趋化因子受体CXCR7及其与肿瘤的关系

CXCR7是继CXCR4之后发现的趋化因子CXCL12的新受体.目前研究表明,CXCL12/CXCR7生物轴对多种肿瘤的发展有重要影响,与CXCL12/CXCR4生物轴的作用有一定相似性.CXCR7广泛表达于多种肿瘤组织及肿瘤细胞,在肿瘤细胞的生长增殖、黏附迁徙中起重要作用.抑制CXCR7表达或阻断其信号传导通路可能为肿瘤治疗提供新策略.     

Oct-4在肿瘤组织中的表达及其临床意义的研究现状

参考文献.结果:转录因子Oct-4属POU家族蛋白,在动物早期胚胎发育过程中起着重要作用,其通过激活或抑制下游靶基因来参与维持细胞的多向潜能性及未分化状态.已在多种实体肿瘤细胞中发现Oct-4异常高表达,由此更进一步证实了肿瘤干细胞学说.Oct-4的表达可能与肿瘤的恶性程度及生物学行为、肿瘤放化疗抵抗密切相关.结论:有关Oct-4的研究可能为判断肿瘤预后提供新的指标,也有利于发展新的抗癌药物作用靶点.     

补体调节蛋白CD 46、CD 55和CD 59在胃肠肿瘤中的研究进展

胃肠肿瘤细胞的细胞膜高表达补体调节蛋白（complement regulatory proteins，CRPs）中的一种或几种分子。这些高表达分子可抑制机体的体液免疫和细胞免疫，可能是导致肿瘤细胞逃避机体免疫监视的机制之一。近年来许多学者在研究CRPs在胃肠肿瘤中的表达及其作用机制，以及将CRPs相关的单克隆抗体（monoclonal antibodies，McAbs）应用于肿瘤免疫治疗，取得了一定疗效。本文将CRPs在胃肠肿瘤研究中所取得的进展作一综述。     

Aurora激酶与肿瘤的相关性

Aurora激酶家族为丝/苏氨酸蛋白激酶,在有丝分裂的染色体排列、分离和胞质分裂中起重要作用.Aurora激酶在人类实体瘤和血液肿瘤中过表达,在肿瘤细胞中表达异常会干扰有丝分裂中检控点的功能,可能导致遗传的不稳定和诱发肿瘤的形成.     

FHIT基因与肿瘤

脆性组氨酸三联体(FHIT)基因是一种定位于人类染色体3p14.2上的抑癌基因,在多种器官中都有表达,其包含的脆性位点FRA3B,是基因组中最脆弱的部分.FHIT可促进细胞凋亡,抑制细胞增殖和细胞癌变.FHIT基因高度甲基化、基因缺失、FRA3B脆性位点的改变以及蛋白合成过程中的异常,可导致FHIT基因功能缺失,促进多种肿瘤的发生与发展.将野生型FHIT导入FHIT表达降低或表达缺失的肿瘤细胞中可促进肿瘤细胞凋亡.FHIT基因与其他基因联合治疗可能为肿瘤的治疗提供新的方向.     

间充质干细胞对肿瘤细胞的分子作用机制

间充质干细胞(MSC)不但对肿瘤细胞具有良好的靶向性,而且可以直接抑制肿瘤生长或作为新兴的基因治疗载体在肿瘤局部持续高效地表达外源基因,抑制肿瘤的生长和转移.同时,MSC也可通过促进肿瘤间质重构和肿瘤血管形成、抑制肿瘤局部机体免疫以及改变肿瘤表型而促进肿瘤生长.相反的作用机制可能与MSC的来源、异质性、肿瘤细胞微环境或...     

四次跨膜蛋白8在肿瘤中的研究进展

四次跨膜蛋白8(tetraspanin 8,Tspan8),又称为CO-029或TM4SF3,是四跨膜超家族(transmembrane 4 super family,TM4SF)中的一员.Tspan8在多种肿瘤中存在高表达现象,其可能通过促进血管再生以及增强肿瘤细胞迁移和侵袭等促进肿瘤的转移与进展.本文旨在对Tspa...     

缺氧诱导因子与肿瘤血管生成

缺氧诱导因子(HIF)是一类重要的缺氧应答调控因子,在部分肿瘤组织中表达明显增高,与肿瘤血管生成密切相关.研究认为肿瘤细胞表型变化或缺氧环境可能导致HIF活性增加,进而通过依赖或非依赖血管内皮生长因子(VEGF)途径促进肿瘤血管的生成.对HIF调控肿瘤血管生成机制的进一步研究,将会为肿瘤防治提供新的思路与方法.     

HLA-Ⅱ类抗原与妇科恶性肿瘤的研究进展

HLA-Ⅱ类抗原主要表达于专职抗原递呈细胞表面,其生物学作用是将外源性抗原肽递呈给CD4 T细胞从而参与机体的免疫应答过程.HLA-Ⅱ类抗原的等位基因具有多态性从而导致其分子的抗原决定簇不同,可能与肿瘤的遗传易感性相关.HLA-II类抗原在恶性肿瘤组织中的异常表达,与肿瘤细胞逃避免疫监视形成肿瘤转移浸润相关.本文就HLA-Ⅱ抗原在妇科恶性肿瘤方面的研究作一综述.     

PAK4促进人乳腺肿瘤细胞G1/S期转化机制探讨

目的研究p21蛋白激活激酶4(p21protein activated kinase 4,PAK4)对人乳腺肿瘤细胞生长的影响。方法人乳腺肿瘤细胞MCF-7转染不同剂量PAK4真核表达载体或慢病毒敲除PAK4表达,收集细胞提取蛋白进行蛋白质印迹法检测PAK4和Cyclin D1表达。流式细胞仪检测PAK4过表达和敲除后对细胞生长周期影响。结果过表达PAK4明显上调人乳腺肿瘤细胞MCF-7中的Cyclin D1蛋白表达,引起G1期细胞减少(从80%下降到55%),导致G1/S期转化细胞增多。慢病毒敲除人乳腺肿瘤细胞MCF-7中的PAK4表达降低了的Cyclin D1蛋白表达,使G1期的细胞增加12%,而S期的细胞下调7%。结论 PAK4调节Cyclin D1表达,促进人乳腺肿瘤细胞MCF-7G1/S期转化,揭示PAK4可能是重要的人乳腺肿瘤治疗靶点。     

PACE4 expression in mouse basal keratinocytes results in basement membrane disruption and acceleration of tumor progression

Collagen type IV degradation results in disruption and breakdown of the normal basement membrane architecture, a key process in the initiation of tumor microinvasion into the connective tissue. PACE4, a proprotein convertase, activates membrane type matrix metalloproteinases (MT-MMPs) that in turn process collagenase type IV. Because PACE4 is overexpressed in skin carcinomas and in vitro overexpression of PACE4 resulted in enhanced invasiveness, we investigated whether or not in vivo PACE4 expression leads to the acquisition of invasiveness and increased tumorigenesis. Two transgenic mouse lines were designed by targeting PACE4 to the epidermal basal keratinocytes. Transgenic keratinocytes showed increased processing of MT1-MMP and MT2-MMP resulting in collagenase IV activation and collagen type IV degradation. Higher collagenolytic activity partially disrupted normal basement membrane architecture favoring epithelial endophytic growth into the dermis and accelerating invasion and metastasis after chemical carcinogenesis. PACE4 overexpression resulted in enhanced susceptibility to carcinogenesis and tumor progression pointing to a new target for blocking tumor cell invasiveness.     

Proprotein Convertase Inhibition Results in Decreased Skin Cell Proliferation,Tumorigenesis, and Metastasis

PACE4 is a proprotein convertase (PC) responsible for cleaving and activating proteins that contribute to enhance tumor progression. PACE4 overexpression significantly increased the susceptibility to carcinogenesis, leading to enhanced tumor cell proliferation and premature degradation of the basement membrane. In the present study, we sought to evaluate a novel approach to retard skin tumor progression based on the inhibition of PACE4. We used decanoyl-RVKR-chloromethylketone (CMK), a small-molecule PC inhibitor, for in vitro and in vivo experiments. We found that CMK-dependent blockage of PACE4 activity in skin squamous cell carcinoma cell lines resulted in impaired insulin-like growth factor 1 receptor maturation, diminished its intrinsic tyrosine kinase activity, and decreased tumor cell proliferation. Two-stage skin chemical carcinogenesis experiments, together with topical applications of CMK, demonstrated that this PC inhibitor markedly reduced tumor incidence, tumor multiplicity, and metastasis, pointing to a significant delay in tumor progression in wild-type and PACE4 transgenic mice. These results identify PACE4, together with other PCs, as suitable targets to slow down or block tumor progression, suggesting that PC inhibition is a potential approach for therapy for solid tumors.     

The proprotein convertases furin and PACE4 play a significant role in tumor progression

Processing of latent precursor proteins by proprotein convertases (PCs) into their biologically active products is a common mechanism required for many important biologic functions. This process is tightly regulated, leading to the generation of active peptides and proteins including neuropeptides and polypeptide hormones, protein tyrosine phosphatases, growth factors and their receptors, and enzymes including matrix metalloproteases (MMPs). These processing reactions occurs at pairs of basic amino acids. Within the past several years, a novel family of Ca(2+)-dependent serine proteases has been identified, all of which possess homology to the endoproteases subtilisin (bacteria) and kexin (yeast). This family of PCs is currently comprised of fewer than a dozen members, known as furin/paired basic amino-acid-cleaving enzyme (PACE), PC1/PC3, PC2, PC4, PACE4, PC5/PC6, and PC7/PC8/lymphoma proprotein convertase. They share a high degree of amino-acid identity of 50-75% within their catalytic domains. Despite the relatively high degree of homology in the PC family, only PACE4 and furin localize to the same chromosome: mouse chromosome 7 and human chromosome 15. Recent reports have supported a possible functional role for PCs in tumorigenesis. For instance, convertases have been shown to be expressed in various tumor lines and human primary tumors. Furin and PACE4 process stromelysin 3 (MMP-11 or Str-3), an MMP involved in tumor invasion, into its mature, active form. Similarly, a growing family of MMPs, known as membrane-type metalloproteinases (MT-MMPs), and growth factors and adhesion molecules such as E-cadherin show similar amino-acid motifs and thus could be activated by furin and PACE4. These data, taken together with the high expression levels of PACE4 in 50% of murine chemically induced spindle cell tumors, confer to PACE4 and possibly other PCs a possible functional role in the activation of MMPs and consequently in tumor cell invasion and tumor progression. This was further supported by the remarkable enhancement in the invasive ability of the PACE4-transfected murine tumor cell lines. Mol. Carcinog. 28:63-69, 2000.     

Malignant conversion of non-tumorigenic murine skin keratinocytes overexpressing PACE4

Proprotein convertases (PCs) have been implicated in tumor cell invasion by processing a variety of substrates including matrix metalloproteinases (MMPs). PACE4, a member of the family of PCs was shown to enhance mouse skin carcinoma progression by increasing tumor cell invasiveness. However, the effects of PACE4 on malignant conversion have not been investigated. In the present study we address the possible role of PACE4 as a trigger of malignant conversion by transfecting with a full-length PACE4 cDNA, three keratinocyte cell lines with no or little tumorigenic potential, i.e. non-tumorigenic BALB/MK-2 cells, tumorigenic non-invasive MT1/2 cells and tumorigenic moderately invasive p117 mouse skin keratinocytes. Overexpression of PACE4 led to a significant increase in the processing of stromelysin-3, a well-characterized substrate of this PC. When assayed for invasive ability, the PACE4-transfected cells were invasive both in vitro and in vivo, whereas their control counterparts were not. In addition, an enhanced processing ability of MT2-MMP a known substrate of PCs was detected in the PACE4-transfected cells. This was accompanied by MMP-2 and MMP-9 activation in PACE4 transfectants. Invasion and MMP processing were remarkably reduced when PACE4 was inhibited with a specific antibody. By triggering the processing of crucial invasion-related proteases, PACE4 is not only able to enhance the invasive ability of malignant cells as demonstrated previously, but also played a significant role in converting non-invasive keratinocytes into malignant cells.     

PACE4-Based Molecular Targeting of Prostate Cancer Using an Engineered 64Cu-Radiolabeled Peptide Inhibitor

The potential of PACE4 as a pharmacological target in prostate cancer has been demonstrated as this proprotein convertase is strongly overexpressed in human prostate cancer tissues and its inhibition, using molecular or pharmacological approaches, results in reduced cell proliferation and tumor progression in mouse tumor xenograft models. We developed a PACE4 high-affinity peptide inhibitor, namely, the multi-leucine (ML), and sought to determine whether this peptide could be exploited for the targeting of prostate cancer for diagnostic or molecular imaging purposes. We conjugated a bifunctional chelator 1,4,7-triazacyclononane-1,4,7- triacetic acid (NOTA) to the ML peptide for copper-64 (⁶⁴Cu) labeling and positron emission tomography (PET)– based prostate cancer detection. Enzyme kinetic assays against recombinant PACE4 showed that the NOTA-modified ML peptide displays identical inhibitory properties compared to the unmodified peptide. In vivo biodistribution of the ⁶⁴Cu/NOTA-ML peptide evaluated in athymic nude mice bearing xenografts of two human prostate carcinoma cell lines showed a rapid and high uptake in PACE4-expressing LNCaP tumor at an early time point and in PACE4-rich organs. Co-injection of unlabeled peptide confirmed that tumor uptake was target-specific. PACE4-negative tumors displayed no tracer uptake 15 minutes after injection, while the kidneys, demonstrated high uptake due to rapid renal clearance of the peptide. The present study supports the feasibility of using a ⁶⁴Cu/NOTA-ML peptide for PACE4-targeted prostate cancer detection and PACE4 status determination by PET imaging but also provides evidence that ML inhibitor–based drugs would readily reach tumor sites under in vivo conditions for pharmacological intervention or targeted radiation therapy.Abbreviations: ACN, acetonitrile; Ac, acetyl; ⁶⁴Cu, copper-64; DCM, dichloromethane; [¹⁸F]-FDG, [¹⁸F]-fluoro-2-deoxy-d-glucose; HR-MS, high-resolution mass spectrometry; K_i, inhibitory constant; ML, multi-leucine; DMF, N,N′-dimethylformamide; NOTA, 1,4,7-triazacyclononane-1,4,7-triacetic acid; PC, proprotein convertase; PET, positron emission tomography     

Role of Proprotein Convertases in Prostate Cancer Progression

Better understanding of the distinct and redundant functions of the proprotein convertase (PC) enzyme family within pathophysiological states has a great importance for potential therapeutic strategies. In this study, we investigated the functional redundancy of PCs in prostate cancer in the commonly used androgen-sensitive LNCaP and the androgen-independent DU145 human cell lines. Using a lentiviral-based shRNA delivery system, we examined in vitro and in vivo cell proliferation characteristics of knockdown cell lines for the endogenous PCs furin, PACE4, and PC7 in both cell lines. Of the three PCs, only PACE4 was essential to maintain a high-proliferative status, as determined in vitro using XTT proliferation assays and in vivo using tumor xenografts in nude mice. Furin knockdowns in both cell lines had no effects on cell proliferation or tumor xenograft growth. Paradoxically, PC7 knockdowns reduced in vitro cellular proliferation but had no effect in vivo. Because PCs act within secretion pathways, we showed that conditioned media derived from PACE4 knockdown cells had very poor cell growth-stimulating effects in vitro. Immunohistochemistry of PACE4 knockdown tumors revealed reduced Ki67 and higher p27^KIP levels (proliferation and cell cycle arrest markers, respectively). Interestingly, we determined that the epidermal growth factor receptor signaling pathway was activated in PC7 knockdown tumors only, providing some explanations of the paradoxical effects of PC7 silencing in prostate cancer cell lines. We conclude that PACE4 has a distinct role in maintaining proliferation and tumor progression in prostate cancer and this positions PACE4 as a relevant therapeutic target for this disease.     

Enhanced UV-Induced Skin Carcinogenesis in Transgenic Mice Overexpressing Proprotein Convertases

The proprotein convertases (PCs) furin and PACE4 process numerous substrates involved in tumor growth, invasion, and metastasis. We have previously shown that PCs increase the susceptibility to chemical skin carcinogenesis. Because of the human relevancy of UV radiation in the etiopathogenesis of human skin cancer, we investigated whether or not transgenic mice overexpressing either furin alone or both furin and PACE4 show increased susceptibility to UV carcinogenesis. After backcrossing our previously described furin and PACE4 transgenic lines, targeted to the epidermis, into a SKH-1 background, we exposed both single and double transgenic mice to UV radiation for 34 weeks. The results showed an increase in squamous cell carcinoma (SCC) multiplicity of approximately 70% in the single furin transgenic mouse line SF47 (P < .002) and a 30% increase in the other single transgenic line SF49 when compared to wild-type (WT) SKH-1 mice. Interestingly, there was also an increase in the percentage of high histologic grade SCCs in the transgenic lines compared to the WT mice, i.e., WT = 9%, SF47 = 15%, and SF49 = 26% (P < .02). Targeting both furin and PACE4 to the epidermis in double transgenic mice did not have an additive effect on tumor incidence/multiplicity but did enhance the tumor histopathologic grade, i.e., a significant increase in higher grade SCCs was seen in the bigenic mouse line SPF47 (P < .02). Thus, we observed an increased susceptibility to UV in single furin transgenic mice that was not substantially enhanced in the double furin/PACE4 transgenic mice.     

Fenretinide-induced caspase-8 activation and apoptosis in an established model of metastatic neuroblastoma

Background

The present study is aimed at identifying potential candidate genes as prognostic markers in human oral tongue squamous cell carcinoma (SCC) by large scale gene expression profiling.

Methods

The gene expression profile of patients (n=37) with oral tongue SCC were analyzed using Affymetrix HG_U95Av2 high-density oligonucleotide arrays. Patients (n=20) from which there were available tumor and matched normal mucosa were grouped into stage (early vs. late) and nodal disease (node positive vs. node negative) subgroups and genes differentially expressed in tumor vs. normal and between the subgroups were identified. Three genes, GLUT3, HSAL2, and PACE4, were selected for their potential biological significance in a larger cohort of 49 patients via quantitative real-time RT-PCR.

Results

Hierarchical clustering analyses failed to show significant segregation of patients. In patients (n=20) with available tumor and matched normal mucosa, 77 genes were found to be differentially expressed (P< 0.05) in the tongue tumor samples compared to their matched normal controls. Among the 45 over-expressed genes, MMP-1 encoding interstitial collagenase showed the highest level of increase (average: 34.18 folds). Using the criterion of two-fold or greater as overexpression, 30.6%, 24.5% and 26.5% of patients showed high levels of GLUT3, HSAL2 and PACE4, respectively. Univariate analyses demonstrated that GLUT3 over-expression correlated with depth of invasion (P<0.0001), tumor size (P=0.024), pathological stage (P=0.009) and recurrence (P=0.038). HSAL2 was positively associated with depth of invasion (P=0.015) and advanced T stage (P=0.047). In survival studies, only GLUT3 showed a prognostic value with disease-free (P=0.049), relapse-free (P=0.002) and overall survival (P=0.003). PACE4 mRNA expression failed to show correlation with any of the relevant parameters.

Conclusion

The characterization of genes identified to be significant predictors of prognosis by oligonucleotide microarray and further validation by real-time RT-PCR offers a powerful strategy for identification of novel targets for prognostication and treatment of oral tongue carcinoma.     

Proprotein convertases: "master switches" in the regulation of tumor growth and progression

Proprotein convertases (PCs) are a group of Ca2+-dependent serine proteases that have homology to the endoproteases subtilisin (bacteria) and kexin (yeast). This group is comprised of less than a dozen members, known as furin/PACE, PC1/PC3, PC2, PC4, PACE4, PC5/PC6, PC7/PC8/LPC, SKI/S1P, and NARC-1/PCSK9. Four PCs (Furin, PACE4, PC5, and PC7) have been localized to several different tissues and epithelial or nervous system tumors. PCs activate their cognate substrates by limited proteolysis at the consensus sequence RXR/KR downward arrow. Many PC substrates are well known cancer-associated proteins such as growth factors, growth factor receptors, integrins, and matrix metalloproteases (MMPs). For example, IGF-1 and its receptor, TGF-beta, VEGF-C, and MT-MMPs have direct roles in tumor progression and metastasis. Furin, a well-studied member of the PC family, has been associated with enhanced invasion and proliferation in head and neck, breast, and lung cancer. Conversely, inhibition of PC activity by PDX or several PC pro-segments, resulted in reduced processing of these key cancer-related substrates in human squamous cell carcinomas (SCC), colon adenocarcinoma, and astrocytoma cell lines. In parallel to these changes in cell proliferation and invasiveness as well as metastatic ability were markedly impaired. By controlling the maturation/activation of key cancer-associated proteins, PCs act as "master switches" at different levels during tumor development and progression. The manifold effects of PCs, influencing tumor cell proliferation, motility, adhesiveness, and invasiveness, should be exploited by further developing competitive/inhibitory therapeutic strategies that would be able to neutralize simultaneously the most salient cancer cell properties.