Proteomic analysis of the proteins that are associated with the resistance to paclitaxel in human breast cancer cells

Transgelin-2, a novel cancer stem cell-related biomarker, is a diagnostic and therapeutic target for biliary tract cancer

BACKGROUND

Biliary tract cancer (BTC) is a relatively rare but aggressive gastrointestinal cancer with a high mortality rate. Cancer stem cell (CSC) populations play crucial roles in tumor biology and are responsible for the low response to anti-cancer treatment and the high recurrence rate. This study investigated the role of Transgelin-2 (TAGLN2), overexpressed in CSC in BTC cells, and analyzed its expression in patient tissues and serum to identify potential new targets for BTC.

METHODS

TAGLN2 expression was suppressed by small-interfering or short hairpin RNAs, and its effects on tumor biology were assessed in several BTC cell lines. Furthermore, the effects of TAGLN2 silencing on gemcitabine-resistant BTC cells, differentially expressed genes, proteins, and sensitivity to therapeutics or radiation were assessed. TAGLN2 expression was also assessed using western blotting and immunohistochemistry in samples obtained from patients with BTC to validate its clinical application.

RESULTS

Suppression of TAGLN2 in BTC cell lines decreased cell proliferation, migration, invasion, and tumor size, in addition to a reduction in CSC features, including clonogenicity, radioresistance, and chemoresistance. TAGLN2 was highly expressed in BTC tissues, especially in cancer-associated fibroblasts in the stroma. Patients with a low stromal immunohistochemical index had prolonged disease-free survival compared to those with a high stromal immunohistochemical index (11.5 vs. 7.4 months, P = 0.013). TAGLN2 expression was higher in the plasma of patients with BTC than that in those with benign diseases. TAGLN2 had a higher area under the curve (0.901) than CA19-9, a validated tumor biomarker (0.799; P < 0.001).

CONCLUSION

TAGLN2 plays a critical role in promoting BTC cell growth and motility and is involved in regulating BTC stemness. Silencing TAGLN2 expression enhanced cell sensitivity to radiation and chemotherapeutic drugs. The expression of TAGLN2 in patient tissue and plasma suggests its potential to serve as a secretory biomarker for BTC. Overall, targeting TAGLN2 could be an appropriate therapeutic strategy against advanced cancer following chemotherapy failure.

Cancer-Associated Fibroblasts: Mechanisms of Tumor Progression and Novel Therapeutic Targets

Simple Summary

The tumor microenvironment plays an important role in determining the biological behavior of several of the more aggressive malignancies. Among the various cell types evident in the tumor “field”, cancer-associated fibroblasts (CAFs) are a heterogenous collection of activated fibroblasts secreting a wide repertoire of factors that regulate tumor development and progression, inflammation, drug resistance, metastasis and recurrence. Insensitivity to chemotherapeutics and metastatic spread are the major contributors to cancer patient mortality. This review discusses the complex interactions between CAFs and the various populations of normal and neoplastic cells that interact within the dynamic confines of the tumor microenvironment with a focus on the involved pathways and genes.

Abstract

Cancer-associated fibroblasts (CAFs) are a heterogenous population of stromal cells found in solid malignancies that coexist with the growing tumor mass and other immune/nonimmune cellular elements. In certain neoplasms (e.g., desmoplastic tumors), CAFs are the prominent mesenchymal cell type in the tumor microenvironment, where their presence and abundance signal a poor prognosis in multiple cancers. CAFs play a major role in the progression of various malignancies by remodeling the supporting stromal matrix into a dense, fibrotic structure while secreting factors that lead to the acquisition of cancer stem-like characteristics and promoting tumor cell survival, reduced sensitivity to chemotherapeutics, aggressive growth and metastasis. Tumors with high stromal fibrotic signatures are more likely to be associated with drug resistance and eventual relapse. Clarifying the molecular basis for such multidirectional crosstalk among the various normal and neoplastic cell types present in the tumor microenvironment may yield novel targets and new opportunities for therapeutic intervention. This review highlights the most recent concepts regarding the complexity of CAF biology including CAF heterogeneity, functionality in drug resistance, contribution to a progressively fibrotic tumor stroma, the involved signaling pathways and the participating genes.

Integrating transcriptomics, proteomics, glycomics and glycoproteomics to characterize paclitaxel resistance in breast cancer cells

Chemoresistance is a major factor driving breast cancer (BC) relapse and the high rates of cancer-related deaths. Aberrant levels of glycans are closely correlated with chemoresistance. The essential functions of glycans in chemoresistance is not systematically studied. In this study, an integrated strategy with a combination of transcriptomics, proteomics, glycomics and glycoproteomics was applied to explore the dysregulation of glycogenes, glycan structures and glycoproteins in chemoresistance of breast cancer cells. In paclitaxel (PTX) resistant MCF7 cells, 19 differentially expressed N-glycan-related proteins were identified, of which MGAT4A was the most significantly down-regulated, consistent with decrease in MGAT4A expression at mRNA level in PTX treated BC cells. Glycomic analysis consistently revealed suppressed levels of multi-antennary branching structures using MALDI-TOF/TOF-MS and lectin microarray. Several target glycoproteins bearing suppressed levels of multi-antennary branching structures were identified, and ERK signaling pathway was strongly suppressed in PTX resistant MCF7 cells. Our findings demonstrated the aberrant levels of multi-antennary branching structures and their target glycoproteins on PTX resistance. Systematically integrative multi-omic analysis is expected to facilitate the discovery of the aberrant glycosyltransferases, N-glycosylation and glycoproteins in tumor progression and chemoresistance. SIGNIFICANCE: An integrated strategy with a combination of transcriptomics, proteomics, glycomics and glycoproteomics is crucial to understand the association between glycans and chemoresistance in BC. In this multi-omic analysis, we identified unique glycan-related protein, glycan and glycoprotein signatures defining PTX chemoresistance in BC. This study might provide valuable information to understand molecular mechanisms underlying chemoresistance in BC.

Knockdown of SERPINE1 reverses resistance of triple‑negative breast cancer to paclitaxel via suppression of VEGFA

Breast cancer (BC) has a poor prognosis and a high number of visceral metastases. Serine protease inhibitor, clade E member 1 (SERPINE1) is a molecule involved in several human malignancies. However, it remains unknown if SERPINE1 plays a role in the development of taxane resistance in TNBC cells. In the present study, the role and mechanism of SERPINE1 in the development of paclitaxel (PTX) resistance in TNBC cells were investigated. A bioinformatics analysis of gene expression profiles in PTX‑resistant cells indicated that SERPINE1 was significantly associated with PTX resistance. Furthermore, the levels of SERPINE1 mRNA and protein were higher in PTX‑resistant cells with respect to those in PTX‑sensitive parent cells. Knockdown of SERPINE1 significantly inhibited cell survival and induced cell apoptosis in vitro. In addition, SERPINE1 silencing led to downregulation of the key angiogenetic vascular endothelial growth factor A (VEGFA). Furthermore, suppression of SERPINE1 markedly attenuated tumor growth in vivo. Collectively, these findings indicated that SERPINE1 significantly contributed to the proliferation and apoptosis of TNBC cells by regulating VEGFA expression. The present study demonstrated SERPINE1 as an oncogene in PTX drug resistance of breast cancer, and revealed that it may serve as a possible target for treating BC.

Antitumor potential of dark sweet cherry sweet (Prunus avium) phenolics in suppressing xenograft tumor growth of MDA-MB-453 breast cancer cells

This study investigated in vivo the antitumor activity of dark sweet cherry (DSC) whole extracted phenolics (WE) and fractions enriched in anthocyanins (ACN) or proanthocyanidins (PCA) in athymic mice xenografted with MDA-MB-453 breast cancer cells. Mice were gavaged with WE, ACN or PCA extracts (150 mg/kg body weight/day) for 36 days. Results showed that tumor growth was suppressed at similar levels by WE, ACN and PCA compared to control group (C) without signs of toxicity or significant changes in mRNA oncogenic biomarkers in tumors or mRNA invasive biomarker in distant organs. Tumor protein analyses showed that WE, ACN and PCA induced at similar levels the stress-regulated ERK1/2 phosphorylation, known to be linked to apoptosis induction. However, ACN showed enhanced antitumor activity through down-regulation of total oncogenic and stress-related Akt, STAT3, p38, JNK and NF-kB proteins. In addition, immunohistochemistry analysis of Ki-67 revealed inhibition of tumor cell proliferation with potency WE ≥ ACN ≥ PCA. Differential quantitative proteomic high-resolution nano-HPLC tandem mass spectrometry analysis of tumors from ACN and C groups revealed the identity of 66 proteins associated with poor breast cancer prognosis that were expressed only in C group (61 proteins) or differentially up-regulated (P<.05) in C group (5 proteins). These findings revealed ACN-targeted proteins associated to tumor growth and invasion and the potential of DSC ACN for breast cancer treatment. Results lead to a follow-up study with highly immunodeficient mice/invasive cell line subtype and advanced tumor development to validate the anti-invasive activity of DSC anthocyanins.

A quantitative N-glycoproteomics study of cell-surface N-glycoprotein markers of MCF-7/ADR cancer stem cells

Isotopic-labeling quantitative N-glycoproteomics characterization of cell-surface differentially expressed N-glycosylation in MCF-7/ADR cancer stem cells (CSCs) relative to MCF-7/ADR cells was carried out at the intact N-glycopeptide level with trypsin digestion, ZIC-HILIC enrichment, isotopic diethyl labeling, RPLC-MS/MS analysis of the 1:1 mixture, and GPSeeker DB search. With a spectrum-level false discovery rate of ≤ 1%, 1,336 intact N-glycopeptides from the combination of 301 unique peptide backbones and 169 putative N-glycan linkages (52 monosaccharide compositions) were identified; the corresponding intact N-glycoproteins and N-glycosites were 289 and 305, respectively, among which 176 N-glycosites were confirmed with GlcNAc-containing site-determining b/y fragment ion pairs. The N-glycan moieties in 546 intact N-glycopeptide IDs were identified with more than one structure-diagnostic fragment ions where multiple linkage structures exist for each of the monosaccharide compositions. With the criteria of ≥ 1.5-fold change and p value < 0.05, 72 cell-surface differentially expressed intact N-glycopeptides (DEGPs) were found in MCF-7/ADR CSCs relative to MCF-7/ADR cells, where 8 and 64 were downregulated and upregulated, respectively. Graphical abstract.

Bioreducible and acid-labile polydiethylenetriamines with sequential degradability for efficient transgelin-2 siRNA delivery

The transgelin-2 (TAGLN2) protein plays an important role in multidrug resistance in human breast cancer. siRNA mediated gene silencing of TAGLN2 is a promising strategy for paclitaxel resistance reversal in breast cancer. In this study, a series of bioreducible and acid-labile polydiethylenetriamines (PDs) with different proportions of cross-linkers were synthesized. TAGLN2 siRNA was condensed by PDs to form dual-responsive nanocomplexes, and these nanocomplexes were hypothesized to partially degrade in the acidic environment of endosomes, and then completely degrade in the reducing environment of the cytoplasm to release siRNA. It was found that PDs have good water solubility, acid-base buffering capacity, suitable degradability and high biocompatibility. Moreover, PDCKM can deliver TAGLN2 siRNA into MCF-7/PTX cells and inhibit the expression of TAGLN2 even better than PEI 25k. Besides, paclitaxel showed higher cytotoxicity in cells incubated with PDCKM/TAGLN2 siRNA nanocomplexes. These results suggested that PDs have great potential for safe and efficient siRNA delivery to reverse paclitaxel resistance in breast cancer.

Transgelin-2 expression in breast cancer and its relationships with clinicopathological features and patient outcome

BACKGROUND

Transgelin-2 is an actin-binding protein that is widely expressed in various tissues and organs of the body, and reportedly may participate in the development and progression of multiple cancers. However, the clinical significance of transgelin-2 still remains controversial. We, therefore, aimed to determine the expression of transgelin-2 in breast cancer as well as its correlation with the tumorigenesis, progression and prognosis of human breast cancer.

METHODS

We collected tissues of 58 breast cancer patients from our hospital and 1090 samples from The Cancer Genome Atlas (TCGA) database. X-tile software was used to divide the transgelin-2 mRNA expression level in the database, logistic regression model was used to identify independent factors influencing transgelin-2 mRNA expression, and then Cox regression and Kaplan-Meier analysis were used to find factors that influence survival of breast cancer.

RESULTS

Transgelin-2 was significantly overexpressed in breast cancer tissues from our hospital and receiver operating characteristic (ROC) curve indicated that transgelin-2 may have diagnostic value. Meanwhile, estrogen receptor (ER) was in inverse correlation with transgelin-2 protein and mRNA expression, and transgelin-2 expression was positively correlated with Ki67 in breast cancer tissues. Logistic regression model revealed that TNM stage, ER and progesterone receptor (PR) status were independent factors for transgelin-2 mRNA expression. Patients with high transgelin-2 mRNA expression showed a poor survival and the trend was statistically significant only in ER-negative patients.

CONCLUSIONS

Transgelin-2 was expressed significantly higher in breast cancer cells and correlated with some clinicopathological factors. High transgelin-2 expression might predict poor prognosis for ER-negative patients.

How Cancer Cells Resist Chemotherapy: Design and Development of Drugs Targeting Protein-Protein Interactions

Background:

Resistance toward chemotherapeutics is one of the main obstacles on the way to effective cancer treatment. Personalization of chemotherapy could improve clinical outcome. However, despite preclinical significance, most of the potential markers have failed to reach clinical practice partially due to the inability of numerous studies to estimate the marker’s impact on resistance properly.

Objective:

The analysis of drug resistance mechanisms to chemotherapy in cancer cells, and the proposal of study design to identify bona fide markers.

Methods:

A review of relevant papers in the field. A PubMed search with relevant keywords was used to gather the data. An example of a search request: drug resistance AND cancer AND paclitaxel.

Results:

We have described a number of drug resistance mechanisms to various chemotherapeutics, as well as markers to underlie the phenomenon. We also proposed a model of a rational-designed study, which could be useful in determining the most promising potential biomarkers.

Conclusion:

Taking into account the most reasonable biomarkers should dramatically improve clinical outcome by choosing the suitable treatment regimens. However, determining the leading biomarkers, as well as validating of the model, is a work for further investigations.

Redox-responsive F127-folate/F127-disulfide bond-d-α-tocopheryl polyethylene glycol 1000 succinate/P123 mixed micelles loaded with paclitaxel for the reversal of multidrug resistance in tumors

Introduction

The development of nanodrug carriers utilizing tumor microenvironment has become a hotspot in reversing multidrug resistance (MDR).

Materials and methods

This study synthesized a redox-sensitive copolymer, Pluronic F127-disulfide bond-d-α-tocopheryl polyethylene glycol 1000 succinate (FSST), through the connection of the reduction-sensitive disulfide bond between F127 and d-α-tocopheryl polyethylene glycol 1000 succinate. This polymer could induce the elevation of reactive oxygen species (ROS) levels, ultimately resulting in cytotoxicity. Moreover, the redox-responsive mixed micelles, F127-folate (FA)/FSST/P123 (FFSSTP), based on FSST, Pluronic F127-FA, and Pluronic P123, were prepared to load paclitaxel (PTX).

Results

The in vitro release study demonstrated that FFSSTP/PTX accelerated the PTX release through the breakage of disulfide bond in reductive environment. In cellular experiment, FFSSTP/PTX induced significant apoptosis in PTX-resistant MCF-7/PTX cells through inhibiting adenosine triphosphate (ATP)-binding cassette proteins from pumping out PTX by interfering with the mitochondrial function and ATP synthesis. Furthermore, FFSSTP/PTX induced apoptosis through elevating the intracellular levels of ROS.

Conclusion

FFSSTP could become a potential carrier for the treatment of MDR tumors.

Contribution of nucleophosmin overexpression to multidrug resistance in breast carcinoma

Multidrug resistance (MDR) is a serious obstacle in breast cancer patients which limits chemotherapeutic drugs application. Our previous study confirmed that overexpression of nucleophosmin (NPM) was closely related to MDR in methotrexate-resistant breast cancer cells (MCF-7/MTX), and NPM could be a potential therapeutic target for chemoresistance. In this work, we aim to investigate NPM-mediated resistance mechanism in breast carcinoma. The NPM level was strongly positive in breast carcinoma tissues compared with adjacent normal samples, which was associated with lymph node metastasis. We found abnormal expression of NPM activated PI3K/Akt pathway and affected downstream apoptosis factors. Then, NPM level was attenuated by RNA interfering technology, the sensitivity of MCF-7/MTX cells to methotrexate was obviously increased, factor level of mitochondria apoptosis pathway was significantly augmented, and Akt phosphorylation was inhibited. Furthermore, examination of Akt and NPM level demonstrated that Akt inhibitor MK-2206 sensitised resistant cells to methotrexate and induced MCF-7/MTX cell apoptosis by PI3K/Akt pathway and mitochondria apoptosis pathway. These suggested NPM-induced resistance and anti-apoptosis were required for Akt activity. NPM has a crucial function in MDR of breast cancer through influencing Akt activity and resistant cell apoptosis, and it could be expected to become a therapeutic target for chemoresistance in breast cancer.

Silencing Aurora A leads to re-sensitization of breast cancer cells to Taxol through downregulation of SRC-mediated ERK and mTOR pathways

While Taxol has been reported to improve the clinical survival of breast cancer patients, subsequently developed drug-resistance of the cancer cells limits its final efficacy and applications. Previous studies suggested that Aurora A is involved in the development of the Taxol-resistance of breast cancer. We established Taxol-resistant breast cancer MCF-7/T cells and xenograft models to explore the role of Aurora A in Taxol resistant ER-positive breast cancer. Compared with their parental MCF-7/C cells, the Taxol-resistant MCF-7/T cells exhibited enhanced colony formation, less cell death and higher invasive ability. The resistant cells presented overexpressed Aurora A, elevated phosphorylated SRC and upregulated Ras/Raf/ERK and Akt/mTOR pathways. Silencing of Aurora A reduced the activity of SRC and downregulated the ERK and Akt/mTOR pathways, which led to re-sensitization of the resistant MCF-7/T cells to Taxol in vitro. These results suggested that the activation of Aurora A and the subsequent upregulation of ERK and Akt through SRC induced Taxol-resistance in breast cancer cells, and inhibiting Aurora A and the related SRC/EKT/Akt pathway could restore the sensitivity of breast cancer cells to Taxol. These results might shed light on the development of strategies to circumvent Taxol-related chemoresistance in breast cancer clinical practice.

Transgelin-2: A potential oncogenic factor

Actin-binding proteins are proteins that could bind to actin or actin fibers. As a member of actin-binding proteins, Transgelin-2 is expressed in smooth muscle cells and non-smooth muscle cells, and its gene, TAGLN2, is differently expressed in all cells and tissues. The deregulation of Transgelin-2 is considered to be correlated with progression of many kinds of diseases, especially the development of malignant tumors, such as invasion, metastasis, and resistance, yet the function and mechanism of action of Transgelin-2 remain elusive. Therefore, we reviewed the basic characteristics and function of Transgelin-2 and its biological role in various types of diseases in order to provide the theoretical basis for further research and new perspectives on cancer development.

SB-T-121205, a next-generation taxane, enhances apoptosis and inhibits migration/invasion in MCF-7/PTX cells

Breast cancer is the leading cause of cancer death among women. Paclitaxel, a mitotic inhibitor, is highly effective in the treatment of breast cancer. However, development of resistance to paclitaxel limits its clinical use. Identifying new compounds and new strategies that are effective against breast cancer, in particular drug-resistant cancer, is of great importance. The aim of the present study was to explore the potential of a next-generation taxoid, SB-T-121205, in modulating the proliferation, migration and invasion of paclitaxel-resistant human breast cancer cells (MCF-7/PTX) and further evaluate the underlying molecular mechanisms. The results of MTT assay showed that SB-T-121205 has much higher potency to human breast cancer cells (MCF-7/S, MCF-7/PTX and MDA-MB-453 cells) than paclitaxel, while that the non-tumorigenic human bronchial epithelial cells (BEAS-2B) were slightly less sensitive to SB-T-121205 than paclitaxel. Flow cytometry and western blot methods revealed that SB-T-121205 induced cell cycle arrest at the G2/M phase and apoptosis in MCF-7/PTX cells through accelerating mitochondrial apoptotic pathway, resulting in reduction of Bcl-2/Bax ratio, as well as elevation of caspase-3, caspase-9, and poly(ADP-ribose) polymerase (PARP) levels. Moreover, SB-T-121205 changed epithelial-mesenchymal transition (EMT) property, and suppressed migration and invasion abilities of MCF-7/PTX cells. Additionally, SB-T-121205 exerted antitumor activity by inhibiting the transgelin 2 and PI3K/Akt pathway. These findings indicate that SB-T-121205 is a potent antitumor agent that promotes apoptosis and also recedes migration/invasion abilities of MCF-7/PTX cells by restraining the activity of transgelin 2 and PI3K/Akt, as well as mitochondrial apoptotic pathway. Such results suggest a potential clinical value of SB-T-121205 in breast cancer treatment.

Biodegradable mixed MPEG-SS-2SA/TPGS micelles for triggered intracellular release of paclitaxel and reversing multidrug resistance

In this study, a type of multifunctional mixed micelles were prepared by a novel biodegradable amphiphilic polymer (MPEG-SS-2SA) and a multidrug resistance (MDR) reversal agent (d-α-tocopheryl polyethylene glycol succinate, TPGS). The mixed micelles could achieve rapid intracellular drug release and reversal of MDR. First, the amphiphilic polymer, MPEG-SS-2SA, was synthesized through disulfide bonds between poly (ethylene glycol) monomethyl ether (MPEG) and stearic acid (SA). The structure of the obtained polymer was similar to poly (ethylene glycol)-phosphatidylethanolamine (PEG-PE). Then the mixed micelles, MPEG-SS-2SA/TPGS, were prepared by MPEG-SS-2SA and TPGS through the thin film hydration method and loaded paclitaxel (PTX) as the model drug. The in vitro release study revealed that the mixed micelles could rapidly release PTX within 24 h under a reductive environment because of the breaking of disulfide bonds. In cell experiments, the mixed micelles significantly inhibited the activity of mitochondrial respiratory complex II, also reduced the mitochondrial membrane potential, and the content of adenosine triphosphate, thus effectively inhibiting the efflux of PTX from cells. Moreover, in the confocal laser scanning microscopy, cellular uptake and 3-(4,5-dimethyl-thiazol-2-yl)-2,5-diphenyl-tetrazolium bromide assays, the MPEG-SS-2SA/TPGS micelles achieved faster release and more uptake of PTX in Michigan Cancer Foundation-7/PTX cells and showed better antitumor effects as compared with the insensitive control. In conclusion, the biodegradable mixed micelles, MPEG-SS-2SA/TPGS, could be potential vehicles for delivering hydrophobic chemotherapeutic drugs in MDR cancer therapy.

Characterization of acquired paclitaxel resistance of breast cancer cells and involvement of ABC transporters

Development of taxane resistance has become clinically very important issue. The molecular mechanisms underlying the resistance are still unclear. To address this issue, we established paclitaxel-resistant sublines of the SK-BR-3 and MCF-7 breast cancer cell lines that are capable of long-term proliferation in 100nM and 300nM paclitaxel, respectively. Application of these concentrations leads to cell death in the original counterpart cells. Both sublines are cross-resistant to doxorubicin, indicating the presence of the MDR phenotype. Interestingly, resistance in both paclitaxel-resistant sublines is circumvented by the second-generation taxane SB-T-1216. Moreover, we demonstrated that it was not possible to establish sublines of SK-BR-3 and MCF-7 cells resistant to this taxane. It means that at least the tested breast cancer cells are unable to develop resistance to some taxanes. Employing mRNA expression profiling of all known human ABC transporters and subsequent Western blot analysis of the expression of selected transporters, we demonstrated that only the ABCB1/PgP and ABCC3/MRP3 proteins were up-regulated in both paclitaxel-resistant sublines. We found up-regulation of ABCG2/BCRP and ABCC4 proteins only in paclitaxel-resistant SK-BR-3 cells. In paclitaxel-resistant MCF-7 cells, ABCB4/MDR3 and ABCC2/MRP2 proteins were up-regulated. Silencing of ABCB1 expression using specific siRNA increased significantly, but did not completely restore full sensitivity to both paclitaxel and doxorubicin. Thus we showed a key, but not exclusive, role for ABCB1 in mechanisms of paclitaxel resistance. It suggests the involvement of multiple mechanisms in paclitaxel resistance in tested breast cancer cells.

Salvianolic acid A reverses the paclitaxel resistance and inhibits the migration and invasion abilities of human breast cancer cells by inactivating transgelin 2

Multidrug resistance and tumor migration and invasion are the major obstacles to effective breast cancer chemotherapy, but the underlying molecular mechanisms remain unclear. This study investigated the potential of transgelin 2 and salvianolic acid A to modulate the resistance and the migration and invasion abilities of paclitaxel-resistant human breast cancer cells (MCF-7/PTX). MCF-7/PTX cells were found to exhibit not only a high degree of resistance to paclitaxel, but also strong migration and invasion abilities. Small interfering RNA-mediated knockdown of TAGLN2 sensitized the MCF-7/PTX cells to paclitaxel, and inhibited their migration and invasion abilities. In addition, we also observed that combined salvianolic acid A and paclitaxel treatment could reverse paclitaxel resistance, markedly inhibit tumor migration and invasion, and suppress the expression of transgelin 2 in MCF-7/PTX cells. These findings indicate that salvianolic acid A can reverse the paclitaxel resistance and inhibit the migration and invasion abilities of human breast cancer cells by down-regulating the expression of transgelin 2, and hence could be useful in breast cancer treatments.

Proteomics in the Assessment of the Therapeutic Response of Antineoplastic Drugs: Strategies and Practical Applications

Uncovering unknown pathological mechanisms and body response to applied medication are the driving forces toward personalized medicine. In this post-genomic era, all eyes are turned to the proteomics field, searching for answers and explanations by investigating the gene end point functional units-proteins and their proteoforms. The development of cutting-edge mass spectrometric technologies and bioinformatics tools have allowed the life-science community to discover disease-specific proteins as biomarkers, which are often concealed by high sample complexity and dynamic range of abundance. Currently, there are several proteomics-based approaches to investigate the proteome. This chapter focuses on gold standard proteomics strategies and related issues toward candidate biomarker discovery, which may have diagnostic/prognostic as well as mechanistic utility in cancer drug resistance.

HDACI regulates the PI3K/Akt signaling pathway to reverse MCF-7/PTX resistance by inhibiting SET

The occurrence of chemoresistance greatly restricts the efficacy of antitumor drugs, and so novel agents are urgently needed to abrogate resistant phenotypes.

Transgelin is upregulated in stromal cells of lymph node positive breast cancer

Transgelin and transgelin-2 have been discussed as potential markers of various cancers. Here we identified increased transgelin level in lymph node positive vs. negative, low grade primary breast cancer tissues using 2-DE in the cohort of 12 patients. We further clinically validated 2-DE results in an independent cohort of 48 low grade breast cancer patients through untargeted and targeted proteomics analysis (iTRAQ-2D-LC-MS/MS, mTRAQ-SRM), at transcript level and using immunohistochemistry. Another group of 48 high grade tumors of different breast cancer subtypes was analyzed together with the low grade samples to test transgelin specificity for low grade tumors and to study transgelin relation to known molecular markers and histological features. The results confirmed transgelin connection with the lymph node metastasis. As a marker of a reactive tumor stroma, transgelin can be connected with the higher risk of metastasis development. Moreover, we observed significant down-regulation of transgelin in high vs. low grade tumors caused by decreased content of stromal cells (mainly expressing transgelin) in high grade tumor tissue. We also analyzed expression of transgelin-2 in the second cohort using proteomics and immunohistochemistry. Transgelin-2 was mainly expressed by epithelial cancer cells and its levels were increased in metastatic and poorly differentiated tumors.

BIOLOGICAL SIGNIFICANCE

Both transgelin and transgelin-2 have been previously described as potential markers of many types of cancer. We are specifying this connection to metastatic affection of lymph nodes and cell differentiation in breast cancer. In the wider context, the results of our study highlight tumor stroma as a source of cancer biomarkers and point out how measured levels of tissue markers can actually reflect cellular feature of cancer mass.

Label-free LC-MS analysis of HER2+ breast cancer cell line response to HER2 inhibitor treatment

BACKGROUND

Human epidermal growth-factor receptor (HER)-2 is overexpressed in 25 % of breast-cancers and is associated with an aggressive form of the disease with significantly shortened disease free and overall survival. In recent years, the use of HER2-targeted therapies, monoclonal-antibodies and small molecule tyrosine-kinase inhibitors has significantly improved the clinical outcome for HER2-positive breast-cancer patients. However, only a fraction of HER2-amplified patients will respond to therapy and the use of these treatments is often limited by tumour drug insensitivity or resistance and drug toxicities. Currently there is no way to identify likely responders or rational combinations with the potential to improve HER2-focussed treatment outcome.

METHODS

In order to further understand the molecular mechanisms of treatment-response with HER2-inhibitors, we used a highly-optimised and reproducible quantitative label-free LC-MS strategy to characterize the proteomes of HER2-overexpressing breast-cancer cell-lines (SKBR3, BT474 and HCC1954) in response to drug-treatment with HER2-inhibitors (lapatinib, neratinib or afatinib).

RESULTS

Following 12 ours treatment with different HER2-inhibitors in the BT474 cell-line; compared to the untreated cells, 16 proteins changed significantly in abundance following lapatinib treatment (1 μM), 21 proteins changed significantly following neratinib treatment (150 nM) and 38 proteins changed significantly following afatinib treatment (150 nM). Whereas following 24 hours treatment with neratinib (200 nM) 46 proteins changed significantly in abundance in the HCC1954 cell-line and 23 proteins in the SKBR3 cell-line compared to the untreated cells. Analysing the data we found that, proteins like trifunctional-enzyme subunit-alpha, mitochondrial; heterogeneous nuclear ribonucleoprotein-R and lamina-associated polypeptide 2, isoform alpha were up-regulated whereas heat shock cognate 71 kDa protein was down-regulated in 3 or more comparisons.

CONCLUSION

This proteomic study highlights several proteins that are closely associated with early HER2-inhibitor response and will provide a valuable resource for further investigation of ways to improve efficacy of breast-cancer treatment.

Comparative Tissue Proteomics of Microdissected Specimens Reveals Novel Candidate Biomarkers of Bladder Cancer

More than 380,000 new cases of bladder cancer are diagnosed worldwide, accounting for ∼150,200 deaths each year. To discover potential biomarkers of bladder cancer, we employed a strategy combining laser microdissection, isobaric tags for relative and absolute quantitation labeling, and liquid chromatography-tandem MS (LC-MS/MS) analysis to profile proteomic changes in fresh-frozen bladder tumor specimens. Cellular proteins from four pairs of surgically resected primary bladder cancer tumor and adjacent nontumorous tissue were extracted for use in two batches of isobaric tags for relative and absolute quantitation experiments, which identified a total of 3220 proteins. A DAVID (database for annotation, visualization and integrated discovery) analysis of dysregulated proteins revealed that the three top-ranking biological processes were extracellular matrix organization, extracellular structure organization, and oxidation-reduction. Biological processes including response to organic substances, response to metal ions, and response to inorganic substances were highlighted by up-expressed proteins in bladder cancer. Seven differentially expressed proteins were selected as potential bladder cancer biomarkers for further verification. Immunohistochemical analyses showed significantly elevated levels of three proteins-SLC3A2, STMN1, and TAGLN2-in tumor cells compared with noncancerous bladder epithelial cells, and suggested that TAGLN2 could be a useful tumor tissue marker for diagnosis (AUC = 0.999) and evaluating lymph node metastasis in bladder cancer patients. ELISA results revealed significantly increased urinary levels of both STMN1 and TAGLN2 in bladder cancer subgroups compared with control groups. In comparisons with age-matched hernia urine specimens, urinary TAGLN2 in bladder cancer samples showed the largest fold change (7.13-fold), with an area-under-the-curve value of 0.70 (p < 0.001, n = 205). Overall, TAGLN2 showed the most significant overexpression in individual bladder cancer tissues and urine specimens, and thus represents a potential biomarker for noninvasive screening for bladder cancer. Our findings highlight the value of bladder tissue proteome in providing valuable information for future validation studies of potential biomarkers in urothelial carcinoma.

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.

Comprehensive assessment of proteins regulated by dexamethasone reveals novel effects in primary human peripheral blood mononuclear cells

Inflammation is a physiological process involved in many diseases. Monitoring proteins involved in regulatory effects may help to improve our understanding of inflammation. We have analyzed proteome alterations induced in peripheral blood mononuclear cells (PBMCs) upon inflammatory activation in great detail using high-resolution mass spectrometry. Moreover, the activated cells were treated with dexamethasone to investigate their response to this antiphlogistic drug. From a total of 6886 identified proteins, 469 proteins were significantly regulated upon inflammatory activation. Data are available via ProteomeXchange with identifiers PXD001415-23. Most of these proteins were counter-regulated by dexamethasone, with some exceptions concerning members of the interferon-induced protein family. To confirm some of these results, we performed targeted MRM analyses of selected peptides. The inflammation-induced upregulation of proteins such as IL-1β, IL-6, CXCL2, and GROα was confirmed, however, with strong quantitative interindividual differences. Furthermore, the inability of dexamethasone to downregulate inflammation-induced proteins such as PTX3 and TSG6 was clearly demonstrated. In conclusion, the relation of cell function as well as drug-induced modulation thereof was successfully mapped to proteomes, suggesting targeted analysis as a novel and powerful drug evaluation method. Although most consequences of dexamethasone were found to be compatible with the expected mode of action, some unexpected but significant observations may be related to adverse effects.

Salvianolic acid A reverses paclitaxel resistance in human breast cancer MCF-7 cells via targeting the expression of transgelin 2 and attenuating PI3 K/Akt pathway

Chemotherapy resistance represents a major problem for the treatment of patients with breast cancer and greatly restricts the use of first-line chemotherapeutics paclitaxel. The purpose of this study was to investigate the role of transgelin 2 in human breast cancer paclitaxel resistance cell line (MCF-7/PTX) and the reversal mechanism of salvianolic acid A (SAA), a phenolic active compound extracted from Salvia miltiorrhiza. Western blotting and real-time quantitative polymerase chain reaction (qRT-PCR) indicated that transgelin 2 may mediate paclitaxel resistance by activating the phosphatidylinositol 3-kinase (PI3 K)/Akt signaling pathway to suppress MCF-7/PTX cells apoptosis. The reversal ability of SAA was confirmed by MTT assay and flow cytometry, with a superior 9.1-fold reversal index and enhancement of the apoptotic cytotoxicity induced by paclitaxel. In addition, SAA effectively prevented transgelin 2 and adenosine-triphosphate binding cassette transporter (ABC transporter) including P-glycoprotein (P-gp), multidrug resistance associated protein 1 (MRP1), and breast cancer resistance protein (BCRP) up-regulation and exhibited inhibitory effect on PI3 K/Akt signaling pathway in MCF-7/PTX cells. Taken together, SAA can reverse paclitaxel resistance through suppressing transgelin 2 expression by mechanisms involving attenuation of PI3 K/Akt pathway activation and ABC transporter up-regulation. These results not only provide insight into the potential application of SAA in reversing 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.