M. Esquenet et al., TRIIODOTHYRONINE MODULATES GROWTH, SECRETORY FUNCTION AND ANDROGEN RECEPTOR CONCENTRATION IN THE PROSTATIC-CARCINOMA CELL-LINE LNCAP, Molecular and cellular endocrinology, 109(1), 1995, pp. 105-111
There is increasing evidence that the course of prostatic carcinoma is
determined by a complex interplay between genetic events, paracrine i
nteractions, and hormonal and dietary factors. These latter factors in
clude several ligands of the nuclear receptor family such as androgens
, vitamin D-3 and retinoids. To test whether thyroid hormones also inf
luence the growth and differentiated function of prostatic carcinoma c
ells, LNCaP cells were treated with or without triiodothyronine (T-3)
in the absence or in the presence of other regulatory factors. Exposur
e of LNCaP cells to T-3 for 6 days in the absence of androgens caused
a dose-dependent increase in [H-3]-thymidine incorporation with a maxi
mal stimulation of 2.5-fold at 10(-9) M T-3 Secretion of prostate-spec
ific antigen (PSA) was also stimulated 2-3-fold. The observed effects
may well be mediated by a nuclear Tg receptor as evidenced by displace
able T-3 binding studies. Combined treatment of LNCaP cells with andro
gens and T-3 revealed intriguing interactions between these two pathwa
ys. Below and up to 10(-10) M of the synthetic androgen R1881, the con
centration that evokes optimal proliferative responses, T-3 stimulated
[H-3]thymidine incorporation. At higher concentrations of androgens,
T-3 displayed antiproliferative effects. No androgen-dependent effects
on T-3 receptor levels were observed. Conversely, T-3 increased andro
gen receptor levels up to twofold. Androgen as well as T-3 stimulation
of proliferation was abolished by high concentrations of the retinoid
9-cis-retinoic acid. These data add T-3 to the list of factors that i
nfluence growth and differentiation of prostatic tumor cells and contr
ibute to our understanding of the intricate pathways that ultimately d
etermine the course of prostatic carcinoma.