Abstract 2785: Beyond the role of transcobalamin 1 (TCN1) as a vitamin B12-binding protein in hepatocellular carcinoma

Abstract

Abstract Hepatocellular carcinoma (HCC) is a common form of primary liver cancer and is associated with poor prognosis. Although sorafenib and lenvatinib have shown promising results in HCC treatment, their clinical benefits for patients have been limited owing to drug resistance and tumor relapse. This may be associated with the presence of tumor-initiating cells (T-ICs), which require further investigation to identify the key pathways or molecules involved in their regulation. Through in vitro enrichment of liver T-IC populations via a series of sphere passages under treatment with chemotherapeutic drugs, subsequent bulk RNA sequencing analysis identified a vitamin B-12 binding protein, transcobalamin 1 (TCN1), as the most upregulated molecule in such enriched T-IC populations. This result was consistent with the enrichment profiles of the stem cell signature in TCN1High HCC samples in the clinical dataset. TCN1 is a secretory protein expressed at high levels in salivary glands and glandular cells; however, its function beyond its native role as a vitamin B12-binding protein in the regulation of T-ICs is unclear. Using lentiviral shRNA overexpression and knockdown approaches, we identified a critical role for TCN1 in regulating the properties of T-ICs, including self-renewal, invasiveness, tumorigenicity, and drug resistance, through in vitro and in vivo assays. Clinically, we also observed a substantial increase in TCN1 mRNA signatures in HCC samples, which was associated with poor prognosis of HCC patients. By analyzing the TCGA-LIHC dataset with confirmation by immunoprecipitation, we report, for the first time, that TCN1 directly interacts with integrin subunit alpha 3 (ITGA3), thereby regulating the Notch signaling pathway. Furthermore, ELISA results revealed the presence of the secretory form of TCN1 in HCC cells, which exerts a T-IC-enhancing effect on HCC cells via autocrine regulation. In conclusion, our study provides novel insights into how TCN1 functions in HCC via a non-canonical mechanism, which goes beyond its conventional role as a vitamin B12-binding protein and uncovers a potential novel therapeutic target for HCC. Citation Format: Gregory Kenneth Muliawan, Carmen Oi Ning Leung, Terence Kin Wah Lee. Beyond the role of transcobalamin 1 (TCN1) as a vitamin B12-binding protein in hepatocellular carcinoma [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 2785.