Heterozygous germline BLM mutations increase susceptibility to asbestos and mesothelioma

Rare biallelic BLM gene mutations cause Bloom syndrome. Whether BLM heterozygous germline mutations (BLM^+/−) cause human cancer remains unclear. We sequenced the germline DNA of 155 mesothelioma patients (33 familial and 122 sporadic). We found 2 deleterious germline BLM^+/− mutations within 2 of 33 families with multiple cases of mesothelioma, one from Turkey (c.569_570del; p.R191Kfs*4) and one from the United States (c.968A>G; p.K323R). Some of the relatives who inherited these mutations developed mesothelioma, while none with nonmutated BLM were affected. Furthermore, among 122 patients with sporadic mesothelioma treated at the US National Cancer Institute, 5 carried pathogenic germline BLM^+/− mutations. Therefore, 7 of 155 apparently unrelated mesothelioma patients carried BLM^+/− mutations, significantly higher (P = 6.7E-10) than the expected frequency in a general, unrelated population from the gnomAD database, and 2 of 7 carried the same missense pathogenic mutation c.968A>G (P = 0.0017 given a 0.00039 allele frequency). Experiments in primary mesothelial cells from Blm^+/− mice and in primary human mesothelial cells in which we silenced BLM revealed that reduced BLM levels promote genomic instability while protecting from cell death and promoted TNF-α release. Blm^+/− mice injected intraperitoneally with asbestos had higher levels of proinflammatory M1 macrophages and of TNF-α, IL-1β, IL-3, IL-10, and IL-12 in the peritoneal lavage, findings linked to asbestos carcinogenesis. Blm^+/− mice exposed to asbestos had a significantly shorter survival and higher incidence of mesothelioma compared to controls. We propose that germline BLM^+/− mutations increase the susceptibility to asbestos carcinogenesis, enhancing the risk of developing mesothelioma.

In the United States, the incidence rate of mesothelioma varies between fewer than one case per 100,000 persons in states with no asbestos industry to two to three cases per 100,000 persons in states with an asbestos industry (1, 2). Asbestos causes DNA damage and apoptosis (3) and promotes a chronic inflammatory reaction that supports the emergence of malignant cells (4). Fortunately, only a small fraction of exposed individuals develop mesothelioma; for example, 4.6% of deaths in miners who worked in asbestos mines for over 10 y were caused by mesothelioma (1). Therefore, multiple cases of mesothelioma in the same family are rare and suggest genetic predisposition (5). In 2001, we discovered that susceptibility to mesothelioma was transmitted in a Mendelian fashion across multiple generations in some Turkish families exposed to the carcinogenic fiber erionite, pointing to gene × environment interaction (G×E) as the cause (6). In 2011, we discovered that carriers of heterozygous germline BRCA1-associated protein–1 (BAP1) mutations (BAP1^+/−) developed mesothelioma and uveal melanoma (5), findings expanded and confirmed by us and by multiple research teams (reviewed in refs. 1, 7, 8). Moreover, heterozygous germline Bap1 mutations (Bap1^+/−) significantly increased susceptibility to asbestos-induced mesothelioma in mice (9, 10), evidence of G×E. Reduced BAP1 levels impair DNA repair (11) as well as different forms of cell death (3, 12) and induce metabolic alterations (13–15) that together favor cancer development and growth.Recent studies revealed that mesothelioma may also develop among carriers of germline mutations of additional tumor-suppressor genes that cause well-defined cancer syndromes, including MLH1 and MLH3 (Lynch syndrome), TP53 (Li–Fraumeni syndrome), and BRCA1-2 (Breast and Ovarian Cancer syndrome) (16, 17). When all germline mutations are combined, it has been estimated that about 12% of mesotheliomas occur in carriers of heterozygous germline mutations of BAP1, the most frequent mutation among patients with mesothelioma, or of other tumor suppressors. Some of these mutations may sensitize the host to asbestos carcinogenesis, according to a G×E scenario (17). Thus, presently, mesothelioma is considered an ideal model to study G×E in cancer (17). As part of the Healthy Nevada Project (HNP), we are studying G×E in northern Nevada, a region with an unusually high risk of exposure to carcinogenic minerals and arsenic, which may be related to the high cancer rates in this region (18). We are investigating genetic variants that may increase cancer risk upon exposure to carcinogens to implement preventive strategies.Biallelic mutations of the Bloom syndrome gene (BLM) cause Bloom syndrome, an autosomal-recessive tumor predisposition syndrome characterized by pre- and postnatal growth deficiency, photosensitivity, type 2 diabetes, and greatly increased risk of developing various types of cancers. BLM is a RecQ helicase enzyme that modulates DNA replication and repair of DNA damage by homologous recombination (19). In patients affected by Bloom syndrome, the absence of the BLM protein causes chromosomal instability, increased number of sister chromatid exchanges, and increased numbers of micronuclei (20–22). In addition, BLM is required for p53-mediated apoptosis (23), a process critical to eliminate cells that have accumulated DNA damage. Impaired DNA repair together with altered apoptosis resulted in increased cancer incidence (17, 24). Of course, inactivating germline BLM heterozygous (BLM^+/−) mutations are much more common than biallelic BLM (BLM^−/−) mutations, with an estimated frequency in the general population of 1 in 900 based on data from the Exome Aggregation Consortium (25). BLM^+/− mutation carriers do not show an obvious phenotype; however, some studies have suggested that carriers of these mutations may have an increased cancer risk (17, 24). Mice carrying Blm^+/− mutations are prone to develop a higher rate of malignancies in the presence of contributing factors, such as concurrent heterozygous mutations of the adenomatous polyposis coli (Apc) gene, or upon infection with murine leukemia virus (26). However, in studies in which Blm^+/− mice were crossed with tuberous sclerosis 1-deficient (Tsc1^+/−) mice that are predisposed to renal cystadenomas and carcinomas, Wilson et al. found that Tsc1^+/− Blm^+/− mice did not show significantly more renal cell carcinomas compared with Tsc1^+/− Blm^WT mice (27). In humans, a large study involving 1,244 patients with colon cancer and 1,839 controls of Ashkenazi Jewish ancestry, in which BLM^+/− frequency is as high as 1 in 100 individuals (28), suggested that carriers of germline BLM^+/− mutations might have a twofold increase in colorectal cancer (CRC) (29). A smaller study did not confirm these results, but reported a trend of increasing incidence of adenomas—premalignant lesions—among BLM^+/− mutation carriers (30). In addition, BLM^+/− mutations were found overrepresented among early-onset (<45 y old) CRC patients (25). Other studies associated BLM^+/− mutations to an increased risk of breast (31, 32) and prostate cancer (33), but the low power of these studies hampered definite conclusions. In summary, it appears possible that BLM^+/− mutations may increase cancer risk in the presence of contributing factors.     

艾灸加强药液穴位皮肤吸收法阻抑BLMA5诱导大鼠肺纤维化的治疗效应研究

目的:观察艾灸加强药液穴位皮肤吸收法对博莱霉素所致肺纤维化大鼠肺组织形态学及生存状况的影响,探索其阻抑肺纤维化的治疗效应,为该法介入肺纤维化的治疗提供实验依据,并为进一步深入探索其作用机制打下实验基础。方法:选用SD大鼠以其气管内注入博莱霉素A5(BLMA5)制作肺纤维化模型,造模成功48只,随机分为4组:模型组?激素治疗组?灸药结合治疗组?单纯艾灸治疗组,每组12只;另设空白对照组12只。造模7天后开始治疗:灸药结合组采用在其"膏肓俞"和"肺俞"穴滴加"化纤方"药液再加以艾灸的方法,每次滴加化纤方药液5滴,艾灸至其穴位皮肤上的药液干掉为止(约10m in);单纯艾灸组只灸其"膏肓俞"和"肺俞"穴;激素治疗组每只腹腔注射5mg/kg泼尼松。以上均每日1次,连续治疗1个月。采用以下方法:(1)肉眼观察大鼠的食欲、神态、反应能力、皮毛、肌肉及呼吸情况并每10天称其体重,观察其肺组织的形状、色泽、表面状态、病灶特征,测其肺系数;(2)光镜观察其肺组织病理学改变。结果:(1)各组体重及生存数量存在较大差异,其中灸药结合治疗组最佳;(2)空白组肺组织基本属正常形态,灸药结合治疗组大鼠肺的基本情况较泼尼松组和单纯艾灸组优,模型组肺组织损害程度明显严重;(3)灸药结合治疗组、单纯艾灸组和泼尼松组肺水含量较模型组减少,其中灸药结合治疗组情况较优;(4)各组肺泡炎及肺纤维化程度分级比较结果提示:①造模比较成功;②灸药结合治疗组肺纤维化程度明显减轻。结论:灸药结合治疗法在一定程度上更能有效地阻抑大鼠肺纤维化的形成和发展,且与激素治疗相比较具有无毒副作用之优势。     

Cellular energetics and glutathione status in NRK-52E cells: toxicological implications

Cellular energetics and redox status were evaluated in NRK-52E cells, a stable cell line derived from rat proximal tubules. To assess toxicological implications of these properties, susceptibility to apoptosis induced by S-(1,2-dichlorovinyl)-L-cysteine (DCVC), a well-known mitochondrial and renal cytotoxicant, was studied. Cells exhibited high activities of several glutathione (GSH)-dependent enzymes, including gamma-glutamylcysteine synthetase, GSH peroxidase, glutathione disulfide reductase, and GSH S-transferase, but very low activities of gamma-glutamyltransferase and alkaline phosphatase, consistent with a low content of brush-border microvilli. Uptake and total cellular accumulation of [14C]alpha-methylglucose was significantly higher when cells were exposed at the basolateral as compared to the brush-border membrane. Similarly, uptake of GSH was nearly 2-fold higher across the basolateral than the brush-border membrane. High activities of (Na(+)+K(+))-ATPase and malic dehydrogenase, but low activities of other mitochondrial enzymes, respiration, and transport of GSH and dicarboxylates into mitochondria were observed. Examination of mitochondrial density by confocal microscopy, using a fluorescent marker (MitoTracker Orange), indicated that NRK-52E cells contain a much lower content of mitochondria than rat renal proximal tubules in vivo. Incubation of cells with DCVC caused time- and concentration-dependent ATP depletion that was largely dependent on transport and bioactivation, as observed in the rat, on induction of apoptosis, and on morphological damage. Comparison with primary cultures of rat and human proximal tubular cells suggests that the NRK-52E cells are modestly less sensitive to DCVC. In most respects, however, NRK-52E cells exhibited functions similar to those of the rat renal proximal tubule in vivo.     

Genetic factors and colorectal cancer in Ashkenazi Jews

The observed increased incidence of colorectal cancer in Ashkenazi Jews compared to other populations is unexplained but likely has a genetic component. The I1307K APC polymorphism/mutation is carried by 6--8% of Ashkenazim and increases the risk of colorectal cancer 1.5–2 fold. There are few differences between the phenotype of colorectal cancer in I1307K carriers and sporadic cases. It is estimated that the mutation accounts for 6% of cases of colorectal cancer in Jews of Eastern European heritage. It should not be the subject of mass screening in Ashkenazi Jews, although it may be important in cases of familial colorectal cancer. Even rarer is the 1906GC MSH2 mutation carried by less than 1% of Ashkenazim, but as with other HNPCC mutations likely associated with a high risk of malignancy. Mutations at 15q13–14 are associated with the colorectal adenoma and carcinoma syndrome (CRAC) described in Ashkenazi families. The prevalence of the mutation is not known, nor its significance as a cause of colorectal cancer. Despite the paucity of genetic explanations for the high risk of colorectal cancer in Ashkenazim, that risk warrants aggressive colorectal cancer screening and particular attention to family history of malignancy in all Jews of Ashkenazi descent.     

人舌癌细胞耐药系Tca8113/BLM的建立及其耐药机理的分析

目的 :建立舌癌平阳霉素 (BleomycinA5Hydrochloride ,BLM)耐药细胞系Tca8113/BLM ;研究Tca8113/BLM细胞P 糖蛋白 (P glycoprotein ,P gp)和多药耐药相关蛋白 (MRP)表达变化与其耐药的相关性。方法 :采用大剂量BLM(30 μg/ml)反复间歇 2 4小时暴露法处理舌癌细胞系Tca8113细胞 ;用MTT法检测该耐药细胞模型的多药耐药性 ;激光共聚焦显微镜和流式细胞仪检测P gp、MRP ;并用流式细胞仪检测细胞周期的分布 ,细胞内阿霉素 (ADM)蓄积 ,以及经典钙离子生物泵阻断剂逆转剂黄体酮 (Progesterone,Prog)对ADM蓄积的影响。结果 :①Tca8113/BLM耐药性稳定 ,耐药指数为 12 ,且对其它化疗药物产生交叉耐药性 ;②Tca8113/BLM的倍增时间延长 ,G1期细胞减少 ,G2和S期细胞增多 ;③P gp和MRP在Tca8113/BLM细胞中强阳性表达 ,在Tca8113细胞中弱阳性表达 ,两者相比差异有显著性 (P <0 .0 1) ;④ADM在Tca8113/BLM细胞内蓄积明显低于Tca8113细胞 (P <0 .0 5 ) ;⑤Prog能显著提高Tca8113/BLM细胞内ADM蓄积 ,而对Tca8113细胞内ADM蓄积无明显作用。结论 :建立了舌癌BLM耐药细胞系Tca8113/BLM ,发现Tca8113/BLM的耐药性与P gp和MRP过表达有密切关系     

Influence of renal compensatory hypertrophy on mitochondrial energetics and redox status

A reduction in functional renal mass is common in numerous renal diseases and aging. The remaining functional renal tissue undergoes compensatory growth primarily due to hypertrophy. This is associated with a series of physiological, morphological and biochemical changes similar to those observed after uninephrectomy. Previous work showed that compensatory renal cellular hypertrophy resulted in an increase in susceptibility to several drugs and environmental chemicals and appeared to be associated with oxidative stress. Compensatory renal cellular hypertrophy was also associated with increases in mitochondrial metabolic activity, uptake of glutathione (GSH) across renal plasma and mitochondrial inner membranes, and intracellular GSH concentrations. Based on these observations, we hypothesize that the morphological, physiological and biochemical changes in the hypertrophied kidney are associated with marked alterations in renal cellular energetics, redox status and renal function in vivo. In this study, we used a uninephrectomized (NPX) rat model to induce compensatory renal growth. Our results show alterations in renal physiological parameters consistent with modest renal injury, altered renal cellular energetics, upregulation of certain renal plasma membrane transporters, including some that have been observed to transport GSH, and evidence of increased oxidative stress in mitochondria from the remnant kidney of NPX rats. These studies provide additional insight into the molecular changes that occur in compensatory renal hypertrophy and should help in the development of novel therapeutic approaches for patients with reduced renal mass.     

重组人血管内皮抑素联合博来霉素置管灌注治疗肺癌恶性胸腔积液的临床观察

目的：观察重组人血管内皮抑素（恩度）联合博来霉素胸腔灌注治疗肺癌恶性胸水的近期疗效及不良反应。方法：65例肺癌伴恶性胸水患者经胸腔置中心静脉导管排尽胸水后随机分为3组。A组（BLM组）21例胸腔内灌注博来霉素40-60mg d1,5每3周为一周期;B（恩度组）20例患者胸腔内灌注恩度60mg,每3周一次;C组（恩度＋BLM组）24例胸腔内联合灌注恩度60mg和博来霉素40-60mg d1,5每3周为一周期。所有患者至少完成2周期。观察3组患者近期疗效及不良反应及Karnofsky评分改善情况。结果：A组有效率为47.6%;B组有效率50.0%;C组83.3%,显著高于A、B两组（P〈0.05）。A组Karnofsky评分改善率为52.3%,B组Karnofsky评分改善率为55.0%。C组Karnofsky评分改善率为8 7.5%,显著高于A、B组（P〈0.05）。三组主要副反应为发热,A组发生率23.8%;B组20.0%;C组25.0%,三组之间无显著差异（P〉0.05）。结论：重组人血管内皮抑素联合博来霉素置管灌注治疗肺癌恶性胸水有效、安全,值得推广。     

Multigene pathway‐based analyses identify nasopharyngeal carcinoma risk associations for cumulative adverse effects of TERT‐CLPTM1L and DNA double‐strand breaks repair

The genetic etiology of nasopharyngeal carcinoma (NPC) and mechanisms for inherited susceptibility remain unclear. To examine genetic risk factors for NPC, we hypothesized that heritable risk is attributable to cumulative effects of multiple common low‐risk variants. With the premise that individual SNPs only confer subtle effects for cancer risk, a multigenic pathway‐based approach was used to systematically examine associations between NPC genetic susceptibility with SNPs in genes in DNA repair pathways and from previously identified cancer genome‐wide association study analyses. This case–control study covers 161 genes/loci and focuses on pathway‐based analyses in 2,349 Hong Kong individuals, allowing stratification according to NPC familial status for meaningful association analysis. Three SNPs (rs401681, rs6774494 and rs3757318) corresponding to TERT/CLPTM1L (OR 95% CI = 0.77, 0.68–0.88), MDS1‐EVI1 (OR 95% CI=0.79 0.69–0.89) and CCDC170 (OR 95% CI = 0.76, 0.66–0.86) conferred modest protective effects individually for NPC risk by the logistic regression analysis after multiple testing adjustment (p_Bonferroni < 0.05). Stratification of NPC according to familial status identified rs2380165 in BLM (OR 95% CI = 1.49, 1.20–1.86, p_Bonferroni < 0.05) association with family history‐positive NPC (FH+ NPC) patients. Multiple SNPs pathway‐based analysis revealed that the combined gene dosage effects for increasing numbers of unfavorable genotypes in TERT‐CLPTM1L and double‐strand break repair (DSBR) conferred elevated risk in FH+ and sporadic NPC patients (ORs per allele, 95% CIs = 1.37, 1.22–1.55, p_Bonferroni = 5.00 × 10^?6; 1.17, 1.09–1.26, p_Bonferroni = 4.58 × 10^?4, respectively, in TERT/NHEJ pathways). Our data suggested cumulative increased NPC risk associations with TERT‐CLPTM1L and DSBR pathways contribute to genetic susceptibility to NPC and have potential translational relevance for patient stratification and therapeutics.