Semiquantitative Analysis for High-Speed Mapping Applications of Biological Samples Using LA-ICP-TOFMS

Laser ablation (LA) in combination with inductively coupled plasma time-of-flight mass spectrometry (ICP-TOFMS) enables monitoring of elements from the entire mass range for every pixel, regardless of the isotopes of interest for a certain application. This provides nontargeted multi-element (bio-)imaging capabilities and the unique possibility to screen for elements that were initially not expected in the sample. Quantification of a large range of elements is limited as the preparation of highly multiplexed calibration standards for bioimaging applications by LA-ICP-(TOF)MS is challenging. In this study, we have developed a workflow for semiquantitative analysis by LA-ICP-TOFMS based on multi-element gelatin micro-droplet standards. The presented approach is intended for the mapping of biological samples due to the requirement of matrix-matched standards for accurate quantification in LA-ICPMS, a prerequisite that is given by the use of gelatin-based standards. A library of response factors was constructed based on 72 elements for the semiquantitative calculations. The presented method was evaluated in two stages: (i) on gelatin samples with known elemental concentrations and (ii) on real-world samples that included prime examples of bioimaging (mouse spleen and tumor tissue). The developed semiquantification approach was based on 10 elements as calibration standards and provided the determination of 136 nuclides of 63 elements, with errors below 25%, and for half of the nuclides, below 10%. A web application for quantification and semiquantification of LA-ICP(-TOF)MS data was developed, and a detailed description is presented to easily allow others to use the presented method.

Oral Anticancer Heterobimetallic PtIV -AuI Complexes Show High In Vivo Activity and Low Toxicity

Au^I -carbene and Pt^IV -Au^I -carbene prodrugs display low to sub-μM activity against several cancer cell lines and overcome cisplatin (cisPt) resistance. Linking a cisPt-derived Pt^IV (phenylbutyrate) complex to a Au^I -phenylimidazolylidene complex 2, yielded the most potent prodrug. While in vivo tests against Lewis Lung Carcinoma showed that the prodrug Pt^IV (phenylbutyrate)-Au^I -carbene (7) and the 1 : 1 : 1 co-administration of cisPt: phenylbutyrate:2 efficiently inhibited tumor growth (≈95 %), much better than 2 (75 %) or cisPt (84 %), 7 exhibited only 5 % body weight loss compared to 14 % for 2, 20 % for cisPt and >30 % for the co-administration. 7 was much more efficient than 2 at inhibiting TrxR activity in the isolated enzyme, in cells and in the tumor, even though it was much less efficient than 2 at binding to selenocysteine peptides modeling the active site of TrxR. Organ distribution and laser-ablation (LA)-ICP-TOFMS imaging suggest that 7 arrives intact at the tumor and is activated there.

Multiparametric Tissue Characterization Utilizing the Cellular Metallome and Immuno-Mass Spectrometry Imaging

In this study, we present a workflow that enables spatial single-cell metallomics in tissue decoding the cellular heterogeneity. Low-dispersion laser ablation in combination with inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOFMS) provides mapping of endogenous elements with cellular resolution at unprecedented speed. Capturing the heterogeneity of the cellular population by metals only is of limited use as the cell type, functionality, and cell state remain elusive. Therefore, we expanded the toolbox of single-cell metallomics by integrating the concepts of imaging mass cytometry (IMC). This multiparametric assay successfully utilizes metal-labeled antibodies for cellular tissue profiling. One important challenge is the need to preserve the original metallome in the sample upon immunostaining. Therefore, we studied the impact of extensive labeling on the obtained endogenous cellular ionome data by quantifying elemental levels in consecutive tissue sections (with and without immunostaining) and correlating elements with structural markers and histological features. Our experiments showed that the elemental tissue distribution remained intact for selected elements such as sodium, phosphorus, and iron, while absolute quantification was precluded. We hypothesize that this integrated assay not only advances single-cell metallomics (enabling to link metal accumulation to multi-dimensional characterization of cells/cell populations), but in turn also enhances selectivity in IMC, as in selected cases, labeling strategies can be validated by elemental data. We showcase the power of this integrated single-cell toolbox using an in vivo tumor model in mice and provide mapping of the sodium and iron homeostasis as linked to different cell types and function in mouse organs (such as spleen, kidney, and liver). Phosphorus distribution maps added structural information, paralleled by the DNA intercalator visualizing the cellular nuclei. Overall, iron imaging was the most relevant addition to IMC. In tumor samples, for example, iron-rich regions correlated with high proliferation and/or located blood vessels, which are key for potential drug delivery.

The copper transporter CTR1 and cisplatin accumulation at the single-cell level by LA-ICP-TOFMS

More than a decade ago, studies on cellular cisplatin accumulation via active membrane transport established the role of the high affinity copper uptake protein 1 (CTR1) as a main uptake route besides passive diffusion. In this work, CTR1 expression, cisplatin accumulation and intracellular copper concentration was assessed for single cells revisiting the case of CTR1 in the context of acquired cisplatin resistance. The single-cell workflow designed for in vitro experiments enabled quantitative imaging at resolutions down to 1 µm by laser ablation-inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-TOFMS). Cisplatin-sensitive ovarian carcinoma cells A2780 as compared to the cisplatin-resistant subline A2780cis were investigated. Intracellular cisplatin and copper levels were absolutely quantified for thousands of individual cells, while for CTR1, relative differences of total CTR1 versus plasma membrane-bound CTR1 were determined. A markedly decreased intracellular cisplatin concentration accompanied by reduced copper concentrations was observed for single A2780cis cells, along with a distinctly reduced (total) CTR1 level as compared to the parental cell model. Interestingly, a significantly different proportion of plasma membrane-bound versus total CTR1 in untreated A2780 as compared to A2780cis cells was observed. This proportion changed in both models upon cisplatin exposure. Statistical analysis revealed a significant correlation between total and plasma membrane-bound CTR1 expression and cisplatin accumulation at the single-cell level in both A2780 and A2780cis cells. Thus, our study recapitulates the crosstalk of copper homeostasis and cisplatin uptake, and also indicates a complex interplay between subcellular CTR1 localization and cellular cisplatin accumulation as a driver for acquired resistance development.

Elemental Mapping of Human Malignant Mesothelioma Tissue Samples Using High-Speed LA–ICP–TOFMS Imaging

This is the first report of the use of laser ablation–inductively coupled plasma time-of-flight mass spectrometry (LA–ICP–TOFMS) to analyze human malignant pleural mesothelioma (MPM) samples at the cellular level. MPM is an aggressive, incurable cancer associated with asbestos exposure, with a long latency and poor overall survival. Following careful optimization of the laser fluence, the simultaneous ablation of soft biological tissue and hard mineral fibers was possible, allowing the spatial detection of elements such as Si, Mg, Ca, and Fe, which are also present in the glass substrate. A low-dispersion LA setup was employed, which provided the high spatial resolution necessary to identify the asbestos fibers and fiber fragments in the tissue and to characterize the metallome at the cellular level (a pixel size of 2 μm), with a high speed (at 250 Hz). The multielement LA–ICP–TOFMS imaging approach enabled (i) the detection of asbestos fibers/mineral impurities within the MPM tissue samples of patients, (ii) the visualization of the tissue structure with the endogenous elemental pattern at high spatial resolution, and (iii) obtaining insights into the metallome of MPM patients with different pathologies in a single analysis run. Asbestos and other mineral fibers were detected in the lung and pleura tissue of MPM patients, respectively, based on their multielement pattern (Si, Mg, Ca, Fe, and Sr). Interestingly, strontium was detected in asbestos fibers, suggesting a link between this potential toxic element and MPM pathogenesis. Furthermore, monitoring the metallome around the talc deposit regions (characterized by elevated levels of Al, Mg, and Si) revealed significant tissue damage and inflammation caused by talc pleurodesis. LA–ICP–TOFMS results correlated to Perls’ Prussian blue and histological staining of the corresponding serial sections. Ultimately, the ultra-high-speed and high-spatial-resolution capabilities of this novel LA–ICP–TOFMS setup may become an important clinical tool for simultaneous asbestos detection, metallome monitoring, and biomarker identification.

Cisplatin Uptake in Macrophage Subtypes at the Single-Cell Level by LA-ICP-TOFMS Imaging

A high-throughput laser ablation–inductively coupled plasma–time-of-flight mass spectrometry (LA-ICP-TOFMS) workflow was implemented for quantitative single-cell analysis following cytospin preparation of cells. For the first time, in vitro studies on cisplatin exposure addressed human monocytes and monocyte-derived macrophages (undifferentiated THP-1 monocytic cells, differentiated M0 macrophages, as well as further polarized M1 and M2 phenotypes) at the single-cell level. The models are of particular interest as macrophages comprise the biggest part of immune cells present in the tumor microenvironment and play an important role in modulating tumor growth and progression. The introduced bioimaging workflow proved to be universally applicable to adherent and suspension cell cultures and fit-for-purpose for the quantitative analysis of several hundreds of cells within minutes. Both, cross-validation of the method with single-cell analysis in suspension for THP-1 cells and with LA-ICP-TOFMS analysis of adherent M0 cells grown on chambered glass coverslips, revealed agreeing platinum concentrations at the single-cell level. A high incorporation of cisplatin was observed in M2 macrophages compared to the M0 and M1 macrophage subtypes and the monocyte model, THP-1. The combination with bright-field images and monitoring of highly abundant endogenous elements such as phosphorus and sodium at a high spatial resolution allowed assessing cell size and important morphological cell parameters and thus straightforward control over several cell conditions. This way, apoptotic cells and cell debris as well as doublets or cell clusters could be easily excluded prior to data evaluation without additional staining.

Albumin-targeting of an oxaliplatin-releasing platinum(iv) prodrug results in pronounced anticancer activity due to endocytotic drug uptake in vivo

Oxaliplatin is a very potent platinum(ii) drug which is frequently used in poly-chemotherapy schemes against advanced colorectal cancer. However, its benefit is limited by severe adverse effects as well as resistance development. Based on their higher tolerability, platinum(iv) prodrugs came into focus of interest. However, comparable to their platinum(ii) counterparts they lack tumor specificity and are frequently prematurely activated in the blood circulation. With the aim to exploit the enhanced albumin consumption and accumulation in the malignant tissue, we have recently developed a new albumin-targeted prodrug, which supposed to release oxaliplatin in a highly tumor-specific manner. In more detail, we designed a platinum(iv) complex containing two maleimide moieties in the axial position (KP2156), which allows selective binding to the cysteine 34. In the present study, diverse cell biological and analytical tools such as laser ablation inductively-coupled plasma mass spectrometry (LA-ICP-MS), isotope labeling, and nano-scale secondary ion mass spectrometry (NanoSIMS) were employed to better understand the in vivo distribution and activation process of KP2156 (in comparison to free oxaliplatin and a non-albumin-binding succinimide analogue). KP2156 forms very stable albumin adducts in the bloodstream resulting in a superior pharmacological profile, such as distinctly prolonged terminal excretion half-life and enhanced effective platinum dose (measured by ICP-MS). The albumin-bound drug is accumulating in the malignant tissue, where it enters the cancer cells via clathrin- and caveolin-dependent endocytosis, and is activated by reduction to release oxaliplatin. This results in profound, long-lasting anticancer activity of KP2156 against CT26 colon cancer tumors in vivo based on cell cycle arrest and apoptotic cell death. Summarizing, albumin-binding of platinum(iv) complexes potently enhances the efficacy of oxaliplatin therapy and should be further developed towards clinical phase I trials.

Modified amino-dextrans as carriers of Gd-chelates for retrograde transport and visualization of peripheral nerves by magnetic resonance imaging (MRI)

Amino-dextrans (AD) conjugated with gadolinium (Gd3+) were developed as neuro-specific contrast agents (CA) for the visualization of the sciatic nerve in rats by magnetic resonance imaging (MRI). AD with 3, 10, and 70 kDa molecular weights were assessed as carrier molecules known to be transported with various speed by axonal microtubules. Detailed spectroscopic characterizations, analyses by Fast Protein Liquid Chromatography (FPLC), Sodium Dodecyl Sulfate Polyacrylamide Gel Electrophoresis (SDS-PAGE), and inductively coupled plasma-mass spectrometry (ICP-MS), were carried out. For MRI, the paramagnetic Gd3+ ion was coupled as a T1 signal enhancer. The well-established linear chelator, diethylenetriaminepentaacetic acid (DTPA), was used and subsequently replaced by the more stable cyclic chelator 1,4,7,10-Tetraazacyclododecane-1,4,7,10-tetraacetic acid (DOTA). In addition, a fluorescently labeled AD-DTPA-Gd was prepared to demonstrate an active transport to the spinal cord by histochemistry. After successful synthesis and characterization, molecular migration of the AD-DTPA-Gd in the sciatic nerve of healthy Sprague Dawley rats was monitored by MRI for up to seven days. Enhancement of nerve structures was evaluated by MRI and correlated with ICP-MS analyses. To investigate the distribution of CA along the neuraxis, all animals were sacrificed after the final MRI monitoring. Nerves, spinal ganglions, and corresponding spinal cord sections were harvested, to determine the localization and concentration of the paramagnetic element. This is the first report that demonstrates the active uptake and transport of AD-Gd conjugates within the sciatic nerve. This new concept may serve as a potential diagnostic tool for the direct visualization and monitoring of the continuity of injured nerves.

Introducing N-, P-, and S-donor leaving groups: an investigation of the chemical and biological properties of ruthenium, rhodium and iridium thiopyridone piano stool complexes

A series of 15 piano-stool complexes featuring either a RuII, RhIII or IrIII metal center, a bidentate thiopyridone ligand, and different leaving groups was synthesized. The leaving groups were selected in order to cover a broad range of different donor atoms. Thus, 1-methylimidazole served as a N-donor, 1,3,5-triaza-7-phosphaadamantane (pta) as a P-donor, and thiourea as a S-donor. Additionally, three complexes featuring different halido leaving groups (Cl, Br, I) were added. Leaving group alterations were carried out with respect to a possible influence on pharmacokinetic and pharmacodynamic parameters, as well as the cytotoxicity of the respective compounds. The complexes were characterized via NMR spectroscopy, X-ray diffraction (where possible), mass spectrometry, and elemental analysis. Cytotoxicity was assessed in 2D cultures of human cancer cell lines by microculture and clonogenic assays as well as in multicellular tumor spheroids. Furthermore, cellular accumulation studies, flow-cytometric apoptosis and ROS assays, DNA plasmid assays, and laser ablation ICP-MS studies for analyzing the distribution in sections of multicellular tumor spheroids were conducted. This work demonstrates the importance of investigating each piano-stool complexes' properties, as the most promising candidates showed advantages over each other in certain tests/assays. Thus, it was not possible to single out one lead compound, but rather a group of complexes with enhanced cytotoxicity and activity.

Micro-droplet-based calibration for quantitative elemental bioimaging by LA-ICPMS

In this work, a novel standardization strategy for quantitative elemental bioimaging is evaluated. More specifically, multi-element quantification by laser ablation-inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-TOFMS) is performed by multi-point calibration using gelatin-based micro-droplet standards and validated using in-house produced reference materials. Fully automated deposition of micro-droplets by micro-spotting ensured precise standard volumes of 400 ± 5 pL resulting in droplet sizes of around 200 μm in diameter. The small dimensions of the micro-droplet standards and the use of a low-dispersion laser ablation setup reduced the analysis time required for calibration by LA-ICPMS significantly. Therefore, as a key advance, high-throughput analysis (pixel acquisition rates of more than 200 Hz) enabled to establish imaging measurement sequences with quality control- and standardization samples comparable to solution-based quantification exercises by ICP-MS. Analytical figures of merit such as limit of detection, precision, and accuracy of the calibration approach were assessed for platinum and for elements with biological key functions from the lower mass range (phosphorus, copper, and zinc). As a proof-of-concept application, the tool-set was employed to investigate the accumulation of metal-based anticancer drugs in multicellular tumor spheroid models at clinically relevant concentrations.

Mass spectrometry techniques for imaging and detection of metallodrugs

Undoubtedly, metallomic approaches based on mass spectrometry have evolved into essential tools supporting the drug development of novel metal-based anticancer drugs. This article will comment on the state-of-the-art instrumentation and highlight some of the recent analytical advances beyond routine, especially focusing on the latest developments in inductively coupled plasma-mass spectrometry (ICP-MS). Mass spectrometry-based bioimaging and single-cell methods will be presented, paving the way to exciting investigations of metal-based anticancer drugs in heterogeneous and structurally, as well as functionally complex solid tumor tissues.

Nano-scale imaging of dual stable isotope labeled oxaliplatin in human colon cancer cells reveals the nucleolus as a putative node for therapeutic effect

Oxaliplatin shows a superior clinical activity in colorectal cancer compared to cisplatin. Nevertheless, the knowledge about its cellular distribution and the mechanisms responsible for the different range of oxaliplatin-responsive tumors is far from complete. In this study, we combined highly sensitive element specific and isotope selective imaging by nanometer-scale secondary ion mass spectrometry (NanoSIMS) with transmission electron microscopy to investigate the subcellular accumulation of oxaliplatin in three human colon cancer cell lines (SW480, HCT116 wt, HCT116 OxR). Oxaliplatin bearing dual stable isotope labeled moieties, i.e. ²H-labeled diaminocyclohexane (DACH) and ¹³C-labeled oxalate, were applied for comparative analysis of the subcellular distribution patterns of the central metal and the ligands. In all the investigated cell lines, oxaliplatin was found to have a pronounced tendency for cytoplasmic aggregation in single membrane bound organelles, presumably related to various stages of the endocytic pathway. Moreover, nuclear structures, heterochromatin and in particular nucleoli, were affected by platinum-drug exposure. In order to explore the consequences of oxaliplatin resistance, subcellular drug distribution patterns were investigated in a pair of isogenic malignant cell lines with distinct levels of drug sensitivity (HCT116 wt and HCT116 OxR, the latter with acquired resistance to oxaliplatin). The subcellular platinum distribution was found to be similar in both cell lines, with only slightly higher accumulation in the sensitive HCT116 wt cells which is inconsistent with the resistance factor of more than 20-fold. Instead, the isotopic analysis revealed a disproportionally high accumulation of the oxalate ligand in the resistant cell line.

Plecstatin-1 induces an immunogenic cell death signature in colorectal tumour spheroids

Organometallic metal(arene) anticancer agents were believed to confer low selectivity for potential cellular targets. However, the ruthenium(arene) pyridinecarbothioamide (plecstatin-1) showed target selectivity for plectin, a scaffold protein and cytolinker. We employed a three-dimensional cancer spheroid model and showed that plecstatin-1 limited spheroid growth, induced changes in the morphology and in the architecture of tumour spheroids by disrupting the cytoskeletal organization. Additionally, we demonstrated that plecstatin-1 induced oxidative stress, followed by the induction of an immunogenic cell death signature through phosphorylation of eIF2α, exposure of calreticulin, HSP90 and HSP70 on the cell membrane and secretion of ATP followed by release of high mobility group box-1.

MR Imaging of Peripheral Nerves Using Targeted Application of Contrast Agents: An Experimental Proof-of-Concept Study

Introduction: Current imaging modalities for peripheral nerves display the nerve's structure but not its function. Based on a nerve's capacity for axonal transport, it may be visualized by targeted application of a contrast agent and assessing the distribution through radiological imaging, thus revealing a nerve's continuity. This concept has not been explored, however, may potentially guide the treatment of peripheral nerve injuries. In this experimental proof-of-concept study, we tested imaging through MRI after administering gadolinium-based contrast agents which were then retrogradely transported. Methods: We synthesized MRI contrast agents consisting of paramagnetic agents and various axonal transport facilitators (HSA-DTPA-Gd, chitosan-DTPA-Gd or PLA/HSA-DTPA-Gd). First, we measured their relaxivity values in vitro to assess their radiological suitability. Subsequently, the sciatic nerve of 24 rats was cut and labeled with one of the contrast agents to achieve retrograde distribution along the nerve. One week after surgery, the spinal cords and sciatic nerves were harvested to visualize the distribution of the respective contrast agent using 7T MRI. In vivo MRI measurements were performed using 9.4 T MRI on the 1st, 3rd, and the 7th day after surgery. Following radiological imaging, the concentration of gadolinium in the harvested samples was analyzed using inductively coupled mass spectrometry (ICP-MS). Results: All contrast agents demonstrated high relaxivity values, varying between 12.1 and 116.0 mM^-1s^-1. HSA-DTPA-Gd and PLA/HSA-DTPA-Gd application resulted in signal enhancement in the vertebral canal and in the sciatic nerve in ex vivo MRI. In vivo measurements revealed significant signal enhancement in the sciatic nerve on the 3rd and 7th day after HSA-DTPA-Gd and chitosan-DTPA-Gd (p < 0.05) application. Chemical evaluation showed high gadolinium concentration in the sciatic nerve for HSA-DTPA-Gd (5.218 ± 0.860 ng/mg) and chitosan-DTPA-Gd (4.291 ± 1.290 ng/mg). Discussion: In this study a novel imaging approach for the evaluation of a peripheral nerve's integrity was implemented. The findings provide radiological and chemical evidence of successful contrast agent uptake along the sciatic nerve and its distribution within the spinal canal in rats. This novel concept may assist in the diagnostic process of peripheral nerve injuries in the future.

Abstract P2-10-05: A breast cancer multi-racial/ethnic polygenic risk score for improved personalized breast cancer screening

Background: Polygenic risk scores (PRS) integrate risk information from breast cancer associated SNPs (single nucleotide polymorphism). The risk scores have mostly been developed in populations of European ancestry, and have been shown to improve risk prediction over standard breast cancer risk models in these populations. The ability of the PRS to personalize screening is currently being studied. We included PRS as a component of breast cancer risk assessment in the WISDOM Study, a trial of personalized vs. annual breast cancer screening. In order to account for race/ethnicity in PRS risk assessment, we developed a race/ethnicity calibrated and inclusive PRS risk score that we incorporated here into the Gail model to determine impact on risk stratification.

Methods: We constructed two different PRS for each race/ethnicity: For Caucasian populations, we constructed two PRS based on SNPs discovered in European-ancestry populations. One PRS was based on 167 SNPs (PRS-167) and the other based on 313 SNPs (PRS-313) from the Breast Cancer Association Consortium studies as previously published. For each of the Asian-, Hispanic- and African-ancestry populations we added additional ancestry specific SNPs to the PRS-167 or the PRS-313, that were literature curated or our own identified race/ethnicity SNPs that we validated to provide independent risk prediction for their ancestry group: Asian added 10 or 4 additional SNPs, Hispanic 2 SNPs, and African 8 and 12 SNPs, respectively to each model. We tested this approach using datasets from several case-control studies of multiple racial/ethnic populations and compared discrimination of the models using area under the receiver operating characteristic curve (AUROC). Furthermore, we applied our multi-racial/ethnic PRS-313 in a sample of ~3000 multi-racial/ethnic women from the Athena Breast Screening Registry, case-control sampled by Gail score to be at elevated (Gail &gt;1.67) or average (Gail≤1.67) risk, to evaluate the impact of our multi-ethnic adjustment on risk stratification.

Results: A multi-race/ethnicity adjusted PRS-313 and PRS-167 plus ethnicity specific SNPs has moderate-high discriminatory power with AUROCs of 0.65 and 0.64, respectively. The specificity of our PRS-167 in the different race/ethnicity ancestries performs relatively well in Asian (AUROC 0.59) and Hispanic (AUROC 0.63) populations, but less so in African-ancestry (AUROC 0.56). Incorporating multi-race/ethnicity PRS into Gail model selected women, resulted in 20% of average-risk women transitioning to risk above 1.67%, and conversely, 38% of elevated risk patients were reclassified to average risk.

Conclusion: We constructed a PRS risk score that can be applied to multi-ethnic populations and found moderate-high discrimination. Additional work is needed for the African-ancestry population. The addition of a multi-race/ethnicity SNP model to risk classification based on the Gail model significantly changes risk stratification and clinical care recommendations due to down- or up-reclassification of women at average versus elevated risk.

Citation Format: Sarah Theiner, Donglei Hu, Scott Huntsman, Yiwey Shieh, Laura Fejerman, Irene Acerbi, Sarah D Sawyer, Paige Kendall, Wei Zheng, Dezheng Huo, Olufunmilayo I Olopade, Christopher Haiman, Karla Kerlikowske, Steven Cummings, Ester John, Gabriela Torres-Mejia, Lawrence H Kushi, Denise Wolf, Jeffery A Tice, David A Pearce, Laura Esserman, Athena Breast Health Network Investigators and Advocate Partners, Laura J van ‘t Veer, Elad Ziv. A breast cancer multi-racial/ethnic polygenic risk score for improved personalized breast cancer screening [abstract]. In: Proceedings of the 2019 San Antonio Breast Cancer Symposium; 2019 Dec 10-14; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2020;80(4 Suppl):Abstract nr P2-10-05.

Laser ablation-ICP-TOFMS imaging of germ cell tumors of patients undergoing platinum-based chemotherapy

A low dispersion laser ablation setup in combination with inductively coupled plasma-time-of-flight mass spectrometry (LA-ICP-TOFMS) was applied to clinical samples of patients undergoing platinum-based chemotherapy.

Quantitative Imaging of Silver Nanoparticles and Essential Elements in Thin Sections of Fibroblast Multicellular Spheroids by High Resolution Laser Ablation Inductively Coupled Plasma Time-of-Flight Mass Spectrometry

We applied high resolution laser ablation inductively coupled plasma time-of-flight mass spectrometry (LA-ICP-TOF-MS) with cellular spatial resolution for bioimaging of nanoparticles uptaken by fibroblast multicellular spheroids (MCS). This was used to quantitatively investigate interactions of silver nanoparticles (Ag NPs) and the distributions of intrinsic minerals and biologically relevant elements within thin sections of a fibroblast MCS as a three-dimensional in vitro tissue model. We designed matrix-matched calibration standards for this purpose and printed them using a noncontact piezo-driven array spotter with a Ag NP suspension and multielement standards. The limits of detection for Ag, Mg, P, K, Mn, Fe, Co, Cu, and Zn were at the femtogram (10^-15 g) level, which is sufficient to investigate intrinsic minerals in thin MCS sections (20 μm thick). After incubation for 48 h, Ag NPs were enriched in the outer rim of the MCS but not detected in the core. The localization of Ag NPs was inhomogeneous in the outer rim, and they were colocalized with a single-cell-like structure visualized by Fe distribution (pixel size of elemental images: 5 × 0.5 μm). The quantitative value for the total mass of Ag NPs in a thin section by the present method agreed with that obtained by ICP-sector field (SF)-MS with a liquid mode after acid digestion.

Mercury, silver, selenium and other trace elements in three cyprinid fish species from the Vaal Dam, South Africa, including implications for fish consumers

The levels of Cr, Cu, Zn, Se, Ag, Cd, Hg, and Pb were determined in muscle and liver samples from 30 specimens of fish belonging to the species Labeobarbus aeneus, Labeobarbus kimberleyensis, and Labeo umbratus from the Vaal Dam. Health risks for human fish consumers were estimated using the target hazard quotient (THQ), the Se:Hg-ratio, and Se health benefit value (Se HBV). This is the first comprehensive report on Hg levels in fish from this lake. Mean concentrations ranging from 0.247-0.481 mg/kg dw in muscle and from 0.170-0.363 mg/kg dw in liver clearly show a contamination with this element. Although levels in muscle did not exceed maximum allowances for human consumption, a calculated THQ of 0.12 and 0.14 for the two Labeobarbus species, respectively, showed a potential risk due to additive effects. All Se:Hg-ratios as well as Se HBVs clearly suggested positive effects for fish consumers. Levels of Cu were remarkably high in the liver of L. umbratus, calling for further investigation on this species. Cadmium levels were above the maximum allowances for fish consumption in the liver of all three species (means between 0.190 and 0.460 mg/kg dw), but below the LOD in all muscle and intestine samples. This is also the first report of Ag in fish from South Africa. Levels were below the LOD in muscle, but well detectable in liver; they varied significantly between the two Labeobarbus species (0.054 ± 0.030 and 0.037 ± 0.016 mg/kg dw) compared to L. umbratus (1.92 ± 0.83 mg/kg dw) and showed a positive correlation with Cu levels (63.7 ± 17.0; 70.3 ± 9.0 and 1300 ± 823 mg/kg dw), possibly due to similar chemical affinities to metallothioneins. The detected Ag levels can serve as a basis to monitor the development of this new pollutant in aquatic environments in South Africa and worldwide.

FI-ICP-TOFMS for quantification of biologically essential trace elements in cerebrospinal fluid – high-throughput at low sample volume

A high-throughput ICP-TOFMS method is presented for multi-element quantification in CSF material requiring low sample volume.

Imaging of Ag NP transport through collagen-rich microstructures in fibroblast multicellular spheroids by high-resolution laser ablation inductively coupled plasma time-of-flight mass spectrometry

We investigated the penetration of silver nanoparticles (Ag NPs) into a three-dimensional in vitro tissue analog using NPs with various sizes and surface coatings, and with different incubation times. A high-resolution laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) time-of-flight (TOF) instrument was applied for imaging the distributions of elements in thin sample sections (20 μm thick). A fibroblast multicellular spheroid (MCS) was selected as the model system and cultured for more than 8 days to produce a natural barrier formed by the extracellular matrix containing collagen. The MCS was then exposed for up to 48 h to one of four types of Ag NPs (∅ 5 nm citrate coated, ∅ 20 nm citrate coated, ∅ 20 nm polyvinylpyrrolidone coated, and ∅ 50 nm citrate coated). Imaging showed that the penetration pathway was strongly related to steric networks formed by collagen fibrils, and Ag NPs with a hydrodynamic diameter of more than 41 nm were completely trapped in an outer rim of the MCSs even after incubation for 48 h. In addition, we examined the impact of these NPs on essential elements (P, Fe, Cu, and Zn) in areas of Ag NP accumulation. We observed a linear increase at the sub-femtogram level in the total concentration of Cu (fg per pixel) in samples treated with small or large Ag NPs (∅ 5 nm or ∅ 50 nm) for 48 h.

Critical assessment of different methods for quantitative measurement of metallodrug-protein associations

Quantitative screening for potential drug-protein binding is an essential step in developing novel metal-based anticancer drugs. ICP-MS approaches are at the core of this task; however, many applications lack in the capability of large-scale high-throughput screenings and proper validation. In this work, we critically discuss the analytical figures of merit and the potential method-based quantitative differences applying four different ICP-MS strategies to ex vivo drug-serum incubations. Two candidate drugs, more specifically, two Pt(IV) complexes with known differences of binding affinity towards serum proteins were selected. The study integrated centrifugal ultrafiltration followed by flow injection analysis, turbulent flow chromatography (TFC), and size exclusion chromatography (SEC), all combined with inductively coupled plasma-mass spectrometry (ICP-MS). As a novelty, for the first time, UHPLC SEC-ICP-MS was implemented to enable rapid protein separation to be performed within a few minutes at > 90% column recovery for protein adducts and small molecules. Graphical abstract Quantitative screening for potential drug-protein binding is an essential step in developingnovel metal-based anticancer drugs.

Silver nanoparticles: Their role as antibacterial agent against Aeromonas salmonicida subsp. salmonicida in rainbow trout (Oncorhynchus mykiss)

The rise of bacterial resistance to antibiotics is one of the great challenges of our age. One of the strategies to limit the development of antibiotics resistance is the investigation of alternative antimicrobials. As silver nanoparticles demonstrated a potent bactericidal activity in vitro, the aim of this study was to evaluate the in vivo antibacterial activity of silver nanoparticles against Aeromonas salmonicida subsp. salmonicida. Rainbow trout (n = 120) were divided into four groups of 30 fish each. First group was challenged with A. salmonicida (Positive control), the second group was challenged with A. salmonicida and exposed to silver nanoparticles by immersion for three hours (100 μg/L), the third group was challenged with A. salmonicida and intraperitoneally injected with silver nanoparticles (17 μg/mL) and the fourth group was sham-treated and served as a negative control group. At the 7th day post challenge, histopathology of the positive control group revealed the presence of bacterial aggregates in tissues with degenerative and necrotic changes, while at the 35th day post challenge, only liver necrosis persisted. Silver nanoparticles-treated and negative control groups did not show any clinical signs, mortalities or histopathological alterations and they were tested negative for A. salmonicida. The immersion in silver nanoparticles did not result in detectable residues of silver in the muscles 35 days after treatment. These findings demonstrate the antibacterial properties of silver nanoparticles against A. salmonicida infection. Therefore, they could be used for development of antibacterial agents in aquaculture.

The impact of whole human blood on the kinetic inertness of platinum(iv) prodrugs - an HPLC-ICP-MS study

The potential advantage of platinum(iv) complexes as alternatives to classical platinum(ii)-based drugs relies on their kinetic stability in the body before reaching the tumor site and on their activation by reduction inside cancer cells. In this study, an analytical workflow has been developed to investigate the reductive biotransformation and kinetic inertness of platinum(iv) prodrugs comprising different ligand coordination spheres (respectively, lipophilicity and redox behavior) in whole human blood. The distribution of platinum(iv) complexes in blood pellets and plasma was determined by inductively coupled plasma-mass spectrometry (ICP-MS) after microwave digestion. An analytical approach based on reversed-phase (RP)-ICP-MS was used to monitor the parent compound and the formation of metabolites using two different extraction procedures. The ligand coordination sphere of the platinum(iv) complexes had a significant impact on their accumulation in red blood cells and on their degree of kinetic inertness in whole human blood. The most lipophilic platinum(iv) compound featuring equatorial chlorido ligands showed a pronounced penetration into blood cells and a rapid reductive biotransformation. In contrast, the more hydrophilic platinum(iv) complexes with a carboplatin- and oxaliplatin-core exerted kinetic inertness on a pharmacologically relevant time scale with notable amounts of the compound accumulated in the plasma fraction.

Abstract P1-05-01: Breast cancer and the human microbiome

The human body harbors ten times more bacterial cells than human cells – a stunning figure that suggests a likely dynamic between our bodies and the bacteria we carry, both in health and disease. In this study, we characterized and compared the gut, oral, and breast tissue microbiomes from women with invasive breast cancer, women with ductal carcinoma in situ (DCIS), and healthy women. Samples were collected prior to any systemic therapy to avoid therapy-associated effects on the microbiomes studied. Kits containing materials for collecting oral and stool swab samples were distributed to patients for self-collection. DNA was isolated from these samples and bacterial 16S rRNA was PCR amplified and sequenced. Based on the sequencing results, bacterial taxa present in the samples were enumerated. In our analyses, we looked at microbial diversity and differential relative abundance of bacterial taxa across the three cohorts. Oral and gut microbial diversity at various taxa levels were assessed using Shannon and Simpson diversity indices. The oral microbiome did not show any significant difference in microbial diversity across the three cohorts. In the gut microbiome, the invasive cohort showed a significant decrease in microbial diversity when compared to the healthy cohort. Differences in phylogenetic and relative abundance of bacterial taxa across the three cohorts were measured using a T-test analysis with a p value less than 0.05 considered significant. In the oral microbiome, there were no significant differences in the relative abundance of bacteria across the three cohorts. In the gut microbiome, there were significant differences in the relative abundance of bacteria within each cohort on the phylum, family, and genus levels. The genus Fusicanterbacter (associated with the Lachnospiracaea family and Firmicutes phylum) was significantly overabundant in gut microbiomes of healthy women when compared to the gut microbiomes of women with DCIS or invasive breast cancer. Meanwhile, the genus Bacteriodes (associated with the Bacteroidaceae family and Bacteriodetes phylum) was significantly overabundant in the gut microbiomes of women with invasive breast cancer when compared to the gut microbiomes of healthy women. Although tissues are often thought of as sterile, there is emerging data indicating that different tissues may harbor their own unique microbiomes. We obtained breast tissue microbiome data from a small subset of our breast cancer and DCIS cohorts, as well as healthy breast tissue from reduction mammaplasty specimens. At the genus level, we observed an enrichment of Lactococcus, Lactobacillus, and Halomonas in healthy breast tissues compared to breast cancer tissues and an enrichment of Hyphomicrobium in breast cancer tissues compared to healthy breast tissues. Understanding how gut, oral, and tissue microbiomes relate to breast cancer may open up new opportunities for the development of novel markers for early detection (or markers of susceptibility) as well as new strategies for prevention and/or treatment.

Citation Format: McCune E, Johnson B, O'Meara T, Theiner S, Campos M, Heditsian D, Brain S, Esserman L, Campbell M. Breast cancer and the human microbiome [abstract]. In: Proceedings of the 2017 San Antonio Breast Cancer Symposium; 2017 Dec 5-9; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2018;78(4 Suppl):Abstract nr P1-05-01.

Bioimaging of isosteric osmium and ruthenium anticancer agents by LA-ICP-MS

Two isosteric organometallic drug candidates revealed distinct in vivo antitumour activities and spatial distributions in mouse tissues.

In vitro assessment of the antimicrobial activity of silver and zinc oxide nanoparticles against fish pathogens

BACKGROUND

Antibiotic resistance is a global issue that threatens public health. The excessive use of antibiotics contributes to this problem as the genes of antibiotic resistance can be transferred between the bacteria in humans, animals and aquatic organisms. Metallic nanoparticles could serve as future substitutes for some conventional antibiotics because of their antimicrobial activity. The aim of this study was to evaluate the antimicrobial effects of silver and zinc oxide nanoparticles against major fish pathogens and assess their safety in vitro. Silver nanoparticles were synthesized by chemical reduction and characterized with UV-Vis spectroscopy, transmission electron microscopy and zeta sizer. The concentrations of silver and zinc oxide nanoparticles were measured using inductively coupled plasma-mass spectrometry. Subsequently, silver and zinc oxide nanoparticles were tested for their antimicrobial activity against Aeromonas hydrophila, Aeromonas salmonicida subsp. salmonicida, Edwardsiella ictaluri, Edwardsiella tarda, Francisella noatunensis subsp. orientalis, Yersinia ruckeri and Aphanomyces invadans and the minimum inhibitory concentrations were determined. MTT assay was performed on eel kidney cell line (EK-1) to determine the cell viability after incubation with nanoparticles. The interaction between silver nanoparticles and A. salmonicida was investigated by transmission electron microscopy.

RESULTS

The tested nanoparticles exhibited marked antimicrobial activity. Silver nanoparticles inhibited the growth of both A. salmonicida and A. invadans at a concentration of 17 µg/mL. Zinc oxide nanoparticles inhibited the growth of A. salmonicida, Y. ruckeri and A. invadans at concentrations of 15.75, 31.5 and 3.15 µg/mL respectively. Silver nanoparticles showed higher cell viability when compared to zinc oxide nanoparticles in the MTT assay. Transmission electron microscopy showed the attachment of silver nanoparticles to the bacterial membrane and disruption of its integrity.

CONCLUSIONS

This is the first study on inhibitory effects of silver and zinc oxide nanoparticles towards A. salmonicida and A. invadans. Moreover, zinc oxide nanoparticles inhibited the growth of Y. ruckeri. In low concentrations, silver nanoparticles were less cytotoxic than zinc oxide nanoparticles and represent an alternative antimicrobial compound against A. hydrophila, A. salmonicida and A. invadans.

Abstract P5-02-03: Evaluating the feasibility of a web-based preference-tolerant randomized trial of risk-based vs. annual breast cancer screening: WISDOM study pilot

Background: The WISDOM Study (Women Informed to Screen Depending on Measures of risk) aims to examine the effectiveness of personalized breast cancer screening and to bring objective recommendations to the current mammography screening debate. The WISDOM Study is a 100,000 woman randomized trial with a preference-tolerant design that will determine if risk-based screening (RBS) vs. annual screening, is as safe, less morbid, enables prevention and is preferred by women. A pilot was conducted to test the logistics of online participation and examine the acceptance of the study design and approach.

Methods: Women were recruited from the UCSF site of the Athena Breast Health Network, a clinical care-research cohort of 110,000 women from the 5 University of California Medical Centers and Sanford Health. The pilot recruited women via email who were 40 -74 years of age with no history of breast cancer and a normal mammogram in the past year. Those interested visited the WISDOM Study website (wisdomstudy.org), signed up, elected randomization or self-selection, provided electronic consent using DocuSign (eConsent), and completed genetic testing (RBS arm). The Breast Cancer Surveillance Consortium (BCSC) model (standard risk factors, ethnicity, and breast density) in addition to genetic testing (9 genes and 75 SNPs) was used to calculate breast cancer risks that informed the start and frequency of screening for women in the RBS arm. BCSC was also used in the annual screening arm but did not inform mammography screening recommendations. The pilot used a mixed method approach (using enrollment data, Exit Survey data, individual interviews and focus groups) to assess enrollment preferences, randomization acceptance and overall study workflow.

Results: The online electronic enrollment process and patient engagement portal was successfully implemented. In total, 639 women were invited, 235 registered (34%), and 171 (27%) consented to the pilot. Of these, 74% (127) elected to be randomized, and 26% chose to self-assign (66% chose annual screening (29)). Mean age was 56 years and the ethnic breakdown of the cohort was: 79% White, 10% Asian, 7% Latino, 3% Black, 1% other. 92% of those in the risk-based arm of the study completed genetic testing and were given results; only one genetic mutation was identified and occurred in CHEK2. Within the RBS arm (78), mammography recommendations were: 61% no further mammography until the age of 50, 22% biennial, 11% annual, and 6% every 6 month alternating MRI and mammogram. Exit Survey data illuminated confusion in study arm names (risk-based vs. annual), randomization acceptance (74%), annual arm preference in the self-selection group (66%), eConsent satisfaction (90%), enrollment process ease of use (88%), and website content, navigation and appearance satisfaction (66%). The pilot concluded in May 2016 to allow for refinements prior to the full trial.

Conclusion: Our pilot demonstrates that the majority of women are willing to be randomized and participate in an online screening study to answer the important question on optimal breast cancer screening. The pilot study results will inform implementation of the 100,000 women WISDOM Study which launches in fall of 2016.

Citation Format: Stover Fiscalini A, Theiner S, Kaplan C, Sarrafan S, Sawyer S, Liang A, Rosenberg-Wohl S, Gordon D, Frick M, Borowsky A, Anton-Culver H, Naeim A, LaCroix A, Cink T, Collaboration Athena Breast Health Network and Advocate Partners, Esserman L, van 't Veer L. Evaluating the feasibility of a web-based preference-tolerant randomized trial of risk-based vs. annual breast cancer screening: WISDOM study pilot [abstract]. In: Proceedings of the 2016 San Antonio Breast Cancer Symposium; 2016 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2017;77(4 Suppl):Abstract nr P5-02-03.

Abstract 2623: Common genetic variants associated with breast cancer risk used in the Athena study to enhance models identifying women for breast cancer chemoprevention

Background: The U.S. Preventive Services Task Force recommends that women with a &gt;3% five-year risk of developing breast cancer consider taking selective estrogen receptor modifiers (SERMs) or aromatase inhibitors (AIs) to reduce their risk. Polygenic risk score (PRS), calculated by adding the individual breast cancer risk association for each common genetic variant (SNP), has been found to predict women at low- to high-risk of breast cancer. We analyze associations between SNP risk alleles and known breast cancer risk factors (ethnicity, family history of breast cancer and number of biopsies); furthermore, we quantify the likely impact on chemoprevention recommendations by adding the PRS to known risk models in a subset of women participating in the University of California 100,000 women Athena Breast Health Network.

Methods: Our research cohort included 838 women with no previous diagnosis of breast cancer from the University of California, San Francisco, and was enriched for women determined to be at elevated risk for developing breast cancer by the Gail model. A panel of 75 breast cancer risk SNPs were evaluated on saliva and blood samples (Akesogen Inc; COGS oncochip array). The PRS for each patient was calculated by converting the odds ratio for each SNP into a likelihood ratio (LR) and combining LR's across SNPs. Breast Cancer Surveillance Consortium (BCSC), Gail, BCSC-PRS and Gail-PRS scores (risk models incorporating PRS within a Bayesian framework), were evaluated for each patient. Associations between variables were assessed using t-test or ANOVA. A threshold of p&lt;0.05 was used to assess significance.

Results: Women in this study carry an average of 65 risk allele SNPs (of 150, 2 per locus). By ANOVA, there is a statistically significant association between the SNPs risk allele count and ethnicity (p = 0.014), with a trend towards association with a family history of a first-degree relative with breast cancer (p = 0.053). PRS is significantly associated with a family history breast cancer (p = 0.031); neither SNP allele count nor PRS associates with previous biopsy status.

We found by adding PRS that 12% (86/707) and 13% (104/776) of patients with a prior BCSC or Gail score &lt;3% five-year risk, respectively, changed classifications and would be eligible for chemoprevention. Conversely, 37% (36/98) and 36% (22/62) of patients with a BCSC or Gail score of &gt;3% five-year risk, respectively, changed classifications by adding PRS and would no longer be eligible for chemoprevention.

Conclusion: The addition of SNP based PRS to BCSC and Gail models significantly changes how women are classified and as a result changes whether risk reducing agents are recommended.

PRS will be combined with BCSC and genetic test results for 9 breast cancer genes to calculate a women's breast cancer risk in the PCORI-funded Athena WISDOM study of 100,000 women, comparing risk-based vs. annual mammography screening.

Citation Format: Sarah Theiner, Sarah D. Sawyer, Paige Kendall, Alexandra S. Perry, Denise Wolf, Scott Huntsman, Bo Pan, Jeffery A. Tice, David A. Pearce, Thomas Cink, Laura Esserman, Elad Ziv, Laura van ‘t Veer. Common genetic variants associated with breast cancer risk used in the Athena study to enhance models identifying women for breast cancer chemoprevention. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 2623.

The role of the equatorial ligands for the redox behavior, mode of cellular accumulation and cytotoxicity of platinum(IV) prodrugs

The current study aims to elucidate the possible reasons for the significantly different pharmacological behavior of platinum(IV) complexes with cisplatin-, carboplatin- or nedaplatin-like cores and how this difference can be related to their main physicochemical properties. Chlorido-containing complexes are reduced fast (within hours) by ascorbate and are able to unwind plasmid DNA in the presence of ascorbate, while their tri- and tetracarboxylato analogs are generally inert under the same conditions. Comparison of the lipophilicity, cellular accumulation and cytotoxicity of the investigated platinum compounds revealed the necessity to define new structure-property/activity relationships (SPRs and SARs). The higher activity and improved accumulation of platinum(IV) complexes bearing Cl(-) in equatorial position cannot only be attributed to passive diffusion facilitated by their lipophilicity. Therefore, further platinum accumulation experiments under conditions where active/facilitated transport mechanisms are suppressed were performed. Under hypothermic conditions (4°C), accumulation of dichloridoplatinum(IV) complexes is reduced down to 10% of the amount determined at 37°C. These findings suggest the involvement of active and/or facilitated transport in cellular uptake of platinum(IV) complexes with a cisplatin-like core. Studies with ATP depletion mediated by oligomycin and low glucose partially confirmed these observations, but their feasibility was severely limited in the adherent cell culture setting.

X-ray Structure Analysis of Indazolium trans-[Tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) Bound to Human Serum Albumin Reveals Two Ruthenium Binding Sites and Provides Insights into the Drug Binding Mechanism

Ruthenium(III) complexes are promising candidates for anticancer drugs, especially the clinically studied indazolium trans-[tetrachlorobis(1H-indazole)ruthenate(III)] (KP1019) and its analogue sodium trans-[tetrachlorobis(1H-indazole)ruthenate(III)] (NKP-1339). Several studies have emphasized the likely role of human serum proteins in the transportation and accumulation of ruthenium(III) complexes in tumors. Therefore, the interaction between KP1019 and human serum albumin was investigated by means of X-ray crystallography and inductively coupled plasma mass spectrometry (ICP-MS). The structural data unambiguously reveal the binding of two ruthenium atoms to histidine residues 146 and 242, which are both located within well-known hydrophobic binding pockets of albumin. The ruthenium centers are octahedrally coordinated by solvent molecules revealing the dissociation of both indazole ligands from the ruthenium-based drug. However, a binding mechanism is proposed indicating the importance of the indazole ligands for binding site recognition and thus their indispensable role for the binding of KP1019.

Macromolecular Pt(IV) Prodrugs from Poly(organo)phosphazenes

The preparation of novel macromolecular prodrugs via the conjugation of two platinum(IV) complexes to suitably functionalized poly(organo)phosphazenes is presented. The inorganic/organic polymers provide carriers with controlled dimensions due to the use of living cationic polymerization and allow the preparation of conjugates with excellent aqueous solubility but long-term hydrolytic degradability. The macromolecular Pt(IV) prodrugs are designed to undergo intracellular reduction and simultaneous release from the macromolecular carrier to present the active Pt(II) drug derivatives. In vitro investigations show a significantly enhanced intracellular uptake of Pt for the macromolecular prodrugs when compared to small molecule Pt complexes, which is also reflected in an increase in cytotoxicity. Interestingly, drug-resistant sublines also show a significantly smaller resistance against the conjugates compared to clinically established platinum drugs, indicating that an alternative uptake route of the Pt(IV) conjugates might also be able to overcome acquired resistance against Pt(II) drugs. In vivo studies of a selected conjugate show improved tumor shrinkage compared to the respective Pt(IV) complex.

Multi-scale imaging of anticancer platinum(iv) compounds in murine tumor and kidney

Nano-scale secondary ion mass spectrometry (NanoSIMS) enables trace element and isotope analyses with high spatial resolution. This unique capability has recently been exploited in several studies analyzing the subcellular distribution of Au and Pt anticancer compounds. However, these studies were restricted to cell culture systems. To explore the applicability to the in vivo setting, we developed a combined imaging approach consisting of laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), NanoSIMS and transmission electron microscopy (TEM) suitable for multi-scale detection of the platinum distribution in tissues. Applying this approach to kidney and tumor samples upon administration of selected platinum(iv) anticancer prodrugs revealed uneven platinum distributions on both the organ and subcellular scales. Spatial platinum accumulation patterns were quantitatively assessed by LA-ICP-MS in histologically heterogeneous organs (e.g., higher platinum accumulation in kidney cortex than in medulla) and used to select regions of interest for subcellular-scale imaging with NanoSIMS. These analyses revealed cytoplasmic sulfur-rich organelles accumulating platinum in both kidney and malignant cells. Those in the tumor were subsequently identified as organelles of lysosomal origin, demonstrating the potential of the combinatorial approach for investigating therapeutically relevant drug concentrations on a submicrometer scale.

Abstract P3-10-01: A pilot feasibility study of the WISDOM study, a preference-tolerant randomized controlled trial evaluating a risk-based breast cancer screening strategy

Background: For almost 30 years, annual mammograms for women over 40 have been a cornerstone of the US strategy to reduce breast cancer mortality. Introduction of the 2009 USPSTF screening guidelines, though based on a thorough review of the scientific literature, has triggered scientific debate and a stalemate. The solution is not to prolong the controversy with repetitious reviews of past studies, but rather to test and implement a personalized model that leverages advances in breast cancer biology, risk assessment, and imaging to provide screening recommendations based upon well-characterized measures of risk. Our WISDOM (Women Informed to Screen Depending On Measures of risk) study, a preference-tolerant randomized controlled trial funded through PCORI, will evaluate whether such a risk-based screening strategy, compared to annual screening, is as safe, is less morbid, enables prevention and is preferred by women. This upcoming pilot study will test the feasibility and technical implementation of the WISDOM trial, focusing on recruitment, enrollment, and randomization processes, a coverage with evidence development approach to enable rapid adoption, and patient experience and satisfaction. Findings will directly inform implementation of the full trial, slated to begin in fall 2015 throughout the Athena Breast Health Network, a research and care collaboration across the five UC Medical Centers and Sanford Health.

Trial Design: 225 participants will be recruited from Athena patients receiving care at UCSF. Participants must be female; between age 40 and 75; have had a normal mammogram at UCSF in the past 6 months; and in the Athena research cohort. Exclusion criteria are a breast cancer or DCIS diagnosis; inability to provide consent; or inability to speak English. After education about the trial, patients will be asked if they are willing to be randomized to either the risk-based or annual screening schedule; if not, they can self-assign to their preferred schedule. The randomized and self-assigned cohorts will receive the same interventions. The risk-based screening strategy will incorporate risk assessment based on the latest Breast Cancer Surveillance Consortium model along with established and recently validated genetic risk factors, co-morbidities, and breast density, and will be used to tailor individual recommendations for starting and stopping age, frequency, and screening modality. A saliva assay will be administered to participants in the risk-based arm to screen for genetic breast cancer risk factors (BRCA1 & BRCA2 + 9 additional genes + 81 single nucleotide polymorphisms).

Statistical Methods: Descriptive statistics for the proportion of women who are willing to be randomized, choose the risk-based arm in the self-assigned cohort, and are willing to accept their assigned or chosen screening schedule, as well as the distribution of participant anxiety scores, will be analyzed. This will inform statistical design for the full trial, including the number of women who should be approached to enroll 65,000 randomized participants and the sample size needed to measure anxiety and decision regret in the randomized cohort. Results from the pilot will be available September 30, 2015.

Citation Format: Narasimmaraj PR, Stover Fiscalini A, Kaplan CP, van't Veer LJ, Hallada AM, Thompson CK, Theiner S, Borowsky A, Naeim A, Anton-Culver H, LaCroix A, Athena Breast Health Network Investigators, Esserman LJ. A pilot feasibility study of the WISDOM study, a preference-tolerant randomized controlled trial evaluating a risk-based breast cancer screening strategy. [abstract]. In: Proceedings of the Thirty-Eighth Annual CTRC-AACR San Antonio Breast Cancer Symposium: 2015 Dec 8-12; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2016;76(4 Suppl):Abstract nr P3-10-01.

Behavior of platinum(iv) complexes in models of tumor hypoxia: cytotoxicity, compound distribution and accumulation

Hypoxia in solid tumors remains a challenge for conventional cancer therapeutics. As a source for resistance, metastasis development and drug bioprocessing, it influences treatment results and disease outcome. Bioreductive platinum(iv) prodrugs might be advantageous over conventional metal-based therapeutics, as biotransformation in a reductive milieu, such as under hypoxia, is required for drug activation. This study deals with a two-step screening of experimental platinum(iv) prodrugs with different rates of reduction and lipophilicity with the aim of identifying the most appropriate compounds for further investigations. In the first step, the cytotoxicity of all compounds was compared in hypoxic multicellular spheroids and monolayer culture using a set of cancer cell lines with different sensitivities to platinum(ii) compounds. Secondly, two selected compounds were tested in hypoxic xenografts in SCID mouse models in comparison to satraplatin, and, additionally, (LA)-ICP-MS-based accumulation and distribution studies were performed for these compounds in hypoxic spheroids and xenografts. Our findings suggest that, while cellular uptake and cytotoxicity strongly correlate with lipophilicity, cytotoxicity under hypoxia compared to non-hypoxic conditions and antitumor activity of platinum(iv) prodrugs are dependent on their rate of reduction.

LA-ICP-MS imaging in multicellular tumor spheroids - a novel tool in the preclinical development of metal-based anticancer drugs

A novel application of advanced elemental imaging offers cutting edge in vitro assays with more predictive power on the efficacy of anticancer drugs in preclinical development compared to two dimensional cell culture models. We propose LA-ICP-MS analysis of multicellular spheroids, which are increasingly being used as three dimensional (3D) models of tumors, for improving the in vitro evaluation of anticancer metallodrugs. The presented strategy is very well suited for screening drug-tumor penetration, a key issue for drug efficacy. A major advantage of tumor spheroid models is that they enable us to create a tissue-like structure and function. With respect to 2D culture on the one hand and in vivo models on the other, multicellular spheroids thus show intermediate complexity, still allowing high repeatability and adequate through-put for drug research. This strongly argues for the use of spheroids as bridging models in preclinical anticancer drug development. Probing the lateral platinum distribution within these tumor models allows visualizing the penetration depth and targeting of platinum-based complexes. In the present study, we show for the first time that spatially-resolved metal accumulation in tumor spheroids upon treatment with platinum compounds can be appropriately assessed. The optimized LA-ICP-MS setup allowed discerning the platinum localization in different regions of the tumor spheroids upon compound treatment at biologically relevant (low micromolar) concentrations. Predominant platinum accumulation was observed at the periphery as well as in the center of the spheroids. This corresponds to the proliferating outermost layers of cells and the necrotic core, respectively, indicating enhanced platinum sequestration in these regions.

Tumor microenvironment in focus: LA-ICP-MS bioimaging of a preclinical tumor model upon treatment with platinum(IV)-based anticancer agents

The selection of drug candidates for entering clinical development relies on in vivo testing in (solid) tumor animal models. However, the heterogeneity of tumor tissue (e.g. in terms of drug uptake or tissue composition) is rarely considered when testing novel drug candidates. Therefore, we used the murine colon cancer CT-26 tumor model to study the spatially-resolved drug distribution in tumor tissue upon repetitive treatment of animals over two weeks with three investigational platinum(IV)-based anticancer agents, oxaliplatin or satraplatin. A quantitative laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) imaging method revealed a heterogeneous platinum distribution, which correlated well with the histologic features of the tumor and surrounding tissue at the microscopic level. In most of the cases, higher amounts of intratumoral platinum were found in the surrounding tissue than in the malignant parts of the sample. This indicates that determination of average platinum amounts (e.g. by microwave-assisted digestion of the sample followed by analysis with ICP-MS) might overestimate the drug uptake in tumor tissue causing misleading conclusions. In addition, we studied the platinum distribution in the kidneys of treated animals to probe if accumulation in the cortex and medulla predict potential nephrotoxicity. A 10-fold increase of platinum in the cortex of the kidney over the medulla was observed for oxaliplatin and satraplatin. Although these findings are similar to those in the platinum distribution of the nephrotoxic anticancer drug cisplatin, treatment with the compounds of our study did not show signs of nephrotoxicity in clinical use or clinical trials (oxaliplatin, satraplatin) and did not result in the alteration of renal structures. Thus, predicting the side effects based on bioimaging data by LA-ICP-MS should be considered with caution. To the best of our knowledge, this is the first LA-ICP-MS study on spatially-resolved platinum accumulation in tissues after repetitive platinum-based anticancer drug treatment of mice bearing a preclinical tumor model.

Extravasation of Pt-based chemotherapeutics – bioimaging of their distribution in resectates using laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS)

Spatially resolved quantification of platinum distribution in patients that exhibited extravasation was feasible up to 4 weeks upon drug application.

Comparative in vitro and in vivo pharmacological investigation of platinum(IV) complexes as novel anticancer drug candidates for oral application

Platinum(IV) complexes are promising candidates as prodrugs for oral application in anticancer chemotherapy. However, only a few Pt(IV) compounds entered (pre)clinical trials, e.g. satraplatin, while most of the others were only tested in vitro. Aim of the study was investigation of the in vivo pharmacological behavior as well as the anticancer activity of two novel platinum(IV) complexes vs. satraplatin. The drugs were selected due to significantly different in vitro cytotoxicity while sharing some physicochemical properties (e.g. lipophilicity). Initial experiments indicated that the highly in vitro cytotoxic compound 1 ((OC-6-33)-dichloridobis((4-ethoxy)-4-oxobutanoato)-bis(ethylamine)platinum(IV)) was also characterized by high drug absorption and tissue platinum levels after oral application. Interestingly, analysis of serum samples using SEC-ICP-MS revealed that the administered drugs have completely been metabolized and/or bound to proteins in serum within 2 h after treatment. With regard to the activity in vivo, the outcomes were rather unexpected: although potent anticancer effect of 1 was observed in cell culture, the effects in vivo were rather minor. Nevertheless, 1 was superior to 2 ((OC-6-33)-diammine(cyclobutane-1,1-dicarboxylato)-bis((4-cyclopentylamino)-4-oxobutanoato)platinum(IV)) after i.p. administration, which was, at least to some extent, in accordance to the cell culture experiments. After oral gavage, both compounds exhibited comparable activity. This is remarkable considering the distinctly lower activity of 2 in cell culture as well as the low platinum levels detected both in serum and tissues after oral application. Consequently, our data indicate that the prediction of in vivo anticancer activity by cell culture experiments is not trivial, especially for orally applied drugs.

A novel class of bis- and tris-chelate diam(m)inebis(dicarboxylato)platinum(IV) complexes as potential anticancer prodrugs

A novel class of platinum(IV) complexes of the type [Pt(Am)(R(COO)2)2], where Am is a chelating diamine or two monodentate am(m)ine ligands and R(COO)2 is a chelating dicarboxylato moiety, was synthesized. For this purpose, the reaction between the corresponding tetrahydroxidoplatinum(IV) precursors and various dicarboxylic acids, such as oxalic, malonic, 3-methylmalonic, and cyclobutanedicarboxylic acid, was utilized. All new compounds were characterized in detail, using 1D and 2D NMR techniques, ESI-MS, FTIR spectroscopy, elemental analysis, TGA, and X-ray diffraction. Their in vitro cytotoxicity was determined in a panel of human tumor cell lines (CH1, SW480 and A549) by means of the MTT colorimetric assay. Furthermore, the lipophilicity and redox properties of the novel complexes were evaluated in order to better understand their pharmacological behavior. The most promising drug candidate, 4b (Pt(DACH)(mal)2), demonstrated low in vivo toxicity but profound anticancer activity against both the L1210 leukemia and CT-26 colon carcinoma models.