Expression of autophagy-related protein LC3B, p62, and cytoplasmic p53 in human retinoblastoma tissues

OBJECTIVE

Dysfunction of autophagy has been implicated in development and progression of diverse human cancers. However, the exact role and mechanism of autophagy have not been fully understood in human cancers, especially in retinoblastoma (Rb).

PATIENTS AND METHODS

We determined the autophagy activity in human Rb tissues by assessing the autophagy markers microtubule-associated protein light chain 3B (LC3) and p62 (SQSTM1) in formalin fixed and paraffin embedded human tissue by immunohistochemistry and then associated their expression with patient clinicopathological features. We further explored the correlation between the expression of LC3B and p62 and the expression of cytoplasmic p53, a newly identified autophagy suppressor, in Rb tissues.

RESULTS

Our data revealed that the expression of LC3B and p62, was significantly associated with disease progression and tumor invasion of Rb. Furthermore, we also revealed that cytoplasmic expression of p53 was inversely associated with the behavior of tumor invasion. Finally, Spearman correlation analysis demonstrated that cytoplasmic expression of p53 was significantly and inversely correlated to the expression of both LC3B and p62.

CONCLUSIONS

Autophagy might play an important role in human Rb progression, and LC3B and p62 may be useful predictors of disease progression in patients with Rb.

Molecular diagnosis in patients with retinoblastoma: Report of a series of cases

OBJECTIVES

To report the benefits of genetic diagnosis in patients with retinoblastoma.

METHOD

Observational study. Patients with retinoblastoma and their families were included. Demographic and clinical data were recorded. Blood and tumour samples were obtained. Next generation sequencing was performed on the samples. When deletion 13 q syndrome was suspected, cytogenetics microarray was performed (Cytoscan® HD, Affymetrix, Santa Clara, CA, USA), with a high density chip of 1.9 million of non-polymorphic probes and 750 thousand SNP probes.

RESULTS

Of the 7 cases were analysed 4 were male. The mean age at diagnosis was 21 months (range 5-36). Three cases had bilateral retinoblastoma, and 4 unilateral. None had family history. In all patients, blood was analysed, and a study was performed on the tissue from 2 unilateral enucleated tumours, in which 6 mutations were identified, all de novo. Just one was novel (c.164delC; case 1). One case of unilateral tumour revealed blood mosaicism, showing that his condition was inheritable, and that there is a high risk of developing retinoblastoma in the unaffected eye. The patient also has an increased risk of presenting with other primary tumours.

CONCLUSION

Molecular diagnosis of RB1 in patients with retinoblastoma impacts on the decision process, costs, treatment, and prognosis of patients, as well as their families.

HOW EXPRESSIONS OF CLAUDIN-1 AND MMP-2 IN RETINOBLASTOMA CORRELATE WITH HISTOLOGICAL DIFFERENTIATION AND OPTIC NERVE INVASION

Retinoblastoma is a commonly seen and dangerous intraocular malignant tumor in infants. Studies have found that Claudin-1 and MMP-2, whose expressions may be connected, play roles in tissues of retinoblastoma. In this study we analyze and discuss changes of Claudin-1 and MMP-2 expressions, and the correlation between the expressions and retinoblastoma histological differentiation and optic nerve invasion. MaxVisionTM was applied to detect expressions of Claudin-1 and MMP-2 in 45 samples of retinoblastoma and 15 paraffin-embedded samples of normal retina. The correlation between Claudin-1 expression and MMP-2 expression was analyzed based on chi-squared test and Spearman’s correlation test. Positive expressions of Claudin-1 in retinoblastoma were fewer than those in retina; higher positive expressions were found in differentiated tissues than in undifferentiated tissues; while compared to expressions in invasive optic nerves, Claudin-1 expressed more positively in optic nerves without invasion. As for MMP-2, its expressions were higher in retinoblastoma than in normal retina; undifferentiated tissues had higher positive expressions than differentiated tissues, which were not statistically significant; higher positive expressions were detected in invasive optic nerves. Thus, it could be concluded that the correlation between Claudin-1 expression and MMP-2 expression in retinoblastoma was negative. Expressions of Claudin-1 were positively related to histological differentiation and optic nerve invasion of retinoblastoma; while MMp-2 expression had negative correlation with histological differentiation and optic nerve invasion of retinoblastoma. Claudin-1 and MMP-2 played a negative role in the optic nerve invasion and tumor development of retinoblastoma.

Identification of effective substrates for the direct analysis of lipids from cell lines using desorption electrospray ionization mass spectrometry

RATIONALE

Various disease conditions, particularly tumours, can be understood easily by studying changes in the lipid profile of cells. While lipid profiles of tissues have been recorded by desorption electrospray ionization mass spectrometric (DESI-MS) imaging, there is paucity in standardized protocols for sample preparation involving cell cultures to generate reliable results. In this study, we report a method for the direct analysis of lipids from cultured cells by incorporating them onto Whatman 42 filter paper as a substrate for reliable DESI-MS analysis.

METHODS

The WERI-RB1 cell line was spotted on commonly used substrates for DESI-MS analysis, such as glass slides, Teflon coated glass slides, thin layer chromatography (TLC) plates, and Whatman 42 filter paper. A comparison of mass spectrometric images with two different lipids was made to understand the behaviour of different surfaces when the same sample was spotted on them. Relative intensities of different lipid peaks in the WERI-RB1 cell line were compared and relative lipid abundances were also compared across two different human retinoblastoma cell lines; WERI-RB1 and Y79.

RESULTS

The study demonstrates that good lipid signals can be obtained by DESI-MS when the cells are spotted on Whatman 42 filter paper. Tandem mass spectrometry was performed to identify the lipids as glycerophosphocholines (PC). Better lipid images from assembly of cells were obtained with distinct boundary when they were spotted on Whatman 42 filter paper than other surfaces.

CONCLUSIONS

We demonstrate the use of a simple substrate for reliable DESI-MS analysis of cultured cells. This method has the potential to understand various interactions of cells with other external agents. The current method would help in the application of DESI-MS for biology in general and medical sciences in particular.

[Efficacy of intravitreal carboplatin plus bevacizumab in refractory retinoblastoma]

OBJECTIVES

To evaluate the efficacy of intravitreal carboplatin plus bevacizumab in refractory retinoblastoma.

METHODS

Perspective study.Eleven patients (11 eyes) with the diagnosis of refractory retinoblastoma were enrolled in Department of Ophthalmology of Peking University People's Hospital from June 2013 to March 2014. They underwent intravitreal carboplatin plus bevacizumab every 4 weeks, an average of 4.5 times of treatment.Observe for 3 months after the last treatment. Aqueous humor was taken for cytological and VEGF detection and retinal funds were taken photos for observation.Statistical analyses between experimental group and control group and before and after intravitreal injection within experimental group were performed with independent samples t test.

RESULTS

Tumor in vitreous cavity reduced significantly in seven patients, however, poor control in four cases, and three of them were recurrent after first-line treatment. Cytology detection for aqueous humor showed no tumor cells in all of them. Aqueous VEGF of patients with retinoblastoma (60.65 ± 6.20) was significantly higher than the control group (21.98 ± 6.91). The difference was statistically significant (t = 13.80, P < 0.01). And the aqueous VEGF content decreased significantly after treatment (t = 2.12, P < 0.05).

CONCLUSION

Intravitreal carboplatin plus bevacizumab, is a relatively safe, effective treatment for refractory retinoblastoma, however, ineffective for recurrent tumor.

Immunohistochemical expression of CD117 and vascular endothelial growth factor in retinoblastoma: possible targets of new therapies

CD117 (C-kit) is thought to play an important role in tumourigenesis. There are limited data in the literature concerning C-kit expression in retinoblastoma. To date, no immunohistochemical studies have been performed to assess the possible association of C-kit with vascular endothelial growth factor (VEGF) in retinoblastoma. This study was designed to investigate C-kit and VEGF immunoexpression in retinoblastoma, their relationship with prognostic parameters as well as the correlation between them. A prospective immunohistochemical study was conducted on 56 retinoblastoma cases. Patients who had received preoperative chemotherapy were excluded. Positive C-kit and VEGF immunoreactivity was observed in 48.2% and 76.8% of retinoblastoma cases respectively. No C-kit immunostaining was seen in the adjacent uninvolved retina. However, VEGF expression was detected within its vasculature. Retinoblastomas with combined pattern of tumour growth revealed a highly significant positive C-kit expression (P = 0.002) compared to cases with endophytic or exophytic growths. Also, positive C-kit expression was statistically higher in cases with optic nerve invasion (P = 0.001) and choroidal invasion (P ≤ 0.01) compared to negative cases. A highly significant positive VEGF expression was detected in cases with optic nerve invasion (P = 0.013) compared to negative cases. Moreover, a highly significant positive correlation was detected between C-kit and VEGF expression (P = 0.006). C-kit is a feature of more aggressive retinoblastomas, with increased expression in tumours spreading beyond the retina. Moreover, VEGF is vastly expressed in retinoblastoma and is associated with optic nerve invasion. Both C-kit and VEGF may represent potential therapeutic targets for retinoblastomas.

Retinoblastoma and retinal astrocytoma: unusual double tumor in one eye

Retinoblastoma is the most common intraocular neoplasm in children. Glial tumor of the retina and optic nerve head are considered to be congenital and are therefore classified as hamartomas. Concurrent occurrence of these tumors in one eye is uncommon and by reviewing the studies, a few cases have been reported. We report a 9 years old boy with eye enucleation and concurrent occurrence of retinoblastoma and astrocytoma in one eye as two separate and different masses. Although retinoblastoma and astrocytoma are two distinct tumors and their concurrent occurrence in one eye is rare, concurrent occurrence of these tumors may suggest differentiation of these two tumors from a neuroectodermal primary cell.

Anterior diffuse retinoblastoma: mutational analysis and immunofluorescence staining

Retinoblastoma is the most common primary intraocular tumor of childhood and may be heritable or occur sporadically. Anterior diffuse retinoblastoma is an uncommon variant that is thought to be sporadic. We describe a child with anterior diffuse retinoblastoma who presented with a pseudohypopyon. Genetic analysis showed a germline mutation of the RB1 allele that is potentially heritable. Immunofluorescence staining was positive for transforming growth factor beta and for vascular endothelial growth factor and negative for inducible nitric oxide synthase and for hypoxia inducible factor alpha in the tumor seeds, indicating acquisition of nonischemia-mediated survival factors of the tumor seeds in the aqueous humor.

Expression of motility-related protein MRP1/CD9, N-cadherin, E-cadherin, alpha-catenin and beta-catenin in retinoblastoma

In our earlier study we showed that invasive retinoblastoma (RB) had down regulated tetraspanin protein KAI1/CD82, a family of cell surface glycoprotein. KAI1 may link to the cell surface molecules, such as integrins, E-cadherin, and other TM4SF members, and loss of KAI1 function may have a significant role in the progression of retinoblastoma. We also showed that epithelial cell adhesion molecule (EpCAM) is overexpressed in invasive RB. EpCAM expression decreases adhesion mediated by cadherins. Thus, we were further interested in studying the role of other adhesion molecules like cadherins and catenins in RB. We studied the expression of Motility-Related Protein 1 (MRP-1)/CD9, E-cadherin, N-cadherin, alpha-catenin and beta-catenin in RB and correlated clinicopathologically in 62 archival paraffin-embedded tumors by immunohistochemistry. There were 29 tumors with no invasion of choroids/optic nerve and 33 tumors with invasion of choroid/optic nerve/orbit. Western blotting was performed on 20 tumors using the same antibodies. We observed higher expression of CD9 (P<0.001), E-cadherin (P<0.001) and alpha-catenin (P<0.001) in the non-invasive RB and higher expression of N-cadherin (P<0.001) in invasive RB. The expression of beta-catenin was not significantly different between two groups of tumors. In Western blotting, we were able to see CD9 and E-cadherin expression in a minority of tumors while N-cadherin, alpha-catenin and beta-catenin were expressed with differing intensities in a majority of tumors. Thus, invasive tumors expressed increased N-cadherin, alpha-catenin and decreased E-cadherin and CD9. Thus, it appears that loss of E-cadherin and gain of N-cadherin expression are features of invasiveness. Further functional studies are required to evaluate the role of beta-catenin in RB.

[Progress of cancer stem cells of solid tumor]

Stem cells have some characteristics similar to tumor cells, and may be the origin of tumor cells. Stem cell-like subpopulation has been isolated and identified from hematopoietic system malignancies and solid tumors, and defined as cancer stem cells. Cancer stem cells play important roles in the initiation and progression of malignancies. Tumor might be a kind of diseases of stem cells, and this finding may help to understand the mechanisms of tumorigenesis and instruct clinical therapeutics.

Stem cell markers: ABCG2 and MCM2 expression in retinoblastoma

BACKGROUND/AIM

The authors studied the expression of cancer stem cell surface marker, ABCG2, and neural stem cell marker, MCM2, in retinoblastoma and correlated clinicopathologically.

METHODS

Among 39 retinoblastomas, 18 tumours were not subjected to preoperative/postoperative chemotherapy, 15 tumours underwent postoperative chemotherapy, and six tumours had preoperative chemotherapy. There were 20 tumours with no invasion and 19 tumours with invasion of choroid/optic nerve. ABCG2 and MCM2 expression was studied by immunohistochemistry.

RESULTS

ABCG2 was positive in six of six and MCM2 was positive in five of six tumours that had recurred in the orbit or metastasised. ABCG2 was positive in 15/19 tumours with invasion. MCM2 was positive in 16/19 tumours with invasion. Invasive tumours showed higher expression of ABCG2 (p < 0.01) and MCM2 (p < 0.01) proteins. There was no correlation with differentiation and laterality of the tumours. Non-neoplastic retina was positive for ABCG2 and MCM2.

CONCLUSION

ABCG2 and MCM2 were expressed more in invasive tumours. Further studies are needed to understand the significance of ABCG2 and MCM2 expression in retinoblastoma.

Multidrug resistant proteins: P-glycoprotein and lung resistance protein expression in retinoblastoma

BACKGROUND/AIM

Retinoblastoma is the commonest primary intraocular tumour in children. Chemotherapy now plays a big part in the treatment of these tumours. There is not much information about the role of the multidrug resistance proteins (MDR)-P-glycoprotein (P-gp) and vault protein lung resistance protein (LRP)-in retinoblastoma. The authors investigated the expression of P-gp and LRP in retinoblastoma and correlated them clinicopathologically.

METHODS

Among 60 retinoblastomas, 40 tumours were not subjected to preoperative or postoperative chemotherapy and 20 tumours were subjected to postoperative chemotherapy. In this cohort 27 tumours had no invasion and 33 tumours had invasion of choroid, optic nerve, and orbit. P-gp and LRP expression were studied by immunohistochemistry. Immunoanalysis was done semiquantitatively.

RESULTS

Among the 60 tumours P-gp was expressed in 23 (38%) tumours and LRP was expressed in 35 (58%). P-gp was expressed in 11/27 (40%) tumours with no invasion and in 12/33 (36%) tumours with invasion. LRP was expressed in 15/27 (55%) tumours with no invasion and in 20/33 (60%) tumours with invasion. Both P-gp and LRP were negative in three tumours with invasion, which had later developed bone marrow metastasis. There was no correlation between P-gp and LRP expression with invasion, differentiation and laterality of the tumours and response to treatment.

CONCLUSION

Retinoblastoma expresses P-gp and LRP intrinsically before chemotherapy and none of these proteins predicted the response to chemotherapy. Thus, further studies are needed to understand the significance of the expression of the P-gp and LRP proteins in retinoblastoma.

Detection of germline mutations in argentine retinoblastoma patients: low and full penetrance retinoblastoma caused by the same germline truncating mutation

Constitutional RB1 gene mutations were studied in a series of 21 families with unilateral and bilateral retinoblastoma patients. Peripheral blood lymphocytes were analyzed by "exon by exon" PCR-heteroduplex and sequencing. Mutations were identified in 6 (29%) of the patients. One mutation corresponded to an intronic polymorphism in g.174351T > A. The other five mutations resulted C to T exonic transitions, four were CGA sequences (g.65386, g.150037 in two patients, and g.162237), creating stop codons and presumably truncated proteins. The fifth one was new and resulted in alanine to valine substitution (g.73774). Two patients had the same the germline truncated mutation (g.150037C > T), one with a familial bilateral early onset retinoblastoma and one with a sporadic unilateral late onset retinoblastoma. The later type has not been previously described. This finding is discussed in the genotype/phenotype correlation context. Additionally, a single nucleotide change was found in six studied samples, where a C to T homozygous transversion was identified in intron 26 (IVS26 + 28). It is worthy the non concordance of the nucleotide with the published sequence. This analysis proved to be a useful method for the detection of mutations in the RB1 gene, and contributed to the adequate genetic counseling to patients and relatives.

Expression of Fas ligand in retinoblastoma

BACKGROUND

The importance of the Fas-Fas ligand (FasL) mechanism for the immune evasion by tumors provided a strong rationale for the examination of FasL expression in retinoblastoma. In an earlier publication, the authors reported that invasive retinoblastomas decreased Fas expression. Because to the authors' knowledge there is not much information regarding the effect of FasL expression on retinoblastoma, the authors studied the expression of FasL in retinoblastoma and correlated it with invasiveness.

METHODS

Thirty-six archival retinoblastoma specimens were divided into 2 groups. Group A (n = 17) was comprised of specimens from tumors with no invasion and Group B (n = 19) was comprised of specimens from tumors with invasion of the choroid (focal, diffuse), optic nerve (laminar, postlaminar, surgical end), and orbit. Sections were immunostained with a monoclonal antibody to FasL and the immunoreactivity was assessed.

RESULTS

In Group A, FasL was negative in 100% (17 of 17) of the tumor specimens. In Group B, FasL was expressed in 79% (15 of 19) of the tumor specimens (positive in 9 tumors and heterogeneous in 6 tumors). The difference in FasL expression between the two groups was significant (P < 0.001)

CONCLUSIONS

Increased expression of FasL was observed in specimens taken from patients with aggressive tumors. Thus, Loss of Fas and gain of aberrant FasL expression were common features of malignant transformation. The data suggested that the Fas/FasL pathway is potentially immunosuppressive and may be involved in the escape of retinoblastoma cells from immune destruction.

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.

Glycosaminoglycans in human retinoblastoma cells: heparan sulfate, a modulator of the pigment epithelium-derived factor-receptor interactions

BACKGROUND

Pigment epithelium-derived factor (PEDF) has binding affinity for cell-surface receptors in retinoblastoma cells and for glycosaminoglycans. We investigated the effects of glycosaminoglycans on PEDF-receptor interactions.

RESULTS

125I-PEDF formed complexes with protease-resistant components of medium conditioned by human retinoblastoma Y-79 cells. Using specific glycosaminoglycan degrading enzymes in spectrophotometric assays and PEDF-affinity chromatography, we detected heparin and heparan sulfate-like glycosaminoglycans in the Y-79 conditioned media, which had binding affinity for PEDF. The Y-79 conditioned media significantly enhanced the binding of 125I-PEDF to Y-79 cell-surface receptors. However, enzymatic and chemical depletion of sulfated glycosaminoglycans from the Y-79 cell cultures by heparitinase and chlorate treatments decreased the degree of 125I-PEDF binding to cell-surface receptors.

CONCLUSIONS

These data indicate that retinoblastoma cells secrete heparin/heparan sulfate with binding affinity for PEDF, which may be important in efficient cell-surface receptor binding.

Expression of survivin, an inhibitor of apoptosis protein, in tumors of the nervous system

Survivin is an inhibitor of apoptosis protein that blocks apoptosis by binding to caspases-3 and -7. It is highly expressed in less-differentiated embryonic cells and rapidly dividing tumors, but not in terminally differentiated adult tissues. Elevated survivin levels are found in malignant systemic tumors, and are associated with chemo-resistance, radiation resistance, and poor prognosis. However, expression of survivin in primary nervous system tumors has not been previously characterized. Immunohistochemistry using anti-human survivin antibody (SURV11-A) was performed on formalin-fixed, paraffin-embedded archival tissue from 112 primary central nervous system tumors. Survivin immunoreactivity was seen in most diffuse astrocytomas [WHO II (2/4), III (3/3), IV (9/10), giant-cell glioblastoma (1), and gliosarcoma (1)]. The intensity and degree of survivin expression showed trends with tumor grade, with glioblastomas having the highest positivity. Pilocytic astrocytomas (5) and pleomorphic xanthoastrocytoma (1) were positive to a lesser degree. In oligodendrogliomas (6) and mixed oligo-astrocytomas [grade II (5), II-III (3), and III (7)], oligodendroglial elements appear to be negative compared to positive mini-gemistocytic oligodendrocytes. Ependymomas [grade II (6) and grade III (1)] were positive. Medulloblastomas (5) and retinoblastoma (1/4) showed focal positivity. All meningiomas [grade I (12), II (9), III (4), and grade I (3) and II (5) with frank brain invasion] were intensely positive. All schwannomas (11) and neurofibromas (6) were intensely positive. Thus, survivin is expressed in the majority of the primary nervous system tumors, particularly in glioblastomas, meningiomas, schwannomas and neurofibromas. Overexpression of survivin in meningiomas and benign peripheral nerve sheath tumors contrasts with previous reports relating it to rapid division and poor prognosis.

Clinicopathologic study of retinoblastoma including MIB-1, p53, and CD99 immunohistochemistry

Retinoblastoma is the most common intraocular tumor of childhood and has served as a model for the understanding or tumorigenesis. This study retrospectively examines the clinicopathologic features of 19 retinoblastomas and defines the MIB-1 (cell proliferation marker), p53 (tumor suppression gene), and CD99 (HBA71 or MIC2 antibody) immunoreactivity in 10 selected cases. Nineteen patients (11 boys), ranging in age from 6 to 47 months (mean, 20 months), were included for study. Clinical presentations included: leukocoria (n = 12), strabismus (n = 6), apparent decreased visual acuity (n = 5), and proptosis (n = 1). Five patients had bilateral tumors and one neoplasm arose in a patient with a known family history of retinoblastoma. All tumors were histologically characterized by a proliferation of small cells with high nuclear-to-cytoplasmic ratios. Commonly encountered histologic features included necrosis (n = 17, 89%), calcification (n = 16, 84%), fleurettes (n = 14, 74%), and Flexner-Wintersteiner rosettes (n = 11, 58%). Retinal involvement was noted in 18 tumors (95%) and optic nerve invasion in six cases (32%). The surgical optic nerve margin was positive in one case. Mitosis counts were evaluable in 18 cases and ranged from 1 to 42 mitotic figures/10 high power field (mean, 13 mitotic figures/10 high power field). Ten tumors were evaluated with MIB-1, p53, and CD99 antibodies by paraffin immunohistochemistry. MIB-1 labeling indices ranged from 31.4 to 77.1 (mean, 49.4). p53 immunostaining was observed in six tumors; less than 10% of tumor cells were noted to be p53 positive in each case. CD99 positivity was demonstrable focally in three tumors. Adjuvant chemotherapy and/or radiation therapy was administered in six patients. Tumor recurrence was not observed in any of the patients with a mean follow-up of 8.9 years. Only one patient died (20 years after enucleation) because of metastatic osteosarcoma.

IN CONCLUSION

(1) Fleurettes and Flexner-Wintersteiner rosettes are variable findings in retinoblastoma. (2) Retinoblastomas are characterized by marked cell proliferation as evidenced by generally high mitosis counts and extremely high MIB-1 labeling indices, but this does not appear to adversely impact on prognosis. (3) Unlike peripheral primitive neuroectodermal tumors, most retinoblastomas do not stain positively with antibody to CD99. (4) Limited p53 immunostaining was present in 60% of tumors studied. (5) Enucleation with negative optic nerve margin is potentially curative in patients with retinoblastoma.

Spectrum of germline RB1 gene mutations in Spanish retinoblastoma patients: Phenotypic and molecular epidemiological implications

Mutation analysis of retinoblastoma is considered important for genetic counseling purposes, as well as for understanding the molecular mechanisms leading to tumors with different degrees of penetrance or expressivity. In the course of an analysis of 43 hereditary retinoblastoma Spanish patients and kindred, using direct PCR sequencing, we have observed 29 mutations; most of them (62%) have not been reported previously. Of the mutations, 69% correspond to nonsense mutations (mainly CpG transitions) and frameshifts, with the expected outcome of a truncated Rb protein that lacks the functional pocket domains and tail. The remainder corresponds to splicing mutations, most of them (62%) targeted to invariant nucleotides, with the predicted consequence of out of frame exon skipping. Two of the splicing mutations in our study were found associated to families with a low-penetrance phenotype. Additionally, most of the mutations affecting splice junctions corresponded to retinoblastoma cases of either sporadic or hereditary nature with delayed onset (32 months on average). In contrast, most of the nonsense and frameshift mutations are associated with an early age at diagnosis (8.7 months on average). These differences are discussed in the context of the relationships between genotype and low expressivity phenotype. The differences in the spectrum of RB1 mutations found in this and other European surveys are also discussed in the context of alternate DNA methylation and mismatch repair phenotypes.

Alterations of cell cycle regulators affecting the RB pathway in nonfamilial retinoblastoma

We undertook the present study to examine alterations affecting the RB pathway in the G1 checkpoint and to determine their potential clinical significance in children affected with nonfamilial retinoblastoma. Using immunohistochemistry, patterns of expression of pRB, p16/INK4A, and E2F1 were analyzed in tissue from a cohort of 86 well-characterized patients with nonfamilial retinoblastoma diagnosed at the "Instituto Nacional de Pediatria" in Mexico City. The relationship of these phenotypes to proliferative index was assessed by analysis of Ki67 antigen expression. pRB expression was found in 11 (13%) cases. Using a hypophosphorylated specific pRB antibody, we observed low levels of underphosphorylated pRB expression in only 1 of 9 evaluable positive cases. These data suggest that the detected pRB products were hyperphosphorylated and thus had decreased functional activity. Increased p16 nuclear expression was found in only 6 tumors. No tumors showed deletions or mobility shifts of the INK4A gene. Undetectable pRB levels were significantly associated with undetectable p16 expression (odds ratio, 10.8; 95% confidence interval, 1.4-81.3; P =.03). All tumors showed nuclear immunoreactivities for E2F1 and Ki67. Increased Ki67 proliferative index was associated with increased staining for E2F1 (r =.44; P =.008) and increasing clinical stage (P =.03). Among children with unilateral disease, the mean Ki67 proliferative index was significantly higher in children with advanced clinical disease (stages 3 and 4) (mean 81.25; SD 6.78) than in those with earlier stage disease (mean 69.50; SD 9.45) (P = 0.001). Among children with bilateral disease, however, the mean proliferative index was not significantly higher for children with advanced clinical stage. When examining all cases together, there was a significant trend toward increasing proliferative index with increasing clinical stage (P =.03). In unilateral tumors, we also found that presence of detectable pRB was associated with a lower percentage of cells expressing E2F1 (46.7% v 70.8%) (P = 0.05), whereas there was no association between presence of pRB and E2F1 among bilateral tumors. We have found that expression of some of the cell cycle markers examined varies according to laterality, suggesting underlying differences in the capacity for cell cycle regulation between these 2 forms of the disease. Differences in capacities for cell cycle regulation may account for some differences in clinical behavior. Thus, the inclusion of molecular markers may become useful adjuncts to clinicopathological staging and subsequent determination of therapy.

Effect of 8-bromo-cyclic AMP on neuron specific enolase, heat shock protein, nitric oxide, nitric oxide synthase and nitric oxide synthase mRNA in human retinoblastoma HXO-Rb44 cells and cell differentiation

OBJECTIVE

To study the effect of 8-bromo-cyclic AMP (8-Br-cAMP) on nitric oxide synthase (NOS) mRNA, NOS and nitric oxide (NO) product, heat shock protein (hsp) 70 and neuron specific enolase (NSE) in human retinoblastoma HXO-Rb44 cells and the effect related to cell differentiation.

METHODS

Cultured human retinoblastoma HXO-Rb44 cells were divided into two aliquots. One was cultured with 2 x 10(-5) mol/L of 8-Br-cAMP for 24 hours as the experiment group; the other was treated with no 8-Br-cAMP as the control group. The cell suspensions in concentration of 1 x 10(7)/ml in both groups were dropped onto the nitrocellulose membrane (NCM). The NOS mRNA was detected with the biotin-labeled NOS cDNA probe by RNA dot blot. The NOS activity was detected by protein dot blot. The immunoreactivity (IR) of hsp70 and NSE was detected by protein dot blot. The NO was detected by nitrate reductase method. NCM specimens were analyzed by a TLC scanner for detection of the dot blot signal intensity.

RESULTS

The signals of NOS mRNA, NOS activity, hsp70-IR, NSE-IR, and NO content in the experiment group were higher than those in the control group (P < 0.05-0.01).

CONCLUSIONS

8-Br-cAMP could increase NO product and the expression of NOS mRNA, NOS, NSE and hsp70. The results indicate that 8-Br-cAMP could facilitate synthesis of NO in the neuroblastoma HXO-Rb44 cells, which could have tendency toward neuron development, suggesting that the increased hsp70, NO and NOS may involve cell differentiation of the retinoblastoma HXO-Rb44.

Cell death in retinoblastoma: electron microscopic, immunohistochemical, and DNA fragmentation studies

Apparent cell loss by apoptosis occurs in carcinomatous tissue. To investigate cell death in retinoblastoma (Rb), ultrastructural examination, ApopTag staining, electrophoresis to detect apoptotic DNA fragmentation, and flow cytometric studies were performed. Immunostaining for the oncogenic products bcl-2 and p53 was also carried out. Relationships between the proliferation fraction (PF), apoptotic index (AI), and the distribution of bcl-2 and p53 were investigated according to the degree of histologic differentiation of Rb. Ultrastructurally, two patterns of cell death were seen. Necrotic cells exhibited vacuolation of cytoplasmic organelles with a marked lytic change in the karyoplasm and cytoplasm. In contrast, apoptotic cells were characterized by crescentic margination of chromatin, condensation of karyoplasm and cytoplasm, and fragmentation of the nucleus. Differentiated Rb had a low AI value (< 1%), whereas undifferentiated Rb had a high AI value (> 8%). The PF of undifferentiated RB (31%) was significantly higher than that of differentiated RB (14%). Analysis of DNA fragmentation using 3'-end labeling with terminal transferase indicated that undifferentiated Rb has increased DNA cleavage. The distribution of apoptotic bodies within Rb was inversely correlated with the expression of bcl-2. A majority of tumor cells of differentiated Rb were negative for p53, whereas 20-40% of tumor cells of undifferentiated Rb showed a positive reaction for p53. These findings suggest that the degree of susceptibility to apoptosis is closely related to PF, is inversely related to the degree of differentiation of Rb, and is protected by oncogene bcl-2.

Behçet's disease and antibody titers to various heat-shock protein 60s

It has been suggested that the 65 kDa heat-shock protein (HSP) of Streptococcus in recurrent aphthae within the oral cavity may be involved in the uveoretinitis of Behçet's disease, possibly through sensitization of the immune system. To investigate this possibility, we examined serum antibody titers for various members of the 60 kDa family of HSPs and their implications with regard to a role for HSP60s in Behçet's disease. We isolated HSP60 of Streptococcus pyogenes from the margin of oral aphthae in one Behçet's disease patient with severe uveoretinitis and the HSP60s of Yersinia enterocolitica, retinoblastoma cell line clone Y79, and bovine retinal extract and investigated the reaction of each of these HSP60s with 100-fold diluted serum samples from 20 Behçet's disease patients using anti-HSP60 antibody titers determined by ELISA. The anti- Streptococcus HSP60 antibody and anti-retinal HSP60 antibody titers of the 100-fold diluted serum samples from the Behçet's disease patients were both significantly higher than those of similarly diluted serum samples from healthy donors. The results of the ELISA antibody titer assay showed that, although the various HSP60s share a common basic antigenicity, they differed in reactivity to the anti-HSP60 antibodies in the sera of the Behçet's disease patients. The results indicate that subtle but significant differences exist in the antigenicity of the various HSP60s tested, all of which share a common basic antigenicity and are of approximately the same molecular weight, and suggest that an immuno-cross-reaction between retinal and streptococcal HSPs and a related autoimmune response may be involved in the development of Behçet's disease.

D-aspartate is present in human retinoblastoma Y79 cells

In mammals, D-aspartate is present in various neuroendocrine cells, being especially abundant in pinealocytes. Although D-aspartate is suggested to be involved in some neuroendocrine function, little is known about its origins as well as its physiological roles. In the present study, we found that an appreciable amount of D-aspartate (50.8 pmol/1 x 10(6) cells) is present in clonal human retinoblastoma Y79 cells. The amount of D-aspartate corresponds to 28% of that in rat pinealocytes. The D-aspartate concentration did not change with the culture duration or passage, suggesting de novo biosynthesis of it. Thus, Y79 cells may constitute a suitable experimental system for studies on the biogenesis and signal transduction of D-aspartate in mammalian cells.

Proliferation not apoptosis as a prognostic indicator in retinoblastoma

The balance between proliferation and cell death is the major determinant of tumour growth. We analysed the proliferative and apoptotic indices (PI and AI, respectively) of 33 children with retinoblastoma. PI and AI were assessed by immunohistochemistry for Ki-67 antigen and TUNEL staining, respectively. The mean PI was 21.0+/-21.1%, and higher PI was associated with more advanced tumour stage (P<0.0001) and poor clinical outcome (P<0.05). Patients in whom amplified N-myc oncogene was found (n=6) determined by the multiplex polymerase chain reaction tended to have a higher PI (37.6+/-27.2%) than those without amplified N-myc (n=27; PI=17.3+/-18.1). A PI value of over 40% was clearly associated with an unfavourable prognosis. The AI, however, did not correlate with any of the other variables analysed. The findings suggest that proliferation, but not apoptosis, is of critical significance in retinoblastoma biology. PI, as determined by the Ki-67 antigen labelling index, seems to be a relevant histopathological parameter that can predict the clinical outcome of retinoblastoma.

Expression of vascular endothelial growth factor (VEGF) and its receptors is regulated in eyes with intra-ocular tumours

The immunolocalization and gene expression of vascular endothelial growth factor (VEGF) and its cognate tyrosine kinase receptors, Flt-1 and KDR, has been studied in ocular melanomas and retinoblastomas using in situ hybridization and immunohistochemistry. Tumour-related alterations in VEGF/VEGF-receptor expression have also been examined in separate and uninvolved iris, retina and choroid of the same eyes. Although VEGF immunoreactivity in the normal retina was virtually absent, low-level VEGF expression was evident in the ganglion cell-bodies, Müller cells and in a distinct population of amacrine cells. VEGF gene expression was absent in the iris and choroid of normal eyes. In tumour-bearing eyes, high levels of VEGF protein and gene expression were observed within the vascularized regions of the tumours, while the adjacent retina and choroid showed increased VEGF levels when compared with normals. Flt-1 and KDR gene expression and immunolocalization occurred in VEGF-expressing ganglion, Müller and amacrine cells in normal eyes. Within the intra-ocular tumours, VEGF-receptor gene expression and protein was evident in the endothelial cells and also in cells close to the vessels, while in the adjacent retina, Flt-1 and KDR levels were elevated over normal, especially in the blood vessels. Flt-1 and KDR were both observed at elevated levels in the choroid and iris blood vessels. This study suggests that VEGF, Flt-1 and KDR are expressed by neural, glial and vascular elements within normal human retina. Intra-ocular tumours demonstrate a high level of VEGF and VEGF-receptor expression; within uninvolved, spatially separate retina, choroid and iris in the same eyes, expression is also elevated, especially within the vasculature. Retinal vascular endothelia may respond to high intra-ocular levels of VEGF by increasing expression of their VEGF receptors, a phenomenon which could have relevance to neoplasm-related ocular neovascularization.

Second primary rhabdomyosarcomas in patients with bilateral retinoblastoma: a clinicopathologic and immunohistochemical study

We reviewed six cases of rhabdomyosarcoma as a rare second primary malignancy in children with bilateral retinoblastoma after irradiation treatment. The patients comprised four females and two males (age range 1 year 4 months-7 years 11 months). Second tumors arose in the temporal muscle inside or close to the previously irradiated fields. All the children were alive and well 24-72 months after diagnosis. Microscopic examination showed proliferation of closely packed, small round cells with scanty cytoplasm, coarse nuclear chromatin, and increased mitotic activity without a myxoid background nor obvious alveolar architecture. The most characteristic feature was the presence of rosette-like structures in four tumors. Immunoreactivity for many skeletal muscle markers was evident, including desmin (six of six), muscle-specific actin (HHF35) (six of six), sarcomeric actin (six of six), myogenin (six of six), vimentin (six of six), and myoglobin (three of six). On reverse transcriptase-polymerase chain reaction examination, three second tumors lacked specific chimeric transcripts for alveolar rhabdomyosarcoma and Ewing's sarcoma. Unexpectedly, variable reactivity for neurofilament (150 kd) was identified in six of six second tumors as well as 15 of 20 sporadic primary rhabdomyosarcomas (75%) examined as controls, the result being confirmed by Western blot analysis. In addition, staining for retinoblastoma-susceptibility gene protein was negative in all second tumors, in contrast to positivity in 14 of 17 sporadic primary tumors (82%). This finding suggests that retinoblastoma-susceptibility gene abnormalities could be associated with the development of second primary rhabdomyosarcoma. We consider that knowledge of the occurrence of rhabdomyosarcoma and appropriate immunohistochemical study are helpful for avoiding a misdiagnosis of recurrent retinoblastoma or Ewing's sarcoma when encountering patients with a history of bilateral retinoblastoma who developed second small round cell neoplasms.

Expression of centrin isoforms in the mammalian retina

Centrin is a calcium-binding phosphoprotein of centrosomes, mitotic spindle poles, and flagellar basal apparatus. Indirect immunofluorescence studies in human and rat retinas reveal centrin localization in two distinct cellular structures: at centrosomes of nonciliated neuronal cells as well as in basal bodies, and in larger amounts in the highly modified cilium--the connecting cilium--of photoreceptor cells. Western blot analyses of mammalian retinal proteins show two closely migrating centrin bands at about 20 kDa, the previously described molecular weight of centrins. Using isoform specific primers in PCR, the expression of two related but distinct forms of centrin (centrin 1 and centrin 2), can be identified in the retina of human and rat as well as in the mammalian testis, tissues where cilia are present. However, only one isoform (centrin 2) is expressed in nondifferentiated, nonciliated retinal cells (retinoblastoma cells), as well as in rat liver, skeletal muscle, and cardiac muscle. These observations suggest centrin 2 message may be universally expressed while centrin 1 message may be restricted to retina and testis which contain cells that have differentiated cilia or flagella, or their modifications.

A novel five-transmembrane hematopoietic stem cell antigen: isolation, characterization, and molecular cloning

Phenotypic analysis of hematopoietic stem and progenitor cells (HSCs) has been an invaluable tool in defining the biology of stem cell populations. We have recently described the production of AC133, a monoclonal antibody (MoAb) that binds to a novel cell surface antigen present on a CD34(bright) subset of human HSCs. This antigen is a glycosylated protein with a molecular weight of 120 kD. Here, we report the molecular cloning of a cDNA encoding this antigen and show that it does not share homology with any previously described hematopoietic or other cell surface antigen(s). The AC133 polypeptide has a predicted size of 97 kD and contains five-transmembrane (5-TM) domains with an extracellular N-terminus and a cytoplasmic C-terminus. Whereas the expression of tetraspan (4-TM) and 7-TM molecules is well documented on mature and immature hematopoietic cells and leukocytes, this 5-TM type of structure containing two large (255-amino acid [aa] and 290-aa) extracellular loops is unique and does not share sequence homology with any known multi-TM family members. Expression of this protein appears limited to bone marrow in normal tissue by immunohistochemical staining; however, Northern analysis suggests that the mRNA transcript is present in a variety of tissues such as the kidney, pancreas, placenta, and fetal liver. The AC133 antigen is also expressed on subsets of CD34+ leukemias, suggesting that it may be an important early marker for HSCs, as well as the first described member of a new class of TM receptors.

Demonstration of S-100 protein immunoreactivity in normal human retina and retinoblastoma

Specimens of 24 enucleated eyes from patients with retinoblastomas in situ were examined by labelled streptavidin biotin (LSAB) method to ascertain the distribution of S-100 protein and compared with 28 normal developing eyes. Polyclonal anti-S-100 antiserum and monoclonal alpha and beta chain anti-S-100 antibodies were used in this study. In the normal retina a weak reaction was observed in astrocytes and ganglion cells at 24 gestational weeks (GW) and there was an increase in the intensity of staining with increasing age. In the morphologically normal retina with retinoblastoma, astrocytes, ganglion cells and Müller cells showed positive reactions for S-100 protein. Examined tumors showed S-100 protein-positive glial cells that were interpreted as reactive astrocytes. No reaction product was detected in the tumor cells. These findings support the concept that in the retinoblastoma, only glial cells are positive for S-100 protein.

Mammalian G1 and G2 phase checkpoints

This present review explores the mechanisms for DNA damage induced G1 and G2 arrest in mammalian cells. The complexity of the TP53 pathway is attested to by the variety of genes regulated by TP53, many of which require further investigation to bring their importance into focus. One gene intensely studied, p21, has been linked to the G1 arrest mechanism and may, like TP53, be involved in some aspect of DNA repair. The outcome of TP53 activation for cell survival is equally complex and relies much upon cellular context and the type of DNA damaging agent employed. Although TP53 may participate in sensing DNA damage, additional components are likely to be required. Much of the focus on defining the mechanism of G2 arrest in mammalian cells has concentrated on the cyclin B1/CDC2 kinase. Activation of this kinase is suppressed by DNA damage, and this may result from the imposition of inhibitory phosphorylations on the CDC2 kinase as well as downregulation of cyclin B1 levels. The logical point where the G2 checkpoint interacts with the CDC2-CDC25C autocatalytic loop to prevent CDC2 activation remains to be defined and could involve inhibition of CDC25C-CDC2 interaction. It is hoped that moving upstream of CDC2 towards the point where DNA damage is sensed by the cell will uncover homologues of yeast components implicated in G2 checkpoint control. The finding that certain G2 checkpoint abrogators preferentially synergize with DNA damaging agents in cells with defective TP53 provides a potential pharmacological route through which TP53 defective cells might be targeted for destruction. Further exploration of this vulnerability might prove useful for future anti-cancer drug discovery efforts.

Observation of surface structure of retinoblastoma cell line

OBJECTIVE

We study the adhesion molecules on the surface of SO-Rb50 retinoblastoma cell line.

METHODS

The distribution of proteoglycans in the retinoblastoma SO-Rb50 cell line was analyzed by histochem-electron microscopy, using Colloidal Iron in combination with a series of enzyme digestions. In addition, immunohistochemistry was performed using a panel of specific antibodies including neuron specific enolase (NSE), glial fibrillary acidic protein (GFAP), S-100 protein, fibronectin, laminin, and collagen IV.

RESULTS

Immunohistochemical stains showed the most marked cytoplasmic reactivity of SO-Rb50 cells with anti-NSE and anti-S100. The cells member and surface was postive with anti-NSE. No reactivity was noted with antibodies against laminin, GFAP, and collagen IV. After incubated with colloidal iron solution, three types of colloidal iron-positive stained material could be distinguished based on differences in shape, size, electron density: (1) electron dense particles, (2) the larger colloidal iron-positive filaments, (3) the smaller colloidal iron-positive filaments, which were observed present on the tumor cells surface and in the extracellular matrix.

CONCLUSION

We think that the cell surface proteoglycans is the main component of adhesion molecules of retinoblastoma, which may play a central role in mediating tumor cell adhesion to extracellular matrix and adjacent host cell.

Increased chromokinesin immunoreactivity in retinoblastoma cells

chromokinesin is a developmentally down-regulated gene with specific expression in proliferating cells during embryonic chick development. It encodes a DNA-binding motor protein localized along the chromosome arm during mitosis, suggesting that the protein may be a component of the long-observed, yet poorly understood 'ejection force' hypothesized to be involved in controlling the direction and speed of chromosome movement. We have isolated human chromokinesin; with affinity-purified antibodies we demonstrated immunocytochemically that Chromokinesin was present at a much higher level in cultured retinoblastoma cells than in primary cultures of human dermal fibroblasts. The increase in immunoreactivity was particularly prominent in interphase cells, whereas in primary cultures of fibroblasts immunopositive cells were predominantly M-phase cells. These observations imply a deregulation of chromokinesin in retinoblastoma cells. Data presented here may be useful in designing strategies to modulate chromosome movement and cell proliferation with either antisense oligonucleotides or specific antibodies, and hence may set the stage for further investigations of the involvement of chromosome motor molecules in mitosis under normal and pathological conditions.

Unilateral retinoblastoma in an adult: report of a case and review of the literature

PURPOSE

The authors report the clinical, cytologic, and histopathologic findings of a unilateral retinoblastoma occurring in a 26-year-old woman. This tumor usually affects young children; the mean age at the time of diagnosis usually ranges from 10 to 25 months.

METHODS

Histopathologic examination of the enucleated right eye included using standard techniques, as well as immunohistochemical stains of formalin-fixed, paraffin-embedded tissues.

RESULTS

Histologic examination of sections of the eye showed a retinal tumor that was centered in the equatorial region and had the typical features of a poorly differentiated retinoblastoma. Focal choroidal invasion and seeding of the anterior and posterior chambers were observed. Immunoreactivity of the tumor cells for neuron-specific enolase confirmed that the tumor is a neuronal neoplasm consistent with retinoblastoma.

CONCLUSION

Retinoblastoma occurring in adults is a rare finding. In most large series of retinoblastomas, no adults are included. Only eight patients 20 years of age or older with retinoblastomas have been documented previously. In the current case, the patient had no evidence of orbital recurrence or metastasis 6 years after enucleation of the eye. It may be important for clinicians to consider this diagnosis when confronted with a retinal mass of unknown etiology in adults.

Failure to detect mutations in the retinoblastoma protein-binding domain of the transcription factor E2F-1 in human cancers

The functions of the transcription factor E2F-1 are regulated by the RB protein through the RB-binding domain of E2F-1 and this factor is considered to be an important molecule that functions downstream of the RB protein. In order to determine whether E2F-1 that cannot bind to RB might be associated with various human cancers, we searched for mutations in the RB-binding domain of E2F-1 using samples of DNA from various clinical specimens obtained from 406 cancer patients (with lung, pancreatic, stomach, colon, esophageal, and hepatic cancers) by analysis of polymerase chain reaction-mediated single-strand conformational polymorphism. No mutations or deletions were detected in genes for E2F-1 from any of the tumor tissues examined. These results suggest that a mutation or deletion in E2F-1 that might affect binding of the RB protein is not involved in human cancers.

Chemotherapy plus local treatment in the management of intraocular retinoblastoma

OBJECTIVE

To describe platinum-based chemotherapy combined with local treatment modalities as an alternative to external beam radiotherapy for intraocular retinoblastoma.

DESIGN

Platinum levels were measured by atomic absorption analysis in the tumors of 2 patients with retinoblastoma given carboplatin 5 or 2.5 hours before enucleation. Platinum levels in heated vs nonheated Greene melanoma tumors in rabbits were compared. A retrospective review of 172 affected eyes in 136 consecutive patients treated for retinoblastoma between January 1990 and December 1995 was performed. From 1990 to 1992, all treatable eyes initially received systemic carboplatin, 560 mg/m2, followed by 15 to 30 minutes of continuous diode laser hyperthermia (thermochemotherapy). Since 1992, larger tumors were treated initially with 3 monthly cycles of carboplatin, etoposide, and vincristine sulfate to reduce tumor volume (chemoreduction) followed by sequential aggressive local therapy (SALT) during examinations under anesthesia every 2 to 3 weeks.

OUTCOME MEASURE

Treatment success was defined as eradication of tumor without enucleation or external beam radiotherapy.

RESULTS

Significant therapeutic platinum levels were measured in the human tumors 2.5 and 5 hours after carboplatin administration. Increasing the temperature by 9 degrees C for 15 minutes doubled platinum levels in the rabbit model. Of the 38 eyes with Reese-Ellsworth group 1 through 5b tumors that were treated primarily with thermochemotherapy, all 24 eyes with group 1 and 2 tumors were treated successfully and two of the 4 eyes with group 3 tumors and all 10 eyes with group 5b tumors were treated unsuccessfully. Chemoreduction plus SALT was the primary treatment in 35 eyes and was successful in all 10 eyes with group 1 through 4 tumors and unsuccessful in all 7 eyes with extensive subretinal seeding and all 18 eyes with group 5b tumors with vitreous seeding. Seventy patients received carboplatin or carboplatin, vincristine, and etoposide, with myelosuppression, occasionally associated with bacteremia, being the main side effect. Transfusions were required in 15% of patients. Radiation retinopathy occurred in all 6 eyes treated with iodine 125 plaques.

CONCLUSIONS

Thermochemotherapy is successful primary treatment for Reese-Ellsworth group 1 and 2 retinoblastomas. For larger tumors in the absence of vitreous or extensive subretinal seeding, 3 cycles of chemoreduction followed by SALT eradicates residual viable tumor. Chemoreduction plus SALT was not successful in eyes with diffuse vitreous or extensive subretinal seeding. Prior chemotherapy increases the risk for radiation retinopathy following 125I plaque therapy. External beam radiotherapy can safely be avoided in the primary treatment of Reese-Ellsworth groups 1 through 4 nondispersed retinoblastoma.

Immunocytochemical features of retinoblastoma in an adult

OBJECTIVE

To describe the clinical course and immunocytochemical characteristics of an unusual intraocular tumor.

METHODS

Immunocytochemical analysis of the enucleated eye with an intraocular mass that markedly waxed and waned in size during 1 year of close observation of a 29-year-old woman.

RESULTS

Most of the tumor was composed of either dying or rapidly proliferating cells. One area located near the retina consisted mostly of well-differentiated cells in uniform sheets (bacillettes) with lacelike glial processes between the tumor cells. Almost all of the differentiated tumor cells were positive for S antigen. In particular, the dominant cell type stained positively for both antibodies known to be specific for those isoforms of S antigen found only in blue cones and rods but not in red or green cones. Only a few of these cells labeled positively with an anti-rhodopsin antibody.

CONCLUSIONS

This is the first case of adult retinoblastoma to be confirmed immunocytochemically. The tumor was unusual because the differentiated regions contained bacillettes composed mostly of blue cones. It is possible that this and other adult retinoblastomas may arise from previously existing retinocytomas.

The generally expressed hnRNP F is involved in a neural-specific pre-mRNA splicing event

The proteins and RNA regulatory elements that control tissue-specific pre-mRNA splicing in mammalian cells are mostly unknown. In this study, a set of proteins is identified that binds to a splicing regulatory element downstream of the neuron specific c-src N1 exon. This complex of proteins bound specifically to a short RNA containing the regulatory sequence in neuronal extracts that splice the N1 exon. It was not seen in non-neuronal cell extracts that fail to splice this exon. UV-cross-linking experiments identified a neuron-specific 75-kD protein and several nontissue-specific proteins, including the 53-kD heterogeneous nuclear ribonucleoprotein F (hnRNP F), as components of this complex. Although present in both extracts, hnRNP F binds tightly to the RNA only in the neuronal extracts. A mutation in the regulatory RNA sequence, that inhibits N1 splicing in vivo, abolished formation of the neuron-specific complex and the binding of the neuron-specific 75-kD protein. Competition experiments in the two extracts show that the binding of the neuronal protein complex to the src pre-mRNA is required to activate N1 exon splicing in vitro. Antibody inhibition experiments indicate that the hnRNP F protein is a functional part of this complex. The assembly of regulatory complexes from both constitutive and specific proteins is likely to be a general feature of tissue-specific splicing regulation.

Immunohistochemical features of the human retina and retinoblastoma

The immunohistochemical features of 24 retinoblastoma specimens from 22 patients, 15 with unilateral and 7 with bilateral disease, were examined by the labelled streptavidin biotin (LSAB) method and compared with those of specimens from the remaining morphologically normal retina. In the normal retina, S-100 protein, glial fibrillary acidic protein (GFAP) and vimentin were detected in astrocytes and/or Müller cells. Neurofilament protein was seen in axons of the ganglion cells, synaptophysin was present in both plexiform layers, bcl-2 oncoprotein was seen in ganglion cells and bipolar cells, and neuron-specific enolase (NSE) was detected in ganglion cells, bipolar cells and photoreceptor cells and in their cell processes. While retinoblastoma (Rb) protein expression was noted in ganglion cells, bipolar cells, and some photoreceptor cells, p53 protein was not expressed at all. In all retinoblastomas, strong NSE expression and weak bcl-2 expression was observed in almost all tumour cells and synaptophysin was localized in rosette-forming cells, while tumour cells were devoid of S-100, GFAP, vimentin and neurofilament protein. These findings support the view that retinoblastomas are composed of neuron-committed cells. In addition, no Rb protein expression was detected in retinoblastomas, whereas p53 expression was found in 18 cases (75%).

Retinoblastoma. Cell of origin

OBJECTIVES

To apply modern techniques of molecular cell biology and to revisit the old question of the cell of origin for retinoblastoma in hopes of gaining a better understanding of the retinoblastoma gene's antioncogenic mechanisms.

METHODS

Twenty-two consecutively accessed retinoblastomas were examined with immunocytochemical techniques for numerous retinal proteins. Both single and double labeling were used. Enzyme histochemistry for carbonic anhydrase was used as well.

RESULTS

Differentiated areas of the tumors contained abundant Müllerlike cells. Fleurettes stained mostly for red and green cone-specific antibodies while features of blue cones and rods predominated in areas with high cytoplasmic-to-nuclear ratios but no fleurettes. All of the differentiated neoplastic cells were either photoreceptors or Müller's cells. No other retinal cell types were found.

CONCLUSIONS

The cells of retinoblastoma are capable only of bipotential differentiation, ie, Müller's cells and photoreceptors. Given this and recent findings concerning retinal embryogenesis, we argue for the rod photoreceptor as the cell of origin. A possible role for the retinoblastoma gene product is discussed.

Coupling of corticotropin-releasing hormone receptors to adenylyl cyclase in human Y-79 retinoblastoma cells

In human Y-79 retinoblastoma cells, corticotropin-releasing hormone (CRH) stimulates adenylyl cyclase activity and increases cyclic AMP accumulation. Different CRH analogues mimic the CRH stimulation of adenylyl cyclase and show similar sensitivity to the CRH receptor antagonist alpha-helical CRH9-41. Vasoactive intestinal peptide (VIP) also increases the enzyme activity but less potently than CRH, and its effect is counteracted by the VIP receptor antagonist [D-p-Cl-Phe6,Leu17]VIP. The VIP antagonist does not affect the response to CRH. The CRH-stimulated adenylyl cyclase activity is amplified by Mg2+, is inhibited by submicromolar concentrations of Ca2+, and requires GTP. Moreover, the CRH stimulation is reduced by pretreatment of cells with cholera toxin and by incubation of membranes with the RM/1 antibody, which recognizes the C-terminus of the alpha subunit of Gs. In immunoblots, the RM/1 antibody identifies a doublet of 45 and 52 kDa. Two proteins of similar molecular weights are ADP-ribosylated by cholera toxin. These data demonstrate that in human Y-79 retinoblastoma cells, specific CRH receptors stimulate cyclic AMP formation by interacting with Gs and by affecting a Ca(2+)-inhibitable form of adenylyl cyclase.

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.

High-performance liquid chromatographic method for the determination of insulin synthesis in biological systems

This paper reports a two-step high-performance liquid chromatographic procedure which permits the study of the incorporation of [3H]leucine into insulin in biological systems. The first step of the procedure was size exclusion chromatography, performed on a GPC-100 column, which was eluted with 0.1 M KH2PO4-methanol (9:1, v/v). By this step the bulk of both protein and radioactivity was separated from tritiated insulin. The second step, which employs reversed-phase chromatography on an octadecylsilyl column, permits the separation of insulin from other contaminants by means of a linear gradient of acetonitrile. This simple and reproducible method was employed to test insulin synthesis in cultured human retinoblastoma Y79 cells.

Lack of detection of p53 expression in retinoblastoma tumor cells

p53 was examined by immunohistochemistry in five cases of retinoblastoma, a neoplasm that is caused by a loss of function of the Retinoblastoma susceptibility gene (Rb), mapped to chromosome 13q14. Object of the study was the identification of eventual further gene mutation in retinoblastoma tumor cells determining the onset of an independent tumoral monoclonal cell subset. We did not observe any positive reaction for p53 protein expression in the five cases we analyzed.

[Retinoblastoma: cell origin and differentiation]

50 retinoblastoma paraffin blocks were studied immunohistochemically (NSE, GFAP) and histochemically (colloidal-iron, RNA), and 13 cases by EM. The Rb cells demonstrated varying degrees of positive or negative reaction to NSE, most F-W and H-W rosettes being positive and the fleuretes weakly positive or negative. The GFAP positive cells were mainly found in the periphery of the tumor mass and around the blood vessels, and sparsely among the NSE positive cells. Fleuretes were clearly shown by RNA-Brachet staining. F-W rosettes and fleuretes showed similar ultrastructures as the photoreceptor of normal retina. The results confirmed that retinoblastoma originates from the retinoblast with potential of differentiation into photoreceptors and neurons. The glial components pertained to reactive gliosis, however, the rare possibility of forming a small portion of the tumor could not be ruled out.

Expression of the retinoblastoma protein is regulated in normal human tissues

The nuclear phosphoprotein encoded by the retinoblastoma gene (pRB) appears to play a central role in control of cell division and differentiation. It is generally accepted that pRB is ubiquitously expressed. We investigated the expression of pRB in normal human tissues using immunochemical techniques to determine the expression of pRB in specific cell types. Maturing cells, both proliferating and nonproliferating, rather than their progenitors possess the highest levels of pRB. Cells of stratified epithelia, such as those from cervix, display strong immunostaining in the nondividing maturing suprabasal layer, whereas basal cells showed low to undetectable levels of pRB. Similar patterns of expression were observed in simple epithelia and hematopoietic cells contained within distinguishable proliferating compartments and in germ cell development. These studies are crucial to our understanding of processes involved in control of differentiation (tumorigenesis) as well as tumor progression.