Short telomeres in an oral precancerous lesion: Q-FISH analysis of leukoplakia Junko Aida 1,2 , Takanori Kobayashi 3 , Takashi Saku 4 , Masatsune Yamaguchi 5 , Naotaka Shimomura 1 , Ken-Ichi Nakamura 1 , Naoshi Ishikawa 1 , Satoshi Maruyama 3 , Jun Cheng 4 , Steven S. S. Poon 6 , Motoji Sawabe 2 , Tomio Arai 2 , Kaiyo Takubo 1,2 1 Research Team for Geriatric Pathology, Tokyo Metropolitan Institute of Gerontology, Itabashi-ku, Tokyo, Japan; 2 Department of Pathology, Tokyo Metropolitan Geriatric Medical Center, Itabashi-ku, Tokyo, Japan; 3 Surgical Pathology Section, Niigata University Hospital, Niigata City, Niigata Prefecture, Japan; 4 Division of Oral Pathology, Department of Tissue Regeneration and Reconstruction, Niigata University Graduate School of Medical and Dental Sciences, Niigata City, Niigata Prefecture, Japan; 5 Department of Dentistry and Oral Surgery, Tokyo Metropolitan Geriatric Hospital, Sakae-cho, Itabashi-ku, Tokyo, Japan; 6 Terry Fox Laboratory, British Columbia Cancer Research Centre, Vancouver, BC, Canada OBJECTIVES: A precancerous condition is a lesion that, if left untreated, leads to cancer or can be induced to become malignant. In the oral region, leukoplakia is a lesion that has been regarded as precancerous. In cases of oral carcinoma, we have frequently noticed that a type of leukoplakia histologically demonstrating hyper-ortho- keratosis and mild atypia (ortho-keratotic dysplasia; OKD) is often associated with carcinoma, either syn- chronously or metachronously. Therefore, we consider OKD-type leukoplakia to be a true precancerous lesion. MATERIALS AND METHODS: In an attempt to clarify the relationship between OKD as a precancerous condi- tion in the oral mucosa and telomere length, we esti- mated telomere lengths in this type of leukoplakia using quantitative fluorescence in situ hybridization, and also quantified the frequency of anaphase–telophase bridges (ATBs) in comparison with squamous cell carcinoma in situ (CIS) and the background tissues of CIS and OKD. RESULTS: Ortho-keratotic dysplasia was frequently associated with squamous cell carcinoma (45.0%) and showed significantly shorter telomeres than normal control epithelium, CIS, or the background of CIS or OKD. The frequency of ATBs was much higher in OKD than in control epithelium or CIS. CONCLUSION: Ortho-keratotic dysplasia appears to be frequently associated with carcinoma, chromosomal instability, and excessively shortened telomeres, not only in the lesion itself but also in the surrounding background. Therefore, when this type of leukoplakia is recognized in the oral region, strict follow-up for oral squamous cell carcinoma is necessary, focusing not only on the areas of leukoplakia, but also the surrounding background. J Oral Pathol Med (2011) Keywords: chromosomal instability; oral leukoplakia; precan- cerous condition; Q-FISH; telomere Abbreviations CIS: squamous cell carcinoma in situ; NTCR: normalized telomere to centromere ratio; OKD: ortho-keratotic dysplasia; Q-FISH: quantitative fluorescence in situ hybridization; TCR: telomere to centromere ratio. Introduction A precancerous condition is a disease, syndrome, or lesion that, if left untreated, leads to cancer or can be induced to become malignant. Well-known examples of precancerous conditions include actinic keratosis, Bar- rett’s esophagus, atrophic gastritis, and cervical dyspla- sia. In the oral region, leukoplakia, erythroplakia, and speckled mucosa are lesions that are considered poten- tially precancerous (1). However, the WHO has defined leukoplakia as a predominantly white lesion of the oral mucosa that cannot be characterized as any other definable lesion (2). The distinguishing feature of leukoplakia that is truly precancerous is the presence of microscopic changes associated with dysplasia (3). Leukoplakias are often observed in cases of oral carcinoma, either synchronously or metachronously. In particular, we have recently noticed that a type of leukoplakia histologically demonstrating hyper-ortho- keratosis and a well-developed granular layer with mild atypia [ortho-keratotic dysplasia: OKD (4)] is often associated with carcinoma. Telomeres are repetitive G-rich DNA sequences found at the ends of linear eukaryotic chromosomes and appear to play a key role in preventing genomic instability (5, 6). It has been hypothesized that aging is intrinsically related to carcinogenesis, as telomere Correspondence: Junko Aida, Research Team for Geriatric Pathol- ogy, Tokyo Metropolitan Institute of Gerontology, 35-2 Sakae-cho, Itabashi-ku, Tokyo 173-0015, Japan. Tel: +81 3 3964 3241, Fax: +81 3 3579 4776, E-mail: aidajs@tmig.or.jp Accepted for publication November 4, 2011 doi: 10.1111/j.1600-0714.2011.01120.x J Oral Pathol Med ª 2011 John Wiley & Sons A/S Æ All rights reserved wileyonlinelibrary.com/journal/jop Journal of Oral Pathology & Medicine