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Aryl hydrocarbon hydroxylase in human prostate.

M W Kahng, W Liu, H Sanefuji

    Chemico-Biological Interactions
    |March 1, 1981
    PubMed
    Summary

    This study examined whether the human prostate contains an enzyme called aryl hydrocarbon hydroxylase (AHH) and how it responds to certain chemicals. The researchers found that AHH is present in prostate tissue and can be activated by a carcinogen called benz[a]anthracene (BA), with activation levels varying up to 150 times higher than normal. They also observed that another carcinogen, 7,12-dimethylbenz[a]anthracene (DMBA), activated AHH less effectively than BA. The enzyme's activity was not affected by a third chemical, N-methyl-N'-nitro-N-nitrosoguanidine (MNNG). These findings suggest that the prostate may be vulnerable to environmental carcinogens, and individual differences in enzyme activation could influence cancer risk.

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    Area of Science:

    • Environmental carcinogenesis in urology
    • Human prostate physiology and pathology
    • Pharmacogenomics of xenobiotic metabolism

    Background:

    The role of xenobiotic-metabolizing enzymes in human prostate tissue remains poorly understood. Prior research has shown that certain enzymes can activate environmental carcinogens, but their presence and variability in prostatic tissue were unclear. This gap motivated investigations into whether the prostate expresses aryl hydrocarbon hydroxylase (AHH), a key enzyme in carcinogen metabolism. No prior work had resolved the extent of AHH inducibility in human prostate cells. The variability of AHH activity among individuals could influence cancer susceptibility. Environmental exposure to polycyclic aromatic hydrocarbons is a known risk factor for various cancers. However, the specific contribution of these compounds to prostate carcinogenesis remains uncertain. This paper's contribution is to establish the presence and inducibility of AHH in human prostate tissue.

    Purpose Of The Study:

    This study aimed to determine whether human prostate tissue contains aryl hydrocarbon hydroxylase (AHH) and whether this enzyme can be induced by environmental carcinogens. The specific problem addressed is the lack of evidence on how the prostate processes polycyclic hydrocarbons. The motivation stems from the need to understand prostate cancer etiology better. The researchers focused on explant cultures and epithelial cells derived from prostate tissue. They tested the effects of benz[a]anthracene (BA) and 7,12-dimethylbenz[a]anthracene (DMBA) on AHH activity. The study also examined whether N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) alters AHH levels. The goal was to assess the prostate's susceptibility to environmental carcinogens.

    Keywords:
    Aryl hydrocarbon hydroxylaseHuman prostate cancerEnvironmental carcinogensXenobiotic metabolism

    Frequently Asked Questions

    The study found that aryl hydrocarbon hydroxylase (AHH) is present in human prostate tissue and can be induced by benz[a]anthracene (BA) with a 14- to 150-fold increase.

    The inducibility of AHH by 7,12-dimethylbenz[a]anthracene (DMBA) was consistently lower than by benz[a]anthracene (BA), with a maximum 63-fold increase.

    N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was used to test whether it could alter aryl hydrocarbon hydroxylase (AHH) activity, but it had no effect.

    The tenfold variation in AHH inducibility among individuals may suggest differing susceptibility to environmental carcinogens and potentially influence prostate cancer risk.

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    Main Methods:

    The study used explant cultures from human prostate tissue obtained during surgery for benign prostatic hyperplasia. Epithelial cells were also grown from these tissues. Aryl hydrocarbon hydroxylase (AHH) activity was measured in these cultures. The researchers tested the effects of benz[a]anthracene (BA) and 7,12-dimethylbenz[a]anthracene (DMBA) on AHH levels. Induction was quantified by comparing treated and control samples. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) was used to assess potential enzyme modulation. Variability in AHH inducibility was analyzed across individuals. The experimental approach focused on enzyme activity rather than gene expression. The study design allowed for comparisons between different carcinogens and their effects on AHH.

    Main Results:

    Aryl hydrocarbon hydroxylase (AHH) was detected in explant cultures of human prostate tissue. The enzyme was inducible by benz[a]anthracene (BA), with induction ranging from 14- to 150-fold. A tenfold variation in AHH inducibility was observed among individuals. Epithelial cells also showed measurable AHH activity. Induction by BA ranged from 2- to 63-fold in these cells. Induction by 7,12-dimethylbenz[a]anthracene (DMBA) was consistently lower than by BA. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) treatment did not alter AHH activity. These findings suggest that the prostate can metabolize environmental carcinogens.

    Conclusions:

    The presence of aryl hydrocarbon hydroxylase (AHH) in human prostate tissue indicates susceptibility to environmental carcinogens. The enzyme's inducibility by benz[a]anthracene (BA) suggests a potential activation pathway for polycyclic hydrocarbons. The observed variability in AHH inducibility may influence individual cancer risk. The lower inducibility by 7,12-dimethylbenz[a]anthracene (DMBA) compared to BA suggests differential enzyme responses. N-methyl-N'-nitro-N-nitrosoguanidine (MNNG) did not affect AHH activity, indicating no direct modulation. These findings support the hypothesis that environmental factors contribute to prostate cancer etiology. The study does not propose new therapeutic targets. The authors suggest that further research is needed to explore the clinical implications of AHH variability.

    Epithelial cells from human prostate tissue containing measurable aryl hydrocarbon hydroxylase (AHH) activity indicate that these cells can metabolize environmental carcinogens.

    The findings suggest that environmental and occupational exposure to polycyclic hydrocarbons may contribute to the etiology of human prostatic carcinoma.