Subject(s)
Early Detection of Cancer/methods , High-Throughput Screening Assays/methods , Neoplasms/radiotherapy , Neoplastic Stem Cells/radiation effects , Biomarkers, Tumor/blood , Cell Survival/radiation effects , Humans , Neoplasm Recurrence, Local/radiotherapy , Radiation Tolerance/radiation effects , Tumor BurdenABSTRACT
BACKGROUND: Tamoxifen is commonly used for breast cancer therapy. However, tamoxifen resistance is an important clinical problem. Continuous treatment with conventional therapy may contribute to cancer progression in recurring cancers through the accumulation of drug-resistant cancer progenitors. METHODS: To investigate signalling mechanisms important for the maintenance and viability of drug-resistant cancer progenitors, we used microarray analysis, PCR array for genes involved in cancer drug resistance and metabolism, flow cytometry, soft agar colony formation assay, in vivo tumourigenicity assay and immunohistochemical analysis using tamoxifen-sensitive and tamoxifen-resistant breast cancer MCF7 cells. RESULTS: Downregulation of CXCR4 signalling by small molecule antagonist AMD3100 specifically inhibits growth of progenitor cell population in MCF7(TAM-R) cells both in vitro and in vivo. Microarray analysis revealed aryl hydrocarbon receptor (AhR) signalling as one of the top networks that is differentially regulated in MCF7(TAM-R) and MCF7 xenograft tumours treated with AMD3100. Further, small molecule antagonists of AhR signalling specifically inhibit the progenitor population in MCF7(TAM-R) cells and growth of MCF7(TAM-R) xenografts in vivo. CONCLUSION: The chemokine receptor CXCR4 maintains a cancer progenitor population in tamoxifen-resistant MCF7 cells through AhR signalling and could be a putative target for the treatment of tamoxifen-resistant breast cancers.
Subject(s)
Antineoplastic Agents, Hormonal/pharmacology , Drug Resistance, Neoplasm/genetics , Receptors, Aryl Hydrocarbon/metabolism , Receptors, CXCR4/genetics , Tamoxifen/pharmacology , ATP Binding Cassette Transporter, Subfamily G, Member 2 , ATP-Binding Cassette Transporters/analysis , Animals , Benzylamines , Breast Neoplasms/drug therapy , Breast Neoplasms/genetics , Cell Line, Tumor , Cyclams , Female , Gene Expression Regulation, Neoplastic , Heterocyclic Compounds/pharmacology , Humans , Mice , Mice, Nude , Neoplasm Proteins/analysis , Neoplasm Transplantation , Neoplastic Stem Cells , Receptors, CXCR4/antagonists & inhibitors , Signal Transduction/drug effects , Transcriptional Activation/drug effects , Transplantation, HeterologousABSTRACT
AIM: To obtain polyclonal antibodies against recombinant proteins recognizing Bcr domain and fusion region of Bcr-Abl and analyze the patterns of intracellular distribution of Bcr and Bcr-Abl proteins in K562 cells of chronic myelogenous leukemia. METHODS: The coding sequences of DH and PH domains of Bcr-Abl were cloned, and the recombinant proteins were expressed in E. coli. The rabbit polyclonal antibodies were produced and used for immunocytochemical study of Bcr and Bcr-Abl localization in K562 cells. RESULTS: The gene constructs containing sequences coding for DH and PH domains of Bcr-Abl have been obtained. The antibodies with relative specificity to corresponding recombinant proteins differ by the patterns of their intracellular reactivity with Bcr- and Bcr-Abl related structures. While Bcr protein is located predominantly perinuclearly, antibody against hybrid Bcr-Abl protein is reacted with the structures in cell periphery, namely on cell membranes. CONCLUSION: Antibodies against DH and PH domains of Bcr-Abl react with proteins located differently in chronic myelogenous leukemia cells. The difference in intracellular localization of Bcr and Bcr-Abl may be attributable to the different domains interacting with different multiprotein complexes.