Therapeutic Effects of AICAR and DOX Conjugated Multifunctional Nanoparticles in Sensitization and Elimination of Cancer Cells via Survivin Targeting

Targeting survivin for cancer therapy: Strategies, small molecule inhibitors and vaccine based therapeutics in development

Survivin is a member of the family of inhibitors of apoptosis proteins (IAPs). It is involved in the normal mitotic process and acts as an anti-apoptotic molecule. While terminally differentiated normal tissues lack survivin, several human malignancies have significant protein levels. Resistance to chemotherapy and radiation in tumor cells is associated with survivin expression. Decreased tumor development, apoptosis, and increased sensitivity to chemotherapy and radiation are all effects of downregulating survivin expression or activity. As a prospective cancer treatment, small molecules targeting the transcription and translation of survivin and molecules that can directly bind with the survivin are being explored both in pre-clinical and clinics. Pre-clinical investigations have found and demonstrated the effectiveness of several small-molecule survivin inhibitors. Unfortunately, these inhibitors have also been shown to have off-target effects, which could limit their clinical utility. In addition to small molecules, several survivin peptide vaccines are currently under development. These vaccines are designed to elicit a cytotoxic T-cell response against survivin, which could lead to the destruction of tumor cells expressing survivin. Some survivin-based vaccines are advancing through Phase II clinical studies. Overall, survivin is a promising cancer drug target. However, challenges still need to be addressed before the survivin targeted therapies can be widely used in the clinics.

Advances in nanotechnology-based platforms for survivin-targeted drug discovery

INTRODUCTION

Due to its unique functional impact on multiple cancer cell circuits including proliferation, apoptosis, tumor dissemination, DNA damage repair and immune response, the inhibitor of apoptosis protein (IAP) survivin has gained high interest as a molecular target and a multitude of therapeutics were developed to interfere with survivin expression and functionality. First clinical evaluations of these therapeutics, however, were disappointing highlighting the need to develop advanced delivery systems of survivin-targeting molecules to increase stability, bioavailability as well as the selective guidance to tumor tissue.

AREAS COVERED

: This review focuses on advancements in nanocarriers to molecularly target survivin in human malignancies. A plethora of nanoparticle platforms, including liposomes, polymeric systems, dendrimers, inorganic nanocarriers, RNA/DNA nanotechnology and exosomes are discussed in the background of survivin-tailored RNA interference, small molecule inhibitors, dominant negative mutants or survivin vaccination or combined modality treatment with chemotherapeutic drugs and photo- dynamic/photothermal strategies.

EXPERT OPINION

Novel therapeutic approaches include the use of biocompatible nanoformulations carrying gene silencing or drug molecules to directly or indirectly target proteins, allow for a more precise and controlled delivery of survivin therapeutics. Moreover, surface modification of these nanocarriers may result in a tumor entity specific delivery. Therefore, nanomedicine exploiting survivin-tailored strategies in a multimodal background is considered the way forwaerd to enhance the development of future personalized medicine.

Cascade therapy with doxorubicin and survivin-targeted tailored nanoparticles: An effective alternative for sensitization of cancer cells to chemotherapy

Chemotherapy frequently involves combination treatment protocols to maximize tumor cell killing. Unfortunately these intensive chemotherapeutic regimes, often show disappointing results due to the development of drug resistance and higher nonspecific toxicity on normal tissues. In cancer treatment, it is critically important to minimize toxicity while preserving efficacy. We have previously addressed this issue and proposed a nanoparticle-based combination therapy involving both a molecularly targeted therapy and chemotherapeutic agent for neutralizing antiapoptotic survivin (BIRC5) to potentiate the efficacy of doxorubicin (DOX). Although the particles exhibited strong anticancer effect on the lung carcinoma A549 and the cervical carcinoma HeLa cells, there were lower-level therapeutic outcomes on the colon carcinoma HCT-116, the leukemia Jurkat and the pancreatic carcinoma MIA PaCa-2 cells. Since targeted therapies are one of the key approaches for overcoming drug resistance, tailoring the treatment of cancer cells with distinct characteristics is necessary to improve the therapeutic outcome of cancer therapy and to minimize potential pharmacokinetic interactions of drugs. In the light of this issue, this study examined whether a cascade therapy with low-dose DOX and survivin-targeted tailored nanoparticles is more effective at sensitizing HCT-116, Jurkat and MIA PaCa-2 cancer cells to DOX-chemotherapy than simultaneous combination therapy. The results demonstrated that the sequential therapy with the protocol comprising addition of the nanoparticles after incubation of cells with DOX clearly advanced the therapeutic outcome of related cancer cells, whereas the reverse protocol resulted in a reduction or delay in apoptosis, emphasizing the critical importance of formulating synergistic drug combinations in cancer therapy.

Environmentally Responsive Dual-Targeting Nanoparticles: Improving Drug Accumulation in Cancer Cells as a Way of Preventing Anticancer Drug Efflux

Drug targeting and stimuli-responsive drug release are 2 active areas of cancer research and hold tremendous potential in the management of cancer drug resistance. In this study, I addressed this issue and focused on the synthesis and characterization of pH-responsive Fe₃O₄@SiO₂(FITC)-BTN/folic acid/DOX multifunctional nanoparticles aiming to increase drug accumulation in malignancies with both dual active targeting and endosomal drug release properties. Dye-doped silica magnetic-fluorescent composite was constructed by a simple coprecipitation of Fe⁺²/Fe⁺³ salts followed by sol-gel formation and dual-targeting function was obtained by conjugating folate and biotin moieties on the silica surface of nanoparticles via an esterification reaction. Doxorubicin was then successfully attached on the amine-functionalized nanoparticles using a pH-sensitive Schiff-base formation. The physicochemical characterization of the structure was performed by dynamic light scattering, zeta potential measurement, X-ray diffraction, Fourier transform infrared spectroscopy, electron microscopy techniques, and an in vitro pH-dependent release study. Cellular uptake and cytotoxicity experiments demonstrated an enhanced intracellular delivery and reduction of cancer cell viability in the cervical carcinoma HeLa cell line. Furthermore, proapoptotic studies showed that the nanoparticles increased the apoptotic rates within the same cancer cells. The preliminary cell tests confirm the potential of these multifunctional nanoparticles against the development of drug resistance in cancer cells.

Nanoformulations for combination or cascade anticancer therapy

Nanoparticle drug formulations have been extensively investigated, developed, and in some cases, approved by the Food and Drug Administration (FDA). Synergistic combinations of drugs having distinct tumor-inhibiting mechanisms and non-overlapping toxicity can circumvent the issue of treatment resistance and may be essential for effective anti-cancer therapy. At the same time, co-delivery of a combined regimen by a single nanocarrier presents a challenge due to differences in solubility, molecular weight, functional groups and encapsulation conditions between the two drugs. This review discusses cellular and microenvironment mechanisms behind treatment resistance and nanotechnology-based solutions for effective anti-cancer therapy. Co-loading or cascade delivery of multiple drugs using of polymeric nanoparticles, polymer-drug conjugates and lipid nanoparticles will be discussed along with lipid-coated drug nanoparticles developed by our lab and perspectives on combination therapy.

Enhancing Tumor Cell Response to Multidrug Resistance with pH-Sensitive Quercetin and Doxorubicin Conjugated Multifunctional Nanoparticles

Classical chemotherapy uses chemotherapeutic agents as a mainstay of anticancer treatment. However, the development of multidrug resistance to chemotherapy limits the effectiveness of current cancer treatment. Nanosized bioconjugates combining a chemotherapeutic agent with a pharmacological approach may improve the curative effect of chemotherapeutic agents. Herein I addressed this issue by describing the synthesis, and testing of, pH-responsive Fe3O4@SiO2(FITC)-BTN/QUR/DOX multifunctional nanoparticles. The particles were designed to modulate resistance-mediating factors and to potentiate the efficacy of DOX against chemoresistance. The physicochemical properties of the nanoparticles were characterized based on the combination of several techniques: dynamic light scattering (DLS), zeta-potential measurement, Fourier transform infrared spectroscopy (FTIR), electron microscopy techniques (SEM and STEM with EDX) and an in vitro pH-dependent release study. Cellular uptake and cytotoxicity experiments demonstrated enhanced intracellular delivery and retention of nanoparticles in the cytoplasm and efficient reduction of cancer cell viability in drug-resistant lung carcinoma A549/DOX cell lines. This did not affect internalization and viability of an immortalized human lung epithelial cell line BEAS-2B. Moreover, proapoptotic and antiproliferative studies showed that Fe3O4@SiO2(FITC)-BTN/QUR/DOX nanoparticles can promote apoptosis, inhibit tumor cell proliferation, and enhance the chemotherapeutic effects of DOX against multidrug resistance. These results confirm that this multifunctional platform possesses significant synergy between QUR and DOX and is promising for development as an antitumor treatment in cancer therapy.