TRANSFORMING GROWTH-FACTOR-ALPHA MESSENGER-RNA AND EPIDERMAL GROWTH-FACTOR RECEPTOR MESSENGER-RNA EXPRESSION IN NORMAL AND NEOPLASTIC MAMMARY-GLANDS OF 4 STRAINS OF MICE WITH DIFFERENT MAMMARY-TUMOR POTENTIALS

Transforming growth factor-alpha (TGF alpha) and epidermal growth fact or receptor (EGF-R) mRNAs were determined by reverse transcriptase-pol ymerase chain reaction (RT-PCR) in the normal and neoplastic mammary g lands of four strains of mice with different mammary tumor potentials (from highest to lowest potential): SHN, GR/A, SLN and C3H/He. At 2 mo nths of age, when the mammary glands of these strains consisted mostly of normal tissue, the samples examined showed the positive expression s of both TGF alpha and EGF-R mRNAs in all strains (4-6 mice per group ), except for EGF-R mRNA in the SLN mice, expressed in only 2 of 4 sam ples associated with no end-bud formation in the mammary glands. At 10 months, all of the samples from all four strains had a positive expre ssion of TGF alpha mRNA. The EGF-R mRNA expression paralleled the degr ee of the formation of preneoplastic hyperplastic alveolar nodules (HA N) in all strains. These findings indicate that TGF alpha and EGF-R pa rticipate in the growth of the mammary glands, and that EGF-R especial ly contributes to the formation of end-buds at younger ages and to tha t of preneoplastic HAN at later ages. All of the samples of mammary tu mors from four strains had positive expressions of both TGF alpha and EGF-R mRNAs.