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Nonlinear growth kinetics of breast cancer stem cells: implications for cancer stem cell targeted therapy.

ABSTRACT: Cancer stem cells (CSCs) have been identified in primary breast cancer tissues and cell lines. The CSC population varies widely among cancerous tissues and cell lines, and is often associated with aggressive breast cancers. Despite of intensive research, how the CSC population is regulated within a tumor is still not well understood so far. In this paper, we present a mathematical model to explore the growth kinetics of CSC population both in vitro and in vivo. Our mathematical models and supporting experiments suggest that there exist non-linear growth kinetics of CSCs and negative feedback mechanisms to control the balance between the population of CSCs and that of non-stem cancer cells. The model predictions can help us explain a few long-standing questions in the field of cancer stem cell research, and can be potentially used to predict the efficicacy of anti-cancer therapy.

SUBMITTER: Liu X

PROVIDER: S-EPMC3747506 | biostudies-literature | 2013

REPOSITORIES: biostudies-literature

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Nonlinear growth kinetics of breast cancer stem cells: implications for cancer stem cell targeted therapy.

Liu Xinfeng X Johnson Sara S Liu Shou S Kanojia Deepak D Yue Wei W Singh Udai P UP Wang Qian Q Wang Qi Q Nie Qing Q Chen Hexin H

Scientific reports 20130101

Cancer stem cells (CSCs) have been identified in primary breast cancer tissues and cell lines. The CSC population varies widely among cancerous tissues and cell lines, and is often associated with aggressive breast cancers. Despite of intensive research, how the CSC population is regulated within a tumor is still not well understood so far. In this paper, we present a mathematical model to explore the growth kinetics of CSC population both in vitro and in vivo. Our mathematical models and suppor ...[more]

PMID: 23959163

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Project description:INTRODUCTION: Triple negative breast cancer is associated with poorer prognosis and unresponsiveness to endocrine and anti-HER2 directed agents. Despite emerging data supporting the use of polyADP-ribose polymerase (PARP) inhibitors, complete and durable responses are rare and exploration of additional targeted therapies is needed. Epidermal growth factor receptor (EGFR) is expressed in triple negative breast cancer and several clinical trials are testing the role of anti-EGFR directed therapy. However, the rate of EGFR mutations is poorly defined. We, therefore, sought to characterize EGFR mutations in triple negative breast cancers. METHODS: Seventy samples were randomly chosen from a cohort of 653 triple negative breast tumours for EGFR mutation analysis. These samples were immunostained for EGFR protein expression and consisted of negatively stained and positively stained cases. DNA was extracted from paraffin blocks and polymerase chain reaction was performed to amplify exon regions 18 to 21 of the EGFR gene. Direct sequencing of the purified PCR products was performed. RESULTS: EGFR mutations were found in 8 of 70 samples (11.4%). Mutations were predominantly exon 19 deletions (4 of 70 samples, 5.7%), which clustered in the region spanning codons 746 to 759 within the kinase domain of EGFR. Two types of exon 19 deletions were seen: a 15 nucleotide deletion (del E746-A750) (2 of 70 samples) and a 24 nucleotide deletion (del S752 - I759) (2 of 70 samples). Other exon 19 mutations observed were the inversion of the complementary strand (1 of 70 samples). Exon 21 mutations included missense substitution, L858R (1 of 70 samples) and T847I (2 of 70 samples). Mutations observed were independent of EGFR protein expression determined by immunohistochemical staining. CONCLUSIONS: This study is among the first to document the presence and estimate the prevalence of EGFR mutations in triple negative breast cancer. These findings have potential implications for the design of clinical trials involving anti-EGFR directed therapy which currently do not select for patients based on presence of activating EGFR mutations, which may hence be underpowered to detect significant benefit in unselected populations. More complete sampling of EGFR mutation status in triple negative breast cancer is needed to determine the true mutation rate.

Project description:BackgroundBreast cancer stem cells (BCSCs) are cells with a higher ability to metastasis and resistance to conventional treatments. They have a phenotype of (CD44high/CD24low) and the unlimited ability for proliferation. Development of strategies to target the BCSC population may lead to the establishment of more effective cancer therapies. Pseudomonas exotoxin A (PE) is a potent cytotoxic protein. CXCR1 promoter provides BCSC and HER2 specificity on transcription level. 5'UTR of the basic fibroblast growth factor-2 (bFGF 5'UTR) provides tumor specificity on translation level. Here, we utilized a mutant form of PE encoding DNA "PE38", CXCR1 promoter and bFGF 5'UTR to target BCSCs.MethodsThe stemness of SK-BR-3, MDA-MB-231 and MCF10A cell lines were evaluated based on the expression of the CD44high/CD24low stem cell signature and the ability to form mammospheres. Then, the cell lines were transfected with constructs encoding luciferase/PE38 under the control of the CMV/CXCR1 promoter with or without bFGF 5'UTR. Luciferase protein expression was evaluated using dual-luciferase reporter assay. PE38 transcript expression was measured by real-time PCR, and the cytotoxic effect of PE38 protein expression was determined by MTT assay.ResultsThe percentage of CD44high/CD24low population did not correlate to mammosphere forming efficiency (MFE). Given that the percentage of CD44 high/CD24 low is not a conclusive BCSC profile, we based our work on the mammosphere assay. However, in comparison with MCF10A, the two tumorigenic cell lines had higher MFE, probably due to their higher BCSC content. Reporter assay and real-time PCR results demonstrated that CXCR1 promoter combined with bFGF 5'UTR increased BCSC-specific gene expression. Meanwhile, tightly regulated expression of PE38 using these two gene regulatory elements resulted in high levels of cell death in the two tumorigenic cell lines while having little toxicity toward normal MCF10A.ConclusionOur data show that PE38, CXCR1 promoter and bFGF 5'UTR in combination can be considered as a promising tool for killer gene therapy of breast cancer.

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Nonlinear growth kinetics of breast cancer stem cells: implications for cancer stem cell targeted therapy.

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Nonlinear growth kinetics of breast cancer stem cells: implications for cancer stem cell targeted therapy.

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