Abstract
Problem
Squamous cell carcinomas arising from various subsites within the head and neck (HNSCC), while histologically identical, have substantial differences in survival and recurrence rates. Controversy exists as to whether this reflects physical differences or fundamental molecular heterogeneity between subsites. In this study, we used two proteomics approaches to evaluate HNSCCs for differences in protein expression between subsites including oral cavity, oropharynx, larynx and hypopharynx.
Methods
Tumor tissue from a total of 85 patients with HNSCC was queried by two complementary proteomics techniques. Frozen tissue from 14 patients with histologically confirmed HNSCC was enriched for tumor and normal tissue by laser capture microdissection. Total protein was extracted, separated by 2D-difference gel electrophoresis (2D-DIGE), and evaluated for differential protein expression between subsites. A tissue microarray (TMA) was constructed consisting of 71 patients with HNSCC. This TMA was queried for expression of 4 cell-cycle and regulatory proteins chosen a priori for their known roles in cancer, using Automated Quantitative Analysis of protein expression (AQUA).
Results
From the first cohort, proteins from tumor and matched normal tissue were successfully isolated and 732 spots identified as matching across >90% of gels. After supervised statistical analysis, we identified no significant differences in protein expression between subsites. AQUA analysis of the second, larger cohort likewise revealed no difference between subsite for cyclin D1, p53, Rb, or p14 expression.
Conclusion
Using two validated, complementary proteomics methods we identified no significant differences between HNSCCs from different head and neck subsites.
Significance
It is possible that heterogeneity among HNSCCs may be based not on anatomic subsite, but rather on fundamentally different carcinogenic pathways – i.e. virally induced versus carcinogenic insult (tobacco, alcohol).
Support
NIHR33-CA-5941(WSD); AAO/HNSF Resident Research Grant 26357 (PMW).
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