Nitrogen-containing bisphosphonates inhibit RANKL- and M-CSF-induced osteoclast formation through the inhibition of ERK1/2 and Akt activation.

Background: Bisphosphonates are an important class of antiresorptive drugs used in the treatment of metabolic bone diseases. Recent studies have shown that nitrogen-containing bisphosphonates induced apoptosis in rabbit osteoclasts and prevented prenylated small GTPase. However, whether bisphosphonates inhibit osteoclast formation has not been determined.

By inhibiting Src, verapamil and dasatinib overcome multidrug resistance via increased expression of Bim and decreased expressions of MDR1 and survivin in human multidrug-resistant myeloma cells.

The calcium channel blocker verapamil inhibits the transport function of multidrug resistance protein 1 (MDR1). Although verapamil acts to reverse MDR in cancer cells, the underlying mechanism remains unclear. In the present study, we investigated the mechanism of reversing MDR by verapamil in anti-cancer drug-resistant multiple myeloma (MM) cell lines.

Activation of NF-κB by the RANKL/RANK system up-regulates snail and twist expressions and induces epithelial-to-mesenchymal transition in mammary tumor cell lines.

Background: Increased motility and invasiveness of cancer cells are reminiscent of the epithelial-mesenchymal transition (EMT), which occurs during cancer progression and metastasis. Recent studies have indicated the expression of receptor activator of nuclear factor-κB (RANK) in various solid tumors, including breast cancer. Although activation of the RANK ligand (RANKL)/RANK system promotes cell migration, metastasis, and anchorage-independent growth of tumor-initiating cells, it remains to be investigated if RANKL induces EMT in breast cancer cells.

Inhibition of the tumour necrosis factor-alpha autocrine loop enhances the sensitivity of multiple myeloma cells to anticancer drugs.

Several autocrine soluble factors, including macrophage inflammatory protein-1α and tumour necrosis factor-alpha (TNF-α), promote the survival and growth of multiple myeloma (MM) cells. We hypothesised that inhibition of the TNF-α autocrine loop may enhance the cytotoxic effect of anticancer drugs in MM cell lines. In the present study, a TNF-α-neutralizing antibody suppressed cell proliferation and enhanced the cytotoxic effect of anticancer drugs on MM cells.

Nitrogen-containing bisphosphonates induce apoptosis of hematopoietic tumor cells via inhibition of Ras signaling pathways and Bim-mediated activation of the intrinsic apoptotic pathway.

Nitrogen-containing bisphosphonates (N-BPs) induce apoptosis in tumor cells by inhibiting the prenylation of small G-proteins. However, the details of the apoptosis-inducing mechanism remain obscure. The present study showed that the induction of apoptosis by N-BPs in hematopoietic tumor cells is mediated by mitochondrial apoptotic signaling pathways, which are activated by the suppression of geranylgeranyl pyrophosphate (GGPP) biosynthesis.

Overexpression of MDR1 and survivin, and decreased Bim expression mediate multidrug-resistance in multiple myeloma cells.

Multidrug resistance represents a major obstacle for the chemotherapy of a wide variety of human tumors. To investigate the underlying mechanisms associated with resistance to anti-cancer drugs, we established anti-cancer drug-resistant multiple myeloma (MM) cell lines RPMI8226/ADM, RPMI8226/VCR, RPMI8226/DEX, and RPMI8226/L-PAM, the 50% inhibitory concentration values of which were 77-, 58-, 79-, and 30-fold higher than their parental cell lines, respectively. The resistant cell lines overexpressed MDR1 and survivin, or showed decreased Bim expression.

Bisphosphonate- and statin-induced enhancement of OPG expression and inhibition of CD9, M-CSF, and RANKL expressions via inhibition of the Ras/MEK/ERK pathway and activation of p38MAPK in mouse bone marrow stromal cell line ST2.

Osteoclast differentiation is influenced by receptor activator of the NF-κB ligand (RANKL), macrophage colony-stimulating factor (M-CSF), and CD9, which are expressed on bone marrow stromal cells and osteoblasts. In addition, osteoprotegerin (OPG) is known as an osteoclastogenesis inhibitory factor. In this study, we investigated whether bisphosphonates and statins increase OPG expression and inhibit the expression of CD9, M-CSF, and RANKL in the bone marrow-derived stromal cell line ST2.