Cancer Research, 2016, 76.

Phytoestrogen Suppresses Efflux of the Diagnostic Marker Protoporphyrin IX in Lung Carcinoma

Hirofumi Fujita, Keisuke Nagakawa, Hirotsugu Kobuchi, et al

Department of Cytology and Histology, Okayama University Graduate School of Medicine, Dentistry and Pharmaceutical Sciences, Okayama, Japan

One promising method to visualize cancer cells is based on the detection of the fluorescent photosensitizer protoporphyrin IX (PpIX) synthesized from 5-aminolevulinic acid (ALA), but this method cannot be used in cancers that exhibit poor PpIX accumulation. PpIX appears to be pumped out of cancer cells by the ABC transporter G2 (ABCG2), which is associated with multidrug resistance. Genistein is a phytoestrogen that appears to competitively inhibit ABCG2 activity. Therefore, we investigated whether genistein can promote PpIX accumulation in human lung carcinoma cells. Here we report that treatment of A549 lung carcinoma cells with genistein or a specific ABCG2 inhibitor promoted ALA-mediated accumulation of PpIX by approximately 2-fold. ABCG2 depletion and overexpression studies further revealed that genistein promoted PpIX accumulation via functional repression of ABCG2. After an extended period of genistein treatment, a significant increase in PpIX accumulation was observed in A549 cells (3.7-fold) and in other cell lines. Systemic preconditioning with genistein in a mouse xenograft model of lung carcinoma resulted in a 1.8-fold increase in accumulated PpIX. Long-term genistein treatment stimulated the expression of genes encoding enzymes involved in PpIX synthesis, such as porphobilinogen deaminase, uroporphyrinogen decarboxylase, and protoporphyrinogen oxidase. Accordingly, the rate of PpIX synthesis was also accelerated by genistein pretreatment. Thus, our results suggest that genistein treatment effectively enhances ALA-induced PpIX accumulation by preventing the ABCG2-mediated efflux of PpIX from lung cancer cells and may represent a promising strategy to improve ALA-based diagnostic approaches in a broader set of malignancies.

美国《癌症研究》, 2016, 76.

在肺癌中植物雌激素抑制诊断标志物原卟啉IX的外流

Hirofumi Fujita，Keisuke Nakagawa，Hirotsugu Kobuchi，et al

冈山大学细胞与组织学系冈山大学大学院医学系，牙科学和药学系，日本冈山

显示癌细胞的一种有希望的方法是基于从5-氨基乙酰丙酸（ALA）合成的荧光光敏剂原卟啉IX（PpIX）的检测，但是该方法不能用于显示差的PpIX积累的癌症。 PpIX似乎通过ABC转运蛋白G2（ABCG2）从癌细胞泵出，其与多药耐药性相关。染料木黄酮是看起来竞争性抑制ABCG2活性的植物雌激素。因此，我们调查是否染料木素可以促进人类肺癌细胞中的PpIX积累。在这里我们报告治疗A549肺癌细胞与染料木素或特定ABCG2抑制剂促进ALA介导积累的PpIX约2倍。 ABCG2消耗和过表达研究进一步揭示染料木素通过ABCG2的功能性抑制促进PpIX积累。在延长的染料木黄酮处理时间之后，在A549细胞（3.7倍）和其它细胞系中观察到PpIX积累的显着增加。在肺癌的小鼠异种移植模型中用染料木黄酮的系统性预处理导致累积的PpIX的1.8倍增加。长期染料木素处理刺激编码涉及PpIX合成的酶的基因的表达，例如胆色素原脱氨酶，尿卟啉原脱羧酶和原卟啉原氧化酶。因此，通过染料木黄酮预处理也加速了PpIX合成的速率。因此，我们的研究结果表明，染料木素治疗有效地增强ALA诱导PpIX积累，通过防止ABCG2介导流出的肺癌细胞PpIX和可能代表一个有希望的策略，以改善基于ALA诊断方法在更广泛的恶性肿瘤。