The human trefoil protein TFF1 is a small cysteine-rich secreted protein that is frequently expressed in breast tumors under the control of estrogen. The function of TFF1 in breast cancer is unknown. To test the hypothesis that it promotes tumor dissemination, we produced recombinant TFF1 and assessed its ability to stimulate the movement of breast cancer cells by using in vitro wounding and migration assays. Recombinant TFF1 stimulated migration at concentrations of TFF1 found in culture medium. Migration of MCF-7 breast cancer cells, which secrete TFF1, was stimulated by lower concentrations of TFF1 than MDA MB231 cells that do not produce TFF1. Dimeric TFF1, linked by a disulfide bond, and monomeric TFF1 are produced by estrogen-responsive breast cancer cell lines. Recombinant TFF1 dimer was eightfold more potent than TFF1 monomer, implying that the interaction of TFF1 with its receptor is facilitated by dimerization. The majority of TFF1-stimulated migration resulted from chemotaxis, but dimeric TFF1 stimulated some chemokinesis. These results show that estrogens can stimulate the motility of breast cancer cells via the induction of TFF1 and suggest that one reason for the efficacy of hormonal therapies is their ability to reduce expression of TFF1 and, hence, the migration of breast tumor cells.

The nm23 gene was identified in murine melanoma cells, in which its expression is associated with the cells' metastatic potential. Expression of nm23 has been detected in human breast tumors by means of hybridization and immunocytochemistry. We measured nm23 mRNA in 71 patients with primary breast cancer and found variable levels of nm23 expression. The nm23 gene was expressed at higher levels in well-differentiated tumors (P less than .02). There was a significant inverse relationship between nm23 expression and nodal status (P less than .02). Expression of nm23 was positively associated with longer disease-free survival and overall survival, and the relationships were significant (P less than .002 and P less than .003, respectively). This study showed that nm23 expression in human breast cancer was associated with good prognosis and a lack of lymph node metastasis and suggests that the nm23 gene product may play an important role in suppressing the metastatic phenotype.

Triple-negative breast cancers have a poor prognosis and are not amenable to endocrine- or HER2-targeted therapies. The prevailing view is that targeting the insulin-like growth factor (IGF) signal transduction pathway will not be beneficial for triple-negative breast cancers because their growth is not IGF-responsive. The present study investigates the importance of IGFs in the proliferation and survival of triple-negative breast cancer cells. Estrogen and progesterone receptors, HER2, type I IGF, and insulin receptors were measured by Western transfer analysis. The effects of IGF-1 on proliferation were assessed by DNA quantitation and on cell survival by poly (ADP-ribose) polymerase cleavage. The effect of IGF-1 on phosphorylation of the IGF receptors, Akt and mitogen-activated protein kinase, was measured by Western transfer analysis. Seven cell lines were identified as models of triple-negative breast cancer and shown to express IGF receptors at levels similar to those present in estrogen-responsive cell lines known to respond to IGFs. IGF-1 increased the proliferation and cell survival of all triple-negative cell lines. Proliferation was attenuated after reduction of type I IGF receptor expression. Cells that express higher levels of receptor were more sensitive to subnanomolar IGF-1 concentrations, but the magnitude of the effects was not correlated simply with the absolute amount or phosphorylation of the IGF receptors, Akt or mitogen-activated protein kinase. These results show that IGFs stimulate cell proliferation and promote cell survival in triple-negative breast cancer cells and warrant investigation of the IGF signal transduction pathway as a therapeutic target for the treatment of triple-negative breast cancer.

Trefoil factors (TFFs) are protease-resistant peptides that promote epithelial cell migration and mucosal restitution during inflammatory conditions and wound healing in the gastrointestinal tract. To date, the molecular mechanism of TFFs action and their possible role in tumor progression are unclear. In the present study, we observed that premalignant human colonic PC/AA/C1 and canine kidney MDCK epithelial cells are not competent to invade collagen gels in response to exogenously added TFFs (pS2, spasmolytic polypeptide, and intestinal trefoil factor). In contrast, activated src and RhoA exert permissive induction of invasion by the TFFs that produce similar parallel dose-response curves in src-transformed MDCKts.src and PCmsrc cells (EC50=20-40 nM). Cell scattering is also induced by TFFs in MDCKts.src cells. Stable expression of the pS2 cDNA promotes constitutive invasiveness in MDCKts.src-pS2 cells and human colonic HCT8/S11-pS2 cells established from a sporadic tumor. Furthermore, we found that TFF-mediated cellular invasion is dependent of several signaling pathways implicated in cell transformation and survival, including phosphoinositide PI3'-kinase, phospholipase C, protein kinase C, and the rapamycin target TOR. Constitutive and intense expression of pS2 was revealed by Western blot analyses and immunohistochemistry in human colorectal tumors and their adjacent control mucosa during the neoplastic progression, from the adenoma to the liver metastases. Our studies indicated that TFFs can be involved in cell scattering and tumor invasion via autocrine loops and may serve as potential targets in the control of colon cancer progression.