Detection of overexpressed and phosphorylated wild-type kit receptor in surgical specimens of small cell lung cancer.
OBJECTIVE
The combinations of various chemotherapeutic drugs currently used to treat advanced small cell lung cancer (SCLC) led to similarly poor survival outcomes, which is why new molecular biology approaches are needed to design and select targeted therapies.


METHODS
Thirteen stage I SCLC surgical specimens were screened for c-Kit gene mutations by sequencing whole cDNA and for KIT receptor expression/activation by immunoprecipitation and Western blotting. Both the paraffin-embedded and frozen materials were analyzed by immunocytochemistry, and the stem cell factor cognate ligand was assessed by retrotranscription PCR.


RESULTS
In all cases, we showed the presence of wild-type KIT receptors by analyzing the entire coding sequence, which together with the detection of the cognate ligand stem cell factor, supports the establishment of an autocrine loop. In addition, the KIT receptor was activated/phosphorylated. The immunoprecipitation/Western blotting data fit the observed immunophenotype. Interestingly, comparison of the level of KIT expression was at least 10 times higher in the tumoral specimens than the normal reference lungs.


CONCLUSIONS
The KIT molecular profile derived from the analysis of SCLC surgical specimens shows that wild-type KIT is overexpressed and phosphorylated in the presence of stem cell factor. This finding, which is consistent with pathological KIT activation driven by an autocrine loop, is particularly interesting in the light of the recent development of new tyrosine kinase inhibitory drugs, which are highly effective in blocking wild-type KIT receptors.
Tamborini
Elena
E
Experimental Molecular Pathology, Department of Pathology, Istituto Nazionale per lo Studio e al Cura dei Tumori, Milan, Italy.
Bonadiman
Lorena
L
Negri
Tiziana
T
Greco
Angela
A
Staurengo
Samantha
S
Bidoli
Paolo
P
Pastorino
Ugo
U
Pierotti
Marco A
MA
Pilotti
Silvana
S
D017398:Alternative Splicing; D015153:Blotting, Western; D018288:Carcinoma, Small Cell / Q000175:diagnosis / Q000235:genetics* / Q000601:surgery; D016022:Case-Control Studies; D006801:Humans; D007124:Immunoenzyme Techniques; D047468:Immunoprecipitation; D008168:Lung / Q000378:metabolism / Q000473:pathology; D008175:Lung Neoplasms / Q000175:diagnosis / Q000235:genetics* / Q000601:surgery; D009154:Mutation / Q000235:genetics*; D010766:Phosphorylation; D020033:Protein Isoforms; D019009:Proto-Oncogene Proteins c-kit / Q000235:genetics* / Q000378:metabolism; D012333:RNA, Messenger / Q000378:metabolism; D019089:Stem Cell Factor / Q000235:genetics / Q000378:metabolism; D015854:Up-Regulation
D020033:Protein Isoforms; D012333:RNA, Messenger; D019089:Stem Cell Factor; D019009:Proto-Oncogene Proteins c-kit