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Cancer-associated fibroblasts (CAFs) constitute a major compartment of the tumor microenvironment. In the present study, we investigated the role for CAFs in breast cancer progression and underlying molecular mechanisms. Human breast cancer MDA-MB-231 cells treated with the CAF-conditioned media manifested a more proliferative phenotype, as evidenced by enhanced messenger RNA (mRNA) expression of Cyclin D1, c-Myc, and proliferating cell nuclear antigen. Analysis of data from The Cancer Genome Atlas revealed that fibroblast growth factor-2 (FGF2) expression was well correlated with the presence of CAFs. We noticed that the mRNA level of FGF2 in CAFs was higher than that in normal fibroblasts. FGF2 exerts its biological effects through interaction with FGF receptor 1 (FGFR1). In the breast cancer tissue array, 42% estrogen receptor-negative patients coexpressed FGF2 and FGFR1, whereas only 19% estrogen receptor-positive patients exhibited coexpression. CAF-stimulated MDA-MB-231 cell migration and invasiveness were abolished when FGF2-neutralizing antibody was added to the conditioned media of CAFs. In a xenograft mouse model, coinjection of MDA-MB-231 cells with activated fibroblasts expressing FGF2 dramatically enhanced tumor growth, and this was abrogated by silencing of FGFR1 in cancer cells. In addition, treatment of MDA-MB-231 cells with FGF2 enhanced expression of Cyclin D1, a key molecule involved in cell cycle progression. FGF2-induced cell migration and upregulation of Cyclin D1 were abolished by siRNA-mediated FGFR1 silencing. Taken together, the above findings suggest that CAFs promote growth, migration and invasion of MDA-MB-231 cells via the paracrine FGF2-FGFR1 loop in the breast tumor microenvironment., (© 2020 Wiley Periodicals LLC.)

Cancer stem cells (CSCs) are responsible for tumor initiation, metastasis and recurrence. Caveolin-1 (Cav-1) is a major protein of caveolae, which participates in various cellular functions, such as vesicle trafficking, cholesterol homeostasis, tumor progression, etc. In the present study, we investigated a role for Cav-1 in regulating the stemness of human breast cancer (MDA-MB-231) cells. Cav-1 expression was significantly lower in tumorspheres than in adherent cells. The silencing of Cav-1 enhanced stemness of MDA-MB-231 cells. Mechanistically, Cav-1 silencing was accompanied by enhanced expression of Bmi-1, which is a representative self-renewal regulator, and promoted epithelial-mesenchymal transition. In a CSC-like state, reduced Cav-1 depends on its destabilization through ubiquitin-proteasome degradation. We further found that Src-mediated phosphorylation of Cav-1 at the Tyr 14 residue is essential for its degradation. Taken together, these findings suggest that Cav-1 destabilization by Src may play a pivotal role in manifestation and maintenance of stemness in breast cancer cells., (Copyright © 2019 Elsevier B.V. All rights reserved.)

15-Hydroxyprostaglandin dehydrogenase (15-PGDH) is the key enzyme that catalyses the conversion of prostaglandin E 2 to a keto metabolite. The expression of 15-PGDH is ubiquitously repressed in various human malignancies. However, the molecular mechanisms underlying down-regulation of 15-PGDH expression remain largely unknown. 15-Deoxy-△ 12,14 -prostaglandin J 2 (15d-PGJ 2 ), an endogenous ligand of peroxisome proliferator-activated receptor γ, has been reported to have anti-inflammatory and anticarcinogenic activities. In the present study, we have found that 15d-PGJ 2 induces expression and catalytic activity of 15-PGDH in human breast cancer (MDA-MB-231) cells. 15d-PGJ 2 decreased the level of CpG methylation in the 15-PGDH promoter in MDA-MB-231 cells as determined by the bisulphite genome sequencing and methyl-specific PCR. 15d-PGJ 2 inhibited the catalytic activity of methyltransferase 1 (DNMT1) but did not influence its expression. Biotinylated 15d-PGJ 2 directly interacted with DNMT1 and reduced its catalytic activity. Chromatin-immunoprecipitation analysis revealed that 15d-PGJ 2 significantly attenuated DNMT1 binding to the activator protein-1 transcription factor present in the 15-PGDH promoter region. A nonelectrophilic analogue 9,10-dihydro-15d-PGJ 2 failed to suppress the methylation of CpG islands present in 15-PGDH promoter and did not affect both DNMT1 activity and 15-PGDH expression. These findings suggest that the α,β-unsaturated carbonyl group present in 15d-PGJ 2 is essential for its inactivation on DNMT1 and expression of 15-PGDH. In conclusion, 15d-PGJ 2 plays as a hypomethylating agent through direct interaction with DNMT1 and consequently suppresses DNMT1-mediated hypermethylation of 15-PGDH promoter, leading to up-regulation of 15-PGDH expression.

Cancer stem cells (CSCs) constitute a subpopulation of transformed cells that possess intrinsic ability to undergo selfrenewal and differentiation, which drive tumour resistance and cancer recurrence. It has been reported that CSCs possess enhanced protection against oxidative stress induced by reactive oxygen species compared with nonstem-like cancer cells. In the present work, we investigated the role of heme oxygenase-1 (HO-1), a representative antioxidant enzyme, on the stemness and selfrenewal of human breast CSCs. We found that pharmacologic or genetic inhibition of HO-1 attenuated the sphere formation, whereas HO-1 inducers enhanced the number and the size of tumourspheres in breast CSCs. Carbon monoxide (CO) is endogenously generated as a consequence of degradation of heme by HO-1. The proportion of populations of CD44 + /CD24 - cells retaining CSC properties was increased in MDA-MB-231 cells treated with a CO-releasing molecule (CORM-2). Following CORM-2 treatment, the expression of Notch-1 and related genes Jagged-1 and Hes1 was increased, which was accompanied by the mammosphere formation. Taken together, these findings suggest that HO-1-derived CO production stimulates the formation of mammospheres in breast cancer cells through activation of Notch-1 signalling.

15-Deoxy-Δ 12,14 -prostaglandin J 2 (15d-PGJ 2 ), one of the terminal products of cyclooxygenase-2-catalized arachidonic acid metabolism, has been shown to stimulate breast cancer cell proliferation and migration through Akt activation, but the underlying mechanisms remain poorly understood. In the present study, we investigated the effects of 15d-PGJ 2 on the activity of PTEN, the inhibitor of the phosphoinositide 3-kinase (PI3K)-Akt axis, in human breast cancer (MCF-7) cells. Since the α,β-unsaturated carbonyl moiety in the cyclopentenone ring of 15d-PGJ 2 is electrophilic, we hypothesized that 15d-PGJ 2 -induced Akt phosphorylation might result from the covalent modification and subsequent inactivation of PTEN that has several critical cysteine residues. When treated to MCF-7 cells, 15d-PGJ 2 bound to PTEN, and this was abolished in the presence of the thiol-reducing agent dithiothreitol. A mass spectrometric analysis by using recombinant and endogenous PTEN protein revealed that the cysteine 136 residue (Cys 136 ) of PTEN is covalently modified upon treatment with 15d-PGJ 2 . Notably, the ability of 15d-PGJ 2 to covalently bind to PTEN as well as to induce Akt phosphorylation was abolished in the cells expressing a mutant form of PTEN in which Cys 136 was replaced by serine (C136S-PTEN). The present study demonstrates for the first time that electrophilic 15d-PGJ 2 directly binds to cysteine 136 of PTEN and provides new insight into PTEN loss in cancer progression associated with chronic inflammation. These observations suggest that 15d-PGJ 2 can undergo nucleophilic addition to PTEN, presumably at Cys 136 , thereby inactivating this tumor suppressor protein with concomitant Akt activation., (Copyright © 2018 Elsevier B.V. All rights reserved.)

Cancer-associated fibroblasts (CAFs) constitute a major compartment of the tumor microenvironment. CAFs produce a variety of cytokines, growth factors and extracellular matrix proteins, thereby stimulating tumor progression. CAFs are distinct from normal fibroblasts for their overexpression of α-smooth muscle actin. Recent studies suggest that CAFs play an important role in proliferation and migration of cancer cells through cross-talk with them. Resveratrol (trans-3,4'5,-trihydroxystilbene), a phytoalexin present in grapes, has been reported to possess chemopreventive and chemotherapeutic activities. In the present study, we examined the effects of resveratrol on CAF-induced migration, invasion and self-renewal activity of breast cancer cells. Resveratrol inhibited proliferation, migration and invasion of human breast cancer cells treated with CAF-conditioned media (CAF-CM). Resveratrol treatment suppressed the CAF-CM-induced expression of Cyclin D1, c-Myc, MMP-2 and MMP-9. In addition, resveratrol inhibited Sox2 expression as well as activation of Akt and STAT3 induced by CAF-CM in breast cancer cells. Further, resveratrol abrogated stemness properties and reduced the expression of self-renewal signaling molecules in stem-like breast cancer cells. Taken together, the present study provides insights into the role of resveratrol in tumor microenvironment with focus on interaction between cancer cells and the hosting niche., (Copyright © 2018 Elsevier Inc. All rights reserved.)

We aimed to evaluate the expression of sarcosine metabolism-related proteins according to site of metastatic breast cancer, and the clinical implications. Immunohistochemical staining for glycine N-methyltransferase (GNMT), sarcosine dehydrogenase (SARDH), and l-pipecolic acid oxidase (PIPOX) was performed on tissue microarrays from 162 metastatic breast cancer (bone metastases = 47, brain metastases = 39, liver metastases = 24, and lung metastases = 52). Sarcosine metabolism-related proteins showed variable expression with regard to metastatic sites. GNMT was expressed in brain and lung metastases, but not in bone and liver metastases (P = 0.016). In view of the sarcosine metabolic phenotype, high sarcosine and intermediate type were only found in the brain and lung metastases, and low sarcosine type was observed more frequently in bone and lung metastases (P = 0.047). By univariate analysis, PIPOX positivity was correlated with shorter overall survival (OS) (P = 0.031). In lung metastases, PIPOX positivity (P = 0.019) and stromal PIPOX positivity (P = 0.001) were associated with shorter OS. In conclusion, in metastatic breast cancer, sarcosine metabolism-related proteins are differently expressed according to the metastatic site. Expression of GNMT and high sarcosine type are predominantly observed in brain and lung metastases.

The purpose of this study is to investigate the expression of succinate dehydrogenase (SDH)A, SDHB, and HIF-1α in phyllodes tumors and the association with clinic-pathologic factors. Using tissue microarray (TMA) for 206 phyllodes tumor cases, we performed immunohistochemical stains for SDHA, SDHB, and HIF-1α and analyzed their expression in regard to clinicopathologic parameters of each case. The cases were comprised of 156 benign, 34 borderline, and 16 malignant phyllodes tumors. The expression of stromal SDHA and epithelial- and stromal- SDHB increased as the tumor progressed from benign to malignant (P⟨0.001). There were five stromal SDHA-negative cases and 31 stromal SDHB-negative cases. SDHB negativity was associated with a lower histologic grade (P=0.054) and lower stromal atypia (P=0.048). Univariate analysis revealed that a shorter disease free survival (DFS) was associated with stromal SDHB high-positivity (P=0.013) and a shorter overall survival (OS) was associated with high-positivity of stromal SDHA and SDHB (P⟨0.001 and P⟨0.001, respectively). The multivariate Cox analysis with the variables stromal cellularity, stromal atypia, stromal mitosis, stromal overgrowth, tumor margin, stromal SDHA expression, and stromal SDHB expression revealed that stromal overgrowth was associated with a shorter DFS (hazard ratio: 24.78, 95% CI: 3.126-196.5, P=0.002) and a shorter OS (hazard ratio: 176.7, 95% CI: 8.466-3691, P=0.001). In conclusion, Tumor grade is positively correlated with SDHA and SDHB expression in the tumor stroma in phyllodes tumors of the breast. This result may be attributed to the increased metabolic demand in high grade tumors.

Background: The goal of this study was to investigate the expression of sarcosine metabolism-related proteins, namely glycine N-methyltransferase (GNMT), sarcosine dehydrogenase (SARDH), and l-pipecolic acid oxidase (PIPOX), in the different breast cancer subtypes and to assess the implications of differences in expression pattern according to subtype., Methods: We analyzed the expression of GNMT, SARDH, and PIPOX in a tissue microarray of 721 breast cancer cases using immunohistochemistry (IHC). We classified breast cancer cases into subtype luminal A, luminal B, HER-2, and triple negative breast cancer (TNBC) according to the status for the estrogen receptor (ER), progesterone receptor (PR), HER-2, and Ki-67. Sarcosine metabolism phenotype was stratified according to IHC results for GNMT, SARDH, and PIPOX: GNMT(+), SARDH and PIPOX(-) was classified as high sarcosine type; GNMT(-), SARDH or PIPOX(-) as low sarcosine type; GNMT(+), SARDH or PIPOX(+) as intermediate sarcosine type, and GNMT(-), SARDH and PIPOX(-) as null type., Results: Expression of sarcosine metabolism-related proteins differed significantly according to breast cancer subtype (GNMT, p=0.005; SARDH, p=0.012; tumoral PIPOX, p=0.008; stromal PIPOX, p<0.001). These proteins were the most frequently expressed in HER-2 type tumors and the least in TNBC. Sarcosine metabolism phenotype also varied according to breast cancer subtype, with high sarcosine type the most common in HER-2, and null type the most common in TNBC (p=0.003). Univariate analysis revealed that GNMT expression (p=0.042), tumoral PIPOX negativity (p=0.039), and high sarcosine type (p=0.021) were associated with shorter disease-free survival (DFS). Multivariate analysis also revealed GNMT expression was an independent factor for shorter DFS (hazard ratio: 2.408, 95% CI: 1.154-5.024, p=0.019)., Conclusion: Expressions of sarcosine metabolism-related proteins varied according to subtype of breast cancer, with HER-2 type tumors showing elevated expression of these proteins, and TNBC subtype showing decreased expression of these proteins. Expression of sarcosine metabolism-related proteins was also associated with breast cancer prognosis.

Objective: The purpose of this study is to investigate molecular subtyping and its implications on metaplastic carcinoma according to surrogate immunohistochemical (IHC) staining., Methods: Following tissue microarray analysis of 34 cases of metaplastic carcinoma, IHC staining for cytokeratin (CK) 5/6, epidermal growth factor receptor (EGFR), claudin-3, claudin-4, claudin-7, E-cadherin, STAT-1, androgen receptor and GGT was performed and classified into basal-like, molecular apocrine, claudin-low, immune-related, mixed and null types., Results: Among the 34 cases of metaplastic carcinoma, 13 were of the basal-like type (35.2%), 9 of the mixed type (26.5%), 8 of the null type (23.5%), 3 of the claudin-low type (8.8%), and 1 was of the molecular apocrine type (2.9%). Depending on the cell type, there were differences between molecular subtypes, with the matrix-producing type occupying the largest proportion in the basal-like, null and mixed types. The spindle cell type represented the largest proportion in the claudin-low and molecular apocrine types, and the squamous cell type characterized the largest proportion in the basal-like type., Conclusion: Following molecular subtyping of metaplastic carcinomas using surrogate IHC markers, the largest number of cases was of the basal-like type, followed by the mixed, null, claudin-low and molecular apocrine types. There were differences between molecular subtypes according to the cell type., (© 2013 S. Karger AG, Basel.)

Local recurrence of phyllodes tumor (PT) of the breast is an adverse outcome that can result in sarcomatous degeneration. The aim of this study was to investigate the histologic and surgical factors associated with local recurrence. A total of 193 PT cases were studied: 145 (75.1 %) benign cases, 33 (17.1 %) borderline cases, and 15 (7.8 %) malignant cases. Stratifying our analysis according to histologic grade, we investigated the relationship between disease-free survival (DFS) and both histologic and surgical factors, including histologic grade, stromal cellularity, stromal atypia, stromal mitosis, stromal overgrowth, tumor margin, type of surgical procedure (local excision, wide excision, and mastectomy), surgical margin status, and radiation therapy. In the case of benign PT, all patients with local recurrences (3.4 %) had been treated with local excision, and all recurrent tumors were also benign. The local recurrence rate for locally excised benign PTs was not associated with surgical margin status or radiation therapy. In the case of borderline PT, local excision was associated with an increased local recurrence rate (P = 0.046). In malignant PT, small tumor size (≤4.0 cm) was associated with an increased local recurrence rate (P = 0.041). Univariate analyses indicated that surgical procedure (mastectomy < local excision < wide excision; P < 0.001) was significantly associated with shorter DFS in borderline PT. A positive surgical resection margin (P < 0.001) was associated with DFS in malignant PT. The factors associated with local recurrence differed with the histologic grade of PT, as did the features of local recurrence itself. In particular, benign PT had very low rate of local recurrence regardless of surgical margin status or radiation therapy, even when treated with local excision. In the case of benign PT, no recurrent tumors had worse histologic grades than the initial tumors.

This study aimed to investigate the associations between the expression of redox-related proteins which regulate reactive oxygen species (ROS) production and the histologic factors in phyllodes tumor (PT). We used tissue microarrays to analyze 193 PTs and performed immunohistochemical staining against five redox-related proteins including catalase, thioredoxin reductase (TxNR), glutathione S-transferase π (GST π), thioredoxin interacting protein (TxNIP), and manganese superoxide dismutase (MnSOD). We then compared the immunohistochemical results and histologic parameters. The 193 PTs were classified as benign (n = 145, 75.1 %), borderline (n = 33, 17.1 %), and malignant (n = 15, 7.8 %). With worsening histologic grade, the expression of catalase, TxNR, TxNIP, and MnSOD in the stromal component increased (P < 0.001), and GST π and MnSOD expression in the epithelial component increased (P = 0.014, and 0.038). Significant associations were found between the expression of catalse-TxNR, catalase-TxNIP, catalase-MnSOD, TxNR-TxNIP, TxNR-MnSOD, and TxNIP-MnSOD in both the epithelial and stromal components (P < 0.05). This study confirmed that the stromal expression of catalase, TxNR, TxNIP, and MnSOD increased with worsening histologic grade in PT, reflecting the change in ROS production during the malignant transformation of PT.

The aim of study was to investigate the metabolism of tumor and stromal cells necessary to determine differential tumor-stroma metabolic interactions according to the molecular subtypes of triple-negative breast cancer (TNBC). Tissues from 132 patients of TNBC were prepared for use as tissue microarrays (TMA). Expression of CK5/6, EGFR, claudin 3, claudin 4, claudin7, E-cadherin, AR, GGT1, STAT1, and interleukin-8 was evaluated by immunohistochemical staining using TMA to classify molecular subtypes of TNBC. In addition, immunohistochemical staining for Glut1, CAIX, BNIP3, MCT4, Beclin-1, LC3A, LC3B, and p62 was performed. According to glycolytic status determined by the immunohistochemical expression of Glut-1 and CAIX in tumor and stroma, the metabolic phenotypes of the TNBCs were defined as follows: Warburg type (tumor: glycolysis, stroma: non-glycolysis), reverse Warburg type (tumor: non-glycolysis, stroma: glycolysis), mixed metabolic type (tumor: glycolysis, stroma: glycolysis), and metabolic null type (tumor: non-glycolysis, stroma: non-glycolysis). TNBCs were classified as follows: 79 Warburg type (59.8 %), 7 reverse Warburg type (5.3 %), 24 mixed metabolic type (18.2 %), and 22 metabolic null type (16.7 %). There was no statistical significance between the metabolic phenotypes and molecular subtypes (P=0.706). Reverse Warburg type showed the most dysfunctional mitochondrial status for stromal cells, while Warburg type showed the most functional mitochondrial status (P=0.036). Regarding stromal autophagy status, reverse Warburg type showed the most activated status, while all of the Warburg and metabolic null types showed a non-activated status (P<0.001). In conclusion, Warburg type was the most common metabolic phenotype in TNBC, while reverse Warburg type was the most unusual. Metabolic phenotypes did not differ among the molecular subtypes of TNBCs.

The aim of this study was to investigate the expression of glutamine metabolism-related proteins to determine whether glutamine is metabolized differently according to breast cancer molecular subtype. We generated a tissue microarray of 702 breast cancer patients and performed immunohistochemical staining for glutamine metabolism-related proteins, including glutaminase 1 (GLS1 (GLS)), glutamate dehydrogenase (GDH (H6PD)), and amino acid transporter-2 (ASCT2 (SLC1A5)), which were separately evaluated in tumor and stroma compartments and then analyzed by breast cancer molecular subtypes. Breast cancers were classified as follows: 293 luminal A (41.7%), 166 luminal B (23.6%), 67 HER2 type (9.6%), and 176 TNBC (25.1%). HER2 type showed the highest stromal GLS1 (P=0.001), tumoral GDH (P=0.001), stromal GDH (P<0.001), and tumoral ASCT (P<0.001) expression. We identified differential expression of glutamine metabolism-related proteins according to molecular subtype of breast cancer. The highest glutamine metabolic activity was seen in HER2-type breast cancer.

Introduction: The aim of this study was to investigate the differential expression of markers related to metabolic, mitochondrial and autophagy status in different molecular subtypes of breast cancer., Methods: Using tissue microarray sections generated from 740 cases of breast cancer, we performed immunohistochemical staining for Glut-1, CAIX, MCT4, ATP synthase, glutaminase, BNIP3, Beclin-1, LC3A, LC3B and p62. Based on the immunohistochemical expression of estrogen receptor (ER), progesterone (PR), HER2, and Ki-67 labeling index, the cases were classified into luminal A, luminal B, HER2 and triple-negative breast cancer (TNBC). We further classified metabolic phenotypes of tumors according to glycolytic status by assessing Glut-1 and CAIX expression as follows: Warburg type: tumor (glycolysis type), stroma (nonglycolysis type); reverse Warburg type: tumor (nonglycolysis type), stroma (glycolysis type); mixed type: tumor (glycolysis type), stroma (glycolysis type); and null type: tumor (nonglycolysis type), stroma (nonglycolysis type)., Results: Expression of Glut-1, MCT4 and LC3A was highest in TNBC and lowest in luminal A type (P < 0.001). Tumors were classified into 298 Warburg type (40.3%), 54 reverse Warburg type (7.3%), 62 mixed type (8.4%) and 326 null type (44.0%). The mixed type had a higher histologic grade, ER negativity, PR negativity and Ki-67 index, whereas the null type showed lower histologic grade, ER positivity, PR positivity and Ki-67 index (P < 0.001). TNBC constituted the major portion of Warburg and mixed types, and luminal A consisted mainly of reverse Warburg and null types (P < 0.001)., Conclusion: Breast cancer is heterogeneous in its metabolic status, and therefore it can be classified into various metabolic phenotypes. Specifically, the Warburg and mixed types had strong associations with TNBC, whereas reverse the Warburg and null types had associations with the luminal type, suggesting a correlation between metabolic phenotype and the biology of breast cancer.

The purpose of this study is to investigate the relationship between expression of immune-related molecules such as STAT1, CD20, IL-8, IFN-γ, tumor genetic phenotype, and the clinical course of invasive breast cancer. We constructed tissue microarrays from the breast cancers of 727 patients and classified the cases as either luminal A, luminal B, HER-2, or triple negative breast cancer (TNBC) based on standard pathological and clinical classifications using genetic phenotype. Surrogate immunohistochemical stains (STAT1, CD20, IL-8, IFN-γ) and HER-2 FISH were performed on each microarray. Of the 727 patients cases, 303 (41.7 %) were luminal A, 169 (23.2 %) were luminal B, 71 (9.8 %) were HER2+, and 184 (25.3 %) were TNBC. The expression of STAT1 in tumor cells was higher in luminal-type cancers than in HER2+ and TNBC (P < 0.001), and the TNBC-type tumors showed the highest levels of stromal STAT1 expression (P < 0.001), stromal IL-8 expression (P = 0.005), and CD20 index (P < 0.001). Luminal A type tumors showed the lowest expression of these markers. The stromal IL-8 positivity was associated with shorter DFS and OS in ER positive group, HER-2 negative group, and luminal A group (P < 0.05). To conclude, the immune-related molecules, STAT1, IFN-γ, IL-8, and CD20 are differentially expressed and define particular molecular subtypes which correlate with genetically defined types of tumors. High expression of STAT1 in tumor cells is observed in luminal-type tumors, whereas stromal expression of STAT1, stromal IL-8, and IL-8 in tumor cells is the highest in TNBC-type tumors.

15-Deoxy-Δ(12,14)-prostaglandin J(2) (15d-PGJ(2)) is a representative J-series cyclopentenone prostaglandin bearing an electrophilic α,β-unsaturated carbonyl group. In the present study, treatment of human breast cancer MCF-7 cells with 15d-PGJ(2) caused the up-regulation of the glutamate cysteine ligase catalytic (GCLC) subunit, the rate-limiting enzyme in glutathione (GSH) synthesis. 15d-PGJ(2) treatment caused nuclear translocation and transactivation of Nrf2, a redox-sensitive transcription factor responsible for induced expression of antioxidant and other cytoprotective genes. siRNA knockdown of Nrf2 abrogated 15d-PGJ(2)-induced GCLC expression. Following 15d-PGJ(2) treatment, the intracellular GSH level was initially diminished but eventually enhanced even above the basal level. The reactive oxygen species (ROS) scavenger N-acetylcysteine (NAC) abolished the 15d-PGJ2-induced Nrf2 activation and GCLC expression. Pharmacologic inhibition or siRNA knockdown of Akt, the target of phosphoinositide 3-kinase (PI3-K), attenuated 15d-PGJ(2)-induced Nrf2 activation and GCLC expression, and NAC treatment inhibited phosphorylation of Akt, and subsequently Nrf2 activation and GCLC upregulation. 9,10-Dihydro-15-PGJ2, a nonelectrophilic analogue of 15d-PGJ(2) that lacks the ability to form a conjugate with GSH, failed to induce activation of Akt and Nrf2 as well as ROS generation. These findings, taken all together, suggest that intracellular accumulation of ROS formed as a consequence of initial depletion of GSH can activate Akt, which in turn induces Nrf2 activation and subsequently the expression of GCLC, leading to the restoration of GSH. Interestingly, the extracellular GSH level was increased, concomitantly with the depletion of the intracellular GSH following 15d-PGJ(2) treatment. However, 15d-PGJ(2) was unable to influence both intra- and extra-cellular GSH levels when multidrug resistance-associated protein 1 (MRP1), the efflux pump for GSH conjugates, was blocked by its antagonist, MK571. Moreover, 15d-PGJ(2)-induced GCLC expression was attenuated by the MK571 and also by siRNA knockdown of MRP1, suggesting that MRP1 contributes to 15d-PGJ(2)-mediated up-regulation of GCLC by pumping out the 15d-PGJ(2)-GSH conjugate. It is speculated that 15d-PGJ(2), once effluxed through MRP, liberates from the GSH conjugate, and the free 15d-PGJ(2) re-enters the cell and forms the GSH conjugate again. In conclusion, MRP1 mediates Nrf2-dependent up-regulation of GCLC in 15d-PGJ(2)-treated MCF-7 cells, possibly via a putative recycling loop of 15d-PGJ(2)-GSH conjugation.

Heme oxygenase-1 (HO-1) has recently been found to be involved in angiogenesis and metastasis. In this study, we investigated whether HO-1 could potentiate the metastatic potential of human breast cancer cells. Treatment of MCF-7 and MDA-MB-231 cells with 30 microM of 15-deoxy-Delta12,14-prostaglandin J2 (15d-PGJ2) increased the expression of HO-1, which preceded the induction of matrix metalloproteinases (MMPs). The 15d-PGJ2-induced upregulation of MMP-1 was abrogated by the HO-1 inhibitor zinc protoporphyrin IX (ZnPP) as well as introduction of HO-1 short interfering RNA. In addition, HO-1 inducers, such as cobalt protoporphyrin IX and hemin, upregulated the expression of MMP-1. Overexpression of HO-1 in the MCF-7 cells caused the induction of MMP-1 expression. Treatment with the HO-1 inhibitor ZnPP abolished the migrative phenotype of 15d-PGJ2-treated MCF-7 cells. MCF-7 cells treated with 15d-PGJ2 exhibited intracellular accumulation of reactive oxygen species (ROS) which was abolished by ZnPP. We hypothesize that excess iron, released as a consequence HO-1 activity induced by 15d-PGJ2, is transiently available for the stimulation of intracellular ROS generation and subsequently MMP-1 expression. 15d-PGJ2-mediated upregulation of MMP-1 expression was blocked by the iron chelator desferrioxamine and the Fe2+-specific chelator 1,10-phenanthroline. The iron chelators as well as the antioxidant N-acetyl-L-cysteine abrogated ROS formation by 15d-PGJ2. In conclusion, 15d-PGJ2 upregulates MMP-1 expression via induction of HO-1 and subsequent production of iron capable of generating ROS, which may contribute to increased metastasis and invasiveness of the human breast cancer cells.

Recent studies suggest that inflammation is causally linked to carcinogenesis. Cyclooxygenase-2 (COX-2), a rate-limiting enzyme in the biosynthesis of prostaglandins, is inappropriately expressed in various cancers and hence recognized as one of the hallmarks of chronic inflammation-associated malignancies. However, the mechanistic role of COX-2 as a link between inflammation and cancer remains undefined. Here, we report that 15-deoxy-Delta(12,14)-prostaglandin J(2) (15d-PGJ(2)), one of the final products of COX-mediated arachidonic acid metabolism, upregulates the expression of COX-2 in the human breast cancer MCF-7 cell line. 15d-PGJ(2)-induced COX-2 expression was mediated by activation of Akt and subsequently activator protein-1 (AP-1). Furthermore, 15d-PGJ(2) formed reactive oxygen species, which led to increased phosphorylation of Akt, DNA binding of AP-1 and expression of COX-2. In contrast to 15d-PGJ(2), 9,10-dihydro-15d-PGJ(2) did not elicit any of effects induced by 15d-PGJ(2) in this study, suggesting that an electrophilic carbon center present in 15d-PGJ(2) is critical for COX-2 expression as well activation of upstream signal transduction induced by this cyclopentenone prostaglandin. Taken together, these observations suggest that 15d-PGJ(2) produced by COX-2 overexpression may function as a positive regulator of COX-2 in human breast cancer MCF-7 cells.