口丸 高弘

Abstract Cancer cells inevitably interact with neighboring host tissue-resident cells during the process of metastatic colonization, establishing a metastatic niche to fuel their survival, growth, and invasion. However, the underlying mechanisms in the metastatic niche are yet to be fully elucidated owing to the lack of methodologies for comprehensively studying the mechanisms of cell–cell interactions in the niche. Here, we improve a split green fluorescent protein (GFP)-based genetically encoded system to develop secretory glycosylphosphatidylinositol-anchored reconstitution-activated proteins to highlight intercellular connections (sGRAPHIC) for efficient fluorescent labeling of tissue-resident cells that neighbor on and putatively interact with cancer cells in deep tissues. The sGRAPHIC system enables the isolation of metastatic niche-associated tissue-resident cells for their characterization using a single-cell RNA sequencing platform. We use this sGRAPHIC-leveraged transcriptomic platform to uncover gene expression patterns in metastatic niche-associated hepatocytes in a murine model of liver metastasis. Among the marker genes of metastatic niche-associated hepatocytes, we identify Lgals3, encoding galectin-3, as a potential pro-metastatic factor that accelerates metastatic growth and invasion.

Abstract Tumors contain various stromal cells, such as immune cells, endothelial cells, and fibroblasts, which contribute to the development of a tumor‐specific microenvironment characterized by hypoxia and inflammation, and are associated with malignant progression. In this study, we investigated the activity of intratumoral hypoxia‐inducible factor (HIF), which functions as a master regulator of the cellular response to hypoxia and inflammation. We constructed the HIF activity‐monitoring reporter gene hypoxia‐response element‐Venus‐Akaluc (HVA) that expresses the green fluorescent protein Venus and modified firefly luciferase Akaluc in a HIF activity‐dependent manner, and created transgenic mice harboring HVA transgene (HVA‐Tg). In HVA‐Tg, HIF‐active cells can be visualized using AkaBLI, an ultra‐sensitive in vivo bioluminescence imaging technology that produces an intense near‐infrared light upon reaction of Akaluc with the D‐luciferin analog AkaLumine‐HCl. By orthotopic transplantation of E0771, a mouse triple negative breast cancer cell line without a reporter gene, into HVA‐Tg, we succeeded in noninvasively monitoring bioluminescence signals from HIF‐active stromal cells as early as 8 days after transplantation. The HIF‐active stromal cells initially clustered locally and then spread throughout the tumors with growth. Immunohistochemistry and flow cytometry analyses revealed that CD11b⁺F4/80⁺ macrophages were the predominant HIF‐active stromal cells in E0771 tumors. These results indicate that HVA‐Tg is a useful tool for spatiotemporal analysis of HIF‐active tumor stromal cells, facilitating investigation of the roles of HIF‐active tumor stromal cells in tumor growth and malignant progression.

Abstract Cancer recurrence due to tumor cell quiescence after therapy and long-term remission is associated with cancer-related death. Previous studies have used cell models that are unable to return to a proliferative state; thus, the transition between quiescent and proliferative states is not well understood. Here, we report monolayer cancer cell models wherein the human non-small cell lung carcinoma cell line H2228 and pancreatic cancer cell line AsPC-1 can be reversibly induced to a quiescent state under hypoxic and serum-starved (HSS) conditions. Transcriptome and metabolome dual-omics profiles of these cells were compared with those of the human lung adenocarcinoma cell line A549, which was unable to enter a quiescent state under HSS conditions. The quiescence-inducible cells had substantially lower intracellular pyruvate and ATP levels in the quiescent state than in the proliferative state, and their response to sudden demand for energy was dramatically reduced. Furthermore, in quiescence-inducible cells, the transition between quiescent and proliferative states of these cells was regulated by the balance between the proliferation-promoting Ras and Rap1 signaling and the suppressive AGE/RAGE signaling. These cell models elucidate the transition between quiescent and proliferative states, allowing the development of drug-screening systems for quiescent tumor cells.

Ras genes are frequently mutated in many cancer types; however, there are currently no conclusively effective anticancer drugs against Ras-induced cancer. Therefore, the downstream effectors of Ras signaling need to be identified for the development of promising novel therapeutic approaches. We previously reported that oncogenic Ras induced the expression of NF-HEV/IL-33, a member of the interleukin-1 family, and showed that intracellular IL-33 was required for oncogenic Ras-induced cellular transformation. In the present study, we demonstrated that the c-Mer proto-oncogene tyrosine kinase (MerTK), a receptor tyrosine kinase, played essential roles in oncogenic Ras/IL-33 signaling. The expression of MerTK was enhanced in transformed NIH-3T3 cells by the expression of oncogenic Ras, H-Ras (G12V), in an IL-33-dependent manner. In human colorectal cancer tissues, MerTK expression also correlated with IL-33 expression. The knockdown of IL-33 or MerTK effectively attenuated the migration of NIH-3T3 cells transformed by H-Ras (G12V) and A549, LoVo, and HCT116 cells harboring an oncogenic K-Ras mutation. Furthermore, the suppression of Ras-induced cell migration by the knockdown of IL-33 was rescued by the enforced expression of MerTK. The present results also revealed that MerTK was effectively phosphorylated in NIH-3T3 cells transformed by Ras (G12V). Ras signaling was essential for the tyrosine phosphorylation of MerTK, and the kinase activity of MerTK was indispensable for accelerating cell migration. Collectively, the present results reveal a novel role for MerTK in cancer malignancy, which may be utilized to develop novel therapeutic strategies that target Ras-transformed cells.

Small antibody mimetics that contain high-affinity target-binding peptides can be lower cost alternatives to monoclonal antibodies (mAbs). We have recently developed a method to create small antibody mimetics called FLuctuation-regulated Affinity Proteins (FLAPs), which consist of a small protein scaffold with a structurally immobilized target-binding peptide. In this study, to further develop this method, we established a novel screening system for FLAPs called monoclonal antibody-guided peptide identification and engineering (MAGPIE), in which a mAb guides selection in two manners. First, antibody-guided design allows construction of a peptide library that is relatively small in size, but sufficient to identify high-affinity binders in a single selection round. Second, in antibody-guided screening, the fluorescently labeled mAb is used to select mammalian cells that display FLAP candidates with high affinity for the target using fluorescence-activated cell sorting. We demonstrate the reliability and efficacy of MAGPIE using daclizumab, a mAb against human interleukin-2 receptor alpha chain (CD25). Three FLAPs identified by MAGPIE bound CD25 with dissociation constants of approximately 30 nM as measured by biolayer interferometry without undergoing affinity maturation. MAGPIE can be broadly adapted to any mAb to develop small antibody mimetics.

During the development of analgesic tolerance to morphine, the V1b vasopressin receptor has been proposed to bind to β-arrestin 2 and the µ-opioid receptor to enable their interaction. However, direct evidence of such a high-order complex is lacking. Using bioluminescent resonance energy transfer between a split Nanoluciferase and the Venus fluorescent protein, the NanoBit-NanoBRET system, we found that β-arrestin 2 closely located near the heteromer µ-V1b receptor in the absence of an agonist and moved closer to the receptor carboxyl-termini upon agonist stimulation. An additive effect of the two agonists for opioid and vasopressin receptors was detected on the NanoBRET between the µ-V1b heteromer and β-arrestin 2. To increase the agonist response of NanoBRET, the ratio of the donor luminophore to the acceptor fluorophore was decreased to the detection limit of luminescence. In the first phase of access, β-arrestin 2 was likely to bind to the unstimulated V1b receptor in both its phosphorylated and unphosphorylated forms. In contrast, the second-phase access of β-arrestin 2 was agonist dependent, indicating a possible pharmacological intervention strategy. Therefore, our efficient method should be useful for evaluating chemicals that directly target the vasopressin binding site in the µ-V1b heteromer to reduce the second-phase access of β-arrestin 2 and thereby to alleviate tolerance to morphine analgesia.

The western pattern diet is rich not only in fat and calorie but also in phosphate. Negative impacts of excessive fat and calorie intake on health are widely accepted, whereas potential harms of excessive phosphate intake are poorly recognized. Here we show the mechanism by which dietary phosphate damages the kidney. When phosphate intake was excessive relative to the functioning nephron number, circulating fibroblast growth factor-23 (FGF23), a hormone that increases phosphate excretion per nephron, was increased to maintain phosphate homeostasis. FGF23 suppressed phosphate reabsorption in renal tubules and thus raised the phosphate concentration in the tubular fluid. Once it exceeded a threshold, microscopic particles containing calcium phosphate crystals appeared in the tubular lumen, which damaged tubular cells through binding to Toll-like receptor-4 expressed on them. Persistent tubular damage induced interstitial fibrosis, reduced the nephron number, and further boosted FGF23 to trigger a deterioration spiral leading to progressive nephron loss. In humans, progression of chronic kidney disease (CKD) ensued when the serum FGF23 level exceeded 53 pg/mL. The present study identified the calcium phosphate particles in the renal tubular fluid as an effective therapeutic target to decelerate nephron loss during the course of aging and CKD progression.

Depolarization of circularly polarized light scattered from biological tissues depends on structural changes in cell nuclei, which can provide valuable information for differentiating cancer tissues concealed in healthy tissues. In this study, we experimentally verified the possibility of cancer identification using scattering of circularly polarized light. We investigated the polarization of light scattered from a sliced biological tissue with various optical configurations. A significant difference between circular polarizations of light scattered from cancerous and healthy tissues is observed, which is sufficient to distinguish a cancerous region. The line-scanning experiments along a region incorporating healthy and cancerous parts indicate step-like behaviors in the degree of circular polarization corresponding to the state of tissues, whether cancerous or normal. An oblique and perpendicular incidence induces different resolutions for identifying cancerous tissues, which indicates that the optical arrangement can be selected according to the priority of resolution.

The current standard murine model of bone metastasis by using intracardiac injection (IC) has some limitations despite the great utility of this model. This fact emphasizes the need for a new murine model to accelerate basic research of bone metastasis. The present protocol provides instructions on caudal artery (CA) injection that is an easy-to-use method to reliably construct a murine bone metastasis model with a variety type of cancer cell lines. Bioluminescence imaging visualized that cancer cells injected via the caudal artery in the tail were efficiently delivered to a hind limb bone, where it is a common site affected with bone metastasis in mice. CA injection rarely causes stress-induced acute death in mice and enables us to inject a large number of cancer cells, thereby greatly increasing the frequency of bone metastasis in hind limb bones. Importantly, CA injection is technically as easy as tail vein injection and causes no lethal stress, indicating that it is a model that also contributes to animal welfare. CA injection model, therefore, could represent a powerful tool for many researchers to study molecular mechanisms of bone metastasis in mice.

This journal is © 2020 The Royal Society of Chemistry. Tumor-binding peptides such as human epidermal growth factor receptor 2 (HER2)-binding peptides are attractive therapeutic and diagnostic options for cancer. However, the HER2-binding peptides (HBPs) developed thus far are susceptible to proteolysis and lose their affinity to HER2 in vivo. In this report, a method to create a HER2-binding fluctuation-regulated affinity protein (HBP-FLAP) consisting of a fibronectin type III domain (FN3) scaffold with a structurally immobilized HBP is presented. HBPs were selected by phage-library screening and grafted onto FN3 to create FN3-HBPs, and the HBP-FLAP with the highest affinity (HBP sequence: YCAHNM) was identified after affinity maturation of the grafted HBP. HBP-FLAP containing the YCAHNM peptide showed increased proteolysis-resistance, binding to HER2 with a dissociation constant (KD) of 58 nM in ELISA and 287 nM in biolayer interferometry and specifically detects HER2-expressing cancer cells. In addition, HBP-FLAP clearly delineated HER2-expressing tumors with a half-life of 6 h after intravenous injection into tumor-bearing mice. FN3-based FLAP is an excellent platform for developing target-binding small proteins for clinical applications.

Monoclonal antibodies (mAbs) are attractive therapeutics for treating a wide range of human disorders, and bind to the antigen through their complementarity-determining regions (CDRs). Small stable proteins containing structurally retained CDRs are promising alternatives to mAbs. In this report, we present a method to create such proteins, named fluctuation-regulated affinity proteins (FLAPs). Thirteen graft acceptor (GA) sites that efficiently immobilise the grafted peptide structure were initially selected from six small protein scaffolds by computational identification. Five CDR peptides extracted by binding energy calculations from mAbs against breast cancer marker human epithelial growth factor receptor type 2 (HER2) were then grafted to the selected scaffolds. The combination of five CDR peptides and 13 GA sites in six scaffolds revealed that three of the 65 combinations showed specific binding to HER2 with dissociation constants (KD) of 270-350 nM in biolayer interferometry and 24-65 nM in ELISA. The FLAPs specifically detected HER2-overexpressing cancer cells. Thus, the present strategy is a promising and practical method for developing small antibody mimetics.

HIF-1 is regarded as a promising target for the drugs used in cancer chemotherapy, and creating readily accessible templates for the development of synthetic drug candidates that could inhibit HIF-1 transcriptional activity is an important pursuit. In this study, indeno[2,1-c]pyrazolones were designed as readily available synthetic inhibitors of HIF-1 transcriptional activity. Nine compounds were synthesized in 4-5 steps from commercially available starting materials. In evaluations of the ability to inhibit the hypoxia-induced transcriptional activity of HIF-1, compound 3c showed a higher level compared with that of known inhibitor, YC-1. The compound 3c suppressed HIF-1α protein accumulation without affecting the levels of HIF-1α mRNA.

Hypoxia inducible factor-1α (HIF-1α) is a key transcription factor that maintains oxygen homeostasis. Hypoxic stress is related to the pathogenesis of amyotrophic lateral sclerosis (ALS), and impaired HIF-1α induces motor neuron degeneration in ALS. Dimethyloxalylglycine (DMOG) upregulates the stability of HIF-1α expression and shows neuroprotective effects, but has not been used in ALS as an anti-hypoxic stress treatment. In the present study, we investigated hypoxic stress in ALS model mice bearing G93A-human Cu/Zn superoxide dismutase by in vivo HIF-1α imaging, and treated the ALS mice with DMOG. In vivo HIF-1α imaging analysis showed enhanced hypoxic stress in both the spinal cord and muscles of lower limbs of ALS mice, even at the pre-symptomatic stage. HIF-1α expression decreased as the disease progressed until 126 days of age. DMOG treatment significantly ameliorated the decrease in HIF-1α expression, the degeneration of both spinal motor neurons and myofibers in lower limbs, gliosis and apoptosis in the spinal cord. This was accompanied by prolonged survival. The present study suggests that in vivo bioluminescence resonance energy transfer (BRET) HIF-1α imaging is useful for evaluating hypoxic stress in ALS, and that the enhancement of HIF-1α is a therapeutic target for ALS patients.

The small number of high-migratory cancer cells in a cell population make studies on high-migratory cancer cells difficult. For the development of migration assays for such cancer cells, several microfluidic devices have been developed. However, they measure migration that is influenced by microstructures and they collect not only high-migratory cells, but also surrounding cells. In order to find high-migratory cells in cell populations while suppressing artifacts and to collect these cells while minimizing damages, we developed a microfluidic high-migratory cell collector with the ability to sort cancer cells according to cellular migration and mechanical detachment. High-migratory cancer cells travel further from the starting line when all of the cells are seeded on the same starting line. The high-migratory cells are detached using a stretch of cell adhesive surface using a water-driven balloon actuator. Using this cell collector, we selected high-migratory HeLa cells that migrated about 100m in 12 h and collected the cells.

With increasing clinical demands for MEK inhibitors in cancer treatment, overcoming the resistance to MEK inhibitors is an urgent problem to be solved. Numerous reports have shown that MEK inhibition results in the activation of PI3K-Akt signaling, which may confer apoptotic resistance to MEK inhibitors. We here demonstrate that the blockade of the mevalonate pathway using the antilipidemic drug statins represses Akt activation following MEK inhibition and induces significant apoptosis when co-treated with CH5126766 or trametinib. These events were clearly negated by the addition of mevalonate or geranylgeranyl pyrophosphate, indicating that the protein geranylgeranylation is implicated in the apoptotic resistance to MEK inhibitors. Furthermore, mechanistically, the combined treatment of CH5126766 with statins upregulated TNF-related apoptosis-inducing ligand (TRAIL), which was dependent on inhibition of the mevalonate pathway and is involved in apoptosis induction in human breast cancer MDA-MB-231 cells. The present study not only revealed that the mevalonate pathway could be targetable to enhance the efficacy of MEK inhibitors, but also proposes that combinatorial treatment of MEK inhibitors with statins may be a promising therapeutic strategy to sensitize cancer cells to apoptosis.

Bioluminescence is a natural light source based on luciferase catalysis of its substrate luciferin. We performed directed evolution on firefly luciferase using a red-shifted and highly deliverable luciferin analog to establish AkaBLI, an all-engineered bioluminescence in vivo imaging system. AkaBLI produced emissions in vivo that were brighter by a factor of 100 to 1000 than conventional systems, allowing noninvasive visualization of single cells deep inside freely moving animals. Single tumorigenic cells trapped in the mouse lung vasculature could be visualized. In the mouse brain, genetic labeling with neural activity sensors allowed tracking of small clusters of hippocampal neurons activated by novel environments. In a marmoset, we recorded video-rate bioluminescence from neurons in the striatum, a deep brain area, for more than 1 year. AkaBLI is therefore a bioengineered light source to spur unprecedented scientific, medical, and industrial applications.

A microfluidic device capable of precise chemical control is helpful to mimic tumor microenvironments in vitro, which are closely associated with malignant progression, including metastasis. Cancer cells under a concentration gradient of oxygen and other sustenance materials inside a tumor in vivo have recently been reported to increase the probability of metastasis. The influence of glucose concentration on cancer cells has not been measured well, whereas that of oxygen concentration has been thoroughly examined using microfluidic devices. This is because glucose concentrations can be controlled using microfluidic concentration gradient generators, which trade off temporal stability of the glucose concentration and shear stress on the cells; by contrast, oxygen concentration can be easily controlled without microfluidic device-induced shear stresses. To study cell division and migration responses as a function of glucose concentration, we developed a microfluidic device to observe cell behaviors under various chemical conditions. The device has small-cross-section microchannels for generating a concentration gradient and a large-cross-section chamber for cell culture. With this design, the device can achieve both a cell culture with sufficiently low shear stress on cell activity and a stable glucose concentration gradient. Experiments revealed that a low glucose concentration increased the total migration length of HeLa cells and that HeLa cells under a glucose concentration gradient exhibit random motion rather than chemotaxis.

Pancreatic cancer is one of the most lethal digestive system cancers with a 5-year survival rate of 4-7%. Despite extensive efforts, recent chemotherapeutic regimens have provided only limited benefits to pancreatic cancer patients. Gemcitabine and TS-1, the current standard-of-care chemotherapeutic drugs for treatment of this severe cancer, have a low response rate. Hypoxia is one of the factors contributing to treatment resistance. Specifically, overexpression of hypoxia-inducible factor, a master transcriptional regulator of cell adaption to hypoxia, is strongly correlated with poor prognosis in many human cancers. TAT-ODD-procaspase-3 (TOP3) is a protein prodrug that is specifically processed and activated in hypoxia-inducible factor-active cells in cancers, leading to cell death. Here, we report combination therapies in which TOP3 was combined with gemcitabine or TS-1. As monotherapy, gemcitabine and TS-1 showed a limited effect on hypoxic and starved pancreatic cancer cells, whereas co-treatment with TOP3 successfully overcame this limitation in vitro. Furthermore, combination therapies of TOP3 with these drugs resulted in a significant improvement in survival of orthotopic pancreatic cancer models involving the human pancreatic cancer cell line SUIT-2. Overall, our study indicates that the combination of TOP3 with current chemotherapeutic drugs can significantly improve treatment outcome, offering a promising new therapeutic option for patients with pancreatic cancer.

In preclinical cancer research, bioluminescence imaging with firefly luciferase and D-luciferin has become a standard to monitor biological processes both in vitro and in vivo. However, the emission maximum (lambda(max)) of bioluminescence produced by D-luciferin is 562 nm where light is not highly penetrable in biological tissues. This emphasizes a need for developing a red-shifted bioluminescence imaging system to improve detection sensitivity of targets in deep tissue. Here we characterize the bioluminescent properties of the newly synthesized luciferin analogue, AkaLumine-HCl. The bioluminescence produced by AkaLumine-HCl in reactions with native firefly luciferase is in the near-infrared wavelength ranges (lambda(max) = 677 nm), and yields significantly increased target-detection sensitivity from deep tissues with maximal signals attained at very low concentrations, as compared with D-luciferin and emerging synthetic luciferin CycLuc1. These characteristics offer a more sensitive and accurate method for non-invasive bioluminescence imaging with native firefly luciferase in various animal models.

Carbon monoxide (CO) has been recognized as a messenger for signal transduction in living cells and tissues. For intracellular CO delivery, several metal carbonyl complexes have been used as CO-releasing molecules (CO-RMs). To improve the properties of CO-RMs, such as the stability and the CO release rate, ligands and carriers of the metal complexes have been exploited. Here we report the development of an efficient intracellular CO delivery system using a protein scaffold. We used a protein needle reconstructed from gene product 5 of bacteriophage T4, which has high cellular permeability and stability. When ruthenium carbonyl complexes are conjugated to the needle using a His-tag triad at the C-terminus, the resulting composite has a significantly higher cellular uptake efficiency of Ru carbonyl and a 12-fold prolonged CO release rate relative to Ru(CO)3Cl(glycinate), a widely used CO-RM. We demonstrate that CO delivered by the composite activates the transcriptional factor nuclear factor-kappaB (NF-κB), which in turn leads to significant induction of expression of its target genes, HO1, NQO1, and IL6, through generation of reactive oxygen species (ROS). The signaling pathway is distinct from that of tumor necrosis factor (TNF)-α-induced activation of NF-κB. The protein needle-based CO-RM can be exploited to elucidate the biological functions of CO and used in the development of protein-based organometallic tools for modulation of cellular signaling.

Hypoxic stress is a risk factor of ocular neovascularization. Hypoxia visualization may provide clues regarding the underlying cause of angiogenesis. Recently, we developed a hypoxia-specific probe, protein transduction domain-oxygen-dependent degradation domain-HaloTag-Rhodamine (POH-Rhodamine). In this study, we observed the localization of HIF-1α proteins by immunohistochemistry and the fluorescence of POH-Rhodamine on RPE-choroid flat mounts. Moreover, we compared the localization of POH-Rhodamine with pimonidazole which is a standard reagent for detecting hypoxia. Next, we investigated the effects of triamcinolone acetonide (TAAC) against visual function that was evaluated by recording electroretinogram (ERG) and choroidal neovascularization (CNV) development. Mice were given laser-induced CNV using a diode laser and treated with intravitreal injection of TAAC. Finally, we investigated POH-Rhodamine on CNV treated with TAAC. In this study, the fluorescence of POH-Rhodamine and HIF-1α were co-localized in laser-irradiated sites, and both the POH-Rhodamine and pimonidazole fluorescent areas were almost the same. Intravitreal injection of TAAC restored the reduced ERG b-wave but not the a-wave and decreased the mean CNV area. Furthermore, the area of the POH-Rhodamine-positive cells decreased. These findings indicate that POH-Rhodamine is useful for evaluating tissue hypoxia in a laser-induced CNV model, suggesting that TAAC suppressed CNV through tissue hypoxia improvement.

Cell-penetrating peptides (CPPs), also referred to as protein transduction domains (PTDs), can mediate the cellular uptake of a wide range of macromolecules including peptides, proteins, oligonucleotides, and nanoparticles, and thus have received considerable attention as a promising method for drug delivery in vivo. Here, we report that CPP/PTDs facilitate the extravasation of fused proteins by binding to neuropilin-1 (NRP1), a vascular endothelial growth factor (VEGF) co-receptor expressed on the surface of endothelial and some tumor cells. In this study, we examined the capacity of the amphipathic and cationic CPP/PTDs, PTD-3 and TAT-PTD, respectively, to bind cells in vitro and accumulate in xenograft tumors in vivo. Notably, these functions were significantly suppressed by pre-treatment with NRP1-neutralizing Ab. Furthermore, co-injection of iRGD, a cyclic peptide known to increase NRP1-dependent vascular permeability, significantly reduced CPP/PTD tumor delivery. This data demonstrates a mechanism by which NRP1 promotes the extravasation of CPP/PTDs that may open new avenues for the development of more efficient CPP/PTD delivery systems.

A crystalline protein assembly of cypovirus polyhedra was engineered to develop a carbon monoxide (CO) releasing extracellular scaffold by immobilizing ruthenium carbonyls. The molecular design includes introduction of a hexahistidine tag to the C-terminus and provides immobilization of about 2-fold more Ru carbonyls per protein monomer and effectively releases three times more CO for activation of nuclear factor kappa B (NF-kappa B) in living cells relative to wild-type polyhedra with Ru carbonyls.

Protein crystals generally are stable solid protein assemblies. Certain protein crystals are suitable for use as nanovessels for immobilizing metal complexes. Here we report the preparation of ruthenium carbonyl-incorporated cross-linked hen egg white lysozyme crystals (Ru·CL-HEWL). Ru·CL-HEWL retains a Ru carbonyl moiety that can release CO, although a composite of Ru carbonyl-HEWL dissolved in buffer solution (Ru·HEWL) does not release CO. We found that treatment of cells with Ru·CL-HEWL significantly increased nuclear factor kappa B (NF-κB) activity as a cellular response to CO. These results demonstrate that Ru·CL-HEWL has potential for use as an artificial extracellular scaffold suitable for transport and release of a gas molecule.

Protein cages have been utilized as templates in the development of biomaterials. Here we report protein engineering of the ferritin (Fr) cage for encapsulating carbon monoxide releasing molecules (CORMs) and release of CO gas which serves as a cell signaling molecule. The protein cages enable us to increase the half-life for CO release, providing a release rate that is 18-fold slower than the rate of a typical CORM, Ru(CO)3Cl(glycinate) (CORM-3). Moreover, the uptake ratio of the composite is about 4-fold greater than that of CORM-3. We found that these effects enhance the activation of nuclear factor κB 10-fold higher than CORM-3. The protein cage of Fr thus provides the basis for new CORMs that can be used for in vitro cell research.

Bone metastasis is a multistep process that includes cancer cell dissemination, colonization, and metastatic growth. Furthermore, this process involves complex, reciprocal interactions between cancer cells and the bone microenvironment. Bone resorption is known to be involved in both osteolytic and osteoblastic bone metastasis. However, the precise roles of the bone resorption in the multistep process of osteoblastic bone metastasis remain unidentified. In this study, we show that bone resorption plays important roles in cancer cell colonization during the initial stage of osteoblastic bone metastasis. We applied bioluminescence/X-ray computed tomography multimodal imaging that allows us to spatiotemporally analyze metastasized cancer cells and bone status in osteoblastic bone metastasis models. We found that treatment with receptor activator of factor-B ligand (RANKL) increased osteoblastic bone metastasis when given at the same time as intracardiac injection of cancer cells, but failed to increase metastasis when given 4days after cancer cell injection, suggesting that RANKL-induced bone resorption facilitates growth of cancer cells colonized in the bone. We show that insulin-like growth factor-1 released from the bone during bone resorption and hypoxia-inducible factor activity in cancer cells cooperatively promoted survival and proliferation of cancer cells in bone marrow. These results suggest a mechanism that bone resorption and hypoxic stress in the bone microenvironment cooperatively play an important role in establishing osteoblastic metastasis.

Bone metastasis is a multistep process that includes cancer cell dissemination, colonization, and metastatic growth. Furthermore, this process involves complex, reciprocal interactions between cancer cells and the bone microenvironment. Bone resorption is known to be involved in both osteolytic and osteoblastic bone metastasis. However, the precise roles of the bone resorption in the multistep process of osteoblastic bone metastasis remain unidentified. In this study, we show that bone resorption plays important roles in cancer cell colonization during the initial stage of osteoblastic bone metastasis. We applied bioluminescence/X-ray computed tomography multimodal imaging that allows us to spatiotemporally analyze metastasized cancer cells and bone status in osteoblastic bone metastasis models. We found that treatment with receptor activator of factor-κB ligand (RANKL) increased osteoblastic bone metastasis when given at the same time as intracardiac injection of cancer cells, but failed to increase metastasis when given 4 days after cancer cell injection, suggesting that RANKL-induced bone resorption facilitates growth of cancer cells colonized in the bone. We show that insulin-like growth factor-1 released from the bone during bone resorption and hypoxia-inducible factor activity in cancer cells cooperatively promoted survival and proliferation of cancer cells in bone marrow. These results suggest a mechanism that bone resorption and hypoxic stress in the bone microenvironment cooperatively play an important role in establishing osteoblastic metastasis. © 2014 The Authors.

Peptides that have high affinity for target molecules on the surface of cancer cells are crucial for the development of targeted cancer therapies. However, unstructured peptides often fail to bind their target molecules with high affinity. To efficiently identify high-affinity target-binding peptides, we have constructed a fluorescent protein scaffold, designated gFPS, in which structurally constrained peptides are integrated at residues K131-L137 of superfolder green fluorescent protein. Molecular dynamics simulation supported the suitability of this site for presentation of exogenous peptides with a constrained structure. gFPS can present 4 to 12 exogenous amino acids without a loss of fluorescence. When gFPSs presenting human epidermal growth factor receptor type 2 (HER2)-targeting peptides were added to the culture medium of HER2-expressing cells, we could easily identify the peptides with high HER2-affinity and -specificity based on gFPS fluorescence. In addition, gFPS could be expressed on the yeast cell surface and applied for a high-throughput screening. These results demonstrate that gFPS has the potential to serve as a powerful tool to improve screening of structurally constrained peptides that have a high target affinity, and suggest that it could expedite the one-step identification of clinically applicable cancer cell-binding peptides.

New YC-1 derivatives were synthesized and evaluated with HIF-1 transcriptional activity, and a potent derivative shows activity in vivo. Furthermore, for the mechanistic study of the YC-1 derivative, we evaluate the antiproliferative activity against 39 human cancer cell lines and the localization of active probes in cells. © The Royal Society of Chemistry.