Effect of estrogens and antiestrogens on growth of human breast cancer cells in athymic nude mice

Endocrine therapy with estrogen deprivation or with antiestrogens results in tumor regression in a subset of patients with advanced breast cancer. To better understand the mechanisms by which estrogens and antiestrogens modulate breast cancer growth in vivo, we have studied the effects of endocrine manipulation on the development and growth of tumors derived from cultured human breast cancer cells in the athymic nude mouse. MCF-7 breast cancer cells were inoculated into 6-week-old female BALB/c athymic nude mice. Tumor growth did not occur in ovariectomized mice. Cells remained viable, however, since estrogen supplementation more than 30 days later resulted in tumor formation. Minimal tumor growth was observed in intact female nude mice which have low circulating estrogen levels. Tumor development and growth in ovariectomized or intact mice supplemented with 17 beta-estradiol in the form of a s.c. pellet were dose dependent; growth rates increased with estrogen doses ranging from 0.01 to 0.5 mg. Antiestrogen treatment with either tamoxifen or LY156758 caused transient stimulation of tumor growth, followed by a prolonged stationary phase. Growth resumed with estrogen supplementation. Treatment of mice bearing established MCF-7 tumors with estrogen withdrawal (removal of estrogen pellet) resulted in cessation of tumor growth, but not in tumor regression. Growth inhibition was also observed with antiestrogens and was dose dependent. However, tumor regression did not occur, even in mice treated with high doses of tamoxifen (serum concentration of 1.0 microM) for as long as 60 days. Tumor growth was restored in these mice with estrogen replenishment. Tumor cells also remained viable histologically despite prolonged (1 month) estrogen deprivation or antiestrogen therapy, although the mitotic index was markedly reduced. Similar observations were made with mice inoculated with the hormone-responsive ZR75-1 human breast cancer cells, but not with hormone-independent MDA-231 cells which were not influenced by estrogen or antiestrogen treatment. In summary, development and growth of MCF-7 and ZR75-1 tumors in nude mice are estrogen dependent. Endocrine therapy by estrogen deprivation or antiestrogen treatment inhibits tumor cell proliferation in nude mice, but does not cause tumor regression or loss of cell viability.     

Stimulation of MCF-7 tumor progression in athymic nude mice by 17beta-estradiol induces WISP-2/CCN5 expression in xenografts: a novel signaling molecule in hormonal carcinogenesis

There was 100% solid tumor formation following inoculation of MCF-7 cells. However, MCF-7 tumor progression was significantly greater in the mice exposed to 17beta-estradiol (17beta-E2) compared to unexposed mice. WISP-2/CCN5 mRNA expression was correspondingly increased in 17beta-E2 exposed MCF-7 tumors compared to unexposed xenografts. Moreover, estrogen exposure followed by anti-estrogen tamoxifen treatment drastically inhibited the tumor growth and WISP-2 expression in nude mice. Therefore, the study suggests that higher WISP-2/CCN5 expression by estrogen may be associated with the estrogen-induced growth of MCF-7 tumors in vivo. Finally, overexpression of WISP-2/CCN5 may be considered as a prognostic marker of estrogen-sensitive tumor growth.     

Inhibited growth in vivo of a mouse pregnancy-dependent mammary tumor (TPDMT-4) by an antiestrogen, 2alpha, 3alpha-epithio-5alpha-androstan-17beta-ol (10275-S).

TPDMT-4 mammary tumors, characterized by growth during pregnancy and postpartum regression, grew continuously in DDD virgin mice carrying pituitary isografts or 17 beta-estradiol plus progesterone pellets. In the experimental models, effects of 2alpha,3alpha-epithio-5alpha-androstan-17beta-ol(10275-S), testosterone, and ovariectomy were investigated. When tumors implanted with pituitary isografts into the fat pad reached palpable volumes, animals were ovariectomized or received 5 s.c. injections of 100 mug to 1 mg 10275-S or 300 mug testosterone weekly. Tumors regressed immediately after ovariectomy or after the start of 10275-S treatment and after approximately the 10th day of testosterone treatment. Cystadenomatous morphology with strong secretory activity was noticed in treated animals. Tumor growth induced by 17beta-estradiol plus progesterone pellets was inhibited completely or partially by 3 s.c. injections of 50 to 500 mug 10275-S or 100 mug testosterone weekly starting from the day after tumor and 17beta-estradiol plus progesterone pellet implantation.     

Mammalian lignans enterolactone and enterodiol, alone and in combination with the isoflavone genistein, do not promote the growth of MCF-7 xenografts in ovariectomized athymic nude mice

This study determined the effect of the mammalian lignans enterolactone (ENL) and enterodiol (END) alone and in combination with the isoflavone genistein (GEN) on the growth of MCF-7 tumors in ovariectomized nude mice. Ovariectomized athymic nude mice with established MCF-7 tumors were fed a basal diet (AIN-93G) and divided into 5 groups that received daily subcutaneous injections (10 mg/kg body weight (BW)) of ENL, END, GEN, a mixture of these compounds (MIX), or vehicle as a negative control for 22 weeks. A positive control group was implanted with an estradiol pellet in order to establish an estrogenic tumor growth response. In the ENL- and END-treated mice, palpable tumors regressed significantly by 91 and 83%, respectively, resulting in final tumors that were similar to the negative control tumors. However, tumor cell apoptosis was significantly enhanced by the lignans. In the GEN-treated mice, tumors initially regressed significantly by 64% but regression ceased following prolonged treatment, resulting in final tumors that were significantly larger compared to negative control, ENL-, and END-treated mice, in part by increasing tumor cell proliferation. The MIX treatment significantly regressed palpable tumors by 87% similar to negative control group, with no effects on tumor cell apoptosis or proliferation. The isoflavone GEN alone promoted the growth of established MCF-7 human breast cancer xenografts after prolonged treatment while the mammalian lignans ENL and END did not. When these phytoestrogens were given in combination, no tumor growth-promoting effects were observed. (c) 2005 Wiley-Liss, Inc.     

The regulatory effect of tamoxifen on fibronectin expression in estrogen-dependent MCF-7 breast carcinoma cells

We investigated the regulatory effect of tamoxifen (TAM) on fibronectin (FN) expression in estrogen-dependent MCF-7 breast carcinoma cells both in vitro and in vivo. in vitro, MCF-7 cells were cultured with 17beta-estradiol (E2) and/or TAM. In the animal experiment in vivo, MCF-7 tumors were grown in ovariectomized athymic mice by implanting a sustained release E2 pellet. The E2 pellets were removed after 3 weeks of E2 treatment. Animals were then divided into four groups: 1) an E2 (0.72 mg/pellet) pellet [E2(+)]; 2) an E2 and a TAM (5 mg/pellet) pellet [E2(+)TAM]; 3) no treatment [E2(-)] and 4) a TAM pellet [E2(-)TAM]. Following each treatment for 4 weeks, all animals were sacrificed and tumors were removed. Specimens, cells (in vitro) or tumors (in vivo), were homogenized and assayed for FN by Western blots. In the in vitro experiment, FN expression in MCF-7 cells decreased by incubating with 10(-9) M E2 and increased with 10(-6) M TAM. The effect of TAM increasing FN expression was inhibited by incubation accompanied with 10(-9) M E2 or 1 microg/ml transforming growth factor-beta (TGF-beta) neutralizing antibody. In the in vivo animal experiment FN expression in the tumors of E2(+) mice was lower than that of E2(-) mice. However, TAM increased FN expression in the tumors regardless of E2 pellet. These results suggest that TAM increases FN expression of MCF-7 breast carcinoma cells and that these regulatory effects of TAM on FN expression are partly mediated by TAM-induced TGF-beta.     

Regulation of estrogen receptor and epidermal growth factor receptor by tamoxifen under high and low estrogen environments in MCF-7 cells grown in athymic mice

The purpose of this study was to investigate whether tamoxifen (TAM) treatment causes a downregulation of estrogen receptor (ER) and whether TAM induces epidermal growth factor receptor-1 (EGFR). We investigated the expression of ER and EGFR after the treatment of TAM in MCF-7 tumors grown in athymic mice under high and low estrogen environments. MCF-7 tumors were grown in ovariectomized athymic mice by implanting a sustained release 17beta-estradiol (E2) pellet. The E2 pellets were removed after 3 weeks of E2 treatment. Animals were then divided into the following 4 groups: i) an E2 (0. 72 mg/pellet) pellet [E2(+)]; ii) an E2 and a TAM (5 mg/pellet) pellets [E2(+)TAM]; iii) no treatment [E2(-)]; iv) a TAM pellet [E2(-)TAM]. A significant reduction in tumor size was observed in the estrogen-depleted group [E2(-) and E2(-)TAM] compared with the estrogen-completed group [E2(+) and E2(+)TAM]. TAM inhibited estrogen-stimulated growth in the estrogen-completed mice. No additional reduction of the tumor by TAM was observed in the estrogen-depleted mice. Both ER and EGFR protein levels in the tumors of the estrogen-depleted mice were higher than in the estrogen-completed mice. Expression of ER and EGFR protein was increased by TAM in the estrogen-completed mice, however it was decreased by TAM in the estrogen-depleted mice. Changes of ER and EGFR protein levels were similar in all treatments. Transforming growth factor-alpha (TGF-alpha) in tumors, which is known as a ligand of EGFR and as an estrogen-inducible protein in ER positive MCF-7 cells, was decreased by TAM in the estrogen-completed mice, by contrast, it was increased by TAM in the estrogen-depleted mice. Downregulation of ER was observed in TAM-treated mice in an estrogen-depleted environment, this action of TAM was similar to E2. These results suggest that increase of EGFR expression does not lead to a loss of ER after short-term TAM treatment in MCF-7 tumors.     

Antiestrogenic action of toremifene on hormone-dependent, -independent, and heterogeneous breast tumor growth in the athymic mouse

The antiestrogen toremifene has been used to study the growth control of hormone-dependent (MCF-7), -independent (MDA-MB-231), or mixed tumor cell populations in athymic mice. Maximal MCF-7 tumor growth was produced in ovariectomized athymic mice by circulating estradiol levels of approximately 200 pg/ml (produced by 0.5-cm silastic capsules implanted s.c.). The antiestrogen toremifene (77 +/- 4 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 on the mouse uterus. The growth of hormone-independent MDA-MB-231 breast tumors implanted in athymic mice was not influenced by either estradiol (0.5-cm capsule) or toremifene (2-cm capsule) when administered alone or in combination. Furthermore, even very large doses of toremifene (5 mg/day p.o.) did not alter the rate of MDA-MB-231 tumor growth. Mixtures of MCF-7 and MDA-MB-231 cells in 9:1 and 99:1 ratios inoculated into athymic mice produced tumors which grew in the absence of estradiol but responded to estradiol supplementation (0.5-cm capsule) with a more rapid rate of tumor growth. Tumors grown from inoculated MCF-7:MDA-MB-231 cells (99:1 ratio) in the presence of estradiol had estrogen receptor levels of 33.2 +/- 9.2 fmol/mg of protein at Day 44 compared to 84.8 +/- 4.8 fmol/mg of protein in pure MCF-7 tumors. Toremifene (2-cm capsule) treatment inhibited the estrogen stimulation of these mixed tumors (99:1 starting ratio) to that of toremifene alone. However, toremifene-alone treatment produced a more rapid rate of tumor growth than control or tumors grown from irradiated MCF-7 cells mixed with viable MDA-MB-231 cells. Increasing the ratio of MCF-7:MDA-MB-231 cells (999:1) initially inoculated resulted in tumors which developed less rapidly than the lower ratio (99:1). Toremifene (2-cm capsule) again produced partial inhibition of 17 beta-estradiol-stimulated tumor growth while increasing tumor growth above control when the antiestrogen was administered alone. These results demonstrate that toremifene is effective in inhibiting estrogen stimulation of hormone-dependent tumors and partially successful at controlling mixed hormone-dependent/independent tumors; however, the antiestrogen cannot control the growth of a hormone-independent tumor in this model.     

Direct inhibiting effects of [D-Trp6]gonadotropin-releasing hormone on the estrogen-sensitive progression of polyoma virus-induced mammary tumors in athymic mice

The direct antitumoral effects of gonadotropin-releasing hormone (GnRH) analogues on breast tumors have been surmised from clinical observations and in vitro studies. The present study aimed to determine the effects of the GnRH agonist [D-Trp6]GnRH (Decapeptyl) on steps of experimental mammary carcinogenesis, and the mechanisms, other than the chemical castration, involved. We chose a recent model, i.e., mammary tumors induced by wild-type A2 polyoma (Py) virus in BALB/c female nu/nu mice, which displays the following characteristics. Tumors are mammary adenocarcinomas similar to well differentiated breast carcinomas. Tumor promotion period ends 20 days after Py virus inoculation and is estradiol dependent. The first palpable tumors occur 60 days after Py virus inoculation, and tumor growth is ovarian hormone independent. The effects of Decapeptyl treatment on tumor induction and tumor growth were studied in normal or ovariectomized 6-week-old nude mice inoculated with 10(7) plaque-forming units Py virus (day 0 of experiments). Normal mice and ovariectomized mice percutaneously supplemented with 0.6 micrograms 17 beta-estradiol every other day until day 30 (OvE2 mice) were treated with monthly s.c. injections of the sustained release form of Decapeptyl (5 mg/kg) until the end of 180-day experiments. Overall values for latency periods were included within a day 60 to day 130 time interval. Hormone-independent outgrowth was not affected. We focused on tumor progression before the outgrowth. Incidences on tumor appearance kinetics account for effects at this stage. 17 beta-Estradiol repletion strongly antagonized (P less than 0.001) the slowing effect of ovariectomy on the tumor appearance kinetics, indicating that tumor progression is estradiol sensitive in its early stages. [D-Trp6]GnRH treatment antagonized tumor appearance profiles, inducing similar kinetics in both normal and OvE2 mice. In normal mice, the antagonism (P less than 0.01) was concomitant with significant decreases (P less than 0.05) in serum levels of estradiol and prolactin, which are critical hormones for mammary tumor development in mice, suggesting a pituitary-mediated effect. In OvE2 mice, the antagonism (P less than 0.01) occurs independently of estradiol and prolactin, suggesting a direct effect at the mammary cell level. Because of alterations in kinetics, this effect is exerted at the early stages of tumor progression on Py virus-transformed, ovarian hormone-sensitive cells in the mammary tissue. This new animal model of breast cancer is shown to be useful in characterizing direct antitumoral effects of GnRH analogues and studying the basic mechanisms of mammary carcinogenesis.     

利用荧光素酶标记的肿瘤细胞建立活体成像动物模型

目的建立稳定表达荧光素酶的人乳腺癌细胞株并构建适用于小动物活体成像系统观察的裸鼠皮下移植瘤模型。方法采用脂质体将携带荧光素酶基因的质粒转染到人乳腺癌细胞株MCF-7中,G418筛选出稳定表达荧光素酶的单克隆细胞株。扩增后接种于裸鼠,建立裸鼠皮下移植瘤模型,通过活体动物成像系统监测肿瘤的生长过程。结果获得了高水平稳定表达荧光素酶的乳腺癌单克隆细胞株,该单克隆细胞株与母细胞系MCF-7具有相似的生长特性。将稳定表达荧光素酶的克隆接种于裸鼠皮下可成瘤,小动物活体成像系统能准确监测肿瘤细胞在体内的生长过程。结论成功建立了稳定表达荧光素酶的乳腺癌单克隆细胞株。采用活体动物成像系统构建的裸鼠皮下移植瘤模型是拓展肿瘤体内生长、转移及治疗相关研究的理想模型。     

Estrogen induced growth of human breast cancer cells (MCF-7) in athymic nude mice is enhanced by secretions from a transplantable pituitary tumor

MCF-7, a human breast carcinoma cell line, was maintained s.c. in female athymic nude mice for a period of 5–6 weeks. Administration of estrogen (s.c. pellet of 17β-estradiol and estrone in drinking water, 0.5 mg/l) to these mice resulted in sustained (P < 0.001) growth of MCF-7 tumors. Grafting of a prolactin and growth hormone secreting rat pituitary tumor to the estrogen-treated mice resulted in an increased (P < 0.05) rate of MCF-7 tumor growth. MCF-7 did not grow in athymic nude mice grafted with rat pituitary tumor alone or in mice without hormone treatment (controls). Thus, secretions of pituitary hormones alone are not capable of promoting in vivo growth of MCF-7 although such secretions significantly enhance estrogen-induced growth of this cell line. A synergism between pituitary hormones and estrogen for in vivo growth of a human breast carcinoma has been demonstrated in this study.     

Programmed cell death during regression of the MCF-7 human breast cancer following estrogen ablation

To study the mechanism of regression of human mammary cancer following estrogen ablation, estrogen-responsive MCF-7 human mammary adenocarcinoma cells were inoculated into ovariectomized female nude mice supplemented with exogenous 17 beta-estradiol (E2) via an E2 implant. Implants were then removed when MCF-7 tumors were 400 mm3 in size. Removal of the E2 implants resulted in a 50% tumor regression by 2 weeks following E2 ablation. Associated with this regression is a rapid (i.e., within 1 day following E2 ablation) enhanced expression of the transforming growth factor beta 1 and TRPM-2-genes, two genes the expression of which has been previously demonstrated to be enhanced in a variety of cell types induced to undergo programmed cell death (i.e., apoptosis). The enhanced expression of transforming growth factor beta 1 and TRPM-2 is not a nonspecific response since the expression of other genes, like c-fos, c-H-ras, and pS2, decrease following E2 ablation. Fragmentation of tumor DNA into nucleosomal oligomers and histological appearance of apoptotic bodies are characteristic early events that precede the dramatic reduction in tumor volume following E2 ablation. These results demonstrate that the regression of MCF-7 human mammary cancers in nude mice following estrogen ablation is due to a sequence of biochemical and morphological changes that result in both the cessation of cell proliferation and activation of programmed death or apoptosis of these MCF-7 cancer cells. Clarification of the biochemical pathway involved in the activation of this programmed cell death should identify new targets of therapy for even estrogen-independent human mammary cancer cells.     

In vivo Antitumor Activity of Hexamethylmelamine against Human Breast, Stomach and Colon Carcinoma Xenografts

We have evaluated the antitumor activity of Altretamine (hexamethylmelamine, HMM) on human carcinoma xenografts serially transplanted in nude mice. Five human breast carcinoma xenografts, MX-1, T-61, MCF-7, R-27 and Br-10, were inoculated subcutaneously into female nude mice. Two human stomach carcinoma xenografts, SC-1-NU and St-4, and three human colon carcinoma xenografts, Co-3, Co-4 and Co-6, were inoculated subcutaneously into male nude mice. One pellet of 17β-estradiol (0.1 mg/mouse) was inoculated subcutaneously in the mice transplanted with MCF-7 when the tumors were inoculated. HMM was administered per os daily for 4 weeks. MX-1 and T-61 tumors regressed completely after treatment with HMM at a dose of 75 mg/kg (the maximum tolerated dose: MTD) for MX-1 and 25 mg/kg for T-61. Br-10 was sensitive, whereas MCF-7 and R-27 were resistant to HMM at its MTD. HMM exerted the most potent antitumor effect against T-61. Against MX-1, it exerted an antitumor effect equivalent to that of cisplatin or cyclophosphamide. In addition, this agent was effective against all stomach and colon carcinoma xenografts, in particular St-4 (T/C%= 10.7: the mean tumor weight of treated group/the mean tumor weight of control group) and Co-3 (T/C%=31.5%) which are insensitive to presently available agents. HMM seems worthy of further clinical investigation as a candidate agent to treat breast, stomach, colon and other carcinomas.     

Hormonal therapy of human endometrial adenocarcinoma in a nude mouse model

The hypothesis that 17 beta-estradiol or tamoxifen (TAM) can potentiate clinical response of endometrial cancer treated with progestin was tested in an ovariectomized nude mouse system, using a sex steroid receptor-positive and a receptor-negative human endometrial carcinoma. Animals were divided into three groups: control; 17 beta-estradiol-treated; and TAM-treated. When tumors of a group reached about 1 cm in diameter, subgroups were given either 0.9% NaCl solution (saline) or medroxyprogesterone acetate (MPA). The receptor-negative tumor grew rapidly in all three groups, and several animals were dead before or during progestin treatment. The growth rate of receptor-containing carcinoma was significantly increased in TAM-treated mice compared to controls (p less than 0.02) but significantly less than that in 17 beta-estradiol-treated animals (p less than 0.01). Endometrial carcinoma in 17 beta-estradiol-saline-treated animals continued to grow rapidly, and all animals were dead by 11 weeks. The growth of tumors in the 17 beta-estradiol-progestin group was suppressed at 11 weeks, and some of these animals lived 20 weeks. Administration of progestin to TAM-exposed animals resulted in a remarkable regression of the tumor compared to TAM-saline-treated group. The growth rate of tumors in control animals (no implants) was unaffected by progestin treatment. We conclude that, in this nude mouse model, treatment with TAM and MPA is superior to MPA alone, or 17 beta-estradiol plus MPA for sex steroid receptor-positive endometrial carcinoma.     

Intratumoral aromatase model: The effects of letrozole (CGS 20267)

An intratumoral aromatase model in the ovariectomized nude mouse was developed which simulated the hormone responsive postmenopausal breast cancer patient. MCF-7, human breast cancer cells transfected with the aromatase gene, inoculated into ovariectomized nude mice are able to synthesize sufficient estrogens to enhance cell proliferation and the development of tumors. These tumors are responsive to both antiestrogens and aromatase inhibitors. However, letrozole was found to be more effective than tamoxifen and caused tumor regression, a result not previously noted in nude mice with endocrine treatments. When the aromatase inhibitors were combined with tamoxifen, tumor growth was suppressed to about the same extent as treatment with the aromatase inhibitors alone. Thus, there was no additive or synergistic effects of combining tamoxifen with aromatase inhibitors. These results suggest that letrozole has the potential to be more effective than tamoxifen for achieving greater reduction in estrogenic effects on tumors and uterus in postmenopausal breast cancer patients. In addition, sequential treatment with these agents is likely to be more beneficial to the patient in terms of longer response to treatment.     

Importance of epidermal growth factor in implantation and growth of mouse mammary tumor in female nude mice

In female nude mice, epidermal growth factor (EGF) was present at a mean concentration of 42.8 +/- 16.9 (SD) ng/mg wet tissue in the submandibular gland and 0.28 +/- 0.13 ng/ml in the plasma. Sialoadenectomy (removal of the submandibular glands) decreased circulating EGF to undetectable levels (less than 0.1 ng/ml). The possible role of EGF in transplantation and growth of mouse mammary tumors in nude mice was examined by sialoadenectomy, anti-EGF treatment, and EGF replacement therapy. The success rate of transplantation of a spontaneous mouse mammary tumor into nude mice was 55% in normal females and 17% in sialoadenectomized animals. Anti-EGF treatment of sialoadenectomized mice completely abolished the implantation of the tumor. Daily administration of EGF at a dose of 5 micrograms per mouse to both normal and sialoadenectomized animals enhanced the success rate of tumor implantation to more than 80%. Sialoadenectomy and/or anti-EGF treatment of tumor-bearing nude mice reduced the growth of implanted mammary tumors. These results suggest that EGF is important for implantation and growth of spontaneous mouse mammary tumor in female nude mice.     

Inhibition of estrogen-dependent breast cancer growth by a reaction product of alpha-fetoprotein and estradiol.

Reaction of picomolar quantities of human or rodent alpha-fetoprotein (AFP) with nanomolar quantities of 17 beta-estradiol (E2) generates a product of unknown structure, designated AFP/E2, that inhibits estrogen-stimulated growth of mouse uterus. We describe herein the effect of rodent AFP/E2 on the in vivo growth of two estrogen-dependent breast cancers, the MCF-7 human breast cancer and the MTW9A rat mammary cancer. Both cancers were grown as xenografts under the kidney capsule of cyclosporine-immunosuppressed male BDF1 mice. In addition, the MTW9A tumor was grown as a homograft in syngeneic ovariectomized Wistar-Furth female rats. Estrogen support was provided by s.c. Silastic E2 implants. Injecting AFP/E2 that was generated by incubating 1.0 microgram of AFP with 0.5 microgram of E2 for 1 h at room temperature resulted in cessation of growth and, in most cases, regression of MCF-7 tumor xenografts. It also produced regression of MTW9A tumor homografts and significantly inhibited growth of MTW9A xenografts. Treatment with AFP alone or E2 alone did not inhibit growth of these tumors. The data suggest that AFP/E2 has a unique property which causes attenuation or shut-down of the biochemical reactions through which estrogen-dependent tumor growth is mediated.     

神经母细胞瘤细胞系裸鼠转移模型及局部皮下荷瘤模型的建立

目的 建立人神经母细胞瘤(NB)裸鼠荷瘤模型,研究NB的侵袭、转移机制以及实验治疗的可能性.方法 体外培养人NB细胞系,取对数生长期瘤细胞,以1×107个/0.1ml细胞悬液接种于裸小鼠右侧前肢肋腹部皮下,观察倚瘤的生物学特性,并进行病理组织学检查及基因芯片分析,检测皮下荷瘤组织、转移瘤组织和患儿原发肿瘤组织的神经元特异性烯醇化酶(NSE)表达.结果 48只裸鼠中,荷瘤成功36只,总荷瘤率为75.0%.其中5只裸鼠肿瘤体积很大,甚至达到裸鼠自身体重的1/2,但未发生转移;4只裸鼠接种部位无肿瘤生长,却发生全身转移;6只裸鼠既有局部肿瘤生长,又发生转移.本组有10只裸鼠发生转移,转移率为20.8%(10/48).结论 成功建立人NB裸鼠荷瘤模型并稳定传代,肿瘤的移植生长率和转移率均较高,是NB体内研究理想的动物模型.NB具有异质性,可能是NB转移的重要原因.     

Soy diets containing varying amounts of genistein stimulate growth of estrogen-dependent (MCF-7) tumors in a dose-dependent manner.

We have demonstrated that the isoflavone, genistein, stimulates growth of estrogen-dependent human breast cancer (MCF-7) cells in vivo (C. Y. Hsieh et al., Cancer Res., 58: 3833-3838, 1998). The isoflavones are a group of phytoestrogens that are present in high concentrations in soy. Whether consumption of genistein from soy protein will have similar effects on estrogen-dependent tumor growth as pure genistein has not been investigated in the athymic mouse tumor implant model. Depending on processing, soy protein isolates vary widely in concentrations of genistein. We hypothesize that soy isolates containing different concentrations of genistein will stimulate the growth of estrogen-dependent cells in vivo in a dose-dependent manner. To test this hypothesis we conducted experiments in which these soy protein isolates were fed to athymic mice implanted s.c. with estrogen-dependent tumors. Genistein content (aglycone equivalent) of the soy isolate diets were 15, 150, or 300 ppm. Positive (with 17beta-estradiol pellet implant) and negative (no 17beta-estradiol) control groups received casein-based (isoflavone-free) diets. Tumor size was measured weekly. At completion of the study animals were killed and tumors collected for evaluation of cellular proliferation and estrogen-dependent gene expression. Incorporation of bromodeoxyuridine into cellular DNA was used as an indicator of cell proliferation, and pS2 mRNA was used as an estrogen-responsive gene. Soy protein diets containing varying amounts of genistein increased estrogen-dependent tumor growth in a dose-dependent manner. Cell proliferation was greatest in tumors of animals given estrogen or dietary genistein (150 and 300 ppm). Expression of pS2 was increased in tumors from animals consuming dietary genistein (150 and 300 ppm). Here we present new information that soy protein isolates containing increasing concentrations of genistein stimulate the growth of estrogen-dependent breast cancer cells in vivo in a dose-dependent manner.     

Formation of metastasis by human breast carcinoma cells (MCF-7) in nude mice

MCF-7 cells, a human breast carcinoma line, forms tumors when injected into athymic nude mice. These tumors are able to metastasize to lungs, liver and spleen. 17 beta-estradiol treatment increases both the growth rate and frequency of metastases. Castration or diabetes prevents metastasis formation, but treatment with estrogen or insulin restores the metastasizing capacity. MCF-7 cells secrete into the culture media collagenases able to lyse types I and IV collagens. Estrogen or insulin addition to the culture enhances collagenase production. Attention is called to the coexistence of enhancement in collagenase production and metastasis formation.     

靶向抑制CXCR7基因表达对结肠癌生长的影响

目的探讨靶向抑制CXCR7基因表达对人结肠癌荷瘤裸鼠瘤体生长的影响。方法建立人结肠癌荷瘤鼠模型。将人结肠癌荷瘤裸鼠随机分为3组,治疗组：瘤体内注射LV-CXCR7shRNA 50μl;阴性对照组：瘤体内注射LV-shRNA negative control 50μl;空白对照组：瘤体内注射PBS 50μl。24天后测量瘤体的体积;处死动物,剥离瘤体,测量其重量。采用Westrn Blotting方法测定瘤体组织中CXCR7蛋白表达水平。结果治疗组瘤体体积显著缩小（P〈0.05）、重量显著减轻（P〈0.05）。治疗组瘤体组织中CXCR7蛋白表达水平显著降低（P〈0.05）。结论靶向抑制CXCR7基因的表达能显著抑制人结肠癌荷瘤裸鼠的瘤体生长,CXCR7是人结肠癌治疗潜在的分子靶标。