Cancer is characterized by abnormal cell proliferation. Cyclins and cyclin-dependent kinases (CDKs) have been recognized as essential regulators of the intricate cell cycle, orchestrating DNA replication and transcription, RNA splicing, and protein synthesis. Dysregulation of the CDK pathway is prevalent in the development and progression of human cancers, rendering cyclins and CDKs attractive therapeutic targets. Several CDK4/6 inhibitors have demonstrated promising anti-cancer efficacy and have been successfully translated into clinical use, fueling the development of CDK-targeted therapies. With this enthusiasm for finding novel CDK-targeting anti-cancer agents, there have also been exciting advances in the field of targeted protein degradation through innovative strategies, such as using proteolysis-targeting chimera, heat shock protein 90 (HSP90)‍-mediated targeting chimera, hydrophobic tag-based protein degradation, and molecular glue. With a focus on the translational potential of cyclin- and CDK-targeting strategies in cancer, this review presents the fundamental roles of cyclins and CDKs in cancer. Furthermore, it summarizes current strategies for the proteasome-dependent targeted degradation of cyclins and CDKs, detailing the underlying mechanisms of action for each approach. A comprehensive overview of the structure and activity of existing CDK degraders is also provided. By examining the structure‍‒‍activity relationships, target profiles, and biological effects of reported cyclin/CDK degraders, this review provides a valuable reference for both CDK pathway-targeted biomedical research and cancer therapeutics.
Humans ; Neoplasms/metabolism* ; Cyclin-Dependent Kinases/antagonists & inhibitors* ; Cyclins/metabolism* ; Proteolysis ; Antineoplastic Agents/pharmacology* ; Molecular Targeted Therapy ; Proteasome Endopeptidase Complex/metabolism* ; Animals

Multiple myeloma (MM) is a common plasma cell malignancy, accounting for the second largest hematological malignancy. Proteasome inhibitors represented by bortezomib (BTZ) have been the main treatment for patients with newly diagnosed and relapsed or refractory myeloma in nearly two decades. Although BTZ has improved the prognosis of MM patients, MM remains incurable in most patients, mainly because MM cells become resistant to BTZ. This review is to better understand the mechanism of MM resistance to BTZ and explore possible new therapeutic strategies.
Humans ; Bortezomib/therapeutic use* ; Multiple Myeloma/pathology* ; Proteasome Inhibitors/pharmacology* ; Prognosis ; Plasma Cells/pathology* ; Drug Resistance, Neoplasm ; Antineoplastic Agents/pharmacology* ; Cell Line, Tumor

OBJECTIVE: To explore the mechanism of proteasome inhibitor MG132 in improving osteoporosis. METHODS: Total of 32 female SD rats, weighing 220 to 250 g and 8 weeks old, were selected. They were randomly divided into 4 groups(n=8). Rats of group A and group B were cut off ovaris on both sides to make model of osteoporosis, and then they were given proteasome inhibitors MG132 and dimethyl sufoxide (DMSO) respectively. Group C was a sham group and rats were given MG132. Group D was a normal group and rats were given MG132 too. The rats were killed in batches at 6 and 12 weeks after administration, and the femoral neck tissues were obtained. Relevant data were analyzed, such as pathomorphological observation, micro-CT analysis, detection of 20S proteasome activity in tissues, and expression of Wnt and β-catenin. RESULTS: Morphological observation showed that the trabecular were slightly thinner, reticulated, and occasionally interrupted in group A, while the trabecular were obviously thinner and discontinuous in group B. And the trabecular were intact and arranged reticulated in group C and D. The analysis results of bone mineral density(BMD), bone surface(BS), bone volume/total volume(BV/TV) and trabecular thickness(Tb.Th) showed that group B was worse than other groups in all parameters at different time points(P<0.05), and group A was worse than group C and group D in BS(P<0.05), there was no significant difference in all parameters between group C and group D. RFU value of 20S proteasome in group B was significantly higher than that in other groups(P<0.05). According to the results of Western blot, the gray values of Wnt protein and β-catenin protein in group A were significantly higher than those in other groups (P<0.05). CONCLUSION MG-132, a ubiquitin proteasome inhibitor, can regulate Wnt/β-catenin signaling pathway by inhibiting the degradation of β-catenin protein, and delaying the occurrence and development of osteoporosis.
Animals ; Bone Density ; Female ; Leupeptins ; Osteoporosis/drug therapy* ; Proteasome Inhibitors/pharmacology* ; Rats ; Rats, Sprague-Dawley ; Wnt Signaling Pathway ; beta Catenin/metabolism*

Objective To investigate the role of proteasome inhibitor bortezomib (BTZ) in inflammatory response in abdominal aortic aneurysm (AAA) formation induced by angiotensin Ⅱ (Ang Ⅱ). Methods Ang Ⅱ-induced ApoEmice AAA models were established. Forty male ApoEmice (8-10-week-old) were randomly and equally divided into four groups:Sham group,BTZ group,Ang Ⅱ group,and Ang Ⅱ+BTZ group.HE staining,immunohistochemical staining,and flow cytometry were used to analyze the inflammatory response. Real-time quantitative polymerase chain reaction (qPCR) was used to analyze the mRNA expression of intercellular cell adhesion molecule-1 (ICAM-1). Western blotting was used to analyze the activation of nuclear factor κB signaling (NF-κB). Results The mean maximum suprarenal aortic diameter (Dmax) of Sham group,BTZ group,Ang Ⅱ group,and Ang Ⅱ+BTZ group were (1.00±0.01),(0.99±0.01),(1.50±0.13),and (1.20±0.04)mm,respectively (F=8.959,P=0.000). The Dmax of Ang Ⅱ group was significantly larger than those of Sham group (P=0.000) and Ang Ⅱ+BTZ group (P=0.015). The incidence of AAA in Ang Ⅱ group,Ang Ⅱ+BTZ group,and Sham group were 60%,17%,and 0,respectively. HE staining revealed that the abdominal aortic wall thickening was more severe in Ang Ⅱ group than in Sham group and Ang Ⅱ+BTZ group,similar with the infiltration of inflammatory cells. Immunohistochemical staining demonstrated that the CD3T lymphocyte count was significantly higher in Ang Ⅱ group than in Sham group (107.9±15.9 vs. 0,P=0.000) and Ang Ⅱ+BTZ group (107.9±15.9 vs. 0.8±0.5,P=0.000). Flow cytometry also demonstrated that the proportion of the CD3T lymphocytes of the Ang Ⅱ group [(13.50±0.69)%] was significantly higher than that in the Ang Ⅱ+BTZ group [(10.40±0.78)%] at week 1 (t=3.009,P=0.040),and the proportion of the CD3T lymphocytes of the Ang Ⅱ group [(22.70±0.93)%] was significantly higher than that in the Ang Ⅱ+BTZ group [(15.10±0.97)%] at week 4 (t=5.654,P=0.005). The qPCR analysis showed that the mRNA expression of ICAM-1 was significantly up-regulated in Ang Ⅱ group than in Sham group (1.93±0.54 vs. 1.00±0.15,P=0.011) and Ang Ⅱ+BTZ group (1.93±0.54 vs. 0.83±0.08,P=0.009). Western blot analysis showed a lower phosphorylation level of inhibitor of NF-κB in the Ang Ⅱ group compared with the Sham group or Ang Ⅱ+BTZ group,accompanied with an increased phosphorylation level of p65. Conclusion Proteasome inhibitor BTZ can attenuate AAA formation partially by regulating T lymphocytes infiltration through regulating the mRNA expression of ICAM-1 regulated by the activation of NF-κB signaling pathway.
Angiotensin II ; adverse effects ; Animals ; Aortic Aneurysm, Abdominal ; chemically induced ; drug therapy ; Apolipoproteins E ; genetics ; Bortezomib ; pharmacology ; Intercellular Adhesion Molecule-1 ; metabolism ; Male ; Mice ; Mice, Inbred C57BL ; Mice, Knockout ; NF-kappa B ; metabolism ; Phosphorylation ; Proteasome Inhibitors ; pharmacology ; Random Allocation ; Signal Transduction ; T-Lymphocytes ; cytology

PURPOSE: Although the proteasome inhibitor known as bortezomib can modulate the inflammatory process through the nuclear factor-kappa B signaling pathway, the immunomodulatory effect of pre-incubated bortezomib has not been fully evaluated for inflammation by infectious agents. Therefore, we evaluated the effect of bortezomib on the expression of inflammatory cytokines and mediators in macrophage cell lines and on survival in a murine peritonitis sepsis model. MATERIALS AND METHODS: Bortezomib was applied 1 hr before lipopolysaccharide (LPS) stimulation in RAW 264.7 cells. The cecal ligation and puncture (CLP) experiments were performed in C57BL/6J mice. RESULTS: Pre-incubation with bortezomib (25 nM or 50 nM) prior to LPS (50 ng/mL or 100 ng/mL) stimulation significantly recovered the number of viable RAW 264.7 cells compared to those samples without pre-incubation. Bortezomib decreased various inflammatory cytokines as well as nitric oxide production in LPS-stimulated cells. The 7-day survival rate in mice that had received bortezomib at 0.01 mg/kg concentration 1 hr prior to CLP was significantly higher than in the mice that had only received a normal saline solution of 1 mL 1 hr prior to CLP. In addition, the administration of bortezomib at 0.01 mg/kg concentration 1 hr before CLP resulted in a significant decrease in inflammation of the lung parenchyma. Collectively, pretreatment with bortezomib showed an increase in the survival rate and changes in the levels of inflammatory mediators. CONCLUSION: These results support the possibility of pretreatment with bortezomib as a new therapeutic target for the treatment of overwhelming inflammation, which is a characteristic of severe sepsis.
Animals ; Boronic Acids/administration & dosage/pharmacology/*therapeutic use ; Cecum/*pathology ; Cell Adhesion Molecules/metabolism ; Cell Line ; Cell Proliferation/drug effects ; Cell Survival/drug effects ; Chymotrypsin/metabolism ; Cytokines/*metabolism ; Disease Models, Animal ; Inflammation Mediators/*metabolism ; Ligation ; Lipopolysaccharides/pharmacology ; Lung/drug effects/metabolism/pathology ; Male ; Mice, Inbred C57BL ; Nitric Oxide/metabolism ; Proteasome Inhibitors/pharmacology ; Punctures ; Pyrazines/administration & dosage/pharmacology/*therapeutic use ; Sepsis/*drug therapy

PURPOSE: To investigate the effects of resveratrol on the expression of hypoxia-inducible factor 1alpha (HIF-1alpha) and vascular endothelial growth factor (VEGF) in human adult retinal pigment epithelial (ARPE-19) cells, and on experimental choroidal neovascularization (CNV) in mice. MATERIALS AND METHODS: ARPE-19 cells were treated with different concentrations of resveratrol and then incubated under hypoxic conditions with subsequent evaluation of cell viability, expression of HIF-1alpha, and expression of VEGF. The effects of resveratrol on the synthesis and degradation of hypoxia-induced HIF-1alpha were evaluated using inhibitors of the PI3K/Akt/mTOR and the ubiquitin proteasome pathways. In animal studies, CNV lesions were induced in C57BL/6 mice by laser photocoagulation. After 7 days of oral administration of resveratrol or vehicle, which began one day after CNV induction, image analysis was used to measure CNV areas on choroidal flat mounts stained with isolectin IB4. RESULTS: In ARPE-19 cells, resveratrol significantly inhibited HIF-1alpha and VEGF in a dose-dependent manner, by blocking the PI3K/Akt/mTOR signaling pathway and by promoting proteasomal HIF-1alpha degradation. In mice experiments, orally administered resveratrol significantly inhibited CNV growth in a dose-dependent manner. CONCLUSION: Resveratrol may have therapeutic value in the management of diseases involving pathological neovascularization.
Adult ; Animals ; Anoxia/metabolism/physiopathology ; Cell Survival/drug effects ; Choroidal Neovascularization/*metabolism/pathology ; Humans ; Hypoxia-Inducible Factor 1, alpha Subunit/*drug effects/metabolism ; Mice ; Mice, Inbred C57BL ; Phosphatidylinositol 3-Kinases/antagonists & inhibitors/*physiology ; Proteasome Endopeptidase Complex ; Proto-Oncogene Proteins c-akt/antagonists & inhibitors/*physiology ; Retinal Pigment Epithelium/*drug effects/metabolism ; Signal Transduction ; Stilbenes/administration & dosage/*pharmacology ; TOR Serine-Threonine Kinases/antagonists & inhibitors/*physiology ; Ubiquitin ; Vascular Endothelial Growth Factor A/*drug effects/metabolism

Hypoxia-inducible factor 1alpha (HIF-1alpha), which transactivates a variety of hypoxia-induced genes, is rapidly degraded under nomoxia through the hydroxylation-ubiquitination-proteasome pathway. In this study, we addressed how HIF-1alpha is stabilized by proteasome inhibitors. The ubiquitin pool was rapidly reduced after proteasome inhibition, followed by the accumulation of non-ubiquitinated HIF-1alpha. The poly-ubiquitination of HIF-1alpha was resumed by restoration of free ubiquitin, which suggests that the HIF-1alpha stabilization under proteasome inhibition is attributed to depletion of the free ubiquitin pool. Ni2+ and Zn2+ also stabilized HIF-1alpha with depletion of the free ubiquitin pool and these effects of metal ions were attenuated by restoration of free ubiquitin. Ni2+ and Zn2+ may disturb the recycling of free ubiquitin, as MG132 does. Based on these results, the state of the ubiquitin pool seems to be another critical factor determining the cellular level of HIF-1alpha.
Cell Hypoxia/physiology ; Cell Line, Tumor ; HCT116 Cells ; HEK293 Cells ; Humans ; Hypoxia-Inducible Factor 1, alpha Subunit/biosynthesis/*metabolism ; Leupeptins/pharmacology ; Nickel/chemistry ; Proteasome Endopeptidase Complex/*metabolism ; Proteasome Inhibitors/*pharmacology ; Ubiquitin/*metabolism ; Ubiquitination/*physiology ; Up-Regulation ; Zinc/chemistry

This study was aimed to elucidate the expression of costimulatory molecule CD80 and CD86 in HL-60 cells induced by proteasome inhibitor MG132 and its effect on allogeneic mixed lymphocyte reaction. Acute myelocytic leukemia cell line HL-60 and chronic myelocytic leukemia cell line K562 were cultured. The viability of the cells was measured by flow cytometry. Proteasome inhibitor MG132 at the concentrations of 2 or 3 µmol/L was used to stimulate the HL-60 cell cultured for 24 h and 48 h respectively, and the Annexin V/7-AAD staining and flow cytomotry were used to detect the apoptosis of the HL-60 cells. HL-60 and K562 cells were treated with 1 µmol/L MG132 for 24 h and 48 h respectively, then CD80 and CD86 antibodies were added, finally the expression of CD80 and CD86 was analysed by flow cytomery. The mRNA expression of CD86 in the HL-60 cells treated with 1 µmol/L MG132 was detected by RT-PCR. HL-60 and K562 cells were treated by 1 µmol/L MG132 and then underwent irradiation of 75 Gy (60)Co to kill the cells with their antigenicity preserved. Peripheral blood mononuclear cells (PBMNCs) of healthy volunteers, as reactive cells, were isolated and inoculated into the (60)Co irradiated HL-60 cells of different concentrations, as stimulating cells, CCK-8 was added and then the A value of absorbance was measured at the wave length of 450 nm in an enzyme labeling instrument. The results showed that the cell viability of the HL-60 cells treated with 1 µmol/L MG132 for 24 h an d 48 h was 92.95% and 85.87% respectively. The apoptotic rates of the HL-60 cells treated with MG132 increased in dose-and time-dependent manner. High-concentration of MG132 directly killed HL-60 cells. Before MG132 treatment K562 cells did not express CD86, but the CD86 expression of the HL-60 cells was up-regulated time-dependently after MG132 treatment (P < 0.01). The mRNA expression of CD86 in the HL-60 treated with MG132 was up-regulated time-dependently (P < 0.01). CCK-8 test showed that the proliferation level of PBMNC gradually increased along with the concentration of HL-60 cells treated with MG132 and reached its peak when the concentration of the HL-60 cells was 1×10(5) (P < 0.01). No remarkable proliferation of PBMNC was observed in the K562 groups no matter if the HL-60 cells had been treated with MG132. It is concluded that the high concentration of MG132 can directly kill HL-60 cells, low-concentration of MG132 can induce the expression of costimulatory molecule CD86 in HL-60 cells, also can improve the proliferation of PBMNC.
Apoptosis ; B7-2 Antigen ; immunology ; Cell Survival ; Flow Cytometry ; HL-60 Cells ; Humans ; K562 Cells ; Leukocytes, Mononuclear ; drug effects ; Leupeptins ; pharmacology ; Lymphocyte Culture Test, Mixed ; Proteasome Inhibitors ; pharmacology ; Reverse Transcriptase Polymerase Chain Reaction ; Up-Regulation

OBJECTIVETo investigate the effect of nuclear transcription factor RelB on the proteasome inhibitor-sensitivity of chronic lymphocytic leukemia (CLL) cells.

METHODSThe mRNA expression of RelB in CD5⁺ CD19⁺ CLL cells from BM was analyzed by reverse transcription PCR (RT-PCR). The RelB activity was examined by electromobility shift assay (EMSA) and an ELISA-based NF-κB family transcription factor activity assay. CLL cells were classified into RelB+ and RelB- groups according to RelB activity. The frequencies of cell death of CLL cells cultured with human bone marrow stromal cells (hBMSCs) after treatment with PS-341, MG-132 or fludarabine were determined by PI staining.

RESULTSRelB mRNA expression and RelB activity could be detected in CLL cells at variable levels. Fludarabine (10 μmol/L), MG-132 (1 μmol/L) and PS-341 (1 μmol/L) could induce cell death of RelB+ and RelB- CLL cells co-cultured with hBMSCs in a time dependent manner. There was no significant difference in the fludarabine sensitivity between RelB+ and RelB- CLL cells, and the frequencies of cell death of RelB+ and RelB- CLL cells were (61.11 ± 6.91)% and (67.57 ± 9.45)%, respectively, when treated with fludarabine for 72 h. RelB+ CLL cells were more sensitive to MG-132 than RelB- CLL cells for 72 h, and the frequencies of cell death were (66.22 ± 3.39)% and (51.07 ± 5.93)%, respectively. RelB+ CLL cells were more sensitive to PS-341 than RelB- CLL cells for 24 and 48 h treatment, and the frequencies of cell death of RelB+ and RelB- CLL cells were (75.50 ± 4.66)% and (66.32 ± 10.20)% for 24 h, (92.11 ± 3.14)% and (85.84 ± 5.81)% for 48 h treatment, respectively.

CONCLUSIONThe alternative NF-κB activity was detected in bone marrow derived CLL cells. Enhancement of RelB activity may increase CLL cells' sensitivity to proteasome inhibitor bortezomib and MG-132. However, the sensitivity of CLL cells to fludarabine had no relationship to RelB activity.

Cell Death ; drug effects ; Drug Resistance, Neoplasm ; Humans ; Leukemia, Lymphocytic, Chronic, B-Cell ; metabolism ; pathology ; NF-kappa B ; metabolism ; Proteasome Inhibitors ; pharmacology ; RNA, Messenger ; genetics ; Transcription Factor RelB ; genetics ; metabolism ; Tumor Cells, Cultured

This study was purposed to investigate the inhibitory effect of macrocalin A (MA) on proteasome of multiple myeloma U266 cells in vitro and molecular mechanism of MA-inducing apoptosis. U266 cells in vitro were incubated with different concentrations (2, 4, 8 µg/mL) of MA, the Hochest staining and Annexin-V/PI double staining were used to detect the apoptosis of U266 cells. The expressions of protein β1, β1i, β2, β2i, β5, β5i, ubiquitous, 19S subunit S6', and BAD,BCL-2, FAS, FAS-L,MAPK, PARP, Pro-caspase 3, cleaved-caspase 3 were detected by Western blot technique. The results showed that along with time prolonging and dose increasing of MA, the small and compact fluorescent particles were observed in cytoplasm and nucleus of U266 cells stained with Hoechst 33258, the Annexin V(+)/PI(-) cells and the total apoptosis cells (Annexin V(+)/PI(-) and Annexin V(+)/PI(+)) increased. MA could elevate the ubiquitylation level in U266 cells, suppress the expression of β1i,β2, β5i and 19S subunit S6', meanwhile the expression of BCJ-2, MAPK, PARP and pro-caspase 3 were down-regulated along with increasing of drug concentrations, but the expressions of BAD, FAS, FAS-L cleaved-caspase 3 were enhanced. It is concluded that MA can inhibit the effect of proteasome, and the mitochondrial pathway and death receptor pathway may play important roles in apoptosis of U266 cells induced by MA.
Apoptosis ; drug effects ; Cell Line, Tumor ; Diterpenes ; pharmacology ; Humans ; Multiple Myeloma ; pathology ; Proteasome Endopeptidase Complex ; metabolism ; Proteasome Inhibitors ; pharmacology