Comparison of mutation frequency in MutSig-identified significantly mutated genes (HPV-positive OSCCs vs. HPV-negative OSCCs). Bar graphs display fractions of all (yellow) HPV-positive and (purple) HPV-negative OSCCs bearing somatic variants (SNVs and small indels) (A) in 24 MutSig genes detected in HPV-positive OSCCs and (B) in 25 genes in HPV-negative OSCCs. (*) adjusted P-value < 0.05, (**) adjusted P-value < 0.01. See also Supplemental Figure S3 and Supplemental Table S3 for frequencies of somatic variants and CNVs in HPV-positive and HPV-negative OSCCs.