isopropyl-thiogalactoside and Breast-Neoplasms

Endocrine resistance is a major problem with anti-estrogen treatments and how to overcome resistance is a major concern in the clinic. Reliable measurement of cell viability, proliferation, growth inhibition and death is important in screening for drug treatment efficacy in vitro. This report describes and compares commonly used proliferation assays for induced estrogen-responsive MCF-7 breast cancer cell cycle arrest including: determination of cell number by direct counting of viable cells; or fluorescence SYBR®Green (SYBR) DNA labeling; determination of mitochondrial metabolic activity by 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium (MTS) assay; assessment of newly synthesized DNA using 5-ethynyl-2'-deoxyuridine (EdU) nucleoside analog binding and Alexa Fluor® azide visualization by fluorescence microscopy; cell-cycle phase measurement by flow cytometry. Treatment of MCF-7 cells with ICI 182780 (Faslodex), FTY720, serum deprivation or induction of the tumor suppressor p14ARF showed inhibition of cell proliferation determined by the Trypan Blue exclusion assay and SYBR DNA labeling assay. In contrast, the effects of treatment with ICI 182780 or p14ARF-induction were not confirmed using the MTS assay. Cell cycle inhibition by ICI 182780 and p14ARF-induction was further confirmed by flow cytometric analysis and EdU-DNA incorporation. To explore this discrepancy further, we showed that ICI 182780 and p14ARF-induction increased MCF-7 cell mitochondrial activity by MTS assay in individual cells compared to control cells thereby providing a misleading proliferation readout. Interrogation of p14ARF-induction on MCF-7 metabolic activity using TMRE assays and high content image analysis showed that increased mitochondrial activity was concomitant with increased mitochondrial biomass with no loss of mitochondrial membrane potential, or cell death. We conclude that, whilst p14ARF and ICI 182780 stop cell cycle progression, the cells are still viable and potential treatments utilizing these pathways may contribute to drug resistant cells. These experiments demonstrate how the combined measurement of metabolic activity and DNA labeling provides a more reliable interpretation of cancer cell response to treatment regimens.

Topics: Antineoplastic Combined Chemotherapy Protocols; Breast Neoplasms; Cell Count; Cell Cycle; Cell Line, Tumor; Cell Proliferation; Colorimetry; Culture Media, Serum-Free; Deoxyuridine; DNA; Drug Design; Estradiol; Estrogens; Fingolimod Hydrochloride; Fluorescent Dyes; Fulvestrant; Humans; Isopropyl Thiogalactoside; Membrane Potential, Mitochondrial; Mitochondria; Propylene Glycols; Reproducibility of Results; Sphingosine; Tetrazolium Salts; Thiazoles; Tumor Suppressor Protein p14ARF

Retinoic acid activation of retinoic acid receptor alpha (RARalpha) induces protein kinase Calpha (PKCalpha) expression and inhibits proliferation of the hormone-dependent T-47D breast cancer cell line. Retinoic acid has no effect on proliferation or PKCalpha expression in a hormone-independent, breast cancer cell line (MDA-MB-231). To test the role of PKCalpha in retinoic acid-induced growth arrest of human breast cancer cells we established MDA-MB-231 cell lines stably expressing PKCalpha. Constitutive expression of PKCalpha did not affect proliferation of MDA-MB-231 cells but did result in partial retinoic acid sensitivity. Retinoic acid treatment of PKCalpha-MDA-MB-231 cells decreased proliferation (by approximately 40%) and inhibited serum activation of MAP kinases and induction of c-fos. Similar results were seen in MDA-MB-231 cells in which transcription of the transfected PKCalpha cDNA was reversibly induced by isopropyl beta-d-thiogalactoside. Expression of RARalpha in PKCalpha expressing MDA-MB-231 cells resulted in even greater retinoic acid responses, as measured by effects on cell proliferation, inhibition of serum signaling, and transactivation of an RARE-CAT reporter plasmid. In summary, PKCalpha synergizes with activated RARalpha to disrupt serum growth factor signaling, ultimately arresting proliferation of MDA-MB-231 cells.

Topics: Antineoplastic Agents; Blood Proteins; Breast Neoplasms; Calcium; Cell Division; Drug Interactions; Epidermal Growth Factor; Female; Gene Expression Regulation, Neoplastic; Genes, Reporter; Humans; Isoenzymes; Isopropyl Thiogalactoside; Mitogen-Activated Protein Kinases; Protein Kinase C; Protein Kinase C-alpha; Proto-Oncogene Proteins c-fos; Proto-Oncogene Proteins c-jun; Receptors, Retinoic Acid; RNA, Messenger; Signal Transduction; Transfection; Tretinoin; Tumor Cells, Cultured

The human progesterone receptor (PR) is expressed as two isoforms, PRA and PRB, which differ in the N-terminal region and exhibit different activities in vitro, with PRA demonstrating dominant negative inhibitory effects on the activity of PRB and other nuclear receptors. PRA and PRB are expressed in target tissues at comparable levels although cells expressing a predominance of one isoform can be identified. In breast cancers, PRA is expressed at high levels in some tumors, and this may be associated with features of poorer prognosis. To investigate the role of PRA overexpression in PR-positive target cells, the effect of PRA induction on cell proliferation and expression of endogenous progestin-sensitive genes, SOX4 and fatty acid synthetase (FAS), was examined using PR-positive T-47D cell lines, which express a predominance of PRB, in which PRA could be increased 2- to 20-fold over basal levels. No effect of PRA induction was noted on cell proliferation, but marked changes in morphology, consistent with loss of adherent properties, were observed. Increases up to 4-fold in the relative PRA levels augmented progestin induction of SOX4 mRNA expression, and RU486 treatment revealed a progestin agonist effect. There was no consistent effect of PRA induction on progestin-mediated increases in FAS mRNA levels under these conditions. Clones with PRA:PRB ratios greater than 15 were associated with diminished progestin responses on both SOX4 and FAS mRNA expression. These data show that PRA overexpression is associated with alteration in adhesive properties in breast cancer cells and effects on endogenous progestin targets that were dependent on the cellular ratio of PRA:PRB. The results of this study are consistent with the view that PRA expression can fluctuate within a broad range in target cells without influencing the nature of progestin action on downstream targets, but that overexpression of PRA, such as is seen in a proportion of breast cancers, may be associated with inhibition of progestin action and features of poor prognosis.

Topics: Breast Neoplasms; Cell Division; Fatty Acid Synthases; Female; Gene Expression Regulation, Neoplastic; High Mobility Group Proteins; Humans; Isopropyl Thiogalactoside; Plasmids; Progestins; Receptors, Progesterone; SOXC Transcription Factors; Time Factors; Trans-Activators; Transcription, Genetic; Transfection; Tumor Cells, Cultured

We have studied the lac repressor (lacR) system in two breast cancer cell lines, MCF-7 and MDA-MB-231, in vitro and in vivo. Breast cancer cell lines were stably transfected with lacR and tested for inducibility by transient transfection with a lac operator/luciferase reporter plasmid. The level of expression of lacR did not appear to correlate with the basal or maximal activation of induction by isopropyl beta-D-thiogalactoside (IPTG). Stable transfection with the same reporter gene resulted in up to 40-fold (MDA-MB-231) and 50-fold (MCF7) induction. In the absence of IPTG, a low level of basal reporter gene expression was seen in all clones. Detailed analysis showed that induction was rapid (maximal at 24 h), reversible (a return to basal expression by 24 h) and dose-dependent. To test if this system was also inducible in vivo, cells were grown as a xenograft tumor in nude mice. Mice were given IPTG (0.53 mmol) by intraperitoneal injection, and the tumors were biopsied at several time points following administration. IPTG caused a 10-fold increase in luciferase activity after 8 h, which persisted for 24 h. Thus, this system allows tightly controlled inducible in vivo and in vitro gene expression with low basal expression, and it may provide an important tool for the study of lethal genes in human breast cancer cells.

Topics: Animals; Bacterial Proteins; Breast Neoplasms; Enzyme Activation; Escherichia coli Proteins; Female; Gene Expression Regulation, Neoplastic; Humans; Isopropyl Thiogalactoside; Lac Repressors; Luciferases; Mammary Neoplasms, Experimental; Mice; Mice, Nude; Neoplasm Transplantation; Repressor Proteins; Transplantation, Heterologous; Tumor Cells, Cultured