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Background: CHIP is a U box type ubiquitin ligase that induces ubiquitination and degradation of its target proteins, which include several oncogenic proteins. We clarified that CHIP suppresses tumor growth and metastasis in human breast cancer by inhibiting oncogenic pathways (Nat Cell Biol 2009;11:312-9). In this study, we investigated the relationship between immunohistochemical CHIP expression and several biomarkers, and evaluated the correlation between CHIP expression and prognosis of patients with invasive breast cancer. Patients and Methods: In this study, 272 consecutive patients with invasive carcinoma of no special type with invasion >5 mm, treated in 2000-2001, were enrolled. We performed immunohistochemical staining with antibodies against CHIP, ER, PgR, and HER2. Cytoplasmic expression patterns of CHIP were scored as 0 (no stain), 1 (weak stain), 2 (moderate stain), and 3 (strong stain), and divided into high CHIP (score 3) and low CHIP (score 2, 1, 0) groups. We investigated the relationship between CHIP expression and ER, PgR, HER2, histological grade (HG) and lymph node status (pN). We also evaluated correlation between CHIP expression and prognosis (RFS) of patients. Results: CHIP expression was as follows: score 0, 49 patients (18.0%); score 1, 91 (33.5%); score 2, 83 (30.5%); score 3, 49 (18.0%). High CHIP correlated significantly with positive ER (p Conclusions: CHIP expression correlated with status of hormone receptors and HER2 and might be a potent prognostic factor in invasive breast cancer patients, especially postmenopausal cases. Immunohistochemical examination of CHIP is thought to be useful for evaluating prognosis of breast cancer patients. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P2-11-18. more...

[Background] Estrogen receptor (ER) positive breast cancer was composed of about 70% of clinical breast cancer and therapy for the ER positive breast cancer have progressed, but some patients recur after endocrine therapy including aromatase inhibitors (AIs). The switch of proliferation drive to human epidermal growth factor receptor 2 was reported as one of AI resistance mechanisms, but ER status of many recurrent patients after AI treatment was maintained or slightly decreased. Moreover, plasma concentration of estrone-sulfate (E1S) is mostly unchanged after menopause and treatment of AI. Thus, we established AI resistant model with conserved ER expression and its activity from MCF-7 cell, and found that E1S contributed to proliferation of the AI-resistant cells. [Material and Method] We introduced plasmids carrying ERE-green fluorescent protein (GFP) gene to MCF-7 (E10), and then aromatase gene was additionally introduced to E10 (E10arom). E10arom was cultured in estrogen-depleted medium including testosterone and letrozole, monitoring GFP as ER activity for about three months. We finally established ER positive Letrozole-Resistant cell lines (LR cells). In addition, to confirm whether E1S-dependent growth in LR cells could be reproduced in ER positive breast cancer cell line, we also established human steroid sulfatase (STS) gene-transfected MCF-7 (MCF-STS) and organic anion transporter peptide (OATP) 4A1 gene-transfected MCF-7 (MCF-4A1). ER activity of these cell lines was examined by ERE-luciferase reporter assay, and response to each steroid and drug was investigated by cell proliferation assay. Quantitative PCR was used for comparing expression of mRNA in these cell lines. [Results] mRNA expression of STS and four OATPs including OATP4A1 increased in LR cells comparing to E10arom. Moreover, there was no change in mRNA expressions of efflux drug transporters, aromatase-metaboic enzyme and enzymes related with production for estrogenic androgen. ERE-luciferase assay with E1S showed higher ER activity of LR cells than E10arom, and LR cells were more proliferated by E1S in dose-dependent manner than the parental cell. STS inhibitor alone and its combination with letrozole were inhibitory to proliferation of LR cells. LR cells were also inhibited by selective estrogen receptor modulator (SERM) and downregulator (SERD). In proliferation assay of MCF-STS and MCF-4A1, we observed that these cell lines also proliferated by E1S in dose-dependent manner as LR cells did. [Discussion] Since ER status of recurrent patients after AI treatment was mostly unchanged, our model could be more practical for analysis of AI resistance in ER positive breast cancer. These results showed that combined induction of STS and OATP contributed to estradiol (E2) production from E1S in LR cells, suggesting that analysis of E1S as alternative E2 productive pathway needed investigation of both STS and transporter of E1S. The combination of STS inhibitor with letrozole was effective to LR cells, and SERM and SERD were also effective to these cells, suggesting that combined therapy of STS inhibitor with AI or switching AI to SERM or SERD was beneficial for AI-resistant breast cancer. Citation Information: Cancer Res 2013;73(24 Suppl): Abstract nr P5-09-16. more...

Background Mutations in phosphatidylinositol 3-kinase (PI3K), which encodes the catalytic subunit of PI3Kα, is one of the most frequent genomic alterations and is found in about 40% of estrogen receptor (ER)-positive, HER2 negative breast cancers. PIK3CA mutations promote the growth and proliferation of cancers via activation of the PI3K/mammalian target of rapamycin pathway and can mediate resistance to endocrine therapies in breast cancer. Although several clinical trials for PI3K inhibitors (PI3Kis) in ER-positive metastatic breast cancers are ongoing, the effects of PI3Kis on endocrine-resistant breast cancers with various characteristics and definitive biomarkers of PI3Kis are unclear. Using endocrine-resistant cells established in our laboratory, we evaluated the efficacy of PI3Ki in these cell lines and identified the characteristics associated with acquired resistance to PI3Kis in endocrine-resistant cells. Results Long-term estrogen deprivation-resistant (EDR) cell lines and fulvestrant-resistant cell lines (MFR and TFR) were established from MCF-7 and T-47D cells in our previous studies. These cell lines showed different ER expression levels, including high expression (EDR-1), low expression (EDR-2, -3), or no expression (MFR, TFR); all of these cell lines had the same PIK3CA mutations as the parental cell lines. The pan-class1 PI3Ki buparlisib (BKM120) and α-specific PI3K inhibitor alpelisib (BYL719) inhibited the proliferation of endocrine-resistant cell lines when compared with their parental cells. Among endocrine-resistant cells, MFR cells were dramatically inhibited by PI3Kis. Colony formation assays indicated that MFR cells were more sensitive to PI3Kis than other cells lines. Next, we established PI3Ki- and everolimus-resistant cell lines from EDR-1, EDR-2, and MFR cells using BKM120, BYL719, and everolimus. Analysis of the time required to generate resistant cells showed that MFR cells required twice as long to acquire resistance compared with EDR cells. Furthermore, the time required to acquire resistance to BYL719 was shorter than that for BKM120. BYL719-resistant (BYL-R) cells were effectively inhibited by BKM120 to a degree similar to that of parental cells; however, BYL-R cells lost sensitivity to BYL719 and everolimus. Evelolimus-resistant (EVE-R) cells were also the same. In contrast, BKM120-resistant (BKM-R) cells showed less sensitivity to BKM120, BYL719, and everolimus. In other words, the pan-PI3Ki BKM120 was able to inhibit the growth of BYL-R and EVE-R cells, whereas BYL719 and everolimus were not able to inhibit BKM-R cells sufficiently. In addition, there were no changes in ER expression in EDR-1, EDR-2, and MFR cells exposed to PI3Kis for 1 h. Interestingly, ER expression on EDR-2 cells with acquired resistance to PI3Kis was increased compared with that in parental cells. Conclusion Our findings showed that PI3Kis exhibited remarkable efficacy in all types of EDR cells, particularly in fulvestrant-resistant cell lines. In PI3Ki- and everolimus-resistant cell lines, BKM120 and BYL719 showed different effects, and BYL719 and everolimus may exhibit cross-resistance. Furthermore, PI3Kis were likely to change the expression of ER. Citation Format: Tokuda E, Komatsu T, Sasaki S, Tsuboi K, Nakamura M, Iida M, Niwa T, Saito M, Hayashi S-I. Effects of PI3K inhibitors on endocrine-resistant cell lines and differences in the characteristics of ER positive breast cancer cells after acquired resistance to the inhibitors [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P4-03-12. more...

Introduction: Aromatase inhibitors (AIs) have been reported to exert their anti-proliferative effects not only by reducing the production of estrogens but also by unmasking the inhibitory effect of androgens such as testosterone (TS) or dihydrotestosterone (DHT) in postmenopausal women with hormone receptor-positive breast cancer. The behavior of androgens in AI-resistance mechanisms is not sufficiently understood. 5α-androstane-3β,17β-diol (3β-diol) generated from DHT by 3β-hydroxysteroid dehydrogenase type 1 (3β-HSD type 1: HSD3B1) has androgenic activity and substantial estrogenic activity, representing a potential mechanism of AI resistance. Methods: To investigate these issues, ERE-GFP-transfected MCF-7-E10 cells were cultured for 3 months under steroid-depleted, TS-supplemented conditions which is the similar as the AI treatment. Among the surviving cells, two stable variants that show ER activity depending on androgen metabolites were selected as AD-EDR (androgen metabolite-dependent and estrogen depletion-resistant) by monitoring GFP expression. Using these cell lines, we investigated the process of adaptation to androgen-abundant conditions and the role of androgens in AI-resistance mechanisms. Results: AD-EDR cell lines showed increased growth and induction of estrogen-responsive genes rather than androgen-responsive genes by androgens or 3β-diol. Further analysis revealed increased expressions of HSD3B1 and reduced expression of androgen receptor (AR) in these cell lines. In parental MCF-7-E10 cells, ectopic expression of HSD3B1 or inhibition of AR resulted in adaptation to estrogen-deprived and androgen-abundant conditions. In coculture with stromal cells replicating the local estrogen production from androgen, AD-EDR cell lines showed AI resistance compared with parental MCF-7-E10 cells. Immunohistochemistry and real-time PCR analyses on 9 pairs of primary and recurrent tissue samples from AI-resistant breast cancer revealed the decrease of AR protein expression in all cases and increase of HSD3B1 mRNA expression in 5. Conclusion: In the present study, we successfully cloned two stable variants that show ER activity depending on androgen metabolites. Investigation of these cell lines suggested that the increased function of 3β-HSD type 1 and reduced function of AR contribute to AI resistance by enhancing the androgen metabolite-dependent growth and reducing the inhibitory effect of androgens. Our data of clinical samples suggest that this mechanism also acts as an AI-resistance in clinical breast cancer in some cases. Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P6-04-17. more...

Background: Endoxifen and 4-hydroxy tamoxifen are both active metabolites of tamoxifen and exert anti-tumor activity for ER+ breast cancer. However, only small numbers of paper reported biological profile of endoxifen. Methods: Cells were incubated with various concentration of endoxifen ( (Z)-4-Hydroxy-N-desmethyl Tamoxifen ( Results: IC50s of endoxifen for MCF-7 were 100 nM in estradiol (E2) deprivation condition and 500 nM in the presence of 1nM E2. These are significantly higher than those of 4-OH tamoxifen, which are 10 nM without E2 and 50 nM with E2, respectively. From the previous reports, plasma endoxifen concentrations in breast cancer patients were ranged from 20 to 200 nM according to CYP2D6 phenotype. Anti-proliferative index of 20 nM endoxifen for MCF-7 was 0.7 (indicating 30% reduction in proliferative activity), and 200 nM endoxifen was 0.5 in the absence of E2. These were 0.95 (20 nM) and 0.75 (200nM), respectively, when incubated with 1 nM E2. 10 nM 4-OH tamoxifen, which is mean concentration in patient plasma, showed about 0.6 anti-proliferative index with no regards to E2 condition. Without E2, endoxifen reduced ERα expression as previously reported, however, endoxifen increased ERα amount in the presence of E2 accompanied with decrease of HER-2 expression. This alternation of ERα and HER2 expression were identical to those observed using 4-OH tamoxifen. There was a weak tendency that ERβ expressing MCF-7 clones showed favorable response to endoxifen compared to parent MCF-7, but this was not significant. Conclusion: Endoxifen is active agent for MCF-7 cell, however, it requires 10-fold higher concentration compared to 4-OH tamoxifen to achieve IC 50. Difference of anti-proliferative effect between 20 nM and 200 nM of endoxifen are relatively small, and it might result in minor difference for clinical response, as expected from recent clinical studies of CYP2D6. This is the first time to show that endoxifen has opposite effect to ERα protein level depending on the presence or absence of E2. ERβ expression did not enhance activity of endoxifen in contrast to previous report. Citation Information: Cancer Res 2011;71(24 Suppl):Abstract nr P4-01-20. more...

In AKR/J mice inoculated intraperitoneally with protoscoleces of Echinococcus multilocularis, the oral administration of alpha-difluoromethylornithine (DFMO) in drinking water had no obvious effect on the development of hydatid cysts. The DFMO treatment also caused no apparent depletion of three major polyamines (putrescine, spermidine, and spermine) in the cysts, although a slight reduction in the putrescine level was detected. The failure of DFMO treatment to reduce the growth of cysts in mice may result from the absence of ornithine decarboxylase in the parasite. more...