The effect of a hydrocarbon-enriched fraction from cigarette smoke on mouse tracheas grown in vitro.

IT is now a well established fact that cigarette smoke contains many noncarcinogenic and carcinogenic hydrocarbons (Cooper and Lindsey, 1955). In previous work the direct effects of several carcinogenic hydrocarbons and of cigarette smoke condensates have been studied in two organs of the respiratory tract, grown in organ culture. Benzopyrene and condensates from cigarette smoke cause hyperplasia with pleomorphism of the newly formed cells in the bronchial epitheliuin of human foetal lung (Lasnitzki 1956, 1958) and benzopyrene, methycholanthrene and DMBA induce similar changes in rat tracheal epithelium (Crocker, Nielsen and Lasnitzki, 1965). Recently, it has become possible to concentrate the hydrocarbons in the cigarette smoke condensate (Whitehead, personal communication) and the action of this particular fraction has been examined in organ cultures of human foetal lung (Lasnitzki, 1968); it produces extensive basal cell hyperplasia with atypical cytological changes in all treated explants. In experiments in vivo smoke or smoke condensates are being tested on rodents

Retinoids Regulate the Formation and Degradation of Gap Junctions in Androgen-Responsive Human Prostate Cancer Cells

The retinoids, the natural or synthetic derivatives of Vitamin A (retinol), are essential for the normal development of prostate and have been shown to modulate prostate cancer progression in vivo as well as to modulate growth of several prostate cancer cell lines. 9-cis-retinoic acid and all-trans-retinoic acid are the two most important metabolites of retinol. Gap junctions, formed of proteins called connexins, are ensembles of intercellular channels that permit the exchange of small growth regulatory molecules between adjoining cells. Gap junctional communication is instrumental in the control of cell growth. We examined the effect of 9-cis-retinoic acid and all-trans retinoic acid on the formation and degradation of gap junctions as well as on junctional communication in an androgen-responsive prostate cancer cell line, LNCaP, which expressed retrovirally introduced connexin32, a connexin expressed by the luminal cells and well-differentiated cells of prostate tumors. Our results showed that 9-cis-retinoic acid and all-trans retinoic acid enhanced the assembly of connexin32 into gap junctions. Our results further showed that 9-cis-retinoic acid and all-trans-retinoic acid prevented androgen-regulated degradation of gap junctions, post-translationally, independent of androgen receptor mediated signaling. Finally, our findings showed that formation of gap junctions sensitized connexin32-expressing LNCaP cells to the growth modifying effects of 9-cis-retinoic acid, all-trans-retinoic acid and androgens. Thus, the effects of retinoids and androgens on growth and the formation and degradation of gap junctions and their function might be related to their ability to modulate prostate growth and cancer

Inhibitory effects of retinoic acid metabolism blocking agents (RAMBAs) on the growth of human prostate cancer cells and LNCaP prostate tumour xenografts in SCID mice

In recent studies, we have identified several highly potent all-trans-retinoic acid (ATRA) metabolism blocking agents (RAMBAs). On the basis of previous effects of liarozole (a first-generation RAMBA) on the catabolism of ATRA and on growth of rat Dunning R3227G prostate tumours, we assessed the effects of our novel RAMBAs on human prostate tumour (PCA) cell lines. We examined three different PCA cell lines to determine their capacity to induce P450-mediated oxidation of ATRA. Among the three different cell lines, enhanced catabolism was detected in LNCaP, whereas it was not found in PC-3 and DU-145. This catabolism was strongly inhibited by our RAMBAs, the most potent being VN/14-1, VN/50-1, VN/66-1, and VN/69-1 with IC50 values of 6.5, 90.0, 62.5, and 90.0 nM, respectively. The RAMBAs inhibited the growth of LNCaP cells with IC50 values in the μM-range. In LNCaP cell proliferation assays, VN/14-1, VN/50-1, VN/66-1, and VN/69-1 also enhanced by 47-, 60-, 70-, and 65-fold, respectively, the ATRA-mediated antiproliferative activity. We then examined the molecular mechanism underlying the growth inhibitory properties of ATRA alone and in combination with RAMBAs. The mechanism appeared to involve the induction of differentiation, cell-cycle arrest, and induction of apoptosis (TUNEL), involving increase in Bad expression and decrease in Bcl-2 expression. Treatment of LNCaP tumours growing in SCID mice with VN/66-1 and VN/69-1 resulted in modest but statistically significant tumour growth inhibition of 44 and 47%, respectively, while treatment with VN/14-1 was unexpectedly ineffective. These results suggest that some of our novel RAMBAs may be useful agents for the treatment of prostate cancer

Reversal of methylcholanthrene-induced changes in mouse prostates in vitro by retinoic acid and its analogues.

The influence of vitamin A-related compounds on hyperplasia and metaplasia induced by methylcholanthrene was studied in mouse prostate glands in organ culture. Methylcholanthrene was found to cause extensive hyperplasia and squamous metaplasia of the prostatic epithelium which persisted after withdrawal of the carcinogen. The retinoids included retinoic acid and 6 of its structural analogues synthesized in an attempt to enhance the anticarcinogenic action and reduce the toxicity of the parent compound. These where the cyclopentenyl analogus 7699, A2-retinoic acid, 13-cis-alpha-retinoic acid and 3 aromatic analogues. Administration of the compounds following the carcinogen reduced the extent and incidence of hyperplasia significantly and with the exception of one compound reversed the squamous metaplasia. Two of the aromatic analogues, one with a terminal ethylamide group (1430), and the other with a terminal ethylester group (9369), proved to be the most potent inhibitors, followed by compound 7699 and (9369), proved to be the most potent inhibitors, followed by compound 7699 and retinoic acid. A2-retinoic acid and 13-cis-alpha-retinoic acid showed the lowest activity. The inhibition of hyperplasia appeared to be mediated via a reduction of DNA synthesis. It seemed unrelated to either the biological growth-promoting activity of the compounds or their surface-active properties. It is tentatively suggested that vitamin A and its analogues may act as hormones