Dendrimer Conjugation Enhances Tumor Penetration and Efficacy of Doxorubicin in Extracellular Matrix-Expressing 3D Lung Cancer Models

Abstract

Doxorubicin (DOX) is a chemotherapeutic agent broadly used in the treatment of a range of solid tumors. In spite of its high potency, as is the case for many other chemotherapeutic drugs, there are many challenges associated with the use of DOX in clinical oncology. This is particularly true for DOX in the treatment of lung cancer, where in vitro potency is shown to be very high, but low lung distribution and off-target toxicity (particularly cardiotoxicity) restrict its use. Nanocarrier-based drug delivery systems (nanoDDS) have been shown to help alter biodistribution and alleviate off-target toxicity associated with DOX. While significant understanding exists regarding the design parameters to achieve those clinical benefits, much less is known regarding the design of nanoDDS capable of enhancing tumor penetration of DOX (and other drugs), which is another major factor leading to DOX's reduced efficacy. The purpose of this study was to design a dendrimer-based nanoDDS capable of enhancing the penetration of DOX as measured in an in vitro 3D lung tumor model and to correlate those results with its efficacy. Spheroids formed with the A549 human lung adenocarcinoma cells/murine fibroblast cell line (NIH/3T3 cell line) are shown to produce the essential components of the extracellular matrix (ECM), which is known as a physical barrier that hinders the transport of DOX. DOX was conjugated to generation 4 succinamic acid-terminated poly(amido-amine) (PAMAM) dendrimers (G4SA) through an enzymeliable tetrapeptide (G4SA-GFLG-DOX), resulting in a nanoDDS with ∼5.5 DOX, −17 mV surface (ζ) potential, and a 10 nm hydrodynamic diameter (HD). The penetration of DOX to the core of the spheroid in terms of DOX fluorescence was determined to be 3.1-fold greater compared to free DOX, which positively correlated with enhanced efficacy as measured by the Caspase 3/7 assay. This improved penetration happens as the interactions between the G4SA-GFLG-DOX and the highly negatively charged ECM are minimized by shielding the protonatable amine of DOX upon conjugation, and the HD of the conjugate is kept smaller than the estimated mesh size of the ECM. Interestingly, the conjugate provided more specificity for DOX to tumor cells compared to fibroblasts, while free DOX is equally distributed in both tumor and fibroblasts as assessed in the coculture spheroids. Growth inhibition studies show that the released DOX maintains its activity and leads to tumor reduction to the same extent as free DOX. The results obtained here are of relevance for the design of dendrimer-based nanoDDS and for the treatment of solid tumors as they provide critical information regarding desirable surface characteristics and sizes for efficient tumor penetration.

Air−Liquid Interface Cultures of the Healthy and Diseased Human Respiratory Tract: Promises, Challenges, and Future Directions

“…[ 147,148 ] Many attempts have been described in the literature to improve the delivery of already‐approved chemotherapeutics, such as paclitaxel or doxorubicin, using nanocarriers. [ 149–151 ] Furthermore, nanocarriers are often used to encapsulate new therapeutic entities for lung cancer treatments such as nucleic acids [ 152 ] and also for codelivery of different therapeutic agents. [ 153 ]…”

Biomedical Applications of Non-Small Cell Lung Cancer Spheroids

“…For better mimicking of the tumor ECM, heterotypic spheroid models have been developed. Introduction of fibroblasts into A549 spheroids resulted in a marked increase in collagen I, laminin, and fibronectin expression in heterotypic spheroids in comparison with homotypic counterparts ( 28 ).…”

“…In another study, the authors compared the distribution of dendrimer-conjugated doxorubicin versus free drug in A549 and A549/NIH3T3 spheroids. It turned out that dendrimer conjugation enhances the penetration and cytotoxic efficacy of doxorubicin in ECM-expressing spheroids ( 28 ).…”

Progress in Natural Compounds/siRNA Co-delivery Employing Nanovehicles for Cancer Therapy

“…Dendrimers are a subcategory of polymeric nanoparticles with three components, including a central core, an internaldendritic structure and an external surface with the functional surface group. Dendrimers are promising candidates for the delivery of anticancer drugs . SiRNA can be loaded into dendrimers for anticancer therapy.…”

“…Dendrimers are promising candidates for the delivery of anticancer drugs. 100 SiRNA can be loaded into dendrimers for anticancer therapy. Dendrimers remarkably enhance the cellular uptake of siRNAs and their release from endosomes.…”