In order to improve the efficacy of chemotherapy an increasing attention is given to the drug transport to tumors. Sonoporation is the application of ultrasound (US) to increase cell membrane permeability. It is thought that US induces expansion, contraction, and explosion of microbubbles (MB) thus creating pores in the cell membrane, enhancing drug delivery and efficacy. It is important to investigate this phenomenon not only into monolayer cultured cells but also into cell spheroids that imitate the biological characteristics of tumor better than 2D cell cultures. The aim of our study was to evaluate the influence of US on the efficacy of three anticancer drugs doxorubicin (DOX), 5-fluorouracil (5-FU) and paclitaxel (PTX) into 2D and 3D A549 non-small cell lung cancer cell cultures.
US pulse repetition frequency of 10 Hz and 1 MHz center frequency were generated with peak negative pressure of 0.5 MPa and 50% duty cycle. SonoVue™ MB were used. The effect of DOX on cell viability was tested by MTT assay. Spheroids were formed using 3D Bioprinting method mixing A549 cells with human fibroblasts. DOX delivery in 2D and 3D cultures was assessed using fluorescence microscopy. DOX toxicity in tumor spheroids was evaluated according to the change of spheroid size.
Separately applied US and MB did not increase DOX cytotoxicity. Meanwhile, the combination of US and MB increased DOX efficacy by approximately 4% when compared to DOX alone. US exposure did not show a positive effect on DOX delivery in 2D cancer cell cultures. On the other hand, US increased DOX delivery in tumor spheroids. 15 sec. of US exposure increased DOX penetration in the edge and middle zones of spheroids from 12 to 60%. 2 min. of US exposure decreased the amount of DOX in these zones. US also increased DOX, 5-FU and PTX toxicity in cancer cell spheroids 8-, 1.2- and 1.5-fold, respectively.
US is a promising physical method to enhance anticancer drug efficacy, especially into 3D cell cultures. However, there is a lack of evidence about its efficacy and further studies are needed.
The authors.
Lithuanian University of Health Sciences; Kaunas University of Technology.
All authors have declared no conflicts of interest.