FOXA1 levels are decreased in pleural breast cancer metastases after adjuvant endocrine therapy, and this is associated with poor outcome

Abstract

Estrogen receptor‐alpha (ERα)‐positive breast cancer is often treated with antihormonal regimens. However, resistance to treatment is common, leading to metastatic disease. ERα activity requires the functional involvement of pioneer factors FOXA1 and GATA3, which enable ERα–chromatin binding and are crucial for ERα‐driven cell proliferation. FOXA1 was found increased in metastatic breast cancers in relation to the primary tumor, but a comprehensive clinical assessment thereof, in relation to different metastatic sites and endocrine therapy usage, is currently lacking. Prior cell line‐based reports, however, have revealed that FOXA1 is required for tamoxifen‐resistant tumor cell proliferation. We studied expression levels of ERα, GATA3, and FOXA1 by immunohistochemistry in samples from both primary tumors and various metastatic sites. For all factors, expression levels varied between the metastatic sites. For pleural metastases, strong variation was found in FOXA1 and GATA3 levels. Although GATA3 levels remained unaltered between primary breast cancer and pleural metastases, FOXA1 levels were reduced exclusively in metastases of patients who received endocrine therapies in the adjuvant setting, even though ERα was still expressed. Importantly, decreased FOXA1 levels in pleural metastases correlated with hormone irresponsiveness in the palliative setting, while no such correlation was found for GATA3. With this, we show divergent clinical correlations of the two ERα pioneer factors FOXA1 and GATA3 in metastatic breast cancer, where endocrine therapy resistance was associated with decreased FOXA1 levels in pleural metastases.

IL6/STAT3 Signaling Hijacks Estrogen Receptor α Enhancers to Drive Breast Cancer Metastasis

“…qPLEX-RIME Primary tumor material from female patients was obtained from the biobank at the Netherlands Cancer Institute and cryosectioned in 30x30 mm. Pleural effusions were collected from female patients treated at the same hospital and processed as described previously (Schrijver et al, 2018). Pellets were stored at -80 C without DMSO.…”

The prognostic relevance of FOXA1 and Nestin expression in breast cancer metastases: a retrospective study of 164 cases during a 10-year period (2004–2014)

“…Robinson et al also reported that breast cancer patients with FOXA1 amplification have a much better prognosis and treatment response [3]. Decreased FOXA1 levels in pleural metastases was associated with endocrine therapy resistance [30].…”

Nuclear Mechanisms Involved in Endocrine Resistance

“…Expression of FoxA1 correlates with ERα expression in primary ERα-positive BCs ( 104 ). As a pioneer TF, FoxA1 facilitates ERα binding to promoters and enhancers and cooperates with ERα to drive ERα-dependent transcription ( 105 ).…”