Evaluation of Small Molecule Drug Uptake in Patient-Derived Prostate Cancer Explants by Mass Spectrometry

Abstract

Patient-derived explant (PDE) culture of solid tumors is increasingly being applied to preclinical evaluation of novel therapeutics and for biomarker discovery. In this technique, treatments are added to culture medium and penetrate the tissue via a gelatin sponge scaffold. However, the penetration profile and final concentrations of small molecule drugs achieved have not been determined to date. Here, we determined the extent of absorption of the clinical androgen receptor antagonist, enzalutamide, into prostate PDEs, using liquid chromatography-tandem mass spectrometry (LC-MS/MS) and matrix-assisted laser/desorption ionisation (MALDI) mass spectrometry imaging (MSI). In a cohort of 11 PDE tissues from eight individual patients, LC-MS/MS quantification of PDE homogenates confirmed enzalutamide (10 µM) uptake by all PDEs, which reached maximal average tissue concentration of 0.24–0.50 ng/µg protein after 48 h culture. Time dependent uptake of enzalutamide (50 µM) in PDEs was visualized using MALDI MSI over 24–48 h, with complete penetration throughout tissues evident by 6 h of culture. Drug signal intensity was not homogeneous throughout the tissues but had areas of markedly high signal that corresponded to drug target (androgen receptor)-rich epithelial regions of tissue. In conclusion, application of MS-based drug quantification and visualization in PDEs, and potentially other 3-dimensional model systems, can provide a more robust basis for experimental study design and interpretation of pharmacodynamic data.

MALDI MSI Reveals the Spatial Distribution of Protein Markers in Tracheobronchial Lymph Nodes and Lung of Pigs after Respiratory Infection

“…Immunohistochemistry (IHC) is a classical technique to study protein localization in tissues, as well as to confirm a protein's identity, and it is therefore complimentary to MALDI MSI studies [35]. IHC analysis was used in many protein or cancer studies as support method for MALDI MSI such as studies of prostate tumor [23,36], skin tumors [31,32], head and neck tumor [37] or non-small cell lung tumor [38].…”

Three-Dimensional Cell Cultures as an In Vitro Tool for Prostate Cancer Modeling and Drug Discovery

“…Based on these premises, an alternative, promising approach consisting of the ex vivo 3D culture of freshly excised PCa specimens, called patient-derived explants (PDEs), has been recently proposed. This protocol, which involves the growth of tissue pieces or slices on sponge scaffolds, offers a cost-effective model that recalls the native tumor mass architecture and allows the direct assessment of treatment responses on an individual patient’s sample, enabling the development of personalized medicine strategies [ 33 , 34 , 35 , 36 , 37 , 38 ].…”

The Space Dimension at the Micro Level: Mass Spectrometry Imaging of Drugs in Tissues

“…To conclude with the drugs used against tumors, Mutuku et al (2019) and Végvári et al (2016) studied enzalutamide and tamoxifen ex vivo with the drugs applied on human biopsies. In the former study, the diffusion of enzalutamide, an androgen receptor antagonist, was determined in prostate explants using MALDI‐MSI.…”