Effect of tamoxifen on serum insulinlike growth factor I levels in stage I breast cancer patients

Plasma insulin-like growth factor-I and prostate cancer risk: a prospective study

Insulin-like growth factor-I (IGF-I) is a mitogen for prostate epithelial cells. To investigate associations between plasma IGF levels and prostate cancer risk, a nested case-control study within the Physicians' Health Study was conducted on prospectively collected plasma from 152 cases and 152 controls. A strong positive association was observed between IGF-I levels and prostate cancer risk. Men in the highest quartile of IGF-I levels had a relative risk of 4.3 (95 percent confidence interval 1.8 to 10.6) compared with men in the lowest quartile. This association was independent of baseline prostate-specific antigen levels. Identification of plasma IGF-I as a predictor of prostate cancer risk may have implications for risk reduction and treatment.

Feasibility, endocrine and anti-tumour effects of a triple endocrine therapy with tamoxifen, a somatostatin analogue and an antiprolactin in post-menopausal metastatic breast cancer: a randomized study with long-term follow-up

Suppression of the secretion of prolactin, growth hormone and insulin-like growth factor 1 (IGF-1) might be important in the growth regulation and treatment of breast cancer. Because oestrogens may counteract the anti-tumour effects of such treatment, the combination of an anti-oestrogen (tamoxifen), a somatostatin analogue (octreotide) and a potent anti-prolactin (CV 205-502) might be attractive. In this respect, we performed a first exploratory long-term study on the feasibility of combined treatment and possible clear differences in endocrine and anti-tumour effects during such combined treatment vs standard treatment with tamoxifen alone. Twenty-two post-menopausal patients with metastatic breast cancer (ER and/or PR positive or unknown) were randomized to receive either 40 mg of tamoxifen per day or the combination of 40 mg of tamoxifen plus 75 microg of CV 205-502 orally plus 3 x 0.2 mg of octreotide s.c. as first-line endocrine therapy. An objective response was found in 36% of the patients treated with tamoxifen alone and in 55% of the patients treated with combination therapy. Median time to progression was 33 weeks for patients treated with tamoxifen and 84 weeks for patients treated with combination therapy, but the numbers are too small for hard conclusions. There was no difference in overall post-relapse survival between the two treatment arms. With respect to the endocrine parameters, there was a significant decrease of plasma IGF-1 levels in both treatment arms, whereas during combined treatment plasma growth hormone tended to decrease and plasma prolactin levels were strongly suppressed; in some patients insulin and transforming growth factor alpha (TGF-alpha) decreased during the triple therapy. Although there was no significant difference in mean decrease of plasma IGF-1 levels between the two treatment arms, combined treatment resulted in a more uniform suppression of IGF-1. Therefore, the addition of a somatostatin analogue and an anti-prolactin may potentially enhance the efficacy of anti-oestrogens in the treatment of breast cancer owing to favourable endocrine and possible direct anti-tumour effects. Large phase III trials using depot formulations (to increase the feasibility) of somatostatin analogues are warranted to demonstrate the potential extra beneficial anti-tumour effects of such combination therapy.

Treatment of pancreatic cancer. Promises and problems of tamoxifen, somatostatin analogs, and gemcitabine

The clinical problem posed by pancreatic cancer is introduced, and the epidemiology and pathology of the disease are briefly presented. The natural history of this tumor is then described in order to highlight the deficiencies of current therapeutic modalities. The extremely poor results of the early drug trials are reviewed, followed by a detailed discussion and critique of the trials of novel treatments that include gemcitabine, somatostatin analogs, and tamoxifen. Finally, areas for future development are indicated.

Effects of tamoxifen on GH and IGF-I levels in acromegaly

Tamoxifen (TAM), a non steroid partially competitive antagonist to the estrogen receptors, has been reported to decrease plasma GH and IGF-I levels both in vitro and in vivo. These data prompted us to evaluate GH and IGF-I changes in acromegaly after acute and chronic TAM administration. Nineteen acromegalic patients (6 M, 13 F, aged 30-70 years) were studied in a prospective open study. Acute TAM test (20 mg po) did not induce any significant change in GH and IGF-I levels. Chronic TAM treatment (20 mg/day for a month and 40 mg/day for another month) induced a transient increase in GH levels (from 9 [3-139] micrograms/l [median, range] to 12 [3-188] micrograms/l, p = 0.0025) and a persistent decrease in IGF-I levels (from 785 [500-1200] micrograms/l to 553 [209-1420] micrograms/l, p = 0.0034). Individual IGF-I values decreased in 13 patients and reached the normal range in 4 of them. At TAM withdrawal hormonal levels increased up to pretreatment values. There was no correlation between GH and IGF-I changes and results were not influenced by age, sex or gonadal status. In this setting it is likely that the observed decrease in plasma IGF-I levels is dependent on TAM activity at the hepatic level.

Synthesis and in vitro evaluation of new potent antagonists of growth hormone-releasing hormone (GH-RH)

In the search for more potent antagonists of hGH-RH, 20 new analogs were synthesized, purified and tested in vitro. All the analogs were based on the N-terminal sequence of 28 or 29 amino acid residues of hGH-RH, but contained D-Arg2 and Nle27 modifications. Most analogs had Phe (pCl)6 and Agm29 substituents. The effect of other substitutions such as Abu8 and/or Abu15 and Ala15 and various hydrophobic and hydrophilic D or L amino acids at position 8 were also investigated. All the peptides were acylated at the N-terminus in an attempt to increase the antagonistic activity. In the superfused rat pituitary cell system, most analogs inhibited more powerfully the GH release induced by GH-RH than the standard antagonist [Ac-Tyr1, D-Arg2]hGH-RH (1-29)-NH2. Some antagonists were long acting. Among the peptides synthesized, antagonist PhAc[D-Arg2, Phe(pCl)6, Abu15, Nle27]hGH-RH (1-28) Agm (MZ-5-156) appeared to be the most potent and inhibited GH release in vitro 63-200 times more powerfully than the standard antagonist. MZ-5-156 and other antagonists showed high binding affinities to membrane receptors for GH-RH. Some of these hGH-RH antagonists could be further developed for possible onocological applications.

The Breast Cancer Prevention Trial: evaluating tamoxifen's efficacy in preventing breast cancer

OBJECTIVE

To review the literature on tamoxifen and breast cancer, focusing on the Breast Cancer Prevention Trial (BCPT).

DATA SOURCES

Computerized searches on MEDLINE and CINAHL.

STUDY SELECTION

Articles from indexed journals in the English language related to the topics in this review and published after 1983 (except for earlier classic pieces) were evaluated.

DATA EXTRACTION

Data were extracted and information was organized under the following headings: magnitude of the problem of breast cancer, definition of chemoprevention, tamoxifen's mode of action, risks and benefits, use as an adjuvant and in chemoprevention, the BCPT, study protocol, pros and cons, and nursing implications.

DATA SYNTHESIS

The BCPT is a study testing tamoxifen's ability to prevent the development of breast cancer in healthy women at increased risk for developing the disease. About 16,000 women who are age 35 years or older are being randomized to receive oral tamoxifen (20 mg/day) or placebo for an initial period of 5 years.

CONCLUSIONS

The BCPT will contribute to our knowledge about tamoxifen's ability to prevent breast cancer in women at increased risk. Nurses have a role to play in implementing this strategy to find a means for preventing breast cancer.

A phase II study of tamoxifen plus melatonin in metastatic solid tumour patients

Preliminary data would suggest that the pineal hormone, melatonin (MLT), may enhance tamoxifen (TMX) anti-tumour efficacy. Both MLT and TMX have been used as single agents in the palliative treatment of metastatic neoplasms, other than the classical hormone-dependent tumours, without, however, any clear efficacy. On this basis, a phase II study with TMX plus MLT has been performed in untreatable metastatic solid tumour patients. The study included 25 metastatic solid tumour patients other than breast cancer and prostate cancer (six unknown primary tumour; four melanoma; four uterine cervix carcinoma; five pancreatic cancer; three hepatocarcinoma; two ovarian cancer; one non-small-cell lung cancer), for whom no other effective standard therapy was available, because of poor clinical conditions, no response to previous chemotherapies and/or chemotherapy-resistant tumours. Both drugs were given orally every day until disease progression (TMX, 20 mg day-1 at noon; MLT, 20 mg day-1 in the evening). Three patients had a partial response (PR) (12%; 95% confidence limits 2-24%) (one cervix carcinoma; one melanoma; one unknown primary tumour). A stable disease (SD) was achieved in 13 other patients, whereas the remaining nine patients progressed. Performance status (PS) improved in 9/25 patients, whose median score increased from 50% to 70%. Finally, a survival longer than 1 year was observed in 7/25 (28%) patients. This phase II study would suggest that the neuroendocrine combination with TMX plus MLT may have some benefit in untreatable metastatic solid tumour patients, either in controlling cancer cell proliferation or improving the PS.

Associations between insulin-like growth factors and their binding proteins and other prognostic indicators in breast cancer

Recent studies have suggested that insulin-like growth factors (IGFs) and insulin-like growth factor binding proteins (IGFBPs) may be implicated in the development and progression of breast cancer. Prostate-specific antigen (PSA), a serine protease, may play a role in the regulation of IGFs' function through cleavage of IGFBP-3, resulting in release of active IGFs from IGFBP-3. As IGFs, IGFBPs and PSA are all present in breast cancer, possible associations among these proteins were speculated. In this study, we have measured PSA, IGF-I, IGF-II, IGFBP-1 and IGFBP-3 in tumour tissue cytosols from 200 women with primary breast cancer, and have examined relationships between IGFs or IGFBPs and PSA along with other markers, including p53 protein, steroid hormone receptors (oestrogen and progesterone), cathepsin-D, epidermal growth factor receptor, Her-2/neu protein, S-phase fraction and DNA ploidy. Correlations or associations between PSA and IGF-I, IGF-II, IGFBP-1 or IGFBP-3 were not observed. IGF-II was positively correlated with both IGFBP-3 and IGFBP-1. IGF-I was not associated with either of the two binding proteins, nor with IGF-II. Both IGF-II and IGFBP-3 were inversely associated with the oestrogen receptor, and IGFBP-3 was also positively associated with S-phase fraction. Our finding of IGF-II and IGFBP-3 in association with unfavourable prognostic indicators of breast cancer suggests that IGFs may be involved in the progression of breast cancer.

Growth hormones and sex steroid interactions at puberty

Puberty is a period of dynamic changes mediated by GH and the gonadal steroid hormones. Although these substances exert important independent effects, their interaction is vital to normal pubertal growth and development. This is supported by observations of blunted growth and diminished levels of GH and IGF-1 during adolescence in individuals with panhypopituitarism in whom adequate replacement with both hormones had not been achieved. The independent roles of androgens and estrogens in mediating the rise in GH secretion at puberty have been studied in individuals with complete androgen insensitivity and through the administration of nonaromatizable androgens and the use of selective androgen- or estrogen-receptor blockade. The preponderance of evidence from studies of nonaromatizable (pure) androgens suggests that GH secretion is not enhanced as it is under the influence of testosterone. In addition, studies have shown increased GH secretion following androgen-receptor blockade and diminished GH release after estrogen-receptor blockade. Together these studies suggest a facilitory role of estrogen receptor-mediated processes on GH secretion and IGF-1 production. If androgens influence the GH/IGF-1 axis, it is most likely by an inhibitory mechanism. Observations of delayed skeletal maturation and deficient bone mineralization in individuals with estrogen receptor defects or mutations of the aromatase gene demonstrate the essential role of estrogen in promoting normal bone maturation, the accrual and maintenance of BMD, and control of the rate of bone turnover.

Influence of treatment with tamoxifen and change in tumor burden on the IGF-system in breast cancer patients

Plasma levels of IGF-I, IGFBP-I and IGFBP-3 were measured before and during treatment with tamoxifen up to 19+ months in 34 post-menopausal patients with advanced breast cancer. In 28 patients, pro-IGF-IIE (IGF-IIE) levels were determined and IGFBP-3 was evaluated by immunoblot in 27 patients. Tamoxifen suppressed plasma levels of IGF-I by a mean value of 25.5%-37.7% at different times. This effect was fully developed after 1-2 months of treatment. IGF-IIE was decreased by a mean value of 7.7-23.2% at different time intervals during treatment with tamoxifen, but this effect was significant after long-term treatment (19 months +) only. Plasma IGFBP-I increased by a mean value varying between 48.6% and 190.1%. Tamoxifen had no significant effect on total IGFBP-3 levels. However, patients responding to treatment had a 28% reduction in fragmentation of IGFBP-3, while patients with progressive disease had a 36% increase in fragmentation. The difference between responders and non-responders was highly significant. These findings confirm and extend previous observations regarding the effects of treatment with tamoxifen on IGF-I and IGFBP-I. The finding that patients responding to tamoxifen achieve a reduction in the ratio of fragmented to intact IGFBP-3, while patients progressing on therapy experience an increase in the IGFBP-3 fragmentation ratio, suggest that the tumor burden influences IGFBP-3 protease activity in breast- cancer patients.

A dose-finding study of lanreotide (a somatostatin analog) in patients with colorectal carcinoma

BACKGROUND

Laboratory data suggest that insulin-like growth factor-1 (IGF-1) may stimulate the growth of different human tumors. At least in acromegalic patients, somatostatin (SMS) analogs, such as lanreotide, suppress the serum levels of growth hormone (GH) and IGF-1.

METHODS

To evaluate the tolerability and biologic activity of different doses of lanreotide in patients with advanced colorectal carcinoma, consecutive groups of 3 patients each were subcutaneous treated with lanreotide at doses of 1, 2, 3, 4, 5, or 6 mg three times a day for 2 months. In the event of Grade 3 side effects, 3 additional patients were treated with the same dose before the next dose escalation. Serum samples were obtained on Days 0, 15, 30, and 60 for serum GH, IGF-1, and lanreotide assessment.

RESULTS

Twenty-four patients were enrolled and all were evaluable. Except for the 3 and 6 mg doses, for which the observation of a Grade 3 side effect required that an additional three patients be treated, it was sufficient to treat 3 patients at each dose. The overall incidence of side effects was as follows: changes in bowel habits, 83%; abdominal cramps, 79%; diarrhea, 17%; vomiting, 17%; nausea, 21%; steatorrhea, 78%; hyperglycemia, 35%; laboratory hypothyroidism, 39%; gallstones, 13%; and weight loss, 17%. No evidence of an increase in the incidence, intensity, or duration of side effects was observed with dose escalation. Serum IGF-1 levels were as follows: Day 15: 63%, 60%, and 67% of the baseline values for the low (1-2 mg), intermediate (3-4 mg), and high (5-6 mg) dose groups, respectively; Day 30: 63%, 59%, and 51%, respectively; and Day 60: 73%, 69%, and 47%, respectively. Serum lanreotide levels declined during treatment in all of the dose groups (90 ng/mL on Day 15, and 35 ng/mL on Day 60 for the 5-6 mg group; 10 ng/mL on Day 15, and 1.5 ng/mL on Day 60 for the 1-2 mg group). No antitumor activity or tumor marker reduction was observed.

CONCLUSIONS

No increase in toxicity was observed when subcutaneous lanreotide doses were escalated to 6 mg three times a day for 2 months. The highest doses seemed to maintain reduced serum IGF-1 levels; with the lowest doses, a "rebound" in serum IGF-1 levels was observed during treatment. Nevertheless, intermittent subcutaneous injections do not ensure constant serum drug concentrations over time.

Influence of droloxifene on plasma levels of insulin-like growth factor (IGF)-I, Pro-IGF-IIE, insulin-like growth factor binding protein (IGFBP)-1 and IGFBP-3 in breast cancer patients

The influence of the novel anti-estrogen droloxifene on the insulin-like growth factor (IGF) system in plasma was studied in two groups of breast cancer patients receiving droloxifene 40 mg o.d. (group 1, n = 6) or 100 mg o.d. (group 2, n = 7). Fasting blood samples were obtained from all patients before treatment and after 3 months (group 1) or 6 months (group 2) on droloxifene treatment, except for two patients in group 2 from whom the second sample was obtained following 2 months on treatment when the drug was to be terminated due to progressive disease. Insulin-like growth factor (IGF)-I, insulin-like growth factor binding protein (IGFBP)-1, IGFBP-3 and pro-IGF-IIE (IGF-IIE) were measured by radioimmunoassay. In patients in group 1, plasma lGF-I levels decreased by a mean value of 20% (P < 0.05) on treatment with droloxifene, while IGFBP-1 increased by a mean value of 45% (P > 0.1). In group 2 we observed a 42% decrease in IGF-I during treatment (P < 0.025), while the level of IGFBP-1 increased by a mean value of 70% (P < 0.025). No significant effect on IGF-IIE or IGFBP-3 was noted in any of the groups. The change in plasma lGF-I and IGFBP-1 observed during treatment with droloxifene resembles what is found in patients treated with tamoxifen. As IGF-I is a potent mitogen for breast cancer cells in vitro, a decrease in the plasma level of this growth factor with an increase in the concentration of IGFBP-1 may contribute to the anti-tumour effects of droloxifene.

Estradiol and antiestrogens regulate a growth inhibitory insulin-like growth factor binding protein 3 autocrine loop in human breast cancer cells

MCF-7 human breast cancer cells are commonly used to model tissues responsive to estrogens and antiestrogens. We examined the effects of estradiol and the antiestrogen ICI 182780 on MCF-7 cell proliferation and insulin-like growth factor binding protein 3 (IGFBP-3) gene expression. ICI 182780-induced growth inhibition was associated with increased transcription of the IG-FBP-3 gene, increased IGFBP-3 mRNA abundance, and increased IGFBP-3 protein accumulation in the conditioned medium. The growth stimulatory effect of estradiol was associated with opposite effects, and the correlation between cellular proliferation and IGFBP-3 mRNA abundance was strong (r = -0.91). Recombinant IGFBP-3 inhibited basal and estradiol-stimulated MCF-7 cell proliferation, and an IGFBP-3 antisense oligodeoxynucleotide abolished antiestrogen-induced growth inhibition. These results provide evidence for an estradiol and antiestrogen-regulated IGFBP-3 growth inhibitory autocrine pathway in MCF-7 cells.

Novel endocrine therapies in breast cancer

Endocrine therapy of breast cancer consists of a variety of both medical and surgical ablative treatment modalities, but ablative therapy is increasingly replaced by medical treatment. Most endocrine therapies have more than one endocrine effect, frequently together with direct growth inhibitory actions via receptors. Endocrine therapy can be effective in all phases of the disease, but curative only in early disease while in advanced cancer it can only prolong survival. In the past decade the number of available endocrine agents has been drastically increased. Novel approaches in the endocrine therapy of breast cancer are application of new antiestrogens, antiprogestins, new potent aromatase inhibitors, analogues of luteinizing hormone-releasing hormone (LHRH-A) and somatostatin, inhibitors of prolactin secretion, vitamin A and D analogues, bisphosphonates, growth factor antagonists, tyrosine protein kinase inhibitors, protease inhibitors, inhibitors of angiogenesis, radiolabeled hormones and monoclonal antibodies. New cell biological factors such as oncogenes and suppressorgenes, secretory proteins and membrane receptors can be used not only as prognostic factors but also for prediction of type of response to endocrine and chemotherapy. Thus, these cell biological parameters can be used to select high and low risk patients, type of systemic treatment, and can also be used as targets for new treatment modalities. Future studies on treatment of all stages of disease will increasingly focus on promising combined treatment modalities.

Mechanisms of action of endocrine treatment in breast cancer

Endocrine treatment plays an important role in the therapy of breast cancer. While the basic mechanisms are understood, additional mechanisms may be of importance to their action and they may also contribute to the mechanism(s) of acquired resistance. Currently, several novel drugs are entering into clinical trials. Observations of the absence or presence of cross resistance to novel 'pure' steroidal antiestrogens and the non-steroidal tamoxifen may add important information to our understanding of the mechanisms of action of both classes of drugs. Similarly, exploration of different aromatase inhibitors in sequence or concert, as well as the combining of different endocrine treatment options may be warranted. Additionally, alterations in different biochemical parameters such as growth factors should not only be carefully explored in relation to treatment options but should also be followed during the course of treatment to asess alterations over time and in relation to the development of drug resistance.

Insulin-like growth factors modulate the growth inhibitory effects of retinoic acid on MCF-7 breast cancer cells

Retinoids are currently being tested for the treatment and prevention of several human cancers, including breast cancer. However, the anti-cancer and growth inhibitory mechanisms of retinoids are not well understood. All-trans retinoic acid (RA) inhibits the growth of the estrogen receptor-positive (ER+) breast cancer cell line, MCF-7, in a reversible and dose-dependent manner. In contrast, insulin-like growth factors (IGF-I, IGF-II) and insulin are potent stimulators of the proliferation of MCF-7 and several other breast cancer cell lines. Pharmacologic doses of RA (> or = 10(-6) M) completely inhibit IGF-I-stimulated MCF-7 cell growth. Published data suggest that the growth inhibitory action of RA on IGF-stimulated cell growth is linear and dose-dependent, similar to RA inhibition of unstimulated or estradiol-stimulated MCF-7 cell growth. Surprisingly, we have found that IGF-I or insulin-stimulated cell growth is increased to a maximum of 132% and 127%, respectively, by cotreatment with 10(-7) M RA, and that 10(-9) - 10(-7) M RA increase cell proliferation compared to IGF-I or insulin alone. MCF-7 cells that stably overexpress IGF-II are also resistant to the growth inhibitory effects of 10(-9) - 10(-7) M RA. Treatment with the IGF-I receptor blocking antibody, alpha IR-3, restores RA-induced growth inhibition of IGF-I-treated or IGF-II-overexpressing MCF-7 cells, indicating that the IGF-I receptor is mediating these effects. IGFs cannot reverse all RA effects since the altered cell culture morphology of RA-treated cells is similar in growth-inhibited cultures and in IGF-II expressing clones that are resistant to RA-induced growth inhibition. These results indicate that RA action on MCF-7 cells is biphasic in the presence of IGF-I or insulin with 10(-9) - 10(-7) M RA enhancing cell proliferation and > or = 10(-6) M RA causing growth inhibition. As IGF-I and IGF-II ligands are frequently detectable in breast tumor tissues, their potential for modulation of RA effects should be considered when evaluating retinoids for use in in vivo experimental studies and for clinical purposes. Additionally, the therapeutic use of inhibitors of IGF action in combination with RA is suggested by these studies.

Raloxifene (LY156758) produces antimetastatic responses and extends survival in the PAIII rat prostatic adenocarcinoma model

The benzothiophene antiestrogen, raloxifene (LY156758), has selective estrogen pharmacological antagonist activity in rats. The PAIII rat prostatic adenocarcinoma model was used to evaluate the effects of this agent on the lymphatic and pulmonary metastasis and survival in tumor-bearing male Lobund-Wistar (LW) rats. Raloxifene was inactive against colony formation of PAIII cells in vitro. Similarly, following subcutaneous (s.c.) implantation of 10(6) PAIII cells in the tail, s.c. administration of raloxifene (2.0, 10.0, or 20.0 mg/kg/day) for 30 days failed to demonstrate cytoreductive activity against primary tumor growth in the tail. However, in these same animals, raloxifene administration produced significant (P < 0.05) inhibition of PAIII metastasis from the primary tumor in the tail to the gluteal and iliac lymph nodes (maximal responses = 89% and 81% from control values, respectively). PAIII metastasis to the lungs was significantly inhibited by raloxifene treatment. Numbers of pulmonary foci in PAIII-bearing rats were significantly (P < 0.05) reduced by raloxifene administration in a dose-related manner (maximal reduction = 97% from control values). In these animals, maximal regression of 20% for ventral prostate and 21% for seminal vesicle were also seen after raloxifene administration (P < 0.05 for both). Coadministration of E2B and raloxifene had no consistent antagonistic effect upon the antitumor responses produced by raloxifene. Raloxifene (40.0 mg/kg/day for 28 days) produced marked decreases in PAIII metastasis in the lymphatic and pulmonary components. Continued administration of the compound produced significant (P < 0.05) extension of survival of PAIII-bearing rats. Further studies are needed to define the maximal antitumor efficacy and the mechanism of action of raloxifene in urogenital solid tumor animal models. These data support the contention that raloxifene represents a class of active antimetastatic agents with potential efficacy in the treatment of hormone-insensitive human prostatic cancer.

Biological and clinical evaluation of lanreotide (BIM 23014), a somatostatin analogue, in the treatment of advanced breast cancer. A pilot study by the I.T.M.O. Group. Italian Trials in Medical Oncology

Biological data support the development of clinical trials designed to evaluate the activity of somatostatin (SMS) analogues in advanced breast cancer (ABC). Although previous clinical trials have failed to show antitumor activity, various factors may have biased their results. In an attempt to improve our understanding of the role of SMS analogues in ABC, 10 patients with favourable prognostic factors and who had not been heavily pretreated for advanced disease were treated with lanreotide 30 mg i.m. fortnightly (depot formulation). Blood samples were periodically taken to evaluate the effect of the drug on growth hormone (GH) and insulin-like growth factor 1 (IGF-1) and to determine drug serum levels. Although the drug was well tolerated, no clinical activity was observed. Serum GH and IGF-1 levels were not properly suppressed over time and drug serum concentrations fluctuated widely. In conclusion, SMS analogues cannot be recommended even as palliative treatment of ABC. Further studies should be undertaken to investigate the effect of higher drug doses, given subcutaneously or by means of continuous infusion, in suppressing GH and IGF-1 serum levels.

Clomiphene citrate reduces serum insulin-like growth factor I and increases sex hormone-binding globulin levels in women with polycystic ovary syndrome

OBJECTIVES

To evaluate the effect of clomiphene citrate (CC) on circulating levels of insulin-like growth factor I (IGF-I) and sex hormone-binding globulin (SHBG) in patients with polycystic ovary syndrome (PCOS).

DESIGN

Prospective open trial.

PATIENTS

Eight women with clinical and biochemical evidence of PCOS.

INTERVENTION

One hundred fifty milligrams CC was administered orally for 5 days.

MAIN OUTCOME MEASURES

Serum IGF-I, SHBG, LH, FSH, and E2 levels were determined for 8 days, beginning 3 days before CC treatment.

RESULTS

A progressive decline in serum IGF-I levels was observed in all subjects reaching a maximum of 30% on the 5th day of therapy (40.6 +/- 5.1 to 28.7 +/- 4.0 nmol/L [conversion factor to SI unit, 0.13]). This was correlated inversely with the expected rises in LH, FSH, and E2 levels. Concomitantly, there was a 23% rise in SHBG levels. The absolute decrease of IGF-I levels was negatively correlated with age and was independent of body mass index.

CONCLUSIONS

These observations suggest that oral administration of CC has an impact on the IGF-I and SHBG systems, which may be involved in the initiation of ovulatory function in PCOS.

Gynaecologic effects of tamoxifen

Tamoxifen, an estrogen antagonist, is widely used as adjuvant therapy in patients with breast cancer. Its efficacy in increasing survival and reducing recurrence rates has been demonstrated in several European and American studies. However, its effects appear to be tissue specific. Tamoxifen exerts an estrogen effect (agonist) on the endometrium, myometrium and vagina. An increase in uterine cancer has been confirmed in several placebo-controlled clinical trials. Due to the widespread use of this drug, it is timely to review the gynecologic effects of tamoxifen.

Modulation of cancer endocrine therapy by melatonin: a phase II study of tamoxifen plus melatonin in metastatic breast cancer patients progressing under tamoxifen alone

Recent observations have shown that the pineal hormone melatonin (MLT) may modulate oestrogen receptor (ER) expression and inhibit breast cancer cell growth. On this basis, we have evaluated the biological and clinical effects of a concomitant MLT therapy in women with metastatic breast cancer who had progressed in response to tamoxifen (TMX) alone. The study included 14 patients with metastasis who did not respond (n = 3) to therapy with TMX alone or progressed after initial stable disease (SD) (n = 11). MLT was given orally at 20 mg day-1 in the evening, every day starting 7 days before TMX, which was given orally at 20 mg day-1 at noon. A partial response was achieved in 4/14 (28.5%) patients (median duration 8 months). The treatment was well tolerated in all cases, and no MLT-induced enhancement of TMX toxicity was seen; on the contrary, most patients experienced a relief of anxiety. Mean serum levels of insulin-like growth factor 1 (IGF-1), which is a growth factor for breast cancer, significantly decreased on therapy, and this decline was significantly higher in responders than in patients with SD or progression. This pilot phase II study would suggest that the concomitant administration of the pineal hormone MLT may induce objective tumour regressions in metastatic breast cancer patients refractory to TMX alone.

Relations between sex hormones, sex hormone binding globulin, insulin-like growth factor-I and insulin-like growth factor binding protein-1 in post-menopausal breast cancer patients

OBJECTIVE

Oestrogens, androgens and anti-endocrine drugs such as tamoxifen and aminoglutethimide influence plasma insulin-like growth factor-I (IGF-I). IGF-I, in turn, has been found to stimulate the peripheral aromatase in vitro. The aim of this study was to examine relations between sex hormones, IGF-I and insulin-like growth factor binding protein-1 (IGFBP-1) in post-menopausal women with breast cancer.

DESIGN

To measure plasma sex steroids, sex hormone binding globulin (SHBG), IGF-I, IGFBP-1, insulin and urinary oestrogen metabolites in post-menopausal women with breast cancer not receiving any endocrine therapy.

PATIENTS

Thirty-two patients had fasting blood samples obtained between 0800 and 1000 h. A sub-group of 10 patients had 24-hour urine oestrogen metabolites determined.

MEASUREMENTS

Plasma steroids and proteins were measured by radioimmunoassays. Urinary oestrogens were measured by GC-MS.

RESULTS

SHBG correlated negatively with plasma androstenedione (P < 0.001), insulin (P < 0.001), IGF-I, height and plasma oestrone sulphate (P < 0.025 for all), but positively with plasma IGFBP-1 (P < 0.025). IGFBP-1 correlated negatively with IGF-I (P < 0.001) and the testosterone/SHBG ratio (P < 0.05). Neither IGF-I nor IGFBP-1 correlated with any of the plasma or urinary sex hormones or with the oestrone/androstenedione and oestradiol/testosterone ratios. Multivariate analysis revealed plasma SHBG to correlate positively with IGFBP-1 (P = 0.029) and negatively with insulin (P = 0.031). Plasma IGFBP-1 correlated negatively with IGF-I (P < 0.0001) but not with insulin.

CONCLUSION

Our results do not suggest any influence of plasma sex steroids in physiological concentrations on IGF-I or IGFBP-1 in post-menopausal breast cancer patients, nor do they indicate IGF-I at physiological concentrations influences the ratios between plasma oestrogens and their androgen precursors.

Regulation of IGFBP-3 expression in breast cancer cells and uterus by estradiol and antiestrogens: correlations with effects on proliferation: a review

This paper reviews actions of antiestrogens on IGF physiology, and discusses the potential significance of the recent observations that (i) effects of antiestrogens on the uterus are correlated with their effects on uterine IGF-I and IGFBP-3 gene expression, and that (ii) the potent antiestrogen and growth inhibitor ICI 182,780 induces autocrine production of IGFBP-3 by estrogen receptor-positive breast cancer cells, while the growth stimulatory action of estradiol is associated with suppression of IGFBP-3 expression.

Low dose octreotide and tamoxifen in the treatment of adenocarcinoma of the pancreas

BACKGROUND

Data from experimental studies suggest that a combination of octreotide, the long acting somatostatin analogue, octreotide, and tamoxifen improves the survival of animals with pancreatic cancer.

METHODS

Twelve patients with a tissue diagnosis of ductal adenocarcinoma of the pancreas were treated with 100 micrograms of octreotide three times per day and tamoxifen 10 mg twice daily. The survival of the octreotide-tamoxifen group was compared with a historic cohort of 68 untreated patients with pancreatic cancer, matched for age, sex, and TNM stage.

RESULTS

The median survival times for the octreotide-tamoxifen-treated group compared with the historic cohort were 12 and 3, months respectively. Actuarial one-year survival rates for the octreotide-tamoxifen-treated group compared with the historic cohort were 59% and 16%, respectively.

CONCLUSIONS

In this study, patients with unresectable and resected ductal adenocarcinoma of the pancreas had an apparently increased survival when treated with a combination of octreotide and tamoxifen. A randomized controlled trial to examine this potential therapeutic benefit is now indicated.

Synthesis and biological activities of highly potent antagonists of growth hormone-releasing hormone

In the search for antagonists of human growth hormone-releasing hormone (hGHRH) with high activity, 22 analogs were synthesized by solid-phase methods, purified, and tested biologically. Within the N-terminal sequence of 28 or 29 amino acids of hGHRH, all the analogs contained D-Arg2, Phe(4-Cl)6 (para-chlorophenylalanine), Abu15 (alpha-aminobutyric acid), and Nle27 and most of them had Agm29 (agmatine) substituents. All the peptides, except one, were acylated at the N terminus with different hydrophobic acids--e.g., isobutyric acid (Ibu) or 1-naphthylacetic acid (Nac) in order to study the effect of N-terminal acylation on the antagonistic activity. In the superfused rat pituitary cell system, all the analogs inhibited more powerfully the GHRH-induced growth hormone (GH) release than the standard GHRH antagonist [Ac-Tyr1,D-Arg2]hGHRH-(1-29)NH2. Antagonists [Ibu0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]hGHRH-(1-28) Agm (MZ-4-71), [Nac0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]hGHRH-(1-28) Agm (MZ-4-243), [Nac0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]hGHRH-(1-29) NH2 (MZ-4-169), [Nac0-His1,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]-hGH RH-(1-29)NH2 (MZ-4-181), and [Nac0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27,Asp28]hGH RH-(1-28)Agm (MZ-4-209) inhibited GH release at 3 x 10(-9) M. Among these peptides, MZ-4-243, MZ-4-169, and MZ-4-181 were also long acting in vitro. Antagonist MZ-4-243 inhibited GH release 100 times more powerfully than the standard antagonist and was the most potent in vitro among GHRH antagonists synthesized. Analogs with high inhibitory effects in vitro were also found to have high affinities to rat pituitary GHRH receptors. In experiments in vivo, antagonists [Ibu0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]-hGHRH-(1-28 )Agm (MZ-4-71), [Nac0,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]hGHRH-(1-29) NH2 (MZ-4-169), and [Nac0-His1,D-Arg2,Phe(4-Cl)6,Abu15,Nle27]hGHR H-(1-29)NH2 (MZ-4-181) induced a significantly greater inhibition of GH release than the standard antagonist. In view of their high antagonistic activity and prolonged duration of action, some of these antagonists of GHRH may find clinical applications, including treatment of certain endocrine disorders and insulin-like growth factor I-dependent tumors.

Role of insulin-like growth factors in steroid modulated proliferation

The mechanism by which steroids influence cell proliferation is poorly understood although an understanding of this process might facilitate the development of strategies to modulate the tissue-specific activity of steroid hormones. In this article, the evidence that steroid hormones interact with the insulin-like growth factor (IGF) signal transduction pathway is reviewed for three different tissues. In osteoblasts, oestradiol stimulates the production of IGF-I which appears to act as an autocrine growth factor. In uterine tissue, oestradiol increases the synthesis of IGF-I in the stroma which then modulates the proliferation of epithelial cells although there is also evidence that oestradiol can modulate the sensitivity of uterine epithelial cells to IGFs. In breast cancer, oestrogens may increase IGF-II synthesis in epithelial cells, increase the sensitivity of breast cancer cells to IGFs (possibly by modulating type I IGF receptor levels) as well as resulting components of the IGF signal transduction pathway resulting in induction of immediate early genes. There therefore appears to be a variety of ways in which oestradiol interact with the IGF signal transduction pathway and these may be applicable to other malignant and normal tissues and other groups of steroid hormones.

Preclinical data for Droloxifene

The new antiestrogen Droloxifene has a 10-60-fold higher binding affinity to the estrogen receptor (ER) compared to the related compound Tamoxifen. A similar relationship was found in growth inhibition studies which showed that Droloxifene inhibited the different ER positive human breast cancer cells more effectively than Tamoxifen, predominantly in drug concentrations which are found in humans during therapy. As another consequence of the high stability of the complex formed by Droloxifene binding to the ER, intermittent exposures with clinically relevant concentrations of Droloxifene brought about effective growth inhibition of human ER positive tumor cells even after short-term application. Droloxifene was found, like Tamoxifen, to block human breast cancer cells in G1-phase of the cell cycle. Moreover, cell-cycle data confirmed the superior growth-inhibiting potency of Droloxifene compared to Tamoxifen. Droloxifene was also found to effectively induce expression of the negative growth factor TGF-beta, to inhibit IGF-I stimulated cell growth and to prevent estrogen-stimulated proto-oncogene c-myc expression. Unlike Tamoxifen, Droloxifene is a potent inhibitor of protein biosynthesis in ER-positive breast cancer cells at physiologically relevant concentrations. Lower estrogenic and higher antiestrogenic effects on immature rat uterus indicate a higher therapeutic index for Droloxifene compared to Tamoxifen. In vivo, Droloxifene displayed increased growth inhibition of different tumors of animal (R3230AC and 13762) and human origin (T61). Furthermore, it was found that the two structurally similar drugs differ in their toxicologic characteristics in the following important respects: Droloxifene is devoid of any in vivo or in vitro carcinogenic or mutagenic effects, whereas Tamoxifen causes liver tumors in rats, induces DNA adduct formation in rats and hamsters and shows transforming activity in SHE-cells (Syrian hamster embryo fibroblasts). Considerably less toxicity and a lower level of intrinsic estrogenicity was observed even after maximum long-term exposure of different animal species to Droloxifene, in comparison with Tamoxifen. Therefore, it can be assumed that Droloxifene may represent an important step forward in the treatment of mammary carcinomas in women through its better tolerability and increased efficacy compared with Tamoxifen. For long-term adjuvant or preventive treatment of breast cancer, Droloxifene may well be the safer choice.

Gonadal steroid hormone regulation of the somatotropic axis during puberty in humans Mechanisms of androgen and estrogen action

The adolescent growth spurt is associated with a sex steroid hormone-dependent rise in GH production; both androgens and estrogens are implicated as positive regulators of the somatotropic axis during puberty. The issue is complicated by the fact that testosterone may act both directly via the androgen receptor and indirectly, after its aromatization to 17beta-estradiol, through the estrogen receptor. Recently, a number of investigators have studied the effects of the administration of androgen and estrogen receptor antagonists, as well as nonaromatizable androgens, on GH secretion. These reports suggest that estrogen receptor-dependent processes play a facilitatory role in the pubertyassociated rise in GH secretion. If androgen receptor-mediated events are involved in the control of the somatotropic axis, their role is likely inhibitory. A hypothalamic site of action of the sex steroids is postulated.

Plasma insulin-like growth factor I and its binding proteins 1 and 3 in postmenopausal patients with breast cancer receiving long term tamoxifen

BACKGROUND

Insulin-like growth factor I (IGF-I) is a potent mitogen for breast cancer cells. The majority of IGF-I in plasma is bound to IGF binding proteins (IGFBPs), which modulate the biologic effects of IGF-I.

METHODS

Plasma concentrations of IGF-I, IGFBP-I, and IGFBP-3 were compared between 40 postmenopausal breast cancer patients receiving long term tamoxifen therapy and 39 breast cancer patients receiving no hormonal treatment. In an additional group of seven patients, serum levels of IGF-I and IGFBP-1 were determined before and during treatment at 6 and 12 months.

RESULTS

The tamoxifen and the control groups did not differ with respect to age, parity, age at menopause, or body mass index. There were no significant differences in the mean concentrations (+/- standard error of the mean) of IGF-I (10.0 +/- 0.4 nmol/l and 11.2 +/- 0.5 nmol/l, respectively) and IGFBP-3 (3.2 +/- 0.1 mg/l and 3.1 +/- 0.1 mg/l, respectively), whereas the mean value of IGFBP-1 was significantly higher in the tamoxifen group (6.0 +/- 0.6 micrograms/l versus 2.8 +/- 0.3 micrograms/L, P = 0.0001). No significant differences were found in the insulin levels. During the treatment, concentrations of IGF-I decreased at 6 months and began increasing at 12 months. IGFBP-1 levels increased at 6 months and remained elevated at 12 months.

CONCLUSIONS

The tamoxifen-induced increase in IGFBP-1 plasma levels may be an important mechanism modulating IGF-I action at the tissue level.

Molecular mechanisms of antiestrogen action in breast cancer

The success of antiestrogen therapy to treat all stages of breast cancer, and the evaluation of tamoxifen as a preventive for breast cancer in normal women, have focused attention on the molecular mechanisms of antiestrogen action and mechanisms of drug resistance. The overall goal of research is to enhance current therapies and to develop new approaches for breast cancer treatment and prevention. Recent studies show that tamoxifen and the new pure antiestrogens appear to have different mechanisms of action: tamoxifen and related compounds cause a change in the folding of the steroid binding domain that prevents gene activation whereas the pure antiestrogens cause a reduced interaction at response elements and cause a rapid loss of receptor complexes. Tamoxifen treatment produces changes in the cellular and circulating levels of growth factors that could influence both receptor negative or receptor positive tumor growth and the metastatic potential of a tumor. These events may explain the survival advantage observed with tamoxifen therapy. However, the current therapeutic challenge is to avoid drug resistance during long-term tamoxifen therapy. Numerous explanations for drug resistance to tamoxifen have been suggested, including elevated estrogen levels, increased tumor antiestrogen binding sites, receptor mutations, and impaired signal transduction. However, it is probable that multiple mechanisms evolve to facilitate tumor survival. Most importantly, current research is examining mechanisms responsible for the beneficial actions of tamoxifen on bones and lipids as well as the potentially deleterious effects of tamoxifen on liver and endometrial carcinogenesis and retinopathy. The urgent need to understand antiestrogenic drug mechanisms and toxicity is being facilitated by the application of the technology developed for basic molecular biology.

The insulin-like growth factor system as a target in breast cancer

Evidence from several experimental systems has shown that the insulin-like growth factors (IGFs) can stimulate breast cancer proliferation. Since IGF action is mediated by interaction with specific cell surface receptors, interruption of these signalling pathways could result in inhibition of cellular growth. In all extracellular fluids, the IGFs are associated with high affinity binding proteins, the IGFBPs can bind the IGFs and prevent receptor activation, and thus might have a role in a targeted approach to breast cancer therapy. Here we present our studies using IGFBP-1 to inhibit growth of the breast cancer cell line MCF-7.

Effect of two-4-hydroxyandrostenedione doses on serum insulin-like growth factor I levels in advanced breast cancer

A number of endocrine treatments for advanced breast cancer seem to affect serum insulin-like growth factor I (IGF-I). The aim of our study was to investigate IGF-I levels in 33 postmenopausal patients with metastatic disease receiving the selective aromatase inhibitor 4-hydroxyandrostenedione: 250 mg (16 patients) or 500 mg (17 patients) i.m. fortnightly. Blood samples were collected before, and at one month and 3 months after the beginning of treatment for radioimmunoassay determinations. The median patient age was 56 and 60 years in the 250 and 500 mg groups respectively. Most patients had a disease free interval > or = 2 years and were oestrogen receptor positive. Objective responses were obtained in 3 patients (complete response, 1) in the 250 mg group, and in 7 patients (complete response, 3) in the 500 mg group. No significant IGF-I variations were seen in the 250 mg group, whereas a significant increase after 3 months (181.57 +/- 84.78 ng/ml versus 272.47 +/- 213.22 ng/ml, p = 0.0032) was observed in the 500 mg group. No IGF-I variations were seen between responsive and unresponsive patients in either treatment group. Our results in the 500 mg group are close to those obtained with aminoglutethimide and seem to agree with the hypothesis of an oestrogen-induced suppression of IGF-I circulating levels.

Natural killer cell activity, phagocytosis, and number of peripheral blood cells in breast cancer patients treated with tamoxifen

The number of leukocytes, proportion and absolute number of granulocytes, lymphocytes, CD4+ cells, CD8+ cells, CD16+ cells, B-lymphocytes, monocytes, natural killer cell (NK) activity, and granulocyte and monocyte phagocytic functions--ingestion and intracellular killing--were determined in a group of 27 patients with ductal invasive breast carcinoma, stage I-III, before and 7 months following postsurgical telecobalt radiotherapy, divided into two subgroups, one of them receiving tamoxifen (TMX group) and the other one not receiving any further therapy (control group). In control group, proportion of all lymphocytes and CD8+ cells as well as absolute number of all lymphocytes, CD4+, CD8+, CD16+ and B lymphocytes were decreased following TCT in comparison to their pre-TCT values, while in TMX group only absolute number of all lymphocytes remained decreased following TCT. Moreover, post-TCT proportions of all and CD8+ lymphocytes as well as absolute numbers of all and CD4+ and CD8+ lymphocytes in TMX patients were significantly increased in comparison to the same parameters in control post-TCT patients, although there was no difference between the two subgroups before TCT. At the other hand, granulocyte ingestion was decreased in post-TCT TMX patients compared to post-TCT values in control patients and NK cell activity showed a similar, although statistically not significant, tendency. It seems that TMX helps recovery of lymphocyte populations decreased by radiotherapy, probably by stimulation of cells carrying estrogen receptors, but its effects on phagocytic functions and probably NK cell activity seemed to be rather inhibitory than stimulatory.

Regulation of insulin-like growth factors by antiestrogen

Insulin-like growth factors are potent mitogens for breast cancer cell proliferation. This effect is modulated by the circulatory and extracellular IGFBPs as well as by the affinity of ligand binding receptors on the target cells. Antiestrogens have been shown to reduce both circulatory and microenvironmental IGF levels and thus suppress the IGF-I-induced growth of both ER-positive and ER-negative breast cancer cells. However, the effects of antiestrogens in down regulation of type I IGF receptor and in altering the autophosphorylation tyrosine kinase activity of EGF receptors are mainly observed in ER-positive cells. Furthermore, alteration of IGFBP by antiestrogens such as a marked increase of IGFBP-I production have been shown to inhibit the proliferative effect of IGF-I on ER-positive, but stimulate this effect, on ER-negative cells. Such differential effects from IGF receptor and IGFBP may explain the clinical outcome that tumor regression from antiestrogens is mainly observed in ER-positive type. This assumption based on IGF regulation alone is certainly an oversimplistic view amid the complexity of autocrine, paracrine, and endocrine functions.

An appraisal of strategies to reduce the incidence of breast cancer

The current focus of breast cancer research is to develop a novel strategy to prevent the disease. In this review a potential model of breast cancer development is proposed based upon the results of laboratory models of the induction of mammary carcinogenesis. It is clear that susceptibility to initiation occurs in young female animals, and a preventive strategy is more effective the sooner it is started after initiation occurs. In humans we do not know the timing or the nature of the carcinogenic insult, but epidemiologic studies suggest that the process is long and initiation is most likely to occur in young adults. Hormones are the key to promotion of the carcinogenic process and it would appear that strategically the earlier an intervention is applied after initiation the better will be the general effect on the population. Hormonal contraception could prevent breast cancer if the appropriate formulation was chosen and used by all young women. This inhibitory strategy might protect women without the need to preselect based on risk factors. Breast cancer prevention would be a side effect of the contraceptive method. Alternatively, tamoxifen, an antiestrogen, is known to prevent mammary carcinogenesis in animals and prevent the appearance of second primary breast cancers in women. This well tested therapeutic agent is currently being evaluated in clinical trials of selected high-risk women aged 35 and above. Finally, retinoids have shown promise as agents in the laboratory to prevent cell replication and inhibit mammary tumorigenesis. A trial of retinoids to prevent second primary tumors in node negative breast cancer patients is currently underway in Italy. The review discusses the relative merits and concerns about these prevention strategies and proposes additional studies to be undertaken.

Survival benefit of tamoxifen therapy in adenocarcinoma of pancreas. A case-control study

BACKGROUND

Clinical data suggest tamoxifen may improve the survival of patients with unresectable ductal adenocarcinoma of pancreas.

METHODS

Eighty patients (50 women and 30 men) with biopsy-documented unresectable or incompletely resected ductal adenocarcinoma of the pancreas were treated with 20 mg of tamoxifen twice daily. The survival of the tamoxifen-treated group was compared with that of a case-control group of another 80 patients with pancreatic cancer, matched for age, sex, TNM stage, and bypass procedure versus biopsy.

RESULTS

The median survival times for the tamoxifen-treated group versus controls were 7 and 3 months, respectively (P < 0.0001). For women older than 60 years of age and treated with tamoxifen, the median survival time was 12 months. Multivariate analysis of the 160 patients showed that tamoxifen therapy, female sex, absence of metastases at diagnosis, and bypass procedure are all of independent prognostic significance for prolonged survival.

CONCLUSIONS

Patients with unresectable or incompletely resected ductal adenocarcinoma of pancreas may have a prolonged survival benefit while receiving tamoxifen treatment. This potential benefit is most prominent in older women.

Cell biological factors associated with the response of breast cancer to systemic treatment

A large number of cell biological parameters are currently available to predict the prognosis of patients with breast cancer, but it is still difficulty accurately to predict the response to treatment. A valuable prognostic factor can be a poor predictive factor for response, and vice versa. High tumor levels of ER, PgR, AR and pS2 predict a relatively good response to endocrine therapy, while EGF-R positively, HER2/neu positivity, aneuploidy, high proliferation indices and possibly high uPA levels indicate a high chance of poor response to endocrine therapy in metastatic breast cancer. With respect to chemotherapy, a high proliferation rate and HER2/neu amplification predict a good response to therapy in metastatic disease, while MDR gene expression and possibly c-myc amplification are related to a worse response. In conclusion, the newer cell biological parameters can be used to select high and low-risk patients, type of systemic treatment, and as targets for new treatment modalities.

Use of endocrine therapy to study the biology of breast cancer

Drug resistance is the main reason for therapeutic failure and death in breast cancer. In vitro investigations have identified some mechanisms that may be responsible for resistance to chemotherapeutic agents in breast cancer, but we know little about the mechanisms responsible for resistance to endocrine treatment in receptor-positive tumors. Accordingly, a major task for future studies is to explore the mechanisms of both primary and acquired resistance to endocrine treatment as well as to chemotherapy in breast cancer. Drug resistance may be related to alterations in endocrine as well as paracrine delivery of certain growth factors or hormones, but it may also be caused by alterations in drug disposition. Primary resistance may be evaluated by comparing the response to drug treatment with the expression of different biochemical parameters in the tumor before treatment. To explore the mechanisms of acquired drug resistance requires study of the changes in biological parameters developing over time during drug therapy. Also, it may be of interest to use certain drugs (like a 'classical' anti-estrogen and a steroidal anti-estrogen) in a particular sequence to explore the possibility of cross-resistance (or lack of it) between particular treatment modalities. Possible implications for the design of future trials in breast cancer treatment are discussed.