Same Ribosomal Protein Messenger RNAs as Colonic Gastric and Hepatocellular Carcinomas Do Not Overexpress the Updated Version

The levels of a number of ribosomal protein mRNAs are reported to be increased in human colon cancer. We have assessed whether selected ribosomal protein mRNAs are overexpressed in other gastrointestinal malignancies, namely gastric and hepatocellular carcinomas. Subtracted complementary DNA libraries were generated from paired samples of human (a) coloréela!carcinoma minus adjacent normal colonie mucosa and (hi hepatocellular carcinoma minus adjacent normal liver. Screening of—3% of these library clones determined that ribosomal protein mRNAs encoding L18 and L37 (not previously reported) and PO and S6 were overexpressed in one or the other library. Their complementary DNA inserts were then used as probes to evaluate their expression in a larger number of paired tumor/normal surgical samples of human colonie, gas tric, and hepatocellular carcinomas, by Northern hybridization. The inKNA signal was greater in the colonie carcinoma than in paired adjacent normal colonie mucosa in 38 of 42 cases for PO [tumor/normal (T/N) ratio = 3.0 ±0.3, mean ±SE, P < 0.001] (G. F. Barnard, R. J. Staniunas, S. Bao, K. Mudine. J. L. Gollan, G. D. Steele, Jr., and L. B. Chen, Cancer Res., 52: 3067-3072, 1992), in 25 of 28 cases for L18 (T/N ratio = 3.7 ±0.5, P < 0.001), in 27 of 28 cases for L37 (T/N ratio = 5.3 ±0.4, P < 0.001), and in 24 of 28 cases for S6 (T/N ratio = 3.1 i 0.5, P < 0.01 ). The level of mRNA overexpression of L18 and S6 did not correlate with the Dukes' stage of disease. In hepatocellular carcinoma samples, using the same four ribo somal protein complementary DNA probes, only PO mRNA was signifi cantly increased (T/N ratio = 2.8 ±0.4, n = 6, P = 0.047). In gastric carcinoma samples, none of these mRNAs was increased (mean T/N ratios = 0.9—1.2,n = 6). Therefore, gastric and hepatocellular carcinomas do not overexpress the same ribosomal protein mRNAs as do colonie carcinoma.