Central role of the threonine residue within the p+1 loop of receptor tyrosine kinase in STAT3 constitutive phosphorylation in metastatic cancer cells.
The receptor tyrosine kinases (RTKs) RET, MET, and RON all carry the Met(p+1loop)-->Thr point mutation (i.e., 2B mutation), leading to the formation of tumors with high metastatic potential. Utilizing a novel antibody array, we identified constitutive phosphorylation of STAT3 in cells expressing the 2B mutation but not wild-type RET. MET or RON with the 2B mutation also constitutively phosphorylated STAT3. Members of the EPH, the only group of wild-type RTK that carry Thr(p+1loop) residue, are often expressed unexpectedly in different types of cancers. Ectopic expression of wild-type but not Thr(p+1loop)-->Met substituted EPH family members constitutively phosphorylated STAT3. In both RTK(Metp+1loop) with 2B mutation and wild-type EPH members the Thr(p+1loop) residue is required for constitutive kinase autophosphorylation and STAT3 recruitment. In multiple endocrine neoplasia 2B (MEN-2B) patients expressing RET(M918T), nuclear enrichment of STAT3 and elevated expression of CXCR4 was detected in metastatic thyroid C-cell carcinoma in the liver. In breast adenocarcinoma cell lines expressing multiple EPH members, STAT3 constitutively bound to the promoters of MUC1, MUC4, and MUC5B genes. Inhibiting STAT3 expression resulted in reduced expression of these metastasis-related genes and inhibited mobility. These findings provide insight into Thr(p+1loop) residue in RTK autophosphorylation and constitutive activation of STAT3 in metastatic cancer cells.
Yuan
Zheng-Long
ZL
Department of Surgery Science, Brown University School of Medicine/Rhode Island Hospital, 593 Eddy St., Providence, RI 02903, USA.
Guan
Ying-Jie
YJ
Wang
Lijuan
L
Wei
Wenyi
W
Kane
Agnes B
AB
Chin
Y Eugene
YE
D000595:Amino Acid Sequence; D000818:Animals; D045744:Cell Line, Tumor; D002467:Cell Nucleus / Q000378:metabolism / Q000473:pathology; D004268:DNA-Binding Proteins / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*; D006801:Humans; D008297:Male; D051379:Mice; D008969:Molecular Sequence Data; D009077:Mucins / Q000235:genetics; D009154:Mutation / Q000235:genetics; D009362:Neoplasm Metastasis / Q000235:genetics / Q000473:pathology; D010766:Phosphorylation; D020794:Receptor Protein-Tyrosine Kinases / Q000737:chemistry / Q000235:genetics* / Q000378:metabolism*; D019718:Receptors, CXCR4 / Q000235:genetics / Q000378:metabolism; D050796:STAT3 Transcription Factor; D016415:Sequence Alignment; D013912:Threonine / Q000235:genetics / Q000378:metabolism*; D015534:Trans-Activators / Q000737:chemistry* / Q000235:genetics / Q000378:metabolism*
D004268:DNA-Binding Proteins; D009077:Mucins; D019718:Receptors, CXCR4; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; C494087:Stat3 protein, mouse; D015534:Trans-Activators; D013912:Threonine; D020794:Receptor Protein-Tyrosine Kinases