Analysis of tyrosine kinase mRNAs including four FGF receptor mRNAs expressed in MCF‐7 breast‐cancer cells

Abstract

The MCF‐7 cell line is a hormone‐responsive human breast‐cancer cell line, which has been extensively used in studies of estrogen regulation of cell growth. These studies have indicated that the growth stimulation of the MCF‐7 cells by estrogens may be effected by an autocrine mechanism involving several growth factors, such as EGF, TGFα and IGF‐I and their receptors. We have amplified and cloned tyrosine‐kinase‐related sequences from the MCF‐7 cell mRNA using the polymerase chain reaction and characterized the partial cDNAs obtained by nucleic acid sequencing. Nine tyrosine kinase cDNAs and one serine/threonine kinase cDNA were identified among the amplified sequences. Four different tyrosine kinase genes encoding receptors for fibroblast growth factors (FGFs) were found to be expressed by the MCF‐7 cells. In addition, differences were observed in the expression of these members of FGF receptor family in different breast‐cancer cells. A putative tyrosine‐kinase receptor and a novel serine/threonine kinase were preferentially expressed in estrogen‐responsive tumor cell lines. However, no estrogen‐dependent regulation of any of the novel tyrosine‐kinase receptor mRNAs was found in any of the cell lines including the MCF‐7 or ZR‐75‐1 cells, where the expression of the neu proto‐oncogene mRNA was decreased during estrogen treatment. The expression of several FGF receptors by breast‐cancer cells suggests that FGFs may be involved in their growth regulation and tumorigenesis.