Deltex E3 ubiquitin ligase 3 inhibits colorectal cancer cell growth and regulates cell cycle progression via upregulating E2F transcription factor 1

Targeting the E2F1/Rb/HDAC1 axis with the small molecule HR488B effectively inhibits colorectal cancer growth

Colorectal cancer (CRC), the third most common cancer worldwide, remains highly lethal as the disease only becomes symptomatic at an advanced stage. Growing evidence suggests that histone deacetylases (HDACs), a group of epigenetic enzymes overexpressed in precancerous lesions of CRC, may represent promising molecular targets for CRC treatment. Histone deacetylase inhibitors (HDACis) have gradually become powerful anti-cancer agents targeting epigenetic modulation and have been widely used in the clinical treatment of hematologic malignancies, while only few studies on the benefit of HDACis in the treatment of CRC. In the present study, we designed a series of small-molecule Thiazole-based HDACis, among which HR488B bound to HDAC1 with a high affinity and exerted effective anti-CRC activity both in vitro and in vivo. Moreover, we revealed that HR488B specifically suppressed the growth of CRC cells by inducing cell cycle G0/G1 arrest and apoptosis via causing mitochondrial dysfunction, reactive oxygen species (ROS) generation, and DNA damage accumulation. Importantly, we noticed that HR488B significantly decreased the expression of the E2F transcription factor 1 (E2F1), which was crucial for the inhibitory effect of HR488B on CRC. Mechanistically, HR488B obviously decreased the phosphorylation level of the retinoblastoma protein (Rb), and subsequently prevented the release of E2F1 from the E2F1/Rb/HDAC1 complex, which ultimately suppressed the growth of CRC cells. Overall, our study suggests that HR488B, a novel and efficient HDAC1 inhibitor, may be a potential candidate for CRC therapy in the future. Furthermore, targeting the E2F1/Rb/HDAC1 axis with HR488B provides a promising therapeutic avenue for CRC.

Deltex E3 ubiquitin ligase 4 promotes thyroid cancer progression through stearoyl-CoA desaturase 1

In this study, we aimed to explore the molecular role of Deltex E3 ubiquitin ligase 4 (DTX4) in thyroid cancer (TC) both in vitro and in vivo. The expression level of DTX4 in TC tissues was compared using The Cancer Genome Atlas (TCGA) database. We subsequently evaluated cell proliferation and migration in DTX4 knock down or DTX4 overexpression TC cell lines (TPC-1 and K1) by CCK-8, cell colony formation, and transwell assays. RNA sequencing and KEGG analysis were employed to identify potential genes that interact with DTX4. Our results showed that DTX4 was expressed at higher levels in both TC tissues and cells compared to normal controls. Knock down of DTX4 expression significantly inhibited TC cell progression in vitro. Furthermore, knockdown of endogenous DTX4 by shDTX4 markedly abrogated tumor growth, with significantly smaller tumor size and lower tumor weight in the shDTX4 group compared to the shCtrl group. Conversely, overexpression of DTX4 enhanced TC cell proliferation and migration. Through RNA sequencing, we identified 590 Differentially Expressed Genes (DEGs), with stearoyl-CoA desaturase 1 (SCD) ranking as the top gene. A positive correlation between DTX4 and SCD was observed in TC samples. Additionally, treatment with an SCD inhibitor, A939572, significantly rescued the enhanced growth effect induced by DTX4 overexpression. In conclusion, this study demonstrated that DTX4 promotes TC progression through SCD, indicating that the DTX4/SCD axis could be a promising target for TC therapy.

The DTX Protein Family: An Emerging Set of E3 Ubiquitin Ligases in Cancer

Until recently, Deltex (DTX) proteins have been considered putative E3 ligases, based on the presence of an E3 RING domain in their protein coding sequence. The human DTX family includes DTX1, DTX2, DTX3, DTX3L and DTX4. Despite the fact that our knowledge of this class of E3-ubiquitin ligases is still at an early stage, our understanding of their role in oncogenesis is beginning to unfold. In fact, recently published studies allow us to define specific biological scenarios and further consolidate evidence-based working hypotheses. According to the current evidence, all DTX family members are involved in the regulation of Notch signaling, suggesting a phylogenetically conserved role in the regulation of this pathway. Indeed, additional evidence reveals a wider involvement of these proteins in other signaling complexes and cancer-promoting mechanisms beyond NOTCH signaling. DTX3, in particular, had been known to express two isoform variants (DTX3a and DTX3b). The recent identification and cloning of a third isoform variant in cancer (DTX3c), and its specific involvement in EphB4 degradation in cancer cells, sheds further light on this group of proteins and their specific role in cancer. Herein, we review the cumulative knowledge of this family of E3 Ubiquitin ligases with a specific focus on the potential oncogenic role of DTX isoforms in light of the rapidly expanding findings regarding this protein family's cellular targets and regulated signaling pathways. Furthermore, using a comparative and bioinformatic approach, we here disclose a new putative motif of a member of this family which may help in understanding the biological and contextual differences between the members of these proteins.