Intact ribonucleic acid (RNA) has been prepared from tissues rich in ribonuclease such as the rat pancreas by efficient homogenization in a 4 M solution of the potent protein denaturant guanidinium thiocyanate plus 0.1 M 2-mercaptoethanol to break protein disulfide bonds. The RNA was isolated free of protein by ethanol precipitation or by sedimentation through cesium chloride. Rat pancreas RNA obtained by these means has been used as a source for the purification of alpha-amylase messenger ribonucleic acid.

Breast cancer frequently metastasizes to the skeleton, and the associated bone destruction is mediated by the osteoclast. Growth factors, including transforming growth factor-β (TGF-β), released from bone matrix by the action of osteoclasts, may foster metastatic growth. Because TGF-β inhibits growth of epithelial cells, and carcinoma cells are often defective in TGF-β responses, any role of TGF-β in metastasis is likely to be mediated by effects on the surrounding normal tissue. However, we present evidence that TGF-β promotes breast cancer metastasis by acting directly on the tumor cells. Expression of a dominant-negative mutant (TβRII∆cyt) of the TGF-β type II receptor rendered the human breast cancer cell line MDA-MB-231 unresponsive to TGF-β. In a murine model of bone metastases, expression of TβRI-I∆cyt by MDA-MB-231 resulted in less bone destruction, less tumor with fewer associated osteoclasts, and prolonged survival compared with controls. Reversal of the dominant-negative signaling blockade by expression of a constitutively active TGF-β type I receptor in the breast cancer cells increased tumor production of parathyroid hormone-related protein (PTHrP), enhanced osteolytic bone metastasis, and decreased survival. Transfection of MDA-MB-231 cells that expressed the dominant-negative TβRII∆− cyt with the cDNA for PTHrP resulted in constitutive tumor PTHrP production and accelerated bone metastases. These data demonstrate an important role for TGF-β in the development of breast cancer metastasis to bone, via the TGF-β receptor-mediated signaling pathway in tumor cells, and suggest that the bone destruction is mediated by PTHrP.

Certain solid tumors metastasize to bone and cause osteolysis and abnormal new bone formation.The respective phenotypes of dysregulated bone destruction and bone formation represent two ends of a spectrum, and most patients will have evidence of both. The mechanisms responsible for tumor growth in bone are complex and involve tumor stimulation of the osteoclast and the osteoblast as well as the response of the bone microenvironment. Furthermore, factors that increase bone resorption, independent of tumor, such as sex steroid deficiency, may contribute to this vicious cycle of tumor growth in bone. This article discusses mechanisms and therapeutic implications of osteolytic and osteoblastic bone metastases.Certain solid tumors, such as breast and prostate cancer, have a propensity to metastasize to bone and cause osteolysis and abnormal new bone formation (1, 2). The respective phenotypes of dysregulated bone destruction and bone formation represent two ends of a spectrum, and most patients will have evidence of both. In fact, bone metastases are heterogeneous: data gleaned from a rapid autopsy program indicate that the same prostate cancer patient often has evidence of osteolytic and osteoblastic disease as shown by histologic examination (3). The mechanisms responsible for tumor growth in bone are complex and involve tumor stimulation of the osteoclast and the osteoblast as well as the response of the bone microenvironment. Furthermore, factors that increase bone resorption, independent of tumor, such as sex steroid deficiency, may contribute to this vicious cycle of tumor growth in bone, illustrated in Fig. 1. This article discusses mechanisms and therapeutic implications of osteolytic and osteoblastic bone metastases. Breast Cancer: The Prototypic OsteolyticTumorBreast cancer commonly metastasizes to and destroys bone, causing pain and fracture. Tumors produce many factors that stimulate osteolysis: parathyroid hormone-related protein (PTHrP), interleukin (IL)-11, IL-8, IL-6, and receptor activator of nuclear factor-nB ligand (RANKL;. Substantial data support a role for bone-derived transforming growth factor-h (TGF-h) and tumor-derived osteolytic factors, such as PTHrP, in a vicious cycle of local bone destruction in osteolytic metastases. Bone matrix stores several immobilized growth factors, particularly TGF-h, which is released in active form during osteoclastic resorption (10) and stimulates PTHrP production by tumor cells. PTHrP in turn mediates bone destruction by stimulating osteoclasts. A dominant-negative mutant of the type II TGF-h receptor inhibited TGF-h-induced PTHrP secretion in vitro and development of bone metastases in an MDA-MB-231 experimental metastasis model (5, 6). In addition, TGF-h regulates several genes that are responsible for enhanced bone metastases in MDA-MB-231: IL-11 and connective tissue growth factor (CTGF; refs. 8, 9). Collectively, these studies provided proof of principle to support a role for TGF-h blockade in the treatment of breast cancer bone metastases.SD-20...

Recombinant bacterial plasmids have been constructed that contain complementary DNA prepared from rat islets of Langerhans messenger RNA. Three plasmids contain cloned sequences representing the complete coding region of rat proinsulin I, part of the preproinsulin I prepeptide, and the untranslated 3' terminal region of the mRNA. A fourth plasmid contains sequences derived from the A chain region of rat preproinsulin II.

Metastasis is a final stage of tumor progression. Breast and prostate cancer cells preferentially metastasize to bone, wherein they cause incurable osteolytic and osteoblastic lesions. The bone matrix is rich in factors, such as transforming growth factor-B and insulin-like growth factors, which are released into the tumor microenvironment by osteolysis. These factors stimulate the growth of tumor cells and alter their phenotype, thus promoting a vicious cycle of metastasis and bone pathology. Physical factors within the bone microenvironment, including low oxygen levels, acidic pH, and high extracellular calcium concentrations, may also enhance tumor growth. These elements of the microenvironment are potential targets for chemotherapeutic intervention to halt tumor growth and suppress bone metastasis. [Mol Cancer Ther 2007;6(10):2609 -17]