Adriamycin inhibits PTH-mediated but not PGE2-mediated stimulation of cyclic AMP formation in isolated bone cells

Risk Factors for Hematopoietic Stem Cell Transplantation-Associated Bone Loss

Hematopoietic stem cell transplantation (HSCT), including bone marrow transplantation, is the treatment of choice for many hematologic diseases, including hematologic malignancies and different types of anemia. The use of HSCT is increasing annually, mainly because advanced research that has been conducted in this area has exponentially expanded the indications for HSCT and significantly improved transplantation techniques and supportive care practices. Collectively, these improvements have led to an increase in the overall survival of HSCT patients. However, as post-HSCT survival is increasing, awareness of the potential late complications of HSCT is also growing. Unpredictable bone loss is one of the major post-HSCT complications that can cause significant morbidity and impair the quality of life of survivors. Although the exact mechanism of post-HSCT bone loss is not yet known, previous studies have suggested that numerous factors, including destructive preparative regimens (eg, high-dose chemotherapy, total body irradiation), treatment-related complications (eg, graft-versus-host disease), endocrine abnormalities (eg, diabetes mellitus, thyroid dysfunction, adrenal insufficiency), lack of physical activity, and the underlying disease itself are responsible for HSCT-associated bone loss. Sufficient data have been collected to suggest that post-HSCT bone loss can be prevented and treated using the same preventive and treatment modalities as used for the general population. Various guidelines have been formulated to help keep a check on HSCT recipients' deteriorating bone health.

Cancer-treatment-induced bone loss, part 1

PURPOSE

The pathophysiology, frequency, sequelae, diagnosis, and treatment of cancer-treatment-induced bone loss (CTIBL) are discussed.

SUMMARY

CTIBL is a long-term complication associated with cancer therapies that can directly or indirectly affect bone metabolism. Although CTIBL can occur in any patient receiving a cancer therapy known to cause bone loss, CTIBL is most common in patients with breast or prostate cancer who receive chemotherapy, hormone therapy, or surgical castration, as these can cause hypogonadism and induce bone loss. CTIBL causes bone fragility and an increased susceptibility to fractures; therefore, prevention, early diagnosis, and treatment of CTIBL are essential to decrease the risk of fracture. Bone loss occurs more rapidly and tends to be more severe in patients with CTIBL compared with those with normal age-related bone loss. Fractures of the hip, vertebra, and wrist are the fractures most commonly associated with bone loss. CTIBL is diagnosed by measuring bone mass using bone densitometry. Treatment of CTIBL consists of changing diet and lifestyle such as optimizing calcium and vitamin D intake, exercising, modifying behaviors known to increase the risk of CTIBL and pharmacologic therapy with hormone replacement therapy (HRT), selective estrogen-receptor modifiers (SERMs), calcitonin, or a bisphosphonate.

CONCLUSION

Early identification and treatment of CTIBL are essential to prevent fractures. Patients should be instructed to optimize calcium and vitamin D intake, exercise regularly, and modify lifestyle behaviors known to cause bone loss. Patients with CTIBL should be treated with an oral or i.v. bisphosphonate; SERMs or HRT may be an option in some patients if contraindications do not exist.

Gender-dependent reductions in vertebrae length, bone mineral density and content by doxorubicin are not reduced by dexrazoxane in young rats: effect on growth plate and intervertebral discs

Doxorubicin (DOX) is widely used in anti-cancer cocktails. Dexrazoxane (DXR) is a cardioprotectant approved for use with DOX. The effect of DOX, with or without DXR, on bone in children is not well understood. The aim of this study was to examine the effect of DOX on vertebrae and femur length and bone density acquisition in young rats, as well as to test the hypothesis that young females are more susceptible to DOX-induced tissue damage than young males. The results of this study suggest that a single injection of DOX in young female and not male rats is associated with low bone turnover resulting in vertebrae and femur bone growth deficits. DOX selectively decreased BMD and BMC accrual in the lumbar vertebrae that was not prevented by DXR. DOX-treated rats also exhibited growth plate and intervertebral disc defects. This information will be useful in the design of interventions to promote bone growth or retard bone loss during DOX treatment.

Osteoporosis due to cancer treatment: pathogenesis and management

Many therapeutic regimens in cancer treatment carry the risk of causing or favoring the development of osteoporosis. Therapies in which hypogonadism may occur are most relevant in this respect. Prompt hormone replacement therapy is indicated in these patients. In patients in whom this is undesirable because of a hormone-dependent tumor, the risk of osteoporosis should be assessed by means of osteodensitometry, and prophylactic or therapeutic measures should be instituted if necessary. Early intervention improves outcome because osteoporosis therapy is most effective in preventing deterioration of bone mass. There remains much uncertainty in assessing the risk of combination chemotherapy with regard to the development of osteoporosis. Negative effects on the skeleton have, however, been demonstrated for individual drugs, such as methotrexate and ifosfamide. Negative effects of the tumor itself on bone metabolism may aggravate the degree of osteoporosis. Detailed data and long-term experience to assess the risk are urgently needed in this area and constitute an important research topic for the coming years and decades. This review discusses the most prevalent mechanisms of osteoporosis caused by cancer treatment and outlines therapeutic strategies for the prevention and treatment of therapy-induced bone loss.

Cell surface actions of adriamycin

Adriamycin has a vast range of reported actions on the structural and functional properties of cells. This review summarizes the literature on the ability of the drug to modulate the cell surface membrane and attempts to address the question of how such actions could be linked to cytotoxicity. In addition, we consider the use of polymer immobilization of adriamycin to separate intracellular from plasma membrane effects of the drug, and show how this approach has been helpful in interpreting the pharmacology of adriamycin. Finally, a range of biophysical and spectroscopic approaches to defining the molecular details of adriamycin-bilayer interactions is surveyed, and the results used to discuss a model for how this antineoplastic agent binds to membranes.

Bone-resorbing agents promote and interferon-gamma inhibits bone cell collagenase production

Parathyroid hormone, prostaglandin E2, 1 alpha,25-dihydroxyvitamin D3, interleukin-1, tumor necrosis factor alpha, and epidermal growth factor, all known stimulators of bone resorption, markedly enhanced collagenase secretion by rat fetus osteoblastlike cells in primary culture as judged by enzyme-linked immunosorbent assay. Untreated cells contained no immunostainable or extractable collagenase. Collagenase was detected in the treated cells and media only after 1-3 h of treatment, and there was no increment in collagenase activity when cells were treated in the presence of actinomycin D or cycloheximide. Cells secreted collagenase in a latent form and also elaborated collagenase inhibitor; chromatographic separation of collagenase from collagenase inhibitor and subsequent activation of the collagenase with trypsin yielded the active species in stimulated but not in unstimulated cells. The ability of individual prostanoids, among seven tested, to promote collagenase production correlated positively with their reported capacity to promote bone resorption. Interferon-gamma (IFN-gamma), a known resorption inhibitor, blocked the increment in collagenase production caused by all agents tested. These results indicate a close linkage between stimulation of bone resorption and collagenase production by osteoblastlike cells. Various resorption stimulators, including some not previously tested for effects on collagenase, augment the de novo synthesis and secretion of collagenase and act by an IFN-gamma-inhibitable mechanism.

Prostaglandins change cell shape and increase intercellular gap junctions in osteoblasts cultured from rat fetal calvaria

Mounting experimental evidence indicates that osteoblasts may be cellular intermediaries in the local activation of bone remodeling. To elucidate the role of these cells in activation, we examined the effects of prostaglandins (PGs), known resorption stimulators, on cell shape and intercellular junctional relationships in osteoblasts cultured from rat fetal calvaria. Exposure to PGE2 and PGE1, promoters of bone resorption, rapidly (within 20 min) converted the osteoblasts from a flattened to a stellate shape (shape change), and markedly increased the appearance of intercellular (gap) junctions within 10 min. Both effects were directly related to the prostaglandin concentration, as little as 1 nM being effective. PGE1, but not PGB1, PGF1 alpha, PGD2, and PGF2 alpha, mimicked the substantial effect of PGE2 on shape change. Shape change and gap junction formation appear to arise independently. PTH, an inducer of shape change, did not affect the number of gap junctions appreciably. Colchicine, a microtubule polymerization inhibitor, and trifluoperazine, an inhibitor of calmodulin action, blunted PGE2-mediated shape change but not the effect of PGE2 on gap junctions. Shape change and gap junction formation may be important events in local activation, shape changes in surface osteoblasts serving to expose bone surfaces which are chemotactic for osteoclasts and gap junctions propagating locally initiated activation messages.