Tumor-Promoting Activity of Phthalate Esters Estimated by in Vitro Transformation Using Bhas Cells.

Abstract

tyl phthalate (DBP), and/or diisononyl phthalate (DINP).1) These compounds have been identified as contaminants of environmental water, soil, and the atmosphere, and have been detected in human serum and plasma.2) Some phthalate diesters induce testicular toxicity and other effects on the male and the female reproductive tract.3) Zeiger et al. found that 16 phthalate diesters had no mutagenic activity in the Ames assay.4) Therefore the hepatocarcinogenic effect of DEHP must be exerted during the promotion phase, since this compound is not genotoxic. 5) Both DEHP and DINP are peroxisome proliferators that induce tumors in the rodent liver.6) This effect is probably not directly exerted by the diesters but by their monoesters and oxidative products.7) In addition, phthalate diesters are metabolized to monoesters by hydrolases in many tissues, such as the intestine, pancreas, and blood, 8) where they are absorbed almost entirely as the corresponding monoesters. 9)Although others have estimated the tumor initiation and/or promotion activity of DEHP, only a few have examined the in vitro promoting activity of other phthalate diesters and related monoesters at low doses. The present study screened the tumorpromoting activity of four phthalate diesters and three monoesters in vitro using BALB/c3T3 cocultured with transformed cells, as well as transformation assays using Bhas cells (v-Ha-ras-transfected BALB/3T3 cells). In addition, we evaluated the influence of monoesters formed by the hydrolysis of phthalate diesters on tumor-promoting activity in Bhas cells. MATERIALS AND METHODSReagents ---DBP and DINP were purchased from Kanto Chemical Co., Inc. (Tokyo, Japan). DiethylThe tumor-promoting activity of four phthalate diesters and three monoesters were tested in vitro in a screening assay using a transformed and non transformed BALB/c3T3 cell mixture and in a transformation assay using Bhas cells (v-Ha-ras-transfected BALB/3T3 cells). Di-2-ethylhexyl phthalate (DEHP), di-n-butyl phthalate (DBP), and their monoesters increased cell proliferation in the screening assay. Monon-butyl phthalate (MBuP) and mono-2-ethylhexyl phthalate (MEHP) promoted Bhas cell transformation, whereas the activities of DBP and DEHP were weak. The activity of MEHP was about 1/500 that of 12-Otetra-decanoyl-phorbol-13-acetate. MBuP and MEHP therefore showed tumor-promoting activity, whereas all the other phthalate esters tested, including di-isononyl phthalate, had little or no such activity. In addition, MBuP and MEHP were formed by hydrolysis in Bhas cells exposed to DBP and DEHP for 4 days. We postulate that MEHP plays a role in the slight ability of DEHP to promote cell proliferation.

Microbial degradation of phthalates: biochemistry and environmental implications

“…Certain PAEs have adverse effects on the development of the male reproductive system due to their anti‐androgenic properties (Latini et al ., ; Lambrot et al ., ). They are also considered as potential carcinogens, teratogens, mutagens, and endocrine disruptors (Fushiwaki et al ., ). Thus, from the beginning there has been great concern about the release of PAEs into the environment (Mayer et al ., ; Giam et al ., ).…”