Expression of the 3-hydroxy-3-methylglutaryl coenzyme A-reductase and LDL-receptor genes in human embryonic tumours and in normal foetal tissues.

The expression of the HMG-CoA-reductase and LDL-receptor genes was examined in primary human embryonic tumours and in normal human first trimester foetal tissues. All embryonic and extra-embryonic tissues examined contained RNA that hybridized with the HMG-CoA-reductase and LDL-receptor cDNA-probes. However, the transcript levels varied considerably between organs. By using Northern blotting, we confirmed that normal foetal tissues contained HMG-CoA-reductase and LDL-receptor transcripts of normal size (4.2 kB and 5.3 kB, respectively). All human developmental tumours examined were characterized by high levels of HMG-Co-A-reductase RNA. However, when the quality of this RNA was examined in greater detail it was found that the 4.2 kB band only accounted for a minor portion of the RNA. Instead we found a range of other transcripts (3.1, 1.1., 0.95, 0.78 and 0.55 kB) that hybridized with the probe. There was a qualitative difference in that only the non-seminomas contained high levels of the three smaller transcripts (0.95, 0.78 and 0.55 kB). In contrast, only one tumor--an embryonal carcinoma--contained increased levels of LDL-receptor transcript. This was found to be of the expected size (5.3 kB).