Abstract 5799: SPINK1-induced tumor plasticity provides a therapeutic window for chemotherapy in hepatocellular carcinoma
Authors: Man Ki-Fong , Zhou Lei , Lam Ying-Tung , Yu Jun , Yun Jing-Ping , Guan Xin-Yuan , Liu Ming , Ma Stephanie 
Published: April 2023

Abstract
Intratumor molecular heterogeneity of hepatocellular carcinoma (HCC) is partly attributed to the presence of cancer stem cells (CSCs), which we now know represents a critical root of tumor recurrence and chemotherapy resistance. CD133 is known to represent an important functional marker of liver CSCs. We have demonstrated CD133 to enrich following chemotherapy treatment, while CD133/Prom1-depletion would enhance sensitivity of HCC tumors to chemotherapy. Yet unfortunately, CD133 is not specific to HCC, but is also expressed in normal regenerating liver. Identifying critical factors expressed specifically in liver CD133+ CSCs, but not in liver normal CD133+ stem/progenitor cells may offer important therapeutic opportunities overcoming chemoresistance in HCC. RNA-seq profiling comparing sorted CD133+ and CD133- subsets of normal regenerating liver induced by DDC diet and HCC induced by either N-nitrosodiethylamine (DEN)/carbon tetrachloride (CCl4) or hydrodynamic tail vein injection of oncogenic plasmids AKT and NRAS identified Serine Peptidase Inhibitor Kazal Type I (SPINK1) to be distinctly expressed in the HCC CD133+ subpopulation but not in normal regenerating liver CD133+ subpopulation. SPINK1 overexpression in HCC clinical samples is correlated with a poor prognosis. Expression of SPINK1 increased during early liver progenitor development, peaked during the premature hepatocyte stage, decreased during hepatocyte maturation and increased progressively from well-differentiated to poorly differentiated HCCs. Enhanced transcriptional activity of SPINK1 was mediated by promoter binding of the epithelial cell-specific transcription factor ELF3, which like CD133, were both increased following chemotherapy treatment. SPINK1 inhibition by lentiviral-based knockdown or a specific monoclonal antibody (mAb) mitigated tumor initiation, self-renewal and chemoresistance. Mechanistically, secretory SPINK1 bound to epidermal growth factor receptor (EGFR) activating MEK/ERK signaling and consequently promoting the formation of CDK4/6-cyclin D1 complex to phosphorylate Rb and release E2F2, allowing the cells to overcome G1/S checkpoint promoting cell cycle progression as well as transcribing stemness, oncogenic dedifferentiation and chemoresistance-related genes. Collectively, our findings suggest SPINK1 to play a critical role in hepatocarcinogenesis and that SPINK1 mAb may represent a novel therapeutic option for the treatment of HCC, targeting at the CD133+ CSC tumor roots and overcoming chemoresistance.
Citation Format: Ki-Fong Man, Lei Zhou, Ying-Tung Lam, Jun Yu, Jing-Ping Yun, Xin-Yuan Guan, Ming Liu, Stephanie Ma. SPINK1-induced tumor plasticity provides a therapeutic window for chemotherapy in hepatocellular carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 5799.