Abstract 6982: The roles of NDRG1 in HCC progression and its clinical significance
Authors: Lu Jingyi , Tian Lu , Tsui Yu-Man , Wong Xia , Zhang Qingyang , Ho Daniel Wai-Hung , Ng Irene Oi-Lin 
Published: March 2024

Abstract
Background: Hepatocellular carcinoma (HCC) is prevalent globally and the third leading cause of cancer-related mortality. N-myc downstream regulated 1 (NDRG1) was found to be tumor promoting in some cancers while suppressive in others. The expression of NDRG1 is induced by stress signals such as DNA damage and hypoxia. In HCC, it has been found to promote proliferation and metastasis. Contradictory results, however, were also suggested on the functions of NDRG1.
Methods: Our own HCC cohort and multiple publicly available databases were examined for NDRG1 expression and clinicopathologic correlation. NDRG1 expression under hypoxic conditions was investigated. Various functional assays were performed for NDRG1-knockdown HCC cell lines Huh-7 and PLC/PRF/5.
Results: With RT-qPCR analysis on our 102 pairs of patients’ HCC tumor and corresponding non-tumorous liver samples, we found NDRG1 to be upregulated in HCC tumors. Similarly, RNA-sequencing analysis comparing 41 pairs of samples confirmed NDRG1 enrichment in HCC tumors. The upregulation was significantly and positively correlated with the absence of tumor encapsulation and cellular differentiation. These were further supported by TCGA and ICGC databases, in which upregulation of NDRG1 was significantly correlated with poor HCC patient overall survival. Interestingly, in the TCGA database, only 17% of the HCC cases were inferred to have copy number amplification of NDRG1 gene while NDRG1 mutations were rarely found. As hypoxia is a major tumor microenvironmental factor in HCC, we investigated NDRG1’s expression level in HCC cells under hypoxic or normoxic conditions and found significant increase in NDRG1 expression under hypoxic environment. We further found that NDRG1 knockdown inhibited cell proliferation, self-renewal ability, and migration. RT-qPCR analysis found lower LGR5 and SOX2 expression upon NDRG1 knockdown. This is in line with the positive correlation between NDRG1 and various cancer stemness-related gene expression, including LGR5, CD24, MYC, SOX2, and NOTCH1, in TCGA database. Lastly, in the resected HCC tumors on which spatial transcriptomics using Visium 10X and single-cell RNA-sequencing using Chromium 10X were performed, we found NDRG1 enrichment in both tumors cells and cancer associated fibroblasts (CAFs).
Conclusion: NDRG1 was found to be significantly upregulated in HCC cells in our in-house cohort and publicly available databases. NDRG1 consistently promotes various oncogenic features of HCC cells, including proliferation, self-renewal ability, and migration. In addition, NDRG1 was found to be enriched in both the HCC cells and CAFs.
Citation Format: Jingyi Lu, Lu Tian, Yu-Man Tsui, Xia Wong, Qingyang Zhang, Daniel Wai-Hung Ho, Irene Oi-Lin Ng. The roles of NDRG1 in HCC progression and its clinical significance [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2024; Part 1 (Regular Abstracts); 2024 Apr 5-10; San Diego, CA. Philadelphia (PA): AACR; Cancer Res 2024;84(6_Suppl):Abstract nr 6982.