Abstract P4-07-13: High microRNA-621 level predicts a better response to neoadjuvant chemotherapy in breast cancer patients

Purpose: Weekly paclitaxel plus carboplatin (PCb) regimen is an effective neoadjuvant chemotherapy for breast cancer. However, some patients respond to this regimen poorly and suffer from side effects. In this study, we aimed to define the microRNA (miRNA) biomarker for predicting sensitivity to PCb chemotherapy in breast cancer patients, and to explore the potential molecular mechanisms.

Experimental Design: 81 patients with stages II and III breast cancer, who received four cycles of weekly PCb regimen preoperative chemotherapy, were included. Gene expression profiles from 31 patients was used as training set to determine differentially expressed genes (DEGs) and to predict miRNAs that may be associated with chemotherapeutic sensitivity. The other 50 patients were analyzed as validation set to test the accuracy of DEG identification and miRNAs prediction by quantitative real-time PCR. In parallel, in vitro and in vivo analyses were carried out to determine the potential mechanisms of miRNA-dependent drug sensitivity.

Results: Gene profiling analyses in the training set revealed significant correlation between high expression level of miR-345 and miR-621 and pathologic complete response (pCR) in breast cancer patients. We further validated that the expression level of miR-621 was significantly higher in tumor tissues of pCR patients than that in non-pCR patients (P = 0.01). In breast cancer cell lines, ectopic overexpression of miR-621 promoted apoptosis and increased chemosensitivity to paclitaxel and carboplatin both in vitro and in vivo. The potential miR-621-target genes were determined by TargetScan and miRNA CLIP-seq database, which were further confirmed as DEGs reversely-correlated to miR-621 in breast cancer patient samples. Among those, FBXO11 was verified as one of the direct targets of miR-621 in breast cancer cells, whose expression level negatively associated with chemosensitivity in breast cancer patients. The molecular mechanisms by which miR-621/FBXO11 axis regulates chemosensitivity may involve regulation of p53 transcriptional activity and epithelial-mesenchymal transition (EMT) in breast cancer cells.

Conclusions: Our study revealed a strong correlation between miR-621 expression and chemosensitivity in breast cancers. High level of miR-621 predicts sensitivity to PCb regimen neoadjuvant chemotherapy in breast cancer patients who tend to achieve pCR. The increased chemosensitivity may be mediated by down-regulation of FBXO11 gene, which leads to enhanced p53 transactivity and reduced EMT in breast cancer cells. Therefore, miR-621 may be used as predictive biomarker and the potential therapeutic target in breast cancer treatment.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P4-07-13.

Abstract P5-04-11: CDK11p58 inhibits estrogen receptor a positive breast cancer invasion via integrinb3 through repressing ERa signaling

Background: The sex steroid estrogen plays a major role in the development and progression of breast cancer. Estrogen promotes breast cancer proliferation through a number of established pathways. CDK11p58, a Ser/Thr kinase which belongs to Cell Division Cycle 2-like 1 (CDC2L1) subfamily, is associated with cell cycle progression, tumorigenesis and apoptotic signaling. In the previous study, we found that CDK11p58 interacted with estrogen receptor a (ERa) in breast tumor cells and repressed ERa transcriptional activity through promoting its ubiquitin/proteasome-mediated degradation. Here we sought to investigate the critical role of CDK11p58 in the carcinogenisis of breast cancer.

Methods and results: We measured the expression of CDK11p58 in 132 pairs of breast cancer tissues and adjacent tissues by IHC and qPCR. The mRNA and protein level of CDK11p58 were significant higher in breast cancer tissues than those in normal breast tissues. Interestingly, low expression of CDK11 was associated with lymph nodes metastasis in patients (P<0.05). Using the ERa + cell lines ZR-75-30 and T47D, we found CDK11p58 could repress the migration and invasion of ERa positive breast cancer cells. We further demonstrated that mRNA of integrinb3 were dramatically repressed by CDK11p58 by the TaqMan® Metastasis Gene Expression Assays. The effect was CDK11p58 kinase activity dependent. Expression of integrinβ3 was highly related with ERa signaling. While overexpression ERa stimulates integrinβ3 expression, knockdown of ERa attenuates integrinβ3 expression. By the Dual-luciferase array and CHIP assay, we found estrogen response elements (ERE) indeed existed in integrinβ3 promoter. ERa bound to the ERE on the integrinβ3 promoter and increased its transcription.

Conclusions: Our findings provide mechanistic insights into how CDK11p58 regulated the expression of integrinβ3 to inhibit the cell invasion though repressing the signaling of ERa in a kinase activity dependent way. These data indicate that CDK11p58 is an antimetastasis gene product in breast cancer and regulation of integrinβ3 by CDK11p58 through ERa could be part of a signaling pathway that determines and explains breast cancer invasion and metastasis.

Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-04-11.

Acclimation of leaf dark respiration to nocturnal and diurnal warming in a semiarid temperate steppe

A better understanding of thermal acclimation of leaf dark respiration in response to nocturnal and diurnal warming could help accurately predict the changes in carbon exchange of terrestrial ecosystems under global warming, especially under the asymmetric warming. A field manipulative experiment was established with control, nocturnal warming (1800-0600hours), diurnal warming (0600-1800hours), and diel warming (24h) under naturally fluctuating conditions in a semiarid temperate steppe in northern China in April 2006. Temperature response curves of in situ leaf dark respiration for Stipa krylovii Roshev. were measured at night (Rn) and after 30min of darkness imposed in the daytime (Rd). Leaf nonstructural carbohydrates were determined before sunrise and at sunset. Results showed that Rn could acclimate to nocturnal warming and diurnal warming, but Rd could not. The decreases in Q10 (temperature sensitivity) of Rn under nocturnal-warming and diurnal warming regimes might be attributed to greater depletion of total nonstructural carbohydrates (TNC). The real-time and intertwined metabolic interactions between chloroplastic and mitochondrial metabolism in the daytime could affect the impacts of warming on metabolite pools and the distinct response of Rn and Rd to warming. Projection on climate change-carbon feedback under climate warming must account for thermal acclimation of leaf dark respiration separately by Rn and Rd.

Note: Characteristic beam parameter for the line electron gun

We have optimized the beam parameters of line source electron gun using Stanford Linear Accelerator Centre electron beam trajectory program (EGUN), utilizing electrostatic focusing only. We measured minimum beam diameter as 0.5 mm that corresponds to power density of 68.9 kW/cm(2) at 13.5 mm in the post-anode region which is more than two-fold (33 kW/cm(2)), of the previously reported results. The gun was operated for the validation of the theoretical results and found in good agreement. The gun is now without any magnetic and electrostatic focusing thus much simpler and more powerful.

Acclimation of foliar respiration and photosynthesis in response to experimental warming in a temperate steppe in northern China

BACKGROUND

Thermal acclimation of foliar respiration and photosynthesis is critical for projection of changes in carbon exchange of terrestrial ecosystems under global warming.

METHODOLOGY/PRINCIPAL FINDINGS

A field manipulative experiment was conducted to elevate foliar temperature (Tleaf) by 2.07°C in a temperate steppe in northern China. Rd/Tleaf curves (responses of dark respiration to Tleaf), An/Tleaf curves (responses of light-saturated net CO2 assimilation rates to Tleaf), responses of biochemical limitations and diffusion limitations in gross CO2 assimilation rates (Ag) to Tleaf, and foliar nitrogen (N) concentration in Stipa krylovii Roshev. were measured in 2010 (a dry year) and 2011 (a wet year). Significant thermal acclimation of Rd to 6-year experimental warming was found. However, An had a limited ability to acclimate to a warmer climate regime. Thermal acclimation of Rd was associated with not only the direct effects of warming, but also the changes in foliar N concentration induced by warming.

CONCLUSIONS/SIGNIFICANCE

Warming decreased the temperature sensitivity (Q10) of the response of Rd/Ag ratio to Tleaf. Our findings may have important implications for improving ecosystem models in simulating carbon cycles and advancing understanding on the interactions between climate change and ecosystem functions.

Asymmetric dimethylarginine and carotid atherosclerosis in Type 2 diabetes mellitus

BACKGROUND

Circulating asymmetric dimethylarginine (ADMA) concentration is elevated in patients with Type 2 diabetes mellitus (T2DM).

AIM

To assess the relationship between plasma ADMA concentration and carotid atherosclerosis in patients with T2DM.

SUBJECTS AND METHODS

A total of 72 newly diagnosed and untreated T2DM individuals and 72 healthy controls were studied. Carotid atherosclerosis was determined by ultrasonographically evaluated intima- media thickness (IMT) and plaque score. Plasma concentration of ADMA was measured by high-performance liquid chromatography.

RESULTS

Plasma ADMA, mean IMT, and plaque score were higher in diabetic patients compared with controls. Univariate and multivariate analyses demonstrated an independent association between ADMA and mean IMT in diabetic patients. On a multiple logistic regression analysis, ADMA was the sole predictor of carotid plaque formation (plaque score ≥1.1) (odds ratio 2.43, 95% confidence interval 1.19 to 4.94, p<0.05).

CONCLUSION

Our results suggest that increased levels of ADMA might be involved in the development of carotid atherosclerosis in T2DM.

Cordycepin as a sensitizer to tumour necrosis factor (TNF)-α-induced apoptosis through eukaryotic translation initiation factor 2α (eIF2α)- and mammalian target of rapamycin complex 1 (mTORC1)-mediated inhibition of nuclear factor (NF)-κB

Cordycepin (3'-deoxyadenosine) is one of the major bioactive substances produced by Cordyceps militaris, a traditional medicinal mushroom. Cordycepin possesses several biological activities, including both pro-apoptotic and anti-apoptotic properties. In the present report, we investigated an effect of cordycepin on the survival of cells exposed to tumour necrosis factor (TNF)-α. We found that subtoxic doses of cordycepin increased susceptibility of cells to TNF-α-induced apoptosis. It was associated with suppression of nuclear factor-κB (NF-κB), a major prosurvival component involved in TNF-α signalling. The adenosine transporter and A₃ adenosine receptor, but not A₁ and A₂ adenosine receptors, mediated both anti-NF-κB and pro-apoptotic effects. We found that cordycepin had the potential to phosphorylate eukaryotic translation initiation factor 2α (eIF2α) and that activation of eIF2α mimicked the suppressive effect of cordycepin on the NF-κB pathway. Furthermore, activation of eIF2α sensitized cells to TNF-α-induced apoptosis. To identify molecular events downstream of eIF2α, the role of mammalian target of rapamycin complex 1 (mTORC1) was examined. Selective activation of ₃eIF2α, as well as treatment with cordycepin, caused phosphorylation of mTORC1. Rapamycin, an inhibitor of mTORC1, significantly reversed the suppressive effects of eIF2α on NF-κB. These results suggest that cordycepin sensitizes cells to TNF-α-induced apoptosis, at least in part, via induction of the eIF2α-mTORC1 pathway and consequent suppression of NF-κB.

A pilot study to evaluate assisted freehand ultrasound elasticity imaging in the sizing of early breast cancer: a comparison of B-mode and AFUSON elasticity ultrasound with histopathology measurements

OBJECTIVE

This pilot study investigates the role of assisted-freehand ultrasound (AFUSON) elasticity imaging of the breast in assessing the contour, size and area of 23 early breast cancers by making comparison of AFUSON with the equivalent B-mode ultrasound images and gold standard histopathology slides.

METHODS

The B-mode, AFUSON and digitised histopathology slides of three early breast cancers were compared for contour, size and area with histopathology scans. AFUSON features that corresponded to areas of known malignant change on the histopathology slides were regarded as diagnostic. These diagnostic criteria were then applied to the B-mode and AFUSON elasticity images of all 23 breast cancers in the pilot study without having the availability of the histopathology scans for reference. Corresponding diameters were measured and the results were compared with the equivalent measurements on the scans of the histology slides. The results were tabulated in histogram form. Diagnostic confidence levels were evaluated.

RESULTS

Size dimension accuracy increased from 66% using B-mode alone to 82% using combined B-mode and AFUSON elasticity images. Tumour area accuracy was also increased. A small number of cases had a striking visual similarity of shape on AFUSON elasticity scans and histopathology slides.

CONCLUSION

In spite of the shortfalls in this study, AFUSON elasticity imaging was capable of acquiring some high-quality images that showed strong correlation between AFUSON elasticity and scans of histology slides. Further studies will be carried out to refine the technique and determine if it has a role in the diagnosis and management of breast cancer.

Endoglin differentially regulates TGF-β-induced Smad2/3 and Smad1/5 signalling and its expression correlates with extracellular matrix production and cellular differentiation state in human chondrocytes

OBJECTIVE

Transforming growth factor-β (TGF-β) plays a critical role in cartilage homeostasis and deregulation of its signalling is implicated in osteoarthritis (OA). TGF-β isoforms signal through a pair of transmembrane serine/threonine kinases known as the type I and type II TGF-β receptors. Endoglin is a TGF-β co-receptor that binds TGF-β with high affinity in the presence of the type II TGF-β receptor. We have previously shown that endoglin is expressed in human chondrocytes and that it forms a complex with the TGF-β signalling receptors. However, the functional significance of endoglin expression in chondrocytes is unknown. Our objective was to determine whether endoglin regulates TGF-β/Smad signalling and extracellular matrix (ECM) production in human chondrocytes and whether its expression varies with chondrocyte differentiation state.

METHOD

Endoglin function was determined by overexpression or antisense morpholino/siRNA knockdown of endoglin in human chondrocytes and measuring TGF-β-induced Smad phosphorylation, transcriptional activity and ECM production. Alterations in endoglin expression levels were determined during subculture-induced dedifferentiation of human chondrocytes and in normal vs OA cartilage samples.

RESULTS

Endoglin enhances TGF-β1-induced Smad1/5 phosphorylation and inhibits TGF-β1-induced Smad2 phosphorylation, Smad3-driven transcriptional activity and ECM production in human chondrocytes. In addition, the enhancing effect of endoglin siRNA knockdown on TGF-β1-induced Smad3-driven transcription is reversed by ALK1 overexpression. Furthermore, endoglin levels are increased in chondrocytes following subculture-induced dedifferentiation and in OA cartilage as compared to normal cartilage.

CONCLUSION

Together, our results suggest that endoglin regulates the balance between TGF-β/ALK1/Smad1/5 and ALK5/Smad2/3 signalling and ECM production in human chondrocytes and that endoglin may represent a marker for chondrocyte phenotype.