Deregulation of cyclin E meets dysfunction in p53: closing the escape hatch on breast cancer

Overexpression of CCNE1 confers a poorer prognosis in triple-negative breast cancer identified by bioinformatic analysis

Background

Triple-negative breast cancer (TNBC) is a major subtype of breast cancer. Due to the lack of effective therapeutic targets, the prognosis is poor. In order to find an effective target, despite many efforts, the molecular mechanisms of TNBC are still not well understood which remain to be a profound clinical challenge.

Methods

To identify the candidate genes in the carcinogenesis and progression of TNBC, microarray datasets GSE36693 and GSE65216 were downloaded from the Gene Expression Omnibus (GEO) database. The differentially expressed genes (DEGs) were identified, and functional and pathway enrichment analyses were performed using the Gene Ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) databases via DAVID. We constructed the protein-protein interaction network (PPI) and performed the module analysis using STRING and Cytoscape. Then, we reanalyzed the selected DEG genes, and the survival analysis was performed using cBioportal.

Results

A total of 140 DEGs were identified, consisting of 69 upregulated genes and 71 downregulated genes. Three hub genes were upregulated among the selected genes from PPI, and biological process analysis uncovered the fact that these genes were mainly enriched in p53 pathway and the pathways in cancer. Survival analysis showed that only CCNE1 may be involved in the carcinogenesis, invasion, or recurrence of TNBC. The expression levels of CCNE1 were significantly higher in TNBC cells than non-TNBC cells that were detected by qRT-PCR (P < 0.05).

Conclusion

CCNE1 could confer a poorer prognosis in TNBC identified by bioinformatic analysis and plays key roles in the progression of TNBC which may contribute potential targets for the diagnosis, treatment, and prognosis assessment of TNBC.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12957-021-02200-x.

SALL2 represses cyclins D1 and E1 expression and restrains G1/S cell cycle transition and cancer-related phenotypes

SALL2 is a poorly characterized transcription factor that belongs to the Spalt‐like family involved in development. Mutations on SALL2 have been associated with ocular coloboma and cancer. In cancers, SALL2 is deregulated and is proposed as a tumor suppressor in ovarian cancer. SALL2 has been implicated in stemness, cell death, proliferation, and quiescence. However, mechanisms underlying roles of SALL2 related to cancer remain largely unknown. Here, we investigated the role of SALL2 in cell proliferation using mouse embryo fibroblasts (MEFs) derived from Sall2^−/− mice. Compared to Sall2^+/+ MEFs, Sall2^−/− MEFs exhibit enhanced cell proliferation and faster postmitotic progression through G1 and S phases. Accordingly, Sall2^−/− MEFs exhibit higher mRNA and protein levels of cyclins D1 and E1. Chromatin immunoprecipitation and promoter reporter assays showed that SALL2 binds and represses CCND1 and CCNE1 promoters, identifying a novel mechanism by which SALL2 may control cell cycle. In addition, the analysis of tissues from Sall2^+/+ and Sall2^−/− mice confirmed the inverse correlation between expression of SALL2 and G1‐S cyclins. Consistent with an antiproliferative function of SALL2, immortalized Sall2^−/− MEFs showed enhanced growth rate, foci formation, and anchorage‐independent growth, confirming tumor suppressor properties for SALL2. Finally, cancer data analyses show negative correlations between SALL2 and G1‐S cyclins’ mRNA levels in several cancers. Altogether, our results demonstrated that SALL2 is a negative regulator of cell proliferation, an effect mediated in part by repression of G1‐S cyclins’ expression. Our results have implications for the understanding and significance of SALL2 role under physiological and pathological conditions.

Protein expression patterns of cell cycle regulators in operable breast cancer

Background-Aim

To evaluate the prognostic role of elaborate molecular clusters encompassing cyclin D1, cyclin E1, p21, p27 and p53 in the context of various breast cancer subtypes.

Methods

Cyclin E1, cyclin D1, p53, p21 and p27 were evaluated with immunohistochemistry in 1077 formalin-fixed paraffin-embedded tissues from breast cancer patients who had been treated within clinical trials. Jaccard distances were computed for the markers and the resulted matrix was used for conducting unsupervised hierarchical clustering, in order to identify distinct groups correlating with prognosis.

Results

Luminal B and triple-negative (TNBC) tumors presented with the highest and lowest levels of cyclin D1 expression, respectively. By contrast, TNBC frequently expressed Cyclin E1, whereas ER-positive tumors did not. Absence of Cyclin D1 predicted for worse OS, while absence of Cyclin E1 for poorer DFS. The expression patterns of all examined proteins yielded 3 distinct clusters; (1) Cyclin D1 and/or E1 positive with moderate p21 expression; (2) Cyclin D1 and/or E1, and p27 positive, p53 protein negative; and, (3) Cyclin D1 or E1 positive, p53 positive, p21 and p27 negative or moderately positive. The 5-year DFS rates for clusters 1, 2 and 3 were 70.0%, 79.1%, 67.4% and OS 88.4%, 90.4%, 78.9%, respectively.

Conclusions

It seems that the expression of cell cycle regulators in the absence of p53 protein is associated with favorable prognosis in operable breast cancer.

A stemness-related ZEB1-MSRB3 axis governs cellular pliancy and breast cancer genome stability

Chromosomal instability (CIN), a feature of most adult neoplasms from their early stages onward, is a driver of tumorigenesis. However, several malignancy subtypes, including some triple-negative breast cancers, display a paucity of genomic aberrations, thus suggesting that tumor development may occur in the absence of CIN. Here we show that the differentiation status of normal human mammary epithelial cells dictates cell behavior after an oncogenic event and predetermines the genetic routes toward malignancy. Whereas oncogene induction in differentiated cells induces massive DNA damage, mammary stem cells are resistant, owing to a preemptive program driven by the transcription factor ZEB1 and the methionine sulfoxide reductase MSRB3. The prevention of oncogene-induced DNA damage precludes induction of the oncosuppressive p53-dependent DNA-damage response, thereby increasing stem cells' intrinsic susceptibility to malignant transformation. In accord with this model, a subclass of breast neoplasms exhibit unique pathological features, including high ZEB1 expression, a low frequency of TP53 mutations and low CIN.

Cell Cycle Regulation in Treatment of Breast Cancer

Cell cycle progression and cell proliferation are under precise and orchestrated control in normal cells. However, uncontrolled cell proliferation caused by aberrant cell cycle progression is a crucial characteristic of cancer. Understanding cell cycle progression and its regulation sheds light on cancer treatment. Agents targeting cell cycle regulators (such as CDKs) have been considered as promising candidates in cancer treatment. Although the first-generation pan-CDK inhibitors failed in clinical trials because of their adverse events and low efficacy, new selective CDK 4/6 inhibitors showed potent efficacy with tolerable safety in preclinical and clinical studies. Here we will review the mechanisms of cell cycle regulation and targeting key cell cycle regulators (such as CDKs) in breast cancer treatment. Particularly, we will discuss the mechanism of CDK inhibitors in disrupting cell cycle progression, the use of selective CDK4/6 inhibitors in treatment of advanced, hormone receptor (HR)-positive postmenopausal breast cancer patients, and other clinical trials that aim to extend the utilization of these agents.

Why (multi)targeting of cyclin-dependent kinases is a promising therapeutic option for hormone-positive breast cancer and beyond

Estrogens, via induction of their specific receptors (e.g., ER-α), regulate cell proliferation, differentiation and morphogenesis in mammary epithelium. Cell-cycle progression is driven by activation of complexes consisting of cyclin-dependent kinases (CDKs) and cyclins, which also modulate the activity of ER-α. Loss of control over the cell-cycle results in accelerated cell division and malignant transformation. Thus, a reciprocal relation exists between estrogen signaling and cell proliferation. Based on these findings, a new concept was developed to reduce ER-α activity and bring the cell cycle in transformed cells to heel. Prevention of ER-α activation and control over the deregulated cell cycle was achieved by supplementation with pharmacological CDK inhibitors alone or in combination with selective antiestrogens.

Immunosuppressive activity of pogostone on T cells: Blocking proliferation via S phase arrest

Pogostone (PO) is one of the major chemical constituents of the essential oil of Pogostemon cablin (Blanco) Benth. In the present study, the effect of PO on T cell responsiveness was investigated to explore its potential in immunosuppression by a Concanavalin A (ConA)-stimulation model using splenocytes isolated from C57BL/6 mice. Cytotoxicity by PO on normal splenocytes was evaluated by MTS assays. Characteristics of apoptosis, proliferation, and cell cycle were analyzed by flow cytometry. Related expressions of cyclins and cyclin-dependent kinases (CDKs) were also determined by flow cytometry. Inflammatory cytokine profiling was performed emplying cytometric beads assays (CBA). Moreover, the T cell-mediated delayed Type hepersensity (DTH) model was applied to evaluate the immunosuppressive activity of PO. Neither viability reduction in normal splenocytes nor apoptosis in ConA-stimulated splenocytes was observed under PO treatments. Meanwhile, PO remarkably reduced the total population of ConA-stimulated T cell, blocked T cell proliferation induced by Con A, and inhibited the production of IFN-γ and IL-10. This blockade of stimulated T cell proliferation by PO was likely attributed to down-regulation of cyclin E, cyclin B and CDK1 and the subsequent S-phase arrest. Additionally, PO could inhibit the DTH reaction by alleviating ear swelling and inflammatory infiltrations in the DNCB-challenged ear. Taken together, PO exhibited an immunosuppressive property by directly blocking T cell proliferation as well as altering inflammatory cytokine profile, suggesting that PO may have clinical implications for treating autoimmune diseases and other immune-based disorders.

Effect of curcumin on aged Drosophila melanogaster: a pathway prediction analysis

OBJECTIVE

To re-analyze the data published in order to explore plausible biological pathways that can be used to explain the anti-aging effect of curcumin.

METHODS

Microarray data generated from other study aiming to investigate effect of curcumin on extending lifespan of Drosophila melanogaster were further used for pathway prediction analysis. The differentially expressed genes were identified by using GeneSpring GX with a criterion of 3.0-fold change. Two Cytoscape plugins including BisoGenet and molecular complex detection (MCODE) were used to establish the protein-protein interaction (PPI) network based upon differential genes in order to detect highly connected regions. The function annotation clustering tool of Database for Annotation, Visualization and Integrated Discovery (DAVID) was used for pathway analysis.

RESULTS

A total of 87 genes expressed differentially in D. melanogaster melanogaster treated with curcumin were identified, among which 50 were up-regulated significantly and 37 were remarkably down-regulated in D. melanogaster melanogaster treated with curcumin. Based upon these differential genes, PPI network was constructed with 1,082 nodes and 2,412 edges. Five highly connected regions in PPI networks were detected by MCODE algorithm, suggesting anti-aging effect of curcumin may be underlined through five different pathways including Notch signaling pathway, basal transcription factors, cell cycle regulation, ribosome, Wnt signaling pathway, and p53 pathway.

CONCLUSION

Genes and their associated pathways in D. melanogaster melanogaster treated with anti-aging agent curcumin were identified using PPI network and MCODE algorithm, suggesting that curcumin may be developed as an alternative therapeutic medicine for treating aging-associated diseases.

An integrative model links multiple inputs and signaling pathways to the onset of DNA synthesis in hepatocytes

During liver regeneration, quiescent hepatocytes re-enter the cell cycle to proliferate and compensate for lost tissue. Multiple signals including hepatocyte growth factor, epidermal growth factor, tumor necrosis factor α, interleukin-6, insulin and transforming growth factor β orchestrate these responses and are integrated during the G₁ phase of the cell cycle. To investigate how these inputs influence DNA synthesis as a measure for proliferation, we established a large-scale integrated logical model connecting multiple signaling pathways and the cell cycle. We constructed our model based upon established literature knowledge, and successively improved and validated its structure using hepatocyte-specific literature as well as experimental DNA synthesis data. Model analyses showed that activation of the mitogen-activated protein kinase and phosphatidylinositol 3-kinase pathways was sufficient and necessary for triggering DNA synthesis. In addition, we identified key species in these pathways that mediate DNA replication. Our model predicted oncogenic mutations that were compared with the COSMIC database, and proposed intervention targets to block hepatocyte growth factor-induced DNA synthesis, which we validated experimentally. Our integrative approach demonstrates that, despite the complexity and size of the underlying interlaced network, logical modeling enables an integrative understanding of signaling-controlled proliferation at the cellular level, and thus can provide intervention strategies for distinct perturbation scenarios at various regulatory levels.

Ribosomal protein L6 promotes growth and cell cycle progression through upregulating cyclin E in gastric cancer cells

Our previous study revealed that human ribosomal protein L6 (RPL6) was upregulated in multidrug-resistant gastric cancer cells and over-expression of RPL6 could protect gastric cancer cells from drug-induced apoptosis. The present study was designed to explore the role of RPL6 in tumorigenesis and development of gastric cancer. The expression of RPL6 in gastric cancer tissues and normal gastric mucosa was evaluated by immunohistochemical staining. It was found RPL6 was expressed at a higher level in gastric cancer tissues than that in normal gastric mucosa. RPL6 was then genetically overexpressed or knocked down in human immortalized gastric mucosa epithelial GES cells. It was demonstrated that upregulation of RPL6 accelerated the growth and enhanced in vitro colony forming ability of GES cells whereas downregulation of RPL6 showed adverse effects. Moreover, over-expression of RPL6 could promote G1 to S phase transition of GES cells. It was further evidenced that upregulation of RPL6 resulted in elevated cyclin E expression while downregulation of RPL6 caused decreased cyclin E expression in GES cells. Taken together, these data indicated that RPL6 was overexpressed in human gastric cancer and its over-expression could promote cell growth and cell cycle progression at least through upregulating cyclin E expression.

Coupling the cell cycle to development

The core machinery that drives the eukaryotic cell cycle has been thoroughly investigated over the course of the past three decades. It is only more recently, however, that light has been shed on the mechanisms by which elements of this core machinery are modulated to alter cell cycle progression during development. It has also become increasingly clear that, conversely, core cell cycle regulators can play a crucial role in developmental processes. Here, focusing on findings from Drosophila melanogaster and Caenorhabditis elegans, we review the importance of modulating the cell cycle during development and discuss how core cell cycle regulators participate in determining cell fates.

AZD5438, a potent oral inhibitor of cyclin-dependent kinases 1, 2, and 9, leads to pharmacodynamic changes and potent antitumor effects in human tumor xenografts

Deregulation of the cell cycle has long been recognized as an essential driver of tumorigenesis, and agents that selectively target key cell cycle components continue to hold promise as potential therapeutics. We have developed AZD5438, a 4-(1-isopropyl-2-methylimidazol-5-yl)-2-(4-methylsulphonylanilino) pyrimidine, as a potent inhibitor of cyclin-dependent kinase (cdk) 1, 2, and 9 (IC(50), 16, 6, and 20 nmol/L, respectively). In vitro, AZD5438 showed significant antiproliferative activity in human tumor cell lines (IC(50) range, 0.2-1.7 micromol/L), causing inhibition of the phosphorylation of cdk substrates pRb, nucleolin, protein phosphatase 1a, and RNA polymerase II COOH-terminal domain and blocking cell cycling at G(2)-M, S, and G(1) phases. In vivo, when orally administered at either 50 mg/kg twice daily or 75 mg/kg once daily, AZD5438 inhibited human tumor xenograft growth (maximum percentage tumor growth inhibition, range, 38-153; P < 0.05). In vivo, AZD5438 reduced the proportion of actively cycling cells. Further pharmacodynamic analysis of AZD5438-treated SW620 xenografts showed that efficacious doses of AZD5438 (>40% tumor growth inhibition) maintained suppression of biomarkers, such as phospho-pRbSer(249)/Thr(252), for up to 16 hours following a single oral dose. A comparison of different schedules indicated that chronic daily oral dosing provided optimal cover to ensure antitumor efficacy. These data indicate that broad cdk inhibition may provide an effective method to impair the dysregulated cell cycle that drives tumorigenesis and AZD5438 has the pharmacologic profile that provides an ideal probe to test this premise.

Imidazoles: SAR and development of a potent class of cyclin-dependent kinase inhibitors

An imidazole series of cyclin-dependent kinase (CDK) inhibitors has been developed. Protein inhibitor structure determination has provided an understanding of the emerging structure activity trends for the imidazole series. The introduction of a methyl sulfone at the aniline terminus led to a more orally bioavailable CDK inhibitor that was progressed into clinical development.

Zebrafish as a powerful vertebrate model system for in vivo studies of cell death

Understanding and manipulating cell death pathways are critical to our ability to treat human degenerative diseases and cancer. The zebrafish Danio rerio, a common aquatic pet, has evolved as a powerful tool for the discovery of genes regulating cellular suicide both during normal vertebrate development and after genetic or environmental insult. In this review, we describe the techniques that can be applied to studying cell death in zebrafish as well as highlighting what has been discovered so far. Finally, we discuss future perspectives in the field and how they relate to human disease.