High-Level Expression of the Ribosomal Protein L19 in Human Breast T\imors That Overexpress erbB-21

The erbK-2 (or III K-2 or neu i gene is amplified and overexpressed in approximately one-third of cancers of the breast, stomach, and ovary. Evidence is accumulating that erbK-2 overexpression is associated with decreased survival of breast cancer patients. In an effort to understand how erbß-2overexpression might impart a more malignant potential to breast cancer cells, we have searched for evidence of changes in gene expression associated with erbß-2 overexpression. Using differential screening of a complementary DNA library we identified several comple mentary DNAs that represent mRNAs the expression of which may vary according to erbß-2level. One complementary DNA was studied in detail. The mRNA encoding the ribosomal protein I.I') (1.9 kilobases) was more abundant in breast cancer samples that express high levels of erbß-2 (P < 6 X 10~7). The level of IA9 mRNA expression varied over a 1to 64-fold range among the tumor samples. No evidence of gene amplification for I.I') was identified. The 1.19 overexpression in these breast tumor samples was not associated with the increased expression of the mRNAs for other ribosomal proteins (SI6 and L26).