天然果蔬有拮抗肿瘤化疗药物致突变毒性的效应

近年来我们河北省肿瘤研究所曾和河北医科大学协作采用三种短期致突变试验技术联合检测过22种常用肿瘤化疗药物的致突变性，结果发现平阳霉素、氟豚嘧啶、顺铂、阿糖胞苷、甲基苄肼、环己亚硝脲、足叶乙甙、长春新碱、呋喃氟脲嘧啶、盐酸氮芥、丝裂霉素C、阿霉素、噻■派、卡铂、甲胺喋呤、环磷酰胺等18种药物有致突变性，国内外其他学者也曾报导过一些化疗药物有远期致癌性，可见这些药物在治疗肿瘤的同时存在着引起新肿瘤的可能性，如长期反复使用这些药物，久而久之，增加病人将来患第二种肿瘤的危险性。我们采用抗突变和致突变同步快速…     

11种天然药材及植物的抗突变与致突变同步试验报告

本文报告用ＳＯＳ噬菌体诱导试验的抗突变与致突变同步试验法，对１１种天然中药及植物甘草、枸杞、半枝莲、柴胡、丹参、黄芪、决明子、仙人球、仙人指、胡萝卜及青萝卜的抗突变及致突变性进行了筛检。经过加和不加大鼠肝微粒体酶代谢活化系统（Ｓ９）的２种试验及重复验证，结果１１种中药及植物均未发现致突变作用，甘草、枸杞、丹参、黄芪、胡萝卜、青萝卜及仙人指可抑制抗肿瘤药物丝裂霉素Ｃ（ＭＭＣ）的致突变性。     

化妆品的致突变和抗突变同步快速试验分析

目的与方法: 为了快速筛选有致突变性的化妆品,采用大肠杆菌溶源性菌GY5027和对噬菌体敏感的指示菌GY4015,对29种化妆品进行致突变和抗突变同步快速试验.同时观察了急性经口试验、急性眼睛刺激试验和急性或多次皮肤刺激试验.结果:在加和不加大鼠肝脏微粒体酶(S-9)条件下,全部样品无抗突变阳性;4种样品呈现致突变阳性,其中2种至少1项急性试验阳性.经SPSS软件作等级相关分析表明,同步试验与急性试验结果相关显著(r-s＝0.392,P=0.036).结论:部分化妆品确实存在致突变性;采用致突变和抗突变同步试验可快速、大量筛选有致突变性的化妆品;急性试验阳性化妆品致突变性也较高.     

对20种抗肿瘤药物的致突变性研究

本文报告用噬菌体诱导试验对20种抗肿瘤药物的致突变性进行筛选,并用Ames试验、SOS固体显色试验和噬菌体诱导试验3种方法联合测试其中11种药物的致突变性,各种试验方法均做加和不加大鼠肝脏微粒体酶代谢活化系统(S9)的两种试验。结果15种药物有致突变作用,阳性率为75％。三种试验方法联合检测的符合率为72.73％。     

樱桃等4种水果的抗突变性初步实验研究

目的:筛选有抗突变作用的水果.方法:采用抗突变和致突变同步快速试验对樱桃、桑葚、葡萄及杏做了加和不加大鼠肝脏微粒体酶(S9)的2种试验.结果与结论:4种检品均未发现致突变性,樱桃、桑葚、葡萄和杏对丝裂霉素C引起的致突变作用有拮抗效应.     

MTT法在卵巢外腹膜乳头状浆液性癌化疗中的应用

采用ＭＴＴ法对卵巢外腹膜乳头状浆液性癌进行化疗药物敏感性测定，并将药敏结果与临床疗效作了对比研究。本组资料共收集７例卵巢外腹膜乳头状浆液性癌患者。本组患者不同个体之间药物敏感性不同（Ｐ＜０．０１）；６种单一药物（顺铂、卡铂、阿霉素、丝裂霉素、长春新碱和５氟脲嘧啶）平均抑制率以铂类药物较高（Ｐ＜０．０１）；联合用药较单一用药更有效（Ｐ＜０．０１）；肿瘤体外药敏试验结果与临床疗效存在良好的相关性（ｒ＝０．８７）。在本组药敏试验中，ＭＴＴ法可靠有效。     

MTT法对原发性肝细胞癌化疗药物敏感性的预测

作者采用噻唑蓝（ＭＴＴ）法，对人体手术切除的原发性肝细胞癌的新鲜标本，作顺铂、卡铂、丝裂霉素、阿霉素和５氟脲嘧啶的抗癌敏感药物试验，试图预测出针对性较强的化疗药物，为临床科学合理地选择用药提供可靠依据。作者共检测４９例原发性肝细胞癌，结果显示，对两种药物敏感者１４例，占２８．６％，对其它药种敏感者很少，敏感药物顺序与临床治疗结果大致相符。此结果可作临床药物选择时参考，在实体瘤药敏试验中，ＭＴＴ法仍     

24例原发性肝癌患者的肿瘤药敏结果分析

目的通过测定原发性肝癌患者对5-氟脲嘧啶(5-Fu)、顺铂(DDP)、阿霉素(ADM)、丝裂霉素(MMC)、氨甲喋呤(MTX)、长春新碱(VCR)6种化疗药物的体外敏感性试验,探讨肿瘤药敏试验对原发性肝癌个体化疗的应用价值。方法采用组织块培养-终点染色-计算机图像分析法(TECIA)。结果24例原发性肝癌细胞对6种化疗药物的敏感性由高到低依次为5-Fu、MMC、DDP、ADM、MTX、VCR。结论TECIA法的体外肿瘤药敏试验在原发性肝癌的临床用药及个体化化疗方面具有重要的指导意义。     

MTT比色分析法检测非小细胞肺癌药物敏感性

选择有效的化疗药物是肿瘤化疗成功的关键，采用常用的９种化疗药物对２５例非小细胞肺癌进行ＭＴＴ法药物敏感试验。在单药使用时，非小细胞肺癌对抗癌药物敏感度由高至低依次为诺维本、丝裂霉素Ｃ、阿霉素、顺铂、鬼臼乙叉甙、卡铂和长春新碱，而对甲氨喋呤和５氟脲嘧啶耐药。此结果为临床个体化化疗方案的制定提供了参考依据     

核形法化学敏感性试验在卵巢癌中的应用

本文采用核损伤形态学变化－核形法对４０例卵巢标本进行短期培养及敏感试验，所检化疗药物丝裂霉素、长春新碱、足叶乙甙、阿霉素、顺铂、５－氟脲嘧啶、阿糖胞苷、氨甲喋呤、平阳霉素及更生霉素等１０种。离体实验１００％成功，且在２４ｈ之内即可筛选出敏感药物，其中１２份标本同时进行３Ｈ－ＴｄＲ掺入法试验，并与核形法比较，Ｈ－ＴｄＲ掺入法的试验８３．３％成功。两种方法药敏试验结果的符合率为８０％，具有很好的相关性     

Evidence for a major premutagenic ethyldeoxythymidine-DNA adduct in an in vivo system: N-nitroso-N-ethylurea-treated Salmonella typhimurium

Mutagenesis induced by N-nitroso-N-ethylurea (NEU) was assayedin four strains of Salmonella typhimurium which are known tobe reverted to histidine prototrophy by mutations at A-T basepairs and by extragenic suppression. NEU-induced revertantswere characterized for the presence of extragenic suppressorsby their sensitivities to the histidine analogue, thiazolealanine.In strains carrying the plasmid, pKM101, only a small percentageof the revertants was due to suppressors, indicating that NEUgives rise to a major pre-mutagenic adenine or thymidine-DNAadduct. In strains without plasmid, mutagenesis was much lessefficient and resulted mainly from suppressors. Apparently error-proneDNA-repair plays an important role in mutagenesis via the Aor T-DNA adduct in the plasmid-containing strains. Ethylmethanesulfonate(EMS), a mutagen known to form ethyladenines but not ethylthymidines,induced mutagenesis that resulted mainly from suppressors inall strains, and there was little inter-strain difference inthe sensitivity to EMS. Since NEU, but not EMS, forms ethylthymidinesin appreciable yield, and only NEU induced high percentagesof revertants with mutations at A-T base pairs, it appears thatat least one ethylthymidine is a major premutagenic adduct inNEU-induced mutagenesis.     

An important role for cytosol in the microsomal metabolism of N-nitrosodimethylamine to a mutagen: evidence for two different mutagenic metabolites

Microsomal-mediated mutagenesis induced by N-nitrosodimethylamine (NDMA) in Salmonella TA100 at neutral pH was only slightly affected by cytosol and was similar in its threshold type dose-response curve to mutagenesis induced by direct-acting N-nitroso-N-methyl compounds. However, mutagenesis in strain TA104 was greatly enhanced by cytosol and this mutagenesis did not exhibit a threshold. In the presence of microsomes alone NDMA was more potent in TA100 than TA104, but in the presence of microsomes plus cytosol (S-9 fraction) this order was reversed at the doses tested. A possible explanation for these results is that NDMA is metabolized by microsomes to a mutagen (presumably methyldiazonium ion; MDI) that is more potent in TA100 than in TA104, but in the presence of S-9 fraction a fraction of the NDMA is metabolized by a pathway leading to a different mutagen with a different specificity. The ratio of metabolism via these pathways appears to be dependent on pH.     

3-Methyladenine mutagenesis under conditions of SOS induction in Escherichia coli.

Under conditions of the induced error-prone SOS response in Escherichia coli, N-methyl-N-nitrosourea (MNU) was found to produce a majority of mutations at A.T base pairs. These mutations included mainly A.T----G.C transitions, followed by A.T----T.A transversions and (-1)A.T frameshifts. The possibility that 3-methyladenine (3-MeAde) significantly contributed to these mutations was investigated. MNU mutagenesis under SOS conditions was studied in E. coli strains deficient in 3-MeAde-DNA glycosylase I (TagI), which is the major constitutively expressed repair enzyme for 3-MeAde. In SOS uninduced cells, the lack of 3-MeAde repair did not increase mutagenesis, suggesting that 3-MeAde does not contribute to mutagenesis under these conditions. In SOS-induced cells, by contrast, MNU induced a 5-fold higher mutation frequency in the TagI-deficient cell strains, suggesting that 3-MeAde is indeed an SOS-dependent premutagenic lesion. Although 3-MeAde is mutagenic under SOS conditions, it is possible that its fast repair in repair-proficient cells might result in the loss of the lesion before its mutagenic properties could be realized. Hence, the contribution of 3-MeAde to SOS-dependent mutagenesis in fully repair-proficient cells was also investigated. 3-MeAde lesions were removed from MNU-treated DNA by the purified TagI protein. This prior removal of 3-MeAde had little effect on mutagenesis in SOS-induced or SOS-uninduced cells. Thus, in repair-proficient cells, 3-MeAde is efficiently removed from DNA and does not contribute in a major way to mutagenesis. These results indicate that some other A or T adduct(s) are responsible for the bulk of the mutagenesis observed under SOS-induced conditions.     

补益复方药冲剂抗诱变作用的探讨

采用微核实验技术对两种补益复方药冲剂抑制诱变作用进行了研究。结果表明，这两种冲剂对诱变剂丝裂霉素Ｃ诱发正常人淋巴细胞微核率有明显的抑制作用。两种冲剂在同一剂量下，没有显著性差异。     

Inactivation of the RAD51 recombination pathway stimulates UV-induced mutagenesis in mammalian cells

We have examined the impact of the RAD51 recombination pathway on recombination and mutagenesis induced by UV-C in mammalian cells. We used hamster CHO cell lines that express different forms of Rad51 protein, resulting in stimulation or inhibition of spontaneous gene conversion. Spontaneous mutagenesis was affected by none of the RAD51 forms. The wild-type mouse MmRAD51 affects neither UV-induced recombination nor UV-induced mutagenesis. In contrast, the dominant negative SMRAD51 strongly impairs UV-induced recombination while it stimulates UV-induced mutagenesis. Our results show that a defect in the RAD51 gene conversion pathway reveals (a) mutagenic alternative pathway(s) to repair UV-damage, in mammalian cells.     

Effect of soy isoflavone supplementation on markers of oxidative stress in men and women

Consumption of lycopene has been associated with reduced risk of prostate cancer. We have investigated the effects of lycopene, fed as a lycopene-rich tomato oleoresin (LTO) at two doses, on in vivo mutagenesis in prostate, colon, and lungs of lacZ mice. Both short-term benzo[a]pyrene (BaP)- induced and long-term spontaneous mutagenesis were monitored. Non-significant inhibition of spontaneous mutagenesis in prostate and colon was observed at the higher dose of LTO, and the observation of inhibition in colon was facilitated by an unusually high spontaneous mutagenesis rate. BaP-induced mutagenesis was slightly inhibited by LTO in prostate. However, enhancement of BaP-induced-mutagenesis was observed in colon and lung. These results indicate that any antimutagenic effects of LTO may be organospecific.     

Origins and selection of p53 mutations in lung carcinogenesis

Molecular epidemiologists usually consider the spectrum of p53 mutations found in human tumors to be a signature of the corresponding environmental carcinogen(s). In lung cancer, this signature is the spectrum of G --> T transversions, presumably induced by polycyclic aromatic hydrocarbons (PAH) from cigarette smoke. What complicates the situation, however, is that in the p53 gene the same codons are preferential targets for not only mutagenesis but also tumorigenic selection. In this review, we compare the G --> T spectra induced by PAH o-quinones and diol epoxides with those in lung cancer and show that the main "shaper" of the latter is selection, not mutagenesis. In addition, we propose the approach that allows to distinguish selection and mutagenesis components of the p53 spectra and, therefore, to test the suspect carcinogens for their "in vivo" mutagenic involvement. Collectively, the reviewed basic premises, concepts and data are consistent with the increasing recognition of environmental cancer risk conditions as selecting rather than inducing tumorigenic mutations.     

Genetic alterations and DNA repair in human carcinogenesis

A causal association between genetic alterations and cancer is supported by extensive experimental and epidemiological data. Mutational inactivation of tumor suppressor genes and activation of oncogenes are associated with the development of a wide range of cancers. The link between mutagenesis and carcinogenesis is particularly evident for cancers induced by chemical exposures, which, in some cases, lead to characteristic patterns of mutations. These "genotoxic," direct-acting carcinogens form covalent adducts with DNA, which cause mutations during DNA replication. The link between mutagenesis and carcinogenesis is also supported by the observation that DNA repair defects are associated with an increased cancer risk. Normally, DNA repair mechanisms serve to suppress mutagenesis by correcting DNA damage before it can lead to heritable mutations. It has been postulated that mutagenesis plays a role in both the initiation phase and the progression phase of carcinogenesis, and that an essential step in the carcinogenic process is the development of a mutator state in which the normal cellular processes that suppress mutagenesis become compromised. Given the link between mutations and cancer, attempts have been made to use the mutational profile of cancer cells as an indicator of the causative agent. While this may be a valid approach in some cases, it is complicated by the role of endogenous processes in promoting mutagenesis. In addition, many important carcinogenic agents may enhance mutagenesis indirectly through suppression of DNA repair functions or stimulation of inappropriate cell proliferation. Epigenetic phenomena may also suppress gene expression without causing overt changes in DNA sequence.     

Inhibitory effect of reducing agents on N-acetoxy- and N-hydroxy-2-acetylaminofluorene-induced mutagenesis.

The effect of cysteine (alpha-amino-beta-mercaptopropionic acid) on the mutagenic activities of the proximate carcinogen, N-hydroxy-2-acetylaminofluorene, and the ultimate carcinogen, N-acetoxy-2-acetylaminofluorene, was examined by estimating the frequency of his+ revertants of Salmonella typhimurium. Nontoxic concentrations of cysteine significantly reduced the formation of revertants when it was applied concurrently with the two carcinogens. Cysteine showed no detectable effect on mutagenesis when added to bacteria before or after exposure to carcinogens. The magnitude of inhibition of mutagenesis depended on the dose of cysteine and the concentration of the carcinogens. Cysteine at equimolar concentrations inhibited to a larger degree the mutagenesis induced by N-hydroxy-2-acetylaminofluorene than it inhibited that elicited by N-acetoxy-2-acetylaminofluorene. The inhibitory action of cysteamine and glutathione was comparable to that of cysteine. The results appear to be consistent with the assumption that cysteine traps electrophiles prior to their action on DNA.     

Mutation spectra of the two guanine adducts of the carcinogen 4-nitroquinoline 1-oxide in Escherichia coli. Influence of neighbouring base sequence on mutagenesis.

When the chemical carcinogen 4-nitroquinoline 1-oxide binds to DNA in vitro, two major adducts are formed, both at guanine residues, but at different positions, i.e. the C8 or the N2 position. Well-defined adducts (either C8 or N2 guanine adducts) can be formed in vitro by reacting DNA with 4-actoxyaminoquinoline 1-oxide (Ac-4HAQO) under different reaction conditions. Forward mutations induced by each of both main 4NQO adducts in the tetracycline resistance gene of pBR322 were determined. In total, 30 independent 4NQO-induced mutations were characterized, showing mainly base-pair substitution mutations and some frameshift mutations. We have observed that the 5' neighbouring base influences the specificity of dGuo-N2-AQO induced base-pair substitutions mutagenesis; a similar effect does not occur with dGuo-C8-AQO. This study reveals the importance of the N2 guanine adduct in the mutagenesis induced by 4NQO in vivo.