Osteoporosis-like Changes in Walker Carcinoma 256-Bearing Rats, Not Accompanied with Hypercalcemia or Parathyroid Hormone-related Protein Production

Walker carcinoma 256 (W256) was reported to induce hypercalcemia dependent on bone metastasis and/or parathyroid hormone-related protein (PTHrP) in the rat, providing a model of the humoral hypercalcemia of malignancy. In this study, after the subcutaneous inoculation of cells of the W256/S line, which is maintained in this laboratory, into young female Wistar Imamichi rats (6 weeks old), serum calcium and phosphorus levels changed only within the control range, whereas serum alkaline phosphatase activity and urinary calcium level significantly increased and urinary phosphorus decreased during the tumor growth, resulting in hypercalciuria and hypophosphaturia. W256/S did not express PTHrP-mRNA, whereas LLC-W256 cells did express it. Serum PTHrP level was not changed in W256/S-bearing rats. Osteoporosis-like changes, bone weight loss, low contents of bone calcium and phosphorus, and a decrease in the bone mineral density (BMD), were observed in the femur 14 days after the tumor inoculation. There was a pronounced decrease in the serum 17β-estradiol level during the tumor growth. The reduction of BMD of femurs in W256/S-bearing rats was significantly inhibited by treatment with salmon calcitonin or 17β-estradiol. On the basis of these results, W256/S carcinoma-bearing rats seem to be a useful model for osteoporosis of hypoovarianism.     

Mechanism of Metabolic Abnormality of Thyroid Hormones in Walker 256 Carcinosarcoma-bearing Rats

We examined the mechanism of abnormality of thyroid hormone metabolism in Walker 256 carcino-sarcoma-bearing rats. The serum levels of thyroxine (T₄), 3,5,3′-triiodothyronine (T₃) and thyroid-stimulating hormone (TSH), and the responses of serum T₄ and T₃ to exogenous TSH in tumor-bearing rats on day 14 after inoculation of tumor cells were significantly less than those in pair-fed control (PFC) rats, suggesting that the metabolic abnormality of thyroid hormones may be caused by disorder of both peripheral and central functions, and that a certain tumor-derived factor may be involved in this abnormality. An active factor responsible for the metabolic abnormality was found in soluble cytosol fraction (SF) of the tumor cells. Administration of the SF to normal rats significantly reduced their serum T₄ and T₃ concentrations, liver 5 -deiodinase (5′-DI) activity, responsiveness of the thyroid gland to TSH and food intake compared with those of PFC rats, but, unlike the tumor, did not reduce the serum TSH level. This biologically active factor in the SF was found to be a heat-labile protein and specific to the tumor. It was tentatively named serum thyroid hormone reducing factor (STRF). STRF was partially purified from the SF by ammonium sulfate fractionation and DEAE-cellulose chromatography. Partially purified STRF preparation significantly diminished the serum T₄ and T₃ concentrations and liver S′-DI activity and food intake of normal rats compared with those of PFC rats, mimicking the changes associated with the tumor in tumor-bearing animals. These results suggested that abnormality of thyroid hormone metabolism in tumor-bearing animals may partly be caused by STRF-mediated modulation at peripheral and thyroid gland levels. Whether STRF actually induces anorexia remains to he clarified.     

Mechanism of metabolic abnormality of thyroid hormones in Walker 256 carcinosarcoma-bearing rats

We examined the mechanism of abnormality of thyroid hormone metabolism in Walker 256 carcinosarcoma-bearing rats. The serum levels of thyroxine (T4), 3,5,3'-triiodothyronine (T3) and thyroid-stimulating hormone (TSH), and the responses of serum T4 and T3 to exogenous TSH in tumor-bearing rats on day 14 after inoculation of tumor cells were significantly less than those in pair-fed control (PFC) rats, suggesting that the metabolic abnormality of thyroid hormones may be caused by disorder of both peripheral and central functions, and that a certain tumor-derived factor may be involved in this abnormality. An active factor responsible for the metabolic abnormality was found in soluble cytosol fraction (SF) of the tumor cells. Administration of the SF to normal rats significantly reduced their serum T4 and T3 concentrations, liver 5'-deiodinase (5'-DI) activity, responsiveness of the thyroid gland to TSH and food intake compared with those of PFC rats, but, unlike the tumor, did not reduce the serum TSH level. This biologically active factor in the SF was found to be a heat-labile protein and specific to the tumor. It was tentatively named serum thyroid hormone reducing factor (STRF). STRF was partially purified from the SF by ammonium sulfate fractionation and DEAE-cellulose chromatography. Partially purified STRF preparation significantly diminished the serum T4 and T3 concentrations and liver 5'-DI activity and food intake of normal rats compared with those of PFC rats, mimicking the changes associated with the tumor in tumor-bearing animals. These results suggested that abnormality of thyroid hormone metabolism in tumor-bearing animals may partly be caused by STRF-mediated modulation at peripheral and thyroid gland levels. Whether STRF actually induces anorexia remains to be clarified.     

Reduced Walker 256 carcinosarcoma growth in vasopressin-deficient Brattleboro rats

The growth pattern of carcinosarcoma Walker 256 was studied in rats with different levels of vasopressin in the blood. The Brattleboro rats are unable to synthesize vasopressin in a consequence of deletion in the coding gene. Hybrids from crossbreeding of the mutant Brattleboro and normal WAG rats inherit the one intact vasopressin gene and hold nearly normal hormone level. It was found that non-strain-specific carcinosarcoma Walker 256 intensively grows in WAG rats and their offsprings from crossbreeding with Brattleboro rats, and tumor development is equally terminated in them by death. Carcinosarcoma grows less intensely in Brattleboro rats; the tumor nodes increased only within the first 2 weeks, after which, the tumor began to decrease and eventually disappeared. Infusion of exogenous vasopressin to Brattleboro rats intensifies a tumor growth in the first 2 weeks after the inoculation of Walker 256 cells; however, it does not prevent a following regression and resorption of tumors.     

Walker 256/B malignant breast cancer cells improve femur angioarchitecture and disrupt hematological parameters in a rat model of tumor osteolysis

This study was designed to assess femur angioarchitecture and hematological effects of Walker 256/B cells in a rat model of tumor osteolysis. Tumor osteolysis was induced by in situ inoculation of Walker 256/B malignant cells. Six other rats were sham operated and served as control. Twenty days later, rats were euthanized, and femurs were collected than radiographed. Angioarchitecture [mean lumen diameter (MLD), wall thickness (WTh), Vessel number, volume, and separation (VNb, VV, and VSp respectively)] was studied by histomorphometry at 2 different positions (P1: diaphysis, and P2: metaphysis) of the operated femora. Some hematological parameters were also assessed. Walker 256/B induced marked tumor osteolysis, with cortical perforation and trabecular destruction, associated increase in bone vascularization (increases of VNb and VV and decrease of VSp). Angioarchitecture of W256/B rats was disorganized and showed large MLD and lower WTh. These effects were more prominent in P2. When compared to Sham group, significantly decreases at levels of red blood cell (RBC), hemoglobin (Hb), hematocrit (Ht), and white blood cell (WBC) were observed in W256/B rats. These results suggest that Walker 256/B cells induced tumor osteolysis, improve hypervasculature especially near the tumoral foci (P2) associated hematological disruption. Besides, tumor vessels showed abnormal (enlarged and thinner) and disorganized morphology.     

Altered distribution and excretion of N-1-methylnicotinamide in rats with Walker 256 carcinosarcoma.

Levels of nicotinamide and N-1-methylnicotinamide in serum, liver, and kidney as well as renal clearances and 24-hr urine levels of N-1-methylnicotinamide were compared in normal rats and rats bearing Walker 256 tumors. There was no significant difference between normal and tumor-bearing rats with regard to nicotinamide levels. With regard to N-1-methylnicotinamide, tumor-bearing rats had significantly lower serum and liver levels and significantly higher 24-hr urine levels and renal clearances. Walker 256 tumor tissue and liver and kidney from a normal and a tumor-bearing rat were separately examined for S-adenosylmethionine:nicotinamide methyltransferase activity. The specific activity in tumor tissue extract was greater than that in each liver extract, which, in turn, was much greater than the specific activity in each tissue (liver and kidney) from the tumor-bearing rat was equal to the specific activity in the corresponding tissue of the normal rat. S-adenosylmethionine:nicotinamide methyltransferase was obtained with 18-fold purification from a tissue extract of Walker 256 tumor. The enzyme activity required activation by thiols, and maximal activity was observed at pH 8.6. The Km's for the substrates, S-adenosylmethionine and nicotinamide, were 7.0 x 10--3 mM and 0.50 mM respectively. The Ki's for the products, S-adenosylhomocysteine and N-1-methylnicotinamide, were respectively, 25 x 10--3 mM and greater than 5 mM.     

Sequential elaboration of lymphocyte-enhancing and -suppressing factors in the sera of tumor-bearing animals

Serum-mediated impairment of lymphocyte function was studied in an animal model. Sprague-Dawley rats inoculated intraperitoneally or subcutaneously with the Walker 256 carcinoma underwent sequential sampling of blood. The effect of these serum samples upon phytohemagglutinin-induced blastogenesis of normal rat splenocytes was monitored in an assay utilizing incorporation of (3H)-thymidine. The effect of serum samples from both the subcutaneously and the intraperitoneally inoculated tumor-bearing animals was biphasic. Early on, serum enhanced blastogenesis and later suppressed blastogenesis. Separation of sera into high and low molecular weight components by ultrafiltration demonstrated the enhancing activity to reside in the high molecular weight fraction. The enhancing activity of sera decreased over time from tumor inoculation. Conversely, suppressor activity increased over time from tumor inoculation. This study demonstrated that suppressor activity of sera obtained from animals with advanced tumors is the result of the lack of enhancing activity coupled with the elaboration of suppressor activity.     

Hormones of the pituitary-adrenal axis in rats bearing the Walker 256 carcinoma

Male Sprague-Dawley rats (125-150 g) were implanted intramuscularly with the Walker 256 carcinoma. After 3, 5 or 7 days, tumor-bearing rats, along with controls, were killed and plasma levels of adrenocorticotropic hormone (ACTH), beta-endorphin and corticosterone were assessed. Plasma levels of all 3 hormones declined with time following tumor implantation. Plasma levels of ACTH and corticosterone were statistically significantly less than plasma levels of these same hormones in control rats by 7 days post-implantation. Levels of these hormones were reduced by 42% and 33%, respectively, relative to control levels by 7 days. beta-Endorphin levels declined much more rapidly following tumor implantation than did either of the other 2 hormones. beta-Endorphin was significantly decreased by 3 days post-implantation and by 7 days the plasma levels of this factor were 83% lower than in control rats.     

Pituitary-ovarian function in breast cancer patients on adjuvant chemoimmunotherapy.

One hundred thirty-one patients with operable breast cancer were treated with adjuvant chemoimmunotherapy consisting of 5-fluorouracil, adriamycin, cyclophosphamide, and BCG (FAC-BCG). Fifty-five of 131 patients were premenopausal of which 71% (38/55) became amenorrheic. To determine the mechanism of amenorrhea, we measured the immunoreactive serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH), and plasma estradiol (E2) before and after intravenous administration of luteinizing hormone-releasing hormone (LH-RH) in 11 unselected premenopausal patients who developed amenorrhea and 11 unselected patients who did not. Serum prolactin (PRL) levels were also measured before and after iv administration of thyrotropin-releasing hormone (TRH). Our results showed that patients who developed amenorrhea had abnormally high serum LH and FSH levels at basal and after LH-RH stimulation and low plasma estradiol. Serum PRL levels were normal. Patients who developed amenorrhea were older than those who did not, but their serum LH and FSH levels were also significantly higher and plasma estrogens were significantly lower than that found in 11 normal women with regular menses of the same age range. These results indicate that amenorrhea that develops in some patients with breast cancer after FAC-BCG therapy is a result of primary ovarian failure.     

Pharmacokinetics of nitrosoureas: levels of 1,3-bis-(2-chloroethyl)-1-nitrosourea (BCNU) in organs of normal and Walker 256/B carcinoma bearing rats after i.v. bolus

The disappearance of 1,3-bis(2-chlorethyl)-1-nitrosourea (BCNU) from plasma, liver, kidney, lung, brain, spleen, tumor tissue and epididymal adipose tissue of Walker 256/B carcinoma-bearing rats and healthy animals was measured by differential pulse polarography after i.v. bolus of the drug. Only BCNU, not its decomposition products, was detected by the polarographic assay. Levels of BCNU in liver of tumor-bearing animals were significantly lower (about 10 times) than those on healthy rats. A bi-exponential fit was used to calculate the kinetics of BCNU in plasma, kidney, lung and brain, but no difference could be found between healthy and Walker tumor-bearing rats. BCNU disappeared faster from adipose tissue of tumor-bearing animals than from normals.     

Pharmacokinetics of fotemustine and BCNU in plasma,liver and tumor tissue of rats bearing two lines of Walker 256 carcinoma

Summary The plasma and tissue pharmacokinetics of fotemustine (diethyl-1-[3-(2-chlorethyl)-3-nitrosoureido]-ethylphosphonate) and BCNU (1,3-bis-[2-chlorethyl]-1-nitrosourea) were investigated in healthy control rats and in animals bearing either the nitrosourea-sensitive line A (W256/A) or the nitrosourea-resistant line B (W256/B) of Walker 256 carcinoma. The antitumor activities of these nitrosoureas were similar following i.v. doses ranging from 10 to 40 mg/kg. For both drugs, the survival of tumor-bearing rats was lower in the W256/B than in the sensitive W256/A line. Some sex differences were observed, female rats being more responsive than males to both drugs. Nitrosourea concentrations were assayed in plasma and tissues by differential pulse polarography so as to assess whether the pharmacokinetics could explain the differences in antitumor activity. The antineoplastic effects of fotemustine seemed to be influenced by its pharmacokinetics. The plasma AUC of the intact nitrosourea was higher in females than in males. Fotemustine was cleared 2–5 times more slowly than BCNU from tumor tissue, and its clearance was higher in W256/B- than in W256/A-bearing rats. This suggests that the antitumor activity in the responsive line might partly be due to longer exposure of the growing tumor to the drug. The distribution volume of both nitrosoureas in plasma was higher in tumor-bearing animals than in healthy controls, indicating that the tumor tissue probably constitutes an additional distribution space.Abbreviations BCNU 1,3-bis-[2-chlorethyl]-1-nitrosourea - W256/A Walker carcinoma 256 line A - W256/B Walker carcinoma 256 line B     

Stimulatory effects of retinoic acid on tumor growth and serum insulin-like growth factor-1 in rats bearing estrogen-responsive pituitary tumor MtT/Se

MtT/Se is one of 4 cell lines derived from an estrogen-dependent pituitary tumor, MtT/F84. The main difference between these tumor types is that MtT/F84 secretes both growth hormone (GH) and prolactin (PRL) whereas MtT/Se secretes only GH. MtT/Se grew slowly in ovariectomized (ovex) rats, but tumor growth was much faster in estrogen-treated ovex rats. Effects of dietary retinoic acid (RA) on tumor growth, serum GH and insulin-like growth factor-1 (IGF-1) levels were examined in ovex rats. Latency of tumor growth was shortened, and tumor take and weight were promoted by all-trans RA both in the presence and absence of exogenous estrogen. Serum GH and IGF-1 levels became increased in tumor-bearing rats whereas PRL levels remained unchanged. Serum IGF-1 levels exhibited a good correlation with tumor weights (r = 0.84). Our results suggest a close relationship between increase of tumor weight and stimulation of serum IGF-1 level by RA in tumor-bearing rats.     

Mechanical analysis of tumor growth regression by the cyclooxygenase-2 inhibitor, DFU, in a Walker256 rat tumor model: importance of monocyte chemoattractant protein-1 modulation.

Cyclooxygenase (COX)-2 inhibition results in tumor regression; however, little is known about the mechanism. In the present study, using a Walker256 tumor model and a rat bone marrow-derived endothelial cell line TR-BME-2, we analyzed the effects of a new selective COX-2 inhibitor, 5,5-dimethyl-3-(3-fluorophenyl)-4-(4-methylsulphonyl)phenyl-2-(5H)-furanone (DFU), on the production of chemokines and growth factors and on the neovascularization. The oral administration of DFU (5 mg/kg/d) significantly suppressed the tumor growth with decreasing microvessel density in vivo, although it showed no direct inhibition of Walker256 cell proliferation in vitro. It was newly found that the recruitment of systemically injected TR-BME-2 cells into the tumor site was significantly inhibited by DFU treatment. In addition, we found that DFU significantly reduced the production of monocyte chemoattractant protein-1 (MCP-1) both in tumor tissues and in the systemic circulation (P < 0.001 and P < 0.001, respectively). Such reduction was not observed in other chemotactic factors, vascular endothelial growth factor and stromal cell-derived factor-1. The induced chemotaxis of TR-BME-2 by serum of tumor-bearing rats was significantly reduced in DFU-treated rat serum, although DFU showed no direct inhibition for TR-BME-2 cells, either cell growth or chemotaxis. Treatment with neutralizing antibodies to soluble mediators, including MCP-1, significantly suppressed the chemotaxis. Regarding the down-regulation machinery of MCP-1 production in vivo, tumor-associated macrophages seem to play crucial roles, because DFU eliminated MCP-1 production in the activated macrophages remarkably but not in Walker256 tumor cells in vitro. In conclusion, COX-2 inhibitor DFU exerts tumor regression activity in a Walker256 tumor model by suppressing MCP-1 production in tumor tissues and in the circulation.     

慢性应激性抑郁对荷瘤大鼠存活期及免疫功能的影响

目的通过动物实验观察不同程度的应激性抑郁对荷瘤大鼠存活期及免疫功能的影响。方法将体重170～180g健康SD雌性大鼠48只随机分为四组：单纯种瘤组（A组）、接种瘤细胞后给予应激性抑郁组（B组）、接种瘤细胞前给予应激性抑郁组（C组），以及接种瘤细胞前后均给予应激性抑郁组（D组），观察各组大鼠皮下接种Walker 256癌肉瘤细胞后的存活期，并检测大鼠的血液T淋巴细胞亚群CD4^＋和CD8^＋细胞百分率及CD4^＋／CD8^＋比值、血清皮质醇等指标。结果与A组相比，D组大鼠生存期显著缩短（P〈0.05），其余各组大鼠相比较，存活期差异无显著性；与A组相比，D组大鼠CD4^＋细胞百分率显著降低（P〈0.05），并且D组大鼠CD4^＋细胞百分率比B、C组亦显著降低（P〈0.05）。各组大鼠CD8^＋细胞百分率差异无显著性（P〉0.05）。与A组相比，B、C、D组大鼠CD4＋／CD8^＋比值显著降低（P〈0.05），D组大鼠CD4^＋／CD8^＋比值比B、C组亦显著降低（P〈0.05）；与A组相比，B、C、D组大鼠血清皮质醇水平显著升高（P〈0.05），D组大鼠血清皮质醇水平比B、C组亦显著升高（P〈0.05）。结论较长时间的慢性应激性抑郁可以显著缩短荷瘤大鼠的生存期，而T淋巴细胞亚群失调以及皮质醇水平升高而导致的免疫功能降低可能是其作用机制之一。     

Host-mediated therapeutic effects produced by appropriately timed administration of bleomycin on a rat fibrosarcoma

The timing of bleomycin (BLM) administration after KMT-17 tumor inoculation was found to be important for optimizing its therapeutic effect on tumor-bearing rats. A remarkable therapeutic effect was observed when BLM (5 mg/kg/day) was administered i.p. for 5 days from the eighth day after tumor inoculation (Day 8 to Day 12) rather than when BLM was administered i.p. for 5 days during the days immediately following tumor inoculation (Day 1 and Day 5) (cured rats/treated rats: 10/21 and 2/16, respectively). By means of a Winn assay, stronger tumor-neutralizing activities were observed in spleen cells from BLM (Day 8 to Day 12)-treated tumor-bearing rats than were observed in spleen cells from BLM (Day 1 to Day 5)-treated tumor-bearing rats (% Inhibition: 70.9 and 49.3%, respectively). These therapeutic effects were thus found to be consistent with the antitumor immunity against KMT-17. The enhanced tumor-neutralizing activities of spleen cells from BLM-treated tumor-bearing rats were suppressed by adding spleen cells from nontreated tumor-bearing rats. In cell transfer experiments, an antitumor transplantation resistance in rats immunized with irradiated KMT-17 cells was abrogated by an adoptive transfer of spleen cells from untreated tumor-bearing rats or BLM (Day 1 to Day 5)-treated tumor-bearing rats but not from BLM (Day 8 to Day 12)-treated tumor-bearing rats. These results suggest that, when BLM is administered during a late stage of tumor growth, it is effective in eliminating suppressor cells and that this leads to an improvement in the therapeutic effects of the drug.     

肿瘤致SD大鼠全骨病变的有效观察指标筛选

建立可靠的大鼠肿瘤模型，针对恶性肿瘤所致的高血钙及肿瘤转移所天才 的骨病变，找出有意义的观察指标。方法将Ｗａｌｋｅｒ２５６癌肉瘤细胞接种于大鼠右后肢胫骨上段骨旁肌肉内，１４天后局部肿瘤生长。随后对血钙、磷、碱性磷酸酶（ＡＫＰ）、尿羟脯氨酸、全身平均骨密度５项指标进行测定和分析。结果与对照组相比，肿瘤生长组大鼠血钙明显升高（Ｐ〈０．０１），全身平均骨度明显降低（Ｐ〈０．０５），尿羟脯氨酸排泄啬而血磷     

~(153)Sm-乙二胺四亚甲基膦酸对 Walker 256癌荷瘤大鼠骨侵袭骨溶解的抑制作用

目的研究１５３Ｓｍ－乙二胺四亚甲基膦酸（１５３Ｓｍ－ＥＤＴＭＰ）对荷瘤大鼠骨侵袭、骨溶解的抑制作用。方法运用Ｘ线骨骼照片和胫骨病理切片，观察Ｗａｌｋｅｒ２５６癌大鼠模型的肿瘤骨侵袭和骨溶解情况。结果荷瘤大鼠静脉注射１５３Ｓｍ－ＥＤＴＭＰ７４，１４８ＭＢｇ／ｋｇ后，遭受Ｗａｌｋｅｒ２５６癌侵袭及发生骨溶解的胫骨数减少近一半，３７ＭＢｇ／ｋｇ组对癌的骨侵袭和骨溶解仍有抑制作用。但各组大鼠的移植瘤重量没有差异。结论１５３Ｓｍ－ＥＤＴＭＰ能抑制Ｗａｌｋｅｒ癌模型大鼠骨侵袭和骨溶解，但对移植瘤生长无抑制作用，故其抗癌骨侵袭、骨溶解的作用不是通过抑制动物移植瘤生长来实现的。     

^153Sm—乙二胺四亚甲基膦酸对Walker256癌荷瘤大鼠骨侵袭骨溶解…

目的 研究＾１５３Ｓｍ－乙二胺四亚甲基膦酸（＾１５３Ｓｍ－ＥＤＴＭＰ）对荷瘤大鼠骨侵袭、骨溶解的抑制作用。方法 运用Ｘ线骨骼照片和胫骨病理切片,观察Ｗａｌｋｅｒ２５６癌大鼠模型的肿瘤骨侵袭和骨溶解情况。结果 荷瘤大鼠静脉注射＾１５３Ｓｍ－ＥＤＴＭＰ７４,１４８ＭＢｇ／ｋｇ后,遭受Ｗａｌｋｅｒ２５６癌侵袭及发生骨溶解的胫骨数减少近一半,３７ＭＢｇ／ｋｇ组对癌的骨侵袭和骨溶解仍有抑制作用。但各组大鼠的     

Restoration of immunologic responsiveness by PSK in tumor-bearing animals

PSK is a protein-bound polysaccharide prepared from cultured mycelium of the Basidiomycete Coriolus versicolor. Effects of PSK on the immunologic responsiveness in tumor-bearing animals were investigated using syngeneic or allogeneic tumors in mice (Lewis lung carcinoma, B16 melanoma, Meth A fibrosarcoma, adenocarcinoma 755, X5563 plasmacytoma, colon 26, MOPC 31C myeloma, sarcoma 180 and Ehrlich carcinoma), rats (BC47 bladder carcinoma, Walker 256 sarcoma and AH7974 hepatoma), hamsters (HA-1T tumor and RPMI 1846 melanoma), guinea pigs (line-10 hepatoma) and rabbit (VX2 and VX7 tumor). Oral or intraperitoneal administration of PSK restored the depressed delayed hypersensitivity against sheep erythrocytes to a normal level in these tumor-host systems. Also, oral administration of PSK lowered the activity of immunosuppressive substances in the serum of tumor-bearing animals. These results suggest that PSK exhibits antitumor effects by restoring the depressed immunologic responsiveness in tumor-bearing animals.     

Effects of the thiazolidinedione derivative CGP 19984 on growth and endocrine function of the MtT-W10 transplantable mammosomatotropic pituitary tumor in female rats

The thiazolidinedione derivative CGP 19984 has previously been shown to suppress the growth of hormone-dependent mammary and prostatic tumors, primarily by reducing gonadotropin and subsequently gonadal steroid secretion. The present study examines the effects of CGP 19984 on the growth and hormone secretion of the autonomous, but estrogen-responsive, MtT-W10 mammosomatotropic transplantable rat pituitary tumor. Intact tumor-bearing Wistar/Furth female rats were administered vehicle or 25, 100, or 250 mg/kg CGP 19984 p.o., 5 x week for 4 weeks. CGP 19984 was found to significantly reduce MtT-W10 tumor growth and weight and reduce prolactin and growth hormone (GH) secretion in a dose-responsive manner. A similar study in ovariectomized rats also showed that CGP 19984 treatment suppressed MtT-W10 pituitary tumor growth, weight and hormone secretion in a dose-responsive manner, suggesting a direct inhibitory action of this drug on the tumor. In a third study, bromocryptine (CB-154; 5 mg/kg) and CGP 19984 (50 mg/kg) were both found to be effective in suppressing growth of the MtT-W10 tumor in intact female rats. However, rats treated with CGP 19984 alone had reduced serum and tumor GH and prolactin concentrations, while rats treated with CB-154 alone had reduced serum and tumor prolactin, but no change in GH concentrations. These results suggest that CGP 19984 effectively inhibits growth and hormone secretion of the autonomous MtT-W10 pituitary tumor by apparently suppressing both somatotropic and lactotropic cell populations within the tumor. Furthermore, these findings indicate that CGP 19984 may be an effective alternative to CB-154 in the clinical treatment of prolactin-producing adenomas, as well as other types of pituitary adenomas.