217nocarcinoma as compared to Barrett esophagus [ 8 ] while SMAD4
mutation was only observed in esophageal adenocarcinoma and
not in high-grade dysplasia [ 2 , 5 ].
Discovering gene mutations and understanding the link
between these mutations and the pathogenesis of the disease can
lead to the identification of potential biomarkers for risk assess-
ment or detection of esophageal adenocarcinoma. Tumor protein
p53 (TP53) mutation (Table 1 ) is a typical example of a good risk
stratification candidate marker for determining the key point of
therapeutic intervention in patients with esophageal adenocarci-
noma [ 2 , 9 – 11 ]. Patients without TP53 mutations did not show
high-grade dysplasia or metaplasia [ 11 ] while patients with TP53
mutations either had esophageal adenocarcinoma or had transition
from low-grade dysplasia to high-grade dysplasia in Barrett esoph-
agus [ 2 , 9 ].
However, TP53 mutations are not detected in approximately
25% of esophageal adenocarcinoma [ 12 , 13 ] suggesting its insuf-
ficiency as a sole biomarker, though it may work better as part of a
panel of biomarkers [ 14 ]. For example, combined mutations of
TP53, CDKN2A [ 10 , 15 , 16 ], and APC [ 15 ] could provide better
prediction for esophageal adenocarcinoma or cancer surveillance in
patients with Barrett esophagus (Table 2 ). Similarly, overexpres-
sion of KRAS and suppression of SMAD4 were proposed to sup-
port progression of esophageal adenocarcinoma and may be good
candidates for inclusion in biomarker panels [ 1 ].
Besides being able to pinpoint the pathogenesis of esophageal
adenocarcinoma, gene mutations have also been associated with
several pathological factors and assisted in the prediction of patient
survival outcomes. For example, TP53 mutation (Table 1 ) was
associated with high cancer grade, advanced tumor/nodes/metas-
tasis (TNM) stages, lymph node metastasis [ 17 , 18 ], and human
papillomavirus (HPV)-negative esophageal adenocarcinoma [ 19 ,
20 ]. Meanwhile, low expression of E-cadherin (Table 1 ) was asso-
ciated with undesirable clinical pathological features and reduced
survival outcome although mutation of this gene was rare [ 21 ].
With such promising outcomes observed with discovering
gene mutations, it is therefore essential to continue the search and
identification of gene mutations in esophageal adenocarcinoma.
Many methods could be used to study the mutations. In this chap-
ter, we will be focusing on Sanger sequencing method, which is
the traditional gold standard method [ 22 ] for mutation detection.
Besides mutation detection, Sanger sequencing is also useful for
several applications (Table 3 ) including human leukocyte antigen
(HLA) typing [ 23 ], multiple region sequencing [ 24 ], next-gen-
eration sequencing (NGS) result validation [ 25 , 26 ], confirma-
tion of plasmid sequences, inserts and/or mutations [ 27 ], single
Single Gene Mutation in Esophageal Adenocarcinoma