CD95-induced JNK activation signals are transmitted by the death-inducing signaling complex (DISC), but not by Daxx.

Here we investigated CD95-mediated JNK activation pathways and their physiological relevance by employing a variety of cell lines with deficiencies in individual signal transmitting proteins. JNK activation was completely dependent on the activation of caspases in type I and type II cells, as revealed by the inhibitory effects of the caspase inhibitors zVAD-fmk or the cowpoxvirus-encoded CrmA protein. Jurkat cells deficient in caspase-8 or expressing a dominant negative (DN) form of FADD were unable to induce JNK in response to CD95 ligation, indicating that these death-inducing signaling complex (DISC) proteins are required for signal transmission. Activation of caspases, JNK and apoptosis occurred with a markedly slower kinetics in cells expressing a DN version of ASK1, revealing an important contribution of ASK1 for these processes. A C-terminally truncated version of Daxx impaired CD95-mediated apoptosis without affecting the JNK signal. DN forms of FADD, MKK4 and MKK7 completely inhibited CD95-mediated JNK activation but remained without impact on cell killing, indicating that JNK activation is not required for the execution process of CD95-mediated cell killing.     

Inhibition of proteasome function induced apoptosis in gastric cancer

The ubiquitin-proteasome pathway plays a critical role in the degradation of cellular proteins and cell cycle control. Dysregulating the degradation of such proteins should have profound effects on tumor growth and causes cells to undergo apoptosis. The aims of this study are to evaluate the ubiquitin-proteasome pathway in gastric cancer and the potential role of pharmacological inhibition of proteasome on induction of apoptosis in gastric cancer cells. Gastric cancer cell lines AGS (p53 wild-type) and MKN-28 (p53 mutant) were treated with proteasome inhibitor MG132. The results showed that MG132 inhibited cell proliferation in AGS and MKN-28 cells in a time- and dose-dependent manner. The inhibition of cell proliferation was caused by apoptosis which was also time- and dose-dependent. AGS cells were more responsive to MG132 than MKN-28 cells. Induction of apoptosis was preceded by the activation of caspase-3, as measured by a colorimetric caspase-3 cellular activity and Western blotting of the cleavage of caspase-3 and its substrate PARP. Activation of caspase-7 was also exhibited. In addition, z-VAD-fmk, a broad spectrum caspase inhibitor, reversed apoptosis induced by MG132 in AGS and MKN28 cells. Although z-DEVD-fmk, a specific caspase-3 inhibitor, suppressed MG132-induced apoptosis in MKN28 cells, it only partially rescued the apoptotic effect in AGS cells. Caspase-3 activation was the result of release of cytochrome c from mitochondria into the cytosol, as a consequence of upregulation of bax. There were overexpressions of all the proteasome-related proteins p53, p21(waf1) and p27(kip1) at 4 hr after proteasome inhibition which was identified by the accumulation of ubiquitin-tagged proteins. This was accompanied by accumulation of cells at G(1) phase. Our present study suggests that inhibition of proteasome function in gastric cancer cells induces apoptosis and proteasomal inhibitors have potential use as novel anticancer drugs in gastric cancer.     

Epstein-Barr virus-encoded latent membrane protein 1 promotes stress-induced apoptosis upstream of caspase-2-dependent mitochondrial perturbation

Previous studies have shown that Epstein-Barr virus (EBV)-encoded latent membrane protein 1 (LMP1) enhances etoposide-induced apoptosis in epithelial cells. Our study was undertaken to further dissect the modulation of tumor cell apoptosis by this viral protein. Using an inducible system of LMP1 expression in HeLa cells, we show herein that etoposide-triggered apoptosis, as evidenced by nuclear condensation and caspase-3 activation, is enhanced by LMP1. LMP1 also potentiates etoposide-induced processing and activation of caspase-2 in this model and enhances the dissipation of mitochondrial transmembrane potential and the release of cytochrome c in response to etoposide. Moreover, cisplatin-triggered activation of caspases 2 and 3 is potentiated upon expression of LMP1. A similar LMP1-mediated enhancement of cisplatin-induced caspase activation was seen upon stable transfection of wild-type LMP1 into the nasopharyngeal carcinoma cell line, TW03. Finally, using deletion mutants of LMP1 to determine the region of LMP1 required for apoptosis potentiation, we found that amino acids 350-386 (located within the CTAR2 domain) were responsible for sensitizing cells to cisplatin. We conclude that LMP1-dependent potentiation of stress-induced apoptosis occurs at an early step in the apoptosis cascade, upstream of the activation of caspase-2, and involves the C-terminal signaling domain of LMP1. These findings could have important ramifications for the treatment of EBV-associated malignancies of epithelial origin, including nasopharyngeal carcinoma.     

Overexpression of RbAp46 facilitates stress-induced apoptosis and suppresses tumorigenicity of neoplastigenic breast epithelial cells

We have found previously that the retinoblastoma (Rb) suppressor associated protein 46 (RbAp46) is a gene upregulated by the Wilms' tumor suppressor, WT1, and functions as a potent growth inhibitor. To investigate the effect of RbAp46 overexpression on early development of breast cancer, we established stable cell lines from neoplastigenic breast epithelial cells, MCF10AT3B, a cell line derived from a model of human proliferative disease, to constitutively express exogenous RbAp46. We have found that expression of RbAp46 suppressed colony formation of MCF10AT3B cells in soft-agar, and inhibited tumor formation of these cells in nude mice. Expression of RbAp46 sensitized MCF10AT3B cells to apoptosis induced by serum deprivation and hydrocortisone withdrawal. Furthermore, we have found that the c-Jun NH2-terminal kinase (JNK) pathway and GADD45, a growth arrest- and DNA damage-inducible gene, are constitutively activated in RbAp46-expressing cells. Our data suggested that high levels of RbAp46 expression inhibit the tumorigenicity of neoplastigenic breast epithelial cells by facilitating JNK-dependent apoptotic cell death. Our data also suggested that dysregulation of RbAp46 gene may be involved in the early development of breast cancer.     

JNK/SAPK mediates doxorubicin-induced differentiation and apoptosis in MCF-7 breast cancer cells

Pharmacologic induction of cancer cell differentiation has potential in the treatment of breast cancer. Doxorubicin, a widely used anthracycline antibiotic, was previously reported to induce differentiation of MCF-7 breast cancer cells. We demonstrate in this study that inhibition of MCF-7 breast cancer cell growth by low dose doxorubicin (0.01 µg/ml) was accompanied by an increase in cytokeratin 8/18 and milk fat globule membrane protein expression, biomarkers for differentiation of breast cancer, as well as an increase in JNK/SAPK phosphorylation. High dose doxorubicin (10.0 µg/ml) induced apoptosis in these cells. Overexpression of dominant-inhibitory forms of JNK1 and c-Jun blocked both the differentiation and apoptotic effects of doxorubicin. These results suggest that JNK/SAPK pathway signaling plays a prominent role in doxorubicin-induced cell cycle withdrawal, differentiation and control of apoptosis in this cell system. These findings support the possibility that JNK/SAPK pathway activation may be a means of therapeutic intervention in breast cancer.     

Activation of SAPK/JNK by camptothecin sensitizes androgen-independent prostate cancer cells to Fas-induced apoptosis

We have previously shown that the androgen-independent prostate cancer cells DU145, despite expressing Fas and FasL, were resistant to anti-Fas-induced apoptosis, and that this resistance could be overcome by pretreating the cells with sublethal doses of camptothecin. Here, we provide evidence that SAPK/JNK activity is required for camptothecin sensitization to anti-Fas-induced apoptosis. Camptothecin, but not Fas ligation, was shown to activate SAPK/JNK in a time-dependent manner, and to induce c-Jun expression. The effects were more prominent in cells treated with both camptothecin and anti-Fas. The expression levels of MKP-1, a phosphatase which regulates SAPK/JNK and which has been implicated in prostate cancer resistance to apoptosis, remained unchanged. Inhibition of caspases had no effect on the SAPK/JNK activation, suggesting that this activation is an upstream event in the Fas-signalling pathway, and is independent of caspase activity. Antisense oligonucleotides targeted to JNK1 and JNK2 reversed the effect of camptothecin. These results suggest that stress kinase activation can significantly influence the fate of androgen-independent prostate cancer cells following Fas receptor ligation.     

抑制JNK通路对TRAIL诱导胃癌细胞凋亡影响的研究

目的:研究JNK信号传导通路对TRAIL诱导胃癌细胞凋亡的影响。方法:四甲基偶氮唑蓝(MTT)比色法测定细胞活力;蛋白质印迹法检测细胞内磷酸化JNK及总JNK的表达水平;流式细胞术碘化丙啶(PI)染色检测细胞凋亡及细胞周期分布。为研究JNK通路活性对TRAIL抗肿瘤作用的影响,将实验分为空白对照组、TRAIL单药组(100μg/L)、JNK抑制剂组(SP600125,20μmol/L)和联合用药组(SP600125+TRAIL)。结果:采用25、50、100和200μg/LTRAIL作用于MGC803细胞24 h,细胞活力仅轻度下降。进一步研究发现,TRAIL作用后细胞内磷酸化JNK水平明显升高,提示JNK信号通路被活化。同TRAIL单药组相比,联合用药组的细胞活力明显降低〔(53.5±3.2)%vs(88.3±1.1)%,P<0.05〕,细胞凋亡明显增加〔(21.3±5.1)%vs(5.7±0.1)%,P<0.05〕,G2/M期细胞比例明显升高〔(38.0±6.0)%vs(25.7±2.9)%,P<0.05〕。结论:抑制JNK通路能明显增强TRAIL对MGC803细胞的抗肿瘤作用,其机制可能与诱导细胞凋亡及G2/M期阻滞有关。     

Telomere homolog oligonucleotides induce apoptosis in malignant but not in normal lymphoid cells: Mechanism and therapeutic potential

Human B‐ or T‐cell lymphoma lines and primary murine lymphomas were treated with DNA oligonucleotides homologous to the telomere (TTAGGG repeat; “T‐oligo”), either alone or in combination with standard, widely‐used anticancer chemotherapeutic agents. T‐oligo induces cell cycle arrest and apoptosis in cultured human or murine B or T‐lymphoma cell lines and primary tumor cells, but exerts no detectable toxicity on normal human or murine primary lymphocytes. Exposure to T‐oligo is hypothesized to mimic exposure of the 3′ telomere repeat sequence, activating the ataxia telangiectasia mutated kinase, which phosphorylates downstream effectors such as p53, but effects are not dependent solely on functional p53. T‐oligo causes early S‐phase arrest and cooperates well with G₂‐ or M‐phase‐specific anticancer agents; when combined at 1/10th of the conventional dose, vincristine and T‐oligo produce greater‐than‐additive killing of human or murine lymphoma cells (78% of cells undergoing apoptosis after 6 hr vs. 5% of control cells). In mice, 1/10th of the conventional dose of a standard combination of cyclophosphamide, adriamycin, vincristine and prednisone is twice as effective when used in combination with low dose T‐oligo. Thus, T‐oligo sensitizes tumors to traditional anticancer agents and represents a potentially important new addition to the therapeutic arsenal for aggressive lymphomas. © 2008 Wiley‐Liss, Inc.     

Role of JNK activation in paclitaxel-induced apoptosis in human head and neck squamous cell carcinoma

It has been reported that paclitaxel activates cell cycle arrest and increases caspase protein expression to induce apoptosis in head and neck squamous cell carcinoma (HNSCC) cell lines. However, the potential signaling pathway regulating this apoptotic phenomenon remains unclear. The present study used OEC-M1 cells to investigate the underlying molecular mechanism of paclitaxel-induced apoptosis. Following treatment with paclitaxel, cell viability was assessed via the MTT assay. Necrosis, apoptosis, cell cycle and mitochondrial membrane potential (∆Ψm) were analyzed via flow cytometric analyses, respectively. Western blot analysis was performed to detect the expression levels of proteins associated with the MAPK and caspase signaling pathways. The results demonstrated that low-dose paclitaxel (50 nM) induced apoptosis but not necrosis in HNSCC cells. In addition, paclitaxel activated the c-Jun N-terminal kinase (JNK), but not extracellular signal-regulated kinase or p38 mitogen-activated protein kinase. The paclitaxel-activated JNK contributed to paclitaxel-induced apoptosis, activation of caspase-3, −6, −7, −8 and −9, and reduction of ∆Ψm. In addition, caspase-8 and −9 inhibitors, respectively, significantly decreased paclitaxel-induced apoptosis. Notably, Bid was truncated following treatment with paclitaxel. Taken together, the results of the present study suggest that paclitaxel-activated JNK is required for caspase activation and loss of ∆Ψm, which results in apoptosis of HNSCC cells. These results may provide mechanistic basis for designing more effective paclitaxel-combining regimens to treat HNSCC.     

Anisomycin activates JNK and sensitises DU 145 prostate carcinoma cells to Fas mediated apoptosis

Treatment of the hormone refractory prostate cancer cell line DU 145 with sublethal concentrations of chemotherapeutic drugs has been reported to sensitise these cells to Fas mediated apoptosis. However, the mechanism by which this occurs has not been determined. Our group has shown that inhibition of JNK activity completely abrogates the effects of chemotherapeutic drugs. Using anisomycin, a potent JNK agonist, we have demonstrated a role for JNK in Fas mediated apoptosis in DU 145 cells. Inhibition of Caspase 8 and Caspase 9 completely inhibits this process which suggests that DU 145 cells require mitochondrial amplification of the Fas apoptotic signal. Furthermore, we have shown that inhibition of Fas mediated apoptosis is an early event in DU 145 cells, occurring upstream of Caspase 8 cleavage. It is hoped that identifying the target of JNK will allow novel therapies to be developed for the treatment of hormone refractory prostate cancer. Such therapies are especially important because no single or combined treatment to date has significantly prolonged survival in patients with hormone refractory prostate cancer.     

JNK pathway regulates estradiol-induced apoptosis in hormone-dependent human breast cancer cells

Estrogen is known to stimulate breast cancer development in humans. Ironically, high doses of estrogen can induce regression of hormone-dependent breast cancer in postmenopausal women. The mechanism by which estrogen induces tumour regression in breast cancer is still unknown. We found that under low growth-stimulated conditions, high concentrations of 17-β-estradiol (estradiol) induces apoptosis and concomitantly increases phosphorylation of c-jun in estrogen receptor (ER)-positive breast cancer cell line, MCF-7, but not in ER-negative breast cancer cell line MDA-MB 231 suggesting an ER-mediated event. Interestingly, when the c-jun NH₂-terminal kinase (JNK) signalling pathway was disrupted by the JNK inhibitor SP600125, the ability of estradiol to inhibit the growth of MCF-7 cells and to induce apoptosis was completely blocked. These data suggest that JNK plays a central role in mediating the anticancer effect of high concentrations of estradiol in MCF-7 cells. Our data showing the apoptotic effect of estradiol in low growth-stimulated conditions suggest potential implications for the pharmacological control of breast cancer with high dose estrogen in postmenopausal women. Furthermore, our results indicate that augmenting JNK activity could be an efficient novel approach for treating breast cancer.     

ERK和SAPK/JNK通路在神经酰胺致HT-29细胞凋亡中的作用

目的： 探讨ERK和SAPK/JNK信号途径在C2-神经酰胺诱导人结肠癌HT-29细胞凋亡中的作用。方法：分别用不同剂量C2-神经酰胺 (0、12.5、25.0和50.0 μmol/L)处理HT-29细胞24 h,分别采用AO/EB染色法观察HT-29细胞凋亡的形态学变化,计算细胞凋亡率;Western Blotting法检测ERK、p-ERK蛋白表达。再分别用不同剂量C2-神经酰胺 (0、12.5、25.0和50.0 μmol/L)处理HT-29细胞24 h,并选择50.0 μmol/L C2-神经酰胺作用3、6、12、24 h后,用SAPK/JNK检测试剂盒结合Western Blotting方法检测phospho-c-Jun蛋白的表达。结果：与溶剂对照组比较,随着C2-神经酰胺剂量的增加,各剂量组HT-29细胞的凋亡率增加 (P＜0.05),ERK总蛋白和p-ERK的表达呈现下降趋势,存在剂量-效应关系 (P＜0.05)。不同浓度和不同时间的C2-神经酰胺作用下,HT-29细胞中phospho-c-jun的表达无明显变化 (P＞0.05)。结论：C2-神经酰胺能够直接诱导人结肠癌HT-29细胞发生凋亡,在此过程中SAPK/JNK活性无显著变化,抑制ERK信号转导通路可能是其诱导凋亡的机制。     

G2 and S phase-expressed-1 induces chromosomal instability in esophageal squamous cell carcinoma cells and inhibits cell apoptosis through ROS/JNK signaling

New diagnostic and therapeutic strategies are urgently needed to improve the prognosis of patients with esophageal squamous cell carcinoma (ESCC), which has high morbidity and mortality. Bioinformatics analysis revealed that cell cycle regulation related molecular G2 and S phase-expressed-1 (GTSE1) was dysregulated in ESCC. In this study, the ectopic expression of GTSE1 was verified in ESCC patients' tissues and cell lines. After overexpression or knockdown of GTSE1 using lentiviral transfection, the effects of GTSE1 on the proliferation, migration, invasion, and apoptosis of ESCC cells were detected. The contribution of GTSE1 in inducing chromosomal missegregation in cells leading to chromosome instability (CIN) has been described. Long-term existence of CIN can increase reactive oxygen species (ROS) generation in ESCC cells, followed by inhibition of apoptosis by activating the c-Jun N-terminal kinase (JNK) signaling pathway, and this inhibition could be relieved after treatment with JNK inhibitor. In vivo experiments, we also confirmed the tumor-promoting effect and mechanism of GTSE1 in ESCC using nude mice model. In this study, we demonstrated that GTSE1 induces CIN in ESCC cells, and increases intracellular ROS production, which leads to cellular oxidative stress, contributes to the activation of the JNK signaling pathway, and thereby inhibits apoptosis leading to ESCC tumorigenesis.     

JNK/FOXO3信号通路介导黄连素促人肺腺癌PC-9细胞凋亡的研究

  目的  探讨黄连素（berberine,Ber）诱导肺腺癌PC-9细胞凋亡及c-Jun氨基末端激酶（c-Jun N-terminal kinase,JNK）/转录因子叉头蛋白3（forkhead box protein O3,FOXO3）信号通路的作用机制。  方法  实验采用完全随机化的分组方法,分为对照组、Ber组（30、60 μM）,分别检测各组PC-9细胞活力值、凋亡率、ROS含量、caspase 3活性、线粒体膜电位,以及JNK/FOXO3通路和凋亡相关蛋白含量的变化。SP600125特异性抑制JNK（磷酸化）激活后,Ber（0、60 μM）处理细胞24 h,重复上述检测。  结果  Ber有效抑制PC-9细胞活力,促进细胞凋亡（P < 0.05）,显著降低PC-9细胞线粒体膜电位,增加ROS含量和caspase 3活性（P < 0.05）,并呈浓度依赖效应;Western blot检测结果显示Ber上调p-JNK、FOXO3和Bax的含量（P < 0.05）,下调p-FOXO3和Bcl-2的含量（P < 0.05）;SP600125特异性抑制JNK激活后,拮抗Ber下调p-FOXO3含量及其促PC-9细胞凋亡作用（P < 0.05）。  结论  Ber可有效抑制肺腺癌PC-9细胞活力、促进细胞凋亡和氧化应激损伤,作用机制可能与上调p-JNK、FOXO3含量和抑制FOXO3磷酸化有关。      

Bax is essential for mitochondrion-mediated apoptosis but not for cell death caused by photodynamic therapy

The role of Bax in the release of cytochrome c from mitochondria and the induction of apoptosis has been demonstrated in many systems. Using immunocytochemical staining, we observed that photodynamic therapy (PDT) with the photosensitiser Pc 4 induced Bax translocation from the cytosol to mitochondria, and the release of cytochrome c from mitochondria as early signalling for the intrinsic pathway of apoptosis in human breast cancer MCF-7c3 cells. To test the role of Bax in apoptosis, MCF-7c3 cells were treated with Bax antisense oligonucleotides, which resulted in as much as a 50% inhibition of PDT-induced apoptosis. In the second approach, Bax-negative human prostate cancer DU-145 cells were studied. Following PDT, the hallmarks of apoptosis, including the release of cytochrome c from mitochondria, loss of mitochondrial membrane potential, caspase activation, and chromatin condensation and fragmentation, were completely blocked in these cells. Restoration of Bax expression in DU-145 cells restored apoptosis, indicating that the resistance of DU-145 cells to PDT-induced apoptosis is due to the lack of Bax rather than to another defect in the apoptotic machinery. However, despite the inhibition of apoptosis, the Bax-negative DU-145 cells were as photosensitive as Bax-replete MCF-7c3 cells, as determined by clonogenic assay. Thus, for Pc 4-PDT, the commitment to cell death occurs prior to Bax activation.     

Inhibition of the Tcf/beta-catenin complex increases apoptosis and impairs adrenocortical tumor cell proliferation and adrenal steroidogenesis

Background

To date, there is no effective therapy for patients with advanced/metastatic adrenocortical cancer (ACC). The activation of the Wnt/beta-catenin signaling is frequent in ACC and this pathway is a promising therapeutic target.

Aim

To investigate the effects of the inhibition of the Wnt/beta-catenin in ACC cells.

Methods

Adrenal (NCI-H295 and Y1) and non-adrenal (HeLa) cell lines were treated with PNU-74654 (5–200 μM) for 24–96 h to assess cell viability (MTS-based assay), apoptosis (Annexin V), expression/localization of beta-catenin (qPCR, immunofluorescence, immunocytochemistry and western blot), expression of beta-catenin target genes (qPCR and western blot), and adrenal steroidogenesis (radioimmunoassay, qPCR and western blot).

Results

In NCI-H295 cells, PNU-74654 significantly decreased cell proliferation 96 h after treatment, increased early and late apoptosis, decreased nuclear beta-catenin accumulation, impaired CTNNB1/beta-catenin expression and increased beta-catenin target genes 48 h after treatment. No effects were observed on HeLa cells. In NCI-H295 cells, PNU-74654 decreased cortisol, testosterone and androstenedione secretion 24 and 48 h after treatment. Additionally, in NCI-H295 cells, PNU-74654 decreased SF1 and CYP21A2 mRNA expression as well as the protein levels of STAR and aldosterone synthase 48 h after treatment. In Y1 cells, PNU-74654 impaired corticosterone secretion 24 h after treatment but did not decrease cell viability.

Conclusions

Blocking the Tcf/beta-catenin complex inhibits the Wnt/beta-catenin signaling in adrenocortical tumor cells triggering increased apoptosis, decreased cell viability and impairment of adrenal steroidogenesis. These promising findings pave the way for further experiments inhibiting the Wnt/beta-catenin pathway in pre-clinical models of ACC. The inhibition of this pathway may become a promising adjuvant therapy for patients with ACC.     

Drug-induced Myc-mediated apoptosis of cancer cells is inhibited by stress protein Hsp70

The Myc oncoprotein serves a dual function by stimulating cells both towards growth and apoptosis. The latter functions are often abrogated during tumor development. The Hsp70 stress protein is a potent anti-apoptotic molecule, but its potential role in protecting cells from Myc-mediated apoptosis has not been investigated. Our results show that activated Myc potentiated apoptosis induced by the cancer drugs etoposide (ETO) and camptothecin (CAMP) in v-Myc-expressing human U-937 monoblastic cells and in Rat1 cells containing a conditionally active Myc/estrogen receptor (MycER) fusion protein. However, both heat shock and ectopic Hsp70 expression protected the cells from Myc-mediated apoptosis after drug treatment in both systems. The increased susceptibility to the anti-tumor drugs by activated Myc was enhanced by siRNA-mediated knockdown of Hsp70 expression in U-937 cells. Addressing the mechanisms by which Myc and Hsp70 promotes and inhibits drug-induced apoptosis, respectively, we found that v-Myc stimulated cytochrome c release and activation of effector caspase-9, -3 and -7, but not of initiator caspase-8. Inhibition of caspase-9 specifically reduced v-Myc-stimulated apoptosis, whereas inhibition of caspase-8 and -3/7 reduced apoptosis both in v-myc-expressing and parental ETO-treated U-937 cells. Interestingly, Myc-stimulated activation of effector caspases was inhibited, but cytochrome c release was not affected by Hsp70 expression, suggesting that Hsp70 interferes with the proapoptotic function of Myc downstream of mitochondria, at the level of caspase-9 and downstream caspases. In conclusion, Hsp70 seems to have key function in inhibition of apoptosis mediated by Myc and may therefore play an important role in Myc-driven oncogenesis.     

Inactivation of Id-1 in prostate cancer cells: A potential therapeutic target in inducing chemosensitization to taxol through activation of JNK pathway

Resistance to anticancer drugs is the major problem in the treatment of many advanced cancers, including androgen-independent prostate cancer. Recently, increased expression of Id-1, a basic helix-loop-helix protein, is reported in several types of advanced cancer. It is suggested that high expression of Id-1 may provide an advantage for cancer cell survival and inactivation of Id-1 may be able to increase cancer cells' susceptibility to apoptosis. To test this hypothesis, in this study, by using RNA interfering technology, we inactivated the Id-1 gene in 2 androgen-independent prostate cancer cell lines, DU145 and PC3, and investigated whether downregulation of Id-1 could lead to increased sensitivity to a commonly used anticancer drug, taxol. By using colony forming assay and MTT assay, we found that inactivation of Id-1 resulted in both decreased colony forming ability and cell viability in prostate cancer cells, after taxol treatment. In addition, the si-Id-1-induced sensitization to taxol was associated with activation of apoptosis pathway, which is demonstrated by increased apoptotic index, DNA laddering, sub-G1 phase of the cell cycle, as well as cleaved-PARP and Caspase 3. Furthermore, c-Jun N-terminal kinase (JNK), one of the common pathways responsible for taxol-induced apoptosis, was also activated in the si-Id-1 transfected cells. Inhibition of JNK activity by a specific inhibitor, SP600125, blocked the si-Id-1-induced sensitivity to taxol. These results indicate that increased Id-1 expression in prostate cancer cells may play a protective role against apoptosis, and downregulation of Id-1 may be a potential target to increase sensitivity of taxol-induced apoptosis in prostate cancer cells.     

P2X7受体激活乳腺癌JNK/SAPK信号通路的研究进展

P2X7受体是ATP门控的离子通道,对二价阳离子有较强的选择性,属于嘌呤受体P2X家族。P2X7受体参与细胞信号转导、细胞因子的分泌等多种生理功能。近年研究发现P2X7受体通过增加氧化磷酸化及细胞内ATP的储备,介导细胞的存活与生长。在乳腺癌中P2X7受体表达异常,并能激活JNK/SAPK途径,诱导乳腺癌细胞凋亡。本文综述了P2X7受体与乳腺癌发生发展分子机制的相关研究。