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Abstract

The gene responsible for transcribing glyceraldehyde-3-phosphate dehydrogenase (GAPDH) is commonly used as a reporter gene to estimate the amount of RNA present in Northern analyses. However, recent data suggest that GAPDH gene expression may vary with the extent of cell proliferation and differentiation. 28S-ribosomal RNA (28S-rRNA) has also been employed to normalize Northern blots prepared with total RNA. In the present study, we compared the expression of GAPDH messenger RNA (mRNA) with 28S-rRNA by Northern blot analyses in human hepatocellular carcinoma tissues (HCC) and adjacent non-HCC tissues from eight patients with chronic viral hepatitis-induced cirrhosis and normal liver tissue from eight healthy control subjects. The results of the study revealed that GAPDH mRNA levels in HCC were significantly higher (14×-16×) than those in adjacent non-HCC and normal liver tissues. Conversely, 28S-rRNA levels did not vary among HCC, adjacent non-HCC, and normal liver tissues. We also demonstrated that the 28S-RNA signal was proportional to the amount of RNA loaded. These findings indicate that 28S-rRNA, rather than GAPDH mRNA, should be used as RNA loading controls for Northern blot analyses involving HCC and nontumor tissues. The findings also raise the possibility that GAPDH mRNA gene expression might serve as a diagnostic indicator for human HCC.