Fibroblast growth factor receptor 4 (FGFR4) is a member of a receptor tyrosine kinase family of enzymes involved in cell cycle control and proliferation. A common single nucleotide polymorphism (SNP) Gly388Arg variant has been associated with increased tumor cell motility and progression of breast cancer, head and neck cancer and soft tissue sarcomas. The present study evaluated the prognostic significance of FGFR4 in oral and oropharynx carcinomas, finding an association of FGFR4 expression and Gly388Arg genotype with tumor onset and prognosis.
Patients and Methods
DNA from peripheral blood of 122 patients with oral and oropharyngeal squamous cell carcinomas was used to determine FGFR4 genotype by PCR-RFLP. Protein expression was assessed by immunohistochemistry (IHC) on paraffin-embedded tissue microarrays.
Presence of allele Arg388 was associated with lymphatic embolization and with disease related premature death. In addition, FGFR4 low expression was related with lymph node positivity and premature relapse of disease, as well as disease related death.
Citation: Dutra RL, Carvalho MBd, Santos Md, Mercante AMdC, Gazito D, Cicco Rd, et al. (2012) FGFR4 Profile as a Prognostic Marker in Squamous Cell Carcinoma of the Mouth and Oropharynx. PLoS ONE 7(11): e50747. https://doi.org/10.1371/journal.pone.0050747
Editor: Muy-Teck Teh, Barts & The London School of Medicine and Dentistry, Queen Mary University of London, United Kingdom
Received: August 16, 2012; Accepted: October 24, 2012; Published: November 30, 2012
Copyright: © 2012 Dutra et al. This is an open-access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Funding: This work was supported by FAPESP grants n° 04/15022-0 and n° 04/12054-9 (Fundação de Apoio à Pesquisa de São Paulo, http://www.fapesp.br/). FAPESP is a Research support institution with the sole role of financing peer reviewed projects of the São Paulo State. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors have declared that no competing interests exist.
The fibroblast growth factor receptor (FGFRs) family comprises structurally related tyrosine kinase receptors (FGFR1-4) involved in signaling via interactions with fibroblast growth factors (FGFs), playing an important role in a wide range of biological processes, including differentiation, proliferation, cell motility and angiogenesis , . Most FGFs have mitogenic activity in a variety of systems, including cell growth, differentiation and migration . The proliferative capacity of FGFs is a function of FGFRs, to which they bind and through which they signal.
Deregulation in FGF/FGFR signaling has been implicated in human malignant diseases –. Functional studies demonstrated that FGFR4 interferes in signaling events leading to normal cell adhesiveness and corresponding invasive properties of pituitary tumors . Although the molecular basis of this function is still a matter of intense research, FGFR4 seems to play a role in a broader range of human cancers –.
A single nucleotide polymorphism (SNP) in exon 9 results in an amino acid change (substitution of a glycine residue for an arginine - Gly388Arg) within FGFR4 transmembrane domain and a positive correlation with prognostic parameters in several human cancers, including breast, colon, lung, prostate and head and neck cancers , –. Nevertheless, the association between the Gly388Arg genotype and cancer prognosis is not yet clear –, especially in head and neck squamous cell carcinomas (HNSCC).
HNSCC ranks among the top ten most common cancers worldwide, with a large incidence variation according to sex and geographical location . No biomarkers are currently available for HNSCC patients; prognosis depends largely on the stage at presentation, with the most important prognostic factor being the presence of neck node metastases .
To our knowledge, there is a lack of studies suggesting the prognostic significance of FGFR4 SNP genotype in HNSCC , . Streit et al  evaluated 104 paraffin-embedded tumors and concluded that high expression of FGFR4 together with the Arg388 allele is associated with poor clinical outcome. In comparison, da Costa Andrade et al  presented results claiming an association between the FGFR4 Arg388 allele and shortened survival in 75 HNSCC patients. Given the small number of patients with tumors of different primary sites evaluated in these studies and the controversial involvement of FGFR family in human cancers, we decided to further investigate the impact the Gly388Arg polymorphism in HNSCC.
The present study evaluated the prognostic significance of FGFR4 expression and the Gly388Arg genotype in oral and oropharynx carcinomas in regard to tumor onset and prognosis. Possible correlations with clinicopathological and prognosis parameters were also analyzed.
Materials and Methods
This study was approved by the Committee of Ethics in Research of the Heliopolis Hospital on 07/12/2005 (CEP # 402) and an informed consent was obtained from all patients enrolled.
Samples were collected by the Head and Neck Genome Project (GENCAPO), a collaborative consortium created in 2002 with more than 50 researchers from 9 institutions in São Paulo State, Brazil, whose aim is to develop clinical, genetic and epidemiological analysis of HNSCC. In this study, 122 DNA and 75 tumoral tissue samples were obtained and used for polymorphism Gly388Arg genotyping and immunohistochemical analysis of the FGFR4 gene, respectively, within a total of 125 patients with oral and oropharyngeal squamous cell carcinomas, surgically treated at the Head and Neck Surgery Department of Heliópolis Hospital and Arnaldo Vieira de Carvalho Câncer Hospital, São Paulo, Brazil, during the period of January/2002 to December/2007. The clinical follow-up was at least 48 months after surgery. Previous surgical treatment, distant metastasis, no removal of cervical lymph nodes and positive surgical margins were exclusion criteria. Histopathological slides were reviewed by a senior pathologists to confirm the diagnosis and select appropriate areas for Immunohistochemical analysis. Tumors were classified according to the TNM system . Clinical, epidemiological and pathological characteristics of tumors are described in Table 1.
Genomic DNA was extracted from peripheral blood samples of 122 patients as previously described . Genotypes were determined by polymerase chain reaction restriction fragment length polymorphism (PCR-RFLP). FGFR4 exon 9 was amplified using primers described by Bange et al,  and analyzed for Gly388Arg polimorfism (rs351855). Selected primers were 5′ - GAC CGC AGC AGC GCC CGA GGC CAG - 3′ and 5′ - AGA GGG AAG AGG GAG AGC TTC TG - 3′ (Life Technologies, Inc®, São Paulo, SP, Brazil), which produce a 168-base pair (bp) fragment. PCR conditions were: a 25-µL reaction mixture containing 200 ng of genomic DNA, 10 mM Tris-HCl (pH 8.3), 50 mM KCl, 200 µM of each deoxyribonucleoside 5′ triphosphates, 1.5 mM de MgCl2, 1 U Taq DNA polimerase (Life Technologies, Inc®, Rockville, MD, USA) and 25 pmol of each primer. PCR initiated with a melting step of 5 minutes at 94°C, followed by 35 cycles of 1 minute at 94°C, 1 minute at 58°C and 1 minute at 72°C. PCR products were digested overnight with BstNI following the manufacturer’s instructions (New England Biolabs®, Berverly, MA, USA). Restriction fragments were resolved on a 12% non-denaturing polyacrylamide gel. SNP Arg388 in FGFR4 gene was characterized by two distinctive fragments of 82 and 27 bp, whereas the FGFR4 Gly388 wild-type allele was identified by a single fragments of 109bp.
Tissue microarrays were made using buffered formalin-fixed paraffin-embedded tissue sections from 75 primary oral and oropharyngeal squamous cell carcinomas treated at the Head and Neck Surgery Department of Heliópolis Hospital, São Paulo, SP, were used for immunohistochemistry (IHC) analysis. Histological characterization of all samples was done by Hematoxylin and Eosin staining, followed by immunohistochemistry analysis of tissue microarrays (TMA). Two 1 mm cylinders were used to represent each sample in the TMA slide (Beecher Instruments®, Silver Spring, MD, USA).
Anti-FGFR4 monoclonal antibody (Santa Cruz Biotechnology®, USA) was used in the IHC reaction, at a 1∶400 dilution –. Positive (lung control) and negative controls (absence of primary or secondary antibody) were used for reaction quality control. Sample scoring was performed by semi-quantitative microscopic analysis, considering the number of stained tumor cells and signal intensity. Two spots were evaluated for each sample and a mean score was calculated. Considering the percentage of FGFR4 immune-positive tumor cells, a score of 1 was given when ≤10% of cells were positive; 2 when 10–50% and 3 when ≥50% of cells were positive. Signal intensity was scored as negative (0), weak (1), moderate (2) and strong (3). Both scores were multiplied ,  and the resulting score was used to categorize FGFR4 expression as negative (≤3), low (>3 and <7) and high (>7).
The chi square and Fisher exact tests were used for association analysis and confirmation was obtained by the Lilliefors test (significance considered when p<0.05). Multivariate logistic regression was used to obtain odds ratio (OR) and confidence intervals (CI≥95%). Survival was calculated by the number of months between surgery and death for each patient or the last appointment in case the patient was alive. In order to calculate disease-free survival, the time endpoint was the date of disease relapse. The Kaplan-Meier model was used for survival analysis, using the Wilcoxon p-value and the Cox Proportional Hazards to adjust p-values and obtain hazard ratio (HR). Statistical calculations were performed using the Epi Info® v3.4.3, 2007 and Statsoft Statistica® v184.108.40.206 softwares. Genotype correlation with certain biological variables such as age and gender were not analyzed because we could not find biological justifications for these analyses.
FGFR4 Gly388Arg Genotype
Regarding the SNP Gly388Arg, 66 (54.1%) cases were genotyped as Gly/Gly (wild type allele), 47 (38.5%) as Gly/Arg and 26 (7.4%) as Arg/Arg. Allele and genotype frequencies were in Hardy-Weinberg equilibrium.
The Gly388Arg polymorphism did not show a significant association with tumor size (p = 0.993), positive lymph nodes (p = 0.262) and differentiation grade (p = 0.700), but was significantly associated with lymphatic embolization (p = 0.022, Table 1). Multivariate analysis showed that presence of at least one allele Arg388 is an independent marker for lymphatic embolization (OR = 3.88, CI = 1.14–13.13, Table 2).
The Gly388Arg polymorphism was significantly associated with disease specific death (p = 0.008, Table 1) and multivariate analysis showed that presence of Arg388 allele is an independent death risk factor, increasing risk 6 times when compared to absence of this allele (OR = 6.88, CI = 1.64–28.87, Table 2). Nevertheless, the Gly388Arg polymorphism was not correlated with disease relapse (p = 0.110, Table 1).
Although disease-free survival did not show a significant association with FGFR4 polymorphisms (p = 0.130), presence of the Arg388 allele was associated with disease specific survival (p = 0.020). According to a 36 month after surgery follow up, approximately 25% of cases with the Gly/Gly genotype died of disease specific causes, as compared to approximately 55% of deaths in patients with the Arg388 allele (Figure 1b). Multivariate analysis revealed that the presence of Arg388 allele is an independent marker of disease specific death, with a 3 fold increased risk when compared with absence of this allele (HR = 3.26, CI = 1.40–7.58, Table 3).
a. and b.: Disease-free survival and disease specific survival according to FGFR4 Gly388Arg polymorphism; c. and d.: Disease-free survival and disease specific survival according to FGFR4 expression; e. and f.: Disease-free survival and disease specific survival according to FGFR4 profile.
FGFR4 expression was detected in 75 tumors, being classified as high in 26 (34.7%) samples and low in 49 (65.3%) (Figure 2a and 2b, respectively. No samples were negative for FGFR4 expression. FGFR4 expression did not show a significant association with tumor characteristics such as size (p = 0.051) and differentiation grade (p = 0.062), but was significantly associated with positive lymph nodes (p = 0.036, Table 1). Multivariate analysis showed that low FGFR4 expression is an independent marker for lymph node positivity (OR = 3.81, CI = 1.12–12.98, Table 2). FGFR4 expression did significantly correlate with disease relapse (p = 0.037) and disease specific death (p = 0.013, Table 1). Multivariate analysis showed that FGFR4 low expression is an independent marker of disease relapse and disease specific death, representing an increased risk of over 6 times for both, in relation to high expression (respectively, OR = 6.73, CI = 1.63–27.85 and OR = 6.86, CI = 1.45–32.40, Table 2).
(a) strong FGFR4 expression; (b) weak FGFR4 expression. Magnification was 400×.
Disease-free and disease specific survival were significantly correlated with FGFR4 expression (p = 0.044 and p = 0.034, respectively). According to a 24 month after surgery follow up, approximately 60% of cases with low expression died of disease specific causes, as compared to approximately 30% of deaths in patients with high expression of FGFR4 (Figure 1c). Additionally, according to a 36 month after surgery follow up, approximately 50% of cases with low expression presented disease relapse, as compared to approximately 20% of recurrence in patients with high expression of FGFR4 (Figure 1d). Multivariate analysis revealed that a low expression of FGFR4 is an independent marker for a faster disease relapse and disease specific death, with a 3 fold increased risk when compared to high expression (respectively, HR = 3.26, CI = 1.44–7.37 and HR = 3.26, CI = 1.21–8.74, Table 3).
FGFR4 Risk Profiles
In an attempt to combine genotype and expression results, we categorized the FGFR4 profile in three classes: low risk (high expression and absence of Arg388 allele); intermediate risk (high expression and presence of Arg388 allele or low expression and absence of Arg388 allele) and high risk (low expression and presence of Arg388 allele). Frequencies of each FGFR4 profile were 11 (15.5%), 43 (60.6%) and 17 (23.9%), respectively for low, intermediate and high risk.
Disease-free and disease specific survival were significantly correlated with FGFR4 profiles (p = 0.002 and p<0.001, respectively). According to a 24 month after surgery follow up, all cases classified as high risk had relapsed and approximately 80% died of disease specific causes, as compared to approximately 30% of recurrence and no deaths of patients classified as low risk (Figure 1e and 1f). Multivariate analysis revealed that the high risk category is an independent marker for a faster disease relapse and disease specific death, with a 4.5 and 13 fold increased risk, respectively, when compared to the low risk profile (HR = 4.50, CI = 1.37–14.82 and HR = 12.90, CI = 1.54–107.69).
Discussion and Conclusions
FGFR4 belongs to the family of fibroblast growth factor receptors (FGFR1-4), transmembrane proteins with tyrosine kinase activity. Multiple signal transduction cascades are initiated after binding of FGF ligand to the extracellular domain of the receptor, ultimately resulting in gene expression changes , . FGFRs have been shown to play important roles in several processes of embryonic development and tissue homeostasis. Their abnormal expression or mutation can cause diverse pathologies, ranging from morphogenetic disorders to cancer . This is a group of proteins of considerable interest in cancer biology, because they regulate essential processes, including mitogenic and angiogenic activity, having important roles in cell differentiation, development, proliferative signaling and motility , , .
Although the presence of FGFR4 Arg388 allele has been shown to indicate a poor prognosis in several tumors , , , , the mechanism by which it affects cancer progression remains unclear. This might be related to signaling cascades that control cell-matrix adhesion and angiogenesis .
Although some mechanisms have been described in the literature, the influence of Gly388Arg polymorphism in tumor aggressiveness may differ in specific tumors.
Our study revealed that low FGFR4 expression in the presence of Arg388 allele is associated with worse survival in patients with oral and oropharyngeal squamous cell carcinoma.
Seitzer, et al,  verified, using an animal model, that low protein expression, even in the presence of FGFR4 Arg388 polymorphism, is related to increased pathway activity. This may be explained by the activation of alternative proteins in the signaling cascade or other cascades.
Recently, it has been reported that the presence of polymorphism Gly388Arg is associated with increased cancer risk and progression of pituitary tumors through recruitment of STAT3 signaling cascade. Activation of this cascade can result in deregulation of cell proliferation and apoptosis, leading to tumor progression . Signaling hiperactivation by specific mutations depends on their resistance to negative feedback loops . In addition, several ubiquitylation proteins bind directly to RTKs altering receptor activation . RTK Ubiquitylation may promote receptor degradation creating an important negative feedback mechanism , .
FGFR4 Arg388 has not been consider an oncogene per se, but rather collaborate with oncogenes involved in cell motility and invasiveness .
Our findings may have important therapeutic implications, because inhibition of one intracellular pathway may lead to activation of parallel signaling pathways, thereby decreasing the effectiveness of single-agent targeted therapies . In support of our hypothesis, the Arg388 allele was associated with resistance to adjuvant therapy in breast cancer .
Ansell et al, , were the first researchers to report that the Gly388 allele showed a significantly higher risk of developing cancer, proposing the Gly388 allele as a risk allele for head and neck cancer.
In contrast, Streit et al,  reported that in head and neck SCC, expression of Gly388 FGFR4 had no impact on disease progression. In another study, da Costa Andrade et al,  observed that the presence of at least one Arg allele was significantly correlated with reduced overall survival and an increased mortality risk of 2.2. In a recent study, Tanuma et al,  reported that FGFR4 Arg388 allele was strongly associated with poor prognosis.
In the present study, we have shown that allele Arg388 is associated with lymphatic embolization and premature disease related death. Furthermore, low expression of FGFR4 is related to lymph node positivity and premature disease relapse and death in patients with SCC of the mouth and oropharynx.
Based on these results, we have classified patients with low FGFR4 expression/Arg388 as high risk for relapse and death. In contrast, high FGFR4 expression/Arg388-negative patients were considered at low risk. In conclusion, we propose FGFR4 profile as a novel prognostic marker in SCC of the mouth and oropharynx.
The GENCAPO (Head and Neck Genome) Project members are the following: Amar A8, Arap SS6, Araújo NSS6, Araújo-Filho V6, Bandeira CM4, Braconi MA4, Brandão LG6, Brandão RM11, Canto AL4, Carmona-Raphe J2, Carvalho MB8, Cerione M5, Cernea CR6, Chagas MJ4, Chedid H8, Cicco R5, Cominato ML5, Correa PMS4, Correia LA8, Costa A12, Cunha BR2, Curioni OA8, Cury PM7, Dias THG3, Dias-Neto E3, Durazzo M6, Ferraz AR6, Figueiredo DLA9, Figueiredo RO12, Fortes CS12, Franzi SA8, Frizzera APZ7, Fukuyama EE5, Gallo J6, Gazito D8, Góis-Filho JF5, Guimarães PEM6, Inamine R12, Kaneto CM11, Lehn CN8, Leopoldino AM15, López RVM12, Macarenco R4, Magalhães MR8, Magalhães RP6, Mamede RCM9, Mendes GS5, Meneses C4, Mercante AMC8, Michaluart-Junior P6, Montenegro FLM6, Moreira-Filho CA1, Moyses RA6, Nóbrega FG4, Nóbrega MP4, Nunes FD13, Ojopi EPB3, Okamoto OK14, Paiva R5, Pinheiro DG11, Polachini GM2, Ramos O6, Rapoport A8, Rodini CO13, Rodrigues AN12, Rodrigues RV2, Rodrigues-Lisoni FC2, Rossi L8, Santos ARD11, Santos M8, Serafini LN10, Settani F5, Severino P1, Silva AMA18, Silva C6, Silva FAM15, Silva IT11, Silva Jr WA11, Silva MJ5, Silva-Filho GB6, Silveira NJF16, Smith RB6, Souza SCOM13, Souza TB8, Stabenow E6, Tajara EH2, Takamori JT8, Tarlá MVC11, Tavares MR6, Turcano R6, Valentim PJ5, Vidotto A2, Volpi EM6, Wünsch-Filho V12, Xavier FCA13, Yamagushi F5, Zago MA17.
1Instituto de Ensino e Pesquisa Albert Einstein, São Paulo; 2Departamento de Biologia Molecular, Faculdade de Medicina de São José do Rio Preto; 3Departamento e Instituto de Psiquiatria, Faculdade de Medicina, Universidade de São Paulo (USP), São Paulo; 4Departamento de Biociências e Diagnóstico Bucal, Faculdade de Odontologia, Universidade Estadual Paulista, São José dos Campos, São Paulo, 5Serviço de Cirurgia de Cabeça e Pescoço, Instituto do Câncer Arnaldo Vieira de Carvalho, São Paulo; 6Departamento de Cirurgia de Cabeça e Pescoço, Faculdade de Medicina, USP, São Paulo; 7Departamento de Patologia, Faculdade de Medicina de São José do Rio Preto; 8Hospital Heliópolis, São Paulo; 9Serviço de Cirurgia de Cabeça e Pescoço, Faculdade de Medicina de Ribeirão Preto, USP; 10Departamento de Patologia, Faculdade de Medicina de Ribeirão Preto, USP; 11Departamento de Genética, Faculdade de Medicina de Ribeirão Preto, USP; 12Departamento de Epidemiologia, Faculdade de Saúde Pública, USP, São Paulo; 13Departamento de Estomatologia, Faculdade de Odontologia da USP, São Paulo; 14Departamento de Neurologia/Neurocirurgia, UNIFESP, São Paulo; 15Departamento de Análises Clínicas, Toxicológicas e Bromatológicas, Faculdade de Ciências Farmacêuticas de Ribeirão Preto, USP; 16Instituto de Pesquisa e Desenvolvimento, UNIVAP, São José dos Campos; 17Departamento de Clínica Médica, Faculdade de Medicina de Ribeirão Preto, USP, SP, Brasil; 18Universidade Federal do Espírito Santo.
Conceived and designed the experiments: AMADS. Performed the experiments: RLD. Analyzed the data: RLD DG IDL AMADS. Contributed reagents/materials/analysis tools: AMDCM GENCAPO EHT AMADS. Wrote the paper: RLD IDL AMADS. Provided samples: RDC GENCAPO EHT.
- 1. Burke D, Wilkes D, Blundell TL, Malcolm S (1998) Fibroblast growth factor receptors: lessons from the genes. Trends Biochem Sci 23: 59–62.
- 2. Powers CJ, McLeskey SW, Wellstein A (2000) Fibroblast growth factors, their receptors and signaling. Endocr Relat Cancer 7: 165–197.
- 3. Jeffers M, LaRochelle WJ, Lichenstein HS (2002) Fibroblast growth factors in cancer: therapeutic possibilities. Expert Opin Ther Targets 6: 469–482.
- 4. Cappellen D, de Oliveira C, Ricol D, de Medina S, Bourdin J, et al. (1999) Frequent activating mutations of FGFR3 in human bladder and cervix carcinomas. Nat Genet 23: 18–20.
- 5. Jebar AH, Hurst CD, Tomlinson DC, Johnston C, Taylor CF, et al. (2005) FGFR3 and Ras gene mutations are mutually exclusive genetic events in urothelial cell carcinoma. Oncogene 24: 5218–5225.
- 6. López-Knowles E, Hernández S, Malats N, Kogevinas M, Lloreta J, et al. (2006) PIK3CA mutations are an early genetic alteration associated with FGFR3 mutations in superficial papillary bladder tumors. Cancer Res 66: 7401–7404.
- 7. Ezzat S, Zheng L, Zhu XF, Wu GE, Asa SL (2002) Targeted expression of a human pituitary tumor-derived isoform of FGF receptor-4 recapitulates pituitary tumorigenesis. J Clin Invest 109: 69–78.
- 8. Bange J, Prechtl D, Cheburkin Y, Specht K, Harbeck N, et al. (2002) Cancer progression and tumor cell motility are associated with the FGFR4 Arg(388) allele. Cancer Res 62: 840–847.
- 9. Streit S, Bange J, Fichtner A, Ihrler S, Issing W, et al. (2004) Involvement of the FGFR4 Arg388 allele in head and neck squamous cell carcinoma. Int J Cancer 111: 213–217.
- 10. Morimoto Y, Ozaki T, Ouchida M, Umehara N, Ohata N, et al. (2003) Single nucleotide polymorphism in fibroblast growth factor receptor 4 at codon 388 is associated with prognosis in high-grade soft tissue sarcoma. Cancer 98: 2245–2250.
- 11. Spinola M, Leoni V, Pignatiello C, Conti B, Ravagnani F, et al. (2005) Functional FGFR4 Gly388Arg polymorphism predicts prognosis in lung adenocarcinoma patients. J Clin Oncol 23: 7307–7311.
- 12. da Costa Andrade V, Parise O, Hors C, Martins P, Silva A, et al. (2007) The fibroblast growth factor receptor 4 (FGFR4) Arg388 allele correlates with survival in head and neck squamous cell carcinoma. Exp Mol Pathol 82: 53–57.
- 13. Frullanti E, Berking C, Harbeck N, Jézéquel P, Haugen A, et al. (2011) Meta and pooled analyses of FGFR4 Gly388Arg polymorphism as a cancer prognostic factor. Eur J Cancer Prev 20: 340–347.
- 14. Marmé F, Hielscher T, Hug S, Bondong S, Zeillinger R, et al. (2012) Fibroblast growth factor receptor 4 gene (FGFR4) 388Arg allele predicts prolonged survival and platinum sensitivity in advanced ovarian cancer. Int J Cancer 131: E586–E591.
- 15. Becker N, Nieters A, Chang-Claude J (2003) The fibroblast growth factor receptor gene Arg388 allele is not associated with early lymph node metastasis of breast cancer. Cancer Epidemiol Biomarkers Prev 12: 582–583.
- 16. Jezequel P, Campion L, Joalland MP, Millour M, Dravet F, et al. (2004) G388R mutation of the FGFR4 gene is not relevant to breast cancer prognosis. Br J Cancer 90: 189–193.
- 17. Spinola M, Leoni VP, Tanuma J, Pettinicchio A, Frattini M, et al. (2005) FGFR4 Gly388Arg polymorphism and prognosis of breast and colorectal cancer. Oncol Rep 14: 415–419.
- 18. Streit S, Mestel DS, Schmidt M, Ullrich A, Berking C (2006) FGFR4 Arg388 allele correlates with tumour thickness and FGFR4 protein expression with survival of melanoma patients. Br J Cancer 94: 1879–1886.
- 19. Ragin CC, Modugno F, Gollin SM (2007) The epidemiology and risk factors of head and neck cancer: a focus on human papillomavirus. J Dent Res 86: 104–114.
- 20. Layland MK, Sessions DG, Lenox J (2005) The influence of lymph node metastasis in the treatment of squamous cell carcinoma of the oral cavity, oropharynx, larynx, and hypopharynx: N0 versus N+. Laryngoscope 115: 629–632.
- 21. Sobin LH, Wittekind C (2002) TNM Classification of Malignant Tumours. sixth ed. John Wiley & Sons: New Jersey.
- 22. Miller SA, Dykes DD, Polesky HF (1988) A simple salting out procedure for extracting DNA from human nucleated cells. Nucleic Acids Res 16: 1215.
- 23. Rimm DL, Camp RL, Charette LA, Olsen DA, Provost E (2001) Amplification of tissue by construction of tissue microarrays. Exp Mol Pathol 70: 255–264.
- 24. Hedvat CV, Hegde A, Chaganti RS, Chen B, Qin J, et al. (2002) Application of tissue microarray technology to the study of non-Hodgkin’s and Hodgkin’s lymphoma. Hum Pathol 33: 968–974.
- 25. Hsu FD, Nielsen TO, Alkushi A, Dupuis B, Huntsman D, et al. (2002) Tissue microarrays are an effective quality assurance tool for diagnostic immunohistochemistry. Mod Pathol 15: 1374–1380.
- 26. Soini Y, Kahlos K, Puhakka A, Lakari E, Saily M, et al. (2000) Expression of inducible nitric oxide synthase in healthy pleura and in malignant mesothelioma. Br J Cancer 3: 880–886.
- 27. Campos AH, Aldred VL, Ribeiro KC, Vassallo J, Soares FA (2009) Role of immunoexpression of nitric oxide synthases by Hodgkin and Reed-Sternberg cells on apoptosis deregulation and on clinical outcome of classical Hodgkin lymphoma. Mol Cell Biochem 321: 95–102.
- 28. Dailey L, Ambrosetti D, Mansukhani A, Basilico C (2005) Mechanisms underlying differential responses to FGF signaling. Cytokine Growth Factor Rev 16: 233–247.
- 29. Triantis V, Saeland E, Bijl N, Oude-Elferink RP, Jansen PL (2010) Glycosylation of fibroblast growth factor receptor 4 is a key regulator of fibroblast growth factor 19-mediated down-regulation of cytochrome P450 7A1. Hepatology 52: 656–666.
- 30. Liwei L, Chunyu L, Jie L, Ruifa H (2011) Association between fibroblast growth factor receptor-4 gene polymorphism and risk of prostate cancer: a meta-analysis. Urol Int 87: 159–164.
- 31. Olson DC, Deng C, Hanahan D (1988) Fibroblast growth factor receptor 4, implicated in progression of islet cell carcinogenesis by its expression profile, does not contribute functionally. Cell Growth Differ 9: 557–564.
- 32. Cavallaro U, Niedermeyer J, Fuxa M, Christofori G (2007) N-CAM modulates tumour-cell adhesion to matrix by inducing FGF-receptor signaling. Nat Cell Biol 3: 650–657.
- 33. Shah RN, Ibbitt JC, Alitalo K, Hurst HC (2002) FGFR4 overexpression in pancreatic cancer is mediated by an intronic enhancer activated by HNF1alpha. Oncogene 21: 8251–8261.
- 34. Xu B, Tong N, Chen SQ, Hua LX, Wang ZJ, et al. (2011) FGFR4 Gly388Arg polymorphism contributes to prostate cancer development and progression: a meta-analysis of 2618 cases and 2305 controls. BMC Cancer 11: 84.
- 35. Tanuma J, Izumo T, Hirano M, Oyazato Y, Hori F, et al. (2010) FGFR4 polymorphism, TP53 mutation, and their combinations are prognostic factors for oral squamous cell carcinoma. Oncol Rep 23: 739–744.
- 36. Seitzer N, Mayr T, Streit S, Ullrich A (2010) A single nucleotide change in the mouse genome accelerates breast cancer progression. Cancer Res 70: 802–812.
- 37. Tateno T, Asa SL, Zheng L, Mayr T, Ullrich A, Ezzat S (2011) The FGFR4-G388R polymorphism promotes mitochondrial STAT3 serine phosphorylation to facilitate pituitary growth hormone cell tumorigenesis. Plos Genet 7: e1002400.
- 38. Chandarlapaty S, Sawai A, Scaltriti M, Rodrik-Outmezguine V, Grbovic-Huezo O, et al. (2011) AKT inhibition relieves feedback suppression of receptor tyrosine kinase expression and activity. Cancer Cell 19: 58–71.
- 39. Hurley JH, Lee S, Prag G (2006) Ubiquitin-binding domains. Biochem J 399: 361–372.
- 40. Kirkin V, Dikic I (2007) Role of ubiquitin- and Ubl-binding proteins in cell signaling. Curr Opin Cell Biol 19: 199–205.
- 41. Lemmon MA, Schlessinger J (2010) Cell signaling by receptor tyrosine kinases. Cell 141: 1117–1134.
- 42. Turke AB, Song Y, Costa C, Cook R, Arteaga CL, et al. (2012) MEK inhibition leads to PI3K/AKT activation by relieving a negative feedback on ERBB receptors. Cancer Res 72: 3228–3237.
- 43. Thussbas C, Nahrig J, Streit S, Bange J, Kriner M, et al. (2006) FGFR4 Arg388 allele is associated with resistance to adjuvant therapy in primary breast cancer. J Clin Oncol 24: 3747–3755.
- 44. Ansell A, Farnebo L, Grénman R, Roberg K, Thunell LK (2009) Polymorphism of FGFR4 in cancer development and sensitivity to cisplatin and radiation in head and neck cancer. Oral Oncol 45: 23–29.