RNA expression profiling of normal and tumor cells following photodynamic therapy with 5-aminolevulinic acid-induced protoporphyrin IX in vitro

Molecular Determinants for Photodynamic Therapy Resistance and Improved Photosensitizer Delivery in Glioma

Gliomas account for 24% of all the primary brain and Central Nervous System (CNS) tumors. These tumors are diverse in cellular origin, genetic profile, and morphology but collectively have one of the most dismal prognoses of all cancers. Work is constantly underway to discover a new effective form of glioma therapy. Photodynamic therapy (PDT) may be one of them. It involves the local or systemic application of a photosensitive compound-a photosensitizer (PS)-which accumulates in the affected tissues. Photosensitizer molecules absorb light of the appropriate wavelength, initiating the activation processes leading to the formation of reactive oxygen species and the selective destruction of inappropriate cells. Research focusing on the effective use of PDT in glioma therapy is already underway with promising results. In our work, we provide detailed insights into the molecular changes in glioma after photodynamic therapy. We describe a number of molecules that may contribute to the resistance of glioma cells to PDT, such as the adenosine triphosphate (ATP)-binding cassette efflux transporter G2, glutathione, ferrochelatase, heme oxygenase, and hypoxia-inducible factor 1. We identify molecular targets that can be used to improve the photosensitizer delivery to glioma cells, such as the epithelial growth factor receptor, neuropilin-1, low-density lipoprotein receptor, and neuropeptide Y receptors. We note that PDT can increase the expression of some molecules that reduce the effectiveness of therapy, such as Vascular endothelial growth factor (VEGF), glutamate, and nitric oxide. However, the scientific literature lacks clear data on the effects of PDT on many of the molecules described, and the available reports are often contradictory. In our work, we highlight the gaps in this knowledge and point to directions for further research that may enhance the efficacy of PDT in the treatment of glioma.

Effect of aza-BODIPY-photodynamic therapy on the expression of carcinoma-associated genes and cell death mode

BACKGROUND

Breast cancer is the most common cancer affecting women worldwide.Photodynamic therapy(PDT) has now proven to be a promising form of cancer therapy due to its targeted and low cytotoxicity to healthy cells and tissues.PDT is a technique used to create cell death localized by light after application of a light-sensitive agent.Aza-BODIPY is a promising photosensitizer for use in PDT. Our results showed that aza-BODIPY-PDT induced apoptosis, probably through p53 and caspase3 in MCF-7 cells. Future studies should delineate the molecular mechanisms underlying aza-BODIPY-PDT-induced cell death for a better understanding of the signaling pathways modulated by the therapy so that this novel technology could be implemented in the clinic for treating breast cancer.

AIM

In this study,we aimed to determine the change in the expression levels of 88 carcinoma-associated genes induced by aza-BODIPY-PDT were analyzed so as to understand the specific pathways that are modulated by aza-BODIPY-PDT.

MATERIAL METHOD

In this study,the molecular basis of the anti-cancer activity of aza-BODIPY-PDT was investigated.Induction of apoptosis and necrosis in MCF-7 breast cancer cells after treatment with aza- BODIPY derivative with phthalonitrile substituents (aza-BODIPY) followed by light exposure was evaluated by Annexin V 7- Aminoactinomycin D (7-AAD) flow cytometry.

RESULTS

Aza-BODIPY-PDT induced cell death in MCF-7 cells treated with aza-BODIPY-PDT; flow cytometry revealed that 28 % of the cells died by apoptosis. Seven of the 88 carcinoma-associated genes that were assayed were differentially expressed -EGF, LEF1, WNT1, TCF7, and TGFBR2 were downregulated, and CASP3 and TP53 were upregulated - in cells subjected to aza-BODIPY-PDT.This made us think that the aza-BODIPY-PDT induced caspase 3 and p53-mediated apoptosis in MCF7 cells.

CONCLUSION

In our study,it was determined that the application of aza-BODIPY-PDT to MCF7 cells had a negative effect on cell connectivity and cell cycle.The fact that the same effect was not observed in control cells and MCF7 cells in the dark field of aza-BODIPY indicates that aza-BODIPY has a strong phodynamic anticancer effect.

Challenges and opportunities of bioprocessing 5-aminolevulinic acid using genetic and metabolic engineering: a critical review

5-Aminolevulinic acid (5-ALA), a non-proteinogenic five-carbon amino acid, has received intensive attentions in medicine due to its approval by the US Food and Drug Administration (FDA) for cancer diagnosis and treatment as photodynamic therapy. As chemical synthesis of 5-ALA performed low yield, complicated processes, and high cost, biosynthesis of 5-ALA via C4 (also called Shemin pathway) and C5 pathway related to heme biosynthesis in microorganism equipped more advantages. In C4 pathway, 5-ALA is derived from condensation of succinyl-CoA and glycine by 5-aminolevulic acid synthase (ALAS) with pyridoxal phosphate (PLP) as co-factor in one-step biotransformation. The C5 pathway involves three enzymes comprising glutamyl-tRNA synthetase (GltX), glutamyl-tRNA reductase (HemA), and glutamate-1-semialdehyde aminotransferase (HemL) from α-ketoglutarate in TCA cycle to 5-ALA and heme. In this review, we describe the recent results of 5-ALA production from different genes and microorganisms via genetic and metabolic engineering approaches. The regulation of different chassis is fine-tuned by applying synthetic biology and boosts 5-ALA production eventually. The purification process, challenges, and opportunities of 5-ALA for industrial applications are also summarized.

Systematic Review and Meta-Analysis of In Vitro Anti-Human Cancer Experiments Investigating the Use of 5-Aminolevulinic Acid (5-ALA) for Photodynamic Therapy

5-Aminolevulinic acid (5-ALA) is an amino acid derivative and a precursor of protoporphyrin IX (PpIX). The photophysical feature of PpIX is clinically used in photodynamic diagnosis (PDD) and photodynamic therapy (PDT). These clinical applications are potentially based on in vitro cell culture experiments. Thus, conducting a systematic review and meta-analysis of in vitro 5-ALA PDT experiments is meaningful and may provide opportunities to consider future perspectives in this field. We conducted a systematic literature search in PubMed to summarize the in vitro 5-ALA PDT experiments and calculated the effectiveness of 5-ALA PDT for several cancer cell types. In total, 412 articles were identified, and 77 were extracted based on our inclusion criteria. The calculated effectiveness of 5-ALA PDT was statistically analyzed, which revealed a tendency of cancer-classification-dependent sensitivity to 5-ALA PDT, and stomach cancer was significantly more sensitive to 5-ALA PDT compared with cancers of different origins. Based on our analysis, we suggest a standardized in vitro experimental protocol for 5-ALA PDT.

Fluorescence-guided surgery for high-grade gliomas

5-aminolevulinic acid (5-ALA) is a prodrug that results in the fluorescence of high-grade gliomas relative to the surrounding brain parenchyma. 5-ALA has been increasingly utilized in fluorescence-guided surgery for these tumors, and its intraoperative use has been associated with a significantly improved extent of resection and progression-free survival. This review outlines the growing body of evidence that has culminated in the recent Food and Drug Administration approval of 5-ALA, as well as emerging applications for this agent.

Novel carbohydrate-substituted metallo-porphyrazine comparison for cancer tissue-type specificity during PDT

A longstanding obstacle to cancer eradication centers on the heterogeneous nature of the tissue that manifests it. Variations between cancer cell resistance profiles often result in a survival percentage following classic therapeutics. As an alternative, photodynamic therapys' (PDT) unique non-specific cell damage mechanism and high degree of application control enables it to potentially deliver an efficient treatment regime to a broad range of heterogeneous tissue types thereby overcoming individual resistance profiles. This study follows on from previous design, characterization and solubility analyses of three novel carbohydrate-ligated zinc-porphyrazine (Zn(II)Pz) derivatives. Here we report on their PDT application potential in the treatment of five common cancer tissue types in vitro. Following analyses of metabolic homeostasis, toxicity and cell death induction, overall Zn(II)Pz-PDT proved comparably efficient between all cancer tissue populations. Differential localization patterns of Zn(II)Pz derivatives between cell types did not appear to influence the overall PDT effect. All cell types exhibited significant disruptions to mitochondrial activity and associated ATP production levels. Toxicity and chromatin structure profiles revealed indiscernible patterns of damage between Zn(II)Pz derivatives and cell type. The subtle differences observed between individual Zn(II)Pz derivatives is most likely due to a combination of carbohydrate moiety characteristics on energy transfer processes and associated dosage optimization requirements per tissue type. Collectively, this indicates that resistance profiles are negated to a significant extent by Zn(II)Pz-PDT making these derivatives attractive candidates for PDT applications across multiple tissue types and subtypes.

5-Aminolaevulinic Acid-Induced Fluorescence in Primary Central Nervous System Lymphoma

OBJECTIVE

Diagnosis of primary central nervous system lymphoma (PCNSL) is usually confirmed by brain biopsy and subsequent neuropathologic workup. 5-Aminolevulinic acid (5-ALA)-induced fluorescence has been established for diagnostic and therapeutic purposes in glioma treatment during the last few years and is discussed for use in other cranial tumors. Its role in diagnosis and treatment of PCNSL is still elusive.

METHODS

This retrospective study includes clinical, magnetic resonance imaging, pathologic and surgical data of selected 11 patients with PCNSL at two university hospitals within the last 4 years undergoing surgical treatment for resection because of imminent mass effect or suspected cerebral glioma. Patients received 5-ALA for fluorescence-guided resection preoperatively.

RESULTS

The 11 subjects age ranged from 59 to 81 years. Postsurgical pathologic workup revealed malignant B cell lymphoma with morphologic features of diffuse large B cell lymphoma. Eight of these 11 patients with PCNSL showed a clear fluorescence induced by 5-ALA. After surgical resection, patients were treated with combination chemotherapy regimens.

CONCLUSION

In patients with glioma, the use of 5-ALA is known to be associated with increased extent of resection and survival benefit. Our data and retrospective analysis of a larger patient cohort suggest that the use of 5-ALA in PCNSL should be included in a surgical approach, if this is reconsidered for select patients within a clinical study. In addition, even photodynamic therapy in combination with 5-ALA might be studied.

Combined treatment with X-ray irradiation and 5-aminolevulinic acid elicits better transcriptomic response of cell cycle-related factors than X-ray irradiation alone

PURPOSE

5-Aminolevulinic acid (ALA) is a precursor of the photosensitizer protoporphyrin (PpIX) used in photodynamic therapy. In our previous work, PpIX enhanced the generation of reactive oxygen species by X-ray irradiation. In this study, we evaluated the potential of ALA as an endogenous sensitizer to X-ray irradiation.

METHODOLOGY

Tumor-bearing C57BL/6J mice implanted with B16-BL6 melanoma cells were subsequently treated with irradiation (3 Gy/day for 10 days; total, 30 Gy) plus local administration of 50 mg/kg ALA 24 hours prior to each irradiation (ALA-XT). Tumor-bearing mice without treatment (NT), those treated with ALA only (ALAT), and those treated with X-ray irradiation only (XT) were used as controls.

RESULTS

ALA potentiated tumor suppression by X-ray irradiation. In microarray analyses using tumor tissue collected after 10 sessions of fractional irradiation, functional analysis revealed that the majority of dysregulated genes in the XT and ALA-XT groups were related to cell-cycle arrest. Finally, the XT and ALA-XT groups differed in the strength of expression, but not in the pattern of expression.

CONCLUSIONS

mRNA analysis revealed that the combined use of ALA and X-ray irradiation sensitized tumors to X-ray treatment. Furthermore, the present results were consistent with ALA's tumor suppressive effects in vivo.

5-ALA Fluorescence in Native Pituitary Adenoma Cell Lines: Resection Control and Basis for Photodynamic Therapy (PDT)?

OBJECTIVE

Pituitary adenomas (PA), especially invasive ones, are often not completely resectable. Usage of 5-aminolevulinic acid (5-ALA) for fluorescence guided surgery could improve the rate of total resection and, additionally, open the doors for photodynamic therapy (PDT) in case of unresectable or partially resected PAs. The aim of this study was to investigate the uptake of 5-ALA and the effect of 5-ALA based PDT in cell lines.

METHODS

GH3 and AtT-20 cell lines were incubated with different concentrations of 5-ALA, protoporphyrin IX (PPIX) fluorescence was measured by flow cytometry and fluorescencespectrometry. WST-1 assays were performed to determine the surviving fraction of cells after PDT. PPIX fluorescence intensities and PDT effect of the pituitary adenoma cells were compared to U373MG, a well-known glioblastoma cell line.

RESULTS

Both cell lines showed a 5-ALA dependent intracellular PPIX fluorescence. Significant differences after 24hrs of incubation were observed in AtT-20 cells in comparison to GH3. Regardless of the incubation or metabolism time, there was a proliferation inhibiting effect after PDT, with no statistical significance.

CONCLUSION

Since GH3 cells showed a heterogenous uptake of 5-ALA in the flow cytometry profile, but not constantly high concentrations they might have a 5-ALA efflux mechanism, which still needs to be determined. In the case of AtT-20, the cells might need a longer time for the uptake due to their size or slow metabolism. We showed that the different cell lines have different uptake and metabolism mechanisms, which needs to be further investigated. The general uptake of 5-ALA allows the possibility of resection control and PDT for pituitary adenomas. But, the role of PDT for unresectable pituitary adenomas deserves further investigations.

Synthesis and photodynamic activity of unsymmetrical A3B tetraarylporphyrins functionalized with l-glutamate and their Zn(II) and Cu(II) metal complex derivatives

Four novel unsymmetrical A3B porphyrins 1, 2, 3 and 4 were synthesized following Lindsey procedure. Porphyrins 3 and 4 include one and three l-glutamate groups, respectively, and all porphyrins were metallated with Zn(II) (1a-4a) or Cu(II) (1b-4b). Porphyrins and metalloporphyrins presented values of singlet oxygen quantum yields (ΦD) ranging from 0.21 to 0.67. The tetraaryl derivatives in this study showed phototoxicity in SiHa cells with IC50 values ranging from <0.01 to 6.56±0.11μM, the metalloporphyrin 4a showed the lowest IC50 value. Comparing the phototoxic activity between all porphyrins, functionalization of porphyrins with glutamate increased 100 times phototoxic activity (1 (IC50 4.81±0.34μM) vs. 3 (IC50 0.04±0.02μM) and 2 (IC50 5.19±0.42μM) vs. 4 (IC50 0.05±0.01μM)). This increased activity could be attributed to reduced hydrophobicity and increased ΦΔ, given by functionalization with l-glutamate. Metalloporphyrins 3a (IC50 0.04±0.01μM) and 4a (IC50<0.01μM) presented the best values ​​of phototoxic activity. Therefore, functionalization and zinc metalation increased the phototoxic activity. SiHa cells treated with porphyrins 3, 4, 3a and 4a at a final concentration of 10μM, showed increased activity of caspase-3 enzyme compared to the negative control; indicating the induction of apoptosis. Differential gene expression pattern in SiHa cells was determined; treatments with metalloporphyrins 4a and 4b were performed, respectively, comparing the expression with untreated control. Treatments in both cases showed similar gene expression pattern in upregulated genes, since they share about 25 biological pathways and a large number of genes. According to the new photophysical properties related to the structural improvement and phototoxic activity, these molecules may have the potential application as photosensitizers in the photodynamic therapy.

Evaluation of the effects of systemic photodynamic therapy in a rat model of acute myeloid leukemia

Systemic PDT (SPDT) approach is developed to treat a variety of hematological diseases, including cancers and blood-borne infections. We evaluated the efficacy of an SPDT method for treating leukemia using a Brown Norway myeloid leukemia (BNML) rat model with the LT12 cells engineered to express GFP. The survival times of animals receiving SPDT at 5 (early-SPDT) and 10 (mid-SPDT) days post-LT12 injection were prolonged by 2 days, the rats in the late-SPDT group (15 days) exhibited a 6-day increase in life span (p<0.05). The percentages of GFP-LT12 cells in the bone marrow of the late-SPDT rats decreased from 61.6% to 56.5% on day 17. Likewise, there was a decrease in the serum expression levels of IL-1β, IL-10, TNF-α, and IFN-γ in the late-SPDT rats (p<0.05). Our findings indicate that SPDT could be an effective method for the treatment of leukemia, and that antitumor immunity may play a key role in this process.

Fluorescence in neurosurgery: Its diagnostic and therapeutic use. Review of the literature

Fluorescent agents, e.g. 5-aminolevulinic acid (5-ALA), fluorescein and indocyanine green (ICG) are in common use in neurosurgery for tumor resection and neurovascular surgery. Protoporphyrine IX (PPIX) as major metabolite of 5-ALA is a strong fluorescent substance accumulated within malignant glioma tissue and a very sensitive and specific tool for visualizing high grade glioma tissue during surgery. Furthermore, 5-ALA or rather PPIX also offers an intratumoral therapeutic option stimulated by laser light in specific wavelength. Fluorescein was demonstrated to show similar fluorescent reactions in neurosurgery, but is controversial in its use, especially in high grade tumor surgery. Intraoperative angiography during resection of arterio-venous malformations, extracranial-intracranial-bypass or aneurysm surgery is supported by ICG fluorescence. Generally ICG will provide beneficial information for both, exposure of the pathology and illustration of healthy structures. This manuscript shows an overview of the literature focussing fluorescence in neurosurgery.

C-MYC and C-FOS expression changes and cellular aspects of the photodynamic reaction with photosensitizers TMPyP and ClAlPcS2

Photodynamic therapy (PDT) is based on the tumor-selective accumulation of photosensitizer followed by irradiation with light of an appropriate wavelength. After irradiation and in the presence of oxygen, photosensitizer induces cellular damage. The aim of this study was to evaluate effects of two photosensitizers TMPyP and ClAlPcS2 on cell lines to obtain better insight into their mechanisms of action. We determined cell viability, reactive oxygen species (ROS) generation and changes in expression levels of two important early response genes, C-MYC and C-FOS, on tumor MCF7 (human breast adenocarcinoma) and G361 (human melanoma) cell lines and non-tumor BJ cell line (human fibroblast) after photodynamic reaction with TMPyP and ClAlPcS2 as photosensitizers. In addition TMPyP and ClAlPcS2 cellular uptake and clearance and antioxidant capacity of the mentioned cell lines were investigated. We found appropriate therapeutic doses and confirmed that both tested photosensitizers are photodynamically efficient in treatment used cells in vitro. TMPyP is more efficient; it had higher ROS production and toxicity after irradiation by intermediate therapeutic doses than ClAlPcS2. We revealed that both TMPyP and ClAlPcS2-PDT increased C-FOS expression on tumor cell lines (G361 and MCF7), but not on non-tumor BJ cell line. Conversely, both TMPyP and ClAlPcS2-PDT decreased C-MYC expression on non-tumor BJ cell line but not on tumor cell lines. As first we tested these photosensitizers in such extent and we believe that it can help to better understand mechanisms of PDT and increase its efficiency and applicability.

Synthesis of meso-substituted dihydro-1,3-oxazinoporphyrins

Novel dihydro-1,3-oxazinoporphyrins and naphtho[e]bis(dihydro-1,3-oxazinoporphyrin) derivatives, in which the porphyrin macrocycle is covalently linked to the dihydro-1,3-oxazine ring system were successfully synthesized from 5-(4-aminophenyl)-10,15,20-triphenylporphyrin in good yields. The structures of the target products were established on the basis of spectral data and elemental analyses.

Photodynamic therapy for enhancing antitumour immunity

BACKGROUND

Photodynamic therapy (PDT) is a new modality in cancer treatment. It is based on the tumour-selective accumulation of a photosensitizer followed by irradiation with light of a specific wavelength. PDT is becoming widely accepted owing to its relative specificity and selectivity along with absence of the harmful side-effects of chemo and radiotherapy. There are three known distinct mechanisms of tumour destruction following PDT, generation of reactive oxygen species which can directly kill tumour cells, tumour vascular shutdown which can independently lead to tumour destruction via lack of oxygen and nutrients and thirdly enhanced antitumour immunity.

METHODS

A review based on the literature acquired from the PubMed database from 1983 with a focus on the enhanced antitumour immunity effects of PTD.

RESULTS AND CONCLUSION

Tumour cell death is accompanied by the release of a large number of inflammatory mediators. These induce a non-specific inflammatory response followed by gradual adaptive antitumour immunity. Further, a combination of PDT with the immunological approach has the potential to improve PDT efficiency and increase the cure rate. This short review covers specific methods for achieving these goals.

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.

Dynamics of signaling, cytoskeleton and cell cycle regulation proteins in glioblastoma cells after sub-lethal photodynamic treatment: antibody microarray study

BACKGROUND

Photodynamic therapy (PDT) that induces oxidative stress and cell death is used for tumor destruction in oncology. To characterize early molecular events in photosensitized glioblastoma cells, we studied expression of 224 proteins after sublethal PDT that doesn't kill but wounds cells.

METHODS

Cultured glioblastoma D54Mg cells were photosensitized with 5-aminolevulinic acid so that cell survival was 95-100%. At following 0.5-5.5h protein expression and phosphorylation was assayed using proteomic antibody microarrays.

RESULTS

Within the first post-treatment hour we observed phosphorylation of protein kinase Raf, adhesion-related kinases FAK and Pyk2, and microtubule-associated protein tau. Protein kinase Cγ and microtubule-associated protein MAP-1B were overexpressed. Dystrophin, calponin, and vinculin, components of the actin cytoskeleton scaffold, microtubule-associated proteins MAP2 and CNP, cytokeratins 4 and 7 were down-regulated that indicated changes in adhesion and cell shape. Down-regulation of cyclins A, D1 and D3, c-Myc, checkpoint proteins chk1/2 and up-regulation of Smad4 could arrest the cell cycle. Overexpression of Bcl-xL and down-regulation of caspase 9 demonstrated anti-apoptotic response. At 2h post-treatment protein expression changed lesser but at 5.5h levels of PKCγ and β-synuclein and phosphorylation of Raf, FAK, Pyk2, and tau increased again.

CONCLUSIONS

Sub-lethal PDT induces complex response of glioblastoma cells including changes in activity and expression of proteins involved in adhesion-mediated signaling, signal transduction, cytoskeleton remodeling, cell cycle regulation and anti-apoptotic processes.

GENERAL SIGNIFICANCE

Multiple reactions of various cellular subsystems including adhesion, cytoskeleton, signal transduction, cell cycle, and apoptosis are integrated into the general cell response to a sublethal impact.

Photodynamic therapy augments the efficacy of oncolytic vaccinia virus against primary and metastatic tumours in mice

Background:

Therapies targeted towards the tumour vasculature can be exploited for the purpose of improving the systemic delivery of oncolytic viruses to tumours. Photodynamic therapy (PDT) is a clinically approved treatment for cancer that is known to induce potent effects on tumour vasculature. In this study, we examined the activity of PDT in combination with oncolytic vaccinia virus (OVV) against primary and metastatic tumours in mice.

Methods:

The effect of 2-[1-hexyloxyethyl-]-2-devinyl pyropheophorbide-a (HPPH)-sensitised-PDT on the efficacy of oncolytic virotherapy was investigated against subcutaneously implanted syngeneic murine NXS2 neuroblastoma and human FaDu head and neck squamous cell carcinoma xenografts in nude mice. Treatment efficacy was evaluated by monitoring tumour growth and survival. The effects of combination treatment on vascular function were examined using magnetic resonance imaging (MRI) and immunohistochemistry, whereas viral replication in tumour cells was analysed by a standard plaque assay. Normal tissue phototoxicity following PDT-OV treatment was studied using the mouse foot response assay.

Results:

Combination of PDT with OVV resulted in inhibition of primary and metastatic tumour growth compared with either monotherapy. PDT-induced vascular disruption resulted in higher intratumoural viral titres compared with the untreated tumours. Five days after delivery of OVV, there was a loss of blood flow to the interior of tumour that was associated with infiltration of neutrophils. Administration of OVV did not result in any additional photodynamic damage to normal mouse foot tissue.

Conclusion:

These results provide evidence into the usefulness of PDT as a means of enhancing intratumoural replication and therapeutic efficacy of OV.

Induction of immune mediators in glioma and prostate cancer cells by non-lethal photodynamic therapy

Background

Photodynamic therapy (PDT) uses the combination of photosensitizing drugs and harmless light to cause selective damage to tumor cells. PDT is therefore an option for focal therapy of localized disease or for otherwise unresectable tumors. In addition, there is increasing evidence that PDT can induce systemic anti-tumor immunity, supporting control of tumor cells, which were not eliminated by the primary treatment. However, the effect of non-lethal PDT on the behavior and malignant potential of tumor cells surviving PDT is molecularly not well defined.

Methodology/Principal Findings

Here we have evaluated changes in the transcriptome of human glioblastoma (U87, U373) and human (PC-3, DU145) and murine prostate cancer cells (TRAMP-C1, TRAMP-C2) after non-lethal PDT in vitro and in vivo using oligonucleotide microarray analyses. We found that the overall response was similar between the different cell lines and photosensitizers both in vitro and in vivo. The most prominently upregulated genes encoded proteins that belong to pathways activated by cellular stress or are involved in cell cycle arrest. This response was similar to the rescue response of tumor cells following high-dose PDT. In contrast, tumor cells dealing with non-lethal PDT were found to significantly upregulate a number of immune genes, which included the chemokine genes CXCL2, CXCL3 and IL8/CXCL8 as well as the genes for IL6 and its receptor IL6R, which can stimulate proinflammatory reactions, while IL6 and IL6R can also enhance tumor growth.

Conclusions

Our results indicate that PDT can support anti-tumor immune responses and is, therefore, a rational therapy even if tumor cells cannot be completely eliminated by primary phototoxic mechanisms alone. However, non-lethal PDT can also stimulate tumor growth-promoting autocrine loops, as seen by the upregulation of IL6 and its receptor. Thus the efficacy of PDT to treat tumors may be improved by controlling unwanted and potentially deleterious growth-stimulatory pathways.

Mechanisms of resistance to photodynamic therapy

Photodynamic therapy (PDT) involves the administration of a photosensitizer (PS) followed by illumination with visible light, leading to generation of reactive oxygen species. The mechanisms of resistance to PDT ascribed to the PS may be shared with the general mechanisms of drug resistance, and are related to altered drug uptake and efflux rates or altered intracellular trafficking. As a second step, an increased inactivation of oxygen reactive species is also associated to PDT resistance via antioxidant detoxifying enzymes and activation of heat shock proteins. Induction of stress response genes also occurs after PDT, resulting in modulation of proliferation, cell detachment and inducing survival pathways among other multiple extracellular signalling events. In addition, an increased repair of induced damage to proteins, membranes and occasionally to DNA may happen. PDT-induced tissue hypoxia as a result of vascular damage and photochemical oxygen consumption may also contribute to the appearance of resistant cells. The structure of the PS is believed to be a key point in the development of resistance, being probably related to its particular subcellular localization. Although most of the features have already been described for chemoresistance, in many cases, no cross-resistance between PDT and chemotherapy has been reported. These findings are in line with the enhancement of PDT efficacy by combination with chemotherapy. The study of cross resistance in cells with developed resistance against a particular PS challenged against other PS is also highly complex and comprises different mechanisms. In this review we will classify the different features observed in PDT resistance, leading to a comparison with the mechanisms most commonly found in chemo resistant cells.

Effect and mechanism of 5-aminolevulinic acid-mediated photodynamic therapy in esophageal cancer

5-aminolevulinic acid-mediated photodynamic therapy (ALA-PDT) provides a novel and promising treatment for esophageal cancer. However, its specific mechanism has not been fully elucidated and its efficacy is remarkably varied. This study investigated the effect of ALA-PDT on esophageal squamous carcinoma cell line Eca-109 in vitro and vivo to explore optimal parameters, and evaluated the significance of cell apoptosis, cell cycle, ALA-protoporphyrin IX (ALA-PpIX) subcellular localization, and expression of Bcl-2 and Bax mRNA in cells to understand the mechanism of ALA-PDT for esophageal cancer. How ALA concentration, incubation time, and laser irradiation dose influenced the cell proliferation was determined by MTT assay. ALA-PpIX subcellular localization was analyzed by confocal microscopy. The mRNA changes were detected by quantitative real-time polymerase chain reaction (QRT-PCR). Tumor models transplanted with Eca-109 cells in nude mice were established (n = 10) and killed (n = 4) at 24 h post-PDT for malondialdehyde (MDA) detection and histological study. The remaining mice were measured the tumor size for 3 weeks after treatment. Our data show that ALA-PDT significantly inhibits cell proliferation (p < 0.05), the PDT efficacy depends on the saturation of ALA concentration, incubation time, and laser irradiation dose, and the best effect in tumor destruction is at 7-14 days post-PDT. ALA-PpIX is localized in mitochondria and cytoplasm. ALA-PDT induces cell apoptosis and arrests cell cycle at G0/G1 phase. Bcl-2 is significantly down-regulated while Bax is up-regulated (p < 0.05). The results of this study provide references in choosing clinical optimal PDT parameters and help in better understanding the PDT mechanism for esophageal cancer.

Advances in photodynamic therapy for gastrointestinal tumors and its propect

This paper reviews the photodynamic therapy for gastrointestinal tumors and its mechanisms, and describes the authors' experience with it. It is feasible and reasonable to use photodynamic therapy for gastrointestinal tumors. It is not in contradiction with PDT and traditional surgical treatment, chemotherapy, radiation and immune therapy, etc. The main mechanisms of photodynamic therapy for gastrointestinal tumors are to damage tumor microvasculature, induce cancer cell apoptosis, injure cancer cell membrane, and trigger immune reactions.

Molecular effectors and modulators of hypericin-mediated cell death in bladder cancer cells

Photodynamic therapy (PDT) is an anticancer approach utilizing a light-absorbing molecule and visible light irradiation to generate, in the presence of O(2), cytotoxic reactive oxygen species, which cause tumor ablation. Given that the photosensitizer hypericin is under consideration for PDT treatment of bladder cancer we used oligonucleotide microarrays in the T24 bladder cancer cell line to identify differentially expressed genes with therapeutic potential. This study reveals that the expression of several genes involved in various metabolic processes, stress-induced cell death, autophagy, proliferation, inflammation and carcinogenesis is strongly affected by PDT and pinpoints the coordinated induction of a cluster of genes involved in the unfolded protein response pathway after endoplasmic reticulum stress and in antioxidant response. Analysis of PDT-treated cells after p38(MAPK) inhibition or silencing unraveled that the induction of an important subset of differentially expressed genes regulating growth and invasion, as well as adaptive mechanisms against oxidative stress, is governed by this stress-activated kinase. Moreover, p38(MAPK) inhibition blocked autonomous regrowth and migration of cancer cells escaping PDT-induced cell death. This analysis identifies new molecular effectors of the cancer cell response to PDT opening attractive avenues to improve the therapeutic efficacy of hypericin-based PDT of bladder cancer.

Mapping of oxidative stress responses of human tumor cells following photodynamic therapy using hexaminolevulinate

Background

Photodynamic therapy (PDT) involves systemic or topical administration of a lesion-localizing photosensitizer or its precursor, followed by irradiation of visible light to cause singlet oxygen-induced damage to the affected tissue. A number of mechanisms seem to be involved in the protective responses to PDT, including activation of transcription factors, heat shock proteins, antioxidant enzymes and apoptotic pathways.

Results

In this study, we address the effects of a destructive/lethal hexaminolevulinate (HAL) mediated PDT dose on the transcriptome by using transcriptional exon evidence oligo microarrays. Here, we confirm deviations in the steady state expression levels of previously identified early defence response genes and extend this to include unreported PDT inducible gene groups, most notably the metallothioneins and histones. HAL-PDT mediated stress also altered expression of genes encoded by mitochondrial DNA (mtDNA). Further, we report PDT stress induced alternative splicing. Specifically, the ATF3 alternative isoform (deltaZip2) was up-regulated, while the full-length variant was not changed by the treatment. Results were independently verified by two different technological microarray platforms. Good microarray, RT-PCR and Western immunoblotting correlation for selected genes support these findings.

Conclusion

Here, we report new insights into how destructive/lethal PDT alters the transcriptome not only at the transcriptional level but also at post-transcriptional level via alternative splicing.

Macromolecular delivery of 5-aminolaevulinic acid for photodynamic therapy using dendrimer conjugates

Intracellular porphyrin generation following administration of 5-aminolaevulinic acid (5-ALA) has been widely used in photodynamic therapy. However, cellular uptake of 5-ALA is limited by its hydrophilicity, and improved means of delivery are therefore being sought. Highly branched polymeric drug carriers known as dendrimers present a promising new approach to drug delivery because they have a well-defined structure capable of incorporating a high drug payload. In this work, a dendrimer conjugate was investigated, which incorporated 18 aminolaevulinic acid residues attached via ester linkages to a multipodent aromatic core. The ability of the dendrimer to deliver and release 5-ALA intracellularly for metabolism to the photosensitizer, protoporphyrin IX, was studied in the transformed PAM 212 murine keratinocyte and A431 human epidermoid carcinoma cell lines. Up to an optimum concentration of 0.1 mmol/L, the dendrimer was significantly more efficient compared with 5-ALA for porphyrin synthesis. The intracellular porphyrin fluorescence levels showed good correlation with cellular phototoxicity following light exposure, together with minimal dark toxicity. Cellular uptake of the dendrimer occurs through endocytic routes predominantly via a macropinocytosis pathway. In conclusion, macromolecular dendritic derivatives are capable of delivering 5-ALA efficiently to cells for sustained porphyrin synthesis.

5-Aminolevulinic acid-based photodynamic therapy suppressed survival factors and activated proteases for apoptosis in human glioblastoma U87MG cells

Glioblastoma is the most common astrocytic brain tumor in humans. Current therapies for this malignancy are mostly ineffective. Photodynamic therapy (PDT), an exciting treatment strategy based on activation of a photosensitizer, has not yet been extensively explored for treating glioblastoma. We used 5-aminolevulinic acid (5-ALA) as a photosensitizer for PDT to induce apoptosis in human malignant glioblastoma U87MG cells and to understand the underlying molecular mechanisms. Trypan blue dye exclusion test showed a decrease in cell viability after exposure to increasing doses of 5-ALA for 4h followed by PDT with a broad spectrum blue light (400-550 nm) at a dose of 18J/cm(2) for 1h and then incubation at 37 degrees C for 4h. Following 0.5 and 1mM 5-ALA-based PDT (5-ALA-PDT), Wright staining and ApopTag assay showed occurrence of apoptosis morphologically and biochemically, respectively. After 5-ALA-PDT, down regulation of nuclear factor kappa B (NFkappaB) and baculovirus inhibitor-of-apoptosis repeat containing-3 (BIRC-3) protein indicated inhibition of survival signals. Besides, 5-ALA-PDT caused increase in Bax:Bcl-2 ratio and mitochondrial release of cytochrome c and apoptosis-inducing factor (AIF). Activation of calpain, caspase-9, and caspase-3 occurred in course of apoptosis. Calpain and caspase-3 activities cleaved alpha-spectrin at specific sites generating 145kD spectrin breakdown product (SBDP) and 120kD SBDP, respectively. The results suggested that 5-ALA-PDT induced apoptosis in U87MG cells by suppression of survival signals and activation of proteolytic pathways. Thus, 5-ALA-PDT can be an effective strategy for inducing apoptosis in glioblastoma.

Transcriptome changes in a colon adenocarcinoma cell line in response to photochemical treatment as used in photochemical internalisation (PCI)

The photochemical internalisation (PCI) technology liberates endocytosed macromolecules like transgenes from endocytic vesicles in response to photochemical treatment. Thereby PCI improves gene transfection and is suggested for use in gene therapy. It has been proposed that PCI might also stimulate transcription of internalised transgenes, especially if they are controlled by photochemically inducible promoters (transcriptional targeting). In order to identify inducible promoters, and to evaluate the treatments influence on cellular transcriptional activity, the effect of the photochemical treatment as used in PCI (with the photosensitizer disulfonated meso-tetraphenylporphin followed by illumination) on gene transcription in WiDr adenocarcinoma cells was evaluated using microarrays. The expression of 390 genes were identified significantly changed (89% were up-regulated), of which genes associated with DNA binding and transcriptional functions were the most represented. This may be important for the expression of a photochemically internalised transgene under a specific promoter control. Real-time PCR verified photochemical up-regulation of the HSP family genes, as well as down-regulation of EGR-1 at 2-10h post-treatment, suggesting that the HSP (particularly HSP70), in addition to the microarray-identified metallothioneins, but not the EGR-1 promoters, could be relevant promoter candidates for transcriptional targeting via PCI. The resulting overview of gene expression changes in WiDr cells exposed to the PCI-relevant photochemical treatment also provide a basis for the design of new PCI-based strategies with respect of transcriptional targeting.

Heme oxygenase-1 protects tumor cells against photodynamic therapy-mediated cytotoxicity

Photodynamic therapy is a promising antitumor treatment modality approved for the management of both early and advanced tumors. The mechanisms of its antitumor action include generation of singlet oxygen and reactive oxygen species that directly damage tumor cells and tumor vasculature. A number of mechanisms seem to be involved in the protective responses to PDT that include activation of transcription factors, heat shock proteins, antioxidant enzymes and antiapoptotic pathways. Elucidation of these mechanisms might result in the design of more effective combination strategies to improve the antitumor efficacy of PDT. Using DNA microarray analysis to identify stress-related genes induced by Photofrin-mediated PDT in colon adenocarcinoma C-26 cells, we observed a marked induction of heme oxygenase-1 (HO-1). Induction of HO-1 with hemin or stable transfection of C-26 with a plasmid vector encoding HO-1 increased resistance of tumor cells to PDT-mediated cytotoxicity. On the other hand, zinc (II) protoporphyrin IX, an HO-1 inhibitor, markedly augmented PDT-mediated cytotoxicity towards C-26 and human ovarian carcinoma MDAH2774 cells. Neither bilirubin, biliverdin nor carbon monoxide, direct products of HO-1 catalysed heme degradation, was responsible for cytoprotection. Importantly, desferrioxamine, a potent iron chelator significantly potentiated cytotoxic effects of PDT. Altogether our results indicate that HO-1 is involved in an important protective mechanism against PDT-mediated phototoxicity and administration of HO-1 inhibitors might be an effective way to potentiate antitumor effectiveness of PDT.