Emerging strategies for the treatment of retinoblastoma

Progress of Cancer Stem Cells in Retinoblastoma

The theory of cancer stem cells is a breakthrough discovery that offers exciting possibilities for comprehending the biological behavior of tumors. More and more evidence suggests that retinoblastoma cancer stem cells promote tumor growth and are likely to be the origin of tumor formation, drug resistance, recurrence, and metastasis. At present, some progress has been made in the verification, biological behavior, and drug resistance mechanism of retinoblastoma cancer stem cells. This article aims to review the relevant research and explore future development direction.

Multi-Functionalized Nanomaterials and Nanoparticles for Diagnosis and Treatment of Retinoblastoma

Retinoblastoma is a rare type of cancer, and its treatment, as well as diagnosis, is challenging, owing to mutations in the tumor-suppressor genes and lack of targeted, efficient, cost-effective therapy, exhibiting a significant need for novel approaches to address these concerns. For this purpose, nanotechnology has revolutionized the field of medicine with versatile potential capabilities for both the diagnosis, as well as the treatment, of retinoblastoma via the targeted and controlled delivery of anticancer drugs via binding to the overexpressed retinoblastoma gene. Nanotechnology has also generated massive advancements in the treatment of retinoblastoma based on the use of surface-tailored multi-functionalized nanocarriers; overexpressed receptor-based nanocarriers ligands (folate, galactose, and hyaluronic acid); lipid-based nanocarriers; and metallic nanocarriers. These nanocarriers seem to benchmark in mitigating a plethora of malignant retinoblastoma via targeted delivery at a specified site, resulting in programmed apoptosis in cancer cells. The effectiveness of these nanoplatforms in diagnosing and treating intraocular cancers such as retinoblastoma has not been properly discussed, despite the increasing significance of nanomedicine in cancer management. This article reviewed the recent milestones and future development areas in the field of intraocular drug delivery and diagnostic platforms focused on nanotechnology.

In vitro characterization of CD133lo cancer stem cells in Retinoblastoma Y79 cell line

Background

Retinoblastoma (Rb), the most common childhood intraocular malignant tumor, is reported to have cancer stem cells (CSCs) similar to other tumors. Our previous investigation in primary tumors identified the small sized cells with low CD133 (Prominin-1) and high CD44 (Hyaluronic acid receptor) expression to be putative Rb CSCs using flow cytometry (FSC^lo/SSC^lo/CD133^lo/CD44^hi). With this preliminary data, we have now utilized a comprehensive approach of in vitro characterization of Y79 Rb cell line following CSC enrichment using CD133 surface marker and subsequent validation to confirm the functional properties of CSCs.

Methods

The cultured Rb Y79 cells were evaluated for surface markers by flow cytometry and CD133 sorted cells (CD133^lo/CD133^hi) were compared for CSC characteristics by size/percentage, cell cycle assay, colony formation assay, differentiation, Matrigel transwell invasion assay, cytotoxicity assay, gene expression using microarray and validation by semi-quantitative PCR.

Results

Rb Y79 cell line shared the profile (CD133, CD90, CXCR4 and ABCB1) of primary tumors except for CD44 expression. The CD133^lo cells (16.1 ± 0.2%) were FSC^lo/SSC^lo, predominantly within the G0/G1 phase, formed larger and higher number of colonies with ability to differentiate to CD133^hi cells, exhibited increased invasive potential in a matrigel transwell assay (p < 0.05) and were resistant to Carboplatin treatment (p < 0.001) as compared to CD133^hi cells. The CD133^lo cells showed higher expression of several embryonic stem cell genes (HOXB2, HOXA9, SALL1, NANOG, OCT4, LEFTY), stem cells/progenitor genes (MSI2, BMI1, PROX1, ABCB1, ABCB5, ABCG2), and metastasis related gene- MACC1, when compared to the CD133^hi cells.

Conclusions

This study validates the observation from our earlier primary tumor study that CSC properties in Rb Y79 cell line are endowed within the CD133^lo population, evident by their characteristics- i.e. small sized, dormant in nature, increased colony forming ability, differentiation to CD133^hi cells, higher invasiveness potential, drug resistance and primitive gene expression pattern. These findings provide a proof of concept for methodological characterization of the retinoblastoma CSCs with future implications for improved diagnostic and treatment strategies.

[Genetic analysis results of patients with a retinoblastoma refractory to systemic chemotherapy]

OBJECTIVE

To analyze the genetic alterations identified in the RB1 gene in retinoblastoma patients who do not respond to systemic chemotherapy.

METHODS

A genetic analysis was performed on 115 patients with retinoblastoma, 40 of whom had received systemic chemotherapy, and 29 of them had bilateral disease. Descriptive and retrospective study. Non-responders were considered as patients who are finally enucleated.

RESULTS

Patients with deletion type mutations are those with less preservation of the eyeball (Pearson Chi-square, P=.055). Patients with an impaired nonsense-frameshift type are more likely to preserve the eyeball. Of the 3 patients who had undergone bilateral enucleation, 2 of them had deletions and one missense alteration. Survival analysis (Kaplan-Meier curve) shows that patients with deletion type mutations are more resistance to chemotherapy, are suffering higher rates of enucleation, and for a shorter period of time (log rank [Mantel-Cox] with a significance level of P=.053), which are also associated with increased rate of being bilateral.

CONCLUSIONS

Patients with a genotype show increased resistance to chemotherapy should be evaluated more closely and treated with various therapeutic weapons early. Patients that have deletions in the RB1 gene are at increased risk of chemoresistance. It is likely that other genetic alterations other than RB1 gene may be related to tumor aggressiveness and treatment resistance.

Expression of P-glycoprotein in human retinoblastoma and its clinical significance

Retinoblastoma is the most common malignant intraocular tumor of childhood. Drug resistance and relapses are major problems with chemotherapy, which is regarded as the mainstay of globe preserving treatment in retinoblastoma. P-glycoprotein (P-gp) expression has been reported to be associated with chemoresistance and poor prognosis in various malignancies. We analyzed P-gp expression in retinoblastoma specimens, enucleated either primarily or after neoadjuvant chemotherapy by immunohistochemistry and immunoblotting, and correlated with the histopathological findings. Variables were statistically analyzed by Fischer's exact and chi-square tests. Tumor tissues were collected from enucleated eyes of 24 children. Fifteen of these were primarily enucleated (group I), and nine (group II) had received chemotherapy prior to enucleation. P-gp was expressed in 4/15 (26.7 %) eyes in group I and in 5/9 (55.6 %) eyes in group II. P-gp was highly expressed in group II as compared to group I. There was no correlation between P-gp expression and tumor differentiation, invasion, or laterality. In conclusion, there was markedly high expression of P-gp in eyes with retinoblastoma enucleated after chemotherapy. This may possibly play a role in chemoresistance or it may be that chemotherapy might have induced high expression. These findings may have important implications for the treatment of retinoblastoma patients but need further prospective investigations in a larger patient population.

Animal models in retinoblastoma research

Advances in animal models of retinoblastoma have accelerated research in this field, aiding in understanding tumor progression and assessing therapeutic modalities. The distinct pattern of mutations and specific location of this unique intraocular tumor have paved the way for two types of models- those based on genetic mutations, and xenograft models. Retinoblastoma gene knockouts with an additional loss of p107, p130, p53 and using promoters of Nestin, Chx10, and Pax6 genes show histological phenotypic changes close to the human form of retinoblastoma. Conditional knockout in specific layers of the developing retina has thrown light on the origin of this tumor. The use of xenograft models has overcome the obstacle of time delay in the presentation of symptoms, which remains a crucial drawback of genetic models. With the advances in molecular and imaging technologies, the current research aims to develop models that mimic all the features of retinoblastoma inclusive of its initiation, progression and metastasis. The combination of genetic and xenograft models in retinoblastoma research has and will help to pave way for better understanding of retinoblastoma tumor biology and also in designing and testing effective diagnostic and treatment modalities.

Outcomes of cataract surgery following radiation treatment for retinoblastoma

PURPOSE

To report the outcomes after cataract extraction in eyes previously treated for retinoblastoma.

METHODS

We reviewed the medical records of consecutive patients treated with cataract extraction at our institution for radiation-induced cataract following retinoblastoma treatment between 1992 and 2007.

RESULTS

Twelve eyes of 11 patients were included. The median age at diagnosis of retinoblastoma was 7.4 months. The median quiescent interval before cataract surgery was 34.6 months (range, 17-240 months). All patients underwent limbal-based extracapsular cataract extraction with scleral-tunnel wound construction. Anterior vitrectomy and posterior capsulotomy were performed in 7 eyes; an intraocular lens was placed in 10 eyes. A laser capsulotomy was subsequently performed in 5 eyes. No postoperative complications occurred. One patient underwent a pars plana vitrectomy for vitreous hemorrhage and proliferative retinopathy 5 years after cataract extraction. The median follow-up after surgery was 6.0 years (range, 1.1-12.3 years). Final visual acuity was between 20/20 and 20/60 in 6 eyes, between 20/70 and 20/200 in 2 eyes, and worse than 20/200 in 4 eyes. No intraocular tumor recurrences or metastases occurred. Two patients developed secondary rhabdomyosarcomas; 1 patient succumbed to the disease.

CONCLUSIONS

Limbal-based cataract extraction in our series was not associated with tumor recurrence or metastasis. The optimal quiescent interval is not known; however, no tumor recurrences occurred in our series when a minimum 17-month quiescent period was achieved. Visual improvement was noted in every patient, although several patients only experienced modest gains.

The addition of ifosfamide/etoposide to cisplatin/teniposide improves the survival of children with retinoblastoma and orbital involvement

This study aimed to determine the impact of the addition of ifosfamide/etoposide to a regimen containing cisplatin/teniposide on the survival of patients with retinoblastoma with orbital involvement. Thirty patients were treated at the A. C. Camargo Hospital, Brazil, from 1986 to 2002. From 1986 to April 1992 (period I, n=12), treatment consisted of 3 cycles of induction chemotherapy with cisplatin and teniposide, followed by maintenance with same drugs alternating with cyclophosphamide, vincristine, and doxorubicin every 21 days for 60 weeks. Since April 1992 (period II, n=18), the treatment consisted of 3 cycles of ifosfamide and etoposide followed by maintenance with same drugs, alternating with cisplatin and teniposide every 21 days for 36 weeks. In both periods, children were submitted to exenteration with eyelid preservation and orbital radiation therapy with 45 cGy, and also received intrathecal therapy with methotrexate plus dexamethasone and cytarabine. Kaplan-Meier method was used for survival analysis. The median age was 31 months. Most patients (86.7%) presented unilateral tumors. The 3-year overall survival was 34.4% and 72.2%, respectively, for patients treated during periods I and II (P=0.061). The addition of ifosfamide/etoposide to chemotherapy with cisplatin/teniposide improves survival in these patients, but further studies are still necessary.

Secondary acute myelogenous leukemia in patients with retinoblastoma: is chemotherapy a factor?

PURPOSE

To describe a series of patients with secondary acute myelogenous leukemia (sAML) and retinoblastoma (RB).

DESIGN

Retrospective observational cases series.

PARTICIPANTS

Ocular and pediatric oncologists at referral centers in Europe and the Americas and the RB databases at the National Institutes of Health and the Ophthalmic Oncology Service at Memorial Sloan-Kettering Cancer Center.

METHODS

Physician survey, retrospective database review, and literature search.

MAIN OUTCOME MEASURES

History of RB and development of sAML, management of RB (surgery, radiotherapy, chemotherapy), age at diagnosis of RB and leukemia, French-American-British (FAB) subtype, and current status of patient (alive or dead).

RESULTS

Fifteen patients with sAML were identified; 13 occurred in childhood. Mean latent period from RB to AML diagnosis was 9.8 years (median, 42 months). Nine cases were of the M2 or M5 FAB subtypes. Twelve patients (79 %) had received chemotherapy with a topoisomerase II inhibitor, 8 (43%) had received chemotherapy with an epipodophyllotoxin. Ten children died of their leukemia.

CONCLUSIONS

Acute myelogenous leukemia is a rare secondary malignancy among retinoblastoma patients, many of whom were treated with primary or adjuvant chemotherapy. Additional studies are needed to assess potential risk factors contributing to sAML development in this cohort.

The expression of cyclooxygenase 2 in retinoblastoma: primary enucleated eyes and enucleation after conservative treatment

PURPOSE

To provide insight into the relationship between cyclooxygenase-2 (COX-2) expression and histopathologic features of retinoblastoma specimens treated either by primary or secondary enucleation.

DESIGN

Laboratory investigation.

METHODS

Twenty-five retinoblastoma specimens received between 1994 and 2003 were retrieved for this study from the Ocular Pathology Registry, Federal University of São Paulo, Brazil and the Henry C. Witelson Ocular Pathology Laboratory and Registry, McGill University, Montreal, Canada. The specimens retrieved were divided into two groups: Group I, enucleation was performed as a form of primary treatment (n = 15) and Group II, enucleation after failure of conservative treatment (n = 10). Patient information and formalin-fixed, paraffin-embedded specimens were obtained. New sections of these blocks were used for hematoxylin and eosin stain and for immunoassay using a monoclonal mouse anti-COX-2 antibody. Two independent ophthalmic pathologists reviewed all of the microslides.

RESULTS

Twenty-three specimens (92%) presented a high expression of COX-2 (15 in Group I; eight in Group II) and there was no statistical difference in COX-2 expression between the two groups (P = .07). However, all specimens expressed COX-2 to a different degree. The areas of tumor invasion were positive for COX-2 in 87.5% of the two groups.

CONCLUSION

Most retinoblastoma specimens revealed a high COX-2 expression. Future studies will be necessary to correlate the high expression of COX-2 in retinoblastoma and a possible applicability of anti-COX-2 medications in the treatment of these tumors.

Treatment of retinoblastoma patients with chemoreduction plus local therapy: experience of the AC Camargo Hospital, Brazil

To evaluate the efficacy of conservative management of intraocular retinoblastoma with chemoreduction combined with local therapy with or without plaque radiation in the preservation of the eye, and avoidance of external beam radiation therapy (EBRT) (success rate). From 1995 to 2000, 84 newly diagnosed patients with intraocular retinoblastoma were admitted to the Pediatric Department of the Hospital do Cancer A.C. Camargo, São Paulo, Brazil. All children were treated with 2 to 6 cycles of chemotherapy (carboplatin, vincristine, and etoposide) plus local therapy (cryotherapy, laser photocoagulation, and thermotherapy), or plaque radiation therapy during and/or after the chemotherapy. The Mann-Whitney test was used to compare means of quantitative variables. The chi test or the Fisher exact test were employed to verify the association between the outcome and the independent variables. For all tests alpha=5% was adopted. Success rate was higher for patients with bilateral tumors (54%) than for children with unilateral tumors (19%) (P=0.003). For patients with Reese-Ellsworth stages I, II, and III, no statistically significant differences in the success rates were noted in the group of unilateral (50%) and bilateral tumors (79.1%) (P=0.179). Among children with Reese-Ellsworth stages IV and V, the success rate was significantly higher for patients with bilateral tumors (40.7%) than for those with unilateral (0%) (P=0.012). Chemoreduction combined with local therapy, with or without plaque radiotherapy, is efficacious in avoiding enucleation and the use of external beam radiation therapy for children with intraocular retinoblastoma.

Fractionated stereotactic radiotherapy for pediatric patients with retinoblastoma

In this report, we discuss the application of a modified Gill‐Thomas‐Cosman (GTC) relocatable head frame to enable fractionated stereotactic radiotherapy (SRT) of infants under anesthesia. This system has been used to treat two infants, ages 12 and 18 months, for bilateral retinoblastoma on a Varian 6/100 linear accelerator. The GTC head frame was used to reproducibly position and treat the orbits of these children to between 2520 cGy and 3960 cGy in 180‐cGy fractions. A standard head and neck tray, with accompanying thermoplastic mask, was adapted to mount to the head frame to enable these treatments. We found the maximum average deviation in the repeat fixations, as compared with the initial fitting data, to be ±2mm. The overall average difference and standard deviation in measurement was 0.47±0.63mm for the first case and 0.19±0.94mm for the second case, with a combined average of 0.35±0.79mm overall from a total of 381 point measurements. The stereotactic treatment plan (Radionics®) incorporated a single isocenter for each orbit and 3 or 4 arcs per isocenter. An intercomparison has been made between this technique and a standard lateral field technique, designed using the stereotactic radiosurgery (SRS) planning system. Dose‐volume histograms and corresponding normal tissue complication probabilities (NTCP) based on pediatric bone growth inhibition have been calculated for each method for the orbital bone areas. We found that the NTCP is reduced from 95% or more in the standard treatment method to 16% or less with SRT. Use of the modified head frame provides excellent setup reproducibility, facilitates access to patients for anesthesia, and reduces the chances of a poor cosmetic result in these growing children.

PACS number: 87.53.Ly

Pars Plana Lensectomy and Intraocular Lens Implantation in Pediatric Radiation-Induced Cataracts in Retinoblastoma

OBJECTIVE

To investigate visual outcomes, surgical complications, and tumor recurrence among children with retinoblastoma (RB) undergoing pars plana lensectomy, vitrectomy, and simultaneous intraocular lens insertion for radiation-related cataract secondary to external beam radiotherapy (EBRT).

DESIGN

Retrospective, noncomparative, consecutive case series.

METHODS

The medical records for all patients treated with pars plana lensectomy, vitrectomy, and posterior chamber intraocular lens implantation for radiation-induced cataract after EBRT for RB at a single institution between January 1, 1990, and December 31, 2000, were reviewed.

PARTICIPANTS

The study included 16 eyes of 12 children with Reese-Ellsworth stage V RB.

MAIN OUTCOME MEASURES

Visual acuity, surgical and postoperative complications, postoperative refraction, and tumor recurrence.

RESULTS

The median age at diagnosis of RB was 6 months (range, 1-49 months). All patients received EBRT as primary treatment and experienced radiation-induced cataracts. The median interval from RB diagnosis to cataract surgery was 42 months (range, 28-95 months). Preoperative mean visual acuity was 20/400, with 12 of 16 eyes (75%) having macular tumor involvement. All patients underwent pars plana lensectomy, vitrectomy, and posterior chamber intraocular lens insertion. Vitreous samples were evaluated by cytopathologic examination, and no viable tumor cells were identified in any of the vitreous specimens. Postoperative complications included transient cystoid macular edema in 5 eyes (31%) and iridocyclitis in 3 eyes (19%). The mean follow-up after cataract surgery was 66 months (range, 30-94 months). Final visual acuity was 20/40 or better in 11 of 16 eyes (69%). No late intraocular recurrence, orbital tumors, or metastatic disease was noted in this study.

CONCLUSIONS

Pars plana lensectomy, vitrectomy, and simultaneous intraocular lens implantation is an effective means of managing EBRT-induced cataracts in eyes with previously treated RB. There was no evidence of active tumor in eyes undergoing surgery at least 28 months after the diagnosis and commencement of therapy for RB, and no late intraocular, orbital, or metastatic tumors were detected. Visual acuity was limited by the presence of primary macular tumor pathologic features in a subset of patients, but final vision better than 20/400 may be achieved in these eyes.

The effect of a selective cyclooxygenase-2 (COX-2) inhibitor on the proliferation rate of retinoblastoma cell lines

PURPOSE

To examine the effect of nepafenac, a selective cyclooxygenase-2 (COX-2) inhibitor, on the proliferation rate of two human retinoblastoma (Rb)cell lines.

METHODS

Two human Rb cell lines (WERI-RB and Y79) were cultured. COX-2 expression in these cell lines was verified by immunocytochemical analysis of cytospin sections and Western blotting. An MTT-based proliferation assay was used to compare Rb cell growth with and without amfenac, the active metabolite of nepafenac. The averaged results per condition were recorded. The Student's t-test was used to compare results from the cells cultured with and without amfenac.

RESULT

The Y79 cell line showed a higher proliferative rate than the WERI-RB cell line. Both cell lines were negative for COX-2 expression by immunocytochemical analysis; however, both cell lines were positive for COX-2 expression by Western blot. When amfenac was added to both of the cell lines, a statistically significant reduction in proliferation was observed in both cell lines. The two Rb cell lines were positive for COX-2 only in the Western blot, indicating that they probably express low levels of COX-2, which was undetectable by immunocytochemical analysis.

CONCLUSION

The selective, anti-COX-2 molecule amfenac inhibited proliferation of both tested Rb cell lines. Further trials should be undertaken to study the effect of selective COX-2 inhibitors on Rb.

Relationship between histopathological features of chemotherapy treated retinoblastoma and P-glycoprotein expression

BACKGROUND

P-glycoprotein (P-gp) has been identified as a possible mediator of chemoresistance in retinoblastoma. The aim of this study was to determine the expression of P-gp in retinoblastoma treated with chemotherapy prior to enucleation.

METHODS

Seventeen enucleated specimens of retinoblastoma from 16 patients were studied. Nine had been treated with chemotherapy alone, and eight had been treated with chemotherapy and other forms of local treatment. Tumour differentiation as well as choroidal and optic nerve invasion were assessed. P-gp immunohistochemical staining was performed and evaluated as negative, low or high.

RESULTS

Histopathological assessment of the cases showed that 14 of 17 eyes (82.3%) had viable retinoblastoma cells. Nine retinoblastomas were considered regressed with a well-differentiated component, five regressed retinoblastomas had viable cells with poor differentiation and three retinoblastomas had regressed leaving no viable cells. Sixteen of 17 retinoblastomas were P-gp positive. In the one case with optic nerve invasion and the three cases with massive choroidal invasion, P-gp expression was found in invading retinoblastoma cells.

CONCLUSION

Almost all retinoblastomas expressed P-gp. High levels of P-gp expression might play a role in chemotherapy resistance of retinoblastoma or, conversely, chemotherapy might induce P-gp expression. These results might have an impact on management of bilateral retinoblastoma.