In addition, within the BRAF inhibitor-associated group, the lesions designated as KAs and BRAF inhibitor-associated verrucous keratoses had a similar mutational profile (mutations in PIK3CA, APC, and HRAS), which was distinct to that seen in squamous cell carcinomas (FGFR3, CDKN2A, and STK11).
Loss of heterozygosity (LOH) at the APC and MCC loci was about twice as common in BSCC as in SCC (40% vs. 21% and 33% vs. 12%, respectively), with co-existence of LOH at both loci occurring only in BSCC.
In AC cases, promoter hypermethylation of the APC and HIC-1 genes was detected at a statistically significant higher frequency than in the SCC cases (APC, 60% versus 13%, P < 0.001; HIC-1, 63% versus 32%, P < 0.03).
Four genetic polymorphisms in the APC and MCC genes at chromosome 5q21 were analysed for loss of heterozygosity (LOH) in 97 primary squamous carcinomas and adenocarcinomas of the lung.
Therefore, although allelic loss at the APC locus is frequent in squamous cell carcinomas of the esophagus, it is likely that a gene on 5q other than APC is involved in esophageal tumorigenesis.
In addition, further analysis of tumors showing loss of heterozygosity at 5q suggests that a gene at or near the APC locus is involved in squamous carcinoma of the head and neck.