Novel epithelial cell adhesion molecule antibody conjugated polyethyleneimine-capped gold nanoparticles for enhanced and targeted small interfering RNA delivery to retinoblastoma cells.

BACKGROUND: Several nanoconjugates have been designed to deliver nucleic acids such as small interfering RNA (siRNA) and DNA to cells to study silencing and expression efficacies. In the present study, we prepared novel epithelial cell adhesion molecule (EpCAM) monoclonal antibody conjugated polyethyleneimine (PEI) capped gold nanoparticles (AuNPs) loaded with EpCAM-specific siRNA molecules to knock-down the EpCAM gene in retinoblastoma (RB) cells. We chose EpCAM as a target moiety to deliver siRNA because this molecule is highly expressed in various epithelial cancers and is an ideal target as it is highly expressed in the apical surface of tumor cells while showing basolateral expression in normal cells. METHODS: The EpCAM antibody was conjugated to AuNP-PEI loaded with siRNA molecules to specifically deliver siRNA to EpCAM-expressing RB cells. Conjugation efficiencies were confirmed with ultraviolet-visible spectrophotometry, Fourier transform infrared spectroscopy, and agarose and SDS-polyacrylamide gel electrophoresis. The size and zeta potential were measured using a Zeta sizer analyzer. Nanoparticle internalization and uptake were studied using fluorescent microscopy and flow cytometry. Gene silencing efficacy was monitored with western blot analysis and real-time quantitative PCR. RESULTS: Optimal size and neutral zeta potential properties of the AuNP-PEI- EpCAM antibody (EpAb) antibody were achieved for the transfection studies. The AuNP-PEI nanoparticles did not show any cytotoxicity to the cells, which means these nanomaterials are suitable for intracellular delivery of siRNA for therapeutic interventions. With EpCAM antibody conjugation, PEI-capped AuNPs loaded with EpCAM siRNA were significantly internalized in the Y79 cells as observed with fluorescence microscopy and flow cytometry and induced a highly significant reduction in the cell viability of the Y79 cells. Through increased binding of EpCAM antibody-conjugated AuNP-PEI nanoparticles, significant downregulation of EpCAM gene was observed in the Y79 cells when compared to the cells treated with the antibody-unconjugated AuNP-PEI nanoparticles. CONCLUSIONS: Thus, a novel antibody conjugated nanocarrier designed to deliver siRNA holds promise as an effective gene therapy strategy for retinoblastoma in the near future. In addition to serving as an siRNA delivery tool for therapy, gold nanoparticles can also serve as imaging modality in diagnosis.

EpCAM is a putative stem marker in retinoblastoma and an effective target for T-cell-mediated immunotherapy.

PURPOSE: The molecular markers cluster of differentiation (CD)24, CD44, adenosine tri-phosphate (ATP) binding cassette protein G2 (ABCG2), and epithelial cell adhesion molecule (EpCAM) are widely used, individually or in combination, to characterize some types of cancer stem cells. In this study we characterized the EpCAM+ retinoblastoma (RB) cells for their cancer stem-like properties in vitro. Additionally, we targeted RB tumor cells via redirecting T cells using bispecific EpCAM×CD3 antibody. METHODS: Flow cytometry was used to study the co-expression of EpCAM with putative cancer stem cell markers, such as CD44, CD24, and ABCG2, in RB primary tumors. In vitro methyl thiazol tetrazolium (MTT) assay, invasion assay, and neurosphere formation assay were performed to characterize EpCAM+ cells for their cancer stem/progenitor cell-like properties. We assessed the in vitro efficacy of bispecific EpCAM×CD3 antibody on RB tumor cell proliferation and validated the results by evaluating effector cytokine production in the culture medium with the ELISA method. RESULTS: EpCAM was co-expressed with all cancer stem cell markers (CD44, CD24, and ABCG2) in primary RB tumors. EpCAM+ cells showed significantly higher proliferative invasive potential and neurosphere formation in vitro compared to EpCAM⁻ Y79 cells. EpCAM+ cells showed higher ß-catenin expression compared to EpCAM- cells. EpCAM×CD3 significantly retarded proliferation of RB primary tumor cells. EpCAM×CD3 effectively induced the secretion of effector cytokines, such as interferon (IFN)-γ, tumor necrosis factor (TNF)-α, interleukin (IL)-10, IL-2, and transforming growth factor (TGF)-ß1, and also perforin levels by pre-activated lymphocytes. CONCLUSIONS: EpCAM might be a novel cancer stem cell marker in RB. EpCAM×CD3 antibody redirecting T cells to attack RB tumor cells may prove effective in RB management. Further preclinical studies are needed to confirm the initial findings of our study.

A novel in vitro three-dimensional retinoblastoma model for evaluating chemotherapeutic drugs.

PURPOSE: Novel strategies are being applied for creating better in vitro models that simulate in vivo conditions for testing the efficacy of anticancer drugs. In the present study we developed surface-engineered, large and porous, biodegradable, polymeric microparticles as a scaffold for three dimensional (3-D) growth of a Y79 retinoblastoma (RB) cell line. We evaluated the effect of three anticancer drugs in naïve and nanoparticle-loaded forms on a 3-D versus a two-dimensional (2-D) model. We also studied the influence of microparticles on extracellular matrix (ECM) synthesis and whole genome miRNA-gene expression profiling to identify 3D-responsive genes that are implicated in oncogenesis in RB cells. METHODS: Poly(D,L)-lactide-co-glycolide (PLGA) microparticles were prepared by the solvent evaporation method. RB cell line Y79 was grown alone or with PLGA-gelatin microparticles. Antiproliferative activity, drug diffusion, and cellular uptake were studied by 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide, a yellow tetrazole (MTT) assay, fluorescent microscope, and flow cytometry. Extra cellular matrix (ECM) synthesis was observed by collagenase assay and whole genome miRNA-microarray profiling by using an Agilent chip. RESULTS: With optimized composition of microparticles and cell culture conditions, an eightfold increase from the seeding density was achieved in 5 days of culture. The antiproliferative effect of the drugs in the 3-D model was significantly lower than in the 2-D suspension, which was evident from the 4.5 to 21.8 fold differences in their IC(50) values. Using doxorubicin, the flow cytometry data demonstrated a 4.4 fold lower drug accumulation in the cells grown in the 3-D model at 4 h. The collagen content of the cells grown in the 3-D model was 2.3 fold greater than that of the cells grown in the 2-D model, suggesting greater synthesis of the extracellular matrix in the 3-D model as the extracellular matrix acted as a barrier to drug diffusion. The microarray and miRNA analysis showed changes in several genes and miRNA expression in cells grown in the 3-D model, which could also influence the environment and drug effects. CONCLUSIONS: Our 3-D retinoblastoma model could be used in developing effective drugs based on a better understanding of the role of chemical, biologic, and physical parameters in the process of drug diffusion through the tumor mass, drug retention, and therapeutic outcome.

Enhanced in vitro antiproliferative effects of EpCAM antibody-functionalized paclitaxel-loaded PLGA nanoparticles in retinoblastoma cells.

BACKGROUND: To specifically deliver paclitaxel (PTX) to retinoblastoma (RB) cells, the anionic surface-charged poly(lactic-co-glycolic acid) (PLGA) NPs loaded with paclitaxel were conjugated with epithelial cell adhesion molecule (EpCAM) antibody for enhancing site-specific intracellular delivery of paclitaxel against EpCAM overexpressing RB cells. METHODS: PTX-loaded PLGA NPs were prepared by the oil-in-water single emulsion solvent evaporation method, and the PTX content in NPs was estimated by the reverse phase isocratic mode of high performance liquid chromatography. Ethyl-3-[3-dimethylaminopropyl] carbodiimide hydrochloride/N-hydroxysuccinimide chemistry was employed for the covalent attachment of monoclonal EpCAM antibody onto the NP surface. In vitro cytotoxicity of native PTX, unconjugated PTX-loaded NPs (PTX-NPs), and EpCAM antibody-conjugated PTX-loaded nanoparticles (PTX-NP-EpCAM) were evaluated on a Y79 RB cell line by a dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay, while cellular apoptosis, cysteinyl-aspartic acid protease (caspase)-3 activation, Poly (adenosine diphosphate-ribose) polymerase (PARP) cleavage, and cell-cycle arrest were quantified by flow cytometry. By employing flow cytometry and fluorescence image analyses, the extent of cellular uptake was comparatively evaluated. RESULTS: PTX-NP-EpCAM had superior antiproliferation activity, increased arrested cell population at the G(2)-M phase, and increased activation of caspase-3, followed by PARP cleavage in parallel with the induction of apoptosis. Increased uptake of PTX-Np-EpCAM by the cells suggests that they were mainly taken up through EpCAM mediated endocytosis. CONCLUSIONS: EpCAM antibody-functionalized biodegradable NPs for tumor-selective drug delivery and overcoming drug resistance could be an efficient therapeutic strategy for retinoblastoma treatment.

Genome-wide changes accompanying the knockdown of Ep-CAM in retinoblastoma.

PURPOSE: Previously we showed that epithelial cell adhesion molecule (Ep-CAM), a cell surface molecule, was highly expressed in primary retinoblastoma tumors. In the present study, we studied the genes regulated by Ep-CAM in a retinoblastoma Y79 cell line in vitro using a combination of short interference RNA and microarray technology. METHODS: Flow cytometry, quantitative reverse transcriptase PCR (Q-RT-PCR), and immunohistochemistry were performed to confirm the Ep-CAM re-expression in the Y79 cells treated with 5'-azacytidine (AZC). Ep-CAM expression in AZC-treated Y79 cells was silenced using synthetic anti-Ep-CAM short interference RNA, and whole genome microarray was performed to determine the gene expression changes post Ep-CAM knockdown. Ep-CAM inhibition was confirmed by Q-RT-PCR, western blotting, and immunofluorescence. RESULTS: Ep-CAM expression was significantly restored in Y79 cells on day 5 of AZC treatment. Ep-CAM inhibition significantly affected Y79 cell proliferation. We identified 465 upregulated genes (>or=1.0 fold) and 205 downregulated genes (

KIF14 and E2F3 mRNA expression in human retinoblastoma and its phenotype association.

PURPOSE: We quantified mRNA expression of candidate genes for proliferation (KIF14 and E2F3) in a large retinoblastoma tumor cohort and associated with disease phenotype. METHODS: KIF14 and E2F3 mRNA expression was quantified by real time PCR in 57 retinoblastoma (RB) tumors, 3 RB cell lines, and control samples that included 4 each fetal, age-matched, adult retinas. Immunohistochemistry was done to confirm KIF14 and E2F3 protein expression in tumor cells. The mRNA expression levels were correlated with disease phenotypes including the significance of chemotherapy on tumors. RESULTS: There was statistically significant overexpression of KIF14 and E2F3 mRNA in tumors compared with control retinas (p<0.0001). Further, E2F3 also showed a significant overexpression compared to RB cell lines (p=0.01). Immunohistochemistry confirmed KIF14 and E2F3 protein overexpression in tumor cells. KIF14 had significant mRNA overexpression with older age (p=0.01) in presenting patients and in unilateral RB patients (p=0.04). Chemotherapy-treated tumors showed a significant decrease in KIF14 and E2F3 expression compared to untreated tumors (p<0.01 and 0.001, respectively). CONCLUSIONS: This report confirms significant mRNA overexpression of KIF14 and E2F3 together in a large cohort of RB tumors. The decreased expression in chemotherapy treated cases needs further validation in a large chemotherapy-treated cohort.

Reversal of stathmin-mediated microtubule destabilization sensitizes retinoblastoma cells to a low dose of antimicrotubule agents: a novel synergistic therapeutic intervention.

PURPOSE: To explore the possibility of stathmin as an effective therapeutic target and to evaluate the synergistic combination of stathmin RNAi and the antimicrotubule agents paclitaxel and vincristine to retinoblastoma Y79 cells. METHODS: RNAi-mediated specific inhibition of stathmin expression in Y79 cells was shown by real-time quantitative RT-PCR (RT-Q-PCR), its effect on cell proliferation by MTT assay, cell invasion using matrigel, microtubule polymerization by immunohistochemistry, apoptosis, cell cycle analysis by flow cytometry analysis, and the changes in FOXM1 protein expression were studied by Western blot. The effect of combination treatment of stathmin siRNA and paclitaxel/vincristine was studied by assessing cell viability and apoptosis. RESULTS: Short interfering RNA-mediated transient stathmin downregulation resulted in a marked inhibition of retinoblastoma cell proliferation and cell invasion in vitro. Stathmin inhibition promoted Y79 cells to G2/M phase, and ultimately there were increased apoptotic events as evidenced by higher caspase-3 activation and cleaved poly(ADP-ribose) polymerase expression. Cells transfected with stathmin siRNA showed long and bundled microtubule polymers and sensitized the Y79 cells significantly to paclitaxel and vincristine. CONCLUSIONS: Stathmin may be a pivotal determinant for retinoblastoma tumorigenesis and chemosensitivity. Strategies to inhibit stathmin will help to enhance the cytotoxic effect of paclitaxel while reducing toxicity (or side effects) to normal cells caused by high doses.

Toxicogenomics of nanoparticulate delivery of etoposide: potential impact on nanotechnology in retinoblastoma therapy.

To develop a suitable formulation with high entrapment efficiency, etoposide-loaded poly(lactide-co-glycolide) nanoparticles (NPs) were formulated by single emulsion-solvent evaporation method by changing different formulation parameters such as drug loading, choice of organic solvent and percentage of emulsifier polyvinyl alcohol. The NPs showed higher entrapment efficiency, ~86% (with 15% (w/w) drug loading). The physicochemical parameters revealed smooth topology with size range (240-320 nm), a negative zeta potential (~19 mV) and in vitro sustained-release activity (~60% drug release in 40 days). Greater anti-proliferative activity ~100 times was observed with NPs (IC50 = 0.002 µg/ml) than that of native etoposide (IC50 = 0.2 µg/ml) in retinoblastoma cell line (Y-79). These NPs demonstrated greater (G1/S) blocking and decreased mitochondrial membrane potential as measured by flow cytometry. There was upregulation of apoptotic gene activity in NPs than native etoposide, as revealed through microarray analysis. However, this is the first ever report demonstrating the intricate modulation of genetic network affected by NPs. Collectively, these results suggest that etoposide-loaded NPs could be potentially useful as a novel drug delivery system for retinoblastoma in the future. FigureNanoparticle-mediated etoposide delivery promotes apoptosis through upregulating several apoptotic inducer genes.

Molecular pathology of retinoblastoma.

Retinoblastoma (RB) is an embryonic neoplasm of retinal origin. For many years, scientists have sought the fundamental origins of tumorigenesis, with the ultimate hope of discovering a cure. Indeed, these efforts have led to a significant understanding that multiple molecular and genetic aberrations, such as uncontrolled proliferation and the inhibition of apoptosis that contribute to the canonical characteristics of tumor biology. Despite these advances, a thorough understanding, such as the precise cells, which are the targets of neoplastic transformation, especially in solid tumors, is currently lacking. The focus of this review is to emphasize the molecular defects involved in the RB tumor progression and mechanisms associated with inhibition of tumor cell apoptotic processes. This review also discusses the importance of target molecules characterization and their potential therapeutic or prognostic use in RB disease.

Enhanced antiproliferative activity of carboplatin-loaded chitosan-alginate nanoparticles in a retinoblastoma cell line.

In the present study the potential of carboplatin-loaded chitosan-alginate nanoparticles (CANPs) for the treatment of retinoblastoma was investigated. The carboplatin-loaded CANPs were approximately 300 nm in size, exhibited a high zeta potential of approximately 36 mV and drug encapsulation of approximately 20 wt.%. The CANPs were further characterized by Fourier transform infrared spectroscopy, differential scanning calorimetry and transmission electron microscopy. In vitro release studies revealed fast release of approximately 25% of the drug during the first 24h, followed by sustained release. CANPs demonstrated greater and sustained antiproliferative activity of the drug in a dose- and time-dependent manner (carboplatin IC(50)=0.56 microg ml(-1), carboplatin-loaded CANPs IC(50)=0.004 microg ml(-1)), as well as an enhanced apoptotic effect as compared with the drug in solution in a retinoblastoma cell line (Y79). The higher cytotoxic effect of CANPs may be due to their greater cellular uptake as compared with native carboplatin. It was also demonstrated that clathrin-mediated endocytosis plays a key role in the internalization of CANPs in the Y79 cell line. In conclusion, biodegradable chitosan nanoparticles could be used as an effective ocular drug delivery system for sustained intracellular delivery of carboplatin for the treatment of retinoblastoma.