Abnormal expression of CDK11p58 in prostate cancer

Mitochondrial ribosomal small subunit (MRPS) MRPS23 protein-protein interaction reveals phosphorylation by CDK11-p58 affecting cell proliferation and knockdown of MRPS23 sensitizes breast cancer cells to CDK1 inhibitors

BACKGROUND

Post-translational modification of some mitoribosomal proteins has been found to regulate their functions. MRPS23 has been reported to be overexpressed in various cancers and has been predicted to be involved in increased cell proliferation. Furthermore, MRPS23 is a driver of luminal subtype breast cancer. However, its exact role and function in cancer remains unknown. METHODS AND RESULTS: Our previous study identified protein-protein interactions involving MRPS23 and CDK11A. In this study, we confirmed the interaction of MRPS23 with the p110 and p58 isoforms of CDK11A. Phosphoprotein enrichment studies and in vitro kinase assay using CDK11A/cyclin D3 followed by MALDI-ToF/ToF analysis confirmed the phosphorylation of MRPS23 at N-terminal serine 11 residue. Breast cancer cells expressing the MRPS23 (S11G) mutant showed increased cell proliferation, increased expression of PI3-AKT pathway proteins [p-AKT (Ser47), p-AKT (Thr308), p-PDK (Ser241) and p-GSK-3β (Ser9)] and increased antiapoptotic pathway protein expression [Bcl-2, Bcl-xL, p-Bcl2 (Ser70) and MCL-1] when compared with the MRPS23 (S11A) mutant-overexpressing cells. This finding indicated the role of MRPS23 phosphorylation in the proliferation and survival of breast cancer cells. The correlation of inconsistent MRPS23 phosphoserine 11 protein expression with CDK11A in the breast cancer cells suggested phosphorylation by other kinases. In vitro kinase assay showed that CDK1 kinase also phosphorylated MRPS23 and that inhibition using CDK1 inhibitors lowered phospho-MRPS23 (Ser11) levels. Additionally, modulating the expression of MRPS23 altered the sensitivity of the cells to CDK1 inhibitors.

CONCLUSION

In conclusion, phosphorylation of MRPS23 by mitotic kinases might potentially be involved in the proliferation of breast cancer cells. Furthermore, MRPS23 can be targeted for sensitizing the breast cancer cells to CDK1 inhibitors.

Casein kinase II activates Bik to induce death of hyperplastic mucous cells in a cell cycle-dependent manner

Extensive inflammation causes epithelial cell hyperplasia in the airways and Bcl-2-interacting killer (Bik) reduces epithelial cell and mucous cell hyperplasia without affecting resting cells to restore homeostasis. These observations suggest that Bik induces apoptosis in a cell cycle-specific manner, but the mechanisms are not understood. Mice were exposed to an allergen for 3, 14, or 30 days and Bik expression was induced in airway epithelia of transgenic mice. Bik reduced epithelial and mucous cell hyperplasia when mice were exposed to an allergen for 3 or 14 days, but not when exposure lasted for 30 days, and Ki67-positivity was reduced. In culture, Bik expression killed proliferating cells but not quiescent cells. To capture the stage of the cell cycle when Bik induces cell death, airway cells that express fluorescent ubiquitin cell cycle indicators were generated that fluoresce red or green during the G0/G1 and S/G2/M phases of the cells cycle, respectively. Regardless of the cell cycle stage, Bik expression eliminated green-fluorescent cells. Also, Bik, when tagged with a blue-fluorescent protein, was only detected in green cells. Bik phosphorylation mutants at threonine 33 or serine 35 demonstrated that phosphorylation activated Bik to induce death even in quiescent cells. Immunoprecipitation and proteomic approaches identified casein kinase IIα to be responsible for phosphorylating and activating Bik to kill cells in S/G2/M. As casein kinase 2 alpha (CKIIα) is expressed only during the G2/M phase, we conclude that Bik activation in airway epithelial cells selectively targets hyperplastic epithelial cells, while leaving resting airway cells unaffected.

MiR-129-5p/DLX1 signalling axis mediates functions of prostate cancer during malignant progression

We mainly corroborated the potential mechanism of DLX1 and miR-129-5p in prostate cancer cells. DLX1 was upregulated in cancer cells according to qRT-PCR assay. We evaluated the functional changes of the transfected cells via Transwell assay, CCK-8 assay and wound healing assay. DLX1 was confirmed as a cancer promoter. In addition, qRT-PCR showed down-regulated miR-129-5p expression in prostate cancer. We further used dual-luciferase reporter detection to elucidate the targeting between these two genes. The inhibition of miR-129-5p on tumour was verified. Besides, co-transfection of oe-DLX1 and miR-129-5p mimics attenuated this inhibition. These data demonstrated functions of DLX1/miR-129-5p axis in prostate cancer: miR-129-5p hindered the biological functions of cancer cells via inhibiting DLX1 expression. We provide a novel biomarker for prostate cancer.

MiR-139-5p/SLC7A11 inhibits the proliferation, invasion and metastasis of pancreatic carcinoma via PI3K/Akt signaling pathway

OBJECTIVE

Pancreatic carcinoma (PANC) is one of the important aggressive cancers, with deficiency in effective therapeutics. The study aimed to investigate the effects and molecular mechanism of miR-139-5p/SLC7A11 on the proliferation and metastasis of PANC.

METHODS

Bioinformatics was used to analyze the differentially expressed genes in the TCGA database. PANC cell lines with overexpressed miR-139-5p and Solute Carrier Family 7, Member 11 (SLC7A11) was established, and have been used to detect cell proliferation, invasion and metastasis of PANC Subsequently, bioinformatic analysis and dual luciferase reporter assay were performed to confirm that SLC7A11 was a target gene of miR-139-5p. Xenograft mice model was used to explore the functions of miR-139-5p in PANC tumorigenicity.

RESULTS

MiR-139-5p could regulate and affect the protein expression of P13K and Akt associated with phosphatidylinositol signaling pathway by inhibiting SLC7A11. MiR-139-5p was found to be lowly expressed in PANC tissues, while SLC7A11 was highly expressed. Low expression of miR-139-5p and high expression of SLC7A11 were positively associated with poor clinical outcomes. PANC cell proliferation, invasion and metastasis could be inhibited by miR-139-5p overexpression and be promoted by SLC7A11 overexpression. MiR-139-5p overexpression could suppress PANC tumor growth and the expressions of SLC7A11, p-PI3K, p-Akt in tumor tissues. Therefore, the inhibitory of miR-139-5p to PANC cell proliferation, invasion and metastasis was partly due to its inhibiting effect on SLC7A11 expression.

CONCLUSION

Our study proves that miR-139-5p/SLC7A11 has important functions on PANC, suggesting that miR-139-5p can be used as a biomarker for PANC patients.

CDK11 is required for transcription of replication-dependent histone genes

Replication-dependent histones (RDH) are required for packaging of newly synthetized DNA into nucleosomes during S-phase when their expression is highly upregulated. However, the mechanisms of this upregulation in metazoan cells remain poorly understood. Using iCLIP and ChIP-seq, we found that human cyclin-dependent kinase 11 (CDK11) associates with RNA and chromatin of RDH genes primarily in the S-phase. Moreover, its N-terminal region binds FLASH, RDH-specific 3´end processing factor, which keeps the kinase on the chromatin. CDK11 phosphorylates serine 2 (Ser2) of the C-terminal domain (CTD) of RNA polymerase II (RNAPII), which is initiated at the middle of RDH genes and is required for further RNAPII elongation and 3´end processing. CDK11 depletion leads to decreased number of cells in S-phase, likely due to the function of CDK11 in RDH gene expression. Thus, the reliance of RDH expression on CDK11 could explain why CDK11 is essential for growth of many cancers.

MiR-139-5p is associated with poor prognosis and regulates glycolysis by repressing PKM2 in gallbladder carcinoma

OBJECTIVES

Gallbladder carcinoma (GBC) is the most highly aggressive cancer of biliary tract, but effective therapeutics are lacking. Emerging evidence has unveiled that miR-139-5p is aberrantly downregulated in cancers, including GBC. However, the functions and mechanisms of miR-139-5p in GBC remain unclear.

MATERIALS AND METHODS

MiR-139-5p-overexpression was established in GBC cell lines, after which cell proliferation, migration, invasion, colony formation, and glucose metabolism were assayed in vitro. Subsequently, bioinformatics prediction and dual-luciferase reporter were performed to confirm that pyruvate kinase M2 (PKM2) was a direct target of miRNA-139-5p. Xenograft mouse models were applied to investigate the role of miR-139-5p in GBC tumourigenicity in vivo. In situ hybridization and immunohistochemical assays were performed to determine the relationships among miR-139-5p, PKM2 expression and clinical malignancies in GBC samples.

RESULTS

We found that miR-139-5p was substantially downregulated in GBC tissues. Low expression of miR-139-5p was significantly associated with poor clinical outcomes. GBC cell proliferation, migration, and invasion could be inhibited by overexpression of miR-139-5p either in vitro or in vivo. In addition, miR-139-5p overexpression could directly inhibit PKM2 expression and lead to suppression of glucose consumption, lactate production, and cellular ATP levels. Moreover, PKM2 was frequently upregulated in GBC and correlated with poor prognosis. Mechanistically, miRNA-139-5p inhibited cell proliferation, migration, and glycolysis in GBC, at least in part, by repressing PKM2.

CONCLUSIONS

These results demonstrated a novel role for miR-139-5p/PKM2 in GBC progression and provided potential prognostic predictors for GBC patients.

GADD45α and γ interaction with CDK11p58 regulates SPDEF protein stability and SPDEF-mediated effects on cancer cell migration

The epithelium-specific Ets transcription factor, SPDEF, plays a critical role in metastasis of prostate and breast cancer cells. While enhanced SPDEF expression blocks migration and invasion, knockdown of SPDEF expression enhances migration, invasion, and metastasis of cancer cells. SPDEF expression and activation is tightly regulated in cancer cells; however, the precise mechanism of SPDEF regulation has not been explored in detail. In this study we provide evidence that the cell cycle kinase CDK11p58, a protein involved in G2/M transition and degradation of several transcription factors, directly interacts with and phosphorylates SPDEF on serine residues, leading to subsequent ubiquitination and degradation of SPDEF through the proteasome pathway. As a consequence of CDK11p58 mediated degradation of SPDEF, this loss of SPDEF protein results in increased prostate cancer cell migration and invasion. In contrast, knockdown of CDK11p58 protein expression by interfering RNA or SPDEF overexpression inhibit migration and invasion of cancer cells. We demonstrate that CDK11p58 mediated degradation of SPDEF is attenuated by Growth Arrest and DNA damage-inducible 45 (GADD45) α and, two proteins inducing G2/M cell cycle arrest. We show that GADD45 α and γ, directly interact with CDK11p58 and thereby inhibit CDK11p58 activity, and consequentially SPDEF phosphorylation and degradation, ultimately reducing prostate cancer cell migration and invasion. Our findings provide new mechanistic insights into the complex regulation of SPDEF activity linked to cancer metastasis and characterize a previously unidentified SPDEF/CDK11p58/GADD45α/γ pathway that controls SPDEF protein stability and SPDEF-mediated effects on cancer cell migration and invasion.

Kinases Involved in Both Autophagy and Mitosis

Both mitosis and autophagy are highly regulated dynamic cellular processes and involve various phosphorylation events catalysed by kinases, which play vital roles in almost all physiological and pathological conditions. Mitosis is a key event during the cell cycle, in which the cell divides into two daughter cells. Autophagy is a process in which the cell digests its own cellular contents. Although autophagy regulation has mainly been studied in asynchronous cells, increasing evidence indicates that autophagy is in fact tightly regulated in mitosis. Here in this review, we will discuss kinases that were originally identified to be involved in only one of either mitosis or autophagy, but were later found to participate in both processes, such as CDKs (cyclin-dependent kinases), Aurora kinases, PLK-1 (polo-like kinase 1), BUB1 (budding uninhibited by benzimidazoles 1), MAPKs (mitogen-activated protein kinases), mTORC1 (mechanistic target of rapamycin complex 1), AMPK (AMP-activated protein kinase), PI3K (phosphoinositide-3 kinase) and protein kinase B (AKT). By focusing on kinases involved in both autophagy and mitosis, we will get a more comprehensive understanding about the reciprocal regulation between the two key cellular events, which will also shed light on their related therapeutic investigations.

Critical role of CDK11(p58) in human breast cancer growth and angiogenesis

Background

A capillary network is needed in cancer growth and metastasis. Induction of angiogenesis represents one of the major hallmarks of cancer. CDK11^p58, a Ser/Thr kinase that belongs to the Cell Division Cycle 2-like 1 (CDC2L1) subfamily is associated with cell cycle progression, tumorigenesis, sister chromatid cohesion and apoptotic signaling. However, its role in breast cancer proliferation and angiogenesis remains unclear.

Methods

Tumorigenicity assays and blood vessel assessment in athymic mice were used to assess the function of CDK11^p58 in tumor proliferation and angiogenesis. CCK-8 assay was used to detect breast cancer cell growth. Immunohistochemistry was used to detect the expression of vascular endothelial growth factor (VEGF), CD31 and CD34 in CDK11 positive patient breast cancer tissues. Dual-Luciferase array was used to analyze the function of CDK11^p58 in the regulation of VEGF promoter activity. Western blot was used to detect related protein expression levels.

Results

CDK11^p58 inhibited breast cancer growth and angiogenesis in breast cancer cells and in nude mice transplanted with tumors. Immunohistochemistry confirmed that CDK11^p58 was negatively associated with angiogenesis-related proteins such as VEGF, CD31 and CD34 in breast cancer patients. Real-time PCR and dual-luciferase assay showed CDK11^p58 inhibited the mRNA levels of VEGF and the promoter activity of VEGF. As CDK11^p58 is a Ser/Thr kinase, the kinase-dead mutant failed to inhibit VEGF mRNA and promoter activity. Western blot analysis showed the same pattern of related protein expression. The data suggested angiogenesis inhibition was dependent on CDK11^p58 kinase activity.

Conclusion

This study indicates that CDK11^p58 inhibits the growth and angiogenesis of breast cancer dependent on its kinase activity.

Electronic supplementary material

The online version of this article (doi:10.1186/s12885-015-1698-7) contains supplementary material, which is available to authorized users.

Hepsin inhibits CDK11p58 IRES activity by suppressing unr expression and eIF-2α phosphorylation in prostate cancer

Hepsin is a type II transmembrane serine protease frequently overexpressed in prostate cancer (PCa). However, the role of hepsin in PCa remains unclear. In this study, we found that hepsin inhibited the internal ribosome entry site (IRES) activity and expression of CDK11p58, which is associated with cell cycle progression and pro-apoptotic signaling in PCa. Hepsin suppressed CDK11p58 IRES activity in PCa by modulating unr expression and eIF-2α phosphorylation. Further studies revealed that hepsin inhibited the expression of unr by directly binding to unr IRES element and suppressing its activity, and also repressed eIF-2α phosphorylation through down-regulating the expression and phosphorylation of general control non-derepressible-2 (GCN2). Taken together, our data suggest a novel role of hepsin in regulating CDK11p58 IRES activity, and imply that hepsin may act on the machinery of translation to modulate cell cycle progression and survival in PCa cells.