RESUMO
Chromosomal amplification at 3q is common to multiple human cancers, but has a specific predilection for squamous cell carcinomas (SCC) of mucosal origin. We identified and characterized a novel oncogene, SCC-related oncogene (SCCRO), which is amplified along the 3q26.3 region in human SCC. Amplification and overexpression of SCCRO in these tumors correlate with poor clinical outcome. The importance of SCCRO amplification in malignant transformation is established by the apoptotic response to short hairpin RNA against SCCRO, exclusively in cancer cell lines carrying SCCRO amplification. The oncogenic potential of SCCRO is underscored by its ability to transform fibroblasts (NIH-3T3 cells) in vitro and in vivo. We show that SCCRO regulates Gli1--a key regulator of the hedgehog (HH) pathway. Collectively, these data suggest that SCCRO is a novel component of the HH signaling pathway involved in the malignant transformation of squamous cell lineage.
Assuntos
Carcinoma de Células Escamosas/genética , Amplificação de Genes , Regulação Neoplásica da Expressão Gênica , Proteínas de Neoplasias/genética , Proteínas Oncogênicas/genética , Oncogenes , Animais , Apoptose/genética , Carcinoma de Células Escamosas/metabolismo , Carcinoma de Células Escamosas/patologia , Linhagem Celular Tumoral , Transformação Celular Neoplásica/genética , Cromossomos Humanos Par 3/genética , Clonagem Molecular , Feminino , Proteínas Hedgehog/fisiologia , Humanos , Peptídeos e Proteínas de Sinalização Intracelular , Camundongos , Camundongos Endogâmicos BALB C , Camundongos Nus , Células NIH 3T3/patologia , Células NIH 3T3/transplante , Proteínas de Neoplasias/metabolismo , Transplante de Neoplasias , Proteínas Oncogênicas/fisiologia , Proteínas , Proteínas Proto-Oncogênicas , RNA Interferente Pequeno/farmacologia , Proteínas Recombinantes de Fusão/fisiologia , Transdução de Sinais , Fatores de Transcrição/genética , Fatores de Transcrição/fisiologia , Proteína GLI1 em Dedos de ZincoRESUMO
PURPOSE: Amplification at chromosome 3q26.3 is a common and crucial event in head and neck squamous cell carcinoma (HNSCC), impacting significantly on tumor progression and clinical outcome. Two novel oncogenes, namely squamous cell carcinoma (SCC)-related oncogene (SCCRO) and PIK3CA (gene encoding phosphatidylinositol-3 kinase catalytic alpha-polypeptide), have been identified as targets of 3q26.3 amplification. This study aimed to delineate the role of SCCRO and PIK3CA in the pathogenesis of oral tongue SCC. EXPERIMENTAL DESIGN: The association between gene copy number for SCCRO and PIK3CA measured by fluorescence in situ hybridization and level of mRNA expression quantitated by real-time reverse transcription-PCR was assessed in a panel of human HNSCC cell lines. In addition, gene expression in 49 consecutive primary SCCs of the oral tongue was determined and correlated with clinicopathological characteristics and outcome. RESULTS: The mRNA level of SCCRO and PIK3CA was significantly correlated to the gene copy number in nine HNSCC cell lines. In addition, the expression level of SCCRO and PIK3CA was significantly greater in malignant tissues compared with those in histologically normal mucosae (2.17- and 2.46-fold, respectively; P < 0.001). Matched tumor normal control analysis revealed that 24.5 and 69.4% of patients expressed high levels of SCCRO and PIK3CA, respectively. Univariate analyses demonstrated that SCCRO overexpression correlated with nodal metastases (P = 0.05) and advanced stage (P = 0.02), whereas PIK3CA overexpression was associated with vascular invasion (P = 0.04). Only SCCRO overexpression was associated with disease-specific (P = 0.04) and overall survival (P = 0.02). Furthermore, SCCRO overexpression remained an independent predictor for cervical nodal metastasis on multivariate regression analysis (chi(2) likelihood ratio = 4.38; P = 0.04). CONCLUSIONS: Although both SCCRO and PIK3CA may play a role in the pathogenesis of oral tongue SCC through amplification at 3q26, SCCRO appears to be a significant predictor of regional metastasis and may be a marker for tumor aggressiveness and clinical outcome.
Assuntos
Carcinoma de Células Escamosas/genética , Oncogenes/fisiologia , Fosfatidilinositol 3-Quinases/fisiologia , Neoplasias da Língua/genética , Adulto , Idoso , Idoso de 80 Anos ou mais , Carcinoma de Células Escamosas/enzimologia , Carcinoma de Células Escamosas/patologia , Linhagem Celular Tumoral , Feminino , Dosagem de Genes , Humanos , Hibridização in Situ Fluorescente , Metástase Linfática , Masculino , Pessoa de Meia-Idade , Subunidades Proteicas , Neoplasias da Língua/enzimologia , Neoplasias da Língua/patologiaRESUMO
Interactions between the p53 and PI3K/AKT pathways play a significant role in the determination of cell death/survival. In benign cells these pathways are interrelated through the transcriptional regulation of PTEN by p53, which is required for p53-mediated apoptosis. PTEN exerts its effects by decreasing the phosphorylated AKT fraction, thereby diminishing prosurvival activities. However, the link between these pathways in cancer is not known. In this study, PIK3CA, encoding the p110alpha catalytic subunit of PI3K, is identified as an oncogene involved in upper aerodigestive tract (UADT) carcinomas. Simultaneous abnormalities in both pathways are rare in primary tumors, suggesting that amplification of PIK3CA and mutation of p53 are mutually exclusive events and either event is able to promote a malignant phenotype. Moreover, the negative effect of p53 induction on cell survival involves the transcriptional inhibition of PIK3CA that is independent of PTEN activity, as PTEN is not expressed in the primary tumors. Conversely, constitutive activation of PIK3CA results in resistance to p53-related apoptosis in PTEN deficient cells. Thus, p53 regulates cell survival by inhibiting the PI3K/AKT prosurvival signal independent of PTEN in epithelial tumors. This inhibition is required for p53-mediated apoptosis in malignant cells.
