Inhibition of androstenediol-dependent LNCaP tumour growth by 17alpha-ethynyl-5alpha-androstane-3alpha, 17beta-diol (HE3235)

Abstract

Androst-5-ene-3beta, 17beta-diol (AED) is an adrenal hormone that has been reported to sustain prostate cancer growth after androgen deprivation therapy (ADT). LNCaP cells express a mutated androgen receptor that confers the ability to respond not only to androgen but also to oestrogen and adrenal hormones such as AED, and thus provide a cell line useful for identifying compounds capable of inhibiting AED-stimulated cell growth. We sought to determine whether structurally related steroids could inhibit AED-stimulated LNCaP cell growth in vitro and tumour growth in vivo. We report here the identification of a novel androstane steroid, HE3235 (17alpha-ethynyl-5alpha-androstan-3alpha, 17beta-diol), with significant inhibitory activity for AED-stimulated LNCaP proliferation. This inhibitory activity is accompanied by an increase in the number of apoptotic cells. Animal studies have confirmed the cytoreductive activity of HE3235 on LNCaP tumours. The results suggest that this compound may be of clinical use in castration-resistant prostate cancer.

Figure 1

LNCaP (▪), PC3 (▴), and DU145 (⧫) cells were incubated with HE3235 at 1 nM, 10 nM, and 50 nM and assayed in duplicate for inhibition of cell growth relative to vehicle as described in Materials and Methods.

Figure 2

Dose-dependent effect of HE3235 on AED-stimulated LNCaP tumour incidence and tumour volume in SCID mice. Grey bars represent the percentage of animals in each dose group with tumour. Dark bars represent the average tumour volume (±s.d.).

Figure 3

Effect of LNCaP of HE3235 on existing AED-stimulated tumours in SCID mice. LNCaP tumours were established according to Materials and Methods. Once the tumours reached at least 50 mm³, mice were separated to treatment (n=9) and vehicle control (n=9) groups and dosed as described in Materials and Methods.

Figure 4

HE3235 activation of LNCaP AR. LNCaP cells were treated with 1 or 10 nM DHT or AED, charcoal-stripped serum (CSS). The fold change above background is shown on the y axis.

Figure 5

HE3235 induced apoptosis in LNCaP. The percentage increase in the number of apoptotic cells after 4 days of incubation with 50 nM HE3235 relative to the vehicle control is represented on the y axis.