Nanoformulation of siRNA silencing Bcl-2 gene and its implication in cancer therapy

Immunotherapy of Dual-Function Vector with Both Immunostimulatory and B-Cell Lymphoma 2 (Bcl-2)-Silencing Effects on Gastric Carcinoma

BACKGROUND Tumorigenesis is a kind of pathology marked by infinite proliferation and restrained apoptosis compared with normal cells. The abnormal expression of some proto-oncogenes and apoptosis inhibition are essential for tumor growth, which has been confirmed by molecular biologic and immunologic studies. The hypofunction of the host immune system also drives the development and metastasis of malignant tumors. Bcl-2, which has a critical role in regulating apoptosis, is overexpressed in several cancers. MATERIAL AND METHODS In this study, we constructed a dual-function small hairpin RNA (shRNA) vector containing an Bcl-2-silencing shRNA and a TLR7-stimulating ssRNA and examined it effect on tumor cell growth and proliferation. RESULTS Stimulation with this bi-functional vector in vitro promoted significant apoptosis of MFC cells by regulating the expression of apoptosis-related proteins and induced secretion of type I IFNs. Most importantly, this bi-functional vector more effectively inhibited subcutaneous MFC cell growth than did single shRNA and ssRNA treatment in vivo. Natural killer (NK) and CD4+ T cells were required for effective tumor suppression, and TLR7 was shown to play a helper role in the activation of NK cells and CD4+ T cells, possibly by regulating the expression of receptors or secretion of cytokines. CONCLUSIONS This bi-functional vector that contained ssRNA and shRNA may represent a promising approach for tumor therapy.

siRNA-Encapsulated Hybrid Nanoparticles Target Mutant K-ras and Inhibit Metastatic Tumor Burden in a Mouse Model of Lung Cancer

There is an unmet need in the development of an effective therapy for mutant K-ras-expressing non-small-cell lung cancer (NSCLC). Although various small molecules have been evaluated, an effective therapy remains a dream. siRNAs have the potential to downregulate mutant K-ras both at the protein and mRNA levels. However, a safe and effective delivery of siRNAs to tumors remains a limitation to their translational application in the treatment of this highly debilitating disease. Here we developed a novel hybrid nanoparticle carrier for effective delivery of anti-mutant K-ras to NSCLC (AKSLHN). The ability of this treatment modality to regress lung tumors in mouse models was evaluated as a monotherapy or as a combination treatment with erlotinib. Further, the toxicity of this treatment modality to healthy tissues was evaluated, along with its ability to elicit immune/inflammatory reactions. The results suggest that this treatment modality is a promising prospect for the treatment of mutant K-ras-expressing NSCLC without any accompanying toxicity. However, further understanding of the cellular-level interaction between AHSLHN and erlotinib needs to be attained before this promising treatment modality can be brought to the bedside.

A nanoformulation of siRNA and its role in cancer therapy: in vitro and in vivo evaluation

Overexpression of anti-apoptotic Bcl-2 is often observed in a wide variety of human cancers. It prevents the induction of apoptosis in neoplastic cells and contributes to resistance to chemotherapy. RNA interference has emerged as an efficient and selective technique for gene silencing. The potential to use small interfering RNA (siRNA) as a therapeutic agent for the treatment of cancer has elicited a great deal of interest. However, insufficient cellular uptake and poor stability have limited its therapeutic applications. The purpose of this study was to prepare chitosan nanoparticles via ionic gelation of chitosan by tripolyphosphate for effective delivery of siRNA to silence the anti-apoptotic Bcl-2 gene in neoplastic cells. Chitosan nanoparticles loaded with siRNA were in the size range 190 to 340 nm with a polydispersive index ranging from 0.04 to 0.2. They were able to completely bind with siRNA, provide protection against nuclease degradation, and enhance the transfection. Cell culture studies revealed that nanoparticles with entrapped siRNA could efficiently silence the antiapoptotic Bcl-2 gene. Studies on Swiss albino mice showed that siRNA could be effectively delivered through nanoparticles. There was significant decrease in the tumor volume. Blocking the expression of anti-apoptotic Bcl-2 can enhance the sensitivity of cancerous cells to anti-cancer drugs and the apoptosis rate. Therefore, nanoformulations with siRNA can be promoted as an adjuvant therapy in combination with anti-cancer drugs.

An MRI-visible non-viral vector for targeted Bcl-2 siRNA delivery to neuroblastoma

Polyethylene glycol-grafted polyethylenimine (PEG-g-PEI) which was functionalized with a neuroblastoma cell-specific ligand, the GD2 single chain antibody (scAb_GD2), was synthesized in order to effectively deliver Bcl-2 siRNA into neuroblastoma cells. This polymer was complexed first with superparamagnetic iron oxide nanoparticle (SPION) to get a MRI-visible targeted non-viral vector (scAb_GD2-PEG-g-PEI-SPION) and then with Bcl-2 siRNA to form nanoparticles showing low cytotoxicity. The targeting capacity of scAb_GD2-PEG-g-PEI-SPION was successfully verified in vivo and in vitro by magnetic resonance imaging. The single chain antibody encoded targeted polyplex was more effective in transferring Bcl-2 siRNA than the nontargeting one in SK-N-SH cells, a human neuroblastoma cell line, resulting in a 46.34% inhibition in the expression of Bcl-2 mRNA. Consequently, a high level of cell apoptosis up to 50.76% and a significant suppression of tumor growth were achieved, which indicates that scAb_GD2-PEG-g-PEI-SPION is a promising magnetic resonance imaging-visible non-viral vector for targeted neuroblastoma siRNA therapy and diagnosis.