A study on epithelial cell adhesion molecule targeted nucleic acid aptamer drug conjugate in gastric cancer targeted treatment / 中华消化外科杂志

ABSTRACT

Objective:To investigate the affinity and toxicity of epithelial cell adhesion molecule (EpCAM) targeted nucleic acid aptamer drug conjugate SYL3C-MMAE on human gastric epithelial cells GES-1 (hereinafter referred to as GES-1 cells) and human gastric cancer cells AGS and MKN45 (hereinafter referred to as AGS cells and MKN45 cells).Methods:The experimental study was conducted. The expression level of EpCAM in gastric cancer tissues was detected using immunohistochemistry. The mRNA expression level of EpCAM in gastric cancer tissues was detected using real-time fluorescence quantitative PCR (RT-PCR). The expression level of EpCAM protein in GES-1, AGS and MKN45 cells was detected using Western blot. The affinity of SYL3C on GES-1, AGS and MKN45 cells was detected using flow cytometry. SYL3C-MMAE was synthesized through a thiol-maleimide reaction. The toxicity of drugs on GES-1, AGS and MKN45 cells was detected using CCK-8 assay. The cell cycle condition of GES-1, AGS and MKN45 cells after drug treatment was detected using propidium iodide (PI) staining. Observation indicators: (1) expression of EpCAM in gastric cancer; (2) affinity of antibodies targeting EpCAM and SYL3C on GES-1, AGS and MKN45 cells; (3) situation of drug synthesis; (4) drug toxicity and inhibition of cell cycle. Measurement data with normal distribution were represented as Mean± SD. One-way ANOVA was used for comparison among multiple groups, and pairwise comparison was conducted using the least significant difference test. Comparison of unequal variances was conducted using the Welch' t test. Measurement data with skewed distribution were represented as M(IQR), and comparison between groups was conducted using the paired rank sum test. Count data were described as absolute numbers, comparison between groups was conducted using the paired chi-square test. Results:(1) Expression of EpCAM in gastric cancer. Results of immunohistochemistry on tissue microarrays showed that the positive rate of EpCAM was 82.9%(29/35) and 22.9%(8/35) in the 35 pairs of gastric cancer and its adjacent tissues (normal tissues), respectively, showing a significant difference between them ( P<0.05). Results of RT-PCR showed that the mRNA relative expression levels of EpCAM was 1.23 (4.13) and 4.04 (1.72) in 12 pairs of gastric cancer and its adjacent tissues respectively, showing a significant difference between them ( Z=-2.67, P<0.05). Results of Western blot showed that the relative expression levels of EpCAM protein in GES-1, AGS, and MKN45 was 0, 1.00, and 0.27, respectively, with the expression level of EpCAM protein in AGS cells as the standard. (2) Affinity of antibodies targeting EpCAM and SYL3C on GES-1, AGS and MKN45 cells. Results of flow cytometry showed that antibodies targeting EpCAM and SYL3C had good affinity on AGS and MKN45 cells but no affinity on GES-1 cells. (3) Situation of drug synthesis. Results of mass spectrometry showed that the drug solution of compound formed by connecting SYL3C with monomethylorestatin E (VcMMAE) exhibited a strong peak at the molecular weight position of 16 355, consistent with the expected molecular weight of the SYL3C-MMAE complex, indicating that SYL3C-MMAE was successfully synthesized. (4) Drug toxicity and inhibition of cell cycle. Results of CCK-8 assay showed that the half maximal inhibitory concentration (IC 50) of VcMMAE on GES-1, AGS and MKN45 cells was 123.00, 30.48 and 51.83 nmol/L, respectively. The IC 50 of SYL3C-MMAE on GES-1, AGS and MKN45 cells was 241.80, 20.66 and 27.64 nmol/L, respectively. Results of PI staining and flow cytometry showed that both VcMMAE and SYL3C-MMAE could induce G2/M phase blockage in the cell cycle of GES-1, AGS and MKN45 cells. Conclusion:The SYL3C-MMAE has a good affinity on gastric cancer cells. Compared with VcMMAE, SYL3C-MMAE exhibits efficient inhibition on gastric cancer cells, but less influence on normal cells.