Potential prognostic value of mitogen‐activated protein kinase activity for disease‐free survival of primary breast cancer patients

Signaling through pathways involving mitogen‐activated protein kinases (MAP kinases) has been implicated in the pathogenesis of cancer. Thus, the activity of MAP kinase is essential in the malignant potential of human breast tumors. p42/44MAPK was significantly higher expressed in tumor samples than in matching normal tissues adjacent to the tumor. p42/44MAPK protein expression correlated with enhanced MAP kinase activity only in a subset of tumors, indicating that over‐expression of MAP kinases does not reflect the activation status of these enzymes. MAP kinase activity was significantly elevated in 131 tissue samples from primary breast tumors when compared to 18 normal tissues adjacent to tumors. A trend for higher MAP kinase activity in primary tumors of node‐positive patients was observed when compared with tumors from node‐negative patients. Similarly, higher MAP kinase activities were observed in specimens from patients who had a relapse within the follow‐up time of 40 months when compared with patients with no relapse. A survival analysis demonstrated that the MAP kinase activity in primary breast tumors is potentially prognostic for relapse‐free survival of patients. Int. J. Cancer 89:384–388, 2000. © 2000 Wiley‐Liss, Inc.