fasn, Acaca, Acly, Elovl, Scd1) and the transcription factors that regulate their expression (Lxr-α, Srebp1, Chreb, and Nr1h3) in WAT. Fasting glucose levels are elevated, glucose clearance is impaired, hepatic gluconeogenesis regulators are aberrantly upregulated (G6pc and Pck1), and glucose transporters are repressed (Slc2a2 and Slc2a4) in Sfrp1-/- mice fed a HFD. Additionally, we observed increased steatosis in the livers of Sfrp1-/- mice. When there is an expansion of adipose tissue there is a sustained inflammatory response accompanied by adipokine dysregulation, which leads to chronic subclinical inflammation. Thus, we assessed the inflammatory state of different tissues and revealed that Sfrp1-/- mice fed a HFD exhibited increased macrophage infiltration and expression of pro-inflammatory markers including IL-6, Nmnat, Tgf-β2, and SerpinE1. Our findings demonstrate that the expression of Sfrp1 is a critical factor required for maintaining appropriate cellular signaling in response to the onset of obesity.

Rhodiola crenulata Induces Death and Inhibits Growth of Breast Cancer Cell Lines

Diverse compounds from many different chemical classes are currently targeted in preclinical analyses for their ability to act as both chemopreventive and chemotherapeutic agents. Phenolic phytochemicals from Rhodiola crenulata has such potential. This Rhodiola species is a perennial plant that grows in the Tundra, Siberia, and high-elevation regions of Tibet. The phenolic secondary metabolites isolated from R. crenulata were recently analyzed in a preclinical setting for their ability to treat lymphosarcomas and superficial bladder cancers. However, the effects of R. crenulata have yet to be examined for its implications in breast cancer prevention or for its chemotherapeutic abilities. Therefore this study investigated the effects of R. crenulata on breast cancer both in vivo and in vitro. Experiments using aggressive human-derived MDA-MB-231 and mouse-derived V14 breast cancer cell lines demonstrated that phenolic-enriched R. crenulata extract was capable of inhibiting the proliferation, motility, and invasion of these cells. In addition, the extracts induced autophagic-like vesicles in all cell lines, eventually leading to death of the tumor cell lines but not the immortal or normal human mammary epithelial cells. Finally, an in vivo experiment showed that phenolic-enriched dietary R. crenulata is effective in preventing the initiation of tumors and slowing down the tumor growth in mice bearing tumor grafts, thereby further demonstrating its possible potential for treatment of breast cancer progression and metastasis.

SFRP1 reduction results in an increased sensitivity to TGF-β signaling

BackgroundTransforming growth factor (TGF)-β plays a dual role during mammary gland development and tumorigenesis and has been shown to stimulate epithelial-mesenchymal transition (EMT) as well as cellular migration. The Wnt/β-catenin pathway is also implicated in EMT and inappropriate activation of the Wnt/β-catenin signaling pathway leads to the development of several human cancers, including breast cancer. Secreted frizzled-related protein 1 (SFRP1) antagonizes this pathway and loss of SFRP1 expression is frequently observed in breast tumors and breast cancer cell lines. We previously showed that when SFRP1 is knocked down in immortalized non-malignant mammary epithelial cells, the cells (TERT-siSFRP1) acquire characteristics associated with breast tumor initiating cells. The phenotypic and genotypic changes that occur in response to SFRP1 loss are consistent with EMT, including a substantial increase in the expression of ZEB2. Considering that ZEB2 has been shown to interact with mediators of TGF-β signaling, we sought to determine whether TGF-β signaling is altered in TERT-siSFRP1 cells.MethodsLuciferase reporter assays and real-time PCR analysis were employed to measure TGF-β transcriptional targets. Western blot analysis was used to evaluate TGF-β-mediated ERK1/2 phosphorylation. Migration chamber assays were utilized to quantify cellular migration. TERT-siSFRP1 cells were transfected with Stealth RNAi™ siRNA in order to knock-down the expression of ZEB2.ResultsTERT-siSFRP1 cells exhibit a significant increase in both TGF-β-mediated luciferase activity as well as TGF-β transcriptional targets, including Integrin β3 and PAI-1. Phosphorylation of ERK1/2 is increased in TERT-siSFRP1 cells in response to enhanced TGF-β signaling. Furthermore, when the TGF-β pathway is blocked with a TGF-βR antagonist (LY364947), cellular migration is significantly hindered. Finally, we found that when ZEB2 is knocked-down, there is a significant reduction in the expression of exogeneous and endogenous TGF-β transcriptional targets and cellular migration is impeded.ConclusionsWe demonstrate that down-regulation of SFRP1 renders mammary epithelial cells more sensitive to TGF-β signaling which can be partially ameliorated by blocking the expression of ZEB2.

Efficacy of PolyMPC–DOX Prodrugs in 4T1 Tumor-Bearing Mice

We report the in vivo efficacy, in tumor-bearing mice, of cancer prodrugs consisting of poly(methacryloyloxyethyl phosphorylcholine) (polyMPC) conjugated to doxorubicin (DOX). Our synthesis of polyMPC–DOX conjugates established prodrugs with tunable drug loading, pH sensitive release kinetics, and a maximum tolerated dose in the range of 30–50 mg/kg (DOX equivalent) in healthy mice. Here we show prolonged circulation of polyMPC–DOX, with a measured in vivo half-life (t1/2) 8 times greater than that of the free drug. We observed reduced drug uptake in healthy tissue, and 2–3 times enhanced drug accumulation in tumors for polyMPC–DOX prodrugs compared to free DOX, using BALB/c mice bearing 4T1 tumors. Prolonged survival and reduced tumor growth were observed in mice receiving the polyMPC–DOX prodrug treatment. Moreover, we evaluated immunogenicity of polyMPC–DOX prodrugs by examining complete blood count (CBC) and characteristic cytokine responses, demonstrating no apparent innate or adaptive immune system response.

Transcriptional Responses to Estrogen and Progesterone in Mammary Gland Identify Networks Regulating p53 Activity

Estrogen and progestins are essential for mammary growth and differentiation but also enhance the activity of the p53 tumor suppressor protein in the mammary epithelium. However, the pathways by which these hormones regulate p53 activity are unknown. Microarrays were used to profile the transcriptional changes within the mammary gland after administration of either vehicle, 17beta-estradiol (E), or progesterone (P) individually and combined (EP). Treatment with EP yielded 1182 unique genes that were differentially expressed compared to the vehicle-treated group. Although 30% of genes were responsive to either E or P individually, combined treatment with both EP had a synergistic effect accounting for 60% of the differentially regulated genes. Analysis of protein-protein interactions identified p53, RelA, Snw1, and Igfals as common targets of genes regulated by EP. RelA and p53 form hubs within a network connected by genes that are regulated by EP and that may coordinate the competing functions of RelA and p53 in proliferation and survival of cells. Induction of early growth response 1 (Egr1) and Stratifin (Sfn) (also known as 14-3-3sigma) by EP was confirmed by reverse transcription-quantitative PCR and shown to be p53 independent. In luciferase reporter assays, Egr1 was shown to enhance transcriptional activation by p53 and inhibit nuclear factor kappaB activity. These results identify a gene expression network that provides redundant activation of RelA to support proliferation as well as sensitize p53 to ensure proper surveillance and integration of their competing functions through factors such as Egr1, which both enhance p53 and inhibit RelA.

Age-Associated Gene Expression in Normal Breast Tissue Mirrors Qualitative Age-at-Incidence Patterns for Breast Cancer

Background: Age is the strongest breast cancer risk factor, with overall breast cancer risk increasing steadily beginning at approximately 30 years of age. However, while breast cancer risk is lower among younger women, young womens breast cancer may be more aggressive. Although, several genomic and epidemiologic studies have shown higher prevalence of aggressive, estrogen-receptor negative breast cancer in younger women, the age-related gene expression that predisposes to these tumors is poorly understood. Characterizing age-related patterns of gene expression in normal breast tissues may provide insights on etiology of distinct breast cancer subtypes that arise from these tissues. Methods: To identify age-related changes in normal breast tissue, 96 tissue specimens from patients with reduction mammoplasty, ages 14 to 70 years, were assayed by gene expression microarray. Results: Significant associations between gene expression levels and age were identified for 802 probes (481 increased, 321 decreased with increasing age). Enriched functions included “aging of cells,” “shape change,” and “chemotaxis,” and enriched pathways included Wnt/beta-catenin signaling, Ephrin receptor signaling, and JAK/Stat signaling. Applying the age-associated genes to publicly available tumor datasets, the age-associated pathways defined two groups of tumors with distinct survival. Conclusion: The hazard rates of young-like tumors mirrored that of high-grade tumors in the Surveillance, Epidemiology, and End Results Program, providing a biologic link between normal aging and age-related tumor aggressiveness. Impact: These data show that studies of normal tissue gene expression can yield important insights about the pathways and biologic pressures that are relevant during tumor etiology and progression. Cancer Epidemiol Biomarkers Prev; 21(10); 1735–44. ©2012 AACR.