Bisphosphonates inhibit the adhesion of breast cancer cells to bone matrices in vitro

Bisphosphonates in bone diseases

Bisphosphonates are a class of drugs which are strongly attracted to the bone where they influence the calcium metabolism, mainly by inhibition of the osteoclast-mediated bone resorption. This property makes these compounds suited for the treatment of several diseases of the bone. In Paget's disease, several bisphosphonates can reduce bone pain and decrease the bone turnover 60-70%. Cyclical oral etidronate and daily oral alendronate both proved to reduce the vertebral fracture rate for postmenopausal osteoporotic woman, while most investigated bisphosphonates can increase spinal bone mass in osteoporosis. Bisphosphonates can help lowering serum calcium and reverse skeletal complications in malignancy mediated bone diseases. Oral and intravenous administration of therapeutic doses is relatively safe. In general, gastrointestinal disturbances are described most often and the oldest, least potent, bisphosphonate etidronate can induce osteomalacia. The various characteristics of bisphosphonates: physicochemical, biological, therapeutic and toxicological, vary greatly depending on the structure of the individual bisphosphonate. Even small changes in the structure can lead to enormous differences in potency. Overall, this class of drugs offers several prospects for the future.

The role of alpha2 beta1 and alpha3 beta1 integrin receptors in the initial anchoring of MDA-MB-231 human breast cancer cells to cortical bone matrix

Molecular mechanisms involved in the rapid attachment of the human breast cancer cell line MDA-MD-231 to cortical bone matrix were studied. The attachment of MDA-MD-231 cells to cortical bone disks could be blocked by 75% when cells were pretreated with a monoclonal antibody to the beta1-subunit of the integrin family. Monoclonal antibodies against the alpha2, alpha3, and alpha5 integrin subunits inhibited the attachment by 76, 26, and 8 % respectively. Collagenase type I and collagen type I antibody blocked the cell attachment by 45 and 50 % whereas pretreatment of the cells with soluble collagen type I blocked the attachment by 85 %. Our study with a panel of cancer cell lines further showed a close correlation between alpha2 beta1 and alpha3 beta1 integrin receptor expression and the capability to attach to cortical bone. These receptors appear to be the key receptors utilized by cancer cells for the initial attachment to cortical bone, and this could facilitate the localization of alpha2 beta1 and alpha3 beta1 expressing cancer cells to the skeleton.

Reduction in new metastases in breast cancer with adjuvant clodronate treatment

BACKGROUND

Bisphosphonates are effective against the increased bone resorption caused by certain diseases because they inhibit the activity of osteoclasts. In patients who have breast cancer and metastatic bone disease, the bisphosphonate clodronate (clodronic acid) reduces the frequency of skeletal complications. Experiments in animals and preliminary clinical observations indicate that early clodronate therapy reduces the incidence of new bony metastases in breast cancer. We investigated the effects of clodronate on the incidence and extent of new metastases in patients with breast cancer.

METHODS

Between 1990 and 1995, 302 patients with primary breast cancer and tumor cells in the bone marrow (the presence of which is a risk factor for the development of distant metastases) were randomly assigned to receive clodronate at a dose of 1600 mg per day orally for two years (157 patients) or standard follow-up (145 patients). The median length of observation was 36 months. All patients in both groups received standard surgical treatment and customary hormonal therapy or chemotherapy.

RESULTS

Distant metastases were detected in 21 patients in the clodronate group and in 42 patients in the control group (P<0.001). The incidence of both osseous and visceral metastases was significantly lower in the clodronate group than in the control group (P=0.003 for both osseous and visceral metastases). Six patients in the clodronate group died, as did 22 in the control group (P=0.001). The mean number of bony metastases per patient in the clodronate group was roughly half that in the control group (3.1 vs. 6.3).

CONCLUSIONS

Clodronate can reduce the incidence and number of new bony and visceral metastases in women with breast cancer who are at high risk for distant metastases.

Enhanced expression of interleukin-6 in bone and serum of metastatic renal cell carcinoma

Interleukin-6 (IL-6) is produced by renal cell carcinoma (RCC) cell lines and primary tumors. Using immunohistochemical staining in two RCC patients with hypercalcemia and high serum levels of free and total IL-6, we showed expression of IL-6 in metastatic bone tissue. The role of IL-6 in hypercalcemia and bone resorption would suggest that bisphosphonates or dexamethasone could be useful as adjuvant therapy for IL-6 dependent bone metastases which fail to respond to interferon alpha (IFN) alpha 2a and all trans retinoic acid (ATRA).

Hematopoietic progenitor cell transplantation in breast cancer: current status and future directions

Breast cancer remains the second leading cause of cancer death despite numerous advances in medical science. In vitro, preclinical, and clinical trials have shown that chemotherapy dose intensity is an important component of therapy. Many clinical trials addressing the use of high-dose chemotherapy and hematopoietic cellular rescue have been conducted over the past decade. Early trials undertaken in heavily pretreated patients who had metastatic disease were associated with high treatment-related mortality rates; good response rates were noted but overall survivals were short. Subsequent technological advances, including the use of recombinant hematopoietic growth factors and peripheral blood progenitor cells as the source of cellular rescue, have dramatically lowered the morbidity and mortality of the procedure, as well as shortened hospital stay and markedly reduced cost. As a result, the high-dose chemotherapy approach has been used earlier in the disease course, both in patients with metastatic disease who were responding and in the adjuvant setting in patients at high risk for relapse. Results of many of these phase II trials are extremely encouraging, and phase III prospective, randomized trials comparing autotransplant to conventional approaches are currently under way. This review discusses past, current, and future initiatives of this modality. Included is a discussion of new preparative regimens, the addition of agents such as biochemical modifiers to enhance antitumor activity, and issues regarding timing of autotransplant, stem cell technology, use of allogeneic stem cells, and posttransplantation therapies.

Pamidronate. A review of its use in the management of osteolytic bone metastases, tumour-induced hypercalcaemia and Paget's disease of bone

Pamidronate (APD) is a potent inhibitor of bone resorption that is useful in the management of patients with osteolytic bone metastases from breast cancer or multiple myeloma, tumour-induced hypercalcaemia or Paget's disease of bone. After intravenous administration, the drug is extensively taken up in bone, where it binds with hydroxyapatite crystals in the bone matrix. Matrix-bound pamidronate inhibits osteoclast activity by a variety of mechanisms, the most important of which appears to be prevention of the attachment of osteoclast precursor cells to bone. In patients with osteolytic bone metastases associated with either breast cancer or multiple myeloma, administration of pamidronate together with systemic antitumour therapy reduces and delays skeletal events, including pathological fracture, hypercalcaemia and the requirement for radiation treatment or surgery to bone. Pamidronate generally improves pain control. Quality-of-life and performance status scores in pamidronate recipients were generally as good as, or better than, those in patients who did not receive the drug. Overall survival does not appear to be affected by pamidronate therapy. Tumour-induced hypercalcaemia also responds well to pamidronate therapy: 70 to 100% of patients achieve normocalcaemia, generally 3 to 5 days after treatment. Response durations vary, but are commonly 3 weeks or longer, In comparative studies, pamidronate produced higher rates of normocalcaemia and longer normocalcaemic durations than other available osteoclast inhibitors, including intravenous etidronate, clodronate and plicamycin (mithramycin). In most patients with Paget's disease of bone, intravenous pamidronate reduces bone pain and produces biochemical response. Serum alkaline phosphatase levels generally fall 50 to 70% from baseline 3 to 4 months after pamidronate treatment. Biochemical response may be prolonged. Pamidronate is well tolerated by most patients. Transient febrile reactions, sometimes accompanied by myalgias and lymphopenia, occur commonly after the first infusion of pamidronate. Other reported adverse events include transient neutropenia, mild thrombophlebitis, asymptomatic hypocalcaemia and, rarely, ocular complications (uveitis and scleritis). Pamidronate should be considered for routine use together with systemic hormonal or cytotoxic therapy in patients with breast cancer or multiple myeloma and osteolytic metastases. At present, pamidronate is the drug of choice for first-line use in the management of patients with tumour-induced hypercalcaemia. It is an effective treatment for Paget's disease and is the treatment of choice where oral bisphosphonates are not an option.