Functional characterization and therapeutic role of interleukin-1 receptor-associated kinase 1 (IRAK1) in hepatocellular carcinoma

Abstract

Hepatocellular carcinoma (HCC) is the fifth most commonly diagnosed and the second most lethal cancer worldwide. Frequent relapse and drug resistance account for its poor prognosis, which could be attributed by the presence of cancer stem cells/tumor initiating cells (CSCs/TICs), a rare cell population sitting at the apex of the hierarchical cancer model which harbors the properties of self-renewal, high tumorigenicity and chemoresistance. Unfortunately, there is currently no effective systemic treatment for HCC, and the only FDA approved drug, sorafenib, could only enhance patient’s survival rate by 3 months, indicating there is an urgent need to devise better novel therapeutic strategies. In this study, I identified Interleukin-receptor associated kinase 1 (IRAK1) from the Toll-like receptor (TLR)/IRAK pathway to be a promising candidate. From transcriptome sequencing of 16 pairs of HCC clinical samples, IRAK1 was found to be significantly upregulated in HCC. IRAK1 overexpression in HCC was further confirmed at mRNA and protein level, and correlated with aggressive clinical pathological features like advanced tumor stage. Through lenti-viral based shRNA knockdown and overexpression approaches, I demonstrated IRAK1 promoted TIC properties, including self-renewability through spheroids formation assay; in vivo tumorigenicity and enrichment of TIC population through rate limiting dilution assay and TIC marker CD24 and CD47 expression analysis; drug resistance to sorafenib and doxorubicin through Annexin V assay. Additionally, IRAK1 also promoted proliferation of HCC cells. IRAK1/4 specific inhibitor which suppressed the phosphorylation of IRAK1 and IRAK4 was evaluated for its therapeutic potentials. Pharmacological inhibition of the IRAK signaling effectively suppressed cancer stemness properties of HCC cells include the expression of TIC markers, self-renewability and in vivo tumorigenicity. Furthermore, IRAK1/4 inhibition dramatically suppressed cell proliferation, migration and invasion. Therapeutically, IRAK1/4 inhibition could sensitize the cells to doxorubicin and sorafenib treatment in vitro, and administration of the IRAK1/4 inhibitor suppressed the tumor growth of established tumors in vivo. Mechanistically, transcriptome sequencing analysis upon IRAK1 knock-down revealed Aldo-Keto Reductase Family 1, Member 10 (AKR1B10) as a potential novel downstream target of IRAK1. AKR1B10 is also overexpressed in HCC and its expression level was positively correlated with IRAK1 expression level in both cell lines and HCC clinical cases. AKR1B10 is known to be regulated by AP-1 signaling and I demonstrated IRAK1 is positive regulator of AP-1 promoter activity through dual-luciferase reporter assay. Lenti-viral based shRNA knock-down of AKR1B10 reduced self-renewability in HCC cells and could partially rescued IRAK1 overexpression induced spheroid formation ability. To conclude, IRAK1 represents a potential therapeutic target against HCC.