Abstract: A method of inhibiting the proliferation and causing the differentiation of undifferentiated cells comprising contacting the undifferentiated cells with an effective amount of an antisense oligonucleotide having a sequence which is complementary to a region of the IGF-1 receptor RNA. The sequence of the antisense oligonucleotide is selected from an oligodeoxynucleotide sequence complementary to codons −29 to −24 of the signal sequence of the IGF-1 receptor and an oligoribonucleotide sequence complementary to codons 1 to 309 of the sequence of the IGF-1 receptor. The oligoribonucleotide sequence may be provided by an expression vector.