MET exon 14 skipping mutation drives cancer progression and recurrence via activation of SMAD2 signalling

Backgroundc-Met encoded by the proto-oncogene MET, also known as hepatocyte growth factor (HGF) receptor, plays a crucial role in cellular processes. MET exon 14 skipping alteration (MET Delta 14EX) is a newly discovered MET mutation. SMAD2 is an important downstream transcription factor in TGF-beta pathway. Unfortunately, the mechanisms by which MET Delta 14EX leads to oncogenic transformation are scarcely understood. The relationship between MET Delta 14EX and SMAD2 has not been studied yet.MethodsWe generate MET Delta 14EX models by CRISPR-Cas9. In vitro transwell, wound-healing, soft-agar assay, in vivo metastasis and subcutaneous recurrence assay were used to study the role of MET Delta 14EX in tumour progression. RNA-seq, Western blotting, co-immunoprecipitation (CO-IP) and immunofluorescent were performed to explore the interaction between c-Met and SMAD2.ResultsOur results demonstrated that MET Delta 14EX, independent of HGF, can prolong the constitutive activation of c-Met downstream signalling pathways by impeding c-Met degradation and facilitating tumour metastasis and recurrence. Meanwhile, MET Delta 14EX strengthens the interaction between c-Met and SMAD2, promoting SMAD2 phosphorylation. Therapeutically, MET inhibitor crizotinib impedes MET Delta 14EX-mediated tumour metastasis by decreasing SMAD2 phosphorylation.ConclusionsThese data elucidated the previously unrecognised role of MET Delta 14EX in cancer progression via activation of SMAD2 independent of TGF-beta, which helps to develop more effective therapies for such patients.MET Delta 14EX alteration significantly triggers tumour progression via activation of SMAD2 signalling that are involved in activating tumour invasion, metastasis and recurrence. On the left, in the MET wild-type (METWT), the juxtamembrane (JM) domain is involved in the regulation of tyrosine kinase activity, receptor degradation, and caspase cleavage. On the right, the MET Delta 14EX mutation leads to the loss of the juxtamembrane domain, resulting in an abnormal MET protein lacking a CBL-binding site. This causes the accumulation of truncated MET receptors followed by constitutive activation of the MET signalling pathway. Thus, the MET Delta 14EX-mutated protein has strong binding and phosphorylation to SMAD2, which results in the phosphorylation of a large number of SMAD2/3 proteins that combine with SMAD4 to form a complex in the nucleus, activating downstream signalling pathways, such as EMT and ECM remodelling, resulting in tumour progression and recurrence. TF transcription factor.ConclusionsThese data elucidated the previously unrecognised role of MET Delta 14EX in cancer progression via activation of SMAD2 independent of TGF-beta, which helps to develop more effective therapies for such patients.MET Delta 14EX alteration significantly triggers tumour progression via activation of SMAD2 signalling that are involved in activating tumour invasion, metastasis and recurrence. On the left, in the MET wild-type (METWT), the juxtamembrane (JM) domain is involved in the regulation of tyrosine kinase activity, receptor degradation, and caspase cleavage. On the right, the MET Delta 14EX mutation leads to the loss of the juxtamembrane domain, resulting in an abnormal MET protein lacking a CBL-binding site. This causes the accumulation of truncated MET receptors followed by constitutive activation of the MET signalling pathway. Thus, the MET Delta 14EX-mutated protein has strong binding and phosphorylation to SMAD2, which results in the phosphorylation of a large number of SMAD2/3 proteins that combine with SMAD4 to form a complex in the nucleus, activating downstream signalling pathways, such as EMT and ECM remodelling, resulting in tumour progression and recurrence. TF transcription factor.

Automated summary

MET Delta 14EX alteration significantly triggers tumor progression via activation of SMAD2 signaling that is involved in tumor invasion, metastasis, and recurrence. The MET Delta 14EX mutation leads to an abnormal MET protein lacking a CBL-binding site, which results in the constitutive activation of the MET signaling pathway and strong binding and phosphorylation to SMAD2.