EOS, an Ikaros family zinc finger transcription factor, interacts with the HTLV-1 oncoprotein Tax and is downregulated in peripheral blood mononuclear cells of HTLV-1-infected individuals, irrespective of clinical statuses

Ikaros Proteins in Tumor: Current Perspectives and New Developments

Ikaros is a zinc finger transcription factor (TF) of the Krüppel family member, which significantly regulates normal lymphopoiesis and tumorigenesis. Ikaros can directly initiate or suppress tumor suppressors or oncogenes, consequently regulating the survival and proliferation of cancer cells. Over recent decades, a series of studies have been devoted to exploring and clarifying the relationship between Ikaros and associated tumors. Therapeutic strategies targeting Ikaros have shown promising therapeutic effects in both pre-clinical and clinical trials. Nevertheless, the increasingly prominent problem of drug resistance targeted to Ikaros and its analog is gradually appearing in our field of vision. This article reviews the role of Ikaros in tumorigenesis, the mechanism of drug resistance, the progress of targeting Ikaros in both pre-clinical and clinical trials, and the potential use of associated therapy in cancer therapy.

HTLV-1 viral oncoprotein HBZ contributes to the enhancement of HAX-1 stability by impairing the ubiquitination pathway

Human T-cell leukemia virus type 1 (HTLV-1) is an oncogenic retrovirus that causes adult T-cell leukemia (ATL). The viral protein HTLV-1 basic leucine-zipper factor (HBZ), which is constitutively expressed in all ATL patient cells, contributes toward the development of ATL; however, the underlying mechanism has not been elucidated yet. Here, we identified HS-1-associated protein X-1 (HAX-1) as a novel binding partner of HBZ. Interestingly, HAX-1 specifically associated with HBZ-US, but not HBZ-SI, in the cytoplasm. HBZ suppressed the polyubiquitination levels of HAX-1 protein by inhibiting the association HAX-1 with F-box protein 25 (FBXO25), which is a member of the SCF E3 ubiquitin ligase complex, and promoted the stabilization of HAX-1 levels. In fact, the protein levels of HAX-1 were significantly increased in HTLV-1 infected and the overexpressing HBZ in uninfected T-cell lines. Enhanced HAX-1 correlated well to suppression of caspase 9 processing, suggesting that HBZ may contribute to the enhancement of antiapoptotic function for HAX-1. Our results revealed a role for HBZ on HAX-1 stabilization by abrogating the ubiquitination-mediated degradation pathway, which may play an important role in understanding the potential mechanisms of HTLV-1 related pathogenesis.