Abstract 1039: Andrographis enhances 5-fluorouracil-induced anti-tumor effect in colorectal cancer through inhibition of DKK1
Authors: Zhao Yinghui , Wang Chuanxin , Goel Ajay 
Published: July 2021

Abstract
Background: Colorectal cancer (CRC) ranks as the third leading cause of cancer-related deaths in the US. In this malignancy, 5-fluorouracil (5FU)-based treatment remains the mainstay as first-line chemotherapy. Unfortunately, ~50-60% of patients treated with 5FU eventually develop resistance, leading to increased mortality. Hence, a better understanding of the molecular mechanisms underlying 5FU-resistance will lead to development of more effective therapeutic strategies. Our previous studies have shown that, andrographis, a botanical with diverse biological activities, synergistically enhanced 5FU-induced pro-apoptotic effects by mediating Wnt/β-catenin pathways. However, a more comprehensive knowledge of andrographis-mediated synergism with 5-FU remains largely unclear.
Methods: We first established 5FU resistant isogenic cell lines of HCT116 and SW480 CRC cells (HCT116 5FUR and SW480 5FUR). To determine the synergistic anti-tumor effects of andrographis and 5FU, we performed cell viability, proliferation and colony formation assays by treating parental and 5FUR cells with andrographis, 5FU and their combination. To explore the molecular mechanisms responsible for the synergistic anti-tumor efficacy, we next performed gene expression microarrays to identify candidate pathways and genes that mediated anti-tumor efficacy of andrographis in 5FUR cells. We analyzed an expression profiling dataset from CRC patients (GSE52735) who either responded or did not respond to 5FU. We also studied the andrographis-mediated synergism with 5FU in a xenograft animal model, and in 3D patient-derived tumor organoids.
Results: Combined treatment with andrographis and 5FU exhibited significantly superior effects on cell viability (P&lt;0.01), proliferation (P&lt;0.001) and colony formation capacity (P&lt;0.001), compared to treatment with individual treatments. In line with our in vitro findings, the combined treatment also significantly reduced tumor growth in mice xenografts (P&lt;0.0001) as well as patient-derived tumoroids (P&lt;0.001). By analyzing gene expression profiling data from cell lines and CRC patients, we identified that overexpression of DKK1 gene was a critical event for 5FU resistance in CRC. Moreover, qRT-PCR and western blotting data revealed that andrographis resulted in downregulation of 5FU-induced DKK1 overexpression accompanied with the synergistic anti-tumor effects in animal xenografts (P&lt;0.001) and patient-derived tumor organoids (P&lt;0.001), which were reversed following siRNA-mediated silencing of DKK1 (P&lt;0.01).
Conclusions: Our data provide novel evidence for andrographis-mediated anti-tumor synergism with 5-FU through DKK1, highlighting that in addition to its preventive efficacy, andrographis may serve as a potential adjunctive treatment to conventional chemotherapeutic drugs in patients with CRC.
Citation Format: Yinghui Zhao, Chuanxin Wang, Ajay Goel. Andrographis enhances 5-fluorouracil-induced anti-tumor effect in colorectal cancer through inhibition of DKK1 [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2021; 2021 Apr 10-15 and May 17-21. Philadelphia (PA): AACR; Cancer Res 2021;81(13_Suppl):Abstract nr 1039.