OPTIMISATION OF THE FORMATION AND DISTRIBUTION OF PROTOPORPHYRIN IX IN THE UROTHELIUM: AN IN VITRO APPROACH

Comparison of hexaminolevulinate (HAL) -guided versus white light transurethral resection for NMIBC: A systematic review and meta-analysis of randomized controlled trials

PURPOSE

We systematically reviewed the effectiveness of hexaminolevulinic acid (HAL) after traditional light cystoscopy vs. only white light cystoscopy (WLC) on nonmuscle-invasive bladder cancer (NMIBC) clinical outcomes.

METHODS

Systematic literature searches of PubMed, Embase, Web of Science, and the Cochrane database and reference lists were performed. A total of 12 randomized controlled trials (RCTs) of HAL fluorescent cystoscopy (FC) and WLC vs. white light cystoscopy alone for the diagnosis of initial or recurrent bladder cancer that reported bladder cancer recurrence, progression, recurrence-free survival (RFS), and other effects were selected for review.

RESULTS

Our results included 2,775 patients identified for analysis and showed that the HAL group had a lower recurrence rate than the white light cystoscopy group with a statistically significant difference (RR=0.77, 95% CI 0.69-0.85. P < 0.05), and this advantage still existed for patients receiving intravesical chemotherapy. There was also a statistically significant difference in favour of fluorescent cystoscopy in recurrence-free survival and progression rate (HR=0.79, 95% CI 0.67-0.92. P < 0.05, RR = 0.63, 95% CI 0.43-0.94. P < 0.05, respectively). The time to first recurrence was not significantly different from that in the WLC group (SMD=0.73, 95% CI, -0.39-1.85. P = 0.2). And the HAL group did not have a significantly reduced residual tumor rate (RR=0.59, 95% CI 0.23-1.51. P = 0.27).

CONCLUSIONS

Fluorescent cystoscopy was associated with a reduced risk of bladder cancer recurrence and reduced progression rate; it also has advantages for RFS. However, there was no significant difference in the rate of residual tumor and the time of first recurrence. More studies are needed to better understand the effects of the photosensitizer used on NMIBC patients.

Modulation and proteomic changes on the heme pathway following treatment with 5-aminolevulinic acid

5-ALA-mediated photodynamic therapy (PDT) has been developed around the heme biosynthesis physiological pathway. It is based on the external supplementation of 5 aminolevulinic acid (5-ALA), increasing the activity of the heme pathway and leading to a significant protoporphyrin IX (PpIX) accumulation. Interestingly, this metbolite accumulation is predominant in cancer cells, induced by a highly active metabolism, therefore limiting off-target side effects and increasing therapy specificity. Nevertheless, the intrinsic mechanism responsible of PpIX accumulation on cells following PDT is still unknown, limiting clinical therapy translation. In order to further understand the mechanisms behind 5-ALA-induced PDT, in this study we aimed to evaluate the proteome changes reported on the physiological heme pathway, in response to an external 5-ALA supplementation. We studied two different scenarios following 5-ALA treatment, 5-ALA accumulation (5-ALA metabolization into the heme pathway blocked with inhibitors) and accumulation of PpIX (normal heme pathway with 5-ALA supplementation). Therefore, we were able to characterize enzymatic changes and to describe bottlenecks in the pathway. Following mass spectrometry analysis, we reported significant differences between 5-ALA and PpIX effects on heme biosynthesis and regulation of degradation. 5-ALA accumulation significantly decreased porphobilinogen deaminase (HMBS) expression, while phorphyrins accumulation (PpIX) upregulated heme synthesis, specifically HMBS and uroporphyrinogen decarboxylase (UROD), and enhanced the enzymatic level of the heme degradation pathway, including Heme oxygenase 1 (HMOX1) and biliverdin reductase A (BLVRA). Interestingly, porphyrins induced a significant downregulation effect on oxygen-dependent coproporphyrinogen-III oxidase (CPOX). In conclusion, in this study we demonstrated that porphyrins play the most relevant role in heme biosynthesis modulation, while 5-ALA alone (PDT substrate) is not responsible of the main changes observed in this pathway during PDT treatment. Understanding heme enzyme modulation would help to design a more rational approach for patient treatment in the clinic. AIM: Effect of 5-ALA and porphyrins on the different Heme biosynthesis and degradation enzymes.

Perspectives on interstitial photodynamic therapy for malignant tumors

SIGNIFICANCE

Despite remarkable advances in the core modalities used in combating cancer, malignant diseases remain the second largest cause of death globally. Interstitial photodynamic therapy (IPDT) has emerged as an alternative approach for the treatment of solid tumors.

AIM

The aim of our study is to outline the advancements in IPDT in recent years and provide our vision for the inclusion of IPDT in standard-of-care (SoC) treatment guidelines of specific malignant diseases.

APPROACH

First, the SoC treatment for solid tumors is described, and the attractive properties of IPDT are presented. Second, the application of IPDT for selected types of tumors is discussed. Finally, future opportunities are considered.

RESULTS

Strong research efforts in academic, clinical, and industrial settings have led to significant improvements in the current implementation of IPDT, and these studies have demonstrated the unique advantages of this modality for the treatment of solid tumors. It is envisioned that further randomized prospective clinical trials and treatment optimization will enable a wide acceptance of IPDT in the clinical community and inclusion in SoC guidelines for well-defined clinical indications.

CONCLUSIONS

The minimally invasive nature of this treatment modality combined with the relatively mild side effects makes IPDT a compelling alternative option for treatment in a number of clinical applications. The adaptability of this technique provides many opportunities to both optimize and personalize the treatment.

The Dark Side: Photosensitizer Prodrugs

Photodynamic therapy (PDT) and photodiagnosis (PD) are essential approaches in the field of biophotonics. Ideally, both modalities require the selective sensitization of the targeted disease in order to avoid undesired phenomena such as the destruction of healthy tissue, skin photosensitization, or mistaken diagnosis. To a large extent, the occurrence of these incidents can be attributed to “background” accumulation in non-target tissue. Therefore, an ideal photoactive compound should be optically silent in the absence of disease, but bright in its presence. Such requirements can be fulfilled using innovative prodrug strategies targeting disease-associated alterations. Here we will summarize the elaboration, characterization, and evaluation of approaches using polymeric photosensitizer prodrugs, nanoparticles, micelles, and porphysomes. Finally, we will discuss the use of 5-aminolevulinc acid and its derivatives that are selectively transformed in neoplastic cells into photoactive protoporphyrin IX.

Novel endoscopic visualization techniques for bladder cancer detection: a review of the contemporary literature

PURPOSE OF REVIEW

To describe the principles of photodynamic diagnosis (PDD), narrow-band imaging (NBI) and Storz Professional Image Enhancement System (SPIES) techniques for the endoscopic management of nonmuscle-invasive bladder cancer (BCa) and to report their impact on clinical practice.

RECENT FINDINGS

PDD is associated with an increased sensitivity for detecting BCa specifically carcinoma in situ (CIS). Moreover, PDD has been shown to lower recurrence rate in comparison with white-light cystoscopy. The impact on progression-free survival is still unclear yet. NBI and, more recently, SPIES are two novel imaging techniques that do not require preoperative instillation of photosensitizing agents. NBI seems to be associated with lower recurrence rates. Nevertheless, further trials are necessary to confirm these results, in particular in high-risk lesions and CIS. Randomized clinical trials addressing the clinical impact of SPIES are ongoing.

SUMMARY

Novel endoscopic imaging techniques are useful diagnostic tools for evaluating BCa during cystoscopic diagnostic surveillance as well as during transurethral resection of the bladder. Although the standard of care remains white-light cystoscopy, these techniques provide higher sensitivity in detecting BCa especially CIS. The continued evidence also suggests that this increased detection leads to lower recurrence rates. The impact on progression and the cost-efficacy as well as selection remains to be refined.

Hexaminolevulinate in the Management of Nonmuscle Invasive Bladder Cancer: A Meta-Analysis

Objective: The objective of this study was to assess the effect of photodynamic diagnosis (PDD) using hexaminolevulinate on the diagnostic and therapeutic outcomes in nonmuscle invasive bladder cancer (NMIBC) patients. Methods: PubMed, Embase, and the Cochrane Library databases together with conference proceedings were searched. Results: Recurrence-free survival was significantly higher at 3, 6, 9, and 12 months in the PDD groups than in the white light cystoscopy (WLC) groups with the cumulative values of differences in recurrence rates at different follow-up intervals ranging from 8% to 11%. PDD identified additional tumors in 25% of all NMIBC patients and in 35% of carcinoma in situ (CIS) patients. In a patient-based analysis mean sensitivity of PDD versus WLC for all tumor detection was 94% and 84%, respectively. The assessed patient-based specificity was comparable for PDD and WLC in all types of tumors (55-56%); however, in CIS it was higher for PDD (82% vs. 72%). Conclusions: The meta-analysis confirms that PDD in conjunction with WLC detects significantly more tumors than WLC alone. Better diagnostic abilities of PDD transpose to significantly lower short-term recurrence rates after transurethral resection procedure and may improve treatment of NMIBC patients.

Urothelial Tumors and Dual-Band Imaging: A New Concept in Confocal Laser Endomicroscopy

OBJECTIVES

Confocal laser endomicroscopy (CLE) uses a low-energy laser light source to obtain microscopic histology images of bladder tissue exposed to a fluorescent dye. To evaluate the feasibility of using CLE with two fluorophores: fluorescein (FLUO) and hexylaminolevulinate (HAL) to determine histologic and cytologic bladder cancer criteria.

METHODS

Patients eligible for HAL-photodynamic diagnosis-assisted transurethral resection of bladder tumor were included. The procedures were performed with the patient under regional or general anesthesia (60-90 minutes) after bladder instillation of HAL (50 mL, 8 mmol/L; Hexvix^®; Ipsen, France). Resected tissue was examined ex vivo using CLE either with Cellvizio^® system (CVI) single laser (488 nm) or with Cellvizio Dual system (CVII) double laser (488, 660 nm).

RESULTS

Twenty-one patients were included, 12 examined by CVI and 9 by CVII. Sample examination on CVI after HAL-CLE-only histologic analysis was not possible because HAL is mostly cytoplasmic and gives poor details on cellular architecture. On the contrary, FLUO-CLE gives good extracellular architecture and not clear information of nucleocytoplasmic abnormality. Samples on CVII for seven out of nine patients clearly showed cytoplasm of suspect cells and nuclei. In real time, fluorescence observed on bandwidth (673-800 nm) with HAL and FLUO was associated with the presence of cancer, with a sensibility and specificity of 80% and 100%, respectively.

CONCLUSIONS

Real-time cytodetection was feasible using two fluorophores (FLUO and HAL) and the new system of CVII. This technology was useful to observe cytoplasm, nuclei, and nucleocytoplasmic abnormality, but an improved system is necessary (to overcome the overlapping of fluorescence) to increase the specificity.

Vulvovaginal photodynamic therapy vs. topical corticosteroids in genital erosive lichen planus: a randomized controlled trial

BACKGROUND

Genital erosive lichen planus (GELP) in women is a chronic inflammatory disease characterized by painful vulval and vaginal erosions. Topical photodynamic therapy (PDT) is increasingly used in premalignant and malignant diseases and may have an effect in inflammatory diseases.

OBJECTIVES

To assess the feasibility, efficacy and safety of hexyl 5-aminolevulinate-hydrocloride (HAL)-PDT in GELP.

METHODS

Forty women, diagnosed with GELP at a specialized vulva clinic, were randomized to one session HAL-PDT in vulva and/or vagina (n = 20) or daily applications of clobetasol propionate 0·05% ointment in vulva and optional hydrocortisone acetate 1·0% foam in vagina for 6 weeks (n = 20). After 6 weeks, all patients were allowed to use topical corticosteroids as needed. Clinical examinations were performed at weeks 0, 6 and 24, using a clinical score developed for the study. All patients wrote a weekly log on pain, topical corticosteroid use and adverse events.

RESULTS

Three patients, all in the corticosteroid group, withdrew from the study after 1-3 weeks. The mean reduction in clinical scores was similar in the PDT group and the corticosteroid group; 25% vs. 22% after 6 weeks (P = 0·787) and 35% vs. 38% after 24 weeks (P = 0·801). The mean reduction in pain visual analogue scale scores was 38% vs. 55% after 6 weeks (P = 0·286) and 39% vs. 12% after 24 weeks (P = 0·452). Patients in the PDT group reported significantly less topical corticosteroid use during weeks 7-24 than those in the corticosteroid group. No major adverse events were reported.

CONCLUSIONS

Vulvovaginal HAL-PDT seems to be an effective and safe treatment for GELP.

Early detection of urothelial premalignant lesions using hexaminolevulinate fluorescence cystoscopy in high risk patients

Background

To evaluate fluorescence cystoscopy with hexaminolevulinate (HAL) in the early detection of dysplasia (DYS) and carcinoma in situ (CIS) in select high risk patients.

Methods

We selected 30 consecutive bladder cancer patients at high risk for progression. After endoscopic resection, all patients received (a) induction BCG schedule when needed, and (b) white light and fluorescence cystoscopy after 3 months. HAL at doses of 85 mg (GE Healthcare, Buckinghamshire, United Kingdom) dissolved in 50 ml of solvent to obtain an 8 mmol/L solution was instilled intravesically with a 12 Fr catheter into an empty bladder and left for 90 minutes. The solution was freshly prepared immediately before instillation. Cystoscopy was performed within 120 minutes of bladder emptying. Standard and fluorescence cystoscopy was performed using a double light system (Combilight PDD light source 5133, Wolf, Germany) which allowed an inspection under both white and blue light.

Results

The overall incidence was 43.3% dysplasia, 23.3% CIS, and 13.3% superficial transitional cell cancer. In 21 patients, HAL cystoscopy was positive with one or more fluorescent flat lesions. Of the positive cases, there were 4 CIS, 10 DYS, 2 association of CIS and DYS, 4 well-differentiated non-infiltrating bladder cancers, and 1 chronic cystitis. In 9 patients with negative HAL results, random biopsies showed 1 CIS and 1 DYS. HAL cystoscopy showed 90.1% sensitivity and 87.5% specificity with 95.2% positive predictive value and 77.8% negative predictive value.

Conclusion

Photodynamic diagnosis should be considered a very important tool in the diagnosis of potentially evolving flat lesions on the bladder mucosa such as DYS and CIS. Moreover, detection of dysplasic lesions that are considered precursors of CIS may play an important role in preventing disease progression. In our opinion, HAL cystoscopy should be recommended in the early follow-up of high risk patients.

Hexyl aminolevulinate fluorescence cystoscopy in bladder cancer

Although bladder cancer occurs frequently, early diagnosis and complete removal of malignant lesions usually lead to good clinical outcomes. In the USA, white light cystoscopy (WLC) is commonly used for bladder cancer diagnosis and guidance of the surgical resection. However, with WLC malignant and precancerous lesions may be missed, resulting in a high rate of disease recurrence. Monitoring for and treating these recurrences carry high direct and indirect costs. Because hexyl aminolevulinate (HAL; 5-ALA-hexylester) fluorescence cystoscopy has greater sensitivity than WLC, especially for detecting early stage lesions, and its use provides more complete resection and lower disease recurrence, it has been recommended in European clinical guidelines. This article reports our own HAL experiences and first time recurrence data, describes how HAL was developed, provides key clinical trial results, and discusses how HAL, which has revolutionized fluorescence cystoscopy and bladder cancer care in Europe, may ultimately revolutionize bladder cancer care in the USA.

Comparation of liposomal formulations of ALA Undecanoyl ester for its use in photodynamic therapy

ALA administration has been used to induce the endogenous photosensitiser Protoporphyrin IX for photodynamic therapy (PDT) of tumours. However, the hydrophilic nature of ALA limits its ability to penetrate through skin restricting the use of ALA-PDT to superficial diseases. Lipophilic derivatives of ALA such as ALA Undecanoyl ester (Und-ALA) were designed to have better diffusing properties. However, Und-ALA, applied topically on the skin over the tumour, induced low porphyrin content. To improve Und-ALA efficacy we tested the efficacy of Und-ALA as porphyrin inducer, delivered in phosphatidylcholine and phosphatidylglycerol (PC-PG) or phosphatidylcholine and phosphatidic acid (PC-PA) liposomal formulations. Entrapment of Und-ALA into PC-PA or PC-PG liposomes resulted in a dramatic impairment of toxicity in the mammary tumour LM3 cells. However, liposomal Und-ALA induced lower intracellular porphyrin content compared to free ALA, although total porphyrins content (intracellular+media) from free Und-ALA resulted equal compared to liposomal Und-ALA, due to induction of porphyrins release induced by the latter. Topical administration of Und-ALA in PC-PG or PC-PA liposomes over the skin of LM3 subcutaneously injected mice, induced equal amount of tumour porphyrins as compared to free Und-ALA. The kinetics of porphyrins synthesis from Und-ALA is similar for free and liposomal formulations both in vivo and in vitro, showing that release of Und-ALA from liposomes is not gradual and suggesting that liposome membranes either fuses or binds to the cell membranes. To sum up, the incorporation of Und-ALA into liposomes of PC-PA or PC-PG composition does not improve the rate of porphyrin synthesis either in vitro or in vivo, due to a massive release of extracellular porphyrins and a poor cytoplasmatic release of the liposome content. The design of new liposome compositions either favouring endocytosis or coated with natural polymers to prevent Und-ALA interaction with cellular membrane are desired to overcome intracellular porphyrin release after long-chained ALA esters treatment.

Screening of nanoparticulate delivery systems for the photodetection of cancer in a simple and cost-effective model

AIMS

In urology, fluorescence-based imaging methods have been proven to significantly improve the detection of small, barely visible tumors and reduce the recurrence rate. Under ethical and economical pressure, new effective screening systems have to be developed to exploit and assess novel strategies for fluorescence photodetection in other areas. For this purpose, the chorioallantoic membrane (CAM) of the developing chick embryo is an attractive alternative model to the mammalian models.

MATERIALS & METHODS

Hypericin encapsulated into nanoparticles for the photodetection of ovarian metastases was evaluated in the CAM model with respect to vascular extravazation and tumor targeting and compared with free drug following intravenous administration.

RESULTS

To validate the CAM model as a valuable screening system for photodetection of cancer, we drew a comparison with results obtained on a conventional rodent model.

CONCLUSION

Rodent and CAM models led to the same conclusion regarding the benefits of nanoencapsulation to improve selective accumulation of drug in ovarian micrometastases.

[Diagnosis of cervical squamous intraepithelial lesions by fluorescence imaging: clinical feasibility study]

OBJECTIVE

Fluorescence diagnosis is still undeveloped in gynaecology. In order to diagnose and localize squamous intraepithelial lesion (SIL) of the cervix, a new method improving the low specificity of colposcopy would be useful. The goal of this study was to assess the feasibility and safety of colposcopic fluorescence diagnosis of SIL after topically application of methyl aminolevulinate (MAL).

PATIENTS AND METHODS

Patients with histologic proved cervical intraepithelial neoplasia (CIN) and planned for loop electrosurgical excision procedure (LEEP) under general anesthesia were included in a prospective study. Before general anesthesia, a thick layer of MAL (Metvix-160 mg/mL cream) was applied on the cervix for 35-150 min. Fluorescent colposcopic inspection of the cervix was performed using a rigid 10-mm laparoscope inserted in the vaginal cavity and connected to D-light AF system (Karl Storz Endoskope, Tuttlingen Germany). In order to confirm neoplasic status, fluorescent foci underwent directed punch biopsy(ies).

RESULTS

Fourteen patients were included in the study. Colposcopic fluorescence imaging revealed red fluorescent foci in 71.4% of cases (10/14) (neoplasic status of fluorescent foci was confirmed in 80%). Concerning MAL, the mean of application time was 73 min (35-150). Two cases presented a false-positive fluorescence and four cases of false-negative fluorescence. For all cases of false-negative fluorescence, application time of MAL was less than 60 min. We observed no systemic or local toxicity of MAL application in any group.

DISCUSSION AND CONCLUSION

Using topical application of MAL to the cervix, we demonstrated that fluorescence diagnosis of SIL is feasible. This study justifies the further development of fluorescence imaging that combines classical white light colposcopy with the use of a photosensitizer.

Preliminary results of intraoperative photodynamic therapy with 5-aminolevulinic acid in dogs with prostate carcinoma

Six client-owned dogs with prostate carcinoma were treated with a combination of (1) partial subcapsular prostatectomy using an Nd:YAG laser, (2) intraoperative photodynamic therapy using a halogen broad band lamp after local administration of a photosensitiser, and (3) systemic treatment with meloxicam. Median survival time was 41days (range 10-68days), which compared negatively with previous reports of subtotal laser prostatectomy combined with topical interleukin-2 administration, and photodynamic therapy alone. Despite treatment, the disease progressed locally, causing signs of stranguria to recur, and in the form of distant metastases. The recurrence of clinical signs due to the primary tumour despite photodynamic therapy is probably largely explained by insufficient penetration of light into the tissue. Better results may be obtained using other light sources (e.g. laser) and alternative techniques of light delivery, such as fibres or catheters allowing interstitial diffusion of light.

Recent developments in fluorescence cystoscopy: do novel agents bring a benefit?

PURPOSE OF REVIEW

In flat bladder cancer and carcinoma in situ, and in multifocal papillary cancer, some smaller lesions may be overlooked at cystoscopy. For 10 years fluorescence cystoscopy has been promoted to solve these problems without wider acceptance. New fluorophobes now promise better clinical applicability.

RECENT FINDINGS

In prospective multicenter studies fluorescence cystoscopy shows significant improvement in the detection of flat bladder cancer and carcinoma in situ. It also permits more reliable identification of all neoplastic lesions with multifocal tumors, hence more precise removal and as a consequence lower recurrence rates.

SUMMARY

New agents bring a significant benefit. Hexyl-aminolevulinate offers more rapid urothelial accumulation, better fluorescence contrast and less photobleaching than previously used fluorophobes. It is simple to use in everyday practice and has a favorable toxicity profile.

Comparison of Aminolevulinic Acid– and Hexylester Aminolevulinate–Induced Protoporphyrin IX Fluorescence for the Detection of Ovarian Cancer in a Rat Model

OBJECTIVES

This study set out to compare the photodetection of peritoneal micrometastases in an ovarian cancer model following administration of two precursors of protoporphyrin IX (PpIX): 5-aminolevulinic acid (ALA) and hexylester aminolevulinate (He-ALA).

METHODS

ALA or He-ALA (100 mg/kg) was injected into the peritoneal cavity of 16 rats with induced peritoneal metastases of ovarian cancer. Two hours later, the tumors were visualized laparoscopically using both white light for standard exploration and blue light for fluorescence. Peritoneal micrometastases were counted. Fluorescence intensities of tumoral and normal surrounding tissues were compared. The distribution of PpIX throughout the peritoneum was studied on frozen biopsies using fluorescence microscopy and correlated with pathological findings.

RESULTS

The number of micrometastases detected by the fluorescence blue mode was significantly higher (p < 0.05) than with standard white light for both ALA (235 versus 198) and He-ALA application (248 versus 199). The mean fluorescence intensity ratio between tumor and normal surrounding tissue was significantly (p < 0.05) higher for He-ALA (1.55 +/- 0.1) compared to ALA (1.45 +/- 0.1). Fluorescence microscopy confirmed that the PpIX fluorescence remained limited to cancer cells. Macroscopically fluorescing nodules were histopathologically confirmed as malignant.

CONCLUSION

He-ALA is an excellent precursor for PpIX synthesis, giving the highest PpIX fluorescence contrast between normal and tumoral peritoneal tissues. Imaging with He-ALA improves the detection of peritoneal metastases compared to ALA.

Hexyl-aminolevulinate-mediated photodynamic therapy: How to spare normal urothelium. An in vitro approach

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) of superficial bladder cancer may cause damages to the normal surrounding bladder wall. Prevention of these is important for bladder healing. We studied the influence of photosensitizer concentration, irradiation parameters, and production of reactive oxygen species (ROS) on the photodynamically induced damage in the porcine urothelium invitro. The aim was to determine the threshold conditions for the cell survival.

METHODS

Living porcine bladder mucosae were incubated with solution of hexylester of 5-aminolevulinic acid (HAL). The mucosae were irradiated with increasing doses and cell alterations were evaluated by scanning electron microscopy and by Sytox green fluorescence. The urothelial survival score was correlated with Protoporphyrin IX (PpIX) photobleaching and intracellular fluorescence of Rhodamine 123 reflecting the ROS production.

RESULTS

The mortality ratio was dependent on PpIX concentration. After 3 hours of incubation, the threshold radiant exposures for blue light were 0.15 and 0.75 J/cm(2) (irradiance 30 and 75 mW/cm(2), respectively) and for white light 0.55 J/cm(2) (irradiance 30 mW/cm(2)). Photobleaching rate increased with decreasing irradiance. Interestingly, the DHR123/R123 reporter system correlated well with the threshold exposures under all conditions used.

CONCLUSIONS

We have determined radiant exposures sparing half of normal urothelial cells. We propose that the use of low irradiance combined with systems reporting the ROS production in the irradiated tissue could improve the in vivo dosimetry and optimize the PDT.

Hexyl Aminolevulinate

Hexyl aminolevulinate, the hexyl ester of 5-aminolevulinic acid, is a photosensitising agent designed to enhance the detection of bladder cancer tumours, in particular highly malignant carcinoma in situ (CIS). After cellular uptake, hexyl aminolevulinate and/or hydrolysed 5-aminolevulinic acid enter the haem biosynthetic pathway and induce accumulation of the photoactive compound protoporphyrin IX (PpIX) in malignant as opposed to nonmalignant cells. PpIX emits red fluorescence when illuminated under blue light. Blue-light fluorescence cystoscopy with hexyl aminolevulinate (hexyl aminolevulinate cystoscopy) was more effective than standard (white-light) cystoscopy for detecting non-muscle-invasive ('superficial') disease in two European, multicentre, phase III trials, which evaluated hexyl aminolevulinate cystoscopy as an adjunct to standard cystoscopy in patients with known or suspected bladder cancer. In one trial, hexyl aminolevulinate cystoscopy detected 96% of the patients with CIS; it identified 28% more patients with CIS than standard cystoscopy. In the other trial, 17% of patients were selected to receive more complete treatment following hexyl aminolevulinate cystoscopy than standard cystoscopy, because of the improved tumour detection rate. Hexyl aminolevulinate cystoscopy is well tolerated as an adjunct to standard cystoscopy; adverse events were those typically associated with standard cystoscopy/biopsy (e.g. postoperative pain).

Enhanced porphyrin accumulation using dendritic derivatives of 5-aminolaevulinic acid for photodynamic therapy: An in vitro study

Intracellular porphyrin generation following administration of 5-aminolaevulinic acid has been widely used in photodynamic therapy for a range of malignant and certain non-malignant lesions. However, cellular uptake of 5-aminolaevulinic acid is limited by its hydrophilic nature and improved means of delivery are therefore being sought. Highly branched polymeric drug carriers known as dendrimers are a promising new approach to drug delivery. The aim of this study was to investigate the efficacy of dendrimers conjugated with 5-aminolaevulinic acid for porphyrin production in the transformed PAM 212 keratinocyte cell line and skin explants. Each dendritic derivative incorporated three 5-aminolaevulinic acid residues which were conjugated as esters via methyl or propyl linkers to a central tertiary carbon whose remaining terminal bore an amino, aminobenzyloxycarbonyl or nitro group. In the cell line, all compounds were more efficient at low concentrations compared to equimolar 5-aminolaevulinic acid for porphyrin production, with the most efficient incorporating the longer propyl linker. This compound was also the most lipophilic according to partition coefficient measurements. The intracellular porphyrin fluorescence levels showed good correlation with cellular phototoxicity following light exposure for all the compounds, together with minimal dark toxicity. Our findings indicate that the key factors influencing the efficacy of the dendritic derivatives are lipophilicity and steric hindrance within the dendritic structure which could restrict access to intracellular esterases for liberation of 5-aminolaevulinic acid. These findings should be taken into account in the design of larger dendrimers of 5-aminolaevulinic acid.

An Open Pharmacokinetic Study of??Hexylaminolevulinate-Induced Photodiagnosis after Intravesical Administration

BACKGROUND AND OBJECTIVES

Hexylaminolevulinate-mediated photodiagnosis of superficial bladder cancer recently gained marketing authorisation in Europe and is therefore being used increasingly, especially to visualise flat tumours such as carcinoma in situ. Although no significant adverse effects related to the drug have been reported to date, precise information with respect to the safety of this procedure in clinical practice has not yet been published. In the present study, we investigated the possible systemic absorption of different hexylaminolevulinate concentrations and characterised the adverse effects after bladder instillation.

METHODS

Twelve patients with known bladder cancer received a 2-hour administration of 50 mL of phosphate-buffered saline containing 4 mmol/L, 8 mmol/L or 16 mmol/L of hexylaminolevulinate. Safety was primarily evaluated by monitoring adverse effects. Standard haematology and clinical biochemistry were assessed by the local hospital laboratory. Measurements of hexylaminolevulinate, 5-aminolevulinate and protoporphyrin IX in plasma and solution collected after instillation were performed, as were fluorescence measurements in the urothelium and the skin by using an optical fibre-based spectrofluorometer.

RESULTS

No hexylaminolevulinate was found in the plasma. Furthermore, 5-aminolevulinate and protoporphyrin IX showed no significant increases in plasma after intravesical instillation of hexylaminolevulinate 4 mmol/L, 8 mmol/L or 16 mmol/L for 2 hours. This implies a very low systemic absorption at the administered doses with a hexylaminolevulinate uptake from the bladder of about 5%. Neither skin sensitivity nor adverse reactions that could be attributed to the drug were reported. Renal and liver function were not affected by the hexylaminolevulinate doses used in this study.

CONCLUSION

We demonstrated for the first time that hexylaminolevulinate-mediated photodiagnosis is a safe procedure for a patient undergoing this examination, the drug being only minimally systemically absorbed after intravesical instillation. Therefore, no or only minimal adverse effects compared with those seen with conventional photosensitising agents can be expected.

BENZO[A]PYRENE-INDUCED ORAL CARCINOGENESIS AND CHEMOPREVENTION: STUDIES IN BIOENGINEERED HUMAN TISSUE

Oral cancer, originating from smoking-induced lesions of the basal cells in the complex stratified oral epithelium, is difficult to treat. Early detection of premalignant lesions, e.g., leukoplakia, has suggested the possibility of chemopreventive measures, such as topical application of antimutagenic/antiproliferative dietary or pharmaceutical agents. As an extension of a study in human oral epithelial cell monolayers, we determined the carcinogen, i.e., benzo[a]pyrene (BaP), transport, bioactivation, and DNA binding in a bioengineered human gingival epithelial tissue construct and the chemopreventive effects of dietary polyphenols. Short-term experiments showed that both types of compounds can traverse this tissue as well as be effectively taken up by the tissue. The model cigarette smoke carcinogen BaP very slowly, but to a great extent, accumulated in the tissue with maximal uptake at 24 h. Such exposure clearly resulted in DNA binding of BaP by the tissue. This DNA binding was associated with BaP-induced CYP1B1 as well as CYP1A1 expression, as evidenced by mRNA measurements. Cotreatment of the oral tissue with dietary polyphenols, including resveratrol and quercetin, and BaP, resulted in significant inhibition of the BaP-DNA binding. Using fluorescence microscopy as well as simultaneous autoradiography, we also demonstrated that quercetin indeed penetrates the entire stratified tissue layer, but that quercetin was also oxidized within the cells. Thus, this bioengineered oral tissue construct opens up improved ways of understanding and preventing/treating smoking-induced oral cancer.

Delivery of hypericin for photodynamic applications

Early cancer detection is critical in improving disease management outcomes. Cancer diagnosis presents unique difficulties mainly due to its pathological presentation and poor accessibility that could limit the usefulness of conventional white light endoscopy in early cancer detection. Fluorescence endoscopy has been proven to improve the sensitivity and specificity of early cancer detection. Hypericin (HY) has been found to be superior to 5-aminolevulinic acid (5-ALA) and its ester derivative hexaminolevulinate (HA) as a fluorescence diagnostic agent, hence its development for delivery in vitro and in vivo, is the subject of this review.

Flexible Cystoscopy Assisted by Hexaminolevulinate Induced Fluorescence: A New Approach for Bladder Cancer Detection and Surveillance?

OBJECTIVE

The aim of this study was the assessment of flexible cystoscopy assisted by hexaminolevulinate (HAL) fluorescence.

METHODS

This study was a prospective controlled, within-patient comparison of flexible HAL cystoscopy with standard flexible cystoscopy, HAL rigid and standard white light rigid cystoscopy. Eligible patients received an intravesical instillation of 50 ml hexylaminolevulinate 8 mM solution. First flexible than rigid cystoscopy was performed in each patient using a Combilight PDD system (Richard Wolf, Germany), which provided standard white light and blue light at 375 to 440 nm, with mapping of all lesions detected. All tumors and suspicious areas identified under white light and by red fluorescence with flexible or rigid cystoscopy were then resected by TUR or biopsied. The specimen was assessed by an independent blinded pathologist.

RESULTS

In the 45 patients studied 41 (91%) patients had exophytic tumors, of which 39 (95.1%) were detected by HAL flexible cystoscopy and 40 (97.5%) by HAL rigid cystoscopy. 17 (37.8%) patients had concomitant or carcinoma in situ only, which was identified by HAL flexible cystoscopy in 14 (82.3%), by HAL rigid cystoscopy in 15 (88.2%), by flexible standard in 11 (64.7%) and by standard white light rigid cystoscopy in 13 (76.7%) patients.

CONCLUSION

HAL fluorescence flexible cystoscopy compared to HAL rigid cystoscopy showed almost equivalent results in detecting papillary and flat lesions in bladder cancer patients. Both procedures were superior to standard white light flexible cystoscopy.

In Vitro Metabolism of 5-ALA Esters Derivatives in Hairless Mice Skin Homogenate and in Vivo PpIX Accumulation Studies

PURPOSE

In topical photodynamic therapy, 5-ALA and its esters are enzymatically converted in the endogenous photosensitizing compounds such as, for example, protoporphyrin IX (PpIX). In order to elucidate in more detail their enzymatic fate, we have determined in vitro the enzymatic degradation of methyl, butyl, hexyl, and octyl-5-ALA ester derivatives in skin homogenate. Furthermore, in vivo porphyrin accumulation was measured in healthy hairless mice skins.

METHODS

Hairless mouse skins were homogenized in isotonic phosphate buffer pH 7.4. 5-ALA esters were added, and aliquots were colleted for HPLC-fluorimetric determinations of remaining content of 5-ALA esters. Furthermore, oil-in-water emulsions containing esters were topically applied to mice skin for 6 h, and the amount of accumulated PpIX in the treated areas was determined by quantitative extraction and confocal fluorescence microscopy.

RESULTS

The enzymatic degradation of esters follows pseudo first-order kinetics. The octyl ester had the largest rate constant for enzymatic degradation, followed by hexyl-, butyl-, and methyl-ALA. The long-chained 5-ALA esters, butyl-, hexyl-, and octyl ester, induced significantly more porphyrins than 5-ALA and 5-ALA methyl ester as shown by confocal microscopy and quantitative extraction studies.

CONCLUSIONS

5-ALA derivatives differ widely with respect to their enzymatic degradation. The presence of alkyl chains in 5-ALA esters significantly influences the in vitro enzymatic metabolism and the in vivo PpIX formation in healthy hairless mice skins.

KINETICS, BIODISTRIBUTION AND THERAPEUTIC EFFICACY OF HEXYLESTER 5-AMINOLEVULINATE INDUCED PHOTODYNAMIC THERAPY IN AN ORTHOTOPIC RAT BLADDER TUMOR MODEL

PURPOSE

To optimize photodynamic therapy (PDT) we investigated the kinetics and biodistribution of hexylester 5-aminolevulinate (hALA) induced protoporphyrin IX (PpIX) and the therapeutic efficacy of PDT at different drug and light doses in an orthotopic rat bladder tumor model.

MATERIALS AND METHODS

Healthy and tumor bearing rats were instilled intravesically with hALA (4, 8 and 16 mM) for 1 hour. Fluorescence was recorded spectroscopically in situ. PpIX fluorescence distribution and quantification across the bladders was visualized with fluorescence microscopy. PDT efficacy at different fluences (15 to 80 J/cm2) was histologically assessed 48 hours and 1 week after treatment.

RESULTS

Spectroscopic analysis in normal or tumor bearing rats showed the highest tumor-to-normal ratios 2 or 3 hours after the end of the 8 or 16 mM hALA instillation (5.4 and 5.7, respectively). Within the same tumor bearing animal the same fluorescence levels were observed in normal epithelium and transitional cell carcinoma, whereas the tumor-to-muscle ratio was 3. Tumor necrosis with an intact normal bladder wall was observed with a fluence of 20 J/cm2 for 8 mM hALA, while 15 J/cm2 was ineffective and 25 J/cm2 induced total wall necrosis. Although it induced comparable PpIX fluorescence, 16 mM hALA did not result in tumor eradication at any fluence.

CONCLUSIONS

An optimal PDT effect was obtained with 8 mM hALA and a fluence of 20 J/cm2. While different hALA concentrations ind uce identical PpIX fluorescence intensities, the PDT outcome was considerably different. Thus, fluorescence does not necessarily predict the therapeutic efficacy of PDT.

Comparative in vitro percutaneous penetration of 5-aminolevulinic acid and two of its esters through excised hairless mouse skin

BACKGROUND AND OBJECTIVES

ALA esters have been developed to improve PpIX production in ALA-PDT, but they do not perform as well in skin as they do in cells and the bladder.

STUDY DESIGN/MATERIALS AND METHODS

The in vitro penetration across normal mouse skin of ALA and its methyl and hexyl ester was determined for different application concentrations. ALA and the esters were also applied to tape stripped skin to determine the effect of the stratum corneum.

RESULTS

The penetration of ALA and the esters was higher through tape stripped skin than through normal skin (P < 0.01), showing that the stratum corneum is an important barrier. The experiments with different application concentrations indicated that the skin penetration through normal skin and tape stripped skin is highest for ALA and lowest for the hexyl ester.

CONCLUSIONS

The differences in skin penetration properties could be (co-)responsible for the finding that ALA esters do not induce substantially higher PpIX levels in in vivo skin.

Improved Detection of Urothelial Carcinoma In Situ With Hexaminolevulinate Fluorescence Cystoscopy

PURPOSE

In this European multicenter study we compared hexaminolevulinate (HAL) fluorescence cystoscopy and standard white light cystoscopy for the detection of carcinoma in situ (CIS) in patients suspected of having high risk bladder cancer.

MATERIALS AND METHODS

This study was a prospective controlled, within-patient comparison of standard and HAL fluorescence cystoscopy. Eligible patients received an intravesical instillation of 50 ml HAL 8 mM solution. Cystoscopy was performed using a D light system, which provided white and blue light at 375 to 440 nm. The bladder wall was inspected and mapped, first under white light, followed by blue light. All tumors and suspicious areas identified under white light and by red fluorescence were resected or biopsied. Histological findings were assessed by an independent central pathologist blinded to the identity of the biopsies.

RESULTS

Of 211 evaluable patients 83 (39%) had CIS, of whom 18 (22%) were detected by HAL cystoscopy only, 62 (75%) were detected by standard and HAL cystoscopy, 2 (2%) were detected by standard cystoscopy only and 1 (1%) was detected by nonguided biopsy. Therefore, HAL cystoscopy identified 28% more patients with CIS than standard cystoscopy. The side effects of HAL instillation were negligible and no unexpected events were reported.

CONCLUSIONS

HAL fluorescence cystoscopy improves the detection of bladder CIS significantly, which has consequences for clinical management and may improve the patient prognosis. The procedure is easily implemented as an adjunct to standard cystoscopy and it adds no significant risk of complications.

Protoporphyrin IX-accumulation in human tumor cells following topical ALA- and h-ALA-application in vivo

The fluorescence monitoring represents an innovative approach to detect tumor tissue by photosensitizer-mediated fluorescence. Therefore, information on cellular uptake, tumor selectivity and accumulation properties of photosensitizers are of essential interest. In this study we compared the accumulation properties of two photosensitizer precursors, the 5-aminolaevulinic acid (ALA) and a hexylester of ALA (h-ALA), in vivo using the hen's egg model and the human larynx carcinoma cell line HEp-2. The formation of the actual photosensitizer, protoporphyrin IX (PpIX), was determined both qualitatively and quantitatively. The intensity of the excited PpIX-fluorescence was observed as an indicator for the presence of PpIX after topical ALA- and h-ALA-applications. PpIX-fluorescence was measured using spatially resolved fluorescence spectroscopy.

Comparison of aminolevulinic acid and hexylester aminolevulinate induced protoporphyrin IX distribution in human bladder cancer

PURPOSE

Successful photodynamic therapy of epithelial cancer requires a specific photosensitization of malignant tissue. We evaluate the intensity and localization of protoporphyrin IX (PpIX) in superficial transitional cell carcinoma and nonmalignant cells of the human bladder following topical administration of its precursor, either aminolevulinic acid (ALA) or hexylester aminolevulinate (HAL).

MATERIALS AND METHODS

Solutions of ALA or HAL were instilled into the bladder of 18 patients presenting with recurrent transitional cell carcinoma. The distribution of PpIX through the bladder wall was studied on frozen biopsies using fluorescence microscopy and correlated with pathological findings.

RESULTS

Topical bladder instillation with 180 mmol (3%) ALA administered for 6 hours or 8 mmol (0.2%) HAL administered for 4 hours gave similar results regarding intensity and tissue distribution of PpIX fluorescence, whereas 8 mmol HAL administered for 2 hours followed by 2 hours of resting time (2+2 hours concept) induced a PpIX fluorescence twice as high. The fluorescence remained limited to cancer cells. Only a trace of PpIX fluorescence was observed in suburothelial connective tissue, that is chorion, but none in the bladder smooth muscle regardless of experiment conditions.

CONCLUSIONS

HAL is an excellent precursor for PpIX synthesis in bladder cancer. With the 2+2 hour topical administration condition it yielded the highest PpIX fluorescence intensity and fluorescence contrast between normal and malignant urothelial cells. This approach allows us to optimize PpIX tissue distribution for photodynamic therapy in superficial bladder cancer.

Hexyl aminolevulinate fluorescence cystoscopy: new diagnostic tool for photodiagnosis of superficial bladder cancer--a multicenter study

PURPOSE

We examined the sensitivity and specificity of Hexvix (PhotoCure ASA, Oslo, Norway) hexyl aminolevulinate (HAL) fluorescence cystoscopy in patients with superficial bladder cancer.

MATERIALS AND METHODS

A total of 52 patients (38 men and 14 women) with a mean age of 72 years were investigated. HAL hydrochloride (100 mg dissolved in 50 ml phosphate buffer solution) (8 mM) was instilled into the bladder 1 hour prior to the endoscopic procedure. Cystoscopy was performed with the Storz D-light (Karl Storz, Tuttlingen, Germany) system, allowing inspection of the bladder wall under white and blue light (380 to 450 nm).

RESULTS

A total of 422 biopsies obtained in fluorescing (165) and nonfluorescing (257) areas, including 5 random biopsies per patient, were analyzed to provide the best reference for the calculation of sensitivity and specificity. There were a total of 143 histologically verified tumors in 45 patients, including carcinoma in situ (CIS), Ta or T1 lesions. A total of 43 patients were diagnosed by fluorescence cystoscopy compared with 33 diagnosed by white light for 96% and 73% per-patient sensitivity, respectively. HAL cystoscopy was found particularly useful for finding CIS tumors. Of 13 patients with CIS tumors all except 1 were diagnosed or confirmed by HAL cystoscopy. HAL cystoscopy was well tolerated with no definite drug related adverse events reported, including effects on standard blood parameters.

CONCLUSIONS

HAL fluorescence cystoscopy is a new, sensitive, promising diagnostic procedure that showed improved detection of bladder tumors, in particular CIS. The procedure is well tolerated and can easily be implemented in current clinical practice.

Photodynamic diagnosis of ovarian cancer using hexaminolaevulinate: a preclinical study

The unfailing detection of micrometastases during surgery of patients suffering from ovarian cancer is mandatory for the optimal management of this disease. Thus, the present study aimed at determining the feasibility of detecting micrometastases in an ovarian cancer model using the intraperitoneal administration of the photosensitiser precursor hexaminolaevulinate (HAL). For this purpose, HAL was applied intraperitoneally at different concentrations (4-12 mM) to immunocompetent Fischer 344 rats bearing a syngeneic epithelial ovarian carcinoma. The tumours were visualised laparoscopically using both white and blue light (D-light, Karl Storz, Tuttlingen, Germany), and the number of peritoneal micrometastases detected through HAL-induced photodiagnosis (PD) was compared to standard white light visualisation. Fluorescence spectra were recorded with an optical fibre-based spectrofluorometer and the fluorescence intensities were compared to the protoporphyrin IX (PpIX) fluorescence induced by 5-aminolevulinic acid under similar conditions. The number of metastases detected by the PD blue light mode was higher than when using standard white light abdominal inspection for all applied concentrations. Twice as many cancer lesions were detected by fluorescence than by white light inspection. The hexyl-ester derivative produced higher PpIX fluorescence than its parent substance aminolevulinic acid at the same concentration and application time. Fluorescence contrast between healthy and cancerous tissue was excellent for both compounds. To overcome poor diagnostic efficiency and to detect peritoneal ovarian carcinoma foci in the large surface area of the human peritoneal cavity, HAL fluorescence-based visualisation techniques may acquire importance in future and lead to a more correct staging of early ovarian cancer.

In vitro skin permeation and retention of 5-aminolevulinic acid ester derivatives for photodynamic therapy

In photodynamic therapy (PDT), 5-aminiolevulinic acid (5-ALA) applied topically is converted, via the heme cycle, into protoporphyrin IX (PpIX), a photosensitizing agent, which upon excitation with light can induce tumor destruction. Due to its hydrophilic and zwitterionic characteristics, 5-ALA has limited penetration into the skin. More lipophilic 5-ALA ester derivatives are expected to cross stratum corneum more easily than 5-ALA. According to the determination of the partition coefficients of 5-ALA methyl, n-butyl, n-hexyl and n-octyl esters, these compounds showed an increased affinity to the SC, with 5-ALA hexyl ester and 5-ALA-octyl ester having the highest partition coefficients. Our in vitro skin permeation studies demonstrated an increased permeated amount for hexyl-ALA after 6 h of incubation, compared to other esters and 5-ALA. After 6 h, more 5-ALA-hexyl ester and -octyl ester were retained at viable epidermis and dermis than 5-ALA. According to these results, and considering that the conversion of 5-ALA into PpIX occurs preferentially in epidermis, it can be supposed that topical use of ester derivatives with longer chains (C(6) or C(8)) is an interesting proposal to optimize topical 5-ALA-PDT

Enhanced delivery of 5-aminolevulinic acid esters by iontophoresis in vitro

The goals of this study were to quantitatively evaluate the iontophoretic delivery of a homologous series of cationic aminolevulinic acid (ALA) esters and to determine the contributions of electromigration and electroosmosis to their overall electrotransport in vitro. Anodal iontophoretic transport of ALA esters through porcine skin in vitro was followed for 2 h at a constant current of 0.5 mA/cm2. To deduce the mechanism, the concomitant transport of an electroosmotic marker, mannitol, was also assessed. Positively charged ALA esters of moderate lipophilicity showed increased iontophoretic flux through the skin. A more than 50-fold enhancement as compared with the zwitterionic parent ALA was observed for the methyl ester. As the size and lipophilicity of the ester increased, the efficiency of electrotransport decreased. The most lipophilic esters reduced the electroosmotic flow presumably because of the association of these cations with negative charges in the skin. Iontophoresis of methyl-ALA and hexyl-ALA also increased the amount of prodrug delivered into the skin. In summary, significant topical delivery of ALA esters can be achieved by iontophoresis, and transport into and across the skin was greatly enhanced compared with that of ALA itself. It remains to be seen whether this enhanced local bioavailability of the protoporphyrin prodrug can allow improved photodynamic therapy for the treatment of skin cancer.