Immunocytochemical demonstration of interphotoreceptor retinoid-binding protein in cerebellar medulloblastoma

Abstract

Previously, immunoreactive rod-opsin and S-antigen (arrestin), two highly characteristic markers of retinal photoreceptors and pinealocytes, were shown to be present in certain medulloblastoma cells. It, thus, has been suggested that such cells differentiate along the photoreceptor lineage. This is corroborated in the present immunocytochemical investigation using antibodies against another photoreceptor-cell marker, the interphotoreceptor retinoid-binding protein (IRBP). As shown in preparations of human retina and pineal organ, IRBP can be successfully demonstrated in formalin-fixed and paraffin-embedded tissue: the IRBP immunoreaction is located to the outer and inner segments of retinal photoreceptor cells and to perikarya of certain pinealocytes. Examination of formalin-fixed, paraffin-embedded biopsy specimens of 66 cerebellar medullo-blastomas revealed varying numbers of IRBP-immuno-reactive tumor cells in 19 cases that were formerly shown to contain rod-opsin and S-antigen immunoreaction. IRBP-immunoreactive tumor cells were also found in a retinoblastoma and a pineocytoma, but not in neuroblastoma, ganglioneuroblastoma, glioblastoma, oligodendroglioma and astrocytoma. The results indicate: (1) cerebellar medulloblastomas are heterogeneous in their differentiation potential; (2) one type of medulloblastoma displays photoreceptor characteristics; (3) this type appears to be closely related to retinoblastoma and pineal cell tumors; and (4) all three types of tumors may display additional common features to be explored in future studies.

Pathobiology of the pineal gland with emphasis on parenchymal tumors

“…Interestingly, these retina-associated substances have not been demonstrated in neuroblastoma and ganglioneuroblastoma, tumors often "lumped" into the PNET category. 46 To date, one small study of medulloblastomas has demonstrated no alterations of the retinoblastoma susceptibility gene. 48 Cytogenetic and molecular genetic studies of PNET and PPT have shown more differences than similarities.…”

The Pineal Gland from Development to Function

“…For instance, Huang, Klein, and Korf (1992) described expression of rod opsin in a small fraction of adult human pinealocytes. Expression of S-arrestin (Perentes, Rubinstein, Herman, & Donoso, 1986) and recoverin (Korf, Korf, Schachenmayr, Chader, & Wiggert, 1992) was also described. The significance of these observations remains unknown.…”

Paraneoplastic retinopathy with multiple detachments of the neurosensory retina and autoantibodies against interphotoreceptor retinoid binding protein (IRBP) in cutaneous melanoma

“…Interphotoreceptor retinoid-binding protein (IRBP) is a glycoprotein with a molecular mass of 145 kDa and is expressed by retinal photoreceptors 1 2. It is thought to mediate the transport of retinoids between the retinal photoreceptor cells and the RPE 1 2.…”

“…It is thought to mediate the transport of retinoids between the retinal photoreceptor cells and the RPE 1 2. IRBP has been widely used for induction of experimental autoimmune uveitis 2.…”

“…IRBP has been widely used for induction of experimental autoimmune uveitis 2. IRBP has also been isolated from cancers such as cerebellar medulloblastoma, retinoblastoma and pineocytoma 1. A possible association of IRBP with retinitis pigmentosa has also been described 3…”