Changes in circulating microRNAs after radiochemotherapy in head and neck cancer patients

Introduction: Circulating microRNAs (miRNAs) are easily accessible
and have already proven to be useful as prognostic markers in
cancer patients. However, their origin and function in the
circulation is still under discussion. In the present study we
analyzed changes in the miRNAs in blood plasma of head and neck
squamous cell carcinoma (HNSCC) patients in response to
radiochemotherapy and compared them to the changes in a cell
culture model of primary HNSCC cells undergoing simulated
anti-cancer therapy. Materials and methods: MiRNA-profiles were
analyzed by qRT-PCR arrays in paired blood plasma samples of HNSCC
patients before therapy and after two days of treatment. Candidate
miRNAs were validated by single qRT-PCR assays. An in vitro
radiochemotherapy model using primary HNSCC cell cultures was
established to test the possible tumor origin of the circulating
miRNAs. Microarray analysis was performed on primary HNSCC cell
cultures followed by validation of deregulated miRNAs via qRT-PCR.
Results: Unsupervised clustering of the expression profiles using
the six most regulated miRNAs (miR-425-5p, miR-21-5p, miR-106b-5p,
miR-590-5p, miR-574-3p, miR-885-3p) significantly (p = 0.012)
separated plasma samples collected prior to treatment from plasma
samples collected after two days of radiochemotherapy. MiRNA
profiling of primary HNSCC cell cultures treated in vitro with
radiochemotherapy revealed differentially expressed miRNAs that
were also observed to be therapy-responsive in blood plasma of the
patients (miR-425-5p, miR-21-5p, miR-106b-5p, miR-93-5p) and are
therefore likely to stem from the tumor. Of these candidate marker
miRNAs we were able to validate by qRT-PCR a deregulation of eight
plasma miRNAs as well as miR-425-5p and miR-93-5p in primary HNSCC
cultures after radiochemotherapy. Conclusion: Changes in the
abundance of circulating miRNAs during radiochemotherapy reflect
the therapy response of primary HNSCC cells after an in vitro
treatment. Therefore, the responsive miRNAs (miR-425-5p, miR-93-5p)
may represent novel biomarkers for therapy monitoring. The
prognostic value of this exciting observation requires confirmation
using an independent patient cohort that includes clinical
follow-up data.