Genetic polymorphisms in the PTPN13 gene and risk of squamous cell carcinoma of head and neck

PTPN13 rs989902 and CHEK2 rs738722 are associated with esophageal cancer

PURPOSE

Individual genetic background can play an essential role in determining the development of esophageal squamous cell carcinoma (ESCC). PTPN13 and CHEK2 play important roles in the pathogenesis of ESCC. This case-control study aimed to analyze the association between gene polymorphisms and ESCC susceptibility.

METHODS

DNA was extracted from the peripheral blood of patients. The Agena MassARRAY platform was used for the genotyping. Statistical analysis was conducted using the chi-squared test or Fisher's exact test, logistic regression analysis, and stratification analysis.

RESULTS

The 'G' allele of rs989902 (PTPN13) and the 'T' allele of rs738722 (CHEK2) were both associated with an increased risk of ESCC (rs989902: OR = 1.23, 95% CI = 1.02-1.47, p = 0.028; rs738722: OR = 1.28, 95% CI = 1.06-1.55, p = 0.011). Stratification analysis showed that SNPs (rs989902 and rs738722) were notably correlated with an increased risk of ESCC after stratification for age, sex, smoking, and drinking status. In addition, rs738722 might be associated with lower stage, while rs989902 had a lower risk of metastasis.

CONCLUSION

Our findings display that PTPN13 rs989902 and CHEK2 rs738722 are associated with an increased risk of ESCC in the Chinese Han population.

Associations of Head and Neck Cancer with Hepatitis B Virus and Hepatitis C Virus Infection

This case-control study investigates the associations between head and neck cancer (HNC), hepatitis B virus (HBV), and hepatitis C virus (HCV) infection. We included 5603 patients who had received a diagnosis of HNC as cases and 16,809 propensity score matching controls. We employed multivariate logistic regression models to evaluate the association of HNC with HBV and HCV infection after taking sociodemographic characteristics and diabetes, hypertension, hyperlipidemia, HPV infection, tobacco use disorder, and alcohol abuse/alcohol dependence syndrome into considerations. Results show that 7.9% of the total sample had been previously diagnosed with HBV infection, with 9.0% prevalence among cases and 7.6% among controls (p < 0.001). The chi-squared test suggests a significant difference in the prevalence of HCV infection between cases and controls (3.3% vs. 2.7%, p = 0.019). The covariate-adjusted odds ratio (OR) of HBV infection in patients with HNC relative to controls was 1.219 (95% CI = 1.093~1.359). Additionally, the adjusted OR of HCV infection in patients with HNC was 1.221 (95% CI = 1.023~1.457) compared to controls. Furthermore, patients with oropharyngeal cancer were more likely to have HCV infection than controls (adjusted OR = 2.142, 95% CI = 1.171~3.918). Our study provides evidence that suggests a potential association between HBV and HCV infections and the risk of HNC.

The environmental carcinogen benzo[a]pyrene regulates epigenetic reprogramming and metabolic rewiring in a two-stage mouse skin carcinogenesis model

Non-melanoma skin cancer (NMSC) is the most common cancer in the world. Environmental exposure to carcinogens is one of the major causes of NMSC initiation and progression. In the current study, we utilized a two-stage skin carcinogenesis mouse model generated by sequential exposure to cancer-initiating agent benzo[a]pyrene (BaP) and promoting agent 12-O-tetradecanoylphorbol-13-acetate (TPA), to study epigenetic, transcriptomic and metabolic changes at different stages during the development of NMSC. BaP/TPA caused significant alterations in DNA methylation and gene expression profiles in skin carcinogenesis, as evidenced by DNA-seq and RNA-seq analysis. Correlation analysis between differentially expressed genes and differentially methylated regions found that the mRNA expression of oncogenes leucine rich repeat LGI family member 2 (Lgi2), kallikrein-related peptidase 13 (Klk13) and SRY-Box transcription factor (Sox5) are correlated with the promoter CpG methylation status, indicating BaP/TPA regulates these oncogenes through regulating their promoter methylation at different stages of NMSC. Pathway analysis identified that the modulation of macrophage-stimulating protein-recepteur d'origine nantais and high-mobility group box 1 signaling pathways, superpathway of melatonin degradation, melatonin degradation 1, sirtuin signaling and actin cytoskeleton signaling pathways are associated with the development of NMSC. The metabolomic study showed BaP/TPA regulated cancer-associated metabolisms like pyrimidine and amino acid metabolisms/metabolites and epigenetic-associated metabolites, such as S-adenosylmethionine, methionine and 5-methylcytosine, indicating a critical role in carcinogen-mediated metabolic reprogramming and its consequences on cancer development. Altogether, this study provides novel insights integrating methylomic, transcriptomic and metabolic-signaling pathways that could benefit future skin cancer treatment and interception studies.

PTPL1 suppresses lung cancer cell migration via inhibiting TGF-β1-induced activation of p38 MAPK and Smad 2/3 pathways and EMT

Epithelial-mesenchymal transition (EMT) enables dissemination of neoplastic cells and onset of distal metastasis of primary tumors. However, the regulatory mechanisms of EMT by microenvironmental factors such as transforming growth factor-β (TGF-β) remain largely unresolved. Protein tyrosine phosphatase L1 (PTPL1) is a non-receptor protein tyrosine phosphatase that plays a suppressive role in tumorigenesis of diverse tissues. In this study we investigated the role of PTPL1/PTPN13 in metastasis of lung cancer and the signaling pathways regulated by PTPL1 in terms of EMT of non-small cell lung cancer (NSCLC) cells. We showed that the expression of PTPL1 was significantly downregulated in cancerous tissues of 23 patients with NSCLC compared with adjacent normal tissues. PTPL1 expression was positively correlated with overall survival of NSCLC patients. Then we treated A549 cells in vitro with TGF-β1 (10 ng/mL) and assessed EMT. We found that knockdown of PTPL1 enhanced the migration and invasion capabilities of A549 cells, through enhancing TGF-β1-induced EMT. In nude mice bearing A549 cell xenografts, knockdown of PTPL1 significantly promoted homing of cells and formation of tumor loci in the lungs. We further revealed that PTPL1 suppressed TGF-β-induced EMT by counteracting the activation of canonical Smad2/3 and non-canonical p38 MAPK signaling pathways. Using immunoprecipitation assay we demonstrated that PTPL1 could bind to p38 MAPK, suggesting that p38 MAPK might be a direct substrate of PTPL1. In conclusion, these results unravel novel mechanisms underlying the regulation of TGF-β signaling pathway, and have implications for prognostic assessment and targeted therapy of metastatic lung cancer.

High-throughput sequencing profile of laryngeal cancers: analysis of co-expression and competing endogenous RNA networks of circular RNAs, long non-coding RNAs, and messenger RNAs

Background

Circular RNAs (circRNAs) and long non-coding RNAs (lncRNAs) have been recently identified as new classes of non-coding RNAs which participate in carcinogenesis and tumor progression. However, the functions of these non-coding RNAs and gene expression patterns are largely unknown.

Methods

We carried out high-throughput sequencing to analyze the differential expression of RNAs in 5 coupled laryngeal cancer (LC) and corresponding adjacent noncancerous tissues. Bioinformatics analyses were performed to predict the functions of these non-coding RNAs via co-expression, competing endogenous RNA networks and pathway enrichment analysis. The differential expression of the selected RNAs were confirmed using RT-qPCR. The CCK8, EDU, Transwell, and wound healing assays were conducted to validate the biological functions of SNHG29 in LC. Western blot assay was performed to identify the effects of SNHG29 having on the epithelial to mesenchymal transition process. Kaplan-Meier analysis was used to investigate whether the expression level of SNHG29 correlated with survival in LC patients. One-way ANOVA was used to analyze the correlation between the expression of SNHG29 and clinicopathological parameters of the included patients.

Results

Compared to normal laryngeal tissues, 31,763 non-coding RNAs were upregulated and 11,557 non-coding RNAs were downregulated in cancer tissues. SNHG29 expression was low in the LC cell lines and tissues predicting a better clinical prognosis. SNHG29 was also found to inhibit the proliferation, migration, and invasion ability of LC, exerting a suppressive role in the epithelial to mesenchymal transition process as well. SNHG29 downregulation was significantly correlated with differentiation (P=0.026), T-stage (P=0.041), lymphatic metastasis (P=0.044), and clinical stage (P=0.037). We found that the biological functions of differentially expressed transcripts included cell adhesion, biological adhesion, and migration and invasion related to adherens junction pathways.

Conclusions

Our study was the first to describe the non-coding RNA profile of LC, and suggested that dysregulated non-coding RNAs could be involved in LC tumorigenesis. SNHG29 was demonstrated to play crucial roles in inhibiting the pathogenesis and progression of LC. Our findings provide a new approach for further analyses of pathogenetic mechanisms, the detection of novel transcripts, and the identification of valuable biomarkers for this tumor.

Dual Role of the PTPN13 Tyrosine Phosphatase in Cancer

In this review article, we present the current knowledge on PTPN13, a class I non-receptor protein tyrosine phosphatase identified in 1994. We focus particularly on its role in cancer, where PTPN13 acts as an oncogenic protein and also a tumor suppressor. To try to understand these apparent contradictory functions, we discuss PTPN13 implication in the FAS and oncogenic tyrosine kinase signaling pathways and in the associated biological activities, as well as its post-transcriptional and epigenetic regulation. Then, we describe PTPN13 clinical significance as a prognostic marker in different cancer types and its impact on anti-cancer treatment sensitivity. Finally, we present future research axes following recent findings on its role in cell junction regulation that implicate PTPN13 in cell death and cell migration, two major hallmarks of tumor formation and progression.

Genome-Wide Search for Tyrosine Phosphatases in the Human Genome Through Computational Approaches Leads to the Discovery of Few New Domain Architectures

Reversible phosphorylation maintained by protein kinases and phosphatases is an integral part of intracellular signalling, and phosphorylation on tyrosine is extensively utilised in higher eukaryotes. Tyrosine phosphatases are enzymes that not only scavenge phosphotyrosine but are also involved in wide range of signalling pathways. As a result, mutations in these enzymes have been implicated in the pathogenesis of several diseases like cancer, autoimmune disorders, and muscle-related diseases. The genes that harbour phosphatase domain also display diversity in co-existing domains suggesting the recruitment of the catalytic machinery in diverse pathways. We have examined the current draft of the human genome, using a combination of 3 sequence search methods and validations, and identified 101 genes encoding tyrosine phosphatase-containing gene products, agreeing with previous reports. Such gene products adopt 37 unique domain architectures (DAs), including few new ones and harbouring few co-existing domains that have not been reported before. This semi-automated computational approach for detection of gene products belonging to a particular superfamily can now be easily applied at whole genome level on other mammalian genomes and for other protein domains as well.

Tumor suppressive protein phosphatases in human cancer: Emerging targets for therapeutic intervention and tumor stratification

Aberrant protein phosphorylation is one of the hallmarks of cancer cells, and in many cases a prerequisite to sustain tumor development and progression. Like protein kinases, protein phosphatases are key regulators of cell signaling. However, their contribution to aberrant signaling in cancer cells is overall less well appreciated, and therefore, their clinical potential remains largely unexploited. In this review, we provide an overview of tumor suppressive protein phosphatases in human cancer. Along their mechanisms of inactivation in defined cancer contexts, we give an overview of their functional roles in diverse signaling pathways that contribute to their tumor suppressive abilities. Finally, we discuss their emerging roles as predictive or prognostic markers, their potential as synthetic lethality targets, and the current feasibility of their reactivation with pharmacologic compounds as promising new cancer therapies. We conclude that their inclusion in clinical practice has obvious potential to significantly improve therapeutic outcome in various ways, and should now definitely be pushed forward.

The PTPN13 Y2081D (T>G) (rs989902) polymorphism is associated with an increased risk of sporadic colorectal cancer

AIM

Colorectal cancer (CRC) is one of the most common cancers worldwide and, although the majority of cases are sporadic, its development and progression depends on a range of factors: environmental, genetic and epigenetic. A variety of genetic pathways have been described as being crucial in CRC, including protein tyrosine phosphatases (PTPs). PTPN13 (also called FAP-1) is a non-receptor PTP and interacts with a number of important components of growth and apoptosis pathways. It is also involved in the inhibition of Fas-induced apoptosis.

METHOD

The single nucleotide polymorphism genotype at Y2081D (T>G) (rs989902) of PTPN13 exon 39 was determined in DNA extracted from blood samples from 174 sporadic CRC patients and 176 healthy individuals. Also, a meta-analysis was performed based on three articles accessed via the PubMed and ResearchGate databases.

RESULTS

The risk of CRC was 2.087 times greater for patients with the GG genotype than for those with the TT genotype (P = 0.0475). In the meta-analysis, a significantly increased risk of cancer associated with the G allele was observed in the squamous cell carcinoma of the head and neck subgroup (TT vs GG+GT, OR 1.23, 95% CI [1.02, 1.47], P = 0.0258), and a significantly decreased risk in the breast cancer subgroup (TT vs GG+GT, OR 0.63, 95% CI [0.41, 0.96], P = 0.0334) and in the CRC subgroup (GT+TT vs GG, OR 0.51, 95% CI [0.41, 0.95], P = 0.0333).

CONCLUSION

PTPN13 rs989902 is significantly associated with the risk of CRC in the Polish population. Given that this report provides the first evidence of an association of PTPN13 rs989902 with the risk of CRC in a Caucasian population, further large scale studies are necessary to confirm this finding.

EphrinB1: novel microtubule associated protein whose expression affects taxane sensitivity

Microtubules (MTs) are components of the cytoskeleton made up of polymerized alpha and beta tubulin dimers. MT structure and function must be maintained throughout the cell cycle to ensure proper execution of mitosis and cellular homeostasis. The protein tyrosine phosphatase, PTPN13, localizes to distinct compartments during mitosis and cytokinesis. We have previously demonstrated that the HPV16 E6 oncoprotein binds PTPN13 and leads to its degradation. Thus, we speculated that HPV infection may affect cellular proliferation by altering the localization of a PTPN13 phosphatase substrate, EphrinB1, during mitosis. Here we report that EphrinB1 co-localizes with MTs during all phases of the cell cycle. Specifically, a cleaved, unphosphorylated EphrinB1 fragment directly binds tubulin, while its phosphorylated form lacks MT binding capacity. These findings suggest that EphrinB1 is a novel microtubule associated protein (MAP). Importantly, we show that in the context of HPV16 E6 expression, EphrinB1 affects taxane response in vitro. We speculate that this reflects PTPN13's modulation of EphrinB1 phosphorylation and suggest that EphrinB1 is an important contributor to taxane sensitivity/resistance phenotypes in epithelial cancers. Thus, HPV infection or functional mutations of PTPN13 in non-viral cancers may predict taxane sensitivity.

Functional single nucleotide polymorphisms of the RASSF3 gene and susceptibility to squamous cell carcinoma of the head and neck

BACKGROUND

RASSF3 suppresses tumour formation through uncertain mechanisms, but it is an important gene of p53-dependent apoptosis. RASSF3 depletion impairs DNA repair after DNA damage, leading to polyploidy. The authors hypothesised that potential functional single-nucleotide polymorphisms (SNPs) of RASSF3 are associated with risk of squamous cell carcinoma of the head and neck (SCCHN).

METHODS

The authors used a functional SNP approach to evaluate the associations between common (minor allele frequency⩾0.05), putative functional variants in RASSF3 and risk of SCCHN. Four selected such functional SNPs (rs6581580 T>G, rs7313765 G>A, rs12311754 G>C and rs1147098 T>C) in RASSF3 were identified and genotyped in 1087 patients and 1090 cancer-free controls in a non-Hispanic white population.

RESULTS

The authors found that two SNPs were significantly associated with SCCHN risk. Carriers of the variant rs6581580G and rs7313765A alleles were at a reduced SCCHN risk, compared with the corresponding common homozygotes [adjusted odds ratio (OR)=0.75 and 0.73 and 95% confidence interval (CI)=0.62-0.91 and 0.60-0.88, respectively, for dominant models; and Ptrend=0.012 and 0.041, respectively, for additive models], particularly for non-oropharyngeal tumours (adjusted OR=0.68 and 0.60 and 95% CI=0.53-0.86 and 0.47-0.77, respectively, for dominant models). In the genotype-phenotype correlation analysis of peripheral blood mononuclear cells from 102 cancer-free controls, the rs6581580 GG genotype was associated with significantly increased expression levels of RASSF3 mRNA (P=0.038), compared with the TT genotype. Additional functional experiments further showed that variant G allele of rs6581580 had a significantly stronger binding affinity to the nuclear protein extracts than the T allele.

CONCLUSION

Taken together, these findings indicate that the RASSF3 promoter rs6581580 T>G SNP is potentially functional, modulating susceptibility to SCCHN among non-Hispanic whites. Larger replication studies are needed to confirm our findings.

Stat3 inhibits PTPN13 expression in squamous cell lung carcinoma through recruitment of HDAC5

Proteins of the protein tyrosine phosphatase (PTP) family are known to be signaling molecules that regulate a variety of cellular processes including cell growth, differentiation, and apoptosis. PTPN13 (also known as FAP1, PTPL1, PTPLE, PTPBAS, and PTP1E), a putative tumor suppressor, is frequently inactivated in lung carcinoma through the loss of either mRNA or protein expression. However, the molecular mechanisms underlying its dysregulation have not been fully explored. Interleukin-6 (IL-6) mediated Stat3 activation is viewed as crucial for multiple tumor growth and progression. Here, we demonstrate that PTPN13 is a direct transcriptional target of Stat3 in the squamous cell lung carcinoma. Our data show that IL-6 administration or transfection of a constitutively activated Stat3 in HCC-1588 and SK-MES-1 cells inhibits PTPN13 mRNA transcription. Using luciferase reporter and ChIP assays, we show that Stat3 binds to the promoter region of PTPN13 and promotes its activity through recruiting HDAC5. Thus, our results suggest a previously unknown Stat3-PTPN13 molecular network controlling squamous cell lung carcinoma development.

Targeting ERBB receptors shifts their partners and triggers persistent ERK signaling through a novel ERBB/EFNB1 complex

Most squamous cell carcinomas of the head and neck (HNSCC) overexpress ERBB1/EGFR, but EGF receptor (EGFR)-targeted therapies have yielded disappointing clinical results in treatment of this cancer. Here, we describe a novel interaction between EGFR and the ligand EphrinB1 (EFNB1), and we show that EFNB1 phosphorylation and downstream signaling persists in the presence of cetuximab. Mechanistically, cetuximab drives a shift in EGFR dimerization partners within the signaling complex, suggesting that targeted drugs may trigger partner rearrangements that allow persistent pathway activation. EFNB1 attenuation slowed tumor growth and increased survival in a murine model of HNSCC, suggesting a substantial contribution of EFNB1 signaling to HNSCC development. Together, our findings suggest that EFNB1 is part of the EGFR signaling complex and may mediate drug resistance in HNSCC as well as other solid tumors.

Protein tyrosine phosphatase variants in human hereditary disorders and disease susceptibilities

Reversible tyrosine phosphorylation of proteins is a key regulatory mechanism to steer normal development and physiological functioning of multicellular organisms. Phosphotyrosine dephosphorylation is exerted by members of the super-family of protein tyrosine phosphatase (PTP) enzymes and many play such essential roles that a wide variety of hereditary disorders and disease susceptibilities in man are caused by PTP alleles. More than two decades of PTP research has resulted in a collection of PTP genetic variants with corresponding consequences at the molecular, cellular and physiological level. Here we present a comprehensive overview of these PTP gene variants that have been linked to disease states in man. Although the findings have direct bearing for disease diagnostics and for research on disease etiology, more work is necessary to translate this into therapies that alleviate the burden of these hereditary disorders and disease susceptibilities in man.

SHP2 is overexpressed and inhibits pSTAT1-mediated APM component expression, T-cell attracting chemokine secretion, and CTL recognition in head and neck cancer cells

PURPOSE

Human leukocyte antigen (HLA) class I antigen processing machinery (APM) component downregulation permits escape of malignant cells from recognition by cytotoxic T lymphocytes (CTL) and correlates with poor prognosis in patients with head and neck cancer (HNC). Activated STAT1 (pSTAT1) is necessary for APM component expression in HNC cells. We investigated whether an overexpressed phosphatase was responsible for basal suppression of pSTAT1 and subsequent APM component-mediated immune escape in HNC cells.

EXPERIMENTAL DESIGN

Immunohistochemical staining and reverse transcription PCR of paired HNC tumors was performed for the phosphatases src homology domain-containing phosphatase (SHP)-1 and SHP2. Depletion of phosphatase activity in HNC and STAT1(-/-) tumor cells was achieved by siRNA knockdown. HLA class I-restricted, tumor antigen-specific CTL were used in IFN-γ ELISPOT assays against HNC cells. Chemokine secretion was measured after SHP2 depletion in HNC cells.

RESULTS

SHP2, but not SHP1, was significantly upregulated in HNC tissues. In HNC cells, SHP2 depletion significantly upregulated expression of pSTAT1 and HLA class I APM components. Overexpression of SHP2 in nonmalignant keratinocytes inhibited IFN-γ-mediated STAT1 phosphorylation, and SHP2 depletion in STAT1(-/-) tumor cells did not significantly induce IFN-γ-mediated APM component expression, verifying STAT1 dependence of SHP2 activity. SHP2 depletion induced recognition of HNC cells by HLA class I-restricted CTL and secretion of inflammatory, T-cell attracting chemokines, RANTES and IP10.

CONCLUSION

These findings suggest for the first time an important role for SHP2 in APM-mediated escape of HNC cells from CTL recognition. Targeting SHP2 could enhance T-cell-based cancer immunotherapy.

Association between single nucleotide polymorphisms in ERCC4 and risk of squamous cell carcinoma of the head and neck

BACKGROUND

Excision repair cross-complementation group 4 gene (ERCC4/XPF) plays an important role in nucleotide excision repair and participates in removal of DNA interstrand cross-links and DNA double-strand breaks. Single nucleotide polymorphisms (SNPs) in ERCC4 may impact repair capacity and affect cancer susceptibility.

METHODOLOGY/PRINCIPAL FINDINGS

In this case-control study, we evaluated associations of four selected potentially functional SNPs in ERCC4 with risk of squamous cell carcinoma of the head and neck (SCCHN) in 1,040 non-Hispanic white patients with SCCHN and 1,046 cancer-free matched controls. We found that the variant GG genotype of rs2276466 was significantly associated with a decreased risk of SCCHN (OR = 0.69, 95% CI 0.50-0.96), and that the variant TT genotype of rs3136038 showed a borderline significant decreased risk with SCCHN (OR = 0.76, 95% CI: 0.58-1.01) in the recessive model. Such protective effects were more evident in oropharyngeal cancer (OR = 0.61, 95% CI: 0.40-0.92 for rs2276466; OR = 0.69, 95% CI: 0.48-0.98 for rs3136038). No significant associations were found for the other two SNPs (rs1800067 and rs1799798). In addition, individuals with the rs2276466 GG or with the rs3136038 TT genotypes had higher levels of ERCC4 mRNA expression than those with the corresponding wild-type genotypes in 90 Epstein-Barr virus-transformed lymphoblastoid cell lines derived from Caucasians.

CONCLUSIONS

These results suggest that these two SNPs (rs2276466 and rs3136038) in ERCC4 may be functional and contribute to SCCHN susceptibility. However, our findings need to be replicated in further large epidemiological and functional studies.

Combined effects of E2F1 and E2F2 polymorphisms on risk and early onset of squamous cell carcinoma of the head and neck

Deregulated expression of most members of the E2F family has been detected in many human cancers. We examined the association of common single nucleotide polymorphisms (SNPs) of E2F transcription factors 1 and 2 (E2F1 and E2F2) with risk of squamous cell carcinoma of the head and neck (SCCHN) in 1,096 SCCHN patients and 1,090 cancer-free controls. We genotyped 10 selected SNPs in E2F1 and E2F2, including those at the near 5'-untranslated region (UTR), microRNA (miRNA)-binding sites at the near 3'-UTR and tagSNPs according to bioinformatics analysis. Although none of the selected SNPs alone was significantly associated with risk of SCCHN, there was a statistically significantly increased risk of SCCHN associated with the combined risk genotypes (i.e., rs3213182 AA, rs3213183 GG, rs3213180 GG, rs321318121 GG, rs2742976 GT+TT, rs6667575 GA+AA, rs3218203 CC, rs3218148 AA, rs3218211 CC, and rs3218123 GT+TT). Compared with those with 0-4 risk genotypes, an increased risk was observed for those who carried 5-8 risk genotypes (adjusted OR = 1.04; 95% CI = 0.86-1.26) and 9-10 risk genotypes (adjusted OR = 1.62; 95% CI = 1.14-2.30) in a dose-response manner (P = 0.045). Furthermore, the joint effect was more pronounced among patients with oropharyngeal cancer, younger adults (≤57 yr old), men, non-smokers, non-drinkers, and individuals with family history of cancer in first-degree relatives. Additionally, we also observed that those with 5-10 risk genotypes had an earlier SCCHN onset than those with 0-4 risk genotypes, particularly for non-smokers and/or non-drinkers. We concluded that E2F1 and E2F2 genetic variants may jointly play important roles in head and neck carcinogenesis.

ErbB2, EphrinB1, Src kinase and PTPN13 signaling complex regulates MAP kinase signaling in human cancers

In non-cancerous cells, phosphorylated proteins exist transiently, becoming de-phosphorylated by specific phosphatases that terminate propagation of signaling pathways. In cancers, compromised phosphatase activity and/or expression occur and contribute to tumor phenotype. The non-receptor phosphatase, PTPN13, has recently been dubbed a putative tumor suppressor. It decreased expression in breast cancer correlates with decreased overall survival. Here we show that PTPN13 regulates a new signaling complex in breast cancer consisting of ErbB2, Src, and EphrinB1. To our knowledge, this signaling complex has not been previously described. Co-immunoprecipitation and localization studies demonstrate that EphrinB1, a PTPN13 substrate, interacts with ErbB2. In addition, the oncogenic V660E ErbB2 mutation enhances this interaction, while Src kinase mediates EphrinB1 phosphorylation and subsequent MAP Kinase signaling. Decreased PTPN13 function further enhances signaling. The association of oncogene kinases (ErbB2, Src), a signaling transmembrane ligand (EphrinB1) and a phosphatase tumor suppressor (PTPN13) suggest that EphrinB1 may be a relevant therapeutic target in breast cancers harboring ErbB2-activating mutations and decreased PTPN13 expression.

A novel functional DEC1 promoter polymorphism -249T>C reduces risk of squamous cell carcinoma of the head and neck

Human DEC1 (deleted in esophageal cancer 1) gene is located on chromosome 9q, a region frequently deleted in various types of human cancers, including squamous cell carcinoma of the head and neck (SCCHN). However, only one epidemiological study has evaluated the association between DEC1 polymorphisms and cancer risk. In this hospital-based case-control study, four potentially functional single-nucleotide polymorphisms -1628 G>A (rs1591420), -606 T>C [rs4978620, in complete linkage disequilibrium with -249T>C (rs2012775) and -122 G>A(rs2012566)], c.179 C>T p.Ala60Val (rs2269700) and 3' untranslated region-rs3750505 as well as the TP53 tumor suppressor gene codon 72 (Arg72Pro, rs1042522) polymorphism were genotyped in 1111 non-Hispanic Whites SCCHN patients and 1130 age-and sex-matched cancer-free controls. After adjustment for age, sex and smoking and drinking status, the variant -606CC (i.e. -249CC) homozygotes had a significantly reduced SCCHN risk (adjusted odds ratio = 0.71, 95% confidence interval = 0.52-0.99) compared with the -606TT homozygotes. Stratification analyses showed that a reduced risk associated with the -606CC genotype was more pronounced in subgroups of non-smokers, non-drinkers, younger subjects (defined as ≤57 years), carriers of the TP53 Arg/Arg (rs1042522) genotype, patients with oropharyngeal cancer or late-stage SCCHN. Further in silico analysis revealed that the -249 T-to-C change led to a gain of a transcription factor-binding site. Additional functional analysis showed that the -249T-to-C change significantly enhanced transcriptional activity of the DEC1 promoter and the DNA-protein-binding activity. We conclude that the DEC1 promoter -249 T>C (rs2012775) polymorphism is functional, modulating susceptibility to SCCHN among non-Hispanic Whites.

The functional IGFBP7 promoter -418G>A polymorphism and risk of head and neck cancer

Insulin-like growth factor binding protein 7 (IGFBP7) functions mostly independent of the IGF signaling pathway and acts as a tumor suppressor in multiple cancers, but roles of IGFBP7 genetic variants in cancer remains unknown. In a hospital-based study of 1065 patients with squamous cell carcinoma of head and neck (SCCHN) and 1112 cancer-free controls of non-Hispanic whites, we investigated associations between two putatively functional IGFBP7 promoter single nucleotide polymorphisms (SNPs) (-702G>C, rs11573014 and -418G>A, rs4075349) and SCCHN risk. A significantly lower SCCHN risk was observed in those subjects carrying -418AG (adjusted OR=0.82, 95% CI=0.67-0.99) and -418AG+AA (adjusted OR=0.82, 95% CI=0.69-0.99) genotypes than those carrying the -418GG genotype, but not for the -702G>C SNP. However, those subjects carrying two common homozygous genotypes of these two SNPs (-418GG and -702GG) had an increased risk (adjusted OR=1.21, 95% CI=1.00-1.46) than did those carrying variant genotypes (-418AG+AA and -702CG+CC). This increased risk was more evident in subgroups of never smokers and subjects with oral cancer. Further functional analysis showed that the IGFBP7 -418A allele had significantly higher promoter and DNA-protein binding activities than did the G allele, suggesting a tumor suppressor role of this allelic change in the SCCHN etiology. We conclude that the functional variant -418G>C in the IGFBP7 promoter is associated with reduced risk of SCCHN, likely by enhancing the IGFBP7 promoter and DNA-protein binding activities. Larger studies are needed to validate our findings.