微管解聚蛋白Ｓｔａｔｈｍｉｎ与肿瘤相关性的研究进展

微管解聚蛋白Ｓｔａｔｈｍｉｎ具有微管解聚活性,在细胞周期的转换过程中起着重要作用。在多种恶性肿瘤细胞中都可以检测到Ｓｔａｔｈｍｉｎ高表达。已有研究证实,Ｓｔａｔｈｍｉｎ蛋白的高表达能够影响某些作用于微管的化疗药物的疗效,抑制其表达可以提高这些药物的疗效。Ｓｔａｔｈｍｉｎ基因为肿瘤基因治疗提供了新的分子靶点。     

Stathmin基因表达与肿瘤的研究进展

Stathmin在多种恶性肿瘤细胞中都有高水平表达，Stathmin蛋白的主要作用是通过促进微管的解聚或阻止微管的聚合从而影响有丝分裂纺锤体的形成，通过抑制其表达可以干扰恶性肿瘤细胞的有丝分裂，影响肿瘤细胞的增殖与凋亡。同时，抑制stathmin表达能够协同增效某些化疗药物的抗癌疗效。Stathmin基因正成为肿瘤基因治疗的一个新靶点。     

Overexpression of the stathmin gene in a subset of human breast cancer.

Stathmin is a highly conserved cytosolic phosphoprotein that destabilizes microtubules. Stathmin, which has been proposed as a relay protein integrating diverse cell signalling pathways, acts in vitro as a tubulin-sequestering protein, and its activity is dramatically reduced by phosphorylation. Interestingly, stathmin expression and phosphorylation are regulated during the control of cell growth and differentiation, and there is much evidence suggesting that in vivo stathmin plays a role in the control of microtubule dynamics during mitosis. Stathmin may thus be considered as one of the key regulators of cell division. We examined 50 human primary breast tumours for stathmin mRNA and protein expression and screened for abnormalities in the chromosome region harbouring the stathmin gene. Overexpression of stathmin was found in 15 tumours (30%). At the present stage, no clear correlation emerged between stathmin expression and several prognosis markers. Interestingly, perfect matching was observed between stathmin mRNA overexpression, protein overexpression and strong staining for stathmin on paraffin-embedded tumour sections when specimens were available. Furthermore, a tentative link between loss of heterozygosity (LOH) in the 1p32-1pter region and stathmin overexpression was observed. Our results suggest that stathmin might play a role in breast carcinogenesis and that stathmin-overexpressing tumours may represent a new subtype of breast cancer.     

A combination of paclitaxel and siRNA-mediated silencing of Stathmin inhibits growth and promotes apoptosis of nasopharyngeal carcinoma cells

Background

Stathmin, a microtubule associated protein (MAP), is an important molecular target for cancer therapy. Paclitaxel is one of the primary antitumor drugs targeting microtubules (MTs). We hypothesized that decreasing the expression level of Stathmin might improve the effectiveness of paclitaxel in the treatment of nasopharyngeal carcinoma (NPC).

Methods

NPC cell lines, CNE1-LMP1 and HNE2, and a CNE1-LMP1 tumor xenograft mouse model were used to test both in vitro and in vivo our siRNA-based Stathmin silencing strategy. The effects of Stathmin silencing on cell proliferation, apoptosis, and viability were investigated using MTT, AO/EB staining, TUNEL, caspase protein detection, and FCM assays. Cell migration and invasion were assayed using a Transwell assay. The combined effects of Stathmin silencing and paclitaxel were investigated using MTT, FCM, Western blot and indirect immunofluorescence assays. The effect of paclitaxel on Stathmin expression in NPC cells and, in addition, A375, MGC and HeLa cells was determined by RT-PCR and Western blotting.

Results

We found that siRNA-mediated silencing of Stathmin suppresses proliferation, induces apoptosis through the mitochondrial pathway, and causes G2/M-phase cell cycle arrest in the NPC cell lines CNE1-LMP1 and HNE2. Also, the migration and invasion of the respective NPC cells were found to be inhibited. In addition, we show that a combination of Stathmin silencing and paclitaxel is more effective than either agent alone in inhibiting proliferation and inducing apoptosis, cell cycle arrest, and MT polymerization. Furthermore, we found that Stathmin expression in the tumor cells is down-regulated by paclitaxel treatment.

Conclusion

siRNA-mediated silencing of Stathmin suppresses the proliferation, invasion and metastasis, and induces the apoptosis of NPC cells. Paclitaxel reduces the expression of Stathmin, and combining Stathmin silencing with paclitaxel treatment enhances MT polymerization. This combined strategy may provide a new approach for clinical NPC treatment.     

A Phase I/pilot study of sequential doxorubicin/vinorelbine: effects on p53 and microtubule-associated protein 4.

PURPOSE: Few molecular determinants of sensitivity to cancer chemotherapy exist. In experimental systems, p53 regulates the sensitivity to antimicrotubule drugs through its effect on microtubule-associated protein 4 (MAP4). MAP4 is the major microtubule-associated protein in nonneuronal tissues and promotes microtubule polymerization. We reported that wild-type p53 induction by doxorubicin in C127 breast cancer cells repressed MAP4, decreased microtubule polymerization, and increased Vinca alkaloid sensitivity. The goals of this Phase I/pilot clinical trial were to determine: (a) the safety of delivering a DNA-damaging agent (doxorubicin) followed in sequence by treatment with an antimicrotubule drug (vinorelbine); and (b) the feasibility of detecting activation of p53 and repression of MAP4 in patients' tissues. EXPERIMENTAL DESIGN: Peripheral blood mononuclear cells (PBMNCs) and tumor were obtained from 16 women with locally advanced (stage IIIb) or metastatic (stage IV) breast cancer before doxorubicin treatment and immediately before treatment with vinorelbine 24 or 48 h later. RESULTS: After doxorubicin treatment, p53 increased in 12 of 14 PBMNC and 4 of 10 tumor samples. Changes in MAP4 were variable; however, in samples in which p53 was induced, MAP4 decreased in 7 of 12 PBMNC and 3 of 4 breast cancer specimens. Immunohistochemistry confirmed lower MAP4 expression in tumor cells after doxorubicin treatment. Seven of 16 patients had a partial response, and treatment was well tolerated. CONCLUSIONS: These data demonstrate the ability to detect the activation of p53 and the repression of MAP4 in normal and malignant tissues in patients treated with a DNA-damaging agent, and that an antimicrotubule drug can be administered safely at a time when cells may be more sensitive to treatment.     

Stathmin is a Marker of Progression and Poor Prognosis in Esophageal Carcinoma

Stathmin, also called oncoprotein 18, is a founding member of the family of microtubule-destabilizing proteinsthat play a critical role in the regulation of mitosis. At the same time stathmin has been recognized as one ofresponsible factors in cancer cells. The aim of this study was to assess stathmin status, its correlations withclinicopathological parameters and its role as a progosnostic marker in EC patients. The protein and mRNAlevels of stathmin were examined byimmunohistochemistry (IHC) and in situ hybridization in 100EC tissuesand adjacent noncancerous tissues. mRNA and protein expression of stathmin in three EC cell lines(EC9706,ECa109, EC1 commonly used in research) were also analyzed using immunocytochemistry, western blot andin situ hybridization. The prognostic value of Stathmin expression within the tumor tissues were assessed byCox regression and Kaplan-Meier analysis. We showed that stathmin expression was significantly higher in ECtissues than in adjacent noncancerous tissues. High stathmin immunostaining score in the EC was positivelycorrelated with tumor differentiation, Tumor invasion, Lymph node metastases, and TNM stage. In addition, wedemonstrated that three EC cell lines examined, were constitutively expressing a high level of stathmin. Of those,EC-1 showed the strongest mRNA and protein expression for the stathmin analyzed. Kaplan-Meier analysisshowed that significantly longer 5-year survival rate was seen in EC patients with high Stathmin expression,compared to those with low expression of Stathmin expression. Furthermore, multivariate Cox proportionalhazard analyses revealed that Stathmin was an independent factors affecting the overall survival probability.In conclusion, our data provide a basis for the concept that stathmin might be associated with EC developmentand progression.. High levels of Stathmin expression in the tumor tissues may be a good prognostic marker forpatients with EC.     

Exposure of human lung cancer cells to 8-chloro-adenosine induces G2/M arrest and mitotic catastrophe

8-Chloro-adenosine (8-Cl-Ado) is a potent chemotherapeutic agent whose cytotoxicity in a variety of tumor cell lines has been widely investigated. However, the molecular mechanisms are uncertain. In this study, we found that exposure of human lung cancer cell lines A549 (p53-wt) and H1299 (p53-depleted) to 8-Cl-Ado induced cell arrest in the G2/M phase, which was accompanied by accumulation of binucleated and polymorphonucleated cells resulting from aberrant mitosis and failed cytokinesis. Western blotting showed the loss of phosphorylated forms of Cdc2 and Cdc25C that allowed progression into mitosis. Furthermore, the increase in Ser10-phosphorylated histone H3-positive cells revealed by fluorescence-activated cell sorting suggested that the agent-targeted cells were able to exit the G2 phase and enter the M phase. Immunocytochemistry showed that microtubule and microfilament arrays were changed in exposed cells, indicating that the dynamic instability of microtubules and microfilaments was lost, which may correlate with mitotic dividing failure. Aberrant mitosis resulted in mitotic catastrophe followed by varying degrees of apoptosis, depending on the cell lines. Thus, 8-Cl-Ado appears to exert its cytotoxicity toward cells in culture by inducing mitotic catastrophe.     

Stathmin蛋白:一个潜在的肿瘤标志物

人stathmin也称原癌基因蛋白18(oncogene protein 18, Op18), 是一种广泛存在于细胞质的蛋白质,其相对分子质量约为19×10~3,可与微管蛋白结合,参与微管和纺锤体的组装;与细胞的增殖、分化、再生和运动均有关,并具有信号活性调节的功能.近年来有研究发现,stathmin在多种肿瘤中高表达,并可通过调节微管的解聚,促进肿瘤细胞的运动及侵袭.Stathmin翻译后修饰状态的改变,可影响与p53蛋白的相互作用,参与肿瘤的发生发展.目前单独或者联合化疗药物使用的抗stathmin效应剂已用于某些肿瘤的治疗.虽然stathmin与肿瘤病因学的内在联系尚不十分清楚,但其作为一个潜在的肿瘤标志物或药物靶点值得进一步研究探讨.     

Taxol and anti-stathmin therapy: a synergistic combination that targets the mitotic spindle

Stathmin is an abundant cytosolic phosphoprotein that plays an important role in the regulation of cellular proliferation. Its major function is to promote depolymerization of the microtubules that make up the mitotic spindle. Taxol is an effective chemotherapeutic agent whose activity is mediated through stabilization of the microtubules of the mitotic spindle. We demonstrate that antisense inhibition of stathmin expression chemosensitizes K562 leukemic cells to the antitumor effects of Taxol and results in a synergistic inhibition of their growth and clonogenic potential. In the presence of stathmin inhibition, exposure to Taxol results in more severe mitotic abnormalities (hypodiploidy and multinucleation). This, in turn, results in increased apoptosis of the aneuploid cells during subsequent cell division cycles. This novel molecular-based therapeutic approach may provide an effective form of cancer therapy that would avoid the severe toxicities associated with the use of multiple chemotherapeutic agents with overlapping toxicity profiles.     

Assessment of microtubule stabilizers by semiautomated in vitro microtubule protein polymerization and mitotic block assays

Paclitaxel (Taxol) a clinically active anticancer agent, exerts its cytotoxicity by inducing tubulin polymerization, leading to cellular mitotic block. In contrast, other antimitotic drugs, such as colchicine, podophyllotoxin, and vinblastine, act by depolymerizing microtubules. We report here (a) a semiautomated assay which measures the tubulin-polymerizing activity of paclitaxel analogs and (b) a cellular assay to measure the potential of these compounds to block cells in mitosis. The microtubule-polymerizing assay measured the turbidity of bovine brain microtubule protein (MTP) polymerized by the test compound in a 96-well plate. We maximized the sensitivity of this assay by conducting the polymerization reaction at 20 °C, at which temperature the baseline reaction, i.e. the basic ability of the untreated MTP control to polymerize, was minimal. At 20 °C, the effect of 0.05 μg/ml of paclitaxel on MTP could be detected, whereas at 37 °C, >1 μg/ml of paclitaxel was required to detect a significant effect relative to untreated MTP. We describe the analysis of the complex curves of MTP polymerization with varying concentrations of test compounds. The polymerization of microtubules leads to cells being blocked in mitosis. This mitotic blocking effect in intact cells was determined using a cell settling chamber which allowed eight samples to be deposited on a slide. This method required a smaller number of cells (10³–10⁵), maintained cell morphology, and allowed for rapid screening of samples. The activity of several new paclitaxel analogs is reported. Received: 9 May 1996 / Accepted: 5 March 1997     

沉默stathmin基因增强食管鳞癌细胞对紫杉醇敏感度的实验

目的 探讨沉默stathmin基因后,食管鳞癌细胞对紫杉醇敏感度的改变。方法 利用RNA干扰技术特异性沉默食管鳞癌KYSE150细胞的stathmin基因;实时定量PCR及蛋白质印迹法检测stathmin表达变化;CCK-8检测紫杉醇敏感度变化;流式细胞仪检测细胞周期变化;细胞分裂指数实验观察细胞有丝分裂改变。结果 特异性转染后,stathmin基因mRNA 和蛋白表达均受抑制。沉默stathmin基因后,KYSE150细胞对紫杉醇敏感度增强191.4倍;紫杉醇对特异性转染和未转染的KYSE150细胞半数抑制浓度分别为0.018 nM和3.445 nM。经紫杉醇（0.01 nM）处理72 h后,相比于未转染细胞,特异性转染的KYSE150细胞出现明显G₂/M周期阻滞[（55.4±6.2%）vs.（19.1±2.7%）, P=0.000], 有丝分裂指数减少[（5.6±0.8%）vs.（13.5±3.7%）, P=0.000]。结论 stathmin基因沉默通过细胞周期G₂/M阻滞增强食管鳞癌细胞对紫杉醇的化疗敏感度。     

p53-Reactivating small molecules induce apoptosis and enhance chemotherapeutic cytotoxicity in head and neck squamous cell carcinoma

We evaluate whether p53-reactivating (p53RA) small molecules induce p53-dependent apoptosis in head and neck squamous cell carcinoma (HNSCC), a question that has not been previously addressed in head and neck cancer. PRIMA-1, CP-31398, RITA, and nutlin-3 were tested in four human HNSCC cell lines differing in TP53 status. Cell growth, viability, cell cycle progression, and apoptosis after treatment with p53RA small molecules individually or in combination with chemotherapeutic agents were assessed. Prominent p53 reactivation was observed in mutant TP53-bearing tumor cell lines treated with PRIMA-1 or CP-31398, and in wild-type TP53-bearing cell lines treated with nutlin-3. Cell-cycle arrest and apoptosis induced by p53RA small molecules were associated with upregulation of p21 and BAX, and cleavage of caspase-3. Nutlin-3 showed maximal growth suppression in tumor cells showing MDM2-dependent p53 degradation. High-dose treatment with p53RA small molecules also induced apoptosis in cell lines independent of p53 or MDM2 expression. In combination therapy, p53RA small molecules enhanced the anti-tumor activity of cisplatin, 5-fluorouracil, paclitaxel, and erlotinib against HNSCC cells. The p53RA small molecules effectively restored p53 tumor-suppressive function in HNSCCs with mutant or wild-type TP53. The p53RA agents may be clinically useful against HNSCC, in combination with chemotherapeutic drugs.     

Influence of the phosphodiesterase-5 inhibitor,sildenafil, on sensitivity to chemotherapy in breast tumor cells

Studies were performed to determine the influence of the phosphodiesterase-5 inhibitor, sildenafil, on sensitivity to Adriamycin (doxorubicin) in four human breast tumor cell lines and one murine breast tumor line. Sildenafil did not interfere with the effectiveness of Adriamycin in any of the cell lines tested. Sildenafil also failed to protect MDA-MB231 cells against the cytotoxicity of cisplatin, taxol or camptothecin. Sildenafil enhanced sensitivity to Adriamycin markedly in the p53 mutant MDA-MB231 and p53 null MCF-7/E6 cells and moderately in the MCF-7/caspase 3 and 4T1 cell lines. In the MDA-MB231 cells, sildenafil increased the extent of DNA damage induced by Adriamycin as well as the extent of apoptotic cell death. Sildenafil did not influence sensitivity to Adriamycin in bone marrow cells or macrophages. In an immunocompetent model of breast cancer (4T1 mammary carcinoma in Balb/c mice), sildenafil did not attenuate the antitumor effects of Adriamycin; furthermore, the combination of sildenafil with Adriamycin was no more toxic to the animals than Adriamycin alone. Given that sildenafil has been shown to have the potential to protect the heart against the toxicity of Adriamycin, these studies suggest that the inclusion of sildenafil with conventional chemotherapeutic protocols involving Adriamycin (and possibly cisplatin, camptothecin and/or paclitaxel) should not compromise the antitumor effectiveness of these drugs nor enhance their toxicity to the patient.