The autocrine loop of epidermal growth factor receptor-epidermal growth factor / transforming growth factor-alpha in malignant rhabdoid tumor cell lines: heterogeneity of autocrine mechanism in TTC549.
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.
Department of Pediatrics, Shiga University of Medical Science, Tsukinowa, Otsu, Shiga 520-2192, Japan.
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Narita
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Taga
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Sugita
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Nakazawa
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Ohta
D000328:Adult; D000911:Antibodies, Monoclonal / Q000494:pharmacology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology*; D002455:Cell Division / Q000502:physiology*; D002460:Cell Line; D002648:Child; D004815:Epidermal Growth Factor / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D066246:ErbB Receptors / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D005260:Female; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D017403:In Situ Hybridization; D008297:Male; D012333:RNA, Messenger / Q000032:analysis / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D018335:Rhabdoid Tumor / Q000235:genetics* / Q000473:pathology; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology; D014158:Transcription, Genetic; D016211:Transforming Growth Factor alpha / Q000032:analysis / Q000235:genetics* / Q000502:physiology; D014407:Tumor Cells, Cultured
D000911:Antibodies, Monoclonal; D012333:RNA, Messenger; D016211:Transforming Growth Factor alpha; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D013755:Tetradecanoylphorbol Acetate