Pamidronate treatment in patients with tumor-associated hypercalcemia: pharmacological effects and pharmacokinetics

Control of bisphosphonate release using hydroxyapatite granules

The efficacy of hydroxyapatite (HAp) as a carrier was investigated to establish a method of local administration of bisphosphonates (Bps), which has currently been administered systemically. HAp granules (300-500 microm in size) with different physicochemical features were prepared by altering the sintering temperature. To ascertain the physicochemical properties of the HAp granules, their crystallinity was assessed using X-ray diffraction, the surface morphology was examined under scanning electron microscopy, and the specific surface area and calcium dissolution were evaluated. Different Bps-HAp composites were subsequently prepared and the concentration of Bps released from these composites was measured. The influence of Bps-HAp composites on the rate of osteoclast survival was also evaluated. The results revealed that (1) HAp solubility depends on the sintering temperature; (2) The concentration of released Bps could be controlled by regulating the sintering temperature of HAp as a carrier; and (3) Bps released from Bps-HAp composites reduced the number of osteoclasts. These findings indicated that Bps-HAp composites could be locally administered as a drug delivery system to areas with bone resorption.

Pamidronate induced anti-proliferative, apoptotic, and anti-migratory effects in hepatocellular carcinoma

BACKGROUND/AIMS

The small GTPase of Ras and Rho families are widely involved in human tumorgenesis and metastasis. It has recently been reported that pamidronate inhibits the mevalonate pathway, which is required for the prenylation of the small GTPase. We demonstrated a possible beneficial use of pamidronate in the treatment of hepatocellular carcinoma (HCC).

METHODS

The effect of pamidronate on cell proliferation was analyzed with five hepatoma cell lines using MTT assay. Apoptosis was evaluated by staining with DAPI and a histon ELISA assay. A cell migration assay was performed using the Modified Boyden Chamber. To analyze anti-proliferation effect of pamidronate in vivo, tumor volumes were monitored with the intraperitoneal injection of pamidronate after subcutaneous inoculation of PLC/PRF/5 cells into nude mice.

RESULTS

Pamidronate inhibited cell growth for all hepatoma cell lines. The amount of membrane associated Ras and phosphorylated extracellular signal-regulated kinase 2 (ERK 2) were reduced after pamidronate treatment. Pamidronate increased apoptosis and cleavage of Caspase-3, and -9. Pamidronate suppressed membrane associated RhoA and cell motility. In vivo, tumor volumes were significantly suppressed by pamidronate at three weeks (P<0.03).

CONCLUSIONS

We conclude that pamidronate has therapeutic potential in inducing anti-proliferative, apoptotic, and anti-migratory effects in HCC.

Investigation of the effect of pamidronate disodium on the in vitro viability of osteosarcoma cells from dogs

OBJECTIVE

To determine the effect of pamidronate disodium on the in vitro viability of osteosarcoma cells and non-neoplastic cells from dogs.

SAMPLE POPULATION

3 osteosarcoma and 1 fibroblast cell lines derived from dogs.

PROCEDURE

Cell counts and cell viability assays were performed in cultures of osteosarcoma cells (POS, HMPOS, and COS31 cell lines) and fibroblasts after 24, 48, and 72 hours of incubation with pamidronate at concentrations of 0.001 to 1000 microM or with no drug (control treatment). Percentage viability was determined in cell samples for each concentration of pamidronate and each incubation time. A DNA fragmentation analysis was performed to assess bisphosphonate-induced apoptosis.

RESULTS

Osteosarcoma cell viability decreased significantly in a concentration- and time-dependent manner at pamidronate concentrations ranging from 100 to 1000 microM, most consistently after 48 and 72 hours' exposure. In treated osteosarcoma cells, the lowest percentage cell viability was 34% (detected after 72 hours' exposure to 1000 microM pamidronate). Conversely, 72 hours' exposure to 1000 microM pamidronate did not significantly reduce fibroblast viability (the lowest percentage viability was 76%). After 72 hours of exposure, pamidronate did not cause DNA fragmentation in POS or HMPOS cells.

CONCLUSIONS AND CLINICAL RELEVANCE

Results indicate that pamidronate may have the potential to inhibit osteosarcoma growth in dogs, possibly through a nonapoptotic mechanism. The clinical relevance of these in vitro findings remains to be determined, but administration of pamidronate may potentially be indicated as an adjuvant treatment in chemotherapeutic protocols used in dogs.

Zoledronic acid induces antiproliferative and apoptotic effects in human pancreatic cancer cells in vitro

Bisphosphonates (BPs) are an emerging class of drugs mostly used in the palliative care of cancer patients. We investigated the in vitro activity of the most potent antiresorptive BP, zoledronic acid (ZOL), on the growth and survival of three human pancreatic cancer (PC) cell lines (BxPC-3, CFPAC-1 and PANC-1). Pancreatic cancer frequently has a dysregulated p21(ras) pathway and therefore appears to be a suitable target for BPs that interfere with the prenylation of small GTP-binding proteins such as p21(ras). We found that ZOL induces growth inhibition (IC(50):10-50 micro M) and apoptotic death of PC cells. The proapoptotic effect was correlated to cleavage/activation of caspase-9 and poly(ADP)-ribose polymerase, but not of caspase-3. Moreover, we studied the p21(ras) signalling in cells exposed to ZOL and detected a reduction of p21(ras) and Raf-1 content and functional downregulation of the terminal enzyme ERK/MAPkinase and of the pKB/Akt survival pathway. Finally, we observed that ZOL induces significant cytoskeletal rearrangements. In conclusion, we demonstrated that ZOL induces growth inhibition and apoptosis on PC cells and interferes with growth and survival pathways downstream to p21(ras). These findings might be relevant for expanding application of BPs in cancer treatment.

Pamidronate causes apoptosis of plasma cells in vivo in patients with multiple myeloma

Anti-resorptive bisphosphonates, such as pamidronate, are an effective treatment for osteolytic disease and hypercalcaemia in patients with multiple myeloma, but have also been shown to cause apoptosis of myeloma cell lines in vitro. In this study, we found that a single infusion of pamidronate, in 16 newly diagnosed patients with multiple myeloma, caused a marked increase in apoptosis of plasma cells in vivo in 10 patients and a minimal increase in four patients (P < 0.05). The nitrogen-containing bisphosphonates pamidronate and zoledronic acid also induced apoptosis of authentic, human bone marrow-derived plasma cells in vitro. Apoptosis of plasma cells in vitro was probably caused by inhibition of the mevalonate pathway and loss of prenylated small GTPases, as even low concentrations (>or= 1 micro mol/l) of zoledronic acid caused accumulation of unprenylated Rap1A in cultures of bone marrow mononuclear cells in vitro. GGTI-298, a specific inhibitor of geranylgeranyl transferase I, also induced apoptosis in human plasma cells in vitro, suggesting that geranylgeranylated proteins play a role in signalling pathways that prevent plasma cell death. Our results suggest that pamidronate may have direct and/or indirect anti-tumour effects in patients with multiple myeloma, which has important implications for the further development of the more potent nitrogen-containing bisphosphonates, such as zoledronic acid, in the treatment of myeloma.

The bisphosphonate pamidronate is a potent inhibitor of human osteosarcoma cell growth in vitro

Bisphosphonates (BPs), such as pamidronate and clodronate, are an important class of drugs for the treatment of bone diseases. It is widely recognized that they inhibit bone resorption by suppressing the action of osteoclasts through antagonizing the mevalonate pathway, thereby reducing osteolytic bone metastases derived from different cancers, i.e. breast carcinoma and multiple myeloma. In contrast, the effects of BPs on primary bone tumors is an issue still to be resolved. Therefore, a systematic approach was set up to test the hypothesis that BPs could act directly on osteosarcoma cells. The effects of pamidronate and clodronate on seven osteosarcoma cell lines (HOS, MG-63, OST, SaOS-2, SJSA-1, U(2)OS and ZK-58) were studied. Pamidronate inhibited cell growth in a time- and dose-dependent manner, and decreased proliferation for up to 73% at 50 microM after 72 h, whereas its monophosphonate analog 3-aminopropyl phosphonate did not reduce cell viability at concentrations up to 2 mM. Clodronate showed less inhibitory effects (maximally 38% reduction at 1 mM after 72 h). Importantly, cell growth of fibroblasts was only very weakly affected by treatment with pamidronate. These results suggest that pamidronate may be a useful agent for the treatment of patients with osteosarcoma.

Selective and sensitive determination of pamidronate in human plasma and urine by gas chromatography with flame photometric detection

A rapid, selective and sensitive method for the determination of pamidronate in human plasma and urine samples by gas chromatography (GC) has been developed. After deproteinization of the sample with trichloroacetic acid, pamidronate was converted into its N-isobutoxycarbonyl methyl ester derivative and measured by GC with flame photometric detection (FPD), using a HP-1 capillary column. The derivative preparation and GC analysis were accomplished within 30 min. The derivative was sufficiently volatile and stable, giving a single and symmetrical peak, and provided an excellent FPD response. The detection limit of pamidronate, at a signal-to-noise ratio of 3, was ca. 100 pg injected, and the calibration curve for this compound in the range 20-1000 ng was linear and sufficiently reproducible for quantitative determination. This method could be successfully applied to plasma and urine samples without a preliminary clean-up except for deproteinization with trichloroacetic acid, and pamidronate could be measured without any influence from coexisting substances. Overall recoveries of pamidronate added to plasma and urine samples were 93-97%. The coefficients of variation for intra-assay and inter-assay of pamidronate in these samples were 1.0-7.9% (n = 3) and 4.1-8.3% (n = 6), respectively.