Additionally, the presence of PIK3CA mutations of cfDNA was significantly correlated with positive androgen receptor phosphorylated form depending on PI3K signaling pathway (pAR) which is independent favorable prognostic factors of TNBC.
We demonstrated that combination of AR antagonist (bicalutamide) and PARP inhibitor (ABT-888) could inhibit cell viability and induce cell apoptosis significantly whatever in vitro or in vivo setting in AR-positive TNBC.
To further substantiate our hypothesis and provide mechanistic insights, we also looked at the expression and regulation of these factors in publically available microarray data and in a panel of TNBCAR-positive cell lines.
Numerous experimental approaches are under way, and several encouraging drug classes, such as immune checkpoint inhibitors, poly(ADP-ribose) polymerase inhibitors, platinum agents, phosphatidylinositol-3-kinase pathway inhibitors, and androgen receptor inhibitors, are being investigated in TNBC.
Studies have shown it to antagonize estrogen receptor alpha (ERα) DNA binding, thereby preventing pro-proliferative gene transcription; whilst others have demonstrated AR to take on the mantle of a pseudo ERα particularly in the setting of triple negative breast cancer.
Recent efforts aimed at molecular characterisation of TNBCs have revealed various emerging therapeutic targets including PARP1, receptor and non-receptor tyrosine kinases, immune-checkpoints, androgen receptor and epigenetic proteins.
A meta-analysis of public gene expression databases indicated that ACSL4 expression is positively correlated with a unique subtype of triple negative breast cancer (TNBC), characterized by the absence of androgen receptor (AR) and therefore referred to as quadruple negative breast cancer (QNBC).