ABCG2 expression is related to low 5-ALA photodynamic diagnosis (PDD) efficacy and cancer stem cell phenotype, and suppression of ABCG2 improves the efficacy of PDD
ABCG2 expression is related to low 5-ALA photodynamic diagnosis (PDD) efficacy and cancer stem cell phenotype, and suppression of ABCG2 improves the efficacy of PDD
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DOI：
10.1371/journal.pone.0216503
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发表时间：
2019-05-13
期刊：
影响因子：
3.7
通讯作者：
Torigoe, Toshihiko
中科院分区：
文献类型：
--
作者：
Kawai, Noriko;Hirohashi, Yoshihiko;Torigoe, Toshihiko
光动力学诊断/治疗（PDD/PDT）是诊断和治疗癌症的新模式。光敏剂原卟啉IX在细胞内从5-氨基乙酰丙酸（5-ALA）代谢，并且使用5-ALA的PDD/PDT已被批准用于皮肤恶性肿瘤和神经胶质瘤。然而，定义PDD/PDT疗效的分子机制尚不清楚。在本研究中，我们分析了ATP结合盒（ABC）转运蛋白在PDD中的功能，使用5-ALA。除了胰腺癌细胞系PANC-1显示出不均匀染色外，大多数检查的人胃肠道癌细胞系细胞显示出5-ALA的均匀染色模式。为了分析这种异质性染色模式，从PANC-1细胞建立单细胞克隆，并评估ABC转运蛋白的表达。在ABC转运蛋白基因检测中，ABCG 2与5-ALA阳性染色率呈负相关。PANC-1克隆#2细胞显示出最高水平的ABCG 2表达和最低水平的5-ALA染色，阳性率仅为0.6%。小分子干扰RNA敲低ABCG 2基因可提高PANC-1野生型和克隆细胞中5-ALA染色的阳性率。有趣的是，PANC-1克隆#2细胞显示出高的球体形成能力和肿瘤形成能力，表明该细胞含有大量的癌症干细胞（CSC）。ABCG 2的敲除或抑制增加了5-ALA染色的速率，但不降低球形成能力。这些结果表明，表达高水平ABCG 2的胃肠癌细胞系富含CSC，并显示出低的5-ALA染色率，但5-ALA染色率可以通过抑制ABCG 2来提高。
Photodynamic diagnosis/therapy (PDD/PDT) are novel modalities for the diagnosis and treatment of cancer. The photosensitizer protoporphyrin IX is metabolized from 5-aminolevulinic acid (5-ALA) intracellularly, and PDD/PDT using 5-ALA have been approved in dermatologic malignancies and gliomas. However, the molecular mechanism that defines the efficacy of PDD/PDT is unknown. In this study, we analyzed the functions of ATP-binding cassette (ABC) transporters in PDD using 5-ALA. Most of the human gastrointestinal cancer line cells examined showed a homogenous staining pattern with 5-ALA, except for the pancreatic cancer line PANC-1, which showed heterogeneous staining. To analyze this heterogeneous staining pattern, single cell clones were established from PANC-1 cells and the expression of ABC transporters was assessed. Among the ABC transporter genes examined, ABCG2 showed an inverse correlation with the rate of 5-ALA-positive staining. PANC-1 clone #2 cells showed the highest level of ABCG2 expression and the lowest level of 5-ALA staining, with only a 0.6% positive rate. Knockdown of the ABCG2 gene by small interfering RNAs increased the positive rate of 5-ALA staining in PANC-1 wild-type and clone cells. Interestingly, PANC-1 clone # 2 cells showed the high sphere-forming ability and tumor-formation ability, indicating that the cells contained high numbers of cancer stem cells (CSCs). Knockdown or inhibition of ABCG2 increased the rate of 5-ALA staining, but did not decrease sphere-forming ability. These results indicate that gastrointestinal cancer cell lines expressing high levels of ABCG2 are enriched with CSCs and show low rates of 5-ALA staining, but 5-ALA staining rates can be improved by inhibition of ABCG2.