, an interaction that may have therapeutic implications for triple-negative disease, a new study suggests.
Up to 80% of triple-negative breast cancers (TNBCs) express ESR2, but its role has been hard to pin down because of conflicting data, according to the investigators, who were led by senior author Gokul M. Das, PhD, of the department of pharmacology and therapeutics, Center for Genetics and Pharmacology, Roswell Park Comprehensive Cancer Center, Buffalo, N.Y. Expression has been found to have both antiproliferative activity and proproliferative activity, depending on the experimental conditions.
Dr. Das and colleagues performed a series of in vitro assays in breast cancer cell lines and a clinical study of patients with basal-like TNBC from the Molecular Taxonomy of Breast Cancer International Consortium (METABRIC) cohort (308 patients with TP53 mutational status determined by sequencing) and a Roswell cohort (46 patients with TP53 mutational status determined by immunohistochemistry).
Results showed that in vitro, ESR2 interaction with wild-type TP53 had proproliferative effects, whereas interaction of ESR2 with mutant TP53 had antiproliferative effects. The report is in the Journal of the National Cancer Institute.
In luminal breast cancer cell lines with wild-type TP53, compared with control, depleting ESR2 increased expression of the TP53 target genes CDKN1A and BBC3 (P = .003 and P = .003, respectively); in contrast, in those with mutant TP53, depleting ESR2 decreased their expression (P = .02 and P = .008). Opposite results were seen when ESR2 was instead overexpressed.
In cells with mutant TP53, tamoxifen treatment increased interaction of ESR2 with the mutant protein, ultimately leading to reactivation of TP73 and apoptosis.
Finally, among women with basal-like TNBC in the METABRIC cohort, high ESR2 expression was associated with better overall survival for those with mutant TP53 tumors (hazard ratio for death, 0.26) but a trend toward poorer overall survival for those with wild-type TP53 tumors (P = .05). Results were similar in the Roswell cohort.