MDR gene product, P-glycoprotein, is a transmembrane protein and is expressed in a wide variey of multidrug-resistance cell lines and in some human cancers. because one of the critical limitations in cancer chemotherapy is the presence of
intrinsic
or
acquired drug resistance population of tumor cells, analysis of expression pattern of MDR gene or its product in cancer may be important to detemine the responsivenss to chemotherapy.
Gastric cancer is one of the most common mallgnant tumor in korea, and early detection, surgical resection of stomach and postoperative chemotherapy are the choice of treatment to increase the survival rate or prolong the survival year. Gastric
cancer
is, however, known to be rather insensitive to various therapeutic agents and the responsiveness of postoperative chemotherapy is not dramatic.
We investigated the expression pattern of MDR gene in 78 cases of gastric adenocarcinoma.
MDR gene product was geerally expressed in cytoplasm and its membrane with granular or agranular pattern in tumor cells and in some of neighboring normal gastric mucosa.
In all adenocarcinomas the expression rate was 64.1% (diffuse 12.8%, focal 51.3%). According to the degree of differentiation, the expression rate was 70.6% (diffuse 17.6%, focal 52.9%) in well differentiated adenocarcinomas, 69.2% (diffuse
15.4%,
focal
53.8%) in moderately differentiated cases and 64.1% (diffuse 12.8%, focal 51.3%) in poorly differentiated case respectively. In mucinous carcinomas, expression reaction were focal in floating cell and its rate was 44.4%.
In 44.0% of 50 expressed cases, the expression of deep infiltrated tumor cells were stronger and more diffuse than superficially located tumor cells and they were usually poorly differentiated tumor cells (60.0%) such as unorganized individual
cells or
cells of indistinct glandular structures regardless of overall type of differentiation. In lymph nodes which were invaded by tumor cells, the expression rate of diffuse and focal reaction was 38.7% and 25.8% respectively.
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