Coding and noncoding somatic mutations in basal cell carcinoma

Basal cell carcinoma (BCC) represents the most commonly diagnosed human cancer among persons of European ancestry with etiology mainly attributed to sun-exposure. In this study we investigated mutations in coding and flanking regions of the PTCH1 and TP53 genes and noncoding alterations in the TERT and DPH3 promoters in 191 BCC tumors. In addition, we measured CpG methylation within the TERT hypermethylated oncological region (THOR) and transcriptions levels of the reverse transcriptase subunit. We observed mutations in PTCH1 in 59% and TP53 in 31% of the tumors. Noncoding mutations in TERT and DPH3 promoters were detected in 59% and 38% of the tumors, respectively. We observed a statistically significant co-occurrence of mutations at the four investigated loci. While PTCH1 mutations tended to associate with decreased patient age at diagnosis; TP53 mutations were associated with light skin color and increased number of nevi; TERT and DPH3 promoter with history of cutaneous neoplasms in BCC patients. TERT promoter mutations but not THOR methylation associated with an increased expression of the reverse transcriptase subunit. Our study signifies, in addition to the protein altering mutations in the PTCH1 and TP53 genes, the importance of noncoding mutations in BCC, particularly functional alterations in the TERT promoter.