Mammography pain in women treated conservatively for breast cancer.

In this study, pain during mammography in women treated conservatively for breast cancer was examined. It studied pain intensity and its relation to a variety of demographic, medical, and pain coping variables as well as to objective measures of breast compression. Ninety-nine women, treated with lumpectomy (with or without radiation) and undergoing follow-up screening mammography, were asked about strategies they use to cope with everyday pain and then were asked to report pain experienced during the mammogram. Treated and untreated breasts were rated separately and compared with a sample of 125 control women with no history of breast cancer. Women reported significantly greater pain in the treated breast (41% greater than the untreated breast and 32% greater than the control group). There was no consistent relationship between mammography pain and pain coping. Average intensity of pain at last mammogram was the best predictor of pain in both breasts. Women treated conservatively for breast cancer experience significantly greater pain during mammography of their treated breast. Radiologists and technologists can identify women at risk for a painful mammogram by asking about the pain at last mammogram. By applying pain-reducing interventions, they might be able to make the mammography experience more tolerable for these women.

Recent advances in bone biology provide insight into the pathogenesis of bone diseases.

Bone is modeled during embryonic development by endochondral and membranous ossification and is continuously remodeled thereafter under the influence of local and systemic factors to provide structural support and assist in calcium homeostasis. Recent studies of knockout and transgenic mice have increased understanding of the regulation of bone modeling during development and of remodeling of mature bone and have shed new light on the pathogenesis of a number of bone disorders. For example, fibroblast growth factor receptor-3, parathyroid hormone-related protein, and tartrate-resistant acid phosphatase affect the function of chondrocytes during endochondral ossification (the latter two by regulating their life spans and thus growth plate thickness and bone length). Some ubiquitously expressed genes seem unexpectedly to have unique functions that are largely confined to bone cells: M-CSF, C-Fos, PU.1, and NF-kappaB are required for osteoclast formation, whereas c-Src and Mitf (microphthalmia transcription factor) are required for osteoclast activity after the cells have formed. Knockout of these genes results in osteopetrosis, a disorder characterized by persistence in marrow cavities of unresorbed osteocartilaginous matrix and, as in some affected humans, by increased mortality. Some proteins seem to act as negative regulators of bone cell function, for example osteoprotegerin (a soluble TNF receptor) in osteoclasts; osteocalcin, bone sialoprotein, and 5-lipoxygenase in osteoblasts. Regulation of osteoclast life span may be an important mechanism by which estrogen and bisphosphonates prevent bone loss in conditions characterized by increased bone resorption, such as postmenopausal osteoporosis. The unique requirement of bone cells for certain gene products raises the possibility that these cells may have specific responses to inhibitory or stimulatory agents, and that signaling molecules in these response pathways could be specific targets for novel therapies to treat or prevent common bone diseases.

Osteoclast formation in bone marrow cultures from two inbred strains of mice with different bone densities.

For the purpose of identifying genes that affect bone volume, we previously identified two inbred mouse strains (C57BL/6J and C3H/HeJ) with large differences in femoral bone density and medullary cavity volume. The lower density and larger medullary cavity volume in C57BL/6J mice could result from either decreased formation or increased resorption or both. We recently reported evidence suggesting that bone formation was increased in vivo and that osteoblast progenitor cells are more numerous in the bone marrow of C3H/HeJ compared with C57BL/6J mice. In the present study, we determined whether osteoclast numbers in vivo and osteoclast formation from bone marrow cells in vitro might also differ between the two mouse strains. We have found that the number of osteoclasts on bone surfaces of distal humerus secondary spongiosa was 2-fold higher in 5.5-week-old C57BL/6J mice than in C3H/HeJ mice of the same age (p < 0.001). Bone marrow cells of C57BL/6J mice cocultured with Swiss/Webster mouse osteoblasts consistently produced more osteoclasts than did C3H/HeJ bone marrow cells at all ages tested from 3.5-14 weeks of age (p < 0.001). Osteoclast formation was also greater from spleen cells of 3.5-week-old C57BL/6J mice than C3H/HeJ mice. The distribution of nuclei per osteoclast and the 1, 25-dihydroxyvitamin D3 dose dependence of osteoclast production from bone marrow cells were similar. Osteoclasts that developed from both C57BL/6J and C3H/HeJ marrow cells formed pits in dentin slices. Cultures from C57BL/6J marrow cells formed 2.5-fold more pits than cultures from C3H/HeJ marrow cells (p < 0.02). We compared the abilities of C57BL/6J and C3H/HeJ osteoblasts to support osteoclast formation. When bone marrow cells from either C57BL/6J or C3H/HeJ mice were cocultured with osteoblasts from either C57BL/6J or C3H/HeJ newborn calvaria, the strain from which osteoblasts were derived did not affect the number of osteoclasts formed from marrow cells of either strain. Together, these observations suggest that genes affecting the bone marrow osteoclast precursor population may contribute to the relative differences in bone density that occur between C3H/HeJ and C57BL/6J mouse strains.

Bisphosphonates promote apoptosis in murine osteoclasts in vitro and in vivo.

Bisphosphonates inhibit bone resorption and are therapeutically effective in diseases of increased bone turnover, such as Paget's disease and hypercalcemia of malignancy. The mechanisms by which they act remain unclear. Proposed mechanisms include inhibition of osteoclast formation from precursors and inhibitory or toxic effect on mature osteoclasts. We have developed a new in vitro model to study osteoclast survival and in this paper present in vitro and in vivo evidence that may explain both the observed reduction in osteoclast numbers and in bone resorption by mature osteoclasts, namely that bisphosphonates induce programmed cell death (apoptosis). Three bisphosphonates (risedronate, pamidronate, and clodronate) caused a 4- to 24-fold increase in the proportion of osteoclasts showing the characteristic morphology of apoptosis in vitro. This observation was confirmed in vivo in normal mice, in mice with increased bone resorption, and in nude mice with osteolytic cancer metastases, with similar-fold increases to those observed in vitro. Of the three compounds, risedronate, the most potent inhibitor of bone resorption in vivo, was the strongest inducer of osteoclast apoptosis in vitro. Osteoclast apoptosis may therefore be a major mechanism whereby bisphosphonates reduce osteoclast numbers and activity, and induction of apoptosis could be a therapeutic goal for new antiosteoclast drugs.

Bisphosphonate risedronate reduces metastatic human breast cancer burden in bone in nude mice.

Human breast cancer frequently metastasizes to the skeleton to cause osteolysis and subsequent pain, pathological fracture, and hypercalcemia. Because bone continuously releases growth factors stored in bone matrix by bone resorption during physiological remodeling and, thus, possibly provides a favorable microenvironment for metastatic breast cancer cells to proliferate, inhibitors of bone resorption used either prophylactically or in patients with established disease, therefore, would seem likely to be useful adjuvant therapy in patients with breast cancer. However, the parameters for monitoring progressive osteolytic bone disease in humans are imprecise. We examined the effects of the third generation bisphosphonate, risedronate, which is a specific inhibitor of osteoclastic bone resorption, in a bone metastasis model in nude mice in which intracardiac injection of the human breast cancer cell line MDA-231 leads to osteolytic bone metastases. Risedronate (4 micrograms/animal/day) was given s.c. to animals (a) after radiologically small but defined osteolytic metastases were observed; (b) simultaneously with MDA-231 cell inoculation through the entire experimental period; or (c) by short-term prophylactic administration before inoculation of MDA-231 cells. In all experiments, risedronate either slowed progression or inhibited the development of bone metastases assessed radiographically. Furthermore, mice treated continuously with risedronate showed significantly longer survival than did control mice. Histomorphometrical analysis revealed that osteoclast numbers were diminished at metastatic tumor sites. Unexpectedly, there was also a marked decrease in tumor burden in bone in risedronate-treated animals. In contrast, the growth of metastatic breast cancer in soft tissues surrounding bones was not affected by risedronate. Moreover, risedronate had no effects on the local growth of s.c. implanted MDA-231 breast cancers in nude mice or on MDA-231 cell proliferation in culture. These data demonstrate that risedronate decreases metastatic MDA-231 breast cancer burden selectively in bone, as well as suppresses progression of established osteolytic lesions and prevents the development of new osteolytic lesions; thus, the data suggest that inhibition of osteoclastic bone resorption may be a useful adjunctive therapy for the treatment of cancers that have colonized in bone.

Osteoclast recruitment and modulation by calcium deficiency, fasting, and calcium supplementation in the rat.

In the rat, 1 week of a calcium-deficient diet will recruit large numbers of osteoclasts to long bone endosteal surfaces. Subsequent calcium supplementation causes the osteoclasts to disappear in 1-3 days but as little as 3 hours of calcium supplementation reduces the extent of their ruffled borders. To test the hypothesis that at some point there is an irreversible inhibition of osteoclasts, male, weanling, calcium-deficient, SD rats were given various amounts of calcium-containing diet followed by a 12-hour fast. No changes in seven morphological indices of osteoclast activity were found. The hypothesis that the fast had reversed the effects of the calcium diet was supported by a second experiment indicating that no inhibition threshold had been reached. Another experiment showed differences in the degree of osteoclast inhibition with different amounts of calcium supplementation, again without evidence of a threshold. These experiments raised two questions: (1) Will fasting recruit osteoclasts in calcium-replete rats? and (2) Is osteoclast recruitment facilitated by the presence of postosteoclasts? The results of experiments testing these hypotheses support the conclusion that fasting and calcium deficiency maintain plasma calcium levels by different mechanisms, and post-osteoclasts are not available for reactivation. It is concluded that inhibition of osteoclasts by dietary calcium is a graded phenomenon, and when osteoclasts have lost contact with the bone surface they are unavailable for reactivation; a threshold has been reached.