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.
Narita
T
T
Department of Pediatrics, Shiga University of Medical Science, Tsukinowa, Otsu, Shiga 520-2192, Japan.
Taga
T
T
Sugita
K
K
Nakazawa
S
S
Ohta
S
S
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