SAIF

Zhong et al.
Bone is constantly formed and resorbed throughout life by coordinated actions of osteoblasts and osteoclasts. However, the molecular mechanisms involved in osteoblast function remain incompletely understood. Here we show, for the first time, that the peptidyl-prolyl isomerase PIN1 controls the osteogenic activity of osteoblasts. Pin1 null mice exhibited an agedependent decrease in bone mineral density and trabecular bone formation without alteration in cortical bone. Further analysis identified a defect in BMP signaling in Pin1 null osteoblasts but normal osteoclast function. PIN1 interacted with SMAD5 and was required for the expression by primary osteoblasts of osteoblast specific transcription factors (CBFA1 and OSX), ECM (collagen I and OCN) and the formation of bone nodules. Our results thus uncover a novel aspect of the molecular underpinning of osteoblast function and identify a new therapeutic target for bone diseases.

Yang et al.
Multifunctional and water-soluble superparamagnetic iron oxide (SPIO) nanocarriers were developed for targeted drug delivery and positron emission tomography/magnetic resonance imaging (PET/MRI) dualmodality
imaging of tumors with integrin avb3 expression. An anticancer drug was conjugated onto the PEGylated SPIO nanocarriers via pH-sensitive bonds. Tumor-targeting ligands, cyclo(Arg-Gly-Asp-D-Phe-Cys) (c(RGDfC)) peptides, and PET 64Cu chelators, macrocyclic 1,4,7-triazacyclononane-N, N0, N00-triacetic acid (NOTA), were conjugated onto the distal ends of the PEG arms. The effectiveness of the SPIO nanocarriers as an MRI contrast agent was evaluated via an in vitro r2 MRI relaxivity measurement. cRGD-conjugated SPIO nanocarriers exhibited a higher level of cellular uptake than cRGD-free ones in vitro. Moreover, cRGD-conjugated SPIO nanocarriers showed a much higher level of tumor accumulation than cRGD-free ones according to non-invasive and quantitative PET imaging, and ex vivo biodistribution studies. Thus, these SPIO nanocarriers demonstrated promising properties for combined targeted anticancer drug delivery and PET/MRI dual-modality imaging of tumors.

Xiao et al.
A multifunctional unimolecular micelle made of a hyperbranched amphiphilic block copolymer was designed, synthesized, and characterized for cancer-targeted drug delivery and non-invasive positron emission tomography (PET) imaging in tumor-bearing mice. The hyperbranched amphiphilic block copolymer, Boltorn
H40-poly(L-glutamate-hydrazone-doxorubicin)-b-poly(ethylene glycol) (i.e., H40-P(LG-Hyd-DOX)-b-PEG), was conjugated with cyclo(Arg-Gly-Asp-D-Phe-Cys) peptides (cRGD, for integrin avb3 targeting) and macrocyclic chelators (1,4,7-triazacyclononane-N, N’, N’’-triacetic acid [NOTA], for 64Cu-labeling and PET imaging) (i.e., H40-P(LG-Hyd-DOX)-b-PEG-OCH3/cRGD/NOTA, also referred to as H40-DOX-cRGD). The anti-cancer drug, doxorubicin (DOX) was covalently conjugated onto the hydrophobic segments of the amphiphilic block copolymer arms (i.e., PLG) via a pH-labile hydrazone linkage to enable pH-controlled drug release. The unimolecular micelles exhibited a uniform size distribution and pH-sensitive drug release behavior. cRGD-conjugated unimolecular micelles (i.e., H40-DOX-cRGD) exhibited a much higher cellular uptake in U87MG human glioblastoma cells due to integrin avb3-mediated endocytosis than non-targeted unimolecular micelles (i.e., H40-DOX), thereby leading to a significantly higher cytotoxicity. In U87MG tumor-bearing mice, H40-DOX-cRGD-64Cu also exhibited a much higher level of tumor accumulation than H40-DOX-64Cu, measured by non-invasive PET imaging and confirmed by biodistribution studies and ex vivo fluorescence imaging.We believe that unimolecular micelles formed by hyperbranched amphiphilic block copolymers that synergistically integrate passive
and active tumor-targeting abilities with pH-controlled drug release and PET imaging capabilities provide the basis for future cancer theranostics.

Xiao et al.
A multifunctional gold nanorod (GNR)-based nanoplatform for targeted anticancer drug de-livery and positron emission tomography (PET) imaging of tumors was developed and char-acterized. An anti-cancer drug (i.e., doxorubicin (DOX)) was covalently conjugated onto PEGylated (PEG: polyethylene glycol) GNR nanocarriers via a hydrazone bond to achieve pH-sensitive controlled drug release. Tumor-targeting ligands (i.e., the cy-clo(Arg-Gly-Asp-D-Phe-Cys) peptides, cRGD) and 64Cu-chelators (i.e., 1,4,7-triazacyclononane-N, N’, N’’-triacetic acid (NOTA)) were conjugated onto the distal ends of the PEG arms to achieve active tumor-targeting and PET imaging, respectively. Based on flow cytometry analysis, cRGD-conjugated nanocarriers (i.e., GNR-DOX-cRGD) exhibited a higher cellular uptake and cytotoxicity than non-targeted ones (i.e., GNR-DOX) in vitro. However, GNR-DOX-cRGD and GNR-DOX nanocarriers had similar in vivo biodistribution according to in vivo PET imaging and biodistribution studies. Due to the unique optical properties of GNRs, this multifunctional GNR-based nanoplatform can potentially be optimized for com-bined cancer therapies (chemotherapy and photothermal therapy) and multimodality imaging (PET, optical, X-ray computed tomography (CT), etc.).

Weichert et al.
Many solid tumors contain an over-abundance of phospholipid ethers relative to normal cells. Capitalizing on this difference, we created cancer-targeted alkylphosphocholine (APC) analogs through structure activity analyses. Depending on the iodine isotope used, radioiodinated APC analog CLR1404 was used as either a PET imaging (124I) or molecular radiotherapeutic (131I) agent. CLR1404 analogs displayed prolonged tumor-selective retention in 55 in vivo rodent and human cancer and cancer stem cell models. 131I-CLR1404 also displayed efficacy (tumor growth suppression, survival extension) in a wide range of human tumor xenograft models. Human PET/CT and SPECT/CT imaging in advanced cancer patients with 124I- or 131I-CLR1404, respectively, demonstrated selective uptake and prolonged retention in both primary and metastatic malignant tumors. Combined application of these chemically identical APC-based radioisosteres will enable personalized dual modality cancer therapy of using molecular 124I-CLR1404 tumor imaging for planning 131I-CLR1404 therapy.

Vivanco et al.
The purpose of this study was to compare computed tomography density (rCT) obtained using typical clinical computed tomography scan parameters to ash density (rash), for the prediction of densities of femoral head trabecular bone from hip fracture patients. An experimental study was conducted to investigate the relationships between rash and rCT and between each of these densities and rbulk and rdry . Seven human femoral heads from hip fracture patients were computed tomography–scanned ex vivo, and 76 cylindrical trabecular bone specimens were collected. Computed tomography density was computed from computed tomography images by using a calibration Hounsfield units–based equation, whereas rbulk , rdry and rash were determined experimentally. A large variation was found in the mean Hounsfield units of the bone cores (HUcore) with a constant bias from rCT to rash of 42.5 mg/cm3. Computed tomography and ash densities were linearly correlated (R2 = 0.55, p \ 0.001). It was demonstrated that rash provided a good estimate of rbulk (R2 =0.78, p \ 0.001) and is a strong predictor of rdry (R2 = 0.99, p \ 0.001). In addition, the rCT was linearly related to rbulk (R2 = 0.43, p \ 0.001) and rdry (R2 = 0.56, p \ 0.001). In conclusion, mineral density was an appropriate predictor of rbulk and rdry, and rCTwas not a surrogate for rash. There were linear relationships between rCT and physical densities; however, following the experimental protocols of this study to determine rCT, considerable scatter was present in the rCT relationships.

Vivanco et al.
Although it is widely known that bone tissue responds to mechanical stimuli, the underlying biological control is still not completely understood. The purpose of this study was to validate required methods necessary to maintain active osteocytes and minimize bone tissue injury in an ex vivo three-dimensional model that could mimic in vivo cellular function. The response of 22 bovine trabecular bone cores to uniaxial compressive load was investigated by using the ZETOS bone loading and bioreactor system while perfused with culture medium for 21 days. Two groups were formed, the ‘‘treatment’’ group (n = 12) was stimulated with a physiological compressive strain (4000me) in the form of a ‘‘jump’’ wave, while the ‘‘control’’ group (n = 10) was loaded only during three measurements for apparent elastic modulus on days 3, 10, and 21. At the end of the experiment, apoptosis and active osteocytes were quantified with histological analysis, and bone formation was identified by means of the calcium-binding dye, calcein. It was demonstrated that the treatment group increased the elastic modulus by 61%, whereas the control group increased by 28% (p\0.05). Of the total osteocytes observed at the end of 21 days, 1.7% (60.3%) stained positive for apoptosis in the loaded group, whereas 2.7% (60.4%) stained positive in the control group. Apoptosis in the center of the bone cores of both groups at the end of 21 days was similar to that observed in vivo. Therefore, the three-dimensional model used in this research permitted the investigation of physiological responses to mechanical loads on morphology adaptation of trabecular bone in a controlled defined load and chemical environment.

Swanson et al.
BACKGROUND: 5-Aminolevulinic acid (5-ALA)-induced tumor fluorescence aids brain tumor resections but is not approved for routine use in the United States. We developed and describe testing of 2 novel fluorescent, cancer-selective alkylphosphocholine analogs, CLR1501 (green) and CLR1502 (near infrared), in a proof-of-principle study for fluorescence-guided glioma surgery.
OBJECTIVE: To demonstrate that CLR1501 and CLR1502 are cancer cell-selective fluorescence agents in glioblastoma models and to compare tumor-to-normal brain (T:N) fluorescence ratios with 5-ALA.
METHODS: CLR1501, CLR1502, and 5-ALA were administered to mice with magnetic resonance imaging-verified orthotopic U251 glioblastoma multiforme- and glioblastoma stem cell-derived xenografts. Harvested brains were imaged with confocal microscopy (CLR1501), the IVIS Spectrum imaging system (CLR1501, CLR1502, and 5-ALA), or the Fluobeam near-infrared fluorescence imaging system (CLR1502). Imaging
and quantitative analysis of T:N fluorescence ratios were performed.
RESULTS: Excitation/emission peaks are 500/517 nm for CLR1501 and 760/778 nm for CLR1502. The observed T:N ratio for CLR1502 (9.28 6 1.08) was significantly higher (P ,.01) than for CLR1501 (3.51 6 0.44 on confocal imaging; 7.23 6 1.63 on IVIS imaging) and 5-ALA (4.81 6 0.92). Near-infrared Fluobeam CLR1502 imaging in a mouse xenograft model demonstrated high- contrast tumor visualization compatible with surgical applications.
CONCLUSION: CLR1501 (green) and CLR1502 (near infrared) are novel tumor-selective fluorescent agents for discriminating tumor from normal brain. CLR1501 exhibits a tumor-to-brain fluorescence ratio similar to that of 5-ALA, whereas CLR1502 has a superior tumor-to-brain fluorescence ratio. This study demonstrates the potential use of CLR1501 and CLR1502 in fluorescence-guided tumor surgery.

Peng et al.
The import of acetyl-CoA into the ER lumen by AT-1/SLC33A1 is essential for the N-lysine acetylation of ER-resident and ER-transiting proteins. A point-mutation (S113R) in AT-1 has been associated with a familial form of spastic paraplegia. Here, we report that AT-1S113R is unable to form homodimers in the ER membrane and is devoid of acetyl-CoA transport activity. The reduced influx of acetyl-CoA into theERlumen results in reduced acetylation ofERproteins and an aberrant form of autophagy. Mice homozygous for the mutation display early developmental arrest. In contrast, heterozygous animals develop to full term, but display neurodegeneration and propensity to infections, inflammation, and cancer. The immune and cancer phenotypes are contingent on the presence of pathogens in the colony, whereas the nervous system phenotype is not. In conclusion, our results reveal a previously unknown aspect of acetyl-CoA metabolism that affects the immune and nervous systems and the risk for malignancies.