Induction of ferroptosis by photodynamic therapy and enhancement of antitumor effect with ferroptosis inducers.

BACKGROUND: Photodynamic therapy (PDT) is an effective tumor treatment that involves the administration of a photosensitizer to generate cytotoxic 1O2 [reactive oxygen species (ROS)] from molecular oxygen that is produced from energy absorption following tumor irradiation at specific wavelengths. Ferroptosis is induced by the disruption of the glutathione peroxidase 4 (GPX4) antioxidant system, leading to lipid peroxidation. We hypothesized that talaporfin sodium-photodynamic therapy (TS-PDT)-generated ROS would lead to ferroptosis via accumulation of lipid peroxidation. METHODS: Cell viability assay in TS-PDT-treated cells in combination with a ferroptosis inhibitor (ferrostatin-1: Fer-1) or ferroptosis inducers (imidazole ketone erastin: IKE, Ras-selective lethal 3: RSL3) was performed. Accumulation of lipid peroxidation, GPX4 antioxidant system and cystine/glutamate antiporter (system xc-) activity in TS-PDT-treated cells was investigated. In xenograft mice, the antitumor effect of TS-PDT in combination with ferroptosis inducers (IKE or sorafenib) was examined. RESULTS: TS-PDT-induced cell death was partly suppressed by Fer-1 and accompanied by lipid peroxidation. TS-PDT combined with IKE or RSL3 enhanced the induction of cell death. TS-PDT inhibited cystine uptake activity via system xc-. In vivo, the combination of TS-PDT and ferroptosis inducers (IKE or sorafenib) reduced tumor volume. CONCLUSION: This study found that the mechanism underlying TS-PDT-induced ferroptosis constitutes direct lipid peroxidation by the generated ROS, and the inhibition of system xc-, and that the combination of a ferroptosis inducer with TS-PDT enhances the antitumor effect of TS-PDT. Our findings suggest that ferroptosis-inducing therapies combined with PDT may benefit cancer patients.

Feasibility of self-expandable metallic stent plus chemotherapy for metastatic gastric cancer with pyloric stenosis.

BACKGROUND AND AIM: Self-expandable metallic stent placement is accepted as palliative therapy for advanced gastric cancer with gastric outlet obstruction, but data are lacking for chemotherapy after self-expandable metallic stent insertion. This study retrospectively compared results between surgery plus chemotherapy and stenting plus chemotherapy for metastatic gastric cancer with pyloric stenosis. METHODS: Subjects comprised 26 patients who received chemotherapy after surgery or endoscopic stenting for metastatic gastric cancer with pyloric stenosis between April 2000 and December 2007 in four Japanese hospitals. Patients were categorized into two groups: 15 patients who received chemotherapy after surgery for pyloric stenosis (Surgery group); and 11 patients who received chemotherapy after self-expandable metallic stent placement for pyloric stenosis (Stent group). RESULTS: Median survival time and median time to treatment failure were 284 days and 226 days in the Surgery group and 337 days and 247 days in the Stent group, respectively. No significant differences were noted between survival and time to treatment failure. No significant differences were found in median oral intake rate (Surgery, 93.1%; Stent, 93.2%) or median hospital stay rate (Surgery, 24.6%; Stent, 23.7%) during survival. Response rate was 45.5% in the Surgery group and 50% in the Stent group, with no significant difference. Likewise, no significant differences were noted between groups for frequencies of toxicity or complications. CONCLUSIONS: The present results suggest that chemotherapy after stenting is as effective and safe as chemotherapy after surgery. Stents may replace surgery in combination therapy with chemotherapy for metastatic gastric cancer with gastric outlet obstruction.

Suppression of proHB-EGF carboxy-terminal fragment nuclear translocation: a new molecular target therapy for gastric cancer.

PURPOSE: Inactivation of epidermal growth factor (EGF) receptor (EGFR) represents a promising strategy for the development of selective therapies against epithelial cancers and has been extensively studied as a molecular target for cancer therapy. However, little attention has been paid to remnant cell-associated domains created by cleavage of EGFR ligands. The present study focused on recent findings that cleavage of membrane-anchored heparin-binding EGF-like growth factor (proHB-EGF), an EGFR ligand, induces translocation of the carboxyl-terminal fragment (CTF) of HB-EGF from the plasma membrane to the nucleus and regulates cell cycle. EXPERIMENTAL DESIGN: Two gastric cancer cell lines, MKN28 and NUGC4, were used. KB-R7785, an inhibitor of proHB-EGF shedding, was used to suppress HB-EGF-CTF nuclear translocation with cetuximab, which inhibits EGFR phosphorylation. Cell growth was analyzed using 3-(4,5-dimethylthiazol-2-yl)-5-(3-carboxymethoxyphenyl)-2-(4-sulfophenyl)-2H-tetrazolium, inner salt assay, apoptosis was evaluated by assay of caspase-3 and caspase-7, and cell cycle was investigated by flow cytometry. RESULTS: Immunofluorescence study confirmed that KB-R7785 inhibited HB-EGF-CTF nuclear translocation under conditions of proHB-EGF shedding induction by 12-O-tetradecanoylphorbol-13-acetate in gastric cancer cells. KB-R7785 inhibited cell growth in a dose-dependent manner and high-dose KB-R7785 induced apoptosis. Moreover, KB-R7785 induced cell cycle arrest and increased sub-G1 DNA content. KB-R7785 suppressed cyclin A and c-Myc expression. All effects of KB-R7785 were reinforced by combination with cetuximab. CONCLUSIONS: These results suggest that both inhibition of EGFR phosphorylation and inhibition of HB-EGF-CTF nuclear translocation play crucial roles in inhibitory regulation of cancer cell growth. Suppression of HB-EGF-CTF nuclear translocation might offer a new strategy for treating gastric cancer.

Effect of plaunotol in combination with clarithromycin against clarithromycin-resistant Helicobacter pylori in vitro and in vivo.

OBJECTIVES: Recently, there has been a decrease in the eradication rate of Helicobacter pylori due to the increase in antibiotic resistance of this bacterium. Plaunotol, a cytoprotective anti-ulcer agent, exhibits antibacterial activity against H. pylori. The purpose of the present study was to investigate the effect of plaunotol in combination with clarithromycin against clarithromycin-resistant H. pylori clinical isolates. METHODS AND RESULTS: In the chequerboard titration method, the combination of plaunotol and clarithromycin showed a synergistic effect against 67% (10/15) clarithromycin-resistant strains and an additive effect against the other strains. No indifferent and antagonistic effects were observed against any of the strains tested. In a gastritis model of Mongolian gerbils infected with clarithromycin-resistant H. pylori, the plaunotol (40 mg/kg) and clarithromycin (66.6 mg/kg) combination exhibited synergistic effects; however, neither plaunotol nor clarithromycin alone showed bactericidal effects. CONCLUSIONS: These results suggest that plaunotol may play a useful role in combination with anti-H. pylori drugs in the treatment of diseases associated with clarithromycin-resistant H. pylori.