Pathophysiology of ocular surface squamous neoplasia

Area of Science:

• Ophthalmology
• Oncology
• Virology

Background:

• Ocular surface squamous neoplasia (OSSN) incidence correlates with solar ultraviolet (UV) radiation, HIV, and human papilloma virus (HPV).
• Africa exhibits the highest global incidence rates, with lesions typically located at the limbus within the interpalpebral fissure, especially the nasal sector.
• The nasal limbus, receiving intense sunlight, contains concentrated limbal epithelial crypts with stem cells, potentially serving as OSSN progenitors.

Purpose of the Study:

• To investigate the potential role of limbal epithelial stem cells as progenitors in OSSN development.
• To elucidate the mechanisms by which UV radiation and HPV contribute to OSSN pathogenesis.
• To understand factors influencing OSSN growth, metastasis, and unilateral presentation.

Main Methods:

• Analysis of UV-induced DNA damage, specifically p53 gene mutations (CC → TT dimers).
• Examination of HPV's role, including E6 and E7 protein functions on p53 and retinoblastoma genes.
• Assessment of immunosuppression's impact (UV, HIV, Vitamin A deficiency) on tumor immune surveillance.
• Investigation of tumor growth factors: telomerase, vascular endothelial growth factor (VEGF), and matrix metalloproteinases (MMPs).

Main Results:

• UV radiation causes DNA damage, leading to p53 mutations that bypass cell cycle checkpoints.
• HPV's E6 and E7 proteins disrupt cell cycle control and promote proliferation.
• Immune suppression compromises tumor surveillance, facilitating aberrant cell survival.
• Telomerase reactivation, VEGF, and MMPs enhance tumor growth and metastasis.

Conclusions:

• OSSN development involves UV-induced DNA damage in limbal stem cells and HPV infection, exacerbated by immunosuppression.
• The precise mechanism of HPV conjunctival entry and the reason for unilateral disease remain unclear.
• Further research is needed to fully understand OSSN pathogenesis and develop targeted therapies.