Silencing of human ferrochelatase causes abundant protoporphyrin-IX accumulation in colon cancer

Kinetic Evaluation of Determinant Factors for Cellular Accumulation of Protoporphyrin IX Induced by External 5-Aminolevulinic Acid for Photodynamic Cancer Therapy

Five-aminolevulinic acid (ALA) is a prodrug to generate phototoxic protoporphyrin IX (PPIX) for photodynamic cancer therapy. It remains unclear how PPIX accumulates in cancer cells; therefore, we aimed to clarify determinant factors by assessing ALA uptake, PPIX biosynthesis, conversion of PPIX to heme (ferrochelatase activity), and PPIX efflux, independently, in 10 human cancer cell lines. ALA-induced PPIX accumulation was not correlated with ALA uptake clearance. ALA uptake rates were far greater than maximum conversion rates of ALA to PPIX in the five cell lines, where ALA uptake activity was detected. A negative correlation of PPIX accumulation with ferrochelatase activity was found, but not statistically significant among all cell lines. As PPIX accumulation was restored in MCF-7 and DU145 cells by adding an inhibitor of PPIX efflux transporter BCRP, a compartment model incorporating PPIX synthesis, ferrochelatase activity, and PPIX efflux, was established, and hybrid parameters (π index) calculated using the model were significantly correlated with ALA-induced PPIX accumulation (r = 0.90, p = 0.005). Accordingly, kinetic analyses indicate that ALA-induced PPIX levels are determined by the three processes of PPIX biosynthesis, conversion of PPIX to heme, and PPIX efflux, suggesting that π index is a useful to predict ALA-induced PPIX accumulation.

Effects of Silencing Heme Biosynthesis Enzymes on 5-Aminolevulinic Acid-mediated Protoporphyrin IX Fluorescence and Photodynamic Therapy

Aminolevulinic acid (ALA)-mediated protoporphyrin IX (PpIX) production is being explored for tumor fluorescence imaging and photodynamic therapy (PDT). As a prodrug, ALA is converted in heme biosynthesis pathway to PpIX with fluorescent and photosensitizing properties. To better understand the role of heme biosynthesis enzymes in ALA-mediated PpIX fluorescence and PDT efficacy, we used lentiviral shRNA to silence the expression of porphobilinogen synthase (PBGS), porphobilinogen deaminase (PBGD) and ferrochelatase (FECH) in SkBr3 human breast cancer cells. PBGS and PBGD are the first two cytosolic enzymes involved in PpIX biosynthesis, and FECH is the enzyme responsible for converting PpIX to heme. PpIX fluorescence was examined by flow cytometry and confocal fluorescence microscopy. Cytotoxicity was assessed after ALA-mediated PDT. Silencing PBGS or PBGD significantly reduced ALA-stimulated PpIX fluorescence, whereas silencing FECH elevated basal and ALA-stimulated PpIX fluorescence. However, compared with vector control cells, the ratio of ALA-stimulated fluorescence to basal fluorescence without ALA was significantly reduced in all knockdown cell lines. PBGS or PBGD knockdown cells exhibited significant resistance to ALA-PDT, while increased sensitivity to ALA-PDT was found in FECH knockdown cells. These results demonstrate the importance of PBGS, PBGD and FECH in ALA-mediated PpIX fluorescence and PDT efficacy.

Native fluorescence spectroscopic characterization of DMBA induced carcinogenesis in mice skin for the early detection of tissue transformation

The objective of the study is to characterize the endogenous porphyrin fluorescence in a dimethylbenz(a)anthracene (DMBA) induced mouse skin tumor model using native fluorescence emission and excitation spectroscopy.

Structure–activity relationship study of dendritic polyglycerolamines for efficient siRNA transfection

Structure–activity relationship studies were performed through in vitro, in silico, and in vivo analysis in order to evaluate the gene transfection potential of dendritic polyglycerolamines with different amine loadings.

Photodynamic diagnostic ureterorenoscopy with orally administered 5-aminolaevulinic acid as photosensitiser: how I do it

OBJECTIVE

To explain our use of photodynamic diagnostic ureterorenoscopy, we provide a detailed description of the choice of photosensitiser, equipment needed, a safety profile, and pointers on our technique.

TECHNIQUE

Patients are given oral 5-aminolaevulinic acid (5-ALA) as a photosensitiser 3-4 h pre-operatively, and by using a Xenon blue light source, an eyepiece which blocks light below 450 nm which is fitted onto the ureterorenoscope, we are able to conduct a thorough photodiagnosis of the upper urinary tract.

CONCLUSION

Our technique of photodynamic diagnostic ureterorenoscopy has shown that the sensitivity, specificity and detection rates of upper urinary tract lesions can be significantly increased with the use of oral 5-ALA. Therefore, we provide a detailed explanation of the use of oral 5-ALA photosensitiser, indications and contraindications of the technique in addition to equipment used and potential complications of the procedures.

Iron chelators in photodynamic therapy revisited: synergistic effect by novel highly active thiosemicarbazones

In photodynamic therapy (PDT), a noninvasive anticancer treatment, visible light, is used as a magic bullet selectively destroying cancer cells by a photosensitizer that is nontoxic in the dark. Protoporphyrin IX (PpIX) is a natural photosensitizer synthesized in the cell, which is also a chelating agent that if bonded to Fe(2+) forms heme, a central component of hemoglobin. Therefore, xenobiotic iron chelators can disturb iron homeostasis, increasing the accumulation of PpIX, obstructing the last step of heme biosynthesis, and enhancing PDT efficiency. However, the attempts to use this promising idea have not proved to be hugely successful. Herein, we revisited this issue by analyzing the application of iron chelators highly toxic in the dark, which should have higher Fe(2+) affinity than the nontoxic chelators used so far. We have designed and prepared thiosemicarbazones (TSC) with the highest dark cellular cytotoxicity among TSCs ever reported. We demonstrate that compound 2 exerts powerful PDT enhancement when used in combination with 5-aminolevulinic acid (ALA), a precursor of PpIX.

Diagnostic accuracy of diffuse reflectance imaging for early detection of pre-malignant and malignant changes in the oral cavity: a feasibility study

Background

Diffusely reflected light is influenced by cytologic and morphologic changes that take place during tissue transformation, such as, nuclear changes, extracellular matrix structure and composition as well as blood flow. Albeit with varying degree of sensitivity and specificity, the properties of diffusely reflected light in discriminating a variety of oral lesions have been demonstrated by our group in multiple studies using point monitoring systems. However, the point monitoring system could not identify the region with the most malignant potential in a single sitting.

Methods

In order to scan the entire lesion, we developed a multi-spectral imaging camera system that records diffuse reflectance (DR) images of the oral lesion at 545 and 575 nm with white light illumination. The diagnostic accuracy of the system for 2-dimensional DR imaging of pre-malignant and malignant changes in the oral cavity was evaluated through a clinical study in 55 patients and 23 healthy volunteers. The DR imaging data were compared with gold standard tissue biopsy and histopathology results.

Results

In total 106- normal/clinically healthy sites, 20- pre-malignant and 29- malignant (SCC) sites were compared. While the median pixel value of the R545/R575 image ratio for normal/clinically healthy tissue was 0.87 (IQR = 0.82-0.94), they were 1.35 (IQR = 1.13-1.67) and 2.44 (IQR = 1.78-3.80) for pre-malignant and malignant lesions, respectively. Area under the ROC curve to differentiate malignant from normal/clinically healthy [AUC = 0.99 (95% CI: 0.99-1.00)], pre-malignant from normal/clinically healthy [AUC = 0.94 (95% CI: 0.86-1.00)], malignant from pre-malignant [AUC = 0.84 (95% CI: 0.73-0.95)] and pre-malignant and malignant from normal/clinically healthy [AUC = 0.97 (95% CI: 0.94-1.00)] lesions were desirable.

Conclusion

We find DR imaging to be very effective as a screening tool in locating the potentially malignant areas of oral lesions with relatively good diagnostic accuracy while comparing it to the gold standard histopathology.

Anti-Stokes fluorescence from endogenously formed protoporphyrin IX--implications for clinical multiphoton diagnostics

Multiphoton imaging based on two-photon excitation is making its way into the clinics, particularly for skin cancer diagnostics. It has been suggested that endogenously formed protoporphyrin IX (PpIX) induced by aminolevulinic acid or methylaminolevulinate can be applied to improve tumor contrast, in connection to imaging of tissue autofluorescence. However, previous reports are limited to cell studies and data from tissue are scarce. No report shows conclusive evidence that endogenously formed PpIX increases tumor contrast when performing multiphoton imaging in the clinical situation. We here demonstrate by spectral analysis that two-photon excitation of endogenously formed PpIX does not provide additional contrast in superficial basal cell carcinomas. In fact, the PpIX signal is overshadowed by the autofluorescent background. The results show that PpIX should be excited at a wavelength giving rise to one-photon anti-Stokes fluorescence, to overcome the autofluorescent background. Thus, this study reports on a plausible method, which can be implemented for clinical investigations on endogenously formed PpIX using multiphoton microscopy.

Techniques for fluorescence detection of protoporphyrin IX in skin cancers associated with photodynamic therapy

Photodynamic therapy (PDT) is a treatment modality that uses a specific photosensitizing agent, molecular oxygen, and light of a particular wavelength to kill cells targeted by the therapy. Topically administered aminolevulinic acid (ALA) is widely used to effectively treat cancerous and precancerous skin lesions, resulting in targeted tissue damage and little to no scarring. The targeting aspect of the treatment arises from the fact that ALA is preferentially converted into protoporphyrin IX (PpIX) in neoplastic cells. To monitor the amount of PpIX in tissues, techniques have been developed to measure PpIX-specific fluorescence, which provides information useful for monitoring the abundance and location of the photosensitizer before and during the illumination phase of PDT. This review summarizes the current state of these fluorescence detection techniques. Non-invasive devices are available for point measurements, or for wide-field optical imaging, to enable monitoring of PpIX in superficial tissues. To gain access to information at greater tissue depths, multi-modal techniques are being developed which combine fluorescent measurements with ultrasound or optical coherence tomography, or with microscopic techniques such as confocal or multiphoton approaches. The tools available at present, and newer devices under development, offer the promise of better enabling clinicians to inform and guide PDT treatment planning, thereby optimizing therapeutic outcomes for patients.

In vitro comparison of hypericin and 5-aminolevulinic acid-derived protoporphyrin IX for photodynamic inactivation of medulloblastoma cells

Background

Hypericin (HYP) is a naturally occurring photosensitizer. Cellular uptake and photodynamic inactivation after incubation with this photosensitizer have neither been examined in medulloblastoma cells in vitro, nor compared with 5-aminolevulinic acid-derived protoporphyrin IX (5-ALA-derived PpIX).

Methods

In 3 medulloblastoma cell lines (D283 Med, Daoy, and D341 Med) the time- and concentration-dependent intracellular accumulation of HYP and 5-ALA-derived PpIX was analyzed by fluorescence microscopy (FM) and FACS. Photocytotoxicity was measured after illumination at 595 nm (HYP) and 635 nm (5-ALA-derived PpIX) in D283 Med cells and compared to U373 MG glioma cells.

Results

All medulloblastoma cell lines exhibited concentration- and time-dependent uptake of HYP. Incubation with HYP up to 10 µM resulted in a rapid increase in fluorescence intensity, which peaked between 2 and 4 hours. 5-ALA-derived PpIX accumulation increased in D283 Med cells by 22% over baseline after 5-ALA incubation up to 1.2 mM. Photocytotoxicity of 5-ALA-derived PpIX was higher in D283 Med medulloblastoma compared to U373MG glioma. The [lethal dose (light dose that is required to reduce cell survival to 50% of control)] of 5-ALA-derived PpIX was 3.8 J/cm² in D283 Med cells versus 5.7 J/cm2 in U373MG glioma cells. Photocytotoxicity of HYP in D283 Med cells was determined at 2.5 µM after an incubation time of 2 h and an illumination wavelength of 595 nm. The value was 0.47 J/cm².

Conclusion

By its 5-fold increase in fluorescence over autofluorescence levels HYP has excellent properties for tumor visualization in medulloblastomas. The high photocytotoxicity of HYP, compared to 5-ALA-derived PpIX, is convincingly demonstrated by its 8- to 13-fold lower . Therefore HYP might be a promising molecule for intraoperative visualization and photodynamic treatment of medulloblastomas.

Sodium butyrate increases the effect of the photodynamic therapy: a mechanism that involves modulation of gene expression and differentiation in astrocytoma cells

OBJECTIVES

In order to evaluate the improvement of the photodynamic therapy (PDT) due to sodium butyrate (NaBu), its effectiveness in U373-MG and D54-MG astrocytoma cell lines was evaluated.

METHODS

Cells were exposed to delta-aminolevulinic acid (δ-ALA) as a precursor to endogenous photosensitizer protoporphyrin IX (PpIX). In both astrocytoma cells, an important increase by ALA was observed in uroporphyrinogen synthetase gene expression: 1.8- and 52-fold for D54-MG and U373-MG cells, respectively. After irradiation, they showed 16.67 and 28.9% of mortality in U373-MG and D54-MG, respectively. These mortalities increased to 70.62 and 96.7% when U373-MG and D54-MG cells, respectively, were exposed 24 h to 8 mM NaBu, before to PpIX induction. NaBu induced expression of caspase-3, caspase-9, and Bcl-2 and increased Bax in U373-MG cells. ALA-induced morphological changes are compatible to differentiation.

CONCLUSIONS

Genes and differentiation induced mainly by NaBu improve cell death performed by PDT in astrocytoma cells. These facts prove the synergistic effect of NaBu on cytotoxic damage induced by PDT.

Detailed analysis of apoptosis and delayed luminescence of human leukemia Jurkat T cells after proton irradiation and treatments with oxidant agents and flavonoids

Following previous work, we investigated in more detail the relationship between apoptosis and delayed luminescence (DL) in human leukemia Jurkat T cells under a wide variety of treatments. We used menadione and hydrogen peroxide to induce oxidative stress and two flavonoids, quercetin, and epigallocatechin gallate, applied alone or in combination with menadione or H₂O₂. 62 MeV proton beams were used to irradiate cells under a uniform dose of 2 or 10 Gy, respectively. We assessed apoptosis, cell cycle distributions, and DL. Menadione, H₂O₂ and quercetin were potent inducers of apoptosis and DL inhibitors. Quercetin decreased clonogenic survival and the NAD(P)H level in a dose-dependent manner. Proton irradiation with 2 Gy but not 10 Gy increased the apoptotic rate. However, both doses induced a substantial G₂/M arrest. Quercetin reduced apoptosis and prolonged the G₂/M arrest induced by radiation. DL spectroscopy indicated that proton irradiation disrupted the electron flow within Complex I of the mitochondrial respiratory chain, thus explaining the massive necrosis induced by 10 Gy of protons and also suggested an equivalent action of menadione and quercetin at the level of the Fe/S center N2, which may be mediated by their binding to a common site within Complex I, probably the rotenone-binding site.

Increased expression of ABCB6 enhances protoporphyrin IX accumulation and photodynamic effect in human glioma

BACKGROUND

Glioma recurrence usually occurs close to the tumor resection margins as a result of residual infiltrating glioma cells. 5-aminolevulinic acid (ALA) fluorescence-guided resection of gliomas has been demonstrated to enhance discrimination of tumor tissue and to improve survival. ALA-based photodynamic therapy is an effective albeit still experimental adjuvant treatment option for gliomas. However, insufficient protoporphyrin IX (PpIX) accumulation may limit the benefits of fluorescence-guided resection and photodynamic therapy.

METHODS

We investigated the expression of the ATP-binding cassette transporter ABCB6, which regulates porphyrin synthesis, in surgical specimens from human gliomas and manipulated ABCB6 in human glioma cell lines.

RESULTS

Our findings demonstrated that expression levels of ABCB6 were greatly elevated in human gliomas compared with normal brain tissues and correlated with World Health Organization histologic grade. A previously undescribed finding was that ABCB6 mRNA expression in solidly fluorescing tumor tissues was higher than that in vaguely fluorescing tumors, suggesting that ABCB6 may be at least in part responsible for PpIX accumulation in glioma cells. Accordingly, ABCB6 overexpression in glioma cell lines caused a marked increase in intracellular levels of PpIX, and was more sensitive to ALA-induced photodynamic therapy-events that could be prevented by silencing ABCB6 via siRNA treatment.

CONCLUSIONS

Our findings indicate a crucial role of ABCB6 in ALA metabolism and accumulation of PpIX in glioma. ABCB6 overexpression is a potential approach to enhance accumulation of PpIX for optimizing the subjective discrimination of vague fluorescence and improving the efficacy of ALA-based photodynamic therapy.

[Advances in endoscopic diagnosis of dysplasia and carcinoma of the larynx]

To improve the preoperative and intraoperative diagnosis of laryngeal cancer and its precursors, various endoscopic imaging techniques have been developed in recent years. These techniques differ markedly in their specific applications and goals. Precisely distinguishing among normal mucosa, dysplasia and invasive carcinoma with these procedures is necessary. Furthermore, the exact identification of tumor margins should be possible. The long-term goal is the development of optical biopsy. Since so far there have only been small studies regarding the evaluation of the presented methods, it is necessary to establish multi-center trials with large sample sizes to accurately estimate the value of these endoscopic imaging techniques.

5-aminolevulinic acid (5-ALA)-induced fluorescence in intracerebral metastases: a retrospective study

BACKGROUND

Microsurgical, circumferential stripping of intracerebral metastases often proves to be insufficient to prevent local tumor recurrence.

OBJECTIVE

We were interested in the potential impact of 5-aminolevulinic acid (5-ALA)-induced-fluorescence (5-AIF) as a diagnostic tool for the resection of intracerebral metastases.

METHODS

A retrospective analysis was performed for 52 patients who underwent 5-AIF-guided resection for intracerebral mass lesions that histologically corresponded to metastases from tumors outside the central nervous system. The presence of ALA fluorescence in the tumor was determined in each patient. In 42 patients, fluorescence of the resection cavity after tumor removal was additionally recorded. Data were correlated with neuropathological findings in tissue specimens.

RESULTS

A total of 32 of the 52 metastases (62%) exhibited 5-AIF in tumor parts. All 5-AIF-positive metastases exhibited an inhomogeneous fluorescence pattern. 5-AIF was neither associated with the histological type nor with the site of origin of the metastases. Residual fluorescence of the resection cavity was detected after macroscopically complete white light resection in 24 patients with 5-AIF positive metastases. Residual tumor tissue was histologically confirmed in 6 of 18 patients with available tissue specimens from such 5-AIF positive areas (33%).

CONCLUSIONS

The majority of metastases (62%) were 5-AIF positive, suggesting a potential impact of 5-AIF for improved visualization of metastatic tumor tissue within the brain. However, residual 5-AIF after macroscopically complete resection of a metastasis needs to be interpreted with caution because of the limited specificity for detection of residual tumor tissue.

Fluorescence diagnosis of metastatic lymph nodes using 5-aminolevulinic acid (5-ALA) in a mouse model of colon cancer

BACKGROUND

Lymph node metastasis is one of the most critical prognostic factors in patients with colorectal cancer. Although regional lymph nodes should be surgically resected and pathologically examined, techniques for the intraoperative diagnosis of lymph node metastasis remain to be well established. Fluorescence diagnosis using 5-aminolevulinic acid (5-ALA) is a promising technique for evaluating various malignancies. After exogenous administration of 5-ALA, protoporphyrin IX (PPIX) accumulates in malignant cells and can be detected as red fluorescence. In this study, we investigated the usefulness of fluorescence diagnosis using 5-ALA for the detection of lymph node metastasis in a mouse model of colon cancer.

MATERIALS AND METHODS

An orthotopic colon cancer model was prepared by inoculating the cecal wall of nude mice with HCA7, a human colon adenocarcinoma cell line. After 3 wk, 40 mg/kg of 5-ALA was administered intraperitoneally (IP) or orally (PO). Fluorescence diagnosis with a D-Light System (Karl Storz) was then performed after 3 or 6 h.

RESULTS

In the IP group, PPIX fluorescence was detected in metastatic lymph nodes as well as in other malignant lesions, including primary tumors and abdominal implantations, while non-metastatic nodes were fluorescence-negative. In contrast, no obvious fluorescence was detected in cancerous tissues in the PO group.

CONCLUSIONS

PPIX fluorescence induced by intraperitoneal injection of 5-ALA allows metastatic lymph nodes to be accurately diagnosed in this mouse model. This technique may facilitate the intraoperative diagnosis of lymph node metastases from colon cancer in a clinical setting.

Modulating ALA-PDT efficacy of mutlidrug resistant MCF-7 breast cancer cells using ALA prodrug

Multi-drug resistance of breast cancer is a major obstacle in chemotherapy of cancer treatments. Recently it was suggested that photodynamic therapy (PDT) can overcome drug resistance of tumors. ALA-PDT is based on the administration of 5-aminolevulinic acid (ALA), the natural precursor for the PpIX biosynthesis, which is a potent natural photosensitizer. In the present study we used the AlaAcBu, a multifunctional ALA-prodrug for photodynamic inactivation of drug resistant MCF-7/DOX breast cancer cells. Supplementation of low doses (0.2mM) of AlaAcBu to the cells significantly increased accumulation of PpIX in both MCF-7/WT and MCF-7/DOX cells in comparison to ALA, or ALA + butyric acid (BA). In addition, our results show that MCF-7/DOX cells are capable of producing higher levels of porphyrins than MCF-7/WT cells due to low expression of the enzyme ferrochelatase, which inserts iron into the tetra-pyrrol ring to form the end product heme. Light irradiation of the AlaAcBu treated cells activated efficient photodynamic killing of MCF-7/DOX cells similar to the parent MCF-7/WT cells, depicted by low mitochondrial enzymatic activity, LDH leakage and decreased cell survival following PDT. These results indicate that the pro-drug AlaAcBu is an effective ALA derivative for PDT treatments of multidrug resistant tumors.

Novel development of 5-aminolevurinic acid (ALA) in cancer diagnoses and therapy

Early detection and intervention are needed for optimal outcomes in cancer therapy. Improvements in diagnostic technology, including endoscopy, photodynamic diagnosis (PDD), and photodynamic therapy (PDT), have allowed substantial progress in the treatment of cancer. 5-Aminolevulinic acid (ALA) is a natural, delta amino acid biosynthesized by animal and plant mitochondria. ALA is a precursor of porphyrin, heme, and bile pigments, and it is metabolized into protoporphyrin IX (PpIX) in the course of heme synthesis. PpIX preferentially accumulates in tumor cells resulting in a red fluorescence following irradiation with violet light and the formation of singlet oxygen. This reaction, utilized to diagnose and treat cancer, is termed ALA-induced PDD and PDT. In this review, the biological significance of heme metabolites, the mechanism of PpIX accumulation in tumor cells, and the therapeutic potential of ALA-induced PDT alone and combined with hyperthermia and immunotherapy are discussed.

Nickel(II) chelatase variants directly evolved from murine ferrochelatase: porphyrin distortion and kinetic mechanism

The heme biosynthetic pathway culminates with the ferrochelatase-catalyzed ferrous iron chelation into protoporphyrin IX to form protoheme. The catalytic mechanism of ferrochelatase has been proposed to involve the stabilization of a nonplanar porphyrin to present the pyrrole nitrogens to the metal ion substrate. Previously, we hypothesized that the ferrochelatase-induced nonplanar distortions of the porphyrin substrate impose selectivity for the divalent metal ion incorporated into the porphyrin ring and facilitate the release of the metalated porphyrin through its reduced affinity for the enzyme. Using resonance Raman spectroscopy, the structural properties of porphyrins bound to the active site of directly evolved Ni(2+)-chelatase variants are now examined with regard to the mode and extent of porphyrin deformation and related to the catalytic properties of the enzymes. The Ni(2+)-chelatase variants (S143T, F323L, and S143T/F323L), which were directly evolved to exhibit an enhanced Ni(2+)-chelatase activity over that of the parent wild-type ferrochelatase, induced a weaker saddling deformation of the porphyrin substrate. Steady-state kinetic parameters of the evolved variants for Ni(2+)- and Fe(2+)-chelatase activities increased compared to those of wild-type ferrochelatase. In particular, the reduced porphyrin saddling deformation correlated with increased catalytic efficiency toward the metal ion substrate (Ni(2+) or Fe(2+)). The results lead us to propose that the decrease in the induced protoporphyrin IX saddling mode is associated with a less stringent metal ion preference by ferrochelatase and a slower porphyrin chelation step.

Silencing of ferrochelatase enhances 5-aminolevulinic acid-based fluorescence and photodynamic therapy efficacy

Background:

Recurrence of glioma frequently occurs within the marginal area of the surgical cavity due to invading residual cells. 5-Aminolevulinic acid (5-ALA) fluorescence-guided resection has been used as effective therapeutic modalities to improve discrimination of brain tumour margins and patient prognosis. However, the marginal areas of glioma usually show vague fluorescence, which makes tumour identification difficult, and the applicability of 5-ALA-based photodynamic therapy (PDT) is hampered by insufficient therapeutic efficacy in glioma tissues.

Methods:

To overcome these issues, we assessed the expression of ferrochelatase (FECH) gene, which encodes a key enzyme that catalyses the conversion of protoporphyrin IX (PpIX) to heme, in glioma surgical specimens and manipulated FECH in human glioma cell lines.

Results:

Prominent downregulation of FECH mRNA expression was found in glioblastoma tissues compared with normal brain tissues, suggesting that FECH is responsible for PpIX accumulation in glioblastoma cells. Depletion of FECH by small interference RNA enhanced PpIX fluorescence after exposure to 5-ALA concomitant with increased intracellular PpIX accumulation in glioma cells. Silencing of FECH caused marked growth inhibition and apoptosis induction by PDT in glioma cells.

Conclusion:

These results suggest that knockdown of FECH is a potential approach to enhance PpIX fluorescent quality for optimising the subjective discrimination of vague fluorescence and improving the effect of 5-ALA-PDT.

Optical and molecular techniques to identify tumor margins within the larynx

Failure to remove tumor cells from the larynx significantly increases the risk of local recurrence following surgical excision. Healthy tissue must be preserved to optimize long-term vocal and swallowing function. It is essential to accurately distinguish between healthy mucosa, dysplasia, and invasive carcinoma. Optical and molecular examining technologies have been developed to improve tumor margin identification in vivo. We aimed to review the efficacy of these technologies. Published articles were identified using MEDLINE, EMBASE, and Cochrane central register of controlled trials (CENTRAL). Randomized clinical trials are required to establish the benefit to patients and cost to the health service of using 5-aminolevulinic acid (ALA)-induced fluorescent imaging, contact endoscopy, and optical coherence tomography (OCT). Furthermore, primary research is required to validate other techniques, such as confocal endomicroscopy and Raman spectroscopy, and to develop their clinical applications in the larynx.

"Triple Observation Method (TOM)" to discriminate optically autofluorescence from porphyrins versus that from copper-metallothioneins

We propose a conclusive difference observed between the excitation conditions required to observe porphyrins and copper-metallothioneins in cells and/or tissues using an ordinary fluorescence microscope. We have emphasized the importance of examining the spectral properties of the emissions to avoid any serious mistakes such as confusing porphyrins with copper-metallothioneins in the liver and kidneys. However, microspectrophotometry is not a conventional method for either histochemical, cytochemical, or pathological studies because microspectrophotometers are both expensive and difficult to operate. Therefore, we demonstrate a simple comparative method using ordinary excitation filter arrangements. When using our technique, it becomes possible to optically discriminate more accurately between the autofluorescence properties arising from porphyrins and those arising from copper-metallothioneins. We would like to name our simple technique "Triple Observation Method (TOM)".

Autofluorescence videoendoscopy system using the SAFE-3000 for assessing superficial gastric neoplasia

BACKGROUND

Autofluorescence (AF) videoendoscopy has an advantage over ordinary videoendoscopy in the diagnosis of gastric neoplasias, and the aim of the present study was to evaluate the effectiveness of using the SAFE-3000 videoendoscopy system to diagnose superficial gastric neoplasias.

METHODS

Ordinary videoendoscopy, AF videoendoscopy, and chromoendoscopy (CE) were used to diagnose the tumor existence and extent in 14 patients with gastric adenoma, 40 patients with intestinal-type early gastric cancer (EGC) (10 protruded, and 30 depressed), and nine patients with diffuse-type EGC. The diagnostic accuracies of the three kinds of images were evaluated by comparison with the results of histopathological assessment of resected specimens.

RESULTS

For gastric adenomas the diagnostic accuracy between the AF images and white light (WL) images did not differ significantly, and for protruded intestinal-type EGCs and diffuse-type EGCs the diagnostic accuracy did not differ significantly between any of the types of images. For depressed intestinal-type EGCs, the diagnostic accuracy of AF images tended to be higher than that of the WL images (P < 0.05) and it was not significantly different from that of the CE images. The detection rate of pink or orange color in AF images was significantly higher for protruded intestinal-type EGCs than gastric adenomas (P = 0.005), depressed intestinal-type EGCs (P < 0.001), and diffuse-type EGCs (P = 0.027).

CONCLUSIONS

Autofluorescence videoendoscopy using the SAFE-3000 system for gastric neoplasias might be useful for diagnosing depressed intestinal-type early gastric cancers. The detection of orange or pink color in AF images may be efficacious in discriminating protruded intestinal-type early gastric cancers from gastric adenomas.

Mechanism of cell death by 5-aminolevulinic acid-based photodynamic action and its enhancement by ferrochelatase inhibitors in human histiocytic lymphoma cell line U937

Photodynamic therapy (PDT) for tumors is based on the tumor-selective accumulation of a photosensitizer, protoporphyrin IX (PpIX), followed by irradiation with visible light. However, the molecular mechanism of cell death caused by PDT has not been fully elucidated. The 5-aminolevulinic acid (ALA)-based photodynamic action (PDA) was dependent on the accumulation of PpIX, the level of which decreased rapidly by eliminating ALA from the incubation medium in human histiocytic lymphoma U937 cells. PDA induced apoptosis characterized by lipid peroxidation, increase in Bak and Bax/Bcl-xL, decrease in Bid, membrane depolarization, cytochrome c release, caspase-3 activation, phosphatidylserine (PS) externalization. PDT-induced cell death seemed to occur predominantly via apoptosis through distribution of PpIX in mitochondria. These cell death events were enhanced by ferrochelatase inhibitors. These results indicated that ALA-based-PDA induced apoptotic cell death through a mitochondrial pathway and that ferrochelatase inhibitors might enhanced the effect of PDT for tumors even at low concentrations of ALA.

Merging molecular imaging and RNA interference: early experience in live animals

The rapid development of non-invasive imaging techniques and imaging reporters coincided with the enthusiastic response that the introduction of RNA interference (RNAi) techniques created in the research community. Imaging in experimental animals provides quantitative or semi-quantitative information regarding the biodistribution of small interfering RNAs and the levels of gene interference (i.e., knockdown of the target mRNA) in living animals. In this review we give a brief summary of the first imaging findings that have potential for accelerating the development and testing of new approaches that explore RNAi as a method for achieving loss-of-function effects in vivo and as a promising therapeutic tool.