Homozygous deletions on the short arm of chromosome 3 in human oral squamous cell carcinomas

An actionable test using loss of heterozygosity in identifying high-risk oral premalignant lesions

OBJECTIVES

To develop an actionable test using fluorescence capillary electrophoresis (FCE) to assess loss of heterozygosity (LOH) of histologically similar low-grade lesions (LGLs) to identify high-risk lesions for oral cancer progression.

STUDY DESIGN

To determine the cutoffs of LOH, the FCE results of 52 surgical margin samples were used to compare with the existing LOH results from the previously validated 32 P-GE approach. Using the developed FCE workflow, an independent set of 102 LGLs with known progression status was used to determine the LOH molecular risk (MR) patterns and associated risk of progression.

RESULTS

Using 65% cutoff LOH-FCE, the agreement of LOH-32 P-GE had an average of 82.3% (76.8-87.8). Compared with nonprogressors (n = 61), anatomic site and MR patterns (LOH at 9 p21, 3 p14, or 17 p13) were independent risk factors. High-risk profile of tongue and MR3 (LOH at 9 p21 and/or 3 p14 and 17 p13) was significantly associated with progression (hazard ratio [HR] 6.7; 95% confidence interval [CI] 2.6-17.6) with specificity of 98.4% at identifying progressors.

CONCLUSIONS

We have developed an objective test using LOH to stratify the risk of LGLs. With further validation, it can be used in the clinical settings to provide clinicians additional information guiding the management of these lesions.

Genetic gains and losses in oral squamous cell carcinoma: impact on clinical management

PURPOSE

The identification of genetic markers associated with oral cancer is considered essential to improve the diagnosis, prognosis, early tumor and relapse detection and, ultimately, to delineate individualized therapeutic approaches. Here, we aimed at identifying such markers.

METHODS

Multiplex Ligation-dependent Probe Amplification (MLPA) analyses encompassing 133 cancer-related genes were performed on a panel of primary oral tumor samples and its corresponding resection margins (macroscopically tumor-free tissue) allowing, in both types of tissue, the detection of a wide arrange of copy number imbalances on various human chromosomes.

RESULTS

We found that in tumor tissue, from the 133 cancer-related genes included in this study, those that most frequently exhibited copy number gains were located on chromosomal arms 3q, 6p, 8q, 11q, 16p, 16q, 17p, 17q and 19q, whereas those most frequently exhibiting copy number losses were located on chromosomal arms 2q, 3p, 4q, 5q, 8p, 9p, 11q and 18q. Several imbalances were highlighted, i.e., losses of ERBB4, CTNNB1, NFKB1, IL2, IL12B, TUSC3, CDKN2A, CASP1, and gains of MME, BCL6, VEGF, PTK2, PTP4A3, RNF139, CCND1, FGF3, CTTN, MVP, CDH1, BRCA1, CDKN2D, BAX, as well as exon 4 of TP53. Comparisons between tumor and matched macroscopically tumor-free tissues allowed us to build a logistic regression model to predict the tissue type (benign versus malignant). In this model, the TUSC3 gene showed statistical significance, indicating that loss of this gene may serve as a good indicator of malignancy.

CONCLUSIONS

Our results point towards relevance of the above mentioned cancer-related genes as putative genetic markers for oral cancer. For practical clinical purposes, these genetic markers should be validated in additional studies.

Frequent allelic loss of 21q11.1∼q21.1 region in advanced stage oral squamous cell carcinoma

A fine mapping of loss of heterozygosity (LOH) was performed in oral squamous cell carcinoma (OSCC), using 12 markers on 21q11.1 approximately q21.1. We studied 43 resected primary invasive tumors and their paired normal tissues, concurrent dysplasia or carcinoma in situ in separate areas from 8 of the specimens, and 6 local recurrent carcinomas. LOH status was compared between lesions of different phases of progression within the same patient. A high frequency of LOH was observed for D21S1410, D21S120, and D21S1433 (60% each) in the primary lesions, constituting two interstitial deleted regions encompassing eight known genes. Cases showing LOH of D21S120 were significantly associated with advanced clinical stages (III and IV; P=0.02). Consistent allelic loss was observed in 64.2% of the informative cases between the precursor lesions and their corresponding invasive tumors, and in 59.5% of those between the primary lesions and their recurrent counterparts. Fewer than half of the different lesions within a given patient showed discordant allelic loss for tested markers. Our results suggest that 21q11.1 approximately q21.1 harbors tumor suppressor genes in OSCC. Genetic divergence may develop during tumor clone evolution.