Fluorescence distribution and photodynamic effect of ALA-induced PP IX in the DMH rat colonic tumour model

Advancements in photodynamic therapy of esophageal cancer

The poor prognosis of patients with esophageal cancer leads to the constant search for new ways of treatment of this disease. One of the methods used in high-grade dysplasia, superficial invasive carcinoma, and sometimes palliative care is photodynamic therapy (PDT). This method has come a long way from the first experimental studies to registration in the treatment of esophageal cancer and is constantly being improved and refined. This review describes esophageal cancer, current treatment methods, the introduction to PDT, the photosensitizers (PSs) used in esophageal carcinoma PDT, PDT in squamous cell carcinoma (SCC) of the esophagus, and PDT in invasive adenocarcinoma of the esophagus. For this review, research and review articles from PubMed and Web of Science databases were used. The keywords used were "photodynamic therapy in esophageal cancer" in the years 2000-2020. The total number of papers returned was 1,000. After the review was divided into topic blocks and the searched publications were analyzed, 117 articles were selected.

A Novel 89Zr-labeled DDS Device Utilizing Human IgG Variant (scFv): "Lactosome" Nanoparticle-Based Theranostics for PET Imaging and Targeted Therapy

“Theranostics,” a new concept of medical advances featuring a fusion of therapeutic and diagnostic systems, provides promising prospects in personalized medicine, especially cancer. The theranostics system comprises a novel ⁸⁹Zr-labeled drug delivery system (DDS), derived from the novel biodegradable polymeric micelle, “Lactosome” nanoparticles conjugated with specific shortened IgG variant, and aims to successfully deliver therapeutically effective molecules, such as the apoptosis-inducing small interfering RNA (siRNA) intracellularly while offering simultaneous tumor visualization via PET imaging. A 27 kDa-human single chain variable fragment (scFv) of IgG to establish clinically applicable PET imaging and theranostics in cancer medicine was fabricated to target mesothelin (MSLN), a 40 kDa-differentiation-related cell surface glycoprotein antigen, which is frequently and highly expressed by malignant tumors. This system coupled with the cell penetrating peptide (CPP)-modified and photosensitizer (e.g., 5, 10, 15, 20-tetrakis (4-aminophenyl) porphyrin (TPP))-loaded Lactosome particles for photochemical internalized (PCI) driven intracellular siRNA delivery and the combination of 5-aminolevulinic acid (ALA) photodynamic therapy (PDT) offers a promising nano-theranostic-based cancer therapy via its targeted apoptosis-inducing feature. This review focuses on the combined advances in nanotechnology and material sciences utilizing the “⁸⁹Zr-labeled CPP and TPP-loaded Lactosome particles” and future directions based on important milestones and recent developments in this platform.

Comparative analysis of the chemical and biochemical synthesis of keto acids

Keto acids are essential organic acids that are widely applied in pharmaceuticals, cosmetics, food, beverages, and feed additives as well as chemical synthesis. Currently, most keto acids on the market are prepared via chemical synthesis. The biochemical synthesis of keto acids has been discovered with the development of metabolic engineering and applied toward the production of specific keto acids from renewable carbohydrates using different metabolic engineering strategies in microbes. In this review, we provide a systematic summary of the types and applications of keto acids, and then summarize and compare the chemical and biochemical synthesis routes used for the production of typical keto acids, including pyruvic acid, oxaloacetic acid, α-oxobutanoic acid, acetoacetic acid, ketoglutaric acid, levulinic acid, 5-aminolevulinic acid, α-ketoisovaleric acid, α-keto-γ-methylthiobutyric acid, α-ketoisocaproic acid, 2-keto-L-gulonic acid, 2-keto-D-gluconic acid, 5-keto-D-gluconic acid, and phenylpyruvic acid. We also describe the current challenges for the industrial-scale production of keto acids and further strategies used to accelerate the green production of keto acids via biochemical routes.

PINPOINT® can be used for photodynamic diagnosis based on 5-aminolevulinic acid-induced protoporphyrinIX in gastric cancer surgery: Report of a case

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We have reported the case that underwent laparoscopic total gastrectomy with photodynamic diagnosis based on 5-aminolevulinic acid induced protoporphyrinIX by using PINPOINT®.

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PINPOINT®, a brightfield color fluorescence camera, could be used for 5-ALA-PDD.

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Administration of 5-ALA through PTEG for a patient with pyloric stenosis was successfully performed.

Introduction

Photodynamic diagnosis (PDD) using 5-aminolevulinic acid (5-ALA) has been used as a diagnostic procedure for malignant diseases. Dedicated laparoscopes (e.g., an IMAGE1 Camera System®) are used for this procedure. We report a case treated with laparoscopic total gastrectomy with 5-ALA-PDD using the PINPOINT® system.

Presentation of case

A patient in his 80 s with diffuse-type gastric cancer with pyloric stenosis and ascites was admitted to our hospital. Double percutaneous transesophageal gastrotubing (dPTEG) for both gastric decompression and enteral nutrition and two cycles of preoperative chemotherapy with S-1 plus oxaliplatin were performed preoperatively.

Additionally, we preoperatively performed an ex vivo experiment that confirmed that the PINPOINT® system can be used to observed protoporphyrin IX (PpIX) fluorescence.

Three hours before surgery, 5-ALA hydrochloride was administered through dPTEG. Observation was performed by PINPOINT®, and Aladuck® was used as an excitation light source.

Peritoneal nodules and sampled lymph nodes with red fluorescence were observed by 5-ALA-PDD. Accordingly, we gave up a radical operation and laparoscopic total gastrectomy without systematic lymphadenectomy to improve anemia and release pyloric stenosis was performed. The patient’s postoperative course was uneventful.

Discussion

It is possible that the connection with each of the scopes and an exclusive light source (Aladuck®) enable the easy use of 5-ALA-PDD without dedicated laparoscopy.

It is expected that 5-ALA-PDD would show the further spread of gastrointestinal cancer if it could be performed with many types of laparoscopes.

Conclusion

We found that 5-ALA-PDD-guided surgery can be easily performed in a short time using the PINPOINT® system.

Photodynamic Therapy in Primary Breast Cancer

Photodynamic therapy (PDT) is a technique for producing localized necrosis with light after prior administration of a photosensitizing agent. This study investigates the nature, safety, and efficacy of PDT for image-guided treatment of primary breast cancer. We performed a phase I/IIa dose escalation study in 12 female patients with a new diagnosis of invasive ductal breast cancer and scheduled to undergo mastectomy as a first treatment. The photosensitizer verteporfin (0.4 mg/kg) was administered intravenously followed by exposure to escalating light doses (20, 30, 40, 50 J; 3 patients per dose) delivered via a laser fiber positioned interstitially under ultrasound guidance. MRI (magnetic resonance imaging) scans were performed prior to and 4 days after PDT. Histological examination of the excised tissue was performed. PDT was well tolerated, with no adverse events. PDT effects were detected by MRI in 7 patients and histology in 8 patients, increasing in extent with the delivered light dose, with good correlation between the 2 modalities. Histologically, there were distinctive features of PDT necrosis, in contrast to spontaneous necrosis. Apoptosis was detected in adjacent normal tissue. Median follow-up of 50 months revealed no adverse effects and outcomes no worse than a comparable control population. This study confirms a potential role for PDT in the management of early breast cancer.

5-Aminolevulinic Acid-Loaded Hyaluronic Acid Dissolving Microneedles for Effective Photodynamic Therapy of Superficial Tumors with Enhanced Long-Term Stability

5-Aminolevulinic acid (5-ALA) is one of the most widely used prodrug in clinical photodynamic therapy of dermatological diseases and cancers; yet, its clinical application is still limited by the shallow skin penetration and unsatisfied stability in any existed formulations. Here, 5-ALA-loaded hyaluronic acid dissolving microneedles (5-ALA@HAMNs) are prepared for photodynamic therapy of superficial tumors. The HAMNs can not only assist the loaded 5-ALA to effectively penetrate the stratum corneum but also provide 5-ALA with an acidic and oxygen-free environment to reduce the dimerization of 5-ALA molecules via Schiff-base bonds and formation of inactive pyrazine derivatives, thus maintaining its chemical structure and biological activity. The chemical stability of 5-ALA in HAMNs is confirmed by UV-vis spectra and mass spectra measurements. The 5-ALA@HAMNs display remarkable tumor elimination both in vitro and in vivo, even after storage at room temperature for nine months, making it a highly potential device for effective delivery of 5-ALA in cancer photodynamic therapy.

Phenomenon of atypical vascular effects of epinephrine and an increase of photodynamic response by nitroglycerin in rats with colon adenocarcinoma: adrenergic and nitrergic mechanisms and novel applied aspects

Using an original model of stress-induced colon adenocarcinoma, we uncover atypical vasorelaxation effects of a mucosa injection of epinephrine assessed by laser speckle contrast imaging and a significant increase of fluorescent intensity of 5-ALA/PpIX from malignant colon tissues by a mucosa injection of nitroglycerine. We clearly demonstrate a high activity of adrenergic and nitrergic mechanisms underlying this phenomenon and discuss their application in improving of optical approaches for effective diagnosis of gastrointestinal cancer.

Fluorescence imaging of meningioma cells with somatostatin receptor ligands: an in vitro study

BACKGROUND

The use of five-aminolevulinic acid (5-ALA) in the staining of malignant glioma cells has significantly improved intraoperative radicality in the resection of gliomas in the last decade. Currently, there is no comparable selective fluorescent substance available for meningiomas. There is however a demand for intraoperative fluorescent identification of, e.g., invasive skull base meningiomas to help improve safe radical resection. Meningiomas show high expression of the somatostatin receptor type 2, offering the possibility of receptor-targeted imaging. The authors used a somatostatin receptor-labeled fluorescence dye in the identification of meningiomas in vitro. The aim of this study was to evaluate the possibility of selective identification of meningioma cells with fluorescent techniques.

METHODS

Twenty-four primary human meningioma cell cultures were analyzed. The tumor cells were incubated with FAM-TOC (5,6-Carboxyfluoresceine-Tyr3-Octreotide). As a negative control, four human dura tissues were cultured as well as a mixed cell culture in vitro and incubated with the same somatostatin receptor-labeled fluorescence substance. After incubation, fluorescence signal and intensity in all cell cultures were analyzed at three different time points using a fluorescence microscope with 488 nm epi-illumination.

RESULTS

Sixteen WHO I, six WHO II, two WHO III meningioma primary cell cultures, and four dura cell cultures were analyzed. Fluorescence was detected in all meningioma cell cultures (22 cell culture stained strongly, 2 cell cultures moderately) directly after incubation up until 4 h later. There were no differences in the quality and quantity of fluorescence signal between the various meningioma grades. The fluorescence signal persisted unchanged during the analyzed period. In the negative control, dura cell cultures remained unstained.

CONCLUSIONS

This study demonstrates the use of FAM-TOC in the selective fluorescent identification of meningioma cells in vitro. Further evaluation of the chemical kinetics of the applied somatostatin receptor ligand and fluorescence dye is warranted. As a next step, an experimental animal model is needed to evaluate these promising results in vivo.

A Phase 1 Dose-Escalation Study of Oral 5-Aminolevulinic Acid in Adult Patients Undergoing Resection of a Newly Diagnosed or Recurrent High-Grade Glioma

BACKGROUND

The utility of oral 5-aminolevulinic acid (5-ALA)/protoporphyrin fluorescence for the resection of high-grade gliomas is well documented. This drug has received regulatory approval in Europe but awaits approval in the United States.

OBJECTIVE

To identify the appropriate dose and toxicity or harms of 5-ALA used for enhanced intraoperative visualization of malignant brain tumors, reported from a single medical center in the United States.

METHODS

Prior to craniotomy for resection of a presumed high-grade glioma, individuals were given oral 5-ALA as part of a rapid dose-escalation scheme. At least 3 patients were selected for each dose level from 10 to 50 mg/kg in 10 mg/kg increments. Adverse events, intensity of tumor fluorescence, and results of biopsies in areas of tumor and the tumor bed under white light and deep blue light were recorded.

RESULTS

A total of 19 patients were studied in this phase 1 study. Serious adverse events were unrelated to the ingestion of 5-ALA. At the highest dose level studied (50 mg/kg), 2 out of 6 patients were observed to have transient dermatologic redness and peeling. These were grade 1 adverse events, which were not serious enough to be dose limiting. Patients at higher dose levels (>40 mg/kg) were more likely to have strong tumor fluorescence. There were no instances of false positive fluorescence.

CONCLUSION

The use of 5-ALA for brain tumor fluorescence is safe and effective to a dose of 50 mg/kg. Dose-limiting toxicity was not reached in this study.

Fluorescent Light-Guided Cystoscopy with 5-ALA Aids in Accurate Surgical Margin Detection for TURBO: A Case Report

Recent studies have revealed that transurethral resection in one piece (TURBO) has several benefits over standard transurethral resection of bladder tumor (TUR-Bt), including a higher rate of containing the bladder muscle tissue and single-block resection. Five-aminolevulinic acid (5-ALA) was approved for the detection of bladder tumor treated with TUR-Bt. A 71-year-old male patient who received right nephroureterectomy developed bladder tumor recurrence on routine cystoscopy follow-up. We planned TURBO using fluorescent light-guided cystoscopy with 5-ALA. We herein report a case of bladder tumor successfully treated with TURBO using fluorescent light-guided cystoscopy with 5-ALA to detect the tumor surgical margin.

Glucose diffusion in colorectal mucosa-a comparative study between normal and cancer tissues

Colorectal carcinoma is a major health concern worldwide and its high incidence and mortality require accurate screening methods. Following endoscopic examination, polyps must be removed for histopathological characterization. Aiming to contribute to the improvement of current endoscopy methods of colorectal carcinoma screening or even for future development of laser treatment procedures, we studied the diffusion properties of glucose and water in colorectal healthy and pathological mucosa. These parameters characterize the tissue dehydration and the refractive index matching mechanisms of optical clearing (OC). We used ex vivo tissues to measure the collimated transmittance spectra and thickness during treatments with OC solutions containing glucose in different concentrations. These time dependencies allowed for estimating the diffusion time and diffusion coefficient values of glucose and water in both types of tissues. The measured diffusion times for glucose in healthy and pathological mucosa samples were 299.2 ± 4.7 ?? s and 320.6 ± 10.6 ?? s for 40% and 35% glucose concentrations, respectively. Such a difference indicates a slower glucose diffusion in cancer tissues, which originate from their ability to trap far more glucose than healthy tissues. We have also found a higher free water content in cancerous tissue that is estimated as 64.4% instead of 59.4% for healthy mucosa.

Recent advances in photodynamic diagnosis of gastric cancer using 5-aminolevulinic acid

Photodynamic diagnosis based on 5-aminolevulinic acid-induced protoporphyrin IX has been clinically applied in many fields based upon its evidenced efficacy and adequate safety. In order to establish a personalized medicine approach for treating gastric cancer patients, rapid intraoperative detection of malignant lesions has become important. Feasibility of photodynamic diagnosis using 5-aminolevulinic acid for gastric cancer patients has been investigated, especially for the detection of peritoneal dissemination and lymph node metastasis. This method enables intraoperative real-time fluorescence detection of peritoneal dissemination, exhibiting higher sensitivity than white light observation without histopathological examination. The method also enables detection of metastatic foci within excised lymph nodes, exhibiting a diagnostic accuracy comparable to that of a current molecular diagnostics technique. Although several complicating issues still need to be resolved, such as the effect of tissue autofluorescence and the insufficient depth penetration of excitation light, this simple and rapid method has the potential to become a useful diagnostic tool for gastric cancer, as well as urinary bladder cancer and glioma.

Fluorescence characteristics of human Barrett tissue specimens grafted on chick chorioallantoic membrane

To improve (pre)malignant lesion identification in Barrett’s esophagus (BE), recent research focuses on new developments in fluorescence imaging and spectroscopy to enhance tissue contrast. Our aim was to validate the chorioallantoic membrane (CAM) model as a preclinical tool to study the fluorescence characteristics such as autofluorescence and exogenously induced fluorescence of human Barrett’s tissue. Therefore, esophageal biopsy specimens from Barrett’s patients were freshly grafted onto the CAM of fertilized hen’s eggs to simulate the in vivo situation. The BE biopsy specimens stayed between 1 and 9 days on the CAM to study the persistence of vitality. Fluorescence spectroscopy was performed using six excitation wavelengths (369, 395, 400, 405, 410, 416 nm). Obtained autofluorescence spectra were compared with in vivo spectra of an earlier study. Exogenous administration of 5-aminolevulinic-acid to the biopsy specimens was followed by fluorescence spectroscopy at several time points. Afterwards, the biopsy specimens were harvested and histologically evaluated. In total, 128 biopsy specimens obtained from 34 patients were grafted on the CAM. Biopsy specimens which stayed on average 1.7 days on the CAM were still vital. Autofluorescence spectra of the specimens correlated well with in vivo spectra. Administered 5-aminolevulinic-acid to the biopsy specimens showed conversion into protoporphyrin-IX. In conclusion, we showed that grafting freshly collected human BE biopsy specimens on the CAM is feasible. Our results suggest that the CAM model might be used to study the fluorescence behavior of human tissue specimens. Therefore, the CAM model might be a preclinical research tool for new photosensitizers.

G-quadruplex DNA/protoporphyrin IX-based synergistic platform for targeted photodynamic cancer therapy

Photodynamic therapy (PDT) is an emerging technique to induce cancer cell death. However, the tumor specificity, cellular uptake and biodistribution of many photosensitizers urgently need to be improved. In this regard, we show here that the integrated nanoassemblies based on G-quadruplex DNAs (GQDs)/protoporphyrin IX (PPIX) can serve as a synergistic platform for targeted high-performance PDT. In the nanoassemblies, GQDs function as carriers of sensitiser PPIX and confers the system cancer cell targeting ability. After nucleolin-mediated efficient binding and cellular uptake of GQDs/PPIX assemblies, the strong red fluorescence of GQDs/PPIX complex provides a powerful tool for biological imaging. Moreover, the reactive oxygen species (ROS) generated by GQDs/PPIX under light illumination can effectively kill cancer cells. The present approach is simply composed by DNA and photosensitizers, thereby avoiding any complicated and time-consuming covalent modification or chemical labeling procedure.

Safe ablation of the anal mucosa and perianal skin in rats using Photodynamic Therapy--a promising approach for treating Anal Intraepithelial Neoplasia

BACKGROUND

Anal Intraepithelial Neoplasia (AIN), a pre-cursor of anal squamous carcinoma, is increasingly detected in individuals with impaired immune function. However, choices for effective, low morbidity treatment are limited. Photodynamic Therapy (PDT) is promising as it is known to ablate more proximal gastrointestinal mucosa with safe healing, without damage to underlying muscle. It can also ablate skin with safe healing and minimal scarring.

METHODS

Pharmacokinetics: Normal rats were sensitised with 200mg/kg 5-aminolaevulinic acid (ALA) and killed 1-8h later. Anal tissues were examined by fluorescence microscopy to quantify the concentration of PPIX (protoporphyrin IX, the active derivative of ALA) in anal mucosa and in the underlying sphincter. PDT: Normal rats were sensitised similarly 3h later, laser light (635 nm) was delivered. Anal canal: 50-150 J/cm using 1cm diffuser fibre; for peri-anal skin, 50-200 J/cm(2), using microlens fibre. In each group, 2 rats were killed 3, 7, 14 and 28 days later and the anal region removed for histological examination.

RESULTS

Pharmacokinetics: Peak concentration of PPIX in mucosa was at 3h, peak ratio mucosa: muscle, 6, seen at same time. PDT. Anal canal 50 J/cm: complete mucosal ablation by 3 days, complete regeneration by 28 days. Higher energies caused muscle damage with scarring. Peri-anal skin: 200 J/cm(2); complete ablation of skin, including appendages, complete healing by 28 days. Minimal effect with lower energy.

CONCLUSION

ALA-PDT can ablate anal mucosa and peri-anal skin with safe healing and no underlying damage. However, over treatment can damage the sphincters. This technique is ready to undergo clinical trials.

Photodynamic Therapy for Barrett's Esophagus and Esophageal Carcinoma

This paper reviews the use of photodynamic therapy (PDT) in patients with Barrett's esophagus and esophageal carcinoma. We describe the history of PDT, mechanics, photosensitizers for PDT in patients with esophageal disease. Finally, we discuss its utility and limitations in this setting.

Label-free G-quadruplex-specific fluorescent probe for sensitive detection of copper(II) ion

An effective G-quadruplex-based probe has been constructed for rapid and sensitive detection of Cu(2+). In this probe, an anionic porphyrin, protoporphyrin IX (PPIX) served as a reference signal, which binds to G-quadruplex specifically and the fluorescence intensity increases sharply. While, in the presence of Cu(2+), the G-quadruplex can catalyze the related Cu(2+) insertion into the protoporphyrin, the fluorescent intensity is decreased. The fluorescence of the response ligand could be selectively quenched in the presence of Cu(2+) and not interfered by other metal ions. The probe provided an effective platform for reliable detection of Cu(2+) with a detection limit as low as 3.0nM, the high sensitivity was attributed to the strong metalation of PPIX with Cu(2+) catalyzed by G-quadruplex (PS5.M). Linear correlations were obtained over the logarithm of copper ion concentration in the range from 8×10(-9)M to 2×10(-6)M (R=0.998). The G-quadruplex-based probe also could be used to detect Cu(2+) in real water samples. Additionally, these striking properties endow the G-quadruplex-ligand with a great promise for analytical applications.

Aminolevulinic Acid (ALA) as a Prodrug in Photodynamic Therapy of Cancer

Aminolevulinic acid (ALA) is an endogenous metabolite normally formed in the mitochondria from succinyl-CoA and glycine. Conjugation of eight ALA molecules yields protoporphyrin IX (PpIX) and finally leads to formation of heme. Conversion of PpIX to its downstream substrates requires the activity of a rate-limiting enzyme ferrochelatase. When ALA is administered externally the abundantly produced PpIX cannot be quickly converted to its final product - heme by ferrochelatase and therefore accumulates within cells. Since PpIX is a potent photosensitizer this metabolic pathway can be exploited in photodynamic therapy (PDT). This is an already approved therapeutic strategy making ALA one of the most successful prodrugs used in cancer treatment.

Parallel G-quadruplex-specific fluorescent probe for monitoring DNA structural changes and label-free detection of potassium ion

Here we demonstrate an anionic porphyrin, protoporphyrin IX (PPIX), as a parallel G-quadruplex-specific fluorescent probe for monitoring DNA structural changes and utilize it to develop a DNA-based K(+) sensor. The interactions of PPIX with different DNA structures in K(+) or Na(+) solution are investigated by using circular dichroism, fluorescence, and UV-vis spectroscopy. The observations reveal that PPIX has an ∼100-fold selectivity for parallel G-quadruplexes against duplexes and antiparallel G-quadruplexes. Meanwhile, the fluorescence intensity of PPIX increases by over 10-fold upon binding to parallel G-quadruplexes. On the basis of the selectivity and fluorescence property of PPIX, we introduce a facile, label-free approach to monitoring DNA structural changes via fluorescence signal readout that is tuned by PPIX binding and release. To illustrate it, we utilize PPIX and a G-rich DNA PS2.M to construct a fluorescent K(+) sensor based on an antiparallel-to-parallel conformation transition of the G-quadruplex. PS2.M adopts an antiparallel quadruplex structure in Na(+) solution, whereas it gradually converts into a parallel G-quadruplex upon addition of increasing K(+). This conformational change is indicated by a sharp increase in the fluorescence intensity of PPIX, owing to the good ability of PPIX to discriminate parallel G-quadruplexes from antiparallel ones. Even in the presence of 100 mM Na(+), such a "turn-on" fluorescent sensor can respond to low concentrations of K(+), with a limit of detection (0.5 mM) for K(+) analysis. In addition, this sensor exhibits a high selectivity for K(+) over other common metal ions, which ensures its practical applications to real samples. These results reveal that PPIX is promising for use as a specific DNA structural probe in sensing applications.

Monitoring blood flow responses during topical ALA-PDT

Photodynamic therapy (PDT) using topical 5-aminolevulinic acid (ALA) is currently used as a clinical treatment for nonmelanoma skin cancers. In order to optimize PDT treatment, vascular disruption early in treatment must be identified and prevented. We present blood flow responses to topical ALA-PDT in a preclinical model and basal cell carcinoma patients assessed by diffuse correlation spectroscopy (DCS). Our results show that ALA-PDT induced early blood flow changes and these changes were irradiance dependent. It is clear that there exists considerable variation in the blood flow responses in patients from lesion to lesion. Monitoring blood flow parameter may be useful for assessing ALA-PDT response and planning.

The role of photodynamic therapy in the esophagus

Photodynamic therapy (PDT) is a drug and device therapy using photosensitizer drugs activated by laser light for mucosal ablation. Porfimer sodium PDT has been used extensively with proven long-term efficacy and durability for the ablation of Barrett esophagus and high-grade dysplasia. and early esophageal adenocarcinoma. However, continued use is hampered by an associated stricture risk and prolonged photosensitivity (4-6 weeks). Promising single-center European studies using other forms of PDT, such as aminolevulinic acid PDT, have not been replicated elsewhere, limiting the widespread use of other forms of PDT. Future use of PDT in esophageal disease depends on the development of improved dosimetry and patient selection to optimize treatment outcomes, while minimizing adverse events and complications.

ALA and its clinical impact, from bench to bedside

ALA-induced protoporphyrin IX (PpIX) is used for fluorescence diagnosis (ALA-FD) and for fluorescence-guided resection of both (pre)malignant and non-malignant diseases. ALA is also applied in photodynamic therapy (ALA-PDT) of superficial (pre)malignant lesions in dermatology, urology, neurosurgery, otorhinolaryngology, gynecology and gastroenterology. Today, ALA is approved as Levulan for actinic keratoses, the ALA-methyl ester Metvix for actinic keratoses and basal cell carcinoma, the ALA-hexyl ester Hexvix for the diagnosis of bladder cancer and Gliolan for malignant glioma. The use of ALA for PDT and FD was established around 25 years ago, with most of the fundamental knowledge gained at the "bench" and implemented at the "bedside" due to the diligence of a few researchers within the first 10 years of research. After 1993 ALA research was taken up by many groups. For patient treatment, several factors are relevant. Administered mainly in a topical or oral form, ALA penetrates tissue in a sub-optimal way, which is currently improved by special techniques and the use of ALA-esters. PpIX accumulation is elevated in many malignant tissues, several tissue abnormalities, and in mucosa. It is also found at elevated levels in macrophages, dendritic cells and activated lymphocytes. Following sufficient PpIX accumulation in the target cells, irradiation is carried out which may be accompanied by a burning sensation at the treatment site. Due to a saturation process of PpIX formation and rapid photobleaching during irradiation the risk of overtreatment is relatively low. Pharmacokinetical studies have demonstrated a low systemic photosensitivity and excretion of PpIX via natural routes.

Photodynamic therapy using meso tetra hydroxy phenyl chlorin (mTHPC) in early prostate cancer

BACKGROUND AND OBJECTIVES

Prostate cancer is increasing in incidence, but current treatments including surgery and radiotherapy have significant side effects. This pilot study was designed to assess the potential of photodynamic therapy (PDT) using meso tetra hydroxy phenyl chlorin (mTHPC) for organ confined prostate cancer.

STUDY DESIGN/PATIENTS AND METHODS

Six men with organ confined prostate cancer were photosensitised with mTHPC (0.15 mg/kg). Between 2 and 5 days later, red light (652 nm) was delivered to areas of biopsy proven cancer via fibres inserted through transperineal needles (50-100 J per site).

RESULTS

After 8 of 10 PDT sessions, the prostate specific antigen (PSA) fell by up to 67%. Early MRI scans showed oedema and patchy necrosis, which resolved over 2 months. Biopsies of treated areas revealed necrosis and fibrosis at 1-2 months.

CONCLUSIONS

PDT for primary prostate cancer appears safe and can reduce PSA levels. As this was a phase I study, no attempt was made to treat the whole prostate; this or targeted tumour ablation could be attempted in a phase II study with an increased number of fibres. This technique merits further investigation in early prostate cancer.

Studies of a vascular-acting photosensitizer, Pd-bacteriopheophorbide (Tookad), in normal canine prostate and spontaneous canine prostate cancer

BACKGROUND AND OBJECTIVES

Photodynamic therapy (PDT) mediated with Tookad (Pd-bacteriopheophorbide, WST09) was investigated pre-clinically as part of a program to develop an alternative modality for treating prostate cancer.

STUDY DESIGN/MATERIALS AND METHODS

Spontaneous canine prostate cancer and normal canine prostate were used as the animal models. Interstitial PDT was performed by IV infusion of the photosensitizer and irradiating the prostates with a diode laser (763 nm). The prostates were harvested 1-week post-PDT and subjected to histopathologic examinations. The effects of the drug doses and light doses were studied for one- and two-session PDT. Pharmacokinetics were studied using HPLC assay. The feasibility of using perfusing CT scans for assessing PDT lesions was also evaluated.

RESULTS

Tookad is a vascular-acting drug and clears rapidly from the circulation. Tookad-PDT-induced lesions, in both normal and cancerous prostates, were characterized by marked hemorrhagic necrosis.

CONCLUSIONS

Tookad-PDT is very effective in ablating prostatic tissue through its vascular effects.

Early neoplastic and metastatic mammary tumours of transgenic mice detected by 5-aminolevulinic acid-stimulated protoporphyrin IX accumulation

A photodynamic technique for human breast cancer detection founded upon the ability of tumour cells to rapidly accumulate the fluorescent product protoporphyrin IX (PpIX) has been applied to transgenic mouse models of mammary tumorigenesis. A major goal of this investigation was to determine whether mouse mammary tumours are reliable models of human disease in terms of PpIX accumulation, for future mechanistic and therapeutic studies. The haeme substrate 5-aminolevulinic acid (5-ALA) (200 mg kg⁻¹) was administered to mouse strains that develop mammary tumours of various histological subtypes upon expression of the transgenic oncogenes HRAS, Polyoma Virus middle T antigen, or Simian Virus 40 large T antigen in the mammary gland. Early neoplastic lesions, primary tumours and metastases showed consistent and rapid PpIX accumulation compared to the normal surrounding tissues, as evidenced by red fluorescence (635 nm) when the tumours were directly illuminated with blue light (380–440 nm). Detection of mouse mammary tumours at the stage of ductal carcinomain situ by red fluorescence emissions suggests that enhanced PpIX synthesis is a good marker for early tumorigenic processes in the mammary gland. We propose the mouse models provide an ideal experimental system for further investigation of the early diagnostic and therapeutic potential of 5-ALA-stimulated PpIX accumulation in human breast cancer patients.

The vascular response to photodynamic therapy with ATX-S10Na(II) in the normal rat colon

The mechanism of tissue damage from photodynamic therapy (PDT) may be cellular, vascular or both, depending on the photosensitising agent and the treatment conditions. Well established photosensitisers like porfimer sodium have an optimum drug light interval of two days and may cause skin photosensitivity lasting several weeks. ATX-S10Na(II) is a new photosensitiser that remains largely in the vasculature after systemic administration and clears from the body within a few hours. The present study looks at the factors controlling the extent of PDT necrosis using ATX-S10Na(II) and correlates these with changes in the circulation after PDT. Normal Wistar rats were sensitised with ATX-S10Na(II), 2 mg/kg. At laparotomy, a laser fibre was positioned just touching the colonic mucosa and 50 J light at 670 nm delivered varying the drug light interval (0.5-24 h) and light delivery regime (100 mW continuous, 20 mW continuous or 100 mW in five fractions). Some animals were killed at three days to document the area of necrosis, others received fluorescein shortly prior to death (from a few minutes to three days after PDT) to outline the zone of PDT induced vascular shutdown. Maximum necrosis was seen with the shortest drug light interval (0.5 h), with no effect by 6 h. Fractionating the light or lowering the power did not increase the necrosis. The area of fluorescein exclusion increased over the first 2 h after PDT (in contrast to the re-perfusion seen with other photosensitisers) and correlated with the area of necrosis. PDT with ATX-S10Na(II) is most effective with a drug light interval of less than one hour. It induces irreversible vascular shutdown that extends after completion of light delivery and which is largely independent of the light delivery regime.

Photodynamic diagnosis in the gastrointestinal tract

Clinical data on photodynamic diagnosis for the detection of premalignant and malignant lesions in the gastrointestinal tract are encouraging so far. A major benefit of using autofluorescence is the lack of side effects because no sensitizer has to be applied.However, highly sophisticated detection systems are needed to enhance the weak autofluorescence-based fluorescent signal. New prototypes of autofluorescence video endoscopes are under way and will be decisive for further clinical use, especially because results of recently published studies have been disappointing.

Fluorescence hysteroscopy using 5-aminolevulinic: a descriptive study

BACKGROUND AND OBJECTIVES

To assess the feasibility of fluorescence hysteroscopy following topical ALA application and to describe the optical appearance of normal and neoplastic endometrium.

STUDY DESIGN/MATERIALS AND METHODS

Fifty-four patients scheduled for routine hysteroscopy and D&C were assigned to the study group using topically applied ALA. Two milliliters of a 2% 5-ALA-solution at pH = 4.0 (ASAT AG/Zug, Switzerland) was administrated into the uterine cavity 4 hours before fluorescence hysteroscopy, using a STORZ-D-Light (Tuttlingen, Germany) system. Hysteroscopic findings were compared to the histological diagnosis of hematoxylin & eosin (H&E) stained sections. In the study group, 60 histological specimens were taken (47 materials of curettage and 13 targeted biopsies). The percentage of fluorescence positive patients was calculated.

RESULTS

The rate of fluorescent endometrial samples was low in atrophic endometrium 1/16 (6.2%). Endometrial carcinoma were diagnosed in two patients. Both cases exhibited selective and intense PpIX-mediated red fluorescence. Fluorescence hysteroscopy could not differentiate between hyperplastic areas with or without atypia. Minimal uterine cramps or discomfort following ALA instillation were complained by 30 (56%) patients, no pain was indicated by 24 patients (44%).

CONCLUSIONS

Fluorescence hysteroscopy following intrauterine application of ALA is feasible. Cancerous, hyperplastic, and secretory endometrial tissue showed high red fluorescence.

Comparison of high- vs low-dose 5-aminolevulinic acid for photodynamic therapy of Barrett's esophagus

BACKGROUND

Barrett's esophagus is the major risk factor for esophageal adenocarcinoma, the incidence of which is increasing rapidly in the Western world. Aminolevulinic acid for photodynamic therapy (ALA-PDT) is effective in the treatment of Barrett's esophagus, but controversy exists regarding optimum ALA dosage. The aim of this study was to establish the optimum dosage regime for ALA-PDT for Barrett's esophagus.

METHODS

Twenty-five patients with Barrett's esophagus were randomized to receive 30 (low-dose) or 60 (high-dose) mg/kg oral ALA at 4 or 6 h or 30 mg/kg in two fractions 4 and 6 h before PDT. PDT was standardized using red (635 nm) light. Biopsy specimens were taken for protoporphyrin IX (PpIX) quantification. Endoscopy was repeated 4 weeks later.

RESULTS

All patients showed a macroscopic response, with squamous re-epithelialization. This response was greatest in the 30 mg/kg and fractionated ALA groups. There was no significant difference in response between dosing 4 or 6 h prior to PDT. Tissue levels of PpIX were similar for all dosage groups and were not predictive of clinical response. Side effects were more common with the higher dose of ALA.

CONCLUSION

Low-dose ALA-PDT appears to be a safe protocol for the ablation of Barrett's esophagus.

Fluorescence emission-based detection and diagnosis of malignancy

Over the past decades, laser use in medicine has expanded from its initial application as a light-based scalpel to a plethora of clinical uses, ranging from surgical treatment through composite polymerization, dental ablation, vision correction, and skin resurfacing to diverse diagnostic modalities. Recently, the concept of light-based diagnostics and therapy has come under investigation. Low light intensities are used to excite endogenous or exogenous fluorophores, some of which have characteristic fluorescence emissions in pathological tissues. Thus, premalignancy and malignancy potentially can be detected and diagnosed. Photosensitized superficial lesions can subsequently be destroyed selectively by using higher intensities of laser light. The application of fluorescence emission-based detection and diagnosis of precancer and cancer is reviewed, based on its application to the oral cavity-the author's primary anatomical area of expertise. This approach is justified as the same principles apply throughout the human body; to any area accessible to the clinician either directly or by some sort of fiber-optic probe.

Clinical outcomes of photodynamic therapy for head-and-neck cancer

Head-and-neck cancers not only carry poor prognoses, but also reduced quality of life for the patients. Disease control is often achieved at the expense of substantial functional loss and disfigurement. Photodynamic therapy (PDT) is particularly well suited to the treatment of head-and-neck-tumors because it has little effect on underlying functional structures and has an excellent cosmetic outcome. Studies in the past decades have shown that PDT is of similar efficacy as traditional measures in the treatment of early-stage head-and-neck cancers with an overall response rate of 85%-100% with up to 75% of the complete responses sustained at 2 years after PDT. For advanced head-and-neck cancers, studies were also conducted to evaluate the palliative effects of PDT. Overall, 58%-70% palliative benefit can be observed in these patients. Using interstitial PDT, median survival of the patients with recurrent unresectable head-and-neck cancers can be improved to 14 months (cf. 226 days by using surface illumination PDT). PDT is thus a therapeutic option that may prove a useful addition to the armamentarium of the integrated head and neck oncology team.

Acceleration of ALA-induced PpIX fluorescence development in the oral mucosa

BACKGROUND AND OBJECTIVES

The development of 5-aminolevulinic acid (ALA)-induced tissue fluorescence is optimal 2-4 hours after ALA application. Goal of this work was to develop a means of accelerating oral topical ALA-induced tissue fluorescence.

STUDY DESIGN/MATERIALS AND METHODS

In 300 hamsters, DMBA (9,10 dimethyl-1,2-benzanthracene) cheek pouch carcinogenesis produced dysplasia in 3-5 weeks. Topical application of 20% ALA in Eucerin was followed by localized ultrasound treatment (1, 3.3 MHz) in 150 animals. In 75 animals, ALA was applied in an Oral Pluronic Lecithin Organogel (OPLO-an absorption enhancer) vehicle. Seventy-five animals received only topical ALA in Eucerin. Hamsters were sacrificed and cryosections underwent fluorescence measurements, histological evaluation, 20-180 minutes after ALA application. One-way ANOVA detected independent effects of pathology on laser-induced fluorescence (LIF). Two-way ANOVA tested for independent effect of pathology and of OPLO, ultrasound, and interaction effects.

RESULTS

Ultrasound significantly (P < 0.05) accelerated tissue fluorescence development.

CONCLUSIONS

Low-frequency ultrasound can accelerate ALA-induced fluorescence development.

Photodynamic therapy: a new approach to prostate cancer

Photodynamic therapy (PDT) is based on the concept that light irradiation can change an inert substance into an active one. In urology, hematoporphyrin derivative (HpD) and Photofrin (Axcan Scandipharm Inc., Birmingham, AL) are used most commonly as photosensitizing agents predominantly for the treatment of transitional cell carcinoma of the bladder. To investigate the basics for PDT of prostate cancer, several studies were performed on the optical characteristics of prostate tissue and prostate carcinoma tissue in vitro and in vivo and on the penetration depths of different laser wavelengths. Initial experimental studies to treat prostate cancer with PDT using HpD were done on Dunning tumors in rats. Combined with interstitial applicators, photodynamic therapy seems to have a great potential in the treatment of prostate carcinoma. However, it is an experimental treatment and even a preliminary evaluation will be possible only after the conclusion of clinical studies with the corresponding long-term results.

Detection and diagnosis of oral cancer by light-induced fluorescence

BACKGROUND AND OBJECTIVE

New techniques for non-invasive early detection and diagnosis of oral dysplasia and carcinoma are required. Our objective was to determine in the hamster cheek pouch model whether differentiation between the healthy tissue and the different stages of oral premalignancy and malignancy is possible using laser-induced fluorescence after tissue exposure to 5-Aminolevulinic acid (ALA).

STUDY DESIGN/MATERIALS AND METHODS

DMBA carcinogenesis was applied to one cheek pouch in 18 hamsters for 0-20 weeks. Prior to sacrifice, 20% ALA was applied to the cheek tissues. Excised cheek tissues were cryosectioned and imaged using fluorescence microscopy with excitation at 405 nm, detection at 635 nm. After fluorescence measurement, H&E staining and histopathological evaluation were performed.

RESULTS

Fluorescence intensity was significantly lower in healthy tissue than in pathological tissues. Significantly higher intensities and more "fluorescence hot spots" occurred in severe dysplasia and carcinoma than in healthy tissue, hyperkeratosis, mild and moderate dysplasia.

CONCLUSIONS

Light-induced fluorescence after ALA exposure can differentiate between the different stages of premalignancy and malignancy. Its ability to differentiate between healthy tissue and early pathology is particularly interesting

Phototoxic effects of 635-nm light on canine transitional cell carcinoma cells incubated with 5-aminolevulinic acid

OBJECTIVE

To determine whether transitional cell carcinoma (TCC) cells incubated in media containing 5-aminolevulinic acid (ALA) would produce sufficient protoporphyrin IX (PpIX) to cause lethal phototoxic effects when exposed to 635-nm light.

SAMPLE POPULATION

Canine TCC cells (K9TCC).

PROCEDURE

Cultured K9TCC cells were exposed to graded doses of ALA, and PpIX concentrations were determined. Cells then were exposed to various doses of 635-nm light from a diode laser, and cell viability was assayed.

RESULTS

Production of PpIX was dependent on time and dose of ALA. The K9TCC cells incubated with ALA produced sufficient PpIX to cause lethal phototoxic effects when exposed to 635-nm light. Phototoxic effects were dependent on time and dose of ALA. Increasing laser power density and energy density decreased cell survival.

CONCLUSIONS AND CLINICAL RELEVANCE

ALA is an effective photosensitizer for in vitro photodynamic treatment of K9TCC cells. Further studies are warranted to assess the safety and efficacy of ALA as a photosensitizer for use in treating dogs with TCC. Impact for Human Medicine-On the basis of this study, dogs with TCC may be useful in the development of protocols for ALA-based photodynamic therapy of humans affected with muscle-invasive bladder cancer.

Protoporphyrin-IX accumulation and cutaneous tumor regression in mice using a ferrochelatase inhibitor

The use of endogenously created porphyrins as an alternative to photosensitizer injection for photodynamic therapy (PDT) of cancer is a rapidly evolving area of study. In-situ accumulation of protoporphyrin-IX (PpIX) by hemebiosynthesis inhibition represents a novel method for PDT of cancer cells. The kinetics of PpIX accumulation and cutaneous tumor regression in mice was studied using lead (a known and effective inhibitor of ferrochelatase). Cutaneous tumors were exposed to various doses of ferrochelatase enzyme inhibitor (lead) and to different durations and doses of visible light. The maximum increase in PpIX levels (blood, skin and tumor) was observed 48 h after the parenteral administration of second injection of lead within a period of 1 month. The maximum tumor regression was observed in mice that were exposed to visible light at a light dose of 648J/cm(2) (1h exposure in four sessions of 15 min, with a gap of 10 min between each exposure). Continuous treatment for 6 consecutive days resulted in almost complete regression of the tumors in most of the animals. Histopathological sections of tumors after light exposure showed necrotic tissue with degenerated lymphocytes, monocytes, and neutrophils. Since the ferrochelatase inhibitor (lead) used in the present study is toxic, the search must continue for a safe, non-toxic inhibitor to enhance sensitizer-mediated PDT.