Serially transplantable chemically induced rat islet cell tumor

Area of Science:

• Endocrinology
• Oncology
• Cell Biology

Background:

• Pancreatic islet cell tumors, particularly insulinomas, are challenging to study due to their rarity and difficulty in establishing reliable models.
• Developing a transplantable tumor model is crucial for investigating the pathogenesis and therapeutic strategies for these neoplasms.

Purpose of the Study:

• To establish and characterize a serially transplantable pancreatic islet cell tumor in Lewis rats.
• To evaluate the tumor's biological behavior, cellular composition, hormonal content, and effects on recipient animals.

Main Methods:

• Chemical induction of pancreatic islet cell tumors using streptozotocin and nicotinamide in Lewis rats.
• Serial transplantation of tumor fragments into recipient rats for tumor maintenance and study.
• Histological and immunocytochemical analyses (peroxidase staining) to identify cell types (insulin, somatostatin, glucagon).
• Electron microscopy to examine cellular ultrastructure.
• Biochemical assays of tumor extracts for hormone content.
• Monitoring of plasma glucose levels and examination of recipient animal islets.

Main Results:

• A transplantable pancreatic islet cell tumor was successfully established and maintained.
• Tumors were encapsulated, non-metastatic, and grew to 0.5–2.0 cm within 3–4 months.
• Immunocytochemistry revealed a predominance of insulin-positive cells, with varying numbers of somatostatin-positive and small numbers of glucagon-positive cells.
• Electron microscopy showed abundant cells with secretory granules similar to nonneoplastic beta-cells.
• Tumor extracts were rich in insulin, somatostatin, and glucagon.
• Tumors induced progressive hypoglycemia in recipients, with plasma glucose levels often below 30 mg/dl.
• Recipient animals exhibited reduced islet size and decreased beta-cell volume.

Conclusions:

• A chemically induced, serially transplantable pancreatic islet cell tumor model was developed in rats.
• This model mimics key features of human insulinomas, including hormone production and hypoglycemia induction.
• The model provides a valuable tool for studying pancreatic islet cell tumor biology and testing potential therapies.