Infrequent genetic alterations of the tumor suppressor gene PTEN/MMAC1 in squamous cell carcinoma of the oral cavity

MicroRNA 142-5p promotes tumor growth in oral squamous cell carcinoma via the PI3K/AKT pathway by regulating PTEN

MicroRNAs (miRNAs) play an important role in carcinogenesis and cancer progression. The purpose of this study was to identify miRNAs associated with carcinoma function in OSCC and to investigate the potential role of the specific miRNAs. First, a comprehensive microarray analysis was performed, and miR-142-5p was identified as a candidate miRNA involved in OSCC. miR-142-5p has been reported to show high expression levels in cancer patients and to be involved in tumor growth and metastasis. However, the expression and function of miR-142-5p in oral squamous cell carcinoma (OSCC) are not fully characterized. We evaluated miR-142-5p expression in both OSCC-derived cell lines and primary OSCC tissues and performed functional analysis of miR-142-5p in OSCC-derived cell lines using mimics and inhibitors. miR-142-5p expression was up-regulated in OSCC tissues and OSCC cell lines. Overexpression of miR-142-5p significantly promoted the proliferation and invasion of OSCC cells. Bioinformatics analysis was performed using TargetScan to predict potential target sites that match the seed region of miR-142-5p. Phosphatase and tensin homolog deleted on chromo-some 10 (PTEN) was identified as a potential target and selected for further analysis. PTEN expression levels were down-regulated and AKT expression levels were up-regulated in miR-142-5p-overexpressing cells. We have shown that miR-142-5p targets the PTEN gene and is involved in cancer progression. Our results suggest that miR-142-5p is involved in the progression of OSCC by controlling the phosphatidylinositol 3-kinase (PI3K)/AKT pathway by targeting the PTEN gene. Our findings suggest that miR-142-5p may be a new target for the treatment of OSCC.

DNA methylation in oral squamous cell carcinoma: from its role in carcinogenesis to potential inhibitor drugs

DNA methylation is one of epigenetic changes most frequently studied nowadays, together with its relationship with oral carcinogenesis. A group of enzymes is responsible for methylation process, known as DNA methyltransferases (DNMT). Although essential during embryogenesis, DNA methylation pattern alterations, including global hypomethylation or gene promoter hypermethylation, can be respectively associated with chromosomal instability and tumor suppressor gene silencing. Higher expression of DNA methyltransferases is a common finding in oral cancer and may contribute to inactivation of important tumor suppressor genes, influencing development, progression, metastasis, and prognosis of the tumor. To control these alterations, inhibitor drugs have been developed as a way to regulate DNMT overexpression, and they are intended to be associated with ongoing chemo- and radiotherapy in oral cancer treatments. In this article, we aimed to highlight the current knowledge about DNA methylation in oral cancer, including main hyper/hypomethylated genes, DNMT expression and its inhibitor treatments.

PTEN and α-SMA Expression and Diagnostic Role in Oral Submucous Fibrosis and Oral Squamous Cell Carcinoma with Concomitant Oral Submucous Fibrosis

Objectives

The diagnostic role and correlation between phosphatase and tensin homologue and alpha-smooth muscle actin in oral submucous fibrosis and oral squamous cell carcinoma with concomitant oral submucous fibrosis was analysed by this case control study. The mechanism by which phosphatase and tensin homologue controls myofibroblast expression was also evaluated.

Material and Methods

Overall, 10 normal mucosa, 30 oral submucous fibrosis (OSF) and 30 oral squamous cell carcinoma (OSCC) with OSF were stained immunohistochemically with phosphatase and tensin homologue (PTEN) and alpha-smooth muscle actin (α-SMA). Percentage positivity, pattern of expression was statistically compared using Pearson’s Chi-square and Fischer exact tests. The correlation between markers was analysed using Spearman correlation.

Results

OSF and OSCC affected males predominantly with majority below 40 years and above 40 years of age respectively. Percentage of PTEN positive cells was statistically significant with gender (P = 0.024) and α-SMA distribution of pattern showed a significant correlation with habits (P = 0.018). A significant decrease in nuclear PTEN positivity (P < 0.001) and a gradual increase in α-SMA cytoplasmic expression was noted from NM to OSF and OSCC. A statistically significant weak inverse correlation existed between PTEN and α-SMA.

Conclusions

A reduced phosphatase and tensin homologue expression in oral submucous fibrosis makes it more prone for malignant transformation. An increase in stromal desmoplasia modifies differentiation, invasive and proliferative capacity of tumour cells. As phosphatase and tensin homologue functions through P-Akt pathway, P-Akt with phosphatase and tensin homologue could be a therapeutic target.

Worldwide prevalence of PI3K-AKT-mTOR pathway mutations in head and neck cancer: A systematic review and meta-analysis

A systematic review (SR) and meta-analysis were conducted to determine the prevalence of PI3K-AKT-mTOR signaling pathway mutations in patients with head and neck cancer (HNC). Overall, 105 studies comprising 8630 patients and 1306 mutations were selected. The estimated mutations prevalence was 13 % for PIK3CA (95 % confidence interval [CI] = 11-14; I² = 82 %; p < 0.0001), 4% for PTEN (95 % CI = 3-5; I² = 55 %; p < 0.0001), 3% for MTOR (95 % CI = 2-4; I² = 5%; p = 0.40), and 2% for AKT (95 % CI = 1-2; I² = 50 %; p = 0.0001). We further stratified the available data of the participants according to risk factors and tumor characteristics, including HPV infection, tobacco use, alcohol exposure, TNM stage, and histological tumor differentiation, and performed subgroup analysis. We identified significant associations between PI3K-AKT-mTOR pathway-associated mutations and advanced TNM stage (odds ratio [OR] = 0.20; 95 % CI = 0.09-0.44; I² = 71 %; p = 0.0001) and oropharyngeal HPV-positive tumors and PIK3CA mutations (OR = 17.48; 95 % CI = 4.20-72.76; I² = 69 %; p < 0.0002). No associations were found between alcohol and tobacco exposure, and tumor differentiation grade. This SR demonstrated that the PI3K-AKT-mTOR pathway emerges as a potential prognostic factor and could offer a molecular basis for future studies on therapeutic targeting in HNC patients.

Prognostic value of the PIK3CA, AKT, and PTEN mutations in oral squamous cell carcinoma: literature review

Over 260,000 (2013) new oral squamous cell carcinoma (OSCC) cases are reported annually worldwide. Despite development in OSCC management, the outcome is still unsatisfactory. Identification of new molecular markers may be of use in prevention, prognosis, and choice of an appropriate therapy. The intracellular molecular signalling pathway of phosphatidyl-inositol-3-kinase is involved in the process of cell growth, differentiation, migration, and survival. The main components of this pathway: PIK3CA (phosphatidylinositol-4,5-bisphosphate-3-kinase catalytic subunit α), PTEN (phosphatase and tensin homologue deleted on chromosome 10), and AKT (serine-threonine kinase) are potential objects of research when introducing new therapeutic agents. The aim of this paper is to evaluate the PIK3CA, PTEN, and AKT gene mutations as prognostic factors in OSCC and to describe their role in aggressive disease progression. This is crucial for oral cancer biology understanding and for indicating which direction new clinical treatments should take.

Loss of heterozygosity and immunoexpression of PTEN in oral epithelial dysplasia and squamous cell carcinoma

INTRODUCTION

Oral epithelial dysplasia (OED) is a risk factor for developing subsequent oral squamous cell carcinoma (OSCC). Loss of heterozygosity (LOH) profiles have been validated as risk predictors of malignant transformation of OED. It is still unclear if Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) allelic loss also occurs in initial stage malignant lesions and if the allelic loss is involved as one of the mechanisms of oral carcinogenesis. Thus, this study objective investigate LOH of PTEN gene and the immunohistochemical expression of the protein in OED and OSCC samples.

MATERIAL AND METHODS

Formalin-fixed paraffin-embedded samples of 19 OEDs and 16 OSCCs were included to immunohistochemistry and LOH analysis. Two polymorphic microsatellite markers (AFMA086WG9 and D10S1765) located in chromosome 10 were used in this study for LOH analysis. For immunohistochemical analysis, 5 random fields with 400× magnification were evaluated quantitatively and qualitatively in epithelial and neoplastic cells.

RESULTS

AFMA086WG9 marker only demonstrated LOH in OEDs cases (10.5%). D10S1765 marker demonstrated LOH in 57.2% of OEDs and 50% of OSCCs. Higher nuclear immunostaining was detected in cases of OSCCs when compared to OEDs (p < .001) and there was strong cytoplasmic immunoexpression in OSCCs (p < .045).

CONCLUSIONS

We provide evidence that the allelic loss of PTEN is present in premalignant oral lesions and OSCCs, however the LOH of PTEN does not seems to influence its protein expression.

Current Insights into Oral Cancer Epigenetics

Epigenetic modifications have emerged into one of the cancer hallmarks, replacing the concept of malignant pathologies as being solely genetic-based conditions. The epigenetic landscape is responsible for normal development but also for the heterogeneity among tissues in terms of gene expression patterns. Dysregulation in these mechanisms has been associated with disease stage, and increased attention is now granted to cancer in order to take advantage of these modifications in terms of novel therapeutic strategies or diagnosis/prognosis tools. Oral cancer has also been subjected to epigenetic analysis with numerous studies revealing that the development and progression of this malignancy are partially induced by an altered epigenetic substrate together with genetic alterations and prolonged exposure to environmental risk factors. The present review summarizes the most important epigenetic modifications associated with oral cancer and also their potential to be used as new therapeutic targets.

Immunohistochemical expression of phosphatase and tensin homolog in histologic gradings of oral squamous cell carcinoma

Context:

Phosphatase and tensin homolog (PTEN) is a tumor suppressor gene located on chromosome 10q23. PTEN has its major function in the regulation of cell adhesion, cell cycle arrest, migration, apoptosis programming, and differentiation. This genomic region suffers loss of heterozygosity in many human cancers.

Aims:

The aim of this study was to compare the immunohistochemical expression of PTEN in normal oral mucosa and oral squamous cell carcinoma (OSCC) and to correlate the PTEN expression in gradings of OSCC.

Materials and Methods:

Thirty cases of paraffin tissue sections of previously diagnosed OSCC were taken. Of thirty cases, ten were well differentiated, ten were moderately differentiated, and ten were poorly differentiated. As a control, ten paraffin sections of oral normal mucosa tissue specimens were taken from patients undergoing extractions. The sections were stained for immunohistochemical expression of PTEN. The cells stained by PTEN antibody were counted, and an immunohistochemical score was obtained.

Statistical Analysis Used:

Statistical analysis was done using Mann–Whitney's test and Kruskal–Wallis test.

Results:

Statistical analysis revealed that there was a significant difference between normal mucosa and OSCC in immunohistochemistry staining. However, there was no significant difference in PTEN expression among gradings of OSCC.

Conclusions:

The study concluded that there was a decrease in PTEN expression in OSCC than normal mucosa. It also concluded that PTEN is a tumor suppressor gene which has a wide role in oral carcinogenesis.

Genome-Wide Loss of Heterozygosity and DNA Copy Number Aberration in HPV-Negative Oral Squamous Cell Carcinoma and Their Associations with Disease-Specific Survival

Oral squamous cell cancer of the oral cavity and oropharynx (OSCC) is associated with high case-fatality. For reasons that are largely unknown, patients with the same clinical and pathologic staging have heterogeneous response to treatment and different probability of recurrence and survival, with patients with Human Papillomavirus (HPV)-positive oropharyngeal tumors having the most favorable survival. To gain insight into the complexity of OSCC and to identify potential chromosomal changes that may be associated with OSCC mortality, we used Affymtrix 6.0 SNP arrays to examine paired DNA from peripheral blood and tumor cell populations isolated by laser capture microdissection to assess genome-wide loss of heterozygosity (LOH) and DNA copy number aberration (CNA) and their associations with risk factors, tumor characteristics, and oral cancer-specific mortality among 75 patients with HPV-negative OSCC. We found a highly heterogeneous and complex genomic landscape of HPV-negative tumors, and identified regions in 4q, 8p, 9p and 11q that seem to play an important role in oral cancer biology and survival from this disease. If confirmed, these findings could assist in designing personalized treatment or in the creation of models to predict survival in patients with HPV-negative OSCC.

PTEN gene polymorphisms and susceptibility to oral squamous cell carcinoma in a Chinese Han population

The tumor suppressor gene phosphatase and tensin homologue (PTEN) plays a significant role in regulating cell growth, proliferation, and apoptosis. However, there are no data regarding the role of PTEN polymorphisms in the development of oral squamous cell carcinoma (OSCC). A hospital-based case-control study was conducted to investigate the potential association between PTEN polymorphisms and the risk of OSCC in a Chinese Han population. The study population comprised 201 patients with OSCC and 199 healthy controls. Seventeen single-nucleotide polymorphisms (SNPs) of PTEN were investigated and genotyped using Sequenom Mass ARRAY and iPLEX-MALDI-TOF technology. The observed genotype frequencies of these polymorphisms were in agreement with Hardy-Weinberg equilibrium in the control group (P > 0.05 for all). The heterozygous CT genotype was not associated with significantly increased risk for OSCC (OR = 0.89, 95 % CI = (0.55-1.42), P = 0.83), the TT genotype was not associated with increased risk for OSCC (OR = 1.01, 95 % CI = (0.58-1.74), P = 0.74) compared to the PTEN SNP rs1234224 homozygous CC genotype. Meanwhile, CT/TT variants were not associated with increased risk for OSCC compared with the CC genotype (OR = 0.93, 95 % CI = 0.60-1.44, P = 0.73). The T allele was not associated with significantly increased risk compared to the C allele (OR = 0.99, 95 % CI = 0.72-1.58, P = 0.69). Similar associations with the risk of OSCC were observed for the other genotypes of PTEN gene polymorphisms. There were no significant differences in the distribution of the genotype and allele frequencies of polymorphisms of the PTEN gene between the OSCC patients and controls in a Chinese Han population. Further studies are needed to clarify the specific roles of PTEN polymorphisms in the etiology of OSCC.

Loss of NDRG2 expression activates PI3K-AKT signalling via PTEN phosphorylation in ATLL and other cancers

Constitutive phosphatidylinositol 3-kinase (PI3K)-AKT activation has a causal role in adult T-cell leukaemia-lymphoma (ATLL) and other cancers. ATLL cells do not harbour genetic alterations in PTEN and PI3KCA but express high levels of PTEN that is highly phosphorylated at its C-terminal tail. Here we report a mechanism for the N-myc downstream-regulated gene 2 (NDRG2)-dependent regulation of PTEN phosphatase activity via the dephosphorylation of PTEN at the Ser380, Thr382 and Thr383 cluster within the C-terminal tail. We show that NDRG2 is a PTEN-binding protein that recruits protein phosphatase 2A (PP2A) to PTEN. The expression of NDRG2 is frequently downregulated in ATLL, resulting in enhanced phosphorylation of PTEN at the Ser380/Thr382/Thr383 cluster and enhanced activation of the PI3K-AKT pathway. Given the high incidence of T-cell lymphoma and other cancers in NDRG2-deficient mice, PI3K-AKT activation via enhanced PTEN phosphorylation may be critical for the development of cancer.

PIK3CA, HRAS and PTEN in human papillomavirus positive oropharyngeal squamous cell carcinoma

Background

Recent genomic evidence suggests frequent phosphatidylinositide 3-kinase (PI3K) pathway activation in human papillomavirus (HPV) positive oropharyngeal squamous cell carcinoma. Mutations/amplification of the gene encoding p110α catalytic subunit of phosphoinositide 3-kinase (PIK3CA), loss of phosphatase and tensin homolog (PTEN) and HRAS mutations are known to activate PI3K pathway.

Methods and results

PIK3CA mutations were identified by Sanger sequencing in 23 of 75 (31%) HPV-positive oropharyngeal carcinomas, including exon 9 (p.E545K [n = 10] and p.E542K [n = 5]) or exon 20 (p.H1047Y, n = 2) mutations. Five rare and one novel (p.R537Q) PIK3CA mutations were identified. HRAS mutation (p.Q61L) was detected in 1 of 62 tested cases. PIK3CA amplification by fluorescence in situ hybridization (FISH) was identified in 4 cases (4/21, 20%), while PTEN loss was seen in 7 (7/21, 33%) cases (chromosome 10 monosomy [n = 4], homozygous deletion [n = 3]).

Conclusions

Overall, genetic alterations that likely lead to PI3K pathway activation were identified in 34 of 75 cases (45%) and did not correlate with disease specific survival. These findings offer a molecular rationale for therapeutic targeting of PI3K pathway in patients with HPV-positive oropharyngeal carcinoma.

Evaluation of PTEN immunoexpression in oral submucous fibrosis: role in pathogenesis and malignant transformation

Oral submucous fibrosis (OSMF) is a chronic debilitating disease and a premalignant condition of the oral cavity characterized by generalized submucosal fibrosis. Despite its precancerous nature, the molecular biology regarding its malignant potential has not been extensively studied. PTEN, a known tumor suppressor gene is mutated in a majority of human cancers and has also been implicated in several fibrotic disorders. The present study aims to evaluate the expression of PTEN in OSMF and oral squamous cell carcinoma (OSCC) and correlate it with the pathogenesis and malignant transformation of OSMF. 60 cases total of OSMF (30) and OSCC (30) were subjected to immunohistochemistry using PTEN antibody. Ten normal oral mucosa (NOM) specimens were also stained as controls. There was progressive loss of PTEN expression from normal mucosa to OSMF and OSCC (p ≤ 0.001). Significant differences were observed for PTEN expression between NOM and OSMF, OSMF and OSCC as well as NOM and OSCC. Though a progressive loss of PTEN was noticed between early OSMF and advanced OSMF, the variation did not reach statistical significance (p ≥ 0.001). Data suggest that there is a significant loss of PTEN expression in OSMF as compared to normal oral mucosa and that this trend increased from OSMF to OSCC. Thus, alteration of PTEN is likely an important molecular event in OSMF pathogenesis and oral carcinogenesis.

Epigenetic disregulation in oral cancer

Squamous cell carcinoma of the oral region (OSCC) is one of the most common and highly aggressive malignancies worldwide, despite the fact that significant results have been achieved during the last decades in its detection, prevention and treatment. Although many efforts have been made to define the molecular signatures that identify the clinical outcome of oral cancers, OSCC still lacks reliable prognostic molecular markers. Scientific evidence indicates that transition from normal epithelium to pre-malignancy, and finally to oral carcinoma, depends on the accumulation of genetic and epigenetic alterations in a multistep process. Unlike genetic alterations, epigenetic changes are heritable and potentially reversible. The most common examples of such changes are DNA methylation, histone modification, and small non-coding RNAs. Although several epigenetic changes have been currently linked to OSCC initiation and progression, they have been only partially characterized. Over the last decade, it has been demonstrated that especially aberrant DNA methylation plays a critical role in oral cancer. The major goal of the present paper is to review the recent literature about the epigenetic modifications contribution in early and later phases of OSCC malignant transformation; in particular we point out the current evidence of epigenetic marks as novel markers for early diagnosis and prognosis as well as potential therapeutic targets in oral cancer.

PTEN-mediated AKT activation contributes to the reduced apoptosis among Indian oral squamous cell carcinoma patients

PURPOSE

The tumor suppressor gene PTEN negatively regulates Akt, a downstream mediator phosphoinositol 3-kinase. Several studies have reported the role of PTEN gene in Akt downregulation and apoptosis induction in different cancers and cell lines. However, the role of loss of PTEN expression in Akt activation and spontaneous apoptosis in oral squamous cell carcinoma clinical specimens is not well established.

METHODS

We investigated the expression of PTEN and phospho-Akt in 146 formalin-fixed (archived) paraffin-embedded oral squamous cell carcinoma tissue sections through immunohistochemical analysis. Programmed cell death (apoptosis) was determined by Terminal deoxynucleotidyl Transferase Biotin-dUTP Nick End Labeling assay.

RESULTS

Sixty-one percent loss of PTEN expression and 68.5% Akt activation was observed in oral squamous cell carcinoma. A significant correlation was found between loss of PTEN expression and Akt activation. Loss of PTEN expression and Akt activation were further correlated with different clinical parameters and found to be significantly correlated with tumor stage. Apoptotic index was estimated and correlated with PTEN expression and Akt activation. The percentage of apoptotic cells varied from 0.2 to 14.1%. Low apoptotic index was observed in 105 (72%) of samples, and it was found to be significantly related with loss of PTEN expression and phospho-Akt

CONCLUSION

The present study confirms the contribution of loss of PTEN expression in Akt phosphorylation and spontaneous apoptosis suppression in the specimens of oral cancer. Both PTEN and phospho-Akt are likely to be concerned with oral cancer progression and reduced incidence of spontaneous apoptosis.

Improving Response Rates to EGFR-Targeted Therapies for Head and Neck Squamous Cell Carcinoma: Candidate Predictive Biomarkers and Combination Treatment with Src Inhibitors

The epidermal growth factor receptor- (EGFR-) directed antibody, cetuximab, was FDA-approved for the treatment of squamous cell carcinoma of the head and neck (SCCHN) in 2006. Additional EGFR-targeting agents in clinical development for SCCHN include other EGFR-directed antibodies, tyrosine kinase inhibitors and antisense DNA. Although the majority of SCCHN overexpress EGFR, SCCHN clinical responses to EGFR-targeting agents have been modest. Molecular predictors for SCCHN response to EGFR-targeted therapies have not been identified. However, molecular correlate studies in lung cancer and colon cancer, which have EGFR-targeted therapeutics FDA-approved for treatment, may provide insights. We describe candidate predictive markers for SCCHN response to EGFR-targeted therapies and their prevalence in SCCHN. Clinical response will likely be improved by targeted therapy combination treatments. Src family kinases mediate EGFR-dependent and -independent tumor progression pathways in many cancers including SCCHN. Several Src-targeting agents are in clinical development for solid malignancies. Molecular correlate studies for Src-targeting therapies are few and biomarkers correlated with patient response are limited. Identifying SCCHN patients who will respond to combined EGFR- and Src-targeting will require further characterization of molecular correlates. We discuss rationale for EGFR and Src co-targeting for SCCHN treatment and describe recent clinical trials implementing combined Src- and EGFR-targeted therapeutics.

Involvement of TSC genes and differential expression of other members of the mTOR signaling pathway in oral squamous cell carcinoma

Background

Despite extensive research, the five-year survival rate of oral squamous cell carcinoma (OSCC) patients has not improved. Effective treatment of OSCC requires the identification of molecular targets and signaling pathways to design appropriate therapeutic strategies. Several genes from the mTOR signaling pathway are known to be dysregulated in a wide spectrum of cancers. However, not much is known about the involvement of this pathway in tumorigenesis of OSCC. We therefore investigated the role of the tumor suppressor genes, TSC1 and TSC2, and other members of this pathway in tumorigenesis of OSCC.

Methods

Expression of genes at the RNA and protein levels was examined by semi-quantitative RT-PCR and western blot analyses, respectively. Loss of heterozygosity was studied using matched blood and tumor DNA samples and microsatellite markers from the TSC1, TSC2 and PTEN candidate regions. The effect of promoter methylation on TSC gene expression was studied by treating cells with methyltransferase inhibitor 5-azacytidine. Methylation status of the TSC2 promoter in tissue samples was examined by combined bisulfite restriction analysis (COBRA).

Results

The semi-quantitative RT-PCR analysis showed downregulation of TSC1, TSC2, EIF4EBP1 and PTEN, and upregulation of PIK3C2A, AKT1, PDPK1, RHEB, FRAP1, RPS6KB1, EIF4E and RPS6 in tumors. A similar observation was made for AKT1 and RPS6KB1 expression in tumors at the protein level. Investigation of the mechanism of downregulation of TSC genes identified LOH in 36.96% and 39.13% of the tumors at the TSC1 and TSC2 loci, respectively. No mutation was found in TSC genes. A low LOH rate of 13% was observed at the PTEN locus. Treatment of an OSCC cell line with the methyltransferase inhibitor 5-azacytidine showed a significant increase in the expression of TSC genes, suggesting methylation of their promoters. However, the 5-azacytidine treatment of non-OSCC HeLa cells showed a significant increase in the expression of the TSC2 gene only. In order to confirm the results in patient tumor samples, the methylation status of the TSC2 gene promoter was examined by COBRA. The results suggested promoter hypermethylation as an important mechanism for its downregulation. No correlation was found between the presence or absence of LOH at the TSC1 and TSC2 loci in 50 primary tumors to their clinicopathological variables such as age, sex, T classification, stage, grade, histology, tobacco habits and lymph node metastasis.

Conclusion

Our study suggests the involvement of TSC genes and other members of the mTOR signaling pathway in the pathogenesis of OSCC. LOH and promoter methylation are two important mechanisms for downregulation of TSC genes. We suggest that known inhibitors of this pathway could be evaluated for the treatment of OSCC.

Expression of PTEN protein in patients with laryngeal squamous cell carcinoma

OBJECTIVE

PTEN (phosphatase and tensin homologue deleted on chromosome 10), also referred to as MMAC1 (mutated in multiple advanced cancers) gene was recently identified as a putative tumor suppressor in a variety of malignant tumors. PTEN expression has been investigated in some squamous cell carcinomas (SCC) of head and neck. However, there is only little knowledge about laryngeal malignancies. Therefore, we examined PTEN product protein immunohistochemically in 30 consecutive laryngeal specimens from patients with laryngeal SCC and compared the results according to the clinicopathologic characteristics of the patients.

METHOD

Surgical resection specimens of patients with laryngeal SCC were stained for PTEN protein using a primary rabbit polyclonal anti-PTEN antibody. Standard avidin-biotin immunohistochemical analysis was used to process the sections. The extent and intensity of PTEN staining in the specimens were compared according to the age and sex of the patients and localization, differentiation, size and stage of the tumor.

RESULTS

Out of 30 tumoral specimens (23 glottic and 7 supraglottic) 22 showed decreased PTEN staining intensity compared to the adjacent normal tissue. The extent of cytoplasmic PTEN staining was significantly less in supraglottic tumors (p < 0.05). When characteristics of the patients were analyzed according to the extent of cytoplasmic PTEN staining no difference was observed according to age, sex, measure, differentiation, T or N status.

CONCLUSION

A significant decrease in the extent of PTEN staining was observed in supraglottic SCC. It could be worthwhile to test if PTEN expression is diminished in patients with more aggressive laryngeal tumors, with special attention to tumor localization in larger series.

Epigenetic Inactivation of IκB Kinase-α in Oral Carcinomas and Tumor Progression

PURPOSE

The loss of epithelial phenotypes in the process of carcinoma progression correlates with clinical outcome, and genetic/epigenetic changes accumulate aggressive clones toward uncurable disease. IkappaB kinase-alpha (IKKalpha) has a decisive role in the development of the skin and establishes keratinocyte phenotypes. We assessed clinical implications of IKKalpha expression in oral carcinomas and epigenetic aberrations for the loss of expression.

EXPERIMENTAL DESIGN

We examined IKKalpha expression in oral carcinomas by immunostaining (n = 64) and genetic instability by microsatellite PCR (n = 46). Promoter methylation status was analyzed by bisulfite-modified sequence (n = 11).

RESULTS

IKKalpha was expressed in the nucleus of basal cells of normal oral epithelium, but not or marginally detected in 32.8% of carcinomas. The immunoreactivity was significantly decreased in less differentiated carcinomas (P < 0.05) and correlated to long-term survival of patients (P < 0.01) with an independent prognostic value (P < 0.05). Although allelic/biallelic loss of the gene was limited to four cases, we detected microsatellite instability in 63.0% cases in which the immunoreactivities were decreased and the promoter was hypermethylated.

CONCLUSION

These results showed that oral carcinomas exhibiting genetic instability and promoter hypermethylation down-regulate expression of IKK and suggest that the epigenetic loss of the expression closely associates with disease progression toward unfavorable prognosis.

The phosphoinositide 3-kinase signalling pathway as a therapeutic target in squamous cell carcinoma of the head and neck

Squamous cell carcinoma of the head and neck (SCCHN) is associated with high morbidity and mortality. Despite significant surgical advances and refinement in the delivery of chemotherapy and radiotherapy, prognosis has improved little in recent decades. Better local control has led to the late presentation of distant metastases and novel therapeutic agents are urgently required to prevent relapse, control disseminated disease and thus improve survival. PIK3CA encodes the p110alpha isoform of phosphoinositide 3-kinase (PI3-K) and is important in SCCHN, aberrations in its activity occurring early in the oncogenic process. PI3-K signalling promotes cell survival, proliferation, invasion and angiogenesis, all contributing to tumour progression. Activation of the PI3-K pathway may also mediate resistance to chemotherapy, radiotherapy and novel therapeutic agents such as epidermal growth factor receptor inhibitors. Elements of this signalling matrix, therefore, offer attractive therapeutic targets in SCCHN as inhibition of many malignant characteristics, as well as sensitisation to multiple treatment modalities, could be anticipated.

Biological significance of c-erbB family oncogenes in head and neck cancer

Squamous cell carcinoma of the head and neck (SCCHN) tends to run an aggressive course and the prognosis has remained virtually unchanged in recent decades. The development of novel therapeutic strategies to improve patient outcome centres on the biology of the disease, namely the pivotal c-erbB family of growth factor receptors. c-erbB1 (or epidermal growth factor receptor, EGFR), is key to the pathogenesis of SCCHN and plays a central role in a complex network of downstream integrated signalling pathways. EGFR overexpression, detected in up to 90% of SCCHN, correlates with an increased risk of locoregional tumour relapse following primary therapy and relative resistance to treatment. The biological sequelae of erbB receptor activation are not simply cell proliferation, but also inhibition of apoptosis, enhanced migration, invasion, angiogenesis and metastasis: the 'hallmarks of cancer' [1]. As EGFR overexpression is associated with a poor clinical outcome in SCCHN, this receptor is attractive as a therapeutic target and the successful development of targeted therapies represents a paradigm shift in the medical approach to head and neck cancer. However, the extensive cross talk between signalling pathways, the multiple molecular aberrations and genetic plasticity in SCCHN all contribute to inherent and acquired resistance to both conventional and novel therapies. Understanding the cancer cell biology, in particular the significance of co-expression of c-erbB (and other) receptors, and the cell survival stimuli from (for example) activation of the phosphoinositide 3-kinase (PI3-kinase) cascade is fundamental to overcome current limitations in biologically targeted therapies.

Expression of PTEN encoding product in malignant lesions of gastric mucosa and its significance

AIM

To observe the expression of PTEN protein in gastric cancer and precancerous lesions, and to investigate the relationship between PTEN expression and the pathogenesis of gastric cancer.

METHODS

Normal gastric mucosa,chronic superficial gastritis, atrophic gastritis without intestinal metaplasia, atrophic gastritis with intestinal metaplasia, moderate and severe dysplasia, early and advanced gastric cancer, 60 cases each group, were selected for PTEN protein expression by SP immunohistochemistry.

RESULTS

The expression of PTEN encoding product in normal gastric mucosa was 100%. For chronic superficial gastritis, atrophic gastritis without intestinal metaplasia, atrophic gastritis with intestinal metaplasia, moderate dysplasia, severe dysplasia, the PTEN protein expression rate was 98.3%, 91.6%, 78.3%, 75%, 63.3%,respectively. The expression of PTEN protein in early stage and advanced gastric cancer was 61.7% and 43.3% respectively. Among the 120 cases of gastric cancer, 76 cases were intestinal type gastric cancer, the PTEN protein expression was 60.5%, 44 cases were diffuse gastric cancer , the PTEN protein expression was 38.6%.

CONCLUSION

The expression of PTEN protein is downregulated in the process of gastric cancer, PTEN protein can be used as a maker to evaluate the biological behaviours of gastric cancer.