Repurposing Dimethyl Fumarate as a Potential Drug for the Treatment of Hepatocellular Carcinoma

富馬酸二甲酯老藥新用作為治療肝細胞癌的潛在藥物

Student thesis: Doctoral Thesis

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Award date2 Mar 2022

Abstract

Hepatocellular carcinoma (HCC) is an aggressive form of liver cancer with an incidence to mortality ratio of approximately 1. HCC accounts for 75–85% of all primary liver malignancies and 8.2% of cancer-related deaths. Notably, the prevalence of HCC is projected to increase owing to the prevalence of metabolic disorders and viral infections. Although diagnostic techniques have improved, recurrence and metastasis remain a severe problem in clinical practice. Surgical resection is the primary treatment approach for early-stage HCC, but this approach does not apply to most patients. Advanced HCC patients are often treated with tyrosine kinase inhibitors (TKIs). However, the therapeutic benefits are short-lived and associated with strong side effects and drug toxicity. Targeting other pathways involved in HCC malignancy has received increased attention because it can improve patients’ long-term survival as a single therapy or in combination with other approved drugs.

In this study, I found that dimethyl fumarate (DMF) exerts profound anticancer effects on the growth and metastasis of HCC. DMF is an alkyl ester of fumaric acid approved for the treatment of psoriasis and multiple sclerosis. DMF treatment significantly decreased tumor growth of HCC compared to the control group (605.84 ± 65.06 mm3 and 232.1± 57.14 mm3, p < 0.01) in the HCC mice model. I performed additional studies using in vitro and zebrafish models to understand the antitumor effects of the drug. DMF induced DNA damage, repressed cell division and triggered caspase-dependent apoptosis in a time and dose-dependent manner. Furthermore, DMF induced mesenchymal-epithelial transition and potently suppressed HCC metastasis in various experimental models.

By combining electron microscopy, transcriptomic, and protein profile analysis, I revealed that the mechanism of action of DMF centres around the mitochondria and is dependent on regulating the nuclear factor E2-related factor 2 (NRF2)/B-cell lymphoma extra-large (Bcl-xL) signaling axis. I also demonstrated that enforced Bcl-xL or NRF2 expression could markedly reverse DMF-induced apoptosis and metastasis inhibition in HCC cells. Importantly, given that NRF2/Bcl-xL signaling axis is an essential player in HCC recurrence and metastasis, our findings highlight DMF as an effective alternative drug. In addition, I revealed that the inactivation of PERK exacerbated the cytotoxic effects of DMF as evidenced by increased apoptotic (annexin V+) cells. In contrast, ER stress-adapted HCC cells respond poorly to DMF treatment, suggesting that the unfolded protein response might influence the cytotoxic effects of DMF in HCC cells.

My study further demonstrated that DMF and sorafenib exhibited synergistic effects on the progression of HCC. The combination therapy reduced cell proliferation and increased apoptosis compared to DMF or sorafenib alone. Similarly, p-STAT3 expression was significantly reduced following co-treatment with sorafenib and DMF. I then verified the in vitro results using HCC mice xenograft models. Consistently, the co-treatment of DMF and sorafenib synergistically inhibited the HCC progression. In summary, our results provide evidence that DMF can target NRF2/Bcl-xL-mediated resistance in HCC and may serve as a potential therapeutic choice for advanced HCC in combination with sorafenib.