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Background: CT120 is a universally expressed protein with seven transmembrane domains. It functions in cell proliferation, survival and apoptosis by activating Raf/MEK/ERK and PI3K/Akt signaling pathways. Evidence suggests that CT120 plays important roles in lung carcinogenesis and oncogenic pathway activation. c-Myc is an important transcription factor modulating cell progression, apoptosis and cellular transformation. Previous studies have shown that MYC gene is amplified in many types of cancer including head and neck squamous cell carcinoma (HNSCC). Myc can regulate expression of many genes by binding to E-boxes. The aim of this study was to investigate the relationship between c-Myc protein and CT120 gene.Methods: Tumor and normal tissue samples from 50 patients with HNSCC were investigated with chromatin immunoprecipitation assay (ChIP), Illumina MiSeq, bisulphite sequencing and qRT-PCR.Results: c-Myc binds to all E-boxes except E-box 5 on CT120 promoter. The CpG dinucleotides were found to be partially methylated in all tumor and normal tissue samples. Bisulphite sequencing showed a 10% down-regulation in the methylation levels of the tumor tissues. CT120 gene was hypomethylated and up-regulated in 56% of the tumor tissue samples. Expression of c-Myc was significantly higher in tumor tissues than in non-cancerous tissue samples. MYC was overexpressed in 68% of the tumor tissue samples compared to normal tissues. The mean MYC levels were 2.42-fold higher in the tumor tissue samples. In 48% of the tumor tissues, MYC and CT120A mRNA were up- or down-regulated simultaneously (p<0.001).Conclusion: We show that CT120 gene is a target of c-Myc and it contributes to cancer progression in HNSCC.

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Background: Wnt signaling pathway is associated with a variety of human cancers, including HNSCC. Wnt proteins control cellular events such as proliferation, fate specification, polarity, and migration by transducing signals to the nucleus through several cytoplasmic relay proteins. Although activation of the Wnt/β-catenin pathway is a frequent event in various cancers, there is limited knowledge on the contribution of this signaling mechanism in HNSCC. The Wwox tumor suppressor protein participates in the regulation of Wnt signaling by interacting with Dvl proteins. Methods: In this study, we used qRT-PCR and western blotting to examine the mRNA and protein levels of the Dvls in association with WWOX in HNSCC cell lines and tumor tissues. Results: We found that silencing of WWOX leads to increased nuclear localization of the Dvl proteins in cell lines. However, we detected an increase only in the nuclear localization of Dvl-1 in tumor tissues. Conclusions: Our results suggest that aberrant WWOX expression contributes to HNSCC through the Wnt signaling pathway. Decreased expression of WWOX may function in HNSCC progression by allowing the nuclear localization of Dvl proteins.

Object. Thyroid cancer (TC) is a rare type of cancer which occurs as a result of environmental and genetic factors. Although different types of genetic and epigenetic changes are associated with TC, the molecular mechanism still remains unclear. SRY-box transcription factor 15 (SOX15) is an important transcription factor, and its expression is altered in many cancer types by epigenetic modifications. Recently, miR-147b overexpression has been associated with SOX15 silencing in TC. Methods. In this study, qRT-PCR was used to investigate the expression levels of the SOX15 gene and of miR-182, miR-183, miR-375, and miR-96 in thyroid tumors and adjacent noncancerous tissues. We also investigated the methylation status of the SOX15 promoter by methylation-specific PCR in tumors and adjacent noncancerous tissues. Results. We observed a statistically significant downregulation of SOX15 expression in tumors compared to noncancerous tissue samples. The methylation levels of tumors and matched noncancerous tissues were similar, but miR-182, miR-183, and miR-375 expression levels were elevated in tumor tissues compared to noncancerous tissue samples. Conclusions. Our results indicate that SOX15 gene expression is associated with the pathogenesis of papillary thyroid carcinoma (PTC), and the epigenetic control of the SOX15 gene is regulated by miRNAs rather than by promoter methylation.

Although thyroid cancer (TC) is a rare cancer with a rate of 2.1%, it is the most common cancer type among endocrine tumors. The molecular mechanisms of thyroid cancer, which develops as a result of environmental and genetic factors, are still unclear. SOX family genes are transcription factors that are expressed in a tissue-specific manner and play a role in the developmental processes. SRY-box transcription factor 15 (SOX15) is an important member of the SOX family and is involved in carcinogenesis. Its downregulation has been associated with the development and progression of different human malignancies. Some SOX family members have been reported to control cell proliferation by acting as negative regulators of the Wnt/β-catenin signaling pathway. MYC, CCND1 and CTNNB1 genes are important components of the Wnt signaling pathway. Recently, we have shown that epigenetic silencing of the SOX15 gene is associated with the pathogenesis of papillary thyroid carcinoma,In the present study, to further the understanding of the molecular mechanisms of SOX15 in papillary thyroid carcinoma (PTC) we investigated SOX15 expression in association with the transcriptional targets of the Wnt/β-catenin pathway.Primary thyroid tumors and adjacent nonmalignant tissue samples were collected from 52 patients, prior to any treatment. Total RNA was isolated from tissue samples and reverse transcription was performed. Expression levels of the SOX15, CTNNB1, c-MYC and CCND1 genes were analyzed by qRT-PCR using the SYBR green and Light-Cycler 480 system (Roche Diagnostics, Germany). β2M was used as the reference to normalize the mRNA levels. Statistical analysis was performed using the SPSS 21.0 (IBM® SPSS® Statistics, IBM Corporation Somers, NY, USA) program.SOX15 gene expression was significantly downregulated in 64.6% of PTC tissues compared to their normal counterparts. In contrast, CCND1, CTNNB1 and c-MYC gene expressions were significantly upregulated in 70.2%, 60% and 57.8% of the patients. Among the group of patients with downregulated SOX15 expression CCND1, CTNNB1 and c-MYC expression were upregulated in 46.8%, 40% and 40% of the subjects, respectively. Our data suggest that SOX15 downregulation may contribute to activation of Wnt signaling and provides further evidence indicating involvement of SOX15 in modulating the Wnt/β-catenin pathway in thyroid carcinogenesis. Citation Format: Ayse Nur Buyru, Ayşegul Soysal, Ahmet Ozaydın, Betul Seyhan, Soykan Arıkan, Nejat Dalay. Expression of SOX15 and Wnt pathway genes in papillary thyroid carcinoma [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 776.

The second most common fragile site in the human genome is the FRA16D region where the WWOX gene is localized which codes for a 414 amino acid protein. WWOX is a member of the WW-domain containing protein family consisting of 2000 members. It is a partner of several transcription factors and therefore functions in multiple physiological and pathological processes such as cell growth, differentiation and tumor suppression. Genomic alterations within the WWOX gene and its differential expression have been found in a variety of human tumors. Although some transcription factor partners of the WWOX protein have been identified its exact mechanism of action is not known. A recent study indicated that WWOX inhibits the Wnt/β-catenin pathway by preventing the nuclear import of the Dishvelled (Dvl) proteins. Dvl proteins are the main down-stream target of Wnt receptors (Frizzled- FRZ). Following binding of Wnt to its receptor alterations of β-catenin degradation lead to β-catenin accumulation in the cytoplasm. Accumulated β-catenin translocates into the nucleus and activates expression of target genes. Therefore dysregulation of the Wnt signaling pathway is a key oncogenic mechanism in many different cancers. Although Wnt and its receptor FRZ have been analyzed in head and neck squamous cell carcinoma (HNSCC) the intracellular components of the pathway have not been investigated. This is the first study in the literature reporting a role for β-catenin and Dvl mRNA level alterations in HNSCC. In our previous study we have identified that the WWOX gene is inactivated in HNSCC as a result of genetic and epigenetic alterations. To identify the mechanism of action of WWOX in HNSCC in this study we investigated its expression in association with Dvl-1, Dvl-2, Dvl-3 and β-catenin expression in 98 HNSCC samples. We observed down-regulation of the WWOX mRNA in 73.5% of the HNSCC tumor samples compared to their non-cancerous counterparts. Up-regulation of the Dvl-1, Dvl-2, Dvl-3 and β-catenin mRNAs were detected in 32.7%, 36%, 38.8% and 24.5% of the same tumor samples, respectively. We also detected a statistically significant correlation between the WWOX gene expression and mRNA levels of the intracellular components of the Wnt pathway genes. Our results indicate that WWOX acts as a tumor suppressor in the HNSCC development and progression by inhibiting the expression of the Dvl proteins. Citation Format: Ayse Nur Buyru, Asuman Celebi, Betul Seyhan. The role of WWOX in HNSCC through Wnt/beta-catenin pathway [abstract]. In: Proceedings of the AACR International Conference: New Frontiers in Cancer Research; 2017 Jan 18-22; Cape Town, South Africa. Philadelphia (PA): AACR; Cancer Res 2017;77(22 Suppl):Abstract nr B33.

HNSCC is the sixth most common form of cancer and represents the third common cause of cancer-related deaths worldwide. Therefore, there is a need to understand the molecular mechanisms involved in the pathogenesis of HNSCC. The c-myc protein belongs to the myc family of transcription factors and plays a fundamental role in cell cycle progression, apoptosis and cellular transformation. In the human genome, the MYC gene is located on chromosome 8 and its protein product regulates expression of 15% of all genes through binding to the Enhancer box (E-box) sequences. An E-box is a DNA sequence found in the promoter regions of eukaryotic genes that acts as a protein binding site to regulate gene expression. The CANNTG consensus sequence of the E-box is known as the canonical E-boxes. There are several other non-canonical E-box motifs such as the GATGTG, CATGCG, CACGCG, CACGAG, CGCGAG and CAACGTG sequences. Amplification of the MYC gene is observed in many different types of cancers including HNSCC. CT120 is a novel gene which encodes a human trans-membrane plasma protein. It has been shown that up-regulation of CT120 is associated with lung and head and neck carcinogenesis. In this study we investigated the promoter region of the CT120 gene and identified 6 E-boxes. To test whether c-myc binds to these E-boxes we performed chromatin immunoprecipitation (ChIP) assays. We demonstrated that c-myc binds strongly to the E-boxes 2, 3 and 4. It is well known that the expression rates of the genes are under the control of epigenetic modifications. Methylation of the CpG islands which are found in the promoter regions is one of the most studied epigenetic modifications. We identified two putative CpG islands in the promoter of the CT120 gene. To investigate the possible epigenetic regulation of CT120 and the effect of the promoter methylation to the binding of c-myc, we also investigated the methylation levels of the two islands in the CT120 promoter by MS-PCR. We observed a slight decrease (3.1%) in the methylation level of the first CpG-rich region. In 56% (28/50) of the tumor tissues methylation was decreased compared to the non-cancerous tissues. However, there was no statistically significant correlation between the promoter methylation and CT120 mRNA level. Depending on these data we investigated the expression levels of the c-myc and CT120 in the 50 HNSCC and normal tissue samples by qRT-PCR and observed a direct correlation between the overexpression of the c-myc and CT120 genes. Overexpression of CT120 and c-myc were observed in 29 (58%) and 34 (68%) of the tumors, respectively, compared to non-cancerous tissues. A total of 24 (48%) patients out of 50 showed a concurrent pattern of either up- or down regulation. Our results indicate that the CT120 gene is a target of c-myc and that both proteins may participate in the progression of HNSCC. Citation Format: Onur Baykara, Elif Baltaci, Betul Seyhan, Nejat Dalay, Nur Buyru. Regulation of CT120 gene as a new target of c-myc in head and neck squamous cell carcinoma (HNSCC). [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 1132.