Osteoprotegerin (OPG) is a robust antiresorptive molecule that acts as a decoy receptor for the receptor activator of nuclear factor κB ligand (RANKL), the mediator of osteoclastogenesis. This study was designed to explore the possible role of serum OPG and RANKL in detecting bone metastasis in breast cancer and its interaction with clinicopathologic parameters. Serum levels of RANKL and OPG were estimated in 44 metastatic and 36 nonmetastatic breast cancer patients using ELISA kits. Serum OPG levels were significantly reduced in patients with bone metastasis and correlated negatively with the number of bone lesions and CA 15-3 levels. At concentrations ≤82 pg/ml, OPG showed a high specificity in identifying the presence of bone metastasis (92%), albeit with low sensitivity (59%), which improved after the exclusion of diabetics and patients treated with aromatase inhibitors (AI). Serum RANKL levels were significantly higher in the presence of bone metastasis and hypercalcemia. At concentrations >12.5 pg/ml, RANKL had an associated sensitivity of 86%, albeit with low specificity (53%), in detecting bone metastasis. The RANKL/OPG ratio significantly increased in the presence of bone metastasis with appropriate sensitivity and specificity (73% and 72%, respectively) at a cutoff of ≥0.14 for the detection of bone metastasis. Serum OPG and RANKL/OPG ratios are promising biomarkers for detecting bone metastasis in breast cancer patients.

Niclosamide is an oral anthelmintic drug, approved for use against tapeworm infections. Recent studies suggest however that niclosamide may have broader clinical applications in cancers, spurring increased interest in the functions and mechanisms of niclosamide. Previously, we reported that niclosamide targets a metabolic vulnerability in p53-deficient tumours, providing a basis for patient stratification and personalised treatment strategies. In the present study, we functionally characterised the contribution of the aniline 4′-NO2 group on niclosamide to its cellular activities. We demonstrated that niclosamide induces genome-wide DNA damage that is mechanistically uncoupled from its antitumour effects mediated through mitochondrial uncoupling. Elimination of the nitro group in ND-Nic analogue significantly reduced γH2AX signals and DNA breaks while preserving its antitumour mechanism mediated through a calcium signalling pathway and arachidonic acid metabolism. Lipidomics profiling further revealed that ND-Nic-treated cells retained a metabolite profile characteristic of niclosamide-treated cells. Notably, quantitative scoring of drug sensitivity suggests that elimination of its nitro group enhanced the target selectivity of niclosamide against p53 deficiency. Importantly, the results also raise concern that niclosamide may impose a pleiotropic genotoxic effect, which limits its clinical efficacy and warrants further investigation into alternative drug analogues that may ameliorate any potential unwanted side effects.