scholarly journals Characterising the Response of Human Breast Cancer Cells to Polyamine Modulation

Biomolecules ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 743
Author(s):  
Oluwaseun Akinyele ◽  
Heather M. Wallace
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Cell Growth ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Breast Cancer Cells ◽  
Growth Responses ◽  
Cancer Management ◽  
Mcf 7

Breast cancer is a complex heterogeneous disease with multiple underlying causes. The polyamines putrescine, spermidine, and spermine are polycationic molecules essential for cell proliferation. Their biosynthesis is upregulated in breast cancer and they contribute to disease progression. While elevated polyamines are linked to breast cancer cell proliferation, there is little evidence to suggest breast cancer cells of different hormone receptor status are equally dependent on polyamines. In this study, we characterized the responses of two breast cancer cells, ER+ (oestrogen receptor positive) MCF-7 and ER- MDA-MB-231 cell lines, to polyamine modulation and determined the requirement of each polyamine for cancer cell growth. The cells were exposed to DFMO (a polyamine pathway inhibitor) at various concentrations under different conditions, after which several growth parameters were determined. Exposure of both cell lines to DFMO induced differential growth responses, MCF-7 cells showed greater sensitivity to polyamine pathway inhibition at various DFMO concentrations than the MDA-MB-231 cells. Analysis of intracellular DFMO after withdrawal from growth medium showed residual DFMO in the cells with concomitant decreases in polyamine content, ODC protein level, and cell growth. Addition of exogenous polyamines reversed the cell growth inhibition, and this growth recovery appears to be partly dependent on the spermidine content of the cell. Similarly, DFMO exposure inhibits the global translation state of the cells, with spermidine addition reversing the inhibition of translation in the breast cancer cells. Taken together, these data suggest that breast cancer cells are differentially sensitive to the antitumour effects of polyamine depletion, thus, targeting polyamine metabolism might be therapeutically beneficial in breast cancer management based on their subtype.

scholarly journals Effect of Estrogen on Heteronemin-Induced Anti-proliferative Effect in Breast Cancer Cells With Different Estrogen Receptor Status

2021 ◽  
Vol 9 ◽  
Author(s):  
Yu-Chen S. H. Yang ◽  
Zi-Lin Li ◽  
Tung-Yung Huang ◽  
Kuan-Wei Su ◽  
Chi-Yu Lin ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Estrogen Receptor ◽  
Cell Growth ◽  
Cancer Cells ◽  
Cancer Cell ◽  
Breast Cancer Cells ◽  
Gene Expressions ◽  
Er Positive ◽  
Mcf 7

Estrogen (E2) has multiple functions in breast cancers including stimulating cancer growth and interfering with chemotherapeutic efficacy. Heteronemin, a marine sesterterpenoid-type natural product, has cytotoxicity on cancer cells. Breast cancer cell lines, MCF-7 and MDA-MB-231, were used for investigating mechanisms involved in inhibitory effect of E2 on heteronemin-induced anti-proliferation in breast cancer cells with different estrogen receptor (ER) status. Cytotoxicity was detected by cell proliferation assay and flow cytometry, gene expressions were determined by qPCR, mechanisms were investigated by Western blot and Mitochondrial ROS assay. Heteronemin exhibited potent cytotoxic effects against both ER-positive and ER-negative breast cancer cells. E2 stimulated cell growth in ER-positive breast cancer cells. Heteronemin induced anti-proliferation via suppressing activation of ERK1/2 and STAT3. Heteronemin suppressed E2-induced proliferation in both breast cancer cells although some gene expressions and anti-proliferative effects were inhibited in the presence of E2 in MCF-7 and MDA-MB-231 cells with a higher concentration of heteronemin. Heteromenin decreased the Bcl-2/Bax ratio to inhibit proliferation in MDA-MB-231 but not in MCF-7 cells. Both heteronemin and E2 increased mitochondrial reactive oxygen species but combined treatment reversed superoxide dismutase (SOD)s accumulation in MCF-7 cells. Heteronemin caused G0/G1 phase arrest and reduced the percentage of cells in the S phase to suppress cancer cell growth. In conclusion, Heteronemin suppressed both ER-positive and ER-negative breast cancer cell proliferation. Interactions between E2 and heteronemin in signal transduction, gene expressions, and biological activities provide insights into the complex pathways by which anti-proliferation is induced by heteronemin in E2-replete environments.

scholarly journals Nuclear receptor 4A1 as a drug target for breast cancer chemotherapy

2015 ◽  
Vol 22 (5) ◽  
pp. 831-840 ◽  
Author(s):  
Erik Hedrick ◽  
Syng-Ook Lee ◽  
Ravi Doddapaneni ◽  
Mandip Singh ◽  
Stephen Safe
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Cancer Cells ◽  
Cell Lines ◽  
Nuclear Receptor ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Breast Cancer Cells ◽  
Induced Apoptosis ◽  
Mcf 7

The orphan nuclear receptor 4A1 (NR4A1) is overexpressed in mammary tumors and breast cancer cell lines. The functional activity of this receptor was investigated by RNA interference with oligonucleotides targeted to NR4A1 (siNR4A1) and by treatment with NR4A1 antagonists. Breast cancer cells were treated with NR4A1 antagonists or transfected with siNR4A. Effects on cell proliferation and apoptosis as well as specific genes associated with these responses were investigated in MCF-7, SKBR3, and MDA-MB-231 cells, and in athymic nude mice bearing MDA-MB-231 cells as xenografts. Transfection of MCF-7, MDA-MB-231, and SKBR3 breast cancer cells with siNR4A1 decreased cell proliferation and induced apoptosis in these cell lines. Transfection of breast cancer cells with siNR4A1 also decreased expression of Sp-regulated genes includingsurvivin,bcl-2, and epidermal growth factor receptor, inhibited mTOR signaling in MCF-7 cells that express WT p53, and activated oxidative and endoplasmic reticulum stress through downregulation of thioredoxin domain-containing 5 and isocitrate dehydrogenase 1. 1,1-Bis(3′-indolyl)-1-(p-substituted phenyl)methanes (C-DIMs) are NR4A1 ligands that act as NR4A1 antagonists. Treatment with selected analogs also inhibited breast cancer cell and tumor growth and induced apoptosis. The effects of C-DIM/NR4A1 antagonists were comparable to those observed after NR4A1 knockdown. Results with siNR4A1 or C-DIMs/NR4A1 antagonists in breast cancer cells and tumors were similar to those previously reported in pancreatic, lung, and colon cancer cells. They demonstrate the potential clinical applications of NR4A1 antagonists in patients with tumors that overexpress this receptor.

scholarly journals Highly expressed SLCO1B3 inhibits the occurrence and development of breast cancer and can be used as a clinical indicator of prognosis

2021 ◽  
Vol 11 (1) ◽  
Author(s):  
Tiantian Tang ◽  
Guiying Wang ◽  
Sihua Liu ◽  
Zhaoxue Zhang ◽  
Chen Liu ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Breast Cancer Cells ◽  
Migration And Invasion ◽  
Breast Cancer Cell Lines

AbstractThe role of organic anion transporting polypeptide 1B3 (SLCO1B3) in breast cancer is still controversial. The clinical immunohistochemical results showed that a greater proportion of patients with negative lymph nodes, AJCC stage I, and histological grade 1 (P < 0.05) was positively correlated with stronger expression of SLCO1B3, and DFS and OS were also increased significantly in these patients (P = 0.041, P = 0.001). Further subgroup analysis showed that DFS and OS were significantly enhanced with the increased expression of SLCO1B3 in the ER positive subgroup. The cellular function assay showed that the ability of cell proliferation, migration and invasion was significantly enhanced after knockdown of SLCO1B3 expression in breast cancer cell lines. In contrast, the ability of cell proliferation, migration and invasion was significantly reduced after overexpress the SLCO1B3 in breast cancer cell lines (P < 0.05). Overexpression or knockdown of SLCO1B3 had no effect on the apoptotic ability of breast cancer cells. High level of SLCO1B3 expression can inhibit the proliferation, invasion and migration of breast cancer cells, leading to better prognosis of patients. The role of SLCO1B3 in breast cancer may be related to estrogen. SLCO1B3 will become a potential biomarker for breast cancer diagnosis and prognosis assessment.

Synthesis and In Vitro Evaluation of Tetrahydroquinoline Derivatives as Antiproliferative Compounds of Breast Cancer via Targeting the GPER

2019 ◽  
Vol 19 (6) ◽  
pp. 760-771 ◽  
Author(s):  
Oscar J. Zacarías-Lara ◽  
David Méndez-Luna ◽  
Gustavo Martínez-Ruíz ◽  
José R. García-Sanchéz ◽  
Manuel J. Fragoso-Vázquez ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Cancer Cells ◽  
Cell Lines ◽  
In Silico ◽  
Breast Cancer Cells ◽  
Breast Cancer Cell Lines ◽  
In Silico Studies ◽  
Mcf 7

Background: Some reports have demonstrated the role of the G Protein-coupled Estrogen Receptor (GPER) in growth and proliferation of breast cancer cells. Objective: In an effort to develop new therapeutic strategies against breast cancer, we employed an in silico study to explore the binding modes of tetrahydroquinoline 2 and 4 to be compared with the reported ligands G1 and G1PABA. Methods: This study aimed to design and filter ligands by in silico studies determining their Lipinski's rule, toxicity and binding properties with GPER to achieve experimental assays as anti-proliferative compounds of breast cancer cell lines. Results: In silico studies suggest as promissory two tetrahydroquinoline 2 and 4 which contain a carboxyl group instead of the acetyl group (as is needed for G1 synthesis), which add low (2) and high hindrance (4) chemical moieties to explore the polar, hydrophobic and hindrance effects. Docking and molecular dynamics simulations of the target compounds were performed with GPER to explore their binding mode and free energy values. In addition, the target small molecules were synthesized and assayed in vitro using breast cancer cells (MCF-7 and MDA-MB-231). Experimental assays showed that compound 2 decreased cell proliferation, showing IC50 values of 50µM and 25µM after 72h of treatment of MCF-7 and MDA-MB-231 cell lines, respectively. Importantly, compound 2 showed a similar inhibitory effect on proliferation as G1 compound in MDA-MB-231 cells, suggesting that both ligands reach the GPER-binding site in a similar way, as was demonstrated through in silico studies. Conclusion: A concentration-dependent inhibition of cell proliferation occurred with compound 2 in the two cell lines regardless of GPER.

Synergistic cytotoxic effects of tamoxifen and black cohosh on MCF-7 and MDA-MB-231 human breast cancer cells: an in vitro studyThis article is one of a selection of papers published in this special issue (part 2 of 2) on the Safety and Efficacy of Natural Health Products.

2007 ◽  
Vol 85 (11) ◽  
pp. 1153-1159 ◽  
Author(s):  
Mahéra Al-Akoum ◽  
Sylvie Dodin ◽  
Ali Akoum
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Cell Growth ◽  
Cancer Cells ◽  
Breast Cancer Cells ◽  
Cytotoxic Effect ◽  
Black Cohosh ◽  
Proliferative Effect ◽  
Dose Dependent ◽  
Mcf 7

Breast cancer cell cultures were exposed to different concentrations of black cohosh, estradiol (E2), and tamoxifen to examine the effect on cell proliferation; cytotoxicity was assessed by using sulforhodamine B (SRB) dye solution. E2 (10−10–10−8 mol/L) markedly stimulated the proliferation of MCF-7 cells (p < 0.01). Tamoxifen stimulated MCF-7 cell proliferation at 10−6 mol/L and 10−5 mol/L (p < 0.005) but inhibited in a dose-dependent fashion the proliferative effect of E2 (p < 0.001). Black cohosh alone did not show any stimulatory effect, but exhibited a cytotoxic effect, which was significant at 103 μg/mL (p < 0.001). Adding black cohosh at 100–103 μg/mL to E2 at 10−9 mol/L also resulted in a dose-dependent inhibition of E2 proliferative effect. Interestingly, the combination of black cohosh (100–103 μg/mL) with increasing tamoxifen concentrations further inhibited MCF-7 cell growth. On MDA-MB-231 cells, neither E2 nor tamoxifen displayed any detectable effect. However, black cohosh inhibited MDA-MB-231 cell proliferation at 103 μg/mL (p < 0.05), and this inhibitory effect was enhanced by increasing tamoxifen concentrations. This study reveals a cytotoxic effect of black cohosh on both estrogen-sensitive and estrogen-insensitive breast cancer cells and a synergism with tamoxifen for inhibition of cancerous cell growth.

scholarly journals WD-3 inhibits the proliferation of breast cancer cells by regulating the glycolytic pathway

2020 ◽  
Author(s):  
Xiaodan Zhu ◽  
Lu Zhao ◽  
Jianliang You ◽  
Yiqun Ni ◽  
Zhipeng Wei ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Breast Cancer Cells ◽  
Cancer Cell Lines ◽  
Breast Cancer Cell Lines ◽  
Hexokinase 2 ◽  
Mcf 7

Number 3 Prescription (WD-3) is an herbal remedy used in traditional Chinese medicine that has been shown to improve the outcomes of patients with advanced colon and gastric cancers. This study aimed to investigate the effect of WD-3 on proliferation, glycolysis, and hexokinase 2 expression in breast cancer cells. Four breast cancer cell lines (MDA-MB-231, BT-549, MCF-7, and MCF-7/ADR-RES) were treated with different concentrations of WD-3 compared with blank control (phosphate-buffered saline). Each of the breast cancer cell lines was also divided into WD-3, paclitaxel, and blank control group. Cell proliferation and morphology were assessed by MTT assay, nuclear Hoechst 33258 staining, or immunofluorescence. Apoptosis was analyzed by flow cytometry. High performance liquid chromatography was used for measurement of ATP, ADP, and AMP. Hexokinase 2 expression was analyzed by Western blot and quantitative reverse transcription PCR. WD-3 inhibited proliferation and increased apoptosis in all four breast cancer cell lines, in a dose-dependent manner. ATP and EC (energy charge) were significantly decreased in WD-3-treated BT-549 and MDA-MB-231 cells. WD-3 significantly downregulated the protein and mRNA expression of hexokinase II in BT-549 cells, however, not in the other three breast cancer cell lines. Our findings indicate that WD-3 targets the glycolytic pathway in breast cancer cells to exert its antitumor activity.

Decrease in Cell Viability of Breast Cancer Cells by a Di-Hydroxylated Derivative of N-(2-hydroxyphenyl)-2-Propylpentanamide

2021 ◽  
Vol 21 ◽  
Author(s):  
Norma Lizeth Galindo-Alvarez ◽  
Humberto L. Mendoza-Figueroa ◽  
Martha Cecilia Rosales-Hernández ◽  
Norbert Bakalara ◽  
José Correa-Basurto
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Proliferative Activity ◽  
Breast Cancer Cells ◽  
Breast Cancer Cell Lines ◽  
Hydroxyl Groups ◽  
Mcf 7

Background: A preliminary study of the biotransformation by cytochrome P450 enzymes (CYP) of N-(2-hydroxyphenyl)-2-propylpentanamide (HO-AAVPA), an HDAC inhibitor, led to the synthesis of two hydroxylated derivatives: N-(2,4-dihydroxyphenyl)-2-propylpentanamide (5a) and N-(2,5-dihydroxyphenyl)-2-propylpentanamide (5b). Objective: The study aims to evaluate the anti-proliferative activity of these di-hydroxylated derivatives in breast cancer cell lines. Methods: MTT assays were conducted in MCF-7 and MDA-MB-231 cell lines. Additionally, in silico studies were carried out to evaluate the affinity of these derivatives with the HDAC1 enzyme. Results: Results showed that only 5b possess an enhanced anti-proliferative effect in breast cancer cell lines MCF-7 and MDA-MB-231. Docking studies revealed that the presence of hydroxyl groups, as well as the position of the additional hydroxyl groups, could have an impact on HDAC1 affinity and could explain the lack of activity of compound 5a. Conclusion: A priori, these results hypothesize that anti-proliferative activity of 5b could be related to HDAC1 inhibition and thus anti-proliferative activity in breast cancer cells.

Endocytosis of pro-cathepsin D into breast cancer cells is mostly independent of mannose-6-phosphate receptors

1998 ◽  
Vol 111 (17) ◽  
pp. 2539-2549 ◽  
Author(s):  
V. Laurent-Matha ◽  
M.R. Farnoud ◽  
A. Lucas ◽  
C. Rougeot ◽  
M. Garcia ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Cathepsin D ◽  
Breast Cancer Cells ◽  
Cancer Cell Lines ◽  
Breast Cancer Cell Lines ◽  
Mannose 6 Phosphate ◽  
Mcf 7

Cathepsin D trafficking is altered in cancer cells, leading to increased secretion of the pro-enzyme, which can be reinternalized by the same cancer cells and by stromal cells. We studied pro-cathepsin D endocytosis in two human breast cancer cell lines (MDA-MB231, MCF-7) and in human normal fibroblasts. Pro-enzyme uptake was studied indirectly through immunofluorescence analysis of anti-pro-cathepsin D monoclonal antibodies internalized in living cells. Both cancer cell lines internalized the pro-cathepsin D-antibody complex into endosomal compartments in the presence of 10 mM mannose-6-phosphate. Non-malignant fibroblasts, which do not secrete pro-cathepsin D, only internalized anti-cathepsin D antibody when purified pro-cathepsin D was added and this endocytosis was totally inhibited by mannose-6-phosphate. Cathepsin D endocytosis in cancer cells was not mediated by lectins or another receptor binding the cathepsin profragment. It was not due to fluid endocytosis, since another protein pS2 secreted by MCF-7 was not endocytosed with its antibody in the same conditions. Double-immunofluorescence and confocal microscopy analyses revealed that antibodies specific to pro-cathepsin D (M2E8) and to the mannose-6-phosphate/IGFII receptor were co-internalized independently in non-permeabilized MDA-MB231 cells and MCF-7 cells, but not in fibroblasts. Moreover, when metabolically labelled pro-cathepsin D secreted by MCF-7 or MDA-MB231 cells was incubated with homologous or heterologous non-radioactive cells, the time-dependent uptake and maturation of the pro-enzyme into fibroblasts were totally inhibited by mannose-6-phosphate, whereas they were not in the two breast cancer cell lines. The percentage of mannose-6-phosphate-independent binding of radioactively labelled pro-cathepsin D to MDA-MB231 cells at 16 degrees C was higher (7–8%) at low pro-cathepsin D concentration than at high concentration (1.5%), indicating the presence of saturable binding site(s) at the cell surface that are different from the mannose-6-phosphate receptors. We conclude that, in contrast to fibroblasts, breast cancer cells can endocytose the secreted pro-cathepsin D by a cell surface receptor that is different from the mannose-6-phosphate receptors or other lectins. The nature of this alternative receptor and its significance in the action of secreted pro-cathepsin D remain to be elucidated.

Soluble Inflammatory Mediators Proteinase-3 and Neutrophil Elastase Are Targeted by PR1-Specific Immunotherapy After Cellular Uptake and Cross Presentation of PR1 Peptide by Breast Cancer Cells

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 2089-2089
Author(s):  
Gheath Alatrash ◽  
Elizabeth Mittendorf ◽  
Anna Sergeeva ◽  
Pariya Sukhumalchandra ◽  
Na Qiao ◽  
...  
Keyword(s):  
Breast Cancer ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Breast Cancer Cells ◽  
Cancer Cell Lines ◽  
Breast Cancer Cell Lines ◽  
Cross Presentation ◽  
Mcf 7

Abstract Abstract 2089 The human leukocyte antigen (HLA)-A2 restricted nonapeptide PR1 (VLQELNVTV) was shown to be immunogenic in leukemia. A phase I/II clinical trial has been initiated with PR1 peptide vaccine and to date has demonstrated clinical efficacy, including complete remission and immunologic responses in patients with acute (AML) and chronic (CML) myeloid leukemia, as well as myelodysplastic syndrome. PR1 is derived from the serine proteases proteinase-3 (P3) and neutrophil elastase (NE), which are normally found within neutrophil azurophil granules and are released into the inflammatory milieu. We have shown that P3 and NE are taken up and cross presented by antigen presenting cells and that their cross presentation elicits PR1 immunity. Because P3 and NE are present in breast cancer biopsies, we hypothesized that P3/NE may be taken up by breast cancer cells and cross presented to PR1-CTL. We recently demonstrated that the breast cancer cell lines MDA-MB-231, MDA-MB-453, MCF-7 and HER18 do not endogenously express NE and that NE is taken up by these cell lines. In this report, using PCR, western blot and flow cytometry, we show that P3 also is NOT endogenously expressed by the breast cancer cell lines MDA-MB-231, MDA-MB-453, MCF-7 or HER18. Using confocal microscopy, we demonstrate that P3 is taken up by these breast cancer cell lines within 10 minutes of pulsing and localizes to LAMP-2 containing lysosomal vesicles by 4 hours, suggesting its processing for presentation by (HLA)-I (i.e. HLA-A2). Using 8F4, the novel PR1-HLA-A2 monoclonal antibody, we show that PR1 is cross presented from P3 by 3 of 4 HLA-A2+ breast cancer cell lines (MDA-MB-231, MDA-MB-453-A2+, MCF-7), and from NE by 1 of 4 breast cancer cell lines (MDA-MB-231). Next, we studied whether PR1 presentation made cells susceptible to PR1-specific killing by PR1-CTL and the 8F4 monoclonal antibody. We show that following 12-hour pulsing of the MDA-MB-231 cell line with NE or P3, PR1 CTLs killed up to 31% and 38% of the NE- or P3-pulsed breast cancer cells respectively, vs. <1% of ovalbumin (ova)-pulsed MDA-MB-231cells. Additionally, in a complement mediated cytotoxicity assay using 8F4 antibody, pulsing of MDA-MB-231 cells with P3 led to 60% cytotoxicity (vs. 40% in ova-pulsed cells). In conclusion, this study shows that 1) PR1 is cross presented by breast cancer cells following uptake of soluble P3 and NE and 2) PR1 expression makes breast cancer a target of PR1-specific immunotherapy. If uptake of P3 or NE, present in the inflammatory milieu of other solid tumors, also leads to PR1 cross presentation, then PR1-based immunotherapy may be useful to treat other non-hematopoietic tumors. These results support a new paradigm linking inflammation and innate immunity to adaptive immune responses to cancer. Disclosures: No relevant conflicts of interest to declare.

Effect of enzastaurin on cell signaling, proliferation and apoptosis in breast cancer cell lines

2007 ◽  
Vol 25 (18_suppl) ◽  
pp. 14121-14121
Author(s):  
B. Spankuch ◽  
E. Kurunci-Csacsko ◽  
T. Bauknecht ◽  
K. Strebhardt
Keyword(s):  
Breast Cancer ◽  
Cell Proliferation ◽  
Cancer Cells ◽  
Cell Lines ◽  
Cancer Cell ◽  
Breast Cancer Cell ◽  
Breast Cancer Cells ◽  
Cancer Cell Lines ◽  
Breast Cancer Cell Lines ◽  
Caspase 9

14121 Background: Enzastaurin, an acyclic bisindolylmaleimide, is a potent selective serine/threonine kinase inhibitor that inhibits PKCβ, targets the PI3K/AKT pathway, and inhibits GSK3β phosphorylation. Enzastaurin induced apoptosis and decreased proliferation of various cancer lines, and decreased VEGF expression and microvessel density in human tumor xenografts. In animal models, enzastaurin had antitumor/antiangiogenic activity in non-small-cell lung, colon, renal cell, hepatocellular, and other cancers. Therefore, we sought to determine enzastaurin’s impact on cellular PKCβ-mediated signaling in breast cancer cells. Secondarily, we sought to determine the induction of the apoptotic cascade by enzastaurin. Methods: Breast cancer cell lines MCF-7, BT-474, MDA-MB-435 and SK-BR-3 were treated with differing enzastaurin concentrations. Western-Blot analyses were performed to examine PKCβ, phospho-GSK3β and caspase 9 expressions. The phenotype and proliferation of enzastaurin-treated cells were also monitored by fluorescence microscopy. Results: Treating all 4 cancer cell lines with ascending enzastaurin doses (0.1–10 μM) led to a significant downregulation of GSK3β phosphorylation (2–17%) compared to control cells. A 48–72 hr incubation with increasing enzastaurin doses also reduced the PKCβ expression significantly (5–50%). Moreover, a dose- dependent reduction of cell proliferation to levels of 15–40% compared to control cells with the highest enzastaurin concentration was detectable. We also saw a marked pro-caspase 9 reduction (0–30%) after enzastaurin compared to control cells. The microscopic inspection of treated cells phenotypically confirmed increasing apoptosis-induced cell death. Conclusions: Enzastaurin has a significant antiproliferative effect in different breast cancer cells. Moreover, enzastaurin suppresses GSK3β phosphorylation, suggesting that it may be a reliable pharmacodynamic marker for enzastaurin activity in breast cancer cells; however, more preclinical analysis is needed. Our study provides evidence for enzastaurin’s potential to directly suppress breast cancer cell proliferation and to induce tumor cell death by apoptotic induction. No significant financial relationships to disclose.

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