Abstract
Triple negative breast cancer (TNBC) is an aggressive subtype of the disease which lacks options for targeted systemic therapies due to a lack of actionable clinical targets. Molecular analysis has revealed that Fn14, a cytokine receptor, is over-expressed in 75% of invasive breast cancers but not in normal mammary epithelia. Ectopic Fn14 overexpression has been shown to induce canonical NF-κB signalling, which in response enhances Fn14 expression configuring an auto-regulatory loop that drives breast cancer cell malignant behavior. We hypothesised that suppression of the Fn14/NF-κB positive feedback loop may reduce Fn14 expression and the associated pro-migratory and pro- invasive characteristics of TNBC.
Previously synthesised curcumin derivatives RL66 and RL71 have been shown to inhibit Fn14 and NF-κB p65 expression in triple negative BT-549 and MDA-MB-231 cell lines, while RL121 and RL118 have been shown to inhibit NF-κB activity in in vitro models of prostate cancer. Thus, we postulated that RL121 and RL118 would modulate Fn14 expression in TNBC. Investigations were conducted using two highly invasive Fn14+ TNBC cell lines, MDA-MB-231 and BT-549. RL121 and RL118 had a similar potency to previous derivatives in MDA-MB-231, IC50 0.57 μM and 0.45 μM respectively, and BT-549 cells, 0.16 μM and 0.30 μM respectively. Following 24 hr treatment with RL121, there was a 65% decrease in Fn14 and a 57% decrease in NF-κB p65 in MDA-MB-231 cells. In parallel, RL121 reduced both the invasive and migration capacity in vitro by 50% and 56%, respectively. RL118 was not found to effectively reduce NF-κB p65 or Fn14 expression and associated invasion and migration in either cell line.
RL121-mediated reduction in Fn14 expression and associated reduction in migration and invasion is likely due to our observed suppression of NF-κB p65 expression, which consequently prevents expression of pro-migratory and pro-invasive genes including Fn14. RL121 and RL118 exhibited contrasting mechanisms of action, while both drugs were cytotoxic, only RL121 inhibited expression of NF-κB p65 and Fn14, and reduced in vitro invasion and migration. The cytotoxic pharmacodynamics of RL118 in TNBC requires further investigation.
Our findings provide evidence that RL121 has potent anti-invasive activity in Fn14+ TNBC cells. Further investigation regarding the temporal downregulation of Fn14 and NF-κB p65, and identification of which invasive genes are being modulated are required.