Targeting non-junctional Claudin-1 with monoclonal antibodies to treat hepatocellular carcinoma [RNA-seq]

Abstract: Hepatocellular carcinoma (HCC) is a leading cause of cancer-related death worldwide. Despite new treatment approvals, treatment response and prognosis of patients with advanced HCC remains poor. Claudin-1 (CLDN1) is a membrane protein expressed in tight junctions but also non-junctionally at the basolateral membrane of hepatocytes. While the function of CLDN1 within tight junctions is well characterized, the role of non-junctional (NJ) CLDN1 in HCC remains unexplored. Here we show that targeting NJ-CLDN1 with a humanized monoclonal antibody (mAb) suppresses tumor growth in different pre-clinical models. Mechanistic studies including single cell RNA sequencing of multicellular patient tumorspheres suggest that non-junctional CLDN1 regulates tumor stemness, metabolism and oncogenic signaling with impact on the tumor immune microenvironment. Our results provide the rationale for targeting NJ-CLDN1 in HCC and pave the way to novel therapeutic interventions with NJ-CLDN1 mAbs aimed at improving the limited efficacy of current therapies. Overall design: Fresh tumor tissues from mice bearing established primary human liver cancer (PDX models LI6280, LI6716, LI6688, LI6723, LI1055 and LI1068) were harvested and cut into small pieces (approximately 2-3 mm in diameter) and inoculated subcutaneously at the upper right dorsal flank into female BALB/c nude mice for tumor development. The randomization started when the mean tumor size reached 100 mm3. A total of 5 mice were enrolled in each model. Randomization into groups receiving CLDN1 mAb (10 mg/kg, 10 mL/kg, once weekly (QW), n=3 mice) or vehicle control (10 mL/kg, QW, n=2 mice) was performed based on "Matched distribution" method. The date of grouping was denoted as day 1 (5/12/2020). Dosing was started on day 1 and continued through day 25. Mice were sacrificed at day 28 and tumor tissue was harvested and stored snap frozen. Liver tissue was lysed in TRI-reagent (Molecular Research Center), and RNA was purified using Direct-zol RNA MiniPrep (Zymo Research) according to the manufacturer's instructions. RNAseq was performed at Biomedical Sequencing Facility (BSF) at Ce-M-M, Vienna.