Inter-relationships among diet, obesity and hippocampal-dependent cognitive function

Intake of a Western diet (WD), which is high in saturated fat and sugar, is associated with deficits in hippocampal-dependent learning and memory processes as well as with markers of hippocampal pathology. In the present study, rats were trained to asymptote on hippocampal-dependent serial feature negative (FN) and hippocampal-independent simple discrimination problems. Performance was then assessed following 7 days on ad libitum chow and after 10, 24, 40, 60, and 90 days of maintenance on WD, on ketogenic (KETO) diet, which is high in saturated fat and low in sugar and other carbohydrates, or continued maintenance on chow (CHOW). Confirming and extending previous findings, diet-induced obese (DIO) rats fed WD showed impaired FN performance, increased blood-brain barrier (BBB) permeability, and increased fasting blood glucose levels compared to CHOW controls and to diet-resistant (DR) rats that did not become obese when maintained on WD. For rats fed the KETO diet, FN performance and BBB integrity were more closely associated with level of circulating ketone bodies than with obesity phenotype (DR or DIO), with higher levels of ketones appearing to provide a protective effect. The evidence also indicated that FN deficits preceded and predicted increased body weight and adiposity. This research (a) further substantiates previous findings of WD-induced deficits in hippocampal-dependent FN discriminations, (b) suggests that ketones may be protective against diet-induced cognitive impairment, and (c) provides evidence that diet-induced cognitive impairment precedes weight gain and obesity.

Investigation of 20 non-HLA (human leucocyte antigen) psoriasis susceptibility loci in Chinese patients with psoriatic arthritis and psoriasis vulgaris

BACKGROUND

Recently, a number of non-HLA (human leucocyte antigen) psoriasis genetic susceptibility loci have been identified through genome-wide association studies, but data on their association with psoriatic arthritis (PsA) are lacking.

OBJECTIVES

To investigate recently identified psoriasis susceptibility loci in a cohort of Chinese patients with PsA, psoriasis vulgaris (PsV) and healthy controls.

METHODS

Twenty single-nucleotide polymorphisms (SNPs) from 20 loci were selected for genotyping in 379 patients with PsA, 595 patients with PsV and 1181 healthy controls using the MassARRAY platform (Sequenom, San Diego, CA, U.S.A.). Data handling, quality control and association were performed using PLINK software, v. 1.07. The Cochran-Armitage trend test was used to test the genotype-phenotype association.

RESULTS

PsA showed a significant association with markers at TNIP1 (rs17728338, P = 2.20 × 10(-8)), IL28RA (rs4649203, P = 5.04 × 10(-6)), IL12B (rs2082412, P = 3.82 × 10(-5)), ERAP1 (rs27524, P = 1.25 × 10(-3)), PTTG1 (rs2431697, P = 1.22 × 10(-3)) and GJB2 (rs3751385, P = 1.48 × 10(-3)) when compared with the control group. In PsV a significant association was found for IL28RA (rs4649203, P = 9.53 × 10(-7)), TNIP1 (rs17728338, P = 1.21 × 10(-4)) and ERAP1 (rs27524, P = 1.17 × 10(-3)). The allele frequencies were not statistically different between PsA and PsV except for SNPs at IL12B and ZNF816A with a nominal P-value of 0.04 and 0·01, respectively.

CONCLUSIONS

This study provides evidence for the involvement of ERAP1, IL28RA, GJB2 and PTTG1 loci in PsA susceptibility and confirmed the previously reported association with PsA and PsV. These results support the hypothesis that genetic aetiology of psoriasis is the same in both PsA and PsV and also support the higher genetic component of PsA than PsV.

Low expression of Mfn2 is associated with mitochondrial damage and apoptosis in the placental villi of early unexplained miscarriage

INTRODUCTION

Early miscarriage is the most common complication of pregnancy and in many cases the etiology is not clearly understood. We aim to profile the expression of Mfn2 and mitochondrial damage in villous tissues, in order to determine the underlying mechanism of unexplained miscarriage.

METHODS

We investigated placental villous samples of 30 women with early unexplained miscarriage (miscarriage group) and 30 women with normal pregnancy (control group). Immunohistochemistry and western blotting were used to detect the Mfn2 expression. We observed trophoblastic cell apoptosis with TUNEL and analyzed Bcl-2 and Bax levels by western blotting. Transmission electron microscopy was used to analyze mitochondrial morphology and phosphomolybdic acid colorimetric method was used to measure the ATP content of all villous samples.

RESULTS

Mfn2 staining showed extra-nuclear localization in the trophoblastic cells. Compared with the control group, the levels of Mfn2 and Bcl-2 were markedly decreased (P < 0.01), while both the levels of Bax protein and apoptosis index (AI) were increased in the miscarriage group (P < 0.01). Mfn2 levels positively correlated with Bcl-2, but negatively correlated with Bax. Moreover, compared to the control group (33.8 ± 6.5 μmol/g), ATP levels in the miscarriage group were significantly decreased (15.8 ± 4.8 μmol/g). In addition, obvious impairment of mitochondrial function was observed in trophoblastic cells from the unexplained miscarriage group.

CONCLUSION

Mitochondrial morphologic and functional changes were observed in trophoblastic cells, and in relation with apoptosis, may be correlated with low levels of Mfn2. Deficient expression of Mfn2 in trophoblastic cells could be an important cause of early miscarriage.

Protective effect of the nitric oxide pathway in L-citrulline renal ischaemia-reperfusion injury in rats

To observe the protective effects of L-citrulline on the renal I/R injury and elucidate the mechanisms involved, 48 rats were randomized into eight groups: Group 1: sham operated; Group 2: I/R (45 min renal ischaemia and 24 h reperfusion); Group 3: I/R + L-citrulline (300 mg/kg, i.g.); Group 4: I/R + L-citrulline (600 mg/kg, i.g.); Group 5: I/R + L-citrulline (900 mg/kg, i.g.); Group 6: I/R + normal saline (NS, i.g.); Group 7: I/R + N sup ω nitro-L-arginine ester (L-NAME, 20 mg/kg, i.p.); Group 8: I/R + L-citrulline (900 mg/kg, i.g.) + L-NAME (20 mg/ kg, i.p.). At the end of the reperfusion period, serum was collected and the kidneys underwent histological and biochemical examinations. Our results showed that pre-treatment with L-citrulline (300, 600, and 900 mg/kg) significantly ameliorated the renal injury caused by I/R. Moreover, L-citrulline prevented induction of lipid peroxidation and increased the activity of superoxide dismutase and the levels of glutathione and nitric oxide. The I/R-induced decreases in total nitric oxide synthase activity, inducible nitric oxide activity, constitutive nitric oxide activity and endothelial nitric oxide protein expression in the renal cortex were significantly prevented. However, the L-citrulline-mediated protection was significantly antagonized by co-administration of L-NAME. These results suggested that L-citrulline administration exhibited significant protection against renal I/R injury. This protective effect, at least in part, via up-regulation of the endothelial nitric oxide protein expression and constitutive nitric oxide synthase activity, maintained production of nitric oxide at the basal level.

Abstract P6-10-03: The PKC inhibitor PKC412 antagonizes breast cancer cell growth and enhances tamoxifen sensitivity

Background: AIB1 (SRC-3, NCoA3), a member of the p160/steroid receptor coactivators family, plays a critical role in cell growth and proliferation. In estrogen receptor-alpha positive (ER+) breast cancer (BC) cells, it coactivates estrogen- and additional transcription factors-dependent gene transcription, reducing the antagonistic activity of tamoxifen and resulting in tamoxifen resistance (TR). We have previously shown that BC patients whose tumors expressed high levels of both AIB1 and HER-2 had worse outcomes with tamoxifen therapy, suggesting that AIB1 may be an important diagnostic and therapeutic target. Our findings that knocking down AIB1 attenuates ER signaling and inhibits breast cancer cell growth further indicate that the manipulation of AIB1 level could be an approach to treating BC and overcoming TR. Recently, it has been shown that protein kinase C (PKC) isoforms phosphorylate AIB1 and prevent its proteasome-mediated degradation. The present study was carried out to test if the multi-targeted kinase and PKC inhibitor PKC412 (midostaurin) is capable of promoting degradation of AIB1, inhibiting BC cell growth, and promoting tamoxifen antagonistic activity.

Methods: The ER+ MCF7, T47D, and ZR75-B BC cells and their tamoxifen-resistant derivatives (TR) were used. The Methylene Blue assay was employed to measure cell viability of BC cell lines after treatment with PKC412 or the combination of PKC412 with tamoxifen. To determine the impact of PKC412 on AIB1 and ER proteins and mRNA levels, we used immunoblotting and RT-qPCR, respectively.

Results: PKC412 successfully inhibited the growth of MCF7, T47D, and ZR75-B cells, and their tamoxifen-resistant derivatives. Treatment with PKC412 depleted AIB1 protein and reduced the level of ER protein without significant alteration in AIB1 mRNA level. Consequently, ER signaling was disrupted, as reflected by decreased expression of ER target genes such as GREB1. PKC412 also enhanced tamoxifen's antagonistic activity in the parental cell lines and sensitized tamoxifen-resistant MCF7 and ZR75-B cells to tamoxifen.

Conclusions: The results of this study suggest that the multi-targeted kinase and PKC inhibitor PKC412 can post-translationally destabilize AIB1 protein and ER, inhibiting BC cell growth and viability. PKC412 enhances tamoxifen's antagonistic activity on BC growth; furthermore, it sensitizes tamoxifen-resistant cells to tamoxifen. Thus, PKC412 is a promising agent to treat BC and, in combination with tamoxifen, to delay or overcome TR.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-10-03.

Abstract PD01-01: Overcoming endocrine therapy resistance related to PTEN loss by strategic combinations with mTOR, AKT, or MEK inhibitors

Background: Hyperactive PI3K signaling is associated with a more aggressive subtype of estrogen receptor (ER) positive breast cancer (BC) and with endocrine resistance. Loss or downregulation of PI3K's inhibitor PTEN is more common in basal and luminal B vs. luminal A BC. However, the role of PTEN in modulating response to various endocrine therapies is unclear. Here we investigated the effects of PTEN knockdown (KD) on endocrine sensitivity and the potential of multiple kinase inhibitors to restore and improve responses.

Methods: Nude mice bearing ER+ BC xenograft tumors of MCF7 cells stably expressing a doxycycline (Dox)-inducible PTEN-shRNA were randomized to four endocrine treatment groups [continued estrogen (E2) supplementation, or E2-deprivation (ED) alone or in combination with tamoxifen (Tam) or fulvestrant (Ful)]; all -/+ Dox. The effects of single or combined kinase inhibitors on these endocrine treatments -/+ Dox were studied in vitro using inhibitors (i) to mTOR (AZD2014, 0.2 μM), AKT (AZD5363, 1 μM), or MEK (Selumetinib/ARRY-142886, 1 μM). Cell growth, apoptosis, and ER and progesterone receptor (PR) signaling were analyzed using cell cytometry, qRT/PCR, and Western blotting. Synergism tests were used to examine the growth effects of the most promising combinatorial therapy with multiple kinase inhibitors in different endocrine settings.

Results: In wild-type (WT) PTEN xenograft tumors, endocrine therapies were very effective, inducing frequent tumor regression. In PTEN KD tumors endocrine therapies were less effective — PTEN KD delayed tumor regression in all endocrine regimens and accelerated tumor progression in the Tam treated group. Furthermore, at day 250, only 1/8 and 0/7 tumors had developed resistance in the ED and the Ful (−Dox) groups, respectively, while with PTEN KD (+Dox), 7/15 and 5/15 tumors developed resistance to ED and to Ful. In vitro PTEN KD also induced resistance to all endocrine therapies. mRNA and/or protein levels of ER and PR were suppressed by PTEN KD and restored by mTORi and AKTi. In cells with WT PTEN, mTORi was highly effective with or without endocrine therapy. However, AKTi and MEKi were more effective in combination with endocrine therapy. All three inhibitors were less effective upon PTEN KD. The mTORi plus AKTi combination resulted in a potent synergistic inhibition in PTEN KD cells in the presence of E2 or with ED. In contrast, in the presence of Tam, AKTi plus MEKi, independent of PTEN status, was the most effective combination at the doses chosen. Finally, these inhibitors and combinations were more effective in the presence of Ful than ED or Tam in WT PTEN cells. AKTi combined with Ful was still highly effective even in PTEN KD cells, but mTORi and MEKi were less effective.

Conclusions: Our results suggest that PTEN loss renders endocrine therapy less effective in in vitro and in vivo experimental models. Single AKT/MEK kinase inhibitors are more potent in the presence of endocrine therapy. In PTEN KD cells, the activity of all three kinase inhibitors is largely diminished, except for AKTi in the presence of fulvestrant. Kinase inhibitor combinations are generally more effective, but the optimal combinations vary by PTEN status and type of endocrine therapy.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr PD01-01.

Microenvironment-dependent homeostasis and differentiation of epidermal basal undifferentiated keratinocytes and their clinical applications in skin repair

Skin homeostasis is maintained by controlling the balance between proliferation and differentiation of epidermal stem cells. The microenvironment, including extrinsic stresses, growth factors, soluble molecules, cell-ECM and cell-cell communications, plays an important role in cell fate determination in vivo and in vitro. In response to external signals, keratinocytes cooperate with other cell types to modulate and facilitate the wound microenvironment during wound healing; however, the aberrant signals or conjunctions in the environment will lead to pathologic abnormalities. In addition, despite some drawbacks, the epidermal stem-cellbased bioengineered skin substitutes have greatly improved the quality of cutaneous repair. Thus, exploring the characteristics and regulation mechanisms of microenvironment-dependent homeostasis and differentiation of epidermal basal undifferentiated keratinocytes is necessary to understand skin development and wound repair and to design novel therapeutic strategies for skin wound healing.

Insights into bone marrow-derived mesenchymal stem cells safety for cutaneous repair and regeneration

Wound healing involves the orchestration of a complex process of interactions between numerous types of cell, components of extracellular matrix and signalling molecules following injury, which is usually a highly successful biological course to reconstruct the integrity of the skin. Nevertheless, when skin is severely damaged, the injured skin is limited in its ability to repair itself and possibly results in the hypertrophic scars or so-called keloids, and non healing wound or ulcer. Bone marrow-derived mesenchymal stem cells (BM-MSCs) are being clinically explored as a promising therapy in the field of tissue repair and regeneration. However, potential risks associated with these cell-based therapies remain uncertain. The aim of this review is to summarise the safety issues accompanying the administration of BM-MSCs for acute or chronic skin repair and regeneration. More importantly, this review highlights the requirement for fundamental research to improve future clinical application of these strategies, as well as for regulatory authorities to establish clinical criteria to identify the qualitative requirements for the manufacture process of cells products, which will ensure the manufacture process of the best benefit-to-risk ratio of cell-based therapy for the patients.

Epidemic reemergence in adaptive complex networks

The dynamic nature of a system gives rise to dynamical features of epidemic spreading, such as oscillation and bistability. In this paper, by studying the epidemic spreading in growing networks, in which susceptible nodes may adaptively break the connections with infected ones yet avoid being isolated, we reveal a phenomenon, epidemic reemergence, where the number of infected nodes is incubated at a low level for a long time and then erupts for a short time. The process may repeat several times before the infection finally vanishes. Simulation results show that all three factors, namely the network growth, the connection breaking, and the isolation avoidance, are necessary for epidemic reemergence to happen. We present a simple theoretical analysis to explain the process of reemergence in detail. Our study may offer some useful insights, helping explain the phenomenon of repeated epidemic explosions.

Autologous transplantation of bone marrow-derived mesenchymal stem cells: a promising therapeutic strategy for prevention of skin-graft contraction

Hypertrophic scars result from abnormal healing of severe burns, and are characterized by loss of the original structure and function of the skin. Transplantation of autologous split skin is the preferred treatment after scar excision; however, there will be some unavoidable degree of contraction within the grafts. To our knowledge, it is very rare that bone marrow-derived mesenchymal stem cells (BM-MSCs) have been used for the treatment of skin-graft contraction. However, in our clinics, we found that during a 2-year follow-up analysis, areas treated with autologous BM-MSCs combined with transplantation of split skin were less likely to have contraction of the skin grafts than areas treated with skin grafts alone. This result indicates that BM-MSCs may be a potential and promising treatment to prevent contraction of skin grafts.

Tacrolimus enhances the invasion potential of hepatocellular carcinoma cells and promotes lymphatic metastasis in a rat model of hepatocellular carcinoma: involvement of vascular endothelial growth factor-C

PURPOSE

The purpose of this study was to elucidate the effect of tacrolimus treatment on tumor growth and metastasis of hepatocellular carcinoma (HCC).

METHODS

The effect of tacrolimus was investigated on tumor growth and lymph node metastasis in a rat model of HCC. Angiogenesis and lymphangiogenesis were assessed by CD31 and vascular endothelial growth factor receptor 3 (VEGFR-3) immunostaining. Cell proliferation and invasion were monitored in vitro using the Cell Counting Kit-8 (CCK8) and Matrigel Invasion Chambers, respectively. Levels of vascular endothelial growth factor-C (VEGF-C) expression were measured using quantitative real-time polymerase chain reaction (qRT-PCR), immunohistochemisty and Western blots.

RESULTS

Tacrolimus had no effect on the proliferation of HCC in vitro or in vivo. Treatment with tacrolimus resulted in a dose-dependent increase in the invasive potential of HCC cells in vitro, in the density of peritumoral lymphatic vessels, and in the number and volume of metastatic lymph nodes in August Copenhagen Irish (ACI) rats. qRT-PCR, immunohistochemisty, and Western blot revealed that tacrolimus increased the levels of expression of VEGF-C in HCC.

CONCLUSIONS

Tacrolimus enhanced the invasive potential of HCC cells, facilitating HCC lymphangiogenesis and promoting lymphatic metastasis in a rat model of HCC. This influence may be the result of an increase in VEGF-C expression by HCC cells. Targeting the VEGF-C/Fms-related tyrosine kinase 4 axis may be a novel treatment for HCC patients after liver transplantation.

P4-01-02: Endocrine Resistance: Mechanism, Tumorigenic Capacities, and New Therapeutic Strategies

Background

Endocrine therapy is the most effective therapies for estrogen receptor positive (ER+) breast cancer, but resistance is still a major clinical problem. Tumor initiating cells (TICs) in drug resistant tumors are believed to be part of the contributing factors for tumor relapse. Here we focused on the TICs and how they are related to HER2 expression and its downstream factors in acquired endocrine resistance models.

Materials and Methods: We have established a panel of endocrine resistant cell models through long-term treatment with tamoxifen (Tam, 10−7M, &gt;6 months). Resistance to tamoxifen treatment in cells (TamR) was confirmed by growth curve assays (Celigo, Cyntellect Inc., San Diego, CA). In vitro mammosphere assays were applied to assess the mammosphere forming ability of parental and resistant cells. Aldefluor assays (StemCell Technology) were performed to measure the aldehyde dehydrogenase (ALDH-1) expressing cell population as a marker of TICs. Flow analysis was performed to evaluate HER2 expression in the ALDH subpopulations of both parental and TamR cells. Immunofluorescence staining was further used to detect the expression of ER, HER2, phosphorylated STAT3, and β-catenin in sorted ALDH+/− subpopulations.

Results: We found that endocrine resistant cells have a higher mammosphere forming ability than their parental counterparts. In addition, we showed that the ALDH+ subpopulation was significantly upregulated in all TamR derivative lines.

P4-01-03: Establishment and Characterization of an Endocrine Resistance Model In Vitro and In Vivo by Inducible PTEN Knockdown

Background

Growth factor receptor and estrogen receptor (ER) are two major driving pathways for initiating and sustaining breast cancer (BC) development and progression. We have previously shown that an inverse correlation exists between the PI3K pathway and ER expression/activity in luminal type BCs. High PI3K activation signaling correlates to the luminal B subtype of BC with low ER expression/activity. However, the involvement of the PI3K pathway tumor suppressor PTEN in resistance to endocrine therapy is less clear. Here we attempt to develop an experimental system to better understand the role of PTEN in this resistance.

Materials and Methods: Two luminal BC cell lines, MCF7L and ZR75-B, were stably infected with a lentivirus pINDUCER (Meerbrey et al., PNAS, 2011), containing Tet-on responsive shPTEN, turboRFP (tRFP) as an inducible tag, and enhanced GFP (eGFP) as a constitutive expressed tag for positive cells selection. Immunoblotting of PTEN, phosphorylated (p) Akt, pMAPK, pc-Jun, ER, and ER's downstream gene products (PR, IGF-1R) was performed on cells after 6 days of doxycycline (Dox) incubation. After pre-starvation for 5 days in estrogen deprivation (ED) conditions, the cells -/+ Dox were subjected to induction with estrogen (E2) or to endocrine treatment [continued ED, tamoxifen (Tam, 10–7M), or fulvestrant (Ful, 10–7M)] in 96-well plate format for 9 days. In situ cell cytometry (Celigo, Cyntellect Inc., San Diego, CA) was applied to count the cell number by scanning the same 96-well plate every other day. Ovariectomized nude mice bearing MCF7L-shPTEN xenografts, established in the presence of E2 supplementation, were randomized to minus and plus Dox groups, with each treatment group continuing E2 or endocrine therapies (ED, Tam, or Ful). The in vivo GFP/RFP imaging was performed with a home-built cooled and image intensified CCD camera system.

Results: Immunoblot analysis showed a striking loss of PTEN, and significant upregulation of pAkt, as well as pMAPK and pc-Jun in cells with +Dox. In contrast, levels of ER, PR and IGF1R were reduced in cells with +Dox compared to -Dox. In all -Dox groups, cell growth was significantly reduced in endocrine treated groups compared to the E2 group, whereas +Dox rescued the endocrine treatment growth suppression, especially in ED and Tam groups. In vivo induction of PTEN shRNA expression was confirmed by RFP imaging after feeding the mice with +Dox water. MCF7L-shPTEN xenografts randomized to +Dox under ED conditions continued to grow over 4 weeks, in contrast to the marked regression of control tumors (−Dox) under this endocrine regimen (p&lt;0.05). Comparison between plus and minus Dox groups under E2, Tam, or Ful treatment is ongoing.

Discussion: These data further support the existence of crosstalk between PI3K and ER pathways in luminal type BC. Decreasing PTEN levels by shRNA renders the luminal type BC cells de novo resistant to endocrine therapy both in vitro and in vivo. The pINDUCER PTEN knockdown system combined with live animal imaging offers successful real-time, noninvasive tracking of endocrine sensitivity by controllably manipulating the level of target gene. Combination therapies to overcome endocrine resistance under PTEN knockdown conditions are currently underway.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-01-03.

P4-01-18: AP-1 Blockade Potentiates the Anti-Tumor Effect of Endocrine Treatment and Reverts the Resistant Phenotype in Hormone Receptor-Positive Breast Cancer

Background: Resistance to endocrine therapy is a major clinical issue. The transcription factor AP-1 is a key regulator of cell growth and survival as well as a downstream signaling component of several pathways deregulated in endocrine-resistant breast cancer. We have previously shown that acquired endocrine resistance is associated with increased AP-1 activity. AP-1 has also been shown to interact with and modulate the ER network and transcriptional program, especially under hyperactive growth factor signaling, which is commonly associated with endocrine resistance. We hypothesized that interfering with AP-1 function would circumvent endocrine resistance possibly due to its role in modulating ER transcriptional activity.

Methods and results: We inhibited AP-1 function by a genetic approach. We used two different MCF7 clones stably transfected with a Doxycycline (Dox)-inducible dominant-negative (DN) c-Jun (MCF7/Tet-Off Tam67 clones 62 and 67) and two vector-alone control MCF7 clones. Xenografts of these clones were established in ovariectomized nude mice supplemented with estrogen (E2). Mice were then randomized to continued E2 supplementation (control) or to endocrine therapy with either estrogen deprivation (ED) or tamoxifen (Tam), all in the presence or absence of Dox to induce the DN c-Jun expression. AP-1 blockade in both MCF7/Tet-Off Tam67 clones significantly enhanced sensitivity to Tam by reducing time to tumor size halving (p=.014 and p=.006 for clone 62 and 67, respectively) and time to complete tumor disappearance (p=.001 and p=.0034 for clone 62 and 67, respectively). Similar results were obtained with ED treatment. In addition, AP-1 blockade significantly delayed the onset of Tam resistance by increasing time to tumor size doubling (p=.0028). Furthermore, induction of DN c-Jun resulted in a dramatic shrinkage of growing tumors after long-term Tam treatment, suggesting reversal of endocrine resistance with AP-1 blockade. None of the above effects was observed in control clones upon Dox removal. Interestingly, no significant effect of AP-1 blockade was observed on E2-stimulated tumor growth. IHC analysis showed that AP-1 blockade induced tumor response by reducing proliferation (i.e., decreased % of Ki67- and phospho-Histone 3-positive cells) and by inducing apoptosis (i.e., increased % of cleaved caspase 3/7-positive cells). Bioinformatic analyses were conducted to intersect our MCF7 xenograft/Tam-resistant gene signature and the datasets of genes associated with ER DNA-binding sites obtained by whole-genome ER cistromic analysis under estrogen or epidermal growth factor (EGF) stimulation of MCF7 cells. A significant enrichment of the genes associated with the EGF-unique ER DNA-binding sites was observed within our Tam-resistant signature (p&lt;2E-16). Remarkably, 90% of these DNA binding sites harbored an AP-1 motif.

Conclusions: We show that AP-1 blockade increases tumor sensitivity and circumvents resistance to endocrine therapy, thus warranting the development of AP-1-targeted therapy to improve endocrine treatment outcomes. Overall, we suggest that AP-1 is critical in induction of a switch in the ER transcriptional program and may be a new hallmark of endocrine resistance.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-01-18.

P3-03-05: Identification of miRNAs and Their Associated Target Genes Involved in Endocrine Resistance in Breast Cancer

Background: Despite the widespread use of the selective estrogen receptor modulator tamoxifen or strategies of estrogen deprivation in the treatment of estrogen receptor-positive breast cancer, tumor resistance to endocrine therapy remains a serious clinical problem. MiRNAs are a class of endogenous, single stranded RNA molecules that play a pivotal role in the regulation of gene expression. Altered expression levels of these molecules have been implicated in a number of malignancies, including breast cancer. The aim of this study was to identify those miRNAs that may be associated with endocrine resistance and to further investigate their role in development of this resistance.

Methods: MCF7L breast cancer cells were cultured in regular parental medium (Par) or in phenol-red free, 10% charcoal-stripped FBS medium treated by estrogen deprivation (ED, &gt;6months), tamoxifen (Tam, 10−7M, &gt;6months), or estrogen (E2, 10−9M,&gt;1month). Cells treated by long-term Tam or ED developed resistance (TamR or EDR) and resumed cell growth, which was confirmed by growth curve assay. Parallel short-term treatment (10 days) with estrogen deprivation or tamoxifen to represent the endocrine-sensitive phase, and short-term E2 treated cells as a control was also performed. A whole-transcriptome miRNA microarray was performed by High Throughput Genomics (Tucson, AZ), using cell lysates from Par, short-term/endocrine sensitive, E2 treated cells, TamR and EDR. The expression levels of several miRNAs were validated by real-time quantitative PCR (Q-PCR). MiRNAs dysregulated in TamR cells were integrated with predicted gene targets showing anti-correlated expression patterns across human breast tumors in The Cancer Genome Atlas (TCGA) datasets.

Results: The miRNA microarray identified 23 miRNAs that are upregulated in TamR cells (&gt;1.7 fold change, p&lt;0.005) compared to parental cells grown in the presence of E2, and 37 miRNAs that were downregulated (&gt;50%, p&lt;0.005). In addition, 6 miRNAs were observed to be upregulated in EDR and 3 downregulated in EDR compared with controls. Validation of four of these upregulated miRNAs within the TamR group, miR221, miR-222, miR-301b and miR-181c, was performed using Q-PCR. Previously identified genes associated with TamR were scanned for potential binding sites of these deregulated miRNAs using miRanda and TargetScan and many potential miRNA targeted genes are downregulated in TamR. Both miR-221 and miR-181c are predicted to target estrogen receptor gene (ESR1), and downregulation of this target gene was confirmed at the mRNA level by Q-PCR. A strong negative correlation was identified between ESR1 and both miR-181c and miR-221 expression levels in breast tumor samples, according to TCGA data. Work is ongoing to identify the role of miR-181c and other miRNAs in tamoxifen resistance, using a loss-of-function approach. Parallel miRNA profiling of multiple endocrine models is underway to identify commonly deregulated miRNAs associated with endocrine resistance.

Conclusions: This study has identified those miRNAs associated with endocrine resistance in breast cancer. These miRNAs may provide potential predictive markers of resistance to endocrine therapy and modulation of these may lead to increased therapeutic sensitivity.

Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P3-03-05.

Relationships of percent body fat and percent trunk fat with bone mineral density among Chinese, black, and white subjects

We examined ethnic difference in the association of body fat and trunk fat with bone mineral density (BMD) among Chinese, white, and black subjects. We found that, with greater body and trunk fat, both white and black subjects were more likely to have a low BMD than Chinese subjects.

INTRODUCTION

Ethnic differences in body fat, abdominal fat distribution, and BMD have been found in previous studies between Chinese and white subjects. However, the associations of body fat and abdominal fat distribution with BMD have not been studied, and whether the ethnic differences have an effect on these associations is unclear.

METHODS

We evaluated 1,147 subjects aged ≥ 18 years (805 Chinese, 193 whites, and 149 blacks). Percent body fat (%BF), percent trunk fat (%TF), and total and regional BMD including that of head, arm, leg, trunk, rib, spine, and pelvis were measured by dual-energy X-ray absorptiometry. Linear regression models were developed to test the association of ethnicity, %BF, and interaction between ethnicity and %BF with BMD. The models were repeated again, replacing %BF with %TF.

RESULTS

Chinese subjects showed lower BMD in total and most regions compared with black and white subjects; however, these differences were eliminated between Chinese and whites within both sexes and between Chinese and black men when age, weight, height, and %BF were added. %BF and %TF were negatively associated with most regional body BMD. The interactions between %BF, %TF, and ethnicity were found in most regional body BMD among Chinese, white, and black subjects for both men and women.

CONCLUSION

Both %BF and %TF have negative associations with BMD. With greater accumulation of %BF and %TF, both white and black subjects may experience a higher risk of low BMD than Chinese subjects.

Uncoupling hypoxia signaling from oxygen sensing in the liver results in hypoketotic hypoglycemic death

As the ultimate electron acceptor in oxidative phosphorylation, oxygen plays a critical role in metabolism. When oxygen levels drop, heterodimeric hypoxia-inducible factor (Hif) transcription factors become active and facilitate adaptation to hypoxia. Hif regulation by oxygen requires the protein von Hippel-Lindau (pVhl) and pVhl disruption results in constitutive Hif activation. The liver is a critical organ for metabolic homeostasis, and Vhl inactivation in hepatocytes results in a Hif-dependent shortening in life span. While albumin-Cre;Vhl^F/F mice develop hepatic steatosis and impaired fatty acid oxidation, the variable penetrance and unpredictable life expectancy has made the cause of death elusive. Using a system in which Vhl is acutely disrupted and a combination of ex vivo liver perfusion studies and in vivo oxygen measurements, we demonstrate that Vhl is essential for mitochondrial respiration in vivo. Adenovirus-Cre mediated acute Vhl disruption in the liver caused death within days. Deprived of pVhl, livers accumulated tryglicerides and circulating ketone and glucose levels dropped. The phenotype was reminiscent of inborn defects in fatty acid oxidation and of fasted PPARα-deficient mice and while death was unaffected by pharmacologic PPARα activation, it was delayed by glucose administration. Ex vivo liver perfusion analyses and acylcarnitine profiles showed mitochondrial impairment and a profound inhibition of liver ketone and glucose production. By contrast, other mitochondrial functions, such as ureagenesis, were unaffected. Oxygen consumption studies revealed a marked suppression of mitochondrial respiration, which, as determined by magnetic resonance oximetry in live mice, was accompanied by a corresponding increase in liver pO₂. Importantly, simultaneous inactivation of Hif-1β suppressed liver steatosis and rescued the mice from death. These data demonstrate that constitutive Hif activation in mice is sufficient to suppress mitochondrial respiration in vivo and that no other pathway exists in the liver that can allow oxygen utilization when Hif is active precluding thereby metabolic collapse.

Associations of fat mass and fat distribution with bone mineral density in pre- and postmenopausal Chinese women

Fat mass (FM) is closely related to bone mineral density (BMD). However, the associations of FM and fat distribution with BMD in pre- and postmenopausal women are still poorly understood. The present study showed android fat mass accumulation after menopause had a negative association with BMD.

INTRODUCTION

FM is closely related to BMD. However, it is unknown whether FM and central fat distribution have different associations with BMD in pre- and postmenopausal women. The study aims to investigate the associations of FM and fat distribution with BMD in pre- and postmenopausal Chinese women.

METHODS

Two hundred sixty premenopausal and 267 postmenopausal women aged 18 to 79 years were analyzed. Lean mass (LM), FM, percent body fat (%BF), android FM, gynoid FM, and total and regional BMD were measured using dual-energy X-ray absorptiometry. Fat distribution was assessed by android to gynoid FM ratio (AOI). Multiple regression analysis was performed to examine the associations of BMD with FM, LM, and AOI.

RESULTS

FM, %BF, android FM, and AOI were significantly higher, whereas total and regional BMD were significantly lower in postmenopausal women (all р < 0.01). In premenopausal women, FM was positively associated with total and regional BMD (all р < 0.05). AOI had no significant association with BMD. In postmenopausal women, FM was significantly associated with total and regional BMD even additionally adjusting for LM (all р < 0.01). AOI had significantly negative association with total, head, arm, and leg BMD (all р < 0.05). The results remained unchanged when replacing FM with %BF.

CONCLUSIONS

There were different associations of FM and fat distribution with BMD in pre- and postmenopausal Chinese women. Increased central body fat had a negative association with BMD. Our findings may have significant implications in the prevention of menopause-related osteoporosis through reducing centralized fat deposition.

Abstract P4-02-20: Plasticity of the ER and HER2 Signaling Networks Results in Compensatory Escape Pathways Contributing to Treatment Resistance

Bidirectional crosstalk between the estrogen receptor (ER) and HER2 has been demonstrated in preclinical model systems. We have previously shown in HER2+ breast cancer cells with low ER that potent HER2- targeted therapy results in ER reactivation that functions as an escape pathway to evade therapeutic inhibition. Here we investigated the role of HER pathway components in resistance to endocrine therapies using UACC812 cells, which are endogenously amplified for HER2. Endocrine resistant (R) derivatives of the UACC812 line were developed through long-term (&gt;6 months) culturing with estrogen deprivation (ED) alone or with 4-OH-tamoxifen (Tam, 10-7M). Endocrine treatment [continued ED, estrogen (E2, 10-9M), Tam (10-7M), or fulvestrant (Ful, 10-7M)] of parental cells slowed cell growth compared to estrogen treatment (P&lt;0.01). EDR and TamR derivatives treated with any of the endocrine therapies, however, exhibited the same growth rates as with estrogen, validating the completely resistant phenotype of our clones. By immunoblot analysis, the resistant derivatives, TamR and EDR, showed a striking and complete loss of ER expression and its downstream gene products including PR, IGF-1R, and IRS-1. In contrast, both resistant lines exhibited significant upregulation of HER pathway components including marked increases in total and phosphorylated (p) EGFR, further upregulation of pHER2, and marked increases in the downstream signaling moieties pMAPK, pAkt, pFAK, pSrc, and pFOXO3a. In contrast, levels of pHER3 were markedly reduced at resistance. Since our in vitro data suggested that ER and HER2 compensate for inhibition of each other's pathways, we next examined whether simultaneous inhibition of both pathways can circumvent the development of resistance in an in vivo xenograft model. Athymic nude mice bearing UACC812 xenografts, established in the presence of E2 supplementation, were randomized to continued E2, endocrine therapies alone (ED, Tam, or Ful), anti-HER2 alone [lapatinib (L), trastuzumab (T), or L+T], or the combination of endocrine and anti-HER2 therapies (ED with L, T, or L+T). We found that tumors were stimulated by E2, as well as by Tam (as a mechanism of de novo resistance), while still being inhibited, though only temporarily (2-3 months), by ED and Ful. Anti-HER2 therapy alone only slowed down (L or T) or stabilized (L+T) tumor growth. In contrast, in the presence of both ED and anti-HER2 therapies, most tumors completely regressed. However, only the potent L+T plus ED regimen achieved continuous long term (&gt;200 days) complete regression in all mice. Our results further illustrate the plasticity of the ER and HER2 pathways and provide additional support for the role of the HER network, especially EGFR, in resistance to endocrine therapy in ER+/HER2+ breast cancer. The data emphasize the need for complete HER blockade for optimal therapy.

Citation Information: Cancer Res 2010;70(24 Suppl):Abstract nr P4-02-20.