Background. We evaluated the mutation status of c-Met in small cell lung cancer (SCLC) and neuroendocrine tumors (NET),
for which relatively limited therapeutic targets have been explored.
Materials and Methods. c-Met was re-sequenced using cell lines and clinical samples. For in vitro studies, DNA constructs containing a
juxtamembrane domain (JMD) and tyrosine kinase domain (TKD) were generated. Detected mutations were introduced into the construct
and effects on c-Met phosphorylation and interaction with tyrosine kinase inhibitor drugs BMS777607 and SU11274 were assessed.
Results. 97 specimens were analyzed: 13 SCLC and 2 pulmonary carcinoid cell lines, 46 SCLC and 36 NET clinical specimens. Mutations
were only detected in the JMD. No mutations were detected in the TKD. Found mutations consisted of the previously reported
R988C and T1010I mutations. One novel JMD mutation, P996S, was detected in a SCLC specimen. The mutation rate in SCLC cell lines
was 25% (31% including a derivative cell line), and 6.5% in clinical specimens. The mutation rate in NET was 8.3%. In vitro, there were
no differences between wild type, R988C or T1010I mutants regarding c-Met phosphorylation at Y1003, located in the JMD, and at
Y1234/1235, located in the TKD. BMS777607 and SU11274 were shown to inhibit phosphorylation of c-Met in wild type and R988C
and T1010I mutants in a similar fashion.
Conclusions. In SCLC and neuroendocrine tumors MET mutations are relatively rare. Detected mutations were located in the juxtamembrane
domain and were of no functional relevance as they did not influence c-Met phosphorylation, regardless of TKI treatment.