Ubiquitin ligase DTX3 empowers mutant p53 to promote ovarian cancer development

RNA expression of 6 genes from metastatic mucosal gastric cancer serves as the global prognostic marker for gastric cancer with functional validation

BACKGROUND

Molecular analysis of advanced tumors can increase tumor heterogeneity and selection bias. We developed a robust prognostic signature for gastric cancer by comparing RNA expression between very rare early gastric cancers invading only mucosal layer (mEGCs) with lymph node metastasis (Npos) and those without metastasis (Nneg).

METHODS

Out of 1003 mEGCs, all Npos were matched to Nneg using propensity scores. Machine learning approach comparing Npos and Nneg was used to develop prognostic signature. The function and robustness of prognostic signature was validated using cell lines and external datasets.

RESULTS

Extensive machine learning with cross-validation identified the prognostic classifier consisting of four overexpressed genes (HDAC5, NPM1, DTX3, and PPP3R1) and two downregulated genes (MED12 and TP53), and enabled us to develop the risk score predicting poor prognosis. Cell lines engineered to high-risk score showed increased invasion, migration, and resistance to 5-FU and Oxaliplatin but maintained sensitivity to an HDAC inhibitor. Mouse models after tail vein injection of cell lines with high-risk score revealed increased metastasis. In three external cohorts, our risk score was identified as the independent prognostic factor for overall and recurrence-free survival.

CONCLUSION

The risk score from the 6-gene classifier can successfully predict the prognosis of gastric cancer.

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.

A multidimensional pan-cancer analysis of DCAF13 and its protumorigenic effect in lung adenocarcinoma

DCAF13 is a substrate recognition protein in the ubiquitin-proteasome system with oncogenic effects in several malignant tumors. However, it is unclear that the relationship between DCAF13 expression pattern and prognosis across different cancer types. Also unknown is the biological function or effects on the immune microenvironment of DCAF13. In this study, we parsed multiple public databases to explore the potential tumorigenic actions of DCAF13, including correlations with prognosis, microsatellite instability (MSI), tumor mutational burden (TMB), immune checkpoint genes, immune cell infiltration, and immunotherapy response in pan-cancer. Moreover, we validated DCAF13 expression in a tissue microarray by immunohistochemistry and investigate its effects in vitro and in vivo. The results showed that DCAF13 was upregulated in 17 cancer types and correlated with poor prognosis in many cancers. Also, the correlation between DCAF13 and TMB was found in 14 cancers as well as MSI in nine. The expression level of DCAF13 was found to be notably correlated with immune cell infiltration, showing a negative correlation with CD4 T cell infiltration and a positive correlation with neutrophil infiltration. The oncogene DCAF13 expression was shown to have a positive correlation with CD274 or ADORA2A and negative correlation with VSIR, TNFRSF4, or TNFRSF14 across large subsets of human cancers. Finally, we observed that DCAF13 was highly expressed in a tissue microarray of lung cancer. In immunocompromised mouse models, xenograft growth of human lung cancer cells was significantly inhibited by DCAF13 knockdown. Our results highlighted the value of DCAF13 as a promising independent predictor of poor prognosis through numerous biological processes. High DCAF13 expression often predicts suppressive immune microenvironment and immunotherapy resistance in a pan-cancer context.

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

Background

The mortality rate of colorectal cancer (CRC) remains high in developing countries. Interventions that can inhibit the proliferation of tumor cells represent promising strategies in CRC treatment. Deltex E3 ubiquitin ligase 3 (DTX3) plays an essential role in tumor development and may predict the outcome of cancer patients. This study aimed to investigate the regulatory mechanisms of DTX3 in CRC progression.

Methods and results

The expression of DTX3 was significantly downregulated in CRC tissues relative to normal colorectal tissues. DTX3 overexpression inhibited, while DTX3 knockout promoted the colony-forming capacity and proliferation of CRC cells. E2F transcription factor 1 (E2F1) is a key mediator of cell cycle progression that participates in the progression, metastasis, and chemoresistance of CRC. Further analysis revealed that DTX3 regulated the transcriptional activity of E2F1 in CRC cells. The transcription by E2F1 was significantly reduced with the increase in the cellular level of DTX3, while DTX3 knockout exerted an opposite effect. DTX3 knockout also increased the expression of E2F1 target genes involved in cell cycle progression, CDC2 and Cyclin D3, while PD 0332991, an inhibitor of E2F1 transcription, inhibited the expression of both proteins.

Conclusions

In conclusion, DTX3 regulated CRC cell growth via regulating E2F1 and its downstream genes. These findings support further exploration of DTX3 as a potential therapeutic target for CRC.