Genetic alterations in head and neck squamous cell carcinomas

Integrated High-Throughput Bioinformatics (Microarray, RNA-Seq, and RNA Interaction) and qRT-PCR Investigation of BMPR1B Axis as a Potential Diagnostic Biomarker of Isfahan Breast Cancer

Background

According to the bioinformatics analyses and previous studies, bone morphogenetic protein receptor type 1B (BMPR1B) dysregulation could remarkably affect breast cancer (BC) status as a potential biomarker and tumor suppressor. Therefore, the analysis of the expression level of BMPR1B and other relevant biological factors such as microRNAs, long non-coding RNAs, downstream proteins in the relevant signaling pathways, and finding the accurate biological mechanism of BMPR1B could be helpful for a better understanding of BC pathogenicity and discovering the new treatment methods and drugs.

Materials and Methods

R Studio software (4.0.2) was used for microarray data analyses. GSE31448 dataset was downloaded by GEOquery package and analyzed by limma package. STRING and miRWalk online databases and Cytoscape software were used for interaction analyses. Quantitative measurement of BMPR1B expression level was performed by qRT-PCR experiment.

Result

Microarray and real-time PCR analysis revealed that BMPR1B has a significant downregulation in the transforming growth factor (TGF)-beta and bone morphogenic protein (BMP) signaling pathways in BC samples. BMPR1B is a potential diagnostic biomarker, regulated by hsa-miR-181a-5p. Also, BMPR1B regulates the function of BMP2, BMP6, SMAD4, SMAD5, and SMAD6 proteins.

Discussion

BMPR1B have a significant role in the development of BC by regulating the potential proteins' function, playing the diagnostic biomarker role, and regulation of TGF-beta and BMP signaling pathways. The high amount of BMPR1B protein helps in increasing the survival rate of the patients.

HER 2/neu Overexpression in Oral Squamous Cell Carcinoma and Its Clinico-Pathological Association at a Tertiary Care Center in Eastern India

Human epidermal growth factor receptor 2/neu (HER2/neu) is known to serve as a prognostic and predictive biomarker in several cancers such as breast, gastric and ovarian cancers. In head and neck squamous cell carcinoma, HER2/neu expression is seen but in a fluctuated manner. Hence, its role as a prognostic factor in oral squamous cell carcinoma (OSCC) needs evaluation. To determine the HER 2/neu overexpression in OSCC patients and its association with clinical and pathological parameters. 74 patients of OSCC treated between 2016 and 2018 were included in the study. Immunohistochemistry was done on tissue samples from these patients and HER2/neu expression was measured. Both biopsy and resected specimens were considered for the study. Out of 74 patients, 47.3% (35) were operated and 52.7% (39) were not operated due to loss to follow-up. No significant association was found (p = 0.636, OR = 0.68, CI = 0.14-3.34) between lymphovascular invasion (LVI) and HER2/neu expression. Similar results were seen for perineural invasion (PNI) (p = 0.490, OR = 0.53, CI = 0.88-3.24), depth of invasion (p = 0.21), grade of tumor (p = 0.214), clinical-stage (p = 0.511) and pathological stage (p = 0.091). No significant association existed between HER2/neu expression and LVI, PNI, clinical-stage, the grade of tumor and the pathological stage of oral squamous cell carcinoma.

Multidimensional Mutational Profiling of the Indian HNSCC Sub-Population Provides IRAK1, a Novel Driver Gene and Potential Druggable Target

Head and neck squamous cell carcinomas (HNSCC) include heterogeneous group of tumors, classified according to their anatomical site. It is the sixth most prevalent cancer globally. Among South Asian countries, India accounts for 40% of HNC malignancies with significant morbidity and mortality. In the present study, we have performed exome sequencing and analysis of 51 Head and Neck squamous cell carcinoma samples. Besides known mutations in the oncogenes and tumour suppressors, we have identified novel gene signatures differentiating buccal, alveolar, and tongue cancers. Around 50% of the patients showed mutation in tumour suppressor genes TP53 and TP63. Apart from the known mutations, we report novel mutations in the genes AKT1, SPECC1, and LRP1B, which are linked with tumour progression and patient survival. A highly curated process was developed to identify survival signatures. 36 survival-related genes were identified based on the correlation of functional impact of variants identified using exome-seq with gene expression from transcriptome data (GEPIA database) and survival. An independent LASSO regression analysis was also performed. Survival signatures common to both the methods led to identification of 4 dead and 3 alive gene signatures, the accuracy of which was confirmed by performing a ROC analysis (AUC=0.79 and 0.91, respectively). Also, machine learning-based driver gene prediction tool resulted in the identification of IRAK1 as the driver (p-value = 9.7 e-08) and also as an actionable mutation. Modelling of the IRAK1 mutation showed a decrease in its binding to known IRAK1 inhibitors.

Human epidermal growth factor receptor 2 neu expression in head and neck squamous cell cancers and its clinicopathological correlation: Results from an Indian cancer center

Background

Human epidermal growth factor receptor 2 (HER2)/neuprotooncogene (neu) is a proven molecular prognostic marker in breast, ovarian, gastric, and ovarian cancers. In head-and-neck cancers, varied expression is documented and therefore its prognostic role is debatable.

Aim of the Study

To find the rate of overexpression of HER2/neu in head-and-neck cancers and to understand its prognostic role by evaluating its association with nodal stage and overall stage of the patient.

Methodology

A total of 70 surgically resected cases of head-and-neck cancers were evaluated for expression of HER2/neu by immunohistochemistry. Scoring was done according to the American Society of Clinical Oncologists/College of American Pathologistsguidelines for Her2/neu testing in breast cancer.

Results

Of the 70 cases studied, 57 were of oral cavity and 13 were laryngeal squamous cell cancers and 14 (20%) were Her2/neu positive. On correlating the expression of HER2/neu in T1/T2 (41 cases) versus T3/T4 (27 cases), the P value was found to be 0.8273 which was statistically insignificant. Furthermore, no statistically significant difference in expression of HER2/neu was found in between node negative and node positive cases (49 vs. 19 cases, respectively), with P = 0.512.

Conclusion

In the current settings, HER2/neu is not found to be a prognostic marker in head-and-neck cancers. Standard immunohistochemistry staining protocols need to be established like in breast cancers to aid uniform reporting and further evaluate the role of this important protooncogene in head-and-neck cancers.

Impact of HPV infection on oral squamous cell carcinoma

BACKGROUND

Head and neck squamous cell carcinomas (HNSCC) are often divided by their aetiology. Noxae associated collectives are compared with the human papilloma virus (HPV)-associated group, whereas different localisations of oral (OSCC) and oropharyngeal (OPSCC) squamous cell carcinomas are mostly discussed as one single group. Our aim was to show that classification by aetiology is not appropriate for OSCC.

RESULTS

HPV DNA was detected by PCR in 7 (3.47%) patients, and we identified 12 (5.94%) positive (+) cases by p16INK4a immunostaining. Only 4 (1.98%) of the p16INK4a+ cases were + for HPV using PCR. Our homogenous collective of OSCC allowed us to compare HPV+ and HPV negative (-) patients without creating bias for tumour localisation, age, gender or tumour stage.

MATERIALS AND METHODS

After testing OSCC samples for HPV positivity, we compared the results of two commonly used HPV detection methods, p16INK4a immunostaining and HPV DNA-related PCR, on 202 OSCC patients. HPV subtypes were determined with an HPV LCD Array Kit. Clinicopathological features of the patients were analysed, and the disease specific survival rates (DSS) for HPV+ and HPV- patients were obtained.

CONCLUSIONS

p16INK4a immunostaining is a not a reliable HPV detection method for OSCC. Positive p16INK4a immunostaining did not agree with + results from PCR of HPV DNA. Furthermore, the influence of HPV-related oncogenic transformation in OSCC is overestimated. The significance of HPV infection remains clinically unclear, and its influence on survival rates is not relevant to OSCC cases.

Omics-based molecular techniques in oral pathology centred cancer: prospect and challenges in Africa

BACKGROUND

The completion of the human genome project and the accomplished milestones in the human proteome project; as well as the progress made so far in computational bioinformatics and "big data" processing have contributed immensely to individualized/personalized medicine in the developed world.

MAIN BODY

At the dawn of precision medicine, various omics-based therapies and bioengineering can now be applied accurately for the diagnosis, prognosis, treatment, and risk stratification of cancer in a manner that was hitherto not thought possible. The widespread introduction of genomics and other omics-based approaches into the postgraduate training curriculum of diverse medical and dental specialties, including pathology has improved the proficiency of practitioners in the use of novel molecular signatures in patient management. In addition, intricate details about disease disparity among different human populations are beginning to emerge. This would facilitate the use of tailor-made novel theranostic methods based on emerging molecular evidences.

CONCLUSION

In this review, we examined the challenges and prospects of using currently available omics-based technologies vis-à-vis oral pathology as well as prompt cancer diagnosis and treatment in a resource limited setting.

Oncogenes and tumor suppressor genes in squamous cell carcinoma of the tongue in young patients

Objectives

The occurrence of squamous cell carcinoma of the tongue (SCCT) of young patients increased. There are still controversies about patient prognosis. The underlying molecular mechanisms remain unclear.

Methods

276 patients (66 ≤45, 210 >45 years) with SCCT were included. Clinical parameters and survival data were assessed. Oncogenes and tumor suppressors were analyzed via immunohistochemistry (p53, CXCR4, p16, EGFR) and qPCR (CDK4, CDKN2A, TP53, MDM2, AKT1, PIK3CA, NRAS, HRAS, KRAS, HGF, MET, EGF, ATM, BRCA1, E2F1, FHIT, RUNX3, STK11, BCL2, CTNNB1).

Results

The median overall survival was 142 (≤45 years) and 34 months (>45 years) (p < 0.0001; HR [95%CI]: 0.37 [0.30–0.58]). Disease specific survival in patients ≤45 years was with 181 months significantly higher than in patients >45 years (p < 0.0001; HR [95%CI]: 0.33 [0.26–0.57]). Immunhistochemistry visualized a comparable expression of analyzed proteins. QPCR demonstrated in patients ≤45 years a higher expression of genes that are associated with carcinogenesis (CTNNB1, STK11, CDKN2A, HGF, MET) as well as tumor suppressors that constitute an enhanced radio-sensitivity (ATM, BRCA1E2F1, FHIT).

Conclusion

Derogation of the WNT-CTNNB1-STK11 and CDKN2A-HGF-MET pathway can constitute the carcinogenesis, while the higher expression of radio-sensitizers ATM, BRCA1E2F1 and FHIT can explain the better OS/DSS in young patients.

Establishment of a novel human papillomavirus-negative and radiosensitive head and neck squamous cell carcinoma cell line

BACKGROUND

The purpose of this study was to develop a CMCSCC-1 cell line for head and neck cancer research into new therapies for head and neck squamous cell carcinoma (HNSCC).

METHODS

The CMCSCC-1 cell line was isolated from a primary oral tongue tumor specimen of a female patient. Tumor cells were evaluated for biomarkers expression by Western blots, reverse transcriptase-polymerase chain reaction (RT-PCR), fluorescence activated cell sorter, and immunostaining. Cell proliferation in response to radiation was measured by the WST-8 assay.

RESULTS

The characterization analyses revealed a typical epithelial morphology; a doubling time of approximately 24 hours, high tumorigenicity in immunodeficient mice, and upregulated biomarkers. CMCSCC-1 cells were negative for human papillomavirus (HPV) infection, but more sensitive to radiation compared with those FaDu cell lines.

CONCLUSION

CMCSCC-1, a novel oral tongue SCC cell line, was established. It will help in the elucidation of the molecular pathogenesis of HPV-negative radiosensitive tumors. © 2015 Wiley Periodicals, Inc. Head Neck 38: E542-E551, 2015.

High-risk human papillomavirus detection in oropharyngeal, nasopharyngeal, and oral cavity cancers: comparison of multiple methods

IMPORTANCE

Human papillomaviruses are now recognized as an etiologic factor in a growing subset of head and neck cancers and have critical prognostic importance that affects therapeutic decision making. There is no universally accepted gold standard for high-risk HPV (hrHPV) assessment in formalin-fixed, paraffin-embedded (FFPE) tissue specimens, nor is there a clear understanding of the frequency or role of hrHPV in sites other than oropharynx.

OBJECTIVE

To determine the optimal assessment of hrHPV in FFPE head and neck tumor tissue specimens.

DESIGN, SETTING, PARTICIPANTS

In the setting of a large Midwestern referral center, assessment of hrHPV by p16 immunohistochemical staining, in situ hybridization, and polymerase chain reaction (PCR)-MassArray (PCR-MA), with L1 PGMY-PCR and sequencing to resolve method discordance, was conducted for 338 FFPE oropharyngeal, nasopharyngeal, and oral cavity tumor tissue specimens. Relative sensitivity and specificity were compared to develop a standard optimal test protocol. Tissue specimens were collected from 338 patients with head and neck cancer treated during the period 2001 through 2011 in the departments of Otolaryngology, Radiation Oncology, and Medical Oncology.

INTERVENTION

Patients received standard therapy.

MAIN OUTCOMES AND MEASURES

Optimal hrHPV identification, detection, and activity in head and neck cancers.

RESULTS

Using combined PCR-MA with L1 PGMY-PCR and sequencing for conclusive results, we found PCR-MA to have 99.5% sensitivity and 100% specificity, p16 to have 94.2% sensitivity and 85.5% specificity, and in situ hybridization to have 82.9% sensitivity and 81.0% specificity. Among HPV-positive tumors, HPV16 was most frequently detected, but 10 non-HPV16 types accounted for 6% to 50% of tumors, depending on the site. Overall, 86% of oropharynx, 50% of nasopharynx, and 26% of oral cavity tumors were positive for hrHPV.

CONCLUSIONS AND RELEVANCE

PCR-MA has a low DNA (5 ng) requirement effective for testing small tissue samples; high throughput; and rapid identification of HPV types, with high sensitivity and specificity. PCR-MA together with p16INK4a provided accurate assessment of HPV presence, type, and activity and was determined to be the best approach for HPV testing in FFPE head and neck tumor tissue specimens.

Prognostic significance of molecular markers in oral squamous cell carcinoma: a multivariate analysis

BACKGROUND

Multiple marker accumulation impacts tumor progression and biologic phenotypes affect clinical outcome of patients with head and neck cancer. Hence, this study investigated a battery of molecular markers that may help to reflect biologic aggressiveness and predict prognosis.

METHODS

Epidermal growth factor receptor (EGFR), Stat3, H-ras, c-myc, p53, cyclin D1, p16, Rb, Ki-67, and Bcl-2 were localized immunohistochemically in 135 oral squamous cell carcinoma patients to assess prognostic value.

RESULTS

In univariate analysis of total patients, p53, Stat3, and p16 predicted both relapse-free survival (RFS) and overall survival (OS). In Cox multivariate analysis, after adjusting for tumor size, nodal status, and lymphatic permeation, p53 was independently associated with RFS and OS, and p16 with RFS only. In only early-stage patients, in univariate analysis, nuclear Stat3 was significant for RFS and OS.

CONCLUSION

Immunostaining of p53, p16, and Stat3 might serve as potential adjuncts in pathologic evaluation of oral tumors to predict risk of relapse.

MYC gene amplification reveals clinical association with head and neck squamous cell carcinoma in Indian patients

BACKGROUND

Amplification of the MYC gene is reported to be associated with the development of head and neck squamous cell carcinoma (HNSCC). This study is focused to analyze the correlation between MYC gene amplification and various clinicopathological features and outcome in a cohort of 49 dysplastic and 187 primary head and neck lesions.

METHODS

MYC gene amplification was assessed by differential polymerase chain reaction using primer sets from the MYC gene as target locus and DRD2 gene as the control locus.

RESULT

The MYC gene amplification was detected in a total of 23.7% (56/236) head and neck lesions comprising 14.2% (7/49) dysplastic lesions and 26% (49/187) HNSCC samples. The clinicopathological association study between MYC gene amplification with the different clinical parameters like sex, tumor stage, tumor differentiation, lymph node status, tobacco habit and HPV 16/18 status determined significant association of MYC amplification with tumor progression (P = 0.009). Kaplan Meier analysis revealed MYC gene has no prognostic significance on survival in HNSCC.

CONCLUSION

In conclusion, our results suggest that MYC gene amplification is associated with tumor progression in HNSCC.

SH3GL2 and CDKN2A/2B loci are independently altered in early dysplastic lesions of head and neck: correlation with HPV infection and tobacco habit

To understand the association of candidate tumour suppressor genes SH3GL2, p16(INK4a), p14(ARF), and p15(INK4b) in the pathogenesis of head and neck squamous cell carcinoma (HNSCC), we studied the deletion, mutation, and methylation of these genes in 61 dysplastic lesions and 94 HNSCC samples. In mild dysplasia, SH3GL2, p16(INK4a), and p14(ARF) showed a higher frequency of overall alterations (60-70%) than in p15(INK4b) (40%). However, in subsequent stages of tumour progression, the alteration frequency of these genes did not change significantly. One novel mutation in common exon 2 of p16(INK4a)/p14(ARF) and three in exon 9 of SH3GL2 were seen. Concordance was seen in the expression of these genes with their molecular alterations. Deletions of INK4A-ARF and p15(INK4b) have a significant poor patient outcome. The alterations of p16(INK4a), p14(ARF), and p15(INK4b) were positively correlated with tobacco and inversely with HPV, while SH3GL2 alterations were independent of these factors. Based on aetiological factors, four tumour subtypes were recognized: HPV(-)tobacco(-) (I), HPV(+)tobacco(-) (II), HPV(-)tobacco(+) (III), and HPV(+)tobacco(+) (IV). Groups III and IV showed a high frequency of p16(INK4a)/p14(ARF)/p15(INK4b) alterations with significant poor patient outcome in comparison to group II. Our findings suggest that deregulation of SH3GL2-associated signalling and p16(INK4a)/p14(ARF)/p15(INK4b)-mediated G1-S/G2-M checkpoints of cell cycle are independent pathways for the development of early dysplastic lesions of the head and neck.

[Exploration of tumor suppressors p16INK4a and p14ARF in oral leukoplakias]

The inactivation of p16 and p14ARF is considered to be an important step in the carcinogenesis of oropharygeal carcinomas. This consideration is supported by the observation of multiple allelic losses in the coding loci of chromosome 9p21 in squamous cell carcinomas and in dysplastic premalignant lesions. The present study hypothesized that comparable alterations already occur in leukoplakia, which are seen as potential predecessors of oral squamous cell carcinomas and that it is possible to differ leukoplakia with from leukoplakia without further malignant transformation. Furthermore we evaluated, whether such leukoplakia show sequence alterations in the genes p16 and p14ARF, which are capable to cause a limitation in gene function. The results show that the LOH pattern in genes p16 and p14ARF occur as well in leuplakia with malignant transformation as in leukoplakia, that do not show clinical alterations. The rate of allelic loss did not differ significantly. Overall, the incidence of allelic loss was lower in leuplakia compared to succeeding squamous-cell carcinomas (p<0,05). The results further illustrated an increase in LOH patterns in dyplastic leukoplakia, without reaching statistical significance. Significant increases in allelic losses were found in heavy smokers, (p < 0,05). PCR analysis of the exons 1-alpha, exon 1-beta and exon 2 in leukoplakia, containing LOH patterns did not show genetic alterations. Thus we concluded, that gene deletion and gene mutation have a minor role in the inactivation process of p16 and p14ARF in oral leukoplakia. Representing an early process in carcinogenesis, gene deletion and mutation occur in leukoplakia with and without malignant transformation. Therefore, taken as a singular parameter they represent an uncertain criteria to assess the potential of malignant transformation. However they could provide information in combination with other genetic factors like chromosomal methylation patterns and histology.

Deletion mapping of chromosome 13q in head and neck squamous cell carcinoma in Indian patients: correlation with prognosis of the tumour

Deletions in chromosome (chr.) 13q occur frequently in head and neck squamous cell carcinoma (HNSCC). Previous studies failed to identify common deleted regions in chr.13q, though several candidate tumour suppressor genes (TSGs) loci, e.g. BRCA2, RB1 and BRCAX have been localized in this chromosome, as well as no prognostic significance of the deletion has been reported. Thus, in the present study, deletion mapping of chr. 13q has been done in 55 primary HNSCC samples of Indian patients using 11 highly polymorphic microsatellite markers of which three were intragenic to BRCA2 gene, one intragenic to RB1 gene and another from BRCAX locus. The deletion in chr.13q was significantly associated with progression of HNSCC. High frequencies (27-39%) of loss of heterozygosity were found in 13q13.1 (BRCA2), 13q14.2 (RB1), 13q21.2-22.1 (BRCAX) and 13q31.1 regions. Deletions in the BRCA2 and RB1 regions were significantly correlated. The four highly deleted regions were associated with clinical stage and histological grades of the tumour as well as poor patient outcome. Deletion in the 13q31.1 region was only found to be associated with HPV infection. High frequencies (11-23%) of microsatellite size alteration (MA) were seen to overlap with the highly deleted regions. Forty per cent of the samples showed rare biallelic alteration whereas loss of normal copy of chromosome 13q was seen in five tumours. Thus, it seems that the putative TSGs located in the BRCAX and 13q31.1 regions as well as the BRCA2 and RB1 genes may have some cumulative effect in progression and poor prognosis of HNSCC. Significant association between deletion in BRCA2 and RB1 gene loci may indicate functional relationship between the genes in this tumour progression.

Approximately 580 Kb surrounding the MYC gene is amplified in head and neck squamous cell carcinoma of Indian patients

Amplification of the MYC gene is reported to be associated with the development of head and neck squamous cell carcinoma (HNSCC). However, there are no data concerning whether the amplification is confined to the MYC gene itself or spans distant 5' and/or 3' regions of this gene in HNSCC as seen in different lymphomas, colon carcinoma, and uterine cervical carcinoma (CaCx). In this study, we analyzed the alterations (amplification/rearrangement) in the 580 Kb surrounding of the MYC gene to understand the status of this locus in primary HNSCC of Indian patients. The MYC alterations were analyzed by Southern blot using the pal-1/MYC/MLVI4 probes. The alterations in the MYC locus (adjacent region of the c-myc gene) were then correlated with the various clinicopathological parameters. The overall amplification involving the MYC locus was seen in 46% of the samples. The MYC gene, pal-1 region, and MLVI4 region were amplified in about 38%, 24%, and 20% of the samples, respectively. Some samples showed co-amplification encompassing pal-1-MYC-MLVI4 or pal-1-MYC or MYC-MLVI4 regions. No significant association was observed between the amplification in the MYC locus and the different clinicopathological parameters except for tumor differentiation. Thus, it seems that, similar to other tumors, the MYC gene may be activated by amplification in its surrounding 5' and/or 3' region in HNSCC.

Novel therapeutic targets in squamous cell carcinoma of the head and neck

The treatment of squamous cell carcinoma of the head and neck (SCCHN) has recently witnessed the introduction of molecularly targeted agents based on disease biology, target discovery, and validation. One class of agents, the epidermal growth factor receptor (EGFR) inhibitors, is currently in phase III trials. There are multiple processes, however, that appear to be suitable for targeted therapy beyond EGFR. These include signal transduction, cell cycle control, prostaglandin synthesis, protein degradation, hypoxia, and angiogenesis. These systems and specific protein targets will be reviewed in detail with emphasis on promising preclinical and early clinical evidence of activity.

Patterns of gene promoter methylation in squamous cell cancer of the head and neck

Promoter methylation is an important pathway in transcriptional silencing of known and candidate tumor suppressor genes in Head and Neck Squamous Cell Carcinoma (HNSCC). In order to study the association of tumor suppressor gene promoter methylation in HNSCC with patient clinical characteristics, especially alcohol consumption and tobacco smoking, we examined promoter methylation of the p16(INK4a), DAP-kinase, E-Cadherin, and RASSF1A genes using methylation-specific PCR (MSP) in 80 patients. The prevalence of p16(INK4a), DAP-kinase, E-Cadherin, and RASSF1A promoter methylation was 26/80 (32.5%), 19/80 (23.8%), 29/80 (36.3%), 6/80 (7.5%) respectively. In 48 cases (60%), at least one of these promoters was methylated. There was a significant association of methylation of any of these genes and ever smoking (P=0.006). p16(INK4a) gene promoter methylation was associated with a younger age of smoking initiation (P<0.03); E-Cadherin promoter methylation was associated with an increased number of pack years smoked (P<0.03). We also found an association of methylation of any gene and T status (OR=2.7, P<0.05). Tumors with p16(INK4a) methylation were significantly less likely to show lymph node metastasis (P<0.001). DAP-kinase promoter methylation was significantly associated with lymph node metastasis and this relationship was dependent upon p16(INK4a) promoter methylation status. Our results suggest that, in HNSCC, promoter methylation of these four genes accumulates with increasing tumor size. This may reflect distinct pathways of somatic inactivation leading to cancer; additional larger studies are needed to further investigate this possibility. Tobacco smoking may play an important role in both the occurrence of promoter methylation as well as delineating the precise pathway that eventually results in a tumorigenic phenotype.