Narita T, Taga T, Sugita K, Nakazawa S, Ohta S
Department of Pediatrics, Shiga University of Medical Science, Tsukinowa, Otsu, Shiga 520-2192, Japan.
Jpn J Cancer Res. 2001 Mar;92(3):269-78. doi: 10.1111/j.1349-7006.2001.tb01091.x.
To investigate the effects of the autocrine loop of epidermal growth factor receptor (EGFR)-epidermal growth factor (EGF) / transforming growth factor-alpha (TGF-alpha) on the proliferation and differentiation of malignant rhabdoid tumor (MRT), we used five MRT cell lines, TM87-16, STM91-01, TTC549, TTC642, and YAM-RTK1. RT-PCR analyses revealed expression of EGFR mRNA in all MRT cell lines. In contrast, the expression of either EGF or TGF-alpha mRNA was detected in all MRT cell lines. Expression of EGF, TGF-alpha, and EGFR as determined by immunocytochemical staining and in situ hybridization, correlated with the results of RT-PCR. Upon differentiation-induction with 12-O-tetradecanoylphorbol-13-acetate (TPA), in TTC549, showing an expression of TGF-alpha but not EGF initially, de novo expression of EGF mRNA appeared abruptly on day 2 of TPA treatment. To confirm the EGFR-EGF / TGF-alpha autocrine loop, we used TGF-alpha, EGF, and their antibodies in the cultures. Monoclonal antibody (mAb) to EGFR alone significantly inhibited the growth of cell line TTC549. However, mAb to EGF or TGF-alpha could inhibit proliferation of this cell line only when administrated together. Our findings would suggest that growth of the TTC549 cell line is constitutionally regulated by TGF-alpha / EGFR, but that inhibition of this autocrine mechanism results in transient activation of an autocrine loop involving EGF / EGFR. Our results may indicate the presence of two different autocrine loops of EGFR-EGF and / or EGFR-TGF-alpha in MRT cell lines. The heterogeneity of autocrine mechanisms found in MRT cell lines would be consistent with the multiphenotypic diversity and aggressive characteristics of this enigmatic tumor.
为研究表皮生长因子受体（EGFR）-表皮生长因子（EGF）/转化生长因子-α（TGF-α）自分泌环对恶性横纹肌样瘤（MRT）增殖和分化的影响，我们使用了5种MRT细胞系，即TM87-16、STM91-01、TTC549、TTC642和YAM-RTK1。逆转录聚合酶链反应（RT-PCR）分析显示，所有MRT细胞系中均有EGFR mRNA表达。相比之下，在所有MRT细胞系中均检测到EGF或TGF-α mRNA的表达。通过免疫细胞化学染色和原位杂交确定的EGF、TGF-α和EGFR的表达与RT-PCR结果相关。在用12-O-十四烷酰佛波醇-13-乙酸酯（TPA）诱导分化时，最初显示TGF-α而非EGF表达的TTC549细胞系，在TPA处理第2天突然出现EGF mRNA的从头表达。为证实EGFR-EGF/TGF-α自分泌环，我们在培养物中使用了TGF-α、EGF及其抗体。单独的抗EGFR单克隆抗体（mAb）显著抑制TTC549细胞系的生长。然而，抗EGF或TGF-α mAb仅在联合使用时才能抑制该细胞系的增殖。我们的研究结果表明，TTC549细胞系的生长由TGF-α/EGFR组成性调节，但抑制这种自分泌机制会导致涉及EGF/EGFR的自分泌环的短暂激活。我们的结果可能表明MRT细胞系中存在两种不同的EGFR-EGF和/或EGFR-TGF-α自分泌环。在MRT细胞系中发现的自分泌机制的异质性与这种神秘肿瘤的多表型多样性和侵袭性特征相一致。
