Correlation of STAT1 with Apoptosis and Cell-Cycle Markers in Esophageal Squamous Cell Carcinoma

We recently found evidence that STAT1 in esophageal squamous carcinoma (ESCC) cells exerts tumor suppressor function, and it regulates five key regulators of apoptosis or cell-cycle progression, including Bcl-2, Bcl-xL, survivin, cyclin D1 and p21. In this study, we confirmed these findings in four ESCC cell lines. Using immunohistochemistry, we also assessed the expression of these proteins in 62 primary tumors. The expression of these markers was heterogeneous, ranging 39 to 69% of the cohort. Significant correlation was found between STAT1 and three proteins (p21, Bcl-xL and survivin), whereas only a trend was identified for cyclin D1 and Bcl-2. We then correlated the expression of these proteins with several clinicopathologic parameters including lymph node metastasis, depth of invasion, clinical stage and overall survival. Significant correlations were found between Bcl-2 and deep invasion (p = 0.033), survivin and lymph node metastasis (p = 0.006), as well as cyclin D1 and clinical stage (p = 0.014). Patients with p21-positive tumors had a significantly longer survival compared to those with p21-negative tumors (p = 0.031). To conclude, our findings support the concept that STAT1 exerts its tumor suppressor effects in ESCC via modulating the expression of key regulators of apoptosis and cell-cycle progression.     

Generation of Reactive Oxygen Species by Polyenylpyrroles Derivatives Causes DNA Damage Leading to G2/M Arrest and Apoptosis in Human Oral Squamous Cell Carcinoma Cells

Oral squamous cell carcinoma (OSCC) accounts for 5.8% of all malignancies in Taiwan and the incidence of OSCC is on the rise. OSCC is also a common malignancy worldwide and the five-year survival rate remains poor. Therefore, new and effective treatments are needed to control OSCC. In the present study we have investigated the efficacy and associated mechanisms of polyenylpyrroles and their analogs in both in vitro cell culture and in vivo nude mice xenografts. Auxarconjugatin B (compound 1a) resulted in cell cycle arrest in the G2/M phase and caspase-dependent apoptosis in OEC-M1 and HSC-3 cells by activating DNA damage and mitochondria dysfunction through the loss of mitochondrial membrane potential, release of cytochrome c, increase in B-cell lymphoma-2-associated X protein level, and decrease in B-cell lymphoma-2 level. Compound 1a-induced generation of intracellular reactive oxygen species through cytochrome P450 1A1 was identified as a major mechanism of its effect for DNA damage, mitochondria dysfunction and apoptosis, which was reversed by antioxidant N-acetylcysteine as well as cytochrome P450 1A1 inhibitor and specific siRNA. Furthermore, compound 1a-treated nude mice showed a reduction in the OEC-M1 xenograft tumor growth and an increase in the caspase-3 activation in xenograft tissue. These results provide promising insights as to how compound 1a mediates cytotoxicity and may prove to be a molecular rationale for its translation into a potential therapeutic against OSCC.     

Bocavirus Infection Induces Mitochondrion-Mediated Apoptosis and Cell Cycle Arrest at G2/M Phase

Bocavirus is a newly classified genus of the family Parvovirinae. Infection with Bocavirus minute virus of canines (MVC) produces a strong cytopathic effect in permissive Walter Reed/3873D (WRD) canine cells. We have systematically characterized the MVC infection-produced cytopathic effect in WRD cells, namely, the cell death and cell cycle arrest, and carefully examined how MVC infection induces the cytopathic effect. We found that MVC infection induces an apoptotic cell death characterized by Bax translocalization to the mitochondrial outer membrane, disruption of the mitochondrial outer membrane potential, and caspase activation. Moreover, we observed that the activation of caspases occurred only when the MVC genome was replicating, suggesting that replication of the MVC genome induces apoptosis. MVC infection also induced a gradual cell cycle arrest from the S phase in early infection to the G₂/M phase at a later stage, which was confirmed by the upregulation of cyclin B1 and phosphorylation of cdc2. Cell cycle arrest at the G₂/M phase was reproduced by transfection of a nonreplicative NS1 knockout mutant of the MVC infectious clone, as well as by inoculation of UV-irradiated MVC. In contrast with other parvoviruses, only expression of the MVC proteins by transfection did not induce apoptosis or cell cycle arrest. Taken together, our results demonstrate that MVC infection induces a mitochondrion-mediated apoptosis that is dependent on the replication of the viral genome, and the MVC genome per se is able to arrest the cell cycle at the G₂/M phase. Our results may shed light on the molecular pathogenesis of Bocavirus infection in general.The Bocavirus genus is newly classified within the subfamily Parvovirinae of the family Parvoviridae (21). The currently known members of the Bocavirus genus include bovine parvovirus type 1 (BPV1) (17), minute virus of canines (MVC) (57), and the recently identified human bocaviruses (HBoV, HBoV2, and HBoV3) (4, 7, 36).MVC was first recovered from canine fecal samples in 1970 (10). The virus causes respiratory disease with breathing difficulty (14, 32, 49) and enteritis with severe diarrhea (11, 39), which often occurs with coinfection with other viruses (39), spontaneous abortion of fetuses, and death of newborn puppies (14, 29). Pathological lesions in fetuses in experimental infections were found in the lymphoid tissue of the lung and small intestine (14). MVC was isolated and grown in the Walter Reed/3873D (WRD) canine cell line (10), which is derived from a subdermoid cyst of an irradiated male dog (10). The full-length 5.4-kb genome of MVC was recently mapped with palindromic termini (60). Under the control of a single P6 promoter, through the mechanism of alternative splicing and alternative polyadenylation, MVC expresses two nonstructural proteins (NS1 and NP1) and two capsid proteins (VP1 and VP2). Like the NS1 proteins of other parvoviruses, the NS1 of MVC is indispensable for genome replication. The NP1 protein, which is unique to the Bocavirus genus, appears to be critical for optimal viral replication, as the NP1 knockout mutant of MVC suffers from severe impairment of replication (60). A severe cytopathic effect during MVC infection of WRD cells has been documented (10, 60).The HBoV genome has been frequently detected worldwide in respiratory specimens from children under 2 years old with acute respiratory illnesses (2, 34, 55). HBoV is associated with acute expiratory wheezing and pneumonia (3, 34, 55) and is commonly detected in association with other respiratory viruses (34, 55). Further studies are necessary, however, to identify potential associations of HBoV infection with clinical symptoms or disease of acute gastroenteritis (7, 36). The full-length sequence of infectious MVC DNA (GenBank accession no. {"type":"entrez-nucleotide","attrs":{"text":"FJ214110","term_id":"219665308","term_text":"FJ214110"}}FJ214110) that we have reported shows 52.6% identity to HBoV, while the NS1, NP1, and VP1 proteins are 38.5%, 39.9%, and 43.7% identical to those of HBoV, respectively (60).The cytopathic effect induced during parvovirus infection has been widely documented, e.g., in infections with minute virus of mice (MVM) (13), human parvovirus B19 (B19V) (58), parvovirus H-1 (25, 52), and BPV1 (1). In Bocavirus, cell death during BPV1 infection of embryonic bovine tracheal cells has been shown to be achieved through necrosis, independent of apoptosis (1). B19V-induced cell death of primary erythroid progenitor cells has been shown to be mainly mediated by an apoptotic pathway (58) in which the nonstructural protein 11kDa plays a key role (16). In contrast, the MVM-induced cytopathic effect has been revealed to be mediated by NS1 interference with intracellular casein kinase II (CKII) signaling (22, 44, 45), a nonapoptotic cell death. Oncolytic parvovirus H-1 infections can induce either apoptosis or nonapoptotic cell death, depending on the cell type (25, 40). Therefore, the mechanisms underlying parvovirus infection-induced cell death vary, although NS1 has been widely shown to be involved in both apoptotic and nonapoptotic cell death. The nature of the cytopathic effect during Bocavirus MVC infection has not been studied.Parvovirus replication requires infected cells at the S phase. Infection with parvovirus has been revealed to accompany a cell cycle perturbation that mostly leads to an arrest in the S/G₂ phase or the G₂/M phase during infection (30, 33, 42, 47, 65). MVM NS1 expression induces an accumulation of sensitive cells in the S/G₂ phase (6, 46, 47). Whether MVC infection-induced cell death is accompanied by an alternation of cell cycle progression and whether the viral nonstructural protein is involved in these processes have not been addressed.In this study, we found, in contrast with other members of the family Parvoviridae, expression of both the nonstructural and structural proteins of MVC by transfection did not induce cell death or cell cycle arrest. However, the cytopathic effect induced during MVC infection is a replication-coupled, mitochondrion-mediated and caspase-dependent apoptosis, accompanied with a gradual cell cycle arrest from the S phase to the G₂/M phase, which is facilitated by the MVC genome.     

AZD2014 Radiosensitizes Oral Squamous Cell Carcinoma by Inhibiting AKT/mTOR Axis and Inducing G1/G2/M Cell Cycle Arrest

Background

Oral squamous cell carcinoma (OSCC) is one of the most common malignant neoplasms in Taiwan. Activation of the mTOR signaling pathway has been linked to decreased radiation responsiveness in human oral cancer, thus it limits efficacy of radiotherapy. To address this question, we investigated the effect of AZD2014, a novel small molecular ATP-competitive inhibitor of mTORC1 and mTORC2 kinase, as a radiosensitizer in primary OSCC and OSCC-derived cell line models.

Methods

We isolated primary tumor cells from OSCC tissues and cell lines. AZD2014 was administered with and without ionizing radiation. The radiosensitizing effect of AZD2014 were then assessed using cell viability assays, clonogenic survival assays, and cell cycle analyses. Western blotting was used to detect protein expression.

Results

Combination treatment with AZD2014 and irradiation resulted in significant reduction in OSCC cell line and primary OSCC cell colony formation due to the enhanced inhibition of AKT and both mTORC1 and mTORC2 activity. Pre-treatment with AZD2014 in irradiated oral cancer cells induced tumor cell cycle arrest at the G1 and G2/M phases, which led to disruption of cyclin D1-CDK4 and cyclin B1-CDC2 complexes. Moreover, AZD2014 synergized with radiation to promote both apoptosis and autophagy by increasing caspase-3 and LC3 in primary OSCC cells.

Conclusions

These findings suggest that in irradiated OSCC cells, co-treatment with AZD2014, which targets mTORC1 and mTORC2 blockade, is an effective radiosensitizing strategy for oral squamous cell carcinoma.     

Piperine Causes G1 Phase Cell Cycle Arrest and Apoptosis in Melanoma Cells through Checkpoint Kinase-1 Activation

In this study, we determined the cytotoxic effects of piperine, a major constituent of black and long pepper in melanoma cells. Piperine treatment inhibited the growth of SK MEL 28 and B16 F0 cells in a dose and time-dependent manner. The growth inhibitory effects of piperine were mediated by cell cycle arrest of both the cell lines in G1 phase. The G1 arrest by piperine correlated with the down-regulation of cyclin D1 and induction of p21. Furthermore, this growth arrest by piperine treatment was associated with DNA damage as indicated by phosphorylation of H2AX at Ser139, activation of ataxia telangiectasia and rad3-related protein (ATR) and checkpoint kinase 1 (Chk1). Pretreatment with AZD 7762, a Chk1 inhibitor not only abrogated the activation of Chk1 but also piperine mediated G1 arrest. Similarly, transfection of cells with Chk1 siRNA completely protected the cells from G1 arrest induced by piperine. Piperine treatment caused down-regulation of E2F1 and phosphorylation of retinoblastoma protein (Rb). Apoptosis induced by piperine was associated with down-regulation of XIAP, Bid (full length) and cleavage of Caspase-3 and PARP. Furthermore, our results showed that piperine treatment generated ROS in melanoma cells. Blocking ROS by tiron protected the cells from piperine mediated cell cycle arrest and apoptosis. These results suggest that piperine mediated ROS played a critical role in inducing DNA damage and activation of Chk1 leading to G1 cell cycle arrest and apoptosis.     

Cucurbitacin E Induces Cell Cycle G2/M Phase Arrest and Apoptosis in Triple Negative Breast Cancer

Triple negative breast cancer (TNBC) is a highly aggressive form of breast cancer resistant to many common treatments. In this study, we compared the effects of 12 phytochemical drugs on four cancer cell lines, and noticed that Cucurbitacin E (CuE) significantly inhibited TNBC cell growth by inducing cell cycle G2/M phase arrest and apoptosis. CuE reduced expression of Cyclin D1, Survivin, XIAP, Bcl2, and Mcl-1 in MDA-MB-468 and SW527, and within MDA-MB-468, CuE significantly increased activation of JNK and inhibited activation of AKT and ERK. Collectively, these results suggest that CuE may be a viable compound for developing novel TNBC therapeutics.     

Human Parvovirus B19 Induces Cell Cycle Arrest at G2 Phase with Accumulation of Mitotic Cyclins

Human parvovirus B19 infects specifically erythroid progenitor cells, which causes transient aplastic crises and hemolytic anemias. Here, we demonstrate that erythroblastoid UT7/Epo cells infected with B19 virus fall into growth arrest with 4N DNA, indicating G(2)/M arrest. These B19 virus-infected cells displayed accumulation of cyclin A, cyclin B1, and phosphorylated cdc2 and were accompanied by an up-regulation in the kinase activity of the cdc2-cyclin B1 complex, similar to that in cells treated with the mitotic inhibitor. However, degradation of nuclear lamina and phosphorylation of histone H3 and H1 were not seen in B19 virus-infected cells, indicating that the infected cells do not enter the M phase. Accumulation of cyclin B1 was persistently localized in the cytoplasm, but not in the nucleus, suggesting that B19 virus infection of erythroid cells raises suppression of nuclear import of cyclin B1, resulting in cell cycle arrest at the G(2) phase. The B19 virus-induced G(2)/M arrest may be the critical event in the damage of erythroid progenitor cells seen in patients with B19 virus infection.     

Pterostilbene Simultaneously Induced G0/G1-Phase Arrest and MAPK-Mediated Mitochondrial-Derived Apoptosis in Human Acute Myeloid Leukemia Cell Lines

Background

Pterostilbene (PTER) is a dimethylated analog of the phenolic phytoalexin, resveratrol, with higher anticancer activity in various tumors. Herein, the molecular mechanisms by which PTER exerts its anticancer effects against acute myeloid leukemia (AML) cells were investigated.

Methodology and Principal Findings

Results showed that PTER suppressed cell proliferation in various AML cell lines. PTER-induced G0/G1-phase arrest occurred when expressions of cyclin D3 and cyclin-dependent kinase (CDK)2/6 were inhibited. PTER-induced cell apoptosis occurred through activation of caspases-8-9/-3, and a mitochondrial membrane permeabilization (MMP)-dependent pathway. Moreover, treatment of HL-60 cells with PTER induced sustained activation of extracellular signal-regulated kinase (ERK)1/2 and c-Jun N-terminal kinase (JNK)1/2, and inhibition of both MAPKs by their specific inhibitors significantly abolished the PTER-induced activation of caspases-8/-9/-3. Of note, PTER-induced cell growth inhibition was only partially reversed by the caspase-3-specific inhibitor, Z-DEVE-FMK, suggesting that this compound may also act through a caspase-independent pathway. Interestingly, we also found that PTER promoted disruption of lysosomal membrane permeabilization (LMP) and release of activated cathepsin B.

Conclusion

Taken together, our results suggest that PTER induced HL-60 cell death via MAPKs-mediated mitochondria apoptosis pathway and loss of LMP might be another cause for cell apoptosis induced by PTER.     

Induction of Apoptosis and Antiproliferative Activity of Naringenin in Human Epidermoid Carcinoma Cell through ROS Generation and Cell Cycle Arrest

A natural predominant flavanone naringenin, especially abundant in citrus fruits, has a wide range of pharmacological activities. The search for antiproliferative agents that reduce skin carcinoma is a task of great importance. The objective of this study was to analyze the anti-proliferative and apoptotic mechanism of naringenin using MTT assay, DNA fragmentation, nuclear condensation, change in mitochondrial membrane potential, cell cycle kinetics and caspase-3 as biomarkers and to investigate the ability to induce reactive oxygen species (ROS) initiating apoptotic cascade in human epidermoid carcinoma A431 cells. Results showed that naringenin exposure significantly reduced the cell viability of A431 cells (p<0.01) with a concomitant increase in nuclear condensation and DNA fragmentation in a dose dependent manner. The intracellular ROS generation assay showed statistically significant (p<0.001) dose-related increment in ROS production for naringenin. It also caused naringenin-mediated epidermoid carcinoma apoptosis by inducing mitochondrial depolarization. Cell cycle study showed that naringenin induced cell cycle arrest in G₀/G₁ phase of cell cycle and caspase-3 analysis revealed a dose dependent increment in caspase-3 activity which led to cell apoptosis. This study confirms the efficacy of naringenin that lead to cell death in epidermoid carcinoma cells via inducing ROS generation, mitochondrial depolarization, nuclear condensation, DNA fragmentation, cell cycle arrest in G₀/G₁ phase and caspase-3 activation.     

Overexpression of Wip1 Is Associated with Biologic Behavior in Human Clear Cell Renal Cell Carcinoma

Wild-type p53-induced phosphatase (Wip1 or PPM1D) has been reported to be aberrantly expressed in various cancers and correlated with the malignant behavior of cancer cells. However, the function of Wip1 in RCC remains unclear. The present study investigated its abnormal expression and dysfunctions in clear cell renal cell carcinoma (ccRCC) in vitro. With the combination of immunohistochemistry, western blotting, immunofluorescence, qRT-PCR, and cell proliferation, migration and invasion assays, we found that levels of Wip1 mRNA and protein were dramatically increased in human ccRCC tissues (P<0.001 for both), and upregulation of Wip1 was significantly associated with depth of invasion (P<0.001), Distant metastasis (P = 0.001), lymph node status (P<0.001) and Fuhrman grade (P<0.001). Wip1 knockdown inhibited the proliferation, migration and invasion of 786-O and RLC-310 cells, whereas Wip1 overexpression promoted the growth and aggressive phenotype of 786-O and RLC-310 cells in vitro. The uni- and multivariate analyses indicated that expression of Wip1 was an independent predictor for survival of ccRCC patients (P = 0.003, P = 0.027 respectively). Wip1- negative patients had a higher tumor-free/overall survival rate than patients with high Wip1 expression (P = 0.001, P = 0.002 respectively). Overexpression of Wip1 is useful in the prediction of survival in ccRCC patients.     

过表达UHRF2通过上调p53及p21表达引起HEK293细胞G1期阻滞

UHRF2（ubiquitin like with PHD and ring finger domains 2）是新近发现的具有多个结构域的核蛋白,在细胞周期调控和表观遗传学中发挥重要作用．近期研究提示,UHRF2是肿瘤抑制蛋白p53的1个E3连接酶,在体内外能与p53相互结合并促进其泛素化,过表达UHRF2能使细胞周期停滞于G1期．然而,UHRF2介导的G1期阻滞及其与p53联系尚不清楚．通过共转染UHRF2质粒及p53特异性小干扰RNA(siRNAs)到HEK293细胞构建细胞模型,探索UHRF2引起细胞周期停滞与p53之间的关系．结果显示,UHRF2能促进HEK293细胞中p53的稳定,从而引起p21 (CIP1/WAF1)基因表达,并使细胞周期停滞于G1期;但在siRNA抑制p53的表达后p21(CIP1/WAF1)表达降低,UHRF2引起的细胞周期阻滞消除．研究结果提示,UHRF2可通过稳定p53,上调p21的表达,从而介导细胞周期阻滞于G1期;同时UHRF2可能参与细胞周期调控及DNA损伤反应（DNA damage response, DDR）．UHRF2稳定p53的具体分子机制及其在DDR中的作用有待进一步研究证明．     

Overexpression of SATB1 Is Associated with Biologic Behavior in Human Renal Cell Carcinoma

Special AT-rich sequence-binding protein-1 (SATB1) has been reported to be aberrantly expressed in various cancers and correlated with the malignant behavior of cancer cells. However, the function of SATB1 in RCC remains unclear. With the combination of immunohistochemistry, western blotting, immunofluorescence, qRT-PCR, and cell proliferation, migration and invasion assays, we found that levels of SATB1 mRNA and protein were dramatically increased in human ccRCC tissues (P<0.001 for both), and upregulation of SATB1 was significantly associated with depth of invasion (P<0.001), lymph node status (P = 0.001) and TNM stage (P = 0.009). SATB1 knockdown inhibited the proliferation, migration and invasion of 786-O cells, whereas SATB1 overexpression promoted the growth and aggressive phenotype of ACHN cells in vitro. Furthermore, SATB1 expression was positively correlated with ZEB2 expression (P = 0.013), and inversely linked to levels of SATB2 and E-cadherin (P = 0.005 and P<0.001, respectively) in ccRCC tissues. Our data provide a basis for the concept that overexpression of SATB1 may play a critical role in the acquisition of an aggressive phenotype for RCC cells through EMT, providing new insights into the significance of SATB1 in invasion and metastasis of ccRCC, which may contribute to fully elucidating the exact mechanism of development and progression of RCC.     

Leptospermum flavescens Constituent-LF1 Causes Cell Death through the Induction of Cell Cycle Arrest and Apoptosis in Human Lung Carcinoma Cells

Leptospermum flavescens Sm. (Myrtaceae), locally known as ‘Senna makki’ is a smallish tree that is widespread and recorded to naturally occur in the montane regions above 900 m a.s.l from Burma to Australia. Although the species is recorded to be used traditionally to treat various ailments, there is limited data on biological and chemical investigations of L. flavescens. The aim of the present study was to investigate and understand the ability of L. flavescens in inducing cell death in lung cancer cells. The cytotoxic potentials of the extraction yields (methanol, hexane, ethyl acetate and water extracts as wells as a semi pure fraction, LF1) were evaluated against two human non-small cell lung carcinoma cell lines (A549 and NCI-H1299) using the MTT assay. LF1 showed the greatest cytotoxic effect against both cell lines with IC₅₀ values of 7.12 ± 0.07 and 9.62 ± 0.50 μg/ml respectively. LF1 treated cells showed a sub-G₁ region in the cell cycle analysis and also caused the presence of apoptotic morphologies in cells stained with acridine orange and ethidium bromide. Treatment with LF1 manifested an apoptotic population in cells that were evaluated using the Annexin V/ propidium iodide assay. Increasing dosage of LF1 caused a rise in the presence of activated caspase-3 enzymes in treated cells. Blockage of cell cycle progression was also observed in LF1-treated cells. These findings suggest that LF1 induces apoptosis and cell cycle arrest in treated lung cancer cells. Further studies are being conducted to isolate and identify the active compound as well to better understand the mechanism involved in inducing cell death.     

过表达NOLC1诱导人非小细胞肺癌细胞凋亡

人核仁磷酸化蛋白1 (Nucleolar and coiledbody phosphoprotein 1,NOLC1)在癌症的发生发展过程中起着至关重要的调控作用,为探讨NOLC1对肺癌细胞的作用,本研究通过Gateway系统构建重组NOLC1腺病毒载体,成功包装NOLC1腺病毒后,分别感染正常人类胚胎肺细胞(HEL)和非小细胞肺癌细胞(A549细胞),过表达NOLC1。通过MTT实验、AnnexinV-APC/PI双染法和线粒体膜电位实验,证明与HEL细胞相比,NOLC1的过表达对A549细胞的活性降低、凋亡增加、线粒体膜电位下降影响较为显著;通过Real-time PCR检测Caspase家族、TNF与受体家族和BCL2家族基因的表达,发现过表达NOLC1明显上调了A549细胞中促凋亡基因的表达,下调了抗凋亡基因的表达,其中两种重要的促凋亡蛋白CASP8和BAX均显著上调,但是在HEL细胞中这种影响不明显。研究结果表明过表达NOLC1蛋白通过对线粒体通路和死亡受体通路的共同作用,对非小细胞癌具有显著的抗肿瘤活性。     

PIAS3α过表达对前列腺癌细胞增殖和凋亡的影响

目的 研究过表达PIAS3α蛋白对人前列腺癌细胞系DU145细胞增殖、细胞周期和凋亡的影响.方法 构建pcDNA3.1(+)-HA-PIAS3α真核表达载体,转染前列腺癌细胞系DU145,以蛋白免疫印迹实验检测外源PIAS3α的表达,通过MTT法检测细胞增殖,以流式细胞术分析细胞周期和细胞凋亡.结果 成功构建PIAS3α真核表达质粒,蛋白免疫印迹实验证实外源性PIAS3蛋白质DU145细胞中获得表达.分析目的 蛋白质过表达后的细胞生物学效应,结果显示在DU145细胞中过表达PIAS3α后,细胞增殖受到抑制;同时,细胞周期G0/G1期细胞显著增加,而S期细胞减少,细胞凋亡比率增加.结论 过表达PIAS3α抑制前列腺癌细胞的增殖并诱导其凋亡.     

Fusarochromanone Induces G1 Cell Cycle Arrest and Apoptosis in COS7 and HEK293 Cells

Fusarochromanone (FC101), a mycotoxin produced by the fungus Fusarium equiseti, is frequently observed in the contaminated grains and feedstuffs, which is toxic to animals and humans. However, the underlying molecular mechanism remains to be defined. In this study, we found that FC101 inhibited cell proliferation and induced cell death in COS7 and HEK293 cells in a concentration-dependent manner. Flow cytometric analysis showed that FC101 induced G₁ cell cycle arrest and apoptosis in the cells. Concurrently, FC101 downregulated protein expression of cyclin D1, cyclin-dependent kinases (CDK4 and CDK6), and Cdc25A, and upregulated expression of the CDK inhibitors (p21^Cip1 and p27^Kip1), resulting in hypophosphorylation of Rb. FC101 also inhibited protein expression of Bcl-2, Bcl-xL, Mcl-1 and survivin, and induced expression of BAD, leading to activation of caspase 3 and cleavage of PARP, indicating caspase-dependent apoptosis. However, Z-VAD-FMK, a pan-caspase inhibitor, only partially prevented FC101-induced cell death, implying that FC101 may induce cell death through both caspase-dependent and -independent mechanisms. Our results support the notion that FC101 executes its toxicity at least by inhibiting cell proliferation and inducing cell death.     

Retinoic Acid-Mediated G1 Arrest Is Associated with Induction of p27 and Inhibition of Cyclin-Dependent Kinase 3 in Human Lung Squamous Carcinoma CH27 Cells

Retinoids are promising agents for the prevention and treatment of several human malignancies including lung cancer. In this study, the effect of retinoic acid (RA) on cell growth and the mechanism of growth modulation were examined in human lung squamous carcinoma CH27 cells. Here we report that RA mediated the dose- and time-dependent growth arrest in G1 phase, accompanied by the up-regulation of p27^Kip1 and the down-regulation of the cyclin-dependent kinase 3 (Cdk3) and p21^CIP1/Waf1 proteins. Furthermore, RA-induced growth arrest of CH27 cells was also associated with increased retinoic acid receptor β (RARβ) and reduced c-Myc expression. However, RA had no effect on the levels of cyclins A, D1, D3, E, or H, or on Cdk2, Cdk4, Cdk5, CDk6, Cdk7, p16^Ink4A, p15^Ink4B, p53, or pRb proteins in CH27 cells. Evaluation of the kinase activity of cyclin–Cdk complexes showed that RA increases p27^Kip1 expression in CH27 cells leading to markedly reduced cyclin A/Cdk2 kinase activity and slightly reduced cyclin E/Cdk2 kinase activity, with no effect on cyclin D/Cdk4 and cyclin D/Cdk6 activities. Moreover, coincident with the decrease in kinase activity was a drastic increase in cyclin A-bound p27^Kip1. These results suggest that increases in the levels of p27^Kip1 and its binding to cyclin A, as well as reduction of Cdk3 protein expression, are strong candidates for the cell cycle regulator that prevents the entry into the S phase in RA-treated CH27 cells, with prolongation of G1 phase and inhibition of DNA synthesis.     

H2-Calponin 在食管鳞癌中的表达及其与食管磷癌预后的关系

目的:探讨H_2-Calponin在食管磷癌组织中的表达及其与食管磷癌患者临床病理特征及预后的相关性。方法:利用免疫组织化学染色技术检测73例食管磷癌及相应癌旁组织中H_2-Calponin的表达情况,并分析其与食管磷癌患者临床病理参数及预后的关系。结果:H_2-calponin在食管磷癌组织中的阳性表达率为95.8%(70/73),显著高于癌旁组织(35.8%,24/67),差异具有统计学意义(p0.0001)。H_2-calponin的表达与食管癌患者的性别、年龄、肿瘤大小、浸润深度及淋巴结转移均无显著相关性,但与AJCC分期显著相关(P0.05)。H_2-calponin的表达水平影响食管癌患者预后及生存期。结论:H_2-Calponin在食管磷癌组织中呈高表达并可预示食管磷癌预后不良。