TTF-1-induced ROR1 is required to sustain EGFR survival signaling in lung adenocarcinoma
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ABSTRACT: Adenocarcinoma is the most common histologic subtype of lung cancer, which is the leading cause of cancer death. We and others previously identified TTF-1, a lineage-specific transcription factor required for branching morphogenesis and physiological lung functions, as a lineage-survival oncogene in lung adenocarcinoma. However, how TTF-1 mediates survival signals remains elusive. Here we show that TTF-1 induces receptor tyrosine kinase-like orphan receptor 1 (ROR1), which in turn mediates TTF-1 survival signaling in lung adenocarcinoma. Inhibition of ROR1 impaired prosurvival signaling through the PI3K-AKT pathway and induced nuclear accumulation of FOXO1. These were found to be imposed, at least in part, through PTEN inactivation via c-Src, while ROR1 was shown to physically interact with and phosphorylate c-Src. ROR1 inhibition also elicited marked p38 activation, provoking ill-balance between prosurvival and proapoptotic signaling, and consequential “oncogenic shock.” In addition, we found that ROR1 is crucially involved in EGFR- and MET-mediated prosurvival signaling. ROR1 knockdown effectively induced apoptosis in lung adenocarcinoma cell lines with acquired EGFR TKI resistance conferred by a secondary T790M EGFR mutation, or HGF-elicited MET signaling and resultant switching of the addicted receptor tyrosine kinases (RTKs). Taken together, our findings indicate that ROR1 RTK is a very promising molecular target for development of a novel therapeutic means to treat this hard-to-cure cancer. Dye-swap experiment, vector control vs. stable TTF-1 transfectant of HPL1D, immortalized human peripheral lung epithelial cell line.
ORGANISM(S): Homo sapiens
SUBMITTER: Takahashi Takashi
PROVIDER: E-GEOD-25830 | biostudies-arrayexpress |
REPOSITORIES: biostudies-arrayexpress
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