Adenosine deaminase activity in estrogen receptor positive and negative human breast cancer cell lines

The aims of this study were to assay the activity of adenosine deaminase [ADA] in estrogen receptor positive [MCF-7] and negative [MDA-MB468] breast cancer cell lines.MDA-MB468 and MCF-7 breast cancer cell lines were cultured in complete medium, striped serum with and without 0.01micro M diethylstilbestrol [DBS], complete medium in the presence and absence of 1micro M tamoxifen for 20 hr. Adenosine deaminase activity was determined using the colorimetric method described by Guisti and Galanti.It was found that the activity of enzyme in estrogen receptor positive [ER+] cell line [MCF-7] was significantly higher than that of estrogen receptor negative breast cancer cell line [MDA-MB468]. ADA activity in MCF-7 cells cultured in the presence of tamoxifen or charcoal-striped serum was significantly lower than that of control. Furthermore addition of diethylstilbestrol [DBS] to the striped serum increased the value of ADA activity to that of control.Unlike MCF-7 cells, the activity of ADA in MDA-MB468 cells remained unchanged upon treatment with tamoxifen or striped serum.These findings suggest estrogen responsiveness of ADA expression in MCF-7 cells

apoptotic effect of extracellular zinc sequestration on HT29/219 and SW742 cell lines

Zn [II] is an important regulator of caspase-3, as well as an antioxidant, microtubule stabilizer, growth cofactor, and anti-inflammatory agent. Over the past 30 years, many researchers have demonstrated the important role of Zn [II] in a variety of physiological processes, including growth and development, maintenance and priming of the immune system, and in tissue repair and regeneration. In this study, we present evidence that chelation of extracellular zinc by diethylenetriaminepentacetic acid [DTPA] in different concentrations causes cell death in carcinoma cell lines, HT29/219 and SW742. Hoechst 33258 staining revealed that cell death was mainly by apoptosis. Additionally, significant increases in the activity of caspase-3 and -9 were observed in both cell lines. Caspase-8 activation was negligible in both cell lines. The cytotoxicity/apoptotic effect of DTPA was inhibited significantly by Zn [II], Cu [II] and N-Acetyl-L-Cysteine [NAC] [P<0.05]. Therefore, DTPA, the membrane-impermeable metal ion chelator, induces apoptosis through the depletion of extracellular zinc ion

Cytotoxicity effect of cladribine on the MCF-7 human breast cancer cell line

Cladribine, an analogue of deoxyadenosine, is highly toxic for both non-dividing and proliferating cells and has shown activity in the treatment of several malignancies. Therefore, the aim of the present study is to investigate the cytotoxicity effect of cladribine [2-CdA] on the breast cancer cell line, MCF-7 [estrogen receptor positive, ER+]. MTT assay, annexin V-Fluorescein/PI and Hoechst 33258 staining were used to detect cytotoxicity and cell apoptosis. The activation of caspase-3 and -9 was assayed using caspase activation assay kits. Gel electrophoresis was performed to detect DNA fragmentation. Treatment of MCF-7 cells with different concentrations of 2-CdA resulted in a significant increase in the cell death. Annexin V-Fluorescein/PI and Hoechst 33258 staining revealed that the cell death was mainly an apoptotic type. A significant [p<0.05] increase in the activity of caspase-9 was observed but Caspase-3 activity was unchanged and DNA laddering profile was not obtained. Pre-treatment of the cells with kinase inhibitor, 5 -amino-5 -deoxyadenosine inhibited the cytotoxicity effect of cladribine. In conclusion, this study has shown that high dose of cladribine [higher than 25 micro M] has an apoptotic effect on MCF-7 cells and that its intracellular phosphorylation is necessary