Immunohistochemical characterization of human retinoblastomas in situ with multiple markers

Neurokinin-1 Receptor Antagonists as Anticancer Drugs

Background::

Human tumor cells lines and tumor samples overexpress the neurokinin-1 receptor (NK-1R). Substance P (SP), after binding to NK-1Rs, induces tumor cell proliferation, an antiapoptotic effect and promotes angiogenesis and the migration of cancer cells for invasion and metastasis.

Methods: :

In contrast, NK-1R antagonists block the previous pathophysiological actions mediated by SP. These antagonists promote the death of tumor cells by apoptosis. Peptide and non-peptide NK-1R antagonists have been reported.

Results: :

Peptide NK-1R antagonists show chemical modifications of the SP molecule (L-amino acids being replaced by D-amino acids), whereas non-peptide NK-1R antagonists include numerous compounds with different chemical compositions while showing similar stereochemical features (affinity for the NK- 1R). Currently, there are more than 300 NK-1R antagonists.

Conclusion::

In combination therapy with classic cytostatics, NK-1R antagonists have additive or synergic effects and minimize the side-effects of cytostatics. The effect of NK-1R antagonists as broad-spectrum anticancer drugs is reviewed and the use of these antagonists for the treatment of cancer is suggested.

The TAg-RB murine retinoblastoma cell of origin has immunohistochemical features of differentiated Muller glia with progenitor properties

PURPOSE

Human retinoblastoma arises from an undefined developing retinal cell after inactivation of RB1. This is emulated in a murine retinoblastoma model by inactivation of pRB by retinal-specific expression of simian virus 40 large T-antigen (TAg-RB). Some mutational events after RB1 loss in humans are recapitulated at the expression level in TAg-RB, supporting preclinical evidence that this model is useful for comparative studies between mouse and human. Here, the characteristics of the TAg-RB cell of origin are defined.

METHODS

TAg-RB mice were killed at ages from embryonic day (E)18 to postnatal day (P)35. Tumors were analyzed by immunostaining, DNA copy number PCR, or real-time quantitative RT-PCR for TAg protein, retinal cell type markers, and retinoblastoma-relevant genes.

RESULTS

TAg expression began at P8 in a row of inner nuclear layer cells that increased in number through P21 to P28, when clusters reminiscent of small tumors emerged from cells that escaped a wave of apoptosis. Early TAg-expressing cells coexpressed the developmental marker Chx10 and glial markers CRALBP, clusterin, and carbonic anhydrase II (Car2), but not TuJ1, an early neuronal marker. Emerging tumors retained expression of only Chx10 and carbonic anhydrase II. As with human retinoblastoma, TAg-RB tumors showed decreased Cdh11 DNA copy number and gain of Kif14 and Mycn. It was confirmed that TAg-RB tumors lose expression of tumor suppressor cadherin-11 and overexpress oncogenes Kif14, Dek, and E2f3.

CONCLUSIONS

TAg-RB tumors displayed molecular similarity to human retinoblastoma and origin in a cell with features of differentiated Müller glia with progenitor properties.

Insights from mouse models into human retinoblastoma

Novel murine models of retinoblastoma based on Rb gene deletion in concert with inactivation of Rb family members have recently been developed. These new Rb knockout models of retinoblastoma provide excellent tools for pre-clinical studies and for the exploration of the genetics of tumorigenesis driven by RB inactivation. This review focuses on the developmental consequences of Rb deletion in the retina and the genetic interactions between Rb and the two other members of the pocket protein family, p107 (Rbl1) and p130 (Rbl2). There is increasing appreciation that homozygous RB mutations are insufficient for human retinoblastoma. Identifying and understanding secondary gene alterations that cooperate with RB inactivation in tumorigenesis may be facilitated by mouse models. Recent investigation of the p53 pathway in retinoblastoma, and evidence of spatial topology to early murine retinoblastoma are also discussed in this review.

Identification of tumorigenic retinal stem-like cells in human solid retinoblastomas

Retinoblastoma (RB) is the most common malignant tumor of the retina in human children. Although it has been hypothesized for a long time that RB derives from multipotent retinal stem cells (RSCs) or retinoblasts, the direct evidence that the presence of tumorigenic RSCs in RB tumors is still lacking. Some studies indicate that malignant tumors contain tumor stem cells similar to their normal tissue stem cell counterparts. With in vitro culture and differentiation method we demonstrate that tumorigenic retinal stem-like cells (RSLCs) indeed exist in RB lesions and that RB tumor-derived cultures encompass undifferentiated cells capable of extensive proliferation as clonal nonadherent neurospheres and can differentiate into different retinal cells in vitro. Interestingly, cultured cells expressed retinal development related genes including nestin, CD133, pax6, chx10 and Rx, and overexpressed Bmi-1, a gene required for self-renewal and proliferation of stem cells. Significantly, when these cultured cells were intraocularly transplanted into SCID mice, they gave rise to new tumors with histomorphological features and immunophenotypes similar to their parental primary RBs. The results show that RBs contain tumorigenic RSLCs that contribute to tumorigenesis. This study provides a new insight to investigate the histogenesis of RBs and establishes a model for other RB research.

Expression of immature and mature retinal cell markers in retinoblastoma

AIM

To clarify the expression of immature and mature retinal cell makers in retinoblastoma cells and to give insights into the cell origin of the retinoblastoma.

MATERIALS AND METHODS

Five samples from five eyes diagnosed with retinoblastomas were analysed by a standard immunohistochemistry using antibodies against Nestin and the hairy and enhancer of split mammalian homologue-1 (HES-1), both as markers for undifferentiated cells, and against Chx10, as a marker for both undifferentiated retinal cells and mature bipolar cells. Photoreceptor-specific nuclear receptor (PNR) was used as a postmitotic rod photoreceptor cell-specific marker, glial fibrillary acidic protein (GFAP) as a mature glia cell marker, and microtubule-associated protein (MAP) 2 as a mature neuronal cell marker.

RESULTS

Nestin was detected in what were possibly Müller cells, but not in the tumour stroma. HES-1 was not detected in the retinoblastoma tissue. Chx10 was detected in one of the five samples. In this one sample, Chx10 expression was confined in a minor portion of the retinoblastoma cells. PNR was not detected in the retinoblastoma tissue. Expression of GFAP was detected only in the stromal cells of the tumour, which presumably represents reactive stromal astrocytes. In contrast, in all the samples, MAP2 was expressed in most of the retinoblastoma cells.

CONCLUSIONS

The results of the current study support that retinoblastomas are derived from mature neural cells but do not originate from tumour stem cell(s).

Lucien J. Rubinstein: enduring contributions to neuro-oncology

Dr. Lucien Rubinstein is best remembered for his significant contributions to the field of neuropathology, particularly in the classification of nervous system tumors. His accomplishments in basic neuro-oncology and in the formulation of diagnostic principles reflected a unique talent for synthesizing fundamental clinicopathological concepts based on skillful diagnostic investigation and a thorough understanding of neurobiology. Dr. Rubinstein was the leader in the establishment of cell cultures from central nervous system (CNS) tumors. He meticulously analyzed both light and electron microscopic features of CNS tumors, recorded his findings, and patiently drew sketches to be shared generously with his colleagues and students. As a pioneer in neuropathology, in his work Dr. Rubinstein set the foundation for many enduring concepts in neurosurgery, neuro-oncology, neurology, and basic tumor biology.

1,25-dihydroxyvitamin D3-induced apoptosis of retinoblastoma cells is associated with reciprocal changes of Bcl-2 and bax

The active vitamin D metabolite 1,25-dihydroxyvitamin D(3) (1,25-(OH)(2)D(3)) and related substances have previously been tested in tissue culture and animal models of retinoblastoma for their use as anti-tumor drugs. However, despite of the potential therapeutic value, the molecular mechanisms through which 1,25-(OH)(2)D(3) inhibits the growth of retinoblastoma cells are incompletely understood. To elucidate possible signalling pathways for the anti-proliferative action of vitamin D compounds in retinal tumor cells, we analyzed the effect of 1,25-(OH)(2)D(3) and its synthetic analogue KH1060 on the growth of human retinoblastoma-derived Y79 cells. Vitamin D receptor (VDR) mRNA was detected by reverse transcription PCR in Y79 cells and in tissue specimens of human retinoblastoma. VDR transcripts were confirmed at the protein level by strong immunostaining of solid retinal tumors for VDR. Incubation with 1,25-(OH)(2)D(3) and KH1060 (10(-10)-10(-6)moll(-1)) decreased the number of Y79 cells in a timely and dose-dependent manner. Treatment with 1,25-(OH)(2)D(3) (10(-10)moll(-1)) for 24 hr caused cell cycle arrest in the G0/1 phase. Apoptosis of Y79 cells in response to 1,25-(OH)(2)D(3) was demonstrated by the means of TdT-dUTP terminal nick-end labelling (TUNEL), annexin V staining, and detection of DNA fragmentation on agarose gels. 1,25-(OH)(2)D(3)-induced programmed death of Y79 cells was accompanied by a concentration-dependent increase in Bax protein and a reduction in Bcl-2 content. These findings suggest that 1,25-(OH)(2)D(3) inhibits the growth of retinoblastoma cells by causing cell cycle arrest and apoptosis. 1,25-(OH)(2)D(3)-induced programmed death of retinoblastoma cells appears to involve reciprocal changes in Bcl-2 and Bax proteins.

Immunohistochemical localization of human pineal tissue antigens in normal retina and retinoblastomas

The normal human retina and retinoblastomas were examined immunohistochemically to assess the localization of pineal antigens in the retina and the oncogenesis and differentiation of retinoblastoma. In the present study, 41 eyes excised from children (aged 4 months to 7 years, all unilateral occurrence) diagnosed to have retinoblastoma and 4 eyes with normal retinas, were used. Retinoblastomas were histopathologically classified into well-differentiated, moderately-differentiated, and poorly-differentiated types. The antibodies used were 9 monoclonal antibodies to human pineal antigens and 6 antibodies to neural tissues. In the normal retina, staining patterns characteristic of retinal cell layers were observed with PP1, PP3, PP5, PP6, PI1, and PI2 antibodies. In retinoblastomas, PP5 antibody, which reacts with horizontal cells and ganglion cells, and PP6 antibody, which reacts with part of the bipolar cells in the inner nuclear layer, showed intense staining in well-differentiated retinoblastomas, but the intensity of staining and the positivity decreased with the degree of dedifferentiation. Antigens recognized by PP3 and PP4 antibodies were positive in all retinoblanstomas. Reactions to GFAP antibody and antibodies that recognize Müller cells were negative. Retinoblanstomas may express markers of not only photoreceptor cells but also other retinal nuclear cells. These results suggest that the retinoblastoma might be developed from visual stem cells, which are common progenitor cells of photoreceptor cells, intermediate neurons, and ganglion cells.

Intermediate-filament expression in ocular tissue

Intermediate-filament proteins (IFPs) occur in the intracellular cytoskeleton of eukaryotic cells, and their expression in diverse tissues is related both to embryology as well as to differentiation. Although the available information concerning their functional properties in vivo is still incomplete, antibodies against individual IFPs are commonly used in immunohistochemical procedures as markers for differentiation, and these antibodies are of outstanding value in the routine histopathological evaluation of tumor specimens. This review presents a compilation of the currently available data concerning IFP expression in normal and diseased ocular tissues. Representatives of every known class of IFP have been detected in normal ocular tissues. The external epithelia exhibit complex expression patterns of cytokeratin (CK) polypeptides, with CK3 and CK12 being specific markers of the corneal epithelium. Recent research has revealed that single mutant CK polypeptides may play a role in the pathogenesis of corneal dystrophies. The internal ocular epithelia reveal simple but specific patterns of IFP expression, these comprising simple-epithelial CKs and/or the mesenchymal IFP, vimentin. The IFP complement of the neuronal structures of the eye embraces several distinct IFP classes and reflects the diversity of the cell types present at these sites. With respect to ocular tumors, the IFP profile of melanomas might be correlated with metastatic potential. In conclusion, IFP analysis may be able to cast light on the pathogenesis of ocular diseases, as well as being a valuable adjunct in ophthalmopathological diagnosis.

Photoreceptor cell differentiation in retinoblastoma demonstrated by a new immunohistochemical marker mucin-like glycoprotein associated with photoreceptor cells (MLGAPC)

AIMS

For further understanding of specific differentiation in retinoblastoma, we studied the expression of newly detected mucin-like glycoprotein associated with photoreceptor cells (MLGAPC), which is specific for photoreceptor cells of retina and analogous to interphotoreceptor matrix proteoglycan-1 (IMPG1).

METHODS AND RESULTS

Surgically enucleated retinoblastomas (n=21; undifferentiated type, n=15, differentiated type, n=6) were immunohistochemically studied with a polyclonal antibody against MLGAPC, and 17/21 cases (81%) showed positive staining of tumour cells. We classified various staining patterns and structures into four groups: type 1 showing a granular intracellular scattered staining pattern with round small cells; type 2 showing a reticular staining pattern between spindle-shaped tumour cells; type 3 showing radiating staining from the centre of Homer-Wright rosettes; type 4 showing ring-shaped, radiating and granular staining associated with Flexner-Wintersteiner rosettes. Eleven of 15 undifferentiated retinoblastomas (73%) showed type 1 or 2, and all the six differentiated cases showed type 3 or 4. Image analysis of immunostaining revealed an increase in MLGAPC-positive area from 0.48% in undifferentiated cases to 1.60% in differentiated cases, and a negative correlation was shown between mitotic frequency and MLGAPC-positive area.

CONCLUSIONS

This study proved MLGAPC as a valuable marker of retinoblastoma, and that photoreceptor differentiation takes place even in 'undifferentiated' retinoblastoma.

The HNK-1 carbohydrate epitope in the eye: basic science and functional implications

The HNK-1 carbohydrate epitope is part of many cell membrane and extracellular matrix molecules. It has been implicated in cell to cell and cell to extracellular matrix adhesion, and antibodies to the HNK-1 epitope are emerging as a versatile tool in eye research. They have been used to identify a novel cell type in the human eye, the subepithelial matrix cells that reside in the inner connective tissue layer (ICTL) of the ciliary body. Although these cells resemble fibroblasts in ultrastructure, they form a distinct cell population that differs in its antigenic profile from fibroblasts of other tissues. These cells are associated with the elastic fiber system of the ICTL. Other structures in the human eye that harbor the HNK-1 epitope in a nonrandom pattern are the ciliary and iris epithelia, the zonular lamella, the lens capsule, the retina, glial cells of the optic and ciliary nerves, and scleral fibroblasts. The HNK-1 epitope in the eye appears early during embryonic development and is phylogenetically conserved, but many interspecies differences exist in its distribution. The role of the HNK-1 epitope may be to structurally stabilize the ciliary body and the retina, and to participate in zonular attachments. The HNK-1 epitope has been linked with many common eye diseases. The subepithelial matrix cells seem to be susceptible to undergo irreversible damage as a result of glaucoma, thermal injury, and tissue compression. This epitope has proved to be useful in identifying intraocular deposits of exfoliation syndrome. It can explain the adhesiveness of exfoliation material. Intraocular exfoliation material differs in HNK-1 immunoreactivity from the extraocular fibrillopathy of exfoliation syndrome and its presence in fellow eyes also argues against the concept of unilateral exfoliation syndrome. The HNK-1 epitope is found in the extracellular matrix of secondary cataract and anterior subcapsular cataract, and it may contribute to their pathogenesis. Finally, the HNK-1 epitope can be used to trace neuroepithelial derivatives of the optic vesicle in developmental anomalies and in tumors of the eye. Eventual identification of molecules that bear the HNK-1 epitope in the eye will likely shed light on many aspects of ocular physiology and pathobiology

Immunoelectron microscopic localization of the HNK-1 carbohydrate epitope in the anterior segment of pseudoexfoliation and normal eyes

PURPOSE

To study the presence of the cell-adhesion related HNK-1 carbohydrate epitope in the anterior segment of pseudoexfoliation and normal eyes by immunoelectron microscopy.

METHODS

Anterior segment tissue of 6 autopsy eyes with pseudoexfoliation (PEX) syndrome (5 eyes without glaucoma and 1 with glaucoma), and 6 normal autopsy eyes without PEX syndrome were studied by an electron microscopic immunogold technique using a monoclonal antibody to the HNK-1 epitope.

RESULTS

In both normal and PEX eyes, the HNK-1 epitope could be immunolocalized to the basement membranes of both ciliary epithelia and posterior iris pigmented epithelium, to the lens capsule and zonular lamella, and to the pigmented epithelial cells of iris and ciliary body. Within the inner connective tissue layer of the ciliary body, the gold label was mainly associated with the periphery of elastic fibers and microfibrillar bundles. PEX material on the surfaces of posterior iris, ciliary body, anterior lens capsule, zonular fibers, and uveal part of the trabecular meshwork reacted strongly with the HNK-1 antibody. In contrast, PEX material accumulations within the iris stroma or the juxtacanalicular tissue of the trabecular meshwork showed only weak immunoreactivity, while PEX material in the conjunctiva was totally negative.

CONCLUSIONS

The wide distribution of the HNK-1 epitope in anterior segment tissues and its association with a variety of extracellular and cellular structures was ultrastructurally demonstrated. In PEX syndrome, the varying labelling density of PEX fibers indicates a deviating carbohydrate composition in different locations of the eye. The HNK-1 epitope might be involved in the adhesiveness of PEX deposits on intraocular surfaces.

Human retinoblastoma: a morphological study of apoptotic, leukocytic, and vascular elements

Retinoblastoma (Rb), derived from retinal neuroepithelial progenitor cells, is the most common intraocular malignancy of childhood. This study examined 10 human Rb biopsy specimens with light and electron microscopy for histopathological features not previously described in detail, including cell death, leukocytic infiltration, and the tumor vasculature. Rb is a solid well-vascularized tumor with regions of viable tumor cells surrounding vessels, interspersed with zones of necrosis; apoptotic cells were seen in all specimens. Mononuclear phagocyte series (MPS) cells and lymphocytes often colocalized, adjacent to tumor vessels, and MPS cells frequently invested the perivascular space. Lymphocytes were rarely seen within areas of viable tumor. Tumor vessels at early stages of formation resembled normal developing retinal vessels. While junctions were often seen between endothelial calls, disruption of these junctions and endothelial fenestrae was sometimes evident. Müller cells and astrocytes extended processes around tumor cells and blood vessels, and contributed to the formation of the vascular glia limitans, which in some mature vessels was disrupted and discontinuous. Overall, this study provides further morphological details of cell death within Rb, particularly apoptotic involution, and describes the presence of a vascular-associated leukocytic infiltration in Rb. Evidence of compromise of the normal blood-retinal barrier (BRB) within the Rb tumor vessels is presented.

The HNK-1 Carbohydrate Epitope and the Human Eye in Health and Disease

The HNK-1 carbohydrate epitope is part of many cell membrane and extracellular matrix molecules, several of which have been implicated in cell adhesion. It is a versatile tool in eye research. In the human eye this epitope is present in the retina, the optic and ciliary nerves, the ciliary and iris epithelia, the zonular lamella, and the sclera. It is phylogenetically conserved, but the positive cell types vary from species to species. In addition to revealing interspecies differences in the vertebrate retina, the HNK-1 epitope has been used to identify a novel cell type in the eye: the subepithelial matrix cells that reside in the inner connective tissue layer (ICTL) of the ciliary body. Although these cells resemble fibroblasts in ultrastructure, they form a distinct cell population that differs in antigenic profile from fibroblasts in other tissues. The HNK-1 epitope is also associated with the elastic fiber system of the ICTL, which may be produced by the subepithelial matrix cells. It may help to structurally stabilize the ciliary body and the retina. The HNK-1 epitope is also involved in many important eye diseases. The subepithelial matrix cells seem to be susceptible to irrreversible atrophy as a result of glaucoma, thermal injury, and tissue compression. On the other hand, the HNK-1 epitope is found in the extracellular matrix of secondary cataracts and may contribute to its pathogenesis. Finally, this epitope has proved to be useful in identifying deposits of exfoliation material, and in tracing neuroepithelial derivatives in developmental anomalies and tumors of the eye.

Immunohistochemical evidence of neuronal and glial differentiation in retinoblastoma

BACKGROUND

The study sought to investigate the histogenesis of retinoblastoma.

METHODS

One hundred specimens of retinoblastomas were examined along with those of 18 astrocytic gliomas and 15 medulloblastomas to compare similarities of glial differentiation in retinoblastoma and the two types of brain tumour. Employing avidin-biotin immunoperoxidase technique, antibodies were applied against neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), and S-100 protein (S-100).

RESULTS

Most rosettes and fleurettes, and some undifferentiated cells in retinoblastomas were NSE positive, but GFAP and S-100 negative. GFAP and S-100 positive cells in retinoblastomas were detected mostly in well differentiated glial cells which were interpreted as reactive or non-neoplastic cells. Some of the GFAP and S-100 positive cells in retinoblastomas were defined as tumour cells that resembled neoplastic astrocytes in astrocytic gliomas and medulloblastomas.

CONCLUSION

Retinoblastoma may arise from primitive bipotential or multipotential cells capable of neuronal and glial differentiation.

Glial-, neuronal- and photoreceptor-specific cell markers in rosettes of retinoblastoma and retinal dysplasia

Previous studies have shown that a rosette formation represents an attempt to form embryonic retinal tissue, primarily rods and cones. To test the theories as to the origin and characteristics of retinoblastoma cells, we compared the characteristics of tumor rosettes with those of dysplastic rosettes seen in retinal dysplasia using the glial, neuronal and photoreceptor markers. Forty-four retinoblastoma and one retinal dysplasia specimens were analyzed by indirect immunohistochemistry, using specific antibodies against glial fibrillary acidic protein, S-100 protein, myelin basic protein, neuron-specific enolase, neurofilament, retinal S-antigen and retinal pigment epithelial antigen. In human retinoblastoma, all the glial, neuronal, retinal pigment epithelial, and photoreceptor cell markers, except for the neurofilament, were present in parts of rosette-forming tumor cells. However, their localization was different for each antigen and it was not clear whether each tumor cell possesses several antigens. These immuno-positive tumor cells were cytologically indistinguishable from other rosette-forming cells at the light microscopic level. In retinal dysplasia, neuron specific enolase and retinal S-antigen were diffusely expressed in the dysplastic rosettes, however, other antigen were not seen in those rosettes. The staining pattern by immunocytochemistry is totally different in tumor rosettes from dysplastic ones. We found varying localizations of different immunoreactivities within tumor rosettes. These results led us to suggest that tumor cells in the rosettes of retinoblastoma may have the ability to differentiate into neural and glial cells. To prove the theory that retinoblastoma cells may have originated from a primitive neuroectodermal cell capable of multipotentiality, further investigation is needed.

Immunohistochemical localization of chondroitin sulfate proteoglycan and tenascin in the human eye compared with the HNK-1 epitope

BACKGROUND

A previous study revealed the HNK-1 epitope in the human ciliary body beneath the ciliary epithelium. The molecules bearing this 3-sulphoglucuronic acid-containing oligosaccharide epitope in the eye remain unknown. As chondroitin sulphate proteoglycan (CSPG) and tenascin are potential candidates as bearers of the HNK-1 epitope, their distribution in the human eye was compared with that of the HNK-1 epitope.

METHODS

Fifty-five formalin-fixed, paraffin-embedded human eyes, including 20 normal eyes and 35 eyes with exfoliation syndrome or glaucoma, were studied immunohistochemically with monoclonal antibody (MAb) CS-56 to CSPG, MAb TN2 to tenascin, and MAbs HNK-1 and VC1.1 to the HNK-1 epitope. Additionally, four frozen lens capsules with exfoliation material were studied by indirect immunofluorescence.

RESULTS

A population of dendritic cells in the inner connective tissue layer of the ciliary body and exfoliation material were immunoreactive with antibodies to the HNK-1 epitope, but no labelling for CSPG and tenascin was seen in them, including frozen sections. The inner surface of the nonpigmented ciliary epithelium was reactive for the HNK-1 epitope, and at the ora serrata also for CSPG. In some eyes with glaucoma, immunoreaction for CSPG and tenascin was seen beneath the epithelium and endothelium of the cornea. The nerve fibre layer of the retina was labelled for tenascin. In the sclera, all antibodies labelled the ground substance, and in some large blood vessels immunoreaction for CSPG and tenascin was seen subendothelially.

CONCLUSION

Apart from the sclera, the distribution of CSPG and tenascin was different form that of the HNK-1 epitope, suggesting that this carbohydrate epitope may not be borne by these molecules in the human ciliary body.

Differential distribution of the HNK-1 carbohydrate epitope in the vertebrate retina

The expression of the cell adhesion-related HNK-1 carbohydrate epitope in the retina and ciliary body was studied in different vertebrates and in man. A series of eyes from 4 fish, 5 bird, and 9 mammalian species was analyzed by immunohistochemistry with monoclonal antibodies (MAb) HNK-1 and VC1.1 to the HNK-1 epitope, and with MAb SY38 to synaptophysin. Additionally, 7 morphologically normal human eyes were studied. In all fishes, as well as in baboons and man, the radial glia and all retinal layers except the photoreceptor cell layer were immunoreactive for the HNK-1 epitope. In all birds, the nerve fiber layer and both plexiform layers were labelled. In nonprimate mammals only the plexiform layers were immunoreactive. Fine differences in this general immunoreaction pattern were seen in different species. Mab SY38 labeled both plexiform layers of mammals only. In the ciliary body, immunoreaction for the HNK-1 epitope was seen in the inner connective tissue layer only in man, but the ciliary nerves were labelled in all species except the mouse and rat. The HNK-1 epitope seems to be phylogenetically conserved in the retina, where the HNK-1 immunoreactive plexiform layers possibly are overlapped with HNK-1 reactive radial glial cells in fishes and primates. Instead in the inner connective tissue layer of the ciliary body, the HNK-1 epitope is not phylogenetically conserved.

Radial asymmetry in the topography of retinoblastoma. Clues to the cell of origin

Retinoblastoma is a malignancy of the human developing retina. In situ as well as in vitro studies have attributed tumoral histogenesis either to a primitive retinoblast with neuronal and glial differentiation potentials, or to a photosensory progenitor cell. Here it is shown in vivo that the retinal topography of 457 retinoblastoma and retinoma foci is radially asymmetrical. Tumor density appears to mimic the horizontal visual streak characteristic of red/green cone cell distribution. Such a non-random distribution seems to invalidate the hypothesis of a primitive multipotential neuroblast as the unique source of retinoblastoma and may support the view that retinoblastoma evolves along the cone cell lineage.

Light-induced retinopathy in the albino rat in long-term studies. An immunohistochemical and quantitative approach

Retinas from male Wistar rats which were housed during a long-term drug safety study at short, medium and long distance from a fluorescent light source were examined. Retinal atrophy was pronounced in the central retina of rats housed closest to the light source, and was characterized by a loss of photoreceptor cells and of S-antigen immunoreactivity in the outer nuclear layer (ONL), absence of synaptophysin immunoreactivity in the outer plexiform layer (OPL), decrease of the number of nuclei in the inner nuclear layer (INL), astrocytic proliferation, and Müller cell activation. The peripheral retina of these rats had a laminated architecture, although the number of photoreceptor cells and nuclei in the INL was reduced. Retinas from rats housed a medium distance from the light source did not have any apparent histological or immunohistochemical changes, except for a lower number of photoreceptor cells and nuclei in the INL. The rats housed a long distance from the light source had the highest number of nuclei in the ONL and INL of the central and peripheral retina, and were used as control group. Our data indicate that retinal atrophy occurs in male Wistar rats maintained under light conditions currently used in long-term toxicity studies, and suggest that photoreceptor cell loss is followed by trans-synaptic anterograde degeneration of neurons in the INL, astrocytic proliferation and Müller cell activation.

A morphological and immunohistochemical study of human retinal pigment epithelial cells, retinal glia, and fibroblasts grown on Gelfoam matrix in an organ culture system. A comparison of structural and nonstructural proteins and their application to cell type identification

Retinal pigment epithelial (RPE) cells, retinal glia, and fibroblasts undergo marked phenotypical change when outside their usual microenvironment, as occurs in epiretinal membrane formation. To explore their phenotypic potential without the influence of other cell types, each was cultured on Gelfoam matrix and assessed immunohistochemically and ultrastructurally. All cell types demonstrated vimentin and a universal beta-tubulin epitope, TU27. RPE and retinal glial cells were positive for cytokeratin, Leu 7, and neuron-specific (gamma gamma) enolase, as were glia and fibroblasts for S-100 protein and RPE cells and fibroblasts for glutamine synthetase. RPE cells alone showed positivity for class III beta-tubulin and retinal S-antigen (monolayer cultures only); occasional retinal glia, which immunohistochemical findings suggest are Müller cell derived, demonstrated GFA protein. Therefore, class III beta-tubulin may be useful in distinguishing RPE cells from retinal glia and fibroblasts, and Leu-7 may help to identify RPE cells and fibroblasts; these cell types are difficult to distinguish in clinical material using more traditional morphological criteria.

A reassessment of histologic classification and an immunohistochemical study of 88 retinoblastomas. A special reference to the advent of bipolar-like cells

BACKGROUND

Despite perpetual efforts of investigators, the histogenesis of retinoblastoma is still in dispute and histologic classification satisfactorily predictive of prognosis does not seem to be in use.

METHODS

The authors studied 88 cases of retinoblastoma clinicopathologically and immunohistochemically, paying special attention to the presence of a "bipolar-like cell" element that would be used as one of the criteria for the diagnosis of differentiated retinoblastoma.

RESULTS

Twelve cases of retinoblastoma with the bipolar-like cell element in the absence of rosettes and 41 cases of the tumor with rosettes were classified as differentiated retinoblastomas. The other 35 cases without rosettes or bipolar-like cells were classified as undifferentiated tumors. Tumor cells forming rosettes usually had positive results for synaptophysin and neuron-specific enolase (NSE) and negative results for glial fibrillary acidic protein (GFAP) and S-100 protein; however, undifferentiated cells had negative results for these four antibodies. The bipolar-like cells had positive results for synaptophysin and NSE but negative results for GFAP and S-100 protein. Twelve tumors with bipolar-like cells that lacked rosettes showed no optic nerve invasion, and the patients had a significantly better prognosis (100% 5-year survival rate) than 35 patients with undifferentiated tumors (71% 5-year survival rate) (P < 0.01).

CONCLUSIONS

The findings support a neuronal origin of the tumor and indicate that, not only the rosettes symbolizing the photoreceptor differentiation, but also other neuronal elements, such as bipolar-like cells, can be used as criteria for histologic classification of retinoblastoma.

Immunohistochemical and histochemical properties of surgically excised subretinal neovascular membranes in age-related macular degeneration

The immunohistochemical and histochemical properties of 16 surgically excised subretinal neovascular membranes from 16 patients with age-related macular degeneration were studied. Primary antisera to c-retinaldehyde-binding protein; leukocyte common antigen; factor VIII-related antigen; S-100 protein; glial fibrillary acid protein; muscle-specific actin; neuron-specific enolase; collagen types I, II, III, IV, and V; laminin; and fibronectin were used for immunohistochemical characterization of the membranes. Histochemical staining for lipid and mucopolysaccharide was performed. The results of the staining in conjunction with histologic examination showed the cellular components of the membranes to be composed of retinal pigment epithelium, inflammatory cells, vascular endothelium, glial cells, myofibroblasts, photoreceptor cells, and fibrocytes. The extracellular matrix of the membranes contained collagen types I, III, IV, and V; fibronectin; laminin; mucopolysaccharide; and lipid. These findings are consistent with the concept that subretinal neovascular membranes in age-related macular degeneration are composed of localized intra-Bruch's membrane granulation tissue proliferation associated with diffuse drusen.

Retinoblastoma: messenger RNA for interphotoreceptor retinoid binding protein

Surgically excised retinoblastomas from 14 patients (age range nine months to two years) were assessed by immunocytochemistry for the expression of photoreceptor-specific proteins and neuronal and glial cell markers. Adjacent tissues were examined for messenger RNA expression of interphotoreceptor retinoid-binding protein (IRBP) using Northern blots. For immunocytochemical stains (ABC method), monoclonal and polyclonal antibodies included S-Ag, rhodopsin, neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), IRBP, neural adhesion molecule (N-CAM), and rod and cone specific transducin (TR alpha and TC alpha). Histopathology revealed mostly poorly differentiated tumors with necrosis and lack of Flexner-Wintersteiner rosettes. Immunocytochemical staining showed focal IRBP expression in one of the tumors and S-antigen in two cases. Immunoreactivity with rhodopsin was negative. N-CAM, a neural adhesive protein which appears to be involved in the regulation of adhesive interaction during neuronal differentiation, was positive except in two cases. All tumors showed immunoreactivity with NSE, whereas GFAP staining was limited to the perivascular glial tissue confirming the essential neuronal nature of retinoblastoma cells. TC alpha was detected in all tumors and TR alpha in one case. Messenger RNA for IRBP was detected in tumors in which IRBP immunoreactivity could not be detected.

Identification of an S-antigen-like molecule in Drosophila melanogaster: an immunohistochemical study

Vision is a highly complex process common to many vertebrate and invertebrate species. The visual system of Drosophila represents a valuable model in which to study this process since its chromosomal makeup has been well mapped and many mutants containing specific photoreceptor defects have been described. S-antigen is a well-characterized photoreceptor cell protein which plays a fundamental role in the visual process. In this study, we used a panel of four monoclonal antibodies (MAbs) specific for amino, mid and carboxy terminal amino acid sequences in S-antigen in order to examine S-antigen immunoreactivity in the Drosophila visual system. Two MAbs, MAb5C6.47 and MAbC10-C10, localized S-antigen to the retinules and ocelli. In contrast, MAbA2-G5 and MAbA9-C6 did not stain. The presence and strong antigenic similarity of an S-antigen homolog in Drosophila suggests that in both vertebrates and invertebrates S-antigen plays a major role in the regulation of the phototransduction of vision.

Neuronal and photoreceptor differentiation of retinoblastoma in culture

This study describes an in vitro system, which favors attachment and differentiation of primary retinoblastoma cells. Indeed, tumor cells from primary retinoblastomas were successfully grown as long-term monolayer cultures, using collagen type-1 coated flasks, preincubation of tumor cells in fetal calf serum and a medium richly supplemented with serum. This reliable system allowed growth and attachment and induced differentiation towards neuronal and photoreceptor morphology. Each of the nine tumors studied showed substantial cell proliferation and differentiation. Cells with glial characteristics were observed in lower numbers. Furthermore, in five cell-lines, some cell clusters showed pigmentation characteristic of pigment epithelial cells (PE). By electron microscopy, a significant proportion of cells showed conventional neuronal differentiation; others formed typical Flexner-Wintersteiner rosettes with individual photoreceptor cells showing a more highly differentiated pattern quite similar to fleurette inner segments. Immunohistochemical studies did not reveal evidence of transition between undifferentiated retinoblastoma cells and glial cells, although foci of multipolar cells were found resembling glial elements and containing glial fibrillary acidic protein. Thus no definite sign of glial differentiation was observed. These results show that most primary retinoblastoma cells can grow in attachment culture and differentiate into at least two distinct morphological cell types. This study also offers a potentially rewarding system to analyse the factors controlling growth and differentiation of human tumor cells in vitro.

A study of 39 retinoblastomas with particular reference to morphology, cellular differentiation and tumour origin

A series of 39 retinoblastomas was studied using light microscopy and immunohistochemistry for localization of neurone-specific enolase and glial fibrillary acidic protein. Thirty-eight retinoblastomas (97.4%) occurred in children less than 6 years of age: one was in a 61-year-old man (2.6%); the mean age, excluding the 61-year-old, was 32.1 months. Unilateral tumours were found in 74.4% of patients and bilateral tumours in 25.6%; bilateral lesions occurred in a younger age group, mean age of 21.7 vs 35.9 months. The male to female ratio was 1.4:1. Morphologically, arrangement of tumour cells into trabeculae was noted in 69.2% of retinoblastomas and glomerulus-like structures in 43.6%. These two patterns of cellular arrangement were encountered where the choroid and sclera were invaded by neoplastic cells. Homer Wright rosettes were observed in all tumours. Flexner-Winstersteiner rosettes in 33.3% and fleurettes in 2.6%. Differentiation into neoplastic neurones as well as in the form of Flexner-Winstersteiner rosettes and fleurettes was noted in 46.1%, neoplastic ependymal cells in 100.0%, astrocytes in 58.9%, oligodendrocytes in 23.1%, and glioblastomas in 2.6%. These data suggest that retinoblastoma is a primitive stem cell neuroectodermal tumour with the capacity for differentiation in both neuronal and neuroglial directions.

Immunohistochemistry of retinoblastoma. A review

Various studies which relate to the immunohistochemical identification of neuronal, glial, carbohydrate and nucleic acid associated antigens in retinoblastoma will be reviewed. The majority of these studies appear to support the concept that retinoblastomas arise, in situ, from neuron committed cells and in some cases specifically into photoreceptor-like cells. In selected cases, however, glial cell differentiation may be a feature of the tumor. In addition, the molecular biology of the retinoblastoma gene and the immunohistochemical characterization of its gene product will be discussed.

The immunohistochemical demonstration of early perineurial change in the development of localized hypertrophic neuropathy

A case of localized hypertrophic mononeuropathy was studied by electron microscopy and immunohistochemistry for S100 protein, epitopes recognized by the Leu-7 monoclonal antibody, 200 kD neurofilament polypeptide, and the epithelial membrane antigen (EMA). The primary role of perineurial cell proliferation without the participation of Schwann cells in this process was directly demonstrated by EMA immunohistochemistry. Focal delamination of the EMA-positive perineurium, increased fibrosis between its layers, and compartmentalization of the fascicles by EMA-positive septae were the first recognizable changes. In practice, recognition of these early changes by EMA immunocytochemistry may be important for the clear definition of functionally unimpaired segmental margins for excision and graft implantation, and also for the future study of the process responsible for aberrant perineurial proliferation.

Diagnostic markers in human neurooncology. A progress report

In this progress report, some of the most commonly used antibodies are discussed in regard to their immunohistochemical application to human neurooncology. The importance of determining the spectrum of antibody immunoreactivity in a wide panel of normal, reactive, and neoplastic tissues is stressed. in atypical and aberrant cases, immunopositivity needs to be interpreted with caution and in the context of all other available data. The demonstration of a well-characterized, cell type-specific marker in a tumor reflects not so much its cytogenesis as its differentiation potential and its capacity for metaplasia. The relation of an abnormal or aberrant expression of antigenic determinants to the process of neoplasia raises a number of intriguing questions to which research in the next few years will likely provide answers.

Recurrent medulloepithelioma of the ciliary body. Immunohistochemical characteristics

A predominantly benign medulloepithelioma of the ciliary body was diagnosed in an 8-year-old girl and resected by iridocyclectomy. It recurred twice during 30 months. Highly malignant histopathologic features developed, and the eye finally perforated and had to be enucleated. No recurrence or metastases have subsequently developed. Histologically, the tumor was a nonteratoid medulloepithelioma consisting of elements resembling embryonic retina, nonpigmented ciliary epithelium, and neuroblasts, but had also areas of obvious glial and neuronal differentiation as judged by immunohistochemistry. The neuroepithelial tumor cells were positive for neuron-specific enolase, vimentin, and often for S-100 protein. The neuroblastic cells were generally positive for neuron-specific enolase and synaptophysin, but were intermixed with glia-like tumor cells positive for vimentin, glial fibrillary acidic protein, and S-100 protein. The results suggest that even a nonteratoid medulloepithelioma may be, unlike retinoblastoma, a truly multipotential tumor.

Retinal S-antigen immunoreactivity in medulloblastomas

A series of 16 cerebellar medulloblastomas were studied immunohistochemically using a four-step immunoperoxidase (PAP) method and a monoclonal antibody (MAbA9-C6) which defines an epitope of the retinal S-antigen, a protein known to occur in retinal photoreceptor cells and pinealocytes of the pineal gland as well as in retinoblastomas, pineocytomas and pineoblastomas. Immunopositivity was demonstrated in a variable number of tumor cells in 50% of the cases. This finding may be an indication of a differentiation potential of medulloblastomas along the photoreceptor cell lineage. Alternatively, it may simply indicate the non-specificity of the retinal antigen in the neoplastic state.

Expression of epithelial membrane antigen in perineurial cells and their derivatives. An immunohistochemical study with multiple markers

Paraffin-embedded surgical pathology specimens from skin (5) and muscle (2) biopsies, from Morton's neuromas (3), traumatic neuromas (8), schwannomas (21), neurofibromas (12), and from one perineurioma and one neurothekeoma were studied by immunoperoxidase histochemistry and antibodies against epithelial membrane antigen (EMA), Leu 7 epitopes (Leu 7), S-100 protein (S-100) and cytokeratins. Normal, reactive and neoplastic perineurial cells stain consistently for EMA, whereas Schwann cells express Leu 7 and/or S-100 positivity. None of the immunoreactive cells stained for cytokeratin. Our findings indicate that perineurial and Schwann cells can easily be distinguished by their different patterns of immunoreactivity with the above markers.