The upregulation of metallothionein-1 expression in areca quid chewing-associated oral squamous cell carcinomas

Revisiting the metallothionein genes polymorphisms and the risk of oral squamous cell carcinoma in a Brazilian population

Background

Metallothioneins (MTs) gene polymorphisms have been associated with the ability of free radical scavenging and detoxification of heavy metals leading to cancer development. Our aim was to revisit, in a Brazilian population, single-nucleotide polymorphisms (SNPs) of the MT gene family previously associated with oral squamous cell carcinoma (OSCC).

Material and Methods

A case-control investigation with 28 OSCC patients and 45 controls was conducted, using conventional risk factors (tobacco use and alcohol consumption) as covariates. SNPs genotyping for rs8052334 (MT1B), rs964372 (MT1B), and rs1610216 (MT2A) was performed by PCR-RFLP, and SNPs for rs11076161 (MT1A) were analyzed by TaqMan assay.

Results

The only SNP associated with increased risk for OSCC was the MT-1A AA genotype (OR = 4.7; p = 0.01). We have also evidenced for the first time a significant linkage disequilibrium between the SNPs of MT-2A and MT-1A in this population with the highest frequency (30%) of the unfavorable haplotype G/A/C/T (rs1610216 / rs11076161 / rs964372 / rs8052334) of MT gene polymorphisms (OR = 6.2; p = 0.04). Interestingly, after removing the effects of conventional risk factors, we have uncovered the significance of the AA genotype of the rs11076161 with increased odds of 19-fold higher towards OSCC development.

Conclusions

This is the first demonstration that a significant linkage disequilibrium among gene polymorphisms of the MT family may affect susceptibility to oral cancer, which is conditioned by the G/A/C/T haplotype (rs1610216/rs11076161/rs964372/ rs8052334) and the MT-1A gene polymorphism has a potential clinical utility for the OSCC risk assessment.

Key words:Oral squamous cell carcinoma, polymorphism, metallothionein, oral cancer.

A Review on Role of Arecoline and Its Metabolites in the Molecular Pathogenesis of Oral Lesions with an Insight into Current Status of Its Metabolomics

Areca nut consumption is a popular habit in Southeast Asian countries. One of the important biologically active alkaloids of areca nut is arecoline, which plays a role in mediating the development of several pathologies of the primary exposure site, the oral cavity. Studies on the metabolism of arecoline revealed the formation of several metabolites which themselves might be toxic. Moreover, polymorphisms in genes encoding enzymes involved in the metabolism of arecoline might predispose an organism towards the development of oral cancer. The present review tries to accumulate all the relevant existing literature and then elucidate the molecular mechanism by which arecoline plays a role in the development of oral submucous fibrosis and oral cancer. Existing information regarding arecoline metabolism, enzymes involved in the metabolic process and biological effects of the metabolites of arecoline have also been compiled and compared to study the toxicity of metabolites with its parent compound arecoline and whether they play any role in the pathogenesis of oral cancer mediated by areca nut consumption. A repertoire of molecular targets has come up in the discussion whose expression profile is perturbed by arecoline. Construction of induction cascade from existing literature has given an idea about the process of molecular pathogenesis. The summarized and analysed data can help to determine the molecular mechanism and drug targets, which in turn could be helpful in the prevention or treatment of these pathological conditions. It also brings into light areas where further research needs to be directed.

Benzo[a]pyrene promotes progression in tongue squamous cell carcinoma

OBJECTIVES

Benzo[a]pyrene (B[a]P) is a member of the polycyclic aromatic hydrocarbon (PAH) family. Although the potent carcinogenicity of high-dose B[a]P has been extensively reported, the effects of long-term exposure to B[a]P on the progression of tongue squamous cell carcinoma (TSCC) are poorly understood.

METHODS

In the present study, TSCC cells were treated with 5 or 50 nM of B[a]P for three months. The proliferation and chemoresistance of B[a]P-treated cells to 5-fluorouracil or cisplatin were detected by CCK8. The motility of the B[a]P-treated cells was evaluated with wound healing analysis, invasion assay, and three-dimensional culture in decellularized mouse tongue matrix. Xenograft assay was used to investigate the aggressiveness of B[a]P-treated cells. Immunofluorescence staining, terminal restriction fragment assay, and whole-genome sequence were used to determine the mutation spectrums.

RESULTS

Long-term 50 nM B[a]P-treated cells exhibited increased aggressiveness and chemoresistance to 5-fluorouracil or cisplatin. In addition, data from whole-genome sequencing demonstrated that C:T to A:T transitions were the predominant nucleotide substitutions occurred in 50 nM B[a]P-treated CAL27 cells. Furthermore, 102 non-synonymous or stop-gain mutations were enriched in the extracellular-matrix-receptor interactive pathway.

CONCLUSIONS

B[a]P exposure may contribute to genomic instability, and therefore, B[a]P may promote the progression of TSCC.

Metallothioneins may be a potential prognostic biomarker for tumors: A Prisma-compliant meta-analysis

BACKGROUND

Metallothioneins (MTs) were reported to be associated with many kinds of tumors' prognosis, although MTs expression varied greatly among tumors. To assess the prognostic value of Metallothioneins (MTs) in different kinds of tumors, comprehensive literature search was conducted to perform a meta-analysis.

METHODS

Eligible studies were identified by PubMed, MEDLINE, Web of Science (WOS), the Cochrane Library of Systematic Reviews, EMBASE, China National Knowledge Infrastructure (CNKI), WANFANG database and SinoMed database up to December 2017, which was designed to assess the prognostic value of MTs in different kinds of tumors. The main endpoint events were overall survival (OS) and disease-free survival (DFS). Hazard ratios (HRs) and its variance were retrieved from the original studies directly or calculated using Engauge Digitizer version 4.1. Random or fixed effects model meta-analysis was employed depending on the heterogeneity. Publication bias was evaluated by funnel plots, Begg and Egger tests.

RESULTS

A total of 22 studies were enrolled in this meta-analysis, including 2843 tumor tissues (1517 were MTs negative/low, and 1326 were MTs high). Results showed that there was significant association between MTs expression and tumors' OS (HR = 1.60; 95%CI 1.34∼1.92, P < .00001). Subgroup analysis showed that high level of MTs expression was associated with prolonged OS in liver cancer (HR = 0.65, 95%CI 0.48∼0.89, P = .007), but it was on the contrary in the tumor of ovary (HR = 1.47, 95%CI 1.01∼2.14, P = .04), bladder (HR = 1.71, 95%CI 1.21∼2.42, P = .002), intestine (HR = 3.13, 95%CI 1.97∼4.97, P < .00001), kidney (HR = 3.31, 95%CI 1.61∼6.79, P = .001). However, there was no significant association between MTs expression and OS in breast (HR = 1.02, 95%CI 0.69∼1.51, P = .93).

CONCLUSIONS

MTs could be taken as a potential prognostic biomarker for tumors, and uniqueness of MTs prognostic value in liver cancer deserved further study.

Nuclear metallothionein in oral squamous cell carcinoma: clinicopathological parameters and patient survival

The aim of this study was to identify the immunoexpression of methallothionein in oral squamous cell carcinoma as well as to address the correlation with clinical features, histological grade and patient survival. Samples were collected from 93 patients with tongue squamous cell carcinoma who presented for follow-up. Immunohistochemical expression of methallothionein in all groups was performed. The scoring system has previously been published by Tsurutani in 2005, which is based on intensity and distribution of staining. We used Kappa index to evaluate the degree of observers' agreement under metallothionein immunostaining and histological grade. Associations between methallothionein expression and clinical parameters (age, gender, smoking, tumor size, lymph node metastasis and disease stage) were examined for statistical significance using the chi-squared test. The overall survival rates were estimated by the Kaplan-Meier method and the relationship between protein expression and survival was compared using the log-rank test (p < 0.05). Our results showed no statistically significant association between methallothionein immunostaining and the selected clinicopathological variables. Immunohistochemistry results showed positive nuclear immunostaining for metallothionein in 62,37% (58/93) and negative for metallothionein 37,63% (35/93). The degree of examiners agreement by Kappa varied from substantial to perfect and both metallothionein immunostaining and histological grade were explored. The present study suggests that positive methallothionein expression found in tongue squamous cell carcinoma may not help to predict survival in the analyzed samples, as well as no relation between the protein and histological grade and clinical features was observed. In conclusion, the present study suggests that metallothionein is not associated with tongue squamous cell carcinoma clinicopathological characteristics and aggressiveness.

Study of trace metal imbalances in the blood, scalp hair and nails of oral cancer patients from Pakistan

Oral cancer is an important cause of cancer morbidity and mortality globally and exposure to trace metals alongside tobacco, alcohol and HPV are the important etiological factors in its development. Selected essential and toxic trace metals (Cd, Cr, Cu, Fe, Mn, Ni, Pb and Zn) were measured in the blood, scalp hair and nails of oral cancer patients and counterpart controls by atomic absorption spectrometry. Mean concentrations of Cd, Ni and Pb were found to be significantly higher (p<0.05) and those of Cu, Fe and Zn were considerably lower in the blood, scalp hair and nails of the patients than the controls. Most of the metal concentrations exhibited higher dispersion and asymmetry in the blood, scalp hair and nails of the patients compared with the controls. The correlation study revealed significantly diverse relationships among the metals in blood, scalp hair and nails of both donor groups. Variations in the metal levels were also noted for various stages (I, II, III & IV) as well as the types (adenocarcinoma and squamous cell carcinoma) of oral cancer. Multivariate cluster analysis of the metal levels in the patients were also significantly dissimilar than the controls. The study evidenced considerably divergent variations in the metal levels in oral cancer patients in comparison with the controls.

Immunoexpression of Metallothionein in Oral Squamous Cell Carcinoma

BACKGROUND AND OBJECTIVES

Metallothionein (MT) is a family of ubiquitous low molecular weight (7 kDa), intracellular (cytoplasmic/nuclear), cysteine rich proteins with high affinity for heavy metals, present in both normal cells and neoplastic cells. Increased expression of MT has been reported to be associated with poor prognosis in various tumours. The objectives of the present study were to compare the expression of MT in normal subjects and in patients with oral squamous cell carcinoma (OSCC), to correlate the expression of MT with respect to clinical staging of OSCC and to evaluate the expression of MT with respect to different histopathological grades of OSCC.

METHODS

Thirty cases of OSCC were staged clinically and graded histopathologically. Immunohistochemical method was used to detect the expression of MT in OSCC. The scores obtained were documented and compared statistically.

RESULTS

MT immunoreactivity was noticed in all cases of OSCC. A statistically significant difference was observed in immunoreactivity of MT between the normal and OSCC, and in different histopathological grades of OSCC (p = 0.00001*). However, no statistical significance was found in a number of immunopositive cells in different clinical stages of OSCC (p = 0.7573).

CONCLUSION

The MT immunoexpression increased from low grade to high grade OSCC. Hence, increased expression of MT may be related to poor prognosis in patients with OSCC.

Metallothionein gene expression is altered in oral cancer and may predict metastasis and patient outcomes

AIMS

Metallothioneins (MTs) are proteins associated with the carcinogenesis and prognosis of various tumours. Previous studies have shown their potential as biomarkers in oral squamous cell carcinoma (OSCC). Aiming to understand more clearly the function of MTs in OSCC we evaluated, for the first time, the gene expression profile of MTs in this neoplasm.

MATERIALS AND RESULTS

Tissue samples from 35 cases of tongue and/or floor of mouth OSCC, paired with their corresponding non-neoplastic oral mucosa (NNOM), were retrieved (2007-09). All tissues were analysed for the following genes using TaqMan(®) reverse transcription-quantitative polymerase chain reaction (RT-qPCR) assays: MT1A, MT1B, MT1E, MT1F, MT1G, MT1H, MT1X, MT2A, MT3 and MT4. The expression of MT1B and MT1H was seldom detected in both OSCC and NNOM. A significant loss of MT1A, MT1X, MT3 and MT4 expression and gain of MT1F expression was observed in OSCC, compared to NNOM. Cases with MT1G down-regulation exhibited the worst prognoses. The up-regulation of MT1X was restricted to non-metastatic cases, whereas up-regulation of MT3 was related to cases with lymph node metastasis.

CONCLUSIONS

Metallothionein mRNA expression is altered significantly in oral squamous cell carcinomas. The expression of MT1G, MT1X and MT3 may aid in the prognostic discrimination of OSCC cases.

Arecoline-induced myofibroblast transdifferentiation from human buccal mucosal fibroblasts is mediated by ZEB1

Oral submucous fibrosis (OSF) is considered as a pre-cancerous condition of the oral mucosa and is highly associated with habitual areca quid chewing. Arecoline is the major alkaloid in areca quid and is thought to be involved in the pathogenesis of OSF. Our previous studies have demonstrated that arecoline could induce epithelial–mesenchymal transition (EMT)-related factors in primary human buccal mucosal fibroblasts (BMFs). Therefore, we investigated the expression of zinc finger E-box binding homeobox 1 (ZEB1), which is a well-known transcriptional factor in EMT, in OSF tissues and its role in arecoline-induced myofibroblast transdifferentiation from BMFs. The expression of ZEB1, as well as the myofibroblast marker α-smooth muscle actin (α-SMA), was significantly increased in OSF tissues, respectively. With immunofluorescence analysis, arecoline induced the formation of α-SMA-positive stress fibres in BMFs expressing nuclear ZEB1. Arecoline also induced collagen contraction of BMFs in vitro. By chromatin immunoprecipitation, the binding of ZEB1 to the α-SMA promoter in BMFs was increased by arecoline. The promoter activity of α-SMA in BMFs was also induced by arecoline, while knockdown of ZEB1 abolished arecoline-induced α-SMA promoter activity and collagen contraction of BMFs. Long-term exposure of BMFs to arecoline induced the expression of fibrogenic genes and ZEB1. Silencing of ZEB1 in fibrotic BMFs from an OSF patient also suppressed the expression of α-SMA and myofibroblast activity. Inhibition of insulin-like growth factor receptor-1 could suppress arecoline-induced ZEB1 activation in BMFs. Our data suggest that ZEB1 may participate in the pathogenesis of areca quid–associated OSF by activating the α-SMA promoter and inducing myofibroblast transdifferentiation from BMFs.

Metallothionein - immunohistochemical cancer biomarker: a meta-analysis

Metallothionein (MT) has been extensively investigated as a molecular marker of various types of cancer. In spite of the fact that numerous reviews have been published in this field, no meta-analytical approach has been performed. Therefore, results of to-date immunohistochemistry-based studies were summarized using meta-analysis in this review. Web of science, PubMed, Embase and CENTRAL databases were searched (up to April 30, 2013) and the eligibility of individual studies and heterogeneity among the studies was assessed. Random and fixed effects model meta-analysis was employed depending on the heterogeneity, and publication bias was evaluated using funnel plots and Egger's tests. A total of 77 studies were included with 8,015 tissue samples (4,631 cases and 3,384 controls). A significantly positive association between MT staining and tumors (vs. healthy tissues) was observed in head and neck (odds ratio, OR 9.95; 95% CI 5.82-17.03) and ovarian tumors (OR 7.83; 1.09-56.29), and a negative association was ascertained in liver tumors (OR 0.10; 0.03-0.30). No significant associations were identified in breast, colorectal, prostate, thyroid, stomach, bladder, kidney, gallbladder, and uterine cancers and in melanoma. While no associations were identified between MT and tumor staging, a positive association was identified with the tumor grade (OR 1.58; 1.08-2.30). In particular, strong associations were observed in breast, ovarian, uterine and prostate cancers. Borderline significant association of metastatic status and MT staining were determined (OR 1.59; 1.03-2.46), particularly in esophageal cancer. Additionally, a significant association between the patient prognosis and MT staining was also demonstrated (hazard ratio 2.04; 1.47-2.81). However, a high degree of inconsistence was observed in several tumor types, including colorectal, kidney and prostate cancer. Despite the ambiguity in some tumor types, conclusive results are provided in the tumors of head and neck, ovary and liver and in relation to the tumor grade and patient survival.

A high IL-4 production diplotype is associated with an increased risk but better prognosis of oral and pharyngeal carcinomas

OBJECTIVE

Interleukin (IL)-4 is a key cytokine in humoral and adaptive immunity. This study aimed to evaluate the association of IL-4 genetic variants (-590C>T and VNTR in intron 3) with the risk and prognosis of oral and pharyngeal squamous cell carcinoma (OPSCC).

DESIGN

A total of 1215 subjects, which included 623 healthy controls and 592 OPSCC cases (463 oral squamous cell carcinoma (OSCC) and 129 pharyngeal squamous cell carcinoma (PSCC) cases), were recruited. The genotypes were determined by TaqMan real-time assay and PCR-based assay.

RESULTS

The IL-4 genotypes at locus -590C>T and intron 3 VNTR were not correlated with increased risk of OSCC, PSCC, and OPSCC, with the exception of early-stage OPSCC (at -590C>T: T/T vs. C/C+C/T, adjusted odds ratio (AOR)=1.42, 95% CI: 1.02-1.98; at intron 3 VNTR: RP1/RP1 vs. RP2/RP2+RP2/RP1, AOR=1.46, 95% CI: 1.05-2.04). Compared with other IL-4 diplotypes, the T,RP1/T,RP1 diplotype was associated with an increased risk of OPSCC (AOR=1.37, 95% CI: 1.03-1.81), particularly early-stage OSCC (AOR=1.43, 95% CI: 1.02-2.00), PSCC (AOR=2.35, 95% CI: 1.06-5.19), and OPSCC (AOR=1.52, 95% CI: 1.10-2.11). Interactions between the IL-4 diplotype and the alcohol drinking status were found to contribute to the risk of early-stage OPSCC (p=0.024). In addition, the T,RP1/T,RP1 diplotype was correlated with better disease-specific survival (T,RP1/T,RP1 vs. other diplotypes, adjusted hazard ratio=0.70, 95% CI: 0.50-0.97).

CONCLUSION

The T, RP1/T, RP1 diplotype of IL-4 was associated with an increased risk but favourable prognosis of OPSCC.

Elevated snail expression mediates tumor progression in areca quid chewing-associated oral squamous cell carcinoma via reactive oxygen species

BACKGROUND

Snail is an important transcription factor implicated in several tumor progression and can be induced by reactive oxygen species (ROS). Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). Therefore, we hypothesize that the major areca nut alkaloid arecoline may induce Snail via ROS and involve in the pathogenesis of areca quid chewing-associated OSCC.

METHODOLOGY/PRINCIPAL FINDING

Thirty-six OSCC and ten normal oral epithelium specimens were examined by immunohistochemistry and analyzed by the clinico-pathological profiles. Cytotoxicity, 2', 7'-dichlorofluorescein diacetate assay, and western blot were used to investigate the effects of arecoline in human oral keratinocytes (HOKs) and oral epithelial cell line OECM-1 cells. In addition, antioxidants N-acetyl-L-cysteine (NAC), curcumin, and epigallocatechin-3 gallate (EGCG) were added to find the possible regulatory mechanisms. Initially, Snail expression was significantly higher in OSCC specimens (p<0.05). Elevated Snail expression was associated with lymph node metastasis (p = 0.031) and poor differentiation (p = 0.017). Arecoline enhanced the generation of intracellular ROS at the concentration higher than 40 µg/ml (p<0.05). Arecoline was also found to induced Snail expression in a dose- and time-dependent manner (p<0.05). Treatment with NAC, curcumin, and EGCG markedly inhibited arecoline induced Snail expression (p<0.05).

CONCLUSION/SIGNIFICANCE

Our results suggest that Snail overexpression in areca quid chewing-associated OSCC is associated with tumors differentiation and lymph node metastasis. Arecoline-upregulated Snail expression may be mediated by ROS generation. In addition, arecoline induced Snail expression was downregulated by NAC, curcumin, and EGCG.

Association between polymorphisms of DNA repair gene ERCC5 and oral squamous cell carcinoma

OBJECTIVE

Short nucleotide polymorphism in ERCC5 (rs751402), a key molecule in DNA damage repair, was analyzed in 575 individuals who were either control subjects with no clinical evidence of malignant transformation of the oral mucosa or subjects with oral squamous cell carcinoma (OSCC).

STUDY DESIGN

All participants provided a blood sample, demographic data, and information on habitual use of tobacco, alcohol, and areca nut.

RESULTS

rs751402 homozygocity for C allele was found to confer a statistically significant protection against OSCC (adjusted odds ratio 0.56, 95% confidence interval 0.35-0.89; P = .01), whereas rs751402 T alleles were associated with increased risk.

CONCLUSIONS

Our findings suggest that there is an association between rs751402 polymorphism and incidence of oral cancer. ERCC rs751402 CC genotype is significantly associated with decreased risk of OSCC, whereas the T allotype is correlated with higher risk of OSCC.

Heat shock protein 27 expression in areca quid chewing-associated oral squamous cell carcinomas

OBJECTIVES

Heat shock protein (HSP) 27 is a low-molecular-weight protein that functions as a molecular chaperone and plays a cytoprotective role through its antioxidant activity during cell stress. Areca quid chewing is associated with the high incidence of oral squamous cell carcinomas (OSCCs) in Taiwan. The aim of this study was to compare heat shock protein 27 (HSP27) expression in OSCCs and the normal oral tissues.

METHODS

Forty-eight OSCCs from areca quid chewers and ten normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry for HSP27. The normal human oral keratinocytes (HOKs) were challenged with arecoline, the major alkaloid of areca nut, by Western blot for HSP27. Furthermore, epigallocatechin-3 gallate (EGCG), glutathione precursor N-acetyl-L-cysteine (NAC), cyclooxygenase-2 inhibitor NS-398, HSP inhibitor quercetin, extracellular signal-regulated protein kinase (ERK) inhibitor PD98059, and p38 inhibitor SB203580 were added to find the possible regulatory mechanisms.

RESULTS

Heat shock protein 27 exhibited higher expression in OSCCs than normal specimens (P < 0.05). Arecoline was found to elevate HSP27 expression in a dose- and time-dependent manner (P < 0.05). The additions of pharmacological agents were found to inhibit arecoline-induced HSP27 expression (P < 0.05).

CONCLUSIONS

Heat shock protein 27 expression is significantly elevated in areca quid chewing-associated OSCCs. Arecoline-induced HSP27 expression was downregulated by EGCG, NS398, NAC, quercetin, PD98059, and SB203580.

β-catenin expression in areca quid chewing-associated oral squamous cell carcinomas and upregulated by arecoline in human oral epithelial cells

BACKGROUND/PURPOSE

Nuclear localization of β-catenin is known to associate with malignant transformation of many squamous cell carcinomas. The aim of this study was to compare β-catenin expression in normal human oral epithelium and areca quid chewing associated oral squamous cell carcinomas (OSCCs) and further to explore the potential mechanisms that may lead to induce β-catenin expression.

METHODS

A total of 40 areca quid chewing-associated OSCCs and 10 normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The oral epithelial cell line GNM cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, extracellular signal-regulated protein kinase inhibitor PD98059, glutathione precursor N-acetyl-l-cysteine (NAC), tyrosine kinase inhibitor herbimycin-A, p38 inhibitor SB203580, and phosphatidylinositaol 3-kinase inhibitor LY294002 were added to find the possible regulatory mechanisms.

RESULTS

β-catenin expression was significantly higher in OSCC specimens than that in normal oral epithelial specimens (p < 0.05). It was demonstrated that normal oral epithelium showed only membranous staining for β-catenin, and membranous staining was lost or reduced with an increase in cytoplasmic/nuclear staining in OSCCs. Arecoline was found to elevate β-catenin expression in a dose-dependent manner (p < 0.05). The addition of PD98059, NAC, herbimycin-A, SB203580, and LY294002 markedly inhibited the arecoline-induced β-catenin expression (p < 0.05).

CONCLUSION

β-catenin expression is significantly upregulated in areca quid chewing-associated OSCC. The localization of β-catenin expression is correlated with the tumor size and clinical stage. In addition, β-catenin expression induced by arecoline is downregulated by PD98059, NAC, herbimycin-A, SB203580, and LY294002.

Arecoline-mediated inhibition of AMP-activated protein kinase through reactive oxygen species is required for apoptosis induction

Arecoline is the major alkaloid of areca nut (AN) and known to induce reactive oxygen species (ROS) production and apoptosis. The metabolic sensor AMP-activated protein kinase (AMPK), activated by ROS, also regulates apoptosis. This study used several types of cells as the experimental model to analyze the roles of ROS and AMPK in arecoline-induced apoptosis. We found that arecoline dose-dependently increased intracellular ROS level, and two antioxidants, N-acetyl-L-cysteine (NAC) and glutathione, attenuated arecoline-induced apoptotic cell death. Interestingly, arecoline dose- and time-dependently inhibited rather than stimulated AMPK-Thr(172) phosphorylation, and both NAC and glutathione relieved this inhibition. The AMPK activator, 5-aminoimidazole-4-carboxamide 1-β-D-ribofuranoside (AICAR), also restored the phosphorylation level of AMPK-Thr(172) and attenuated apoptotic cell death under arecoline insult. In contrast, the AMPK inhibitor, compound C, and RNA interference of AMPK expression increased the cytotoxicity of arecoline. Collectively, these results suggest that arecoline may inhibit AMPK through intracellular ROS, responsible for the execution of apoptosis.

Heat shock protein 47 expression in oral squamous cell carcinomas and upregulated by arecoline in human oral epithelial cells

BACKGROUND

Heat shock protein 47 (HSP47) is a product of CBP2 gene located at chromosome 11q13.5, a region frequently amplified in human cancers. Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). The aim of this study was to compare HSP47 expression in normal human oral epithelium and OSCC and further to explore the potential mechanisms that may lead to induce HSP47 expression.

METHODS

Thirty-two OSCC specimens and ten normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The oral epithelial cell line OC2 cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), extracellular signal-regulated protein kinase (ERK) inhibitor PD98059, phosphatidylinositol 3-kinase (PI3K) inhibitor LY294002, cyclooxygenase-2 inhibitor NS-398, and tyrosine kinase inhibitor herbimycin A were added to find the possible regulatory mechanisms.

RESULTS

HSP47 expression was significantly higher in OSCC specimens than normal epithelium (P<0.05). No significant difference in HSP47 expression was observed with respect to age, sex, T category, stage, and differentiation (P>0.05). The lower HSP47 expression was associated with lymph node metastasis (P=0.015). Arecoline was found to elevate HSP47 expression in a dose- and time-dependent manner (P<0.05). The addition of NAC, PD98059, LY294002, NS398, and herbimycin A markedly inhibited the arecoline-induced HSP47 expression (P<0.05).

CONCLUSION

  Our findings demonstrated that HSP47 expression is significantly upregulated in areca quid chewing-associated OSCCs. HSP47 could be used clinically as a marker for lymph node metastasis of oral carcinogenesis. In addition, arecoline-induced HSP47 expression was downregulated by NAC, PD98059, LY294002, NS398, and herbimycin A.

Hypoxia inducible factor-1α expression in areca quid chewing-associated oral squamous cell carcinomas

OBJECTIVES

Hypoxia inducible factor (HIF)-1α gene expression is mainly induced by tissue hypoxia. Overexpression of HIF-1α has been demonstrated in a variety of cancers. The aim of this study was to compare HIF-1α expression in normal human oral epithelium and areca quid chewing-associated oral squamous cell carcinoma (OSCC) and further to explore the potential mechanisms that may lead to induce HIF-1α expression.

METHODS

Twenty-five OSCC from areca quid chewing-associated OSCC and 10 normal oral tissue biopsy samples without areca quid chewing were analyzed by immunohistochemistry. The oral epithelial cell line GNM cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), AP-1 inhibitor curcumin, extracellular signal-regulated protein kinase inhibitor PD98059, and protein kinase C inhibitor staurosporine were added to find the possible regulatory mechanisms.

RESULTS

Hypoxia inducible factor-1α expression was significantly higher in OSCC specimens than normal specimen (P<0.05). Arecoline was found to elevate HIF-1α expression in a dose- and time-dependent manner (P<0.05). The addition of NAC, curcumin, PD98059, and staurosporine markedly inhibited the arecoline-induced HIF-1α expression (P<0.05).

CONCLUSIONS

Hypoxia inducible factor-1α expression is significantly upregulated in areca quid chewing-associated OSCC and HIF-1α expression induced by arecoline is downregulated by NAC, curcumin, PD98059, and staurosporine.

Metallothionein-1 genotypes in the risk of oral squamous cell carcinoma

BACKGROUND

We conducted an independent analysis of metallothionein 1 (MT-1) rs8052394, rs11076161, rs8052334, rs964372, rs7191779, and rs708274 in 587 individuals who were either healthy controls or subjects with oral squamous cell carcinoma (OSCC).

METHODS

All participants provided a nucleic acid sample (blood) as well as epidemiologic information on covariates or "risk factors" for OSCC, including tobacco, alcohol, and areca quid use. The genotyping result was used in a logistic regression model that examined main effects as well as statistical interactions while controlling for confounders.

RESULTS

MT-1 is involved in regulation of zinc and copper homeostasis. It also is a potent antioxidant and its polymorphisms correlate with the risk for OSCC. Rs11076161 A, rs964372 C, and rs7191779 C alleles were protective against OSCC (adjusted OR = 0.53, 0.49, 0.36, respectively; p < 0.05), whereas rs8052394 A alleles were associated with increased risk. Areca quid chewing and tobacco use were strong risk factors for developing the disease and were associated with 20- and 8-fold increases in adjusted risk (p < 0.05), respectively.

CONCLUSIONS

Controlling for the effects of age, gender, areca quid, tobacco, and alcohol use, individuals with inherited the MT-1 rs11076161 AA, rs964372 CC, and rs7191779 GC genotypes may experience significant protection against OSCC, whereas individuals carrying the MT-1 rs8052394 A allele seem exposed to higher risk.

Arecoline induced disruption of expression and localization of the tight junctional protein ZO-1 is dependent on the HER 2 expression in human endometrial Ishikawa cells

Background

Approximately 600 million people chew Betel nut, making this practice the fourth most popular oral habit in the world. Arecoline, the major alkaloid present in betel nut is one of the causative agents for precancerous lesions and several cancers of mouth among those who chew betel nut. Arecoline can be detected in the human embryonic tissue and is correlated to low birth weight of newborns whose mothers chew betel nut during pregnancy, suggesting that arecoline can induce many systemic effects. However, few reports exist as to the effects of arecoline in human tissues other than oral cancer cell lines. Furthermore, in any system, virtually nothing is known about the cellular effects of arecoline treatment on membrane associated signaling components of human cancer cells.

Results

Using the human Ishikawa endometrial cancer cell line, we investigated the effects of arecoline on expression, localization and functional connections between the ZO-1 tight junction protein and the HER2 EGF receptor family member. Treatment of Ishikawa cells with arecoline coordinately down-regulated expression of both ZO-1 and HER2 protein and transcripts in a dose dependent manner. Biochemical fractionation of cells as well as indirect immunofluorescence revealed that arecoline disrupted the localization of ZO-1 to the junctional complex at the cell periphery. Compared to control transfected cells, ectopic expression of exogenous HER2 prevented the arecoline mediated down-regulation of ZO-1 expression and restored the localization of ZO-1 to the cell periphery. Furthermore, treatment with dexamethasone, a synthetic glucocorticoid reported to up-regulate expression of HER2 in Ishikawa cells, precluded arecoline from down-regulating ZO-1 expression and disrupting ZO-1 localization.

Conclusion

Arecoline is known to induce precancerous lesions and cancer in the oral cavity of betel nut users. The arecoline down-regulation of ZO-1 expression and subcellular distribution suggests that arecoline potentially disrupts cell-cell interactions mediated by ZO-1, which may play a role in arecoline-mediated carcinogenesis. Furthermore, our study has uncovered the dependency of ZO-1 localization and expression on HER2 expression, which has therefore established a new cellular link between HER2 mediated signaling and apical junction formation involving ZO-1.

Expression of functional metallothionein isoforms in papillary thyroid cancer

Metallothionein (MT) isoforms have not been studied in papillary thyroid cancer. We examined how the functional MT1 and MT2 isoforms were expressed in papillary thyroid cancer (KAT5) cells. We demonstrated that KAT5 cells expressed eight functional MT1 and MT2 isoforms induced by cadmium. Elevated calcium and activated ERK1/2 predated MT expression. The inhibition of either calcium or ERK1/2 significantly blocked the isoform expression. The induction of these isoforms accompanied an increased progression of cell cycle from G0/G1 to G2-M. The alternation in cell cycle disappeared when the expression of MT isoforms was blocked by calcium inhibitor or ERK1/2 inhibitor. Collectively, KAT5 cells express eight functional MT1 and MT2 isoforms in a pathway controlled by calcium and ERK1/2. The elevation of the MT isoforms contributes to the decreased G0/G1 but increased G2-M phase. These results reveal a novel pathway for the expression of the functional MT in papillary thyroid cancer.

Study of Interactions between Metallothionein and Cisplatin by using Differential Pulse Voltammetry Brdickás reaction and Quartz Crystal Microbalance

Treatment strategies for tumour diseases are progressively focusing on personalization of medicine. However, this focus requires methods revealing the early general biological mechanisms, including the formation anti-cancer drugs’ resistance. The low molecular mass protein metallothionein is thought to be the crucial for the formation of resistance in tumour treatment based on the platinum-cytostatics. The interactions between metallothionein (MT) and cisplatin were determined by the adsorptive transfer stripping technique coupled with the differential pulse votlammetry Brdickás reaction. The signals related to the MT-cisplatin complex appeared at −0.9 V. The formation of this complex depended on the time of interaction between cisplatin and MT. The complex formation was consequently confirmed by quartz crystal microbalance analyses. The formation of this complex was detectable even after a 20 s long interaction. Moreover, we detected presence of MT-cisplatin complex in the blood of male rats treated with this drug.

Inhibition of ischemia-induced angiogenesis by benzo[a]pyrene in a manner dependent on the aryl hydrocarbon receptor

We have investigated the effect of benzo[a]pyrene (B[a]P), a carcinogen of tobacco smoke and an agonist for the aryl hydrocarbon receptor (AHR), on hypoxia-induced angiogenesis. Ischemia was induced by femoral artery ligation in wild-type and AHR-null mice, and the animals were subjected to oral administration of B[a]P (125 mg/kg) once a week. Exposure to B[a]P up-regulated the expression of metallothionein in the ischemic hindlimb and markedly inhibited ischemia-induced angiogenesis in wild-type mice. The amounts of interleukin-6 and of vascular endothelial growth factor (VEGF) mRNA in the ischemic hindlimb of wild-type mice were reduced by exposure to B[a]P. These various effects of B[a]P were markedly attenuated in AHR-null mice. Our observations suggest that the loss of the inhibitory effect of B[a]P on ischemia-induced angiogenesis apparent in AHR-null mice may be attributable to maintenance of interleukin-6 expression and consequent promotion of angiogenesis through up-regulation of VEGF expression.

Metallothionein induction by hypoxia involves cooperative interactions between metal-responsive transcription factor-1 and hypoxia-inducible transcription factor-1alpha

Mammalian metallothionein (MT) genes are transcriptionally activated by the essential metal zinc as well as by environmental stresses, including toxic metal overload and redox fluctuations. In addition to playing a key role in zinc homeostasis, MT proteins can protect against metal- and oxidant-induced cellular damage, and may participate in other fundamental physiologic and pathologic processes such as cell survival, proliferation, and neoplasia. Previously, our group reported a requirement for metal-responsive transcription factor-1 (MTF-1) in hypoxia-induced transcription of mouse MT-I and human MT-IIA genes. Here, we provide evidence that the protumorigenic hypoxia-inducible transcription factor-1alpha (HIF-1alpha) is essential for induction of MT-1 by hypoxia, but not zinc. Chromatin immunoprecipitation assays revealed that MTF-1 and HIF-1alpha are both recruited to the mouse MT-I promoter in response to hypoxia, but not zinc. In the absence of HIF-1alpha, MTF-1 is recruited to the MT-I promoter but fails to activate MT-I gene expression in response to hypoxia. Thus, HIF-1alpha seems to function as a coactivator of MT-I gene transcription by interacting with MTF-1 during hypoxia. Coimmunoprecipitation studies suggest interaction between MTF-1 and HIF-1alpha, either directly or as mediated by other factors. It is proposed that association of these important transcription factors in a multiprotein complex represents a common strategy to control unique sets of hypoxia-inducible genes in both normal and diseased tissue.

The upregulation of heat shock protein 70 expression in areca quid chewing-associated oral squamous cell carcinomas

Heat shock protein 70 (HSP70) is an important stress-induced protein. Areca quid chewing is a major risk factor of oral squamous cell carcinoma (OSCC). The aim of this study was to compare HSP70 expression in normal human oral epithelium and OSCC and further to explore the potential mechanisms that may lead to induce HSP70 expression. 41 OSCC and 10 normal epithelium specimens were examined by immunohistochemistry and analyzed by the clinico-pathological profiles. The oral epithelial cell line GNM cells were challenged with arecoline, a major areca nut alkaloid, by using Western blot analysis. Furthermore, glutathione precursor N-acetyl-l-cysteine (NAC), AP-1 inhibitor curcumin, extracellular signal-regulated protein kinase inhibitor PD98059, and protein kinase C inhibitor staurosporine were added to find the possible regulatory mechanisms. The results from immunohistochemistry demonstrated that HSP70 expression was significantly higher in OSCC specimens (p<0.05). No significant difference in HSP70 expression was observed with respect to age, sex, T category, and stage (p>0.05). The low HSP70 expression was associated with lymph node metastasis (p=0.005). The high HSP70 expression was found in poor differentiated tumor groups (p=0.036). Arecoline was found to elevate HSP70 expression in a dose- and time-dependent manner (p<0.05). The addition of NAC, curcumin, PD98059, and staurosporine markedly inhibited the arecoline-induced HSP70 expression (p<0.05). Taken together, HSP70 expression is significantly upregulated in areca quid chewing-associated OSCC. HSP70 could be used clinically as a marker for tumors possessing the potential for differentiation as well as lymph node metastasis. In addition, arecoline-induced HSP70 expression was downregulated by NAC, curcumin, PD98059, and staurosporine.

Physiological responses and expression of metallothionein (MT) and superoxide dismutase (SOD) mRNAs in olive flounder, Paralichthys olivaceus exposed to benzo[a]pyrene

We cloned complementary DNA (cDNA) encoding metallothionein (MT) and superoxide dismutase (SOD) from the liver of olive flounder, Paralichthys olivaceus. The full-length MT cDNA consists of 183 base pairs (bp) and encodes a protein of 60 amino acids; partial SOD cDNA consists of 326 bp and encodes a protein of 109 amino acids. We investigated the dose- and time-related effects of the polycyclic aromatic hydrocarbon benzo[a]pyrene (BaP) on MT and SOD mRNA using quantitative polymerase chain reaction (QPCR). The expression levels of MT mRNA were highest at 24 h (about five times) in 10 microg/L BaP, and at 6 h (about twelve times) in 30 microg/L BaP. The expression levels of SOD mRNA were highest at 12 h (about three times) in 10 microg/L BaP, and at 6 h (about six times) in 30 microg/L BaP, and then decreased toward the end of the experiment. We also measured plasma glucose and cortisol, all of which increased with BaP exposure. These results suggest that MT and SOD play an important role in the detoxification of reactive oxygen species (ROS) caused by BaP exposure, and thus may be indicators of oxidative stress responses.