Imaging of prostate cancer: optimizing affinity to prostate specific membrane antigen by spacer modifications in a tumor spheroid model

Affinity probes based on small-molecule inhibitors for tumor imaging

Methods for molecular imaging of target areas, including optical imaging, radionuclide imaging, magnetic resonance imaging and other imaging technologies, are helpful for the early diagnosis and precise treatment of cancers. In addition to cancer management, small-molecule inhibitors are also used for developing cancer target probes since they act as the tight-binding ligands of overexpressed proteins in cancer cells. This review aims to summarize the structural designs of affinity probes based on small-molecule inhibitors from the aspects of the inhibitor, linker, dye and radionuclide, and discusses the influence of the modification of these structures on affinity and pharmacokinetics. We also present examples of inhibitor affinity probes in clinical applications, and these summaries will provide insights for future research and clinical translations.

A Supramolecular Self-Assembling Nanoagent by Inducing Intracellular Aggregation of PSMA for Prostate Cancer Molecularly Targeted Theranostics

Prostate cancer (PCa) with prostate-specific membrane antigen (PSMA)-specific high expression is well suited for molecularly targeted theranostics. PSMA expression correlates with the malignancy of PCa, and its dimeric form can promote tumor progression by exerting enzymatic activity to activate downstream signal transduction. However, almost no studies have shown that arresting the procancer signaling of the PSMA receptors themselves can cause tumor cell death. Meanwhile, supramolecular self-assembling peptides are widely used to design anticancer agents due to their unique and excellent properties. Here, a PSMA-targeting supramolecular self-assembling nanotheranostic agent, DBT-2FFGACUPA, which actively targets PSMA receptors on PCa cell membranes and induces them to enter the cell and form large aggregates, is developed. This process not only selectively images PSMA-positive tumor cells but also suppresses the downstream procancer signals of PSMA, causing tumor cell death. This work provides an alternative approach and an advanced agent for molecularly targeted theranostics options in PCa that can induce tumor cell death without relying on any reported anticancer drugs.

Agarose Micro-Well Platform for Rapid Generation of Homogenous 3D Tumor Spheroids

In recent years, 3D culture of tumor spheroids has managed to revolutionize cancer research and drug discovery. 2D monolayer cells grown in cell culture flasks undergo radical changes in cell behavior, structure, and function owing to varying environmental cues and are unable to provide predictive data for preclinical evaluation. 3D tumor spheroids can better recapitulate tumor architecture, cell-cell and cell-matrix connectivity, and the tissue complexity of tumors grown in animal models. However, many of the existing techniques to culture 3D spheroids are time-consuming and ineffective and produce irregular-shaped spheroids that cannot be easily incorporated in biological assays. The set of protocols described herein makes use of a commercial hair brush as a template to create concave micro-well impressions in agarose. This technique is easy, inexpensive, and adaptable and also has the ability to produce uniform, homogenous cancer spheroids, with large diameter (∼1000 μm) and thickness (∼250 μm), within 24 to 48 hr after cell seeding. The 3D spheroids produced using the agarose micro-well platform function as an excellent 3D in vitro model for understanding the extent of penetration, uptake, and distribution of targeted cargos such as a diagnostic or therapeutic agents for identification and treatment of cancer. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Fabrication of agarose micro-well scaffold for growing tumor spheroids using a commercial hair brush Basic Protocol 2: Formation of homogenous tumor spheroids in agarose micro-well platform Basic Protocol 3: Assessing viability of 3D tumor spheroids grown in agarose micro-wells using confocal microscopy Basic Protocol 4: Analyzing uptake and penetration of targeted fluorescent bioconjugate in 3D tumor spheroids using two-photon imaging.