The effect of imatinib mesylate on the proliferation, invasive ability, and radiosensitivity of retinoblastoma cell lines

The Role of Intraarterial Chemotherapy in the Management of Retinoblastoma

Introduction. Retinoblastoma is the most common primary intraocular neoplasm in children. With the advances in medicine, the armamentarium of available treatment modalities has grown. Intraarterial chemotherapy is a relatively new treatment method with promising outcomes. The purpose of this literature review is to evaluate its role in the management of retinoblastoma.

Targeting tyrosine kinases for treatment of ocular tumors

Uveal melanoma is the most common intraocular primary malignant tumor in adults, and retinoblastoma is the one in children. Current mainstay treatment options include chemotherapy using conventional drugs and enucleation, the total removal of the eyeball. Targeted therapies based on profound understanding of molecular mechanisms of ocular tumors may increase the possibility of preserving the eyeball and the vision. Tyrosine kinases, which modulate signaling pathways regarding various cellular functions including proliferation, differentiation, and attachment, are one of the attractive targets for targeted therapies against uveal melanoma and retinoblastoma. In this review, the roles of both types of tyrosine kinases, receptor tyrosine kinases and non-receptor tyrosine kinases, were summarized in relation with ocular tumors. Although the conventional treatment options for uveal melanoma and retinoblastoma are radiotherapy and chemotherapy, respectively, specific tyrosine kinase inhibitors will enhance our armamentarium against them by controlling cancer-associated signaling pathways related to tyrosine kinases. This review can be a stepping stone for widening treatment options and realizing targeted therapies against uveal melanoma and retinoblastoma.

HER2 Overexpression in Retinoblastoma: A Potential Therapeutic Target?

Background

Retinoblastoma (RB) is the most common primary intraocular malignancy. Current therapies are associated with high morbidity in the short- and long-term. Human epidermal growth factor receptor 2 (HER2) is a transmembrane protein detected in 15-30% of breast cancers, but it has also been described in other malignancies. Recently, it has been claimed that a truncated version of this protein is expressed in RB, responsive to directed therapies in vitro. We scored HER2 overexpression in RB tissue samples and discussed its potential clinical utility.

Methods

HER2 overexpression was investigated using immunohistochemistry; the overexpression was evaluated with a score ranging from 0 to 3+ according to the membranous staining pattern in archival formalin-fixed, paraffin-embedded RBs.

Results

A total of 60 RB cases and a RB cell line (Y79) were considered. The mean age at enucleation was 31.6 ± 31.5 months. The mean time from diagnosis to enucleation was 11.8 ± 11.2 months (range 1-44). Five (8%) cases were multifocal. HER2 overexpression was negative in all RB cases (49 cases scored 0 and 11 scored 1+) and in the Y79 cell line.

Conclusions

Overall, we were not able to demonstrate the overexpression of HER2. Further studies should clarify and better elucidate the potential role of HER2-targeted therapies in RB.

Overexpression of KAI1 inhibits retinoblastoma metastasis in vitro

The present study aimed to investigate the expression of cluster of differentiation 82 (KAI1), a gene involved in the suppression of tumor metastasis, in human retinoblastoma (RB) tissue and to study the effect of KAI1 expression on RB cell migration and invasion. KAI1 expression was examined in 26 patients with non-invasive and invasive retinoblastoma using reverse transcription-quantitative polymerase chain reaction and western blot analysis. A lentiviral vector containing KAI1 cDNA was used to transfect the two RB cell lines, HXO-Rb44-Gl and Y79. Following successful transfection, the migratory and invasive capacity of the two RB cell lines was evaluated using a Transwell^® migration assay. KAI1 expression was observed to be downregulated in invasive RB compared to non-invasive RB. The migratory and invasive capacities of KAI1 transfected cell lines were significantly decreased compared to those of the control cells. KAI1 may be involved in retinoblastoma metastasis, and increased expression of KAI1 significantly inhibits the metastatic ability of RB cells in vitro.

In cancer cell lines inhibition of SCF/c-Kit pathway leads to radiosensitization only when SCF is strongly over-expressed

Background and purpose

The SCF/c-Kit pathway is often overexpressed in human tumors leading to an enhanced tumorigenesis, proliferation and migration. It was now tested for NSCLC and prostate cancer cells growing in 2D and 3D whether the inhibition of this pathway can be used to achieve a significant radiosensitization and whether a respective biomarker may be identified.

Material and methods

Experiments were performed with different cancer cell lines (NSCLC: H23, H520, H226, H1975 and PrCa: DU145) growing either under 2D or 3D conditions. Expression of SCF and c-Kit was determined by RT-PCR and Western blot, SCF was knocked down by siRNA, c-Kit was inhibited by ISCK03 inhibitor and cell survival was determined by colony formation assay.

Results

There is a profound variation in the expression of both c-Kit and SCF with no association between each other. Neither levels did correlate with the respective cellular radiosensitivity determined for 2D or 3D with only a trend seen for SCF. Knock-down of SCF was generally found to result in no or only minor reduction of plating efficiency or cellular radioresistance. A significant reduction was only obtained for H520 cells characterized by an extreme over-expression of SCF. The inhibition of c-Kit by a specific inhibitor was also found to result only in minor radiosensitization.

Conclusion

Generally, the SCF/c-Kit pathway does not have a dominant effect on both, cell survival and radioresponse and, as a consequence, knockdown of this pathway does not result in a strong effect on radioresistance, except when SCF is strongly over-expressed.

Effects of NF-κB and hypoxia on the biological behavior of Y79 retinoblastoma cells

We aimed to investigate the influence of nuclear factor-κB (NF-κB) on the biological behavior of Y79 retinoblastoma cells exposed to hypoxia and its possible mechanism. The cells were administrated with hypoxia, and/or 5 μM pyrrolidine dithiocarbamate (PDTC) (a selective NF-κB inhibitor) to inhibit the NF-κB activity, expressions of NF-κB was measured by western blot, and the translocation of NF-κB was detected. To examine the proliferation of Y79 cells, MTT assay was applied. Transwell assay was used to detect the invasion and migration ability of cells. The expressions of molecules involved in invasion was analyzed including HIF-1α, MMP-2, 9, and VEGF. We found that hypoxia significantly activated NF-κB activity. While once the NF-κB was inhibited, the proliferation, invasion and migration ability of Y79 cells were also blocked. Interestingly, the expressions of invasion-involved molecules elevated by hypoxia induction were also decreased when NF-κB was inhibited. Hypoxia could significantly change the adhesive and invasive ability of Y79 retinoblastoma cells, NF-κB signal might be one of the main mediators for these hypoxia induced cell changes of biological behavior via downregulation of HIF-1α and the invasion related molecules, and the mechanism still needs further investigation.