MYC can induce DNA breaks in vivo and in vitro independent of reactive oxygen species

MYC overexpression is thought to initiate tumorigenesis by inducing cellular proliferation and growth and to be restrained from causing tumorigenesis by inducing cell cycle arrest, cellular senescence, and/or apoptosis. Here we show that MYC can induce DNA breaks both in vitro and in vivo independent of increased production of reactive oxygen species (ROS). We provide an insight into the specific circumstances under which MYC generates ROS in vitro and propose a possible mechanism. We found that MYC induces DNA double-strand breaks (DSBs) independent of ROS production in murine lymphocytes in vivo as well as in normal human foreskin fibroblasts (NHFs) in vitro in normal (10%) serum, as measured by gammaH2AX staining. However, NHFs cultured in vitro in low serum (0.05%) and/or ambient oxygen saturation resulted in ROS-associated oxidative damage and DNA single-strand breaks (SSBs), as measured by Ape-1 staining. In NHFs cultured in low versus normal serum, MYC induced increased expression of CYP2C9, a gene product well known to be associated with ROS production. Specific inhibition of CYP2C9 by small interfering RNA was shown to partially inhibit MYC-induced ROS production. Hence, MYC overexpression can induce ROS and SSBs under some conditions, but generally induces widespread DSBs in vivo and in vitro independent of ROS production.     

Mitochondrial DNA mutations in primary leukemia cells after chemotherapy: clinical significance and therapeutic implications.

Mitochondrial DNA (mtDNA) codes for 13 respiratory chain subunits and is more vulnerable to damage than nuclear DNA due, in part, to a lack of histone protection and a weak repair capacity. While mtDNA alterations have been observed in human cancer, their roles in oncogenesis and chemosensitivity remain unclear. We investigated the relationship between mtDNA mutations, reactive oxygen species (ROS) generation, and clinical outcomes in chronic lymphocytic leukemia (CLL) patients. An analysis of mtDNA from 20 CLL patients revealed that primary CLL cells from patients with prior chemotherapy had a significantly higher frequency of heteroplasmic mutations than did those from untreated patients. Overall, mtDNA mutations appeared to be associated with increased ROS generation. Patients refractory to conventional therapeutic agents tended to have higher mutation rates than patients who responded to treatment. Analysis of paired blood samples from the same patient led to the identification of a heteroplasmic mutation in the cytochrome c oxidase II gene several months after chemotherapy. The mutation was associated with increased ROS generation. Our results suggest for the first time that chemotherapy with DNA-damaging agents may cause mtDNA mutations in primary leukemia cells, which often exist in heteroplasmy, and are associated with increased ROS generation.     

Metformin reduces endogenous reactive oxygen species and associated DNA damage

Pharmacoepidemiologic studies provide evidence that use of metformin, a drug commonly prescribed for type II diabetes, is associated with a substantial reduction in cancer risk. Experimental models show that metformin inhibits the growth of certain neoplasms by cell autonomous mechanisms such as activation of AMP kinase with secondary inhibition of protein synthesis or by an indirect mechanism involving reduction in gluconeogenesis leading to a decline in insulin levels and reduced proliferation of insulin-responsive cancers. Here, we show that metformin attenuates paraquat-induced elevations in reactive oxygen species (ROS), and related DNA damage and mutations, but has no effect on similar changes induced by H(2)0(2), indicating a reduction in endogenous ROS production. Importantly, metformin also inhibited Ras-induced ROS production and DNA damage. Our results reveal previously unrecognized inhibitory effects of metformin on ROS production and somatic cell mutation, providing a novel mechanism for the reduction in cancer risk reported to be associated with exposure to this drug.     

Mitochondrial subversion in cancer

Mitochondria control essential cellular activities including generation of ATP via oxidative phosphorylation. Mitochondrial DNA (mtDNA) mutations in the regulatory D-loop region and somatic mtDNA mutations are common in primary human cancers. The biological impact of a given mutation may vary, depending on the nature of the mutation and the proportion of mutant mtDNAs carried by the cell. Identification of mtDNA mutations in precancerous lesions supports their early contribution to cell transformation and cancer progression. Introduction of mtDNA mutations in transformed cells has been associated with increased ROS production and tumor growth. Studies reveal that increased and altered mtDNA plays a role in the development of cancer but further work is required to establish the functional significance of specific mitochondrial mutations in cancer and disease progression. This review offers some insight into the extent of mtDNA mutations, their functional consequences in tumorigenesis, mitochondrial therapeutics, and future clinical application.     

Moderate hypermutability of a transgenic lacZ reporter gene in Myc-dependent inflammation-induced plasma cell tumors in mice

Mutator phenotypes, a common and largely unexplained attribute of human cancer, might be better understood in mouse tumors containing reporter genes for accurate mutation enumeration and analysis. Previous work on peritoneal plasmacytomas (PCTs) in mice suggested that PCTs have a mutator phenotype caused by Myc-deregulating chromosomal translocations and/or phagocyte-induced mutagenesis due to chronic inflammation. To investigate this hypothesis, we generated PCTs that harbored the transgenic shuttle vector, pUR288, with a lacZ reporter gene for the assessment of mutations in vivo. PCTs exhibited a 5.5 times higher mutant frequency in lacZ (40.3 +/- 5.1 x 10(-5)) than in normal B cells (7.36 +/- 0.77 x 10(-5)), demonstrating that the tumors exhibit the phenotype of increased mutability. Studies on lacZ mutant frequency in serially transplanted PCTs and phagocyte-induced lacZ mutations in B cells in vitro indicated that mutant levels in tumors are not determined by exogenous damage inflicted by inflammatory cells. In vitro studies with a newly developed transgenic model of inducible Myc expression (Tet-off/MYC) showed that deregulated Myc sensitizes B cells to chemically induced mutations, but does not cause, on its own, mutations in lacZ. These findings suggested that the hypermutability of PCT is governed mainly by intrinsic features of tumor cells, not by deregulated Myc or chronic inflammation.     

Somatic LMCD1 mutations promoted cell migration and tumor metastasis in hepatocellular carcinoma

Common genetic alteration in cancer genomes is implicated for embracing an aberrant cancer gene participated in tumor progression. In this study, we identified a somatic mutated LIM and cysteine-rich domains-1 (LMCD1) as a putative metastatic oncogene in human hepatocellular carcinoma (HCC) using integrated genomic approaches. In addition to revealing genomic amplification and gene upregulation, we identified recurrent E135K (3/48 cases) mutations in HCC tissues and K237R mutation in the PLC/PRF/5 HCC cell line. Expression of mutant LMCD1 E135K or K237R reduced the stress fiber assembly, increased cortical actin accumulation and induced lamellipodial extension. Consistently, these mutations enhanced cell migration and showed activation of the Rac1-signaling pathway. Inhibition of the LMCD1/Rac1 pathway by an LMCD1 short-hairpin RNA (shLMCD1) or the Rac1 inhibitor NSC23766 suppressed the mutation-mediated lamellipodial protrusion and cell migration. In PLC/PRF/5 cells with endogenous K237R mutation, cell migration was enhanced by estrogen-induced LMCD1 expression but reversed by shLMCD1 treatment. Moreover, overexpression of LMCD1 E135K mutation significantly promoted systemic lung metastasis in a murine tail vein injection model. Together, our results suggest that LMCD1 mutations are potential oncogenic events in HCC metastasis to promote cell migration through the Rac1-signaling pathway.     

Characterization of novel cell lines established from three human oral squamous cell carcinomas

Human oral squamous cell carcinoma cell lines (KOSCC-11, -25A, -25B, -25C, -25D, -25E, -33A, and -33B) were established by explantation culture from these oral squamous cell carcinomas. The histopathology of the primary tumors, in vitro growth characteristics, epithelial origin, in vitro anchorage-independency, in vivo tumorigenicity, the frequency of human papillomavirus (HPV) infections, and the status of proto-oncogenes, tumor suppressor genes, DNA mismatch repair genes, and microsatellite instability were investigated in the cell lines. KOSCC-11 is a well-differentiated oral squamous cell carcinoma (OSCC) derived from mandibular gingiva. KOSCC-25A, -25B, -25C, -25D, and -25E cell lines were derived from the same OSCC. KOSCC-33A and -33B were established from the same tumor that originated from the maxillary sinus. All tumor lines studied grew as monolayers and showed: i) epithelial origin by the presence of desmosome and keratin; ii) in vitro anchorage-independent growth ability; and iii) tumorigenic potential in nude mice. The cancer cell lines did not contain HPV DNA and did not express viral genes. Northern blot analysis revealed: i) overexpression of EGFR in four cell lines, ii) overexpression of c-H-ras in four cell lines, iii) overexpression of c-myc in three cell lines, iv) decreased expression of TGF-alpha in seven cell lines, and v) decreased expression of c-jun in five cancer cell lines compared with normal human oral keratinocytes. In all KOSCC cell lines and their corresponding tumor tissues, mutations were identified in highly-conserved functional regions of the p53 gene. The KOSCC-11 cell line contained a frameshift mutation and the other cell lines harbored an identical p53 mutation at codon 175 from CGC (Arg) to CTC (Leu). In five cell lines, a significant reduction of p21WAF1/Cip1 protein was evident. Cancer cell lines expressed higher level of Rb protein than normal human oral keratinocytes. DCC, a tumor suppressor gene, was not detected in KOSCC-25C. The KOSCC-33A cell line displayed microsatellite instability and showed a loss of hMSH2 expression. These well-characterized human OSCC cell lines should serve as useful tools for understanding the biological characteristics of oral cancer.     

Stimulation of mitochondrial activity by p43 overexpression induces human dermal fibroblast transformation

Mitochondrial dysfunctions are frequently reported in cancer cells, but their direct involvement in tumorigenesis remains unclear. To understand this relation, we stimulated mitochondrial activity by overexpression of the mitochondrial triiodothyronine receptor (p43) in human dermal fibroblasts. In all clones, this stimulation induced morphologic changes and cell fusion in myotube-like structures associated with the expression of several muscle-specific genes (Myf5, desmin, connectin, myosin, AchRalpha). In addition, these clones displayed all the in vivo and in vitro features of cell transformation. This phenotype was related to an increase in c-Jun and c-Fos expression and extinction of tumor suppressor gene expression (p53, p21WAF1, Rb3). Lastly, reactive oxygen species (ROS) production was increased in positive correlation to the stimulation of mitochondrial activity. The direct involvement of mitochondrial activity in this cell behavior was studied by adding chloramphenicol, an inhibitor of mitochondrial protein synthesis, to the culture medium. This inhibition resulted in partial restoration of the normal phenotype, with the loss of the ability to fuse, a strong decrease in muscle-specific gene expression, and potent inhibition of the transformed phenotype. However, expression of tumor suppressor genes was not restored. Similar results were obtained by using N-acetylcysteine, an inhibitor of ROS production. These data indicate that stimulation of mitochondrial activity in human dermal fibroblasts induces cell transformation through events involving ROS production.     

Silent mating‐type information regulation 2 homolog 1 overexpression is an important strategy for the survival of adapted suspension tumor cells

Characterization of circulating tumor cells (CTC) is important to prevent death caused by the metastatic spread of cancer cells because CTC are associated with distal metastasis and poor prognosis of breast cancer. We have previously developed suspension cells (SC) using breast cancer cell lines and demonstrated their high metastatic potential. As survival of CTC is highly variable from a few hours to decades, herein we cultured SC for an extended time and named them adapted suspension cells (ASC). Silent mating‐type information regulation 2 homolog 1 (SIRT1) expression increased in ASC, which protected the cells from apoptosis. High SIRT1 expression was responsible for the suppression of nuclear factor kappa B (NF‐κB) activity and downregulation of reactive oxygen species (ROS) in ASC. As the inhibition of NF‐κB and ROS production in SIRT1‐depleted ASC contributed to the development of resistance to apoptotic cell death, maintenance of a low ROS level and NF‐κB activity in ASC is a crucial function of SIRT1. Thus, SIRT1 overexpression may play an important role in growth adaptation of SC because SIRT1 expression is increased in long‐term rather than in short‐term cultures.     

非小细胞肺癌ROS1突变与EGFR突变及临床病理特征的关系

目的 探讨非小细胞肺癌（NSCLC）中ROS1融合突变与表皮生长因子受体（EGFR）突变及临床病理特征的关系。方法 采用实时荧光定量PCR（QPCR）检测2014年12月至2017年12月收治的3487例中国西北地区NSCLC患者ROS1基因的突变情况，同时采用ARMS法检测ROS1基因突变患者的EGFR基因突变情况，分析ROS1和EGFR共突变患者的临床病理特征。结果 3487例NSCLC患者中，ROS1基因突变54例（1.5％）。ROS1基因突变与年龄、性别、吸烟史、病理类型和临床分期有关（P＜0.05）。54例ROS1融合基因突变患者中有3例（5.6％）同时存在EGFR基因突变，其中19外显子缺失突变（19-del）2例，L858R突变1例。3例ROS1突变均为突变体2型（R2）。结论 中国西北地区NSCLC患者ROS1融合基因突变率为1.5％，与EGFR基因突变可以共存。     

Bcl-2 Overexpression Inhibits Generation of IntracellularReactive Oxygen Species and Blocks Adriamycin-inducedApoptosis in Bladder Cancer Cells

Resistance to induction of apoptosis is a major obstacle for bladder cancer treatment. Bcl-2 is thought to beinvolved in anti-apoptotic signaling. In this study, we investigated the effect of Bcl-2 overexpression on apoptoticresistance and intracellular reactive oxygen species (ROS) generation in bladder cancer cells. A stable Bcl-2overexpression cell line, BIU87-Bcl-2, was constructed from human bladder cancer cell line BIU87 by transfectingrecombinant Bcl-2 [pcDNA3.1(+)-Bcl-2]. The sensitivity of transfected cells to adriamycin (ADR) was assessed byMTT assay. Apoptosis was examined by flow cytometry and acridine orange fluorescence staining. IntracellularROS was determined using flow cytometry, and the activities of superoxide dismutase (SOD) and catalase (CAT)were also investigated by the xanthinoxidase and visible radiation methods using SOD and CAT detection kits.The susceptibility of BIU87-Bcl-2 cells to ADR treatment was significantly decreased as compared with controlBIU87 cells. Enhanced expression of Bcl-2 inhibited intracellular ROS generation following ADR treatment.Moreover, the suppression of SOD and CAT activity induced by ADR treatment was blocked in the BIU87-Bcl-2case but not in their parental cells. The overexpression of Bcl-2 renders human bladder cancer cells resistant toADR-induced apoptosis and ROS might act as an important secondary messenger in this process.     

Mitochondrial DNA somatic mutations are frequent in nasopharyngeal carcinoma

Nasopharyngeal carcinoma (NPC) is one of the most common cancers in southern China, and is highly sensitive to radiotherapy. The control region (D-loop) of mtDNA is a polymorphic region in which point mutations occur frequently. In this study, point mutation and common deletion (CD) mutations were investigated in 23 samples of NPC tumor tissue and in the radiation-treated NPC cell line CNE2. Polymorphisms at 72 (7.28%, 72/988) nucleotide positions in D-loop region and 6 (0.75%, 6/795) nucleotide positions in part of the functional gene encoding regions were detected in all NPC patients. Of the detected polymorphisms, 8 are novel. These variants are nonencoding transitions, including np292T-->C , np517G-del, np16038A-->G, np513G-del, np16242C-->A, np513G-del, np16242C-->A and np15787T-->C transition. A total of 39 point mutations in the D-loop region of mtDNA were detected in 43.5% (10/23) of the NPC patients. Three point mutations in the functional gene encoding regions of mtDNA were detected in only 8.7% (2/23) of NPC patients. The effect of he mutation at np709G-->A in the 12sRNA gene is unclear, and the A-->G substitution at np15769 in the cytochrome B gene is a synonymous mutation. The C-->T substitution at np15970 in the T Psi C loop of the tRNA(pro) gene could alter the position of the proline residue. After irradiation, the survival fraction of CNE2 cells decreased as X-ray dose increased. Moreover, X-ray radiation could induce apoptosis and the CD mutation in a time- and dose-dependent manner, but did not induce mtDNA point mutations. A positive correlation between the apoptosis index and the ratio of CD/WT mtDNA was observed in irradiated CNE2 cells. Our results suggest that CD mutation induced by irradiation is one of the late events after apoptosis of the cancer cells, and the mtDNA CD mutation may associated with the susceptibility of NPC cells to IR-induced apoptosis.     

Metastatic suppressor CD44 is related with oxidative stress in breast cancer cell lines

Evidence has accumulated on the role of reactive oxygen species (ROS) in metastasis since surgical removal of tumors generates oxidative stress promoting metastasis and cell growth. Metastasis consists of a cascade of events which allow the cell to survive in target tissues and influence several processes such as dissemination from tumor tissue, transport in blood/lymphatic vessels, invasion and homing of malignant cells. A cDNA oligoarray was used to determine whether alterations of metastatic genes are associated with oxidative stress in breast cancer cell lines. The cell lines used for the experiments were derived from a pre-existent in?vitro breast cancer progression model originated in our laboratory. The cDNA array showed alterations in functional gene groups related with cell-cell and cell-matrix interaction molecules, such as caveolin-1; metastasis suppressor genes, such as CD44; metastasis-associated proteases, such as cathepsin?D and the protease inhibitor, plasminogen activator inhibitor type?1. The changes of the selected genes were validated by differential display-RT-PCR as well as by protein expression assessed by Western blot analysis. It was found that the cell line, called Tumor2 with down-regulation of basal ROS and manganese superoxide dismutase (MnSOD) expression as a constitutive pattern of this cell line, presented alterations in genes that confer metastatic potential in comparison to the Alpha5 cell line, showing overexpression of basal MnSOD and high levels of ROS. Interesting, it was to found that CD44, considered a metastatic suppressor gene, was influenced by ROS, measured by hydrogen peroxide treatments, as seen by decreased CD44 protein expression in the Alpha5 cell line in a compensatory response to increased MnSOD protein expression. In conclusion, alterations of metastatic genes in malignant breast cancer cell lines were observed in relation to ROS and basal levels of antioxidant enzymes.     

Few point mutations in elongation factor-1γ gene in gastrointestinal carcinoma

Elongation factor-1 (EF-1) γ is overexpressed in a high proportion of gastrointestinal cancers. The mechanism of overexpression has not been determined. The purpose of this study was to examine cDNA specimens from pancreatic and colorectal cancer for mutation in this gene, which would allow us to determine whether gene mutations are responsible for overexpression of EF-1γ. In one colorectal carcinoma, we detected an A→G transition at amino-acid codon 158 (T→C in the sense strand) resulting in a change from a leucine to a serine. The base change was not detected in cDNA isolated from normal-appearing tissue from the same patient. We did not find mutations in another five colorectal carcinoma and five pancreatic cancer samples. Thus, although we detected a mutation in one tumor, the frequency of mutations was too low to account for the high frequency of overexpression of the EF-1γ RNA in colorectal cancer. We also investigated other possible mechanisms of overexpression of the EF-1γ RNA in this study. Slot-blot analysis of DNA isolated from colorectal cancers showed that the overexpression was not due to gene amplification. Using serum starvation to synchronize cultured cells, we showed that the overexpression was also not due to an increase in the number of cycling cells, as occurs in cancer. Using Southern blot analysis, we were unable to detect genome rearrangements that could have been responsible for the overexpression. In conclusion, the mechanism for overexpression of the EF-1γ gene in colorectal and pancreatic cancer remains unknown. However, mutations in the coding sequence of the gene, gene amplification, and gene rearrangement do not account for the high frequency of overexpression of this gene, and the overexpression is not due to an increase in the number of cycling cells. Mol. Carcinog. 22:9–15, 1998. © 1998 Wiley-Liss, Inc.     

Proline oxidase, encoded by p53-induced gene-6, catalyzes the generation of proline-dependent reactive oxygen species

The p53-dependent initiation of apoptosis is accompanied by the induction of proline oxidase (POX), a mitochondrial enzyme catalyzing the conversion of proline to pyrroline-5-carboxylate with the concomitant transfer of electrons to cytochrome c. However, the contribution of increased POX activity to apoptosis, if any, remains unknown. Using Adriamycin to initiate p53-dependent apoptosis, we showed that the expression of POX is up-regulated in a time- and dose-dependent manner in a human colon cancer cell line (LoVo). In cells expressing POX, the addition of proline increases reactive oxygen species (ROS) generation in a concentration-dependent manner; glutamate, a downstream product of proline oxidation, had no effect. Induction of POX was dependent on the p53 status of the cell. In the conditionally immortalized murine colonic epithelial cell line YAMC, where the p53 phenotype can be modulated by temperature, proline oxidase expression and ROS production could only be induced when the cells were phenotypically p53-positive. To confirm that the observed ROS production was not secondary to some other effect of p53, we also conditionally expressed POX in a p53-negative colon cancer line. Again, we found a proline-dependent ROS increase with POX expression. We hypothesize that proline oxidation supports the generation of ROS by donating reducing potential to an electron transport chain altered either by p53-dependent mechanisms or by overexpression of POX.     

中国新疆维吾尔族人群中肺癌驱动基因的表达

背景与目的：肺癌的发病率和肿瘤相关死亡率居当前世界各地恶性肿瘤的首位。肺癌亦存在多种驱动基因。各民族间的差异反映出肺癌的不同基因突变存在差异。该研究旨在探讨新疆维吾尔族患者中肺癌驱动基因的表达状况。方法：收集维吾尔族肺癌患者组织标本43例,采用扩增受阻突变系统(amplification refractory mutation system,ARMS)检测EGFR基因表达,采用实时荧光定量聚合酶链反应(real-time fluorescent quantitative polymerase chain reaction,RTFQ-PCR)检测K-ras、ALK、ROS1、BRAF及PIK3CA基因表达,分析肺癌驱动基因突变与新疆维吾尔族肺癌患者临床病理特征之间的相关性。结果：43例标本中,EGFR基因突变率为11.63%,其中腺癌及鳞癌EGFR基因突变检出率分别为26.67%和4.76%;大细胞癌、腺鳞癌及小细胞肺癌均未测出EGFR基因突变。肺腺癌患者EGFR基因突变率为26.67%,明显高于非腺癌者的3.57%,差异有统计学意义(P=0.024)。K-ras12/13杂合突变6例,突变检出率为16.28%(6/43);PIK3CA杂合突变2例,突变检出率为4.65%(2/43)。1例发生EGFR基因与K-ras基因同时突变。维吾尔族肺癌患者EGFR基因突变与年龄、性别、吸烟状况、TNM分期、ECOG评分均无关。43例标本中均未见ALK、ROS1融合基因及BRAF基因突变。结论：与亚洲人群相比,新疆维吾尔族肺癌患者EGFR突变率较低,K-ras突变率高,类似于欧美高加索人群的突变特点。     

Overexpression of tuberous sclerosis complex 2 exerts antitumor effect on oral cancer cell lines

Tuberous sclerosis is caused by mutations in tuberous sclerosis complex (TSC) 2 on chromosome 16p13.3, encoding tuberin which is thought to be essential for p27^Kip1 to regulate the cell cycle. In this study, we conducted to examine whether overexpression of TSC2 can affect the growth of oral cancer cells which have different expression level of p27^Kip1 protein. We constructed an expression vector containing sense-oriented rat TSC2 cDNA with pcDNA3.1. We transfected oral cancer cells, B88t (high expression of p27^Kip1 protein) and HI (low expression of p27^Kip1 protein) with the sense expression vector to up-regulate the expression of TSC2 gene. Overexpression of TSC2 exerted the growth inhibitory effect of B88t and HI in vitro and in vivo. These findings suggest that overexpression of TSC2 may exert the antitumor effect on oral cancer cells whether they have high expression of p27^Kip1 protein or not.     

p53 alterations in all stages of breast cancer.

Overexpression of the nuclear phosphoprotein p53 is one of the most frequently detected abnormalities in human cancer and appears to be associated with mutation of the p53 gene. In this study of breast cancer, p53 overexpression was detected in two (15%) of 15 pure intraductal tumors, 73 (25%) of 291 primary invasive carcinomas, 13 (50%) of 26 lymph nodes containing metastatic breast cancer, and two of four established breast cancer cell lines. Sequence analysis of selected specimens confirmed that p53 overexpression was associated with mutation of the gene, while no mutations were detected in specimens without p53 overexpression. Thus, overexpression of p53 occurs in all stages of breast cancer and is consistently associated with the production of mutant proteins. Immunohistochemical analysis is a simple method which reliably predicts the presence of most p53 gene mutations in breast cancer specimens.     

Detection of p53 mutations in precancerous gastric tissue

Intestinal-type gastric cancer is preceded by gastritis and intestinal metaplasia. There is uncertainty regarding the stage at which genetic alterations in the p53 gene occur. Reactive oxygen species (ROS) may participate in the production of mutations and the inactivation of p53 is due to infection by the bacterium Helicobacter pylori. We have investigated whether alterations of the p53 gene can be detected in gastritis and intestinal metaplasia using the restriction site mutation assay. We also assessed the potential contribution of ROS to p53 inactivation using electron spin resonance spectroscopy (ESR) and correlated with the presence of H. pylori. In all, 35% of the gastritis samples and 45% of the intestinal metaplasia samples were found to contain mutations in exons 5-8 of the p53 gene. Electron spin resonance spectroscopy analysis showed a significant increase in free radical levels in gastritis samples compared with normal, intestinal metaplasia and cancer samples, suggesting that free radicals present in gastritis may contribute to p53 mutations. There was no significant difference in free radical levels between the H. pylori-positive and -negative groups. However, a small subpopulation of the H. pylori-negative patients had much higher levels of free radicals. This suggests a more prominent role for other factors in ROS production.     

Antioxidants potentiate American ginseng-induced killing of colorectal cancer cells

Colorectal cancer is the third leading cause of cancer-related deaths in the United States. Novel prevention or therapeutic agents are needed to better manage this disease. American ginseng is a commonly used herb and is believed to have lots of health benefits, including anti-cancer activities. However there have been very few in-depth studies of the activities of this herb at the molecular level. In this report we showed that 4 h-steamed American ginseng root extract (S4h) induced mitochondrial damage, increased reactive oxygen species (ROS), and apoptosis in colorectal cancer cells. We showed that the NF-κB pathway was activated by S4h and that removal of ROS inhibited S4h-induced NF-κB activation. We further showed that both antioxidants and a specific inhibitor of the NF-κB pathway enhanced S4h-induced cell death. Finally, we showed that protecting the mitochondria decreased both the level of ROS and apoptosis. Taken together, these results indicate that S4h-induced apoptosis in colorectal cancer cells is mediated by mitochondria damage and that damage to the mitochondria activates both the apoptosis pathway and the ROS/NF-κB mediated survival pathway. These results further suggest that the anti-cancer effect of steamed ginseng can be enhanced by antioxidants or inhibitors of the NF-κB pathway.