Monitoring of hexyl 5-aminolevulinate-induced photodynamic therapy in rat bladder cancer by optical spectroscopy

Investigations on correlations between changes of optical tissue properties and NMR relaxation times

BACKGROUND

Accurate light dosimetry is a complex remaining challenge in interstitial photodynamic therapy (iPDT) for malignant gliomas. The light dosimetry should ideally be based on the tissue morphology and the individual optical tissue properties of each tissue type in the target region. First investigations are reported on using NMR information to estimate changes of individual optical tissue properties.

METHODS

Porcine brain tissue and optical tissue phantoms were investigated. To the porcine brain, supplements were added to simulate an edema or high blood content. The tissue phantoms were based on agar, Lipoveneous, ink, blood and gadobutrol (Gd-based MRI contrast agent). The concentrations of phantom ingredients and tissue additives are varied to compare concentration-dependent effects on optical and NMR properties. A 3-tesla whole-body MRI system was used to determine T1 and T2 relaxation times. Optical tissue properties, i.e., the spectrally resolved absorption and reduced scattering coefficient, were obtained using a single integrating sphere setup. The observed changes of NMR and optical properties were compared to each other.

RESULTS

By adjusting the NMR relaxation times and optical tissue properties of the tissue phantoms to literature values, recipes for human brain tumor, white matter and grey matter tissue phantoms were obtained that mimic these brain tissues simultaneously in both properties. For porcine brain tissue, it was observed that with increasing water concentration in the tissue, both NMR-relaxation times increased, while µa decreased and µs' increased at 635 nm. The addition of blood to porcine brain samples showed a constant T1, while T2 shortened and the absorption coefficient at 635 nm increased.

CONCLUSIONS

In this investigation, by changing sample contents, notable changes of both NMR relaxation times and optical tissue properties have been observed and their relations examined. The developed dual NMR/optical tissue phantoms can be used in iPDT research, clinical training and demonstrations.

Antitumor Effect and Induced Immune Response Following Exposure of Hexaminolevulinate and Blue Light in Combination with Checkpoint Inhibitor in an Orthotopic Model of Rat Bladder Cancer

Previous studies have found that use of hexaminolevulinate (HAL) and blue light cystoscopy (BLC) during treatment of bladder cancer had a positive impact on overall survival after later cystectomy, indicating a potential treatment effect beyond improved diagnostic accuracy. The aim of our study was to determine whether HAL and BL mimicking clinically relevant doses in an orthotopic rat model could have therapeutic effect by inducing modulation of a tumor-specific immune response. We also assessed whether administration with a checkpoint inhibitor could potentiate any effects observed. Rats were subjected to HAL BL alone and in combination with anti-PD-L1 and assessed for anti-tumor effects and effects on immune markers. Positive anti-tumor effect was observed in 63% and 31% of rats after, respectively, 12 and 30 days after the procedure, together with a localization effect of CD3+ and CD8+ cells after 30 days. Anti-tumor effect at 30 days increases from 31% up to 38% when combined with intravesical anti-PD-L1. In conclusion, our study demonstrated treatment effects with indications of systemic immune activation at diagnostic doses of HAL and blue light. The observed treatment effect seemed to be enhanced when used in combination with intravesically administrated immune checkpoint inhibitor.

Amphiphilic Rhenium-Oxo Corroles as a New Class of Sensitizers for Photodynamic Therapy

A set of rhenium(V)-oxo meso-triarylcorroles bearing ester and carboxylic acid functionalities were synthesized with a view to determining their potential for photodynamic therapy. Toward this end, we measured their near-IR phosphorescence and their ability to sensitize singlet oxygen formation. The two esters studied, Re^VO 5,10,15-tris(meta-carbomethoxyphenyl)corrole and Re^VO 5,10,15-tris(para-carbomethoxyphenyl)corrole, were found to exhibit phosphorescence quantum yields of around 1% and fairly long phosphorescence lifetimes of about 60 μs in toluene. The corresponding carboxylic acids, which were examined in ethanolic/aqueous media, in contrast, showed much lower phosphorescence quantum yields on the order of 0.01% and somewhat shorter phosphorescent lifetimes. The quantum yields for singlet oxygen formation, on the other hand, turned out to be equally high (0.72 ± 0.02) for the esters and corresponding carboxylic acids. For the two carboxylic acids, we also carried out photocytotoxicity measurements on rat bladder cancer cells (AY27) and human colon carcinoma cells (WiDr). Cell viability measurements (MTT assays) indicated 50% cell death (LD₅₀) for AY27 cells upon 5 min of blue light exposure with the meta carboxylic acid and upon 7 min of exposure with the para carboxylic acid; complete cell death resulted after 20 min for both compounds. The WiDr cells proved less sensitive, and LD₅₀ values were reached after 8 and 12 min illumination with the meta and para carboxylic acids, respectively.

Fluorescence and Treatment Light Monitoring for Interstitial Photodynamic Therapy

In interstitial photodynamic therapy, light is distributed to the tumor via light diffusers. The light dose and the related phototoxic effect achieved throughout the target volume critically depend on absorption, scattering and diffuser positioning. Using liquid tissue phantoms, we investigated the dependencies of treatment light transmission and protoporphyrin IX (PpIX) fluorescence on these parameters. This enabled monitoring hemoglobin oxygenation and methemoglobin formation during irradiation (635 nm, 200 mW cm^-1 diffuser length). Starting with two parallel cylindrical diffusers at 10 mm radial separation, the light transmitted between the fibers was largely determined by the minimal distance between the diffusers, but rather insensitive to an additional axial displacement or tilting of one fiber with respect to the other. For fixed distance between the diffusor centers, however, tilting up to direct contact resulted in a 10-fold signal increase. For hemoglobin within erythrocytes, irradiation leads to photobleaching of PpIX without marked change in hemoglobin oxygenation until hemolysis occurs. Afterward, hemoglobin is rapidly deoxygenized and methemoglobin is formed, leading to a dramatic increase in absorption. For lysed blood, these effects start immediately. A comparison of intraoperative monitoring of the signals with the experimental results might help prevent insufficient treatment by reconsidering treatment planning or prolonging irradiation.

In vitro and in vivo effects of HAL on porphyrin production in rat bladder cancer cells (AY27)

Aminolevulinic acid and hexyl-aminolevulinate serve as biological precursors to produce photosensitive porphyrins in cells via the heme biosynthetic pathway. This pathway is integral to porphyrin-based photodynamic diagnosis and therapy. By adding exogenous hexyl-aminolevulinate to rat bladder cancer cells (AY27, in vitro) and an animal bladder cancer model (in vivo), fluorescent endogenous porphyrin production was stimulated. Lipophilic protoporphyrin IX was identified as the dominant species by reverse high-pressure liquid chromatography. Subcellular porphyrin localization in the AY27 cells was evaluated by confocal laser scanning microscopy and showed almost quantitative bleaching after 20 s. From this study, we ascertained that the protocol described herein is suitable for hexyl-aminolevulinate-mediated photodynamic therapy and diagnosis when protoporphyrin IX is the active agent.

"Two hits - one stone"; increased efficacy of cisplatin-based therapies by targeting PCNA's role in both DNA repair and cellular signaling

Low response rate and rapid development of resistance against commonly used chemotherapeutic regimes demand new multi-targeting anti-cancer strategies. In this study, we target the stress-related roles of the scaffold protein PCNA with a cell-penetrating peptide containing the PCNA-interacting motif APIM. The APIM-peptide increased the efficacy of cisplatin-based therapies in a muscle-invasive bladder cancer (MIBC) solid tumor model in rat and in bladder cancer (BC) cell lines. By combining multiple omics-levels, from gene expression to proteome/kinome and metabolome, we revealed a unique downregulation of the EGFR/ERBB2 and PI3K/Akt/mTOR pathways in the APIM-peptide-cisplatin combination treated cells. Additionally, the combination treatment reduced the expression of anti-apoptotic proteins and proteins involved in development of resistance to cisplatin. Concurrently, we observed increased levels of DNA breaks in combination treated cells, suggesting that the APIM-peptide impaired PCNA - DNA repair protein interactions and reduced the efficacy of repair. This was also seen in cisplatin-resistant cells, which notably was re-sensitized to cisplatin by the APIM-peptide. Our data indicate that the increased efficacy of cisplatin treatment is mediated both via downregulation of known oncogenic signaling pathways and inhibition of DNA repair/translesion synthesis (TLS), thus the APIM-peptide hits both nuclear and cytosolic functions of PCNA. The novel multi-targeting strategy of the APIM-peptide could potentially improve the efficacy of chemotherapeutic regiments for treatment of MIBC, and likely other solid tumors.

Photochemical internalization in bladder cancer - development of an orthotopic in vivo model

The possibility of using photochemical internalization (PCI) to enhance the effects of the cytotoxic drug bleomycin is investigated, together with photophysical determination and outlines of a possible treatment for intravesical therapy of bladder cancer. In vitro experiments indicated that the employment of PCI technology using the novel photosensitizer TPCS_2a® can enhance the cytotoxic effect of bleomycin in bladder cancer cells. Furthermore, experiments in an orthotopic in vivo bladder cancer model show an effective reduction in both the necrotic area and the bladder weight after TPCS_2a based photodynamic therapy (PDT). The tumor selectivity and PDT effects may be sufficient to destroy tumors without damaging the detrusor muscle layer. Our results present a possible new treatment strategy for non-muscle invasive bladder cancer, with the intravesical instillation of the photosensitizer and bleomycin followed by illumination through an optic fiber by using a catheter.

Early assessment of tumor response to photodynamic therapy using combined diffuse optical and diffuse correlation spectroscopy to predict treatment outcome

Photodynamic therapy (PDT) of cancer involves the use of a photosensitizer that can be light-activated to eradicate tumors via direct cytotoxicity, damage to tumor vasculature and stimulating the body's immune system. Treatment outcome may vary between individuals even under the same regime; therefore a non-invasive tumor response monitoring system will be useful for personalization of the treatment protocol. We present the combined use of diffuse optical spectroscopy (DOS) and diffuse correlation spectroscopy (DCS) to provide early assessment of tumor response. The relative tissue oxygen saturation (rStO2) and relative blood flow (rBF) in tumors were measured using DOS and DCS respectively before and after PDT with reference to baseline values in a mouse model. In complete responders, PDT-induced decreases in both rStO2 and rBF levels were observed at 3 h post-PDT and the rBF remained low until 48 h post-PDT. Recovery of these parameters to baseline values was observed around 2 weeks after PDT. In partial responders, the rStO2 and rBF levels also decreased at 3 h post PDT, however the rBF values returned toward baseline values earlier at 24 h post-PDT. In contrast, the rStO2 and rBF readings in control tumors showed fluctuations above the baseline values within the first 48 h. Therefore tumor response can be predicted at 3 to 48 h post-PDT. Recovery or sustained decreases in the rBF at 48 h post-PDT corresponded to long-term tumor control. Diffuse optical measurements can thus facilitate early assessment of tumor response. This approach can enable physicians to personalize PDT treatment regimens for best outcomes.

Ruthenium porphyrin-induced photodamage in bladder cancer cells

Photodynamic therapy (PDT) is a noninvasive treatment for solid malignant and flat tumors. Light activated sensitizers catalyze photochemical reactions that produce reactive oxygen species which can cause cancer cell death. In this work we investigated the photophysical properties of the photosensitizer ruthenium(II) porphyrin (RuP), along with its PDT efficiency onto rat bladder cancer cells (AY27). Optical spectroscopy verified that RuP is capable to activate singlet oxygen via blue and red absorption bands and inter system crossing (ISC) to the triplet state. In vitro experiments on AY27 indicated increased photo-toxicity of RuP (20μM, 18h incubation) after cell illumination (at 435nm), as a function of blue light exposure. Cell survival fraction was significantly reduced to 14% after illumination of 20μM RuP with 15.6J/cm(2), whereas the "dark toxicity" of 20μM RuP was 17%. Structural and morphological changes of cells were observed, due to RuP accumulation, as well as light-dependent cell death was recorded by confocal microscopy. Flow cytometry verified that PDT-RuP (50μM) triggered significant photo-induced cellular destruction with a photoxicity of (93%±0.9%). Interestingly, the present investigation of RuP-PDT showed that the dominating mode of cell death is necrosis. RuP "dark toxicity" compared to the conventional chemotherapeutic drug cisplatin was higher, both evaluated by the MTT assay (24h). In conclusion, the present investigation shows that RuP with or without photoactivation induces cell death of bladder cancer cells.

Increased Anticancer Efficacy of Intravesical Mitomycin C Therapy when Combined with a PCNA Targeting Peptide

Non-muscle-invasive bladder cancers (NMIBCs) are tumors confined to the mucosa or the mucosa/submucosa. An important challenge in treatment of NMIBC is both high recurrence and high progression rates. Consequently, more efficacious intravesical treatment regimes are in demand. Inhibition of the cell's DNA repair systems is a new promising strategy to improve cancer therapy, and proliferating cell nuclear antigen (PCNA) is a new promising target. PCNA is an essential scaffold protein in multiple cellular processes including DNA replication and repair. More than 200 proteins, many involved in stress responses, interact with PCNA through the AlkB homologue 2 PCNA-interacting motif (APIM), including several proteins directly or indirectly involved in repair of DNA interstrand crosslinks (ICLs). In this study, we targeted PCNA with a novel peptide drug containing the APIM sequence, ATX-101, to inhibit repair of the DNA damage introduced by the chemotherapeutics. A bladder cancer cell panel and two different orthotopic models of bladder cancer in rats, the AY-27 implantation model and the dietary BBN induction model, were applied. ATX-101 increased the anticancer efficacy of the ICL-inducing drug mitomycin C (MMC), as well as bleomycin and gemcitabine in all bladder cancer cell lines tested. Furthermore, we found that ATX-101 given intravesically in combination with MMC penetrated the bladder wall and further reduced the tumor growth in both the slow growing endogenously induced and the rapidly growing transplanted tumors. These results suggest that ATX-101 has the potential to improve the efficacy of current MMC treatment in NMIBC.

Tissue responses to hexyl 5-aminolevulinate-induced photodynamic treatment in syngeneic orthotopic rat bladder cancer model: possible pathways of action

Orthotopic bladder cancer model in rats mimics human bladder cancer with respect to urothelial tumorigenesis and progression. Utilizing this model at pT1 (superficial stage), we analyze the tissue responses to hexyl 5-aminolevulinate-induced photodynamic therapy (HAL-PDT). In comparison to untreated rats, HAL-PDT causes little change in tumor-free rat bladder but induces inflammatory changes with increased lymphocytes and mononuclear cell infiltration in rat bladders with tumor. Immunohistochemistry reveals that HAL-PDT is without effect on proliferating cell nuclear antigen expression within the tumor and increases caspase-3 expression in both normal urothelium and the tumor. Transmission electron microscopy reveals severe mitochondrial damage, formations of apoptotic bodies, vacuoles, and lipofuscin bodies, but no microvillus-formed niches in HAL-PDT-treated bladder cancer rats. Bioinformatics analysis of the gene expression profile indicates an activation of T-cell receptor signaling pathway in bladder cancer rats without PDT. HAL-PDT increases the expression of CD3 and CD45RA in the tumor (determined by immunohistochemistry). We suggest that pathways of action of HAL-PDT may include, at least, activations of mitochondrial apoptosis and autophagy, breakdown of cancer stem cell niches, and importantly, enhancement of T-cell activation.

Monitoring interstitial m-THPC-PDT in vivo using fluorescence and reflectance spectroscopy

BACKGROUND AND OBJECTIVE

In order to understand the mechanisms of photodynamic therapy (PDT) it is important to monitor parameters during illumination that yield information on deposited PDT dose. The aim of this study is to investigate the possibility of monitoring implicit parameters, such as photobleaching, in addition to monitoring explicit parameters (fluence (rate), oxygenation, photosensitizer concentration) directly or indirectly. These parameters are monitored during PDT without interrupting the therapeutic illumination.

MATERIALS AND METHODS

Rats were injected with 0.3 mg kg(-1) m-THPC. Sixteen hours after administration the abdominal muscle in rats was irradiated for 1,500 seconds using clinically relevant fluence rates of 50, 100, and 250 mW cm(-1) of diffuser length at 652 nm. In addition to the linear diffuser for delivering treatment light, isotropic fiber-optic probes and fiber-optic probes for differential path-length spectroscopy (DPS) were placed on both sides of the muscle to monitor tissue physiological parameters, fluence rate, and fluorescence.

RESULTS

The m-THPC treatment groups show a decrease in fluence rate throughout PDT of 16%, 19%, and 27% for the 50, 100, and 250 mW cm(-1) groups, respectively. Both during and post-PDT differences in vascular response between treatment groups and animals within the same treatment group are observed. Furthermore we show fluence rate dependent bleaching of m-THPC up to a measured fluence rate of 100 mW cm(-1).

CONCLUSION

The data presented in this study show the possibility of simultaneously monitoring fluence (rate), fluorescence, hemoglobin oxygen saturation, and blood volume during PDT without interruptions to the therapeutic illumination. Differences in saturation profiles between animals and treatment groups indicate differences in vascular response during illumination. Furthermore, the relationship between fluence rate and m-THPC fluorescence photobleaching is complex in an interstitial environment.

Time- and Spectral-resolved two-photon imaging of healthy bladder mucosa and carcinoma in situ

Combined non-linear imaging techniques were used to deeply image human ex-vivo fresh biopsies of bladder as well as to discriminate between healthy bladder mucosa and carcinoma in situ. Morphological examination by two-photon excited fluorescence and second-harmonic generation has shown a good agreement with corresponding common routine histology performed on the same samples. Tumor cells appeared slightly different in shape and with a smaller cellular-to-nuclear dimension ratio with respect to corresponding normal cells. Further differences between the two tissue types were found in both spectral emission and fluorescence lifetime distribution by performing temporal- and spectral- resolved analysis of fluorescence. This method may represent a promising tool to be used in a multi-photon endoscope, in a confocal endoscope or in a spectroscopic probe for in-vivo optical diagnosis of bladder cancer.