Abstract 5972: HLJ1 deficiency enhanced diethylnitrosamine-induced hepatocarcinogenesis in a gene targeting mouse model
Authors: Luo Wei-Jia , Chien Min-Hui , Chen Jeremy J. W. , Yu Sung-Liang , Yang Pan-Chyr , Su Kang-Yi 
Published: September 2020

Liver cancer is the sixth most common cancer and the fourth leading cause of cancer-related death worldwide. The conventional treatments such as surgical resection and liver transplantation are applicable to only a small proportion of patients and prolongation of survival is restricted. Therefore, it is urgent to develop cancer biomarkers for defining cancer risk, diagnosis, prognosis and even find new therapeutic targets. Human Liver DnaJ-Like Protein (HLJ1), which belongs to DnaJ heat shock protein family (HSP40) member B4 (DNAJB4), has been reported to act as a tumor suppressor in NSCLC, colorectal cancer, melanoma metastasis. However, the precise role of HLJ1 in liver cancer tumorigenesis and the progress of HCC carcinogenesis has not been elucidated yet. Thus, we investigate whether HLJ1 has tumor-suppressive or oncogenic role on DEN-induced liver cancer development in a mouse model.

Wild-type (WT) and HLJ1 knockout (HLJ1−/−) mice are injected with 20 mg/kgbw DEN at postnatal day 15. Thereafter, 50 mg/kgbw DEN is administrated weekly to mice between age 4 to 12 weeks. Mice were sacrificed at age 30 and 36 weeks to assess the tumor count and size. In another group, mice are injected with DEN and age day 15 and then 500 ppm PB is administrated in drinking water until mice were sacrifice at age 52 weeks. The liver tissues are frozen and fixed for western blotting and IHC analysis. For cDNA microarray analysis, gene expression microarray samples were from 6-8 weeks wild-type and HLJ1−/− mice livers.

When sacrificed at age 30 and 36 weeks, HLJ1−/− mice exhibited higher tumor multiplicity, serum ALT, AST levels, and larger macroscopic tumor nodules than WT mice. In DEN+PB treatment group, higher incidence rate can be observed in HLJ1−/− mice than in WT mice. This indicated HLJ1 protects liver from DEN-induced HCC carcinogenesis and knockout of HLJ1 confers to more severe HCC induction. Furthermore, p-STAT3 expression was higher in normal part of HLJ1−/− mice liver compared to that of WT mice liver, which suggest the role of HLJ1 in regulating p-STAT3 signaling in the early stage of tumor formation. Using IHC staining and western blotting to analyze HLJ1 expression level, we found half of the tumors express higher HLJ1 than adjacent normal part did, which suggested a tumor-promoting role of HLJ1 after tumor initiation and formation. In cDNA microarray analysis, network analysis of genes enriched in HCC map folder revealed involved objects JunB, c-Myc, p21 and Cyclin D1, which was further confirmed by quantitative PCR. p21 and Cyclin D1 were highly expressed in the liver of HLJ1−/− comparing to that of WT mice, which suggested HLJ1-related genes p21 and Cyclin D1 may have roles in HCC formation. Clinical information of 362 liver cancer patients from TCGA database exhibited that higher expression of HLJ1 in tumor part is correlated to lower disease-specific survival rate. It indicated that HLJ1 may be a tumor marker for HCC prognosis and clinical outcome prediction. It also suggested that HLJ1 may play an oncogenic role after tumor formation.

In summary, HLJ1 has protective role against DEN-induced hepatocarcinogenesis through down-regulated p-STAT3 and cyclin D1 whereas it could also be an enhancer to promote tumor progression after tumor formation. Hence, HLJ1 could be a target for liver cancer therapy and a prognostic biomarker in the future.

Citation Format: Wei-Jia Luo, Min-Hui Chien, Jeremy J. W. Chen, Sung-Liang Yu, Pan-Chyr Yang, Kang-Yi Su. HLJ1 deficiency enhanced diethylnitrosamine-induced hepatocarcinogenesis in a gene targeting mouse model [abstract]. In: Proceedings of the Annual Meeting of the American Association for Cancer Research 2020; 2020 Apr 27-28 and Jun 22-24. Philadelphia (PA): AACR; Cancer Res 2020;80(16 Suppl):Abstract nr 5972.