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Identification, Culture and Targeting of Cancer Stem Cells. Life (Basel) 2022; 12:life12020184. [PMID: 35207472 PMCID: PMC8879966 DOI: 10.3390/life12020184] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/31/2021] [Revised: 01/19/2022] [Accepted: 01/20/2022] [Indexed: 12/12/2022] Open
Abstract
Chemoresistance, tumor progression, and metastasis are features that are frequently seen in cancer that have been associated with cancer stem cells (CSCs). These cells are a promising target in the future of cancer therapy but remain largely unknown. Deregulation of pathways that govern stemness in non-tumorigenic stem cells (SCs), such as Notch, Wnt, and Hedgehog pathways, has been described in CSC pathogenesis, but it is necessary to conduct further studies to discover potential new therapeutic targets. In addition, some markers for the identification and characterization of CSCs have been suggested, but the search for specific CSC markers in many cancer types is still under development. In addition, methods for CSC cultivation are also under development, with great heterogeneity existing in the protocols used. This review focuses on the most recent aspects of the identification, characterization, cultivation, and targeting of human CSCs, highlighting the advances achieved in the clinical implementation of therapies targeting CSCs and remarking those potential areas where more research is still required.
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Gwynne WD, Shakeel MS, Girgis-Gabardo A, Hassell JA. The Role of Serotonin in Breast Cancer Stem Cells. Molecules 2021; 26:molecules26113171. [PMID: 34073226 PMCID: PMC8198186 DOI: 10.3390/molecules26113171] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/23/2021] [Revised: 05/21/2021] [Accepted: 05/24/2021] [Indexed: 02/07/2023] Open
Abstract
Breast tumors were the first tumors of epithelial origin shown to follow the cancer stem cell model. The model proposes that cancer stem cells are uniquely endowed with tumorigenic capacity and that their aberrant differentiation yields non-tumorigenic progeny, which constitute the bulk of the tumor cell population. Breast cancer stem cells resist therapies and seed metastases; thus, they account for breast cancer recurrence. Hence, targeting these cells is essential to achieve durable breast cancer remissions. We identified compounds including selective antagonists of multiple serotonergic system pathway components required for serotonin biosynthesis, transport, activity via multiple 5-HT receptors (5-HTRs), and catabolism that reduce the viability of breast cancer stem cells of both mouse and human origin using multiple orthologous assays. The molecular targets of the selective antagonists are expressed in breast tumors and breast cancer cell lines, which also produce serotonin, implying that it plays a required functional role in these cells. The selective antagonists act synergistically with chemotherapy to shrink mouse mammary tumors and human breast tumor xenografts primarily by inducing programmed tumor cell death. We hypothesize those serotonergic proteins of diverse activity function by common signaling pathways to maintain cancer stem cell viability. Here, we summarize our recent findings and the relevant literature regarding the role of serotonin in breast cancer.
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Affiliation(s)
- William D. Gwynne
- Department of Surgery, McMaster University, Hamilton, ON L8S 4L8, Canada;
| | - Mirza S. Shakeel
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada; (M.S.S.); (A.G.-G.)
| | - Adele Girgis-Gabardo
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada; (M.S.S.); (A.G.-G.)
| | - John A. Hassell
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, ON L8S 4L8, Canada; (M.S.S.); (A.G.-G.)
- Correspondence:
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Gwynne WD, Shakeel MS, Girgis-Gabardo A, Kim KH, Ford E, Dvorkin-Gheva A, Aarts C, Isaac M, Al-Awar R, Hassell JA. Antagonists of the serotonin receptor 5A target human breast tumor initiating cells. BMC Cancer 2020; 20:724. [PMID: 32758183 PMCID: PMC7404930 DOI: 10.1186/s12885-020-07193-6] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/27/2020] [Accepted: 07/17/2020] [Indexed: 12/11/2022] Open
Abstract
Background Breast tumor initiating cells (BTIC) are stem-like cells that initiate and sustain tumor growth, and drive disease recurrence. Identifying therapies targeting BTIC has been hindered due primarily to their scarcity in tumors. We previously reported that BTIC frequency ranges between 15% and 50% in multiple mammary tumors of 3 different transgenic mouse models of breast cancer and that this frequency is maintained in tumor cell populations cultured in serum-free, chemically defined media as non-adherent tumorspheres. The latter enabled high-throughput screening of small molecules for their capacity to affect BTIC survival. Antagonists of several serotonin receptors (5-HTRs) were among the hit compounds. The most potent compound we identified, SB-699551, selectively binds to 5-HT5A, a Gαi/o protein coupled receptor (GPCR). Methods We evaluated the activity of structurally unrelated selective 5-HT5A antagonists using multiple orthogonal assays of BTIC frequency. Thereafter we used a phosphoproteomic approach to uncover the mechanism of action of SB-699551. To validate the molecular target of the antagonists, we used the CRISPR-Cas9 gene editing technology to conditionally knockout HTR5A in a breast tumor cell line. Results We found that selective antagonists of 5-HT5A reduced the frequency of tumorsphere initiating cells residing in breast tumor cell lines and those of patient-derived xenografts (PDXs) that we established. The most potent compound among those tested, SB-699551, reduced the frequency of BTIC in ex vivo assays and acted in concert with chemotherapy to shrink human breast tumor xenografts in vivo. Our phosphoproteomic experiments established that exposure of breast tumor cells to SB-699551 elicited signaling changes in the canonical Gαi/o-coupled pathway and the phosphoinositide 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) axis. Moreover, conditional mutation of the HTR5A gene resulted in the loss of tumorsphere initiating cells and BTIC thus mimicking the effect of SB-699551. Conclusions Our data provide genetic, pharmacological and phosphoproteomic evidence consistent with the on-target activity of SB-699551. The use of such agents in combination with cytotoxic chemotherapy provides a novel therapeutic approach to treat breast cancer.
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Affiliation(s)
- William D Gwynne
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada
| | - Mirza S Shakeel
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada
| | - Adele Girgis-Gabardo
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada
| | - Kwang H Kim
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada
| | - Emily Ford
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada
| | - Anna Dvorkin-Gheva
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada
| | - Craig Aarts
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada
| | - Methvin Isaac
- Drug Discovery Group, The Ontario Institute for Cancer Research, 661 University Ave Suite 510, Toronto, ON, M5G 0A3, Canada
| | - Rima Al-Awar
- Drug Discovery Group, The Ontario Institute for Cancer Research, 661 University Ave Suite 510, Toronto, ON, M5G 0A3, Canada
| | - John A Hassell
- Department of Biochemistry and Biomedical Sciences, McMaster University, 1280 Main Street West, Hamilton, ON, L8S 4L8, Canada.
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Gwynne WD, Shakeel MS, Wu J, Hallett RM, Girgis-Gabardo A, Dvorkin-Gheva A, Hassell JA. Monoamine oxidase-A activity is required for clonal tumorsphere formation by human breast tumor cells. Cell Mol Biol Lett 2019; 24:59. [PMID: 31754354 PMCID: PMC6852929 DOI: 10.1186/s11658-019-0183-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/11/2019] [Accepted: 10/01/2019] [Indexed: 12/15/2022] Open
Abstract
Background Breast tumor growth and recurrence are driven by an infrequent population of breast tumor-initiating cells (BTIC). We and others have reported that the frequency of BTIC is orders of magnitude higher when breast tumor cells are propagated in vitro as clonal spheres, termed tumorspheres, by comparison to adherent cells. We exploited the latter to screen > 35,000 small molecules to identify agents capable of targeting BTIC. We unexpectedly discovered that selective antagonists of serotonin signaling were among the hit compounds. To better understand the relationship between serotonin and BTIC we expanded our analysis to include monoamine oxidase-A (MAO-A), an enzyme that metabolizes serotonin. Methods We used the Nanostring technology and Western blotting to determine whether MAO-A is expressed in human breast tumor cell lines cultured as tumorspheres by comparison to those grown as adherent cells. We then determined whether MAO-A activity is required for tumorsphere formation, a surrogate in vitro assay for BTIC, by assessing whether selective MAO-A inhibitors affect the frequency of tumorsphere-forming cells. To learn whether MAO-A expression in breast tumor cells is associated with other reported properties of BTIC such as anticancer drug resistance or breast tumor recurrence, we performed differential gene expression analyses using publicly available transcriptomic datasets. Results Tumorspheres derived from human breast tumor cell lines representative of every breast cancer clinical subtype displayed increased expression of MAO-A transcripts and protein by comparison to adherent cells. Surprisingly, inhibition of MAO-A activity with selective inhibitors reduced the frequency of tumorsphere-forming cells. We also found that increased MAO-A expression is a common feature of human breast tumor cell lines that have acquired anticancer drug resistance and is associated with poor recurrence-free survival (RFS) in patients that experienced high-grade, ER-negative (ER−) breast tumors. Conclusions Our data suggests that MAO-A activity is required for tumorsphere formation and that its expression in breast tumor cells is associated with BTIC-related properties. The discovery that a selective MAO-A inhibitor targets tumorsphere-forming cells with potencies in the nanomolar range provides the first evidence of this agent’s anticancer property. These data warrant further investigation of the link between MAO-A and BTIC.
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Affiliation(s)
- William D Gwynne
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario Canada
| | - Mirza S Shakeel
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario Canada
| | - Jianhan Wu
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario Canada
| | - Robin M Hallett
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario Canada
| | - Adele Girgis-Gabardo
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario Canada
| | - Anna Dvorkin-Gheva
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario Canada
| | - John A Hassell
- Department of Biochemistry and Biomedical Sciences, McMaster University, Hamilton, Ontario Canada
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Chitwood CA, Dietzsch C, Jacobs G, McArdle T, Freeman BT, Banga A, Noubissi FK, Ogle BM. Breast tumor cell hybrids form spontaneously in vivo and contribute to breast tumor metastases. APL Bioeng 2018; 2:031907. [PMID: 31069316 PMCID: PMC6324215 DOI: 10.1063/1.5024744] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2018] [Accepted: 07/18/2018] [Indexed: 12/15/2022] Open
Abstract
Cancer cell fusion was suggested as a mechanism of metastasis about a century ago. Since then, many additional modes of material transfer (i.e., tunneling nanotubes, and exosomes) to generate cell hybrids have been identified. However, studies documenting spontaneous tumor hybrid formation in vivo as a mechanism that enables metastasis are still lacking. Here, we tested whether spontaneous hybrid formation in vivo contributes to bona fide metastatic tumors. We first used single cell RNASeq to analyze the gene expression profile of spontaneously formed cancer cell-stromal hybrids, and results revealed that hybrids exhibit a clustering pattern that is distinct from either parental cell and suggestive of substantial diversity of individual hybrids. Despite the newly gained diversity, hybrids can retain expression of critical genes of each parental cell. To assess the biological impact of cancer cell hybrids in vivo, we transfected murine mammary tumor cells, isolated from FVB/N-Tg(MMTV-PyVT)634Mul/J mice (PyVT) with Cre recombinase prior to injection to the murine fat pad of FVB.129S6(B6)-Gt(ROSA)26Sortm1(Luc)Kael/J mice such that luciferase expression is induced with hybrid formation; luciferase expression was tracked for up to four months. We observed that hybrid formation occurs spontaneously in vivo and that a significantly higher number of hybrids reside in metastases compared to the primary tumor, supporting the possibility that hybrids can emerge from the primary tumor and proliferate to help create a new tumor at a distant site. Additional studies are now warranted to delineate the mechanisms of cancer cell hybrid transit to metastases since drugs to inhibit hybrid formation might prevent metastatic spread.
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Affiliation(s)
| | | | | | | | | | | | - Felicite K Noubissi
- Department of Biology/RCMI, Jackson State University, Jackson, Mississippi 39217, USA
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Toosi BM, El Zawily A, Truitt L, Shannon M, Allonby O, Babu M, DeCoteau J, Mousseau D, Ali M, Freywald T, Gall A, Vizeacoumar FS, Kirzinger MW, Geyer CR, Anderson DH, Kim T, Welm AL, Siegel P, Vizeacoumar FJ, Kusalik A, Freywald A. EPHB6 augments both development and drug sensitivity of triple-negative breast cancer tumours. Oncogene 2018; 37:4073-4093. [PMID: 29700392 PMCID: PMC6062499 DOI: 10.1038/s41388-018-0228-x] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2017] [Revised: 01/30/2018] [Accepted: 02/27/2018] [Indexed: 12/20/2022]
Abstract
Triple-negative breast cancer (TNBC) tumours that lack expression of oestrogen, and progesterone receptors, and do not overexpress the HER2 receptor represent the most aggressive breast cancer subtype, which is characterised by the resistance to therapy in frequently relapsing tumours and a high rate of patient mortality. This is likely due to the resistance of slowly proliferating tumour-initiating cells (TICs), and understanding molecular mechanisms that control TICs behaviour is crucial for the development of effective therapeutic approaches. Here, we present our novel findings, indicating that an intrinsically catalytically inactive member of the Eph group of receptor tyrosine kinases, EPHB6, partially suppresses the epithelial–mesenchymal transition in TNBC cells, while also promoting expansion of TICs. Our work reveals that EPHB6 interacts with the GRB2 adapter protein and that its effect on enhancing cell proliferation is mediated by the activation of the RAS-ERK pathway, which allows it to elevate the expression of the TIC-related transcription factor, OCT4. Consistent with this, suppression of either ERK or OCT4 activities blocks EPHB6-induced pro-proliferative responses. In line with its ability to trigger propagation of TICs, EPHB6 accelerates tumour growth, potentiates tumour initiation and increases TIC populations in xenograft models of TNBC. Remarkably, EPHB6 also suppresses tumour drug resistance to DNA-damaging therapy, probably by forcing TICs into a more proliferative, drug-sensitive state. In agreement, patients with higher EPHB6 expression in their tumours have a better chance for recurrence-free survival. These observations describe an entirely new mechanism that governs TNBC and suggest that it may be beneficial to enhance EPHB6 action concurrent with applying a conventional DNA-damaging treatment, as it would decrease drug resistance and improve tumour elimination.
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Affiliation(s)
- Behzad M Toosi
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Amr El Zawily
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada.,Faculty of Science, Damanhour University, Damanhour, 22516, Egypt
| | - Luke Truitt
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Matthew Shannon
- Department of Computer Science, University of Saskatchewan, 176 Thorvaldsen Bldg., 110 Science Place, Saskatoon, SK, S7N 5C9, Canada
| | - Odette Allonby
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Mohan Babu
- Department of Chemistry and Biochemistry, Faculty of Science, University of Regina, Room 232, Research and Innovation Centre, Regina, SK, S4S 0A2, Canada
| | - John DeCoteau
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Darrell Mousseau
- Cell Signaling Laboratory, Department of Psychiatry, College of Medicine, University of Saskatchewan, GB41 Health Sciences Building, 107 Wiggins Road, Saskatoon, SK, S7N 5E5, Canada
| | - Mohsin Ali
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Tanya Freywald
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Amanda Gall
- Department of Biochemistry, College of Medicine, University of Saskatchewan, Room 2D01 Health Science Building, 107 Wiggins Road, Saskatoon, SK, S7N 5E5, Canada
| | - Frederick S Vizeacoumar
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Morgan W Kirzinger
- Department of Computer Science, University of Saskatchewan, 176 Thorvaldsen Bldg., 110 Science Place, Saskatoon, SK, S7N 5C9, Canada
| | - C Ronald Geyer
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada
| | - Deborah H Anderson
- Saskatchewan Cancer Agency, University of Saskatchewan, 4D30.2 Health Sciences Building, 107 Wiggins Road, Saskatoon, SK, S7N 5E5, Canada
| | - TaeHyung Kim
- Donnelly Centre for Cellular and Biomolecular Research and Department of Computer Science, University of Toronto, Toronto, ON, M5S 3E1, Canada
| | - Alana L Welm
- Department of Oncological Sciences, Huntsman Cancer Institute, University of Utah, 2000 Circle of Hope, Salt Lake City, UT, 84112, USA
| | - Peter Siegel
- Goodman Cancer Research Centre, McGill University, 1160 Pine Avenue West, Montreal, QC, H3A 1A3, Canada
| | - Franco J Vizeacoumar
- Saskatchewan Cancer Agency, University of Saskatchewan, 4D30.2 Health Sciences Building, 107 Wiggins Road, Saskatoon, SK, S7N 5E5, Canada
| | - Anthony Kusalik
- Department of Computer Science, University of Saskatchewan, 176 Thorvaldsen Bldg., 110 Science Place, Saskatoon, SK, S7N 5C9, Canada.
| | - Andrew Freywald
- Department of Pathology and Laboratory Medicine, College of Medicine, University of Saskatchewan, Room 2841, Royal University Hospital, 103 Hospital Drive, Saskatoon, SK, S7N 0W8, Canada.
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Gwynne WD, Hallett RM, Girgis-Gabardo A, Bojovic B, Dvorkin-Gheva A, Aarts C, Dias K, Bane A, Hassell JA. Serotonergic system antagonists target breast tumor initiating cells and synergize with chemotherapy to shrink human breast tumor xenografts. Oncotarget 2018; 8:32101-32116. [PMID: 28404880 PMCID: PMC5458271 DOI: 10.18632/oncotarget.16646] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/25/2016] [Accepted: 03/01/2017] [Indexed: 12/24/2022] Open
Abstract
Breast tumors comprise an infrequent tumor cell population, termed breast tumor initiating cells (BTIC), which sustain tumor growth, seed metastases and resist cytotoxic therapies. Hence therapies are needed to target BTIC to provide more durable breast cancer remissions than are currently achieved. We previously reported that serotonergic system antagonists abrogated the activity of mouse BTIC resident in the mammary tumors of a HER2-overexpressing model of breast cancer. Here we report that antagonists of serotonin (5-hydroxytryptamine; 5-HT) biosynthesis and activity, including US Federal Food and Drug Administration (FDA)-approved antidepressants, targeted BTIC resident in numerous breast tumor cell lines regardless of their clinical or molecular subtype. Notably, inhibitors of tryptophan hydroxylase 1 (TPH1), required for 5-HT biosynthesis in select non-neuronal cells, the serotonin reuptake transporter (SERT) and several 5-HT receptors compromised BTIC activity as assessed by functional sphere-forming assays. Consistent with these findings, human breast tumor cells express TPH1, 5-HT and SERT independent of their molecular or clinical subtype. Exposure of breast tumor cells ex vivo to sertraline (Zoloft), a selective serotonin reuptake inhibitor (SSRI), reduced BTIC frequency as determined by transplanting drug-treated tumor cells into immune-compromised mice. Moreover, another SSRI (vilazodone; Viibryd) synergized with chemotherapy to shrink breast tumor xenografts in immune-compromised mice by inhibiting tumor cell proliferation and inducing their apoptosis. Collectively our data suggest that antidepressants in combination with cytotoxic anticancer therapies may be an appropriate treatment regimen for testing in clinical trials.
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Affiliation(s)
- William D Gwynne
- Department of Biochemistry and Biomedical Sciences, McMaster University, Canada
| | - Robin M Hallett
- Department of Biochemistry and Biomedical Sciences, McMaster University, Canada
| | | | - Bojana Bojovic
- Department of Biochemistry and Biomedical Sciences, McMaster University, Canada
| | - Anna Dvorkin-Gheva
- Department of Pathology and Molecular Medicine, McMaster University, Canada
| | - Craig Aarts
- Department of Biochemistry and Biomedical Sciences, McMaster University, Canada
| | - Kay Dias
- Department of Pathology and Molecular Medicine, McMaster University, Canada
| | - Anita Bane
- Department of Pathology and Molecular Medicine, McMaster University, Canada
| | - John A Hassell
- Department of Biochemistry and Biomedical Sciences, McMaster University, Canada.,Department of Pathology and Molecular Medicine, McMaster University, Canada
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Serotonin transporter antagonists target tumor-initiating cells in a transgenic mouse model of breast cancer. Oncotarget 2018; 7:53137-53152. [PMID: 27447971 PMCID: PMC5288174 DOI: 10.18632/oncotarget.10614] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2016] [Accepted: 06/09/2016] [Indexed: 12/18/2022] Open
Abstract
Accumulating data suggests that the initiation and progression of human breast tumors is fueled by a rare subpopulation of tumor cells, termed breast tumor-initiating cells (BTIC), which resist radiotherapy and chemotherapy. Consequently, therapies that abrogate BTIC activity are needed to achieve durable cures for breast cancer patients. To identify such therapies we used a sensitive assay to complete a high-throughput screen of small molecules, including approved drugs, with BTIC-rich mouse mammary tumor cell populations. We found that inhibitors of the serotonin reuptake transporter (SERT) and serotonin receptors, which include approved drugs used to treat mood disorders, were potent inhibitors of mouse BTIC activity as determined by functional sphere-forming assays and the initiation of tumor formation by transplant of drug-exposed tumor cells into syngeneic mice. Moreover, sertraline (Zoloft), a selective serotonin reuptake inhibitor (SSRI), synergized with docetaxel (Taxotere) to shrink mouse breast tumors in vivo. Hence drugs targeting the serotonergic system might be repurposed to treat breast cancer patients to afford more durable breast cancer remissions.
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9
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Cbx8 Acts Non-canonically with Wdr5 to Promote Mammary Tumorigenesis. Cell Rep 2016; 16:472-486. [PMID: 27346354 DOI: 10.1016/j.celrep.2016.06.002] [Citation(s) in RCA: 75] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2015] [Revised: 05/04/2016] [Accepted: 05/21/2016] [Indexed: 12/15/2022] Open
Abstract
Chromatin-mediated processes influence the development and progression of breast cancer. Using murine mammary carcinoma-derived tumorspheres as a functional readout for an aggressive breast cancer phenotype, we performed a loss-of-function screen targeting 60 epigenetic regulators. We identified the Polycomb protein Cbx8 as a key regulator of mammary carcinoma both in vitro and in vivo. Accordingly, Cbx8 is overexpressed in human breast cancer and correlates with poor survival. Our genomic analyses revealed that Cbx8 positively regulates Notch signaling by maintaining H3K4me3 levels on Notch-network gene promoters. Ectopic expression of Notch1 partially rescues tumorsphere formation in Cbx8-depleted cells. We find that Cbx8 associates with non-PRC1 complexes containing the H3K4 methyltransferase complex component WDR5, which together regulate Notch gene expression. Thus, our study implicates a key non-canonical role for Cbx8 in promoting breast tumorigenesis.
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Deng T, Liu JC, Chung PED, Uehling D, Aman A, Joseph B, Ketela T, Jiang Z, Schachter NF, Rottapel R, Egan SE, Al-Awar R, Moffat J, Zacksenhaus E. shRNA kinome screen identifies TBK1 as a therapeutic target for HER2+ breast cancer. Cancer Res 2014; 74:2119-30. [PMID: 24487029 DOI: 10.1158/0008-5472.can-13-2138] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022]
Abstract
HER2(+) breast cancer is currently treated with chemotherapy plus anti-HER2 inhibitors. Many patients do not respond or relapse with aggressive metastatic disease. Therefore, there is an urgent need for new therapeutics that can target HER2(+) breast cancer and potentiate the effect of anti-HER2 inhibitors, in particular those that can target tumor-initiating cells (TIC). Here, we show that MMTV-Her2/Neu mammary tumor cells cultured as nonadherent spheres or as adherent monolayer cells select for stabilizing mutations in p53 that "immortalize" the cultures and that, after serial passages, sphere conditions maintain TICs, whereas monolayer cells gradually lose these tumorigenic cells. Using tumorsphere formation as surrogate for TICs, we screened p53-mutant Her2/Neu(+) tumorsphere versus monolayer cells with a lentivirus short hairpin RNA kinome library. We identified kinases such as the mitogen-activated protein kinase and the TGFβR protein family, previously implicated in HER2(+) breast cancer, as well as autophagy factor ATG1/ULK1 and the noncanonical IκB kinase (IKK), TANK-binding kinase 1 (TBK1), which have not been previously linked to HER2(+) breast cancer. Knockdown of TBK1 or pharmacologic inhibition of TBK1 and the related protein, IKKε, suppressed growth of both mouse and human HER2(+) breast cancer cells. TBK1/IKKε inhibition promoted cellular senescence by suppressing p65-NF-κB and inducing p16(Ink4a). In addition, TBK1/IKKε inhibition cooperated with lapatinib, a HER2/EGFR1-targeted drug, to accelerate apoptosis and kill HER2(+) breast cancer cells both in culture and in xenografts. Our results suggest that patients with HER2(+) breast cancer may benefit from anti-TBK1/IKKε plus anti-HER2 combination therapies and establish conditions that can be used to screen for additional TIC-specific inhibitors of HER2(+) breast cancer.
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Affiliation(s)
- Tao Deng
- Authors' Affiliations: Division of Advanced Diagnostics, Toronto General Research Institute-University Health Network; Medicinal Chemistry Platform, Ontario Institute for Cancer Research; The Donnelly Centre, University of Toronto; Program in Developmental and Stem Cell Biology, Department of Molecular Genetics, The Hospital for Sick Children; Ontario Cancer Institute, University of Toronto, and Drug Discovery Program, Department of Pharmacology and Toxicology; Toronto, Ontario, Canada
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