A leukotriene B4 receptor-2 is associated with paclitaxel resistance in MCF-7/DOX breast cancer cells

Epigenomic Profiling Advises Therapeutic Potential of Leukotriene Receptor Inhibitors for a Subset of Triple-Negative Breast Tumors

Triple-negative breast cancer (TNBC) is the most aggressive molecular subtype, with a poor survival rate compared to others subtypes. For a long time, chemotherapy was the only systemic treatment for TNBC, and the identification of actionable molecular targets might ultimately improve the prognosis for TNBC patients. We performed a genome-wide analysis of DNA methylation at CpG islands on a collection of one hundred ten breast carcinoma samples and six normal breast tissue samples using reduced representation bisulfite sequencing with the XmaI restriction enzyme (XmaI-RRBS) and identified a subset of TNBC samples with significant hypomethylation at the LTB4R/LTB4R2 genes' CpG islands, including CpG dinucleotides covered with cg12853742 and cg21886367 HumanMethylation 450K microarray probes. Abnormal DNA hypomethylation of this region in TNBC compared to normal samples was confirmed by bisulfite Sanger sequencing. Gene expression generally anticorrelates with promoter methylation, and thus, the promoter hypomethylation detected and confirmed in our study might be revealed as an indirect marker of high LTB4R/LTB4R2 expression using a simple methylation-sensitive PCR test. Analysis of RNA-seq expression and DNA methylation data from the TCGA dataset demonstrates that the expression of the LTB4R and LTB4R2 genes significantly negatively correlates with DNA methylation at both CpG sites cg12853742 (R = -0.4, p = 2.6 × 10-6; R = -0.21, p = 0.015) and cg21886367 (R = -0.45, p = 7.3 × 10-8; R = -0.24, p = 0.005), suggesting the upregulation of these genes in tumors with abnormal hypomethylation of their CpG island. Kaplan-Meier analysis using the TCGA-BRCA gene expression and clinical data revealed poorer overall survival for TNBC patients with an upregulated LTB4R. To this day, only the leukotriene inhibitor LY255283 has been tested on an MCF-7/DOX cell line, which is a luminal A breast cancer molecular subtype. Other studies compare the effects of Montelukast and Zafirlukast (inhibitors of the cysteinyl leukotriene receptor, which is different from LTB4R/LTB4R2) on the MDA-MB-231 (TNBC) cell line, with high methylation and low expression levels of LTB4R. In our study, we assess the therapeutic effects of various drugs (including leukotriene receptor inhibitors) with the DepMap gene effect and drug sensitivity data for TNBC cell lines with hypomethylated and upregulated LTB4R/LTB4R2 genes. LY255283, Minocycline, Silibinin, Piceatannol, Mitiglinide, 1-Azakenpaullone, Carbetocin, and Pim-1-inhibitor-2 can be considered as candidates for the additional treatment of TNBC patients with tumors demonstrating LTB4R/LTB4R2 hypomethylation/upregulation. Finally, our results suggest that the epigenetic status of leukotriene B4 receptors is a novel, potential, predictive, and prognostic biomarker for TNBC. These findings might improve individualized therapy for TNBC patients by introducing new therapeutic adjuncts as anticancer agents.

Hepatocellular carcinoma progression promoted by 5-lipoxygenase activity in CD163(+) tumor-associated macrophages

Arachidonic acid 5-lipoxygenase (5-LOX), an enzyme that synthesizes leukotrienes (LTs), is involved in cancer development including proliferation, invasion, metastasis and drug resistance. However, the functional role of 5-LOX in hepatocellular carcinoma (HCC) remains to be elucidated. In this study, we analyzed the contribution of 5-LOX in HCC progression and investigated the potential of targeted therapy. Analysis of 86 resected HCC specimens and the clinical data of 362 cases of liver cancer from The Cancer Genome Atlas Liver Hepatocellular Carcinoma dataset, showed that 5-LOX expression was associated with postoperative survival. The cancer proliferative and stem cell potential were correlated with the levels of 5-LOX in CD163(+) tumor-associated macrophages (TAMs). In an HCC mouse model, CD163(+) TAMs expressed 5-LOX and produced LTB4 and LTC/D/E4; the 5-LOX inhibitor, zileuton, suppressed HCC progression. LTB4 and LTC/D/E4 promoted cancer proliferation and stem cell capacity via phosphorylation of extracellular signal-regulated kinase 1/2 and stem cell-associated genes. Taken together, we identified a novel mechanism of HCC progression in which CD163(+) TAMs express 5-LOX and produce LTB4 and LTC/D/E4, thereby enhancing the proliferative and stem cell potential of HCC cells. Furthermore, inhibition of 5-LOX activity regulates HCC progression, suggesting it has potential as a new therapeutic target.

Leukotriene B4 receptor 2 correlates with prognosis and immune infiltration in clear cell renal cell carcinoma

BACKGROUND

Clear cell renal cell carcinoma (ccRCC) is the most common renal cancer. According to reports, leukotriene B4 receptor 2 (LTB4R2, also known as BLT2), a chemokine receptor, is upregulated in different tumors. However, the correlation between BLT2 expression and its prognostic value in ccRCC remains to be explored.

METHODS

This study used the The Cancer Genome Atlas (TCGA) and Gene Expression Omnibus (GEO) databases to evaluate the association between BLT2 expression and the clinical outcome of ccRCC. Based on TIMER2.0, the correlation between BLT2 expression in ccRCC and tumor immune characteristics was evaluated.

RESULTS

The expression of BLT2 in ccRCC was higher than that in normal tissues. Kaplan-Meier survival analysis indicated that high BLT2 expression was significantly correlated with poor overall survival (HR = 1.75, p < 0.001) and disease-specific survival (HR = 1.60, p = 0.014) for patients with ccRCC. In addition, our findings revealed that there was no significant correlation between the M1 marker genes and the expression of BLT2 in ccRCC, while moderate correlations were observed between the BLT2 expression and the M2 marker genes. Tregs and T cell exhaustion marker genes were positively correlated with BLT2 expression in ccRCC (p < 0.001).

CONCLUSION

BLT2 may serve as a novel prognostic biomarker and is related to the shaping of tumor immune microenvironment in ccRCC. The expression of BLT2 potentially contributes to the regulation of TAMs, T cell exhaustion, and Tregs activation in ccRCC, providing new approaches to promote the development of new immunotherapeutic strategies for ccRCC.

The SGLT-2 inhibitor empagliflozin improves myocardial strain, reduces cardiac fibrosis and pro-inflammatory cytokines in non-diabetic mice treated with doxorubicin

BACKGROUND

Empagliflozin (EMPA), a selective inhibitor of the sodium glucose co-transporter 2, reduced the risk of hospitalization for heart failure and cardiovascular death in type 2 diabetic patients in the EMPA-REG OUTCOME trial. Recent trials evidenced several cardio-renal benefits of EMPA in non-diabetic patients through the involvement of biochemical pathways that are still to be deeply analysed. We aimed to evaluate the effects of EMPA on myocardial strain of non-diabetic mice treated with doxorubicin (DOXO) through the analysis of NLRP3 inflammasome and MyD88-related pathways resulting in anti-apoptotic and anti-fibrotic effects.

METHODS

Preliminary cellular studies were performed on mouse cardiomyocytes (HL-1 cell line) exposed to doxorubicin alone or combined to EMPA. The following analysis were performed: determination of cell viability (through a modified MTT assay), study of intracellular ROS production, lipid peroxidation (quantifying intracellular malondialdehyde and 4-hydroxynonenal), intracellular Ca2+ homeostasis. Moreover, pro-inflammatory studies were also performed: expression of NLRP3 inflammasome, MyD88 myddosome and p65/NF-κB associated to secretion of cytokines involved in cardiotoxicity (Interleukins 1β, 8, 6). C57Bl/6 mice were untreated (Sham, n = 6) or treated for 10 days with doxorubicin (DOXO, n = 6), EMPA (EMPA, n = 6) or doxorubicin combined to EMPA (DOXO-EMPA, n = 6). DOXO was injected intraperitoneally. Ferroptosis and xanthine oxidase were studied before and after treatments. Cardiac function studies, including EF, FS and radial/longitudinal strain were analysed through transthoracic echocardiography (Vevo 2100). Cardiac fibrosis and apoptosis were histologically studied through Picrosirius red and TUNEL assay, respectively and quantified through pro-collagen-1α1, MMP-9 and Caspase-3 expression. Tissue NLRP3, MyD88 and cytokines were also quantified before and after treatments through ELISA methods.

RESULTS

Cardiomyocytes exposed to doxorubicin increased the intracellular Ca2+ content and expression of several pro-inflammatory markers associated to cell death; co-incubation with EMPA reduced significantly the magnitude of the effects. In preclinical study, EMPA increased EF and FS compared to DOXO groups (p < 0.05), prevented the reduction of radial and longitudinal strain after 10 days of treatment with doxorubicin (RS) 30.3% in EMPA-DOXO vs 15.7% in DOXO mice; LS - 17% in EMPA-DOXO vs - 11.7% in DOXO mice (p < 0.001 for both). Significant reductions in ferroptosis, xanthine oxidase expression, cardiac fibrosis and apoptosis in EMPA associated to DOXO were also seen. A reduced expression of pro-inflammatory cytokines, NLRP3, MyD88 and NF-kB in heart, liver and kidneys was also seen in DOXO-EMPA group compared to DOXO (p < 0.001).

CONCLUSION

EMPA reduced ferroptosis, fibrosis, apoptosis and inflammation in doxorubicin-treated mice through the involvement of NLRP3 and MyD88-related pathways, resulting in significant improvements in cardiac functions. These findings provides the proof of concept for translational studies designed to reduce adverse cardiovascular outcomes in non-diabetic cancer patients treated with doxorubicin.

Specific c-Jun N-Terminal Kinase Inhibitor, JNK-IN-8 Suppresses Mesenchymal Profile of PTX-Resistant MCF-7 Cells through Modulating PI3K/Akt, MAPK and Wnt Signaling Pathways

Paclitaxel (PTX) is a widely used chemotherapeutic agent in the treatment of breast cancer, and resistance to PTX is a common failure of breast cancer therapy. Therefore, understanding the effective molecular targets in PTX-resistance gains importance in identifying novel strategies in successful breast cancer therapy approaches. The aim of the study was to investigate the functional role of PTX resistance on MCF-7 cell survival and proliferation related to PI3K/Akt and MAPK pathways. The generated PTX-resistant (PTX-res) MCF-7 cells showed enhanced cell survival, proliferation, and colony formation potential with decreased cell death compared to wt MCF-7 cells. PTX-res MCF-7 cells exhibited increased motility profile with EMT, PI3K/Akt, and MAPK pathway induction. According to the significant SAPK/JNK activation in PTX-res MCF-7 cells, specific c-Jun N-terminal kinase inhibitor, JNK-IN-8 is shown to suppress the migration potential of cells. Treatment of JNK inhibitor suppressed the p38 and SAPK/JNK and Vimentin expression. However, the JNK inhibitor further downregulated Wnt signaling members in PTX-res MCF-7 cells. Therefore, the JNK inhibitor JNK-IN-8 might be used as a potential therapy model to reverse PTX-resistance related to Wnt signaling.

Extracellular pyruvate kinase M2 facilitates cell migration by upregulating claudin-1 expression in colon cancer cells

Extensive studies have been reported the non-canonical functions of pyruvate kinase M2 (PKM2) as a kinase, transcriptional regulator, and even cell-to-cell communicator, emphasizing its importance in various signaling pathways. However, the role of secreted PKM2 in cancer progression and its signaling pathway is yet to be elucidated. In this study, we found that extracellular PKM2 enhanced the migration of low-metastatic, benign colon cancer cells by upregulating claudin-1 expression and internalizing it to the cytoplasm and nucleus. Knock-down of claudin-1 significantly reduced extracellular PKM2-induced cell migration. Inhibition of either protein kinase C (PKC) or epidermal growth factor receptor (EGFR) resulted in a reduction of extracellular PKM2-mediated claudin-1 expression, suggesting EGFR-PKC-claudin-1 as a signaling pathway in the extracellular PKM2-mediated tumorigenesis of colon cancer cells.

Comparing the effects of vitamin E tocotrienol-rich fraction supplementation and α-tocopherol supplementation on gene expression in healthy older adults

OBJECTIVES

This study aims to compare the differential gene expression resulting from tocotrienol-rich fraction and α-tocopherol supplementation in healthy older adults.

METHODS

A total of 71 eligible subjects aged 50 to 55 years from Gombak and Kuala Lumpur, Malaysia, were divided into three groups and supplemented with placebo (n=23), α-tocopherol (n=24) or tocotrienol-rich fraction (n=24). Blood samples were collected at baseline and at 3 and 6 months of supplementation for microarray analysis.

RESULTS

The number of genes altered by α-tocopherol was higher after 6 months (1,410) than after 3 months (273) of supplementation. α-Tocopherol altered the expression of more genes in males (952) than in females (731). Similarly, tocotrienol-rich fraction modulated the expression of more genes after 6 months (1,084) than after 3 months (596) and affected more genes in males (899) than in females (781). α-Tocopherol supplementation modulated pathways involving the response to stress and stimuli, the immune response, the response to hypoxia and bacteria, the metabolism of toxins and xenobiotics, mitosis, and synaptic transmission as well as activated the mitogen-activated protein kinase and complement pathways after 6 months. However, tocotrienol-rich fraction supplementation affected pathways such as the signal transduction, apoptosis, nuclear factor kappa B kinase, cascade extracellular signal-regulated kinase-1 and extracellular signal-regulated kinase-2, immune response, response to drug, cell adhesion, multicellular organismal development and G protein signaling pathways.

CONCLUSION

Supplementation with either α-tocopherol or tocotrienol-rich fraction affected the immune and drug response and the cell adhesion and signal transduction pathways but modulated other pathways differently after 6 months of supplementation, with sex-specific responses.

Mediatory role of BLT2 in the proliferation of KRAS mutant colorectal cancer cells

Inflammatory lipid mediators play various roles in colorectal cancer progression through complex pathways. However, the mechanism by which lipoxygenase-derived inflammatory lipid mediators contribute to colorectal cancer progression remains elusive. In this study, we found that BLT2, a cell surface GPCR for leukotriene B₄ and 12‑hydroxyeicosatetraenoic acid, is highly upregulated in KRAS mutant LOVO and SW480 colorectal cancer cells and plays critical roles in mediating proliferation through activation of phosphatidylinositol 3‑kinase (PI3K)/protein kinase B (Akt) and subsequent upregulation of cyclin D1. Exposure to BLT2 siRNA or LY255283, a specific BLT2 inhibitor, clearly suppressed the proliferation of KRAS mutant colorectal cancer cells and markedly increased cell cycle arrest by downregulating the PI3K/Akt-cyclin D1 cascade. Xenograft tumor formation by LOVO and SW480 cells in athymic mice was also substantially reduced by treatment with the BLT2 inhibitor in vivo. Together, our study demonstrates that BLT2 is necessary for the proliferation of LOVO and SW480 cells and thus may be a potential therapeutic target for the treatment of KRAS mutant colorectal cancer.

Shikonin induces mitochondria-mediated apoptosis and attenuates epithelial-mesenchymal transition in cisplatin-resistant human ovarian cancer cells

Cisplatin-based chemotherapy often results in the development of chemoresistance when used to treat ovarian cancer, which is difficult to overcome. The present study investigated the cytotoxic and anti-migratory effects of shikonin, a naphthoquinone compound, on cisplatin-resistant human ovarian cancer A2780 cells (A2780-CR). Shikonin had a potent dose-dependent cytotoxic effect on A2780-CR cells, with 9 µM shikonin treatment reducing A2780-CR cell viability by 50%, validate using an MTT assay. Shikonin induced apoptosis, as evidenced by the increased number of apoptotic bodies, following staining with Hoechst 33342, and terminal deoxynucleotidyl cell transferase dUTP nick end labeling-positive cells following treatment. Flow cytometry and fluorescent microscope imaging, following JC-1 staining, revealed that shikonin increased mitochondrial membrane depolarization. Also it altered the levels of apoptosis-associated proteins, leading to diminished expression of B cell lymphoma-2 (Bcl-2), enhanced expression of Bcl-associated X, and cleavage of caspase-9 and −3, as revealed using western blot analysis. Shikonin activated mitogen-activated protein kinases; while treatment with specific inhibitors of these kinases attenuated the decline in cell viability induced by shikonin treatment. In addition, the cell migration assay and western blot analysis indicated that shikonin decreased the migratory capacity of A2780-CR cells via the upregulation of epithelial-cadherin and downregulation of neural-cadherin. Taken together, the results of the present study indicated that shikonin induces mitochondria-mediated apoptosis and attenuates the epithelial-mesenchymal transition in A2780-CR cells.

Preclinical studies for the combination of paclitaxel and curcumin in cancer therapy (Review)

Cancer is one of the most common causes of death and remains the first in China and the second in the US. The common treatments for cancer include surgery, radiation, chemotherapy, targeted therapy and immunotherapy, while chemotherapy remains one of the most important treatments. However, the efficacy of chemotherapy is limited due to drug induced-toxicities and resistance, particularly multiple drug resistance (MDR). Therefore, discovery and development of novel therapeutic drugs and/or combination therapy are urgently needed to reduce toxicity and improve efficacy. Paclitaxel has been widely used to treat various cancers including cervical, breast, ovarian, brain, bladder, prostate, liver and lung cancers. However, its therapeutic efficacy is limited and MDR is a major obstacle. Recently, numerous preclinical studies have shown that the combination of paclitaxel and curcumin may be an ideal strategy to reverse MDR and synergistically improve their therapeutic efficacy in cancer therapy. This review mainly focuses on the current development and progress of the combination of paclitaxel and curcumin in cancer therapy preclinically.

LC-MS Based Sphingolipidomic Study on A2780 Human Ovarian Cancer Cell Line and its Taxol-resistant Strain

Drug resistance elicited by cancer cells continue to cause huge problems world-wide, for example, tens of thousands of patients are suffering from taxol-resistant human ovarian cancer. However, its biochemical mechanisms remain unclear. Sphingolipid metabolic dysregulation has been increasingly regarded as one of the drug-resistant mechanisms for various cancers, which in turn provides potential targets for overcoming the resistance. In the current study, a well-established LC-MS based sphingolipidomic approach was applied to investigate the sphingolipid metabolism of A2780 and taxol-resistant A2780 (A2780T) human ovarian cancer cell lines. 102 sphingolipids (SPLs) were identified based on accurate mass and characteristic fragment ions, among which 12 species have not been reported previously. 89 were further quantitatively analyzed by using multiple reaction monitoring technique. Multivariate analysis revealed that the levels of 52 sphingolipids significantly altered in A2780T cells comparing to those of A2780 cells. These alterations revealed an overall increase of sphingomyelin levels and significant decrease of ceramides, hexosylceramides and lactosylceramides, which concomitantly indicated a deviated SPL metabolism in A2780T. This is the most comprehensive sphingolipidomic analysis of A2780 and A2780T, which investigated significantly changed sphingolipid profile in taxol-resistant cancer cells. The aberrant sphingolipid metabolism in A2780T could be one of the mechanisms of taxol-resistance.

Myeloid differentiation primary response gene 88-leukotriene B4 receptor 2 cascade mediates lipopolysaccharide-potentiated invasiveness of breast cancer cells

Inflammation and local inflammatory mediators are inextricably linked to tumor progression through complex pathways in the tumor microenvironment. Lipopolysaccharide (LPS) exposure to tumor cells has been suggested to promote tumor invasiveness and metastasis. However, the detailed signaling mechanism involved has not been elucidated. In this study, we showed that LPS upregulated the expression of leukotriene B₄ receptor-2 (BLT2) and the synthesis of BLT2 ligands in MDA-MB-231 and MDA-MB-435 breast cancer cells, thereby promoting invasiveness. BLT2 depletion with siRNA clearly attenuated LPS-induced invasiveness. In addition, we demonstrated that myeloid differentiation primary response gene 88 (MyD88) lies upstream of BLT2 in LPS-potentiated invasiveness and that this ‘MyD88-BLT2’ cascade mediates activation of NF-κB and the synthesis of IL-6 and IL-8, which are critical for the invasiveness and aggression of breast cancer cells. LPS-driven metastasis of MDA-MB-231 cells was also markedly suppressed by the inhibition of BLT2. Together, our results demonstrate, for the first time, that LPS potentiates the invasiveness and metastasis of breast cancer cells via a ‘MyD88-BLT2’-linked signaling cascade.

Targeted tumor therapy by Rubia tinctorum L.: analytical characterization of hydroxyanthraquinones and investigation of their selective cytotoxic, adhesion and migration modulator effects on melanoma cell lines (A2058 and HT168-M1)

Background

Alizarin and purpurin are di- and trihydroxyanthraquinones derived from Rubia tinctorum L. Previous pharmacological studies have demonstrated that they exhibit certain degree of selective inhibitory effects towards cancer cells suggesting their application as a targeted drug for cancer. Our present work was aimed to investigate the suitability of hydroxyanthraquinones of Rubia tinctorum L. for targeted tumor therapy. The effects of alizarin, purpurin and an aqueous extract from transformed hairy root culture of Rubia tinctorum L. were examined on (1) cell proliferation, (2) apoptosis, (3) cell adhesion/morphology and (4) migration (chemotaxis, chemokinesis) of human melanoma cell lines (A2058, HT168-M1) and human fibroblast cells (MRC-5), as well as (5) the aqueous extract was analytically characterized.

Methods

The aqueous extract was prepared from R. tinctorum hairy root culture and qualitatively analyzed by HPLC and ESI–MS methods. The cell growth inhibitory activity of anthraquinones was evaluated by MTT-assay and by flow cytometry. The effect of anthraquinones on cell adhesion was measured by an impedance based technique, the xCELLigence SP. For the chemotaxis assay NeuroProbe^® chamber was used. Computer based holographic microscopy was applied to analyze chemokinetic responses as well as morphometry. Statistical significance was determined by the one-way ANOVA test.

Results

In the aqueous extract, munjistin (M_r = 284, t_R = 18.4 min) as a principal component and three minor anthraquinones (pseudopurpurin, rubiadin and nordamnacanthal) were identified. The purpurin elicited a stronger but not apoptosis-mediated antitumor effect in melanoma cells (A2058: 10⁻⁶–10⁻⁵ M: 90.6–64.1 %) than in normal fibroblasts (10⁻⁶–10⁻⁵ M: 97.6–84.8 %). The aqueous extract in equimolar concentrations showed the most potent cytotoxicity after 72 h incubation (A2058: 10⁻⁶–10⁻⁵ M: 87.4–55.0 %). All tested substances elicited chemorepellent effect in melanoma cells, while in MRC-5 fibroblasts, only the alizarin exhibited such a repellent character. Indices of chemokinesis measured by holographic microscopy (migration, migration directness, motility and motility speed) were significantly enhanced by alizarin and purpurin as well, while morphometric changes were weak in the two melanoma cell lines.

Conclusions

Our results highlight the effective and selective inhibitory activity of purpurin towards melanoma cells and its possible use as a targeted anticancer agent. The anthraquinones of the cytotoxic extract are suggested to apply in drug delivery systems as an anticancer drug.

Electronic supplementary material

The online version of this article (doi:10.1186/s12935-015-0271-4) contains supplementary material, which is available to authorized users.

Leukotriene B4 receptor-2 contributes to chemoresistance of SK-OV-3 ovarian cancer cells through activation of signal transducer and activator of transcription-3-linked cascade

Inflammation and inflammatory mediators are intimately linked with chemoresistance through complex pathways in the tumor microenvironment. However, the mechanism by which inflammatory mediators (e.g., eicosanoids) contribute to chemoresistance remains elusive. In this study, we found that the low-affinity leukotriene B4 receptor-2 (BLT2) and its ligand leukotriene B4 were highly up-regulated in cisplatin-resistant SK-OV-3 ovarian cancer cells and play critical roles in mediating the chemoresistance through the activation of signal transducer and activator of transcription-3 (STAT-3) and the subsequent up-regulation of interleukin-6 (IL-6). BLT2 depletion with siRNA clearly abolished the chemoresistance to cisplatin in SK-OV-3 ovarian cancer cells and further increased cell sensitivity to cisplatin chemotherapy by down-regulating the 'STAT-3-IL-6' cascade. Enlarged tumor formation due to the cisplatin resistance of SK-OV-3 cells in cisplatin-treated athymic mice was also substantially reduced by co-treatment with the BLT2 inhibitor in vivo. Our study demonstrates that BLT2 is a novel contributor to cisplatin resistance in SK-OV-3 ovarian cancer cells and thus may be a potential therapeutic target for the treatment of cisplatin-resistant ovarian cancer.

LPS Up-Regulates ICAM-1 Expression in Breast Cancer Cells by Stimulating a MyD88-BLT2-ERK-Linked Cascade, Which Promotes Adhesion to Monocytes

Monocytes are the major inflammatory cells that infiltrate most solid tumors in humans. The interaction of tumor cells with infiltrating monocytes and their adhesion to these monocytes play a significant role in altering the tumor to become more aggressive. Recently, exposure to lipopolysaccharide (LPS) was suggested to promote cancer cell adhesion to monocytes; however, little is known about the details of the signaling mechanism involved in this process. In this study, we found that LPS up-regulates ICAM-1 expression in MDA-MB-231 breast cancer cells, which facilitates their adhesion to THP-1 monocytes. In addition, we analyzed the signaling mechanism underlying the up-regulation of ICAM-1 and found that the siRNA-mediated depletion of BLT2 markedly suppressed the LPS-induced expression of ICAM-1 in MDA-MB-231 cells and the subsequent adhesion of these cells to THP-1 monocytes. Moreover, we demonstrated that myeloid differentiation primary response gene 88 (MyD88) lies downstream of LPS/TLR4 and upstream of BLT2 and that this 'MyD88-BLT2' cascade mediates ERK activation and subsequent ICAM-1 expression, which is critical for the adhesion of MDA-MB-231 cells to THP-1 monocytes. Taken together, our results demonstrate for the first time that LPS up-regulates ICAM-1 expression in breast cancer cells via a MyD88-BLT2-ERK-linked signaling cascade, leading to the increased adhesion of breast cancer cells to monocytes.

Clinical management of breast cancer heterogeneity

Traditionally, intertumour heterogeneity in breast cancer has been documented in terms of different histological subtypes, treatment sensitivity profiles, and clinical outcomes among different patients. Results of high-throughput molecular profiling studies have subsequently revealed the true extent of this heterogeneity. Further complicating this scenario, the heterogeneous expression of the oestrogen receptor (ER), progesterone receptor (PR), and HER2 has been reported in different areas of the same tumour. Furthermore, discordance, in terms of ER, PR and HER2 expression, has also been reported between primary tumours and their matched metastatic lesions. High-throughput molecular profiling studies have confirmed that spatial and temporal intratumour heterogeneity of breast cancers exist at a level beyond common expectations. We describe the different levels of tumour heterogeneity, and discuss the strategies that can be adopted by clinicians to tackle treatment response and resistance issues associated with such heterogeneity, including a rationally selected combination of agents that target driver mutations, the targeting of deleterious passenger mutations, identifying and eradicating the 'lethal' clone, targeting the tumour microenvironment, or using adaptive treatments and immunotherapy. The identification of the most-appropriate strategies and their implementation in the clinic will prove highly challenging and necessitate the adoption of radically new practices for the optimal clinical management of breast malignancies.

Paclitaxel resistance in MCF-7/PTX cells is reversed by paeonol through suppression of the SET/phosphatidylinositol 3-kinase/Akt pathway

Breast cancer is one of the most prevalent types of malignant tumor. Paclitaxel is widely used in the treatment of breast cancer; however, the major problem contributing to the failure of chemotherapy in breast cancer is the development of drug resistance. Therefore, it is necessary to identify novel therapeutic targets and reversal agents for breast cancer. In the present study, the protein expression levels of SET, protein phosphatase 2A (PP2A) and phosphatidylinositol 3-kinase (PI3K)/Akt pathway were determined in MCF-7/PTX human breast carcinoma paclitaxel-resistant cells using western blot analysis. Small interference RNAs (siRNAs) were used to knock down the gene expression of SET in MCF-7/PTX cells and the cell viability was assessed following treatment with paclitaxel, using 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide assays and flow cytometry. In addition, western blot analysis was used to determined PI3K/Akt pathway activity following SET knockdown. Furthermore, the reversal effects of paeonol on paclitaxel, and its underlying mechanisms of action, were investigated using western blot analysis and reverse transcription-quantitative polymerase chain reaction. The results demonstrated that increased levels of SET and PI3K/Akt pathway proteins were present in the MCF-7/PTX cells, compared with normal MCF-7 cells. Knockdown of SET significantly sensitized MCF-7/PTX cells to paclitaxel and induced cell apoptosis. In addition, the expression levels of the adenosine triphosphate binding cassette (ABC) transporter proteins were significantly reduced in the MCF-7/PTX cells compared with the normal MCF-7 cells. SET-induced paclitaxel resistance was found to be associated with the activation of the PI3K/Akt pathway. Paeonol significantly reduced the mRNA and protein expression levels of SET in the MCF-7/PTX cells. Furthermore, paeonol significantly sensitized the MCF-7/PTX to paclitaxel via regulation of ABC transporters, B cell lymphoma-2 (Bcl-2) and Bcl-2-associated X protein. In addition, paeonol inhibited SET-mediated paclitaxel resistance by attenuating PI3K/Akt pathway activity in the MCF-7/PTX cells. In conclusion, the results of the present study demonstrated that SET was associated with paclitaxel resistance in MCF-7/PTX cells, and that paeonol reversed paclitaxel resistance in MCF-7/PTX cells by downregulating the activity of the SET/PP2A/Akt pathway.

Paeonol reverses paclitaxel resistance in human breast cancer cells by regulating the expression of transgelin 2

Paclitaxel (PTX) is a first-line antineoplastic drug that is commonly used in clinical chemotherapy for breast cancer treatment. However, the occurrence of drug resistance in chemotherapeutic treatment has greatly restricted its use. There is thus an urgent need to find ways of reversing paclitaxel chemotherapy resistance in breast cancer. Plant-derived agents have great potential in preventing the onset of the carcinogenic process and enhancing the efficacy of mainstream antitumor drugs. Paeonol, a main compound derived from the root bark of Paeonia suffruticosa, has various biological activities, and is reported to have reversal drug resistance effects. This study established a paclitaxel-resistant human breast cancer cell line (MCF-7/PTX) and applied the dual-luciferase reporter gene assay, MTT assay, flow cytometry, transfection assay, Western blotting and the quantitative real-time polymerase chain reaction (qRT-PCR) to investigate the reversing effects of paeonol and its underlying mechanisms. It was found that transgelin 2 may mediate the resistance of MCF-7/PTX cells to paclitaxel by up-regulating the expressions of the adenosine-triphosphate binding cassette transporter proteins, including P-glycoprotein (P-gp), multidrug resistance associated protein 1 (MRP1), and breast cancer resistance protein (BCRP). Furthermore, the ability of paeonol to reverse paclitaxel resistance in breast cancer was confirmed, with a superior 8.2-fold reversal index. In addition, this study found that paeonol down-regulated the transgelin 2-mediated paclitaxel resistance by reducing the expressions of P-gp, MRP1, and BCRP in MCF-7/PTX cells. These results not only provide insight into the potential application of paeonol to the reversal of paclitaxel resistance, thus facilitating the sensitivity of breast cancer chemotherapy, but also highlight a potential role of transgelin 2 in the development of paclitaxel resistance in breast cancer.