Pharmacological Inhibition of NF\u03baB Reduces Prostate Cancer Related Osteoclastogenesis In Vitro and Osteolysis Ex Vivo

Silvia Marino,John G Logan,Aymen I Idris,Ryan T Bishop,Giovana Carrasco,Boya Li

doi:10.1007/s00223-019-00538-9

Abstract

NFκB is implicated in cancer and bone remodelling, and we have recently reported that the verified NFκB inhibitor Parthenolide (PTN) reduced osteolysis and skeletal tumour growth in models of metastatic breast cancer. Here, we took advantage of in vitro and ex vivo bone cell and organ cultures to study the effects of PTN on the ability of prostate cancer cells and their derived factors to regulate bone cell activity and osteolysis. PTN inhibited the in vitro growth of a panel of human, mouse and rat prostate cancer cells in a concentration-dependent manner with a varying degree of potency. In prostate cancer cell—osteoclast co-cultures, the rat Mat-Ly-Lu, but not human PC3 or mouse RM1-BT, enhanced RANKL stimulated osteoclast formation and PTN reduced these effects without affecting prostate cancer cell viability. In the absence of cancer cells, PTN reduced the support of Mat-Ly-Lu conditioned medium for the adhesion and spreading of osteoclast precursors, and survival of mature osteoclasts. Pre-exposure of osteoblasts to PTN prior to the addition of conditioned medium from Mat-Ly-Lu cells suppressed their ability to support the formation of osteoclasts by inhibition of RANKL/OPG ratio. PTN enhanced the ability of Mat-Ly-Lu derived factors to increase calvarial osteoblast differentiation and growth. Ex vivo, PTN enhanced bone volume in calvaria organ—Mat-Ly-Lu cell co-culture, without affecting Mat-Ly-Lu viability or apoptosis. Mechanistic studies in osteoclasts and osteoblasts confirmed that PTN inhibit NFκB activation related to derived factors from Mat-Ly-Lu cells. Collectively, these findings suggest that pharmacological inhibition of the skeletal NFκB signalling pathway reduces prostate cancer related osteolysis, but further studies in the therapeutic implications of NFκB inhibition in cells of the osteoblastic lineage are needed.

Highlights

NFκB is implicated in cancer and bone remodelling [1,2,3,4,5,6,7,8,9]
NFκB plays a key role in RANK ligand (RANKL)-induced osteoclastogenesis [11,12,13], and previous studies have shown that PTN reduces osteolysis in models of breast cancer bone metastasis [44,45,46,47,48,49]
In view of the fact that the canonical NFκB signalling pathway plays a major role in the regulation of bone growth, osteoclastic bone resorption and osteoblastic bone formation [11,12,13], we employed a pharmacological approach to test if the verified inhibitor of the canonical NFκB signalling pathway PTN disrupts the ability of prostate cancer cells to influence osteoclast formation, osteoblast differentiation and osteolysis

Summary

Introduction

NFκB is implicated in cancer and bone remodelling [1,2,3,4,5,6,7,8,9]. Previous studies have shown that pharmacological and genetic inhibition of key components of the NFκB1 3 Vol.:(0123456789)signalling pathway reduce bone loss associated with various bone disorders including bone metastasis, oestrogen deficiency, rheumatoid arthritis and Paget’s disease of bone [10,11,12,13,14]. Activation of cancer- and host-specific NFκB signalling by these factors plays a key role in the initiation and progression of cancer related osteolytic and osteosclerotic bone metastases [17,18,19,20,21]. The majority of prostatic bone metastases in patients are predominately osteosclerotic and are frequently accompanied by enhanced osteoblast differentiation and ectopic bone formation [25, 26]. The ability of prostate cancer cells to enhance the formation, survival and activity of osteoclasts by both directly and indirectly acting on osteoblasts, contributes to the development of osteolytic lesions [24, 26,27,28,29,30,31]

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Results

Conclusion