DMBT1 has been implicated as a candidate tumor suppressor gene on chromosome 10q for brain, gastrointestinal and lung cancer. Homozygous deletion and lack of expression are 2 known mechanisms for inactivating DMBT1. We evaluated whether somatic mutation, which represents a major inactivation mechanism for most tumor suppressor genes, occurs in the DMBT1 gene. A total of 102 primary brain tumors, consisting of 25 glioblastoma multiforme, 24 medulloblastoma and 53 oligodendroglial tumors, were analyzed by conformation-sensitive gel electrophoresis in all 54 coding exons of DMBT1. Twelve different base substitutions were detected in 26 (25%) tumors. Eight base substitutions resulted in amino acid changes and 4 were silent. These base changes were also detected in tumor-matched blood samples, however, indicating that the base variations represent genetic polymorphisms. We also assessed homozygous deletions of the DMBT1 gene in the series and found that 16 of 95 (5 glioblastomas, 5 medulloblastomas, 6 oligodendroglial tumors; total 17%) tumors harbor such alteration. High-quality blood DNA samples were available in 5 tumors carrying homozygous deletion and, using long-range PCR, 3 of these blood samples showed germline hemizygous deletions in a region between introns 10 and 26 of DMBT1. Our results showed that mutation does not play a role in inactivation of DMBT1 in brain tumors. Intragenic homozygous deletion of DMBT1 is common in brain tumors and is likely a result of a germline deletion of 1 allele followed by loss of the second allele during tumor development.

Objectives: This systematic review and meta-analysis aims to evaluate the evidence on the malignant potential of oral lichenoid conditions (OLCs) including oral lichen planus (OLP), oral lichenoid lesions (OLL), and lichenoid mucositis dysplasia (LMD). In addition, it aims to compare the rate of malignant transformation (MT) in OLP patients diagnosed according to different diagnostic criteria, and to investigate the possible risk factors for OLP MT into OSCC. Materials and methods: A standardized search strategy was applied across four databases (PubMed, Embase, Web of Science, and Scopus). Screening, identification and reporting followed the PRISMA framework. Data on MT were calculated as a pooled proportion (PP), subgroup analyses and possible risk factors for MT were pooled as odds ratios (ORs). Results: Among 54 studies with 24,277 patients, the PP for OLCs MT was 1.07% (95% CI [0.82, 1.32]). The estimated MT rate for OLP, OLL and LMD was 0.94%, 1.95% and 6.31%, respectively. The PP OLP MT rate using the 2003 modified WHO criteria group was lower than that using the non-2003 criteria (0.86%; 95% CI [0.51, 1.22] versus 1.01%; 95% CI [0.67, 1.35]). A higher odds ratio of MT was observed for red OLP lesions (OR = 3.52; 95% CI [2.20, 5.64]), smokers (OR = 1.79; 95% CI [1.02, 3.03]), alcohol consumers (OR = 3.27, 95% CI [1.11, 9.64]) and those infected with HCV (OR = 2.55, 95% CI [1.58, 4.13]), compared to those without these risk factors. Conclusions: OLP and OLL carry a low risk of developing OSCC. MT rates differed based on diagnostic criteria. A higher odds ratio of MT was observed among red OLP lesions, smokers, alcohol consumers, and HCV-positive patients. These findings have implications for practice and policies.

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