| 1. |
- Aguilar, Helena, et al.
(författare)
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VAV3 mediates resistance to breast cancer endocrine therapy
- 2014
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Ingår i: Breast Cancer Research. - : BioMed Central. - 1465-5411 .- 1465-542X. ; 16:3, s. R53-
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Tidskriftsartikel (refereegranskat)abstract
- INTRODUCTION: Endocrine therapies targeting cell proliferation and survival mediated by estrogen receptor alpha (ERalpha) are among the most effective systemic treatments for ERalpha-positive breast cancer. However, most tumors initially responsive to these therapies acquire resistance through mechanisms that involve ERalpha transcriptional regulatory plasticity. Here, we identify VAV3 as a critical component in this process.METHODS: A cell-based chemical compound screen was carried out to identify therapeutic strategies against resistance to endocrine therapy. Binding to ERalpha was evaluated by molecular docking analyses, an agonist fluoligand assay, and short-hairpin (sh) RNA-mediated protein depletion. Microarray analyses were performed to identify altered gene expression. Western blot of signaling and proliferation markers and shRNA-mediated protein depletion in viability and clonogenic assays were performed to delineate the role of VAV3. Genetic variation in VAV3 was assessed for association with the response to tamoxifen. Immunohistochemical analyses of VAV3 were carried out to determine the association with therapy response and different tumor markers. An analysis of gene expression association with drug sensitivity was carried out to identify a potential therapeutic approach based on differential VAV3 expression.RESULTS: The compound YC-1 was found to comparatively reduce the viability of cell models of acquired resistance. This effect was probably not due to activation of its canonical target (soluble guanylyl cyclase) but instead a result of binding to ERalpha. VAV3 was selectively reduced upon exposure to YC-1 or ERalpha depletion and, accordingly, VAV3 depletion comparatively reduced the viability of cell models of acquired resistance. In the clinical scenario, germline variation in VAV3 was associated with response to tamoxifen in Japanese breast cancer patients (rs10494071 combined P value = 8.4 x 10-4). The allele association combined with gene expression analyses indicated that low VAV3 expression predicts better clinical outcome. Conversely, high nuclear VAV3 expression in tumor cells was associated with poorer endocrine therapy response. Based on VAV3 expression levels and the response to erlotinib in cancer cell lines, targeting EGFR signaling may be a promising therapeutic strategy.CONCLUSIONS: This study proposes VAV3 as a biomarker and rationale signaling target to prevent and/or overcome resistance to endocrine therapy in breast cancer.
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| 2. |
- Bostner, Josefine, et al.
(författare)
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Activation of Akt, mTOR, and the estrogen receptor as a signature to predict tamoxifen treatment benefit
- 2013
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Ingår i: Breast Cancer Research and Treatment. - : Springer Verlag (Germany). - 0167-6806 .- 1573-7217. ; 137:2, s. 397-406
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Tidskriftsartikel (refereegranskat)abstract
- The frequent alterations of the PI3K/Akt/mTOR-growth signaling pathway are proposed mechanisms for resistance to endocrine therapy in breast cancer, partly through regulation of estrogen receptor alpha (ER) activity. Reliable biomarkers for treatment prediction are required for improved individualized treatment. We performed a retrospective immunohistochemical analysis of primary tumors from 912 postmenopausal patients with node-negative breast cancer, randomized to either tamoxifen or no adjuvant treatment. Phosphorylated (p) Akt-serine (s) 473, p-mTOR-s2448, and ER phosphorylations-s167 and -s305 were evaluated as potential biomarkers of prognosis and tamoxifen treatment efficacy. High expression of p-mTOR indicated a reduced response to tamoxifen, most pronounced in the ER+/progesterone receptor (PgR) + subgroup (tamoxifen vs. no tamoxifen: hazard ratio (HR), 0.86; 95 % confidence interval (CI), 0.31-2.38; P = 0.78), whereas low p-mTOR expression predicted tamoxifen benefit (HR, 0.29; 95 % CI, 0.18-0.49; P = 0.000002). In addition, nuclear p-Akt-s473 as well as p-ER at -s167 and/or -s305 showed interaction with tamoxifen efficacy with borderline statistical significance. A combination score of positive pathway markers including p-Akt, p-mTOR, and p-ER showed significant association with tamoxifen benefit (test for interaction; P = 0.029). Cross-talk between growth signaling pathways and ER-signaling has been proposed to affect tamoxifen response in hormone receptor-positive breast cancer. The results support this hypothesis, as an overactive pathway was significantly associated with reduced response to tamoxifen. A clinical pre-treatment test for cross-talk markers would be a step toward individualized adjuvant endocrine treatment with or without the addition of PI3K/Akt/mTOR pathway inhibitors.
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| 3. |
- Bostner, Josefine, et al.
(författare)
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Amplification of CCND1 and PAK1 as predictors of recurrence and tamoxifen resistance in postmenopausal breast cancer.
- 2007
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Ingår i: Oncogene. - : Springer Science and Business Media LLC. - 0950-9232 .- 1476-5594. ; 26:49, s. 6997-7005
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Tidskriftsartikel (refereegranskat)abstract
- The 11q13 region is amplified in approximately 15% of all breast tumors. Situated in this region are the cyclin D1 gene (CCND1) and the p-21-activated kinase 1 (PAK1) gene. Both genes encode proteins shown to activate the estrogen receptor (ER), leading to transcription of CCND1 and other ER-responsive genes. Here, we investigate the prognostic and treatment predictive role of CCND1 and PAK1 gene amplification in postmenopausal breast cancer patients randomized to tamoxifen treatment or no adjuvant treatment. Amplification of CCND1 and PAK1, assessed by real-time PCR, was observed in 12.5 and 9.3%, respectively. Amplification of PAK1 was seen in 37% of the CCND1-amplified tumors, indicating coamplification (P<0.001). In ER-positive patients, amplification of at least one of the genes indicated a reduced recurrence-free survival (P=0.025). When response to tamoxifen treatment was analysed, patients with PAK1 amplification showed decreased benefit from the drug (ER+; relative risk ratio (RR)=1.62; 95% confidence interval (CI), 0.47-5.55) compared to patients without amplification (ER+; RR=0.53; 95% CI, 0.32-0.88). This was not evident for CCND1 amplification. We show that PAK1 may be a predictor of tamoxifen resistance and furthermore, we do not discard PAK1 as a potential candidate oncogene in the 11q13 amplicon. In addition, we show that high pak1 protein levels may predict tamoxifen insensitivity.
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| 4. |
- Bostner, Josefine, et al.
(författare)
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Estrogen Receptor-alpha Phosphorylation at Serine 305, Nuclear p21-Activated Kinase 1 Expression, and Response to Tamoxifen in Postmenopausal Breast Cancer
- 2010
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Ingår i: Clinical Cancer Research. - : American Association for Cancer Research, Inc.. - 1078-0432 .- 1557-3265. ; 16:5, s. 1624-1633
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Tidskriftsartikel (refereegranskat)abstract
- Purpose: In vitro, p21-activated kinase 1 (Pak1) phosphorylates the serine 305 residue of the estrogen receptor alpha (ER alpha) and influences the response of breast cancer cells to tamoxifen. We investigated the influence of Pak1 and pER alpha(ser305) on breast cancer prognosis and results of tamoxifen therapy. Experimental Design: We examined Pak1 and pER alpha(ser305) protein by immunohistochemistry in a series of 912 tumors from node-negative breast cancer patients randomized to tamoxifen or no adjuvant endocrine treatment. Results: Cytoplasmic Pak1 correlated to large tumors and ER negativity, whereas nuclear Pak1 and pER alpha(ser305) correlated to small tumors and ER positivity. Nuclear expression of Pak1 and pER alpha(ser305) predicted reduced response to tamoxifen in patients with ER alpha-positive tumors (tamoxifen versus no tamoxifen: hazard ratio (HR), 1.33; 95% confidence interval (95% CI), 0.42-4.2; P = 0.63), whereas patients lacking this combination benefitted significantly from tamoxifen (HR, 0.43; 95% CI, 0.30-0.62; P less than 0.0001). Similar nonsignificant trends were detected in analyses of the proteins separately. Pak1 in the cytoplasm was an independent prognostic marker, indicating increased recurrence rate (HR, 1.79; 95% CI, 1.17-2.74; P = 0.0068) and breast cancer mortality (HR, 1.98; 95% CI, 1.14-3.46; P = 0.016) for patients randomized to no adjuvant treatment. Conclusion: Our results suggest that patients with tumors expressing Pak1 and pER alpha(ser305) in combination are a group in which tamoxifen treatment is insufficient. In addition, the pathway may be of interest as a drug target in breast cancer. Furthermore, the findings support previous studies showing that Pak1 has differential roles in the cytoplasm and the nucleus.
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| 5. |
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| 6. |
- Bostner, Josefine, et al.
(författare)
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Raptor localization predicts prognosis and tamoxifen response in estrogen receptor-positive breast cancer
- 2018
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Ingår i: Breast Cancer Research and Treatment. - : SPRINGER. - 0167-6806 .- 1573-7217. ; 168:1, s. 17-27
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Tidskriftsartikel (refereegranskat)abstract
- Deregulated PI3K/mTOR signals can promote the growth of breast cancer and contribute to endocrine treatment resistance. This report aims to investigate raptor and its intracellular localization to further understand its role in ER-positive breast cancer. Raptor protein expression was evaluated by immunohistochemistry in 756 primary breast tumors from postmenopausal patients randomized to tamoxifen or no tamoxifen. In vitro, the MCF7 breast cancer cell line and tamoxifen-resistant MCF7 cells were studied to track the raptor signaling changes upon resistance, and raptor localization in ER alpha-positive cell lines was compared with that in ER alpha-negative cell lines. Raptor protein expression in the nucleus was high in ER/PgR-positive and HER2-negative tumors with low grade, features associated with the luminal A subtype. Presence of raptor in the nucleus was connected with ER alpha signaling, here shown by a coupled increase of ER alpha phosphorylation at S167 and S305 with accumulation of nuclear raptor. In addition, the expression of ER alpha-activated gene products correlated with nuclear raptor. Similarly, in vitro we observed raptor in the nucleus of ER alpha-positive, but not of ER-negative cells. Interestingly, raptor localized to the nucleus could still be seen in tamoxifen-resistant MCF7 cells. The clinical benefit from tamoxifen was inversely associated with an increase of nuclear raptor. High cytoplasmic raptor expression indicated worse prognosis on long-term follow-up. We present a connection between raptor localization to the nucleus and ER alpha-positive breast cancer, suggesting raptor as a player in stimulating the growth of the luminal A subtype and a possible target along with endocrine treatment.
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| 7. |
- Bostner, Josefine, et al.
(författare)
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S6 kinase signaling and tamoxifen response in breast cancer cells and in two randomized breast cancer cohorts
- 2013
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Annan publikation (övrigt vetenskapligt/konstnärligt)abstract
- Detecting signals in the mammalian target of rapamycin (mTOR), and the estrogen receptor (ER) pathways for prediction of treatment response may be a future clinical tool in primary breast cancer. Here, we investigated the validity and value of the mTOR targets p70-S6 kinase (S6K) 1 and 2 as biomarkers for tamoxifen sensitivity in vitro and in two independent tamoxifen randomized postmenopausal breast cancer cohorts. In addition, the prognostic value of the S6Ks was evaluated. A simultaneous knockdown of the S6Ks in ER-positive breast cancer cells resulted in G1 arrest, and tamoxifen-induced G1 arrest was in part S6K1+S6K2 dependent, suggesting separate roles in proliferation and in tamoxifen response. We found S6K1 to correlate with HER2 and cytoplasmic Akt activity, whereas S6K2 and phosphorylated S6K were closer connected with ER positivity, low proliferation and nucleic p-Akt. Treatment prediction and prognosis were evaluated by immunohistochemical staining. Nuclear accumulation of S6K1 was indicative of a reduced tamoxifen treatment effect, compared with a significant benefit from tamoxifen treatment in patients without tumor S6K1 nuclear accumulation. Patients with a combination of S6K1 nuclear accumulation and S6K2 cytoplasmic accumulation in the tumor cells had no tamoxifen benefit. Also, S6K1 and S6K2 activation, indicated by p-S6K-t389 expression, was associated with low benefit from tamoxifen compared with untreated patients. In addition, high protein expression of S6K1, independent of localization, predicted worse prognosis. This was not evident for variations in S6K2 or p-S6K-t389 expression.In conclusion, the mTOR targeted kinases S6K1 and S6K2 interfere with proliferation and response to tamoxifen. Monitoring their activity andintracellular localization may provide biomarkers for breast cancer treatment, allowing for identification of a group of patients less likely tobenefit from tamoxifen and thus in need of an alternative or additional treatment.
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| 8. |
- Bostner, Josefine, et al.
(författare)
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S6 kinase signaling: tamoxifen response and prognostic indication in two breast cancer cohorts
- 2015
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Ingår i: Endocrine-Related Cancer. - : BioScientifica. - 1351-0088 .- 1479-6821. ; 22:3, s. 331-343
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Tidskriftsartikel (refereegranskat)abstract
- Detection of signals in the mammalian target of rapamycin (mTOR) and the estrogen receptor (ER) pathways may be a future clinical tool for the prediction of adjuvant treatment response in primary breast cancer. Using immunohistological staining, we investigated the value of the mTOR targets p70-S6 kinase (S6K) 1 and 2 as biomarkers for tamoxifen benefit in two independent clinical trials comparing adjuvant tamoxifen with no tamoxifen or 5 years versus 2 years of tamoxifen treatment. In addition, the prognostic value of the S6Ks was evaluated. We found that S6K1 correlated with proliferation, HER2 status, and cytoplasmic AKT activity, whereas high protein expression levels of S6K2 and phosphorylated (p) S6K were more common in ER-positive, and low-proliferative tumors with pAKT-s473 localized to the nucelus. Nuclear accumulation of S6K1 was indicative of a reduced tamoxifen effect (hazard ratio (HR): 1.07, 95% CI: 0.53-2.81, P=0.84), compared with a significant benefit from tamoxifen treatment in patients without tumor S6K1 nuclear accumulation (HR: 0.42, 95% CI: 0.29-0.62, Pless than0.00001). Also S6K1 and S6K2 activation, indicated by pS6K-t389 expression, was associated with low benefit from tamoxifen (HR: 0.97, 95% CI: 0.50-1.87, P=0.92). In addition, high protein expression of S6K1, independent of localization, predicted worse prognosis in a multivariate analysis, P=0.00041 (cytoplasm), P=0.016 (nucleus). In conclusion, the mTOR-activated kinases S6K1 and S6K2 interfere with proliferation and response to tamoxifen. Monitoring their activity and intracellular localization may provide biomarkers for breast cancer treatment, allowing the identification of a group of patients less likely to benefit from tamoxifen and thus in need of an alternative or additional targeted treatment.
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| 9. |
- Bostner, Josefine, 1981-
(författare)
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The Akt/mTOR Pathway and Estrogen Receptor Phosphorylations : a crosstalk with potential to predict tamoxifen resistance in breast cancer
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Estrogen receptor α content is the primary breast cancer biomarker distinguishing the patients responsive from the non-responsive to endocrine treatments. Tamoxifen is an estrogen competitor with large potential to treat breast cancer patients and prolongs time to recurrence. Despite the estrogen receptor positivity and tamoxifen treatment, many women face recurrence of the disease. An important mechanism of resistance to endocrine treatments is upregulated growth factor signaling, and the subsequent effect on the estrogen receptor, rendering an active receptor that stimulates cell proliferation or reduced estrogen-receptor dependence.This thesis concerns the investigation of biomarkers, as a complement to the existing markers, for determining optimal treatment for patients with primary invasive breast cancer. Randomized patient tumor materials were used in order to measure variations in gene copies, proteins, and protein phosphorylations and to further relate these variations to time-to-recurrence. Endocrine untreated groups within the patient tumor sets gave us the opportunity to study the prognostic potential of selected markers and to compare tamoxifen-treated patients with endocrine untreated, thus obtaining a treatment-predictive value of each marker or marker combination.In endocrine-dependent cancer the 11q13 chromosomal region is frequently amplified, harboring the genes encoding the cell cycle stimulator cyclin D1 and the estrogen receptor phosphorylating kinase Pak1, respectively. Amplification of the genes was associated with reduced time-torecurrence, indicating a prognostic value, whereas PAK1 gene amplification predicted reduced response to tamoxifen treatment. Moreover, the protein expression of Pak1 tended to predict treatment response, which led to the investigation of this protein in a larger cohort. Together with one of its targets, the estrogen receptor phosphorylation at serine 305, Pak1 predicted reduced response to tamoxifen treatment when detected in the nucleus of tumor cells, suggesting activation of this pathway as a mechanism for tamoxifen-treatment resistance. The estrogen receptor is phosphorylated by several growth factor stimulated kinases. The role of serine-167 phosphorylation has been debated, with inconsistent results. To study the biomarker value of this site the upstream activity of Akt, mTOR, and the S6 kinases were analyzed individually and in combinations. As a prognostic factor, serine 167 indicated an improved breast cancer survival, and as a treatment predictive factor we could not detect a significant value of serine 167 as a single marker. However, in combination with serine 305, and Akt/mTOR-pathway activation, the response to tamoxifen treatment was reduced. The mTOR effector protein S6K1 was found to be associated with HER2 positivity and a worse prognosis. In the group of patients with S6K1 accumulation in the tumor cell nuclei, treatment did not prolong time-to-recurrence, similarly as observed with expression of active S6 kinases. In vitro, a simultaneous knockdown of the S6 kinases in estrogen receptor-positive breast cancer cells resulted in G1 arrest, and tamoxifen-induced G1 arrest was in part S6 kinase dependent.The results presented herein suggest biomarkers that would improve treatment decisions in the clinic, specifically for estrogen receptor-positive breast cancer and tamoxifen treatment but in a broader perspective, also for other endocrine treatments and targeted treatments.
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| 10. |
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