Pheophorbide co-encapsulated with Cisplatin in folate-decorated PLGA nanoparticles to treat nasopharyngeal carcinoma: Combination of chemotherapy and photodynamic therapy

Highlights

• Cisplatin and Pheophorbide was successfully loaded in a single nanocarrier.

• Achieved significant tumor regression in a Cisplatin-resistant tumor model at very low drug doses.

• Folate targeting and combinational treatment modalities enhanced antitumor activity in nasopharyngeal carcinoma.

Abstract

The adverse effect and drug resistance of Cisplatin (CDDP) could be potential reduced by delivering in targeted nanoparticles and by combining with adjuvant therapy such as photodynamic therapy. In this study, F/CDPR-NP was formulated and characterized for all the physicochemical, biological and in vivo analysis. The results obtained from various in vitro and biological studies showed that encapsulation of CDDP and PBR in PLGA nanoparticles results in controlled release of encapsulated drugs and exhibited significantly low cell viability in CNE-1 and HNE-1 cancer cells. F/CDPR-NP significantly prolonged the blood circulation of the encapsulated drugs. The AUC of CDDP from F/CDPR-NP (4-fold) was significantly higher compared to that of free CDDP and similarly significantly higher t1/2 for CDDP from F/CDPR-NP was observed. F/CDPR-NP in the presence of laser irradiation showed significant reduction in the tumor burden with low tumor cell proliferations compared to either CDPR-NP or free CDDP indicating the potential of targeted nanoparticles and photodynamic therapy. Overall, combination of treatment modalities and active targeting approach paved way for the higher antitumor activity in nasopharyngeal carcinoma model. The positive results from this study will show new horizon for the treatment of other cancer models.

Introduction

Nasopharyngeal carcinoma (NPC) is a malignancy of nasopharyngeal epithelium in the head and neck and is highly prevalent in Southeast Asia and China [1]. More than 70 % of NPC patients are diagnosed at late or advanced stages leading to poor 5-year survival rate. Concurrent or adjuvant cisplatin (CDDP)-based chemo-radiotherapy has been regarded as a standard therapy in the treatment of locoregionally advanced NPC [[2], [3], [4]]. However, two important factors including drug toxicity and drug resistance becomes a major hurdle towards the effective treatment. Significant proportions of patients showed less sensitivity towards CDDP and suffered from relapses [5]. There might be many contributing factors for the failure of CDDP including the imbalance between DNA damage and DNA repair, inability of sufficient intracellular accumulation in the tumor cells [6]. To overcome the drug resistance, researchers have targeted the gene or protein expression such as BST2 or COX-2 or STAT3 and so on; however, drug resistance is controlled by multiple factors not by single factors to target [7].

Photodynamic therapy (PDT) is a unique strategy wherein irradiation of photosensitizer (PS) at appropriate wavelength generates the singlet oxygen and free radicals in the cancer cells [8,9]. PDT is applied in the treatment of multiple cancers including breast cancer, gastric cancer, prostate cancer, and pancreatic cancer and head/neck cancers [10,11]. The important salient feature of PDT is the fact that it works by different mechanism and thereby overcomes the multidrug resistance of chemotherapy making it an alternative or adjuvant treatment modality [12]. In this work, we have used a pheophorbide (PBR) as an appropriate photosensitizer.

To achieve the successful PDT, it is important to target the PS to the tumor microenvironment. The guided delivery of PS to the cancer cells enhances the efficiency of PDT and limits the associated adverse reactions in the normal tissues [13]. Besides, efficiency of CDDP could be improved and multidrug resistance (MDR) could be curtailed by delivering it to the cancer microenvironment [14]. In this regard, various nanoparticles (NP) have been designed and developed as a novel drug delivery system and shown promising effects against the cancer treatment [[15], [16], [17], [18]]. The nanoparticles could stably encapsulate the hydrophobic and hydrophilic drugs, increase its solubility, improve its pharmacokinetic performance in the systemic circulation and could potential improve the accumulation of therapeutic agents in the specific tumor microenvironment [19,20]. Despite the development of numerous nanoparticles, only few are used in the clinics till date owing to toxicity concerns and lack of FDA approval [21]. Herein, we have designed a FDA-approved material, PLGA NPs for the targeted application of CDDP and PS [22]. PLGA is a biodegradable polymer with excellent biocompatibility and non-immunogenic in nature [23]. The hydrophobic nature of PLGA allows loading the hydrophobic drug in the core. The surface of the NP was made with polyethylene glycol (PEG) chain prolongs the systemic circulation in the body by preventing the aggregation. The nanoparticle surface could be modified to direct the NP to the tumor site in a preferential manner [24]. Folic acid (FA) is a ligand with high affinity towards the folate receptors which are overexpressed in the multiple cancer cells [25]. There are numerous reports of the folate conjugation to the nanoparticles and its successful targeting to the cancer cells [26,27].

Herein, goal of this study was to design a CDDP and PBR-loaded FA-conjugated PLGA NP to improve the therapeutic efficacy of NPC. This study is an attempt to utilize the advantage of chemotherapy and photodynamic therapy using a single NP system. The formulated NP was characterized for detailed physicochemical parameters including size, charge, and release kinetics and particle stability. In vitro cell viability assays were NPC cell lines, CNE-1 and HNE-1. Therapeutic efficacy was evaluated in CNE-1-based xenograft tumor model and histopathological analysis was performed.