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Octreotide treatment suppresses malignant somatotrophic pituitary tumor cell growth in rats
1The First Department of Internal Medicine, Nagasaki University School of Medicine, Nagasaki 852-8501, Japan.
Abstract:
We have recently established an in vitro cell line (metastatic mGH3) derived from lymph node metastases of the rat pituitary somatotroph. Here we examined the in vivo effects of octreotide, a somatostatin analog, against malignant pituitary tumors. Wistar-Furth rats (n=8) were inoculated subcutaneously with mGH3 cells while control rats received injections of equal volumes of the vehicle only. Four rats were treated with octreotide three times daily while another group of four rats were treated with saline only. After 6 weeks of treatment, histopathological and immunohistological analyses were performed. The tumor weights of rats treated with octreotide were significantly lighter than those of untreated rats. All rats implanted mGH3, but not administered treatment, developed inguinal lymph node metastases, whereas none of those implanted mGH3 and treated with octreotide developed such metastases. The proportion of PCNA-stained tumor cells was higher in tumors of untreated rats than in those of octreotide-treated rats. However, the proportion of apoptotic cells in the tumor was not different between treated and untreated rats. Our results suggest that octreotide might be potentially effective for invasive and malignant human pituitary tumors by regulating the tumor cell cycle.
Insights
Octreotide, a somatostatin analog, significantly reduced tumor weight and prevented lymph node metastases in rats with malignant pituitary tumors. This suggests potential efficacy for invasive human pituitary tumors by influencing the tumor cell cycle.
Area of Science:
- Endocrinology
- Oncology
- Pharmacology
Background:
- Malignant pituitary tumors, particularly somatotroph tumors, pose significant clinical challenges.
- An in vitro cell line (metastatic mGH3) derived from rat pituitary somatotroph lymph node metastases was established.
- The therapeutic potential of somatostatin analogs in pituitary tumors requires further investigation.
Purpose of the Study:
- To evaluate the in vivo efficacy of octreotide, a somatostatin analog, against experimentally induced malignant pituitary tumors.
- To assess the impact of octreotide on tumor growth, metastasis, and cell proliferation/apoptosis in a rat model.
Main Methods:
- Establishment of a metastatic rat pituitary somatotroph cell line (mGH3).
- Subcutaneous inoculation of mGH3 cells into Wistar-Furth rats, followed by treatment with octreotide or vehicle.
- Histopathological and immunohistological analyses, including assessment of tumor weight, lymph node metastasis, and cell proliferation (PCNA) and apoptosis markers.
Main Results:
- Octreotide treatment resulted in significantly lighter tumor weights compared to controls.
- None of the octreotide-treated rats developed lymph node metastases, unlike the untreated group.
- A higher proportion of PCNA-stained cells was observed in untreated tumors, indicating increased cell proliferation.
- No significant difference in the proportion of apoptotic cells was found between treated and untreated groups.
Conclusions:
- Octreotide demonstrates significant anti-tumor effects, including reduced tumor growth and prevention of metastasis, in a rat model of malignant pituitary tumors.
- The mechanism appears to involve regulation of the tumor cell cycle, specifically reducing proliferation.
- These findings suggest that octreotide holds potential as a therapeutic agent for invasive and malignant human pituitary tumors.