The MIP-1α autocrine loop contributes to decreased sensitivity to anticancer drugs.

Several autocrine soluble factors, including macrophage inflammatory protein-1α (MIP-1α), tumor necrosis factor-α, and hepatocyte growth factor, promote cell survival and growth in multiple myeloma (MM) cells. We hypothesized that inhibition of the MIP-1α autocrine loop may enhance the cytotoxic effect of anticancer drugs in MM cell lines. In the present study, an MIP-1α neutralizing antibody suppressed cell proliferation and enhanced the cytotoxic effect of melphalan or bortezomib on MM cells. In addition, melphalan resistance cells (RPMI8226/L-PAM and HS-sultan/L-PAM cells) secreted MIP-1α and neutralizing antibody of MIP-1α partially overcame melphalan resistance. Moreover, combination treatment with MIP-1α neutralizing antibody and melphalan or bortezomib inhibited extracellular signal regulated kinase 1/2 (ERK1/2), Akt, and mammalian target of rapamycin (mTOR) activation, Bcl-2, Bcl-xL, and Survivin expression, and upregulated the expression of Bim and cleaved Poly (ADP-ribose) polymerase (PARP). Treatment of IM9 cells with MIP-1α siRNA suppressed the activation of ERK1/2, Akt, and mTOR, and enhanced the cytotoxic effect of melphalan and bortezomib. These results indicate that MIP-1α neutralizing antibodies or MIP-1α siRNA enhance the cytotoxic effect of melphalan and bortezomib by suppressing the chemokine receptor/ERK and chemokine receptor/Akt/mTOR pathways. The inhibition of MIP-1α may thus provide a new therapeutic approach to control tumor progression and bone destruction in patients with MM.

Statins inhibited the MIP-1α expression via inhibition of Ras/ERK and Ras/Akt pathways in myeloma cells.

Macrophage inflammatory protein-1alpha (MIP-1α) is detected at high concentrations in patients with multiple myeloma. It is thought to play an important role in the etiology of multiple myeloma and osteolysis. Thus, inhibiting MIP-1α expression may be useful in developing therapeutic treatments for multiple myeloma-induced osteolysis. In this study, we investigated the potential of statins to inhibit mRNA expression and secretion of MIP-1α in mouse myeloma cells (MOPC-31C). We found that statins inhibited the lipopolysaccharide (LPS)-induced MIP-1α mRNA expression and protein secretion in MOPC-31C cells. This inhibition was reversed when farnesyl pyrophosphate (FPP) and geranylgeranyl pyrophosphate (GGPP), intermediates of the mevalonate pathway, were combined with statins. Furthermore, statins reduced the GTP form of Ras, a phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2), and phosphorylated Akt. Our results indicate that statins inhibit biosynthesis of FPP and GGPP and thereby down regulate signal transduction of Ras/ERK and Ras/Akt pathways. The net effect suppresses LPS-induced MIP-1α mRNA expression and protein secretion in MOPC-31C cells. Thus, statins hold great promise for developing effective therapies against myeloma-induced osteolysis.

Statins improve survival by inhibiting spontaneous metastasis and tumor growth in a mouse melanoma model.

Metastatic melanoma is a life-threatening disease for which no effective treatment is currently available. In melanoma cells, Rho overexpression promotes invasion and metastasis. However, the effect of statins on spontaneous metastasis and tumor growth remains unclear. In the present study, we investigated the mechanism of statin-mediated tumor growth and metastasis inhibition in an in vivo model. We found that statins significantly inhibited spontaneous metastasis and tumor growth. Statins inhibited the mRNA expression and enzymatic activities of matrix metalloproteinases (MMPs) in vivo and also suppressed the mRNA and protein expression of very late antigens (VLAs). Moreover, statins inhibited the prenylation of Rho as well as the phosphorylation of LIM kinase, serum response factor (SRF), and c-Fos downstream of the Rho signaling pathway. In addition, statins enhanced p53, p21, and p27 expression and reduced phosphorylation of cyclin-dependent kinase and expression of cyclin D1 and E2. These results indicate that statins suppress Rho signaling pathways, thereby inhibiting tumor metastasis and growth. Furthermore, statins markedly improved the survival rate in a metastasis model, suggesting that statins have potential clinical applications for the treatment of metastatic cancers.

Bisphosphonates and statins inhibit expression and secretion of MIP-1α via suppression of Ras/MEK/ERK/AML-1A and Ras/PI3K/Akt/AML-1A pathways.

Osteolytic bone disease in multiple myeloma (MM) is associated with upregulated osteoclast activity. Macrophage inflammatory protein-1α (MIP-1α) is crucially involved in the development of osteolytic bone lesions in MM. We previously reported that minodronate inhibited lipopolysaccharide-induced MIP-1α secretion in mouse myeloma cells. However, it remains unknown whether bisphosphonates and statins inhibit MIP-1α secretion by human MM cells. In present study, we investigated whether bisphosphonates and statins had any inhibitory effect on MIP-1α secretion by human myeloma cells and the mechanism underlying this effect. In this study, we found that bisphosphonates and statins inhibited MIP-1α mRNA and MIP-1α secretion and suppressed extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt phosphorylation by inhibiting Ras prenylation. Moreover, bisphosphonates and statins suppressed the expression of acute myeloid leukemia-1A (AML-1A) mRNA, a MIP-1α transcription factor. These results indicate that bisphosphonates and statins suppress the Ras/mitogen-activated protein kinase kinase/ERK/AML-1A and Ras/phosphatidylinositol-3 kinase/Akt/AML-1A pathways, thereby inhibiting MIP-1α secretion by MM cells. Therefore, use of MIP-1α expression inhibitors such as bisphosphonates and statins may provide a new therapeutic approach to inhibiting tumour progression and bone destruction in MM patients.

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. In the present study, we investigated the inhibitory effect of minodronate and alendronate on the osteoclast formation and clarified the mechanism involved in a mouse macrophage-like cell lines C7 and RAW264.7. RESULTS: It was found that minodronate and alendronate inhibited the osteoclast formation of C7 cells induced by receptor activator of NF-κB ligand and macrophage colony stimulating factor, which are inhibited by the suppression of geranylgeranyl pyrophosphate (GGPP) biosynthesis. It was also found that minodronate and alendronate inhibited the osteoclast formation of RAW264.7 cells induced by receptor activator of NF-κB ligand. Furthermore, minodronate and alendornate decreased phosphorylated extracellular signal-regulated kinase 1/2 (ERK1/2) and Akt; similarly, U0126, a mitogen protein kinase kinase 1/2 (MEK1/2) inhibitor, and LY294002, a phosphatidylinositol 3-kinase (PI3K) inhibitor, inhibited osteoclast formation. CONCLUSIONS: This indicates that minodronate and alendronate inhibit GGPP biosynthesis in the mevalonate pathway and then signal transduction in the MEK/ERK and PI3K/Akt pathways, thereby inhibiting osteoclast formation. These results suggest a novel effect of bisphosphonates that could be effective in the treatment of bone metabolic diseases, such as osteoporosis.

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. We found that verapamil suppresses MDR1 and survivin expressions and increases Bim expression via suppression of Src activation. Furthermore, dasatinib reversed the drug-resistance of the drug-resistant cell lines. These findings suggest that Src inhibitors are potentially useful as an anti-MDR agent for the treatment of malignant tumor cells.

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. In this study, we investigated whether RANKL induces EMT in normal breast mammary epithelial cells and breast cancer cells, and the mechanism underlying such induction. METHODS: Expression levels of vimentin, N-cadherin, E-cadherin, Snail, Slug, and Twist were examined by real-time polymerase chain reaction. Cell migration and invasion were assessed using Boyden chamber and invasion assays, respectively. The effects of RANKL on signal transduction molecules were determined by western blot analyses. RESULTS: We found that stimulation by RANKL altered the cell morphology to the mesenchymal phenotype in normal breast epithelial and breast cancer cells. In addition, RANKL increased the expression levels of vimentin, N-cadherin, Snail, and Twist and decreased the expression of E-cadherin. We also found that RANKL activated nuclear factor-κB (NF-κB), but not extracellular signal-regulated kinase 1/2, Akt, mammalian target of rapamycin, c-Jun N-terminal kinase, and signal transducer and activator of transcription 3. Moreover, dimethyl fumarate, a NF-κB inhibitor, inhibited RANKL-induced EMT, cell migration, and invasion, and upregulated the expressions of Snail, Twist, vimentin, and N-cadherin. CONCLUSIONS: The results indicate that RANKL induces EMT by activating the NF-κB pathway and enhancing Snail and Twist expression. These findings suggest that the RANKL/RANK system promotes tumor cell migration, invasion, and metastasis via the induction of EMT.

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. In addition, combination treatment with the TNF-α-neutralizing antibody and the chemotherapy agent melphalan inhibited nuclear factor κB (NF-κB) p65 nuclear translocation and mammalian target of rapamycin (mTOR) activation and upregulated the expression of Bax and Bim. Treatment of ARH-77 cells with the NF-κB inhibitor dimethyl fumarate or the mTOR inhibitor rapamycin suppressed NF-κB p65 nuclear translocation and enhanced the cytotoxic effect of melphalan. Furthermore, infliximab, a monoclonal antibody against TNF-α, also enhanced the cytotoxic effect of anticancer drugs in ARH-77 cells. These results indicated that TNF-α-neutralizing antibodies or infliximab enhanced the cytotoxic effect of anticancer drugs by suppressing the TNF receptor/mTOR/NF-κB pathways. The inhibition of TNF-α may thus provide a new therapeutic approach to control tumour progression and bone destruction in MM patients.