DPYD and head and neck squamous cell carcinoma: Also, the inhibition of tumoral dihydropyrimidine dehydrogenase increased the sensitivity threshold of cancer cells to this medication.29 Gao et al30 evaluated mRNA expression by the cancer cells in 399 patients with HNSCC and showed that high expression of interleukin 6 was associated with poor prognosis and chemical resistance in many cancer cells, without requiring any mediator.