Dim light during darkness stimulates tumor progression by enhancing tumor fatty acid uptake and metabolism

Tumor linoleic acid uptake and metabolism, and growth are suppressed by mel atonin, the synthesis of which is inhibited by light. Linoleic acid, via it s mitogenic metabolite 13-hydroxyoctadecadienoic acid (13-HODE) is an impor tant growth stimulant of rat hepatoma 7288CTC. Here we compared the effects of an alternating light:dark cycle (12L:12D), dim light (0.25 lux) present during the dark phase of a diurnal light cycle, and constant light on grow th and fatty acid metabolism in hepatoma 7288CTC. Our results show that dim light suppressed melatonin release by the pineal gland, increased tumor li noleic acid uptake and 13-HODE production, and promoted tumor growth as eff ectively as did constant light. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.