Abstract 312: Multicellular spheroids of A549 cells: A clinically relevant model of lung cancer
Authors: Pei Xinyu , Ling Henry , Lu Yifan , Vadlamudi Mallika , Huang Yingbo , Huang Ruiqi , Zhao Shen , Xu Zizhao , Yuan Zhongyue , Zhu Yong , Kim Myo-Kyoung , Guo Xin 
Published: September 2020

Abstract
Purpose: This project aims to test the hypothesis that multicellular spheroids (MCS) of human lung cancer cells A549 can better mimic non-small cell lung cancer's (NSCLC) sensitivity to anticancer drugs in clinic than the corresponding monolayer cells.
Methods: 2D monolayers and MCS of A549 cells were treated with anticancer drugs cisplatin, carboplatin, and doxorubicin. The ability of the drugs to suppress cell growth was compared. A549 cells were seeded in 96 well plates (monolayer) and 96 well ultra-low attachment plates (MCS) at 5000 cells/well. The drugs were given in a series of concentrations 24 hours or 5 days after seeding. IC50 values were obtained from cell viability assays after 72 h drug exposure. MCS of fluorescently labeled A549 cells (A549-iRFP) were treated with select anticancer drugs by a cycled dosing schedule based on guidelines for NSCLC from National Comprehensive Cancer Network with modifications to accommodate for the life span of MCS. MCS were treated by 4 cycles, 7 days/cycle. In each cycle, carboplatin was dosed on day 1, and gemcitabine on day 1 and day 4. Drug concentration was reduced by media change according to the blood half-life of the drug to mimic its pharmacokinetics (PK). Drug dosage was based on the target clinical AUC or 1/10 of the peak plasma concentration. IC50 values were obtained from MCS fluorescence and viability.
Results: IC50 values of cisplatin in A549 monolayer and MCS were 9.73 μM and 20.71 μM, respectively; those of carboplatin 131.80 μM and 188.90 μM; those of doxorubicin 0.61 μM and 6.57 μM; those of gemcitabine 0.027 μM and &gt;250 μM. Ratios of IC50 value in MCS to monolayer were calculated for each drug, which were 2.13 in cisplatin, 1.43 in carboplatin and 10.74 in doxorubicin. Cisplatin and Carboplatin are indicated in NSCLC but require much higher concentration to inhibit 50% of monolayer cell growth than Doxorubicin, which is not indicated in NSCLC cancer. Although IC50 values in the monolayer cell model would suggest doxorubicin as a more promising drug than platinum drugs against lung cancer, the ratio of doxorubicin's IC50 values in MCS over monolayers is as high as 10.74 folds, which is 3 to 7 times as high as the two platinum drugs. The two different drug dosages based on target clinical AUC and on 1/10 of peak plasma concentration yielded similar suppression of MCS growth after the cycled drug treatment. However, at the same drug dosage for the cycled drug treatment, PK-mimetic media exchange substantially decreased the MCS growth suppression compared to 48 h continuous drug exposure, which is commonly used in current cell culture assays on anticancer drugs.
Conclusion: MCS of A549 cells better correlated with the efficacy of an anticancer drug in clinic than the monolayer. MCS can also evaluate anticancer drugs by pulsed drug exposure based on its pharmacokinetics, and by cycled dosing regiments as commonly used in clinic.
Citation Format: Xinyu Pei, Henry Ling, Yifan Lu, Mallika Vadlamudi, Yingbo Huang, Ruiqi Huang, Shen Zhao, Zizhao Xu, Zhongyue Yuan, Yong Zhu, Myo-Kyoung Kim, Xin Guo. Multicellular spheroids of A549 cells: A clinically relevant model of lung cancer [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 312.