Das Jharna R, Fryar Elizabeth B, Green S, Southerland William M, Bowen Donnell
Department of Pharmacology, College of Medicine, Howard University, Washington, DC 20059, USA.
Anticancer Res. 2006 Nov-Dec;26(6B):4279-86.
Currently, one of the most effective strategies for the treatment and prevention of breast cancer is the use of drugs that block estrogen action in the breast. The success of the first clinically relevant selective estrogen receptor modulator (SERM), tamoxifen, provided the foundation for further testing of this drug to reduce breast cancer incidence in high-risk women. However, the negative effects associated with the long-term use of tanrhoxifen have initiated the search for compounds that are more effective but less toxic. The discovery of raloxifene (RAL), which functions as a potent antiestrogen in the breast but an estrogen receptor (ER) agonist in the bone and cardiovascular system with very little uterotropic activity, provided an alternative strategy to the targeted use of tamoxifen. The aim of this study was to evaluate RAL in combination with 5-fluorouracil (5-FU)/trimetrexate (TMX) to determine the most effective regimes and cellular mechanism of action to mitigate trimetrexate cytotoxicity in human bone marrow cells.
The cell viability was performed using the Quick Cell Proliferation Assay by exposing the cells to TMX, 5-FU and RAL alone; RAL 24 h prior to 5-FU followed 2 h by TMX, and 5-FU 2 h prior to TMX followed 24 h by RAL determined the sequence-dependent interaction between TMX, 5-FU and RAL on the proliferation.
The growth rate in MCF-7 in late RAL was 34.75 +/- 4.79% of the control, whereas in bone marrow the same drug combination exhibits a significant protection against TMX cytotoxicity with late RAL yielding 51.25 +/- 4.43% of the control. The findings were also supported by Cell flow cytometry and Western blot analysis.
Sequence-dependent administration of RAL in combination with 5-FU/TMX can act against TMX toxicity in human bone marrow, while not affecting the maximum inhibitory effect of TMX in breast cancer.
目前，治疗和预防乳腺癌最有效的策略之一是使用能阻断雌激素在乳腺中作用的药物。首个具有临床相关性的选择性雌激素受体调节剂（SERM）他莫昔芬的成功，为进一步测试该药物以降低高危女性乳腺癌发病率奠定了基础。然而，长期使用他莫昔芬带来的负面影响促使人们寻找更有效但毒性更小的化合物。雷洛昔芬（RAL）的发现提供了一种替代他莫昔芬靶向使用的策略，RAL在乳腺中作为强效抗雌激素发挥作用，但在骨骼和心血管系统中是雌激素受体（ER）激动剂，且子宫促生长活性极低。本研究的目的是评估RAL与5-氟尿嘧啶（5-FU）/三甲曲沙（TMX）联合使用，以确定减轻三甲曲沙对人骨髓细胞细胞毒性的最有效方案和细胞作用机制。
通过将细胞单独暴露于TMX、5-FU和RAL；在5-FU前24小时给予RAL，随后2小时给予TMX，以及在TMX前2小时给予5-FU，随后24小时给予RAL，使用快速细胞增殖测定法检测细胞活力，以确定TMX、5-FU和RAL之间对增殖的序列依赖性相互作用。
晚期给予RAL时，MCF-7中的生长率为对照组的34.75±4.79%，而在骨髓中，相同的药物组合对TMX细胞毒性具有显著保护作用，晚期给予RAL时为对照组的51.25±4.43%。细胞流式细胞术和蛋白质免疫印迹分析也支持了这些发现。
RAL与5-FU/TMX联合使用时，序列依赖性给药可对抗TMX对人骨髓的毒性，同时不影响TMX对乳腺癌的最大抑制作用。
