We then hypothesised that the 5 upregulated genes (namely, ATPase phospholipid transporting 8A1 [ATP8A1], BAHD1, cathepsin [CTSD], janus kinase 1 [JAK1], and myosin regulatory light chain interacting protein [MYLIP]) play a role in radioresistance of prostate and head and neck cancers. The gene discussed is CTSD; the disease is head and neck cancer.