HOXB7 Overexpression Leads Triple-Negative Breast Cancer Cells to a Less Aggressive Phenotype

Abstract

HOX genes appear to play a role in breast cancer progression in a molecular subtype-dependent way. The altered expression of HOXB7, for example, was reported to promote breast cancer progression in specific subtypes. Here we induced HOXB7 overexpression in MDA-MB-231 cells, a cellular model of the Triple-Negative breast cancer molecular subtype, and evaluated the phenotypic changes in cell viability, morphogenesis, migration, invasion, and colony formation. During the phenotypic characterization of the HOXB7-overexpressing cells, we consistently found less aggressive behavior represented by lower cell viability, inhibition of cell migration, invasion, and attachment-independent colony formation capacities added to the more compact and organized spheroid growth in 3D cultures. We then evaluated the expression of putative downstream targets and their direct binding to HOXB7 comparing ChIP-qPCR data generated from HOXB7-overexpressing cells and controls. In the manipulated cells, we found enriched biding of HOXB7 to CTNNB1, EGFR, FGF2, CDH1, DNMT3B, TGFB2, and COMMD7. Taken together, these results highlight the plasticity of the HOXB7 function in breast cancer, according to the cellular genetic background and expression levels, and provide evidence that in Triple-Negative breast cancer cells, HOXB7 overexpression has the potential to promote less aggressive phenotypes.

Epigenetic Regulation of CDH1 Is Altered after HOXB7-Silencing in MDA-MB-468 Triple-Negative Breast Cancer Cells

“…These data are in agreement with previous reports suggesting that CDH1 is a methylation-silenced gene in these cells [35]. We then investigate whether HOXB7 overexpression may have an impact on the methylation of E-cadherin in MDA-MB-468 cells, as reported recently for other triple-negative breast cancer cells [21]. To this end, we characterized the CDH1 methylation status in HOXB7-silenced cells and controls using bisulfite conversion followed by sequencing analyses.…”

“…Our data showed that with the silencing of HOXB7 in MDA-MB-468 cells, the expression of CDH1 increased. Recent functional assays performed in MDA-MB-231 cells revealed enriched interactions between the HOXB7 protein and CDH1 [21]. Thus, we hypothesize that HOXB7 deregulation may affect CDH1 expression in multiple triple-negative BC cells.…”

“…The role of HOXB7 was also addressed in triple-negative breast cancer (TNBC) basal B cell line MDA-MB-231 [21]. These cells, which are derived from metastatic sites (pleural infusion), present some degree of HOXB7 overexpression [14].…”

“…These cells, which are derived from metastatic sites (pleural infusion), present some degree of HOXB7 overexpression [14]. Here, the HOXB7 protein was proposed to bind to downstream targets such as CDH1 and DNMT3b, among others [21]. CDH1 encodes a cell adhesion molecule (E-cadherin), which is present in the adherent's junctions of epithelial cells, preventing their transition to a mesenchymal migratory state [22].…”

“…To explore the hypothesis that HOXB7 overexpression may affect CDH1 expression in TNBC cells directly or indirectly through an effect on DNMT3b transcription, we transiently silenced HOXB7 in another triple-negative cellular model, MDA-MB-468. However, that belongs to the basal A types, known to have much higher expression of CDH1 and more prominent overexpression of HOXB7 than the MDA-MB-231 cells [21]. This cell line is also derived from metastatic sites (pleural infusion) and presents an altered expression of p53, PTEN, and EGFR [29].…”