SLC44A2 and head and neck squamous cell carcinoma: Kaplan-Meier survival analysis showed that patients with lower SLC44A2 expression had worse overall survival (OS) in renal clear cell carcinoma (KIRC), pan-kidney cohort (KIPAN), glioma (GBMLGG), head and neck squamous cell carcinoma (HNSC), and skin cutaneous melanoma (SKCM) (Fig. S1C).