Background: Cancer is the disease that causes the most death after cardiovascular diseases all over the world these days. Breast cancer is the most common type of cancer among women and ranks the second among cancer-related deaths after lung cancer. Chemotherapeutics act by killing cancer cells, preventing their spread and slowing their growth. Recent studies focus on the effects of chemotherapeutics on cancer cells and new chemotherapy approaches that targeting enzymes that catalyze important metabolic reactions in the cell. Objective: The aim of this study was to investigate the effects of chemotherapeutic agents, Tamoxifen and 5-FU, on MCF-7 cell line and human erythrocyte GST, an important enzyme of intracellular antioxidant metabolism. Methods: In this study, it was investigated that the effect of chemotherapeutic agents, Tamoxifen and 5-FU, on MCF-7 breast cancer cell line and performed ROS analyzes. In addition, it was purified glutathione S-transferase (GST), one of the important enzymes of intracellular antioxidant mechanism, from human erythrocytes by using ammonium sulfate precipitation and glutathione agarose affinity chromatography, and investigated in vitro effects of chemotherapeutic agents, 5-FU and Tamoxifen, on the activity of this enzyme for the first time. Results: It was determined that Tamoxifen and 5-FU inhibited cellular viability and 5-FU increased intracellular levels of ROS, whereas Tamoxifen reduced intracellular levels of ROS. In addition, human erythrocyte GST enzyme with 16.2 EU/mg specific activity was purified 265.97-fold with a yield of 35% using ammonium sulfate precipitation and glutathione agarose affinity chromatography. The purity of the enzyme was checked by the SDS-PAGE method. In vitro effects of chemotherapeutics, 5-FU and Tamoxifen, on GST activity purified from human erythrocytes were investigated. The results showed that 5-FU increased the activity of GST in the concentration range of 77 to 1155 µM and that Tamoxifen increased the activity of GST in the concentration range of 0.54 to 2.70 µM. Conclusion: In this study, the effects of tamoxifen and 5-FU chemotherapeutic agents on both MCF-7 cell line and human GST enzyme were examined together for the first time. Our study showed that chemotherapeutic agents (5-FU and Tamoxifen) inhibited cellular viability and Tamoxifen reduced intracellular levels of ROS whereas 5-FU increased intracellular levels of ROS. In addition, 5-FU and Tamoxifen were found to increase the activity of GST enzyme purified from the human erythrocyte.
Öz: Meme kanseri dünyanın hemen her bölgesinde kadınlar arasında en sık görülen kanser türüdür. Kansere bağlı ölümlerde akciğer kanserinden sonra ikinci sırada yer almaktadır. 5-Fluorourasil (5-FU) urasil ile aynı taşıma mekanizmasını kullanarak hücrelere girmeyi hedefleyen, hidrojenin yerine C-5 pozisyonunda bir flor atomu olan bir pirimidin analoğudur. C 60 fulleren, antioksidan ve antitümör potansiyeli olan bir nanopartiküldür ve 5-FU'ya hücre tepkilerini modüle etmede faydalı olabilir. p53 proteini tümör gelişimini baskılayan bir transkripsiyon faktörü, TIGAR esas olarak glukoz metabolizmasının düzenleyicisi olarak işlev görür. Bu çalışmada 5-FU, C 60 ve 5-FU+C 60 kombinasyonunun MCF-7 insan meme kanseri hücreleri üzerindeki sitotoksik etkileri WST-1 analizi ile gerçekleştirildi. Ek olarak, DCFDA kullanılarak reaktif oksijen türleri düzeylerinin tespiti araştırıldı. Çalışmamızda zamana ve konsantrasyona bağlı olarak 5-FU'nun MCF-7 hücre canlılığını inhibe ettiği, C 60 nanopartikülünün MCF-7 hücreleri üzerine tek başına uygulanması sonucunda anlamlı bir etkinin olmadığı görüldü. 5-FU+C 60 'ın birlikte kullanımının ise hücreler üzerinde sitotoksik etkisinin olduğu gösterildi. Öte yandan hücreler üzerine 5-FU, C 60 ve 5-FU+C 60 uygulamalarının ROS düzeylerinde anlamlı bir fark (artma ya da azalma) oluşturmadıkları belirlendi. İlaveten p53 ve TIGAR proteinlerinin ekspresyon düzeyleri Western Blot yöntemi ile incelenerek hücreler üzerindeki apoptotik etkileri araştırıldı. 5-FU ve 5-FU+C 60 gruplarında p53 gen ekspresyonunun arttığı görüldü. 5-FU+C 60 kombinasyonunun TIGAR ifadesini indükleyerek hücrelerin apoptoza gitmesine yardımcı olduğu gözlendi.
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