In vivo long-term investigation of tumor bearing mKate2 by an in-house fluorescence molecular imaging system.

BACKGROUND: Optical imaging is one of the most common, low-cost imaging tools used for investigating the tumor biological behavior in vivo. This study explores the feasibility and sensitivity of a near infrared fluorescent protein mKate2 for a long-term non-invasive tumor imaging in BALB/c nude mice, by using a low-power optical imaging system. METHODS: In this study, breast cancer cell line MDA-MB-435s expressing mKate2 and MDA-MB-231 expressing a dual reporter gene firefly luciferase (fLuc)-GFP were used as cell models. Tumor cells were implanted in different animal body compartments including subcutaneous, abdominal and deep tissue area and closely monitored in real-time. A simple and low-power optical imaging system was set up to image both fluorescence and bioluminescence in live animals. RESULTS: The presence of malignant tissue was further confirmed by histopathological assay. Considering its lower exposure time and no need of substrate injection, mKate2 is considered a superior choice for subcutaneous imaging compared with fLuc. On the contrary, fLuc has shown to be a better option when monitoring the tumor in a diffusive area such as abdominal cavity. Furthermore, both reporter genes have shown good stability and sensitivity for deep tissue imaging, i.e. tumor within the liver. In addition, fLuc has shown to be an excellent method for detecting tumor cells in the lung. CONCLUSIONS: The combination of mKate2 and fLuc offers a superior choice for long-term non-invasive real-time investigation of tumor biological behavior in vivo.

The response mechanism analysis of HMX1 knockout strain to levulinic acid in Saccharomyces cerevisiae.

Levulinic acid, a hydrolysis product of lignocellulose, can be metabolized into important compounds in the field of medicine and pesticides by engineered strains of Saccharomyces cerevisiae. Levulinic acid, as an intermediate product widely found in the conversion process of lignocellulosic biomass, has multiple applications. However, its toxicity to Saccharomyces cerevisiae reduces its conversion efficiency, so screening Saccharomyces cerevisiae genes that can tolerate levulinic acid becomes the key. By creating a whole-genome knockout library and bioinformatics analysis, this study used the phenotypic characteristics of cells as the basis for screening and found the HMX1 gene that is highly sensitive to levulinic acid in the oxidative stress pathway. After knocking out HMX1 and treating with levulinic acid, the omics data of the strain revealed that multiple affected pathways, especially the expression of 14 genes related to the cell wall and membrane system, were significantly downregulated. The levels of acetyl-CoA and riboflavin decreased by 1.02-fold and 1.44-fold, respectively, while the content of pantothenic acid increased. These findings indicate that the cell wall-membrane system, as well as the metabolism of acetyl-CoA and riboflavin, are important in improving the resistance of Saccharomyces cerevisiae to levulinic acid. They provide theoretical support for enhancing the tolerance of microorganisms to levulinic acid, which is significant for optimizing the conversion process of lignocellulosic biomass to levulinic acid.

Erratum to "[18F]ML-10 Imaging for Assessment of Apoptosis Response of Intracranial Tumor Early after Radiosurgery by PET/CT".

[This corrects the article DOI: 10.1155/2018/9365174.].

[18F]ML-10 Imaging for Assessment of Apoptosis Response of Intracranial Tumor Early after Radiosurgery by PET/CT.

[18F]ML-10 is a novel apoptosis radiotracer for positron emission tomography (PET). We assess the apoptosis response of intracranial tumor early after CyberKnife (CK) treatment by [18F]ML-10 PET imaging. 29 human subjects (30 lesions), diagnosed with intracranial tumors, underwent CK treatment at 14-24 Gy in 1-3 fractions, had [18F]ML-10 positron emission tomography/computed tomography (PET/CT) before (pre-CK) and 48 hours after (post-CK) CK treatment. Magnetic resonance imaging (MRI) scans were taken before and 8 weeks after CK treatment. Voxel-based analysis was used for the imaging analysis. Heterogeneous changes of apoptosis in tumors before and after treatment were observed on voxel-based analysis of PET images. A positive correlation was observed between the change in radioactivity (X) and subsequent tumor volume (Y) (r=0.862, p < 0.05), with a regression equation of Y=1.018∗X - 0.016. Malignant tumors tend to be more sensitive to CK treatment, but the treatment outcome is not affected by pre-CK apoptotic status of tumor cells; [18F]ML-10 PET imaging could be taken as an assessment 48 h after CK treatment.

Validation of Bevacizumab Therapy Effect on Colon Cancer Subtypes by Using Whole Body Imaging in Mice.

PURPOSE: Preclinical imaging offers a useful tool for monitoring cancer biological behavior and therapy in vivo without the necessity of animal surgery. The following paper describes our examination of tumor progress and anti-angiogenic therapy with Bevacizumab on colon cancer subtypes (SW480 and SW620) by using different non-invasive real-time in vivo imaging techniques. PROCEDURES: Color Doppler ultrasound imaging (CDUI) was used to observe the formation of new blood vessels; a homemade fluorescence reflectance imaging (FRI) apparatus was mainly used to test the difference in VEGFR2 expression between the tumor subtypes. Briefly, 15 Balb/c nude mice bearing subcutaneous SW480 and SW620 xenografts were randomly divided into Control and Drug groups. Bevacizumab treatment lasted for 3 weeks. All images were captured pre- and post-treatment. At the end of experiment, all mice were euthanized, and tumor tissue was collected and analyzed by immunohistochemical staining. RESULTS: Expression of VEGFR2 was found to be slightly (10 %) but significantly higher for the SW620 cells than for SW480 cells. In addition, SW620 has shown to be more vascularized than SW480 subtype. After 3-week Bevacizumab therapy, no blood vessels were found within 83 % of SW620, while it was 67 % in SW480; the increase of SW620 tumor volume post-treatment was only 3.17-fold compared with the tumor volume pre-treatment, and 4.51-fold higher in SW480. CONCLUSION: Our data suggest that SW480 and SW620 cell lines respond differently to Bevacizumab therapy in vivo. Because of higher vascularization, and subsequently higher reduction by drug of new blood vessels and tumor growth rate, xenografts derived from the metastatic SW620 cell line have a better chance of being successfully treated with Bevacizumab compared with those derived from the primary tumor SW480 cell line.

An integrated quad-modality molecular imaging system for small animals.

UNLABELLED: We developed a novel integrated quad-modality system that included 3 molecular imaging methods (PET, SPECT, and fluorescence molecular imaging [FMI]) and 1 anatomic imaging modality (CT). This system could study various biologic processes in the same animal using multiple molecular tracers. In addition to the technology development, we also discussed the optimization strategy of the imaging protocols. The performance of this system was tested, and the in vivo animal experiment showed its power to trace 3 different molecular probes in living tissues. Our results demonstrated that this system has a great potential for the preclinical study of diseases. METHODS: A prototype system integrating PET, SPECT, CT, and a charge-coupled device-based free-space FMI system has been developed. Imaging and fusion capabilities of the system were evaluated by a multimodality phantom. In addition, a mouse disease model with both tumor and inflammation was studied by this system to examine the in vivo performance. The 3 types of molecular probes-(18)F-FDG, [(99m)Tc(HYNIC-3PRGD2)(tricine)(TPPTS)] ((99m)Tc-3PRG2) (HYNIC = 6-hydrazinonicotinyl; TPPTS = trisodium triphenylphosphine-3,3',3″-trisulfonate; 3PRGD2 = PEG4-E[PEG4-c(RGDfK)]2), and 3-(triethoxysilyl) propyl-Cy7-entrapped core-cross-linked polymeric micelle (Cy7-entrapped CCPM) nanoparticles-were used to target 3 different biologic processes in the tumor caused by pulmonary adenocarcinoma A549 cells. Moreover, the strategy to optimize multimodal molecular imaging procedure was studied as well, which could significantly reduce the total imaging time. RESULTS: The imaging performance has been validated by both phantom and in vivo animal experiments. With this system and optimized imaging protocol, we successfully differentiated diseases that cannot be distinguished by a single molecular imaging modality. CONCLUSION: We developed a novel quad-modality molecular imaging system that integrated PET, SPECT, FMI, and CT imaging methods to obtain whole-body multimodality images of small animals. The imaging results demonstrated that this system provides more comprehensive information for preclinical biomedical research. With optimized imaging protocols, as well as novel molecular tracers, this quad-modality system can help in the study of the physiology mechanism at an unprecedented level.