Selective inhibition of Rab prenylation by a phosphonocarboxylate analogue of risedronate induces apoptosis, but not S‐phase arrest, in human myeloma cells

Abstract

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. © 2006 Wiley‐Liss, Inc.

Proteomic analysis of protein expression in human tonsillar cancer differentially expressed proteins characterize human tonsillar cancer

“…In a semi quantitative reverse transcriptase PCR, they showed that members of the Rab6 gene family were significantly down regulated in the MCF7 breast cancer cell line [30]. Roelofs et al demonstrated that a selective inhibition of prenylation induces apoptosis but not s-phase arrest [31]. Down-regulation of this protein was also found in our tonsillar cancer samples.…”

Genes associated with the tumour microenvironment are differentially expressed in cured versus primary chemotherapy‐refractory diffuse large B‐cell lymphoma

“…The seven genes that were up-regulated within the refractory cohort were not obviously linked to chemotherapy resistance although RABGGTB, a potential target of farnesyl transferase inhibitors and bisphosphonates (Lackner et al, 2005;Roelofs et al, 2006) and POLE, a target for antimetabolite nucleosides (Miura & Izuta, 2004) might be of interest for further studies.…”

Molecular Mechanisms of Action of Bisphosphonates: Current Status

“…3), thereby selectively preventing the prenylation and membrane localization of Rab GTPases without affecting Rho or Ras family GTPases (75,76). 3-PEHPC is a weak inhibitor of bone resorption, probably by disrupting Rab-dependent vesicular trafficking in osteoclasts (75,76), induces apoptosis in human myeloma cells (77), and inhibits invasion of breast and prostate cancer cells (51).…”

“…66) and may therefore have a different adverse effect profile. Furthermore, 3-PEHPC treatment of myeloma cells does not induce the S-phase arrest characteristic of N-BPs (77). Although more potent phosphonocarboxylates than 3-PEHPC would be required for further development, the lower bone affinity of such agents compared with the parent N-BPs (78) might be an attractive property in situations where long-term retention in bone is undesirable, for example, in the treatment of pediatric bone disease.…”