cyclin-d1 and Uveal-Neoplasms

Melanoma has one of the highest somatic mutational burdens among solid malignancies. Although the rapid progress in genomic research has contributed immensely to our understanding of the pathogenesis of melanoma, the clinical significance of the vast array of genomic alterations discovered by next-generation sequencing is far from being fully characterized. Most mutations prevalent in melanoma are simply neutral "passengers," which accompany functionally significant "drivers" under transforming conditions. The delineation of driver mutations from passenger mutations is critical to the development of targeted therapies. Novel advances in genomic data analysis have aided in distinguishing true driver mutations involved in tumor progression. Here, the authors review the current literature on important somatic driver mutations in melanoma, along with the implications for treatment. Cancer 2017;123:2104-17. © 2017 American Cancer Society.

Topics: Cyclin D1; GTP Phosphohydrolases; GTP-Binding Protein alpha Subunits; GTP-Binding Protein alpha Subunits, Gq-G11; Guanine Nucleotide Exchange Factors; High-Throughput Nucleotide Sequencing; Humans; Melanoma; Membrane Proteins; Metalloproteins; Microphthalmia-Associated Transcription Factor; Mutation; Neurofibromin 1; Nuclear Proteins; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-kit; PTEN Phosphohydrolase; rac1 GTP-Binding Protein; Ribosomal Proteins; RNA-Binding Proteins; Sequence Analysis, DNA; Skin Neoplasms; Telomerase; Tumor Suppressor Protein p53; Uveal Neoplasms

Uveal melanoma (UM) is the most common intraocular malignancy in adults with a poor prognosis and a high recurrence rate. Currently there is no effective treatment for UM. Multi-kinase inhibitors targeting dysregulated pro-tumorigenic signalling pathways have revolutionised anti-cancer treatment but, as yet, their efficacy in UM has not been established. Here, we identified the multi-kinase inhibitor afatinib as a highly effective agent that exerts anti-UM effects in in vitro, ex vivo and in vivo models.. We assessed the anti-cancer effects of afatinib using cell viability, cell death and cell cycle assays in in vitro and ex vivo UM models. The signaling pathways involved in the anti-UM effects of afatinib were evaluated by Western blotting. The in vivo activity of afatinib was evaluated in UM xenograft models using tumour mass measurement, PET scan, immunohistochemical staining and TUNEL assays.. We found that afatinib reduced cell viability and activated apoptosis and cell cycle arrest in multiple established UM cell lines and in patient tumour-derived primary cell lines. Afatinib impaired cell migration and enhanced reproductive death in these UM cell models. Afatinib-induced cell death was accompanied by activation of STAT1 expression and downregulation of Bcl-xL and cyclin D1 expression, which control cell survival and cell cycle progression. Afatinib attenuated HER2-AKT/ERK/PI3K signalling in UM cell lines. Consistent with these observations, we found that afatinib suppressed tumour growth in UM xenografted mice.. Our data indicate that afatinib activates UM cell death and targets the HER2-mediated cascade, which modulates STAT1-Bcl-xL/cyclin D1 signalling. Thus, targeting HER2 with agents like afatinib may be a novel therapeutic strategy to treat UM and to prevent metastasis.

Topics: Afatinib; Animals; Antineoplastic Agents; Apoptosis; Cell Line, Tumor; Cell Proliferation; Cyclin D1; Humans; Melanoma; Mice; Protein Kinase Inhibitors; Uveal Neoplasms; Xenograft Model Antitumor Assays

Ocular melanoma is a disorder that is rarely found but is deadly. Four tissues in the eye that can be attacked by melanoma include the uveal tract, conjunctiva, eyelids, and orbit. Uveal melanoma is the most common case, while melanoma conjunctiva is very rare.. This study aimed to investigate the effect of giving genistein on cyclin D1 expression in malignant melanoma.. When confluent, CRL1872 malignant melanoma cells will be divided into treatment groups, the group giving genistein dose 25 μM, the group giving genistein a dose of 50 μM, and the group giving genistein a dose of 100 μM. Cyclin D1 analysis was measured by immunofluorescence using confocal laser scan microscopy.. There was a significant increase in the expression of cyclin D1, in the group given genistein 25 μM and 50 μM (p < 0.05). For the administration of the genistein dose of 100 μM, cyclin D1 expression decreased significantly compared to the control group (p < 0.05).. It was concluded that genistein had a biphasic effect on cyclin D1 expression in malignant melanoma cells. Thus, genistein at the right dose can be a treatment of malignant melanoma.

Topics: Cyclin D1; Genistein; Humans; Melanoma; Skin Neoplasms; Uveal Neoplasms

Uveal melanoma (UM) is an intraocular malignant tumor in adults that is characterized by rapid progression and recurrence. Irradiation has become the primary therapy for UM patients who are not candidates for surgery. However, after large-dose fraction irradiation treatment, some patients undergo subsequent enucleation because of radiotherapy-related complications. This situation has raised concerns on how to optimize the effectiveness of radiation treatment. Recent investigations of microRNAs are changing our understanding of UM tumor biology and are helping to identify novel targets for radiotherapy. The radioresistant UM cell lines OM431 and OCM1 were selected and exposed to irradiation, and let-7b was found to be downregulated after exposure. We then confirmed that let-7b mimics could inhibit UM growth both in vitro and in vivo. More specifically, transfection with let-7b mimics markedly resensitized OCM1 and OM431 cells to irradiation by reducing the population of S-phase cells. Cyclin D1 plays a vital role in cell cycle arrest, which is induced by let-7b overexpression. Cyclin D1 is also a target of let-7b and its expression is suppressed by upregulation of let-7b. Collectively, our results indicate that let-7b overexpression can in turn downregulate cyclin D1 expression and enhance the radiosensitivity of UM through cell cycle arrest. Let-7b could serve as a marker for radiosensitivity and could enhance the therapeutic benefit of UM cell irradiation.

Topics: Animals; Cell Line, Tumor; Cell Proliferation; Cyclin D1; Dose-Response Relationship, Radiation; Gene Expression Regulation, Neoplastic; Humans; Melanoma; Mice, Nude; MicroRNAs; S Phase Cell Cycle Checkpoints; Time Factors; Transfection; Tumor Burden; Up-Regulation; Uveal Neoplasms; Xenograft Model Antitumor Assays

Intraocular melanocytoma is a rare naevus variant that can be located at the optic disc or within the uvea, and belongs to the group of non-epithelial-associated melanocytic lesions. We wanted to gain an understanding of the role of GNAQ, GNA11 and BRAF V600E in the pathogenesis of uveal melanocytoma and in cases of transformation to uveal melanoma and also to perform a differential immunohistochemical study comparing melanocytoma with uveal melanoma.. Two patients were identified with melanocytoma, one of which had transformed to melanoma. In the latter case, the melanocytoma exhibited an immunophenotype that featured nuclear p27 and no HMB45 staining, with very low Cyclin D1 expression compared with the melanoma that featured little nuclear but more cytoplasmic p27 positivity, much higher Cyclin D1 expression and HMB45 positivity. The melanocytomas were negative for CD68 allowing distinction from melanophages. Both melanocytomas and the melanoma harboured mutations in GNAQ, with no mutations of GNA11 or BRAF V600E.. GNAQ mutations are present in uveal melanocytomas and in a case of transformation to melanoma, implicating GNAQ-dependent mitogen activation signals, in the pathogenesis of uveal melanocytoma. This assists in explaining why a proportion of uveal melanocytoma can transform to uveal melanoma, known to harbour high-frequency GNAQ mutations at exon 5, codon 209.

Topics: Adolescent; Adult; Cell Transformation, Neoplastic; Chromosomes, Human, Pair 3; Chromosomes, Human, Pair 8; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p27; gp100 Melanoma Antigen; GTP-Binding Protein alpha Subunits; GTP-Binding Protein alpha Subunits, Gq-G11; Humans; Immunoenzyme Techniques; In Situ Hybridization, Fluorescence; Male; MART-1 Antigen; Melanoma; Melanoma-Specific Antigens; Mutation; Nevus, Pigmented; Polymerase Chain Reaction; Proto-Oncogene Proteins B-raf; Retrospective Studies; Uveal Neoplasms

GNAQ mutations at codon 209 have been recently identified in approximately 50% of uveal melanomas (UM) and are reported to be oncogenic through activating the MAPK/Erk1/2 pathway. Protein kinase C (PKC) is a component of signaling from GNAQ to Erk1/2. Inhibition of PKC might regulate GNAQ mutation-induced Erk1/2 activation, resulting in growth inhibition of UM cells carrying GNAQ mutations. UM cells carrying wild type or mutant GNAQ were treated with the PKC inhibitor enzastaurin. Effects on proliferation, apoptosis, and signaling events were evaluated. Enzastaurin downregulated the expression of several PKC isoforms including PKCβII PKCθ, PKCε and/or their phosphorylation in GNAQ mutated cells. Downregulation of these PKC isoforms in GNAQ mutated cells by shRNA resulted in reduced viability. Enzastaurin exhibited greater antiproliferative effect on GNAQ mutant cells than wild type cells through induction of G1 arrest and apoptosis. Enzastaurin-induced G1 arrest was associated with inhibition of Erk1/2 phosphorylation, downregulation of cyclin D1, and accumulation of cyclin dependent kinase inhibitor p27(Kip1). Furthermore, enzastaurin reduced the expression of antiapoptotic Bcl-2 and survivin in GNAQ mutant cells. Inhibition of Erk1/2 phosphorylation with a MEK specific inhibitor enhanced the sensitivity of GNAQ wild type cells to enzastaurin, accompanied by p27(Kip1) accumulation and/or inhibition of enzastaurin-induced survivin and Bcl-2 upregulation. PKC inhibitors such as enzastaurin have activity against UM cells carrying GNAQ mutations through inhibition of the PKC/Erk1/2 pathway and induction of G1 arrest and apoptosis. Inhibition of the PKC pathway provides a basis for clinical investigation in patients with UM.

Topics: Apoptosis; Bromodeoxyuridine; Cell Cycle Checkpoints; Cell Line, Tumor; Cell Proliferation; Cell Survival; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p27; Drug Screening Assays, Antitumor; Enzyme Activation; Extracellular Signal-Regulated MAP Kinases; GTP-Binding Protein alpha Subunits; GTP-Binding Protein alpha Subunits, Gq-G11; Humans; Indoles; Isoenzymes; Melanoma; Mitogen-Activated Protein Kinase Kinases; Molecular Sequence Data; Mutation; Protein Kinase C; Protein Kinase Inhibitors; Proto-Oncogene Proteins c-akt; Uveal Neoplasms

RASSF1A gene, found at the 3p21.3 locus, is a tumor suppressor gene frequently hypermethylated in human cancers. In this study, we report that compared with melanocytes in normal choroid, RASSF1A is downregulated in uveal melanoma samples and in uveal melanoma cell lines. LOH at 3p21.3 was detected in 50% of uveal melanoma. Moreover, methylation of the RASSF1A promoter was detected in 35 of 42 tumors (83%) and RASSF1A was also weakly expressed at the mRNA level. These data indicate that LOH at the RASSF1A locus or RASSF1A promoter methylation may partly account for the suppression of RASSF1A expression observed in uveal melanoma. Furthermore, following ectopic expression in three RASSF1A-deficient melanoma cell lines (OCM-1, Mel270, and 92.1), RASSF1A weakly reduces cell proliferation and anchorage-independent growth of uveal melanoma cells without effect on ERK1/2 activation, cyclin D1 and p27(Kip1) expression. This study explored biological functions and underlying mechanisms of RASSF1A in the ERK1/2 pathway in normal uveal melanocytes. We showed that siRNA-mediated depletion of RASSF1A increased ERK1/2 activation, cyclin D1 expression, and also decreased p27(Kip1) expression in normal uveal melanocytes. Moreover, that the depletion of RASSF1A induced senescence-associated β-galactosidase activity and increased p21(Cip1) expression suggests that RASSF1A plays a role in the escape of cellular senescence in normal uveal melanocytes. Interestingly, we found that RASSF1A was epigenetically inactivated in long-term culture of uveal melanocytes. Taken together, these data show that depletion of RASSF1A could be an early event observed during senescence of normal uveal melanocytes and that additional alterations are acquired during malignant transformation to uveal melanoma.

Topics: Cell Line, Tumor; Cell Proliferation; Cellular Senescence; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p21; Cyclin-Dependent Kinase Inhibitor p27; DNA Methylation; Gene Expression Regulation, Neoplastic; Humans; Loss of Heterozygosity; MAP Kinase Signaling System; Melanocytes; Melanoma; Promoter Regions, Genetic; RNA, Small Interfering; Tumor Suppressor Proteins; Uveal Neoplasms

Primary melanoma of the iris, for reasons unknown has a lower metastatic rate compared with primary ciliary-body melanoma. Six histology cases of ciliary-body melanoma were identified that had spread onto the iris surface and into the stroma, representing a change in tumour microenvironment from aqueous humour non-exposure (ciliary-body component) to aqueous humour exposure (iris surface component). This provided an ideal paradigm for investigating the effects of different environments on melanoma.. Conventional light microscopy was performed on stained paraffin sections of the identified cases, followed by immunohistochemistry to cell cycle proteins p27 and Cyclin D1. Fluorescence in situ hybridisation (FISH) analysis was conducted on the paraffin sections for changes of chromosomes 3 and 8, associated with poor uveal melanoma prognosis.. Iris surface melanoma cells were smaller compared with the adjacent deeper iris stromal melanoma cells and with those in the ciliary body. Fewer iris surface melanoma cells expressed Cyclin D1 protein, but more expressed p27 protein, compared with the larger iris stromal melanoma cells (paired Wilcoxon signed ranks test: Cyclin D1 p = 0.028; p27 p = 0.046) and with the ciliary-body melanoma cells (paired Wilcoxon signed ranks test: Cyclin D1 p = 0.028; p27 p = 0.028). With FISH, chromosome 3 and 8 alterations were less common among the iris surface melanoma cells than the deeper iris stromal melanoma cells and the ciliary-body melanoma cells, which were consistently characterised by a relative genetic imbalance for chromosomes 3 and 8.. These data suggest that there are tumour-modulatory factors within the anterior chamber environment that probably select populations of ciliary-body melanoma cells, with a less aggressive, better-differentiated status. Furthermore, it may help explain why iris melanomas generally have a less aggressive course than ciliary-body and choroidal melanomas.

Topics: Aged; Aged, 80 and over; Anterior Chamber; Chromosomes, Human, Pair 3; Chromosomes, Human, Pair 8; Ciliary Body; Cyclin D1; Female; Humans; In Situ Hybridization, Fluorescence; Iris; Male; Melanoma; Middle Aged; Neoplasm Invasiveness; Neoplasm Proteins; Proliferating Cell Nuclear Antigen; Tissue Fixation; Uveal Neoplasms

Mutated B-Raf-mediated constitutive activation of ERK1/2 is involved in about 66% of cutaneous melanoma. By contrast, activating mutations in B-RAF are rare in ocular melanoma. This study aimed to determine the role of wild-type B-Raf ((WT)B-Raf) in uveal melanoma cell growth. We used cell lines derived from primary tumors of uveal melanoma to assess the role of (WT)B-Raf in cell proliferation and to characterize its upstream regulators and downstream effectors. Melanoma cell lines expressing (WT)B-Raf and (WT)Ras grew with similar proliferation rates, showed constitutive activation of ERK1/2, and had similar levels of B-Raf expression and B-Raf kinase activity as melanoma cell lines expressing the activating V600E mutation ((V600E)B-Raf). They were equally as sensitive to pharmacological inhibition of MEK1/2 for cell proliferation and transformation as (V600E)B-Raf cells. siRNA-mediated depletion of Raf-1 did not affect either ERK1/2 activation, whereas siRNA-mediated depletion of B-Raf reduced cell proliferation by up to 65% through the inhibition of ERK1/2 activation, irrespective of the mutational status of B-Raf. Pharmacological inhibition of cAMP-dependent protein kinase (PKA) and siRNA-mediated depletion of PKA greatly reduced B-Raf activity, ERK1/2 activation, and cell proliferation in (WT)B-Raf cells, whereas it did not affect (V600E)B-Raf cells, demonstrating a key role of PKA in mediating (WT)B-Raf/ERK signaling for uveal melanoma cell growth. Moreover, inactivation or depletion of PKA did not affect Rap-1 activity, and Rap-1 depletion did not affect either B-Raf activity or ERK1/2 activation. This ruled out a role for Rap1 in the PKA-mediated B-Raf/ERK activation in (WT)B-Raf cells. Finally, we demonstrated the importance of cyclin D1 in mediating PKA/(WT)B-Raf signaling for cell proliferation. Altogether, our results suggest that the PKA/B-Raf pathway is a potential target for therapeutic strategies against (WT)B-Raf-expressing uveal melanoma.

Topics: Cell Proliferation; Cell Transformation, Neoplastic; Cyclic AMP; Cyclic AMP-Dependent Protein Kinases; Cyclin D1; Extracellular Signal-Regulated MAP Kinases; Humans; Isoenzymes; Melanoma; Mitogen-Activated Protein Kinase 1; Mitogen-Activated Protein Kinase 3; Proto-Oncogene Proteins B-raf; Proto-Oncogene Proteins c-raf; Signal Transduction; Tumor Cells, Cultured; Uveal Neoplasms

To examine the expression of proteins in the Rb and p53 tumor suppressor pathways in uveal melanomas following plaque radiotherapy.. Immunohistochemistry and cell culture studies. Immunohistochemistry for Rb, p16, cyclin D1, p53, HDM2, and Bcl-2 was performed on twelve eyes containing posterior uveal melanomas that were enucleated following plaque radiotherapy. Cell culture studies were performed in three cases.. The irradiated eyes were enucleated for radiation complications (five cases), local tumor recurrence (three cases), and other reasons (four cases). On histopathologic examination, all cases showed evidence of tumor cell loss. However, residual tumor cells were present in all cases, including those that were clinically regressed. Residual cells from three of the clinically regressed cases were cultured and demonstrated minimal cell division, marked cell death, and extensive chromosomal damage. Strong p53 staining was observed in six cases (50%) and was significantly associated with recent radiotherapy (P = .04). Abnormal cytoplasmic staining for Rb was observed in four cases (33%).. Plaque radiotherapy of uveal melanomas induces DNA damage, inhibits cell division, and promotes cell death. These changes may be due, at least in part, to induction of p53, which activates genes involved in both cell cycle arrest and apoptosis. Plaque radiotherapy can also cause alterations in the expression of Rb, but the significance of this finding will require further study.

Topics: Adult; Aged; Brachytherapy; Cobalt Radioisotopes; Cyclin D1; Cyclin-Dependent Kinase Inhibitor p16; DNA Damage; DNA, Neoplasm; Eye Enucleation; Female; Humans; Immunoenzyme Techniques; Iodine Radioisotopes; Male; Melanoma; Middle Aged; Nuclear Proteins; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-mdm2; Retinoblastoma Protein; Tumor Cells, Cultured; Tumor Suppressor Protein p53; Uveal Neoplasms

Malignant uveal melanoma is the commonest primary intraocular tumour in adults. It metastasizes frequently and 50% of patients die within 10 years of diagnosis. The expression of cyclin D1, p53, and MDM2 in uveal melanoma and their relationship to metastasis-free 5-year survival was determined, in order to investigate whether these proteins help to distinguish those patients with a favourable prognosis from those with a poorer one. Ninety-six eyes enucleated for uveal melanomas were immunohistochemically analysed for the protein expression of cyclin D1 and related cell-cycle markers, p53 and MDM2. The evaluation of the specimens was undertaken by two independent pathologists without knowledge of the outcome. Statistical analysis of clinical, morphological, and immunohistological features was performed. A 'favourable outcome' was defined as survival of at least 5 years after diagnosis, without metastases (n=57). An 'unfavourable outcome' was defined as death from metastases within the first 5 years after diagnosis of uveal melanoma (n=39). Cyclin D1 positivity (>15% positive tumour cells) as well as p53 positivity (>15% positive tumour cells) was associated with an unfavourable outcome (for cyclin D1: odds ratio=4. 2, 95% confidence interval 1.5-11.8, p=0.006; for p53: odds ratio=3. 2, 95% confidence interval 1.1-9.3, p=0.03). In addition, cyclin D1 positivity was associated with the presence of extraocular extension of the tumour (p=0.01), with the mixed or epithelioid cell type (p=0. 02), and with the tumour cell MIB-1 positivity (p=0.0001). MDM2 immunoreactivity of the tumour cells showed a potential correlation with clinical outcome (odds ratio=2.1, 95% confidence interval 0.8-5. 8, p=0.13). Multiple logistic regression models showed that cyclin D1 positivity is an independent prognostic factor after control for other prognostic markers. The expression of cyclin D1 in uveal melanoma is associated with a more aggressive course and histologically unfavourable disease. This could serve as a further independent prognostic factor in uveal melanoma.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Confidence Intervals; Cyclin D1; Disease-Free Survival; Female; Humans; Male; Melanoma; Middle Aged; Neoplasm Metastasis; Nuclear Proteins; Odds Ratio; Predictive Value of Tests; Prognosis; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-mdm2; Regression Analysis; Tumor Suppressor Protein p53; Uveal Neoplasms

Uveal melanoma is the most common primary eye cancer, yet its molecular pathogenesis is poorly understood. In this study, we investigated the immunohistochemical expression of proteins in the Rb and p53 tumor suppressor pathways in 33 uveal melanomas from enucleated eyes. Strong nuclear staining for Rb was present in most tumors. However, a few cases displayed weak nuclear staining and strong cytoplasmic staining (possibly indicating Rb mutation), and this aberrant staining correlated strongly with failed radiotherapy or thermotherapy before enucleation. Staining for cyclin D1 was positive in most tumors and was associated with advanced age and larger tumor size, which are both poor prognostic factors. Generally, immunostaining for p53 was weak (suggesting a lack of p53 mutations), although p53 positivity correlated strongly with staining for phosphorylated Rb, supporting the notion that inappropriate phosphorylation of Rb can induce p53. Strong immunostaining for MDM2, which can functionally block p53 activity, was observed in most tumors and correlated significantly with female sex. Strong cytoplasmic staining was observed for Bcl2, which can inhibit both p53-dependent and -independent apoptosis. We conclude that Rb and p53 are mutated infrequently in uveal melanoma, but their respective pathways may be functionally inactivated.

Topics: Adult; Aged; Cell Nucleus; Cyclin D1; Female; Humans; Immunohistochemistry; Male; Melanoma; Middle Aged; Nuclear Proteins; Phosphorylation; Proto-Oncogene Proteins; Proto-Oncogene Proteins c-bcl-2; Proto-Oncogene Proteins c-mdm2; Retinoblastoma Protein; Sex Characteristics; Tumor Suppressor Protein p53; Uveal Neoplasms

A checkpoint mechanism in late G1, whose regulation via loss of retinoblastoma protein (pRB) or p16, or overexpression of cyclin D1 or cyclin dependent kinase 4 (CDK4), has been proposed to constitute a common pathway to malignancy. The aims of this study were (a) to compare markers of cell cycle G1-S phase transition in an intraocular tumour with known pRB deficiency (retinoblastoma) and compare it with one with an apparently functional pRB (uveal melanoma); (b) to determine if one of these markers may have a role in the pathogenesis of uveal melanoma; and (c) to determine if there is a difference in cell cycle marker expression following treatment of uveal melanoma and retinoblastoma.. 90 eyes were enucleated from 89 patients for retinoblastoma (n = 24) or for choroidal or ciliary body melanoma (n = 66). Conventional paraffin sections were assessed for cell type and degree of differentiation. Additional slides were investigated applying standard immunohistochemical methods with antibodies specific for cyclin D1 protein, pRB, p53, p21, p16, BCL-2, and MIB-1.. Cyclin D1 protein and pRB were negative in retinoblastoma using the applied antibodies. In contrast, cyclin D1 protein expression was observed in 65% of uveal melanomas; a positive correlation between cyclin D1 cell positivity and tumour cell type, location, growth fraction, as well as with pRB positivity was observed. p53, p21, and p16 could be demonstrated in both tumours. An inverse relation between p53 and p21 expression was demonstrated in most choroidal melanomas and in some retinoblastomas. Apart from a decrease in the growth fractions of the tumours as determined by MIB-1, a significant difference in the expression of G1-S phase transition markers in vital areas of uveal melanoma and retinoblastoma following treatment with radiotherapy and/or chemotherapy was not observed.. Retinoblastomas and uveal melanomas, two tumours of differing pRB status, differ also in their immunohistochemical pattern for markers of the G1-S phase transition of the cell cycle. The results of the present study support the concept of (a) an autoregulatory loop between pRB and cyclin D1 in tumours with a functional pRB and the disruption of this loop in the presence of pRB mutation, as well as (b) a checkpoint mechanism in late G1, whose regulation via loss of p16 or pRB, or overexpression of cyclin D1 constitutes a common pathway to malignancy. Further, the results raise the possibility of cyclin D1 overexpression having a role in the pathogenesis of uveal melanoma.

Topics: Adolescent; Adult; Aged; Aged, 80 and over; Child; Child, Preschool; Cyclin D1; Female; G1 Phase; Humans; Immunoenzyme Techniques; Infant; Male; Melanoma; Neoplasm Proteins; Retinal Neoplasms; Retinoblastoma; Retinoblastoma Protein; S Phase; Uveal Neoplasms