Effective and safe delivery of anticancer agents is among the major challenges in cancer therapy. The majority of anticancer agents are toxic to normal cells, have poor bioavailability, and lack in vivo stability. Recent advancements in nanotechnology provide safe and efficient drug delivery systems for successful delivery of anticancer agents via nanoparticles. The physicochemical and functional properties of the nanoparticle vary for each of these anticancer agents, including chemotherapeutics, nucleic acid-based therapeutics, small molecule inhibitors, and photodynamic agents. The characteristics of the anticancer agents influence the design and development of nanoparticle carriers. This review focuses on strategies of nanoparticle-based drug delivery for various anticancer agents. Recent advancements in the field are also highlighted, with suitable examples from our own research efforts and from the literature.

Successful chemotherapeutic intervention for management of lung cancer requires an efficient drug delivery system. Gold nanoparticles (GNPs) can incorporate various therapeutics; however, GNPs have limitations as drug carriers. Nano-sized cellular vesicles like exosomes (Exo) can ferry GNP-therapeutic complexes without causing any particle aggregation or immune response. In the present study, we describe the development and testing of a novel Exo-GNP-based therapeutic delivery system -‘nanosomes’- for lung cancer therapy. This system consists of GNPs conjugated to anticancer drug doxorubicin (Dox) by a pH-cleavable bond that is physically loaded onto the exosomes (Exo-GNP-Dox). The therapeutic efficacy of Dox in nanosomes was assessed in H1299 and A549 non-small cell lung cancer cells, normal MRC9 lung fibroblasts, and Dox-sensitive human coronary artery smooth muscle cells (HCASM). The enhanced rate of drug release under acidic conditions, successful uptake of the nanosomes by the recipient cells and the cell viability assays demonstrated that nanosomes exhibit preferential cytotoxicity towards cancer cells and have minimal activity on non-cancerous cells. Finally, the underlying mechanism of cytotoxicity involved ROS-mediated DNA damage. Results from this study mark the establishment of an amenable drug delivery vehicle and highlight the advantages of a natural drug carrier that demonstrates reduced cellular toxicity and efficient delivery of therapeutics to cancer cells.

HuR is an mRNA-binding protein whose overexpression in cancer cells has been associated with poor prognosis and resistance to therapy. While reports on HuR overexpression contributing to chemoresistance exist, limited information is available on HuR and radioresistance especially in triple-negative breast cancer (TNBC).In this study we investigated the role of HuR in radiation resistance in three TNBC (MDA-MB-231, MDA-MB-468 and Hs578t) cell lines. Endogenous HuR expression was higher in TNBC cells compared to normal cells. siRNA mediated knockdown of HuR (siHuR) markedly reduced HuR mRNA and protein levels compared to scrambled siRNA (siScr) treatment. Further, siHuR treatment sensitized TNBC cells to ionizing radiation at 2 Gy compared to siScr treatment as evidenced by the significant reduction in clonogenic cell survival from 59%, 49%, and 65% in siScr-treated cells to 40%, 33%, and 46% in siHuR-treated MDA-MB-231, MDA-MB-468 and Hs578t cells, respectively. Molecular studies showed increased ROS production and inhibition of thioredoxin reductase (TrxR) in HuR knockdown cells contributed to radiosensitization. Associated with increased ROS production was evidence of increased DNA damage, demonstrated by a significant increase (p < 0.05) in γ-H2AX foci that persisted for up to 24 h in siHuR plus radiation treated cells compared to control cells. Further, comet assay revealed that HuR-silenced cells had larger and longer-lasting tails than control cells, indicating higher levels of DNA damage. In conclusion, our studies demonstrate that HuR knockdown in TNBC cells elicits oxidative stress and DNA damage resulting in radiosensitization.

BackgroundHuman antigen R (HuR) is an RNA binding protein that is overexpressed in many human cancers, including lung cancer, and has been shown to regulate the expression of several oncoproteins. Further, HuR overexpression in cancer cells has been associated with poor-prognosis and therapy resistance. Therefore, we hypothesized that targeted inhibition of HuR in cancer cells should suppress several HuR-regulated oncoproteins resulting in an effective anticancer efficacy. To test our hypothesis, in the present study we investigated the efficacy of folate receptor-α (FRA)-targeted DOTAP:Cholesterol lipid nanoparticles carrying HuR siRNA (HuR-FNP) against human lung cancer cells.ResultsThe therapeutic efficacy of HuR-FNP was tested in FRA overexpressing human H1299 lung cancer cell line and compared to normal lung fibroblast (CCD16) cells that had low to no FRA expression. Physico-chemical characterization studies showed HuR-FNP particle size was 303.3 nm in diameter and had a positive surface charge (+4.3 mV). Gel retardation and serum stability assays showed that the FNPs were efficiently protected siRNA from rapid degradation. FNP uptake was significantly higher in H1299 cells compared to CCD16 cells indicating a receptor-dose effect. The results of competitive inhibition studies in H1299 cells demonstrated that HuR-FNPs were efficiently internalized via FRA-mediated endocytosis. Biologic studies demonstrated HuR-FNP but not C-FNP (control siRNA) induced G1 phase cell-cycle arrest and apoptosis in H1299 cells resulting in significant growth inhibition. Further, HuR-FNP exhibited significantly higher cytotoxicity against H1299 cells than it did against CCD16 cells. The reduction in H1299 cell viability was correlated with a marked decrease in HuR mRNA and protein expression. Further, reduced expression of HuR-regulated oncoproteins (cyclin D1, cyclin E, and Bcl-2) and increased p27 tumor suppressor protein were observed in HuR-FNP-treated H1299 cells but not in C-FNP-treated cells. Finally, cell migration was significantly inhibited in HuR-FNP-treated H1299 cells compared to C-FNP.ConclusionsOur results demonstrate that HuR is a molecular target for lung cancer therapy and its suppression using HuR-FNP produced significant therapeutic efficacy in vitro.

Development of resistance toward anticancer drugs results in ineffective therapy leading to increased mortality. Therefore, overriding resistance and restoring sensitivity to anticancer drugs will improve treatment efficacy and reduce mortality. While numerous mechanisms for drug resistance in cancer have previously been demonstrated, recent studies implicate a role for proteasome and the autophagy regulatory protein P62/SQSTM1 (P62) in contributing to drug resistance. Specifically, reduction in the expression of the β5 subunit of the proteasome and/or enhanced P62 protein expression is known to contribute to cancer drug resistance such as cisplatin (CDDP) in ovarian cancer cells. Therefore, we hypothesized that restoration of β5 expression and/or suppression of P62 protein expression in CDDP-resistant ovarian cancer cells will lead to restoration of sensitivity to CDDP and enhanced cell killing. To test our hypothesis we developed a biodegradable multifunctional nanoparticle (MNP) system that codelivered P62siRNA, β5 plasmid DNA, and CDDP and tested its efficacy in CDDP resistant 2008/C13 ovarian cancer cells. MNP consisted of CDDP loaded polylactic acid nanoparticle as inner core and cationic chitosan (CS) consisting of ionically linked P62siRNA (siP62) and/or β5 expressing plasmid DNA (pβ5) as the outer layer. The MNPs were spherical in shape with a hydrodynamic diameter in the range of 280-350 nm, and demonstrated encapsulation efficiencies of 82% and 78.5% for CDDP and siRNA respectively. MNPs efficiently protected the siRNA and showed superior serum stability compared to naked siRNA as measured by gel retardation and spectrophotometry assays. The MNPs successfully delivered siP62 and pβ5 to cause P62 knockdown and restoration of β5 expression in 2008/C13 cells. Combined delivery of siP62, pβ5, and CDDP using the MNPs resulted in a marked reduction in the IC50 value of CDDP in 2008/C13 cells from 125 ± 1.3 μM to 98 ± 0.6 μM (P < 0.05; 21.6% reduction) when compared to the reduction in the IC50 of CDDP observed in cells that had only siP62 delivered (IC50 = 106 ± 1.1 μM; P < 0.05; 15.2% reduction) or pβ5 delivered (IC50 = 115 ± 2.8 μM; 8% reduction) via MNPs. Finally, our studies showed that the CDDP resistance index in 2008/C13 cells was reduced from 4.62 for free CDDP to 3.62 for MNP treatment. In conclusion our study results demonstrated the efficacy of our MNP in overcoming CDDP resistance in ovarian cancer cells.