RGD liposome-protamine-siRNA (LPR) nanoparticles targeting PAX3-FOXO1 for alveolar rhabdomyosarcoma therapy.

Alveolar rhabdomyosarcoma (ARMS) are aggressive soft tissue tumors harboring specific fusion transcripts, notably PAX3-FOXO1 (P3F). Current therapy concepts result in unsatisfactory survival rates making the search for innovative approaches necessary: targeting PAX3-FOXO1 could be a promising strategy. In this study, we developed integrin receptor-targeted Lipid-Protamine-siRNA (LPR) nanoparticles using the RGD peptide and validated target specificity as well as their post-silencing effects. We demonstrate that RGD-LPRs are specific to ARMS in vitro and in vivo. Loaded with siRNA directed against the breakpoint of P3F, these particles efficiently down regulated the fusion transcript and inhibited cell proliferation, but did not induce substantial apoptosis. In a xenograft ARMS model, LPR nanoparticles targeting P3F showed statistically significant tumor growth delay as well as inhibition of tumor initiation when injected in parallel with the tumor cells. These findings suggest that RGD-LPR targeting P3F are promising to be highly effective in the setting of minimal residual disease for ARMS.

New approaches for pediatric rhabdomyosarcoma drug discovery: targeting combinatorial signaling.

INTRODUCTION: Rhabdomyosarcomas (RMS) are rare heterogeneous pediatric tumors that are treated by surgery, chemotherapy and irradiation. New therapeutic approaches are needed, especially in the advanced stages to target the pro-oncogenic signals. Exploring the molecular interactions of the regulatory signals and their roles in the developmental aspects of different subtypes of RMS is essential to identify potential targets and develop new therapeutic drugs. AREAS COVERED: Insights into different drug discovery approaches are discussed with specific emphasis on gene expression profiling, fusion protein, role of small interfering RNA (siRNA)- and microRNA (miRNA)-based discovery approaches, targeting cancer stem cells, and in vitro and in vivo model systems. Targeting some overexpressed signals along with the possibilities of combination therapy of validated drug targets is discussed. Additionally, methods to overcome the limitations of discovery-based research are briefly discussed. EXPERT OPINION: Due to drug resistance, ineffective therapy in advanced stages and relapse, there is a demand to explore new drug targets and discovery approaches. Implementing miRNA-based profiling would reveal the extent of miR-based regulation, various biomarkers and potential targets in RMS. A suitable combination of innovative techniques and the use of model systems might assist the identification and validation of novel targets and drug discovery methods. Combining specific drugs along with type-specific target inhibition of overexpressed mRNAs through siRNA approaches would enable the development of personalized therapy.

Small interfering ribonucleic acid design strategies for effective targeting and gene silencing.

INTRODUCTION: Gene silencing mediated by siRNAs is becoming a promising therapeutic approach. Although many strategies and technologies have been applied to siRNA design, a key issue lies in the selection of efficient design predictors. Furthermore, the development of systemic siRNA delivery strategies, which would enhance the therapeutic effect, remains a central issue. AREAS COVERED: The review discusses the basic principles of the sequence-specific design criteria of functional siRNAs and possible chemical modifications. Some of the most recent advances in the development of siRNA design algorithms and delivery strategies are also presented. Emphasis is given to the important design rule sets and predictors which determine the functionality of an efficient siRNA. EXPERT OPINION: The potential and limitations of efficient design predictors obtained from computational algorithms play a crucial role in the development of target-specific siRNAs. Furthermore, the future success of RNA interference therapeutics will depend on their ability to efficiently cross the physiological barriers, selectively target cells-of-interest and finally silence the gene-of-interest without any side effects.

Nonviral siRNA delivery for gene silencing in neurodegenerative diseases.

Linking genes with the underlying mechanisms of diseases is one of the biggest challenges of genomics-driven drug discovery research. Designing an inhibitor for any neurodegenerative disease that effectively halts the pathogenicity of the disease is yet to be achieved. The challenge lies in crossing the blood-brain barrier (BBB)/blood-cerebrospinal fluid barrier (BCSFB) to reach the catalytic pockets of the enzyme/protein involved in the molecular mechanism of the disease process. Designing siRNA with exquisite specificity may result in selective suppression of the disease-linked gene. Although siRNA is the most promising method, it loses its potency in downregulating the gene due to its inherent instability, off-target effects, and lack of on-target effective delivery systems. Viral as well as nonviral delivery methods have been effectively tested in vivo for silencing of molecular targets and have resulted in significant efficacy in animal models of Alzheimer's disease, amyotrophic lateral sclerosis (ALS), anxiety, depression, encephalitis, glioblastoma, Huntington's disease, neuropathic pain, and spinocerebellar ataxia. To realize the full therapeutic potential of siRNA for neurodegenerative diseases, we need to overcome many hurdles and challenges such as selecting suitable tissue-specific delivery vectors, minimizing the off-target effects, and achieving distribution in sufficient concentrations at the target tissue without any side effects. Cationic nanoparticle-mediated targeted siRNA delivery for therapeutic purposes has gained considerable clinical importance as a result of its promising efficacy.