Trial Information

Background:

Gastric carcinoma (GC) remains among the most frequent malignancies in Taiwan as well as in
the world and also one of leading causes of cancer-related death. Accumulating evidence
shows that chronic inflammation leads to the occurrence of cancers, including GC, via
multiple mechanisms.

Cyclooxygenase-2 (COX-2) is a crucial enzyme in inflammatory process and is shown to be
up-regulated in a variety of cancers. Therefore, COX-2 may play an important role in
carcinogenesis. The hallmarks of cancer include continuing proliferation, evading apoptosis,
prohibiting immunity, promoting angiogenesis, enhancing invasion and metastasis. We
hypothesize that COX-2 induces carcinogenesis through multiple mechanistic strategies and
interactions of multiple genes simultaneously.

Laser capture microdissection (LCM) for obtaining pure cancer cells and microarray
technology and analysis are now generally accepted as powerful tools in genomic research,
providing reliable microdissection of cancer cells and simultaneous analysis of whole
genome.

Aim:

Use microarray technology to investigate patterns of genomic change related to differential
COX-2 expression and their clinicopathological association in GC.

Materials:

GC cell lines are transfected with COX-2-expressing vector to establish cell lines with
differential levels of COX-2 expression. Clinical specimens are obtained from surgical
resection of GC proved by pathology at the Surgical Department of National Taiwan University
Hospital, which COX-2 expression is evaluated by Western blotting and immunohistochemical
staining.

Methods:

The present project will use microarray for analysis of genome clustering patterns of
surgical tissue (GC cells procured by LCM) and GC cell lines based on differential COX-2
expression levels, to discover significantly positively or negatively associated gene
clusterings which contain candidate genes for studies of carcinogenesis mechanisms and
establishment of animal experiment models in another component project.

Execution:

In the first year of this 3-year project, we will establish GC cell lines expressing
differential COX-2 levels by transfection of COX-2-expressing vector and focus on analyzing
their genomes by microarray. We also start to collect surgical specimens of GC, record
clinicopathological characteristics, procure cells by LCM and assess RNA quality, perform
microarray experiments. In the second year, we will continue LCM, RNA extraction, and
microarray experiments. In the third year, microarray experiment of a total of 60 pairs,
including 30 high-COX-2 cases and 30 low-COX-2 cases, of tumor and non-tumoral tissues are
completed. Final analysis is carried out to identify clustering, to select candidate genes,
and investigate their relationship to clinicopathological characteristics, according to
COX-2 expression. These genes are to be subjected to mechanism and animal studies. We expect
a better understanding of patterns of gene clustering in differential COX-2 gene expression.