Rapid Detection of Missense Mutations
in the Prostatic Steroid Sa-Reductase Gene
Using Real-Time Fluorescence PCR
and Melting Curve Analysis
MARKUS NAUCK*, WINFRIED MARZ, HEINRICH WIELAND
Introduction
Prostate cancer is a very common disease in more developed countries, but its
cause is largely unknown. It is an androgen-dependent cancer, and it has been
proposed that variations in androgen metabolism may affect a man's risk of this
disease [1]. There is accumulating evidence that increased intraprostatic androgen metabolism, particularly through the enzyme steroid Sa-reductase, may have
an important role in predisposition to prostate cancer [2]. This enzyme catalyses
the conversion of testosterone to dihydrotestosterone - the most potent androgen
in the prostate. Thus, genetic variants encoded by the steroid Sa-reductase gene
(SRD5A2) may affect the risk of developing prostate cancer. Makridakis et al.
recently reported a missense mutation in SRD5A2, which results in the replacement of an alanine residue at codon 49 with threonine (A49T) [3]. This A49T
amino acid substitution increased the risk of clinically significant disease 7.2-fold
in African-American men and 3.6-fold in Hispanic men. This clinical association
is further supported by data obtained in vitro showing that the mutant enzyme
had a higher enzymatic activity, indicating an increased metabolic activation of
testosterone to dihydrotestosterone in carriers of the 49T allele. Furthermore,
finasteride, a competitive inhibitor of SRD5A2, showed a much lower efficacy in
inhibiting the enzymatic activity.
A second polymorphism in SRD5A2, which substitutes leucine for valine at
codon 89, has also been implicated in the predisposition to prostate cancer and
early tumor progression. Although the V89L substitution has been shown to
result in a significantly reduced steroid Sa-reductase enzyme activity in vivo, to
date no consistent differences in the frequency of the V89L SRD5A2 gene polymorphism between cases and controls have been observed [4]. There are ongoing
studies to determine the association between SRDSA2 genotypes and prostate
cancer in Caucasians.
The identification of genetic variants in the SRD5A2 gene has important implications for identification of men at risk before symptoms arise and for development of chemopreventive strategies.
* Markus Nauck (~) (e-mail: msnauck@medl.ukl.uni-freiburg.de)
University Hospital Freiburg, Department of Clinical Chemistry, Hugstetter Strasse 55,
79106 Freiburg, Germany
in the Prostatic Steroid Sa-Reductase Gene
Using Real-Time Fluorescence PCR
and Melting Curve Analysis
MARKUS NAUCK*, WINFRIED MARZ, HEINRICH WIELAND
Introduction
Prostate cancer is a very common disease in more developed countries, but its
cause is largely unknown. It is an androgen-dependent cancer, and it has been
proposed that variations in androgen metabolism may affect a man's risk of this
disease [1]. There is accumulating evidence that increased intraprostatic androgen metabolism, particularly through the enzyme steroid Sa-reductase, may have
an important role in predisposition to prostate cancer [2]. This enzyme catalyses
the conversion of testosterone to dihydrotestosterone - the most potent androgen
in the prostate. Thus, genetic variants encoded by the steroid Sa-reductase gene
(SRD5A2) may affect the risk of developing prostate cancer. Makridakis et al.
recently reported a missense mutation in SRD5A2, which results in the replacement of an alanine residue at codon 49 with threonine (A49T) [3]. This A49T
amino acid substitution increased the risk of clinically significant disease 7.2-fold
in African-American men and 3.6-fold in Hispanic men. This clinical association
is further supported by data obtained in vitro showing that the mutant enzyme
had a higher enzymatic activity, indicating an increased metabolic activation of
testosterone to dihydrotestosterone in carriers of the 49T allele. Furthermore,
finasteride, a competitive inhibitor of SRD5A2, showed a much lower efficacy in
inhibiting the enzymatic activity.
A second polymorphism in SRD5A2, which substitutes leucine for valine at
codon 89, has also been implicated in the predisposition to prostate cancer and
early tumor progression. Although the V89L substitution has been shown to
result in a significantly reduced steroid Sa-reductase enzyme activity in vivo, to
date no consistent differences in the frequency of the V89L SRD5A2 gene polymorphism between cases and controls have been observed [4]. There are ongoing
studies to determine the association between SRDSA2 genotypes and prostate
cancer in Caucasians.
The identification of genetic variants in the SRD5A2 gene has important implications for identification of men at risk before symptoms arise and for development of chemopreventive strategies.
* Markus Nauck (~) (e-mail: msnauck@medl.ukl.uni-freiburg.de)
University Hospital Freiburg, Department of Clinical Chemistry, Hugstetter Strasse 55,
79106 Freiburg, Germany