The Induction of Prostaglandin E2 Production, Interleukin-6 Production, Cell Cycle Arrest, and Cytotoxicity in Primary Oral Keratinocytes and KB Cancer Cells by Areca Nut Ingredients Is Differentially Regulated by MEK/ERK Activation

There are about 200–600 million betel quid (BQ) chew-ers in the world. BQ chewing is one of the major risk factor of hepatocarcinoma, oropharyngeal, and esopha-gus cancers in Taiwan, India, and Southeast Asian coun-tries. Thus, the precise molecular mechanisms deserve investigation. We used cultured primary keratinocytes and KB cells, RT-PCR, flow cytometry, Western blotting, and ELISA to evaluate whether alterations in early gene expression is crucial in the carcinogenic processes of BQ. We observed the induction of c-Fos mRNA expres-sion in human gingival keratinocyte (GK) and KB carci-noma cells by areca nut (AN) extract and arecoline. A maximal increment in c-fos gene expression was shown at about 30 min after challenge. AN extract (100–800 g/ml) and arecoline (0.1– 0.8 mM) also stimulated ERK1/ ERK2 phosphorylation with a maximal stimulation at 5–10 min of exposure. Pretreatment by U0126 (30 M), a MEK inhibitor, markedly inhibited the c-Fos, cyclooxy-genase- 2 (COX-2), and IL-6 mRNA expression of the KB epithelial cells. In addition, U0126 and PD98059 (50 M) also decreased AN extract- and arecoline-associated PGE2 and IL-6 production in GK and KB cells. However, U0126 by itself arrested the cells in G0 /G1 phase, but was not able to prevent AN- and arecoline-induced cell death or apoptosis. In contrast, U0126 enhanced the AN-in-duced apoptosis of KB cells. AN ingredients thus play a significant role in the pathogenesis of oropharyngeal cancer by activation of MEK1/ERK/c-Fos pathway, which promotes keratinocyte inflammation, cell sur-vival, and affects cell cycle progression