Probing Hexaminolevulinate Mediated PpIX Fluorescence in Cancer Cell Suspensions in the Presence of Chemical Adjuvants

5-Aminolevulinic Acid: A Novel Approach to Improving Radioresistance in Prostate Cancer

Background/Objectives: Prostate cancer (PCa) cells may acquire radioresistance during radiation therapy (RT), resulting in PCa recurrence. This study was aimed at investigating the radiosensitizing effect of 5-aminolevulinic acid (5-ALA) on radioresistant PCa cells. Methods: Radioresistant PCa cells were developed through successive irradiation of two human PCa cell lines (PC-3 and DU 145) and a murine PCa cell line (Myc-CaP). The radiosensitivity of these PCa cells and the radiosensitizing effect of 5-ALA were evaluated using clonogenic assays. Mitochondrial accumulation of protoporphyrin IX (PpIX) and mitochondrial reactive oxygen species (ROS) were evaluated. A syngeneic mouse model with radioresistant PCa was established, and the immunohistochemistry of cell specimens from PCa patients with local recurrence after primary RT was examined. Results: Radioresistant PCa cells showed lower radiosensitivity compared to parental PCa cells. In radioresistant PCa cells with 5-ALA administration, compared to the group administered irradiation alone, the survival rate after irradiation was significantly reduced by promoting mitochondria-mediated apoptosis caused by increased PpIX accumulation and mitochondrial ROS generation. Similar results were observed in vivo. However, compared with parental PCa cells, radioresistant PCa cells were less affected by the radiosensitizing effect of 5-ALA, owing to decreased PpIX accumulation and mitochondrial ROS production caused by upregulated expression of the drug transporter ABCG2. ABCG2 expression was upregulated in human PCa specimens with post-RT recurrence. Conclusions: 5-ALA enhanced the antitumor effects of RT in radioresistant PCa cells; however, ABCG2 upregulation decreased PpIX accumulation, resulting in a reduced radiosensitizing effect of 5-ALA on radioresistant PCa cells compared with that on parental PCa cells. ABCG2 could be a potential therapeutic target for overcoming radioresistance.

Biomimetic Nanovesicle with Mitochondria-Synthesized Sonosensitizer and Mitophagy Inhibition for Cancer Sono-Immunotherapy

Mitochondria are crucial for both sonodynamic therapy and antitumor immunity. However, how to accurately damage mitochondria and meanwhile prevent the mitophagy and immune checkpoint inhibition is still a great challenge. Herein, hexyl 5-aminolevulinate hydrochloride (HAL) and 3-methyladenine (3MA) are loaded into the tumor cell-derived microparticle (X-MP), which can direct the target delivery of the prepared HAL/3MA@X-MP to the tumor cells. HAL induces the confined biosynthesis and accumulation of sonosensitizer PpIX in mitochondria, leading to the localized generation of reactive oxygen species (ROS) upon ultrasound irradiation and, thus, the efficient mitochondrial damage. Meanwhile, 3MA not only inhibits mitophagy but also down-regulates the PD-L1 expression, promoting the immunogenic cell death (ICD) while blocking the immune checkpoint recognition. The smart synergism of precise mitochondrial damage, mitophagy inhibition and antitumor immunity results in potent therapeutic efficacy without obvious side effects.

Effects of Supplemental Drugs on Hexaminolevulinate (HAL)-Induced PpIX Fluorescence in Bladder Cancer Cell Suspensions

Seven different inhibitors of the heme metabolic pathway were applied in combination with HAL to study the formation of PpIX in bladder cancer HT1197 and normal fibroblast HFFF2 cells ex vivo, specifically with the aim to increase the fluorescence contrast between cancer and non-cancer cells. The mRNA expression of enzymes involved in the heme biosynthesis pathway were measured via PCR following incubation with the drugs in order to link the fluorescence levels and metabolic activity. The exogenous administration of HAL does lead to cancer-specific PpIX accumulation. However, the contrast between cancer and normal cells in suspension was not enhanced by the enzyme inhibitors and iron-chelating agents tested, nor did the mRNA expression necessarily correlate with the fluorescence intensity. The results indicate that a difference in the metabolic activity of cells in suspension may limit the applicability of exogenous enzyme inhibitor administration as a mean to improve the fluorescence-based detection of cancer cells shed in body fluids.

Fluid Flow Dependency in Immunoselective Cell Capture via Liquid Biopsy

Liquid biopsy targets rare cells that overexpress disease-specific membrane markers and capture these cells via immunoaffinity. The diagnosis efficiency of liquid biopsy can be impaired by the presence of healthy adherent cells also expressing the same biomarkers. Here, we investigated the effect of settling times and rinsing flow rates on the efficiency of EpCAM-based immunocapture using both simulation and experiments with three different cell types. Cell-surface adhesion forces and shear rates were calculated to define the range of rinsing flow rates to test experimentally. Healthy adherent cells did not adhere to blocked immunofunctionalized surfaces within the timeframe of the experiment; however, healthy EpCAM positive cells did bind to the surface to some extent. The greatest difference in capture efficiency was obtained using a high rinsing flow rate of 25 mL/min following 40 min static incubation, indicating that optimizing rinsing flow rates could be a viable option to capture, more specifically, cancer cells overexpressing EpCAM.

Smart Tumor-Cell-Derived Microparticles Provide On-Demand Photosensitizer Synthesis and Hypoxia Relief for Photodynamic Therapy

Positioning essential elements of photodynamic therapy (PDT) near to mitochondria can conquer the rigorous spatiotemporal limitations of reactive oxygen species (ROS) transfer and make considerable differences in PDT. However, precise accumulation of photosensitizer (PS) and oxygen within mitochondria is still challenging. We simultaneously encapsulated hexyl 5-aminolevulinate hydrochloride (HAL) and 3-bromopyruvic acid (3BP) into microparticles collected from X-ray-irradiated tumor cells (X-MP). After systemic administration, the developed HAL/3BP@X-MP can specifically target and recognize tumor cells, where HAL induces efficient accumulation of PpIX in mitochondria via the intrinsic haem biosynthetic pathway. Meanwhile, 3BP remarkably increases the oxygen supply by inhibiting mitochondrial respiration. The accurate co-localization and prompt encounter of PpIX and oxygen produce sufficient ROS to directly disrupt mitochondria, resulting in significantly improved PDT outcomes.

Improving hexaminolevulinate enabled cancer cell detection in liquid biopsy immunosensors

Hexaminolevulinate (HAL) induced Protoporphyrin IX (PpIX) fluorescence is commonly used to differentiate cancer cells from normal cells in vivo, as for instance in blue light cystoscopy for bladder cancer diagnosis. A detailed approach is here provided to use this diagnostic principle ex vivo in an immunosensor device, towards enabling non-invasive cancer diagnostic from body fluids, such as urine. Several factors susceptible to affect the applicability of HAL-assisted diagnosis in body fluids were tested. These included the cell viability and its impact on PpIX fluorescence, the storage condition and shelf life of HAL premix reagent, light exposure (360–450 nm wavelengths) and its corresponding effect on both intensity and bleaching of the PpIX fluorescence as a function of the microscopy imaging conditions. There was no significant decrease in the viability of bladder cancer cells after 6 h at 4 °C (student’s t-test: p > 0.05). The cellular PpIX fluorescence decreased in a time-dependent manner when cancer cells were kept at 4 °C for extended period of time, though this didn’t significantly reduce the fluorescence intensity contrast between cancer and non-cancer cells kept in the same condition for 6 h. HAL premix reagent kept in long term storage at 4 °C induced stronger PpIX fluorescence than reagent kept in the − 20 °C freezer. The PpIX fluorescence was negatively affected by repeated light exposure but increased with illumination intensity and exposure time. Though this applied to both healthy and cancer cell lines, and therefore did not statistically improved the differentiation between cell types. This study revealed important experimental settings that need to be carefully considered to benefit from the analytical potential of HAL induced fluorescence when used in technologies for the diagnosis of cancer from body fluids.

Peptide-targeted dendrimeric prodrugs of 5-aminolevulinic acid: A novel approach towards enhanced accumulation of protoporphyrin IX for photodynamic therapy

Photodynamic therapy (PDT) is a promising approach for the targeted treatment of cancer and various other human disorders. An effective, clinically approved approach in PDT involves the administration of 5-aminolevulinic acid (ALA) to generate elevated levels of the natural photosensitiser protoporphyrin IX (PpIX). The development of prodrugs of ALA is of considerable interest as a means to enhance the efficiency and cell selectivity of PpIX accumulation for PDT applications. In this work a novel peptide-targeted dendrimeric prodrug of 5-aminolevulinic acid (ALA) 13 was synthesised which displays nine copies of ALA on a core structure that is linked to a homing peptide for targeted delivery to a specific cancer cell type. The synthesis was accomplished effectively via a flexible, modular solid phase and solution phase route, using a combination of solid phase peptide synthesis and copper-catalysed azide-alkyne cycloaddition chemistry. The prodrug system shows a sustained and enhanced production of protoporphyrin IX (PpIX) in the MDA-MB-231 cell line that over-expresses the epidernal growth factor receptor (EGFR+) in comparison to equimolar ALA and the corresponding non-targeted ALA dendrimer (nine copies of ALA). This study provides a proof of concept for the development of a new generation of prodrugs for ALA-based photodynamic therapy that can deliver an enhanced ALA payload to specific tissue types.

Cancer cell detection device for the diagnosis of bladder cancer from urine

Bladder cancer is common and has one of the highest recurrence rates. Cystoscopy, the current gold standard diagnosis approach, has recently benefited from the introduction of blue light assisted photodynamic diagnostic (PDD). While blue light cystoscopy improves diagnostic sensitivity, it remains a costly and invasive approach. Here, we present a microfluidic-based platform for non-invasive diagnosis which combines the principle of PDD with whole cell immunocapture technology to detect bladder cancer cells shed in patient urine ex vivo. Initially, we demonstrate with model cell lines that our non-invasive approach achieves highly specific capture rates of bladder cancer cells based on their Epithelial Cell Adhesion Molecule expression (>90%) and detection by the intensity levels of Hexaminolevulinic Acid-induced Protoporphyrin IX fluorescence. Then, we show in a pilot study that the biosensor platform successfully discriminates histopathologically diagnosed cancer patients (n = 10) from non-cancer controls (n = 25). Our platform can support the development of a novel non-invasive diagnostic device for post treatment surveillance in patients with bladder cancer and cancer detection in patients with suspected bladder cancer.