The effect of Tookad-mediated photodynamic ablation of the prostate gland on adjacent tissues--in vivo study in a canine model

Recent advances in photodynamic therapy for cancer and infectious diseases

Photodynamic therapy (PDT) is a treatment by combining light and a photosensitizer to generate reactive oxygen species (ROS) for cellular damage, and is used to treat cancer and infectious diseases. In this review, we focus on recent advances in design of new photosensitizers for increased production of ROS and in genetic engineering of biological photosensitizers to study cellular signaling pathways. A new concept has been proposed that PDT-induced acute inflammation can mediate neutrophil infiltration to deliver therapeutics in deep tumor tissues. Combination of PDT and immunotherapies (neutrophil-mediated therapeutic delivery) has shown the promising translation of PDT for cancer therapies. Furthermore, a new area in PDT is to treat bacterial infections to overcome the antimicrobial resistance. Finally, we have discussed the new directions of PDT for therapies of cancer and infectious diseases. In summary, we believe that rational design and innovations in nanomaterials may have a great impact on translation of PDT in cancer and infectious diseases. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Recent advances in photodynamic therapy for cancer and infectious diseases

Photodynamic therapy (PDT) is a treatment by combining light and a photosensitizer to generate reactive oxygen species (ROS) for cellular damage, and is used to treat cancer and infectious diseases. In this review, we focus on recent advances in design of new photosensitizers for increased production of ROS and in genetic engineering of biological photosensitizers to study cellular signaling pathways. A new concept has been proposed that PDT-induced acute inflammation can mediate neutrophil infiltration to deliver therapeutics in deep tumor tissues. Combination of PDT and immunotherapies (neutrophil-mediated therapeutic delivery) has shown the promising translation of PDT for cancer therapies. Furthermore, a new area in PDT is to treat bacterial infections to overcome the antimicrobial resistance. Finally, we have discussed the new directions of PDT for therapies of cancer and infectious diseases. In summary, we believe that rational design and innovations in nanomaterials may have a great impact on translation of PDT in cancer and infectious diseases. This article is categorized under: Therapeutic Approaches and Drug Discovery > Nanomedicine for Oncologic Disease Therapeutic Approaches and Drug Discovery > Nanomedicine for Infectious Disease Nanotechnology Approaches to Biology > Nanoscale Systems in Biology.

Photosensitizers in prostate cancer therapy

The search for new therapeutics for the treatment of prostate cancer is ongoing with a focus on the balance between the harms and benefits of treatment. New therapies are being constantly developed to offer treatments similar to radical therapies, with limited side effects. Photodynamic therapy (PDT) is a promising strategy in delivering focal treatment in primary as well as post radiotherapy prostate cancer. PDT involves activation of a photosensitizer (PS) by appropriate wavelength of light, generating transient levels of reactive oxygen species (ROS). Several photosensitizers have been developed with a focus on treating prostate cancer like mTHPC, motexafin lutetium, padoporfin and so on. This article will review newly developed photosensitizers under clinical trials for the treatment of prostate cancer, along with the potential advantages and disadvantages in delivering focal therapy.

Transplantation of Amniotic Scaffold-Seeded Mesenchymal Stem Cells and/or Endothelial Progenitor Cells From Bone Marrow to Efficiently Repair 3-cm Circumferential Urethral Defect in Model Dogs

The treatment options for patients with a urethral defect are limited by the availability of autologous tissues. We hypothesized that transplantation of decellularized human amniotic scaffolds (dHAS) seeded with allogeneic bone marrow mesenchymal cells (BMSCs) and/or endothelial progenitor cells (EPCs) may serve as a promising repair strategy for long segment of circumferential urethral defect. To verify the hypothesis, with urinary catheterization, a 3-cm segment of whole urethra in 25 male mongrel dogs was excised and replaced by dHAS seeded with allogeneic BMSCs and/or EPCs. Postoperative observation and ascending urethrogram found that dHAS+BMSCs+EPCs and dHAS+EPCs groups demonstrated unhindered urination and capacious urethral caliber, which were similar to the normal group, while urethrostenosis was revealed in dHAS+BMSCs, dHAS, and sham-operated groups, with the shortest narrow section in dHAS+BMSCs group and the longest in sham-operated group. Urethral anatomy check and histological analyses showed that new urethral mucosa composed of stratified columnar epithelium completely covered on the inner surface of the graft site in dHAS+BMSCs+EPCs and dHAS+EPCs groups, but the middle epithelium was thin in dHAS+EPCs group, while incompletely covered in dHAS+BMSCs, dHAS, and sham-operated groups, and there were monolayer epithelial cells at the urethrostenosis in dHAS+BMSCs and dHAS groups. In addition, abundant new vessel and blood sinus showed at submucosa in dHAS+BMSCs+EPCs and dHAS+EPCs groups, instead of the scar tissue of collagen deposition and structural distortion at the urethrostenosis in dHAS+BMSCs, dHAS, and sham-operated groups. This study demonstrates that dHAS seeded with BMSCs+EPCs or EPCs can successfully repair a 3-cm circumferential urethral defect in model dogs, but the former works best. This technology may provide some references for human clinical trials on long segment of circumferential urethral defect repair.

Treatment of localized prostate cancer using WST-09 and WST-11 mediated vascular targeted photodynamic therapy-A review

BACKGROUND

Photodynamic therapy (PDT) is well known for its direct cytotoxicity of the free radical-producing photochemical reaction, indirect mechanisms of action including modulation of intrinsic anti-tumour immune activity, and occlusion of pathologically altered tumour vessels leading to tumour ischaemia. The aim of this work is to critically review the evidence base for the use of vascular targeted PDT (VTP) to treat low-risk prostate cancer, and to discuss perspectives and challenges yet to be overcome. A brief general overview of focal prostate cancer therapy was provided, followed by a discussion of both basic and clinical research pertaining to prostate cancer VTP, with a focus on the palladium-based WST-09 and WST-11 photosensitisers.

MATERIALS AND METHOD

Literature on VTP for prostate cancer with the fallowing medical subject headings search terms: prostate cancer, photodynamic therapy, vascular targeted photodynamic therapy, bacteriopheophorbide were reviewed. The articles were selected by their relevance to the topic.

RESULTS

The clinical and basic research data available to date show much promise for WST-09, and WST-11 based VTP eventually joining the standard urologist's armamentarium against prostate cancer. With good reported tolerability and efficacy VTP can be proposed as an intermediate treatment for local low risk disease, halfway between watchful waiting and radical therapy.

Clinical use of photodynamic therapy in ocular tumors

Although the introduction of intravitreal anti-vascular endothelial growth factor drugs reduced the indications for photodynamic therapy in ophthalmology, it may still be used in various ocular tumors. Although many studies have shown that photodynamic therapy is effective in ocular tumors, the literature consists of case reports and series. In this review, we systematically performed a meta-analysis for the use of photodynamic therapy in circumscribed choroidal hemangioma, diffuse choroidal hemangioma, retinal capillary hemangioma, von Hippel-Lindau angiomatosis, choroidal melanoma, retinal astrocytoma, retinoblastoma, eyelid tumors, conjunctival tumors, and choroidal metastasis.

Synthesis and evaluation of cationic bacteriochlorin amphiphiles with effective in vitro photodynamic activity against cancer cells at low nanomolar concentration

Bacteriochlorins are attractive candidates as photosensitizers for photodynamic therapy (PDT) due to their intense absorption in the near-infrared (NIR) region of the spectrum where light transmission through tissue is maximal. Many naturally occurring bacteriochlorins are inherently unstable due to adventitious atmospheric oxidation. A de novo synthesis affords bacteriochlorins that contain a geminal dimethyl group in each reduced pyrrole ring to increase stability against oxidation. Here, three new synthetic bacteriochlorins, each bearing a single side-chain containing one or two positive charges, were investigated for their in vitro PDT activity against HeLa human cancer cells. All bacteriochlorins were active at low nanomolar concentration when activated with NIR light; those bearing a single positive charge exhibited faster uptake and higher activity. The bacteriochlorins were localized in mitochondria, lysosomes and endoplasmic reticulum as shown by organelle specific fluorescent probes. Cell death was via apoptosis as shown by cell morphology and nuclear condensation. Taken together, the results show the importance of appropriate peripheral groups about a photosensitizer for effective PDT applications.

Stable synthetic bacteriochlorins for photodynamic therapy: role of dicyano peripheral groups, central metal substitution (2H, Zn, Pd), and Cremophor EL delivery

A series of four stable synthetic bacteriochlorins was tested in vitro in HeLa cells for their potential in photodynamic therapy (PDT). The parent bacteriochlorin (BC), dicyano derivative (NC)(2)BC and corresponding zinc chelate (NC)(2)BC-Zn and palladium chelate (NC)(2)BC-Pd were studied. Direct dilution of a solution of bacteriochlorin in an organic solvent (N,N-dimethylacetamide) into serum-containing medium was compared with the dilution of bacteriochlorin in Cremophor EL (CrEL; polyoxyethylene glycerol triricinoleate) micelles into the same medium. CrEL generally reduced aggregation (as indicated by absorption and fluorescence) and increased activity up to tenfold (depending on bacteriochlorin), although it decreased cellular uptake. The order of PDT activity against HeLa human cancer cells after 24 h incubation and illumination with 10 J cm(-2) of near-infrared (NIR) light is (NC)(2)BC-Pd (LD(50)=25 nM) > (NC)(2)BC > (NC)(2)BC-Zn ≈ BC. Subcellular localization was determined to be in the endoplasmic reticulum, mitochondria and lysosomes, depending on the bacteriochlorin. (NC)(2)BC-Pd showed PDT-mediated damage to mitochondria and lysosomes, and the greatest production of hydroxyl radicals as determined using a hydroxyphenylfluorescein probe. The incorporation of cyano substituents provides an excellent motif for the enhancement of the photoactivity and photostability of bacteriochlorins as PDT photosensitizers.

Combination of photodynamic therapy and immunomodulation for skin diseases--update of clinical aspects

In dermatology, photodynamic therapy (PDT) has become a well established treatment modality which has been shown to be effective and safe for many skin and mucosal disorders. Pre-clinical and clinical studies demonstrate that, in addition to the direct local cytotoxicity and vascular effects, PDT can induce various host immune responses. Recent clinical data also show that improved clinical outcomes can be obtained through the sequential use of PDT and immunomodulation. This article will provide an update on the current status of such a combination in dermatological applications.

Diffusion-weighted MRI for monitoring tumor response to photodynamic therapy

PURPOSE

To examine diffusion-weighted MRI (DW-MRI) for assessing the early tumor response to photodynamic therapy (PDT).

MATERIALS AND METHODS

Subcutaneous tumor xenografts of human prostate cancer cells (CWR22) were initiated in athymic nude mice. A second-generation photosensitizer, Pc 4, was delivered to each animal by a tail vein injection 48 h before laser illumination. A dedicated high-field (9.4 Tesla) small animal MR scanner was used to acquire diffusion-weighted MR images pre-PDT and 24 h after the treatment. DW-MRI and apparent diffusion coefficients (ADC) were analyzed for 24 treated and 5 control mice with photosensitizer only or laser light only. Tumor size, prostate specific antigen (PSA) level, and tumor histology were obtained at different time points to examine the treatment effect.

RESULTS

Treated mice showed significant tumor size shrinkage and decrease of PSA level within 7 days after the treatment. The average ADC of the 24 treated tumors increased 24 h after PDT (P < 0.001) comparing with pre-PDT. The average ADC was 0.511 +/- 0.119 x 10(-3) mm(2)/s pre-PDT and 0.754 +/- 0.181 x 10(-3) mm(2)/s 24 h after the PDT. There is no significant difference in ADC values pre-PDT and 24 h after PDT in the control tumors (P = 0.20).

CONCLUSION

The change of tumor ADC values measured by DW-MRI may provide a noninvasive imaging marker for monitoring tumor response to Pc 4-PDT as early as 24 h.

Peripheral neural cell sensitivity to mTHPC-mediated photodynamic therapy in a 3D in vitro model

Background:

The effect of photodynamic therapy (PDT) on neural cells is important when tumours are within or adjacent to the nervous system. The purpose of this study was to investigate PDT using the photosensitiser, meta-tetrahydroxyphenyl chlorin (mTHPC), on rat neurons and satellite glia, compared with human adenocarcinoma cells (MCF-7).

Methods:

Fluorescence microscopy confirmed that mTHPC was incorporated into all three cell types. Sensitivity of cells exposed to mTHPC-PDT (0–10 μg ml^–1) was determined in a novel 3-dimensional collagen gel culture system. Cell death was quantified using propidium iodide and cell types were distinguished using immunocytochemistry. In some cases, neuron survival was confirmed by measuring subsequent neurite growth in monolayer culture.

Results:

MCF-7s and satellite glia were significantly more sensitive to PDT than neurons. Importantly, 4 μg ml^–1 mTHPC-PDT caused no significant neuron death compared with untreated controls but was sufficient to elicit substantial cell death in the other cell types. Initially, treatment reduced neurite length; neurons then extended neurites equivalent to those of untreated controls. The protocol was validated using hypericin (0–3 μg ml^–1), which caused neuron death equivalent to other cell types.

Conclusion:

Neurons in culture can survive mTHPC-PDT under conditions sufficient to kill tumour cells and other nervous system cells.

Photocytotoxicity of the fluorescent nonsteroidal androgen receptor ligand TDPQ

1,2,3,4-tetrahydro-2,2-dimethyl-6-(trifluoromethyl)-8-pyridono[5,6-g]quinoline (TDPQ), a selective nonsteroidal androgen receptor (AR) ligand, is a fluorescent compound. We characterized its spectral properties in comparison with the structural precursor carbostyril 151 (C151) and with its racemic structural isomer 4-ethyl-1,2,3,4-tetrahydro-6-(trifluoromethyl)-8-pyridino[5,6-g]quinoline (ETPQ). The absorption maximum in CH3CN of either TDPQ or ETPQ is 400 nm whereas that of C151 is 350 nm. The fluorescence lifetimes (tau) and quantum yields (phif) in CH3CN are typical of fluorescent dyes: TDPQ (4.2 ns, 0.8) and ETPQ (4.6 ns, 0.76). C151 showed lower tau and phif of 0.2 ns and 0.02, respectively. TDPQ can function as a fluorescent label at (sub)micromolar concentrations. We detected TDPQ fluorescence in human breast tumor cells using confocal microscopy. While the fluorescence maxima of the compounds were solvent insensitive, the phif for ETPQ decreased in aqueous solutions regardless of the presence of albumin or DNA. The phif of TDPQ was less affected. The quantum yield of singlet oxygen (1O2) photosensitization (phiso) by TDPQ and ETPQ was about 7% in CH3CN, sufficient to induce photocytotoxicity. TDPQ was photocytotoxic in AR-positive MDA-MB-453 breast cancer cells but not in AR-negative MDA-MB-231 cells. The combination of AR selectivity with photocytotoxicity makes TDPQ a promising candidate for selective targeting of AR-positive cells during photodynamic therapy.

Focal therapy for prostate cancer: revolution or evolution?

The face of prostate cancer has been dramatically changed since the late 1980s when PSA was introduced as a clinical screening tool. More men are diagnosed with small foci of cancers instead of the advanced disease evident prior to PSA screening. Treatment options for these smaller tumors consist of expectant management, radiation therapy (brachytherapy and external beam radiotherapy) and surgery (cryosurgical ablation and radical prostatectomy). In the highly select patient, cancer specific survival employing any of these treatment options is excellent, however morbidity from these interventions are significant. Thus, the idea of treating only the cancer within the prostate and sparing the non-cancerous tissue in the prostate is quite appealing, yet controversial. Moving forward if we are to embrace the focal treatment of prostate cancer we must: be able to accurately identify index lesions within the prostate, image cancers within the prostate and methodically study the litany of focal therapeutic options available.

New treatments for localized prostate cancer

Interest in focal therapy for prostate cancer has recently been renewed owing to downward stage migration, improved biopsy and imaging techniques, and the prevalence of either unifocal cancer or a dominant cancer with secondary tumors of minimal malignant potential. Several techniques have potential for focal ablation of prostate cancer. Cryotherapy has been used for some time as primary therapy for complete ablation of the prostate or local recurrence after radiotherapy. Enthusiasm for cryotherapy as the primary therapy has been tempered by the uncertainty about complete ablation of the cancer, the frequent persistence of measurable prostate-specific antigen levels after the procedure, and a high rate of erectile dysfunction. Studies have reported "focal ablation" of prostate cancer with cryotherapy, targeting 1 side of the gland to eliminate a cancer confined to that side with less risk of urinary or sexual complications. Whether cryotherapy has sufficient power to eradicate focal cancer and can be targeted with sufficient accuracy to avoid damage to surrounding structures remains to be demonstrated in prospective clinical trials. High-intensity focused ultrasound (HIFU) has been used widely in Europe for complete ablation of the prostate, especially in elderly men who are unwilling or unable to undergo radical therapy. For low- or intermediate-risk cancer, the short- and intermediate-term oncologic results have been acceptable but need confirmation in prospective multicenter trials presently underway. Whole gland therapy with transrectal ultrasound guidance has been associated with a high risk of acute urinary symptoms, often requiring transurethral resection before or after HIFU. Adverse effects on erectile function seem likely after a therapy that depends on heat to eradicate the cancer, but erectile function after HIFU has not been adequately documented with patient-reported questionnaires. HIFU holds promise for focal ablation of prostate cancer. As with cryotherapy, focal HIFU should reduce the adverse sexual, urinary, and bowel effects of whole gland ablation. New techniques are being developed to allow HIFU treatment under real-time guidance using magnetic resonance imaging, which could improve the precision and reduce the adverse effects further. Another promising technique, currently in clinical trials, is vascular-targeted photodynamic therapy, which has been used for whole gland ablation of locally recurrent cancer after radiotherapy and, more recently, for focal ablation of previously untreated cancer. In combination with a new, systemically administered photodynamic agent, laser light is delivered through fibers introduced into the prostate under ultrasound guidance. This technique does not heat the prostate but destroys the endothelial cells and cancer by activating the photodynamic agent. Damage to surrounding structures appears to be limited and can be controlled by the duration and intensity of the light. We have reviewed the principles of focal therapy and these new therapeutic modalities.

Photodynamic therapy for treatment of solid tumors--potential and technical challenges

Photodynamic therapy (PDT) involves the administration of photosensitizer followed by local illumination with visible light of specific wavelength(s). In the presence of oxygen molecules, the light illumination of photosensitizer can lead to a series of photochemical reactions and consequently the generation of cytotoxic species. The quantity and location of PDT-induced cytotoxic species determine the nature and consequence of PDT. Much progress has been seen in both basic research and clinical application in recent years. Although the majority of approved PDT clinical protocols have primarily been used for the treatment of superficial lesions of both malignant and non-malignant diseases, interstitial PDT for the ablation of deep-seated solid tumors are now being investigated worldwide. The complexity of the geometry and non-homogeneity of solid tumor pose a great challenge on the implementation of minimally invasive interstitial PDT and the estimation of PDT dosimetry. This review will discuss the recent progress and technical challenges of various forms of interstitial PDT for the treatment of parenchymal and/or stromal tissues of solid tumors.

Focal treatment of prostate cancer with vascular-targeted photodynamic therapy

Epidemiologic and pathologic features of prostate cancer have given rise to an interest in focal treatment for carefully selected patients. Prostate cancer remains highly prevalent, particularly in the U.S. and Europe. As screening programs have become more aggressive and widespread, a substantial proportion of men diagnosed with localized prostate cancer have disease characteristics associated with a low risk of progression. Treatments such as radical prostatectomy and radiation therapy can lead to durable recurrence-free survival in most patients, but carry variable risks of bowel, urinary, and sexual side effects. Few men and few urologists are comfortable leaving a potentially curable prostate cancer untreated. Focal therapy offers an attractive alternative for the patient faced with a choice between aggressive local intervention (radiation or surgery) and watchful waiting. Contemporary diagnostic biopsy strategies and imaging tools, and the development of predictive statistical models (nomograms), have led to improvements in tumor characterization and risk stratification, making focal therapy a viable treatment option for specific men. This article reviews the rationale and indications for focal therapy and highlights vascular-targeted photodynamic therapy (PDT) as one of many promising focal therapy techniques.