Theodossiou Theodossis A, Olsen Cathrine E, Jonsson Marte, Kubin Andreas, Hothersall John S, Berg Kristian
Department of Radiation Biology, Institute for cancer Research, Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway.
Department of Radiation Biology, Institute for cancer Research, Radium Hospital, Oslo University Hospital, Montebello, 0379 Oslo, Norway.
Redox Biol. 2017 Aug;12:191-197. doi: 10.1016/j.redox.2017.02.018. Epub 2017 Feb 24.
The diverse responses of different cancers to treatments such as photodynamic therapy of cancer (PDT) have fueled a growing need for reliable predictive markers for treatment outcome. In the present work we have studied the differential response of two phenotypically and genotypically different breast adenocarcinoma cell lines, MCF7 and MDA-MB-231, to hypericin PDT (HYP-PDT). MDA-MB-231 cells were 70% more sensitive to HYP PDT than MCF7 cells at LD. MCF7 were found to express a substantially higher level of glutathione peroxidase (GPX4) than MDA-MB-231, while MDA-MB-231 differentially expressed glutathione-S-transferase (GSTP1), mainly used for xenobiotic detoxification. Eighty % reduction of intracellular glutathione (GSH) by buthionine sulfoximine (BSO), largely enhanced the sensitivity of the GSTP1 expressing MDA-MB-231 cells to HYP-PDT, but not in MCF7 cells. Further inhibition of the GSH reduction however by carmustine (BCNU) resulted in an enhanced sensitivity of MCF7 to HYP-PDT. HYP loading studies suggested that HYP can be a substrate of GSTP for GSH conjugation as BSO enhanced the cellular HYP accumulation by 20% in MDA-MB-231 cells, but not in MCF7 cells. Studies in solutions showed that L-cysteine can bind the GSTP substrate CDNB in the absence of GSTP. This means that the GSTP-lacking MCF7 may use L-cysteine for xenobiotic detoxification, especially during GSH synthesis inhibition, which leads to L-cysteine build-up. This was confirmed by the lowered accumulation of HYP in both cell lines in the presence of BSO and the L-cysteine source NAC. NAC reduced the sensitivity of MCF7, but not MDA-MB-231, cells to HYP PDT which is in accordance with the antioxidant effects of L-cysteine and its potential as a GSTP substrate. As a conclusion we have herein shown that the different GSH based cell defense mechanisms can be utilized as predictive markers for the outcome of PDT and as a guide for selecting optimal combination strategies.
不同癌症对诸如癌症光动力疗法（PDT）等治疗的多样反应，促使人们对可靠的治疗结果预测标志物的需求日益增长。在本研究中，我们研究了两种表型和基因型不同的乳腺腺癌细胞系MCF7和MDA-MB-231对金丝桃素光动力疗法（HYP-PDT）的差异反应。在致死剂量下，MDA-MB-231细胞对HYP PDT的敏感性比MCF7细胞高70%。发现MCF7表达的谷胱甘肽过氧化物酶（GPX4）水平显著高于MDA-MB-231，而MDA-MB-231差异表达谷胱甘肽-S-转移酶（GSTP1），其主要用于外源性物质解毒。丁硫氨酸亚砜胺（BSO）使细胞内谷胱甘肽（GSH）减少80%，在很大程度上增强了表达GSTP1的MDA-MB-231细胞对HYP-PDT的敏感性，但对MCF7细胞无效。然而，卡莫司汀（BCNU）进一步抑制GSH减少，导致MCF7对HYP-PDT的敏感性增强。HYP负载研究表明，HYP可能是GSTP用于GSH共轭的底物，因为BSO使MDA-MB-231细胞中的细胞HYP积累增加了20%，但对MCF7细胞无效。溶液研究表明，在没有GSTP的情况下，L-半胱氨酸可以结合GSTP底物CDNB。这意味着缺乏GSTP的MCF7可能利用L-半胱氨酸进行外源性物质解毒，特别是在GSH合成抑制期间，这会导致L-半胱氨酸积累。在BSO和L-半胱氨酸来源NAC存在的情况下，两种细胞系中HYP积累降低证实了这一点。NAC降低了MCF7细胞对HYP PDT的敏感性，但对MDA-MB-231细胞无效，这与L-半胱氨酸的抗氧化作用及其作为GSTP底物的潜力一致。作为结论，我们在此表明，基于GSH的不同细胞防御机制可作为PDT结果的预测标志物，并作为选择最佳联合策略的指导。
