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Curea FG, Hebbar M, Ilie SM, Bacinschi XE, Trifanescu OG, Botnariuc I, Anghel RM. Current Targeted Therapies in HER2-Positive Gastric Adenocarcinoma. Cancer Biother Radiopharm 2018; 32:351-363. [PMID: 29265917 DOI: 10.1089/cbr.2017.2249] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Gastric cancer is one of the most common types of cancer in the world, usually diagnosed at an advanced stage. Despite the advances in specific anticancer agents' development, the survival rates remain modest, even in early stages. In 15%-20% of cases, the human epidermal growth factor receptor 2 (HER2) overexpression was identified. We conducted a general review to summarize the progress that has been made in the targeted treatment of HER2-positive esogastric junction or gastric adenocarcinoma. According to our findings, trastuzumab is the only validated anti-HER2 agent in locally advanced or metastatic disease and its adjuvant effectiveness is assessed in a RTOG phase III study. In a previously treated advanced disease, the maytansine derivate TDM 1 failed to be approved as a second-line regimen, and the tyrosine kinase inhibitor, lapatinib, shows modest results. The antiangiogenics have not been analyzed in specific populations and targeting the mesenchymal-epithelial transition factor (MET) receptor, overexpressed in up to 46% of the advanced disease, seems encouraging. Regarding the checkpoint inhibitors, based on KEYNOTE 059 multilevel ongoing trial, stratified according to the HER2 and programmed death-ligand (PD-L) 1 status, pembrolizumab was approved for third-line treatment of gastric or gastroesophageal junction adenocarcinoma.
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Affiliation(s)
- Fabiana G Curea
- 1 Department of Oncology-Radiotherapy, Institute of Oncology "Prof. Dr. Alexandru Trestioreanu," Bucharest, Romania
| | - Mohamed Hebbar
- 2 Department of Medical Oncology, University Hospital , Lille, France
| | - Silvia M Ilie
- 1 Department of Oncology-Radiotherapy, Institute of Oncology "Prof. Dr. Alexandru Trestioreanu," Bucharest, Romania .,3 University of Medicine and Pharmacy "Carol Davila," Bucharest, Romania
| | - Xenia E Bacinschi
- 1 Department of Oncology-Radiotherapy, Institute of Oncology "Prof. Dr. Alexandru Trestioreanu," Bucharest, Romania .,3 University of Medicine and Pharmacy "Carol Davila," Bucharest, Romania
| | - Oana G Trifanescu
- 1 Department of Oncology-Radiotherapy, Institute of Oncology "Prof. Dr. Alexandru Trestioreanu," Bucharest, Romania .,3 University of Medicine and Pharmacy "Carol Davila," Bucharest, Romania
| | - Inga Botnariuc
- 1 Department of Oncology-Radiotherapy, Institute of Oncology "Prof. Dr. Alexandru Trestioreanu," Bucharest, Romania
| | - Rodica M Anghel
- 1 Department of Oncology-Radiotherapy, Institute of Oncology "Prof. Dr. Alexandru Trestioreanu," Bucharest, Romania .,3 University of Medicine and Pharmacy "Carol Davila," Bucharest, Romania
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Pascual T, Apellániz-Ruiz M, Pernaut C, Cueto-Felgueroso C, Villalba P, Álvarez C, Manso L, Inglada-Pérez L, Robledo M, Rodríguez-Antona C, Ciruelos E. Polymorphisms associated with everolimus pharmacokinetics, toxicity and survival in metastatic breast cancer. PLoS One 2017; 12:e0180192. [PMID: 28727815 PMCID: PMC5519037 DOI: 10.1371/journal.pone.0180192] [Citation(s) in RCA: 23] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/11/2017] [Accepted: 06/12/2017] [Indexed: 11/18/2022] Open
Abstract
PURPOSE Metastatic breast cancer (MBC) progressing after endocrine therapy frequently activates PI3K/AKT/mTOR pathway. The BOLERO-2 trial showed that everolimus-exemestane achieves increased progression free survival (PFS) compared with exemestane. However, there is great inter-patient variability in toxicity and response to exemestane-everolimus treatment. The objective of this study was to perform an exploratory study analyzing the implication of single nucleotide polymorphisms (SNPs) on outcomes from this treatment through a pharmacogenetic analysis. PATIENTS AND METHODS Blood was collected from 90 postmenopausal women with hormone receptor-positive, HER2-negative MBC treated with exemestane-everolimus following progression after prior treatment with a non-steroidal aromatase inhibitor. Everolimus pharmacokinetics was measured in 37 patients. Twelve SNPs in genes involved in everolimus pharmacokinetics and pharmacodynamics were genotyped and associations assessed with drug plasma levels, clinically relevant toxicities (non-infectious pneumonitis, mucositis, hyperglycemia and hematological toxicities), dose reductions or treatment suspensions due to toxicity, progression free survival (PFS) and overall survival. RESULTS We found that CYP3A4 rs35599367 variant (CYP3A4*22 allele) carriers had higher everolimus blood concentration compared to wild type patients (P = 0.019). ABCB1 rs1045642 was associated with risk of mucositis (P = 0.031), while PIK3R1 rs10515074 and RAPTOR rs9906827 were associated with hyperglycemia and non-infectious pneumonitis (P = 0.016 and 0.024, respectively). Furthermore, RAPTOR rs9906827 was associated with PFS (P = 0.006). CONCLUSIONS CYP3A4*22 allele influenced plasma concentration of everolimus and several SNPs in PI3K/AKT/mTOR pathway genes were associated with treatment toxicities and prognosis. These results require replication, but suggest that germline variation could influence everolimus outcomes in MBC.
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Affiliation(s)
- Tomas Pascual
- Medical Oncology Department, 12 de Octubre University Hospital, Madrid, Spain
| | - María Apellániz-Ruiz
- Hereditary Endocrine Cancer Group, Human Cancer Genetics Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
| | - Cristina Pernaut
- Medical Oncology Department, 12 de Octubre University Hospital, Madrid, Spain
| | | | - Pablo Villalba
- Biochemistry Department, 12 de Octubre University Hospital, Madrid, Spain
| | - Carlos Álvarez
- Biochemistry Department, 12 de Octubre University Hospital, Madrid, Spain
| | - Luis Manso
- Biochemistry Department, 12 de Octubre University Hospital, Madrid, Spain
| | - Lucia Inglada-Pérez
- Hereditary Endocrine Cancer Group, Human Cancer Genetics Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Mercedes Robledo
- Hereditary Endocrine Cancer Group, Human Cancer Genetics Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Cristina Rodríguez-Antona
- Hereditary Endocrine Cancer Group, Human Cancer Genetics Programme, Spanish National Cancer Research Centre (CNIO), Madrid, Spain
- Centro de Investigación Biomédica en Red de Enfermedades Raras (CIBERER), Madrid, Spain
| | - Eva Ciruelos
- Medical Oncology Department, 12 de Octubre University Hospital, Madrid, Spain
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Li X, Oprea-Ilies GM, Krishnamurti U. New Developments in Breast Cancer and Their Impact on Daily Practice in Pathology. Arch Pathol Lab Med 2017; 141:490-498. [DOI: 10.5858/arpa.2016-0288-sa] [Citation(s) in RCA: 38] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
Advances in research have transformed our understanding of breast cancers and have altered the daily practice of pathology. Theranostic evaluations performed by pathologists are now critical in triaging the patients into appropriate treatment groups, as are new guidelines that were recently established for the evaluation of HER2/neu gene amplification. Emerging molecular classifications of breast cancers bring novel perspectives to the assessment of individual cases, and opportunities for better treatments. Molecular studies have particularly shed light on distinct biological subsets of triple-negative breast cancers, for which new targeted therapies are being developed. The prognostic and therapeutic utility of new histopathologic parameters, such as tumor-infiltrating lymphocytes, are also being elucidated, and new protocols have been devised for the pathologic evaluation of breast specimens that have undergone neoadjuvant treatment. Novel clinical practices, such as radioactive seed localization, also affect the way breast specimens are processed and evaluated. In this brief review, we highlight the developments that are most relevant to pathology and are changing or could potentially impact our daily practice.
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Affiliation(s)
| | | | - Uma Krishnamurti
- From the Department of Pathology and Laboratory Medicine, Emory University, Atlanta, Gerogia
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Activation of PI3K/Akt/mTOR signaling in the tumor stroma drives endocrine therapy-dependent breast tumor regression. Oncotarget 2016; 6:22081-97. [PMID: 26098779 PMCID: PMC4673148 DOI: 10.18632/oncotarget.4203] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/21/2015] [Accepted: 05/27/2015] [Indexed: 12/21/2022] Open
Abstract
Improved efficacy of neoadjuvant endocrine-targeting therapies in luminal breast carcinomas could be achieved with optimal use of pathway targeting agents. In a mouse model of ductal breast carcinoma we identify a tumor regressive stromal reaction that is induced by neoadjuvant endocrine therapy. This reparative reaction is characterized by tumor neovascularization accompanied by infiltration of immune cells and carcinoma-associated fibroblasts that stain for phosphorylated ribosomal protein S6 (pS6), downstream the PI3K/Akt/mTOR pathway. While tumor variants with higher PI3K/Akt/mTOR activity respond well to a combination of endocrine and PI3K/Akt/mTOR inhibitors, tumor variants with lower PI3K/Akt/mTOR activity respond more poorly to the combination therapy than to the endocrine therapy alone, associated with inhibition of stromal pS6 and the reparative reaction. In human breast cancer xenografts we confirm that such differential sensitivity to therapy is primarily determined by the level of PI3K/Akt/mTOR in tumor cells. We further show that the clinical response of breast cancer patients undergoing neoadjuvant endocrine therapy is associated with the reparative stromal reaction. We conclude that tumor level and localization of pS6 are associated with therapeutic response in breast cancer and represent biomarkers to distinguish which tumors will benefit from the incorporation of PI3K/Akt/mTOR inhibitors with neoadjuvant endocrine therapy.
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Huang DP, Luo RC. MLF1IP is correlated with progression and prognosis in luminal breast cancer. Biochem Biophys Res Commun 2016; 477:923-926. [PMID: 27378428 DOI: 10.1016/j.bbrc.2016.06.159] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2016] [Accepted: 06/30/2016] [Indexed: 11/15/2022]
Abstract
Myeloid leukemia factor 1-interacting protein (MLF1IP) has been found to be involved in the progression of several malignancies. The potential correlation between MLF1IP and clinical outcome in patients with luminal breast cancer, however, remains unknown. In the present study, we demonstrated that MLF1IP was significantly upregulated in luminal breast cancer tissue compared with adjacent normal tissue both in validated cohort and TCGA cohort. Upregulated expression of MLF1IP was correlated with more often lymph node metastasis and negative progesterone receptor expression in TCGA cohorts. Kaplan-Meier analysis indicated that patients with high MLF1IP expression had significantly lower overall survival. Moreover, multivariate analysis revealed that high MLF1IP expression was independent high risk factor as well as old age (>60) and distant metastasis. This study provides new insights and evidences that MLF1IP over-expression plays important roles in progression of luminal breast cancer. However, the precise cellular mechanisms for MLF1IP in luminal breast cancer need to be further explored.
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Affiliation(s)
- Du-Ping Huang
- Cancer Center, TCM-Integrated Hospital of Southern Medical University, Guangzhou, Guangdong, PR China.
| | - Rong-Cheng Luo
- Cancer Center, TCM-Integrated Hospital of Southern Medical University, Guangzhou, Guangdong, PR China.
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Sabine VS, Crozier C, Brookes CL, Drake C, Piper T, van de Velde CJH, Hasenburg A, Kieback DG, Markopoulos C, Dirix L, Seynaeve C, Rea DW, Bartlett JMS. Mutational analysis of PI3K/AKT signaling pathway in tamoxifen exemestane adjuvant multinational pathology study. J Clin Oncol 2015; 32:2951-8. [PMID: 25071141 DOI: 10.1200/jco.2013.53.8272] [Citation(s) in RCA: 89] [Impact Index Per Article: 9.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
PURPOSE Deregulation of key PI3K/AKT pathway genes may contribute to endocrine resistance in breast cancer (BC). PIK3CA is the most frequently mutated gene in luminal BC (35%); however, the effect of mutations in helical versus kinase domains remains controversial. We hypothesize that improved outcomes occur in patients with estrogen receptor–positive (ER positive) BC receiving endocrine therapy and possessing PIK3CA mutations. MATERIALS AND METHODS DNA was extracted from 4,540 formalin-fixed paraffin-embedded BC samples from the Exemestane Versus Tamoxifen-Exemestane pathology study. Mutational analyses were performed for 25 mutations (PIK3CAx10, AKT1x1, KRASx5, HRASx3, NRASx2 and BRAFx4). RESULTS PIK3CA mutations were frequent (39.8%), whereas RAS/RAF mutations were rare (1%). In univariable analyses PIK3CA mutations were associated with significantly improved 5-year distant relapse-free survival (DRFS; HR, 0.76; 95% CI, 0.63 to 0.91; P = .003). However, a multivariable analysis correcting for known clinical and biologic prognostic factors failed to demonstrate that PIK3CA mutation status is an independent prognostic marker for DRFS (HR, 0.92; 95% CI, 0.75 to 1.12; P = .4012). PIK3CA mutations were more frequent in low-risk luminal BCs (e.g., grade 1 nodev 3, node-negative v -positive), confounding the relationship between mutations and outcome. CONCLUSION PIK3CA mutations are present in approximately 40% of luminal BCs but are not an independent predictor of outcome in the context of endocrine therapy, whereas RAS/RAF mutations are rare inluminal BC. A complex relationship between low-risk cancers and PIK3CA mutations was identified. Although the PI3K/AKT pathway remains a viable therapeutic target as the result of ahigh mutation frequency, PIK3CA mutations do not seem to affect residual risk following treatment with endocrine therapy.
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Gombos A, Barthélémy P, Awada A. Evaluating the pharmacokinetics and pharmacodynamics of everolimus for treating breast cancer. Expert Opin Drug Metab Toxicol 2015; 11:823-34. [PMID: 25659402 DOI: 10.1517/17425255.2015.1013464] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
INTRODUCTION The aberrant activation of the phosphoinositide 3-kinase-Akt-mTOR signaling pathway is a common mechanism of resistance to endocrine therapy and human epidermal growth factor receptor 2 (HER2)-targeted treatments in breast cancer. Data from large clinical trials have shown that the combination of everolimus , an orally bioavailable mTOR inhibitor with exemestane improves outcome of metastatic breast cancer resistant to non-steroidal aromatase inhibitors. On the other hand, the addition of everolimus to trastuzumab in order to overcome resistance did not show meaningful clinical benefit in recent reported Phase III clinical trials. Everolimus has a favorable pharmacokinetic (PK) profile in early breast cancer studies. The association of endocrine therapy and HER2-targeted agents did not influence the main PK parameters of the drugs. AREAS COVERED This review article focuses on the biological rationale of using everolimus in breast cancer and on latest advances in the field of everolimus-based combinations with an emphasis on the PK and pharmacodynamic parameters of the drug throughout different studies. EXPERT OPINION Better identification of patients who sustain benefit or who are resistant to everolimus-based combinations in the treatment of advanced breast cancer remains an unmet need. New combination strategies based on the understanding of resistance mechanisms and intracellular feedback loops should be studied further in the future.
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Affiliation(s)
- Andrea Gombos
- Université Libre de Bruxelles, Institut Jules Rue Héger-Bordet 1 , Medical Oncology Clinic , Rue Héger 1, Brussels 1000 , Belgium
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Yan F, Yu Y, Chow DC, Palzkill T, Madoux F, Hodder P, Chase P, Griffin PR, O'Malley BW, Lonard DM. Identification of verrucarin a as a potent and selective steroid receptor coactivator-3 small molecule inhibitor. PLoS One 2014; 9:e95243. [PMID: 24743578 PMCID: PMC3990629 DOI: 10.1371/journal.pone.0095243] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2014] [Accepted: 03/24/2014] [Indexed: 12/22/2022] Open
Abstract
Members of the steroid receptor coactivator (SRC) family are overexpressed in numerous types of cancers. In particular, steroid receptor coactivator 3 (SRC-3) has been recognized as a critical coactivator associated with tumor initiation, progression, recurrence, metastasis, and chemoresistance where it interacts with multiple nuclear receptors and other transcription factors to enhance their transcriptional activities and facilitate cross-talk between pathways that stimulate cancer progression. Because of its central role as an integrator of growth signaling pathways, development of small molecule inhibitors (SMIs) against SRCs have the potential to simultaneously disrupt multiple signal transduction networks and transcription factors involved in tumor progression. Here, high-throughput screening was performed to identify compounds able to inhibit the intrinsic transcriptional activities of the three members of the SRC family. Verrucarin A was identified as a SMI that can selectively promote the degradation of the SRC-3 protein, while affecting SRC-1 and SRC-2 to a lesser extent and having no impact on CARM-1 and p300 protein levels. Verrucarin A was cytotoxic toward multiple types of cancer cells at low nanomolar concentrations, but not toward normal liver cells. Moreover, verrucarin A was able to inhibit expression of the SRC-3 target genes MMP2 and MMP13 and attenuated cancer cell migration. We found that verrucarin A effectively sensitized cancer cells to treatment with other anti-cancer drugs. Binding studies revealed that verrucarin A does not bind directly to SRC-3, suggesting that it inhibits SRC-3 through its interaction with an upstream effector. In conclusion, unlike other SRC SMIs characterized by our laboratory that directly bind to SRCs, verrucarin A is a potent and selective SMI that blocks SRC-3 function through an indirect mechanism.
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Affiliation(s)
- Fei Yan
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Yang Yu
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Dar-Chone Chow
- Department of Pharmacology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Timothy Palzkill
- Department of Pharmacology, Baylor College of Medicine, Houston, Texas, United States of America
| | - Franck Madoux
- Department of Molecular Therapeutics, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Peter Hodder
- Department of Molecular Therapeutics, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Peter Chase
- Department of Molecular Therapeutics, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Patrick R. Griffin
- Department of Molecular Therapeutics, The Scripps Research Institute, Scripps Florida, Jupiter, Florida, United States of America
| | - Bert W. O'Malley
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
| | - David M. Lonard
- Department of Molecular and Cellular Biology, Baylor College of Medicine, Houston, Texas, United States of America
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Bilici A. Treatment options in patients with metastatic gastric cancer: current status and future perspectives. World J Gastroenterol 2014; 20:3905-15. [PMID: 24744580 PMCID: PMC3983446 DOI: 10.3748/wjg.v20.i14.3905] [Citation(s) in RCA: 65] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/07/2013] [Revised: 12/27/2013] [Accepted: 01/20/2014] [Indexed: 02/06/2023] Open
Abstract
Despite advances in the treatment of gastric cancer, it remains the world's second highest cause of cancer death. As gastric cancer is often diagnosed at an advanced stage, systemic chemotherapy is the mainstay of treatment for these patients. However, no standard palliative chemotherapy regimen has been accepted for patients with metastatic gastric cancer. Palliative chemotherapy including fluoropyrimidine, platin compounds, docetaxel and epirubicin prolongs survival, and improves a high quality of life to a greater extent than best supportive care. The number of clinical investigations associated with targeted agents has recently increased. Agents targeting the epidermal growth factor receptor 1 and human epidermal growth factor receptor 2 (HER2) have been widely tested. Trastuzumab was the first target drug developed, and pivotal phase III trials showed improved survival when trastuzumab was integrated into cisplatin/fluoropyrimidine-based chemotherapy in patients with metastatic gastric cancer. Trastuzumab in combination with chemotherapy was thus approved to be a new standard of care for patients with HER2-positive advanced esophagogastric adenocarcinoma. Thus, the evaluation of HER2 status in all patients with metastatic gastroesophageal adenocarcinoma should be considered. Other agents targeting vascular endothelial growth factor, mammalian target of rapamycin, and other biological pathways have also been investigated in clinical trials, but showed little impact on the survival of patients. In this review, systemic chemotherapy and targeted therapies for metastatic gastric cancer in the first- and second-line setting are summarized in the light of recent advances.
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Jordan NJ, Dutkowski CM, Barrow D, Mottram HJ, Hutcheson IR, Nicholson RI, Guichard SM, Gee JMW. Impact of dual mTORC1/2 mTOR kinase inhibitor AZD8055 on acquired endocrine resistance in breast cancer in vitro. Breast Cancer Res 2014; 16:R12. [PMID: 24457069 PMCID: PMC3978713 DOI: 10.1186/bcr3604] [Citation(s) in RCA: 48] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2013] [Accepted: 01/15/2014] [Indexed: 12/18/2022] Open
Abstract
Introduction Upregulation of PI3K/Akt/mTOR signalling in endocrine-resistant breast cancer (BC) has identified mTOR as an attractive target alongside anti-hormones to control resistance. RAD001 (everolimus/Afinitor®), an allosteric mTOR inhibitor, is proving valuable in this setting; however, some patients are inherently refractory or relapse during treatment requiring alternative strategies. Here we evaluate the potential for novel dual mTORC1/2 mTOR kinase inhibitors, exemplified by AZD8055, by comparison with RAD001 in ER + endocrine resistant BC cells. Methods In vitro models of tamoxifen (TamR) or oestrogen deprivation resistance (MCF7-X) were treated with RAD001 or AZD8055 alone or combined with anti-hormone fulvestrant. Endpoints included growth, cell proliferation (Ki67), viability and migration, with PI3K/AKT/mTOR signalling impact monitored by Western blotting. Potential ER cross-talk was investigated by immunocytochemistry and RT-PCR. Results RAD001 was a poor growth inhibitor of MCF7-derived TamR and MCF7-X cells (IC50 ≥1 μM), rapidly inhibiting mTORC1 but not mTORC2/AKT signalling. In contrast AZD8055, which rapidly inhibited both mTORC1 and mTORC2/AKT activity, was a highly effective (P <0.001) growth inhibitor of TamR (IC50 18 nM) and MCF7-X (IC50 24 nM), and of a further T47D-derived tamoxifen resistant model T47D-tamR (IC50 19 nM). AZD8055 significantly (P <0.05) inhibited resistant cell proliferation, increased cell death and reduced migration. Furthermore, dual treatment of TamR or MCF7-X cells with AZD8055 plus fulvestrant provided superior control of resistant growth versus either agent alone (P <0.05). Co-treating with AZD8055 alongside tamoxifen (P <0.01) or oestrogen deprivation (P <0.05) also effectively inhibited endocrine responsive MCF-7 cells. Although AZD8055 inhibited oestrogen receptor (ER) ser167 phosphorylation in TamR and MCF7-X, it had no effect on ER ser118 activity or expression of several ER-regulated genes, suggesting the mTOR kinase inhibitor impact was largely ER-independent. The capacity of AZD8055 for ER-independent activity was further evidenced by growth inhibition (IC5018 and 20 nM) of two acquired fulvestrant resistant models lacking ER. Conclusions This is the first report demonstrating dual mTORC1/2 mTOR kinase inhibitors have potential to control acquired endocrine resistant BC, even under conditions where everolimus fails. Such inhibitors may prove of particular benefit when used alongside anti-hormonal treatment as second-line therapy in endocrine resistant disease, and also potentially alongside anti-hormones during the earlier endocrine responsive phase to hinder development of resistance.
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