Development of MicroRNAs as Potential Therapeutics against Cancer.

MicroRNAs (miRNAs) are small noncoding RNAs that function at the posttranscriptional level in the cellular regulation process. miRNA expression exerts vital effects on cell growth such as cell proliferation and survival. In cancers, miRNAs have been shown to initiate carcinogenesis, where overexpression of oncogenic miRNAs (oncomiRs) or reduced expression of tumor suppressor miRNAs has been reported. In this review, we discuss the involvement of miRNAs in tumorigenesis, the role of synthetic miRNAs as either mimics or antagomirs to overcome cancer growth, miRNA delivery, and approaches to enhance their therapeutic potentials.

Targeting Cell Adhesion Molecules via Carbonate Apatite-Mediated Delivery of Specific siRNAs to Breast Cancer Cells In Vitro and In Vivo.

While several treatment strategies are applied to cure breast cancer, it still remains one of the leading causes of female deaths worldwide. Since chemotherapeutic drugs have severe side effects and are responsible for development of drug resistance in cancer cells, gene therapy is now considered as one of the promising options to address the current treatment limitations. Identification of the over-expressed genes accounting for constitutive activation of certain pathways, and their subsequent knockdown with specific small interfering RNAs (siRNAs), could be a powerful tool in inhibiting proliferation and survival of cancer cells. In this study, we delivered siRNAs against mRNA transcripts of over-regulated cell adhesion molecules such as catenin alpha 1 (CTNNA1), catenin beta 1 (CTNNB1), talin-1 (TLN1), vinculin (VCL), paxillin (PXN), and actinin-1 (ACTN1) in human (MCF-7 and MDA-MB-231) and murine (4T1) cell lines as well as in the murine female Balb/c mice model. In order to overcome the barriers of cell permeability and nuclease-mediated degradation, the pH-sensitive carbonate apatite (CA) nanocarrier was used as a delivery vehicle. While targeting CTNNA1, CTNNB1, TLN1, VCL, PXN, and ACTN1 resulted in a reduction of cell viability in MCF-7 and MDA-MB-231 cells, delivery of all these siRNAs via carbonate apatite (CA) nanoparticles successfully reduced the cell viability in 4T1 cells. In 4T1 cells, delivery of CTNNA1, CTNNB1, TLN1, VCL, PXN, and ACTN1 siRNAs with CA caused significant reduction in phosphorylated and total AKT levels. Furthermore, reduced band intensity was observed for phosphorylated and total MAPK upon transfection of 4T1 cells with CTNNA1, CTNNB1, and VCL siRNAs. Intravenous delivery of CTNNA1 siRNA with CA nanoparticles significantly reduced tumor volume in the initial phase of the study, while siRNAs targeting CTNNB1, TLN1, VCL, PXN, and ACTN1 genes significantly decreased the tumor burden at all time points. The tumor weights at the end of the treatments were also notably smaller compared to CA. This successfully demonstrates that targeting these dysregulated genes via RNAi and by using a suitable delivery vehicle such as CA could serve as a promising therapeutic treatment modality for breast cancers.

Oncogenic Signaling in Tumorigenesis and Applications of siRNA Nanotherapeutics in Breast Cancer.

Overexpression of oncogenes and cross-talks of the oncoproteins-regulated signaling cascades with other intracellular pathways in breast cancer could lead to massive abnormal signaling with the consequence of tumorigenesis. The ability to identify the genes having vital roles in cancer development would give a promising therapeutics strategy in combating the disease. Genetic manipulations through siRNAs targeting the complementary sequence of the oncogenic mRNA in breast cancer is one of the promising approaches that can be harnessed to develop more efficient treatments for breast cancer. In this review, we highlighted the effects of major signaling pathways stimulated by oncogene products on breast tumorigenesis and discussed the potential therapeutic strategies for targeted delivery of siRNAs with nanoparticles in suppressing the stimulated signaling pathways.

Transfection with p21 and p53 tumor suppressor plasmids suppressed breast tumor growth in syngeneic mouse model.

Treatment of breast cancer by delivering important tumor suppressor plasmids is a promising approach in the field of clinical medicine. We transfected p21 and p53 tumor suppressor plasmids, into different breast cancer cell lines using inorganic nanoparticles (NPs) of carbonate apatite to evaluate the effect of gene expression on reducing breast cancer cell growth. In triple negative MDA-MB-231 breast cancer cell line, the cytotoxicity assay upon combined delivery of p21 and p53 plasmid loaded NPs showed significant decrease in cell growth compared to distinct p21 or p53 treatments. Also, in MCF-7 and 4T1 cell lines, significant reduction in cellular growth was observed following p21 or p53 plasmid transfection. The Western blot data showed that NP loaded p21 and p53 transgene delivery in MDA-MB-231 cell line resulted in a noteworthy decrease in phosphorylated form of MAPK protein of MAPK/ERK pathway. The in vivo studies in syngeneic breast cancer mouse model demonstrated that the rate of growth and final tumor volume were reduced to a greater extent in mice that received intravenous injection of p21 + NP and p53 + NP therapeutics.

siRNAs Targeting Growth Factor Receptor and Anti-Apoptotic Genes Synergistically Kill Breast Cancer Cells through Inhibition of MAPK and PI-3 Kinase Pathways.

Breast cancer, the second leading cause of female deaths worldwide, is usually treated with cytotoxic drugs, accompanied by adverse side-effects, development of chemoresistance and relapse of disease condition. Survival and proliferation of the cancer cells are greatly empowered by over-expression or over-activation of growth factor receptors and anti-apoptotic factors. Identification of these key players that cross-talk to each other, and subsequently, knockdown with their respective siRNAs in a synchronous manner could be a promising approach to precisely treat the cancer. Since siRNAs demonstrate limited cell permeability and unfavorable pharmacokinetic behaviors, pH-sensitive nanoparticles of carbonate apatite were employed to efficiently carry the siRNAs in vitro and in vivo. By delivering selective siRNAs against the mRNA transcripts of the growth factor receptors, such as ER, ERBB2 (HER2), EGFR and IGFR, and anti-apoptotic protein, such as BCL2 in human (MCF-7 and MDA-MB-231) and murine (4T1) breast cancer cell lines, we found that ESR1 along with BCL-2, or with ERBB2 and EGFR critically contributes to the growth/survival of the cancer cells by activating the MAPK and PI-3 kinase pathways. Furthermore, intravenous delivery of the selected siRNAs aiming to suppress the expression of ER/BCL2 and ER/ERBB2/EGFR groups of proteins led to a significant retardation in tumor growth in a 4T1-induced syngeneic mouse model.

Carbonate apatite nanoparticles carry siRNA(s) targeting growth factor receptor genes egfr1 and erbb2 to regress mouse breast tumor.

Cancer cells lose their control on cell cycle by numerous genetic and epigenetic alterations. In a tumor, these cells highly express growth factor receptors (GFRs), eliciting growth, and cell division. Among the GFRs, epidermal growth factor receptor-1 (EGFR1) (Her1/ERBB1) and epidermal growth factor receptor-2 (EGFR2) (Her2/ERBB2) from epidermal growth factor (EGF) family and insulin-like growth factor-1 receptor (IGF1R) are highly expressed on breast cancer cells, thus contributing to the aggressive growth and invasiveness, have been focused in this study. Moreover, overexpression of these receptors is related to suppression of cell death and conferring resistance against the classical drugs used to treat cancer nowadays. Therefore, silencing of these GFRs-encoding genes by using selective small interfering RNAs (siRNAs) could be a powerful approach to treat breast cancer. The inorganic pH sensitive carbonate apatite nanoparticles (NPs) were used as a nano-carrier to deliver siRNA(s) against single or multiple GFR genes in breast cancer cells as well as in a mouse model of breast carcinoma. Silencing of egfr1 and erbb2 simultaneously led to a reduction in cell viability with an increase in cell death signal in the cancer cells and regression of tumor growth in vivo.