Cooperative regulation of the invasive and metastatic phenotypes by different domains of the type I insulin-like growth factor receptor beta subunit

The receptor for the type 1 insulin-like growth factor (IGF-1) regulates mu ltiple cellular functions impacting on the metastatic phenotype of tumor ce lls, including cellular proliferation, anchorage-independent growth, surviv al, migration, synthesis of the 72-kDa type IV collagenase and invasion. We have used site-directed mutagenesis to generate domain-specific mutants of the receptor beta subunit to analyze the role of specific tyrosines in the regulation of the invasive/metastatic phenotype. Poorly invasive M-27 carc inoma cells expressing low receptor numbers were transfected with a plasmid vector expressing IGF-1 receptor cDNA in which single or multiple tyrosine codons in the kinase domain, namely Tyr-1131, Tyr-1135, and Tyr-1136 or th e C-terminal tyrosines 1250 and 1251 were substituted with phenylalanine. C hanges in the invasive and metastatic properties, were analyzed relative to M-27 cells expressing the wild type receptor. We found that cells expressi ng the Y1131F,Y1135F,Y1136F or Y1135F receptor mutants lost all IGF-ER.-dep endent functions and their phenotypes were indistinguishable from, or suppr essed relative to, the parent line. The Y1250F,Y1251F substitution abolishe d anchorage-independent growth, cell spreading, and the anti-apoptotic effe ct of IGF-I whereas all other IGF-IR-dependent phenotypes were either unper turbed (i.e. mitogenicity) or only partially reduced (migration and invasio n). The results identify three types of receptor-dependent functions in thi s model: those dependent only on an intact kinase domain (DNA synthesis), t hose dependent equally on kinase domain and Tyr-1250/1251 signaling (e.g. a poptosis, soft agar cloning) and those dependent on kinase domain and enhan ced through Tyr-1250/1251 signaling (migration, invasion). They suggest tha t signals derived from both regions of the receptor cooperate to enhance tu mor metastasis.