Simple quantitative reverse transcribed-polymerase chain reaction (RT-PCR) method involving recombinant RNA generated by a false-priming PCR product

The role of caspase 3 in producing cytokeratin 19 fragment (CYFRA21-1) in human lung cancer cell lines

The CYFRA 21-1 assay, which detects cytokeratin 19 (CK19) fragment, is widely used as a tumor marker for lung cancer, particularly non-small cell lung cancer. However, the reason that some lung cancer cell lines release CYFRA 21-1 in culture supernatants and others do not remains unclear. We hypothesized that the release of CYFRA 21-1 might be related to the expression of CK19 and caspase 3. In order to prove this, the quantities of mRNA for CK19 were evaluated by the competitive reverse transcriptase-polymerase chain reaction (RT-PCR). CK19 protein synthesis was also evaluated by Western blotting and immunohistochemistry, and the levels of CYFRA 21-1 in the culture supernatant were measured by an immunoradiometric assay. The expression of mRNA for caspase 3 was evaluated by the RT-PCR, and caspase 3 protein synthesis was also evaluated by immunohistochemistry. In 13 lung cancer cell lines, the amounts of mRNA for CK19 correlated with the levels of CYFRA 21-1 in culture supernatants, results of Western blotting for CK19, and positivities of immunohistochemistry for CK19. In 5 cell lines that produced a significant amount of CYFRA 21-1, the level of CYFRA 21-1 correlated with the positivity of RT-PCR for caspase 3 and immunohistochmistry for caspase 3. This suggests that caspase 3 played a role in the formation of CYFRA 21-1. In addition, the specific inhibitor of caspase 3 significantly inhibited the release of CYFRA 21-1 in culture supernatants. In conclusion, we demonstrate that caspase 3, which cleaves several intermediate filaments and carries out cell apoptosis, played an important role in producing CYFRA 21-1 in human lung cancer cell lines.

Mechanisms of the release of CYFRA21-1 in human lung cancer cell lines

The CYFRA 21-1 assay which detects cytokeratin 19 (CK19) fragment is widely used as a tumor marker for lung cancer. However, the reason why some lung cancer cell lines release CK19 fragment in culture supernatants and others do not, remains unclear. It was hypothesized that the release of CK19 fragment may be elucidated by the expression of mRNA for CK19. In order to prove this, the mRNA for CK19 was quantitatively evaluated by the competitive reverse transcriptase-polymerase chain reaction (competitive RT-PCR). The level of CYFRA 21-1 in the culture supernatant was measured by an immunoradiometric assay. CK19 protein synthesis was evaluated by a Western blotting and immunohistochemistry. Fourteen lung cancer cell lines were evaluated, and the amount of mRNA correlated well with the level of CYFRA 21-1 in culture supernatants. Analysis of genomic DNA for CK19 demonstrated that three cell lines which could not produce CYFRA 21-1, conjectured that some abnormalities in exon 1 or the 5'-region upstream from exon 1. In conclusion, it was demonstrated that the release of CK19 fragment was closely related to the expression of mRNA for CK19, and the possibility that genomic change of CK19 DNA down-regulated the expression of mRNA for CK19 was suggested.

Molecular cloning and gene expression of growth hormone-releasing peptide receptor in rat tissues

We cloned a fragment of the rat GH-releasing peptide (GHRP) receptor homologue and examined the tissue distribution of GHRP receptor mRNA in rats. Sequence analysis showed that the open reading frame is well conserved between rat and human with 96% identity in a 364-amino acid overlap. By reverse transcription-polymerase chain reaction we detected GHRP receptor mRNAs in the rat brain including the hypothalamus, anterior pituitary, and renal pelvis in twenty-eight tissues tested. Microdissection revealed that GHRP receptor mRNAs were localized predominantly in the arcuate nucleus and ventromedial hypothalamus.

Effects of adrenalectomy and glucocorticoid receptor antagonist, RU38486, on pituitary growth hormone-releasing hormone receptor gene expression in rats

We examined the effects of adrenalectomy and a glucocorticoid receptor antagonist, RU38486, on pituitary GH-releasing hormone (GRH) receptor gene expression in rats. GRH receptor mRNA levels were significantly decreased in adrenalectomized rats and replacement of dexamethasone reversed the decrease to normal. GH secretion was inhibited by adrenalectomy, whereas dexamethasone replacement failed to restore the impaired GH secretion. A high dose of RU38486 had an agonistic effect on GRH receptor mRNA levels. These results suggest that endogenous glucocorticoid is necessary for normal expression of pituitary GRH receptor mRNA in rats.