Escape from Cellular Senescence Is Associated with Chromosomal Instability in Oral Pre-Malignancy

SIMPLE SUMMARY: Cancer cells commonly escape cell death and proliferate endlessly. We review the molecular mechanisms that are fundamental to this process and suggest that these changes also lead to instability in the genetic make-up (genes and chromosomes) of putative cancer cells. In this way, cells in the very early stages of cancer development acquire unlimited growth potential and also develop cellular diversity, which may facilitate more aggressive cell behaviour and the development of overt cancer. These observations have important clinical implications. We highlight a recent sensitive technique to detect chromosome instability in cells that are shed into the saliva, which can be used for the detection of the early stages of cancer of the mouth. In addition, we discuss new drug developments that are designed to target chromosome instability and, therefore, eliminate potentially dangerous cells before cancer development. ABSTRACT: An escape from cellular senescence through the development of unlimited growth potential is one of the hallmarks of cancer, which is thought to be an early event in carcinogenesis. In this review, we propose that the molecular effectors of senescence, particularly the inactivation of TP53 and CDKN2A, together with telomere attrition and telomerase activation, all lead to aneuploidy in the keratinocytes from oral potentially malignant disorders (OPMD). Premalignant keratinocytes, therefore, not only become immortal but also develop genotypic and phenotypic cellular diversity. As a result of these changes, certain clonal cell populations likely gain the capacity to invade the underlying connective tissue. We review the clinical implications of these changes and highlight a new PCR-based assay to identify aneuploid cell in fluids such as saliva, a technique that is extremely sensitive and could facilitate the regular monitoring of OPMD without the need for surgical biopsies and may avoid potential biopsy sampling errors. We also draw attention to recent studies designed to eliminate aneuploid tumour cell populations that, potentially, is a new therapeutic approach to prevent malignant transformations in OPMD.