Insulin-like growth factor I gene expression in the uterus is stimulated by tamoxifen and inhibited by the pure antiestrogen ICI 182780

Estrogen-induced uterine insulin-like growth factor I (IGF-I) expression has been demonstrated to mediate at least in part the uterotrophic action of estradiol. We studied the effects of tamoxifen, a partial antagonist to the estrogen receptor widely used in the treatment of breast cancer, and ICI 182780, a pure antagonist to the estrogen receptor, on uterine weight and uterine IGF-I gene expression in the rat. Tamoxifen increased uterine weight to 125% of control values and doubled uterine IGF-I expression. In contrast, ICI 182780 reduced uterine weight to 60% of control and uterine IGF-I gene expression to 13% of control. These results demonstrate for the first time that uterine IGF-I expression is a molecular marker that correlates with the effects of partial agonists and antagonists to the estrogen receptor on the uterus. Furthermore, the induction of uterine IGF-I expression by tamoxifen provides a molecular mechanism to account for the uterotrophic effects which are commonly seen with tamoxifen therapy and which have been associated with endometrial neoplasia.

The human insulin-like growth factor-binding protein 4 gene maps to chromosome region 17q12-q21.1 and is close to the gene for hereditary breast-ovarian cancer

The gene for insulin-like growth factor-binding protein 4 (IGFBP4) codes for a serum protein that binds to the family of insulin-like growth factors and modulates their activity. It has been mapped by in situ hybridization to chromosome region 17q12-q21.1. We have developed a CA-repeat polymorphism from a cosmid clone containing IGFBP4. By linkage analysis, IGFBP4 maps to the chromosome 17q interval THRA1-D17S579. This interval also contains the gene for hereditary breast-ovarian cancer, BRCA1. Genetic recombination between IGFBP4 and BRCA1 places IGFBP4 centromeric to the cancer susceptibility gene and effectively excludes it as a candidate gene for BRCA1. IGFBP4 is, however, one of the closest known centromeric markers for BRCA1; the estimated recombination fraction is 0.015. IGFBP4 and D17S579 together define a 2.8-cM interval that contains BRCA1.

Pregnancy complicated by medulloblastoma with metastases to the placenta

BACKGROUND

Maternal malignancy may complicate as many as one in 1000 pregnancies. Rarely, the tumor may metastasize to the products of conception. We here describe a case of medulloblastoma metastatic to the placenta.

CASE

A 21-year-old woman who had previously undergone resection of a posterior fossa medulloblastoma was admitted at 20 weeks' gestation complaining of low back pain. Investigation revealed medulloblastoma metastatic to the bone marrow. The pregnancy was prolonged to 29 weeks' gestation, at which time she was delivered by cesarean. The postoperative course was complicated by coagulopathy, massive bleeding, and pneumonia leading to death. Autopsy showed medulloblastoma metastatic to the bone marrow and placenta.

CONCLUSION

Primary intracranial neoplasms may metastasize to the products of conception. The dramatic course of the disease in this patient may suggest that medulloblastoma is responsive to hormonal therapy.

In vivo inhibition of insulin-like growth factor I gene expression by tamoxifen

Tamoxifen, a partial antagonist to the estrogen receptor, is widely used in the treatment of breast cancer and is currently being evaluated as a breast cancer preventative agent in large-scale clinical trials. Recent clinical research has demonstrated that tamoxifen administration is associated with a reduction of serum insulin-like growth factor I (IGF-I) concentration. We demonstrate here that tamoxifen, when administered in an in vivo experimental system previously used to demonstrate its cytostatic effect on breast cancer cell proliferation, inhibits the expression of the IGF-I gene in common target organs for breast cancer metastasis. Furthermore, while our prior experimental studies have demonstrated an inhibitory effect of tamoxifen on growth hormone output, we show here for the first time that the suppression of IGF-I gene expression associated with tamoxifen administration is in part a consequence of a pituitary-independent action of the drug. Because IGF-I is a potent mitogen for breast cancer cells, this newly described activity of tamoxifen may contribute to its antineoplastic properties, particularly with regard to inhibition of metastasis seen both in animal models and clinically.

Suppression of serum insulin-like growth factor-1 levels in breast cancer patients during adjuvant tamoxifen therapy

Serial IGF-1 levels in patients prior to and during adjuvant tamoxifen (TAM) treatment were followed in a retrospective study. Serum IGF-1 levels were determined by radioimmunoassay in 19 patients taking TAM and 19 controls, matched for age, body weight and other treatments. IGF-1 levels at 2 years were significantly lower in TAM patients (P < or = 0.05) compared to control patients. We observed a significant mean drop from pretreatment to treatment IGF-1 levels by 19.9% in the TAM group (P < or = 0.005), but also noted a mean 11.4% decline in the control group (P < or = 0.025). A subgroup analysis suggested that premenopausal were relatively resistant to the IGF-1 lowering effects of TAM as compared to postmenopausal women.

Potential role for somatostatin analogues in breast cancer: rationale and description of an ongoing trial

Somatostatin analogues such as octreotide have been shown in experimental systems to exhibit antineoplastic activity. Further laboratory and clinical research is needed to clarify the mechanism of action of somatostatin analogues as antineoplastics, and to determine if the encouraging preclinical results will lead to novel endocrine approaches to the treatment of breast cancer.

Impact on the general public of media campaigns against AIDS: a French evaluation

The article presents the results of the first national survey in a representative sample of the French population of 18 years of age and over (n = 1000; March 1990) about knowledge, attitudes, beliefs and practices toward HIV infection. It focuses on the impact of the media campaigns about AIDS and condom promotion that were initiated since April 1987 by French public health authorities. A total of 53.2% of respondents were able to correctly quote at least one of the slogans of the campaigns and 48.4% felt they have been personally influenced by the campaigns. Respectively 25.4%, 12.1%, and 11.2% declared that the campaigns have made them more concerned of individual risk of HIV infection and prompted them to condom use and HIV testing. Among heterosexually active respondents, 16.9% declared condom use in the past 12 months, age, marital status, level of education, HIV testing and self-acknowledgement of influence of campaigns being the main factors related to condom use in multidimensional analysis. Respondents who recognise having been influenced by campaigns are less likely to believe in HIV transmission through casual contact and to express discriminatory attitudes toward HIV carriers but more likely to support HIV mandatory screening for the general population. The difficulties to properly evaluate media campaigns for AIDS prevention are discussed as well as the complex trade-offs that general public information has to face between promotion of both individual behavioural change and societal support and empathy for HIV carriers and persons with AIDS.

Inhibition of metastatic behavior of murine osteosarcoma by hypophysectomy

BACKGROUND

We recently reported that human osteogenic sarcoma cells are mitogenically responsive in tissue culture to insulin-like growth factor I (IGF-I), a mitogen important in the regulation of cellular proliferation of many tissues, including bone.

PURPOSE

The present study was designed to determine whether these in vitro observations could be extended to an in vivo experimental system and whether reduction of IGF-I levels by hypophysectomy could inhibit the aggressive metastatic behavior of osteosarcoma.

METHODS

We used standard competitive binding and affinity-labeling techniques to characterize the IGF-I-binding sites of MGH-OGS, a model of human osteosarcoma. Radioimmunoassay of serum, preprocessed to remove IGF-binding proteins, was used to quantitate IGF-I levels. In vitro proliferative response of MGH-OGS cells to IGF-I and other pituitary-dependent factors was determined by thymidine-incorporation experiments. In vivo growth of the neoplasm in 12 hypophysectomized C3H mice and in 14 control C3H mice was determined by serial measurements of implanted tumors and by gross and microscopic examination of the lungs for metastases.

RESULTS

MGH-OGS exhibited specific binding sites for 1.39 pmol IGF-I per milligram MGH-OGS cellular membrane protein, a concentration similar to that which we previously reported for human osteosarcoma. In tissue culture, MGH-OGS exhibited mitogenic response to IGF-I (P less than .01) but not to other pituitary-dependent factors. Hypophysectomy reduced levels of circulating IGF-I to 15% of control, significantly inhibited local growth of MGH-OGS tumors (increased time for growth to 1 cm3 from 49 to 84 days, P less than .001), and profoundly inhibited metastatic behavior (decrease in mean number of metastases per host from 16 to less than one; P less than .001).

CONCLUSIONS

This study is the first to document the profound inhibitory effect of hypophysectomy on the metastatic behavior of an experimental sarcoma. We conclude that the metastatic behavior exhibited by MGH-OGS osteosarcoma is dependent on pituitary factors, and we suggest that the inhibitory effects of hypophysectomy are related, at least in part, to the reduction of IGF-I levels.

Tamoxifen attenuates pulsatile growth hormone secretion: mediation in part by somatostatin

Tamoxifen, a partial competitive antagonist to the estrogen receptor, is a potent inhibitor of the proliferation of experimental mammary carcinoma in the rat and is widely used clinically in the treatment of breast cancer. Blockade of estrogen receptors present on neoplastic cells represents the classic mechanism of action of tamoxifen, but the drug has a variety of other actions that may contribute to its antiproliferative properties. While it is recognized that estrogens play an important role in modulating pulsatile GH release, the effect of antagonists to sex steroid receptors on GH secretory dynamics has not previously been described. In the present study we examined the effect of tamoxifen on pulsatile GH secretion in free-moving adult male and female rats. The drug, when administered in a manner previously shown to be associated with antineoplastic activity, caused a marked suppression of the amplitude of spontaneous GH secretory bursts and significantly reduced mean 6-h plasma GH levels in both sexes compared to those in their respective peanut oil-injected controls. Inhibition of spontaneous GH pulses persisted for up to 7 weeks after tamoxifen administration in both sexes. Immunoneutralization of endogenous somatostatin in tamoxifen-treated male rats completely restored both GH pulse amplitude (121.6 +/- 9.5 vs. 62.5 +/- 13.5 ng/ml in tamoxifen-treated rats given normal sheep serum; P less than 0.02) and mean 6-h plasma GH levels (53.3 +/- 6.6 vs. 17.9 +/- 3.6 ng/ml in normal sheep serum-treated rats; P less than 0.01) to levels observed in our peanut oil-injected controls. These results demonstrate that 1) tamoxifen has potent inhibitory effects on pulsatile GH secretion; and 2) the blunting of GH pulse amplitude by tamoxifen is mediated at least in part by increased release of endogenous somatostatin. These findings motivate further investigation of the clinical significance of tamoxifen-induced suppression of GH secretion in relation to the antineoplastic activity of this commonly used drug.

The ability of suramin to block CD4-gp120 binding is reversed in the presence of albumin

We have shown that suramin can directly inhibit the binding of the human immunodeficiency virus type 1 gp120 envelope protein to immobilized CD4, thus helping to explain the previously described antiviral properties of suramin. However, physiological concentrations of serum albumin significantly attenuated suramin's antiviral effects, suggesting that only free suramin has antiviral properties. Reported discrepancies between in vitro and clinical activities of suramin may be due to differences between free suramin levels in experimental assays and those achievable clinically.

Interferon-induced modulation of epidermal growth factor-stimulated growth of a human breast tumor cell line

We have determined that interferon-alpha (IFN-alpha) and IFN-gamma inhibit the growth of a human breast tumor cell line, S4, in vitro. Cells were more sensitive to the antiproliferative effects of low-dose IFN-gamma than IFN-alpha. As the growth of the S4 cell line is enhanced by epidermal growth factor (EGF), we examined the effect of IFN on EGF-dependent growth of S4 cells. Cells plated in 2.5% serum alone failed to grow. EGF stimulated these cells to grow more than twofold. IFN substantially attenuated the EGF-stimulated growth of S4 cells. Binding of EGF to its receptor was unaffected by pretreatment of cells with IFN-alpha. However, a 24-h exposure of cells to IFN-gamma significantly increased the number of EGF receptors on S4 cells. Internalization of the EGF receptor was unaffected by IFN treatment. Binding remained elevated through 4 days of IFN-gamma exposure. Scatchard analysis of receptor binding data revealed that IFN-gamma increased the number of binding sites without changing the affinity of the receptor for its ligand. These results demonstrate that IFN inhibits EGF-stimulated growth of a breast tumor cell line and suggest that the antiproliferative effect of IFN may be due, in part, to its interaction with growth factor-initiated pathways.

A mathematical model describing consequences of abnormally high levels of epidermal growth factor receptor on the proliferation of neoplastic cells

Recent laboratory and clinical data suggest that some human neoplasms exhibit unusually high levels of cell-surface receptors for epidermal growth factor, and that this abnormality is associated with rapid cellular proliferation and poor prognosis. We propose that the existence of an abnormally high number of mitogen receptors is not merely correlated with rapid proliferation but is pathophysiologically responsible for such behavior. Cells with high levels of mitogen receptors may be rendered 'hypersensitive' to mitogenic stimuli, and hence may be stimulated to divide even when ambient mitogen concentrations are at a low 'background' level, insufficient to prompt the division of cells with a normal number of receptors. To investigate this hypothesis further, we have developed a mathematical model that describes proliferative behavior of cells as a function of mitogen concentration and receptor number. The model enables us to simulate the proliferative behavior of cells with various receptor levels at various mitogen concentrations and predicts a growth advantage associated with excess mitogen receptors. Computer simulations based on the model are consistent with previously published experimental data. This work provides support for the view that overexpression of genes encoding normal growth factor receptors can contribute to the inappropriate proliferation of neoplastic cells.

Trimetrexate in untreated and previously treated patients with metastatic breast cancer: a Cancer and Leukemia Group B study

Twenty-two patients with previously untreated metastatic breast cancer and nineteen patients with refractory metastatic breast cancer were treated with trimetrexate (TMTX). Patients received TMTX 8 mg/m2/day if previously treated or 12 mg/m2/day if previously untreated, both given by intravenous bolus days 1-5, every 21 days. None of the patients previously treated for metastatic disease responded to TMTX. There was one partial responder among the 22 patients with previously untreated metastatic disease. The primary toxicity was hematologic and occurred more frequently in patients with a pleural effusion, low serum protein or albumin, or poor performance status. There were three toxic deaths. The study for previously untreated patients required cyclophosphamide, doxorubicin, and 5-fluorouracil (CAF) after 4 cycles of TMTX. This study design for previously untreated patients allows the Cancer and Leukemia Group B (CALGB) to prospectively evaluate the activity of new agents in "chemotherapy-sensitive" metastatic breast cancer.

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

Insulinlike growth factor I (IGF-I) has been shown to be a potent mitogen for breast cancer cells in vitro, and IGF-I receptors have been demonstrated on human primary breast neoplasms. In a randomized, placebo-controlled study, we document that administration of the antiestrogen tamoxifen to patients with breast cancer was associated with a statistically significant (P = .002) reduction in the serum level of IGF-I. The mean IGF-I level was 1.4 U/mL in the placebo-treated group and 0.9 U/mL in the tamoxifen-treated group. Because serum IGF-I level is growth hormone (GH) dependent and because data suggest that the pubertal surge in GH and IGF-I levels is sex steroid dependent, we speculate that the mechanism underlying our observation may involve blockade by tamoxifen of estrogen action in the hypothalamic-pituitary axis. We conclude that tamoxifen treatment reduces IGF-I levels and that this reduction may contribute to the therapeutic effect of the drug.

Mitomycin C and mitoxantrone chemotherapy for advanced breast cancer: efficacy with minimal gastrointestinal toxicity and alopecia

In an attempt to examine the possibility of decreased toxicity in patients with advanced breast cancer who had not previously received chemotherapy, 33 women were given combination chemotherapy consisting of mitomycin C (10 mg/m2) every 6 weeks and mitoxantrone (6 mg/m2) every 3 weeks. The patients had predominantly visceral disease and received a median of two cycles of therapy. Of the 32 evaluable subjects, 15 (47%) achieved a partial response lasting a median of 7 months. Hematological toxicity was generally mild, although there were two episodes of sepsis. One patient developed hemolytic-uremic syndrome, and one subject developed pulmonary fibrosis, both presumably attributable to treatment with mitomycin C. Another patient died of hepatic failure (hepar lobatum). Thus, there were five patients who sustained life-threatening toxicities; this may have been due to the poor performance status and advanced age of some of the patients. Gastrointestinal toxicity and alopecia were minimal. Patient acceptance was high and there was an improvement in symptomatology in the majority of patients. In conclusion, mitomycin C and mitoxantrone chemotherapy is an active drug combination for the treatment of advanced breast cancer that seldom causes significant distressing gastrointestinal side effects or alopecia; however, the duration of response to this regimen appears to be shorter than that obtained with either cyclophosphamide - methotrexate - 5-fluorouracil (CMF) or cyclophosphamide - Adriamycin - 5-fluorouracil (CAF) combination chemotherapy.

Suramin blockade of insulinlike growth factor I-stimulated proliferation of human osteosarcoma cells

The polyanionic compound suramin is currently being evaluated for antineoplastic activity. On the basis of previous in vitro studies, it has been suggested that the mechanism of action of suramin may be related to its ability to attenuate the mitogenic effects of peptide growth factors, such as platelet-derived growth factor and epidermal growth factor. We recently reported that MG-63 human osteosarcoma cells are mitogenically responsive to insulinlike growth factor I (IGF-I). We now demonstrate for the first time that suramin interferes with the interaction between IGF-I and its receptor and abolishes in vitro IGF-I-stimulated proliferation of these osteosarcoma cells. The fact that cell proliferation resumes when suramin is removed indicates that this is not a cytotoxic effect. We conclude that IGF-I should be added to the list of growth factors whose bioactivity can be attenuated by suramin and that clinical studies of suramin and its analogues are indicated in IGF-I-receptor-positive malignancies such as osteogenic sarcoma.