Evidence of thyroid volume increase in normal subjects receiving excess iodide.

A prospective study was conducted on 10 normal male volunteers to investigate the effect of the administration of excess iodide on thyroid volume. After 1 week of dietary iodide restriction, all subjects were given daily oral doses (27 mg daily total iodine dose) of licorice lecithin-bound iodine tablets for 4 weeks. Thyroid function studies, total serum iodine concentration, and urinary iodine excretion were monitored. Thyroid volume was measured by high resolution echoscanner before treatment, on the day of the last treatment, and 1 month after the treatment. There was a significant rise in serum TSH levels, with a small decline in serum free T4 concentration during iodide administration; the values remained within the normal range except for two subjects. Serum thyroglobulin levels were increased in parallel with serum TSH levels, which became higher than normal after 1 week of treatment. The volume of the thyroid gland became significantly enlarged after 28 days of iodide intake. When iodide was discontinued, thyroid volume and function returned to baseline levels within 1 month for all subjects. This is the first documentated objective evidence that the compensatory rise in serum TSH in response to iodide administration elicits reversible thyroid hypertrophy in normal subjects.

Inhibitory effect of prostaglandin delta 12-PGJ2 on cell proliferation and alpha-fetoprotein expression in HuH-7 human hepatoma cells.

9-deoxy-delta 9,delta 12-13,14-dihydro-prostaglandin D2 (delta 12-PGJ2) is a potent inhibitor of proliferation of tumor cells. In the present study, the effect of delta 12-PGJ2 on the alpha-fetoprotein(AFP) and the albumin gene expression was analyzed in HuH-7 human hepatoma cells. delta 12-PGJ2 inhibited the cell growth and reduced the medium AFP concentrations dose-dependently. To determine whether this decline of AFP depends only on the relative decrease in cell numbers by delta 12-PGJ2, or is in part, due to the decrease in the cellular AFP synthesis by delta 12-PGJ2, Northern blot analysis was performed in this study. By Northern blotting, it was shown that delta 12-PGJ2 caused a marked reduction in the levels of the AFP mRNA and the albumin mRNA. In contrast, the level of the beta-actin mRNA was not changed by delta 12-PGJ2. In the transient chloramphnicol acetyltransferase plasmid transfection experiments, delta 12-PGJ2 did not suppress the AFP enhancer activity, which possibly regulates both the AFP and the albumin gene expression in HuH-7 hepatoma cells, but resulted in the selective repression of the AFP and the albumin promoter activity. These results suggest that delta 12-PGJ2 suppresses not only cell growth but also expression of the AFP gene and the albumin gene at the transcriptional level in human hepatoma cells.

Transcriptional regulation of alpha-fetoprotein expression by dexamethasone in human hepatoma cells.

The level of alpha-fetoprotein (AFP) mRNA in HuH-7 human hepatoma cells is elevated by the addition of dexamethasone to the culture medium. To locate the DNA region involved in hormonal regulation of the AFP gene, we constructed recombinant plasmids in which various lengths of the 5'-flanking sequence of the human AFP gene were fused to the CAT gene. Various cell lines were transfected with the recombinant plasmids, incubated with or without 3 x 10(-6) M dexamethasone, and then assayed for chloramphenicol acetyltransferase expression. In hepatoma cells that produce AFP, the dexamethasone treatment resulted in the stimulated chloramphenicol acetyltransferase expression when the transfected plasmids contained 169 base pairs (bp) or longer AFP 5'-flanking sequence. No dexamethasone effect was observed when the 5'-flanking sequence was less than 98 bp long. The dexamethasone stimulation was effectively suppressed by the glucocorticoid antagonist RU486, indicating that this effect is mediated by glucocorticoid receptors. The 71-bp region between positions -169 and -98 contains a nucleotide stretch which is similar to the consensus sequence of the glucocorticoid responsive element (GRE). Partial alterations of this sequence resulted in decreased dexamethasone response. The GRE-containing region stimulated heterologous (SV40) promoter activity in response to dexamethasone treatment in an orientation- and position-independent manner. The GRE and the upstream AFP enhancer function independently from each other.

Analysis of alpha-fetoprotein gene expression in hepatocellular carcinoma and liver cirrhosis by in situ hybridization.

The expression of the alpha-fetoprotein (AFP) gene in hepatocellular carcinoma (HCC) and liver cirrhosis by in situ hybridization analysis of AFP mRNA in cryostat and paraffin-embedded tissue sections was studied. In HCC sections the majority of tumor cells showed positive hybridization with a 3H-labeled AFP complementary DNA probe. The number of radioactive hybrid grains detected in HCC sections generally paralleled the level of serum AFP in the patient. In liver cirrhosis sections a small number of cells showed positive hybridization. These cells were dispersed in the tissue and morphologically indistinguishable from surrounding hepatocytes. Each of these cells contained a high level of hybridization signals to permit easy identification. In situ hybridization analysis of AFP mRNA may be of use in detecting preneoplastic cells in liver cirrhosis that cannot be defined on the morphologic and immunohistochemical basis.