The expression of four genes (HPRT1, CTNS, SHMT1, SLC38A7) was further verified by reverse transcription-polymerase chain reaction (RT–PCR) in patients with HNSCC and in vivo to validate their oncogenic role, and their relationships with the expression of immunological cell markers were also explored. Here, SHMT1 is linked to head and neck squamous cell carcinoma.