Pigmented uveal tumours in a transgenic mouse model

Area of Science:

• Oncology
• Genetics
• Ophthalmology

Background:

• Transgenic mouse models are crucial for studying cancer development.
• Targeted gene expression allows investigation of specific cellular pathways in disease.
• Melanin-producing cells, including those in the eye, are susceptible to oncogenic mutations.

Purpose of the Study:

• To characterize intraocular tumors in transgenic mice engineered to express a mutated Ha-ras gene in melanin-producing cells.
• To investigate the histopathological and ultrastructural features of these tumors using light and electron microscopy.

Main Methods:

• Development of transgenic mouse strains (TPras) using a tyrosinase promoter to target mutated T24 Ha-ras expression.
• Histopathological analysis of formalin-fixed tissues from TPras and control mice.
• Electron microscopy of glutaraldehyde/formalin-fixed tissues to examine cellular ultrastructure.

Main Results:

• Bilateral pigmented melanocytic/RPE proliferations were observed in six of eight TPras mice.
• Tumor cytology revealed low N:C ratios and abundant melanin in benign cases.
• Electron microscopy identified distinct spindle-shaped and cuboidal cell populations with varying melanin granule morphology.
• Two TPras mice exhibited higher-grade melanocytic proliferation morphologically consistent with melanoma, characterized by increased N:C ratios and nuclear pleomorphism.

Conclusions:

• Transgenic expression of a mutated Ha-ras gene in melanin-producing cells induces intraocular pigmented tumors in mice.
• The observed tumors represent a spectrum from benign melanocytic/RPE proliferations to malignant melanoma.
• This mouse model provides a valuable tool for studying the pathogenesis of uveal tract melanomas.