Sclerostin, the protein product of the Sost gene, is a potent inhibitor of bone formation. Among bone cells, sclerostin is found nearly exclusively in the osteocytes, the cell type that historically has been implicated in sensing and initiating mechanical signaling. The recent discovery of the antagonistic effects of sclerostin on Lrp5 receptor signaling, a crucial mediator of skeletal mechanotransduction, provides a potential mechanism for the osteocytes to control mechanotransduction, by adjusting their sclerostin (Wnt inhibitory) signal output to modulate Wnt signaling in the effector cell population. We investigated the mechanoregulation of Sost and sclerostin under enhanced (ulnar loading) and reduced (hindlimb unloading) loading conditions. Sost transcripts and sclerostin protein levels were dramatically reduced by ulnar loading. Portions of the ulnar cortex receiving a greater strain stimulus were associated with a greater reduction in Sost staining intensity and sclerostin-positive osteocytes (revealed via in situ hybridization and immunohistochemistry, respectively) than were lower strain portions of the tissue. Hindlimb unloading yielded a significant increase in Sost expression in the tibia. Modulation of sclerostin levels appears to be a finely tuned mechanism by which osteocytes coordinate regional and local osteogenesis in response to increased mechanical stimulation, perhaps via releasing the local inhibition of Wnt/Lrp5 signaling.Low bone mass and poor bone structure are two major risk factors for osteoporotic fracture (1, 2). A simple yet effective means to enhance bone mass and architecture is through mechanical stimulation of the resident bone cell population (3, 4). Mechanical loading (e.g. exercise) improves bone mass and strength by stimulating the addition of new bone onto surfaces experiencing high strains, whereas surfaces that experience small strains largely remain quiescent. This phenomenon occurs both across the skeleton (limb bones adapt to locomotive loading, whereas nonbearing bones (e.g. skull) do not) and within a loaded bone (tension/compression surfaces undergo bone formation, whereas surfaces straddling the neutral bending axis do not). The cellular mechanisms involved in directing new bone formation to the high strain regions of a loaded bone are unclear, but elucidation of these mechanisms would provide an attractive target for pharmaceutical intervention aimed at mimicking the adaptive response to loading (5).Despite these gaps in our understanding, significant progress has been made in delineating some of the basic mechanisms of mechanotransduction in bone, in large part because of the creation of genetically engineered mice. A key finding in this arena is the requirement for Wnt signaling through Lrp5 (the low density lipoprotein receptor-related protein 5) in mechanically induced bone formation. We reported recently that mice engineered with a loss-of-function mutation in Lrp5 recapitulate the low bone mass phenotype observed in humans with inactivating mutations of LRP...

Immunity to collagen V [col(V)] contributes to lung 'rejection.' We hypothesized that ischemia reperfusion injury (IRI

Purpose: The transcription factor nuclear factor-B (NF-B) promotes the production of angiogenic, antiapoptotic, and prometastatic factors that are involved in carcinogenesis.Experimental Design: Electromobility gel shift assays were used to evaluate NF-B DNA binding in vitro. The functional relevance of NF-B DNA binding was assessed by both cDNA array analyses and proliferation assays of prostate cancer cells with and without exposure to an NF-B inhibitor, parthenolide. Immunohistochemistry staining for the p65 NF-B subunit was used to determine the frequency and location of NF-B in 97 prostatectomy specimens. The amount of staining was quantified on a 0 -3؉ scale.Results: An electromobility gel shift assay confirmed the presence of NFB DNA binding in all four prostate cancer cell lines tested. The binding was inhibited by parthenolide, and this agent also decreased multiple gene transcripts under the control of NF-B and inhibited proliferation of prostate cancer cells. The staining results revealed overexpression of p65 in the prostatic intraepithelial neoplasia and cancer compared with the benign epithelium. Specifically, there was a predominance of 1؉ and 2؉ with no 3؉ staining in benign epithelium, whereas there was only 2؉ and 3؉ staining (30 and 70%, respectively) in the cancerous areas. These differences were statistically different. There was no correlation with tumor grade or stage.Conclusions: NF-B is constitutively activated in prostate cancer and functionally relevant in vitro. Immunohistochemistry of human prostatectomy specimens demonstrated overexpression of the active subunit of NF-B, p65, and that this occurs at an early stage in the genesis of prostate cancer. This work supports the rationale for targeting NF-B for the prevention and/or treatment of prostate cancer.

In most cases, small-cell carcinoma of the urinary bladder is admixed with other histological types of bladder carcinoma. To understand the pathogenetic relationship between the two tumor types, we analyzed histologically distinct tumor cell populations from the same patient for loss of heterozygosity (LOH) and X chromosome inactivation (in female patients). We examined five polymorphic microsatellite markers located on chromosome 3p25-26 (D3S3050), chromosome 9p21 (IFNA and D9S171), chromosome 9q32-33 (D9S177), and chromosome 17p13 (TP53) in 20 patients with small-cell carcinoma of the urinary bladder and concurrent urothelial carcinoma. DNA samples were prepared from formalin-fixed, paraffin-embedded tissue sections using laser-assisted microdissection. A nearly identical pattern of allelic loss was observed in the two tumor types in all cases, with an overall frequency of allelic loss of 90% (18 of 20 cases). Three patients showed different allelic loss patterns in the two tumor types at a single locus; however, the LOH patterns at the remaining loci were identical. Similarly, the same pattern of nonrandom X chromosome inactivation was present in both carcinoma components in the four cases analyzed. Concordant genetic alterations and X chromosome inactivation between small-cell carcinoma and coexisting urothelial carcinoma suggest that both tumor compo- Small-cell carcinoma of the urinary bladder histologically resembles that occurring in the lung and has been reported with an increasing frequency in recent years. [1][2][3][4][5][6][7][8][9][10] It has been estimated to represent 0.5% of bladder malignancies and develops more frequently in older men, with hematuria as the most common presenting symptom. 8 Small-cell carcinoma of the urinary bladder behaves aggressively, often with locally advanced or metastatic disease at the time of presentation. 11 Over the years, three principal theories have been proposed to account for the development of small-cell carcinoma in the urinary bladder. The first theory is that small-cell carcinomas originate from multipotential, undifferentiated cells or stem cells in the urothelium. 5,8,12,13 The frequent association of this tumor with coexisting urothelial carcinoma supports this theory. The second theory is that these tumors arise from neuroendocrine cells within normal or metaplastic urothelium. 14 The third theory is that small-cell carcinomas are derived from an undefined population of submucosal neuroendocrine cells. 1 In this study, we investigated the clonal relationships between small-cell carcinoma and coexisting urothelial carcinoma using loss of heterozygosity (LOH) and X chromosome inactivation analysis. Materials and Methods PatientsTwenty patients with small-cell carcinoma of the urinary bladder and concurrent urothelial carcinoma were included in our study. Archival materials from the 20 cases

Purpose: These studies were designed to determine whether ritonavir inhibits breast cancer in vitro and in vivo and, if so, how. Experimental Design: Ritonavir effects on breast cancer cell growth were studied in the estrogen receptor (ER)^positive lines MCF7 and T47D and in the ER-negative lines MDA-MB-436 and MDA-MB-231. Effects of ritonavir on Rb-regulated and Akt-mediated cell proliferation were studied. Ritonavir was tested for inhibition of a mammary carcinoma xenograft. Results: ER-positive estradiol-dependent lines (IC 50 , 12-24 Amol/L) and ER-negative (IC 50 , 45 Amol/L) lines exhibit ritonavir sensitivity. Ritonavir depletes ER-a levels notably in ER-positive lines. Ritonavir causes G 1 arrest, depletes cyclin-dependent kinases 2, 4, and 6 and cyclin D 1 but not cyclin E, and depletes phosphorylated Rb and Ser 473 Akt. Ritonavir induces apoptosis independent of G 1 arrest, inhibiting growth of cells that have passed the G 1 checkpoint. Myristoyl-Akt, but not activated K-Ras, rescues ritonavir inhibition. Ritonavir inhibited a MDA-MB-231 xenograft and intratumoral Akt activity at a clinically attainable serum C max of 22 F 8 Amol/L. Because heat shock protein 90 (Hsp90) substrates are depleted by ritonavir, ritonavir effects on Hsp90 were tested. Ritonavir binds Hsp90 (K D , 7.8 Amol/L) and partially inhibits its chaperone function. Ritonavir blocks association of Hsp90 with Akt and, with sustained exposure, notably depletes Hsp90. Stably expressed Hsp90a short hairpin RNA also depletes Hsp90, inhibiting proliferation and sensitizing breast cancer cells to low ritonavir concentrations. Conclusions: Ritonavir inhibits breast cancer growth in part by inhibiting Hsp90 substrates, including Akt. Ritonavir may be of interest for breast cancer therapeutics and its efficacy may be increased by sustained exposure or Hsp90 RNA interference.