The cell cycle is a complex process that involves DNA replication, protein expression, and cell division. Dysregulation of the cell cycle is associated with various diseases. Cyclin-dependent kinases (CDKs) and their corresponding cyclins are major proteins that regulate the cell cycle. In contrast to inhibition, a new approach called proteolysis-targeting chimeras (PROTACs) and molecular glues can eliminate both enzymatic and scaffold functions of CDKs and cyclins, achieving targeted degradation. The field of PROTACs and molecular glues has developed rapidly in recent years. In this article, we aim to summarize the latest developments of CDKs and cyclin protein degraders. The selectivity, application, validation and the current state of each CDK degrader will be overviewed. Additionally, possible methods are discussed for the development of degraders for CDK members that still lack them. Overall, this article provides a comprehensive summary of the latest advancements in CDK and cyclin protein degraders, which will be helpful for researchers working on this topic.
Humans ; Cell Cycle/physiology* ; Cell Division ; Cyclin-Dependent Kinases/metabolism* ; Cyclins/metabolism*

Cell cycle plays a crucial role in cell development. Cell cycle progression is mainly regulated by cyclin dependent kinase (CDK), cyclin and endogenous CDK inhibitor (CKI). Among these, CDK is the main cell cycle regulator, binding to cyclin to form the cyclin-CDK complex, which phosphorylates hundreds of substrates and regulates interphase and mitotic progression. Abnormal activity of various cell cycle proteins can cause uncontrolled proliferation of cancer cells, which leads to cancer development. Therefore, understanding the changes in CDK activity, cyclin-CDK assembly and the role of CDK inhibitors will help to understand the underlying regulatory processes in cell cycle progression, as well as provide a basis for the treatment of cancer and disease and the development of CDK inhibitor-based therapeutic agents. This review focuses on the key events of CDK activation or inactivation, and summarizes the regulatory processes of cyclin-CDK at specific times and locations, as well as the progress of research on relevant CDK inhibitor therapeutics in cancer and disease. The review concludes with a brief description of the current challenges of the cell cycle process, with the aim to provide scientific references and new ideas for further research on cell cycle process.
Cyclin-Dependent Kinases/metabolism* ; Cyclins/metabolism* ; Protein Serine-Threonine Kinases ; Cell Cycle Proteins/metabolism* ; Cell Cycle/physiology* ; Cyclin-Dependent Kinase 2

PURPOSE: This study was conducted to verify the induction and mechanism of selective apoptosis in G361 melanoma cells using anti-HER2 antibody-conjugated gold nanoparticles (GNP-HER2). MATERIALS AND METHODS: Following GNP-HER2 treatment of G361 cells, cell cycle arrest and apoptosis were measured by WST-1 assay, Hemacolor staining, Hoechst staining, immunofluorescence staining, fluorescence-activated cell sorting analysis, and Western blotting.
Actins ; Apoptosis Inducing Factor ; Apoptosis ; Blotting, Western ; Caspase 3 ; Caspases ; Cell Adhesion ; Cell Cycle ; Cell Cycle Checkpoints ; Cell Death ; Cyclin A ; Cyclin D1 ; Cyclin E ; Cyclins ; Cytochromes c ; Cytoplasm ; DNA Fragmentation ; Down-Regulation ; Flow Cytometry ; Fluorescent Antibody Technique ; Focal Adhesions ; Melanoma ; Mitochondria ; Nanoparticles ; Phosphotransferases ; Receptor, Epidermal Growth Factor ; Up-Regulation

After FDA approval of cetuximab at 2006, receptor tyrosine kinase, including an epidermal growth factor receptor, blocking agents have been evaluated for head and neck squamous cell carcinoma (HNSCC). Agents targeting PI3K/Akt/mTOR, IL-6/JAK/STAT3, vascular endothelial growth factor receptor, and cyclin D-CDK-4/6-INK4/Rb pathway have developed. Most of them have failed to demonstrate better treatment outcome in recurrent and/or metastatic (R/M) HNSCC than conventional chemotherapy. Since a pivotal role of PD-1/PD-L1 pathway in immunological tumor microenvironment was revealed, the immune checkpoint inhibitors, including pembrolizumab and nivolumab, have opened new paradigm of cancer treatment modality and propagates other immune-based therapies for R/M HNSCC. Various types of combination trials consisting of immunotherapy with other class of immunotherapy, targeted agents, radiation therapy, or conventional chemotherapy have been under investigation to improve treatment outcome. Biomarker studies to find an optimal candidate for the newly developed agents are accompanied. These clinical trials lead to tailored approach based on immunotherapy with precision medicine is expected to lead to promising results.
Carcinoma, Squamous Cell ; Cetuximab ; Cyclins ; Drug Therapy ; Epithelial Cells ; Head ; Immunotherapy ; Molecular Targeted Therapy ; Neck ; Precision Medicine ; Protein-Tyrosine Kinases ; Receptor, Epidermal Growth Factor ; Receptors, Vascular Endothelial Growth Factor ; Treatment Outcome ; Tumor Microenvironment

PURPOSE: To determine the possible effects of chronic exposure of low dose benzalkonium chloride (BAK) on trabecular meshwork cells, and to characterize the pathways involved in the effects. METHODS: Trabecular meshwork cells were treated with 0.0005%, 0.00075%, 0.001%, and 0.0025% BAK for 10 minutes; then, the cells were transferred to a new medium for 24 hours. This process was repeated three times. Cell survival was assessed using the MTT assay to determine the non-apoptotic BAK concentration. Senescence-associated (SA)-β-gal staining was performed to compare quantitatively the cellular senescence of BAK-treated cells with the control group. Cells treated with BAK were analyzed by western blot to determine whether the expressions of cell cycle regulators were affected. RESULTS: Two concentrations (0.0005% and 0.00075%) showed persistent cell viability and were chosen for further experiments. After SA-β-gal staining, cells treated with 0.0005% and 0.00075% BAK showed 28% (± 2.08), 37% (± 2.08) increases in cellular senescence expression, respectively, when compared with control cells (p < 0.05). To identify the molecular pathways involved in cell cycle arrest via BAK, western blot analysis was performed on trabecular meshwork cells, resulting in decreased expressions of cyclin E/CDK2, and increased expressions of the upper stream control molecules, p53 and p21. CONCLUSIONS: Chronic exposure to low dose BAK accelerated cell senescence through cell cycle arrest. Because senescent cells of the trabecular meshwork can inhibit its outflow pathway function and ultimately worsen the glaucomatous process, long-term usage of topical glaucoma medications containing BAK should be conducted with caution.
Aging ; Benzalkonium Compounds ; Blotting, Western ; Cell Aging ; Cell Cycle ; Cell Cycle Checkpoints ; Cell Survival ; Cyclins ; Glaucoma ; Rivers ; Trabecular Meshwork

Tannic acid (TA) is a water-soluble polyphenol compound found in various herbal plants. We investigated the chemopreventive effects of TA on FaDu hypopharyngeal squamous carcinoma cells. In an 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide (MTT) assay, TA showed dose-dependent cytotoxicity with a half maximal inhibitory concentration (IC50) of 50 µM. Cell cycle analysis and immunofluorescence imaging demonstrated that under low-dose (25 µM) treatment, FaDu cells were arrested in G2/M phase, and as the dose of TA was increased, apoptosis was induced with the increase of cell population at sub-G1 phase. The expressions of various cyclins, including cyclin D1 and cyclin-dependent kinases (CDK-1 and CDK-2), were down-regulated at low doses of TA, whereas apoptotic effectors such as cleaved caspase 3, cleaved caspase 7, and poly (ADP-ribose) polymerase (PARP) were expressed in a dose-dependent manner in Western blotting. In addition, TA-induced apoptosis of FaDu cells might be mediated by the extracellular signal-regulated kinase (ERK)/mitogen-activated protein kinase pathway, with the upregulation of p-AKT/p-PKB (phosphorylated protein kinase B) and p-ERK. Overall, our data support the hypothesis that TA is a potential candidate agent for the treatment of hypopharyngeal cancer.
Apoptosis ; Blotting, Western ; Carcinoma, Squamous Cell ; Caspase 3 ; Caspase 7 ; Cell Cycle ; Cyclin D1 ; Cyclin-Dependent Kinases ; Cyclins ; Epithelial Cells ; Fluorescent Antibody Technique ; Hypopharyngeal Neoplasms ; Phosphotransferases ; Protein Kinases ; Tannins ; Up-Regulation

BACKGROUND: Helicobacter pylori infection is a major risk factor in the development of gastric cancer. H. pylori infection of gastric epithelial cells increases the levels of reactive oxygen species (ROS), activates oncogenes, and leads to β-catenin-mediated hyper-proliferation. β-Carotene reduces ROS levels, inhibits oxidant-mediated activation of inflammatory signaling and exhibits anticancer properties. The present study was carried out to determine if β-carotene inhibits H. pylori-induced cell proliferation and the expression of oncogenes c-myc and cyclin E by reducing the levels of β-catenin and phosphorylated glycogen synthase kinase 3β (p-GSK3β). METHODS: Gastric epithelial AGS cells were pre-treated with β-carotene (5 and 10 μM) for 2 hours prior to H. pylori infection and cultured for 6 hours (for determination of the levels of p-GSK3β, GSK3β, and β-catenin) and 24 hours (for determination of cell viability and protein levels of c-myc and cyclin E). Cell viability was determined by the MTT assay and protein levels were determined via western blot-based analysis. RESULTS: β-Carotene inhibited H. pylori-induced increases in the percentage of viable cells, phosphorylated GSK3β (p-GSK3β), and the levels of β-catenin, c-myc and cyclin E. CONCLUSIONS: β-Carotene inhibits H. pylori-induced hyper-proliferation of gastric epithelial cells by suppressing β-catenin signaling and oncogene expression.
beta Carotene ; beta Catenin ; Cell Proliferation ; Cell Survival ; Cyclin E ; Cyclins ; Epithelial Cells ; Glycogen Synthase Kinases ; Helicobacter pylori ; Helicobacter ; Oncogenes ; Reactive Oxygen Species ; Risk Factors ; Stomach Neoplasms

BACKGROUND: 15,16-dihydrotanshinone I (DHTS) is a natural abietane diterpenoid that is mainly found in the roots of Salvia miltiorrhiza Bunge (Labiatae). DHTS exhibits a potential anti-proliferative effect in various human cancer cells. However, the mechanisms of action of DHTS as an anti-cancer agent have not been fully elucidated. Therefore, the present study investigated the anti-cancer effect of DHTS in terms of cell cycle regulation and the regulation of the AMP-activated protein kinase (AMPK)/Akt/mTOR signaling pathway in SK-HEP-1 human hepatocellular carcinoma cells. METHODS: The anti-proliferative effects of DHTS were evaluated by the sulforhodamine B assay in SK-HEP-1 cells. Cell cycle distribution was analyzed by flow cytometry. The elucidation of mechanisms of action such as the AMPK/AKT/mTOR and mitogen-activated protein kinase (MAPK) pathway was assessed by Western blot analysis. RESULTS: DHTS showed a significant anti-proliferative activity against SK-HEP-1 cells. DHTS induced cell cycle arrest in the G0/G1 phase, which was mediated by downregulation of cyclin D1, cyclin A, cyclin E, CDK4, CDK2, c-Myc and p-Rb expression and with increased expression of the CDK inhibitor p21. DHTS also activated the AMPK signaling. In addition, DHTS downregulated the Akt/mTOR and MAPK signaling pathways. CONCLUSIONS: Our results suggest that the anti-proliferative activity of DHTS might be associated with the induction of G0/G1 phase cell cycle arrest and regulation of AMPK/Akt/mTOR and MAPK signaling pathways in SK-HEP-1 cells.
AMP-Activated Protein Kinases ; Blotting, Western ; Carcinoma, Hepatocellular ; Cell Cycle Checkpoints ; Cell Cycle ; Cyclin A ; Cyclin D1 ; Cyclin E ; Cyclins ; Down-Regulation ; Flow Cytometry ; Humans ; Protein Kinases ; Salvia miltiorrhiza

Because of the unsatisfactory treatment options for breast cancer (BC), there is a need to develop novel therapeutic approaches for this malignancy. One such strategy is chemotherapy using non-toxic dietary substances and botanical products. Studies have shown that Panduratin A (PA) possesses many health benefits, including anti-inflammatory, anti-bacterial, anti-oxidant and anti-cancer activities. In the present study, we provide evidence that PA treatment of MCF-7 BC cells resulted in a time- and dose-dependent inhibition of cell growth with an IC50 of 15 µM and no to little effect on normal human MCF-10A breast cells. To define the mechanism of these anti-proliferative effects of PA, we determined its effect critical molecular events known to regulate the cell cycle and apoptotic machinery. Immunofluorescence and flow cytometric analysis of Annexin V-FITC staining provided evidence for the induction of apoptosis. PA treatment of BC cells resulted in increased activity/expression of mitochondrial cytochrome C, caspases 7, 8 and 9 with a significant increase in the Bax:Bcl-2 ratio, suggesting the involvement of a mitochondrial-dependent apoptotic pathway. Furthermore, cell cycle analysis using flow cytometry showed that PA treatment of cells resulted in G0/G1 arrest in a dose-dependent manner. Immunoblot analysis data revealed that, in MCF-7 cell lines, PA treatment resulted in the dose-dependent (i) induction of p21WAF1/Cip1 and p27Kip1, (ii) downregulation of Cyclin dependent kinase (CDK) 4 and (iii) decrease in cyclin D1. These findings suggest that PA may be an effective therapeutic agent against BC.
Apoptosis* ; Breast Neoplasms* ; Breast* ; Caspases ; Cell Cycle Checkpoints* ; Cell Cycle* ; Cell Proliferation* ; Cyclin D1 ; Cyclins ; Cytochromes c ; Down-Regulation ; Drug Therapy ; Flow Cytometry ; Fluorescent Antibody Technique ; Humans ; Inhibitory Concentration 50 ; Insurance Benefits ; MCF-7 Cells ; Phosphotransferases

A type of breast cancer with a defect in three molecular markers such as the estrogen receptor, progesterone receptor, and human epidermal growth factor receptor is called triple-negative breast cancer (TNBC). Many patients with TNBC have a lower survival rate than patients with other types due to a poor prognosis. In this study, we confirmed the anti-cancer effect of a natural compound, Gomisin G, in TNBC cancer cells. Treatment with Gomisin G suppressed the viability of two TNBC cell lines, MDA-MB-231 and MDA-MB-468 but not non-TNBC cell lines such as MCF-7, T47D, and ZR75-1. To investigate the molecular mechanism of this activity, we examined the signal transduction pathways after treatment with Gomisin G in MDA-MB-231 cells. Gomisin G did not induce apoptosis but drastically inhibited AKT phosphorylation and reduced the amount of retinoblastoma tumor suppressor protein (Rb) and phosphorylated Rb. Gomisin G induced in a proteasome-dependent manner a decrease in Cyclin D1. Consequently, Gomisin G causes cell cycle arrest in the G1 phase. In contrast, there was no significant change in T47D cells except for a mild decrease in AKT phosphorylation. These results show that Gomisin G has an anti-cancer activity by suppressing proliferation rather than inducing apoptosis in TNBC cells. Our study suggests that Gomisin G could be used as a therapeutic agent in the treatment of TNBC patients.
Apoptosis ; Breast Neoplasms ; Cell Cycle ; Cell Cycle Checkpoints ; Cell Line ; Cell Proliferation ; Cyclin D1* ; Cyclins* ; Estrogens ; G1 Phase ; Humans ; Phosphorylation* ; Prognosis ; Receptor, Epidermal Growth Factor ; Receptors, Progesterone ; Retinoblastoma ; Signal Transduction ; Survival Rate ; Triple Negative Breast Neoplasms*