Yasushi Morita

Clinical significance of urokinase‐type plasminogen activator activity in hepatocellular carcinoma

Background and Methods : The plasminogen activation system plays a crucial role in the process of cancer invasion and metastasis. To evaluate the most effective factor in the invasion, metastasis and prognosis of hepatocellular carcinoma (HCC), we examined urokinase‐type plasminogen activator (uPA), plasminogen activator inhibitor (PAI)‐1, PAI‐2 and uPA activity by enzyme‐linked immunosorbent assays (ELISA) in HCC tissues obtained from 46 patients. The results were compared with the patients’ clinicopathological features and prognoses.

Telomerase activity in hepatocellular carcinoma as a predictor of postoperative recurrence

Telomerase is a ribonucleoprotein that stabilizes telomeres and allows unlimited cell division. It has been reported that most cancer cells evince reactivated telomerase. We examined telomerase activity in 29 patients with hepatocellular carcinoma (HCC) by a polymerase chain reaction-based semiquantitative assay. Of 24 HCCs, telomerase activity was positive in 23 (95,8%), of which 16 showed strong activity. In 11 well differentiated HCCs, telomerase activity was strong in 5, weak in 5, and undetected in 1 and in 13 moderately differentiated HCCs, it was strong in 11 and weak in 2. Five of 6 HCCs less than 2 cm in diameter expressed strong telomerase activity, while weak telomerase activity was detected in 7 of 19 (36.8%) resected noncancerous liver tissues from the HCC patients. Five of these 7 patients (71%) manifested recurrence within 6 months after surgery. The recurrence rate in these patients whose noncancerous liver tissue was positive for telomerase activity was significantly higher than that in patients in whom it was negative (P=0.017). These results suggest that the presence of telomerase activity may be a useful diagnostic marker of HCC, regardless of tumor size, and that its detection in resected noncancerous liver tissues may serve as a useful predictor of postoperative recurrence.

Inhibitory Role of Plasminogen Activator Inhibitor-1 in Invasion and Proliferation of HLE Hepatocellular Carcinoma Cells

Plasminogen activator inhibitor (PAI)‐1, a serine protease inhibitor, inactivates urokinase‐type plasminogen activator (uPA) and regulates degradation of the extracellular matrix; whether it functions for or against tumor progression, however, has been the subject of controversy. To assess the role of PAI‐1 in invasion and proliferation of hepatocellular carcinoma (HCC) cells, HLE cells were transfected with a vector capable of expressing an antisense PAI‐1 transcript. Analysis of seven stably transfected clones (PAI‐1−) showed reductions of 81% in PAI‐1 mRNA by northern blot analysis and 63% in the cellular PAI‐1 antigen level by enzyme‐linked immunosorbent assay(ELISA). There was no change in the levels of secreted PAI‐1 or PAI‐2. The activity of cellular uPA increased by 54%, without change in the protein level or the secreted uPA activity evaluated by ELISA. Morphologically, PAI‐1 antisense induced a spindle shape with narrower cytoplasmic processes in HLE cells. The forced inhibition of PAI‐1 increased the invasion and the growth of PAI‐1− cells by 75% and 82%, respectively. These results suggest that PAI‐1 plays a role in inhibiting invasion and proliferation, and the balance between uPA and PAI‐1 expression is important to assess the invasiveness of HCC cells.

Expression of urokinase-type plasminogen activator receptor and plasminogen activator inhibitor-1 in gastric cancer

In gastric cancer, the urokinase‐type plasminogen activator (uPA) system plays important roles in invasion and metastasis, processes which entail proteolysis and adhesion. Both the urokinasetype plasminogen activator receptor (uPAR) and the plasminogen activator inhibitor‐1 (PAI‐1) are thought to be important factors in this system. To clarify the relationship between these two factors and gastric cancer invasiveness, we evaluated the expression of uPAR and PAI‐1 in 91 cases of gastric cancer by immunohistochemistry and in situ hybridization. Urokinase‐type plasminogen activator receptor‐mRNA, PAI‐1‐mRNA, uPAR and PAI‐1 protein were diffusely distributed in the cytoplasm of the cancer cells and concentrated at invasive foci. Urokinase‐type plasminogen activator receptor protein expression correlated with lymphatic, venous invasion (P<.01) and lymph node metastasis (P<0.05); uPAR‐mRNA expression correlated with lymphatic, venous invasion and lymph node metastasis (P<0.05). Plasminogen activator inhibitor‐1 protein expression correlated with lymphatic, venous invasion, lymph node metastasis and depth of invasion (P<0.01); PAI‐1‐mRNA expression was linked to lymphatic, venous invasion (P<0.01), lymph node metastasis and depth of invasion (P<0.05). This suggests that the proteolytic activity of uPAR and the cellular motility of PAI‐1 in gastric cancer cells may determine penetration of lymphatic and blood vessels, whereby lymph node metastasis may be promoted and that the promotion of cellular motility by PAI‐1 may influence the depth of cancer invasion.