Regulation of Actinomycin D induced upregulation of Mdm2 in H1299 cells

Mechanistic Insights and Therapeutic Potentials of Ubiquitin-Proteasome System in Non-Small Cell Lung Cancer

Non-small cell lung cancer (NSCLC) remains a leading cause of cancer mortality. Despite advancements in gene targeted therapies and immunotherapies, high heterogeneity contributes to limited efficacy and therapeutic resistance. Ubiquitination, a crucial post-translational modification that regulates protein stability and degradation, plays a significant role in cancer pathogenesis by influencing key oncogenic pathways and tumour progression. This review systematically explores the ubiquitin-proteasome system (UPS) and its potential as a therapeutic target for NSCLC. We highlight recent preclinical and clinical studies focusing on ubiquitination-related biomarkers, drug targets and emerging therapies like proteasome inhibitors and Proteolysis-targeting chimeras (PROTACs). By exploring the impact of the UPS on tumour biology, the progression of NSCLC and its response to therapy, we aim to underscore the potential of targeting the ubiquitination-deubiquitination system as a complementary or synergistic approach to existing therapeutic strategies in NSCLC, thereby enhancing patient outcomes and overcoming treatment resistance.

RPL15 promotes hepatocellular carcinoma progression via regulation of RPs-MDM2-p53 signaling pathway

Backround

RPL15 has been found to participate in human tumorigenesis. However, its function and regulatory mechanism in hepatocellular carcinoma (HCC) development are still unclear. Current study investigated the effects of RPL15 in HCC.

Methods

The expression of RPL15 in clinical tissues and cell lines of HCC was detected by RT-qPCR, Western blotting, and Immunohistochemistry (IHC). Colony formation, CCK-8, flow cytometry, Wound healing and Transwell invasion assays, were used to detect the carcinoma progression of HCC cells with RPL15 overexpression or knockdown in vitro. A xenograft model was constructed to assess the effect of RPL15 knockdown on HCC cells in vivo. The expression of CDK2 and Cyclin E1 related to cell cycles, Bax and Bcl-2 related to cell apoptosis, E-cadherin, N-cadherin and Vimentin related to epithelial–mesenchymal transition (EMT), p53 and p21 related to p53 signaling pathway, were detected by Western blotting. The connection between p53, MDM2 and RPL5/11 affected by RPL15 was analyzed using immunoprecipitation and Cycloheximide (CHX) chase assay.

Results

Elevated RPL15 was identified in HCC tissues, which was not only a prediction for the poor prognosis of HCC patients, but also associated with the malignant progression of HCC. RPL15 silencing arrested HCC cell cycle, suppressed HCC cell colony formation, proliferation, invasion, and migration, and induce cell apoptosis. On the contrary, RPL15 upregulation exerted opposite effects. Results also indicated that HCC cell invasion and migration were associated with EMT, and that the RPs-MDM2-p53 pathway was implicated in RPL15-mediated oncogenic transformation. In addition, RPL15 knockdown significantly suppressed HCC xenografts growth.

Conclusions

RPL15 played crucial roles in HCC progression and metastasis, serving as a promising candidate for targeted therapies.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12935-022-02555-5.

Antitumor Activity of a 5-Hydroxy-1H-Pyrrol-2-(5H)-One-Based Synthetic Small Molecule In Vitro and In Vivo

Alternative chemo-reagents are in great demand because chemotherapy resistance is one of the major challenges in current cancer treatment. 5-hydoxy-1H-pyrrol-2-(5H)-one is an important N-heterocyclic scaffold that is present in natural products and medicinal chemistry. However, its antitumor activity has not been systematically explored. In this study, we screened a panel of 5-hydoxy-1H-pyrrol-2-(5H)-one derivatives and identified compound 1d as possessing strong anti-proliferative activity in multiple cancer cell lines. Cell cycle analysis revealed that 1d can induce S-phase cell cycle arrest and that HCT116 was sensitive to 1d-induced apoptosis. Further analysis indicated that 1d preferentially induced DNA damage and p53 activation in HCT116 cells and that 1d-induced apoptosis is partly dependent on p53. Furthermore, we showed that 1d significantly suppressed tumor growth in xenograft tumor models in vivo. Taken together, our results suggest that 5-hydoxy-1H-pyrrol-2-(5H)-one derivatives bear potential antitumor activity and that 1d is an effective agent for cancer treatment.

The ribosomal protein S26 regulates p53 activity in response to DNA damage

Ribosomal proteins have emerged as novel regulators of the Mdm2-p53 feedback loop, especially in the context of ribosomal stress. RPS26 is a recently identified Diamond-Blackfan Anemia-related ribosomal protein and its role in p53 activation has not been previously explored. In this study we found knockdown of RPS26 induced p53 stabilization and activation via a RPL11-dependent mechanism, resulting in p53-dependent cell growth inhibition. Moreover, RPS26 has the ability to interact with Mdm2 and inhibits Mdm2-mediated p53 ubiquitination that leads to p53 stabilization upon overexpression. Importantly, we discovered that RPS26 knockdown impaired p53's ability to transcriptionally activate its target genes in response to DNA damage, without affecting its stability. Accordingly, the cells lost the ability to induce G2/M cell cycle arrest. We further found that upon RPS26 knockdown, the DNA damage induced recruitment of p53 to the promoters of its target genes and p53 acetylation were both greatly reduced. In addition, RPS26 can interact with p53 independent of Mdm2 and coexist in a complex with p53 and p300. These data establish a role of RPS26 in DNA damage response by directly influencing p53 transcriptional activity, and suggest that RPS26 acts distinctively in different scenarios of p53 activation. Our finding also implicates p53 transcriptional activity control as an important mechanism of p53 regulation by ribosomal proteins.