Mécanismes de résistance aux in hibiteurs de CYP17A1 dans le cancer de la prostate résistant à la castration

Environmental inhibitors of the expression of cytochrome P450 17A1 in mammals

Cytochrome P450 17A1 (CYP17A1; EC: 1.14.14.19) is a critically important bifunctional enzyme with nicotinamide adenine dinucleotide phosphate (NADPH) as its cofactor that catalyzes the formation of all endogenous androgens. Its hydroxylase activity catalyzes the 17α-hydroxylation of pregnenolone (PREG)/progesterone (P4) to 17α-OH-pregnenolone/17α-OH-progesterone, and its 17,20-lyase activity converts 17α-OH-pregnenolone/17α-OH-progesterone to dehydroepiandrosterone/androstenedione. Androgens are required for male reproductive development, so androgen deficiency resulting from CYP17A1 inhibition may lead to reproductive disorders. There has been some advances on the study of environmental chemicals inhibiting mammalian CYP17A1 expression but no related review was available so we think it now necessary to review their characteristics and inhibiting properties.

[Mechanisms of castration resistance: Intratumoral hypoxia stimulates the androgen receptor expression]

PURPOSE

Tumor hypoxia and its biological consequence lead to microenvironment adaptation of tumor initiation, promotion and progression. The aim of the study was to observe the influence of hypoxia on the expression of the androgen receptor (AR), using an original model of multicellular spheroids obtained from castration-resistant prostate tumor cells.

MATERIAL

Two human castration-resistant prostate cancer cell lines have been used to generate multicellular tumor spheroids (MTS). The conditions and duration of incubation modulated the final size of the MTS and the intrinsic hypoxia gradient. The expression of AR was studied by immunohistochemistry (IHC) and secretion of PSA measured in the culture medium.

RESULTS

The IHC expression of AR was characterized by a decreasing gradient from the periphery to the center of MTS (less intense in central hypoxic zone), corresponding to a nuclear translocation of activated AR. This result was proportionally correlated with the duration of hypoxic incubation period. Hypoxia caused significant increase in AR expression at 6h of oxygen deprivation. This activation of AR was correlated with transcriptional activity increase of target genes, including increased secretion of PSA.

CONCLUSION

This demonstration of activation, increased expression and increased transcriptional activity of AR by hypoxia is the first to have been made with an original model of hypoxia, closer to reality than previous models, i.e. close to tissue hypoxia observed in primary prostate cancer.

LEVEL OF EVIDENCE

4.