Analysis of retinoblastoma age incidence data using a fully stochastic cancer model

Minimum latency effects for cancer associated with exposures to radiation or other carcinogens

BACKGROUND

In estimating radiation-associated cancer risks a fixed period for the minimum latency is often assumed. Two empirical latency functions have been used to model latency, continuously increasing from 0. A stochastic biologically-based approach yields a still more plausible way of describing latency and can be directly estimated from clinical data.

METHODS

We derived the parameters for a stochastic biologically-based model from tumour growth data for various cancers, and least-squares fitted the two types of empirical latency function to the stochastic model-predicted cumulative probability.

RESULTS

There is wide variation in growth rates among tumours, particularly slow for prostate and thyroid cancer and particularly fast for leukaemia. The slow growth rate for prostate and thyroid tumours implies that the number of tumour cells required for clinical detection cannot greatly exceed 106. For all tumours, both empirical latency functions closely approximated the predicted biological model cumulative probability.

CONCLUSIONS

Our results, illustrating use of a stochastic biologically-based model using clinical data not tied to any particular carcinogen, have implications for estimating latency associated with any mutagen. They apply to tumour growth in general, and may be useful for example, in planning screenings for cancer using imaging techniques.

Second hit impels oncogenesis of retinoblastoma in patient-induced pluripotent stem cell-derived retinal organoids: direct evidence for Knudson's theory

Retinoblastoma (Rb) is a type of malignant tumor due to abnormal retinogenesis with biallelic mutations of the RB1 gene. Its pathogenesis has been proposed as a "two-mutation hypothesis" by Knudson since 1971; however, there remain some debates on disease onset sufficiency of the biallelic RB1 mutations. To obtain straightforward evidence for this hypothesis, we investigated whether two-hit mutations of the RB1 gene drive tumorigenesis in patient-induced pluripotent stem cell (hiPSC)-derived human retinal organoids (hROs) and whether single allelic mutation hiPSC-derived hROs exhibit molecular and cellular defects. We generated hiPSCs with a heterozygous germline mutation (RB1^{m1/ wt} ) from a Rb patient. A second-allele RB1 gene mutation was knocked in to produce compound heterozygous mutations (RB1^m1/m2 ) in the hiPSCs. These two hiPSC lines were independently developed into hROs through a stepwise differentiation. The hiPSC-RB1^m1/m2 derived organoids demonstrated tumorigenesis in dishes, consistent with Rb profiles in spatiotemporal transcriptomes, in which developmentally photoreceptor fate-determining markers, CRX and OTX2, were highly expressed in hiPSC-RB1^m1/m2 derived hROs. Additionally, ARR3⁺ maturing cone precursors were co-labeled with proliferative markers Ki67 or PCNA, in agreement with the consensus that human Rb is originated from maturing cone precursors. Finally, we demonstrated that retinal cells of hROs with monoallelic RB1 mutation were abnormal in molecular aspects due to its haploinsufficiency. In conclusion, this study provides straightforward supporting evidence in a way of reverse genetics for "two-hit hypothesis" in the Rb tumorigenesis and opens new avenues for development of early intervention and treatment of Rb.

CASC8 lncRNA Promotes the Proliferation of Retinoblastoma Cells Through Downregulating miR34a Methylation

Background

CASC8 lncRNA has been proven to be oncogenic in a variety of cancers, but its role in other types of cancer remains unclear. This study was to investigate the role of CASC8 in retinoblastoma (Rb).

Methods

RT-qPCR was performed to determine the expression of CASC8 and miR34a in paired Rb and nontumor tissue. Overexpression of CASC8 and miR34a in Rb cells was achieved to evaluate the interaction between them. Methylation-specific PCR was used to analyze the effect of CASC8 overexpression on MIR34A gene methylation. CCK8 assays were used to analyze cell proliferation.

Results

The results showed that CASC8 expression was upregulated and miR34a expression downregulated in Rb tissue. Moreover, miR34a expression was negatively correlated with the of CASC8 expression in Rb tissue. Overexpression of CASC8 decreased expression of miR34a and increased methylation of MIR34A in Rb cells. In addition, overexpression of CASC8 reduced the inhibitory effects of miR34a on Rb-cell proliferation.

Conclusion

CASC8 may promote Rb cell proliferation by downregulating miR34a methylation.

Next-Generation Technologies and Strategies for the Management of Retinoblastoma

Retinoblastoma (RB) is an inherited retinal disorder (IRD) caused by the mutation in the RB1 gene or, rarely, by alterations in the MYCN gene. In recent years, new treatment advances have increased ocular and visual preservation in the developed world. The management of RB has improved significantly in recent decades, from the use of external beam radiation to recently, more localized treatments. Determining the underlying genetic cause of RB is critical for timely management decisions. The advent of next-generation sequencing technologies have assisted in understanding the molecular pathology of RB. Liquid biopsy of the aqueous humor has also had significant potential implications for tumor management. Currently, patients' genotypic information, along with RB phenotypic presentation, are considered carefully when making treatment decisions aimed at globe preservation. Advances in molecular testing that improve our understanding of the molecular pathology of RB, together with multiple directed treatment options, are critical for developing precision medicine strategies to treat this disease.

PRC1 gene silencing inhibits proliferation, invasion, and angiogenesis of retinoblastoma cells through the inhibition of the Wnt/β-catenin signaling pathway

Retinoblastoma is an ocular malignancy occurring in childhood. The current study evaluates the ability of silenced PRC1 on retinoblastoma cell proliferation, and angiogenesis via the Wnt/β-catenin signaling pathway. A total of 36 cases of retinoblastoma tissues (n = 36) and normal retinal tissues (n = 10) were selected in the current study. Retinoblastoma cells presenting with the high PRC1 messenger RNA (mRNA) expression were selected among the WERI-Rb-1, HXO-RB44, Y79, SO-Rb50, and SO-Rb70 cells lines, and were transfected with siRNA-PRC1 and LiCl (the activator of the Wnt/β-catenin pathway). The expressions of PRC1, VEGF, Wnt1, β-catenin, CyclinD1, extent of β-catenin, and GSK-3β phosphorylation were evaluated. Cell proliferation, cell-cycle distribution, and cell invasion of retinoblastoma cells were evaluated by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, flow cytometry, and Transwell assay. The angiogenesis of retinoblastoma cells was detected by tube formation assay. HXO-RB44 and WERI-Rb-1 cells were selected owing to the highest PRC1 mRNA expression. Meanwhile, PRC2 gene silencing presented lower expression levels of PRC1, VEGF, Wnt1, β-catenin, CyclinD1, extent of β-catenin and GSK-3β phosphorylation, decreased proliferation and invasion abilities, extended G0/G1 phase, and shortened S and G2/M phases of HXO-RB44 and WERI-Rb-1 cells, suggesting the silenced PRC2 inactivated Wnt/β-catenin pathway, so as to further restrain the retinoblastoma cell proliferation, invasion, and angiogenesis. These results support the view that PRC1 gene silencing could suppress the proliferation, and angiogenesis of retinoblastoma cells by repressing the Wnt/β-catenin pathway.

Retinoblastoma: The importance of early diagnosis

INTRODUCTION

Retinoblastoma is the most frequent malignant intraocular tumour in childhood, and both its cure and the sequelae arising from it, mainly depend on an early diagnosis. There is currently no consensus on its diagnostic and therapeutic management.

PATIENTS AND METHODS

A descriptive, retrospective, and non-randomised study was conducted on a series of cases (39 patients -58 eyes), treated during the period 2006-2013, in the Regional Reference Centre for Tumours of the National Health Service Quality Agency.

RESULTS

The most frequent presentation sign is leukocoria (71.8%), followed by strabismus (17.9%). All cases of bilateral tumour had a germline mutation of the RB1 gene, and 20% had a family history. Stage E was observed in 55% of the patients, and 90% required chemotherapy treatment. The eye was maintained in 57% of those who had mild stages, compared to 43% who maintained it in advanced stages.

CONCLUSIONS

This analysis included 58 eyes. There are no previous studies in our community and there are few series so numerous throughout the country. Based on non-standardised treatment, the most appropriate is chosen according to the characteristics of the tumour. The multidisciplinary management, formed by ophthalmology, paediatric oncology, radiotherapy, and radiophysical oncology, is fundamental for the selection of the most appropriate treatment. Chemo-reduction, along with consolidation treatments, offers encouraging results in the control of these tumours, especially in those of less severity. Enucleation continues to be the method of choice in the most advanced staging with vitreous involvement, with the importance of early diagnosis being highlighted.

Parental occupational exposures and the risk of childhood sporadic retinoblastoma: a report from the Children's Oncology Group

OBJECTIVES

We examined associations between parental occupational chemical exposures up to 10 years before conception and the risk of sporadic retinoblastoma among offspring.

METHODS

In our multicentre study on non-familial retinoblastoma, parents of 187 unilateral and 95 bilateral cases and 155 friend controls were interviewed by telephone. Exposure information was collected retroactively through a detailed occupational questionnaire that asked fathers to report every job held in the 10 years before conception, and mothers 1 month before and during the index pregnancy. An industrial hygienist reviewed all occupational data and assigned an overall exposure score to each job indicating the presence of nine hazardous agents.

RESULTS

We estimated elevated ORs for unilateral and bilateral retinoblastoma among offspring of fathers who were exposed to polycyclic aromatic hydrocarbons or paints in the 10 years before conception. However, only for exposure to paints did confidence limits exclude the null for bilateral disease (OR: 8.76, 95% CI: 1.32 to 58.09). Maternal prenatal exposure to at least one of the nine agents was related to increased risk of unilateral disease in their children (OR: 5.25, 95% CI: 1.14 to 24.16). Fathers exposed to at least one of the nine agents and who were ≥30 years of age were at increased risk of having a child diagnosed with bilateral retinoblastoma (OR: 6.59, 95% CI: 1.34 to 32.42).

CONCLUSIONS

Our results suggest a role for several hazardous occupational exposures in the development of childhood retinoblastoma.

Residential Pesticide Exposures in Pregnancy and the Risk of Sporadic Retinoblastoma: A Report From the Children's Oncology Group

PURPOSE

To examine whether parental pesticide exposure contributes to the development of sporadic retinoblastoma.

DESIGN

Case-control study.

METHODS

Data were collected by a large multicenter study of sporadic retinoblastoma in which parents of 99 unilateral and 56 bilateral age-matched case-control pairs were interviewed by telephone. Retrospective exposure information was collected on the type, location, timing, and frequency of residential pesticide use. We used conditional logistic regression analyses to estimate odds ratios for maternal pesticide exposure in the month before or during pregnancy and to assess whether the type of product, and the circumstances under which it was applied, were associated with risk of disease.

RESULTS

Unilateral retinoblastoma was associated with parental insecticide use (odds ratio [OR], 2.8; confidence interval [CI], 1.1-6.7) and the use of professional lawn or landscape services (OR, 2.8; CI, 1.0-8.2). For bilateral disease we observed large point estimates for several exposures but the small number of cases rendered these results uninformative (ie, resulted in wide confidence intervals). Whether parents used the pesticide inside vs outside the home did not appear to modify risk estimates for unilateral retinoblastoma (OR, 2.5; CI, 0.9-7.0 vs OR, 2.5; CI, 1.0-6.5), nor did the type, frequency, timing related to pregnancy, or applicator of pesticide used influence estimates to an appreciable degree for disease.

CONCLUSIONS

Our results suggest that parental pesticide exposure before or during pregnancy may play a role in the development of childhood retinoblastoma. Retrospectively collected exposure data introduces the possibility of recall bias; therefore, results should be interpreted cautiously until additional studies are conducted.

Mathematical models of tissue stem and transit target cell divisions and the risk of radiation- or smoking-associated cancer

There is compelling biological data to suggest that cancer arises from a series of mutations in single target cells, resulting in defects in cell renewal and differentiation processes which lead to malignancy. Because much mutagenic damage is expressed following cell division, more-rapidly renewing tissues could be at higher risk because of the larger number of cell replications. Cairns suggested that renewing tissues may reduce cancer risk by partitioning the dividing cell populations into lineages comprising infrequently-dividing long-lived stem cells and frequently-dividing short-lived daughter transit cells. We develop generalizations of three recent cancer-induction models that account for the joint maintenance and renewal of stem and transit cells, also competing processes of partially transformed cell proliferation and differentiation/apoptosis. We are particularly interested in using these models to separately assess the probabilities of mutation and development of cancer associated with "spontaneous" processes and with those linked to a specific environmental mutagen, specifically ionizing radiation or cigarette smoking. All three models demonstrate substantial variation in cancer risks, by at least 20 orders of magnitude, depending on the assumed number of critical mutations required for cancer, and the stem-cell and transition-cell mutation rates. However, in most cases the conditional probabilities of cancer being mutagen-induced range between 7-96%. The relative risks associated with mutagen exposure compared to background rates are also stable, ranging from 1.0-16.0. Very few cancers, generally <0.5%, arise from mutations occurring solely in stem cells rather than in a combination of stem and transit cells. However, for cancers with 2 or 3 critical mutations, a substantial proportion of cancers, in some cases 100%, have at least one mutation derived from a mutated stem cell. Little difference is made to relative risks if competing processes of proliferation and differentiation in the partially transformed stem and transit cell population are allowed for, nor is any difference made if one assumes that transit cells require an extra mutation to confer malignancy from the number required by stem cells. The probability of a cancer being mutagen-induced correlates across cancer sites with the estimated cumulative number of stem cell divisions in the associated tissue (p<0.05), although in some cases there is sensitivity of findings to removal of high-leverage outliers and in some cases only modest variation in probability, but these issues do not affect the validity of the findings. There are no significant correlations (p>0.3) between lifetime cancer-site specific radiation risk and the probability of that cancer being mutagen-induced. These results do not depend on the assumed critical number of mutations leading to cancer, or on the assumed mutagen-associated mutation rate, within the generally-accepted ranges tested. However, there are borderline significant negative correlations (p = 0.08) between the smoking-associated mortality rate difference (current vs former smokers) and the probability of cancer being mutagen-induced. This is only the case where values of the critical number of mutations leading to cancer, k, is 3 or 4 and not for smaller values (1 or 2), but does not strongly depend on the assumed mutagen-associated mutation rate.

Downregulation of HDAC9 inhibits cell proliferation and tumor formation by inducing cell cycle arrest in retinoblastoma

Histone deacetylase 9 (HDAC9) is a member of class II HDACs, which regulates a wide variety of normal and abnormal physiological functions. Recently, HDAC9 has been found to be overexpressed in some types of human cancers. However, the role of HDAC9 in retinoblastoma remains unclear. In this study, we found that HDAC9 was commonly expressed in retinoblastoma tissues and HDAC9 was overexpressed in prognostically poor retinoblastoma patients. Through knocking down HDAC9 in Y79 and WERI-Rb-1 cells, the expression level of HDAC9 was found to be positively related to cell proliferation in vitro. Further investigation indicated that knockdown HDAC9 could significantly induce cell cycle arrest at G1 phase in retinoblastoma cells. Western blot assay showed downregulation of HDAC9 could significantly decrease cyclin E2 and CDK2 expression. Lastly, xenograft study in nude mice showed that downregulation of HDAC9 inhibited tumor growth and development in vivo. Therefore, our results suggest that HDAC9 could serve as a novel potential therapeutic target in the treatment of retinoblastoma.

Spatiotemporal Patterns of Tumor Occurrence in Children with Intraocular Retinoblastoma

PURPOSE

To accurately map the retinal area covered by tumor in a prospectively enrolled cohort of children diagnosed with retinoblastoma.

METHODS

Orbital MRI in 106 consecutive retinoblastoma patients (44 bilateral) was analyzed. For MRI-visible tumors, the polar angle and angle of eccentricity of points defining tumor perimeter on the retina were determined by triangulation from images in three orthogonal planes. The centroid of the mapped area was calculated to approximate tumor origin, and the location and cumulative tumor burden were analyzed in relation to mutation type (germline vs. somatic), tumor area, and patient age at diagnosis. Location of small tumors undetected by MRI was approximated with fundoscopic images.

RESULTS

Mapping was successful for 129 tumors in 91 eyes from 67 patients (39 bilateral, 43 germline mutation). Cumulative tumor burden was highest within the macula and posterior pole and was asymmetrically higher within the inferonasal periphery. Tumor incidence was lowest in the superotemporal periphery. Tumor location varied with age at diagnosis in a complex pattern. Tumor location was concentrated in the macula and superonasal periphery in patients <5.6 months, in the inferotemporal quadrant of the posterior pole in patients 5.6-8.8 months, in the inferonasal quadrant in patients 8.8-13.2 months, and in the nasal and superotemporal periphery in patients >13.2 months. The distribution of MRI-invisible tumors was consistent with the asymmetry of mapped tumors.

CONCLUSIONS

MRI-based mapping revealed a previously unrecognized pattern of retinoblastoma localization that evolves with age at diagnosis. The structured spatiotemporal distribution of tumors may provide valuable clues about cellular or molecular events associated with tumorigenesis in the developing retina.

Breast cancer risk after radiotherapy for heritable and non-heritable retinoblastoma: a US-UK study

BACKGROUND

Retinoblastoma is a rare childhood eye cancer caused by germline or somatic mutations in the RB1 gene. Previous studies observed elevated breast cancer risk among retinoblastoma survivors. However, there has been no research on breast cancer risk in relation to radiation (primarily scatter radiation from the primary treatment) and genetic susceptibility of retinoblastoma survivors.

METHODS

Two groups of retinoblastoma survivors from the US and UK were selected, and breast cancer risk analysed using a case-control methodology, nesting within the respective cohorts, matching on heritability (that is to say, having bilateral retinoblastoma or being unilateral cases with at least one relative with retinoblastoma), and using exact statistical methods. There were a total of 31 cases and 77 controls.

RESULTS

Overall there was no significant variation of breast cancer risk with dose (P>0.5). However, there was a pronounced and significant (P=0.047) increase in the risk of breast cancer with increasing radiation dose for non-heritable retinoblastoma patients and a slight and borderline significant (P=0.072) decrease in risk of breast cancer with increasing radiation dose for heritable retinoblastoma patients, implying significant (P=0.024) heterogeneity in radiation risk between the heritable and non-heritable retinoblastoma groups; this was unaffected by the blindness status. There was no significant effect of any type of alkylating-agent chemotherapy on breast cancer risk (P>0.5).

CONCLUSIONS

There is significant radiation-related risk of breast cancer for non-heritable retinoblastoma survivors but no excess risk for heritable retinoblastoma survivors, and no significant risk overall. However, these results are based on very small numbers of cases; therefore, they must be interpreted with caution.

Childhood and adult cancers: contrasts and commonalities

Tumours occurring in children differ considerably from those occurring at older ages but exhibit common features. Those occurring in the teenage/young adult (TYA) years represent a transitional mixture of child and adult tumours and pose a considerable challenge for optimal clinical management and service provision. Nevertheless the fundamental processes of malignant change, arising from genetic/epigenetic interaction with environmental exposures, seem to operate across all ages and the entire tumour spectrum. We focus here on the ways in which genotype (and epigenetic modification), growth processes (particularly in utero), and exposure to ionising radiation (in conjunction with genetic susceptibility) affect cancer risk from childhood to adulthood, whether as a primary occurrence, or a second primary tumour following earlier primary occurrence and treatment.

Sarcomas in hereditary retinoblastoma

Children diagnosed with the hereditary form of retinoblastoma (Rb), a rare eye cancer caused by a germline mutation in the RB1 tumor suppressor gene, have excellent survival, but face an increased risk of bone and soft tissue sarcomas. This predisposition to sarcomas has been attributed to genetic susceptibility due to inactivation of the RB1 gene as well as past radiotherapy for Rb. The majority of bone and soft tissue sarcomas among hereditary Rb survivors occur in the head, within the radiation field, but they also occur outside the radiation field. Sarcomas account for almost half of the second primary cancers in hereditary Rb survivors, but they are very rare following non-hereditary Rb. Sarcomas among hereditary Rb survivors arise at ages similar to the pattern of occurrence in the general population. There has been a trend over the past two decades to replace radiotherapy with chemotherapy and other focal therapies (laser or cryosurgery), and most recently, chemosurgery in order to reduce the incidence of sarcomas and other second cancers in Rb survivors. Given the excellent survival of most Rb patients treated in the past, it is important for survivors, their families and health care providers to be aware of the heightened risk for sarcomas in hereditary patients.

Variation of second cancer risk by family history of retinoblastoma among long-term survivors

PURPOSE

To evaluate the risk of second cancer (SC) in long-term survivors of retinoblastoma (Rb) according to classification of germline mutation, based on family history of Rb and laterality.

PATIENTS AND METHODS

We assembled a cohort of 1,852 1-year survivors of Rb (bilateral, n = 1,036; unilateral, n = 816). SCs were ascertained by medical records and self-reports and confirmed by pathology reports. Classification of RB1 germline mutation, inherited or de novo, was inferred by laterality of Rb and positive family history of Rb. Standardized incidence ratios and cumulative incidence for all SCs combined and for soft tissue sarcomas, bone cancers, and melanoma were calculated. The influence of host- and therapy-related risk factors for SC was assessed by Poisson regression for bilateral survivors.

RESULTS

We observed a relative risk (RR) of 1.37 (95% CI, 1.00 to 1.86) for SCs in bilateral survivors associated with a family history of Rb, adjusted for treatment, age, and length of follow-up. The risk for melanoma was significantly elevated for survivors with a family history of Rb (RR, 3.08; 95% CI, 1.23 to 7.16), but risks for bone or soft tissue sarcomas were not elevated. The cumulative incidence of SCs 50 years after diagnosis of bilateral Rb, with adjustment for competing risk of death, was significantly higher for survivors with a family history (47%; 95% CI, 35% to 59%) than survivors without a family history (38%; 95% CI, 32% to 44%; P = .004).

CONCLUSION

Rb survivors with bilateral disease and an inherited germline mutation are at slightly higher risk of an SC compared with those with a de novo germline mutation, in particular melanoma, perhaps because of shared genetic alterations.