Background/aims: Matrix metalloproteinase-7 (MMP-7) is thought to play an important role in the progression of cancer invasion. However, the expression of MMP-7 in primary and nodal lesions of gastric cancer is unknown.
Methodology: Expression of MMP-7 protein in primary and nodal lesions of human gastric cancer was evaluated by immunohistochemistry. Expression of MMP-7 mRNA in the sentinel node, i.e. the first lymph node in the lymphatic basin to receive metastases from the primary tumor, was evaluated by reverse transcription-polymerase chain reaction (RT-PCR).
Results: Among primary lesions, 73 (48%) of 153 tumors were strongly positive for MMP-7. Strong positivity rates in the primary lesion were associated with deep invasion of the gastric wall, nodal metastases, and infiltration of vessels or lymphatics. Five-year survival rates were 43.8% in patients with strongly positive tumors and 75.0% in patients with weakly positive tumors. Among nodal metastases, 53 (76%) of 70 lesions were strongly positive for MMP-7, which was significantly higher than the strong positivity rate for primary lesions. Strong positivity rates in metastatic lesions were significantly higher when metastatic lymph nodes were present in group 2 or more. All of six patients with peritoneal dissemination in the absence of gastric serosal invasion had nodal metastases strongly positive for MMP-7. Five-year survival rates were 17.5% in patients with strongly positive nodal metastases and 68.6% in patients with weakly positive nodal metastases. RT-PCR demonstrated MMP-7 expression in sentinel nodes of 3 cases of 30. All 3 cases had metastases not only in the sentinel node but also in non-sentinel nodes. However, in 27 cases, including 24 without metastases and 3 with metastases in the sentinel nodes only, expression of MMP-7 in the sentinel nodes was not observed.
Conclusions: MMP-7 may contribute to the invasion of both primary and nodal lesions in patients with gastric cancer. The MMP-7 expression is a useful prognostic factor, and evaluating the expression in sentinel node may help surgeons determine what level of lymph node dissection should be performed.