Search

Introduction: We have previously demonstrated that RRP15 (Ribosomal RNA Processing 15 Homolog) was significantly elevated in hepatocellular carcinoma (HCC) and correlated directly with poor prognosis. RRP15 suppression curtails HCC progression through induction of cellular senescence and apoptosis. However, the impact of RRP15 on the precise therapeutic potential of lenvatinib has remained underexplored., Objective: To investigate the relationship between RRP15 expression and sensitivity of lenvatinib in HCC treatment, and also explore the potential of targeting RRP15 by lenvatinib to inhibit HCC progression., Methods: RRP15 and KBTBD8 (Kelch Repeat and BTB Domain Containing 8) expression was examined using western blot and immunohistochemistry. Cell viability, proliferation, migration and invasion as well as apoptosis were assessed using CCK-8, clonogenic assays, transwell, TUNEL (Terminal Deoxynucleotidyl Transferase mediated dUTP Nick-End Labeling) and Annexin V staining assays. The interaction between RRP15 and KBTBD8 was identified through pull-down and mass spectrometry analysis and further validated by immunofluorescence and co-immunoprecipitation assays. RRP15 ubiquitination and degradation were assessed using cycloheximide treatment, plasmid transfection and co-immunoprecipitation, followed by western blot analysis. Tail vein injection lung metastasis model was performed to determine tumor metastasis in vivo., Results: We reveled a correlation between RRP15 downregulation and enhanced sensitivity to lenvatinib, presenting marked suppression of metastasis and invasiveness. Proteomic analyses and subsequent validation disclosed the pivotal role of the E3 ubiquitin ligase KBTBD8 in mediating the ubiquitination and subsequent degradation of RRP15 protein post-lenvatinib treatment in HCC cells. KBTBD8 inhibition stalled RRP15 ubiquitination and degradation, while its overexpression accelerated these processes. Moreover, RRP15 overexpression fosters HCC cell proliferation and metastasis, a pathological effect mitigated by KBTBD8 overexpression. In vivo experiments further validate the role of lenvatinib in promoting RRP15 degradation via KBTBD8 upregulation., Conclusions: Our study elucidated a previously unidentified mechanism of lenvatinib action and identified the RRP15-KBTBD8 axis as a novel therapeutic target in HCC, offering new avenues for treatment strategies in combating HCC., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024. Published by Elsevier B.V.)

Abstract Objectives Kelch repeat and BTB domain-containing protein 8, KBTBD8, has been identified as a female fertility factor. However, there have been no reports on the role of KBTBD8 in the progression of epithelial ovarian cancer, EOC. Our study aimed to address this issue. Methods We first examine KBTBD8 expression in EOC tissues and cells. Next, we performed RNA sequencing to reveal the overall mechanism. Then we investigated the roles of KBTBD8 in the proliferation, migration, and health status of cultured EOC cells. Finally, we employed tumor xenograft models to evaluate the role of KBTBD8 in vivo. Results First, KBTBD8 level was significantly higher in EOC tissues and cells. Next, comparative RNA sequencing identified more tumorigenesis-related genes that KBTBD8 might regulate. Then we found that KBTBD8 knockdown significantly decreased EOC cell proliferation, migration, and the activities of multiple tumorigenesis-related kinases. Finally, KBTBD8 knockdown significantly diminished ovarian tumor formation in vivo. Conclusion Proper KBTBD8 level is essential for the healthy growth of ovarian somatic cells, such as ovarian epithelial cells. Excessive KBTBD8 might be a significant impetus for EOC progression. KBTBD8 reduction greatly inhibits EOC proliferation and migration.

Proteins of the BTB-kelch family are known to be involved in multiple biological processes such as migration, cytoskeleton arrangement, regulation of cell morphology, protein ubiquitination and gene expression. KBTBD8 is a new member of this family. The gene was found in a comparative transcriptome analysis of pluripotent stem cells and was therefore suggested to play a role in the regulation of pluripotency. Comparative analysis of the gene and protein sequences revealed a high conservation throughout evolution especially in the characteristic domains of BTB, BACK and kelch. We identified the Golgi apparatus as the subcellular localization of the KBTBD8 protein in non-dividing cells and could show that KBTBD8 co-localizes with α-tubulin on the spindle apparatus of mitotic cells suggesting a role in cell proliferation. In conclusion, KBTBD8 is a new member of the BTB-kelch superfamily that is located in the Golgi apparatus and translocates to the spindle apparatus during mitosis. [ABSTRACT FROM AUTHOR]

Tight control of energy metabolism is essential for normal cell function and organism survival. PKM (pyruvate kinase, muscle) isoforms 1 and 2 originate from alternative splicing of PKM pre-mRNA. They are key enzymes in oxidative phosphorylation and aerobic glycolysis, respectively, and are essential for ATP generation. The PKM1:PKM2 expression ratio changes with development and differentiation, and may also vary under metabolic stress and other conditions. Until now, there have been no reports about the function and regulation of PKM isozymes in oocytes. Here, we demonstrate that PKM1 or PKM2 depletion significantly disrupts ATP levels and mitochondrial integrity, and exacerbates free-radical generation and apoptosis in mouse oocytes. We also show that KBTBD8, a female fertility factor in the KBTBD ubiquitin ligase family, selectively regulates PKM1 levels through a signaling cascade that includes Erk1/2 and Aurora A kinases as intermediates. Finally, using RNA sequencing and protein network analysis, we identify several regulatory proteins that may be govern generation of mature PKM1 mRNA. These results suggest KBTBD8 affects PKM1 levels in oocytes via a KBTBD8→Erk1/2→Aurora A axis, and may also affect other essential processes involved in maintaining oocyte quality.