PTP LAR expression compared to prognostic indices in metastatic and non-metastatic breast cancer

Several prognostic indices in breast cancer, including c-erbB2, epithelial growth factor receptors (EGFR), estrogen and progesterone receptors are sig nal transduction molecules. Recently, expression of another signal transduc tion molecule, the protein tyrosine phosphatase LAR, has been suggested to be increased in breast cancer. The objective of the current investigation w as to examine the relationship between LAR expression and prognostic parame ters in breast cancer. LAR expression was associated with metastatic potent ial in the well-characterized 13762NF rat mammary adenocarcinoma clones. Th e metastatic MTLn3 and MTLn2 clones expressed sizable amounts of LAR. The e ssentially non-metastatic MTC clone had little LAR expression. C-erbB2 had highest expression in the highly metastatic MTLn3 clone, but c-erbB2 levels were sizeable in the weakly metastatic MTLn2 and non-metastatic MTC clone. EGFR expression had the strongest association with a clone's metastatic po tential, being very high in MTLn3, weak in MTLn2, and undetectable in MTC. In human breast cancer specimens, LAR expression was strongly positive in 5 0% of metastatic cases but in only 21% of 'non-metastatic' cases. As with t he 13762NF-derived clones, c-erbB2 expression was strongly positive indepen dent of metastatic phenotype. However, 46% (6/13) of cases that were strong ly positive for c-erbB2 were strongly positive for LAR. Only 17% (2/11) of negative or weakly c-erbB2 positive samples were strongly positive for LAR. All ER+ positive tumors (n = 15) were positive for LAR and 53% of these tu mors were strongly positive for LAR. In ER- negative cases, only 1 of 11 wa s strongly positive for LAR. While the current data indicate a strong assoc iation between ER and LAR expression in breast cancer tissue (p = 0.003), a dditional studies are warranted to further explore the relationship between LAR and prognostic indices of breast cancer progression.