Microsatellite instability and loss of heterozygosity in human pterygia

Study of biomarkers p53, Ki-67, Bcl-2, and VEGF in pterygium

PURPOSE

To study the biomarkers present in primary pterygium samples of patients of Indian ethnicity and compare it with the samples obtained from the unaffected conjunctiva of the same eye.

METHODS

A prospective case-control study of 17 eyes in patients above 10 years of age with primary pterygium who underwent pterygium excision using limbal conjunctival autograft technique. The pterygium samples (cases) and conjunctival samples (controls) were sent for immunohistochemical (IHC) staining for the following biomarkers: p53, Bcl-2, Ki-67, and vascular endothelial growth factor (VEGF).

RESULT

The immunohistochemistry of the samples and the controls revealed p53 positivity in 47.05% of pterygium samples and 29.4% of controls ( P < 0.587). Nine cases each in pterygium and control samples were positive for Ki-67 expression. Differences in the staining pattern between the two groups were not statistically significant ( P < 1.000). Bcl-2 positivity was seen in 10 pterygium samples (58.8%) and 12 controls (70.5%), with no statistical difference between the two groups ( P < 0.455). VEGF expression was seen in both epithelial and endothelial cells of the samples and controls, with no statistical difference between the two groups, with P = 1.000 for the epithelial staining and P = 0.637 for endothelial staining.

CONCLUSION

The expression of biomarkers was comparable in both groups. We conclude that pterygium, against common belief, might not be a localized disease process but a global ocular phenomenon where the apparently healthy tissue also has some ongoing disease process at a molecular level.

State of the Art of Pharmacological Activators of p53 in Ocular Malignancies

The pivotal role of p53 in the regulation of a vast array of cellular functions has been the subject of extensive research. The biological activity of p53 is not strictly limited to cell cycle arrest but also includes the regulation of homeostasis, DNA repair, apoptosis, and senescence. Thus, mutations in the p53 gene with loss of function represent one of the major mechanisms for cancer development. As expected, due to its key role, p53 is expressed throughout the human body including the eye. Specifically, altered p53 signaling pathways have been implicated in the development of conjunctival and corneal tumors, retinoblastoma, uveal melanoma, and intraocular melanoma. As non-selective cancer chemotherapies as well as ionizing radiation can be associated with either poor efficacy or dose-limiting toxicities in the eye, reconstitution of the p53 signaling pathway currently represents an attractive target for cancer therapy. The present review discusses the role of p53 in the pathogenesis of these ocular tumors and outlines the various pharmacological activators of p53 that are currently under investigation for the treatment of ocular malignancies.

The roles of mouse double minute 2 (MDM2) oncoprotein in ocular diseases: A review

Mouse double minute 2 (MDM2), an E3 ubiquitin ligase and the primary negative regulator of the tumor suppressor p53, cooperates with its structural homolog MDM4/MDMX to control intracellular p53 level. In turn, overexpression of p53 upregulates and forms an autoregulatory feedback loop with MDM2. The MDM2-p53 axis plays a pivotal role in modulating cell cycle control and apoptosis. MDM2 itself is regulated by the PI3K-AKT and RB-E2F-ARF pathways. While amplification of the MDM2 gene or overexpression of MDM2 (due to MDM2 SNP T309G, for instance) is associated with various malignancies, numerous studies have shown that MDM2/p53 alterations may also play a part in the pathogenetic process of certain ocular disorders (Fig. 1). These include cancers (retinoblastoma, uveal melanoma), fibrocellular proliferative diseases (proliferative vitreoretinopathy, pterygium), neovascular diseases, degenerative diseases (cataract, primary open-angle glaucoma, age-related macular degeneration) and infectious/inflammatory diseases (trachoma, uveitis). In addition, MDM2 is implicated in retinogenesis and regeneration after optic nerve injury. Anti-MDM2 therapy has shown potential as a novel approach to treating these diseases. Despite major safety concerns, there are high expectations for the clinical value of reformative MDM2 inhibitors. This review summarizes important findings about the role of MDM2 in ocular pathologies and provides an overview of recent advances in treating these diseases with anti-MDM2 therapies.

Analysis of WWOX gene expression and protein levels in pterygium

PURPOSE

Pterygium, a degenerative and hyperplastic lesion, has premalignant properties as a tumor analog. WWOX is a tumor suppressor gene and involved in many signal pathways, such as cell proliferation, embryonic development, metabolism and apoptosis. In many cancers, the loss of WWOX or the presence of abnormal transcripts indicates the tumor suppressor activity of WWOX. In this study, it was aimed to determine WWOX gene expression and protein levels in pterygium which may be a tumor analog.

METHODS

For this purpose, the WWOX gene expression change in 27 pterygium tissue was investigated by real-time PCR method, and the change in WWOX protein was investigated using the Western blot method.

RESULTS

According to our results, it was found that the expression and protein levels of WWOX gene in pterygium tissue decreased significantly compared to control tissue (p < 0.05).

CONCLUSION

This information indicates that a decrease in expression and protein level in pterygium tissue of WWOX, a tumor suppressor gene, supports claims that pterygium may be a cancer analog tissue.

K-ras oncogene mutation in pterygium

PurposePterygium is claimed to be a benign proliferation triggered by prolonged exposure to ultraviolet radiation. The frequency of K-ras oncogene mutation, which is among the initial mutations in tumorigenesis, is evaluated in this study.Patients and methodsIn this prospective randomized clinical, trial pterygium tissues and normal conjunctiva tissue specimens are obtained from the superotemporal quadrant of patients who underwent primary pterygium excision with autograft transplantation. DNA extraction from tissues was performed using the QIAamp DNA FFPE tissue kit. A PCR reaction was performed to amplify sequences containing codons 12, 13, and 61 of the K-ras gene in DNA. These PCR products then underwent the 'pyrosequencing' procedure for mutations at these codons.ResultsPterygium and normal conjunctival tissue samples of 25 patients (10 females, 15 males) were evaluated in the study. The mean age of the patients was 54.54±13.13 years. Genetic analysis revealed no K-ras mutations in normal conjunctival tissues, whereas pterygium tissues of the same cases demonstrated mutation at codon 12 in one case and mutations at codon 61 in seven cases, which was statistically significant (P<0.05). The point missense mutations at codon 61 were glutamine to arginine (Glu61Arg CAA>CGA) in four cases and glutamine to leucine (Glu61Leu CAA>CTA) in three cases.ConclusionThe significantly higher frequency of codon 61 mutation of the ras oncogene in primary and bilateral pterygium specimens compared with normal conjunctiva supports the tumoral origin of pterygium, and thus set the stage for research into a targeted therapy for pterygium with better outcomes than surgical excision.

Expression of WW domain-containing oxidoreductase WWOX in pterygium

PURPOSE

Pterygium was traditionally regarded as a degenerative disease, but certain characteristics suggest that pterygium is probably premalignant tissue. The human WWOX gene, encoding the WW domain containing oxidoreductase (WWOX, FOR, or WOX1), is a candidate tumor suppressor gene. In this study, we investigated the WWOX gene and protein expression in pterygium.

METHODS

Pterygium tissues were obtained from patients (n=16, primary=8, recurrent=8) who received surgical excisions. Each tissue sample was further divided into head and body regions. The WWOX gene and protein expression were examined with immunohistochemistry, western blot, and quantitative PCR. For comparison, normal superior temporal bulbar conjunctivas were used as controls.

RESULTS

Compared to the controls, upregulation of WWOX and its Tyr33 phosphorylation was observed in the head region of all pterygium specimens. In the head and body of the pterygium specimens, WWOX expression was significantly higher than in the controls. In addition, WWOX expression was stronger in recurrent pterygia than in primary pterygia.

CONCLUSIONS

Increased WWOX expression, especially in the head region, is probably due to the invasiveness of the pterygium. Our results indicate that WWOX may play a role in pterygium progression and recurrence.

human adenoviruses role in ophthalmic pterygium formation

Background:

Ophthalmic pterygium is a common benign lesion of unknown origin and the pathogenesis might be vision-threatening. This problem is often associated with exposure to solar light. Recent evidence suggests that potentially oncogenic viruses such as human papillomavirus and Epstein-Barr virus may be involved in the pathogenesis of pterygia. Expression of specific adenovirus genes such as E1A and E1B, which potentially have many functions, may contribute to their oncogenic activity as well as relevance to cellular immortalization.

Objectives:

For the first time, we aimed to investigate involvement of adenoviruses in pterygium formation.

Patients and Methods:

Fifty tissue specimens of pterygium from patients undergoing pterygium surgery (as cases), 50 conjunctival swab samples from the same patients and 10 conjunctival biopsy specimens from individuals without pterygium such as patients undergoing cataract surgery (as controls) were analyzed for evidence of adenovirus infection with polymerase chain reaction using specific primers chosen from the moderately conserved region of the hexon gene. Furthermore, β-globin primers were used to access the quality of extracted DNA. Data was analyzed using SPSS (version 16) software.

Results:

Of 50 patients, 20 were men and 30 women with mean age of 61.1 ± 16.9 years ranged between 22 and 85 years. All samples of pterygia had positive results for adenoviruses DNA with polymerase chain reaction, but none of the negative control groups displayed adenoviruses. The pterygium group and the control groups were β-globin positive. Direct sequencing of PCR products confirmed Adenovirus infection.

Conclusions:

Adenoviruses might act as a possible cause of pterygium formation and other factors could play a synergistic role in the development. However, further larger studies are required to confirm this hypothesis.

Expression of vascular endothelial growth factor C in human pterygium

Vascular endothelial growth factor C (VEGF-C) and its receptor VEGFR-3 mediate lymphangiogenesis. In this study, we analyzed the expression of VEGF-C and VEGFR-3 as well as lymphatic vessels in the pterygium and normal conjunctiva of humans. Fifteen primary nasal pterygia and three normal bulbar conjunctivas, surgically removed, were examined in this study. The lymphatic vessel density (LVD) and blood vessel density were determined by the immunolabeling of D2-40 and CD31, markers for lymphatic and blood vessels, respectively. VEGF-C and VEGFR-3 expression in pterygial and conjunctival tissue proteins was detected by Western blotting and were evaluated using immunohistochemistry. The LVD was significantly higher in the pterygium than normal conjunctiva (p < 0.05). Western blot demonstrated high-level expression of VEGF-C and VEGFR-3 in the pterygium compared with normal conjunctiva. VEGF-C immunoreactivity was detected in the cytoplasm of pterygial and normal conjunctival epithelial cells. The number of VEGF-C-immunopositive cells in pterygial epithelial cells was significantly higher than in normal conjunctival cells (p < 0.05). VEGFR-3 immunoreactivity was localized in the D2-40-positive lymphatic endothelial cells. The present findings suggest the potential role of VEGF-C in the pathogenesis and development of a pterygium through lymphangiogenesis and the VEGF-C/VEGFR-3 pathway as a novel therapeutic target for the human pterygium.

Tissue factor expression in human pterygium

PURPOSE

A pterygium shows tumor-like characteristics, such as proliferation, invasion, and epithelial-mesenchymal transition (EMT). Previous reports suggest that tissue factor (TF) expression is closely related to the EMT of tumor cells, and subsequent tumor development. In this study, we analyzed the expression and immunolocalization of TF in pterygial and normal conjunctival tissues of humans.

METHODS

Eight pterygia and three normal bulbar conjunctivas, surgically removed, were used in this study. Formalin-fixed, paraffin-embedded tissues were submitted for immunohistochemical analysis with anti-TF antibody. Double staining immunohistochemistry was performed to assess TF and alpha-smooth muscle actin (α-SMA) or epidermal growth factor receptor (EGFR) expression in the pterygia.

RESULTS

Immunoreactivity for TF was detected in all pterygial tissues examined. TF immunoreactivity was localized in the cytoplasm of basal, suprabasal, and superficial epithelial cells. The number of TF-immunopositive cells in pterygial epithelial cells was significantly higher than in normal conjunctival epithelial cells (p<0.001). TF immunoreactivity was detected in α-SMA-positive or -negative pterygial epithelial cells. EGFR immunoreactivity was detected in pterygial epithelium, which was colocalized with TF.

CONCLUSIONS

These results suggest that TF plays a potential role in the pathogenesis and development of a pterygium, and that TF expression might be involved through EMT-dependent and -independent pathways.

Presence of human papillomavirus in pterygium in Taiwan

PURPOSE

To evaluate the prevalence and possible role of human papillomavirus (HPV) in the formation of pterygia in patients in Taiwan, a tropical country with high prevalence of pterygium.

METHODS

A total of 62 patients with 65 pterygia were retrospectively examined. Ten normal conjunctiva, 8 conjunctival nevi, and 2 malignant conjunctival melanomas served as controls. HPV detection and typing were accomplished using polymerase chain reaction amplification of the viral sequences. HPV-positive specimens underwent further investigation with fluorescence in situ hybridization. Clinical histories were recorded for each patient.

RESULTS

Based on polymerase chain reaction analysis, 2 of 65 pterygia harbored HPV type 18, and they were also fluorescence in situ hybridization positive. No conjunctival control had HPV. There was no statistically significant correlation between pterygium and the presence of HPV. The presence of HPV was not significantly different between primary and recurrent pterygia.

CONCLUSIONS

The limited presence of HPV DNA in pterygium does not conclude that HPV is necessary or acting alone in the formation of pterygium, but HPV may still be implicated to play a role in some pterygia in Taiwan.

Investigation of human papillomavirus and Epstein-Barr virus DNAs in pterygium tissue

PURPOSE

Recent studies postulated the presence of a probable relationship between pterygium and neoplasia. This study aimed to investigate the role of two oncogenic viruses, human papillomavirus (HPV) and Epstein-Barr virus (EBV), in the development of conjunctival pterygia.

METHODS

Polymerase chain reaction was used to identify the presence of HPV and EBV in 30 primary and 10 recurrent pterygia samples. Twenty conjunctival samples obtained from patients undergoing cataract surgeries were used as the control group. Patient groups had similar sex, race, and age distribution to eliminate bias. For exploration of HPV in groups, two different PCR methods (in-house PCR with two different primer sets and one real-time PCR method) were studied. The presence of EBV was shown by real-time PCR method.

RESULTS

HPV was identified in none of the pterygia and control group patients. However, EBV was detected in 3 out of 30 (10%) primary pterygia patients and in none of the recurrent pterygia and control patients.

CONCLUSIONS

Up to now, HPV has been blamed as the major viral pathogen in the etiopathogenesis of pterygium. The current results suggest that EBV may also be involved in the pathogenesis of pterygium, but further larger studies with larger cohorts are required to confirm this hypothesis.

Herpes simplex virus and pterygium in Taiwan

PURPOSE

To evaluate the presence of herpes simplex virus (HSV) in pterygia to study the possible association between HSV and pterygia in Taiwan, a tropical country with a high prevalence of pterygium.

METHODS

Sixty-five pterygia, 10 normal conjunctiva, 8 conjunctival nevi, and 2 malignant conjunctival melanomas were obtained. Clinical histories were recorded for each patient. HSV detection was accomplished by polymerase chain reaction amplification of viral sequences. HSV-positive specimens underwent subsequent DNA in situ hybridization. Results were statistically analyzed.

RESULTS

By using polymerase chain reaction, HSV was detected in 3 (5%) pterygia, and no conjunctival control displayed HSV. All 3 HSV-positive pterygia studies were DNA in situ hybridization negative. There was no statistically significant correlation between pterygium and the presence of HSV.

CONCLUSIONS

HSV is not associated with pterygium formation in Taiwan; the pathogenesis of pterygia is still incompletely understood.

Apport de la microscopie confocale in vivo à l’étude des ptérygions

PURPOSE

To describe the pterygium structure with a high-resolution in vivo confocal microscope and to show the typical components of active pterygium.

METHODS

In this study, 15 patients with 20 pterygia were examined. None of them had had prior pterygium surgery. Slit lamp examination and in vivo confocal microscopy imaging (Heidelberg Retina Tomograph II Rostock Cornea Module) were performed.

RESULTS

The images obtained consisted of two-dimensional high-resolution optical sections. We could identify the pterygial epithelium and its border, pterygial stroma and its vascularization, the pterygium corneal limits, and numerous inflammatory cells in active pterygia.

DISCUSSION

Many reports have been written about pterygium structure. In vivo confocal microscopy imaging is a new approach to this pathology and provides a precise evaluation of active pterygium.

MLH1 and MSH2 Expression in Pterygia

PURPOSE

Pterygia have been reported to share some of the genetic defects seen in cancers, including microsatellite instability (MSI). We examined pterygia for the presence of proteins typically missing or defective in adenocarcinomas with MSI. We also performed microsatellite analysis on DNA from pterygia to test for instability in the size of the microsatellites, using markers conventionally used to characterize MSI in tumors (Bethesda convention markers).

METHODS

We examined 13 pterygia by immunohistochemistry for MLH1 and MSH2, 2 proteins involved in DNA mismatch repair. In addition, we amplified the pterygial DNA with primers specific for 5 Bethesda markers (BAT25, BAT26, D2S123, D5S346, and D17S250).

RESULTS

MLH1 staining was present at low levels in the basal cells of the cornea and migrating limbal cells of the pterygia. MSH2 staining was present in basal and in maturing epithelial cells of the cornea and migrating limbal cells of pterygia. We observed no reproducible examples of MSI or loss of heterozygosity (LOH).

CONCLUSIONS

We were unable to confirm the presence of MSI and LOH by using the markers we examined. MSH2 staining appeared to be normal in pterygia. MLH1 staining was present but in reduced amounts compared with that seen in the conjunctiva.

Ultramicrostructure and clinical implications of satellite foci in front of the head of pterygium

In our previous studies, grey satellite foci were found in the front of heads of pterygia. This research was designed to investigate the ultramicrostructure and clinical implications of these satellite foci. The satellite foci were observed and counted under slit lamp biomicroscope. The patients with eye pterygia were divided into groups in terms of occupation, sex, age, length of history, grade of congestion, and size of the heads. The SPSS 13.0 software was used for statistical analysis. The cap areas and satellite foci were ultramicrostructurally examined. Among the total 62 eyes with pterygium, satellite foci were found in 34. The overall incidence of satellite foci was 54.8%. There were no significant differences in incidence among the subjects of different sex, age, and length of history. There were significant differences in incidence among the patients of different occupation, grades of congestion, and size of heads. Higher grades of congestion, outdoor occupations and larger pterygium heads were associated with higher incidence of satellite foci. High grades of congestion and bigger heads were also correlated with the number of satellite foci. Length of history bore no correlation with number of satellite foci. Histologically, the components of the cap areas and the foci were identical, with both consisting of mass of active fibroblasts. The activated fibroblasts existed in the natural tissue planes between Bowman's layer and basal cell layer. The fibroblasts in the satellite foci and the cap areas of a pterygium show some features of tumor cells and may play a vital role in the development and progression of a pterygium. The presence and amount of satellite foci around a pterygium can be used as an indicator for the speed of its growth.

Intraoperative ethanol treatment as an adjuvant therapy of pterygium excision

Recurrence of pterygium is the main concern for ophthalmic surgeons after the excision of pterygium. To evaluate the efficacy and safety of ethanol treatment during pterygium excision in preventing the recurrence of pterygia. A prospective randomized study was performed of 78 eyes in primary pterygium patients treated by excision. Primary pterygium patients were randomly assigned to ethanol group (38 eyes given intraoperative ethanol) or mitomycin-c (MMC) group (40 eyes given intraoperative MMC). Ethanol (20%) was applied for 60 seconds to the pterygial and its adjacent corneal surfaces before pterygium excision. After excision, the excised site of sclera was soaked with 20% Ethanol for 60 seconds. In group 2, MMC (0.25 mg/ml) was applied for 60 seconds to the bare sclera after pterygium excision. The outcomes were followed for more than one year. Pterygium recurred in 2 (5.3%) of 38 eyes in ethanol group and 4 (10.0%) of 40 eyes in MMC group. Final appearance of the pterygium excision area was satisfactory in 73.6% of group1 and 67.5% of group 4. No patients experienced severe complications postoperatively. In comparison with MMC treatment, intraoperative ethanol is more efficacious in preventing recurrence of pterygium and causes fewer complications. It suggests this regimen as an alternative for the treatment of pterygium, especially for those patients of high risk group for MMC treatment complications.

Fibroblasts isolated from human pterygia exhibit altered lipid metabolism characteristics

To determine whether the fibrovascular proliferation observed in pterygium, may be, at least in part, mediated by an increased activity of cholesterol metabolism. The correlation between lipid metabolism and rate of growth was studied in human normal conjunctival (NCF) and primary pterygium fibroblasts (PFs) in primary culture. The expression of two proliferation markers (Ki-67 and p53) was evaluated by immunohistochemical staining techniques. Proliferation was evaluated by [(3)H]thymidine incorporation and by immunohistochemical assays. Lipid metabolism was evaluated by (14)C-oleate incorporated into cholesterol esters as well as by oil red O staining. Moreover, the cultures of pterygium fibroblasts were supplemented with two antiproliferative drugs in order to confirm the effective alterations in cholesterol metabolism related to proliferation. Immunohistochemistry of frozen sections from primary pterygium demonstrated an increased staining in Ki-67 and p53 compared with staining observed in normal conjunctiva. A dramatically increased activity of intracellular cholesterol metabolism was demonstrated in pterygium fibroblasts obtained from four different patients. This finding was confirmed by the reduction of cholesterol metabolism in pterygium fibroblasts treated with antiproliferative drugs. Collectively, these data support the hypothesis that alterations of cholesterol metabolism are involved in the development of pterygia. This finding may represent a target of new therapeutic approaches for treatment and prevention of pterygium.

Frequency of Chromosome 17 Aneuploidy in Primary and Recurrent Pterygium by Interphase-Fluorescence in situ Hybridization

AIM

To investigate chromosome 17 numerical aberrations by using fluorescence in situ hybridization (FISH) in pterygia and to find out whether there is any association between chromosome 17 aneuploidy and recurrent pterygia.

METHODS

Pterygium tissue samples were taken from 21 patients by surgical excision. Eighteen of them had primary and 3 had recurrent pterygium. Peripheral whole blood interphase cells obtained from 11 healthy subjects were assigned as control group. The cells from pterygium tissue and peripheral blood were incubated with a hypotonic solution and fixed in order to obtain interphase nuclei. FISH analysis with chromosome-17-specific alpha-satellite DNA probe was performed on both the interphase nuclei of pterygium tissue (of patients) and peripheral whole blood cells of controls.

RESULTS

The mean percentage of chromosome 17 aneuploidy was 4.71% for the pterygia group and 4.41% for the controls. No significant difference of chromosome 17 aneuploidy was observed between the patients and the controls. When the group of patients with recurrences was compared with the group without recurrences, there was a significant difference in the frequency of chromosome 17 aneuploidy (U = 17, p = 0.029).

CONCLUSIONS

Chromosome 17 aneuploidy is probably not an important factor in the formation of pterygium, but it may be related to recurrence.

Genomic rearrangements on VCAM1, SELE, APEG1and AIF1 loci in atherosclerosis

The inflammatory nature of atherosclerosis has been well established. However, the initial steps that trigger this response in the arterial intima remain obscure. Previous studies reported a significant rate of genomic alterations in human atheromas. The accumulation of genomic rearrangements in vascular endothelium and smooth muscle cells may be important for disease development. To address this issue, 78 post-mortem obtained aortic atheromas were screened for microsatellite DNA alterations versus correspondent venous blood. To evaluate the significance of these observations, 33 additional histologically normal aortic specimens from age and sex-matched cases were examined. Loss of heterozygosity (LOH) was found in 47,4% of the cases and in 18,2% of controls in at least one locus. The LOH occurrence in aortic tissue is associated to atherosclerosis risk (OR 4,06, 95% CI 1,50 to 10,93). Significant genomic alterations were found on 1p32-p31, 1q22-q25, 2q35 and 6p21.3 where VCAM1, SELE, APEG1 and AIF1 genes have been mapped respectively. Our data implicate somatic DNA rearrangements, on loci associated to leukocyte adhesion, vascular smooth muscle cells growth, differentiation and migration, to atherosclerosis development as an inflammatory condition.

Pathogenesis of pterygia: role of cytokines, growth factors, and matrix metalloproteinases

Pterygium is a common ocular surface disease apparently only observed in humans. Chronic UV exposure is a widely accepted aetiological factor in the pathogenesis of this disease and this concept is supported by epidemiological data, ray tracing models and histopathological changes that share common features with UV damaged skin. The mechanism(s) of pterygium formation is incompletely understood. Recent data have provided evidence implicating a genetic component, anti-apoptotic mechanisms, cytokines, growth factors, extracellular matrix remodelling (through the actions of matrix metalloproteinases), immunological mechanisms and viral infections in the pathogenesis of this disease. In this review, the current knowledge on pterygium pathogenesis is summarised, highlighting recent developments. In addition, we provide novel data further demonstrating the complexity of this intriguing disease.

Loss of heterozygosity and p53 expression in Pterygium

While the pathogenesis of pterygium is still not well understood, environmental factors such at UV light, appear to play an important role in its development. UV radiation can cause mutations in genes such as the p53 tumor suppressor gene, that when inactivated through mutation and loss of heterozygosity can lead to cell proliferation and genomic instability. However, aside from mutations in the gene, other mechanisms have been identified that can lead to loss of p53 function. These include the interaction of the p53 protein with cellular or viral gene products that lead to the inactivation of p53 or to its rapid degradation as well as the silencing of transcription of the p53 gene through the aberrant expression of factors that control p53 expression. We have analyzed the status and expression of the p53 gene in epithelial cells derived from pterygium and have demonstrated that the p53 gene has undergone a monoallelic deletion. Assays for both p53 protein and mRNA revealed that the remaining allele in these cells is not expressed at detectable levels. Furthermore, the remaining allele, by DNA sequence analysis appears to remain wild type. The mechanism of silencing the p53 gene and the loss of p53 expression in these cells is currently under investigation.

Overexpression of p53 tumor suppressor gene in pterygia

PURPOSE

To assess p53 gene expression in pterygia with and without recurrence. The pathogenesis of pterygium has not yet been determined. The most widely recognized etiologic factor is ultraviolet radiation, which leads to degeneration of the conjunctiva. However, pterygium was recently found to have several tumor-like characteristics. The p53 gene is a common marker for neoplasia, and is known to control cell cycle, cell differentiation and apoptosis. In this study we examined the expression of the p53 gene in primary pterygia with and without recurrence, searching for the pathogenesis of this very common lesion and for a prognostic factor for recurrence.

METHODS

Immunohistochemical staining using a monoclonal antibody to human p53 (DO-7) was performed on 13 consecutive patients with primary pterygia, four pterygia without recurrence and nine pterygia which recurred during a 12-month follow-up. As a control we used two specimens of normal conjunctiva.

RESULTS

Seven of the 13 pterygia specimens (54%) were positive for abnormal p53 expression. There was no difference between the groups with and without recurrence. Two out of four pterygia (50%) without recurrence and five out of nine (55.5%) pterygia with recurrence were positive. No pathological staining was observed in the control specimens.

CONCLUSIONS

In this study, abnormal p53 expression was found in pterygial epithelium, suggesting that pterygium could be a result of uncontrolled cell proliferation, and not as a degenerative lesion. There seems to be no connection between abnormal p53 expression and recurrence.

Proliferative activity and p53 expression in primary and recurrent pterygia

PURPOSE

To assess p53 expression and proliferative activity in primary and recurrent pterygia from the same eyes.

DESIGN

Retrospective comparative human tissue study.

PARTICIPANTS

Tissue from excised primary pterygia that did not recur (group A, n = 10) was compared with tissue from primary pterygia that recurred (group B, n = 10) and to the recurrent pterygia tissue that was excised from subjects in group B (group C, n = 10). Ten normal conjunctivas served as controls (group D).

METHODS

Sections from each pterygium were immunostained with the MIB-1 and bp53. 12 monoclonal antibodies that react with Ki-67 and p53 antigens, respectively.

MAIN OUTCOME MEASURES

Proliferative activity was calculated as the mean of the MIB-1 positive cell count per eyepiece grid in high magnification (x40) (positive cell count/grid). Percentage of positive cells of all cells in the grid area was evaluated in the p53-stained sections.

RESULTS

Proliferative activity was found in the epithelium overlying the pterygia and normal conjunctiva. The mean MIB-1 positive cell count/grid +/- standard error was 2.84 +/- 1.07, 1.74 +/- 0.82, 3.83 +/- 1.35, and 0.86 +/- 0.33 in groups A, B, C, and D, respectively (P = 0.17, Kruskal-Wallis). P53 staining was found in 50% of pterygia in groups A, B, and C; none of the normal conjunctival tissues showed p53 immunoreactivity. Four of five p53-positive tissues in group B were p53-negative in group C. In the p53-positive pterygia, less than 10% of cells were p53 positive. However, p53-positive pterygia had higher mean MIB-1 positive cell count/grid +/- standard error as compared with the p53-negative lesions, 4.56 +/- 0.94 vs 1.39 +/- 0.59 (P = 0.021, Mann-Whitney).

CONCLUSIONS

p53 immunoreactivity and high proliferative activity in the epithelium overlying the pterygium are not associated with recurrence of pterygium.

Detection of herpes simplex virus and human papilloma virus in ophthalmic pterygium

PURPOSE

To evaluate the presence of herpes simplex virus (HSV) and human papilloma virus (HPV) in pterygia and phenotypically normal conjunctiva and the possible relation between viral presence and clinical information.

METHODS

Fifty pterygia and respective conjunctival specimens were obtained. A personal and family history was recorded for each patient. HSV and HPV detection and typing were accomplished by polymerase chain reaction amplification of viral sequences. Results were statistically analyzed.

RESULTS

HSV (type 1) was detected in 11 (22%), HPV (type 18) in 12 (24%), and both HSV-1 and HPV-18 in 3 (6%) of pterygia. No conjunctival specimen displayed HSV, whereas HPV was detected in four (8%). Postoperative recurrence and history of conjunctivitis were significantly more common in patients with simultaneous detection of HSV and HPV.

CONCLUSION

The fact that HSV was not detected in conjunctival specimens implies a more specific correlation with pterygium, as compared with HPV. The detection of potentially oncogenic viruses, such as HSV and HPV, supports the concept that pterygium can be considered a neoplastic condition. The correlation of postoperative recurrence and a history of conjunctivitis with the simultaneous detection of HPV and HSV, implies a possible viral cooperation affecting the clinical profile of pterygium.

Allelic loss in chromosomal region 1q21-23 in breast cancer is associated with peritumoral angiolymphatic invasion and extensive intraductal component

AIMS

Breast cancer is the most frequent cancer in the female population and the involvement of chromosomal alterations is often implicated in the development of cancer. The aim of our study was to assess loss of heterozygosity (LOH) in chromosome 1 in relation to clinical and pathological parameters.

METHODS

Tumours, corresponding normal tissues and peripheral blood samples from 50 women with operable breast cancer, were analysed by polymerase chain reaction (PCR) at 16 polymorphic DNA markers, on both the long and short arm of chromosome 1.

RESULTS

There was a significant correlation between chromosomal region 1q21-23 and the presence of extensive intraductal component (EIC) and peritumoral angiolymphatic (PALI) invasion, both independent markers of local recurrence.

CONCLUSIONS

Allelic loss in region 1q21-23 may be a valuable prognostic biological marker for the detection of local relapse in breast cancer, in combination with other histological and clinical parameters.

Apoptosis and apoptosis related gene expression in normal conjunctiva and pterygium

BACKGROUND

Pterygium is a relatively common eye disease in the tropics whose aetiology and pathogenesis remain uncertain. As such, interest has focused on understanding the underlying mechanism of pterygia development.

METHODS

15 specimens of pterygia from 15 eyes were examined, together with normal conjunctival tissue from the same eyes for the pattern of gene expression of genes associated with the induction or repression of apoptosis (p53, bcl-2, and bax). In addition, the samples directly for apoptotic cells were examined by the terminal deoxynucleotide transferase (TdT) mediated nick end labelling (TUNEL) methodology.

RESULTS

In pterygia specimens apoptotic cells were found mainly confined to the basal layer of cells of the epithelial layer, situated immediately adjacent to the fibrovascular support layer. These cells were shown to express significant levels of p53 and bax, as well as the apoptosis inhibiting protein bcl-2. In contrast, normal conjunctival specimens displayed no bcl-2 expression and apoptotic cells were seen throughout the entire width of the epithelial layer, coupled with high levels of bax expression.

CONCLUSION

These results support a model whereby pterygia development is a result of disruption of the normal process of apoptosis occurring in the conjunctiva.

Microsatellite DNA instability and loss of heterozygosity in pulmonary sarcoidosis

In the present study we investigated the incidence of microsatellite instability (MI) and loss of heterozygosity (LOH) in sarcoidosis, a multisystem disease of unknown origin. We examined sputum cytological specimens from 30 patients with sarcoidosis and 30 healthy, matched subjects, using 10 highly polymorphic microsatellite markers located at several chromosomal arms. The electrophoretic pattern of each specimen was compared with the corresponding pattern of peripheral blood and any difference in the mobility of the microsatellite alleles was interpreted as MI-positive. LOH was scored as decrease in intensity of one allele relative to the other as determined from comparison of sputum and normal (blood) DNA. We found that 14 (47%) sarcoidosis patients showed genetic alterations, either MI or LOH. Six (20%) patients exhibited MI and nine (30%) exhibited LOH in at least one microsatellite marker. One of the patients exhibited MI in two microsatellite markers and three (10%) showed LOH in more than one marker. One patient showed complete deletion of the chromosomal arm 17q11.2-q21. None of the healthy subjects exhibited any genetic alteration in the studied markers. No correlation was found between the genetic alterations detected and age, disease duration, blood gases, or spirometric parameters of the patients. Our findings suggest that MI is a detectable phenomenon in sarcoidosis and seems not to be related with the severity of the disease. The detection of LOH indicates the presence of putative tumor suppressor genes at loci examined, which may play an important role in the etiopathogenesis of sarcoidosis.

The pathogenesis of pterygia

Pterygium is an active, invasive, inflammatory process, a key feature of which is focal limbal failure. In a two-stage process, "conjunctivalization" of the cornea occurs with tissue characterized by extensive chronic-inflammation, cellular proliferation, connective tissue remodeling, and angiogenesis. An understanding of this process has resulted in efforts aimed at limbal reconstruction, which is considered the gold standard for surgical care. Although good results have been obtained with other treatment methods, a long-term approach to follow-up with at least 5-year survival figures is desirable. Sophisticated analyses of the tear film and surface epithelium in patients with pterygium may help explain symptoms. The efficacy, at least in the short term, of nonsteroidal anti-inflammatory drugs in the treatment of inflamed pterygia has been confirmed. Corneal topographic analysis has shown that surgery reduces induced astigmatism and also causes subtle changes that may explain postsurgical improvements in vision.

Radiation therapy for benign disease of the orbit

Benign diseases of the orbit can cause significant impairment of visual function through direct effects on the eye or supporting orbital tissues. Persistent moderate-to-severe inflammatory symptoms, diplopia, and visual loss may prompt therapeutic intervention. Low doses of external-beam irradiation (20 Gy in 2-Gy fractions) have an efficacy equivalent to corticosteroid medications in the treatment of both Graves' ophthalmopathy and orbital pseudotumor, with response rates of 50% to 80%. Appropriate patient selection, coordination with other medical subspecialties, and careful treatment planning are important in maximizing benefit from radiation therapy. In the case of Graves' ophthalmopathy, quantitative assessment of orbital disease severity and thyroid status as well as attainment of cross-sectional imaging should be performed before treatment. Patients whose thyroid disease is controlled but who have moderate-to-severe active orbital involvement can be offered orbital radiation therapy with a high likelihood of response. Stability of disease is generally obtained within 6 months; surgical correction of residual abnormalities may be required. For orbital pseudotumor, attainment of histological material before treatment is important in excluding benign or malignant systemic diseases, including malignant lymphoma. Genotypic abnormalities may exist in patients with reactive lymphoid hyperplasia, some of whom ultimately develop systemic lymphoma. Within the dose range recommended for treatment of Graves' ophthalmopathy and pseudotumor, late radiation effects on the retina or optic nerve should be nonexistent. Adequate lens shielding is required, however, to prevent cataract formation. This may require individualized treatment planning with computed tomography at the time of simulation. Pterygia recurrence after bare sclera excision occurs in at least 30% of cases, usually within 6 months of surgery. Radiation of the surgical bed using a strontium-90 source, beginning within 24 hours postoperatively, reduces the risk of recurrence substantially. Late scleral complications have been associated with large single-fraction treatments. To achieve maximal efficacy with minimal complications, fractionated treatment should be given by radiation oncologists experienced with the technique using sources calibrated by the National Bureau of Standards.

Evidence for loss of heterozygosity in human psoriatic lesions

Psoriasis, a disease of human skin, is characterized by abnormal differentiation and hyperproliferation of keratinocytes; it has a genetic background. Using 11 highly polymorphic microsatellite markers on eight chromosome arms, we performed an allelotype analysis in 14 psoriatic plaques, in order to reveal any chromosome deletions involved in the development of the disease. We detected loss of heterozygosity (LOH) on at least one microsatellite marker in nine of 14 (64%) cases. We also observed particular genetic loci altered with LOH, on chromosomes 3p, 7p/q and 8p. Our results suggest that LOH is an important phenomenon in the development of psoriatic plaques, providing evidence for deletion of regulatory genes.

Evaluation of loss of heterozygosity and microsatellite instability in human pterygium: clinical correlations

AIMS

To evaluate the incidence of loss of heterozygosity (LOH) and microsatellite instability (MI) in pterygia and their possible correlation with clinical variables.

METHODS

50 pterygia, blood, and conjunctival specimens were obtained. A personal and family history was recorded for each patient. Amplification of 15 microsatellite markers at regions 17p, 17q, 13q, 9p, and 9q was performed using the polymerase chain reaction. The electrophoretic pattern of DNA from pterygia was compared with the respective pattern from blood and conjunctiva.

RESULTS

LOH incidence was the highest at 9p (48%), followed by 17q (42%). Only three cases displayed MI. LOH incidence at individual markers was positively correlated with recurrence (D9S59, p = 0.11 and D9S270, p = 0.16), family history of neoplasia (D13S175, p = 0.09), altitude of present residence (D9S112, p = 0.1), duration of the existence of pterygium (D9S144, p = 0.06), and inversely correlated with age (D9S59, p = 0.09). Concerning chromosome arms, LOH was positively correlated with the altitude of present residence (13q and 17p, p = 0.03) and duration of the existence of pterygium (13q and 17p, p = 0.09).

CONCLUSIONS

LOH is a common event whereas MI is a very uncommon one at the examined markers in pterygium, indicating the presence of putative tumour suppressor genes implicated in the aetiopathogenesis of the disease. The fact that LOH at 9q31-33 was more frequent in recurrent pterygia and also correlated with known risk factors such as young age and high altitude of residence, implies a possible predictive value of this finding for postoperative recurrence.