Beyhan Cengiz

C-kit protein expression correlated with activating mutations in KIT gene in oral mucosal melanoma.

C-kit is a trans-membrane receptor tyrosine kinase (RTK) encoded by the proto-oncogene KIT located at 4q11-12. Gain-of-function mutations arising to c-kit activation independent of its ligand were observed in various tumors related to germ cells, mast cells, and interstitial cells of Cajal. C-kit also participates in melanocyte development; hence, its involvement in oral mucosal melanoma (OMM) tumorigenesis was investigated. Immunohistochemistry and mutation analysis were performed using 18 cases of human primary OMM. Results revealed 16 cases positive to c-kit protein. Atypical melanocytes expressed c-kit. All in situ components expressed c-kit, but only four cases exhibited intense expression in the invasive component. Missense mutations were observed in four cases, and two of those correlated with increased protein expression. C-kit expression in atypical melanocytes suggests the role of c-kit in the early stage of OMM tumorigenesis. C-kit protein expression correlated with activating mutations indicating the pertinent role of the proto-oncogene KIT in the tumorigenesis of OMM.

Expression and mutation analysis of epidermal growth factor receptor in head and neck squamous cell carcinoma.

The epidermal growth factor receptor (EGFR)–RAS–RAF–mitogen‐activated protein kinase signaling cascade is an important pathway in cancer development and recent reports show that EGFR and its downstream signaling molecules are mutated in a number of cancers. We have analyzed 91 Japanese head and neck squamous cell carcinomas (HNSCC) and 12 HNSCC cell lines for mutations in EGFR, ErbB2, and K‐ras. Exons encoding the hot‐spot regions in the tyrosine kinase domain of both EGFR (exons 18, 19, and 21) and ErbB2 (exons 18–23), as well as exons 1 and 2 of K‐ras were amplified by polymerase chain reaction and sequenced directly. EGFR expression was also analyzed in 65 HNSCC patients using immunohistochemistry. Only one silent mutation, C836T, was found in exon 21 of EGFR in the UT‐SCC‐16A cell line and its corresponding metastasic cell line UT‐SCC‐16B. No other mutation was found in EGFR, ErbB2, or K‐ras. All tumors showed EGFR expression. In 21 (32%) tumors, EGFR was expressed weakly (+1). In 27 (42%) tumors it was expressed (+2) moderately, and in 17 (26%) tumors high expression (+3) was detected. Overexpression (+2, +3) was found in 44 tumors (68%). A worse tumor differentiation and a positive nodal stage were significantly associated with EGFR overexpression (P = 0.02, P = 0.032, respectively). Similar to patients from western ethnicity, mutations are absent or rare in Japanese HNSCC. Protein overexpression rather than mutation might be responsible for activation of the EGFR pathway in HNSCC. (Cancer Sci 2008; 99: 1589–1594)

Tumor‐specific mutation and downregulation of ING5 detected in oral squamous cell carcinoma

Our previous study showed high frequency of allelic loss at chromosome 2q37 region in oral cancer. This location contains several candidate tumor suppressor genes such as PPP1R7, ILKAP, DTYMK and ING5. We previously showed 3 members of inhibitor of growth (ING) family, ING1, ING3 and ING4 as tumor suppressor gene in head and neck cancer. As ING5 shows high homology with other members of ING genes including highly conserved carboxy‐terminal plant homeodomain and nuclear localization signal, we first picked up ING5 and examined it as a possible tumor suppressor in oral cancer. For this aim, mutation and mRNA expression status of ING5 in paired normal and oral squamous cell carcinoma samples were examined by reverse transcription polymerase chain reaction (RT‐PCR) and sequencing. Three missense mutations located within leucine zipper like (LZL) finger and novel conserved region (NCR) domains in ING5 protein were detected, probably abrogating its normal function. We also found 5 different alternative splicing variants of ING5. Then, we examined mRNA level of ING5 by quantitative real time reverse transcription polymerase chain reaction (qRT‐PCR) analysis, which demonstrated decreased expression of ING5 mRNA in 61% of the primary tumors as compared to the matched normal samples. In conclusion, tumor‐specific mutation and downregulation of ING5 mRNA suggested it as a tumor suppressor gene in oral squamous cell carcinoma.

Increased mRNA expression of ADAMTS metalloproteinases in metastatic foci of head and neck cancer.

Although contribution of matrix metalloproteinases in cancer progression and dissemination is now well known, roles of recently discovered metalloproteinases, a disintegrin and metalloproteinase with thrombospondin motifs (ADAMTS), in cancer development and progression remain mostly unknown.

Loss of heterozygosity at chromosome 14q is associated with poor prognosis in head and neck squamous cell carcinomas

Purpose and methodsLoss of heterozygosity (LOH) in a chromosomal location indicates the presence of an inactivated tumor suppressor gene (TSG). Inactivation of TSG has a functional role in the tumorigenesis of head and neck squamous cell carcinoma (HNSCC). Based on the recent evidences of a putative TSG on chromosome 14, we examined LOH on chromosome 14q using eight polymorphic microsatellite markers in 50 cases of HNSCCs.ResultsThree regions were detected to have a high LOH rate which included 14q21.2-22.3 (42.5%), 14q31 (55%), and 14q32.1 (37%). The correlation between LOH and clinicopathological findings was investigated through statistical analyses. A strong correlation was observed between the highest LOH marker and the overall and disease-free survival.ConclusionsThe results suggest that the distal part of chromosome 14 may host a TSG that may lead to the development and/or progression of HNSCCs. Several genes such as CHES1, BMP4, SAV, and PNN have arisen as candidate tumor suppressors in the region.

Comprehensive loss of heterozygosity analysis and identification of a novel hotspot at 3p21 in salivary gland neoplasms

OBJECTIVES: We sought to assess loss of heterozygosity (LOH) profiles of 3p, 6q, 8q, 10q, 12q, 13q, and 17p and to identify the tumor suppressor genes involved in salivary gland neoplasms. STUDY DESIGN: LOH analysis was performed using 26 microsatellite markers by polymerase chain reaction—polyacrylamide gel electrophoresis method in 20 benign and 6 malignant salivary gland tumors. RESULTS: Overall, LOH was detected in at least one informative locus in 18 of 20 (90%) of benign tumors and in all of 6 cases of malignant tumors. High LOH frequencies were revealed at the loci D3S1307 (22%, 3p26), D3S966 (41%, 3p21), D6S255 (27%, 6q25), D8S166 (25%, 8q12), D8S199 (21%, 8q24), and D10S1765 (28%, 10q23) in benign tumors, defining the hotspot regions for putative tumor suppressor genes. CONCLUSIONS AND SIGNIFICANCE: The hotspot regions defined by the present study suggest that new tumor suppressor genes related to the development of salivary gland tumors may reside at several chromosomal loci, including loci at 3p, 6q, 8q and 10q.

NADPH oxidase p22phox gene expression in ulcerative colitis.

BACKGROUND/AIMSnNicotinamide adenine dinucleotide phosphate (NADPH) oxidase, which catalyzes the formation of reactive oxygen species (ROS) in phagocytic cells, has five subunits: p67phox (phoxrefers to phagocyte oxidase), p47phox, p40phox, p22phox, and gp91phox (catalytic subunit). Oxidative stress resulting from the accumulation of ROS and/or defective removal of ROS by antioxidants has detrimental effects on cellular functions and may contribute to chronic inflammation. Disruption of the colonic mucosa due to the dysregulation of antioxidants or transformation enzymes may play a role in the pathogenesis of ulcerative colitis (UC) and influence the clinical features of this disease. In this study, we examined the expression of the gene encoding NADPH oxidase subunit p22phox cytochrome b-245, alphapolypeptidein the colonic mucosa to test its possible contribution in the pathogenesis of UC.nnnMATERIALS AND METHODSnExpression levels of mRNA in the inflamed and non-inflamed colonic mucosa (determined using colonoscopy)of 22 patients with UC and in the normal mucosa of 22 healthy controls were analyzed using real-time polymerase chain reaction.nnnRESULTSnExpression levels of mRNA were not significantly different between patients with inflamed and non-inflamed colonic mucosa (p>0.05) and betweenpatients with inflamed colonicmucosa and healthy controls (p>0.05).nnnCONCLUSIONnAlthough our data suggest that expression of the gene encoding p22phox is not associated with chronic inflammation in patients with UC, other mechanisms can affect oxidative stress in these patients.