The stimulation of male duct derivatives in female guinea-pig with an antiandrogen, cyproterone acetate

Major impact of hormonal therapy in localized prostate cancer--death can already be an exception

For about 50 years, androgen blockade in prostate cancer has been limited to monotherapy (surgical castration) or high doses of estrogens in patients with advanced disease and bone metastases. The discovery of medical castration with LHRH agonists has led to fundamental changes in the endocrine therapy of prostate cancer. In 1979, the first prostate cancer patient treated with an LHRH agonist received such treatment at the Laval University Medical Center. A long series of studies have clearly demonstrated that medical castration with an LHRH agonist has inhibitory effects on prostate cancer equivalent to those of surgical castration. The much higher acceptability of LHRH agonists has been essential to permit a series of studies in localized disease. Based upon the finding that the testicles and adrenals contribute approximately equal amounts of androgens in the human prostate, the combination of medical (LHRH agonist) or surgical castration associated with a pure antiandrogen (flutamide, nilutamide or bicalutamide) has led to the first demonstration of a prolongation of life in prostate cancer, namely a 10-20% decreased risk of death according to the various metaanalyses of all the studies performed in advanced disease. In analogy with the other types of advanced cancers, the success of combined androgen blockade in metastatic disease is limited by the development of resistance to treatment. To avoid the problem of resistance to treatment while taking advantage of the relative ease of diagnosis of prostate cancer at an "early" stage, the much higher acceptability of LHRH agonists has permitted a series of studies which have demonstrated a major reduction in deaths from prostate cancer ranging from 31% to 87% at 5 years of follow-up in patients with localized or locally advanced prostate cancer. Most importantly, recent data show that the addition of a pure antiandrogen to an LHRH agonist in order to block the androgens made locally in the prostate leads to a 90% long-term control or probable cure of prostate cancer.

Mechanism of action and pure antiandrogenic properties of flutamide

Although treatment of intact adult male rats with the pure antiandrogen flutamide or a luteinizing hormone-releasing hormone (LHRH) agonist alone leads to partial inhibition of ventral prostate weight, maximal inhibition is achieved by combination of the two drugs. Potentializing effects of the two compounds were observed even on prostatic ornithine decarboxylase activity. Because LHRH agonists are widely used to achieve medical castration in men treated for prostate cancer, it is of interest to observe that in the dog, known for being the best model for studies of the action of LHRH agonists, flutamide does not interfere with the potent desensitizing action of the LHRH agonist on pituitary LH secretion, thus supporting the combined use of flutamide with an LHRH agonist for maximal androgen blockade without loss of efficiency of the LHRH agonist. Because prostate cancer is known to show a high degree of heterogeneity of its sensitivity to androgens, we analyzed the effect of combined antiandrogen therapy on parameters more sensitive to androgens than ventral prostatic weight itself. In agreement with its pure antiandrogenic characteristics, flutamide alone has no stimulatory effect on the intraprostatic level of mRNA encoding the C1 or C3 component of prostatic binding protein (PBP), whereas cyproterone acetate (CPA), megestrol acetate (MEG), and, especially, medroxyprogesterone acetate (MPA) markedly stimulate PBP-C1 and PBP-C3 mRNA levels, an effect reversed by flutamide, thus further supporting the intrinsic androgenic activity of all these steroidal derivatives. Similar androgenic effects of the steroidal derivatives were observed on prostatic ornithine decarboxylase activity. Androgen-sensitive Shionogi tumor cells were then used to assess the antiandrogenic/androgenic properties of flutamide and the above-indicated steroidal derivatives. MPA, MEG, CPA as well as spironolactone-stimulated cell proliferation under both in vivo and in vitro conditions, thus illustrating the intrinsic androgenic activity of all these compounds. Flutamide was inactive by itself and reversed the stimulatory effect of all other compounds, thus indicating its pure antiandrogenic activity. Although castration reduces intraprostatic dihydrotestosterone (DHT) to undetectable levels in the rat and guinea pig, the concentration remains at about 50% of the value found in intact men after castration, thus indicating an important contribution of the adrenals to DHT in the human prostate, a finding that requires the addition of an antiandrogen to block the action of this important amount of DHT remaining after castration.

Suppression of plasma androgens by the antiandrogen flutamide in prostatic cancer patients treated with Zoladex, a GnRH analogue

Chronic treatment with the GnRH (gonadotrophin hormone releasing hormone) agonist Zoladex causes suppression of testicular androgens. Use of antiandrogens has been advocated to block the effects of the initial surge of androgens, and to block any presumed effects of adrenal androgens. We have measured plasma concentrations of androgens and possible precursors before and during treatment in the following prostate cancer patients: 10 who received Zoladex alone (Z), nine who received Zoladex + the anti-androgen flutamide (Z + F) and five who were orchidectomized (O). Testosterone fell in the Z + F group to 0.84 +/- 0.21 nmol/l (mean +/- SD) significantly lower (Wilcoxon P less than 0.05) than after Z (1.58 +/- 1.84 nmol/l) alone. Progesterone and 17 alpha-hydryxyprogesterone did not change significantly in any group. Androstenedione and dehydroepiandrosterone sulphate (DHAS) showed significant falls in Z + F (from 3.44 +/- 0.34 to 1.92 +/- 0.18 mumol/l and from 3.88 +/- 0.64 to 1.92 +/- 0.36 mumol/l respectively) but not in other groups. These results are consistent with our demonstration of an inhibitory effect of flutamide, hydroxyflutamide and other antiandrogens on human adrenal microsomal 17 alpha-hydroxylase and 17,20-lyase activities in vitro.

Synthetic progestins stimulate prostatic binding protein messenger RNAs in the rat ventral prostate

In order to assess the intrinsic androgenic activity of the synthetic progestins currently used as antiandrogens for the treatment of prostate cancer and other androgen-sensitive diseases, cyproterone acetate (CPA), medroxyprogesterone acetate (MPA) and megestrol acetate (MEG) were administered for 4 days to adult rats castrated 4 days previously. The effects of these compounds were measured on highly specific and sensitive markers of androgen action in the rat ventral prostate, namely the levels of messenger RNAs encoding the C1 (PBP-C1) and C3 (PBP-C3) components of rat prostatic binding protein (PBP). Steady-state mRNA levels were measured by dot-blot hybridization as well as by in situ hybridization. Treatment with CPA or MEG, at the twice daily dose of 10 mg, caused respective 2- and 4.5-fold increases in the steady-state levels of mRNA encoding PBP-C1. MPA, at the dose of 0.45 mg, twice daily, was approximately 40 times as potent as MEG, leading to an 8-fold increase in PBP-C1 mRNA levels. While the pure nonsteroidal antiandrogen flutamide (10 mg, twice daily) did not cause accumulation of PBP mRNAs when administered to castrated rats, it completely reversed the stimulatory effects of the synthetic progestins CPA, MPA and MEG. The results obtained by in situ hybridization were similar to those obtained by dot-blot analysis. Moreover, the synthetic progestins caused similar androgenic effects on PBP-C3 mRNA levels. The present data indicate that all three synthetic progestins currently used for the treatment of prostate cancer possess significant intrinsic androgenic activity as evidenced by their stimulatory effects on the accumulation of mRNAs sensitive to androgen action. Consequently, as indicated by this sensitive and androgen-specific in vivo rat model, such compounds are not recommended for the treatment of conditions requiring an optimal blockade of androgens, especially prostate cancer.

Androgenic activity of synthetic progestins and spironolactone in androgen-sensitive mouse mammary carcinoma (Shionogi) cells in culture

A series of compounds designed to block the action of androgens in target tissues, and called antiandrogens, have been developed for the treatment of androgen-sensitive diseases, especially prostate cancer, hirsutism, precocious puberty and deviant sexual behavior. In order to further assess the androgenic activity of these compounds, we have studied their effect on the growth of an androgen-sensitive clone of the mouse mammary carcinoma Shionogi SC-115 cells in culture. Hydroxy-flutamide did not affect the doubling time (7.40 +/- 0.09 vs 7.20 +/- 0.12 days) characteristic of these cells. However, all of the other compounds tested stimulated cell growth. Thus, in the presence of cyproterone acetate, cells had an accelerated growth rate and shorter generation time of 6.28 +/- 0.06 days (P less than 0.01). In the presence of 1 microM spironolactone, the generation time was 4.96 +/- 0.04 days (P less than 0.01). With chlormadinone acetate, the doubling time was reduced to 3.79 +/- 0.08 days while for megestrol acetate, the doubling time was 3.63 +/- 0.04 days (P less than 0.01). The synthetic progestin Medroxyprogesterone acetate had the most potent androgenic effect reducing the doubling time to 1.85 +/- 0.05 days (P less than 0.01). For comparison, dihydrotestosterone gave a doubling time of 1.76 +/- 0.07 days. When hydroxy-flutamide (5 microM) was added simultaneously with each "progestin", the ED50 value of action of all the compounds was increased in a competitive manner, thus indicating that the mitogenic effect on cell growth of all compounds is mediated by the androgen receptor. Of all the compounds used, only hydroxy-Flutamide was devoid of any androgenic activity and thus meets the criteria of a pure antiandrogen.

Stimulatory effect of synthetic progestins currently used for the treatment of prostate cancer on growth of the androgen-sensitive Shionogi tumor in mice

In order to assess the androgenic activity of synthetic progestins currently used as "antiandrogens" for the treatment of prostate cancer in men, the effect of a series of these compounds has been studied in mice on the growth of the androgen-sensitive Shionogi tumor. Female mice (DD/S strain) were inoculated subcutaneously with 10(6) viable cells and divided into groups who received, respectively, the synthetic "progestins" medroxyprogesterone acetate (MPA), megestrol acetate (MEG), cyproterone acetate (CPA) or chlormadinone acetate (CMA), compared with the non-steroidal antiandrogen Flutamide (Flu), each administered at the twice-daily dose of 250 micrograms. Each synthetic "progestin" exerted a marked stimulatory effect on the growth of the tumor. The most impressive effect on growth was observed with MPA. In fact, in MPA-treated mice, tumor size was 17 times larger than control at 4.92 +/- 0.36 cm2/mouse 21 days after inoculation. CPA, CMA and MEG also stimulated the growth of this androgen-sensitive tumor, the percentages of stimulation of tumor size being 3.1-, 3.2- and 11.0-fold above control, respectively, on day 21, while Flu had no significant stimulatory effect. The present data clearly show that all the above-mentioned progestins have variable levels of stimulatory activity on the growth of the androgen-sensitive Shionogi tumor and indicate that such drugs are unlikely to be recommendable for the treatment of prostate cancer.

Combination therapy in stage C and D prostatic cancer: rationale and five year clinical experience

In 1941, Huggins and his colleagues discovered that testicular androgens exert a stimulatory effect on prostate cancer growth. Our group has made the key observations that the human adrenals, in addition to the tests, also secrete important amounts of androgens and cancer cells exhibit a marked heterogeneity of androgen sensitivity. In fact, human adrenals secrete large amounts of precursor steroids that are converted into active androgens in peripheral tissues (including the prostate), thus providing 40% to 50% of total androgens in adult men. The action of these androgens remaining after castration can be inhibited in prostatic cancer tissue by administering a pure antiandrogen that also decreases the local concentration of dihydrotestosterone (DHT). The castration levels of serum testosterone left in men after castration have an important stimulatory activity on the growth of androgen-sensitive normal as well as cancer tissues. Cancer cells have markedly different requirements for androgens. Some cell clones can grow in the presence of minimal amounts of androgens, requiring more complete androgen blockade and more potent antiandrogens for inhibiting growth. Among the compounds recommended as antiandrogens, the most unexpected finding is that many of them are devoid of any antiandrogenic activity. In fact, medroxyprogesterone acetate, chlormadinone acetate, and megestrol acetate have androgenic activity, but do not inhibit the peripheral action of DHT in prostatic tissue. These compounds should not be classified as antiandrogens. Cyproterone acetate, on the other hand, is a mixed agonist-antagonist. The only compounds showing pure antiandrogenic activity are Flutamide and its analogues. There is thus a need for a more complete blockade of androgens of both testicular and adrenal origins in order to exert a maximal inhibitory effect on cancer growth. We have therefore performed clinical studies in previously untreated stage D2 and C prostate cancer patients with the combination therapy using the LHRH agonist [D-Trp6, des Gly NH2(10)] LHRH ethylamide and the antiandrogen Flutamide. There was a significant increase in patients with a complete response, as compared with studies limited to the removal or blockade of testicular androgens. There was also a significant decrease in the number of non-responders, an increased duration of positive response, and a decrease in the death rate. This was achieved with minimal or no side effects, thus preserving a good quality of life.

Analysis of the androgenic activity of synthetic "progestins" currently used for the treatment of prostate cancer

In order to assess the androgenic activity of synthetic "progestins" currently used as "antiandrogens" for the treatment of prostate cancer in men, the effect of a series of these compounds has been measured following 14 days of treatment of adult castrated rats on specific and sensitive parameters of androgenic activity, namely ventral prostate weight and prostatic ornithine decarboxylase (ODC) activity. Medroxyprogesterone acetate (MPA) is almost equipotent with 5 alpha-dihydrotestosterone (DHT), a 49% increase in prostatic weight being observed at the low dose of 0.15 mg, twice daily (P less than 0.01). Megestrol acetate (Megace), chlormadinone acetate (CMA) and spironolactone were less potent but caused a 36-59% increase in prostatic weight at the highest dose used, namely 10 mg. At the 5 mg dose, cyproterone acetate (CPA) caused a 75% increase in prostatic weight. The androgenic activity of the compounds is even more clearly illustrated by their marked stimulatory effect on prostatic ornithine decarboxylase (ODC) activity. MPA, at the low dose of 0.15 mg, caused a 20-fold increase (relative to the effect of placebo) in the activity of the enzyme while the same dose of DHT caused a 15-fold stimulation of enzymatic activity. At the 10 mg dose, megestrol acetate, CMA and spironolactone caused 13.1, 11.8 and 8.6-fold stimulations of ODC activity, respectively. Flutamide, on the other hand, had no stimulatory effect on either ventral prostate weight or prostatic ODC activity. In agreement with glucocorticoid activity, MPA, megestrol acetate and CMA caused a marked inhibition (45-64%) of adrenal weight. The present data show that MPA is a highly potent androgen while megestrol acetate, CMA, CPA and spironolactone have lower but significant androgenic activity on all the parameters measured. It should be added that MPA, megestrol acetate and CMA are completely devoid of antiandrogenic activity while spironolactone shows weak antiandrogen action and CPA is a mixed agonist-antagonist. Flutamide, the compound used as reference, is the only compound devoid of any androgenic action and is thus acting as a pure antiandrogen on both ventral prostate weight and prostatic ODC activity. The present data have major implications for the choice of drug to be used for the treatment of androgen-sensitive diseases, especially prostate cancer. As shown by the present data, the synthetic "progestins" so-far available all possess variable levels of androgenic activity and are thus not recommended for the treatment of prostate cancer.

Effect of cyproterone acetate in comparison to flutamide and megestrol acetate on the ventral prostate, seminal vesicle, and adrenal glands of adult male rats

Cyproterone acetate (CPA) has a stronger inhibitory effect than megestrol acetate (MGA) and flutamide (FL) on the prostate and seminal vesicle of intact adult rats. Only in the clinically irrelevant regimen of castration and simultaneous androgen substitution is FL as a competitive androgen antagonist more potent than CPA and MGA. The latter inhibit complete involution of the ventral prostate but not of the seminal vesicle of castrated adult rats. This effect is very small in magnitude, cannot be increased by the use of higher doses, and is only reduced but not blocked by simultaneous treatment with high doses of FL. Further, CPA is unable to stimulate proliferation or restore the function of the involuted rat prostate. CPA and MGA inhibit adrenal weight in rats, thus indicating a glucocorticoidlike activity in this species. A critical review of all available data on the antiandrogenic, glucocorticoidlike, and possible paradoxical androgenlike activities of CPA in different animal experiments has no important bearing on the clinical effectiveness of CPA in the treatment of prostatic cancer.

Comparison of the antiandrogenic/androgenic activities of flutamide, cyproterone acetate and megestrol acetate

Flutamide is approximately 2-fold more potent than cyproterone acetate in reversing the stimulatory effect of dihydrotestosterone (DHT) on ventral prostate weight. Even at the highest dose of cyproterone acetate, prostate weight remains 40% above control while flutamide completely reverses the stimulatory action of DHT, thus suggesting some partial androgenic activity of cyproterone acetate. Megestrol acetate, on the other hand, is devoid of any antiandrogenic activity and it even increases the stimulatory effect of DHT on prostate weight. While flutamide completely reverses the inhibitory effect of DHT on plasma LH levels in castrated animals, cyproterone acetate reverses the value of this parameter by only 30% while megestrol acetate further inhibits plasma LH levels at all the doses used. Both cyproterone acetate and megestrol acetate inhibit adrenal weight to approximately 25% of control, thus indicating their glucocorticoid activity. As direct measure of androgenic activity, cyproterone acetate and megestrol acetate increased prostate weight in castrated animals by 60 and 100%, respectively (P less than 0.01) while flutamide had no effect. The present data show that cyproterone acetate and megestrol acetate, in addition to their well-known progestational and glucocorticoid action, have intrinsic androgenic activity. Since it is the only compound having pure antiandrogenic activity, flutamide provides the best scientific arguments for its successful use for the treatment of androgen-sensitive diseases.

Androgenic, synandrogenic, and antiandrogenic actions of progestins

In addition to their action on the uterus and vagina, progestins exert diverse metabolic effects on a variety of tissues. These actions include androgenic, synandrogenic, and antiandrogenic effects on androgen-responsive tissues of rats and mice. The androgenic and antiandrogenic effects of progestins have been demonstrated in multiple tissues. These actions appear to be mediated via the androgen receptor. A synandrogenic effect of progestins has also been detected in some tissues. However, there are few data to indicate how this response is mediated. Progestins may also alter androgen action indirectly through changes in steroid synthesis and metabolism. The overall biologic effect of a steroid may thus be determined by the sum of its actions on a variety of tissues.