title: Wnt-5a signaling restores tamoxifen sensitivity in estrogen receptor-negative breast cancer cells.
abstract: One third of all breast cancers are estrogen receptor alpha (ERalpha) negative, carry a poor overall prognosis, and do not respond well to currently available endocrine therapies. New treatment strategies are therefore required. Loss of Wnt-5a has previously been correlated with loss of ERalpha in clinical breast cancer samples, and we sought to investigate this association further. Three breast cancer cell lines (MDA-MB-231, MDA-MB-468, and 4T1) lacking expression of ERalpha and Wnt-5a, and one breast cancer cell line (T47D) expressing both proteins were used in this study. Wnt-5a signaling was generated in ERalpha-negative cell lines via stimulation with either recombinant Wnt-5a protein or a Wnt-5a-derived hexapeptide (Foxy-5) possessing Wnt-5a signaling properties. ERalpha expression was restored at both mRNA and protein level, after treatment with recombinant Wnt-5a or Foxy-5. This restoration of expression occurred in parallel with a reduction in methylation of the ERalpha promoter. Up-regulated ERalpha could be activated, initiate transcription of progesterone receptor and pS2, and activate an estrogen response element reporter construct. Significantly, breast cancer cells re-expressing ERalpha responded to treatment with the selective estrogen receptor modulator tamoxifen, as measured by induction of apoptosis and cell growth inhibition. Finally, Foxy-5 also increased ERalpha expression in an in vivo model of ERalpha-negative breast cancer. This represents the first evidence that Wnt-5a signaling acts to re-establish ERalpha expression in ERalpha-negative breast cancer cells. Our data suggest that combinatorial therapy with Foxy-5 and tamoxifen should be considered as a future treatment possibility for ERalpha-negative breast cancer patients.
authors.affiliation: Cell and Experimental Pathology, Department of Laboratory Medicine, Lund University, Malmö University Hospital, Malmö, 20502, Sweden. caroline.ford@med.lu.se
authors.forename: Caroline E
authors.initials: CE
authors.lastname: Ford
authors.forename: Elin J
authors.initials: EJ
authors.lastname: Ekström
authors.forename: Tommy
authors.initials: T
authors.lastname: Andersson
mesh_terms: D000818:Animals; D001943:Breast Neoplasms / Q000378:metabolism*; D045744:Cell Line, Tumor; D019175:DNA Methylation / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D047628:Estrogen Receptor alpha / Q000235:genetics / Q000378:metabolism*; D015972:Gene Expression Regulation, Neoplastic / Q000187:drug effects; D006801:Humans; D051379:Mice; D011401:Promoter Regions, Genetic; D011518:Proto-Oncogene Proteins / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects*; D013629:Tamoxifen / Q000494:pharmacology*; D014158:Transcription, Genetic / Q000187:drug effects; D015854:Up-Regulation / Q000187:drug effects; D051153:Wnt Proteins / Q000378:metabolism*; D000071818:Wnt-5a Protein
chemical_list: D047628:Estrogen Receptor alpha; D011518:Proto-Oncogene Proteins; C085389:WNT5A protein, human; D051153:Wnt Proteins; D000071818:Wnt-5a Protein; D013629:Tamoxifen