Porphyrin and haem biosynthesis and its control

Fluorescence-Guided Surgery in the Surgical Treatment of Gliomas: Past, Present and Future

Simple Summary

Gliomas are aggressive central nervous system tumours. The emergence and recent widespread adoption of 5-aminolevulinic acid and fluorescence guided surgery have improved the extent of resection, with implications for improved survival and progression-free survival. This review describes the history, rationale and mechanism behind the use of 5-aminolevulinic acid and fluorescence-guided surgery. We also discuss current limitations and future directions for this important adjunct to glioma surgery. This review aims to provide readers with an up-to-date overview and evidence base on this important topic.

Abstract

Gliomas are central nervous systems tumours which are diffusely infiltrative and difficult to treat. The extent of surgical resection is correlated with improved outcomes, including survival and disease-free progression. Cancerous tissue can be directly visualised intra-operatively under fluorescence by administration of 5-aminolevulinic acid to the patient. The adoption of this technique has allowed surgeons worldwide to achieve greater extents of resection, with implications for improved prognosis. However, there are practical limitations to use of 5-aminolevulinic acid. New adjuncts in the field of fluorescence-guided surgery aim to improve recognition of the interface between tumour and brain with the objective of improving resection and patient outcomes.

Comparison of in vitro photodynamic antimicrobial activity of protoporphyrin IX between endoscopic white light and newly developed narrowband endoscopic light against Helicobacter pylori 26695

Helicobacter pylori might be readily affected with photodynamic therapy (PDT) by weak wavelengths, because it has few repair genes. Recently, gastrointestinal endoscopy emitting specific wavelengths (narrowband imaging, NBI) has been developed for the early detection of tumors. Coincidentally, its wavelength (415 nm) is very similar to the wavelength (410 nm) that activates protoporphyrin IX (PpIX) as a photosensitizer (PS). Therefore, we studied in vitro PDT against H. pylori using NBI and conventional white light (WL) according to low or high concentration of PpIX along with exposure time. The bactericidal effects, the degree of oxidative DNA damage and membrane integrity of H. pylori after PDT were evaluated. In the control, the numbers of viable cells remained constant during the experiment. Viable cells after PDT using both endoscopic light irradiation, were decreased approximately 10(3) - 10(5) fold at low concentration of PpIX and below 0.80 × 10 at high concentration of PpIX. Only membrane damage after PDT was observed microscopically in H. pylori without DNA injury. Conclusively, either the bactericidal effect in high concentration or the decrease of bacterial loading in low concentration of PpIX, would be expected with PDT using endoscopic light (NBI or WL).

[Accumulation of porphyrins in cells of system of blood induced by 5-aminolaevulinic acid]

The levels and rates of accumulation of porphyrins in lymphoid cells and bone marrow cells treated with exogenous 5-aminolaevulinic acid (ALA) were studied. The dependence of the quantity of porphyrins accumulated in cell on ALA concentrations in the medium had maximum at 0.7-1.0 mM ALA for all the cell types studied (splenocytes, thymocytes, peripheral blood lymphocytes and bone marrow cells). The rate of accumulation of uro-, copro- and protoporphyrins depended on cell types. The lowest and the highest levels were found in splenocytes and highest in bone marrow cells respectively. It is suggested that photodynamic therapy employing ALA is potentially dangerous for blood cells.

Synchronous fluorescence spectroscopic characterization of DMBA-TPA-induced squamous cell carcinoma in mice

While initially confined to the epidermis, squamous cell carcinoma can eventually penetrate into the underlying tissue if not diagnosed early and treated. The noninvasive early detection of the carcinoma is important to achieve a complete treatment of the disease. Of the various non-invasive optical techniques, the synchronous fluorescence (SF) technique is considered to provide a simplified spectral profile with more sharp spectral signatures of the endogenous fluorophores in complex systems. The potential use of the SF technique in the characterization of the sequential tissue transformation in 7,12-dimethylbenz(a)anthracene-12-O-tetradecanoylphorbol-13-acetate (DMBA-TPA)-induced mouse skin tumor model in conjunction with simple statistical analysis is explored. The SF spectra show distinct differences during the earlier weeks of the tumor-induction period. Intensity ratio variables are calculated and used in three discriminant analyses. All the discriminant analyses show better classification results with accuracy greater than 80%. From the observed differences in the spectral characteristics and the ratio variables that resulted in better classification between groups, it is concluded that tryptophan, collagen, and NADH are the key fluorophores that undergo changes during tissue transformation process and hence they can be targeted as tumor markers to diagnose normal from abnormal tissues using the SF technique.

Mechanistic studies on delta-aminolevulinic acid uptake and efflux in a mammary adenocarcinoma cell line

Delta-aminolevulinic acid (ALA) is the precursor in the biosynthesis of porphyrins. The knowledge of both the regulation of ALA entrance and efflux from the cells and the control of porphyrin biosynthesis is essential to improve ALA-mediated photodynamic therapy. In this work, we studied the regulation of ALA uptake and efflux by endogenously accumulated ALA and/or porphyrins in murine mammary adenocarcinoma cells. Under our set of conditions, the haem synthesis inhibitor succinyl acetone completely prevented porphobilinogen and porphyrin synthesis from ALA, and led to an increase in the intracellular ALA pool. However, neither intracellular ALA nor porphyrin pools regulate ALA uptake or efflux during the first 15 min of the process. Based on temperature dependence data, ALA but not gamma-aminobutyric acid (GABA) efflux is mediated by a diffusion mechanism. Moreover, the addition of extracellular GABA not only did not influence the rate of ALA efflux but on the contrary it affected ALA uptake, showing the contribution of a saturable mechanism for the uptake, but not for the efflux of ALA from the cells.

Does new photosensitizer improve photodynamic therapy in advanced esophageal carcinoma?

BACKGROUND AND OBJECTIVE

Polyhematoporphyrin (Photosan) as sensitizers for photodynamic therapy (PDT) in advanced esophageal cancer carry the risk of prolonged photosensitivity of the skin. New sensitizers such as 5-aminolaevulinic acid (ALA) with low rates of skin phototoxicity appear to be promising alternatives. The aim of this study was to evaluate the efficacy of ALA compared to Photosan for PDT in advanced esophageal carcinoma regarding phototoxicity of the skin, reduction of dysphagia, tumor stenosis, and tumor length and Karnovsky performance status.

STUDY DESIGN/MATERIALS AND METHODS

After diagnostic work-up, photosensitization was done in 22 patients with ALA (60 mg/kg body weight, oral, 6-8 hours prior to PDT) and in 27 patients with Photosan (2 mg/kg body weight, i.v., 48 hours before PDT). The light dose was calculated as 300 J/cm fibre tip. Light at 630 nm was applied using a pumped dye laser. In both groups, additional hyperbaric oxygenation was applied at a level of 2 absolute atmospheric pressure.

RESULTS

Improvement regarding dysphagia, stenosis diameter, and tumor length could be obtained in both treatment arms with a significant difference in favour of the Photosan-group, P = 0.02; P = 0.0000; and P = 0.000014, respectively. The Karnovsky performance status also improved in both groups and showed no significant difference (P = 0.12). The median survival time for the ALA-group was 8.0 months, compared with 9.0 months for the Photosan group. No sunburn or other major treatment related complication occurred in both treatment arms. Thirty-day mortality was 0%.

CONCLUSION

Despite the limitations of a non-randomized study, photosensitzation with Photosan seems to be more effective in PDT of advanced esophageal carcinoma compared to ALA.

Fluorescence induced with 5-aminolevulinic acid for the endoscopic detection and follow-up of esophageal lesions

BACKGROUND

The aim of this study was to investigate the use of orally administered 5-aminolevulinic acid (ALA) for in vivo photodynamic diagnosis and follow-up of premalignant and malignant esophageal lesions.

METHODS

Twenty-two patients with known or treated malignant and precancerous esophageal lesions were sensitized with orally administered ALA (15 mg/kg). Six patients had Barrett's esophagus, with or without severe dysplasia, 5 squamous cell cancer or early-stage (uT1N0M0) adenocarcinoma, 1 advanced-stage (uT3N1) adenocarcinoma, and 1 patient a lesion with an appearance that suggested esophageal cancer. Nine patients underwent photodynamic diagnosis for follow-up after treatment of esophageal cancer with curative intent; 6 had no macroscopically visible lesion and 3 a barely visible lesion under standard (white-light) endoscopy. Photodynamic diagnosis was conducted 6 to 7 hours after oral administration of ALA by using a special light source capable of delivering either white or violet-blue light. Red fluorescence was detected with a charged coupled device camera attached to a fiberoptic endoscope. Corresponding endoscopic, fluorescence, and microscopic findings were compared.

RESULTS

By using histology as the reference standard (n = 86 biopsies), 85% of the biopsy sites with premalignant or malignant histopathology exhibited red fluorescence, whereas only 25% were detected with white-light endoscopy.

CONCLUSION

ALA-induced fluorescence might be useful for the early endoscopic detection of malignant esophageal lesions and follow-up after treatment of such lesions with curative intent.

Photosensitization with hematoporphyrin derivative compared to 5-aminolaevulinic acid for photodynamic therapy of esophageal carcinoma

BACKGROUND

Hematoporphyrin derivatives (HpD) as sensitizers for photodynamic therapy (PDT) in advanced esophageal cancer carry the risk of prolonged photosensitivity of the skin. New sensitizers such as 5-aminolaevulinic acid (ALA) with low rates of skin phototoxicity appear to be promising alternatives. The aim of this study was to evaluate the efficacy of ALA compared with HpD for PDT in advanced esophageal carcinoma regarding phototoxicity of the skin, reduction of dysphagia, tumor stenosis and length, and Karnovsky performance status.

METHODS

After diagnostic workup, photosensitization was done in 22 patients with ALA (60 mg/kg body weight, oral, 6 to 8 hours before PDT) and in 27 patients with a hematoporphyrin derivative (2 mg/kg body weight, intravenously, 48 hours before PDT). The light dose was calculated as 300 J/cm fiber tip. Light at 630 nm was applied using a pumped dye laser. In both groups, additional hyperbaric oxygenation was applied at a level of 2 absolute atmospheric pressure.

RESULTS

Improvement regarding dysphagia, stenosis diameter, and tumor length could be obtained in both treatment arms with a significant difference in favor of the HpD group (p = 0.02; p = 0.0000; and p = 0.000014, respectively). A questionnaire of patients in the HpD group confirmed that the ability of swallowing a meal was superior compared with the discomfort from limitation to sun exposure. No sunburn or other major treatment-related complication occurred in both treatment arms.

CONCLUSIONS

Despite the limitations of a nonrandomized study, photosensitzation with HpD seems to be more effective in PDT of advanced esophageal carcinoma compared with ALA.

Endoscopic photodynamic diagnosis: oral aminolevulinic acid is a marker of GI cancer and dysplastic lesions

BACKGROUND

Dysplasia and early cancer of the upper gastrointestinal (GI) tract often are undetected at white-light endoscopy. We describe oral administration of 5-aminolevulinic acid for the in vivo photodynamic diagnosis of premalignant and malignant lesions during endoscopy.

METHODS

Four patients with known gastric adenoma (n = 1), macroscopically undetected but histologically proven esophageal squamous cell cancer (n = 1), suspected early cancer of the esophagus (n = 1), and multiple duodenal adenomas (n = 1) were sensitized with 5-aminolevulinic acid administered orally (15 mg/kg body weight). Photodynamic diagnosis was conducted after a retention time of 6 to 7 hours with a special light source capable of delivering either white or violet-blue light. Red fluorescence was detected through the gastroscope with an image-intensifying camera.

RESULTS

All malignant lesions exhibited red or bluish fluorescence during photodynamic diagnosis. Fluorescence-negative mucosal areas proved to be histologically benign.

CONCLUSION

Fluorescence induced with 5-aminolevulinic acid might be useful for the endoscopic detection of dysplasia and early carcinoma in the upper GI tract. Further investigations are needed to evaluate the sensitivity and specificity of photodynamic diagnosis for different tumor entities.

In vitro and in vivo porphyrin accumulation by C6 glioma cells after exposure to 5-aminolevulinic acid

Several malignant tissues synthesize endogenous porphyrins after exposure to 5-aminolevulinic acid (5-ALA). The present experiments have been designed to elucidate whether the C6 glioma cell, a model cell for human malignant glioma, similarly synthesizes porphyrins when exposed to 5-ALA, and whether specific synthesis occurs when C6 cells are inoculated into rat brains to form a tumor. In this situation the blood-brain barrier may interfere with 5-ALA availability, and spreading of porphyrins with edema outside the tumor may occur. Flow cytometry is used to determine the course of cell volume and porphyrin fluorescence intensities in cultured C6 cells which are incubated in 1 mM 5-ALA. For the induction of experimental brain tumors, 10(4) untreated C6 cells are inoculated into the brains of rats. After 9 days animals receive 100 mg 5-ALA/kg body weight. Brains are removed after 3, 6, or 9 h and frozen coronal sections obtained for H/E staining or fluorescence spectography. Cultured C6 cells show a linear increase of protoporphyrin IX fluorescence after exposure to 5-ALA, which begins to plateau after 85 min. Marked fluorescence is also observed in solid and infiltrating experimental tumor. However, faint fluorescence also occurs in normal tissue, basal pia, choroid plexus, and, more obviously, in white-matter tracts bordering the tumor (maximal distance: 1.5 +/- 0.7 mm). The observations demonstrate that C6 cells synthesize protoporphyrin IX after exposure to 5-ALA in vitro and in vivo. However, when utilizing 5-ALA for fluorescence detection or photodynamic therapy of brain tumors, attention should be paid to the possibility of protoporphyrin IX occurring outside the tumor.

Photodynamic therapy on the normal rabbit larynx with phthalocyanine and 5-aminolaevulinic acid induced protoporphyrin IX photosensitisation

Photodynamic therapy (PDT) is a promising technique for the treatment of small tumours in organs where it is essential to minimise damage to immediately adjacent normal tissue as PDT damage to many tissues heals by regeneration rather than scarring. As preservation of function is one of the main aims of treating laryngeal tumours, this project studied the effects of PDT on the normal rabbit larynx with two photosensitisers, endogenous protoporphyrin IX (PPIX) induced by the administration of 5-aminolaevulinic acid (ALA) and disulphonated aluminium phthalocyanine (AIS2Pc). The main aims of the study were to examine the distribution of protoporphyrin IX and AIS2Pc by fluorescence microscopy in the different regions of the larnyx and to assess the nature and subsequent healing of PDT damage. Peak levels of PPIX were found 0.5-4 h after administration of ALA (depending on dose) with highest levels in the epithelium of the mucosa. With 100 mg kg-1, PDT necrosis was limited to the mucosa, whereas with 200 mg kg-1 necrosis extended to the muscle. With 1 mg kg-1 AIS2Pc, 1 h after administration, the drug was mainly in the submucosa and muscle, whereas after 24 h, it was predominantly in the mucosa. PDT at 1 h caused deep necrosis whereas at 24 h it was limited to the mucosa. All mucosal necrosis healed by regeneration whereas deeper effects left some fibrosis. No damage to cartilage was seen in any of the animals studied. The results of this study have shown that both photosensitisers are suitable for treating mucosal lesions of the larynx, but that for both it is important to optimise the drug dose and time interval between drug and light to avoid unacceptable changes in normal areas.

Photodynamic therapy of oral cancer: photosensitisation with systemic aminolaevulinic acid

Photodynamic therapy with intravenous photosensitising drugs has been shown to be effective in the ablation of superficial cancers, but long-lasting photosensitivity is a serious disadvantage. Similar photosensitivity is a feature of certain types of porphyria. We present the first report of tumour necrosis brought about by photodynamic activation of a temporary endogenous porphyrin accumulation, after an oral dose of the haem precursor, 5-aminolaevulinic acid. In 4 patients, quantitative fluorescence microscopy showed that accumulation of the photoactive intermediate protoporphyrin IX peaked after 4-6 h in 4 oral cavity squamous cell carcinomas, returning to background in 24 h. Irradiation with non-thermal red laser light caused tumour necrosis in 3 patients.

Photodynamic therapy of the normal rat stomach: a comparative study between di-sulphonated aluminium phthalocyanine and 5-aminolaevulinic acid

Dysplasia in the upper gastrointestinal tract carries a risk of invasive malignant change. Surgical excision of the affected organ is the only treatment available. Photodynamic therapy has been shown to be promising in the treatment of early and superficial tumours and may be useful for the ablation of dysplastic mucosa. Because of the diffuse nature of the disease, such treatment would necessarily involve destruction of large areas of mucosa and it is desirable to confine its effect to the mucosa in order that safe healing can take place. By means of photometric fluorescence microscopy, we have studied the pattern of photosensitisation in the normal rat stomach using di-sulphonated aluminium phthalocyanine (AlS2Pc) and 5-aminolaevulinic acid (ALA) as photosensitisizers. AlS2Pc resulted in a panmural photosensitisation of the gastric wall with the highest level encountered in the submucosa. The mucosa and muscularis propria were sensitised to equal extent. Following light exposure, a full thickness damage resulted. ALA is a natural porphyrin precursor and exogenous administration gave rise to accumulation of protoporphyrin IX (PPIX) in the cells. The resultant pattern of photosensitisation was predominantly mucosal and its photodynamic effect was essentially confined to the mucosa. ALA produced a selective photosensitisation of the gastric mucosa for its photodynamic ablation with sparing the underlying tissue layers.