LACK OF GROWTH-INHIBITION OR ENHANCEMENT OF GAP JUNCTIONAL INTERCELLULAR COMMUNICATION AND CONNEXIN43 EXPRESSION BY BETA-CAROTENE IN MURINELUNG EPITHELIAL-CELLS IN-VITRO

The carotenoid, beta-carotene, has been examined in human trials as a possible lung cancer chemopreventive agent, but initial results indica te that the compound is ineffective. Here we have considered whether b eta-carotene could enhance gap junctional intercellular communication (GJIC) and affect the growth of lung epithelial cells, since these eff ects may be involved in the carotenoid's chemopreventive actions. In a ccordance with its lack of lung cancer chemopreventive activity, beta- carotene (1-10 mu M; 1-5 days treatment durations) did not affect GJIC , gap junction protein (connexin43; Cx43) expression, or growth in vit ro of non-transformed (C10) or neoplastic (E9 and 82-132) murine lung epithelial cells. beta-Carotene enhanced GJIC and Cx43 expression and reduced the growth of C3H10T1/2 murine fibroblasts, however. These dat a indicate that the effects of beta-carotene on GJIC and growth are ce ll-specific which may partly explain why the carotenoid is an ineffect ive lung cancer chemopreventive agent.