Permanent occlusion of feeding arteries and draining veins in solid mouse tumors by vascular targeted photodynamic therapy (VTP) with Tookad

Photodynamic Therapy: Current Trends and Potential Future Role in the Treatment of Bladder Cancer

Bladder cancer (BC) is the 10th most common cancer in the world. The therapeutic spectrum of BC is broad and is constantly expanding. Despite the wide clinical use of photodynamic diagnosis (PTD) for BC, PDT has not been sufficiently investigated in the treatment landscape of BC. We performed an online search of the PubMed database using these keywords: photodynamic therapy, bladder cancer, urothelial carcinoma, in vivo, in vitro, cell line, animal model. Reviews, case reports, and articles devoted to photodynamic diagnostics and the photodynamic therapy of tumors other than urothelial carcinoma were excluded. Of a total of 695 publications, we selected 20 articles with clinical data, 34 articles on in vivo PDT, and 106 articles on in vitro data. The results presented in animal models highlight the potential use of PDT in the neoadjuvant or adjuvant setting to reduce local recurrence in the bladder and upper urinary tracts. Possible regimens include the combination of PDT with intravesical chemotherapy for improved local tumor control or the integration of vascular-targeted PDT in combination with modern systemic drugs in order to boost local response. We summarize available evidence on the preclinical and clinical application of PDT for urothelial carcinoma in order to explain the current trends and future perspectives.

Pyrrolopyrrole aza-BODIPY-based NIR-II fluorophores for in vivo dynamic vascular dysfunction visualization of vascular-targeted photodynamic therapy

Real-time monitoring vascular responses is crucial for evaluating the therapeutic effects of vascular-targeted photodynamic therapy (V-PDT). Herein, we developed a highly-stable and bright aggregation induced emission (AIE) fluorophore (PTPE3 NP) for dynamic fluorescence (FL) imaging of vascular dysfunction beyond 1300 nm window during V-PDT. The superior brightness (ϵ_maxΦ_{f>1000 nm} ≈ 180.05 M^-1 cm^-1) and high resolution of PTPE3 NP affords not only high-clarity images of whole-body and local vasculature (hindlimbs, mesentery, and tumor) but also high-speed video imaging for tracking blood circulation process. By virtue of the NPs' prolonged blood circulation time (t_1/2 ≈ 86.5 min) and excellent photo/chemical (pH, RONS) stability, mesenteric and tumor vascular dysfunction (thrombosis formation, vessel occlusion, and hemorrhage) can be successfully visualized during V-PDT by FL imaging for the first time. Furthermore, the reduction of blood flow velocity (BFV) can be monitored in real time for precisely evaluating efficacy of V-PDT. These provide a powerful approach for assessing vascular responses during V-PDT and promote the development of advanced fluorophores for biological imaging.

Use of photoacoustic imaging for monitoring vascular disrupting cancer treatments

Vascular disrupting agents disrupt tumor vessels, blocking the nutritional and oxygen supply tumors need to thrive. This is achieved by damaging the endothelium lining of blood vessels, resulting in red blood cells (RBCs) entering the tumor parenchyma. RBCs present in the extracellular matrix are exposed to external stressors resulting in biochemical and physiological changes. The detection of these changes can be used to monitor the efficacy of cancer treatments. Spectroscopic photoacoustic (PA) imaging is an ideal candidate for probing RBCs due to their high optical absorption relative to surrounding tissue. The goal of this work is to use PA imaging to monitor the efficacy of the vascular disrupting agent 5,6-Dimethylxanthenone-4-acetic acid (DMXAA) through quantitative analysis. Then, 4T1 breast cancer cells were injected subcutaneously into the left hind leg of eight BALB/c mice. After 10 days, half of the mice were treated with 15 mg/kg of DMXAA and the other half were injected with saline. All mice were imaged using the VevoLAZR X PA system before treatment, 24 and 72 hours after treatment. The imaging was done at six wavelengths and linear spectral unmixing was applied to the PA images to quantify three forms of hemoglobin (oxy, deoxy and met-hemoglobin). After imaging, tumors were histologically processed and H&E and TUNEL staining were used to detect the tissue damage induced by the DMXAA treatment. The total hemoglobin concentration remained unchanged after treatment for the saline treated mice. For DMXAA treated mice, a 10% increase of deoxyhemoglobin concentration was detected 24 hours after treatment and a 22.6% decrease in total hemoglobin concentration was observed by 72 hours. A decrease in the PA spectral slope parameters was measured 24 hours after treatment. This suggests that DMXAA induces vascular damage, causing red blood cells to extravasate. Furthermore, H&E staining of the tumor showed areas of bleeding with erythrocyte deposition. These observations are further supported by the increase in TUNEL staining in DMXAA treated tumors, revealing increased cell death due to vascular disruption. This study demonstrates the capability of PA imaging to monitor tumor vessel disruption by the vascular disrupting agent DMXAA.

Tumour irradiation combined with vascular-targeted photodynamic therapy enhances antitumour effects in pre-clinical prostate cancer

BACKGROUND

There is a need to improve the treatment of prostate cancer (PCa) and reduce treatment side effects. Vascular-targeted photodynamic therapy (VTP) is a focal therapy for low-risk low-volume localised PCa, which rapidly disrupts targeted tumour vessels. There is interest in expanding the use of VTP to higher-risk disease. Tumour vasculature is characterised by vessel immaturity, increased permeability, aberrant branching and inefficient flow. FRT alters the tumour microenvironment and promotes transient 'vascular normalisation'. We hypothesised that multimodality therapy combining fractionated radiotherapy (FRT) and VTP could improve PCa tumour control compared against monotherapy with FRT or VTP.

METHODS

We investigated whether sequential delivery of FRT followed by VTP 7 days later improves flank TRAMP-C1 PCa tumour allograft control compared to monotherapy with FRT or VTP.

RESULTS

FRT induced 'vascular normalisation' changes in PCa flank tumour allografts, improving vascular function as demonstrated using dynamic contrast-enhanced magnetic resonance imaging. FRT followed by VTP significantly delayed tumour growth in flank PCa allograft pre-clinical models, compared with monotherapy with FRT or VTP, and improved overall survival.

CONCLUSION

Combining FRT and VTP may be a promising multimodal approach in PCa therapy. This provides proof-of-concept for this multimodality treatment to inform early phase clinical trials.

Combined OX40 Agonist and PD-1 Inhibitor Immunotherapy Improves the Efficacy of Vascular Targeted Photodynamic Therapy in a Urothelial Tumor Model

PURPOSE

Vascular targeted photodynamic therapy (VTP) is a nonsurgical tumor ablation approach used to treat early-stage prostate cancer and may also be effective for upper tract urothelial cancer (UTUC) based on preclinical data. Toward increasing response rates to VTP, we evaluated its efficacy in combination with concurrent PD-1 inhibitor/OX40 agonist immunotherapy in a urothelial tumor-bearing model.

EXPERIMENTAL DESIGN

In mice allografted with MB-49 UTUC cells, we compared the effects of combined VTP with PD-1 inhibitor/OX40 agonist with those of the component treatments on tumor growth, survival, lung metastasis, and antitumor immune responses.

RESULTS

The combination of VTP with both PD-1 inhibitor and OX40 agonist inhibited tumor growth and prolonged survival to a greater degree than VTP with either immunotherapeutic individually. These effects result from increased tumor infiltration and intratumoral proliferation of cytotoxic and helper T cells, depletion of Treg cells, and suppression of myeloid-derived suppressor cells.

CONCLUSIONS

Our findings suggest that VTP synergizes with PD-1 blockade and OX40 agonist to promote strong antitumor immune responses, yielding therapeutic efficacy in an animal model of urothelial cancer.

Neoadjuvant vascular-targeted photodynamic therapy improves survival and reduces recurrence and progression in a mouse model of urothelial cancer

Locally advanced urothelial cancer has high recurrence and progression rates following surgical treatment. This highlights the need to develop neoadjuvant strategies that are both effective and well-tolerated. We hypothesized that neoadjuvant sub-ablative vascular-targeted photodynamic therapy (sbVTP), through its immunotherapeutic mechanism, would improve survival and reduce recurrence and progression in a murine model of urothelial cancer. After urothelial tumor implantation and 17 days before surgical resection, mice received neoadjuvant sbVTP (WST11; Tookad Soluble, Steba Biotech, France). Local and systemic response and survival served as measures of therapeutic efficacy, while immunohistochemistry and flow cytometry elucidated the immunotherapeutic mechanism. Data analysis included two-sided Kaplan-Meier, Mann-Whitney, and Fischer exact tests. Tumor volume was significantly smaller in sbVTP-treated animals than in controls (135 mm3 vs. 1222 mm3, P < 0.0001) on the day of surgery. Systemic progression was significantly lower in sbVTP-treated animals (l7% vs. 30%, P < 0.01). Both median progression-free survival and overall survival were significantly greater among animals that received sbVTP and surgery than among animals that received surgery alone (P < 0.05). Neoadjuvant-treated animals also demonstrated significantly lower local recurrence. Neoadjuvant sbVTP was associated with increased early antigen-presenting cells, and subsequent improvements in long-term memory and increases in effector and active T-cells in the spleen, lungs, and blood. In summary, neoadjuvant sbVTP delayed local and systemic progression, prolonged progression-free and overall survival, and reduced local recurrence, thereby demonstrating therapeutic efficacy through an immune-mediated response. These findings strongly support its evaluation in clinical trials.

Tissue Factor-Targeted "O2-Evolving" Nanoparticles for Photodynamic Therapy in Malignant Lymphoma

Vascular-targeted PDT (vPDT) has produced promising results in the treatment of many cancers, including drug-resistant ones, but little is known about its efficacy in lymphoma. Unfortunately, the lack of a specific therapeutic target and a hypoxic microenvironment for lymphoma jeopardizes the efficacy of vPDT severely. In this study, we designed a lymphoma tissue factor-targeted “O₂-evolving” strategy combining PDT with catalase and HMME-encapsulated, EGFP-EGF1-modified PEG-PLGA nanoparticles (CENPs) to boost PDT efficiency; this combination takes advantage of the low oxygen tension of lymphoma. In our results, CENPs accumulated effectively in the vascular lymphoma in vivo and in vitro, and this accumulation increased further with PDT treatment. Per positron emission tomography imaging, combining CENPs with PDT inhibited lymphoma glucose metabolism significantly. The expression of hypoxia-inducible factor (HIF)-1α in the entrapped catalase groups reduced markedly. These data show that the combined administration of PDT and CENPs can prompt tissue factor-cascade-targeted and self-supply of oxygen and that it has a good therapeutic effect on malignant lymphoma.

Developments in Vascular-Targeted Photodynamic Therapy for Urologic Malignancies

With improved understanding of cancer biology and technical advancements in non-invasive management of urological malignancies, there is renewed interest in photodynamic therapy (PDT) as a means of focal cancer treatment. The application of PDT has also broadened as a result of development of better-tolerated and more effective photosensitizers. Vascular-targeted PDT (VTP) using padeliporfin, which is a water-soluble chlorophyll derivative, allows for tumor-specific cytotoxicity and has demonstrated efficacy in the management of urologic malignancies. Herein, we describe the evolution of photodynamic therapy in urologic oncology and the role of VTP in emerging treatment paradigms.

Photodynamic therapy, priming and optical imaging: Potential co-conspirators in treatment design and optimization - a Thomas Dougherty Award for Excellence in PDT paper

Photodynamic therapy is a photochemistry-based approach, approved for the treatment of several malignant and non-malignant pathologies. It relies on the use of a non-toxic, light activatable chemical, photosensitizer, which preferentially accumulates in tissues/cells and, upon irradiation with the appropriate wavelength of light, confers cytotoxicity by generation of reactive molecular species. The preferential accumulation however is not universal and, depending on the anatomical site, the ratio of tumor to normal tissue may be reversed in favor of normal tissue. Under such circumstances, control of the volume of light illumination provides a second handle of selectivity. Singlet oxygen is the putative favorite reactive molecular species although other entities such as nitric oxide have been credibly implicated. Typically, most photosensitizers in current clinical use have a finite quantum yield of fluorescence which is exploited for surgery guidance and can also be incorporated for monitoring and treatment design. In addition, the photodynamic process alters the cellular, stromal, and/or vascular microenvironment transiently in a process termed photodynamic priming, making it more receptive to subsequent additional therapies including chemo- and immunotherapy. Thus, photodynamic priming may be considered as an enabling technology for the more commonly used frontline treatments. Recently, there has been an increase in the exploitation of the theranostic potential of photodynamic therapy in different preclinical and clinical settings with the use of new photosensitizer formulations and combinatorial therapeutic options. The emergence of nanomedicine has further added to the repertoire of photodynamic therapy's potential and the convergence and co-evolution of these two exciting tools is expected to push the barriers of smart therapies, where such optical approaches might have a special niche. This review provides a perspective on current status of photodynamic therapy in anti-cancer and anti-microbial therapies and it suggests how evolving technologies combined with photochemically-initiated molecular processes may be exploited to become co-conspirators in optimization of treatment outcomes. We also project, at least for the short term, the direction that this modality may be taking in the near future.

The Role of Photoactivated and Non-Photoactivated Verteporfin on Tumor

Verteporfin (VP) has long been clinically used to treat age-related macular degeneration (AMD) through photodynamic therapy (PDT). Recent studies have reported a significant anti-tumor effect of VP as well. Yes-associated protein (YAP) is a pro-tumorigenic factor that is aberrantly expressed in various cancers and is a central effector of the Hippo signaling pathway that regulates organ size and tumorigenesis. VP can inhibit YAP without photoactivation, along with suppressing autophagy, and downregulating germinal center kinase-like kinase (GLK) and STE20/SPS1-related proline/alanine-rich kinase (SPAK). In addition, VP can induce mitochondrial damage and increase the production of reactive oxygen species (ROS) upon photoactivation, and is an effective photosensitizer (PS) in anti-tumor PDT. We have reviewed the direct and adjuvant therapeutic action of VP as a PS, and its YAP/TEA domain (TEAD)-dependent and independent pharmacological effects in the absence of light activation against cancer cells and solid tumors. Based on the present evidence, VP may be repositioned as a promising anti-cancer chemotherapeutic and adjuvant drug.

Vascular Shutdown by Photodynamic Therapy Using Talaporfin Sodium

Photodynamic therapy (PDT) is an attractive cancer treatment modality. Talaporfin sodium, a second-generation photosensitizer, results in lower systemic toxicity and relatively better selective tumor destruction than first-generation photosensitizers. However, the mechanism through which PDT induces vascular shutdown is unclear. In this study, the in vitro effects of talaporfin sodium-based PDT on human umbilical vein endothelial cells (HUVECs) were determined through cell viability and endothelial tube formation assays, and evaluation of the tubulin and F-actin dynamics and myosin light chain (MLC) phosphorylation. Additionally, the effects on tumor blood flow and tumor vessel destruction were assessed in vivo. In the HUVECs, talaporfin sodium-based PDT induced endothelial tube destruction and microtubule depolymerization, triggering the formation of F-actin stress fibers and a significant increase in MLC phosphorylation. However, pretreatment with the Rho-associated protein kinase (ROCK) inhibitor, Y27632, completely prevented PDT-induced stress fiber formation and MLC phosphorylation. The in vivo analysis and pathological examination revealed that the PDT had significantly decreased the tumor blood flow and the active area of the tumor vessel. We concluded that talaporfin sodium-based PDT induces the shutdown of existing tumor vessels via the RhoA/ROCK pathway by activating the Rho-GTP pathway and decreasing the tumor blood flow.

Recent advances in strategies for overcoming hypoxia in photodynamic therapy of cancer

The selectivity of photodynamic therapy (PDT) derived from the tailored accumulation of photosensitizing drug (photosensitizer; PS) in the tumor microenvironment (TME), and from local irradiation, turns it into a "magic bullet" for the treatment of resistant tumors without sparing the healthy tissue and possible adverse effects. However, locally-induced hypoxia is one of the undesirable consequences of PDT, which may contribute to the emergence of resistance and significantly reduce therapeutic outcomes. Therefore, the development of strategies using new approaches in nanotechnology and molecular biology can offer an increased opportunity to eliminate the disadvantages of hypoxia. Emerging evidence indicates that wisely designed phototherapeutic procedures, including: (i) ROS-tunable photosensitizers, (ii) organelle targeting, (iii) nano-based photoactive drugs and/or PS delivery nanosystems, as well as (iv) combining them with other strategies (i.e. PTT, chemotherapy, theranostics or the design of dual anticancer drug and photosensitizers) can significantly improve the PDT efficacy and overcome the resistance. This mini-review addresses the role of hypoxia and hypoxia-related molecular mechanisms of the HIF-1α pathway in the regulation of PDT efficacy. It also discusses the most recent achievements as well as future perspectives and potential challenges of PDT application against hypoxic tumors.

Inducing Angiogenesis, a Key Step in Cancer Vascularization, and Treatment Approaches

Angiogenesis is a term that describes the formation of new blood and lymphatic vessels from a pre-existing vasculature. This allows tumour cells to acquire sustenance in the form of nutrients and oxygen and the ability to evacuate metabolic waste. As one of the hallmarks of cancer, angiogenesis has been studied extensively in animal and human models to enable better understanding of cancer biology and the development of new anti-cancer treatments. Angiogenesis plays a crucial role in the process of tumour genesis, because solid tumour need a blood supply if they are to grow beyond a few millimeters in size. On the other hand, there is growing evidence that some solid tumour exploit existing normal blood supply and do not require a new vessel formation to grow and to undergo metastasis. This review of the literature will present the current understanding of this intricate process and the latest advances in the use of angiogenesis-targeting therapies in the fight against cancer.

High-resolution optoacoustic imaging of tissue responses to vascular-targeted therapies

The monitoring of vascular-targeted therapies via magnetic resonance imaging, computed omography or ultrasound is limited by their insufficient spatial resolution. By taking advantage of the intrinsic optical properties of haemoglobin, here we show that raster-scanning optoacoustic mesoscopy (RSOM) provides high-resolution images of the tumour vasculature and of the surrounding tissue, and that the detection of a wide range of ultrasound bandwidths enables the distinction of vessels of differing size, allowing for detailed insights into vascular responses to vascular-targeted therapy. By using RSOM to examine the responses to vascular-targeted photodynamic therapy in mice with subcutaneous xenografts, we observed a significant and immediate occlusion of the tumour vessels, followed by haemorrhage within the tissue and the eventual collapse of the entire vasculature. By using dual-wavelength RSOM, which distinguishes oxyhaemoglobin from deoxyhaemoglobin, we observed an increase in oxygenation of the entire tumour volume immediately after the application of the therapy, and a second wave of oxygen reperfusion approximately 24 h thereafter. We also show that RSOM allows for the quantification of differences in neo-angiogenesis that predict treatment efficacy.

Photodynamic Therapy and the Biophysics of the Tumor Microenvironment

Targeting the tumor microenvironment (TME) provides opportunities to modulate tumor physiology, enhance the delivery of therapeutic agents, impact immune response and overcome resistance. Photodynamic therapy (PDT) is a photochemistry-based, nonthermal modality that produces reactive molecular species at the site of light activation and is in the clinic for nononcologic and oncologic applications. The unique mechanisms and exquisite spatiotemporal control inherent to PDT enable selective modulation or destruction of the TME and cancer cells. Mechanical stress plays an important role in tumor growth and survival, with increasing implications for therapy design and drug delivery, but remains understudied in the context of PDT and PDT-based combinations. This review describes pharmacoengineering and bioengineering approaches in PDT to target cellular and noncellular components of the TME, as well as molecular targets on tumor and tumor-associated cells. Particular emphasis is placed on the role of mechanical stress in the context of targeted PDT regimens, and combinations, for primary and metastatic tumors.

Lipophilicity of Bacteriochlorin-Based Photosensitizers as a Determinant for PDT Optimization through the Modulation of the Inflammatory Mediators

: Photodynamic therapy (PDT) augments the host antitumor immune response, but the role of the PDT effect on the tumor microenvironment in dependence on the type of photosensitizer and/or therapeutic protocols has not been clearly elucidated. We employed three bacteriochlorins (F2BOH, F2BMet and Cl2BHep) of different polarity that absorb near-infrared light (NIR) and generated a large amount of reactive oxygen species (ROS) to compare the PDT efficacy after various drug-to-light intervals: 15 min. (V-PDT), 3h (E-PDT) and 72h (C-PDT). We also performed the analysis of the molecular mechanisms of PDT crucial for the generation of the long-lasting antitumor immune response. PDT-induced damage affected the integrity of the host tissue and developed acute (protocol-dependent) local inflammation, which in turn led to the infiltration of neutrophils and macrophages. In order to further confirm this hypothesis, a number of proteins in the plasma of PDT-treated mice were identified. Among a wide range of cytokines (IL-6, IL-10, IL-13, IL-15, TNF-α, GM-CSF), chemokines (KC, MCP-1, MIP1α, MIP1β, MIP2) and growth factors (VEGF) released after PDT, an important role was assigned to IL-6. PDT protocols optimized for studied bacteriochlorins led to a significant increase in the survival rate of BALB/c mice bearing CT26 tumors, but each photosensitizer (PS) was more or less potent, depending on the applied DLI (15 min, 3 h or 72 h). Hydrophilic (F2BOH) and amphiphilic (F2BMet) PSs were equally effective in V-PDT (>80 cure rate). F2BMet was the most efficient in E-PDT (DLI = 3h), leading to a cure of 65 % of the animals. Finally, the most powerful PS in the C-PDT (DLI = 72 h) regimen turned out to be the most hydrophobic compound (Cl2BHep), allowing 100 % of treated animals to be cured at a light dose of only 45 J/cm2.

Therapeutic Enhancement of Verteporfin-mediated Photodynamic Therapy by mTOR Inhibitors

Photodynamic therapy (PDT) with photosensitizer verteporfin is a clinically approved vascular disrupting modality that is currently in clinical trial for cancer treatment. In this study, we evaluated PDT in combination with either mTORC1 inhibitor rapamycin or mTORC1/C2 dual inhibitor AZD2014 for therapeutic enhancement in SVEC endothelial cells. Verteporfin-PDT alone induced cell apoptosis by activating the intrinsic apoptotic pathway. However, it increased the expression of anti-apoptotic protein MCL-1 and the phosphorylation of S6, a downstream molecule of mTOR signaling. In contrast, mTOR inhibitors rapamycin and AZD2014 did not induce apoptosis in SVEC cells. They suppressed MCL-1 expression and S6 phosphorylation and imposed a potent inhibition on cell proliferation. PDT in combination with mTOR inhibitors activated the intrinsic apoptotic pathway and resulted in increased apoptosis. Combination treatments also led to sustained inhibition of cell proliferation. Although AZD2014 was more effective for cell growth inhibition and PDT enhancement than rapamycin at the higher concentrations examined in the study, both inhibitors effectively enhanced PDT response, suggesting that inhibition of mTORC1 is crucial for PDT enhancement. Our results indicate that mTOR inhibitors mechanistically cooperate with PDT for enhanced cell death and sustained growth inhibition, supporting a combination approach for therapeutic enhancement.

The Course of Immune Stimulation by Photodynamic Therapy: Bridging Fundamentals of Photochemically Induced Immunogenic Cell Death to the Enrichment of T-Cell Repertoire

Photodynamic therapy (PDT) is a potentially immunogenic and FDA-approved antitumor treatment modality that utilizes the spatiotemporal combination of a photosensitizer, light and oftentimes oxygen, to generate therapeutic cytotoxic molecules. Certain photosensitizers under specific conditions, including ones in clinical practice, have been shown to elicit an immune response following photoillumination. When localized within tumor tissue, photogenerated cytotoxic molecules can lead to immunogenic cell death (ICD) of tumor cells, which release damage-associated molecular patterns and tumor-specific antigens. Subsequently, the T-lymphocyte (T cell)-mediated adaptive immune system can become activated. Activated T cells then disseminate into systemic circulation and can eliminate primary and metastatic tumors. In this review, we will detail the multistage cascade of events following PDT of solid tumors that ultimately lead to the activation of an antitumor immune response. More specifically, we connect the fundamentals of photochemically induced ICD with a proposition on potential mechanisms for PDT enhancement of the adaptive antitumor response. We postulate a hypothesis that during the course of the immune stimulation process, PDT also enriches the T-cell repertoire with tumor-reactive activated T cells, diversifying their tumor-specific targets and eliciting a more expansive and rigorous antitumor response. The implications of such a process are likely to impact the outcomes of rational combinations with immune checkpoint blockade, warranting investigations into T-cell diversity as a previously understudied and potentially transformative paradigm in antitumor photodynamic immunotherapy.

Positron Emission Tomography/Computed Tomography with Gallium-68-labeled Prostate-specific Membrane Antigen Detects Relapse After Vascular-targeted Photodynamic Therapy in a Prostate Cancer Model

BACKGROUND

Evaluating the efficacy of focal therapy for prostate cancer is limited by current approaches and may be improved with biological imaging techniques.

OBJECTIVE

We assessed whether positron emission tomography/computed tomography with gallium-68-labeled prostate-specific membrane antigen (⁶⁸Ga-PSMA PET/CT) can be used to predict relapse after vascular-targeted photodynamic therapy (VTP).

DESIGN, SETTING, AND PARTICIPANTS

A total of 1×10⁶ LNCaP cells were grafted subcutaneously in the flanks of 6-8-wk-old SCID mice. Of 24 mice with measurable tumors 6 wk after tumor implantation, 20 were treated with VTP (150mW/cm²) to ablate the tumors. Blood prostate-specific antigen (PSA) levels were assessed, and ⁶⁸Ga-PSMA PET/CT images were performed 1 d before VTP and 1 and 4 wk after.

OUTCOME MEASUREMENTS AND STATISTICAL ANALYSIS

Local tumor relapse was evaluated by histology, and tumors were analyzed by prostate-specific membrane antigen (PSMA) and PSA immunohistochemistry. T tests and Kruskal-Wallis tests were used to determine significance.

RESULTS AND LIMITATIONS

Four weeks after VTP, 11 (65%) mice had complete responses and six (35%) had tumor relapses confirmed by histology (hematoxylin and eosin, and PSMA immunohistochemistry). All mice with local relapse had positive ⁶⁸Ga-PSMA PET/CT findings 4 wk after VTP; all complete responders did not. One week after VTP, the relapse detection sensitivity of ⁶⁸Ga-PSMA PET/CT was 75%, whereas the sensitivity of PSA was only 33%. Compared with controls, relapsed tumors had a three-fold reduction in the number of cells with strong PSA staining by immunohistochemistry (1.5% vs 4.5%; p=0.01).

CONCLUSIONS

In a preclinical prostate cancer model, we show that ⁶⁸Ga-PSMA PET/CT can identify and predict relapse earlier than blood PSA level. These findings support further testing in clinical trials.

PATIENT SUMMARY

Positron emission tomography/computed tomography with gallium-68-labeled prostate-specific membrane antigen may be used to follow and evaluate treatment outcomes in men who receive focal therapy for prostate cancer.

Effectiveness of the combination of vascular targeted photodynamic therapy and anti-cytotoxic T-lymphocyte-associated antigen 4 in a preclinical mouse model of urothelial carcinoma

OBJECTIVE

To investigate the effectiveness of combination treatment of vascular targeted photodynamic therapy and anti-cytotoxic T-lymphocyte-associated antigen 4 immunotherapy in a mouse model of urothelial carcinoma.

METHODS

We used C57BL/6 mice injected with murine bladder 49 cell line. Mice were randomly allocated into four treatment groups: vascular targeted photodynamic therapy only, anti-cytotoxic T-lymphocyte-associated antigen 4 only, combination therapy and control. We carried out three separate experiments that used distinct cohorts of mice: tumor growth and development of lung metastases monitored with bioluminescent imaging (n = 91); survival evaluated with Kaplan-Meier curves (n = 111); and tumor cell population studied with flow cytometry (n = 20). In a fourth experiment, we re-challenged tumors in previously treated mice and compared tumor growth with that of naïve mice.

RESULTS

Combination therapy provided significant benefits over the other three treatment groups: prolonged survival (P < 0.0001), lower tumor signal (P < 0.0001) and decreased lung signal uptake (P ≤ 0.002). We also observed that mice previously treated with vascular targeted photodynamic therapy only or combination therapy did not present tumor growth after re-challenged tumors.

CONCLUSIONS

Combination of vascular targeted photodynamic therapy with anti-cytotoxic T-lymphocyte-associated antigen 4 is an effective therapy in a urothelial carcinoma syngeneic mouse model. The present results suggest this therapy as a potential treatment option for both bladder and upper tract tumors in future clinical trials.

Systemic Antitumor Immunity by PD-1/PD-L1 Inhibition Is Potentiated by Vascular-Targeted Photodynamic Therapy of Primary Tumors

Purpose: PD-1/PD-L1 pathway inhibition is effective against advanced renal cell carcinoma, although results are variable and may depend on host factors, including the tumor microenvironment. Vascular-targeted photodynamic (VTP) therapy with the photosensitizer WST11 induces a defined local immune response, and we sought to determine whether this could potentiate the local and systemic antitumor response to PD-1 pathway inhibition.Experimental Design: Using an orthotopic Renca murine model of renal cell carcinoma that develops lung metastases, we treated primary renal tumors with either VTP alone, PD-1/PD-L1 antagonistic antibodies alone, or a combination of VTP and antibodies and then examined treatment responses, including immune infiltration in primary and metastatic sites. Modulation of PD-L1 expression by VTP in human xenograft tumors was also assessed.Results: Treatment of renal tumors with VTP in combination with systemic PD-1/PD-L1 pathway inhibition, but neither treatment alone, resulted in regression of primary tumors, prevented growth of lung metastases, and prolonged survival in a preclinical mouse model. Analysis of tumor-infiltrating lymphocytes revealed that treatment effect was associated with increased CD8+:regulatory T cell (Treg) and CD4+FoxP3-:Treg ratios in primary renal tumors and increased T-cell infiltration in sites of lung metastasis. Furthermore, PD-L1 expression is induced following VTP treatment of human renal cell carcinoma xenografts.Conclusions: Our results demonstrate a role for local immune modulation with VTP in combination with PD-1/PD-L1 pathway inhibition for generation of potent local and systemic antitumor responses. This combined modality strategy may be an effective therapy in cancers resistant to PD-1/PD-L1 pathway inhibition alone. Clin Cancer Res; 24(3); 592-9. ©2017 AACR.

WST11 Vascular Targeted Photodynamic Therapy Effect Monitoring by Multispectral Optoacoustic Tomography (MSOT) in Mice

Objective: Monitoring emerging vascular-targeted photodynamic therapy (VTP) and understanding the time-dynamics of treatment effects remains challenging. We interrogated whether handheld multispectral optoacoustic tomography (MSOT) could noninvasively monitor the effect of VTP using WST11, a vascular-acting photosensitizer, on tumor tissues over time using a renal cell cancer mouse model. We also investigated whether MSOT illumination can induce VTP, to implement a single-modality theranostic approach. Materials and Methods: Eight BalB/c mice were subcutaneously implanted with murine renal adenocarcinoma cells (RENCA) on the flank. Three weeks later VTP was performed (10 min continuous illumination at 753 nm following intravenous infusion using WST11 or saline as control. Handheld MSOT images were collected prior to VTP administration and subsequently thereafter over the course of the first hour, at 24 and 48 h. Data collected were unmixed for blood oxygen saturation in tissue (SO₂) based on the spectral signatures of deoxy- and oxygenated hemoglobin. Changes in oxygen saturation over time, relative to baseline, were examined by paired t-test for statistical significance (p < 0.05). In-vivo findings were corroborated by histological analyses of the tumor tissue. Results: MSOT is shown to prominently resolve changes in oxygen saturation in tumors within the first 20 min post WST11-VTP treatment. Within the first hour post-treatment, SO₂ decreased by more than 60% over baseline (p < 0.05), whereas it remained unchanged (p > 0.1) in the sham-treated group. Moreover, unlike in the control group, SO₂ in treated tumors further decreased over the course of 24 to 48 h post-treatment, concomitant with the propagation of profound central tumor necrosis present in histological analysis. We further show that pulsed MSOT illumination can activate WST11 as efficiently as the continuous wave irradiation employed for treatment. Conclusion: Handheld MSOT non-invasively monitored WST11-VTP effects based on the SO₂ signal and detected blood saturation changes within the first 20 min post-treatment. MSOT may potentially serve as a means for both VTP induction and real-time VTP monitoring in a theranostic approach.

Targeted Ablative Therapies for Prostate Cancer

Men diagnosed with low- to intermediate-risk, clinically localized prostate cancer (PCa) often face a daunting and difficult decision with respect to treatment: active surveillance (AS) or radical therapy. This decision is further confounded by the fact that many of these men diagnosed, by an elevated PSA, will have indolent disease and never require intervention. Radical treatments, including radical prostatectomy and whole-gland radiation, offer greater certainty for cancer control, but at the risk of significant urinary and/or sexual morbidity. Conversely, AS preserves genitourinary function and quality of life in exchange for burdensome surveillance and the psychological impact of living with cancer.

Overcoming obstacles in the tumor microenvironment: Recent advancements in nanoparticle delivery for cancer theranostics

Despite rapid advancements in the field of nanotechnology, there is mounting frustration in the scientific community regarding the translational impact of nanomedicine. Modest therapeutic performance of FDA-approved nanomedicines combined with multiple disappointing clinical trials (such as phase III HEAT trial) have raised questions about the future of nanomedicine. Encouraging breakthroughs, however, have been made in the last few years towards the development of new classes of nanoparticles that can respond to tumor microenvironmental conditions and successfully deliver therapeutic agents to cancer cells. Concurrently, a great deal of effort has also been devoted to alter various parameters of tumor pathophysiology to pre-treat tumors before nanoparticles are administered. Such 'priming' treatments improve access of the systemically administered agents to the tumor and promote drug penetration into the deeper layers of tumor tissue. This review will highlight recent advances in cancer nanomedicine exploiting both nanoparticle design and tumor microenvironment modification; and provide a critical perspective on the future development of nanomedicine delivery in oncology.

Contrast enhanced ultrasound imaging can predict vascular-targeted photodynamic therapy induced tumor necrosis in small animals

AIMS

To evaluate the accuracy of contrast-enhanced ultrasound (CEUS) for monitoring tumor necrosis following WST-11 vascular targeted photodynamic therapy (VTP) using imaging-pathology correlation.

METHODS

Renal adenocarcinoma cells were injected into the hindlimb of 13 BalB/c mice resulting in tumors ranging from 9.8 to 194.3mm³. US guidance was used to place a laser fiber into the tumor, and VTP was performed. CEUS was performed prior to animal sacrifice, 24h post-VTP. Whole tumors were extracted for histopathologic analysis using H&E and TUNEL staining. Pathology samples corresponding to the CEUS imaging plane were prepared in order to compare the size and extents of tumor necrosis.

RESULTS

Tumor necrosis following VTP appeared as a central region of non-enhancement on CEUS, while viable tumor appeared as patchy regions of enhancement in the tumor periphery. The region of tumor necrosis measured in mean 66% and 64.8% of total tumor area on CEUS and pathology respectively (p=0.2). The size and location of the necrosis on CEUS images and pathology samples were found correlative with no inter-observer difference (weighted kappa of 0.771 and 0.823, respectively).

CONCLUSION

CEUS allows accurate monitoring of VTP induced tumor necrosis in a small animal model.

Targeting Phosphatidylinositol 3-Kinase Signaling Pathway for Therapeutic Enhancement of Vascular-Targeted Photodynamic Therapy

Vascular-targeted photodynamic therapy (PDT) selectively disrupts vascular function by inducing oxidative damages to the vasculature, particularly endothelial cells. Although effective tumor eradication and excellent safety profile are well demonstrated in both preclinical and clinical studies, incomplete vascular shutdown and angiogenesis are known to cause tumor recurrence after vascular-targeted PDT. We have explored therapeutic enhancement of vascular-targeted PDT with PI3K signaling pathway inhibitors because the activation of PI3K pathway was involved in promoting endothelial cell survival and proliferation after PDT. Here, three clinically relevant small-molecule inhibitors (BYL719, BKM120, and BEZ235) of the PI3K pathway were evaluated in combination with verteporfin-PDT. Although all three inhibitors were able to synergistically enhance PDT response in endothelial cells, PDT combined with dual PI3K/mTOR inhibitor BEZ235 exhibited the strongest synergism, followed in order by combinations with pan-PI3K inhibitor BKM120 and p110α isoform-selective inhibitor BYL719. Combination treatments of PDT and BEZ235 exhibited a cooperative inhibition of antiapoptotic Bcl-2 family protein Mcl-1 and induced more cell apoptosis than each treatment alone. In addition to increasing treatment lethality, BEZ235 combined with PDT effectively inhibited PI3K pathway activation and consequent endothelial cell proliferation after PDT alone, leading to a sustained growth inhibition. In the PC-3 prostate tumor model, combination treatments improved treatment outcomes by turning a temporary tumor regrowth delay induced by PDT alone to a more long-lasting treatment response. Our study strongly supports the combination of vascular-targeted PDT and PI3K pathway inhibitors, particularly mTOR inhibitors, for therapeutic enhancement. Mol Cancer Ther; 16(11); 2422-31. ©2017 AACR.

Vascular targeted photodynamic therapy with TOOKAD® Soluble (WST11) in localized prostate cancer: efficiency of automatic pre-treatment planning

Vascular targeted photodynamic therapy (VTP) with WST11 is a novel non-thermal focal treatment for localized prostate cancer that has shown favorable and early efficacy results in previously published studies. In this work, we investigate the efficiency of automatic dosimetric treatment planning. An action model established in a previous study was used in an image-guided optimization scheme to define the personalized optimal light dose for each patient. The calculated light dose is expressed as the number of optical cylindrical fibers to be used, their positions according to an external insertion grid, and the lengths of their diffuser parts. Evaluation of the method was carried out on data collected from 17 patients enrolled in two multi-centric clinical trials. The protocol consisted of comparing the method-simulated necrosis to the result observed on day 7 MR enhanced images. The method performances showed that the final result can be estimated with an accuracy of 10%, corresponding to a margin of 3 mm. In addition, this process was compatible with clinical conditions in terms of calculation times. The overall process took less than 10 min. Different aspects of the VTP procedure were already defined and optimized. Personalized treatment planning definition remained as an issue needing further investigation. The method proposed herein completes the standardization of VTP and opens new pathways for the clinical development of the technique.

Bombesin Antagonist-Based Radiotherapy of Prostate Cancer Combined with WST-11 Vascular Targeted Photodynamic Therapy

Purpose: DOTA-AR, a bombesin-antagonist peptide, has potential clinical application for targeted imaging and therapy in gastrin-releasing peptide receptor (GRPr)-positive malignancies when conjugated with a radioisotope such as ⁹⁰Y. This therapeutic potential is limited by the fast washout of the conjugates from the target tumors. WST-11 (Weizmann STeba-11 drug; a negatively charged water-soluble palladium-bacteriochlorophyll derivative, Tookad Soluble) vascular targeted photodynamic therapy (VTP) is a local ablation approach recently approved for use in early-stage prostate cancer. It generates reactive oxygen/nitrogen species within tumor blood vessels, resulting in their instantaneous destruction followed by rapid tumor necrosis. We hypothesize that the instantaneous arrest of tumor vasculature may provide a means to trap radiopharmaceuticals within the tumor, thereby improving the efficacy of targeted radiotherapy.Experimental Design: GRPr-positive prostate cancer xenografts (PC-3 and VCaP) were treated with ⁹⁰Y-DOTA-AR with or without VTP. The uptake of radioisotopes was monitored by Cherenkov luminescence imaging (CLI). The therapeutic efficacy of the combined VTP and ⁹⁰Y-DOTA-AR in PC-3 xenografts was assessed.Results: CLI of ⁹⁰Y-DOTA-AR demonstrated longer retention of radiotracer within the VTP-treated PC-3 xenografts compared with the non-VTP-treated ones (P < 0.05) at all time points (24-144 hours) after ⁹⁰Y-DOTA-AR injection. A similar pattern of retention was observed in VCaP xenografts. When ⁹⁰Y-DOTA-AR administration was combined with VTP, tumor growth delay was significantly longer than for the control or the monotherapy groups.Conclusions: Tumor vascular arrest by VTP improves ⁹⁰Y-DOTA-AR retention in the tumor microenvironment thereby enhancing therapeutic efficacy. Clin Cancer Res; 23(13); 3343-51. ©2017 AACR.

Treatment Effects of WST11 Vascular Targeted Photodynamic Therapy for Urothelial Cell Carcinoma in Swine

PURPOSE

Surgical management of upper tract urothelial carcinoma requires kidney and ureter removal, compromising renal function. Nonsurgical alternatives have potentially prohibitive safety concerns. We examined the feasibility and safety of ablation of the ureter and renal pelvis using endoluminal vascular targeted photodynamic therapy in a porcine model. We also report the efficacy of WST11 vascular targeted photodynamic therapy in a murine model.

MATERIALS AND METHODS

After receiving approval we performed a total of 28 endoluminal ablations in the ureters and renal pelvis of 18 swine. Intravenous infusion of WST11 (4 mg/kg) followed by 10-minute laser illumination was done via percutaneous access or a retrograde ureteroscopic approach. Animals were followed clinically with laboratory testing, imaging and histology, which were evaluated at several postablation time points. A murine xenograft was created with the 5637 human urothelial cell carcinoma line to determine sensitivity to this therapy.

RESULTS

At 24 hours 50 mW/cm laser fluence produced superficial necrosis of the ureter. Deeper necrosis penetrating the muscularis propria or adventitia was produced by treatment with 200 mW/cm in the ureter and the renal pelvis. At 4 weeks superficial urothelium had regenerated over the treatment site. No symptomatic obstruction, clinically relevant hydronephrosis or abnormality of laboratory testing was noted up to 4 weeks. Of the mice 80% had no evidence of tumor 19 days after WST11 vascular targeted photodynamic therapy.

CONCLUSIONS

Urothelial cell carcinoma appears to be sensitive to WST11 vascular targeted photodynamic therapy. The depth of WST11 vascular targeted photodynamic therapy treatment effects can be modulated in a dose dependent manner by titrating light intensity. Moreover, when applied to the porcine upper urinary tract, this treatment modality is feasible via antegrade and retrograde access.

Final Results of a Phase I/II Multicenter Trial of WST11 Vascular Targeted Photodynamic Therapy for Hemi-Ablation of the Prostate in Men with Unilateral Low Risk Prostate Cancer Performed in the United States

PURPOSE

Vascular targeted photodynamic therapy with WST11 (TOOKAD® Soluble) is a form of tissue ablation that may be used therapeutically for localized prostate cancer. To study dosing parameters and associated treatment effects we performed a prospective, multicenter, phase I/II trial of WST11 vascular targeted photodynamic therapy of prostate cancer.

MATERIALS AND METHODS

A total of 30 men with unilateral, low volume, Gleason 3 + 3 prostate cancer were enrolled at 5 centers after local institutional review board approval. Light energy, fiber number and WST11 dose were escalated to identify optimal dosing parameters for vascular targeted photodynamic therapy hemi-ablation. Men were treated with photodynamic therapy and evaluated by posttreatment magnetic resonance imaging and biopsy. Prostate specific antigen, light dose index (defined as fiber length/desired treatment volume), toxicity and quality of life parameters were recorded.

RESULTS

After dose escalation 21 men received optimized dosing of 4 mg/kg WST11 at 200 J energy. On posttreatment biopsy residual prostate cancer was found in the treated lobe in 10 men, the untreated lobe in 4 and both lobes in 1. At a light dose index of 1 or greater with optimal dosing in 15 men 73.3% had a negative biopsy in the treated lobe. Six men undergoing retreatment with the optimal dose and a light dose index of 1 or greater had a negative posttreatment biopsy. Minimal effects were observed on urinary and sexual function, and overall quality of life.

CONCLUSIONS

Hemi-ablation of the prostate with WST11 vascular targeted photodynamic therapy was well tolerated and resulted in a negative biopsy in the treated lobe in the majority of men. Dosing parameters and the light dose index appear related to tissue response as determined by magnetic resonance imaging and biopsy. These parameters may serve as the basis for further prospective studies.

Tumor Stroma, Tumor Blood Vessels, and Antiangiogenesis Therapy

Solid tumors generally require a vascularized connective tissue stroma if they are to grow beyond minimal size. They generate that stroma in part by secreting vascular endothelial growth factor (VEGF), a potent vascular permeability and angiogenic factor. Increased vascular permeability leads to deposition of a provisional fibrin stroma, which supports tumor, connective tissue, and inflammatory cell migration and plays an active role in the formation of mature vascularized stroma. Vascular endothelial growth factor-induced tumor blood vessels are heterogeneous, of at least 6 distinct types, and develop linearly over time. They include both angiogenic (mother vessels, glomeruloid microvascular proliferations, vascular malformations, capillaries) and arteriovenogenic (feeding arteries, draining veins) blood vessels. Attacking the tumor vasculature with drugs that target VEGF or its receptors (VEGFR) has come into vogue but has been less effective than had been hope for. One reason for this is that anti-VEGF/VEGFR therapy attacks only a subset of tumor blood vessels, the earliest to form. New targets on late-forming blood vessels such as feeding arteries would be useful in helping antivascular cancer therapy fulfill its promise.

Nonthermal Ablation by Using Intravascular Oxygen Radical Generation with WST11: Dynamic Tissue Effects and Implications for Focal Therapy

Purpose To examine the hypothesis that vascular-targeted photodynamic therapy (VTP) with WST11 and clinically relevant parameters can be used to ablate target tissues in a non-tumor-bearing large-animal model while selectively sparing blood vessels and collagen. Materials and Methods By using an institutional animal care and use committee-approved protocol, 68 ablations were performed in the kidneys (cortex and medulla) and livers of 27 adult pigs. Posttreatment evaluation was conducted with contrast material-enhanced computed tomography in the live animals at 24 hours. Immunohistochemistry was evaluated and histologic examination with hematoxylin-eosin staining was performed at 4 hours, 24 hours, and 7 days. Intravenous infusion of WST11 (4 mg per kilogram of body weight) was followed by using near-infrared illumination (753 nm for 20 minutes) through optical fibers prepositioned in target tissues by using a fixed template. Treated areas were scanned, measured, and statistically analyzed by using the Student t test and two-way analysis of variance. Results Focal WST11 VTP treatment in the liver and kidney by using a single optical fiber resulted in well-demarcated cylindrical zones of nonthermal necrosis concentrically oriented around the light-emitting diffuser, with no intervening viable parenchymal cells. The radius of ablated tissue increased from approximately 5 mm at 150 mW to approximately 7 mm at 415 mW (P < .01). Illumination through fiber triads at 1-cm separation resulted in confluent homogeneous necrosis. Patterns of acute injury within 24 hours were consistent with microcirculatory flow arrest and collagen preservation (demonstrated with trichrome staining). In the peripheral ablation zone, blood vessels at least 40 μm in diameter were selectively preserved and remained functional at 7 days. Ablated tissues exhibited progressive fibrosis and chronic inflammatory cell infiltrates. No histologic changes consistent with thermal injury were observed in blood vessels or collagen. The renal hilum and collecting system did not show treatment effect, despite treatment proximity. Conclusion WST11 VTP induces nonthermal tissue ablation in target tissue while preserving critical organ structures and bystander blood vessels within solid organs. (©) RSNA, 2016 Online supplemental material is available for this article.

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.

TOOKAD® Soluble focal therapy: pooled analysis of three phase II studies assessing the minimally invasive ablation of localized prostate cancer

Purpose

To evaluate the 6-month effects of the recommended drug and light dosage in focal vascular-targeted photodynamic therapy (VTP) using TOOKAD^® Soluble in patients with localized prostate cancer (LPCa).

Methods

We performed a pooled analysis of 117 men with LPCa, PSA <10 ng/mL, and Gleason score ≤7 (3 + 4), from 3 studies who received a 10-min intravenous infusion of a single dose of 4 mg/kg TOOKAD^® Soluble, activated by a 753-nm light at 200 J/cm delivered in the prostate by transperineal fibres under transrectal ultrasound guidance. Primary endpoint was 6-month negative biopsies in the treated lobe(s). PSA was measured at month 1, 3, and 6. Magnetic resonance imaging was performed at day 7, month 3, and 6. International Prostate Symptom Score (IPSS), International Index of Erectile Function (IIEF-5) and adverse events were reported at day 7, month 1, 3, and 6.

Results

Month 6 negative biopsy rate was 68.4 % in the overall evaluable population (N = 114) and 80.6 % for patients treated by hemiablation with light density index (LDI) ≥ 1 (N = 67). Mean prostate necroses at week-1 were 76.5 and 86.3 %, respectively. In both groups, PSA levels at month 6 decreased by 2.0 ng/mL. Small changes from baseline for IPSS and IIEF-5 indicated a slight improvement in urinary function and a slight deterioration in sexual function.

Conclusions

Focal VTP treatment with TOOKAD^® Soluble at 4 mg/kg and 200 J/cm resulted in a negative 6-month biopsy rate of 68.4 % for the whole population and 80.6 % for patients treated by hemiablation with LDI ≥ 1. The treatment was well tolerated. Two phase III studies will reach completion in early 2015.

Apoptosis and associated phenomena as a determinants of the efficacy of photodynamic therapy

Failure of neoplastic cells to respond to conventional chemotherapy is usually associated with factors that limit access of drugs to subcellular sites, differences in cell-cycle kinetics or mutations leading to loss of drug-activation pathways or other processes that govern response factors. For PDT, efficacy depends mainly on selective uptake of photosensitizers by neoplastic cells, oxygenation levels, the suitable direction of irradiation and the availability of pathways to cell death that are highly conserved among mammalian cell types. While it is possible to engineer PDT-resistant cell types, current evidence suggests that the major obstacles to cancer control relate to drug, light and oxygen distribution. This review discusses some of the factors that can govern PDT-induced cell death.

[Photodynamic therapy of bladder cancer. A new option]

BACKGROUND

Bladder cancer (BCa) is the third most common tumor in Germany. Currently, resection therapy for superficial BCa (Ta, CIS) includes photodynamic diagnostics (PDD) using HEXVIX® for improved assessment of tumor spread. Trials using these photosensitizers for photodynamic therapy (PDT) showed only limited success. Especially low tissue penetration due to short-wave excitation was a limiting factor.

METHODS

This study which was funded by the German Research Foundation (DFG) examined the feasibility of the novel photosensitizer tetrahydroporphyrin-tetratosylate (THPTS) for PDT in a rat bladder cancer model.

RESULTS

As THPTS is very effectively excitable at a near infrared wavelength of 760 nm it is within the so-called phototherapeutic window and allows tissue penetration of up to 15 mm. Thus THPTS can also be used for PDT of larger, solid tumors as was previously demonstrated for other tumor entities. Therefore, effective treatment of even muscle-invasive bladder cancer (≥T2) may become an option using THPTS. In this current study the effectiveness and safety of THPTS-PDT was examined in an orthotopic bladder cancer rat model.

Heterogeneity of tumor vasculature and antiangiogenic intervention: insights from MR angiography and DCE-MRI

PURPOSE

Solid tumor vasculature is highly heterogeneous, which presents challenges to antiangiogenic intervention as well as the evaluation of its therapeutic efficacy. The aim of this study is to evaluate the spatial tumor vascular changes due to bevacizumab/paclitaxel therapy using a combination approach of MR angiography and DCE-MRI method.

EXPERIMENTAL DESIGN

Tumor vasculature of MCF-7 breast tumor mouse xenografts was studied by a combination of MR angiography and DCE-MRI with albumin-Gd-DTPA. Tumor macroscopic vasculature was extracted from the early enhanced images. Tumor microvascular parameters were obtained from the pharmacokinetic modeling of the DCE-MRI data. A spatial analysis of the microvascular parameters based on the macroscopic vasculature was used to evaluate the changes of the heterogeneous vasculature induced by a 12 day bevacizumab/paclitaxel treatment in mice bearing MCF-7 breast tumor.

RESULTS

Macroscopic vessels that feed the tumors were not affected by the bevacizumab/paclitaxel combination therapy. A higher portion of the tumors was within close proximity of these macroscopic vessels after the treatment, concomitant with tumor growth retardation. There was a significant decrease in microvascular permeability and vascular volume in the tumor regions near these vessels.

CONCLUSION

Bevacizumab/paclitaxel combination therapy did not block the blood supply to the MCF-7 breast tumor. Such finding is consistent with the modest survival benefits of adding bevacizumab to current treatment regimens for some types of cancers.

TOOKAD(®) Soluble vascular-targeted photodynamic (VTP) therapy: determination of optimal treatment conditions and assessment of effects in patients with localised prostate cancer

OBJECTIVES

To evaluate the optimal treatment conditions and effects of TOOKAD(®) Soluble vascular-targeted photodynamic (VTP) therapy in patients with localised prostate cancer. To evaluate the safety and quality of life after TOOKAD(®) Soluble VTP treatment in patients with localised prostate cancer.

PATIENTS AND METHODS

Men (aged >18 years) diagnosed with localised prostate cancer, who were suitable for active surveillance, were invited to take part in the study. Patients who had received prior or current treatment for their cancer were excluded. There were two parts to the study: in part one, patients were assigned to one of two treatment groups based on the size of their prostates (patients with prostate size <60 mL would receive 4 mg/kg TOOKAD(®) Soluble and patients with prostate size ≥60 mL would receive 6 mg/kg TOOKAD(®) Soluble both activated with 200 J/cm light). In part two, patients were assigned to one of two treatment groups based on predefined criteria and received either 4 or 6 mg/kg TOOKAD(®) Soluble and 200 or 300 J/cm light. VTP was conducted under general anaesthesia using TOOKAD(®) Soluble administered intravenously and activated by light-diffusing fibres within the prostate via the perineum. Follow-up was conducted for 6 months. Magnetic resonance imaging (MRI) carried out at 1 week after VTP and transrectal prostate biopsy at 6 months were the key endpoints. Adverse event (AE) recording and patient-reported outcome measures were collected.

RESULTS

In all, 86 patients were enrolled in the study and 85 patients received treatment. Of the 85 treated patients, one patient discontinued (due to withdrawal of consent). At 6 months, 61/83 (74%) patients who underwent prostate biopsy had histopathology that was negative for prostate cancer (95% confidence interval (CI) 62.7-82.6%). Considering patients who received 4 mg/kg TOOKAD(®) Soluble and 200 J/cm light (unilateral), which are considered optimal treatment parameters, 38/46 (83%) patients had histopathology from the biopsies that was negative for prostate cancer at 6 months (95% CI 68.6-92.2%; P < 0.001). The mean percentage of necrosis of the targeted prostate tissue at 7 days after VTP was 78% overall (83 patients) with extraprostatic necrosis reported in 76% (63/83) of patients. Considering patients who received 4 mg/kg TOOKAD(®) Soluble and 200 J/cm light (unilateral), the mean 7-day necrosis percentage was 88% (46 patients) with extraprostatic necrosis reported in 72% (33/46) of patients. All occurrences of extraprostatic necrosis were considered clinically acceptable and none were associated with any clinical sequelae. The mean percentage prostate necrosis at 7 days was statistically significantly higher (P < 0.001) in patients treated with a therapeutic light density index (LDI) of ≥1 than those treated with a LDI of <1. The percentage of patients with negative biopsies at 6 months was also higher in patients treated with a therapeutic LDI of ≥1 than those treated with a LDI of <1 (78.6% and 63.0%, respectively). In all, 87% (75/86) of patients reported at least one treatment-emergent AE during the study. Most AEs were mild or moderate in intensity and considered related to the technical procedures of the study. No treated patients had hypotension or discontinued due to AEs. Eight patients (9.3%) had serious AEs; none resulted in discontinuation from the study.

CONCLUSIONS

Biopsy data, post-treatment dynamic contrast-enhancement MRI at 1 week after VTP and analysis of the safety data have shown that 4 mg/kg TOOKAD(®) Soluble and 200 J/cm light are the optimal treatment conditions for the VTP procedure resulting in >80% of patients treated with this regimen having a negative biopsy at 6 months. Overall, the treatment was well tolerated and exhibited early signs of efficacy for minimally invasive focal treatment of localised prostate cancer.

Experimental model of transthoracic, vascular-targeted, photodynamically induced myocardial infarction

We describe a novel model of myocardial infarction (MI) in rats induced by percutaneous transthoracic low-energy laser-targeted photodynamic irradiation. The procedure does not require thoracotomy and represents a minimally invasive alternative to existing surgical models. Target cardiac area to be photodynamically irradiated was triangulated from the thoracic X-ray scans. The acute phase of MI was histopathologically characterized by the presence of extensive vascular occlusion, hemorrhage, loss of transversal striations, neutrophilic infiltration, and necrotic changes of cardiomyocytes. Consequently, damaged myocardium was replaced with fibrovascular and granulation tissue. The fibrotic scar in the infarcted area was detected by computer tomography imaging. Cardiac troponin I (cTnI), a specific marker of myocardial injury, was significantly elevated at 6 h (41 ± 6 ng/ml, n = 4, P < 0.05 vs. baseline) and returned to baseline after 72 h. Triphenyltetrazolium chloride staining revealed transmural anterolateral infarcts targeting 25 ± 3% of the left ventricle at day 1 with a decrease to 20 ± 3% at day 40 (n = 6 for each group, P < 0.01 vs. day 1). Electrocardiography (ECG) showed significant ST-segment elevation in the acute phase with subsequent development of a pathological Q wave and premature ventricular contractions in the chronic phase of MI. Vectorcardiogram analysis of spatiotemporal electrical signal transduction revealed changes in inscription direction, QRS loop morphology, and redistribution in quadrant areas. The photodynamically induced MI in n = 51 rats was associated with 12% total mortality. Histological findings, ECG abnormalities, and elevated cTnI levels confirmed the photosensitizer-dependent induction of MI after laser irradiation. This novel rodent model of MI might provide a platform to evaluate new diagnostic or therapeutic interventions.

Cellular and vascular effects of the photodynamic agent temocene are modulated by the delivery vehicle

The effects of the drug delivery system on the PDT activity, localization, and tumor accumulation of the novel photosensitizer temocene (the porphycene analogue of temoporfin or m-tetrahydroxyphenyl chlorin) were investigated against the P815 tumor, both in vitro and in DBA/2 tumor bearing mice. Temocene was administered either free (dissolved in PEG(400)/EtOH mixture), or encapsulated in Cremophor EL micelles or in DPPC/DMPG liposomes, chosen as model delivery vehicles. The maximum cell accumulation and photodynamic activity in vitro was achieved with the free photosensitizer, while temocene in Cremophor micelles hardly entered the cells. Notwithstanding, the micellar formulation showed the best in vivo response when used in a vascular regimen (short drug light interval), whereas liposomes were found to be an efficient drug delivery system for a tumor cell targeting strategy (long drug-light interval). PEG/EtOH formulation was discarded for further in vivo experiments as it provoked lethal toxic effects caused by photosensitizer aggregation. These results demonstrate that drug delivery systems modulate the vascular and cellular outcomes of photodynamic treatments with temocene.

Anti-VEGF/VEGFR therapy for cancer: reassessing the target

Judah Folkman recognized that new blood vessel formation is important for tumor growth and proposed antiangiogenesis as a novel approach to cancer therapy. Discovery of vascular permeability factor VEGF-A as the primary tumor angiogenesis factor prompted the development of a number of drugs that targeted it or its receptors. These agents have often been successful in halting tumor angiogenesis and in regressing rapidly growing mouse tumors. However, results in human cancer have been less impressive. A number of reasons have been offered for the lack of greater success, and, here, we call attention to the heterogeneity of the tumor vasculature as an important issue. Human and mouse tumors are supplied by at least 6 well-defined blood vessel types that arise by both angiogenesis and arterio-venogenesis. All 6 types can be generated in mouse tissues by an adenoviral vector expressing VEGF-A(164). Once formed, 4 of the 6 types lose their VEGF-A dependency, and so their responsiveness to anti-VEGF/VEGF receptor therapy. If therapies directed against the vasculature are to have a greater impact on human cancer, targets other than VEGF and its receptors will need to be identified on these resistant tumor vessels.

How to improve exposure of tumor cells to drugs: promoter drugs increase tumor uptake and penetration of effector drugs

Solid tumors are characterized by an abnormal architecture and composition that limit the uptake and distribution of antitumor drugs. Over the last two decades, drugs have been identified that improve the tumor uptake and distribution of drugs that have direct antitumor effects. We propose to refer to these drugs as promoter drugs, and as effector drugs to drugs that have direct antitumor effects. Some promoter drugs have received regulatory approval, while others are in active clinical development. This review gives an overview of promoter drugs, by classifying them according to their mechanism of action: promoter drugs that modulate tumor blood flow, modify the barrier function of tumor vessels, induce tumor cell killing, and overcome stromal barriers. Eventually, we discuss those that we feel are the main conclusions to be drawn from promoter drug research that has been performed so far, and suggest areas of future investigation to improve the efficacy of promoter drugs in cancer therapy.

In vivo characterization of tumor and tumor vascular network using multi-modal imaging approach

We present a multi-modal optical diagnostic approach utilizing a combined use of Fluorescence Intravital Microscopy (FIM), Dynamic Light Scattering (DLS) and Spectrally Enhanced Microscopy (SEM) modalities for in vivo imaging of tumor vascular network and blood microcirculation. FIM is used for imaging of tumor surroundings and microenvironment, SEM provides information regarding blood vessels topography, whereas DLS is applied for functional imaging of vascular network and blood microcirculation. This complementary combination of the imaging approaches is extremely useful for functional in vivo imaging of blood vasculature and tumor microenvironment. The technique has also a great potential in vascular biology and can significantly expand the capabilities of tumor angiogenesis studies and notably contribute to the development of cancer treatment.