Strong inhibition of estrone-3-sulfatase activity by pregnenolone 16alpha-carbonitrile but not by several analogs lacking a 16alpha-nitrile group.
In recent years, development of potent inhibitors for estrogen sulfatases has become an actively pursued strategy for chemoprevention and/or chemotherapy of estrogen-dependent human breast cancers. We report here our findings that pregnenolone 16alpha-carbonitrile (PCN) is a potent inhibitor of estrone-3-sulfatase activity of rats and also humans. PCN inhibited in a concentration-dependent manner the desulfation of estrone-3-sulfate catalyzed by liver microsomal and nuclear fractions of female Sprague-Dawley rats. The inhibition of estrone-3-sulfatase activity in these two subcellular fractions showed a biphasic pattern, with a highly sensitive phase seen at 78 nM to 1.25 microm of PCN followed by a markedly less-sensitive phase at > 2.5 microm of PCN. Interestingly, several of PCN's structural analogs without a 16alpha-nitrile group showed little or no inhibitory effect on rat liver microsomal E(1)-3-sulfatase activity. Double-reciprocal analysis showed that the inhibition of rat liver microsomal E(1)-3-sulfatase activity by PCN was essentially competitive in nature. When microsomes from six human term placentas were tested for their E(1)-3-sulfatase activity, PCN showed a similar biphasic inhibition of placental E(1)-3-sulfatase. Likewise, several of its structural analogs showed little or no inhibitory effect on placental E(1)-3-sulfatase activity. Computational analysis of the D-ring structure of PCN and other structurally similar analogs used in the study suggests that the potent sulfatase-inhibiting activity of PCN may be partly due to its unique steric orientation and size of the 16alpha-nitrile group. This knowledge may be useful for the rational design of more potent steroidal inhibitors of E(1)-3-sulfatase by introducing an additional nitrile group to their C16alpha-position.
Zhu
B T
BT
Department of Basic Pharmaceutical Sciences, College of Pharmacy, University of South Carolina, 700 Sumter Street,Columbia, SC 29208, USA. BTZhu@Pharm.SC.edu
Kosh
J W
JW
Fu
J
J
Cai
M X
MX
Xu
S
S
Conney
A H
AH
D000818:Animals; D000970:Antineoplastic Agents / Q000737:chemistry / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000737:chemistry / Q000494:pharmacology; D005260:Female; D006801:Humans; D008862:Microsomes, Liver / Q000201:enzymology; D008958:Models, Molecular; D008968:Molecular Conformation; D009570:Nitriles / Q000737:chemistry / Q000494:pharmacology; D010920:Placenta / Q000201:enzymology / Q000648:ultrastructure; D011247:Pregnancy; D011285:Pregnenolone Carbonitrile / Q000031:analogs & derivatives / Q000737:chemistry / Q000494:pharmacology*; D051381:Rats; D020318:Rats, Long-Evans; D017207:Rats, Sprague-Dawley; D055672:Static Electricity; D013329:Structure-Activity Relationship; D013347:Subcellular Fractions / Q000201:enzymology; D013429:Sulfatases / Q000037:antagonists & inhibitors*
D000970:Antineoplastic Agents; D004791:Enzyme Inhibitors; D009570:Nitriles; D011285:Pregnenolone Carbonitrile; D013429:Sulfatases; C020121:estrone sulfatase