Lower GI
cancers are among the top three most frequent cancers in the United States
and many western countries while upper GI cancers rank as the most prevalent
type in many Asian countries, especially in central and eastern Asia. GI
cancers are usually diagnosed in more advanced stages and in the absence of
effective early diagnostic tools and therapeutic modalities, the survival rates
are generally disappointingly low. Then the era of biomarkers came to solve the
issue of the GI Cancer diagnosis.
Biomarker refers to
a measurable indicator of some biological state or condition. This is also referring
to a substance whose detection indicates the existence of a living organism. This
is also used to evaluate or to examine normal biological processes, pathogenic
processes, or pharmacologic responses to a therapeutic intervention.
Currently, serum
biomarkers, which are sufficiently sensitive and specific for early detection
and risk classification of gastric cancers. In future Three-dimensional
combined biomarkers assay could improve diagnostic accuracy for gastric cancer.
For cancer research MicroRNAs (miRNAs) have become the center of focus. However,
there have been inconsistencies in the literature regarding the suitability of
circulating miRNAs for early detection of gastrointestinal cancers.
Last few years major
advances have been made to understand the role of epigenetic alterations in
carcinogenesis, particularly for DNA methylation, histone modifications and
non-coding RNAs. Aberrant hypermethylation of DNA at CpG islands is a
well-established phenomenon that mediates transcriptional silencing of tumor
suppressor genes, and it is an early event integral to gastrointestinal cancer
development.
As such, detection of
aberrant DNA methylation is being developed as biomarkers for prognostic and
diagnostic purposes in gastrointestinal cancers. Diverse tissue types are
suitable for the analyses of methylated DNA, such as tumor tissues, blood,
plasma, and stool, and some of these markers are already utilized in the clinical
setting.
Recent advances in the
genome-wide epigenomic approaches are enabling the comprehensive mapping of the
cancer methylome, thus providing new avenues for mining novel biomarkers for
disease prognosis and diagnosis.
The biomarkers in GI
cancers are useful not only for screening, diagnosis, and prognosis but also
for prediction of the response to mechanism-based interventions, such as
chemoprevention. On-going assessment of these diagnostic and predictive factors
will probably lead to a change in the current staging of many GI cancers.
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