MutT Homolog 1 Expression Research Articles

Prognostic impact of MutT homolog-1 expression on esophageal squamous cell carcinoma.

MutT homolog‐1 (MTH1) is a pyrophosphatase that acts on oxidized nucleotides and hydrolyzes 8‐oxo‐2’‐deoxyguanosine triphosphate in deoxynucleoside triphosphate pool to prevent its incorporation into nuclear and mitochondrial DNA, result in reduce cytotoxicity in tumor cells. MTH1 is overexpressed in various cancers and is considered as a therapeutic target. Environmental factors such as cigarette smoking and alcohol consumption are critical risk factors for the development and progression of esophageal squamous cell carcinoma (ESCC), suggesting that oxidative stress contributes to the pathogenesis of ESCC. We examined the expression of MTH1 and the accumulation of 8‐oxo‐2’‐deoxyguanosine (8‐oxo‐dG) in 84 patients with ESCC who underwent curative resection without neoadjuvant therapy. MTH1 mRNA level was quantified by performing quantitative reverse transcription‐PCR. Immunohistochemical analysis of paraffin‐embedded cancer tissues was performed to determine MTH1 protein expression and 8‐oxo‐dG accumulation. MTH1 mRNA expression was higher in cancerous tissues than in the corresponding normal epithelium (P < 0.0001). Immunohistochemical analysis showed that high MTH1 expression was significantly associated with deeper tumor invasion and venous invasion, advanced cancer stage, and poor overall survival (P = 0.0021) and disease‐specific survival (P = 0.0013) compared with low MTH1 expression. Furthermore, high MTH1 expression was an independent predictor of poor disease‐specific survival (P = 0.0121). In contrast, 8‐oxo‐dG accumulation was not associated with any clinicopathological factor and poor prognosis. These results suggest that MTH1 overexpression is a predictor of ESCC progression and poor prognosis and that MTH1 can serve as a therapeutic target for treating patients with ESCC.

P08.67 Inhibition of MutT homolog 1 (MTH1) in glioblastoma multiforme results in impaired cell migration and tumor growth

AbstractIntroduction:MutT homolog1 (MTH1) is required for survival of cancer cells. These have irregular redox formation resulting in the production of reactive oxygen species which damage the deoxynucleoside triphosphate pool and subsequent the DNA. MTH1 plays a crucial role by inhibiting the incorporation of oxidized bases into the DNA that avoid apoptosis of cancer cells. Our aim was to analyze the pathophysiological role of MTH1 in glioma.Materials and methods:MTH1 expression was analyzed in human glioma specimens by quantitative RT-PCR, immunohistochemistry and Western Blot. U87 cell migration in vitro and tumor growth in an orthotopic rat model was monitored after knock-down of MTH1 by siRNA or inhibition by crizotinib. In addition, progression free survival of patients was correlated to the MTH1 level.Results:Higher expression of MTH1 was observed in glioblastoma than in lower grade astrocytomas (p<0.05) and peritumoral tissue, both, on the gene and protein level. MTH1 siRNA transfected U87 cells showed slower migration compared to control U87 cells (p<0.01). Furthermore, treatment with crizotinib, an inhibitor of MTH1, also lowered cell migration. In rats, tumor growth was significantly impaired in MTH1 siRNA U87 grafts (p<0.01).Discussion:These results show that MTH1 might play an essential role in both, malignization of glioma and disease progression in recurrent glioblastoma. Moreover, the MTH1 level in patients seems to influence tumor growth and could be targeted by crizotinib indicating a role for potential future therapies.

Protective effect of Yiguanjian decoction against DNA damage on concanavalin A-induced liver injury mice model

ObjectiveTo investigate the inhibitory effect of Yiguanjian decoction (YD) on DNA damage in Concanavalin A (Con A)-induced liver injury mice model and to explain the possible mechanism. MethodsTotally 120 male BALB/c mice were randomly divided into 6 groups, 20 mice each: normal group, model group, Bifendate group, YD low dose group, YD middle dose group and YD high dose group. Except normal group, liver injury model induced by Con A was established. While modeling, each mouse in YD group was given YD (0.4 mL/20 g per day) by intragastric administration (0.13 g YD for YD low dose group; 0.26 g for YD middle dose group; 0.52 g for YD high dose group). Bifendate group was given Bifendate (0.2 g·kg−1·d−1) by gavage. Normal group and model group were fed with same volume of physiological saline daily. After 8 weeks, the serum alanine transaminase (ALT) and aspartate transaminase (AST) were tested. The hematoxylin-eosin staining was used to evaluate the grade of liver inflammation and liver fibrosis stage. Hepatocellular DNA damage was detected by single cell gel electrophoresis technology. The protein expression of tumor necrosis factor-α (TNF-α), Bax and MutT Homolog 1 (MTH1) was detected by western blotting and enzyme linked immunosorbent assay. Bax mRNA and MTH1 mRNA were detected by Real-time Polymerase Chain Reaction (PCR). ResultsYD can improve the degree of liver inflammation and fibrosis in the liver of chronic hepatitis mice, the dose effect relationship is remarkable (P < 0.05). YD can reduce liver cell DNA damage. The difference between YD middle dose group and model group was statistically significant (P < 0.05). YD middle dose group had decreased the protein expression of TNF-α in the mice liver of immunological liver injury (P < 0.05). YD can increase the protein expression of Bax (P < 0.05). Compared with normal group, the protein expression of MTH1 was decreased (P < 0.05), but there was no statistical significance between YD group and model group (P > 0.05). YD can increase the mRNA expression of Bax and MTH1 (both P < 0.05). ConclusionYD can effectively inhibit the DNA damage in immunological liver injury mice, the mechanism may be that it can decrease the TNF-α and increase the Bax and MTH1 expression.

Abstract 1259: MutT homolog 1 (MTH1) is upregulated in glioblastoma multiforme: its inhibition by siRNA or crizotinib results in impaired cell migration and tumor growth in vivo

Abstract Introduction: MutT homolog1 (MTH1) is required for the survival of cancer cells. These are characterized by irregular redox formation resulting in the production of reactive oxygen species which damage the deoxynucleoside triphosphate pool and subsequently the DNA. MTH1 inhibits the incorporation of oxidized bases into the DNA thus avoiding apoptosis of cancer cells. Our aim was to analyze the pathophysiological role of MTH1 in glioma. Materials and Methods: MTH1 expression was analyzed using quantitative PCR and Western Blot analysis in human glioma tissue (n = 80). We compared peritumoral tissue with grade II, III, and IV gliomas. Moreover, we compared primary to secondary GBM and initial tumors with recurrent tumors after temozolomide treatment. U87 cell migration was tested after siRNA knock-down of MTH1 and treatment with the MTH1 inhibitor crizotinib by scratch assays. After orthotopic implantation of MTH1-siRNA treated U87 into rats, tumor size was measured after 8 days. Results: In RT-PCR and Western blot we found a significantly higher expression of MTH1 in primary and secondary glioblastoma than in lower grade brain tumor. Immunofluorescence staining of histological sections of glioblastoma showed also a higher level of MTH1 than in lower grade tumors. By nucleofection, we transfected siRNA MTH1 into the U-87 glioblastoma cells and a slower migration was investigated applying migration assay. Furthermore, treatment with the drug crizotinib inhibited MTH1 and decreased U-87 cell migration. The xenograft study showed a slower tumor growth when U87 cells were transfected with MTH1 siRNA compared to normal U87. Conclusion: These results show that MTH1 plays an essential role in migration and proliferation of glioma cells resulting in clinically observed malignization of glioma and disease progression in recurrent glioblastoma. Moreover, MTH1 can be targeted by Crizotinib indicating a role for potential future therapies. Citation Format: Marco Timmer, Sara Gerdi Kannampuzha, Gabriele Röhn, Roland Goldbrunner. MutT homolog 1 (MTH1) is upregulated in glioblastoma multiforme: its inhibition by siRNA or crizotinib results in impaired cell migration and tumor growth in vivo. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1259.

CBIO-41MutT HOMOLOG1 EXPRESSION IS UP-REGULATED IN MALIGNANT GLIOMA

INTRODUCTION: MutT homolog1 (MTH1) is required for the survival of cancer cells. Generally, cancer cells have irregular redox formation that result in production of reactive oxygen species, which damage the deoxynucleoside triphosphate pool and subsequent the DNA. MTH1 plays a crucial role by inhibiting the incorporation of oxidized bases into the DNA that avoid apoptosis of the cancer cells. Our aim was to analyze the pathophysiological role of MTH1 in glioma. METHODS: We analyzed the expression of MTH1 in surgical specimens of brain tumors of different WHO grades. Moreover, we compared primary and secondary glioblastomas, as well as tumors before and after chemotherapy. Western Blot, quantitative PCR, immunohisto- and immunocytochemistry were applied. RESULTS: Our work showed a significant higher level of MTH1 in brain tumor with higher WHO grade. Furthermore, patients treated with chemotherapy showed significantly lesser expression of MTH1. CONCLUSION: These results indicate that MTH1 might play an essential role in both, the malignization of glioma and disease progression in recurrent GBM. Inhibitors of MTH1 may develop towards targeted therapies in GBM.

MTH1 expression is required for effective transformation by oncogenic HRAS.

Due to sustaining elevated reactive oxygen species (ROS), oncogenic RAS-transformed cells upregulate redox-protective genes, among them the mammalian 8-oxodGTPase, MutT Homolog 1 (MTH1). We previously showed MTH1 abrogates RAS oncogene-induced senescence (OIS) in normal cells and that its inhibition compromises the tumorigenicity of established oncogenic RAS-harboring cancer cells. Here, we investigated how pre-transformation MTH1 levels in immortalized cells influence HRASV12-induced oncogenic transformation. We find MTH1 suppression prior to HRASV12 transduction into BEAS2B immortalized epithelial cells compromised maintenance of high RASV12- and oncogenic ROS-expressing cell populations. Furthermore, pre-transformation MTH1 levels modulated the efficiency of HRASV12-mediated soft agar colony formation. Downstream transformation-associated traits such as the epithelial-mesenchymal transition (EMT) were also compromised by MTH1 inhibition. These collective effects were observed to a greater degree in cells harboring high vs. low RASV12 levels, suggesting MTH1 is required for tumor cells to accumulate RAS oncoprotein. This is significant as, a priori, one cannot ascertain whether tumor-promoting adaptations wrought by introducing oncogenic RAS into an immortalized cell are capable of overcoming pre-transformation deficiencies. Our results suggest nucleotide pool sanitization comprises an important transformation-promoting requirement that, if compromised, cannot be adequately compensated post-transformation and thus is likely to affect optimal development and progression of RAS-driven tumors.

Abstract B14: Human Mut T homolog 1 (MTH1) as a novel facilitator of KRAS-driven lung cancer

Abstract Non-small cell lung carcinoma (NSCLC), a chemoresistant form of lung cancer, is characterized by oncogenic KRAS mutations that confer multiple tumor-promoting traits. Several of these traits are mediated by oncogene-induced reactive oxygen species (ROS). However, oncogenic ROS also produce DNA damage, a major effector of tumor suppressor mechanisms. We previously reported overexpression of the mammalian 8-oxo-dGTP triphosphatase, human MutT Homolog 1 (MTH1), inhibits RAS oncogene-induced senescence (OIS) and any associated DNA damage without substantially affecting ROS levels. Here we report that MTH1 expression is elevated in NSCLC tumors relative to adjacent normal tissue, particularly in tumors with high KRAS expression. We show that MTH1 overexpression facilitates transformation of lung epithelial cells by oncogenic KRAS. We further report that MTH1 suppression in NSCLC cell lines reduces proliferation and tumorigenicity either via DNA strand break-induced elevation of the p53/p21 pathway or by inhibition of Akt activation in p53-nonfunctional tumor cells. Collectively our results indicate MTH1 as a novel potential chemotherapeutic target in NSCLC with activating KRAS mutations. Citation Format: Asmita Patel, Katherine Halvorsen, Wayne Balkan, Alexander Cohen, Teresita Reiner, David Robbins, Dao Nguyen, Priyamvada Rai. Human Mut T homolog 1 (MTH1) as a novel facilitator of KRAS-driven lung cancer. [abstract]. In: Proceedings of the AACR Special Conference on RAS Oncogenes: From Biology to Therapy; Feb 24-27, 2014; Lake Buena Vista, FL. Philadelphia (PA): AACR; Mol Cancer Res 2014;12(12 Suppl):Abstract nr B14. doi: 10.1158/1557-3125.RASONC14-B14

MutT Homolog 1 (MTH1) maintains multiple KRAS-driven pro-malignant pathways.

Oncogenic RAS promotes production of reactive oxygen species (ROS), which mediate pro-malignant signaling but can also trigger DNA damage-induced tumor suppression. Thus RAS-driven tumor cells require redox-protective mechanisms to mitigate the damaging aspects of ROS. Here we show that MutT Homolog 1 (MTH1), the mammalian 8-oxodGTPase that sanitizes oxidative damage in the nucleotide pool, is important for maintaining several KRAS-driven pro-malignant traits in a nonsmall cell lung carcinoma (NSCLC) model. MTH1 suppression in KRAS-mutant NSCLC cells impairs proliferation and xenograft tumor formation. Furthermore, MTH1 levels modulate KRAS-induced transformation of immortalized lung epithelial cells. MTH1 expression is upregulated by oncogenic KRAS and correlates positively with high KRAS levels in NSCLC human tumors. At a molecular level, in p53-competent KRAS-mutant cells, MTH1 loss provokes DNA damage and induction of oncogene-induced senescence (OIS). In p53-nonfunctional KRAS-mutant cells, MTH1 suppression does not produce DNA damage but induces a reduced proliferative rate and an adaptive decrease in KRAS expression levels. Thus, MTH1 not only enables evasion of oxidative DNA damage and its consequences but can also function as a molecular rheostat for maintaining oncogene expression at optimal levels. Accordingly, our results indicate MTH1 is a novel and critical component of oncogenic KRAS-associated malignancy and its inhibition is likely to yield significant tumor-suppressive outcomes in KRAS-driven tumors.

Enhanced elimination of oxidized guanine nucleotides inhibits oncogenic RAS-induced DNA damage and premature senescence

Approximately 20% of tumors contain activating mutations in the RAS family of oncogenes. As tumors progress to higher grades of malignancy, the expression of oncogenic RAS has been reported to increase, leading to an oncogene-induced senescence (OIS) response. Evasion of this senescence barrier is a hallmark of advanced tumors indicating that OIS serves a critical tumor-suppressive function. Induction of OIS has been attributed to either RAS-mediated production of reactive oxygen species (ROS) or to induction of a DNA damage response (DDR). However, functional links between these two processes in triggering the senescent phenotype have not been explicitly described. Our previous work has shown that, in cultured untransformed cells, preventing elimination of oxidized guanine deoxyribonucleotides, which was achieved by suppressing expression of the cellular 8-oxo-dGTPase, human MutT homolog 1 (MTH1), sufficed to induce a DDR as well as premature senescence. Here, we demonstrate that overexpression of MTH1 can prevent the oncogenic H-RAS-induced DDR and attendant premature senescence, although it does not affect the observed elevation in ROS levels produced by RAS oncoprotein expression. Conversely, we find that loss of MTH1 preferentially induces an in vitro proliferation defect in tumorigenic cells overexpressing oncogenic RAS. These results indicate that the guanine nucleotide pool is a critical target for intracellular ROS produced by oncogenic RAS and that RAS-transformed cells require robust MTH1 expression to proliferate.