Identification of the molecular mechanisms underlying the enhanced cellular radiosensitivity of HPV-positive HNSCC cells using CRISPR/Cas activator and repressor libraries

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Squamous cell carcinoma of the head and neck (HNSCC) consists of two biologically distinct entities, HPV-negative and HPV-positive HNSCC. While the numbers of HPV-negative tumors are declining in many countries due to reduced smoking, the numbers of HPV-positive tumors are continuously rising. HPV-positive tumors, which are mostly located in the oropharynx, respond far better to curative therapeutic regimes than the HPV-negative ones. In fact, current clinical studies are mostly testing means of safe therapy deintensification in order to reduce severe side effects instead of testing ways to further improve outcome. Especially an enhanced response of these tumors to radiotherapy is clearly established through clinical data and we could show that already on the cellular level HPV-positive HNSCC are characterized by an enhanced radiosensitivity. A variety of molecular mechanisms have been suggested to explain the enhanced sensitivity but at present none of these are generally accepted. Using a broader panel of HPV-positive and –negative cell lines we actually failed to recapitulate a number of these findings. We do believe, though, that determining the molecular mechanisms of the intrinsic cellular radiosensitivity of HPV-positive HNSCC can identify target structures for future targeted interventions and may well contribute to a better understanding of tumor radiobiology in general, which in the long term can help to establish better treatment options for other tumor entities with so far unsatisfactory cure rates.The goal of this project is therefore the identification of the molecular mechanisms of the enhanced cellular radiation sensitivity of HPV-positive HNSCC. We will use an open experimental approach utilizing novel genome-wide CRISPR/Cas-activator and repressor libraries to achieve genome-wide changes in protein expression levels, followed by a selection characterization of radioresistant clones. The open experimental approach was deliberately chosen because it enables the detection of so far unexpected contributing factors. The project requires complementary expertise in the radiobiology of HPV-positive HNSCC as well as in lentiviral transduction and genome editing. The two collaborating applicants ideally meet these requirements and we therefore strongly believe that we can provide optimal conditions to successfully accomplish this interesting and innovative task.