Expression of NHERF1 in colonic tumors induced by 1,2-dimethylhydrazine in rats is independent of plasma ovarian steroids.

In normal embryonic fibroblasts, the Na(+)/H(+) exchanger regulator factor 1 (NHERF1) stabilizes E-cadherin/ß-catenin binding and the lack of NHERF1 expression promotes cell transformation thus acting as a tumor suppressor gene. We here tested the hypothesis that NHERF1 could act as a tumor suppressor gene in colon cancer as a mediator of estrogens' protective actions in colon carcinogenesis. We studied the expression and localization of NHERF1 and ß-catenin by immunohistochemistry in colonic tumors induced by 1,2 dimethylhidrazine (DMH) in Sprague-Dawley rats. One group of the rats treated with the carcinogen was ovariectomized (OVX) in the middle of the tumor induction, simulating a human menopausal condition. We observed a protective role of estrogens in colon cancer, as non-ovariectomized rats (DMH) had a reduced tumor area compared with the ovariectomized group (DMH + OVX; mean ± SE) 28.98 ± 4.65 vs. 67.58 ± 8.69 (p < 0.00380). Despite the lack of plasma estrogen stimulation, we found abundant expression of NHERF1 in colon tumors from ovariectomized rats. NHERF1 was mainly localized in the cytoplasm of the adenocarcinoma cells and lost the apical localization previously reported in normal colon tissue. We also detected expression of NHERF1 by western blot in the SW48, CACO-2, and HT29 colon cancer cell lines. Non-estrogenic factors in plasma or the tumor microenvironment may regulate NHERF1 expression in transformed colon epithelial cells. Further studies are required to understand the regulation of NHERF1 expression in colon cancer tissue.

P-cadherin and beta-catenin are useful prognostic markers in breast cancer patients; beta-catenin interacts with heat shock protein Hsp27.

The cadherin-catenin proteins have in common with heat shock proteins (HSP) the capacity to bind/interact proteins of other classes. Moreover, there are common molecular pathways that connect the HSP response and the cadherin-catenin protein system. In the present study, we have explored whether in breast cancer the HSP might interact functionally with the cadherin-catenin cell adhesion system. Beta-catenin was immunoprecipitated from breast cancer biopsy samples, and the protein complexes isolated in this way were probed with antibodies against HSP family members. We are thus the first to demonstrate a specific interaction between beta-catenin and Hsp27. However, beta-catenin did not bind Hsp60, Hsp70, Hsp90, gp96, or the endoplasmic reticulum stress response protein CHOP. To confirm the finding of Hsp27-beta-catenin interaction, the 27-kDa immunoprecipitated band was excised from one-dimensional polyacrylamide gel electrophoresis gels and submitted to liquid chromatography-tandem mass spectrometry with electrospray ionization, confirming a role for Hsp27. In addition, beta-catenin interacted with other proteins including heat shock transcription factor 1, P-cadherin, and caveolin-1. In human breast cancer biopsy samples, beta-catenin was coexpressed in the same tumor areas and in the same tumor cells that expressed Hsp27. However, this coexpression was strong when beta-catenin was present in the cytoplasm of the tumor cells and not when beta-catenin was expressed at the cell surface only. Furthermore, murine breast cancer cells transfected with hsp25 showed a redistribution of beta-catenin from the cell membrane to the cytoplasm. When the prognostic significance of cadherin-catenin expression was examined by immunohistochemistry in breast cancer patients (n = 215, follow-up = >10 years), we found that the disease-free survival and overall survival were significantly shorter for patients expressing P-cadherin and for patients showing expression of beta-catenin in the cytoplasm only (not at the cell surface). The interactions of beta-catenin with Hsp27 and with HSF1 may explain some of the molecular pathways that influence tumor cell survival and the clinical significance in the prognosis of the breast cancer patients.