Abstract 1835: Antitumor activity of a novel irinotecan analog, ZBH-01
Authors: Li Yongqi , Tu Zhengkun , Zhao Dawei , Zhang Wenqiu , Yang Miaomiao , Wu Zhihui , Shi Weiguo , lan Shijie , Guo Zhen , Yu Hong , Wu Di 
Published: September 2020

Camptothecin (CPT) is considered one of the most important antitumor agents in the treatment of colon cancer. We synthesized a series of novel CPT (irinotecan, CPT-11) derivatives, which have impressive effects in various tumors. This study investigated the antitumor mechanism of one representative compound, ZBH-01 in colon cancer both in vitro and in vivo.

The antiproliferative effect of ZBH-01 on tumor cells was evaluated by MTT assay. Topoisomerase I (Topo I) function and expression were assessed using DNA relaxation assay,qRT-PCR and western blot. Different gene expression among ZBH-01, CPT-11, and SN38 group was analyzed by RNA-seq and verified using qRT-PCR. GO and KEGG pathway analysis of DEmRNAs was performed by “R”. Protein-protein interaction (PPI) networks were constructed by STRING. The screened out mRNAs were functionally annotated. Cell cycle progression and cell apoptosis were assessed by flow cytometry. ZBH-01's inhibition of tumor growth was assessed using xenografts models established from SW1116 cells and colon cancer tissue samples.

The results showed that ZBH-01 has comparable or superior antitumor activity against multiple tumor cell lines as compare with CPT-11 and SN38 (7-Ethyl-10-hydroxy camptothecin). It reduced colon tumor growth superior to CPT-11 in vivo with lower toxicity. ZBH-01 showed a similar mechanism but weaker inhibitory activity on Topo I compared to CPT-11 or SN38. The screening criteria for DEmRNAs are P-value &lt; 0.05 and |log2 fold change | &gt; 1. A total of 100 DEmRNAs (62 downregulated and 38 upregulated mRNAs) have the same expression pattern in the three drug groups. Notably, there are 1769 DEmRNAs (842 downregulated and 927 upregulated mRNAs) specifically expressed in ZBH-01 group as compare with CPT-11 and SN38 group. GO analysis stratified these DEmRNAs in BP (sister chromatid segregation, DNA-dependent DNA replication), MF (catalytic activity, acting on DNA), CC (chromosomal region, condensed chromosome) classifications. The most significantly enriched KEGG pathways for the DEmRNAs in ZBH-01 group were DNA replication, P53 signaling pathway, and cell cycle etc. PPI network construction identified a significant cluster containing 73 genes, which include 14 genes involved in cell cycle process that were verified by qRT-PCR. More precisely, 50 nmol/L ZBH-01 significantly induced cell cycle arrest and apoptosis of colon cancer cells with the changes in gene expression such as p53, CDK2, CCNA2, Bax, Bcl-2, caspase 3, PARP. The further significant result is that ZBH-01 can rapidly exert cytotoxicity after 4 hours of dosing. In contrast, CPT-11 and SN38 had no detectable effect on tumor cells at this time point.

In conclusions, ZBH-01 has higher potency in inhibiting colon tumor growth than CPT-11 and SN38 both in vitro and in vivo. It rapidly induces tumor cell apoptosis and cell cycle arrest through regulation of cell cycle signaling pathway. The more precise mechanism of ZBH-01 need to be further studied.

Citation Format: Yongqi Li, Zhengkun Tu, Dawei Zhao, Wenqiu Zhang, Miaomiao Yang, Zhihui Wu, Weiguo Shi, Shijie lan, Zhen Guo, Hong Yu, Di Wu. Antitumor activity of a novel irinotecan analog, ZBH-01 [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 1835.