Prognostic significance of GSTP1 in patients with triple negative breast cancer

A Switch-On Affinity-Based Iridium(III) Conjugate Probe for Imaging Mitochondrial Glutathione S-Transferase in Breast Cancer Cells

Glutathione S-transferase is heterogeneously expressed in breast cancer cells and is therefore emerging as a potential diagnostic biomarker for studying the heterogeneity of breast cancers. However, available fluorescent probes for GSTs depend heavily on GSTs-catalyzed glutathione (GSH) nucleophilic substitution reactions, making them susceptible to interference by the high concentration of nucleophilic species in the cellular environment. Moreover, the functions of subcellular GSTs are generally overlooked due to the lack of suitable luminescence probes. Herein, we report a highly selective affinity-based luminescence probe 1 for GST in breast cancer cells through tethering a GST inhibitor, ethacrynic acid, to an iridium(III) complex. Compared to activity-based probes which require the use of GSH, this probe could image GST-pi in the mitochondria by directly adducting to GST-pi (or potentially GST-pi/GS) in living cells. Probe 1 possesses desirable photophysical properties including a lifetime of 911 ns, a Stokes shift of 343 nm, and high photostability. The "turn on" luminescence mode of the probe enables highly selective detection of the GST with a limit of detection of 1.01 μM, while its long emission lifetime allows sensitive detection in organic dye-spiked autofluorescence samples by a time-resolved mode. The probe was further applied to specifically and quantitatively visualize MDA-MB-231 cells via specific binding to mitochondrial GST, and could differentiate breast cell lines based on their expression levels of GST. To the best of our knowledge, this probe is the first affinity-based iridium(III) imaging probe for the subcellular GST. Our work provides a valuable tool for unmasking the diverse roles of a subcellular GST in living systems, as well as for studying the heterogeneity of breast cancers.

Perturbation of HSP Network in MCF-7 Breast Cancer Cell Line Triggers Inducible HSP70 Expression and Leads to Tumor Suppression

BACKGROUND

Heat shock protein 70 (HSP70) is constitutively expressed in normal cells but aberrantly expressed in several types of tumor cells, helping their survival in extreme conditions. Thus, specific inhibition of HSP70 in tumor cells is a promising strategy in the treatment of cancer. HSP70 has a variety of isoforms in the cellular organelles and form different functions by coordinating and cooperating with cochaperones. Cancer cells overexpress HSPs during cell growth and proliferation and HSP network provides resistance against apoptosis. The present study aimed to evaluate quantitative changes in HSPs- and cancerassociated gene expressions and their interactions in the presence of 2-phenylethyenesulfonamide (PES) in MCF-7 cells.

METHODS

Antiproliferative activity of PES was evaluated using the XTT assay. Inducible HSP70 (HSP70i) levels in the PES-treated cells were determined using the ELISA kit. PCR Array was performed to assess the HSPs- and cancer-pathway focused gene expression profiling. Gene network analysis was performed using the X2K, yEd (V.3.18.1) programs, and web-based gene list enrichment analysis tool Enrichr.

RESULTS

The results demonstrated that PES exposure increased the amount of both HSP70i gene and protein expression surprisingly. However, the expression of HSP70 isoforms as well as other co-chaperones, and 17 cancer-associated genes decreased remarkably as expected. Additionally, interaction network analysis revealed a different mechanism; PES induction of HSP70i employs a cell cycle negative regulator, RB1, which is a tumor suppressor gene.

CONCLUSION

PES treatment inhibited MCF-7 cell proliferation and changed several HSPs- and cancer-related gene expressions along with their interactions through a unique mechanism although it causes an interesting increase at HSP70i gene and protein expressions. RB1 gene expression may play an important role in this effect as revealed by the interaction network analysis.

Coupled Genome-Wide DNA Methylation and Transcription Analysis Identified Rich Biomarkers and Drug Targets in Triple-Negative Breast Cancer

Triple-negative breast cancer (TNBC) has poor clinical prognosis. Lack of TNBC-specific biomarkers prevents active clinical intervention. We reasoned that TNBC must have its specific signature due to the lack of three key receptors to distinguish TNBC from other types of breast cancer. We also reasoned that coupling methylation and gene expression as a single unit may increase the specificity for the detected TNBC signatures. We further reasoned that choosing the proper controls may be critical to increasing the sensitivity to identify TNBC-specific signatures. Furthermore, we also considered that specific drugs could target the detected TNBC-specific signatures. We developed a system to identify potential TNBC signatures. It consisted of (1) coupling methylation and expression changes in TNBC to identify the methylation-regulated signature genes for TNBC; (2) using TPBC (triple-positive breast cancer) as the control to detect TNBC-specific signature genes; (3) searching in the drug database to identify those targeting TNBC signature genes. Using this system, we identified 114 genes with both altered methylation and expression, and 356 existing drugs targeting 10 of the 114 genes. Through docking and molecular dynamics simulation, we determined the structural basis between sapropterin, a drug used in the treatment of tetrahydrobiopterin deficiency, and PTGS2, a TNBC signature gene involved in the conversion of arachidonic acid to prostaglandins. Our study reveals the existence of rich TNBC-specific signatures, and many can be drug target and biomarker candidates for clinical applications.

Glutathione S-transferase Pi 1 is a valuable predictor for cancer drug resistance in esophageal squamous cell carcinoma

Esophageal squamous cell carcinoma (ESCC) is a lethal malignancy. However, there are few useful markers for diagnosis and treatment. Glutathione S‐transferase Pi 1 (GSTP1) has been reported as a predictor of malignancy or anticancer drug resistance in some cancers. We investigated the association of GSTP1 expression with the malignancy or drug resistance in ESCC cell lines and clinical tissue samples. Proliferation and apoptosis assays regarding GSTP1 expression were examined in ESCC cell lines. Proliferation of GSTP1 knockdown cells was significantly decreased (P < .01), and the frequency of early apoptosis was increased (P < .05). Invasion capacity of GSTP1 knockdown cells was slightly decreased in transwell assay. These results suggest that GSTP1 plays an important role in malignant potential. To examine the effects of GSTP1 on drug resistance, chemosensitivity assay and apoptosis assay under cisplatin exposure were carried out. Viability of GSTP1 knockdown cells treated with cisplatin was lower than that of control cells (P < .01). Moreover, the frequency of early and late apoptosis in GSTP1 knockdown cells was markedly increased over that of control cells by cisplatin exposure (P < .01). In immunohistochemistry assay of resected tissue samples, GSTP1 expression was significantly associated with clinical downstaging (P = .04) in 72 ESCC patients with neoadjuvant chemotherapy. Furthermore, there was a significant association between GSTP1 expression in resected tissue and biopsy samples in 34 ESCC patients without neoadjuvant chemotherapy (P = .02). In summary, GSTP1 was related to malignant potential and may be a predictive marker of drug resistance in ESCC patients.

Association of GSTP1 and P16 promoter methylation with the risk of HBV-related hepatocellular carcinoma: a meta-analysis

Background

Study on the relationship between glutathione-S-transferase Pi 1 (GSTP1) and P16 promoter region methylation and the risk of hepatitis B virus-related hepatocellular carcinoma (HBV-related HCC) has produced inconsistent results.

Objectives

To assess the correlation between GSTP1 and P16 promoter methylation frequency and HBV-related HCC susceptibility.

Methods

All relevant studies were identified by searching PubMed, Embase, Web of Science, and China National Knowledge Infrastructure literature databases before December, 2017. The OR and the corresponding 95% CI were calculated to investigate the risk of GSTP1 and P16 promoter methylation rate and HBV-related HCC. Sensitivity analysis was performed and publication bias was estimated using the Begg’s and Egger’s test.

Results

Our meta-analysis identified the relationships of GSTP1 (six studies including 213 HBV-related HCC tumor tissues) and P16 (nine studies with 287 HBV-related HCC tumor tissue) promoter methylation with HCC risk. Compared with normal liver tissue and cirrhosis, the pooled ORs of GSTP1 promoter region methylation in HBV-related HCC cancer tissues were 6.05 (95% CI =1.20–30.52) and 5.21 (95% CI =2.19–12.41), respectively. Compared with paracancerous tissue, normal liver tissue, cirrhosis, and chronic hepatitis B as controls, the pooled ORs of P16 promoter region methylation in HBV-related HCC cancer tissues were 7.18 (95% CI =2.31–22.33), 24.89 (95% CI =3.38–183.03), 5.92 (95% CI =1.78–19.68), and 12.12 (95% CI =0.75–196.50).

Conclusion

In summary, our meta-analysis found strong associations between GSTP1 and P16 gene promoter methylation and an increased HBV-related HCC susceptibility. Moreover, GSTP1 and P16 methylation in promoter region could obviously increase the risk of HBV-related HCC in patients with cirrhosis, indicating that these would be promising biomarkers for early clinical diagnosis of HBV-related HCC.