Abstract 2481: Human osteoclast assays for studying the effects of bone metastasis treatments with different mechanisms of action

Abstract

Abstract Metastasis to bone is one of the common complications associated with different types of advanced cancer. Zoledronic acid, a third generation nitrogen containing bisphosphonate, accumulates in bones where it binds to hydroxyapatite crystals. For years, zoledronic acid has been regarded as the standard of care for patients with advanced cancer and bone metastasis to prevent skeletal complications. As an alternative therapeutic option, denosumab has also been found to be effective in delaying skeletal-related events in advanced cancer. Denosumab, a human monoclonal antibody against receptor activator of nuclear factor kappa-B ligand (RANKL), blocks the RANKL/RANK signalling pathway. In addition to the skeletal effects, both zoledronic acid and denosumab have shown direct effect on cancer cells. In this study, effects of zoledronic acid and denosumab on osteoclast differentiation and bone resorption activity were studied using human CD34+ osteoclast precursor cells that were cultured on bovine bone slices in 96-well plates for 7 days in the presence of RANKL and M-CSF, allowing them to differentiate into mature osteoclasts. In the osteoclast differentiation assay, zoledronic acid (0.0001 - 1 000 µM) and denosumab (0.01 - 10 µg/ml) were added into the culture medium at day 0. Tartrate-resistant acid phosphatase 5b (TRACP 5b) activity was measured in the culture medium at day 7 as an index of osteoclast differentiation. In the osteoclast activity assay, the test compounds were added into the culture medium at day 7, and the formed osteoclasts were allowed to resorb bone for 3 days. C-terminal crosslinked telopeptides of type I collagen (CTX-I) was measured in the culture medium at day 10 as an index of bone resorption. Denosumab and zoledronic acid showed strong concentration dependent inhibition of osteoclast differentiation and resorption activity. We conclude that this osteoclast culture system can be used for identifying new potential compounds affecting the disease process of bone metastases with different mechanisms of action. The manifold effects of zoledronic acid and denosumab on cancer cells remain to be studied in more detail. Citation Format: Katja M. Fagerlund, Mervi Ristola, Mari I. Suominen, Jenni H. Mäki-Jouppila, Jukka P. Rissanen. Human osteoclast assays for studying the effects of bone metastasis treatments with different mechanisms of action [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 1 (Regular and Invited Abstracts); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(7_Suppl):Abstract nr 2481.