Estrogen and antiestrogen modulation of the levels of mouse natural killer activity and large granular lymphocytes

Impact of HLA Class I Antigen, Killer Inhibitory Receptor, and FCGR3A Genotypes on Breast Cancer Susceptibility and Tumor Stage

BACKGROUND

The identification in breast cancer (BC) of novel genetic biomarkers regulating natural killer (NK) cell function, including the HLA, KIR, and CD16A (FCGR3A), may be still a challenge.

OBJECTIVE

We aimed to evaluate whether the combined effect of these polymorphisms has an impact on BC susceptibility and progression.

METHODS

47 BC Italian patients and healthy individuals (39 females and 66 males/ females) were genotyped by Sanger sequencing (HLA-C exon 2-4 and FCGR3A- 158V/F, 48L/R/H) and PCR-SSP typing (KIR genes).

RESULTS

HLA-C gene allele analysis showed the group C1, with HLA-C*07:02:01 allele, to be significantly associated with tumor progression (16.7% vs. 4.0%, p=0.04, OR=4.867), and instead, group C2, with HLA-C*05:01:01, was protective against disease susceptibility (0.0% vs. 7.2%, p=0.019, OR=0.087). In addition, we highlighted a significant reduction of the KIR2DS4ins in BC patients (pcorr.=0.022) and an increased combined presence of KIR2DL1 and KIR2DS1 genes in advanced BC patients compared to earlier stages (66.7% vs. 19.2%, p=0.002). The concurrent lack of KIR2DL2 and KIR2DS4 genes in the presence of HLA-C2 alleles was significantly associated with increased susceptibility to BC (p=0.012, OR=5.020) or with lymph node involvement (p=0.008, OR=6.375). Lastly, we identified different combinations of the FCGR3A-48/158 variants and KIR genes in BC patients compared to controls.

CONCLUSION

Our findings suggest that in the development of BC probably exists a disorder of the NK innate immunity influenced by KIR/HLA-C gene content and FCGR3A-158 polymorphisms and that the combined analysis of these biomarkers might help predict genetic risk scores for tailored screening of BC patients in therapy.

Reconstitution of GABA, Glycine and Glutamate Transporters

In contrast to water soluble enzymes which can be purified and studied while in solution, studies of solute carrier (transporter) proteins require both that the protein of interest is situated in a phospholipid membrane and that this membrane forms a closed compartment. An additional challenge to the study of transporter proteins has been that the transport depends on the transmembrane electrochemical gradients. Baruch I. Kanner understood this early on and first developed techniques for studying plasma membrane vesicles. This advanced the field in that the experimenter could control the electrochemical gradients. Kanner, however, did not stop there, but started to solubilize the membranes so that the transporter proteins were taken out of their natural environment. In order to study them, Kanner then had to find a way to reconstitute them (reinsert them into phospholipid membranes). The scope of the present review is both to describe the reconstitution method in full detail as that has never been done, and also to reveal the scientific impact that this method has had. Kanner's later work is not reviewed here although that also deserves a review because it too has had a huge impact.

Immune Tumor Microenvironment in Breast Cancer and the Participation of Estrogen and Its Receptors in Cancer Physiopathology

Breast cancer is characterized by cellular and molecular heterogeneity. Several molecular events are involved in controlling malignant cell process. In this sense, the importance of studying multiple cell alterations in this pathology is overriding. A well-identified fact on immune response is that it can vary depend on sex. Steroid hormones and their receptors may regulate different functions and the responses of several subpopulations of the immune system. Few reports are focused on the function of estrogen receptors (ERs) on immune cells and their roles in different breast cancer subtypes. Thus, the aim of this review is to investigate the immune infiltrating tumor microenvironment and prognosis conferred by it in different breast cancer subtypes, discuss the current knowledge and point out the roles of estrogens and its receptors on the infiltrating immune cells, as well as to identify how different immune subsets are modulated after anti-hormonal treatments in breast cancer patients.

Survival outcomes and prognostic factors in mycosis fungoides/Sézary syndrome: validation of the revised International Society for Cutaneous Lymphomas/European Organisation for Research and Treatment of Cancer staging proposal

PURPOSE

We have analyzed the outcome of mycosis fungoides (MF) and Sézary syndrome (SS) patients using the recent International Society for Cutaneous Lymphomas (ISCL)/European Organisation for Research and Treatment of Cancer (EORTC) revised staging proposal.

PATIENTS AND METHODS

Overall survival (OS), disease-specific survival (DSS), and risk of disease progression (RDP) were calculated for a cohort of 1,502 patients using univariate and multivariate models.

RESULTS

The mean age at diagnosis was 54 years, and 71% of patients presented with early-stage disease. Disease progression occurred in 34%, and 26% of patients died due to MF/SS. A significant difference in survival and progression was noted for patients with early-stage disease having patches alone (T1a/T2a) compared with those having patches and plaques (T1b/T2b). Univariate analysis established that (1) advanced skin and overall clinical stage, increased age, male sex, increased lactate dehydrogenase (LDH), and large-cell transformation were associated with reduced survival and increased RDP; (2) hypopigmented MF, MF with lymphomatoid papulosis, and poikilodermatous MF were associated with improved survival and reduced RDP; and (3) folliculotropic MF was associated with an increased RDP. Multivariate analysis established that (1) advanced skin (T) stage, the presence in peripheral blood of the tumor clone without Sézary cells (B0b), increased LDH, and folliculotropic MF were independent predictors of poor survival and increased RDP; (2) large-cell transformation and tumor distribution were independent predictors of increased RDP only; and (3) N, M, and B stages; age; male sex; and poikilodermatous MF were only significant for survival.

CONCLUSION

This study has validated the recently proposed ISCL/EORTC staging system and identified new prognostic factors.

Clinical implication of natural killer cells and reproduction

The regulation of natural killer (NK) cells in the peripheral blood and endometrial layers has been associated with reproductive immunopathology such as recurrent spontaneous abortions (RSA), infertility of implantation failures, or pre-eclampsia. The placenta has a complex anatomical structure and different subsets of NK cells with various functional roles can directly interact with trophoblasts. NK cell subpopulations and their functions, putative roles of NK cells in peripheral blood and endometrium are reviewed in relation to RSA and infertility. An increase in NK cell numbers and /or activity in pre- or post-conceptional period in women with RSA or infertility with multiple implantation failures are a significant clinical concern. In addition, immuno-phenotypic characteristics of NK cells in these women support the changes for their increased activity status. Further studies are needed to explore underlying mechanism of NK cells in RSA, infertility, and other reproductive immunopathologies. Possible neurological and hormonal control of NK cells and NK cell interaction with various leukocyte populations need further investigation in women with reproductive failures.

Innate and adaptive immunity in female genital tract: cellular responses and interactions

The mucosal immune system in the female reproductive tract (FRT) has evolved to meet the unique requirements of dealing with sexually transmitted bacterial and viral pathogens, allogeneic spermatozoa, and the immunologically distinct fetus. Analysis of the FRT indicates that the key cells of the innate and adaptive immune systems are present and functionally responsive to antigens. Acting through Toll-like receptors in the Fallopian tubes, uterus, cervix, and in the vagina, epithelial cells, macrophages, natural killer cells, and neutrophils confer protection through the production of chemokines and cytokines, which recruit and activate immune cells, as well as bactericidal and virucidal agents, which confer protection at times when adaptive immunity is downregulated by sex hormones to meet the constraints of procreation. The overall goal of this paper is to define the innate immune system in the FRT and, where possible, to define the regulatory influences that occur during the menstrual cycle that contribute to protection from and susceptibility to potential pathogens. By understanding the nature of this protection and the ways in which innate and adaptive immunity interact, these studies provide the opportunity to contribute to the foundation of information essential for ensuring reproductive health.

Sex-specific effects of neonatal exposures to low levels of cadmium through maternal milk on development and immune functions of juvenile and adult rats

Cadmium (Cd) is a major environmental contaminant. Although immunotoxic effects have been associated with Cd exposure, the inconsistency of experimental results underlines the need of an experimental approach more closely related to environmental conditions. We investigated the effects of exposing neonatal Sprague-Dawley rats to environmentally relevant doses of Cd through maternal milk. Dams received 10 parts per billion (ppb) or 5 parts per million (ppm) Cd chloride (CdCl2) in drinking water from parturition until the weaning of the pups. Half of the offspring was sampled at weaning time. The remaining juvenile rats received water without addition of Cd until adulthood. Cd accumulation in kidneys of juvenile rats fed from dams exposed to Cd indicated the transfer of the metal from mother to pups through maternal milk. This neonatal exposure resulted in decreased body, kidney and spleen weights of just weaned females but not of males. This effect was more pronounced in the less exposed females fed from dams exposed to 10 ppb Cd, which also displayed lower hepatic metallothionein-1 (MT-1) mRNA levels. The effect of Cd exposure on body and organ weights did not persist to adulthood. In contrast, we observed gender-specific effects of neonatal Cd exposure on the cytotoxic activity of splenic NK-cells of both juvenile and adult rats. Cd also strongly inhibited the proliferative response of Con A-stimulated thymocytes in both male and female adult rats 5 weeks after the cessation of Cd exposure. These immunotoxic effects were observed at doses much lower than those reported to produce similar effects when exposure occurred during adulthood. In conclusion, neonatal exposures to environmentally relevant levels of Cd through maternal milk represent a critical hazard liable to lead to both transitory and persistent immunotoxic effects.

Targeted disruption of the 2B4 gene in mice reveals an in vivo role of 2B4 (CD244) in the rejection of B16 melanoma cells

Murine 2B4 (CD244) is a cell surface receptor expressed on all NK cells, gammadelta-T cells, a subset of CD8(+) T cells, and all CD14(+) monocytes. 2B4 binds to CD48 with high affinity, and cross-linking 2B4 with anti-2B4 Ab in vitro causes activation of NK cells. To study its physiological role, we have generated, by gene targeting, mice deficient in the expression of this cell surface molecule. The expression of lymphoid cell surface markers on PBMC and splenocytes of mice homozygous for the mutation in 2B4 (2B4(-/-)) is identical to that in wild-type mice. However, thymocytes from female 2B4(-/-) mice, but not male 2B4(-/-) mice, have an increase in the immature CD4(-)/CD8(-) population. To investigate the in vivo role of 2B4, wild-type and 2B4(-/-) mice were injected with CD48(+) and CD48(-) metastatic B16 melanoma cells. Wild-type mice rejected CD48(+) melanoma poorly compared with CD48(-) tumor cells, suggesting that ligation of 2B4 by CD48 on melanoma cells is inhibitory. In keeping with this, male 2B4(-/-) mice showed enhanced ability to reject CD48(+) melanoma cells. However, female 2B4(-/-) mice poorly rejected both CD48(+) and CD48(-) melanoma cells, revealing a gender-specific and CD48-independent defect in mice lacking 2B4. In vitro and in vivo experiments reveal a complex role of NK cells in gender specificity.

Natural killer cells in pregnancy and recurrent pregnancy loss: endocrine and immunologic perspectives

The endocrine system and the immune system interact closely during implantation and maintenance of pregnancy. One of the most striking examples of this communication is at the level of the decidua (endometrium of pregnancy). Here, under the influence of sex steroids, there is a dramatic increase of a unique population of lymphocytes, the uterine natural killer (uNK) cells, in early pregnancy. These cells derive predominantly from a subset of peripheral blood NK cells, which under hormonal influence gets recruited to the uterus. In mice, uNK cells play an important role in the development of placental vasculature. The role of these cells in human pregnancy is still not definitively established; however, they are believed to promote placental and trophoblast growth and provide immunomodulation at the maternal-fetal interface. In contrast to their presumptive role in the maintenance of a healthy pregnancy, uNK cells and peripheral NK cells are dysregulated in unexplained recurrent pregnancy loss. Herein, we review NK cell populations, their changes in number and function in altered endocrine environments during the menstrual cycle and pregnancy, the current data on their potential role in unexplained recurrent pregnancy loss, and mechanisms for potential therapies targeted to NK cell function for this enigmatic disorder.

Role of TGF-beta in cancer and the potential for therapy and prevention

Transforming growth factor (TGF)-beta is a naturally occurring potent inhibitor of cell growth. TGF-beta binds first to a Type II (TGFBR2), then a Type I receptor (TGFBR1). TGFBR1 activation results in the phosphorylation of intracellular messengers, the SMADs. Unrestricted cell growth due to decreased growth inhibitory activity is a paramount feature of a defect in TGF-beta function. There is growing evidence that common variants of the TGF-beta pathway ligand and receptors that alter TGF-beta signaling modify cancer risk. Approximately 14% of the general population carry TGFBR1*6A, a variant of the TGFBR1 gene that results in decreased TGF-beta-mediated growth inhibition. Recent studies show that overall cancer risk is increased by 70 and 19% among TGFBR1*6A homozygotes and heterozygotes, respectively. This suggests that TGFBR1*6A may contribute to the development of a large proportion of common forms of cancer and may become a target for cancer chemoprevention. While decreased TGF-beta signaling increases cancer risk, TGF-beta secretion and activated TGF-beta signaling enhances the aggressiveness of several types of tumors. The activated TGF-beta signaling pathway is emerging as an attractive target in cancer and the authors predict that assessment of functionally relevant variants of this pathway will lead to the identification of individuals with a higher cancer risk and account for some forms of familial cancer susceptibility. In addition, it is predicted that inhibitors of the TGF-beta signaling pathway will find their way into cancer clinical trials, leading to delays in tumor progression and improvements in overall survival.

Effects of 17alpha-ethinylestradiol on immune parameters in the lizard Sceloporus occidentalis

We examined the effect of 17alpha-ethinylestradiol on immunity of the Western fence lizard, Sceloporus occidentalis. Injection of 17alpha-ethinylestradiol resulted in dose-dependent suppression of peripheral blood leukocyte levels as determined by cell counts, whereas total spleen cell levels were decreased only at higher doses of 17alpha-ethinylestradiol. In contrast, spleen cell proliferation was enhanced by 17alpha-ethinylestradiol as measured by reduction of MTT to formazan following a two-way mixed lymphocyte reaction. Antibody responses were unaffected. Effects on peripheral blood leukocyte levels and spleen cell proliferation similar to those observed in response to injection of 17alpha-ethinylestradiol were observed following injection of a single dose of hydrocortisone. However, injection of lizards with 17alpha-ethinylestradiol did not result in a significant increase in serum cortisol. Results of this study suggest that exposure of Western fence lizards to 17alpha-ethinylestradiol leads to decreased numbers of circulating leukocytes and total spleen cell numbers and the enhancement of spleen cell proliferation in a two-way mixed lymphocyte reaction. These effects probably involve mechanisms other than or in addition to the induction of cortisol release.

Natural killer cells express estrogen receptor-alpha and estrogen receptor-beta and can respond to estrogen via a non-estrogen receptor-alpha-mediated pathway

Natural killer (NK) cells play a crucial role in host defense against pathogens and immune surveillance against cancer. Given that estrogens have been reported to suppress NK cell activity, we sought to elucidate the mechanisms by which estrogen mediates this effect. We demonstrate by immunocytochemical staining with estrogen receptor-alpha (ERalpha)- and estrogen receptor-beta (ERbeta)-specific antibodies that both ERalpha and ERbeta are expressed in murine NK cells. We also compared the ability of high doses of 17beta-estradiol ( approximately 800 pg/ml) to regulate NK cell activity in wild-type and estrogen receptor-alpha-deficient (ERalphaKO) mice. 17beta-estradiol elicited a significant decrease in NK cell activity in both wild-type and ERalphaKO mice (P < 0.001). These data suggest that ERbeta or possibly a novel receptor is involved in mediating estrogen action on NK cell activity and raise the potential for therapeutic modulation of NK cell activity with selective estrogen receptor modulators (SERMS).

Sex-associated hormones and immunity to protozoan parasites

Numerous epidemiological and clinical studies have noted differences in the incidence and severity of parasitic diseases between males and females. Although in some instances this may be due to gender-associated differences in behavior, there is overwhelming evidence that sex-associated hormones can also modulate immune responses and consequently directly influence the outcome of parasitic infection. Animal models of disease can often recreate the gender-dependent differences observed in humans, and the role of sex-associated hormones can be confirmed by experimentally altering their levels. Under normal circumstances, levels of sex hormones not only differ between males and females but vary according to age. Furthermore, not only are females of reproductive age subject to the regular hormonal cycles which control ovulation, they are also exposed to dramatically altered levels during pregnancy. It is thus not surprising that the severity of many diseases, including those caused by parasites, has been shown to be affected by one or more of these circumstances. In addition, infection with many pathogens has been shown to have an adverse influence on pregnancy. In this article we review the impact of sex-associated hormones on the immune system and the development and maintenance of immunity to the intracellular protozoan parasites Toxoplasma gondii, Plasmodium spp., and Leishmania spp.

The effects of sex, menstrual cycle, and oral contraceptives on the number and activity of natural killer cells

OBJECTIVES

The aim of this study was to study the impact of sex, the menstrual cycle, and the use of oral contraceptives (OC) on the number and activity of natural killer (NK) cells.

METHODS

Both the number and the activity of NK cells were assessed per milliliter of blood, and NK activity (NKA) per NK cell and per lymphocyte was calculated. NKA was measured in each subject using a whole blood assay, which preserves the plasma and all blood cells, and using a washed blood assay, in which plasma is replaced with an artificial medium. The subjects were young (20-29 years old) women with a regular menstrual cycle (n = 39; 26 tested on both the follicular and the luteal phases), age-matched women who use OC (n = 26), and age-matched men (n = 20).

RESULTS

Men showed markedly and significantly higher NKA than women with regular menstrual cycles or women using OC, who had the lowest levels of NKA. No significant differences in blood concentration of NK cell were found. Differences in NKA were of similar magnitude in the whole and washed blood assays per milliliter of blood, per NK cell, or per lymphocyte. The menstrual cycle had no significant effect on activity levels of NK cells, but during the periovulatory phase, the number of NK cells per milliliter of blood increased significantly.

CONCLUSIONS

The observed differences are independent of the presence of serum factors during the in vitro assessment of NKA, but may be related to chronic exposure to sex steroids and to fluctuation in the NK cell expression of beta-adrenoceptors.

Role of oestrogen receptors alpha and beta in immune organ development and in oestrogen-mediated effects on thymus

Oestrogens affect the development and regulation of the immune system. To determine the role of oestrogen receptors alpha (ER-alpha) and beta (ER-beta) on the development of the immune system, male ER-alpha (ERKO) and ER-beta (BERKO) mice, as well as alphabeta-double knockout (DERKO) mice, were studied. Deletion of ER-alpha led to hypoplasia of both thymus and spleen. Interestingly, a higher frequency of immature double CD4+ CD8+ thymocytes was found in ER-alpha(-) mice compared with ER-alpha(+) mice. Female oophorectomized BERKO mice given oestradiol (E2) displayed a similar degree of thymic atrophy compared with the wild-type strain but showed only limited involution of thymus cortex and no alteration of thymic CD4/CD8 phenotype expression. Our data demonstrate that expression of ER-alpha, but not ER-beta, is mandatory in males for development of full-size thymus and spleen, whereas expression of ER-beta is required for E2-mediated thymic cortex atrophy and thymocyte phenotype shift in females. A potential background for the above findings may be down-regulated activity in the growth hormone/insulin-like growth factor-1 (GH/IGF-1) axis in males lacking ER-alpha and suppressed sensitivity of females lacking ER-beta to E2-mediated suppression of IGF-1.

Effects of raloxifene, a selective estrogen receptor modulator, on thymus, T cell reactivity, and inflammation in mice

Raloxifene is a selective estrogen receptor modulator approved for prevention of osteoporosis in postmenopausal women. It is selective by virtue of having estrogen agonistic effects in bone, vessels, and blood lipids, while it is antagonistic with mammary and uterine tissue. The aim of the study was to examine whether the raloxifene analogue LY117018 (LY) has estrogenic effects on the thymus, T cell responsiveness, and inflammation. Oophorectomized normal mice were treated with subcutaneous injections of equipotent antiosteoporotic doses of LY (3 mg/kg) and 17beta-estradiol (E2) (0.1 mg/kg) or vehicle as controls. Effects on thymus were studied by analyses of thymus weight, cellularity, and CD4 and CD8 phenotype expression and histology, while inflammation was determined as T-cell-mediated delayed-type hypersensitivity (DTH) and granulocyte-mediated footpad swelling. LY lacked the suppressive properties of E2 on DTH and granulocyte-mediated inflammation. Furthermore, LY induced only minor thymus atrophy compared with E2 and did not, in contrast to E2, alter the thymic CD4/CD8 phenotypes. These results clearly demonstrate that raloxifene principally lacks the modulatory effects of estrogen on T cell responsiveness and inflammation. Our data are discussed in the context of recent findings in estrogen receptor biology and also with respect to estrogen-mediated alteration of autoimmune rheumatic diseases.

Supraphysiological level of estrogen exposure in vivo increases lymphoid cell death in mice

Estrogen can enhance or reduce lymphocyte functions in vitro depending on dose and exposure duration. The purpose of this study was to determine the effect of in vivo 17 beta-estradiol (E2) on apoptosis and necrosis in lymphoid tissue of female C567BL/6 mice. Animals were ovariectomized (OVX), ovariectomized and 17 beta-estradiol supplemented (OVX + E2; 71 micrograms E2 per day for 14 days), sham ovariectomized (SHAM), or unhandled controls (CONTROL). Thymus and spleen were removed aseptically, cells dispersed into single cell suspensions in RPMI-1640, and measures of cell damage performed: an annexin V flow cytometric assay for markers of apoptosis and an enzyme-linked immunoassay for measures of DNA fragmentation and necrosis. OVX + E2 mice had 620 +/- 72 pg/ml 17 beta-estradiol in serum in contrast to OVX mice which had 7.6 +/- 5 pg/ml, the SHAM mice which had 2.8 +/- 1 pg/ml of serum E2, and the CONTROL mice which had 3.9 +/- 0.8 pg/ml of serum E2 (p < 0.001). There was a significantly lower percentage of viable thymocytes in OVX + E2 mice compared to the other treatment conditions (p < 0.001, respectively). There was also a significantly higher percentage of annexin V positive thymocytes in OVX + E2 mice (p < 0.005). Measures of DNA fragmentation by ELISA were higher in splenocytes from OVX + E2 mice than in the OVX, SHAM or CONTROL mice (p < 0.005). These results suggest that supraphysiological levels of estrogen in vivo induce damage in lymphoid cells; however, the impact of estrogen associated lymphoid tissue damage on specific immune functions remains to be determined.

Reversal of tamoxifen resistance of human breast carcinomas in vivo by neutralizing antibodies to transforming growth factor-beta

BACKGROUND

Overexpression of transforming growth factor (TGF)-beta has been reported in human breast carcinomas resistant to antiestrogen tamoxifen, but the role of TGF-beta in this resistant phenotype is unclear. We investigated whether inhibition of TGF-beta2, which is overexpressed in LCC2 tamoxifen-resistant human breast cancer cells, could modify antiestrogen resistance.

METHODS

TGF-beta2 expression was evaluated in LCC2 cells and tamoxifen-sensitive LCC1 cells by northern blot analysis. Secreted TGF-beta activity was quantified by use of an 125I-TGF-beta competitive radioreceptor assay. Sensitivity to tamoxifen was measured in a soft agarose colony-forming assay and in a xenograft model in nude and beige/nude mice. Natural killer (NK) cell cytotoxicity was measured by 51Cr release from LCC1 and LCC2 cell targets coincubated with human peripheral blood mononuclear cells. Decrease in TGF-beta2 expression in LCC2 cells was achieved by treatment with antisense oligodeoxynucleotides and confirmed by TGF-beta2 immunoblot analysis.

RESULTS AND CONCLUSIONS

The proliferative response of LCC2 cells to tamoxifen in vitro was not altered by TGF-beta neutralizing antibodies. However, established LCC2 tumors in nude mice treated with tamoxifen plus TGF-beta antibodies failed to grow, whereas tumors treated with tamoxifen plus a control antibody continued to proliferate. This reversal of tamoxifen resistance by TGF-beta antibodies did not occur in beige/nude mice, which lack NK-cell function, suggesting that immune mechanisms may be involved in the antitumor effects of tamoxifen. Antisense TGF-beta2 oligodeoxynucleotides enhanced the NK sensitivity of LCC2 cells in the presence of tamoxifen. Finally, LCC1 tumors were markedly more sensitive to tamoxifen in NK-active than in NK-deficient mice.

IMPLICATIONS

These data suggest that host NK function mediates, in part, the antitumor effect of tamoxifen and that TGF-beta2 may abrogate this mechanism, thus contributing to tamoxifen resistance.

A role for NK cells in greater susceptibility of young rats to metastatic formation

Cancer is the second leading cause of death in children (after accidents) and is more prevalent in the first 5 years of life than in the subsequent 10 years. Very young animals have been shown to be more susceptible to malignant growth and whether such increased susceptibility is attributable to reduced resistance of the host to tumor development or to increased incidence of cancerous cells is, as yet, unclear. In the current study, we used 36 day old male and female rats and adult rats to specifically study the role of natural killer (NK) cell activity, as well as hormones known to regulate their activity, in mediating reduced resistance to tumor metastasis at prepubescence. A mammary adenocarcinoma cell line (MADB106) syngeneic to the Fischer 344 rat was used. Following i.v. injection, MADB106 tumor cells seed and colonize only in the lungs, a process shown in adult rats to be controlled by NK cells during the first 24 hours after tumor inoculation. As was found in our previous studies, young rats demonstrated a 10-fold higher percentage of lung tumor cell retention compared to adult rats. Importantly, this higher percentage of tumor cell retention was evident using the same number of tumor cells per kg of body weight in young and adult rats, and maintained even when young rats were challenged with 10- and 100-fold fewer MADB106 cells per kg than adults. Selective depletion of NK cells markedly increased tumor cell retention in all rats, indicating that NK cells play a crucial role in resistance against MADB106 retention in both young and adult rats. Employing in vitro assessment of whole blood NK cytotoxicity. young animals exhibited markedly less specific killing compared to the mature animals. Taken together, these findings indicate a reduced resistance of the young rats against MADB106 retention that is mediated by diminished NK activity in these rats. Factors other than NK cells appear to play a minor role determining age differences in this model. Age- and sex-related differences in plasma beta-endorphin and corticosterone levels were also found, suggesting different activation levels of the HPA axis. These differences, however, seen unlikely to underlie the reduced NK activity in young rats.

Influence of ovarian hormones on urogenital infection

Numerous studies have examined the influence of hormones on infectious diseases and there is now a wealth of data relating to the more specific effect of the sex hormones, oestrogen and progesterone, on urogenital infections. The interaction between these hormones and the immune system is complex and the variation of hormonal effect between species further complicates the true picture as related to humans. Although it is difficult therefore to draw general conclusions regarding predominant effects of specific hormones, there is the suggestion that oestrogen enhances the pathogenicity of many urogenital micro-organisms. Our understanding of the influential role played by sex hormones in disease pathogenesis is at an early stage and illustrates well the importance of drawing together and interpreting as a whole both epidemiological and molecular studies.

Combined tacrine and estrogen replacement therapy in patients with Alzheimer's disease

In light of evidence that estrogen replacement might affect cholinergic function, we examined possible effects of estrogen replacement therapy (ERT) on clinical response to the cholinesterase inhibitor tacrine in women with Alzheimer's disease (AD). In a previously reported 30-week, randomized, double-blind, placebo-controlled, multicenter clinical trial, 14.5% of 318 women with evaluable data had been receiving ERT before randomization. They were randomly assigned to receive placebo or tacrine. Women receiving ERT who were randomized to tacrine improved more than women not receiving ERT who were randomized either to tacrine or to placebo as assessed by cognitive (p < 0.01) and clinical global (p = 0.02) tests. These results provide evidence that prior and continuing ERT may enhance response to tacrine in women with AD. Furthermore, among women on ERT receiving tacrine, there tended to be greater improvement relative to placebo among those without an APOE-epsilon 4 allele. Randomized trials are needed.

Potential role for estrogen replacement in the treatment of Alzheimer's dementia

In light of evidence that estrogen replacement therapy (ERT) might affect cholinergic function, we examined possible effects of ERT on clinical and cognitive responses to the cholinesterase inhibitor tacrine in women with Alzheimer's disease (AD). In a previously reported 30-week, randomized, double-blind, placebo-controlled, multicenter clinical trial, 14.5% of 318 women with evaluable data had been receiving ERT prior to randomization. Patients were randomly assigned to receive placebo or one of three ascending dosages of tacrine (maximum dosages of 80 mg/day, 120 mg/day, or 160 mg/day). Women completing the trial receiving ERT and tacrine improved more than women not receiving ERT who were randomized to tacrine or to placebo as assessed by cognitive (p <0.01), clinical (p = 0.02), caregiver (p = 0.006), and mental status (p = 0.07) ratings. Using an intent-to-treat analysis, they improved significantly on cognitive ratings (p = 0.01). These results provide evidence that prior and continuing ERT may enhance response to tacrine in women with AD. Randomized trials are needed.

Can estrogens prevent neurodegeneration?

Estrogen replacement therapy appears to have significant beneficial effects on cognition and mood in the elderly. In recent studies, its use has been associated with short term symptomatic cognitive improvement and with a decreased risk of (or a delay in) developing Alzheimer's disease (AD). Clinical reports are supported by substantial basic scientific evidence of the neuroprotective effects of estrogens. Their specific effects on dementia and cognitive impairment remain to be delineated. Ongoing randomised trials in AD will only provide information on the symptomatic effects of estrogen. Although basic research will progress, there is currently sufficient knowledge to promote active clinical research on the possible disease-modifying or neuroprotective effects of estrogens in the elderly.

Increased susceptibility to metastasis during pro-oestrus/oestrus in rats: possible role of oestradiol and natural killer cells

It has been suggested that tumour development and immunocompetence are affected by the menstrual and the oestrous cycle, and sex hormones have been shown to modulate lymphokine production, neuroendocrine activity and immunity. In this study, we assessed natural killer cell activity and host susceptibility to metastasis during the oestrous cycle in the Fischer 344 inbred rat strain. Females were inoculated intravenously with MADB106 tumour cells, a syngeneic mammary adenocarcinoma cell line that metastasises only to the lungs. The susceptibility to metastatic development of this tumour was found to be significantly higher during pro-oestrus and oestrus than during metoestrus and dioestrus. Two days of exposure to oestradiol benzoate caused similar effects in ovariectomised females, and a single administration of progesterone reduced this effect of oestradiol to a statistically non-significant level. The tumour was found to be negative for oestradiol receptors, and its in vitro proliferation rate was not affected by oestradiol or progesterone, suggesting that the effects of sex hormones on the metastatic process are not attributable to a direct effect on tumour cells. Because the metastatic process of MADB106 tumour cells is known, and confirmed here, to be highly controlled by large granular lymphocyte/natural killer (LGL/NK) cell activity, we assessed their role in mediating the effects of the oestrous cycle. The number and activity levels of circulating blood LG/NK cells (NKR-PI+ bright) were studied. Findings indicated oestrous-dependent alterations in the number of LGL/NK cells and suggested a diminished NK activity per LGL/NK cell during pro-oestrus/ oestrus, the same phases that were characterised by higher susceptibility to metastatic development. These findings provide the first empirical evidence for a causal relationship between a short-term exposure to elevated oestradiol/low progesterone levels and decreased resistance to tumour metastasis, and it is hypothesised that an alteration in LGL/NK cell activity underlies these effects. Homologies and relevance to clinical phenomena are discussed.

Effect of estrogen replacement therapy on natural killer cell activity in postmenopausal women

OBJECTIVE

To evaluate the impact of menopause and estradiol substitution on natural killer cell activity.

METHODS

Natural killer cell activity and antibody-dependent cellular cytotoxicity were measured in peripheral blood of 53 postmenopausal and 20 premenopausal women in an interval of 3 weeks. Postmenopausal patients were randomly assigned to receive either estradiol valerate (2 mg daily) orally (n = 18), estradiol (50 micrograms/24 h) transcutaneously (n = 18) or no substitution (n = 17), and the testing was repeated 3 weeks later.

RESULTS

Natural killer cell activity but not antibody-dependent cellular cytotoxicity was significantly (P < 0.01) higher in unsubstituted postmenopausal compared to premenopausal subjects. Natural killer cell activity decreased both in orally and transcutaneously estradiol-treated patients (mean [S.D.] before vs. after 3 weeks; oral: 60.8 [9.2]% vs. 52.8 [8.2]% P < 0.01; transcutaneous: 61.5 [10.6]% vs. 54.3 [9.1]% P < 0.01; no substitution: 60.6 [10.6]% vs. 59.3 [8.9]% P > 0.1), whereas antibody-dependent cellular cytotoxicity showed no changes. The addition of 0.1 to 10 ng/ml estradiol to peripheral blood mononuclear cells of untreated postmenopausal women in vitro had no influence upon natural killer cell activity.

CONCLUSION

Postmenopausal women receiving no estrogen replacement exhibited an increased natural killer cell activity which decreased during estrogen substitution.

An analysis of the uterine lymphocyte-derived hybridoma cell line GWM 1-2 for expression of receptors for estrogen, progesterone and interleukin 2

Characterisation of murine hybridoma cell lines derived from the fusion of lymphocytes migrating from explant cultures of early, pregnancy-associated metrial glands (days 6-8 of gestation) to SP 2/0 cells, has been extended (van den Heuvel et al., J. Reprod. Immunol., 27 (1994) 13-36). These hybridomas have been grown in culture for over 2 years and are thought to represent the only immortalized lines of murine pregnancy-associated, uterine natural killer (uNK) cells. Previous studies had shown that these hybridomas, known as GWM cells, lack uNK cell surface markers, but share with uNK cells the expression of the lytic protein perforin and the ability to lyse YAC cells, a natural killer cell target (van den Heuvel et al., J. Reprod. Immunol., 27 (1994) 13-36). We report here, the evaluation of the transcription and expression of genes encoding the estrogen receptor (ER), the progesterone receptor (PR) and the interleukin 2 receptor complex (IL 2R alpha, beta and gamma) by uNK cells at day 8 of gestation and by GWM 1-2 cells and SP 2/0 cells. Our investigations indicate that expression of these genes divides day 8 uNK cells into subsets, with the predominant population being ER+, PR-, IL 2R alpha +, IL 2R beta + and IL 2R gamma +. Like day 8 uNK cells, most GWM 1-2 cells expressed all three chains of the IL 2R complex. In addition, GWM 1-2 cells expressed the ER but the PR was not detected on this cell line. Only the IL 2R alpha was detected on the SP 2/0 myeloma cell line. These studies further validate the use of GWM hybridomas as models for pregnancy-associated uNK cells.

Human breast cancer cell line xenografts as models of breast cancer. The immunobiologies of recipient mice and the characteristics of several tumorigenic cell lines

The ability to maintain and study human tissues in an in vivo environment has proved to be a valuable tool in breast cancer research for several decades. The most widely studied tissues have been xenografts of established human breast cancer cell lines into athymic nude mice. Human breast tumor xenografts provide the opportunity to study various important interactions between the tumor and host tissues, including endocrinologic, immunologic, and tumor-stroma interactions. The nude mouse is not the only immune-deficient recipient system in which to study xenografts. Additional single and combined mutant strains have been used successfully, including mice homozygous for the severe combined immune deficiency mutation (scid), both the beige (bg) and nude (nu) mutations in combination (bg/nu), and mice bearing the combined bg/nu/xid mutations. The differing immunobiologies are discussed, with particular reference to the immunobiology of breast cancer, as are the characteristics of several of the more frequently utilized breast cancer xenografts and cell lines. The ability of several endocrine treatments to modulate effectors of cell mediated immunity, e.g., estrogens and antiestrogens, and the effect of site of inoculation on tumor take and metastasis, also are described.

Animal models of breast cancer: their diversity and role in biomedical research

Animal models of breast cancer have been widely used to study various aspects of breast cancer biology, and are remarkably diverse, encompassing chemically and virally induced tumors, human tumor xenografts, and transgenic mouse models. Several novel models have become available during the past few years, including tumors induced by polyomavirus and adenovirus, and a series of human cell line variants. The several following articles describe, in some detail, the characteristics of these models and their relevance to the human disease. Descriptions of each of the major models, e.g., 7,12-dimethylbenz(a)anthracene-induced, MMTV-associated, and human breast cancer cell line xenografts, also are included. The limitations and advantages of several of these models, and some issues relating to the choice of models, are briefly discussed in this overview.

The development of sexual dimorphism in natural killer cell activity and resistance to tumor metastasis in the Fischer 344 rat

The development of sexual dimorphism in the number and activity level of natural killer (NK) cells was studied in the inbred Fischer 344 rat from prepubescence to maturity. Additionally, in view of the biological significance of NK cells in controlling cancer, especially the metastatic process, we used a syngeneic mammary tumor (MADB106) to assess the host anti-metastatic activity. This tumor model was used because NK cells control the lung clearance of i.v.-injected MADB106 tumor cells, a process that critically affects the metastatic colonization of these tumor cells in the lungs. The results indicated that although prepubescent (36 days of age) males and females exhibited greater NK cytotoxicity (assessed in vitro) and higher anti-metastatic activity, evidenced by fewer tumor cells retained in the lungs. On the other hand, the mature males (140-170 days of age) displayed greater LGL/NK number and activity per ml blood, retained fewer tumor cells, and developed fewer lung tumor colonies compared to the females. During early postpubescence (63 days of age), a transitional stage between prepubescence and maturity, females and males exhibited equivalent numbers of circulating LGL/NK cells, and females displayed slightly greater NK cytotoxicity per ml blood yet retained somewhat greater numbers of tumor cells compared to the males. Overall, whereas the males exhibited increasing levels of NK number and activity throughout the age span tested, the females, despite displaying greater NK function compared to the males at prepubescence and slight improvement at postpubescence, fell behind the males in these indices of NK function at maturity.

Increase of a guinea pig natural killer cell (Kurloff cell) during leukemogenesis

The guinea pig Kurloff cell (KC) is an estradiol-dependent circulating mononuclear cell that had natural killer cytotoxic activity in vitro. We studied the variation of KC number during the development of transplanted leukemia in inbred strain 2 (S2) leukemia-sensitive guinea pigs. Grafts of leukemic cells (L2C) produced a significant increase in the number of KC. Leukemia occurred in 35.5% of non-estrogenized animals and in 18.3% of estrogenized guinea pigs. The increased number of KC seems to have antileukemia activity in vivo. This could be part of the general phenomenon of cancer resistance in guinea pigs.

Heavy-metal modulation of the human intercellular adhesion molecule (ICAM-1) gene expression

The intercellular adhesion molecule 1 (ICAM-1) can be induced on many different cell types by a set of various modulators (IL1 beta, TNF, LPS, IFN-gamma), which are released during the inflammatory process. We have investigated the possibility that other factors, related to the stress and biophysical perturbations of the inflammatory response, may also modulate ICAM-1. Here, we report that heavy metals, in particular zinc, can enhance the expression of the ICAM-1 gene on cells actively involved at different levels during inflammation. Kinetic studies of ICAM-1 gene expression shows a maximum level of induction 4 h after treatment with metals, followed by a rapid decrease to basal levels within 12 h. The effect on enhanced gene expression is mostly due to a rapid increase of the transcriptional rate as shown by nuclear run-on experiments. In B lymphoblastoid cells, but not in fibroblasts, the increase in RNA expression seems significantly greater that the subsequent increase in protein expression, suggesting that a further point of post-transcriptional regulation of ICAM-1 occurs and may be linked to the cellular specificity. may be linked to the cellular specificity.

Modulation of natural killer cell-mediated cytotoxicity by tamoxifen and estradiol

BACKGROUND

The nonsteroidal antiestrogenic drug, tamoxifen, inhibits the growth of estrogen receptor-positive tumors by interfering with the growth-stimulatory effect of estradiol. However, there is compelling evidence that tamoxifen treatment also is beneficial for patients with estrogen receptor-negative tumors. The hypothesis that tamoxifen is capable of enhancing the immunologic defense of tumor-bearing hosts was been investigated as a possible method for targeting receptor-negative neoplasms.

METHODS

Natural killer (NK) cells in the spleen of female Fisher and Wistar-Furth rats were used against the YAC-1 murine lymphoma target in 51Cr-release assays. The effect of various concentrations of estradiol and tamoxifen (1 nM-1 microM) and of the metabolic inhibitors actinomycin D and cyclohexamide on target-cell killing was investigated.

RESULTS

Tamoxifen enhanced and estradiol inhibited killing if applied for the entire 5 hours of the cytotoxic reaction. When applied jointly in this experimental setup, estradiol interfered with the enhancing effect of tamoxifen. Pretreatment of target cells with tamoxifen led to highly significant enhancement of cytotoxicity; estradiol also enhanced target cell killing, but to a lesser extent. After joint treatment, the level of cytotoxicity was comparable with that obtained with tamoxifen alone. Both pharmacologic (100 nM and 1 microM) and physiologic (1 or 10 nM) concentrations of estradiol and equimolar tamoxifen enhanced target cell lysis. However, pharmacological levels of estradiol inhibited effector cells when applied alone or in combination with tamoxifen. Highly significant enhancement of target-cell destruction occurred if both target and effector cells were pretreated with tamoxifen, whereas estradiol treatment of both cell types led to slight enhancement or no effect on cytotoxicity. Treatment of the target cells with actinomycin D or cycloheximide inhibited the lysis of untreated and tamoxifen- or estradiol-exposed cells. Treatment of YAC-1 target cells with tamoxifen or estradiol also enhanced the NK cell-mediated release of the nuclear label, 3H-thymidine, indicating DNA degradation. Similarly treated P815 cells resisted lysis by NK cells, but showed sensitization when the NK cells were stimulated by interleukin-2 for 48 hours before the lytic reaction. Estradiol and tamoxifen changed the kinetics of 3H-thymidine incorporation by YAC-1 cells, but the cells were capable of growing with the highest drug concentrations (1 microM) used in the cytotoxicity experiments. YAC-1 cells have no cytosolic estradiol receptors and are weakly positive for cytosolic progesterone receptors.

CONCLUSIONS

These experiments indicate that NK cell-mediated target-cell destruction can be enhanced by tamoxifen primarily through sensitizing the target for lysis. Estradiol also sensitizes the target but inhibits the effector cells simultaneously so that little or no change results in cytolysis. Target-cell sensitization is not mediated by classical estrogen receptors and requires the active metabolic participation of the cells treated. A likely mechanism of this phenomenon is priming the target cell for apoptosis.

A randomised controlled trial of the effect of hormone replacement therapy on disease activity in postmenopausal rheumatoid arthritis

OBJECTIVE

To assess the effects of hormone replacement therapy (HRT) on disease activity in postmenopausal rheumatoid arthritis (RA).

METHODS

Two hundred postmenopausal outpatients (aged 45-65 years) were admitted into a single blind randomised placebo controlled trial of transdermal oestradiol (50 micrograms daily) over six months. Patients continued with routine antirheumatic medications. Compliance with HRT was monitored using serum oestradiol (E2) levels. Disease activity was monitored at entry, three and six months using erythrocyte sedimentation rate (ESR), articular index (AI), visual analogue pain scale (VPS) and early morning stiffness (EMS).

RESULTS

Ninety one and 77 patients completed six months treatment with placebo and HRT respectively. There were no significant differences in baseline characteristics between the groups and no overall effects of treatment. However, 35 patients (41.6%), who completed HRT, failed to achieve serum E2 levels > 100 pmol/l at either three or six months and were considered 'poor-compliers'. In the remaining HRT 'compliers' (58.4%) there were significant improvements after six months in articular index (28.9%; p < 0.01) and pain score (21.7%; p < 0.05) compared with placebo, as well as reductions in ESR (8.9%; NS) and morning stiffness (25.2%; NS). Comparisons between HRT 'compliers' and 'poor-compliers' confirmed significant improvements in articular index (p < 0.001), pain score (p < 0.05) and morning stiffness (p < 0.001) in the 'compliers'.

CONCLUSIONS

This study did not show an overall effect of HRT on disease activity when used as an adjunct therapy in postmenopausal patients. A subgroup of patients, who had greater increments in serum E2 whilst taking HRT, demonstrated improvements in some parameters of disease activity, suggesting a potential beneficial effect with good compliance and higher dose HRT. Most importantly, in the treatment of RA associated bone loss, HRT can be prescribed without fear of a disease flare up.

Enhancing effect of 17 beta-estradiol on human NK cell activity

The in vitro effect of 17 beta-estradiol on NK activity was studied. The proliferation and NK activity of YT-N17 (a human NK-like cell line) were enhanced by 17 beta-estradiol (E2), and the enhancement was blocked by tamoxifen (Tx), an antagonist of E2. On the contrary, other steroid hormones such as Tx, progesterone, and testosterone had no effect. YT-N17 contained 11.8 fmol/mg protein of estrogen receptor (mean of two independent assays), a value which was 5-10-fold higher than that of other hematopoietic cell lines. An enhancement of NK activity by E2 was also seen in large granular lymphocytes obtained from normal subjects, and it was again suppressed by Tx. These data suggest that E2 is one of the activating factors for NK/LGL cells.

Enhancement of natural-killer-cell susceptibility of human breast-cancer cells by estradiol and v-Ha-ras oncogene

Natural killer (NK) cells are putative components of the cellular immune response to transformed cells. Since both estradiol treatment and ras-oncogene overexpression enhance tumorigenicity of hormone-dependent breast-cancer cells, we studied the effects of estrogen and of the activated v-Ha-ras oncogene on NK susceptibility of MCF-7 human breast-cancer cells. MCF-7 cells were sensitive to cytolysis mediated by resting and IL2-activated peripheral-blood non-adherent lymphocytes. Lysis appeared to be mediated by NK cells, since it was abrogated by treatment of effector cells with alpha-CD16 monoclonal antibody (MAb) plus complement (c'). Estradiol treatment of MCF-7 cells was able to significantly increase their sensitivity to the lysis by IL2-activated and unactivated peripheral-blood lymphocytes, as early as 24 hr throughout 10 days of hormone treatment. Hormone-insensitive, estrogen-receptor-negative breast-cancer cells (BT20) did not change their NK susceptibility after estradiol treatment. Increased NK susceptibility was also observed in v-Ha-ras-transfected and oncogene product overexpressing MCF-7 cells (MCF-7-ras) with respect to cells transfected with the selectable gene marker gpt alone (MCF-7-gpt). Overexpression of v-Ha-ras appeared to be able to bypass the need for estrogen to increase NK susceptibility, since estradiol-treated MCF-7-ras cells were not lysed more than untreated MCF-7-ras cells. The enhancement of NK susceptibility observed after both estradiol treatment and v-Ha-ras overexpression suggests that the hormone-mediated and the ras-oncogene-mediated signalling systems share events involved in the control of tumor-cell/host-effector-cell interactions.

Antiestrogen therapy for breast cancer: current strategies and potential causes for therapeutic failure

There is an enormous literature that supports the use of tamoxifen as the treatment of choice for breast cancer. However, preliminary evidence suggests that long-term treatment with tamoxifen may expose the women to an increased risk of liver and endometrial cancer. This is probably only of concern to young women with stage I (node negative) disease. It remains to be seen whether any of the new strategies, including the new antiestrogens discussed here and novel endocrine therapies, will prove any better as an antitumor treatment. Treatments will probably be directed initially at treating patients after tamoxifen failure and ultimately at treating hormone-independent cancers. These therapies may involve the autocrine growth factors produced by breast cancer cells as potential targets. Such development of novel treatments will be extremely beneficial to these women, who face a worrying lack of therapeutic opportunities, with the exception of chemotherapy.

Effects of subchronic d-fenfluramine on splenic immune functions in young and old male and female Fischer 344 rats

The present study was designed to demonstrate age- and sex-related differences in immune functions, and to determine whether subchronic elevations in serotonin (5-HT) availability in vivo would alter immune functions assessed subsequently in vitro. Male and female F344 rats (5 and 21 months of age) were administered the 5-HT releaser and reuptake inhibitor, d-fenfluramine (d-Fen), in their drinking water for 30-38 days then killed. The young animals received a higher dose (1.8 mg/kg/day) of d-Fen than the old rats (0.6 mg/kg/day) in order to compensate for age-related decreases in drug biotransformation and clearance. Brain and spleen d-Fen and metabolite concentrations, however, were considerably higher in the young than in the old rats. d-Fen treatment did not affect body weight or fluid intake. Although substantial sex differences in immune function were not discerned, age-related decreases were observed in absolute splenic cellularity, recombinant interleukin-2 (rIL-2) stimulated natural killer (NK) cytotoxicity, LPS stimulated B-cell mitogenesis, and in the level of Ox19 (CD5) positive cells. d-Fen caused an increase in absolute spleen weight and a decrease in absolute splenic cellularity only in the old rats of both sexes. Spleen cells from young male and old female rats receiving d-Fen had relatively more large granular lymphocytes and enhanced baseline and rIL-2 activated killing of YAC-1 cells than their vehicle matched or opposite sex counterparts. The drug also increased Con A-induced T-cell proliferation in young males and LPS induced B-cell proliferation in old females. d-Fen decreased Ox39 (CD25) levels by 19%, but did not affect any of the other phenotypes examined. The results suggest that 5-HT has a selective stimulatory effect on young male and old female NK activity, and that old female rats are more sensitive to the immunological effects of d-Fen than old male rats.

Fatty acid modulation of antiestrogen action and antiestrogen-binding protein in cultured lymphoid cells

Nonsteroidal antiestrogens reversibly and specifically inhibited the proliferation of two estrogen receptor-negative lymphoid cell lines (EL4 and Raji) in a dose-dependent manner. [3H]Thymidine incorporation of concanavalin A-stimulated primary splenocytes was also inhibited by 10(-6) M clomiphene (1-[4-(2-diethylaminoethoxy)phenyl]-1,2-diphenyl-2-chloroethylene). The antiproliferative effect could be prevented by the simultaneous presence in the growth medium of 10(-5) M linoleic acid or 10(-5) M arachidonic acid but not by 10(-6) M estradiol. Both lymphoid cell lines had high affinity antiestrogen-binding sites whose affinity could be altered by conditions of growth. Growth of EL4 cells in RPMI 1640 medium supplemented with charcoal-pretreated 5% fetal calf serum (charcoal-stripped medium) resulted in significantly higher affinity (Kd 0.54 nM +/- 0.11 nM; n = 6) than growth in medium supplemented with untreated serum (complete medium) (Kd = 1.68 nM +/- 0.48 nM; n = 6) (p less than 0.001). This change in affinity was partly due to removal of fatty acids from the growth medium by charcoal pretreatment, since addition of 10(-5) M linoleic acid or 10(-5) M gamma-linolenic to charcoal-stripped medium decreased the affinity of the antiestrogen-binding protein. In contrast, growth in 10(-5) M stearic acid or 10(-5) M oleic acid did not significantly alter the affinity of the antiestrogen-binding protein, whereas 10(-5) M palmitic acid significantly increased its affinity. The same fatty acids were also tested for their intrinsic effects on EL4 cell proliferation. Oleic, linoleic and gamma-linolenic acids were growth stimulatory while stearic and palmitic acids were not. Thus linoleic and gamma-linolenic acids whose presence in the growth medium was associated with decreased affinity of [3H]tamoxifen (1-[4-(2-dimethylaminoethoxy)phenyl]-1,2-diphenylbut-1(Z)-ene) binding to the intracellular antiestrogen-binding protein were also growth stimulatory. Unsaturated fatty acids have previously been shown to inhibit binding of [3H]tamoxifen to the antiestrogen-binding protein in a cell-free system. The present observations demonstrate that unsaturated fatty acids also modify the affinity of the antiestrogen-binding protein in intact cells.

Preclinical studies with toremifene as an antitumor agent

Toremifene is a nonsteroidal antiestrogen currently being evaluated for the treatment of breast cancer. Toremifene (10(-10)-10(-6) M) inhibited the growth of MCF-7 breast cancer cells in vitro but was ineffective against hormone-independent MDA-MB-231 cells. This activity was reproduced in vivo using the athymic mouse model. Maximal MCF-7 tumor growth was produced in athymic mice by circulating estradiol levels of approximately 200 pg/ml (from a 0.5 cm silastic capsule implanted sc). Toremifene (77 +/- 44 micrograms/day from a 2 cm silastic capsule) inhibited estradiol (0.5 cm capsule)-stimulated growth by more than 70%. No tumor growth was observed in mice treated with toremifene alone, although toremifene acted as a weak partial agonist and potent antagonist on the mouse uterus. The growth of MDA-MB-231 tumors was not influenced by either estradiol or toremifene. Toremifene (200 micrograms/day) was effective in preventing the development of 7,12-dimethylbenzanthracene-induced rat mammary tumors when given po from day 28 after carcinogen administration. The antitumor activity was reversed if the toremifene was stopped. These findings indicate toremifene is a tumoristatic agent rather than a tumoricidal agent. Clinical trials with toremifene should employ an indefinite treatment strategy to control tumor recurrence in adjuvant studies.

Association of increased lytic effector cell function with high estrogen receptor levels in tumor-bearing patients with breast cancer

Tumor-bearing patients with breast cancer were assayed for their natural killer (NK) cell activity and for the function of activated cytotoxic T-cells, as assessed by lectin-dependent cellular cytotoxicity (LDCC). Tumor-bearing patients with breast cancer had a significant increase in NK activity and in LDCC, as compared with healthy control individuals. Although the enhanced NK cell activity and LDCC were closely associated with high levels (greater than 31 fmol/mg) of estrogen receptor (ER) content in the primary tumor, no other clinical or histologic correlation between the increase in either parameter of cytotoxic effector cell function could be found. Thus, ER levels greater than 31 fmol/mg might be associated with increased cytotoxic effector cell function in tumor-bearing patients with breast cancer.

Biology of natural killer cells

Studies of cytotoxicity by human lymphocytes revealed not only that both allogeneic and syngeneic tumor cells were lysed in a non-MHC-restricted fashion, but also that lymphocytes from normal donors were often cytotoxic. Lymphocytes from any healthy donor, as well as peripheral blood and spleen lymphocytes from several experimental animals, in the absence of known or deliberate sensitization, were found to be spontaneously cytotoxic in vitro for some normal fresh cells, most cultured cell lines, immature hematopoietic cells, and tumor cells. This type of nonadaptive, non-MHC-restricted cellmediated cytotoxicity was defined as “natural” cytotoxicity, and the effector cells mediating natural cytotoxicity were functionally defined as natural killer (NK) cells. The existence of NK cells has prompted a reinterpretation of both the studies of specific cytotoxicity against spontaneous human tumors and the theory of immune surveillance, at least in its most restrictive interpretation. Unlike cytotoxic T cells, NK cells cannot be demonstrated to have clonally distributed specificity, restriction for MHC products at the target cell surface, or immunological memory. NK cells cannot yet be formally assigned to a single lineage based on the definitive identification of a stem cell, a distinct anatomical location of maturation, or unique genotypic rearrangements.