Knudson's hypothesis revisited in Indian retinoblastoma patients

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.

Analysis of the p53 pathway in peripheral blood of retinoblastoma patients; potential biomarkers

Loss of retinoblastoma (RB) function in the cone cells during retina development is necessary but not sufficient for retinoblastoma development. It has been reported that in the absence of RB activity, a retinoma is generated, and the onset of retina cancer occurs until the p53 pathway is altered. Unlike other types of cancer, in retinoblastoma the p53 tumour suppressor is mostly wild type, although its two primary regulators, MDMX and MDM2, are commonly dysregulated. A mutated RB form is inherited in around 35% of the cases, but normally two, somatic mutations are needed to alter the RB function. Here we investigated the mRNA levels of RB, p53, MDMX and MDM2 in peripheral blood samples of retinoblastoma patients to monitor the pathway status of p53 in somatic cells. We sought to investigate the involvement of these genes in the development of retina cancer, with the aim of identifying biomarkers for early diagnosis of this disease.

Epidemiology and risk factors of retinoblastoma in Chongqing area

AIM

To investigate the risk factors of retinoblastoma in Chongqing and offer the bases for scientific measures.

METHODS

One hundred and thirty-three retinoblastoma patients were taken as case group, and 133 children were taken as control group in 1:1 ratio. The relevant factors were collected from a questionnaire survey which was made by our research group. First, Chi-square and t-test were used to discuss the various factors, and then the logistic regression analysis was made by statistics software SPSS17.0 based on the result of 266 people.

RESULTS

Single factor analysis results showed the differences between the two groups were statistically significant (P<0.05) in 17 factors which were education level of their parents, occupation of their parents, exposure to harmful chemicals of their parents 6mo before pregnancy, the history of pelvic inflammatory disease of mother before pregnancy, childbearing history of their parents, pregnant age of their parents, the medication history of father 6 mo before pregnancy, living place of their parents, the pollution living place of mother, hobbies of their parents. Multivariate analysis showed that the living place of parents, mother who feed pets before pregnancy, and exposure to harmful chemicals of father before pregnancy were the independent risk factors of retinoblastoma (P<0.05).

CONCLUSION

The living place of parents, mother who feed pets before pregnancy, exposure to harmful chemicals of father before pregnancy were the risk factors of retinoblastoma which affects the occurrence of retinoblastoma in a certain extent.