Molecular assay to detect metastatic head and neck squamous cell carcinoma

Background: The presence or absence of metastatic disease in cervical lymph nodes is the single most important determinant of therapy and prognosis for patients with head and neck squamous cell carcinoma (HNSCC). However, histologic examination fails to detect metastatic disease in a subset of neck dissection specimens. The accuracy of neck staging may be improved by the use of molecular techniques. Cytokeratins 5, 14, and 20 may be appropriate markers for HNSCC because they are expressed in HNSCC but not in lymphatic tissue. Design: To test the sensitivity of detection of cytokeratin 5, 14, and 20 messenger RNA by quantitative reverse transcription polymerase chain reaction (RT-PCR), full-length coding DNA sequences were cloned and transcribed. The expression of cytokeratin 5, 14, and 20 messenger RNA was quantified in 4 HNSCC cell lines and 11 tumors. A cell culture lymph node model was created. Results: As few as 32 molecules of cytokeratin 14 could be detected using quantitative RT-PCR. Cytokeratins 5 and 14 were easily detected in all 4 HNSCC cell lines and almost all tumors. Cytokeratin 20 was not a useful marker, as expression was absent or significantly reduced in cell lines and tumors. In the lymph node model, cytokeratin 14 quantitative RT-PCR was able to detect 1 cancer cell in a background of 10 million lymphatic cells. Conclusions: Quantitative RT-PCR detection of cytokeratin 5 or 14 is a sensitive new molecular technique that may be used for detection of cervical micrometastases in head and neck cancer.