scholarly journals p21 and p27: roles in carcinogenesis and drug resistance

2008 ◽  
Vol 10 ◽  
Author(s):  
Abde M. Abukhdeir ◽  
Ben Ho Park
Keyword(s):  
Cell Cycle ◽  
Drug Resistance ◽  
Cell Death ◽  
Cell Growth ◽  
Cdk Inhibitors ◽  
Paradoxical Effect ◽  
Cyclin Dependent Kinases ◽  
Functional Loss ◽  
Growing Body ◽  
Identification Function

Human cancers arise from an imbalance of cell growth and cell death. Key proteins that govern this balance are those that mediate the cell cycle. Several different molecular effectors have been identified that tightly regulate specific phases of the cell cycle, including cyclins, cyclin-dependent kinases (CDKs) and CDK inhibitors. Notably, loss of expression or function of two G1-checkpoint CDK inhibitors – p21 (CDKN1A) and p27 (CDKN1B) – has been implicated in the genesis or progression of many human malignancies. Additionally, there is a growing body of evidence suggesting that functional loss of p21 or p27 can mediate a drug-resistance phenotype. However, reports in the literature have also suggested p21 and p27 can promote tumours, indicating a paradoxical effect. Here, we review historic and recent studies of these two CDK inhibitors, including their identification, function, importance to carcinogenesis and finally their roles in drug resistance.

scholarly journals Transcriptional CDK inhibitors, CYC065 and THZ1 promote Bim-dependent apoptosis in primary and recurrent GBM through cell cycle arrest and Mcl-1 downregulation

2021 ◽  
Vol 12 (8) ◽  
Author(s):  
Viktorija Juric ◽  
Lance Hudson ◽  
Joanna Fay ◽  
Cathy E. Richards ◽  
Hanne Jahns ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Cell Cycle Arrest ◽  
Cortical Neurons ◽  
Apoptotic Cell ◽  
Cdk Inhibitors ◽  
Induce Cell Death ◽  
Viability Loss ◽  
Cycle Arrest ◽  
Recurrent Gbm

AbstractActivation of cyclin-dependent kinases (CDKs) contributes to the uncontrolled proliferation of tumour cells. Genomic alterations that lead to the constitutive activation or overexpression of CDKs can support tumourigenesis including glioblastoma (GBM), the most common and aggressive primary brain tumour in adults. The incurability of GBM highlights the need to discover novel and more effective treatment options. Since CDKs 2, 7 and 9 were found to be overexpressed in GBM, we tested the therapeutic efficacy of two CDK inhibitors (CKIs) (CYC065 and THZ1) in a heterogeneous panel of GBM patient-derived cell lines (PDCLs) cultured as gliomaspheres, as preclinically relevant models. CYC065 and THZ1 treatments suppressed invasion and induced viability loss in the majority of gliomaspheres, irrespective of the mutational background of the GBM cases, but spared primary cortical neurons. Viability loss arose from G2/M cell cycle arrest following treatment and subsequent induction of apoptotic cell death. Treatment efficacies and treatment durations required to induce cell death were associated with proliferation velocities, and apoptosis induction correlated with complete abolishment of Mcl-1 expression, a cell cycle-regulated antiapoptotic Bcl-2 family member. GBM models generally appeared highly dependent on Mcl-1 expression for cell survival, as demonstrated by pharmacological Mcl-1 inhibition or depletion of Mcl-1 expression. Further analyses identified CKI-induced Mcl-1 loss as a prerequisite to establish conditions at which the BH3-only protein Bim can efficiently induce apoptosis, with cellular Bim amounts strongly correlating with treatment efficacy. CKIs reduced proliferation and promoted apoptosis also in chick embryo xenograft models of primary and recurrent GBM. Collectively, these studies highlight the potential of these novel CKIs to suppress growth and induce cell death of patient-derived GBM cultures in vitro and in vivo, warranting further clinical investigation.

Manipulating the onset of cell cycle withdrawal in differentiated erythroid cells with cyclin-dependent kinases and inhibitors

Blood ◽  
2000 ◽  
Vol 96 (8) ◽  
pp. 2755-2764 ◽  
Author(s):  
Igor Matushansky ◽  
Farshid Radparvar ◽  
Arthur I. Skoultchi
Keyword(s):  
Cell Cycle ◽  
Terminal Differentiation ◽  
Cdk Inhibitors ◽  
Cyclin D ◽  
Erythroid Cells ◽  
Stable Transfectants ◽  
Cyclin Dependent Kinases ◽  
Erythroleukemia Cells ◽  
Murine Erythroleukemia ◽  
Murine Erythroleukemia Cells

Abstract Terminal differentiation of erythroid cells results in terminal cell divisions followed by irreversible cell cycle withdrawal of hemoglobinized cells. The mechanisms leading to cell cycle withdrawal were assessed in stable transfectants of murine erythroleukemia cells, in which the activities of cyclin-dependent kinases (CDKs) and CDK inhibitors (CDKIs) could be tightly regulated during differentiation. Cell cycle withdrawal of differentiating cells is mediated by induction of several CDKIs, thereby leading to inhibition of CDK2 and CDK4. Manipulation of CDK activity in differentiating cells demonstrates that the onset of cell cycle withdrawal can be either greatly accelerated or greatly delayed without affecting hemoglobin levels. Extending the proliferation of differentiating cells requires the synergistic action of CDK2 and CDK4. Importantly, CDK6 cannot substitute for CDK4 in this role, which demonstrates that the 2 cyclin D–dependent kinases are functionally different. The results show that differentiating hemoglobinized cells can be made to proliferate far beyond their normal capacity to divide.

Preclinical Efficacy and Biological Effects of Venetoclax and Ixazomib in Combination in Lymphoma Cells

Blood ◽  
2020 ◽  
Vol 136 (Supplement 1) ◽  
pp. 37-38
Author(s):  
Maria Cosenza ◽  
Stefano Sacchi ◽  
Samantha Pozzi
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
Cell Growth ◽  
Cell Lines ◽  
Stromal Cells ◽  
Biological Effects ◽  
Lymphoma Cell ◽  
Lymphoma Cells ◽  
Induction Of Apoptosis ◽  
Preclinical Efficacy

Introduction. Bcl-2 family proteins comprise anti-apoptotic and pro-apoptotic proteins. Interaction between these proteins, as well as severe regulation of their expression, mediates cell survival and can quickly induce cell death. Venetoclax is Bcl-2-targeting that has shown preclinical and clinical activity in hematologic malignancies. Due to the development of resistance and the loss of dependence on the target protein, the monotherapy may be insufficient for maximal effectiveness. To circumvent the resistance mechanisms, many preclinical studies have shown that combination of venetoclax with other agents may represent a more effective therapeutic strategy. Ubiquitin-proteasome signaling pathway is a potential target that plays an important role in the proteolysis of key regulatory proteins. Proteasome inhibitors include ixazomib that inhibits cell growth and induces apoptosis in hematological malignancies cells resistant to conventional therapies and bortezomib. Objective: To analyze the preclinical efficacy and associated biological effects of venetoclax combined with ixazomib in a panel of lymphoma cell lines with diverse expression levels of Bcl-2 and other Bcl-2 family proteins. Methods: 12 lymphoma cell lines including FL (RL, WSU-NHL, Karpas422), MCL (Jeko1, Granta519), DLBCL (OCI-LY3, OCI-LY18), CTCL (Hut-78), ALCL (Karpas299), HL (L1236, L540), CLL (Mec1) and two MCL primary patient samples were exposed to venetoclax (0.01 - 8 µM) and ixazomib (10 - 2000 nM) alone for 24 - 72 hours to calculate IC50. Subsequently, lymphoma cells were exposed to venetoclax (0.015 - 25 nM) in combination with ixazomib (0.015 - 0.5 nM) for 24 hours. Cell viability was determined by MTT. Coefficient of synergy (combination index - CI) was calculated using CalcuSyn. Cell cycle and induction of apoptosis were evaluated by flow cytometry and changes in Bcl-2 family members, caspase activation and AKT phosphorylation were determined by western blotting. Results. In vitro, venetoclax and ixazomib alone induced cell death in a dose- and time-dependent manner against lymphoma cell lines. The IC50 is between 0.5 and 8 µM for venetoclax and between 12 and 1250 nM for ixazomib. The combination of venetoclax (0.03, 0.06, 12.5, 25 nM) with ixazomib (0.03, 0.06, 0.25, 0.5 nM) produced a synergistic effect (CI < 1) after 24 h of treatment in the most lymphoma cells lines leading to inhibition of cell growth and induction of apoptosis between 26 % and 59 % accompanied by increased with cleavage of caspases-3, -9 and PARP. We observed an additive effect (CI = 1) in Jeko1 (MCL) and MEC1 cells (CLL) and antagonist effect (CI > 1) Hut-78 cells (CTCL). Synergistic effect has been seen in two MCL primary patient samples (CI = 0.5 - 0.7). In sensitive lymphoma cells, the combination abrogated colony formation in the methylcellulose medium. When lymphoma cell lines were co-cultured with mesenchymal stromal cells with both drugs we observed a decrease of cell viability and a fraction of apoptotic cells indicating that drug combination may overcome the tumor promoting effects of stromal cells. The apoptosis induced in FL and Granta519 cells (MCL) by drug combination was accompanied by partial downregulation of Bcl-2 and strong upregulation of Bax, Bad, Bim and Noxa proteins. Jeko-1 cells were less sensitive to venetoclax-ixazomib combination-induced apoptosis. Western blot analysis showed a differential expression of Bcl-2, Mcl-1 and Bcl-XL proteins in FL, MCL and HL cell lines. Jeko-1 cells showed a normal expression of Bcl-2 and Mcl-1 proteins and high Bcl-xL protein level. Co-expression of related anti-apoptotic Bcl-2 family proteins could limit activity of treatment. Combined treatment induced G0/G1 cell cycle arrest and increased the sub-G1 population that was linked by the upregulation of p27 and p21. In addition, in RL, WSU-NHL and Granta519, enhanced cell death is associated with AKT inactivation and with a reduction of p-4EBP1, leading to decreased levels of c-MYC. Conclusion. Venetoclax exhibits strong synergistic activity with ixazomib in lymphoma cells. Studies are still ongoing and signaling pathways that promote the combination of venetoclax with ixazomib are to be analyzed. These data offer a rationale to continue exploring venetoclax-ixazomib combination and suggest that suppression of Bcl-2 family protein driven survival signaling may be one important mechanism for combination synergy. Disclosures No relevant conflicts of interest to declare.

KRN5500, a Spicamycin Derivative, Exerts Anti-Myeloma Effects through Impairing Both Myeloma Cells and Osteoclasts.

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 1669-1669
Author(s):  
Hirokazu Miki ◽  
Shuji Ozaki ◽  
Osamu Tanaka ◽  
Shingen Nakamura ◽  
Ayako Nakano ◽  
...  
Keyword(s):  
Bone Marrow ◽  
Drug Resistance ◽  
Cell Death ◽  
Cell Growth ◽  
Cell Lines ◽  
G1 Arrest ◽  
Dependent Manner ◽  
Osteolytic Bone Disease ◽  
Rpmi 8226

Abstract Multiple myeloma (MM) is a plasma cell malignancy characterized by devastating bone destruction due to enhanced bone resorption and suppressed bone formation. Although high-dose chemotherapy and new agents such as thalidomide, lenalidomide, and bortezomib have shown marked anti-MM activity in clinical settings, MM remains incurable due to drug resistance mediated by interactions with osteoclasts or stroma cells. Moreover, osteolytic bone disease continues to be a major problem for many patients. Therefore, alternative approaches are necessary to overcome drug resistance and inhibit osteoclasts activity in MM. KRN5500 is a new derivative of spicamycin produced by Streptomyces alanosinicus (Kirin Pharma, Tokyo, Japan), which potently inhibits protein synthesis and induces cell death in human tumor cell lines. Phase I studies of KRN5500 in patients with solid tumors such as colon cancer and gastric cancer showed acceptable toxicity with Cmax values of 1000––3000 nM. In this study, we investigated the effects of KRN5500 against MM cells and osteoclasts in vitro and in vivo. MM cell lines such as RPMI 8226, MM.1S, INA-6, KMS12-BM, UTMC-2, TSPC-1, and OPC were incubated with various concentrations of KRN5500 for 3 days. Cell proliferation assay showed marked inhibition of cell growth with G1 arrest in these MM cells (IC50: 4–100 nM). KRN5500 (100 nM) also induced 30–90% of cell death in primary MM cells (n=7). Annexin V/propidium iodide staining showed that KRN5500 induced apoptosis of MM cells in a dose- and time-dependent manner. Western blot analysis confirmed activation of caspase-8, -9, and −3, cleavage of poly (ADP-ribose) polymerase (PARP), and down-regulation of Mcl-1. We next examined the effect of KRN5500 against MM cell lines and primary MM cells in the presence of bone marrow stroma cells and osteoclasts. Co-culture of these cells enhanced viability of MM cells; however, KRN5500 still induced strong cytotoxicity to MM cells. Of interest, KRN5500 specifically mediated apoptosis in osteoclasts but not stroma cells as assessed by TUNEL staining. More than 90% of osteoclasts were killed even at a low concentration of KRN5500 (20 nM). Finally, we evaluated the effect of KRN5500 against MM cells and osteoclasts in vivo. Two xenograft models were established in SCID mice by either subcutaneous injection of RPMI 8226 cells or intra-bone injection of INA-6 cells into subcutaneously implanted rabbit bones (SCID-rab model). These mice were treated with intraperitoneal injection of KRN5500 (5 mg/kg/dose) or saline thrice a week for 3 weeks after tumor development. In a subcutaneous tumor model, KRN5500 inhibited the tumor growth compared with control mice (increased tumor size, 232 ± 54% vs 950 ± 422%, p<0.001, n=6 per group). In a SCID-rab model, KRN5500 also inhibited MM cell growth in the bone marrow (increase of serum human sIL6-R derived from INA-6, 134 ± 19% vs 1112 ± 101%, p<0.001, n=5 per group). Notably, the destruction of the rabbit bones was also prevented in the KRN5500-treated mice as evaluated by radiography. Therefore, these results suggest that KRN5500 exerts anti-MM effects through impairing both MM cells and osteoclasts and that this unique mechanism of action provides a valuable therapeutic option to improve the prognosis in patients with MM.

AT7519, a Potent Multi-Targeted CDK Inhibitor, Is Active in CLL Patient Samples Independent of Stage

Blood ◽  
2008 ◽  
Vol 112 (11) ◽  
pp. 3161-3161
Author(s):  
Vicky Lock ◽  
Laurence Cooke ◽  
Murray Yule ◽  
Neil T Thompson ◽  
K. Della Croce ◽  
...  
Keyword(s):  
Cell Cycle ◽  
Cell Death ◽  
B Cell ◽  
Rna Polymerase Ii ◽  
Parp Cleavage ◽  
Regulation Of Transcription ◽  
Cytotoxic Effects ◽  
Rna Pol Ii ◽  
Pol Ii ◽  
Cyclin Dependent Kinases

Abstract Cyclin Dependent Kinases (CDKs) play a central role in the eukaryotic cell cycle. The activation of these kinases is modulated by the expression and binding of their regulatory cyclin partners. Their key role in cell cycle progression, coupled to evidence that pathways leading to their activation are deregulated in a number of human cancers makes them attractive therapeutic targets. More recently the role of CDKs 7, 8 and 9 in the regulation of transcription has been explored. CDK9 has been shown to play a role in the regulation of transcription via phosphorylation of RNA polymerase II (RNA pol II). The outcome of transcriptional inhibition via CDK9 exhibits significant variation between cell lines. B-Cell lymphoproliferative disorders, including CLL, rely on the expression of transcripts with a short half-life such as Mcl-1, Bcl-2 and XIAP for survival. In vitro studies have demonstrated that compounds with transcriptional inhibitory effects are effective pro-apoptotic agents in models of this disease. AT7519 is a potent inhibitor of cyclin dependent kinases 1, 2 and 9 and is currently in early phase clinical development. These studies profile the mechanism of action of AT7519 on CLL cells isolated from patients. Primary cell samples were isolated from a total of 15 patients with CLL with various stages of disease (8 Stage 0, 0/I or II and 7 Stage IV) and who were either treatment naïve or had received a variety of prior therapies. Patient samples were characterised for cytogenetic abnormalities (11q, 17p and 13q deletion or trisomy 12) as well IgVH mutation and ZAP70 expression. AT7519 was shown to induce apoptosis (by MTS, morphology and PARP cleavage) in these samples at concentrations of 100–700nM. AT7519 appears equally effective at inhibiting the survival of CLL cells harbouring a variety of mutations including those representative of patients that fall within poorer prognosis treatment groups. The amount of AT7519 required to induce cell death in 50% of the CLL cell population increased as exposure time was decreased but significant cell death was obtained at doses approximating to 1uM following 4–6h of treatment. These doses are equivalent to exposures achieved in ongoing AT7519 clinical studies indicating that cytotoxic doses can be achieved in patients on well tolerated schedules. The mechanism of AT7519 cytotoxic effects was investigated by western blotting for a variety of cell cycle and apoptotic markers following incubation with compound. Short term treatments (4–6h) resulted in inhibition of phosphorylation of the transcriptional marker RNA pol II and the downregulation of the anti-apoptotic protein Mcl-1. Additional antiapoptotic proteins including XIAP and Bcl-2 remained unchanged. The reduction in Mcl-1 protein levels was associated with an increase in the apoptotic marker cleaved PARP. No inhibition of cell cycle markers such as phospho-retinoblastoma protein was observed in the same samples suggesting that the cytotoxic effects of AT7519 in CLL patient samples is due to its transcriptional activity alone. Together the data suggest AT7519 offers a promising treatment strategy for patients with advanced B-cell leukemia and lymphoma.

Manipulating the onset of cell cycle withdrawal in differentiated erythroid cells with cyclin-dependent kinases and inhibitors

Blood ◽  
2000 ◽  
Vol 96 (8) ◽  
pp. 2755-2764 ◽  
Author(s):  
Igor Matushansky ◽  
Farshid Radparvar ◽  
Arthur I. Skoultchi
Keyword(s):  
Cell Cycle ◽  
Terminal Differentiation ◽  
Cdk Inhibitors ◽  
Cyclin D ◽  
Erythroid Cells ◽  
Stable Transfectants ◽  
Cyclin Dependent Kinases ◽  
Erythroleukemia Cells ◽  
Murine Erythroleukemia ◽  
Murine Erythroleukemia Cells

Terminal differentiation of erythroid cells results in terminal cell divisions followed by irreversible cell cycle withdrawal of hemoglobinized cells. The mechanisms leading to cell cycle withdrawal were assessed in stable transfectants of murine erythroleukemia cells, in which the activities of cyclin-dependent kinases (CDKs) and CDK inhibitors (CDKIs) could be tightly regulated during differentiation. Cell cycle withdrawal of differentiating cells is mediated by induction of several CDKIs, thereby leading to inhibition of CDK2 and CDK4. Manipulation of CDK activity in differentiating cells demonstrates that the onset of cell cycle withdrawal can be either greatly accelerated or greatly delayed without affecting hemoglobin levels. Extending the proliferation of differentiating cells requires the synergistic action of CDK2 and CDK4. Importantly, CDK6 cannot substitute for CDK4 in this role, which demonstrates that the 2 cyclin D–dependent kinases are functionally different. The results show that differentiating hemoglobinized cells can be made to proliferate far beyond their normal capacity to divide.

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