Roelofs Anke J, Hulley Philippa A, Meijer Annemieke, Ebetino Frank H, Russell R Graham G, Shipman Claire M
Botnar Research Centre, Nuffield Orthopaedic Centre, University of Oxford, Oxford, United Kingdom.
Int J Cancer. 2006 Sep 15;119(6):1254-61. doi: 10.1002/ijc.21977.
Bisphosphonates (BPs) are widely used in the treatment of osteolytic bone disease associated with multiple myeloma, and have been demonstrated to exert antitumor effects both in vitro and in vivo. However, the precise molecular mechanisms involved in the direct antitumor effects of BPs in vitro are not known. Nitrogen-containing BPs, such as risedronate (RIS), act by inhibiting protein prenylation. A phosphonocarboxylate analogue of RIS, 3-PEHPC, has previously been shown in osteoclasts and macrophages to specifically inhibit prenylation of Rab GTPases. The aim of this study was to identify the molecular targets of RIS and 3-PEHPC in human myeloma cells and to determine the cellular effects of selective inhibition of Rab prenylation by 3-PEHPC as compared to nonspecific inhibition of protein prenylation by RIS in human myeloma cells. RIS dose-dependently inhibited prenylation of both Rap1A and Rab6, whereas 3-PEHPC only inhibited Rab6 prenylation. Both RIS and 3-PEHPC dose-dependently increased apoptosis in human myeloma cells. RIS induced an accumulation of cells in the S-phase of the cell cycle, associated with inhibition of DNA replication. In contrast, 3-PEHPC did not cause cell-cycle arrest. Furthermore, geranylgeraniol could prevent inhibition of prenylation, induction of apoptosis, and cell-cycle arrest in response to RIS, but not inhibition of Rab prenylation and apoptosis induced by 3-PEHPC, consistent with specific inhibition of Rab geranylgeranyl transferase by 3-PEHPC. In conclusion, our studies demonstrate that selective inhibition of Rab prenylation induces apoptosis, but not S-phase arrest, thus identifying distinct molecular pathways that mediate the antimyeloma effect of nitrogen-containing BPs.
双膦酸盐（BPs）被广泛用于治疗与多发性骨髓瘤相关的溶骨性骨病，并且已被证明在体外和体内均具有抗肿瘤作用。然而，BPs在体外直接抗肿瘤作用所涉及的精确分子机制尚不清楚。含氮双膦酸盐，如利塞膦酸盐（RIS），通过抑制蛋白质异戊二烯化发挥作用。RIS的一种膦酰基羧酸盐类似物3-PEHPC，先前已在破骨细胞和巨噬细胞中显示出能特异性抑制Rab GTP酶的异戊二烯化。本研究的目的是确定RIS和3-PEHPC在人骨髓瘤细胞中的分子靶点，并确定与RIS在人骨髓瘤细胞中对蛋白质异戊二烯化的非特异性抑制相比，3-PEHPC对Rab异戊二烯化的选择性抑制的细胞效应。RIS剂量依赖性地抑制Rap1A和Rab6的异戊二烯化，而3-PEHPC仅抑制Rab6的异戊二烯化。RIS和3-PEHPC均剂量依赖性地增加人骨髓瘤细胞的凋亡。RIS诱导细胞周期S期细胞积累，与DNA复制抑制有关。相比之下，3-PEHPC未引起细胞周期停滞。此外，香叶基香叶醇可以预防RIS诱导的异戊二烯化抑制、凋亡诱导和细胞周期停滞，但不能预防3-PEHPC诱导的Rab异戊二烯化抑制和凋亡，这与3-PEHPC对Rab香叶基香叶基转移酶的特异性抑制一致。总之，我们的研究表明，Rab异戊二烯化的选择性抑制诱导凋亡，但不诱导S期停滞，从而确定了介导含氮双膦酸盐抗骨髓瘤作用的不同分子途径。
