Micrometastasis and expression of nm23 messenger RNA of lymph nodes from lung cancer and the postoperative clinical outcome.

Background: Based on the metastatic route in lymph nodes from lung cancer, we investigated micrometastasis in the dissected lymph nodes by genetic analysis of keratin 19 and nm23-H1 (the expression of a tumor-metastatic suppressor gene) and evaluated the postoperative outcomes. Methods: Ten patients operated with lung cancer were 4 males and 6 females, who were stage IA; 2, stage IB; 3, stage IIA; 2, stage IIB; 1, and stage IIIA; 2, respectively. After total RNA extraction from the dissected lymph nodes, the expression of nm23-H1 and keratin 19 messenger ribonucleic acid (mRNA) were analyzed with reverse-transcripted polymerase chain reaction (RT-PCR). Results: The confirmation of micrometastasis in lymph nodes was realized in seven of 10 cases (70%), in their 5-year follow-up term. In three patients there was recurrence (43%, 3/7), and the one of them had died from the mediastinal recurrence. On the expression of nm23-H1 mRNA in lymph nodes, there was no significant difference between the pathologically lymph-node metastasis positive group and the negative one, and between the group with a tumor size over 30 mm and the group with a tumor size under 30 mm, respectively. The expression ratio of nm23-H1 gene was significantly expressed in the group with micrometastasis in lymph nodes (47%, 9/19) as compared to those without micrometastasis (10%, 1/10) (p<0.05). On the all-positive expression of nm23-H1 in the examined lymph nodes (n=4), no patient had recurrence (0%, 0/4). However, in the rest of the six patients without the all-positive expression of nm23-H1 in those lymph nodes (n=6), four patients had recurrence (67%, 4/6). There was no significance between the recurrent ratio in the all-positive expression of nm23-H1 suggesting lower incidence as compared to that in patients without all-positive expression of nm23-H1. Conclusion: A detection of micrometastasis in lymph nodes could be a useful tool to identify the subpopulation of patients who might have a higher risk of recurrence and distant metastases. The nm23-H1 gene might be involved in a suppression role for micrometastasis in lymph nodes through the lymphatic route in lung cancer. (Ann Thorac Cardiovasc Surg 2004; 10: 152‐9)