253 J at 0.2†Hz, LD pumped cryogenic helium gas cooled Yb:YAG ceramics laser.

A 253 J with 26 ns at 0.2 Hz laser performance was demonstrated using a LD pumped cryogenically cooled Yb:YAG ceramics laser amplifier. A high energy storage of 344 J was achieved with a stored energy density of 0.58 J/cm3 using a 1 kJ output multidirectional-pumping system. High energy-extraction efficiency of 56.5% was achieved with high energy fluence of 4.63 J /cm2. To the best of our knowledge, this is the highest output energy obtained with a repetitive nanosecond pulse by LD pumped solid-state laser. This paper presented a design of 1 kJ amplifier based on experimentally proven numerical data.

COL8A1 facilitates the growth of triple-negative breast cancer via FAK/Src activation.

PURPOSE: Triple-negative breast cancer (TNBC) is one of the most aggressive breast cancer subtypes, and treatment options are limited because of the lack of signature molecules and heterogeneous properties of cancer. COL8A1 expression is higher in breast cancer than in normal tissues and is strongly correlated with worse overall survival in patients with breast cancer. However, the biological function of COL8A1 on cancer progression is not fully understood. In this study, we investigated the biological function of COL8A1 on TNBC progression. METHODS: COL8A1-deficient cells were generated using the CRISPR-Cas9 system. The tumor growth and metastasis of TNBC cells were evaluated using three-dimensional culture (3D) methods and xenograft mouse models. The activation of focal adhesion kinase (FAK)/Src by COL8A1 in TNBC cells was evaluated by immunoblotting. RESULTS: COL8A1 expression was primarily distributed into TNBC cell lines. Further, relapse-free survival in TNBC patients with the MSL subtype was strongly associated with the COL8A1 expression. MDA-MB-231 and Hs578T cells, classified as the MSL subtype, strongly express COL8A1, and COL8A1 protein expression was induced by hypoxia in both cell lines. Loss of COL8A1 expression inhibited spheroid /tumor growth and metastasis in vitro and in vivo. Further, exogenous COL8A1 promoted TNBC growth via the FAK/Src activation. Finally, the spheroid growth of MDA-MB-231 and Hs578T cells was inhibited by defactinib, a FAK inhibitor, without cytotoxicity. CONCLUSION: These results indicate that COL8A1-mediated FAK/Src activation produces a more aggressive phenotype in TNBC, and its target inhibition may be an efficacious treatment for TNBC.

Effect of CYP3A5*3 genetic variant on the metabolism of direct-acting antivirals in vitro: a different effect on asunaprevir versus daclatasvir and beclabuvir.

Direct-acting antivirals, asunaprevir (ASV), daclatasvir (DCV), and beclabuvir (BCV) are known to be mainly metabolized by CYP3A enzymes; however, the differences in the detailed metabolic activities of CYP3A4 and CYP3A5 on these drugs are not well clarified. The aim of the present study was to elucidate the relative contributions of CYP3A4 and CYP3A5 to the metabolism of ASV, DCV, and BCV, as well as the effect of CYP3A5*3 genetic variant in vitro. The amount of each drug and their major metabolites were determined using LC-MS/MS. Recombinant CYP3As and CYP3A5*3-genotyped human liver microsomes (CYP3A5 expressers or non-expressers) were used for the determination of their metabolic activities. The contribution of CYP3A5 to ASV metabolism was considerable compared to that of CYP3A4. Consistently, ASV metabolic activity in CYP3A5 expressers was higher than those in CYP3A5 non-expresser. Moreover, CYP3A5 expression level was significantly correlated with ASV metabolism. In contrast, these observations were not found in DCV and BCV metabolism. To our knowledge, this is the first study to directly demonstrate the effect of CYP3A5*3 genetic variants on the metabolism of ASV. The findings of the present study may provide basic information on ASV, DCV, and BCV metabolisms.

Minor contribution of CYP3A5 to the metabolism of hepatitis C protease inhibitor paritaprevir in vitro.

Paritaprevir (PTV) is a non-structural protein 3/4A protease inhibitor developed for the treatment of hepatitis C disease as a fixed dose combination of ombitasvir (OBV) and ritonavir (RTV) with or without dasabuvir. The aim of this study was to evaluate the effects of cytochrome P450 (CYP) 3A5 on in vitro PTV metabolism using human recombinant CYP3A4, CYP3A5 (rCYP3A4, rCYP3A5) and human liver microsomes (HLMs) genotyped as either CYP3A5*1/*1, CYP3A5*1/*3 or CYP3A5*3/*3. The intrinsic clearance (CLint, Vmax/Km) for the production of a metabolite from PTV in rCYP3A4 was 1.5 times higher than that in rCYP3A5. The PTV metabolism in CYP3A5*1/*1 and CYP3A5*1/*3 HLMs expressing CYP3A5 was comparable to that in CYP3A5*3/*3 HLMs, which lack CYP3A5. CYP3A4 expression level was significantly correlated with PTV disappearance rate and metabolite formation. In contrast, there was no such correlation found for CYP3A5 expression level. This study represents that the major CYP isoform involved in PTV metabolism is CYP3A4, with CYP3A5 having a minor role in PTV metabolism. The findings of the present study may provide foundational information on PTV metabolism, and may further support dosing practices in HCV-infected patients prescribed PTV-based therapy.

Quantification and tracking of genetically engineered dendritic cells for studying immunotherapy.

PURPOSE: Genetically encoded reporters can assist in visualizing biological processes in live organisms and have been proposed for longitudinal and noninvasive tracking of therapeutic cells in deep tissue. Cells can be labeled in situ or ex vivo and followed in live subjects over time. Nevertheless, a major challenge for reporter systems is to identify the cell population that actually expresses an active reporter. METHODS: We have used a nucleoside analog, pyrrolo-2'-deoxycytidine, as an imaging probe for the putative reporter gene, Drosophila melanogaster 2'-deoxynucleoside kinase. Bioengineered cells were imaged in vivo in animal models of brain tumor and immunotherapy using chemical exchange saturation transfer MRI. The number of transduced cells was quantified by flow cytometry based on the optical properties of the probe. RESULTS: We performed a comparative analysis of six different cell lines and demonstrate utility in a mouse model of immunotherapy. The proposed technology can be used to quantify the number of labeled cells in a given region, and moreover is sensitive enough to detect less than 10,000 cells. CONCLUSION: This unique technology that enables efficient selection of labeled cells followed by in vivo monitoring with both optical and MRI. Magn Reson Med 79:1010-1019, 2018. © 2017 International Society for Magnetic Resonance in Medicine.

Direct Cell Labeling to Image Transplanted Stem Cells in Real Time Using a Dual-Contrast MRI Technique.

Exogenous direct cell labeling with superparamagnetic iron oxide nanoparticles (SPIONs) is currently the most employed cell-labeling technique for tracking transplanted cells using magnetic resonance imaging (MRI). Although SPION-based cell labeling is effective for monitoring cell delivery and migration, monitoring cell survival is still a challenge. This unit describes an MRI technique that permits detection of the delivery, migration, and death of transplanted cells. This dual-contrast technique involves labeling cells with two different classes of MRI contrast agents, possessing different diffusion coefficients: SPIONs (T2 /T2* contrast agents, with lower diffusion coefficients) and gadolinium chelates (T1 contrast agents, with higher diffusion coefficients). In live cells, where both agents are in close proximity, the T2 /T2* contrast predominates and the T1 contrast is quenched. In dead cells, where the cell membrane is breached, gadolinium chelates diffuse from the SPIONs and generate a signature T1 contrast enhancement in the vicinity of dead cells. © 2017 by John Wiley & Sons, Inc.

Controlled Secretion of the Anticancer Protein MDA-7 from Engineered Mesenchymal Stem Cells.

Mesenchymal stem cells (MSCs) have been explored as a "live" carrier of cytokines for targeted cancer therapy, but, in earlier reports in the literature, the secretion process of therapeutic cytokines was not regulated. The purpose of this study was to generate MSCs to conditionally secrete the melanoma differentiation-associated gene-7 (MDA-7) tumor-suppressor protein. To control the secretion of MDA-7 from MSCs, a well-established tetracycline-controlled transcriptional activation system was incorporated into MDA-7 plasmid. MDA-7 gene expression was induced in the engineered MSCs only in the presence of doxycycline, as characterized by quantitative reverse transcription (qRT)-PCR. Enzyme-linked immunosorbent assay (ELISA) also revealed that the MDA-7 protein was secreted from the engineered MSCs only after the cells had been exposed to doxycycline. Both recombinant human MDA-7 protein and the conditioned medium from the engineered MSCs in the presence of doxycycline significantly inhibited tube formation of human umbilical vascular endothelial cells (HUVECs), indicating that our system could be used for targeted, antiangiogenic therapy. Overall, this study provides useful information on the potential use of engineered MSCs for the controlled secretion of therapeutic proteins, in this case MDA-7, for targeted cancer therapy.

Endocan as a prognostic biomarker of triple-negative breast cancer.

PURPOSE: Triple-negative breast cancer (TNBC) has aggressive characteristics and fewer treatment options than other subtypes. The purpose of this study was to explore prognostic biomarkers for TNBC that can be easily detected from the blood samples. METHODS: MDA-MB-231 and MDA-MB-231BR, a brain metastatic variant of the human TNBC cell line MDA-MB-231, were used as less and more aggressive models of TNBC, respectively. The extent to which the candidate gene/protein identified by RNA sequencing correlated well with aggressiveness of TNBC and how much protein was detected from the blood of tumor-bearing mice were evaluated. RESULTS: Both the in vitro proliferation and in vivo tumor growth of MDA-MB-231BR were more rapid than those of MDA-MB-231. RNA sequencing identified ESM1 as a gene that was expressed significantly more in MDA-MB-231BR than in MDA-MB-231, and qRT-PCR confirmed a significantly higher expression of ESM1 in MDA-MB-231BR xenograft in vivo. Furthermore, Kaplan-Meier analysis of relapse-free survival demonstrated that TNBC patients with high ESM1 expression had clearly worse relapse-free survival than those with low ESM1 expression, which was consistent with our preclinical findings. Endocan, a protein of ESM1 gene product, was successfully detected in both conditioned medium from MDA-MB-231BR and plasma samples from mice bearing MDA-MB-231BR xenograft, which showed a significantly distinct pattern from less aggressive MDA-MB-231. Moreover, bisulfite sequence analysis revealed that overexpression of ESM1 in MDA-MB-231BR might be attributed to DNA demethylation in an upstream region of the ESM1 gene. CONCLUSION: This study indicates that endocan could be used as a blood-based prognostic biomarker in TNBC patients.

Linezolid-Induced Thrombocytopenia Is Caused by Suppression of Platelet Production via Phosphorylation of Myosin Light Chain 2.

Linezolid (LZD) is an antimicrobial that is commonly used for treatment of vancomycin-resistant Enterococci and methicillin-resistant Staphylococcus aureus infections. However, the development of thrombocytopenia, one of the most frequent adverse side effects of this antimicrobial, can lead to discontinuation of LZD treatment. While clinical studies indicate that risk factors for the development of LZD-induced thrombocytopenia include treatment for >14 consecutive days, renal dysfunction, and chronic liver disease, the fundamental mechanism governing the pathogenesis of this disorder remains unclear. In this study, we aimed to elucidate the mechanism of LZD-induced thrombocytopenia by investigating the impact of LZD treatment on platelet destruction and production using rat platelet-rich plasma (PRP) and human immortalized cell lines, respectively. Compared to the control population, an increase in lactate dehydrogenase release was not detected upon exposure of rat PRP to varying concentrations of LZD, indicating that this compound is not cytotoxic towards platelets. Meanwhile, LZD treatment resulted in a significant dose-dependent increase in the proliferation of HEL human erythroleukemia and MEG-01 human megakaryoblast cells in vitro, but did not influence the differentiation of these cell lines. Lastly, LZD treatment yielded elevated levels of phosphorylation of myosin light chain 2 (MLC2), which regulates platelet release, in MEG-01 cells. Based on these results, we speculate that LZD induces thrombocytopenia by promoting MLC2 phosphorylation and thereby suppressing the release of platelets from mature megakaryocytes. These findings provide the first insight into the mechanism of LZD-mediated thrombocytopenia and may facilitate the development of strategies to treat and/or prevent this disease.

Intrinsic Resistance to 5-Fluorouracil in a Brain Metastatic Variant of Human Breast Cancer Cell Line, MDA-MB-231BR.

Although drug resistance is often observed in metastatic recurrence of breast cancer, little is known about the intrinsic drug resistance in such metastases. In the present study, we found, for the first time, that MDA-MB-231BR, a brain metastatic variant of a human breast cancer cell line, was refractory to treatment with 5-fluorouracil (5-FU) even without chronic drug exposure, compared to its parent cell line, MDA-MB-231, and a bone metastatic variant, MDA-MB-231SCP2. Both the mRNA and protein levels of COX-2 and BCL2A1 in MDA-MB-231BR were significantly higher than those in MDA-MB-231 or MDA-MB-231SCP2. Neither the COX-2 inhibitor celecoxib nor the NF-κB inhibitor BAY11-7082 could sensitize MDA-MB-231BR to 5-FU, indicating that COX-2 plays little, if any, role in the resistance of MDA-MB-231BR to 5-FU. Although BCL2-family inhibitor ABT-263 failed to sensitize MDA-MB-231BR to 5-FU at a dose at which ABT-263 is considered to bind to BCL2, BCL2-xL, and BCL2-w, but not to BCL2A1, ABT-263 did sensitize MDA-MB-231BR to 5-FU to a level comparable to that in MDA-MB-231 at a dose of 5 µM, at which ABT-263 may disrupt intracellular BCL2A1 protein interactions. More importantly, BCL2A1 siRNA sensitized MDA-MB-231BR to 5-FU, whereas the overexpression of BCL2A1 conferred 5-FU-resistance on MDA-MB-231. These results indicate that BCL2A1 is a key contributor to the intrinsic 5-FU-resistance in MDA-MB-231BR. It is interesting to note that the drug sensitivity of MDA-MB-231BR was distinct from that of MDA-MB-231SCP2 even though they have the same origin (MDA-MB-231). Further investigations pertinent to the present findings may provide valuable insight into the breast cancer brain metastasis.

Non-Temperature Induced Effects of Magnetized Iron Oxide Nanoparticles in Alternating Magnetic Field in Cancer Cells.

This paper reports the damaging effects of magnetic iron-oxide nanoparticles (MNP) on magnetically labeled cancer cells when subjected to oscillating gradients in a strong external magnetic field. Human breast cancer MDA-MB-231 cells were labeled with MNP, placed in the high magnetic field, and subjected to oscillating gradients generated by an imaging gradient system of a 9.4T preclinical MRI system. Changes in cell morphology and a decrease in cell viability were detected in cells treated with oscillating gradients. The cytotoxicity was determined qualitatively and quantitatively by microscopic imaging and cell viability assays. An approximately 26.6% reduction in cell viability was detected in magnetically labeled cells subjected to the combined effect of a static magnetic field and oscillating gradients. No reduction in cell viability was observed in unlabeled cells subjected to gradients, or in MNP-labeled cells in the static magnetic field. As no increase in local temperature was observed, the cell damage was not a result of hyperthermia. Currently, we consider the coherent motion of internalized and aggregated nanoparticles that produce mechanical moments as a potential mechanism of cell destruction. The formation and dynamics of the intracellular aggregates of nanoparticles were visualized by optical and transmission electron microscopy (TEM). The images revealed a rapid formation of elongated MNP aggregates in the cells, which were aligned with the external magnetic field. This strategy provides a new way to eradicate a specific population of MNP-labeled cells, potentially with magnetic resonance imaging guidance using standard MRI equipment, with minimal side effects for the host.

Bioorthogonal two-component drug delivery in HER2(+) breast cancer mouse models.

The HER2 receptor is overexpressed in approximately 20% of breast cancers and is associated with tumorigenesis, metastasis, and a poor prognosis. Trastuzumab is a first-line targeted drug used against HER2(+) breast cancers; however, at least 50% of HER2(+) tumors develop resistance to trastuzumab. To treat these patients, trastuzumab-based antibody-drug conjugates (ACDs) have been developed and are currently used in the clinic. Despite their high efficacy, the long circulation half-life and non-specific binding of cytotoxic ADCs can result in systemic toxicity. In addition, standard ADCs do not provide an image-guided mode of administration. Here, we have developed a two-component, two-step, pre-targeting drug delivery system integrated with image guidance to circumvent these issues. In this strategy, HER2 receptors are pre-labeled with a functionalized trastuzumab antibody followed by the delivery of drug-loaded nanocarriers. Both components are cross-linked by multiple bioorthogonal click reactions in situ on the surface of the target cell and internalized as nanoclusters. We have explored the efficacy of this delivery strategy in HER2(+) human breast cancer models. Our therapeutic study confirms the high therapeutic efficacy of the new delivery system, with no significant toxicity.

A preclinical murine model for the early detection of radiation-induced brain injury using magnetic resonance imaging and behavioral tests for learning and memory: with applications for the evaluation of possible stem cell imaging agents and therapies.

Stem cell therapies are being developed for radiotherapy-induced brain injuries (RIBI). Magnetic resonance imaging (MRI) offers advantages for imaging transplanted stem cells. However, most MRI cell-tracking techniques employ superparamagnetic iron oxide particles (SPIOs), which are difficult to distinguish from hemorrhage. In current preclinical RIBI models, hemorrhage occurs concurrently with other injury markers. This makes the evaluation of the recruitment of transplanted SPIO-labeled stem cells to injury sites difficult. Here, we developed a RIBI model, with early injury markers reflective of hippocampal dysfunction, which can be detected noninvasively with MRI and behavioral tests. Lesions were generated by sub-hemispheric irradiation of mouse hippocampi with single X-ray beams of 80 Gy. Lesion formation was monitored with anatomical and contrast-enhanced MRI and changes in memory and learning were assessed with fear-conditioning tests. Early injury markers were detected 2 weeks after irradiation. These included an increase in the permeability of the blood-brain barrier, demonstrated by a 92 ± 20 % contrast enhancement of the irradiated versus the non-irradiated brain hemispheres, within 15 min of the administration of an MRI contrast agent. A change in short-term memory was also detected, as demonstrated by a 40.88 ± 5.03 % decrease in the freezing time measured during the short-term memory context test at this time point, compared to that before irradiation. SPIO-labeled stem cells transplanted contralateral to the lesion migrated toward the lesion at this time point. No hemorrhage was detected up to 10 weeks after irradiation. This model can be used to evaluate SPIO-based stem cell-tracking agents, short-term.

Ganetespib radiosensitization for liver cancer therapy.

Therapies for liver cancer particularly those including radiation are still inadequate. Inhibiting the stress response machinery is an appealing anti-cancer and radiosensitizing therapeutic strategy. Heat-shock-protein-90 (HSP90) is a molecular chaperone that is a prominent effector of the stress response machinery and is overexpressed in liver cancer cells. HSP90 client proteins include critical components of pathways implicated in liver cancer cell survival and radioresistance. The effects of a novel non-geldanamycin HSP90 inhibitor, ganetespib, combined with radiation were examined on 3 liver cancer cell lines, Hep3b, HepG2 and HUH7, using in vitro assays for clonogenic survival, apoptosis, cell cycle distribution, γH2AX foci kinetics and client protein expression in pathways important for liver cancer survival and radioresistance. We then evaluated tumor growth delay and effects of the combined ganetespib-radiation treatment on tumor cell proliferation in a HepG2 hind-flank tumor graft model. Nanomolar levels of ganetespib alone exhibited liver cancer cell anti-cancer activity in vitro as shown by decreased clonogenic survival that was associated with increased apoptotic cell death, prominent G2-M arrest and marked changes in PI3K/AKT/mTOR and RAS/MAPK client protein activity. Ganetespib caused a supra-additive radiosensitization in all liver cancer cell lines at low nanomolar doses with enhancement ratios between 1.33-1.78. These results were confirmed in vivo, where the ganetespib-radiation combination therapy produced supra-additive tumor growth delay compared with either therapy by itself in HepG2 tumor grafts. Our data suggest that combined ganetespib-radiation therapy exhibits promising activity against liver cancer cells, which should be investigated in clinical studies.

NZ51, a ring-expanded nucleoside analog, inhibits motility and viability of breast cancer cells by targeting the RNA helicase DDX3.

DDX3X (DDX3), a human RNA helicase, is over expressed in multiple breast cancer cell lines and its expression levels are directly correlated to cellular aggressiveness. NZ51, a ring-expanded nucleoside analogue (REN) has been reported to inhibit the ATP dependent helicase activity of DDX3. Molecular modeling of NZ51 binding to DDX3 indicated that the 5:7-fused imidazodiazepine ring of NZ51 was incorporated into the ATP binding pocket of DDX3. In this study, we investigated the anticancer properties of NZ51 in MCF-7 and MDA-MB-231 breast cancer cell lines. NZ51 treatment decreased cellular motility and cell viability of MCF-7 and MDA-MB-231 cells with IC50 values in the low micromolar range. Biological knockdown of DDX3 in MCF-7 and MDA-MB-231 cells resulted in decreased proliferation rates and reduced clonogenicity. In addition, NZ51 was effective in killing breast cancer cells under hypoxic conditions with the same potency as observed during normoxia. Mechanistic studies indicated that NZ51 did not cause DDX3 degradation, but greatly diminished its functionality. Moreover, in vivo experiments demonstrated that DDX3 knockdown by shRNA resulted in reduced tumor volume and metastasis without altering tumor vascular volume or permeability-surface area. In initial in vivo experiments, NZ51 treatment did not significantly reduce tumor volume. Further studies are needed to optimize drug formulation, dose and delivery. Continuing work will determine the in vitro-in vivo correlation of NZ51 activity and its utility in a clinical setting.

Dynamic glucose enhanced (DGE) MRI for combined imaging of blood-brain barrier break down and increased blood volume in brain cancer.

PURPOSE: Recently, natural d-glucose was suggested as a potential biodegradable contrast agent. The feasibility of using d-glucose for dynamic perfusion imaging was explored to detect malignant brain tumors based on blood brain barrier breakdown. METHODS: Mice were inoculated orthotopically with human U87-EGFRvIII glioma cells. Time-resolved glucose signal changes were detected using chemical exchange saturation transfer (glucoCEST) MRI. Dynamic glucose enhanced (DGE) MRI was used to measure tissue response to an intravenous bolus of d-glucose. RESULTS: DGE images of mouse brains bearing human glioma showed two times higher and persistent changes in tumor compared with contralateral brain. Area-under-curve (AUC) analysis of DGE delineated blood vessels and tumor and had contrast comparable to the AUC determined using dynamic contrast enhanced (DCE) MRI with GdDTPA, both showing a significantly higher AUC in tumor than in brain (P < 0.005). Both CEST and relaxation effects contribute to the signal change. CONCLUSION: DGE MRI is a feasible technique for studying brain tumor enhancement reflecting differences in tumor blood volume and permeability with respect to normal brain. We expect DGE will provide a low-risk and less expensive alternative to DCE MRI for imaging cancer in vulnerable populations, such as children and patients with renal impairment.

Imaging transplanted stem cells in real time using an MRI dual-contrast method.

Stem cell therapies are currently being investigated for the repair of brain injuries. Although exogenous stem cell labelling with superparamagnetic iron oxide nanoparticles (SPIONs) prior to transplantation provides a means to noninvasively monitor stem cell transplantation by magnetic resonance imaging (MRI), monitoring cell death is still a challenge. Here, we investigate the feasibility of using an MRI dual-contrast technique to detect cell delivery, cell migration and cell death after stem cell transplantation. Human mesenchymal stem cells were dual labelled with SPIONs and gadolinium-based chelates (GdDTPA). The viability, proliferation rate, and differentiation potential of the labelled cells were then evaluated. The feasibility of this MRI technique to distinguish between live and dead cells was next evaluated using MRI phantoms, and in vivo using both immune-competent and immune-deficient mice, following the induction of brain injury in the mice. All results were validated with bioluminescence imaging. In live cells, a negative (T2/T2*) MRI contrast predominates, and is used to track cell delivery and cell migration. Upon cell death, a diffused positive (T1) MRI contrast is generated in the vicinity of the dead cells, and serves as an imaging marker for cell death. Ultimately, this technique could be used to manage stem cell therapies.

PLGA nanoparticle formulation of RK-33: an RNA helicase inhibitor against DDX3.

BACKGROUND: The DDX3 helicase inhibitor RK-33 is a newly developed anticancer agent that showed promising results in preclinical research (Bol et al. EMBO Mol Med, 7(5):648-649, 2015). However, due to the physicochemical and pharmacological characteristics of RK-33, we initiated development of alternative formulations of RK-33 by preparing sustained release nanoparticles that can be administered intravenously. METHODS: In this study, RK-33 was encapsulated in poly(lactic-co-glycolic acid) (PLGA), one of the most well-developed biodegradable polymers, using the emulsion solvent evaporation method. RESULTS: Hydrodynamic diameter of RK-33-PLGA nanoparticles was about 245 nm with a negative charge, and RK-33-PLGA nanoparticles had a payload of 1.4 % RK-33. RK-33 was released from the PLGA nanoparticles over 7 days (90 ± 5.7 % released by day 7) and exhibited cytotoxicity to human breast carcinoma MCF-7 cells in a time-dependent manner. Moreover, RK-33-PLGA nanoparticles were well tolerated, and systemic retention of RK-33 was markedly improved in normal mice. CONCLUSIONS: PLGA nanoparticles have a potential as a parenteral formulation of RK-33.

Noninvasive Imaging of Liposomal Delivery of Superparamagnetic Iron Oxide Nanoparticles to Orthotopic Human Breast Tumor in Mice.

PURPOSE: Magnetic resonance imaging (MRI) is widely used for diagnostic imaging in preclinical studies and in clinical settings. Considering the intrinsic low sensitivity and poor specificity of standard MRI contrast agents, the enhanced delivery of MRI tracers into tumors is an important challenge to be addressed. This study was intended to investigate whether delivery of superparamagnetic iron oxide nanoparticles (SPIONs) can be enhanced by liposomal SPION formulations for either "passive" delivery into tumor via the enhanced permeability and retention (EPR) effect or "active" targeted delivery to tumor endothelium via the receptors for vascular endothelial growth factor (VEGFRs). METHODS: In vivo MRI of orthotopic MDA-MB-231 tumors was performed on a preclinical 9.4 T MRI scanner following intravenous administration of either free/non-targeted or targeted liposomal SPIONs. RESULTS: In vivo MRI study revealed that only the non-targeted liposomal formulation provided a statistically significant accumulation of SPIONs in the tumor at four hours post-injection. The EPR effect contributes to improved accumulation of liposomal SPIONs in tumors compared to the presumably more transient retention during the targeting of the tumor vasculature via VEGFRs. CONCLUSIONS: A non-targeted liposomal formulation of SPIONs could be the optimal option for MRI detection of breast tumors and for the development of therapeutic liposomes for MRI-guided therapy.

Structure-function studies of the bHLH phosphorylation domain of TWIST1 in prostate cancer cells.

The TWIST1 gene has diverse roles in development and pathologic diseases such as cancer. TWIST1 is a dimeric basic helix-loop-helix (bHLH) transcription factor existing as TWIST1-TWIST1 or TWIST1-E12/47. TWIST1 partner choice and DNA binding can be influenced during development by phosphorylation of Thr125 and Ser127 of the Thr-Gln-Ser (TQS) motif within the bHLH of TWIST1. The significance of these TWIST1 phosphorylation sites for metastasis is unknown. We created stable isogenic prostate cancer cell lines overexpressing TWIST1 wild-type, phospho-mutants, and tethered versions. We assessed these isogenic lines using assays that mimic stages of cancer metastasis. In vitro assays suggested the phospho-mimetic Twist1-DQD mutation could confer cellular properties associated with pro-metastatic behavior. The hypo-phosphorylation mimic Twist1-AQA mutation displayed reduced pro-metastatic activity compared to wild-type TWIST1 in vitro, suggesting that phosphorylation of the TWIST1 TQS motif was necessary for pro-metastatic functions. In vivo analysis demonstrates that the Twist1-AQA mutation exhibits reduced capacity to contribute to metastasis, whereas the expression of the Twist1-DQD mutation exhibits proficient metastatic potential. Tethered TWIST1-E12 heterodimers phenocopied the Twist1-DQD mutation for many in vitro assays, suggesting that TWIST1 phosphorylation may result in heterodimerization in prostate cancer cells. Lastly, the dual phosphatidylinositide 3-kinase (PI3K)-mammalian target of rapamycin (mTOR) inhibitor BEZ235 strongly attenuated TWIST1-induced migration that was dependent on the TQS motif. TWIST1 TQS phosphorylation state determines the intensity of TWIST1-induced pro-metastatic ability in prostate cancer cells, which may be partly explained mechanistically by TWIST1 dimeric partner choice.