A 3 Dimensional in Vitro Model to Test HL-60 Cell Line Sensitivity to Chemotherapy
Authors: Aljitawi Omar S. , Li Dandan , Zhang Da , Mahnken Jonathan , Kambhampati Suman , Van Veldhuizen Peter , Garimella Rama 
Published: October 2019

Abstract
Abstract 4882

Introduction:
Current in vitro drug testing models are based on 2-dimensional (2D) cell culture systems and therefore do not always predict in vivo responses. This lack of predictability of the 2D assays is believed to be related to the 3-dimensional (3D) microenvironment present in tissues or tumors. This 3D microenvironment, were cell-cell and cell-extracellular matrix (ECM) interactions occur, is fundamental for cell biologic activities. This is especially true for acute myeloid leukemia, were current 2-D cell culture models do not always predict clinical responses. This discrepancy in leukemia cell responses to chemotherapy in vivo, in comparison to in vitro, is at least partly related to leukemia cells interaction with the bone marrow microenvironment and their ability to establish niches. These niches offer partial protection from the effects of cytotoxic chemotherapy, otherwise termed cell adhesion-mediated drug resistance. In these experiments, we investigate the apoptotic effects of cytotoxic chemotherapy on HL-60 cell line cultured in a designed 3D AML cell culture model. In this 3D microenvironment, HL-60 cells were co-cultured with ex vivo expanded bone marrow mesenchyaml stem cells in a 3D synthetic scaffold.

Aim:
To examine the apoptotic effect of cytotoxic chemotherapy on HL-60 co-cultured with human bone marrow mesenchymal stem cells (huBM-MSCs) in 3D conditions.

Methods:
After several passages, expanded huBM-MSCs were seeded into PGA/PLLA 90/10 copolymer discs, 5-mm in diameter and 2-mm in thickness and allowed to attach to scaffold fibers and to expand over 2 weeks. Then, HL-60 were added and allowed to grow in the 3D culture system for another 10 days. HL-60 cells in 3D culture system were then exposed to doxorubicin given in two concentrations (25 and 50 μM) and incubated for 24 hours. HL-60 were then retrieved applying a combination of mechanical forces and using cell dissociation solution. FITC Annexin V Apoptosis Detection Kit was used to determine apoptosis. Apoptosis was confirmed by TUNEL assay. Proliferation of HL-60 cells in the 3D scaffold was assessed using Ki-67 stain of scaffold's cryosections. All tests were done in triplicates, and untreated HL-60 served as controls for treatment. Comparison was made with HL-60 cells alone and with HL-60 cells growing on a hu-BM-MSC monolayer. SAS version 9.2 (SAS Institute, Inc., 2002–2008) was used for statistical analysis

Results:
Virtually, all HL-60 cells treated with 25 or 50 μM underwent late apoptosis. Around.03% of HL-60 cells survived 25 μM concentration, none, however, survived 50 μM concentration. In 2D, most of HL-60 cells underwent necrosis, and to lesser extent late apoptosis. In sharp contrast, 17.8% of HL-60 cells survived 25μM concentration, nevertheless, only.27% of HL-60 cells treated with 50 μM concentration survived. The differences in apoptosis patterns between the three groups was statistically significant (P<.0001).

Conclusion:
compared to traditional cell culture conditions, the designed 3D culture conditions protected a higher percentage of HL-60 cells from undergoing apoptosis and necrosis.

Disclosures:
No relevant conflicts of interest to declare.