Impact of chromosome 9 numerical imbalances in oral squamous cell carcinoma: A pilot grid-based centromere analysis

Abstract

Oral squamous cell carcinoma (OSCC) is considered an aggressive malignancy, mainly due to its increased propensity to provide local and distant lymph node metastases. Gross chromosome instability (CI; polysomy/aneuploidy/monosomy), combined or not with specific gene alterations, is implicated in the development and progression of solid malignancies, including OSCC. In order to further study the relationship between these genetic alterations and the aggressive biological behavior of OSCCs, we investigated the frequency and impact of chromosome 9 numerical imbalances in these tumors. Fifty (n = 50) formalin-fixed, paraffin-embedded primary OSCC tissue sections were used. Chromogenic in situ hybridization (CISH) was implemented for detecting chromosome 9 (CEN-centromere enumeration) numerical alterations. Concerning the screening process in CISH slides, a novel, real-time reference and calibration grid platform was implemented. Chromosome 9 polysomy was observed in 8/50 (16%) tissue sections, whereas the rest of them demonstrated a normal, diploid pattern (42/50; 84%). Chromosome 9 polysomy was associated with the grade of differentiation of the examined tumors (p = 0.036). Chromosome 9 numerical imbalances (polysomy) were observed in sub-groups of OSCCs correlating with a progressive dedifferentiation of the malignant tissues. Concerning the implementation of the proposed grid-based platform as described above on CISH slides, it provides a novel, fast, and accurate screening mapping mechanism for detecting chromosome numerical imbalances.