P53 Functional Assay (FASAY) in Head and Neck Squamous Cell Carcinoma : preanalytical issues and value as indicator of field cancerization?
(2012)
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- Authors
- Supervisors
- Gala, Jean-Luc
- Abstract
- (en) Head and Neck Squamous Cell Carcinoma (HNSCC) is a complex disease arising in various localisations of the upper aerodigestive tract, caused by tobacco and alcohol consumption or by high-risk types of human papillomavirus. These tumors often develop within pre-neoplastic fields of genetically altered cells that often extend out of the clinically and macroscopically involved area where the focus of treatment is. This phenomenon is a major cause of locoregional recurrences or second primary tumors and subsequently of poor survival improvement in HNSCC patients. Among the numerous genetic alterations found in HNSCC carcinogenesis, mutations of TP53 tumor suppressor gene were found to be one of the earliest and the most significant events of invasive cancer development. TP53 gene encodes the p53 protein that plays a crucial role in apoptosis and cell cycle control, making it a plausible predictive biomarker for HNSCC survival. The purpose of the study was to investigate the field cancerization through the analysis of p53 functionality on both tumoral and histologically normal tissue distant from the tumor. As expected, alteration of p53 functionality was encountered in 88% of tumoral samples. More interestingly, the loss of p53 transcriptional activity was detected in 18% of distant histologically normal samples and was significantly associated with loco-regional recurrences. We demonstrated that FASAY positivity indicates field cancerization in a subgroup of patients with HNSCC. These findings prompted us to pursue the study on p53 functional status of normal mucosa in patients with HNSCC in a homogeneous cohort of patients with oropharyngeal squamous cell carcinoma, stratified for HPV status, obtained by multicentric study. In order to avoid underestimation of the FASAY positive rate in histologically normal surrounding mucosa, we developed a non-invasive collection method allowing the study of a wider mucosal surface. While this sample collection method deals with scarce tissue material and in order to circumvent the material loss due to manual homogenization of samples, we studied an automated extraction process. This technique appeared to be a versatile, quick, safe, and reliable homogenization method, especially useful for small ≤10 mg oral squamous cell carcinoma samples. With the improved rate of RNA extraction obtained when using an automated method, FASAY on scant target cells obtained by scraping the oral mucosa appeared feasible and reproducible. Our experience with the FASAY technique showed that both tissue quantity and quality are mandatory. Keeping in mind the perspective of a multicentric trial, we set up a method to store and transport easily and safely our tissue samples in optimal conditions for further RNA extraction and FASAY processing. This work demonstrated that FASAY positivity is the hallmark of HNSCC and a reliable and sensitive tool to demonstrate the presence of field cancerization in a subgroup of patients. A prospective multicentric study on the p53 functional status of normal mucosa in patients with HNSCC or even who are still cancer-free but heavily exposed to HNSCC risk factors is needed.
- Affiliations
Citations
Van Der Vorst, S. (2012). P53 Functional Assay (FASAY) in Head and Neck Squamous Cell Carcinoma : preanalytical issues and value as indicator of field cancerization? https://hdl.handle.net/2078.5/76197