Eum Won Sik, Li Ming Zhen, Sin Gye Suk, Choi Soo Young, Park Jae-Bong, Lee Jae Yong, Kwon Hyeok Yil
Department of Physiology, College of Medicine, Hallym University, Chunchon 200-702, Korea.
Exp Mol Med. 2003 Oct 31;35(5):379-84. doi: 10.1038/emm.2003.50.
Dexamethasone converts pluripotent pancreatic AR42J cells into exocrine cells expressing digestive enzymes. In order to address molecular mechanism of this differentiation, we have investigated the role of mitogen-activated protein (MAP) kinase pathway and gene expressions of p21(waf1/cip1) and nuclear oncogenes (c-fos and c-myc) during AR42J cell differentiation. Dexamethasone markedly increased the intracellular and secreted amylase contents as well as its mRNA level. However, cell growth and DNA content were significantly decreased. With these phenotypic changes, AR42J cells induced transient mRNA expression of p21(waf1/cip1) gene, which reached maximal level by 6 h and then declined gradually toward basal state. In contrast to p21(waf1/cip1), c-fos gene expression was transiently inhibited by 6 h and then recovered to basal level by 24 h. Increased c-myc expression detected after 3 h, peaked by 12 h, and remained elevated during the rest of observation. Dexamethasone inhibited epidermal growth factor-induced phosphorylation of extracellular signal regulated kinase. Inhibition of MAP kinase pathway by PD98059 resulted in further elevation of the dexamethasone-induced amylase mRNA and p21(waf1/cip1) gene expression. These results suggest that p21(waf1/cip1) and nuclear oncogenes are involved in dexamethasone-induced differentiation and inhibition of MAP kinase pathway accelerates the conversion of undifferentiated AR42J cells into amylase-secreting exocrine cells.
地塞米松可将多能胰腺AR42J细胞转化为表达消化酶的外分泌细胞。为了探究这种分化的分子机制，我们研究了丝裂原活化蛋白（MAP）激酶途径以及p21（waf1/cip1）和核癌基因（c-fos和c-myc）在AR42J细胞分化过程中的基因表达作用。地塞米松显著增加了细胞内和分泌的淀粉酶含量及其mRNA水平。然而，细胞生长和DNA含量显著降低。伴随这些表型变化，AR42J细胞诱导了p21（waf1/cip1）基因的瞬时mRNA表达，该表达在6小时达到最高水平，然后逐渐下降至基础状态。与p21（waf1/cip1）相反，c-fos基因表达在6小时被瞬时抑制，然后在24小时恢复到基础水平。3小时后检测到c-myc表达增加，12小时达到峰值，并在其余观察期间保持升高。地塞米松抑制表皮生长因子诱导的细胞外信号调节激酶磷酸化。用PD98059抑制MAP激酶途径导致地塞米松诱导的淀粉酶mRNA和p21（waf1/cip1）基因表达进一步升高。这些结果表明，p21（waf1/cip1）和核癌基因参与了地塞米松诱导的分化，并且MAP激酶途径的抑制加速了未分化的AR42J细胞向分泌淀粉酶的外分泌细胞的转化。
