Survival Of Tumor-bearing Rats Research Articles

Pterostilbene promotes mitochondrial apoptosis and inhibits proliferation in glioma cells

Glioma is the most general primary and lethal intracranial malignant tumor. Pterostilbene (PTE), an analog of stilbene and resveratrol, has attracted attention in recent years due to its significant antitumor activity in multiple solid tumors; however, its effect on drug-resistant glioma cells and the underlying mechanism have not yet been reported. In this study, we found that pterostilbene inhibited proliferation, induced intrinsic mitochondria-mediated apoptosis and caused S phase arrest, inhibited migration and excessive invasion in glioma cells. Pretreatment with the pan-caspase-inhibitor Z-VAD-FMK attenuated the PTE-induced apoptosis of glioma cells. Moreover, PTE significantly increased the production of reactive oxygen species (ROS) and reduce the mitochondrial membrane potential (MMP). Inhibition of ROS with N-acetyl-l-cysteine not only rescued PTE-induced reduction of cellular viability but also prevented glioma cell apoptosis. We also discovered ERK 1/2 and JNK signaling pathways were activated by PTE and contributed to induce glioma cell apoptosis. In addition, specific inhibitors of ERK 1/2 and JNK attenuated PTE-induced apoptosis. Besides, PTE significantly reduced tumor volume and prolonged median survival of tumor-bearing rats in vivo. In summary, the results of this study indicate that the anti-tumor effect of PTE on glioma cells may provide a new treatment option for glioma patients.

Preventative effect of celecoxib in dimethylbenz[a]anthracene-induced ovarian cancer in rats.

The present study investigated the preventive effect of the cyclooxygenase (COX)-2 inhibitor, celecoxib, in 7,12-dimethylbenz[a]anthracene (DMBA)-induced ovarian cancer in a rat model. A diet containing celecoxib (1500ppm) was started 2weeks before the introduction of DMBA. DMBA-soaked cotton threads were surgically applied to induce ovarian cancer in female Wistar rats. Tumor growth and survival were observed for 24weeks. During the study period, an overall tumor incidence of 97.5% was observed and 65% of tumors were ovarian adenocarcinoma. The celecoxib diet significantly reduced the incidence and size of DMBA-induced ovarian cancers and significantly improved survival of tumor-bearing rats. The preventive effect of celecoxib was associated with increased apoptosis. DMBA-induced ovarian cancer in rats recapitulates many pathophysiological features of the human counterpart. Our results provide supportive evidence that celecoxib has a preventive effect on development of ovarian cancer in a rat model.

Ambiguous effect of signals transmitted by the vagus nerve on fibrosarcoma incidence and survival of tumor-bearing rats

While the parasympathetic nervous system appears to be involved in the regulation of tumor progression, its exact role is still unclear. Therefore, using a rat BP6-TU2 fibrosarcoma tumor model, we investigated the effect of (1) reduction of vagal activity produced by subdiaphragmatic vagotomy; and (2) enhancement of vagal activity produced by continuous delivery of electric impulses to the cervical part of the vagus nerve on tumor development and survival of tumor-bearing rats. We also evaluated the expression of cholinergic receptors within in vitro cultivated BP6-TU2 cells. Interestingly, we found that both, vagal stimulation and subdiaphragmatic vagotomy slightly reduced tumor incidence. However, survival of tumor-bearing rats was not affected by any of the experimental approaches. Additionally, we detected mRNA expression of the α1, α2, α5, α7, and α10 subunits of nicotinic receptors and the M1, M3, M4, and M5 subtypes of muscarinic receptors within in vitro cultivated BP6-TU2 cells. Our data indicate that the role of the vagus nerve in modulation of fibrosarcoma development is ambiguous and uncertain and requires further investigation.

Comparison of biological characteristics between C6 glioma cells and a stable C6 glioma cell line expressing enhanced green fluorescent protein

Objective To establish a stable C6 glioma line expressing enhanced green fluorescent protein (EGFP).Methods C6 glioma cells were transfected with the lentivirus vector enhancer promoter CMV and elongation factor-1α (EF-1α).C6 cells expressing EGFP were observed under the fluorescence microscopy and screened by flow cytometry.Tumorigenicity was evaluated by establishment of mouse skin and intracranial glioma model.Tumor volume was measured,and hematoxylin and eosin (HE) staining,immunohistochemical glial fibrillary acidic protein (GFAP) staining and MRI were used to monitor the tumor volume.Results Morphology observed under a fluorescence microscope and proliferation detected by methyl thiazol tetrazolium (MTT) of EGFP-C6 cells were similar to those of C6 cells (0.53 ±0.02 vs.0.51 ± 0.01).Subcutaneous model results showed there were no significant differences in tumor volume [C6:(2.20 ±0.91) cm3 and EGFP-C6:(2.10 ±0.84) cm3],HE staining and GFAP staining between EGFP-C6 and C6 cells.Intracranial model results showed there were no significant differences in tumor volume calculated by MRI [C6:(20.5±2.3) cm3 and EGFP-C6:(19.5±2.3) cm3],the survival of tumor-bearing rats,tumor formation rate,and the extracranial metastasis rate.Conclusion EGFP-C6 cell line expressing EGFP as a marker was established.Biological characteristics of EGFP-C6 cells were similar to those of C6 cells. Key words: Glioma; Biological characteristics; Enhanced green fluorescent protein

Abstract 2447: Measurement of tumor vascular integrity changes in an orthotopic glioma model in rats induced by antiangiogenic treatment using DCE-MRI

Abstract Background Glioblastoma is the most aggressive subtype of brain tumors. Antiangiogenic compounds are being tested in clinical trials, for this pathology, mostly in combination with other molecules. The availability of an imaging biomarker of efficacy could help optimize the dosing and scheduling of these combinations. The aim of this study was to validate DCE-MRI, using two contrast agents of different molecular weight, as an imaging biomarker of the efficacy of sorafenib (Nexavar®, BAY 43-9006) in an orthotopic glioma model in Nude rats. Methods U-87 MG human glioma cells were inoculated by stereotactic injection in the right caudate nucleus of 24 Nude rats. All rats were first imaged 10 days after cell injection to measure their baseline tumor volume (TV) using T2-weighted MRI (Bruker Pharmascan, 4.7T). Based on their TV, 20 rats were selected and imaged at D-1 (14 days after cell injection). The rats were then randomized into 2 groups of 8 rats according to their tumor vascular status following a full DCE-MRI protocol using either Gd-DTPA (Magnevist®) or P846 (two parameters: Ktrans from pharmaco-kinetic modeling of the contrast agent uptake curve, and iAUC60, the initial area under the gadolinium concentration time curve after 60 seconds). P846 is a medium-molecular weight, gadolinium-based contrast agent provided by Dr P. Robert (Guerbet). In both subgroups of 8 rats, each animal received a daily per os administration of either sorafenib (100 mg/kg/adm) or its vehicle. All 16 rats were then imaged at D1, D3 and D7. At each time point, voxelwise maps of DCE-MRI parameters were derived from imaging data and their distribution analyzed within regions of interest within the tumor and the contralateral lesion-free tissue. Results Sorafenib was well tolerated and it increased the median survival of tumor-bearing rats by 20%. At D7, despite no difference in tumor growth kinetics, DCE-MRI parameters (Ktrans and iUAC60) showed significant differences between sorafenib-treated and control groups using either Magnevist® or P846. Visual assessment showed that the heterogeneity of contrast agent uptake was reduced by antiangiogenic treatment with sorafenib. The quantification of this phenomenon by statistical analysis of the parameter distributions within the ROIs is pending. Conclusions In conclusion, we have shown that DCE-MRI, with either Magnevist® or P846 contrast agents, is a suitable non-invasive imaging technique to show changes of tumor vasculature integrity induced by antiangiogenic treatment such as sorafenib in orthotopically-implanted glioma in Nude rats. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 103rd Annual Meeting of the American Association for Cancer Research; 2012 Mar 31-Apr 4; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2012;72(8 Suppl):Abstract nr 2447. doi:1538-7445.AM2012-2447

Prolonged survival of rats with intracranial C6 gliomas by treatment wit~ TGF-β antisense gene

Using an intracranial rat C6 glioma model, we tested the hypothesis that gene modification ofglioma cells to block the expression of the immunosuppressive cytokine TGF-[3 (transforming growth factor (3) may enhance anti-tumor immune responses and thereby prolong survival of tumor-bearing animals. The cDNA for simian TGF-β2 was ligated in antisense orientation into the episomal plasmid mammalian expression vector pCEP-4. This TGF-β-antisense vector was transfected into C6 glioma cells by standard electroporation techniques. PCR was used to determine that the rat C6 clones were successfully transfected with the antisense-TGFβ construct. Twenty-nine adult female Wistar rats harboring 7-day-old intracranial C6 tumors were then subcutaneously injected with either saline (n = 9), unmodified C6 glioma cells (n =10), or TGF-β-antisense-modified C6 cells (n =70). Animals were followed, for survival, and Fisher!s exact method was used to interpret the significance of differences between experimental groups. The survival of tumor-bearing rats injected with TGF-β-antisense-modified C6 cells was significantly prolonged! relative to the survival of rats receiving injections of saline or unmodified C6 cells alone. Six of the ten (60%) TGF-β-antisense treated animals survived for 72 weeks! whereas none of the nine (0%) animals treated with saline and none of ten (0%) of those treated with C6 cells alone survived past 5 weeks. These results indicate that the genetic inhibition of immunosuppressive cytokines (such as TGF-(3) may reverse the phenotypic immunosuppression caused by such factors, and thereby prolong the survival of C6 tumorbearing animals. Future investigations using cytokine gene modifications in other brain tumor models are warranted. [Neural Res 1998; 20: 742–747]

Peculiarities of tumor growth in pregnant rats

The development of a transplantable tumor (Zajdela ascitic hepatoma) is studied in pregnant rats. Pregnancy is shown to retard tumor growth and influence its course. It prolongs the survival of tumor-bearing rats and induces total regression of the tumor in 15–20% of cases; pregnancy causes the ascitic growth to be transformed into a solid form, and prevents the development of hemorrhagic ascites.

Effect of aging and interval between primary and secondary treatment in carcinogenesis induced by neonatal exposure to 5-bromodeoxyuridine and subsequent administration of N-nitrosomethylurea in rats.

LIO rats were exposed to s.c. injections (3.2 mg) of a synthetic analogue of thymidine, 5-bromo-2'-deoxyuridine (BrdUrd) on the 1st, 3rd, 7th and 21st days of life and at the age of 3 or 15 months they were i.v. injected with N-nitrosomethylurea (NMU) at a single dose of 10 or 50 mg/kg or with solvent. It was shown that early neonatal exposure to BrdUrd was followed by the increase in the incidence of tumor development and by the decrease of their latency. The carcinogenic effect of NMU alone correlated with the dose of the carcinogen in 3-month-old rats total and malignant tumors and tumors of some localization was decreased in the elder ones, but survival of tumor-bearing rats was decreased in the elder group as compared to the younger one. These data suggests the age-related decrease in both the carcinogenic effect of NMU and in the number of events which are necessary for a tumor development. The exposure to BrdUrd was followed by the increase in the susceptibility of rats to subsequent carcinogenic effect of NMU injected at the doses of 10 or 50 mg/kg into 3- and 15-month-old rats, mostly to the tissues being target to NMU. Our data have demonstrated that the exposure to BrdUrd in the early life was followed by the irreversible initiating effect which persists over a long time in a several tissues.

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

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.

Suppression of rat tumor colonies in the lung by oxygen at high pressure is a local effect

The effect of hyperbaric oxygen (HBO) on the growth of anaplastic carcinoma colonies in rat lungs after intravenous tumor cell injection was studied. From the first day after tumor cell injection, the rats were exposed to HBO for 16-21 days, 90 min per day. Oxygen at a pressure of 300 kPa (3.0 ATA) significantly decreased the number of lung tumor colonies and increased the survival of tumor-bearing rats, whereas the application of oxygen at a pressure of 100 kPa had no effect. An oxygen-nitrogen normoxic mixture balanced with nitrogen to 300 kPa (3.0 ATA) did not affect the number of colonies, suggesting that the effect was specific for oxygen and not for the increased pressure itself. A 6-day application of oxygen at a 300 kPa pressure suppressed the growth of lung tumor colonies when applied on days 1-6 and 7-12 after intravenous tumor cell injection, but had no effect when applied on days 13-18. In contrast to dramatic effects of HBO on the development of artificial lung metastases, the oxygen at the same 300 kPa pressure had no effect on the growth of tumor cells injected in the hind foot. Thus it appears that the suppression of lung tumor colonies by HBO was due to local oxygen effects in the lungs.

Effects of short-term dietary restriction on survival of mammary ascites tumor-bearing rats.

We studied the effects of short-term dietary restriction on the survival of 3-4-month-old tumor-free and tumor-bearing Fisher rats. The diet-restricted food regimen consisted of alternate day ad libitum feeding followed by alternate day fasting. Diet-unrestricted control rats were fed ad libitum daily. Six tumor-free rats on the diet-restricted regimen compensated for the dietary restriction by an increase in food consumption during the alternate feeding days, and lost an average of only 2-3% of their weight in 13 days. Six tumor-free rats on a daily ad libitum feeding regimen gained an average of 6.8% in 15 days. The above dietary-restricted regimen was initiated 1 week before 24 rats were inoculated intraperitoneally with 15 million Mat 13762 ascites tumor cells. Sixteen of 24 (66.7%) diet-restricted tumor-bearing hosts and 5/24 (20.8%) diet-unrestricted tumor-bearing hosts survived at 9 days after tumor inoculation (p less than 0.005). Twelve of 24 (50%) diet-restricted tumor-bearing hosts, and 3 of 24 (12.5%) diet-unrestricted tumor-bearing hosts, survived at 10 days after tumor inoculation (p less than 0.025). Thus, the survival of tumor-bearing rats was enhanced by short-term relatively mild dietary restrictions. We suggest that relatively mild dietary restrictions should be included in clinical trials designed to inhibit cancer growth and enhance the survival of human cancer patients.