Over-expression of p27kip1 induces growth arrest and apoptosis mediated by changes of pRb expression in lung cancer cell lines

Chemical Composition, Antitumor Properties, and Mechanism of the Essential Oil from Plagiomnium acutum T. Kop

Plagiomnium acutum T. Kop. (P. acutum) has been used as a traditional Chinese medicine for thousands of years to treat cancer but lacks evidence. The objective of this work was to reveal the chemical composition of P. acutum essential oil (PEO) and explore its potential antitumor activity and molecular mechanism. PEO was prepared by the simultaneous distillation-extraction method and characterized by gas chromatography/mass spectroscopy. CCK8 assay, flow cytometry, western blot, and immunofluorescence techniques were used to analyze the effects and mechanism of PEO against cancer cells. A total of 74 constituents of PEO were identified, with diterpenes (26.5%), sesquiterpenes (23.89%), and alcohols (21.81%) being the major constituents. Two terpenoids, selina-6-en-4-ol and dolabella-3,7-dien-18-ol, were detected in PEO for the first time. PEO showed significant cell growth inhibitory activity on HepG2 and A549 cells by blocking the G1 phase and inducing apoptosis, which may be attributed to its upregulation of p21^Cip1 and p27^Kip1 proteins and interference with mitochondrial membrane potential effect. Dolabella-3,7-dien-18-ol accounts for 25.5% of PEO and is one of the main active components of PEO, with IC₅₀ values in HepG2 and A549 cells of (25.820 ± 0.216) µg/mL and (23.597 ± 1.207) μg/mL, respectively. These results confirmed the antitumor medicinal value of P. acutum and showed great application potential in the pharmaceutical industry.

The AMPK/p27Kip1 Pathway as a Novel Target to Promote Autophagy and Resilience in Aged Cells

Once believed to solely function as a cyclin-dependent kinase inhibitor, p27^Kip1 is now emerging as a critical mediator of autophagy, cytoskeletal dynamics, cell migration and apoptosis. During periods of metabolic stress, the subcellular location of p27^Kip1 largely dictates its function. Cytoplasmic p27^Kip1 has been found to be promote cellular resilience through autophagy and anti-apoptotic mechanisms. Nuclear p27^Kip1, however, inhibits cell cycle progression and makes the cell susceptible to quiescence, apoptosis, and/or senescence. Cellular location of p27^Kip1 is regulated, in part, by phosphorylation by various kinases, including Akt and AMPK. Aging promotes nuclear localization of p27^Kip1 and a predisposition to senescence or apoptosis. Here, we will review the role of p27^Kip1 in healthy and aging cells with a particular emphasis on the interplay between autophagy and apoptosis.

Regulation of p27Kip1 and p57Kip2 Functions by Natural Polyphenols

In numerous instances, the fate of a single cell not only represents its peculiar outcome but also contributes to the overall status of an organism. In turn, the cell division cycle and its control strongly influence cell destiny, playing a critical role in targeting it towards a specific phenotype. Several factors participate in the control of growth, and among them, p27^Kip1 and p57^Kip2, two proteins modulating various transitions of the cell cycle, appear to play key functions. In this review, the major features of p27 and p57 will be described, focusing, in particular, on their recently identified roles not directly correlated with cell cycle modulation. Then, their possible roles as molecular effectors of polyphenols’ activities will be discussed. Polyphenols represent a large family of natural bioactive molecules that have been demonstrated to exhibit promising protective activities against several human diseases. Their use has also been proposed in association with classical therapies for improving their clinical effects and for diminishing their negative side activities. The importance of p27^Kip1 and p57^Kip2 in polyphenols’ cellular effects will be discussed with the aim of identifying novel therapeutic strategies for the treatment of important human diseases, such as cancers, characterized by an altered control of growth.

Skp2 inhibitor SKPin C1 decreased viability and proliferation of multiple myeloma cells and induced apoptosis

Multiple myeloma (MM) is a malignant neoplasm of plasma, and exhibits several harmful effects including osteolytic injuries, hypercalcemia, and immune dysfunction. Many patients with MM succumb to the underlying malignancy. An S-phase kinase-related protein 2 (Skp2) inhibitor, designated SKPin C1, has been developed and confirmed to have an inhibitory effect on metastatic melanoma cells. This study aimed to determine the effect of SKPin C1 on MM. Normal B lymphocytes, THP-1 cells, and MM U266 and RPMI 8226 cells were exposed to various dosages of SKPin C1 for 48 h. Cell proliferation was determined by MTT, EdU staining, and cell cycle assays. Western blot assays were performed to assess intracellular protein levels of Skp2, p27, and cleaved caspase-3. The amount of ubiquitin attached to p27 was determined using an immunoprecipitation assay. The viability of U266 and RPMI 8226 cells was significantly inhibited by 10 μM SKPin C1 and the inhibitory effect was enhanced with increasing doses of SKPin C1. In contrast, 50 μM SKPin C1 only marginally decreased viability of normal B lymphocytes in 12 h. Skp2 and p27 expression in U266 and RPMI 8226 cells was higher and lower, respectively, than that in the normal B lymphocytes. Treatment with SKPin C1 or Skp2 knockdown increased p27 protein levels in U266 and RPMI 8226 cells by preventing p27 from being ubiquitinated, which slowed the cell cycle, inhibited cell proliferation, and triggered apoptosis. Therefore, this study suggested SKPin C1 as a potent inhibitor against aberrant proliferation and immortalization of MM.

Multiple functions of p27 in cell cycle, apoptosis, epigenetic modification and transcriptional regulation for the control of cell growth: A double-edged sword protein

The cell cycle is controlled by precise mechanisms to prevent malignancies such as cancer, and the cell needs these tight and advanced controls. Cyclin dependent kinase inhibitor p27 (also known as KIP₁) is a factor that inhibits the progression of the cell cycle by using specific molecular mechanisms. The inhibitory effect of p27 on the cell cycle is mediated by CDKs inhibition. Other important functions of p27 include cell proliferation, cell differentiation and apoptosis. Post- translational modification of p27 by phosphorylation and ubiquitination respectively regulates interaction between p27 and cyclin/CDK complex and degradation of p27. In this review, we focus on the multiple function of p27 in cell cycle regulation, apoptosis, epigenetic modifications and post- translational modification, and briefly discuss the mechanisms and factors that have important roles in p27 functions.

Growth suppression by MYC inhibition in small cell lung cancer cells with TP53 and RB1 inactivation

Small cell lung cancer (SCLC) is the most aggressive type of lung cancer with high mortality. One of the MYC family genes, MYC, MYCL or MYCN, is amplified in ~20% of the SCLCs; therefore, MYC proteins are potential therapeutic targets in SCLC patients. We investigated the therapeutic impact of Omomyc, a MYC dominant negative, in a panel of SCLC cell lines. Strikingly, Omomyc suppressed the growth of all tested cell lines by inducing cell cycle arrest and/or apoptosis. Induction of G1 arrest by Omomyc was found to be dependent on the activation of CDKN1A, in part, through the TP73 pathway. Our results strongly indicate that SCLC cells carrying amplification of MYC, MYCL or MYCN are addicted to MYC function, suggesting that MYC targeting would be an efficient therapeutic option for SCLC patients.

Activation of tachykinin, neurokinin 3 receptors affects chromatin structure and gene expression by means of histone acetylation

The tachykinin, neurokinin 3 receptor (NK3R) is a g-protein coupled receptor that is broadly distributed in the nervous system and exerts its diverse physiological actions through multiple signaling pathways. Despite the role of the receptor system in a range of biological functions, the effects of NK3R activation on chromatin dynamics and gene expression have received limited attention. The present work determined the effects of senktide, a selective NK3R agonist, on chromatin organization, acetylation, and gene expression, using qRT-PCR, in a hypothalamic cell line (CLU 209) that expresses the NK3R. Senktide (1 nM, 10nM) caused a relaxation of chromatin, an increase in global acetylation of histone H3 and H4, and an increase in the expression of a common set of genes involved in cell signaling, cell growth, and synaptic plasticity. Pretreatment with histone acetyltransferase (HAT) inhibitor (garcinol and 2-methylene y-butylactone), that inhibits p300, p300/CREB binding protein (CBP) associated factor (PCAF), and GCN 5, prevented the senktide-induced increase in expression of most, but not all, of the genes upregulated in response to 1 nM and 10nM senktide. Treatment with 100 nM had the opposite effect: a reduction in chromatin relaxation and decreased acetylation. The expression of four genes was significantly decreased and the HAT inhibitor had a limited effect in blocking the upregulation of genes in response to 100 nM senktide. Activation of the NK3R appears to recruit multiple pathways, including acetylation, and possibly histone deactylases, histone methylases, or DNA methylases to affect chromatin structure and gene expression.

Growth inhibition of the pulmonary metastatic tumors by systemic delivery of the p27 kip1 gene using lyophilized lipid-polycation-DNA complexes

BACKGROUND

p27(kip1) (p27), a cyclin-dependent kinase inhibitor (CDKI), is an important regulator of cell cycle progression and a putative tumor suppressor gene, and plays an important role in the inhibition of genesis and progression of several kinds of cancers. The present study aimed to evaluate the anti-tumor effects of p27 gene therapy by a nonviral gene delivery strategy on pulmonary metastatic tumors.

METHODS

A recombinant plasmid composed of a p27 sequence was constructed and identified; it was then formulated with condensing agent protamine sulfate and entrapped into cationic liposomes. The resulting lipid-polycation-DNA complexes (LPD) were prepared into lyophilized forms. 5 x 10(5) of CT26 colorectal adenocarcinoma cells were inoculated into female Balb/c mice via the tail vein to establish lung tumor models. On the second day, mice were randomly divided into six groups for different intravenous treatments: phosphate-buffered saline, empty liposomes, naked pDNA, LPD-p27 kip1, Cisplatin (DPP), and LPD-p27 kip1 plus DPP, respectively.

RESULTS

The growth curve of tumor and the growth inhibition rate of tumor showed that p27-LPDs could prolong the lifespan of the mice significantly, whereas the combination of p27-LPDs and DPP could further prolong the lifespan of the tumor-bearing animals. The histology of tumors examined by hematoxylin and eosin staining indicated that p27-LPDs had a stronger inhibition effect. Significant expression of p27 was detected in tumors using an immunohistochemical technique.

CONCLUSIONS

Lyophilized LPD could be used as a potential in vivo gene delivery carrier for lung cancer gene therapy.

Nkx3.1 and p27(KIP1) cooperate in proliferation inhibition and apoptosis induction in human androgen-independent prostate cancer cells

Prostate cancer (PC), which responds well to androgen ablation initially, invariably progresses to treatment resistance. The so-called androgen-independent PC is also a concern, since there is no effective therapy so far. Nkx3.1 is a putative prostate tumor suppressor that is expressed exclusively in the prostate under the regulation of androgen, and p27(KIP1) functions as a cell proliferation inhibitor and apoptosis trigger by disrupting the cyclin-dependent kinase (CDK)-cyclin complex. Lack of expressions of Nkx3.1 and/or p27(KIP1) have been detected in most advanced PC and is associated with poor clinical progression. Here, we show that endogenous expressions of both Nkx3.1 and p27(KIP1) are lost in the androgen-independent PC3 PC cells, while remaining intact in LNCaP PC cells, which contain functional androgen receptor (AR) and are hormone-responsive. Ectopic restoration of either Nkx3.1 or p27(KIP1) in PC3 cells results in reduced cell proliferation, and increased cell death. Both effects are synergistically enhanced when the two molecules are coexpressed. p27(KIP1) overexpression in PC3 results in increased cell population ceased at the G0/G1 phase, and this cell-cycle-arresting effect is significantly enhanced by the coexpression of Nkx3.1. Flow cytometry further revealed that Nkx3.1 and p27(KIP1) also cooperatively render more PC3 cells undergoing apoptosis. Consistently, the coexpression of Nkx3.1 and p27(KIP1) leads to the decreased expression of Bcl-2 oncogene and a concomitantly upregulated Bax expression. It also activates caspase 3 and leads to increased cleavage of PARP. Our findings thus reveal the crucial relevance of the combined antiproliferative and proapoptotic activities of Nkx3.1 and p27(KIP1) in androgen-independent PC cells, and further suggest that a combined, rather than single gene manipulation may be of clinical value for hormone-refractory PC.

Antitumor bioactivity of adenovirus-mediated p27mt in colorectal cancer cell line SW480

AIM: To explore the antitumor bioactivity of adenovirus-mediated mutant type p27^kip1 gene in a colorectal cancer cell line SW480.

METHODS: We constructed recombinant adenovirus vector expressing a mutant type p27^kip1 gene (ad-p27mt), with mutation of Thr-187/Pro-188 (ACGCCC) to Met-187/Ile-188 (ATGATC), and transduced into SW480 cells. Then we detected expression of p27, Bcl-2 and Bax protein in the transductants by Western blotting, cell cycle of transductants by a digital flow cytometric system, migrating potential with Boyden Chamber and SW480 tumor cell growth inhibition in vitro and in vivo.

RESULTS: We found that a recombinant adenovirus vector of expressing ad-p27mt, with mutation of Thr-187/Pro-188 (ACGCCC) to Met-187/Ile-188 (ATGATC) has potent inhibition of SW480 tumor cell growth in vitro and in vivo. Furthermore, ad-p27mt induced cell apoptosis via regulating bax and bcl-2 expressions, and G₁/S arrest in SW480 cells and inhibited cell migration.

CONCLUSION: ad-p27mt has a strong anti-tumor bioactivity and has the potential to develop into new therapeutic agents for colorectal cancer.

Mutant p27(Kip1) and its potential effect as hepatocellular gene therapy

BACKGROUND

The cyclin-dependent kinase (cdk) inhibitor p27(Kip1) is an important regulator of cell cycle progression as it negatively regulates G(0/1) progression and plays a major role in controlling the cell cycle. The screening of the p27(Kip1) sequence identified many potential phosphorylation sites. To investigate the effects of the overexpression of exogenous p27(Kip1) protein lacking the Thr157 sites on subcellular localization, cell cycle, and proliferation, a plasmid was constructed containing mutations of p27(Kip1) at Thr157 (T157A p27), and transfected into the SMMC7721 cell line with Lipofectamine. Wild-type and mutant p27 plasmids T157A were transfected separately as control groups.

METHODS

We detected the proliferation of SMMC7721 cells by the Cell Counting Kit and FACS/Calibur Flow Cytometer and analyzed the expression and localization of p27(Kip1) by Western blotting analysis and cell fractionation. The cdk2 dependent kinase activity was determined by in vitro kinase assay.

RESULTS

Proliferation of SMMC7721 cells was greatly inhibited and cell cycle was arrested in G(0/1) phase after exogenous p27(Kip1) mutant expression much more than wild-type p27(Kip1). The expressed T157A p27(Kip1) proteins were translocated from the cytoplasm into nucleus much more compare with wild-type. Compared with pcDNA3.1-Myc control, transient transfection of T157A p27(Kip1) decreased expression of cyclin D1 and the phosphorylated form of retinoblastoma protein.

CONCLUSIONS

These findings support the potential effectiveness of a PI3K/Akt-resistant phosphorylated form of p27 in hepatocellular carcinoma gene therapy.

A limited screen for protein interactions reveals new roles for protein phosphatase 1 in cell cycle control and apoptosis

Protein phosphatase 1 (PP1) catalytic subunits typically combine with other proteins that modulate their activity, direct them to distinct substrates, or serve as substrates for PP1. More than 50 PP1-interacting proteins (PIPs) have been identified so far. Given there are approximately 10 000 phosphoproteins in mammals, many PIPs remain to be discovered. We have used arrays containing 100 carefully selected antibodies to identify novel PIPs that are important in cell proliferation and cell survival in murine fetal lung epithelial cells and human A549 lung cancer cells. The antibody arrays identified 31 potential novel PIPs and 11 of 17 well-known PIPs included as controls, suggesting a sensitivity of at least 65%. A majority of the interactions between PP1 and putative PIPs were isoform- or cell type-specific. We confirmed by co-immunoprecipitation that 9 of these proteins associate with PP1: APAF-1, Bax, E-cadherin, HSP-70, Id2, p19Skp1, p53, PCNA, and PTEN. We examined two of these interactions in greater detail in A549 cells. Exposure to nicotine enhanced association of PP1 with Bax (and Bad), but also induced inhibitory phosphorylation of PP1. In addition to p19Skp1, PP1alpha antibodies also coprecipitated cullin 1, suggesting that PP1alpha is associated with the SCF1 complex. This interaction was only detectable during the G1/S transition and S phase. Forced loss of PP1 function decreased the levels of p27Kip1, a well-known SCF1 substrate, suggesting that PP1 may rescue proteins from ubiquitin/proteasome-mediated destruction. Both of these novel interactions are consistent with PP1 facilitating cell cycle arrest and/or apoptosis.

p27kip1 overexpression promotes paclitaxel-induced apoptosis in pRb-defective SaOs-2 cells

p27kip1 is a cyclin-dependent kinase (CDK) inhibitor, which controls several cellular processes in strict collaboration with pRb. We evaluated the role of p27kip1 in paclitaxel-induced apoptosis in the pRb-defective SaOs-2 cells. Following 48 h of exposure of SaOs-2 cells to 100 nM paclitaxel, we observed an increase in p27kip1 expression caused by the decrease of the ubiquitin-proteasome activity. Such increase was not observed in SaOs-2 cells treated with the caspase inhibitors Z-VAD-FMK, suggesting that p27kip1 enhancement at 48 h is strictly related to apoptosis. Finally, we demonstrated that SaOs-2 cells transiently overexpressing the p27kip1 protein are more susceptible to paclitaxel-induced apoptosis than SaOs-2 cells transiently transfected with the empty vector. Indeed, after 48 h of paclitaxel treatment, 41.8% of SaOs-2 cells transiently transfected with a pcDNA3-p27kip1 construct were Annexin V-positive compared to 30.6% of SaOs-2 cells transfected with the empty vector (P < 0.05). In conclusion, we demonstrated that transfection of the pRb-defective SaOs-2 cells with the p27kip1 gene via plasmid increases their susceptibility to paclitaxel-induced apoptosis. The promoting effect of p27kip1 overexpression on apoptosis makes p27kip1 and proteasomal inhibitors interesting tools for therapy in patients with pRb-defective cancers.

Reduction of Cytosolic p27Kip1Inhibits Cancer Cell Motility, Survival, and Tumorigenicity

We generated a p27(Kip1) mutant (p27deltaNLS) that localized exclusively in cell cytosol. Expression of p27deltaNLS in MCF7 breast cancer cells down-regulated RhoA and increased motility, survival, and Akt levels without an effect on cell cycle distribution. RNA interference of p27 in U87 glioma cells, which express p27 predominantly in the cytoplasm, inhibited motility and survival. Conversely, knockdown of p27 in COS7 cells, with >95% nuclear p27 expression, accelerated proliferation but had no effect on motility or survival. U87 cells in which p27 had been eliminated by RNA interference exhibited lower Akt levels, shorter Akt turnover, and markedly impaired tumorigenicity in vivo. These xenografts were less invasive and exhibited increased apoptosis compared with p27-expressing tumors. Expression of cytosolic p27 in primary human breast carcinomas correlated linearly with Akt content as measured by immunohistochemistry. These data suggest that cytoplasmic p27 can exert oncogenic functions by modulating Akt stability, cell survival, and tumorigenicity.

Inducible expression of a degradation-resistant form of p27Kip1 causes growth arrest and apoptosis in breast cancer cells

The cyclin-dependent kinase (CDK) inhibitor p27(Kip1) (p27) is an important regulator of cell cycle progression controlling the transition from G to S-phase. Low p27 levels or accelerated p27 degradation correlate with excessive cell proliferation and poor prognosis in several forms of cancer. Phosphorylation of p27 at Thr187 by cyclin E-CDK2 is required to initiate the ubiquitination-proteasomal degradation of p27. Protecting p27 from ubiquitin-mediated proteasomal degradation may increase its potential in cancer gene therapy. Here we constructed a non-phosphorylatable, proteolysis-resistant p27 mutant containing a Thr187-to-Ala substitution (T187A) which is not degraded by ubiquitin-mediated proteasome pathway, and compared its effects on cell growth, cell-cycle control, and apoptosis with those of wild-type p27. In muristerone A-inducible cell lines overexpressing wild-type or mutant p27, the p27 mutant was more resistant to proteolysis in vivo and more potent in inducing cell-cycle arrest and other growth-inhibitory effects such as apoptosis. Transduction of p27(T187A) in breast cancer cells with a doxycycline-regulated adenovirus led to greater inhibition of proliferation, more extensive apoptosis, with a markedly reduced protein levels of cyclin E and increased accumulation of cyclin D1, compared with wild-type p27. These findings support the potential effectiveness of a degradation-resistant form of p27 in breast cancer gene therapy.

Down-regulation of Cdk inhibitor p27 in oral squamous cell carcinoma

Oral squamous cell carcinoma (OSCC) is the most frequent malignant neoplasm of the head and neck region. Conversion of normal cells to cancer cells is achieved through a multi-step process that is closely associated with the accumulation of multiple gene changes including both oncogenes and tumour suppressor genes. The proliferation and progression of cancer may be caused by abnormalities of various positive and negative cell cycle regulators. Cell cycle progression is positively regulated by multiple cyclins and cyclin-dependent kinases (Cdks) and cyclin/Cdk complexes are negatively regulated by a number of Cdk inhibitors including p27. p27 is a Cdk inhibitor and plays an important role in negative regulation of the cell cycle during G0 and G1 phases. Degradation of p27 is a critical event for the G1/S transition and occurs through ubiquitination by SCF(Skp2) and subsequent degradation by the 26S proteasome. It has been revealed that down-regulation of p27 is frequently found in various cancers, including OSCC, and is due to an enhancement of its degradation. Importantly, down-regulation of p27 is well associated with its malignancy including poor prognosis in various cancers. Moreover, aggressive human cancers express low levels of p27 because of its decreased stability. More recent evidence suggests that Skp2 and Cks1, the specific recognition factors for p27 ubiquitination, have oncogenic properties. This review will focus on down-regulation of p27 and mechanism of its down-regulation in OSCC.

Oxidative stress in the brain: novel cellular targets that govern survival during neurodegenerative disease

Despite our present knowledge of some of the cellular pathways that modulate central nervous system injury, complete therapeutic prevention or reversal of acute or chronic neuronal injury has not been achieved. The cellular mechanisms that precipitate these diseases are more involved than initially believed. As a result, identification of novel therapeutic targets for the treatment of cellular injury would be extremely beneficial to reduce or eliminate disability from nervous system disorders. Current studies have begun to focus on pathways of oxidative stress that involve a variety of cellular pathways. Here we discuss novel pathways that involve the generation of reactive oxygen species and oxidative stress, apoptotic injury that leads to nuclear degradation in both neuronal and vascular populations, and the early loss of cellular membrane asymmetry that mitigates inflammation and vascular occlusion. Current work has identified exciting pathways, such as the Wnt pathway and the serine-threonine kinase Akt, as central modulators that oversee cellular apoptosis and their downstream substrates that include Forkhead transcription factors, glycogen synthase kinase-3beta, mitochondrial dysfunction, Bad, and Bcl-x(L). Other closely integrated pathways control microglial activation, release of inflammatory cytokines, and caspase and calpain activation. New therapeutic avenues that are just open to exploration, such as with brain temperature regulation, nicotinamide adenine dinucleotide modulation, metabotropic glutamate system modulation, and erythropoietin targeted expression, may provide both attractive and viable alternatives to treat a variety of disorders that include stroke, Alzheimer's disease, and traumatic brain injury.

TNF receptor 1 is involved in the induction of apoptosis by the cyclin dependent kinase inhibitor p27Kip1 in the prostate cancer cell line PC-3

Loss of p27Kip1, a cyclin-dependent kinase inhibitor, is observed in aggressive prostate cancers. We demonstrated that intratumoral injections of recombinant adenovirus overexpressing p27Kip1 (Adp27) reduced the growth of prostate cancer xenografts in nude mice. Presently, we studied the mechanism(s) of cell death induced by Adp27 in prostate cancer cell line PC-3. Cells were infected with Adp27 and compared with those infected by empty virus or were non-infected. Cell cycle and typical markers of apoptosis were analyzed by flow cytometry in the presence of the following reagents: cycloheximide, pan-caspase inhibitor ZVAD-fmk, neutralizing anti-TNFR1, and anti-TNFR2. Overexpression of p27Kip1 protein and cell cycle arrest were noted within 24 h after Adp27-infection. Sub-G1 fraction, chromatin margination, and phosphatidylserine exposure were evident by the third day of treatment. Cycloheximide elevated sub-G1 fraction in Adp27-infected cells by threefold, while ZVAD-fmk reduced sub-G1 to control levels. Caspase-dependent apoptosis occurred in a third of the population, while two-thirds were ZVAD-fmk insensitive but TUNEL-positive. Flow cytometry showed increased expression of TNFR1 and TNFR2 in Adp27-infected cells. Neutralizing anti-TNFR1 decreased TUNEL-positive score, while anti-TNFR2 did not affect p27Kip1-induced apoptosis. This is the first report showing that p27Kip1 induces caspase-dependent and -independent stages of cell death that may involve TNF-signaling through TNFR1.

Characteristics of antitumor activity of mutant type p27Kip1 gene in an oral cancer cell line

It is well known that loss of the cyclin-dependent kinase inhibitor p27Kip1 protein correlates with the poor prognosis of various cancers including oral squamous cell carcinoma (SCC). Posttranslational degradation of p27Kip1 protein is mediated by phosphorylation of Thr-187 of p27Kip1 protein, which follows ubiquitination. In this study, we constructed an expression vector expressing mutant type p27Kip1 gene (pcDNA3.1-p27Kip1 mt), with mutation of Thr-187/Pro-188 (ACGCCC) to Met-187/Ile-188 (ATGATC), which is not influenced by ubiquitin-mediated degradation. We transfected mutant and wild type p27Kip1 genes into an oral SCC cell line, B88 to up-regulate the expression of mutant or wild p27Kip1 gene in each transfectant. B88-p27Kip1 mt showed significant growth inhibition than B88-p27Kip1 wt or B88-neo in vitro (p < 0.01). Also, both types of B88-p27Kip1 showed G1 arrest and apoptosis, however, B88-p27Kip1 mt showed remarkable G1 arrest. In addition, B88-p27Kip1 mt and B88-p27Kip1 wt showed markedly inhibition of the migration and out-growth of cancer cells than B88-p27Kip1 wt or B88-neo. Moreover, B88-p27Kip1 mt also showed remarkable suppression of tumor growth and cervical lymph metastasis than B88-p27Kip1 wt or B88-neo in vivo (p < 0.01). In short, the mutant type p27Kip1 gene could show more potent antitumor effects than wild type p27Kip1 gene in B88 cells. These findings suggest that mutant type p27Kip1 gene has the potential to become a novel and powerful gene therapy tool for patients with oral cancers.

The prognostic and therapeutic relevance of p27kip1 in Ewing's family tumors

PURPOSE

Ewing's family tumors (EFTs) display the characteristic fusion gene EWS-Fli1. We have reported EWS-Fli1 may promote the cell cycle progression accompanied by the suppression of the expression of cyclin-dependent kinase inhibitor p27(kip1) in EFT cells. Here, we describe the prognostic and therapeutic relevance of p27 in EFTs.

EXPERIMENTAL DESIGN

We examined tumor samples taken from 21 patients with primary EFTs for the expression of p27 protein immunohistochemically and evaluated its correlation with clinical outcome. We also investigated the usefulness of p27 as a therapeutic strategy in vitro and in vivo using p27 expression adenovirus. Finally, we examined the process of EWS-Fli1-mediated reduction of p27 expression.

RESULTS

Immunohistochemical analysis showed that a low expression level of p27 protein was related to poor event-free survival in an univariate analysis and that the expression level of p27 correlated more significantly with patient survival than several clinical factors in a multivariate survival analysis. Overexpression of p27 with the adenoviral vector remarkably inhibited the cell growth in all EFT cells tested and further induced apoptosis in the wild-type p53 EFT cells. In vivo studies demonstrated a reduction in tumor growth of EFT xenograft in nude mice treated with the intratumoral injection of p27-expressing adenovirus. EWS-Fli1 did not significantly affect the p27 promoter activity and p27 mRNA levels. However, the challenge of the proteasome inhibitor caused accumulation of p27 protein in EFT cells. These data strongly suggest EWS-Fli1 might attenuate p27 protein level via activation of the proteasome-mediated degradation pathway.

CONCLUSIONS

Our findings provide the first evidence of the prognostic relevance of p27 expression in EFTs. We propose p27 as a novel and powerful therapeutic factor for the molecular target therapy of EFTs.

Gene therapy of lung cancer

It is estimated that there will be 157,200 deaths from lung cancer in 2003. Current regimens of surgery, chemotherapy and radiation have not significantly changed overall 5-year survival rates for this disease. Thanks to intensive molecular studies over the last three decades, new targets for treatment have been identified, including replacement of tumor suppressor genes, prevention of angiogenesis and tumor growth, and regulation of programmed cell death. Promising advances have been made but obstacles still abound before effective use of these strategies at the patient bedside can occur. One area of concentration lies in developing more accurate and complete delivery of the therapeutic constructs. In the evolution of gene therapy approaches, from beginning theory to translational research, investigators in thoracic malignancies have played a leading role, utilizing a number of methods and delivery vehicles. The objective of this review is to discuss some of the major molecular targets available for manipulation in lung cancer, describe vectors and techniques currently used by thoracic researchers to deliver therapy, and provide the p53 model as an example of progression from bench research to clinical treatment.

Adrenocortical adenoma and carcinoma: histopathological and molecular comparative analysis

We compared histomorphological features and molecular expression profiles of adrenocortical adenomas (ACAd) and carcinomas (ACCa). A critical histopathological review (mean, 11 slides per patient) was conducted of 37 ACAd and 67 ACCa. Paraffin-embedded tissue cores of ACAd (n = 33) and ACCa (n = 38) were arrayed in triplicate on tissue microarrays. Expression profiles of p53, mdm-2, p21, Bcl-2, cyclin D1, p27, and Ki-67 were investigated by immunohistochemistry and correlated with histopathology and patient outcome using standard statistical methodology. Median follow-up period was 5 years. Tumor necrosis, atypical mitoses, and >1 mitosis per 50 high-power fields were factors that were highly specific for ACCa (P <.001). Number (0 to 4) of unfavorable markers [Ki-67 (+), p21 (+), p27 (+), mdm-2(-)] expressed was significantly associated with mitotic activity and morphologic index (i.e., number of adverse morphologic features) and highly predictive of malignancy (P <.001). Ki-67 overexpression occurred in 0 ACAd and 36% ACCa (P <.001) and was significantly associated with mitotic rate and unfavorable morphologic index (P <.001). Tumor necrosis, atypical mitoses, >5 mitoses per 50 high-power fields, sinusoidal invasion, histologic index of >5, and presence of more than two unfavorable molecular markers were associated significantly with metastasis in ACCa. Well-established histopathologic criteria and Ki-67 can specifically distinguish ACCAd from ACCa. Tumor cell proliferation (Ki-67) correlates with mitotic activity and morphologic index. Tumor morphology is a better predictor of metastatic risk in ACCa than current immunohistochemistry-detected cell cycle regulatory and proliferation-associated proteins.

Ceramide induces cell cycle arrest and upregulates p27kip in nasopharyngeal carcinoma cells

Ceramide mediates differentiation, growth arrest, apoptosis, proliferation, cytokine biosynthesis and secretion, and a variety of other cellular functions. However, little is known regarding ceramide signaling linked to the cell cycle. In the present study, the effect of ceramide on cell cycle in nasopharyngeal carcinoma cell line CNE2 was investigated. The results showed that ceramide inhibited cell proliferation and induced cell cycle arrest in G1 phase in CNE2 cells. Exposure of CNE2 cells to ceramide resulted in a dose-dependent up-regulation of the cyclin-dependent kinase inhibitor p27 and a decrease of phospho-Akt without reduced expression of total AKT protein. The activation of phosphatidylinositol-3-kinase (PI3K) and the protein expression of PTEN were unaffected following ceramide treatment. We concluded that ceramide induced cell cycle arrest in G1 phase in CNE2 cells and p27 up-regulation was involved in this process. In addition, up-regulation of p27 resulting from ceramide treatment may be due to the interruption of Akt, but decrease of phospho-Akt is independent of PI3K function or PTEN protein expression.

Proliferation of cancer cells despite CDK2 inhibition

We have investigated the contribution of CDK4 and CDK2 inhibition to G1 arrest in colon cancers following inhibition of the MEK/MAP kinase pathway. CDK4 inhibition is sufficient to cause arrest, but inhibition of CDK2 by p27 Kip1 redistribution or ectopic expression has no effect on proliferation. Likewise, inhibition of CDK2 through expression of dominant-negative (DN) CDK2 or antisense oligonucleotides did not prevent cell proliferation in these cells. We therefore tested whether CDK2 activity is dispensable in other cells. Surprisingly, osteosarcomas and Rb-negative cervical cancers continued to proliferate after depletion of CDK2 through antisense oligonucleotides or small interfering (si) RNA. Here we report of sustained cell proliferation in the absence of CDK2, and we suggest that CDK2 is not a suitable target for cancer therapy.

Inducible p27(Kip1) expression inhibits proliferation of K562 cells and protects against apoptosis induction by proteasome inhibitors

Overexpression of the cyclin-dependent kinase inhibitor p27(Kip1) has been demonstrated to induce cell cycle arrest and apoptosis in various cancer cell lines, but has also been associated with the opposite effect of enhanced survival of tumor cells and increased resistance towards chemotherapeutic treatment. To address the question of how p27(Kip1) expression is related to apoptosis induction, we studied doxycycline-regulated p27(Kip1) expression in K562 erythroleukemia cells. p27(Kip1) expression effectively retards proliferation, but it is not sufficient to induce apoptosis in K562 cells. p27(Kip1)-expressing K562 cells, however, become resistant to apoptosis induction by the proteasome inhibitors PSI, MG132 and epoxomicin, in contrast to wild-type K562 cells that are efficiently killed. Cell cycle arrest in the S phase by aphidicolin, which is not associated with an accumulation of p27(Kip1) protein, did not protect K562 cells against the cytotoxic effect of the proteasome inhibitor PSI. The expression levels of p27(Kip1) thus constitute an important parameter, which decides on the overall sensitivity of cells against the cytotoxic effect of proteasome inhibitors.

Rapamycin specifically interferes with GM-CSF signaling in human dendritic cells, leading to apoptosis via increased p27KIP1 expression

The longevity of dendritic cells (DCs) is a critical regulatory factor influencing the outcome of immune responses. Recently, we demonstrated that the immunosuppressive drug rapamycin (Rapa) specifically induces apoptosis in DCs but not in other myeloid cell types. The present study unraveled the mechanism used by Rapa to induce apoptosis in human monocyte-derived DCs. Our data demonstrate that granulocyte-macrophage colony-stimulating factor (GM-CSF) preserves DC survival specifically via the phosphatidylinositol-3 lipid kinase/mammalian target of rapamycin (PI3K/mTOR) signaling pathway, which is abrogated by Rapa at the level of mTOR. Disruption of this GM-CSF signaling pathway induced loss of mitochondrial membrane potential, phosphatidyl-serine exposure, and nuclear changes. Apoptosis of these nonproliferating DCs was preceded by an up-regulation of the cell cycle inhibitor p27(KIP1). Overexpression of p27(KIP1) in DCs using adenoviral gene transduction revealed that apoptosis is directly regulated by p27(KIP1). Furthermore, both overexpression of p27(KIP1) and disruption of the GM-CSF/PI3K/mTOR signaling pathway decreased the expression of the antiapoptotic protein mcl-1. This mTOR/p27(KIP1)/mcl-1 survival seems unique for DCs and may provide novel opportunities to influence immune responses by specific interference with the life span of these cells.

Intercellular trafficking and enhanced in vivo antitumour activity of a non-virally delivered P27-VP22 fusion protein

VP22, a structural protein from herpes simplex virus type I, exhibits the unique property of intercellular trafficking. This protein is exported from primary expressing cells and subsequently imported into neighbouring cells. This property is conserved when VP22 is genetically fused to a protein, making it a promising tool to enhance the delivery of a gene product. We chose to study the intercellular transport and biological effect of a fusion protein between the putative tumour suppressor gene p27(Kip1) and VP22. We show that in vitro, P27VP22 is able to spread as efficiently as VP22. Functionality of the P27VP22 protein was demonstrated by its ability to inhibit cyclin/CDK2 complexes activity. In proliferation and clonogenicity assays, transfection with the P27VP22 plasmid resulted in a stronger cell growth inhibition when compared to transfection with the p27(Kip1) vector. In vivo, sub cutaneous tumours established in nude mice were injected with naked DNA encoding P27 or P27VP22. Our results show that P27VP22 can spread in vivo and that injections of the P27VP22 plasmid resulted in a significantly greater antitumour activity than injections of the P27 plasmid. This study confirms the usefulness of VP22-mediated delivery and suggests that P27VP22 may have applications in cancer gene therapy.

Transfection of p27(Kip1) threonine residue 187 mutant type gene, which is not influenced by ubiquitin-mediated degradation, induces cell cycle arrest in oral squamous cell carcinoma cells

OBJECTIVE

It is well known that reduction of the cyclin-dependent kinase inhibitor p27(Kip1) protein correlates with the malignant behavior of various cancers including oral squamous cell carcinoma (OSCC). The loss of p27(Kip1) protein is suggested to be due to the enhancement of its posttranslational degradation. In the present study, to evaluate the effects of p27(Kip1) transfection on the cell cycle, we transfected OSCC cell lines with a high activity of p27(Kip1) degradation with p27(Kip1) threonine 187-to-alanine (T187A) mutant gene, which is not influenced by ubiquitin-mediated degradation, as well as with wild type gene.

METHODS

We transfected p27(Kip1) T187A mutant and wild type gene into OSCC cell lines (HSC2 and HSC3) by using an ecdysone-inducible gene expression system.

RESULTS

After treatment with ponasterone A, we could find an induction of both p27(Kip1) wild type and T187A mutant protein. Both wild type and T187A mutant protein induced by 5 microM ponasterone A inhibited cell growth and increased cell number at the G1 phase. After treatment with 1 microM ponasterone A, ectopic p27(Kip1) protein was degraded in wild type clones, but not in T187A mutant clones. Moreover, transfection of the T187A mutant gene was more effective in inhibiting cell growth even by induction of a small amount of protein.

CONCLUSION

We suggest that the transfection of the p27(Kip1) T187A mutant gene can be a modality of cancer gene therapy for OSCC.

Deguelin inhibits the growth of colon cancer cells through the induction of apoptosis and cell cycle arrest

As previously demonstrated, deguelin [(7aS, BaS)-13, 13a-dihydro-9,10-dimethoxy-3,3-dimethyl-3H-bis[1]benzo-pyrano[3,4-b:6',5'-e]pyran-7(7aH)-one mediates anti-proliferative properties in a variety of cell types. In the present study, deguelin was found to suppress the growth of HT-29 colon cancer cells with an IC(50) of 4.32 x 10(-8) M. The cells were arrested in the G1-S-phase of the cycle. Investigations of G1/S regulatory proteins by Western blot analyses showed an upregulation of p27, and decreased expression levels of cyclin E and CDK4. Furthermore, by 24 h, exposure to deguelin resulted in an increase in the hypophosphorylated form of Rb. Since hypophosphorylated pRb binds to and inactivates E2F1, additional studies were performed and downregulation of E2F1 was observed after 24 h of treatment with deguelin. These results are consistent with the observation that deguelin arrested cells in the G1-S- phase. In addition, based on ethidium bromide/acridine orange staining, detection of digoxigenin-labelled genomic 3'-OH DNA ends, and DNA laddering, it was found that deguelin exerts its growth inhibitory effects via the induction of apoptosis. Based on these data, the potential of deguelin to serve as a cancer chemotherapeutic agent for colon cancer may be suggested.

Induction of cell cycle arrest and apoptosis in human prostate carcinoma cells by a recombinant adenovirus expressing p27(Kip1)

BACKGROUND

Adp27(Kip1), a recombinant adenovirus, was evaluated for expression of p27, a cyclin-dependent kinase inhibitor (CDKI) and tumor suppressor protein, in human prostate carcinoma cells. Effects of p27(Kip1) on cell cycle and apoptosis were analyzed.

METHODS

We evaluated the effects of overexpression of p27(Kip1) in the human prostate carcinoma cell lines LNCaP, DU-145, and PC-3 in vitro and in vivo. Growth curve studies, cell cycle analysis, terminal deoxynucleotidyl transferase-mediated nick end-labeling (TUNEL), and annexin V-fluorescein isothiocyanate apoptosis analyses were conducted to determine effects of p27(Kip1) on cell cycle. CDKI activity assays and Western blots were conducted to determine presence/activities of CDKIs.

RESULTS

Adp27(Kip1)-induced protein levels increased in a dose-dependent manner; p27(Kip1) protein was detected within 6 hr of infection with Adp27(Kip1) and remained stable for at least 48 hr. The activities of Cdk2, Cdk4, and Cdc2 kinases were inhibited 24 hr after infection with Adp27(Kip1). Bromodeoxyuridine incorporation demonstrated a dose-dependent decrease in S-phase cells 24 hr postinfection. TUNEL analysis revealed an induction of apoptosis (10 pfu/cell) within 48 hr of infection in all cell lines. Growth curve analyses demonstrated that Adp27(Kip1) infection inhibited proliferation of all cell lines tested and decreased cell numbers for Adp27(Kip1)-infected LNCaP and PC-3 cells by 96 hr. Cell cycle analysis of DNA content demonstrated an accumulation of cells in G0/G1-phase 24-120 hr after Adp27(Kip1)-infection. In vivo studies demonstrated a reduction in LNCaP xenograft tumor growth rates in mice injected with Adp27(Kip1).

CONCLUSION

Exogenous p27(Kip1) overexpression results in cell cycle regulation in the human prostate carcinoma cell lines tested, representing the first use of this vector on prostate cancer cell lines in vitro and in vivo. Moreover, p27(Kip1) expression is associated with an increase in early apoptosis, which represents a recently discovered function for this protein. It also represents the first time this association has been observed in prostate carcinoma cell lines. This study provides support for the further development of Adp27(Kip1) as a potential therapeutic vector in the treatment of adenocarcinoma of the prostate.

High-throughput tissue microarray analysis used to evaluate biology and prognostic significance of the E-cadherin pathway in non-small-cell lung cancer

PURPOSE

E-cadherin (E-cad) and its associated intracellular molecules, catenins, are critical for intercellular epithelial adhesion and are often expressed in non-small-cell lung carcinomas (NSCLCs). We constructed tissue microarrays (TMAs) to investigate the expression of cadherins and catenins and their prognostic significance in NSCLC.

PATIENTS AND METHODS

Tumor tissue samples from 193 patients with stages I to III NSCLC were obtained from the University of Colorado Cancer Center and Johns Hopkins Medical Institutions. Viable tumor was sampled in triplicate for the TMAs, and slides were stained by immunohistochemistry with antibodies against E-cad, N-cadherin, alpha (alpha)-, beta (beta)-, and gamma (gamma)-catenin, p120, p27, and adenomatous polyposis coli (APC) gene product. Clinical data were collected by the tumor registries. Patients were followed for a median period of 51 months (range, 18 to 100 months).

RESULTS

Absent or severely reduced membranous expression for E-cad, alpha-, beta-, and gamma-catenin, and p120 were observed in 10%, 17%, 8%, 31%, and 61% of the cases, respectively. Tumor cell dedifferentiation correlated with reduced expression for E-cad, beta-catenin, gamma-catenin, and p120 in squamous cell carcinomas but not in adenocarcinomas. There was an inverse correlation between nodal metastasis and expression of E-cad and gamma-catenin. Besides the traditional clinical prognostic variables, E-cad and alpha-, beta-, and gamma-catenin expression were of positive prognostic value in univariate survival analyses. In multivariate analysis, E-cad expression was the only independent prognostic factor for survival in addition to age, node status, tumor status, and pathologic surgical margins.

CONCLUSION

Reduced expression of E-cad and catenins is associated with tumor cell dedifferentiation, local invasion, regional metastasis, and reduced survival in NSCLC. E-cad is an independent prognostic factor for NSCLC survival.

EGFR tyrosine kinase inhibitor AG1478 inhibits cell proliferation and arrests cell cycle in nasopharyngeal carcinoma cells

Nasopharyngeal carcinoma (NPC), which occurs with a high incidence in southern China and southeast Asia, is of epithelial origin with overexpression of EGF receptor. To study the effect of inhibition of EGFR signaling on nasopharyngeal carcinoma cell proliferation and cell cycle distribution, EGFR tyrosine kinase inhibitor AG1478 was employed to treat Nasopharyngeal Carcinoma CNE2 cells. The results showed that AG1478 inhibited proliferation of CNE2 cells. Immunoblot showed that AG1478 inhibited EGFR phosphorylation in CNE2 cells without reduced expression of EGFR protein. The activation of Akt and MAPK which are downstream molecules of EGFR signaling pathway, were also inhibited by AG1478. AG1478 induced cell cycle arrest in G1 phase, and the levels of protein p27 were significantly up-regulated. We concluded that inhibition of the EGFR signaling induced cell cycle arrest in G1 phase in CNE2 cells and p27 up-regulation was involved in this process. The EGFR kinase specific inhibitor is of potential to be developed into drugs for NPC treatment.

p27(Kip1): regulation and function of a haploinsufficient tumor suppressor and its misregulation in cancer

A major function of p27, also known as Kip1, is to bind and inhibit cyclin/cyclin-dependent kinase complexes, thereby blocking cell cycle progression. As p27 operates at the heart of the cell cycle, it is perhaps not surprising that it is emerging as a key player in multiple cell fate decisions including proliferation, differentiation, and cell death. The central role of p27 makes it important in a variety of disease processes that involve aberrations in cellular proliferation and other cell fates. Most notable among these processes is neoplasia. A large number of studies have reported that p27 expression is frequently downregulated in human tumors. In most tumor types, reduced p27 expression correlates with poor prognosis, making p27 a novel and powerful prognostic marker. In addition to these practical implications, murine and tissue culture models have shown that p27 is a potent tumor suppressor gene for multiple epithelially derived neoplasias. Loss of p27 cooperates with mutations in several oncogenes and tumor suppressor genes to facilitate tumor growth, indicating that p27 may be a "nodal point" for tumor suppression. In contrast to most tumor suppressor genes studied to date, which are recessive at the cellular level, p27 is haploinsufficient for tumor suppression. The fact that tumor suppression by p27 is critically dependent on the absolute level of p27 expression indicates that p27 acts as a rheostat rather than as an on/off switch to control growth and neoplasia.