talaporfin and Stomach-Neoplasms

Photodynamic therapy (PDT) utilizes photochemical reactions induced by a photosensitizer and light in the target tissue and is used to treat various cancers. There is a high degree of anticipation of success regarding the application of PDT with talaporfin (photosensitizer) for gastric cancer. Olaparib is an oral inhibitor of Poly (ADP-Ribose) polymerase (PARP) and has demonstrated optimal efficacy and clinical activity in trials. Therefore, the aim of the present study was to investigate the efficacy of talaporfin PDT combined with olaparib for gastric cancer. MKN45, a gastric cancer cell line, was incubated with talaporfin, followed by irradiation, in the presence/absence of olaparib. Talaporfin PDT and olaparib exhibited excellent synergistic action in a concentration-dependent manner. PARP-DNA complexes were characterized based on bound chromatin using Western blot analyses. The combination of talaporfin PDT and olaparib enhanced PARP1 accumulation (the entrapment of PARP1-DNA complexes) in bound chromatin. The combination of talaporfin PDT and olaparib induced DNA double-strand breaks, which was confirmed by evaluating phosphorylated histone H2AX. Xenograft tumor mouse models were established, and antitumor effects were analyzed. In vivo, tumor growth was significantly suppressed following PDT with talaporfin and olaparib. Our results demonstrated that olaparib enhances the efficacy of talaporfin PDT by inducing the formation of PARP-DNA complexes. Therefore, our results suggest that the combination of talaporfin PDT and olaparib is a potential antitumor therapy for gastric cancer.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Cell Line, Tumor; Cell Survival; Combined Modality Therapy; Drug Synergism; Humans; Mice; Mice, Inbred BALB C; Mice, Nude; Photochemotherapy; Photosensitizing Agents; Phthalazines; Piperazines; Poly(ADP-ribose) Polymerase Inhibitors; Porphyrins; Stomach Neoplasms; Xenograft Model Antitumor Assays

Photodynamic therapy (PDT) is a potential treatment for the peritoneal dissemination of gastric cancer, because its cytotoxicity is limited to superficial lesions. We examined the accumulation of talaporfin in peritoneal metastatic nodules and determined the optimal laser condition for these nodules. We also evaluated the pathological response after therapy. We created a peritoneal metastasis model in nude mice using the MKN-45 EGFP cell line. We evaluated the accumulation of talaporfin in peritoneal metastatic nodules and normal organs by spectrophotometric analysis 2-8 h after i.p. talaporfin. To determine optimal PDT conditions, we treated metastatic nodules and the small intestine using multiple laser doses (2, 5, and 10 J/cm2, respectively). Accumulation of talaporfin was detected in metastatic nodules in higher intensities than in the small intestine. The fluorescent intensity of the peritoneal metastatic nodules gradually decreased dependent on the time interval between the laser treatment and talaporfin administration. Fluorescent intensity in the small intestine decreased more than in the metastatic nodules. The pathological response rates by dose were 52.5% at 2 J/cm2, 43.2% at 5 J/cm2, and 64.4% at 10 J/cm2, respectively, when the laser treatment was used 2 h after talaporfin administration, whereas at 4 h, they were 20.8, 25.5, and 26.2%, respectively. Finally, the recommended treatment conditions were considered to be a 2 J/cm2 laser dose and a 4-h interval in terms of toxicity. Talaporfin-mediated PDT may be an effective treatment modality for patients with advanced gastric adenocarcinoma and metastatic peritoneal nodules.

Topics: Animals; Disease Models, Animal; Male; Mice; Mice, Nude; Peritoneal Neoplasms; Photochemotherapy; Photosensitizing Agents; Porphyrins; Stomach Neoplasms; Tissue Distribution