INSULIN-LIKE GROWTH-FACTOR-I IS AN AUTOCRINE REGULATOR FOR THE BRAIN METASTATIC VARIANT OF A HUMAN NONSMALL CELL LUNG-CELL LINE

Insulin-like growth factor (IGF-I) is associated with autocrine and pa racrine stimulation for cell growth and development of brain tumor cel ls. The function of IGF-I in the brain metastatic variant of human lun g cancer cells is investigated. The cells used here were derived in vi vo with intracarotid injection of human non-small cell lung carcinoma NCI-H226. The tumor was developed as a cultured cell line, H226Br, Unl ike the parental cells, H226Br was tumorigenic in nu/nu nude mice. Rev erse transcriptase-polymerase chain reaction showed that IGF-I transcr ipt of H226Br is increased compared to that of parental cells. The amo unt of IGF-I secreted in cultured medium of H226Br is higher than that of cultured parental cells. The IGF-I receptor-specific antibody, alp ha IR3, inhibits H226Br growth in serum-flee culture. The results esta blished that IGF-I is an autocrine growth regulator for human non-smal l cell lung cancer cells that progressed to brain.