Cancer is the second leading cause of death in the USA, following cardiovascular disease. Treating cancer using conventional therapies is associated with low response rates and high toxicity, because these therapies usually lack specific tumor accumulation. Loading anticancer drugs into intelligently designed polymeric nanoparticles (NPs) can serve in delivering these drugs specifically to the tumor site, thus boosting their efficacy and reducing any associated off target toxicity. Targeting NPs to the tumor site can occur through either passive or active means. In passive targeting, NPs of specific size and surface characteristics can exploit the tumor’s erratic vasculature and occluded lymphatic drainage to extravasate the systemic circulation and accumulate preferentially at the tumor site. Active targeting mandates grafting the surface of NPs with a ligand that specifically interacts with a protein expressed at higher levels at the tumor site, in comparison to elsewhere in the body. In the current research, we independently investigated the utilization of passive and active targeting strategies to treat aggressive forms of cancer.
Initially, passively targeted poly(lactic-co-glycolic acid) (PLGA) NPs to treat aggressive forms of endometrial cancer (EC) were investigated. A novel combination of soluble paclitaxel (PTX), a first line chemotherapy for EC, and soluble BIBF1120 (BIBF, nintedanib), an antiangiogenic molecular inhibitor, was first tested against three EC cell lines bearing different p53 mutations. The results showed that only EC cells with loss of function (LOF) p53 were sensitive to the combination therapy, indicating the potential of this combination to engender synthetic lethality to PTX. Next, NPs loaded with PTX were investigated with respect to the impact of varying the polymer lactic acid to glycolic acid ratio and the surfactant type on the major physicochemical properties of the prepared nanoparticles, drug loading, cellular uptake, cytotoxicity, and drug release. The optimum formulation was then loaded with BIBF and the combination of independently loaded passively targeted NPs were further evaluated for in vivo activity against a xenograft model of LOF p53 EC. The combination of independently loaded NPs exhibited the highest reduction in tumor volume and prolonged survival when compared to soluble PTX, PTX NPs or untreated control. These data highlight this specific combination of NPs as a novel promising therapy for LOF p53 EC.
In a second study, the use of actively targeted NPs to treat liver cancer was explored. In this study, a combination of small interfering RNA (siRNA) against astrocyte elevated gene-1 (AEG-1), and all-trans retinoic acid (ATRA) was investigated as a new therapy for hepatocellular carcinoma (HCC). AEG-1 is a highly expressed oncogene that is directly involved in HCC progression and aggressiveness, in addition to reducing the ability of retinoic acid to induce apoptosis in HCC cells. First, a new conjugate was synthesized that was capable of delivering siRNA selectively to HCC cells, using galactose as a targeting moiety. The conjugate was prepared by linking poly(amidoamine) (PAMAM) dendrimers, polyethylene glycol (PEG) and lactobionic acid (Gal, disaccharide containing galactose) (PAMAM-PEG-Gal). We confirmed the synthesis of the conjugate using 1H-NMR, Mass spectrometry and Matrix-Assisted Laser Desorption/Ionization (MALDI) Mass Spectrometry. Next, nanoplexes of the synthesized conjugate, PAMAM-PEG-Gal, and AEG-1 siRNA were prepared. Nanoplexes were further characterized for their size, surface charge, morphology, and electrophoretic mobility to identify the optimum complexation ratio between PAMAM-PEG-Gal and the siRNA. Then, mice bearing orthotopic luciferase expressing HCC cells were treated with the optimum nanoplex formulation. Results showed that a combination of AEG-1 nanoplexes and ATRA results in a significant reduction in luciferase expression, reduced liver weight, lower AEG-1 mRNA levels and increased apoptosis, when compared to utilizing nanoplexes with silencing control (siCon), siCon+ATRA, or AEG-1 nanoplexes alone. The results indicate that the combination of liver-targeted AEG-1 nanoplexes and ATRA may be a potential treatment for aggressive HCC.
These data place targeted NPs as a promising efficient delivery system for cancer treatment.