Biomedical applications of vibrational spectroscopy: Oral cancer diagnostics

Vibrational spectroscopy, based on either infrared absorption or Raman scattering, has attracted increasing attention for biomedical applications. Proof of concept explorations for diagnosis of oral potentially malignant disorders and cancer are reviewed, and recent advances critically appraised. Specific examples of applications of Raman microspectroscopy for analysis of histological, cytological and saliva samples are presented for illustrative purposes, and the future prospects, ultimately for routine, chairside in vivo screening are discussed.

Genetic polymorphism of tumor necrosis factor alpha (TNF-α) and tumor necrosis factor beta (TNF-β) genes and risk of oral pre-cancer and cancer in North Indian population

OBJECTIVE

There are inconclusive data connecting single-nucleotide polymorphisms (SNPs) of TNF-α (rs361525) and TNF-β (rs909253) to potential malignant oral disorder (PMOD) such as lichen planus and oral fibrosis. Here, we have investigated the risk of oral squamous cell carcinoma as well as oral pre-cancerous lesions in North Indian population with the polymorphism of the TNFα/ β genes.

MATERIAL AND METHODS

A total 500 patients with oral pre-cancer and OSCC and 500 healthy volunteers were genotypes for the TNF-α (-238) G/A (rs361525) and TNF-β (252) A/G (rs909253) gene polymorphism. Genotypes were identified by polymerase chain reaction (PCR) restriction fragment length polymorphism (RFLP). Genotype frequencies were evaluated by Chi-square test.

RESULTS

Compared to the GG genotype, the GA genotype of TNF-α (G238A) polymorphism (rs361525) has been found to significantly increase the risk of oral disease (OR = 1.99) and especially the risk of lichen planus and OSCC (OR = 2.805 and 5.790, respectively). Similarly, the risk of oral disease was also more in the heterozygote (AG) than the common allele homozygote (AA) of TNF-β (A252G) polymorphism (rs909253) (OR = 1.483).

CONCLUSION

We conclude that the SNPs rs361525 and rs909253 were significantly associated with oral pre-cancer and OSCC.

DNA methylation markers for oral pre-cancer progression: A critical review

Although oral cancers are generally preceded by a well-established pre-cancerous stage, there is a lack of well-defined clinical and morphological criteria to detect and signal progression from pre-cancer to malignant tumours. We conducted a critical review to summarize the evidence regarding aberrant DNA methylation patterns as a potential diagnostic biomarker predicting progression. We identified all relevant human studies published in English prior to 30th April 2015 that examined DNA methylation (%) in oral pre-cancer by searching PubMed, Web-of-Science and Embase databases using combined key-searches. Twenty-one studies (18-cross-sectional; 3-longitudinal) were eligible for inclusion in the review, with sample sizes ranging from 4 to 156 affected cases. Eligible studies examined promoter region hyper-methylation of tumour suppressor genes in pathways including cell-cycle-control (n=15), DNA-repair (n=7), cell-cycle-signalling (n=4) and apoptosis (n=3). Hyper-methylated loci reported in three or more studies included p16, p14, MGMT and DAPK. Two longitudinal studies reported greater p16 hyper-methylation in pre-cancerous lesions transformed to malignancy compared to lesions that regressed (57-63.6% versus 8-32.1%; p<0.01). The one study that explored epigenome-wide methylation patterns reported three novel hyper-methylated loci (TRHDE; ZNF454; KCNAB3). The majority of reviewed studies were small, cross-sectional studies with poorly defined control groups and lacking validation. Whilst limitations in sample size and study design preclude definitive conclusions, current evidence suggests a potential utility of DNA methylation patterns as a diagnostic biomarker for oral pre-cancer progression. Robust studies such as large epigenome-wide methylation explorations of oral pre-cancer with longitudinal tracking are needed to validate the currently reported signals and identify new risk-loci and the biological pathways of disease progression.