Masaru Furuta

The significance of microscopic mass spectrometry with high resolution in the visualisation of drug distribution

The visualisation and quantitative analysis of the native drug distribution in a pre-clinical or clinical setting are desirable for evaluating drug effects and optimising drug design. Here, using matrix-assisted laser desorption ionisation imaging mass spectrometry (MALDI-IMS) with enhanced resolution and sensitivity, we compared the distribution of a paclitaxel (PTX)-incorporating micelle (NK105) with that of PTX alone after injection into tumour-bearing mice. We demonstrated optically and quantitatively that NK105 delivered more PTX to the tumour, including the centre of the tumour, while delivering less PTX to normal neural tissue, compared with injection with PTX alone. NK105 treatment yielded a greater antitumour effect and less neural toxicity in mice than did PTX treatment. The use of high-resolution MALDI-IMS may be an innovative approach for pharmacological evaluation and drug design support.

Imaging mass spectrometry for the precise design of antibody-drug conjugates

Antibody-drug conjugates (ADCs) are a class of immunotherapeutic agents that enable the delivery of cytotoxic drugs to target malignant cells. Because various cancers and tumour vascular endothelia strongly express anti-human tissue factor (TF), we prepared ADCs consisting of a TF-specific monoclonal antibody (mAb) linked to the anticancer agent (ACA) monomethyl auristatin E (MMAE) via a valine-citrulline (Val-Cit) linker (human TF ADC). Identifying the most efficient drug design in advance is difficult because ADCs have complicated structures. The best method of assessing ADCs is to examine their selectivity and efficiency in releasing and distributing the ACA within tumour tissue. Matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS) can be used to directly detect the distributions of native molecules within tumour tissues. Here, MALDI-IMS enabled the identification of the intratumour distribution of MMAE released from the ADC. In conclusion, MALDI-IMS is a useful tool to assess ADCs and facilitate the optimization of ADC design.

Novel In Situ Pretreatment Method for Significantly Enhancing the Signal In MALDI-TOF MS of Formalin-Fixed Paraffin-Embedded Tissue Sections

The application of matrix-assisted laser desorption/ionization (MALDI)-based mass spectrometry (MS) to the proteomic analysis of formalin-fixed paraffin-embedded (FFPE) tissue presents significant technical challenges. In situ enzymatic digestion is frequently used to unlock formalin-fixed tissues for analysis, but the results are often unsatisfactory. Here, we report a new, simplified in situ pretreatment method for preparing tissue sections for MS that involves heating with vapor containing acetonitrile in a small airtight pressurized space. The utility of the novel method is shown using FFPE tissue of human colon carcinoma. The number and intensity of MALDI peaks obtained from analysis of pretreated tissue was significantly higher than control tissue not subjected to pretreatment. A prominent peak (m/z 850) apparently specific to cancerous tissue was identified as a fragment of histone H2A in FFPE tissue pretreated using our method. This highly sensitive treatment may enable MALDI-MS analysis of archived pathological FFPE samples, thus leading to the identification of new biomarkers.

Development of Antibody–Drug Conjugates Using DDS and Molecular Imaging

Antibody-drug conjugate (ADC), as a next generation of antibody therapeutics, is a combination of an antibody and a drug connected via a specialized linker. ADC has four action steps: systemic circulation, the enhanced permeability and retention (EPR) effect, penetration within the tumor tissue, and action on cells, such as through drug delivery system (DDS) drugs. An antibody with a size of about 10 nm has the same capacity for passive targeting as some DDS carriers, depending on the EPR effect. In addition, some antibodies are capable of active targeting. A linker is stable in the bloodstream but should release drugs efficiently in the tumor cells or their microenvironment. Thus, the linker technology is actually a typical controlled release technology in DDS. Here, we focused on molecular imaging. Fluorescent and positron emission tomography (PET) imaging is useful for the visualization and evaluation of antibody delivery in terms of passive and active targeting in the systemic circulation and in tumors. To evaluate the controlled release of the ADC in the targeted area, a mass spectrometry imaging (MSI) with a mass microscope, to visualize the drug released from ADC, was used. As a result, we succeeded in confirming the significant anti-tumor activity of anti-fibrin, or anti-tissue factor-ADC, in preclinical settings by using DDS and molecular imaging.

Imaging and Molecular Identification of Biomolecules on Tissue Sections with AXIMA-QIT: Shimadzu Corporation

In MALDI-IMS experiments, because of the complex MALDI process on the tissue surface, the ability to both visualize and identify molecules directly on the tissue surface by tandem mass spectrometry (MS n ) is essential. Here we introduce an imaging system based on a MALDI-quadrupole ion trap time-of-flight type instrument (AXIMA-QIT; Shimadzu Corporation), which is compatible with both imaging and highly sensitive MS n . In this chapter, we present the attractive features of the AXIMA-QIT as an imaging instrument and introduce the variety of application topics. The visualized biomolecules were successfully identified by MS n directly on the tissue surface, with a strong ability to isolate precursor ions. The presented IMS system with AXIMA-QIT covers a wide range of molecular imaging including phospholipids and other endogenous metabolites and also tryptic-digested proteins in various biological samples.

Abstract 4012: Visualization of EPR effect and active targeting by using microscopic mass spectrometry

Microscopic mass spectrometry (MMS), in which a microscope is coupled with an atmospheric pressure matrix-assisted laser desorption/ionization (MALDI) and quadruple ion trap time-of-flight (TOF) analyzer has been developed for the investigation of the distribution of various molecules including drugs. The matrix-coated drug sample is ionized and then separated on the basis of its mass-to-charge ratio (m/z). Images were acquired from imaging mass spectrometry (IMS) or tandem mass spectrometry (MS/MS) data. Recently, pharmacokinetic (PK) and pharmacodynamic (PD) studies have become important to evaluate the efficacy and toxicity of the drugs. In these analyses, tissue homogenates are generally used for the quantification by high-performance liquid chromatography (HPLC) or liquid chromatography mass spectrometry (LC-MS). However, they lack the information regarding the drug distribution in a specific anatomical area. The information of the drug distribution would allow us to optimize the drug design enabling more efficient drug delivery. (1) We studied the tissue distribution of paclitaxel (PTX) and its micellar formulation (NK105) using a MMS. NK105 showed much stronger antitumor effects on a human pancreatic cancer BxPC3 xenograft than PTX. In the drug imaging, we demonstrated that NK105 delivered more PTX to the whole tumor tissue. In the mouse model, PTX caused the peripheral neurotoxicity but NK105 did not. Multiple high drug-signal areas surrounding and inside the caudal nerve were observed in the case of PTX, whereas the signals after NK105 administration were quite low. (2) The tissue distribution and controlled drug release of ADC (antibody-drug conjugate) consisting of a tissue factor specific antibody (TF) linked to the anticancer agent monomethyl auristatin E (MMAE) was evaluated in comparison with control-ADC (control antibody-MMAE conjugation). TF-ADC showed stronger antitumor effect on BxPC3 xenograft than control-ADC. We then established the selective detection method of MMAE for distinguishing free MMAE and its conjugated form. The released MMAE signal detected following the accumulation of TF-ADC was greatest 24 h after the administration, compared with the control-ADC at the same time (P Citation Format: Masahiro Yasunaga, Masaru Furuta, Koretsugu Ogata, Yuki Fujiwara, Yoshikatsu Koga, Yasuhiro Matsumura. Visualization of EPR effect and active targeting by using microscopic mass spectrometry [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 4012. doi:10.1158/1538-7445.AM2017-4012

Abstract 203: Visualization of drug delivery by using high resolution microscopic mass spectrometry

Pharmacokinetic (PK) and pharmacodynamic (PD) studies are important to evaluate the efficacy and toxicity of the drugs. In these analyses, tissue homogenates are generally used for the quantification by high-performance liquid chromatography (HPLC) or liquid chromatography mass spectrometry (LC-MS). However, they lack the information regarding the drug distribution in a specific anatomical area. The information of the drug distribution allows us to optimize the drug design enabling more efficient targeted delivery. We studied the tissue distribution of paclitaxel (PTX) and its micellar formulation (NK105) using a microscopic mass spectroscopy (MMS). A MMS in which a microscope is coupled with an atmospheric pressure matrix-assisted laser desorption/ionization (MALDI) and quadruple ion trap time-of-flight (TOF) analyser was used. The matrix-coated drug sample is ionised and then separated on the basis of its mass-to-charge ratio (m/z). Images were acquired from imaging mass spectrometry (IMS) or tandem mass spectrometry (MS/MS) data. (1) We established the drug imaging system with enhanced resolution and sensitivity. In the analysis, MS and MS/MS were used for quantification and validation, respectively. (2) NK105 showed much stronger antitumor effects on a human pancreatic cancer BxPC3 xenograft than PTX. In the drug imaging, we demonstrated that NK105 delivered more PTX to the whole tumor tissue (including the center lesion). In the mouse model, PTX caused the peripheral neurotoxicity but NK105 did not. Multiple high drug-signal areas surrounding and inside the caudal nerve were observed in the case of PTX, whereas the signals after NK105 injection were significantly low. We succeeded in visualising the EPR (Enhanced Permeability and Retention) effect using MMS. The data obtained by the drug imaging may be useful for facilitating DDS-drug design. The significance of microscopic mass spectrometry with high resolution in the visualisation of drug distribution. Sci Rep. 3:3050. 2013. Citation Format: Masahiro Yasunaga, Masaru Furuta, Koretsugu Ogata, Yoshikatsu Koga, Yasuhiro Matsumura. Visualization of drug delivery by using high resolution microscopic mass spectrometry. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 203. doi:10.1158/1538-7445.AM2015-203