恶性转化试验及其相关试验体系在环境致癌因素检测中的应用

恶性转化试验及在其基础上建立起来的相关试验体系是当前用于环境致癌因素检测的主要手段,本以各种试验方法为核心,以试验中应用的靶材料为依据,从体内,体外两个方面,对现有的环境致癌因素检测方法进行了综述。     

水中痕量有机污染物对细胞的转化效应

本文研究由水中有机污染物引起的细胞转化。水中有机物通过高分子树脂402吸附得到富集,CHO细胞经与SOS显色试验主阳性的有机富集物共孵育后,诱导出现转化灶。转化灶细胞经分离、克隆化和连续传代而建系的细胞,具有恶性细胞的生物学特性。本文所介绍的方法为环境致癌研究提供了经验。     

人支气管上皮细胞16HBE和其经硫化镍、反式-BPDE诱导的恶性转化细胞对脂质体转染效率的差异性比较

目的:通过脂质体法转染不同荧光蛋白质粒到多种接种密度细胞的效率差异探讨恶性转化细胞的癌变过程。方法:以16HBE、结晶型NiS诱导的16HBE恶性转化细胞和反式-BPDE诱导的16HBE恶性转化细胞为实验对象,采用不同的细胞接种密度,用脂质体法对它们分别转染两种不同的表达荧光蛋白的质粒,通过荧光显微镜观察细胞的转染情况。结果:无论转染eGFP质粒还是GFP-LC3质粒,在多种细胞密度下,正常细胞16HBE都比恶性转化细胞的转染效率低。结论:恶性转化细胞在癌变过程中可能发生了细胞膜通透性的改变。     

人巨细胞病毒转化作用的研究进展

人巨细胞病毒（ＨＣＭＶ）属于ＤＮＡ肿瘤病毒,有３个可导致细胞恶性转化的形态转化区,另有病毒即刻早期（ＩＥ）基因的编码产物对细胞生长进行调探。本文最后探讨了病毒导致细胞恶性转化的可能机制。     

樱桃砧木叶片和叶柄再生体系的构建

以樱桃的两个砧木品种大青叶和大叶的组培苗为试材,通过5个激素因子的正交试验设计,建立了叶圆盘和叶柄片段的再生体系,研究出最佳愈伤组织形成和根苗分化的培养基,以提高组培快繁系数,并为基础转化提供技术保证。     

新早期胃癌标志物PRDX4通过清除ROS促进胃癌的发生发展（英文）

胃癌是全球第四大最常见的癌症,也是全球癌症中引起死亡的第二大原因。为了降低胃癌的死亡率,目前亟需解决的问题是发现新的早期胃癌特异性的标志物,提高早期胃癌的检出率,从而从根本上解决胃癌死亡率高的问题。实验室前期研究发现过氧化物酶4 (Peroxiredoxin 4,PRDX4)具有早期胃癌标志物的潜能,文中通过建立恶性转化模型及转化细胞过表达等方法,研究PRDX4在转化细胞中的作用。结果显示PRDX4通过减少转化细胞中活性氧(Reactive oxygen species,ROS)含量,使细胞处在利于生长增殖的微环境中,从而促进细胞发生恶性转化,即PRDX4通过清除ROS促进胃癌的发生发展。     

新早期胃癌标志物PRDX4通过清除ROS促进胃癌的发生发展

胃癌是全球第四大最常见的癌症,也是全球癌症中引起死亡的第二大原因。为了降低胃癌的死亡率,目前亟需解决的问题是发现新的早期胃癌特异性的标志物,提高早期胃癌的检出率,从而从根本上解决胃癌死亡率高的问题。实验室前期研究发现过氧化物酶4 (Peroxiredoxin 4,PRDX4)具有早期胃癌标志物的潜能,文中通过建立恶性转化模型及转化细胞过表达等方法,研究PRDX4在转化细胞中的作用。结果显示PRDX4通过减少转化细胞中活性氧(Reactive oxygen species,ROS)含量,使细胞处在利于生长增殖的微环境中,从而促进细胞发生恶性转化,即PRDX4通过清除ROS促进胃癌的发生发展。     

人乳头瘤病毒16型亚基因DNA体外转化功能的细胞学研究

利用HZIP16和HZIP16K(见材料和方法)质粒,将人乳头瘤病毒16型(HPV-16)的全早期区基因及其开放读码框架(ORF)E6-E7分别转入ψ2细胞,所产生的重组病毒能诱导NIH3T3细胞发生转化。转化细胞具有恶性细胞的生物学和形态学特征,可在0.3％软琼脂中形成集落,可使裸鼠致瘤。Southern blot证明,HPV-16 E6-E7 ORFs序列以整合形式存在于转化细胞和裸鼠肿瘤细胞DNA中,表明HPV-16 DNA具有体外诱导NIH3T3细胞恶性转化的作用,E6-E7 ORFs是诱导细胞转化的关键基因。     

微丝骨架蛋白分子重组与细胞转化

本文介绍正常细胞微丝骨架组装特点和与细胞贴壁及运动的关系;细胞转化后,应力纤维和粘着斑破坏,微丝骨架蛋白分子重组装,肌动蛋白小体形成等变化与转化细胞恶性行为的相关性。本文并提出今后有关本领域的研究方向。     

Oltipraz对细胞恶性转化抑制作用的研究

选用人胚肺为实验材料,研究了十字花科蔬菜提取物ｏｌｔｉｐｒａｚ对人肺癌病变早期细胞恶性转化的阻断作用。将阻断按时间分为ｏｌｔｉｐｒａｚ在ＣＳＣ作用前、后和同时三组,并设ＣＳＣ、ｏｌｔｉｐｒａｚ、ＤＭＳＯ三组对照,将上述６组体外培养处理的人胚肺组织,提取ＤＮＡ转染Ｒａｔ－１细胞,用低血清筛选、作软琼脂培养、裸鼠接种鉴定,结果在ＣＳＣ、ＣＳＣ→ｏｌｔｉｐｒａｚ两组获得恶性转化细胞,ＣＳＣ组恶性度更大。提示ｏｌｔｉｐｒａｚ对ＣＳＣ所致的细胞恶性转化具有一定阻断作用,ｏｌｔｉｐｒａｚ在ＣＳＣ运用前或同时运用效果较好;进一步推断ｏｌｔｉｐｒａｚ对人肺癌变早期具有一定防治作用。     

The peritoneal cell carcinogenicity test

The peritoneal cell carcinogenicity test, which is a new short-term in vivo-in vitro transformation test invented by Nashed (1981), was evaluated in the present report. The experimental design and materials used were as close as possible to those used by Nashed (1981). Test compounds were the two carcinogenic/non-carcinogenic analog pairs benzo[a]pyrene/pyrene and 2-acetylamidofluorene/4-acetylamidofluorene. All 4 compounds were administered orally. Al(OH)3 was injected intraperitoneally to act as mitogen for peritoneal macrophages. The criterium for transformation was colony growth of macrophages in soft agar. Two transformed cell types formed colonies under the conditions used. Pulmonary and peritoneal macrophages formed colonies when colony-stimulating factor was added. No colony growth was observed on plates with macrophages from 256 animals tested (100 carcinogen treated, 80 treated with noncarcinogenic analogs and 76 untreated controls). Thus we were not able to confirm results published previously by the inventor of this test (Nashed, 1981).     

Mobile phone base station radiation does not affect neoplastic transformation in BALB/3T3 cells

A large-scale in vitro study focusing on low-level radiofrequency (RF) fields from mobile radio base stations employing the International Mobile Telecommunication 2000 (IMT-2000) cellular system was conducted to test the hypothesis that modulated RF fields affect malignant transformation or other cellular stress responses. Our group previously reported that DNA strand breaks were not induced in human cells exposed to 2.1425 GHz Wideband Code Division Multiple Access (W-CDMA) radiation up to 800 mW/kg from mobile radio base stations employing the IMT-2000 cellular system. In the current study, BALB/3T3 cells were continuously exposed to 2.1425 GHz W-CDMA RF fields at specific absorption rates (SARs) of 80 and 800 mW/kg for 6 weeks and malignant cell transformation was assessed. In addition, 3-methylcholanthrene (MCA)-treated cells were exposed to RF fields in a similar fashion, to assess for effects on tumor promotion. Finally, the effect of RF fields on tumor co-promotion was assessed in BALB/3T3 cells initiated with MCA and co-exposed to 12-O-tetradecanoylphorbol-13-acetate (TPA). At the end of the incubation period, transformation dishes were fixed, stained with Giemsa, and scored for morphologically transformed foci. No significant differences in transformation frequency were observed between the test groups exposed to RF signals and the sham-exposed negative controls in the non-, MCA-, or MCA plus TPA-treated cells. Our studies found no evidence to support the hypothesis that RF fields may affect malignant transformation. Our results suggest that exposure to low-level RF radiation of up to 800 mW/kg does not induce cell transformation, which causes tumor formation.     

Human papillomavirus in oral leukoplakia is no prognostic indicator of malignant transformation

Background: Oral leukoplakia is considered as a premalignant lesion for the development of oral squamous cell carcinoma (OSCC); several risks factors have been reported to contribute to this step-wise carcinogenesis; including human papillomavirus (HPV). Nevertheless, few reports have analyzed both the HPV status and the genotype in a single individual who develops OSCC from pre-existing oral leukoplakia. In this study, we surveyed the HPV status, genotype and clinicopathological risk factors in cases of malignant transformation from pre-existing oral leukoplakia. Methods: HPV genomic DNA was detected by PCR (MY09/MY11 in conjugation with nested primer-GP05+/GP06+) from paraffin sections, and the genotype was determined by direct DNA sequencing. Fisher's exact test and logistic regression were used to analyze risk factors for malignant transformation of oral cavity leukoplakia. Results: One hundred and sixty-seven patients with oral leukoplakia were enrolled; including 12 who had malignant transformation from the pre-existing oral leukoplakia. HPV prevalence was 22.8% in cases with oral leukoplakia. The risk factor associated with malignant transformation was recurrence of leukoplakia after treatment (p = 0.03), nevertheless, HPV status was not statistically significant by logistic regression analysis. Among these 12 patients with malignant transformation from pre-existing oral leukoplakia, the status or genotype of HPV was chaotic; the oral habits of these patients might contribute to malignant transformation. Conclusions: Our data suggest that HPV in oral leukoplakia is no prognostic indicator of malignant transformation.     

A new location-scale test based on a combination of the ideas of Levene and Lepage

Lepage's test combines the Wilcoxon rank-sum and the Ansari-Bradley statistics. We propose to replace the latter statistic by a Wilcoxon rank-sum calculated after Levene's transformation. We use the medians for this transformation, i.e. absolute deviations from sample medians are calculated. The new location-scale test can be carried out as a permutation test based on permutations of the original observations, the Levene transformation has to be applied for each permutation in an intermediate step to calculate the test statistic. Simulations indicate that the new test can be more powerful than an O'Brien-type test and Lepage's test, the latter is the standard nonparametric location-scale test. The new test is illustrated using real data about colony sizes of yellow-eyed penguins and an SAS program to perform the test is freely available.     

Studies on the transformation of rat embryo cells of low passage by carcinogenic fluorenylhydroxamic acids and their acetate esters

Rat embryo cells of low passage subjected to a single treatment with certain carcinogenic fluorenylhydroxamic acids and their respective acetate esters showed signs of transformation in vitro, such as changes in phenotype, growth in soft agar and agglutination with concanavalin A. In addition, certain changes in karyotype and loss of diploidy were observed. There was no evidence, either by electron microscopy or by assay of RNA-dependent DNA polymerase, for the presence of virus. None of these cell lines produced tumors after inoculation into the isologous host. The results of these study lead us to suggest that malignant transformation is a multistep process and that certain criteria of transformation of rat embryo cells are associated with the initial stage(s) in which the cells are transformed without being tumorigenic. The ultimate test for malignant transformation of rat embryo cells remains the production of tumors in a susceptible host after inoculation of treated cells.     

Malignant transformation of rat bone marrow-derived mesenchymal stem cells treated with 4-nitroquinoline 1-oxide

Recent studies indicated that extensive culture of bone marrow-derived mesenchymal stem cells (BMSCs) can lead to malignant transformation, supporting the concept that tumor may originate from adult stem cells. Also, neoplastic transformation of BMSCs induced by virus and ionizing radiation were verified. However, the capacity for BMSCs to become mutated by chemical carcinogens and become precursors of cancer is still poorly understood. In this study, BMSCs were used to test the hypothesis that tumorigenesis can originate from the mutation of stem cells induced by chemical carcinogen. BMSCs were intermittently treated with 10^?6 M 4-nitroquinoline 1-oxide (4-NQO) from population doublings level (PDL) 3 until senescence occurred. Proliferation data demonstrated that BMSCs treated with 4-NQO bypassed the senescence phase and exhibited unlimited proliferation and anchorage independence. These cells underwent a malignant transformation that resulted in tumor formation in 12/12 immunodeficient mice that received the cells by tail vein injection. In contrast, spontaneous transformation of BMSCs was observed in 6/12 immunodeficient mice injected with BMSCs that had been cultured over PDL 30 in vitro. For both BMSCs treated with 4-NQO, and BMSCs maintained in long-term culture, their transformation into neoplastic cells was found to involve chromosomal abnormalities, increased telomerase activity, and reduced, or absent, expression of p53. Our results also indicate that BMSCs are susceptible to carcinogen-induced malignant transformation rather than spontaneous transformation. Therefore, carcinogen-induced BMSCs transformation models may be ideal for studying mechanisms associated with the promotion of tumor formation by chemical carcinogens.     

A fluorescence quenching test for the detection of flavonoid transformation

A novel fluorescence quenching test for the detection of flavonoid degradation by microorganisms was developed. The test is based on the ability of the flavonoids to quench the fluorescence of 1,6-diphenyl-1,3,5-hexatriene (DPH). Several members of the anthocyanidins, flavones, isoflavones, flavonols, flavanones, dihydroflavanones, chalcones, dihydrochalcones and catechins were tested with regard to their quenching properties. The anthocyanidins were the most potent quenchers of DPH fluorescence, while the flavanones, dihydroflavanones and dihydrochalcones, quenched the fluorescence only weakly. The catechins had no visible impact on DPH fluorescence. The developed test allows a quick and easy differentiation between flavonoid-degrading and flavonoid-non-degrading bacteria. The investigation of individual reactions of flavonoid transformation with the developed test system is also possible.     

Comprehensive bioinformatics analysis combined with experimental validation to screen biomarkers for malignant transformation of oral leukoplakia

Oral leukoplakia (OLK) is the most common potentially malignant disorders in the oral cavity. This study aimed to screen the key genes of OLK malignant transformation using the Gene Expression Omnibus (GEO) database and experiments. In this study, the GEO database was employed to screen OLK malignant transformation-related genes, which were subsequently identified with a series of bioinformatic analyses. External validation showed that the model based on LAPTM4B, NR3C1, and COX6A1 had high accuracy in diagnosing OLK malignant transformation. Furthermore, the DMBA-induced potentially malignant disorders and OSCC models in vivo and real-time PCR experiment in vitro further verified the database analysis results. In conclusion, three key genes (LAPTM4B, NR3C1, and COX6A1) were screened as potential biomarkers for the diagnosis and treatment of OLK malignant transformation.     

Homogeneity test of rate ratios in stratified matched-pair studies

This paper investigates homogeneity test of rate ratios in stratified matched-pair studies on the basis of asymptotic and bootstrap-resampling methods. Based on the efficient score approach, we develop a simple and computationally tractable score test statistic. Several other homogeneity test statistics are also proposed on the basis of the weighted least-squares estimate and logarithmic transformation. Sample size formulae are derived to guarantee a pre-specified power for the proposed tests at the pre-given significance level. Empirical results confirm that (i) the modified score statistic based on the bootstrap-resampling method performs better in the sense that its empirical type I error rate is much closer to the pre-specified nominal level than those of other tests and its power is greater than those of other tests, and is hence recommended, whilst the statistics based on the weighted least-squares estimate and logarithmic transformation are slightly conservative under some of the considered settings; (ii) the derived sample size formulae are rather accurate in the sense that their empirical powers obtained from the estimated sample sizes are very close to the pre-specified nominal powers. A real example is used to illustrate the proposed methodologies.