Photodynamic therapy (PDT) is a promising option for minimal-invasive treatment of bladder cancer. Efficacy of PDT in muscle-invasive urothelial cancer is still hampered by low tissue penetration of most photosensitizers due to short excitation wavelength. The novel light reactive agent tetrahydroporphyrin-tetratosylat (THPTS) is excitable at near-infrared (760 nm), allowing tissue penetration of up to 15 mm. Here, we established an orthotopic rat bladder cancer model and examined the effects of THPTS-PDT on tumor growth in vivo, and analyzed molecular mechanisms in vitro.We examined pharmacokinetics and subcellular localization, and evoked cell death mode in cultured rat urothelial carcinoma cells (AY-27). We used female F344 Fischer rats for in vivo studies. Ten rats each were used for THPTS-PDT and light-only control. Bladders were evaluated by macro-scopy and histology. Temperature-dependent THPTS uptake resulted in endosomal/lysosomal localization. PDT (0-50 mmol/L THPTS; 10 J/cm 2 ) induced early onset of apoptosis leading to dose-dependent cytotoxicity in AY-27 cells. Singletime transurethral THPTS-PDT (100 mmol/L THPTS; 10 J/cm 2 ) in F344 rats led to significant reduction of muscle-invasive tumor number (2/10 vs. 7/10 in controls) and total tumor volume (60% reduction) 2 weeks after PDT, while sparing healthy tissue. Here, we report for the first time effective tumor growth control by PDT in vivo. THPTS is a promising new photosensitizer with the advantage of higher therapeutic depth and the potential of high-selective therapy in muscleinvasive urothelial cancer. This approach possibly allows minimal-invasive bladder preserving treatment of bladder cancer without systemic side effects.

<p>Figure S3 shows bladder evaluation exemplarily.</p>

<div>Abstract<p>Photodynamic therapy (PDT) is a promising option for minimal-invasive treatment of bladder cancer. Efficacy of PDT in muscle-invasive urothelial cancer is still hampered by low tissue penetration of most photosensitizers due to short excitation wavelength. The novel light reactive agent tetrahydroporphyrin-tetratosylat (THPTS) is excitable at near-infrared (760 nm), allowing tissue penetration of up to 15 mm. Here, we established an orthotopic rat bladder cancer model and examined the effects of THPTS-PDT on tumor growth <i>in vivo</i>, and analyzed molecular mechanisms <i>in vitro</i>. We examined pharmacokinetics and subcellular localization, and evoked cell death mode in cultured rat urothelial carcinoma cells (AY-27). We used female F344 Fischer rats for <i>in vivo</i> studies. Ten rats each were used for THPTS-PDT and light-only control. Bladders were evaluated by macroscopy and histology. Temperature-dependent THPTS uptake resulted in endosomal/lysosomal localization. PDT (0–50 μmol/L THPTS; 10 J/cm²) induced early onset of apoptosis leading to dose-dependent cytotoxicity in AY-27 cells. Single-time transurethral THPTS-PDT (100 μmol/L THPTS; 10 J/cm²) in F344 rats led to significant reduction of muscle-invasive tumor number (2/10 vs. 7/10 in controls) and total tumor volume (60% reduction) 2 weeks after PDT, while sparing healthy tissue. Here, we report for the first time effective tumor growth control by PDT <i>in vivo</i>. THPTS is a promising new photosensitizer with the advantage of higher therapeutic depth and the potential of high-selective therapy in muscle-invasive urothelial cancer. This approach possibly allows minimal-invasive bladder preserving treatment of bladder cancer without systemic side effects.</p></div>

<p>Table S2 shows raw data of microscopic tumor evaluation.</p>

<p>Figure S4 shows cytotoxic effects of in vitro PDT determined by cell-based assays.</p>

<p>Table S1 shows current bladder Tumor classification (modified to our needs).</p>

<p>Figure S2 shows optimization of light dose used for PDT.</p>

<p>Figure S4 shows cytotoxic effects of in vitro PDT determined by cell-based assays.</p>