Chemokine and Chemokine Receptor Expression in Two Models of Primary Intraocular Lymphoma

Abstract

Purpose: : Two murine models of primary intraocular lymphoma (PIOL) have been recently developed by intraocular injection of either T– [murine Rev–2–T–6 cell (T)] or B– [human Burkitt’s lymphoma cell (B)] lymphoma cell lines. In both models, lymphoma cells migrate to the RPE beneath the neuroretina, which is characteristic of human PIOL. This study compares the immunopathology and molecular pathology between both models to better understand the molecular, cellular and immunologic mechanisms of the malignancy and the homing of PIOL cells.

Methods: : EBV–negative B (0.2– or 5 X 10⁵) cells were inoculated intravitreally into 6 SCID adult mice. T (0.5– or 1 X 10⁵) cells were inoculated intravitreally into 6 BALB/c adult mice. Control SCID and BALB/c mice were injected with PBS intravitreally. Two weeks post inoculation, all mice were euthanized and the eyes were harvested and frozen. Routine histology was performed. Microdissection of tumor or retina was done for RNA isolation. Gene expression was quantified via real–time RT–PCR for chemokines (T–cell: CCL3, B–cell: CXCL12), chemokine receptors (T–cell: CCR1, B–cell: CXCR4), and cytokines (IL–6, TNF–α, and IL–10).

Results: : In both models, lymphoma cells were found mainly in the vitreous, retina, and subretinal space above the RPE. In severe cases, tumor invaded into the choroid, sclera and even the orbit. All control mice had normal morphology. Compared to controls, retina from SCID B– and BALB/c T–inoculated mice had a 1.33– and 0.7–fold change in CXCL12 expression, respectively. Retinas from SCID B– and BALB/c T–inoculated mice had a 0.72– and 1.93–fold change in CCL3 expression compared to controls. B–lymphoma cells had a 3.22–fold change in CXCR4 compared to human cDNA. T–lymphoma cells had a 1.54–fold change in CCR1 expression compared to mice controls. Compared to controls, retina from BALB/c T– and SCID B–inoculated mice had a 10.23– and 2.84–fold change in IL–6 expression, a 0.19– and 0.65–fold change in IL–10 expression, and a 5.07– and 4.20–fold change in TNF–α expression, respectively; indicating a low inflammatory response in SCID mice.

Conclusions: : Ocular chemokine gene profiles correlated well with chemokine receptors of B– and T– lymphomas. Chemokines could attract the respective lymphoma–expressed chemokine receptors to specific retinal sites. Targeting specific chemokines may be useful to treat PIOL.

Keywords: oncology • cytokines/chemokines • pathology: experimental