Strain Difference in Regulation of Pituitary Tumor Transforming Gene (PTTG) in Estrogen–induced Pituitary Tumorigenesis in Rats

Recently a novel oncogene, PTTG (pituitary tumor transforming gene) was isolated from a rat pituitary tumor cell line whose expression is apparently correlated with pituitary tumorigenesis. In the rat, estradiol (E₂) is known to induce anterior pituitary hyperplasia. The effects of E₂, however, vary greatly among rat strains. Therefore we examined the expression of PTTG and its regulation by E₂ in F344, Wistar, Brown–Norway and Donryu rats. Four–week–old females were ovariecto–mized and a pellet containing 10 mg of E₂ was given s.c. Total RNA was isolated from the pituitary gland and PTTG mRNA was measured with a competitive RT–PCR technique. The F344 strain was the most susceptible to E₂ induction of pituitary tumorigenesis, followed by Wistar and Brown–Norway, while no increase in pituitary weight was noted in Donryu rats. PTTG mRNA in the gland was induced by E₂ within 48–72 h in F344 and Wistar, but not in Brown–Norway or Donryu strains. These data suggest that PTTG expression may at least in part be responsible for strain differences in E₂–induced pituitary tumorigenesis     

The Edpm5 locus prevents the 'angiogenic switch' in an estrogen-induced rat pituitary tumor

Edpm5 is one member of a group of quantitative trait loci that are responsible for the difference in susceptibility to estrogen-induced prolactinoma between the Fischer 344 (F344) and Brown Norway (BN) strains. Upon chronic estrogen treatment F344 rats develop large, hemorrhagic and invasive pituitary tumors, which exhibit both tumor angiogenesis and neoplasia. In contrast, BN rats do not develop a tumor despite an estrogen-induced increase in lactotroph density. To investigate the role of Edpm5 in the development of these tumors, we have generated a novel congenic rat strain F344.BN-Edpm5BN by introgressing the segment of rat chromosome bearing Edpm5 from BN into the F344 strain background. Phenotypic differences between F344 and F344.BN-Edpm5BN must be due to a gene(s) within the chromosomal interval encompassing Edpm5. Through use of these strains, we find that Edpm5 specifically regulates the switch to angiogenic phenotype, independent of neoplasia. The F344.BN-Edpm5BN rats developed tumors, which exhibited significant growth, 7-fold greater mass than the pituitary of untreated rats, and neoplasia indistinguishable from that of the F344 strain. However, the F344.BN-Edpm5BN rat tumor had a non-angiogenic phenotype. After chronic estrogen treatment, there was no increase in microvessel count over untreated controls in F344.BN-Edpm5BN tumors, whereas F344 rat tumors showed a significant increase (P < 0.0005). The ultrastructural morphology of the pituitary blood vessels also did not show significant angiogenesis associated changes in F344.BN-Edpm5BN rat pituitary tumors. In contrast the parental strain F344 had pronounced angiogenic activity. The F344.BN-Edpm5BN strain also fails to express VEGF at the high levels seen in the F344 rat pituitary after estrogen treatment. Hence at least one gene that has a large impact, directly or indirectly, on the switch to angiogenic phenotype must reside within the chromosomal interval that is the Edpm5 quantitative trait locus.     

雌激素对垂体催乳素细胞致瘤机制的探讨

【摘要】 背景与目的： 探讨雌激素诱发大鼠垂体催乳素(PRL)瘤的发病机制。 材料与方法： 制备雌激素诱发大鼠PRL瘤模型: 成年雄性Wistar大鼠16只,随机分为对照组(n=8)和PRL瘤组(n=8) 。对照组皮下植入空白硅胶管,PRL瘤组皮下植入含有乙烯雌酚的硅胶管,用药8周后乙醚麻醉大鼠,心脏穿刺取血,分离血清,并开颅摘取垂体。采用放免法测定大鼠血清PRL水平;垂体称重并做组织病理学观察;用免疫组织化学方法检测垂体组织PRL蛋白的表达和分布;用RT_PCR方法检测c_fos 和垂体肿瘤转化基因(PTTG)在PRL瘤组织中的表达,计算机凝胶成像系统分析其表达量。 结果： 雌激素作用8周后,根据大鼠垂体重量以及组织学和免疫组化的改变,证实已诱发出PRL瘤模型。在PRL瘤组中,c_fos和PTTG的表达量均明显高于对照组,二者差异具有统计学意义彩 (P<0.001)。 结论： 雌激素刺激垂体PRL细胞表达癌基因c_fos以及PTTG,在雌激素诱发大鼠PRL细胞增生以至最终形成PRL瘤的过程中起一定的作用。     

Estrogen induction of prolactin-producing pituitary tumors in the Fischer 344 rat: Modulation by dietary-energy but not protein consumption

Our laboratory is examining the hypothesis that diet may modulate the ability of estrogens to regulate cell proliferation and survival, either of which could affect development of neoplasms in estrogen-responsive tissues. In this study, we examined whether the amount of energy and protein consumed in the diet modulates the ability of the synthetic estrogen diethylstilbestrol (DES) to induce development of prolactin-producing pituitary tumors in two strains of rat, Fischer 344 (F344) and Holtzman, that differ in their propensity to develop pituitary tumors when treated with estrogens. Male F344 rats treated with DES for 8 wk developed pituitary tumors (defined as grossly enlarged pituitary masses that displayed diffuse lactotroph hyperplasia but lacked adenomatous foci). In contrast, male Holtzman rats displayed only a modest increase in pituitary weight in response to DES. Energy consumption but not protein consumption modulated DES-induced pituitary tumorigenesis in the male F344 rat. Relative to that observed in untreated animals, pituitary weights in F344 rats treated with DES increased 11.2- and 9.2-fold in animals fed either the control diet or an equicaloric high-protein diet, respectively, but only 3.5-fold in animals fed an energy-restricted diet. In contrast, neither the amount of energy nor protein consumed in the diet affected the modest pituitary growth response of male Holtzman rats to administered DES. Energy restriction had no apparent effect on pituitary cell proliferation, either basal or DES stimulated, in these rat strains. We concluded that dietary energy restriction inhibits the ability of administered DES to induce pituitary tumor development in the F344 rat by acting at a step after induction of pituitary cell proliferation. Mol. Carcinog. 23:96–105, 1998. © 1998 Wiley-Liss, Inc.     

Estrogen-induced pituitary tumor development in the ACI rat not inhibited by dietary energy restriction

We have demonstrated that a 40% restriction of dietary energy consumption virtually abolishes the development of prolactin (PRL)-producing pituitary tumors in Fischer 344 (F344) rats treated chronically with estrogen, apparently by inhibiting the ability of estrogen to enhance survival within a rapidly proliferating lactotroph population. The purpose of the study reported here was to determine whether energy restriction exerts a similar antitumorigenic action in another rat strain, August x Copenhagen-Irish (ACI), in which PRL-producing pituitary tumors develop in response to estrogen treatment. Ovariectomized female ACI rats were either allowed to consume a control diet ad libitum or were fed a modified diet that restricted energy consumption by 40% relative to the amount of energy consumed by animals fed the control diet. We also examined the ability of 17beta-estradiol (E2) administered for 20 wk via subcutaneous Silastic implants to induce development of PRL-producing pituitary tumors. Treatment with E2 increased pituitary weight as well as the pituitary weight-to-body weight ratio and induced gross hyperprolactinemia to the same extent in ACI rats fed either the control or the energy-restricted diet. Moreover, dietary energy restriction did not affect the ability of E2 to induce pituitary cell proliferation or inhibit apoptosis, as evidenced by quantification of two surrogate markers. These data provide compelling evidence that a 40% restriction of energy consumption does not inhibit the ability of E2 to induce pituitary tumor development in the ACI rat. In conjunction with our published studies of the F344 rat strain, the data presented herein indicate that the inhibitory effects of dietary energy restriction on estrogen-induced pituitary tumor development are rat-strain specific and suggest that sensitivity to specific antitumorigenic actions of energy restriction is strongly affected by genetic background.     

Genetic properties for the suppression of development of putative preneoplastic glutathione S-transferase placental form-positive foci in the liver of carcinogen-resistant DRH strain rats

The post-initiation stage of hepatocarcinogenesis was investigated in carcinogen-resistant inbred DRH rats and the parental strain, carcinogen-sensitive Donryu rats. Male rats at 5 weeks of age from both strains were treated with N-nitrosodiethylamine (200 mg/kg i.p.) followed by feeding with a diet containing 3′-methyl-4-dimethylaminoazobenzene (3′-Me-DAB) from 2 weeks later and were then subjected to partial hepatectomy at 1 week later. At 8 weeks after the start of treatment, the mean area occupied by glutathione S-transferase placental form (GST-P)-positive lesions was about 30% in Donryu rats but less than 4% in DRH rats despite the presence of comparable numbers of foci in the livers of both strains. These observations suggested that clonal expansion of GST-P-positive foci in DRH rat liver was significantly suppressed under these conditions. Furthermore, this genetic property was dominantly inherited in the Fl rats by crosses of DRH and carcinogen-sensitive inbred F344 rats; that is, the induction of GST-P mRNA in the livers of F344×DRH Fl rats was dominantly suppressed after administration of 3′-Me-DAB for 8 weeks as compared with parental F344 rats under the same conditions. We compared the intrinsic properties related to growth potential of liver cells between adult DRH and Donryu rats. DRH rat liver showed retarded and/or reduced DNA synthesis after partial hepatectomy or a single i.v. injection of lead nitrate and lower activity of telomerase induced by 3′-Me-DAB administration for 1 week, as compared with the Donryu rat liver. The intrinsic properties observed in this study may be related, at least in part, to the low incidence of liver tumors induced by hepatocarcinogens in DRH rats.     

Spontaneous neoplastic and non-neoplastic lesions in aging Donryu rats

Spontaneous neoplastic and non-neoplastic lesions in 95 male and 96 female Donryu rats which were observed up to 120 weeks of age, were examined. The incidence of spontaneous tumors was 73.7% in males and 88.5% in females. In males, the most frequent tumors were pituitary adenomas, followed by pheochromocytomas and insulinomas. In females, uterine adenocarcinomas, mammary fibroadenomas and pituitary adenomas were the most common. Other tumors with relatively high incidences in both sexes included cortical adenomas of the adrenal gland, histiocytic sarcomas of the hematopoietic organs and granular cell tumors of the brain. Various tumors were also found in many other organs and/or tissues, although their incidences were low. The organ distribution and incidences of spontaneous tumors observed in Donryu rats were different from those in other strains of rats such as the ACI, Wistar, F344 or Sprague-Dawley strains. The main non-neoplastic lesions were observed in the lung, cervical lymph nodes and kidney of both sexes. In addition, lesions were also observed in the urinary bladder, prostate and peripheral nerves (spinal nerve roots and peripheral nerves) and/or femoralis muscle of males. Histologically, the most characteristic lesion was radiculoneuropathy with degeneration of the peripheral nerves.     

Different carcinogenic responses in a variety of organs, including the prostate, of five different rat strains given 3,2'-dimethyl-4-aminobiphenyl

Tumorigemc response in the prostate of F344, ACI, Lewis, CDand Wistar rat strains to 3,2'-dimethyl-4-amtnobiphenyl (DMAB)was examined in relation to development of other types of tumors.Rats of each strain aged 6 weeks were divided into two groupsreceiving DMAB S.C. at a dose of 50 mg/kg body wt once everyother week for 10 times, with or without 1 week dietary ethynylestradiol (EE) pretreatment. The experiment was terminated atweek 60, carcinomas of the ventral prostate, all of microscopicsize, being respectively found in 50, 17, 21, 15 and 0% of F344,ACI, Lewis, CD and Wistar strain animals treated with EE plusDMAB. The tumor yield correlated well with DMAB–DNA adductfor mation. One invasive adenocarcinoma also developed in theperlurethral part (occupying both of lateral and dorsal areas)of the prostate. The final survival rates were 46, 24, 65, 4and 0% in F344, ACI, Lewis, CD and Wistar rats respec tively.DMAB administration without EE pretreatment resulted in similarincidences of prostate tumors and mor talities. Tumors arosein >14 dIfferent sites with strain dependency, lesions predominatingin the skin/subcutis of ACI and F344, preputial gland of F344,urinary bladder of ACI, and mammary glands of CD rats respectively.Consideration of mortality and the relative incidence of prostatecancer and other types of tumors indicates the F344 rat strainto be the most appropriate for investigation of DMAB prostatecarcinogenesis.     

非霍奇金淋巴瘤患者骨髓垂体瘤转化基因、c-myc基因表达的研究

目的 探讨非霍奇金淋巴瘤（NHL）患者骨髓垂体瘤转化基因（PTTG）与c-myc基因的表达及其临床意义.方法 采用反转录聚合酶链反应（RT-PCR）法检测38例NHL患者骨髓及10例慢性淋巴结炎患者骨髓单个核细胞（BMMNC）中PTTG及c-myc基因的表达.结果 NHL患者骨髓中PTTG和c-myc基因的表达水平均明显高于慢性淋巴结炎组,差异有统计学意义（PTTG：0.567 7±0.270 7比0.071 2±0.020 1,t=4.706,P＜0.05; c-myc：0.352 6±0.185 4比0.107 3±0.043 5,t=3.303,P=0.002）.外周T细胞淋巴瘤和弥漫大B细胞淋巴瘤患者PTTG及c-myc基因表达水平差异均无统计学意义（PTTG：0.556 8±0.211 3比0.602 8±0.244 6,t=0.640,P=0.527;c-myc：0.350 1±0.177 6比0.361 0±0.190 2,t=0.302,P=0.765）.PTTG基因的表达与NHL骨髓浸润、国际预后指数（IPI）评分呈正相关（r=0.422,r=0.387;均P＜0.05）.c-myc基因的表达与NHL骨髓浸润、IPI评分呈正相关（r=0.431,r=0.344,均P＜0.05）.NHL患者骨髓PTTG基因和c-myc基因的表达呈正相关（r=0.490,P＜0.05）.结论 NHL中PTTG、c-myc呈高表达状态,PTTG可能通过直接或间接途径促进c-myc的高表达.     

Effects of genetic background on prostate and taste bud carcinogenesis due to SV40 T antigen expression under probasin gene promoter control

The incidence of prostate carcinomas in African-American men is greater than in white men, indicating genetic factors are involved in risk of this neoplasia. Recently, we have developed a transgenic rat model of prostate cancer, featuring development of malignancies within 15 weeks of age at very high incidence. Male transgenic rats with a Sprague-Dawley genetic background were mated with wild-type females of F344, Wistar and ACI strains. F1 male transgenic hybrids with female Wistar and ACI rats had significantly lowered incidences of prostate carcinomas. However, the serum level of testosterone, and expression of the transgene, probasin, and the androgen receptor did not correlate with the strain variation in tumor development. Furthermore, immunohistochemical analysis of the SV40 Tag and the androgen receptor also did not reveal any differences between the strains. The transgenic rats additionally developed taste bud neuroblastomas at 100% incidence and this was suppressed in F1 male transgenic offspring with the ACI, but not the other strains. These results clearly show that genetic background influences prostate carcinogenesis and taste bud tumorigenesis in rats and that the present transgenic rats could provide a good model to identify specific factors.     

三苯氧胺对胶质瘤C6细胞垂体瘤转化基因表达及肿瘤生长影响的体内研究

目的 探讨体内三苯氧胺对胶质瘤C6细胞垂体瘤转化基因(PTTG)表达及细胞生长的影响.方法 建立SD大鼠C6胶质瘤移植动物模型,将32只荷瘤裸鼠随机分为4组:空白对照组、高(2 mg·kg-1·d-1)、中(0.2 mg·kg-1·d-1)、低(0.02 mg·kg-1·d-1)剂量三苯氧胺作用组,共给药20 d.空白对照组给等量的生理盐水.定期观察肿瘤生长情况,测量肿瘤体积,计算抑瘤率.处死全部动物模型,剔出肿瘤,逆转录-聚合酶链反应(RT-PCR)检测FITG mRNA表达.结果 与空白对照组相比,各组三苯氧胺均能抑制肿瘤生长,其体积抑瘤率分别为47.6%、35.5%、21.2%,各组间差异均有统计学意义(P<0.05);FITG mRNA的表达在低、中、高剂量组均降低,各组间差异均有统计学意义(P<0.05).结论 三苯氧胺能以量效的方式抑制胶质瘤PTTG的表达和肿瘤生长,本研究为临床应用三苯氧胺治疗胶质瘤提供了理论基础.     

hpttg is over-expressed in pituitary adenomas and other primary epithelial neoplasias.

The role of oncogenes in pituitary tumorigenesis remains elusive since few genetic changes have been identified so far in pituitary tumors. Pituitary tumor-transforming gene (pttg) has been recently cloned from rat GH4 pituitary tumor cells. We have previously isolated and characterized hpttg from human thymus. In the present study, we analyse the expression of hpttg mRNA in a series of human pituitary adenomas. We show that hpttg is highly expressed in the majority of pituitary adenomas while only very low levels of mRNA can be detected in normal pituitary gland by Northern blot analysis. hPTTG protein was immunolocalized mainly in the cytoplasm of adenoma cells. Other common extra-cranial malignant tumors were also analysed by immunohistochemistry. Interestingly, strong hPTTG immunoreactivity was detected in most adenocarcinomas of mammary and pulmonary origins.     

Role of resistant Drh1 locus in chemical carcinogen-induced hepatocarcinogenesis in rats: analysis with a speed congenic strain

The DRH is an inbred rat strain established by selective mating of the 3'-Me-DAB resistant progeny of closed colony Donryu rats over 20 generations. Genetic analysis shows that two semidominant QTLs, Drh1 and Drh2, are responsible for strong resistance to chemical-induced hepatocarcinogenesis in DRH strain rats. To evaluate the effect of the single Drh1 locus on various stages of liver carcinogenesis, we constructed a speed congenic strain DRH.F344-Drh1 by transferring a susceptible Drh1 allele of F344 to DRH rats by marker-assisted backcrossing. The DRH.F344-Drh1 rats had a approximately 43 cM segment of chromosome 1 bearing Drh1 but the Drh2 was of the DRH allele. After oral administration of 3'-Me-DAB for 8 weeks, DRH.F344-Drh1 had as many enzyme altered foci as F344, whereas the quantitative parameters of fibrosis, enzyme altered foci, GST-P expression and proliferation of liver cells in DRH.F344-Drh1 rats were intermediate between F344 and DRH. In the liver of carcinogen-fed DRH rats, there was intensive apoptosis as detected by TUNEL stain, but not in the liver of F344 and DRH.F344-Drh1 rats. Injection of lead nitrate (100 micromol/kgB.W) induced a wave of liver cell proliferation, as seen by BrdU uptake within a few days in F344 and DRH.F344-Drh1 rats, but not in DRH rats. Instead, there were numerous TUNEL-positive nuclei in the DRH liver after lead nitrate injection. Apparently, the hepatocytes were removed by apoptosis during transition from G0 to G1. The major role of Drh1 is effective removal of the hepatocytes newly recruited to proliferate after chemical injury. Resistance to preneoplastic lesions in DRH rats may well be based on similar mechanism.     

Role of the pituitary tumor transforming gene 1 in the progression of hepatocellular carcinoma

In order to demonstrate the role of the pituitary tumor transforming gene 1 (PTTG1) in the development of hepatocellular carcinoma (HCC) and its value as a molecular target for cancer therapy, we analyzed the expression of PTTG1 mRNA and protein, and their relation to clinicopathological characteristics and basic fibroblast growth factor (bFGF) expression in HCC. It was observed that the level of PTTG1 mRNA and the positive rate of PTTG1 protein in cancerous tissues were significantly higher than that in adjacent non-cancerous tissues (both P< 0.001). The PTTG1 protein levels were correlated with several clinicopathological parameters, including alpha-fetoprotein level, portal vein tumor thrombosis, tumor stage, and bFGF protein level (P< 0.05). The proliferation indices were significantly less and the apoptotic rates were significantly higher in the HepG2 and SMMC-7721 cells treated with PTTG1 siRNA transfection than their untransfected counterparts. The expressions of Caspase-3, Bax, p21 and p53 in HepG2 and SMMC-7721 cells were significantly increased after siRNA knockdown of PTTG1 expression. In conclusion, the PTTG1 gene is up-regulated in the cancerous tissue from patients with HCC and involved in the progression of HCC. Inhibiting PTTG1 expression decreases cell proliferation and induces apoptosis in hepatic cancer cell lines, indicating that PTTG1 may be a new therapeutic target for HCC treatment.     

垂体肿瘤转化基因PTTG在NHL中的表达及其意义

目的:探讨垂体肿瘤转化基因PTTG(pituitary tumor transforming gene)在非霍奇金淋巴瘤(NHL)中的表达,并研究其表达与NHL临床病理指标的关系。方法:采用原位杂交法和免疫组化法检测50例NHL患者肿瘤组织和20例良性淋巴结炎组织中PTTG mRNA及其蛋白的表达。结果:PTTG mRNA在NHL和对照组的阳性表达率分别为54.0%(27/50)和20.0%(4/20),PTTG蛋白在NHL和对照组的阳性表达率分别为50.0%(25/50)和15.0%(3/20),NHL中PTTG mRNA及其蛋白的阳性表达率及表达分级比较均高于对照组。PTTG mRNA的表达与NHL的恶性程度和临床分期呈正相关(r=0.366,P=0.009;r=0.438,P=0.001)。NHL中PTTG mRNA表达与其蛋白表达成等级正相关(r=0.831,P<0.01)。NHL中PT-TG mRNA表达与近期疗效呈负相关(r=-0.354,P<0.05)。结论:NHL中PTTG高表达。PTTG表达水平与NHL生物学行为可能有关。     

PTTG 在垂体腺瘤各亚型中的表达与分析

目的:研究PTTG与垂体瘤的各亚型的相关性.方法:用免疫组化方法检测92例垂体肿瘤病人PTTG.其中29例GH,20例PRL,10例ACTH,11例FSH/LH,9例TSH和13例无功能腺瘤.结果:PTTG在细胞质内显著表达,各亚型中GH型是表达最高,PRL腺瘤表达最低,各亚型的阳性表达率与PRL亚型阳性表达率对比均有统计学意义.结论:重体腺瘤不同垂体亚型中PTTG的表达阳性率及表达强度不同,PTTG检测,可为早期诊断垂体腺瘤( GH、PRL、ACTH、FSH/LH、TSH)亚型和无功能型提供参考.     

脑膜瘤组织中PTTG1、E2F3、EphA2蛋白水平与患者预后的关系研究

目的 探讨脑膜瘤组织中垂体肿瘤转化基因1(PTTG1)、E2F转录因子3(E2F3)和上皮细胞激酶(EphA2)蛋白水平与患者预后的关系.方法 选择65例脑膜瘤患者作为观察组,另取同期收治的63例脑膜瘤旁组织作为对照组,测定PTTG1、E2F3、EphA2蛋白在脑膜瘤组织和瘤旁组织中的表达水平,并分析其与患者临床病理特...     

Overexpression of vascular endothelial growth factor164 and its co-receptor neuropilin-1 in estrogen-induced rat pituitary tumors and GH3 rat pituitary tumor cells

We have shown previously that the VEGF system plays a crucial role in regulation of tumor angiogenesis during the development of estrogen-induced prolactin-secreting pituitary tumors in Fisher 344 rats. Studies also suggested that both endothelial and non-endothelial cells expressed VEGF. However, several questions concerning the VEGF signals in regulation of estrogen-induced angiogenesis in rat pituitary remained unanswered. VEGF exists in a number of isoforms in human and rodent tissue (i.e., VEGF206h/205r, VEGF189h/188r, VEGF165h/164r, VEGF145h/144r and VEGF121) that differ in their molecular masses and biological activities. The VEGF isoforms bind with two tyrosine-kinase receptors, KDR/flk-1 and flt-1. In addition, VEGF165 binds with a newly identified co-receptor, neuropilin-1, which is expressed in human endothelial cells and several types of non-endothelial cells including tumor cells. The present study was undertaken to elucidate which isoforms of VEGF are predominantly expressed in normal Fisher 344 rat pituitaries, estrogen-induced prolactin secreting rat pituitary tumors and in prolactin secreting rat pituitary tumor cell line (GH3 cell line). To identify the isoform, RT-PCR with primer pairs derived from exon 1 and exon 8 of the VEGF gene, cloning, sequencing and Western blot analysis were performed. The status of neuropilin-1 in the rat pituitaries (normal and transformed) and GH3 pituitary tumor cell line has also been investigated using RT-PCR and Western blot analysis. These studies demonstrate that normal rat pituitaries, estrogen-induced rat pituitary tumors and GH3 pituitary tumor cells expressed VEGF164 and co-receptor, neuropilin-1. The VEGF164 was the predominant form in all of these cells. The VEGF164 and neuropilin-1 mRNA and protein levels were significantly higher in the estrogen-induced pituitary tumors and GH3 tumor cell line, as compared to normal pituitary. The data suggest that both VEGF164 and neuropilin-1 may actively participate in modulation of tumor angiogenesis and the development of pituitary tumors in Fisher 344 rats.