M867, a novel selective inhibitor of caspase-3 enhances cell death and extends tumor growth delay in irradiated lung cancer models

• Published in: PloS one 2008-05, Vol.3 (5), p.e2275
• Main Authors: Kim, Kwang Woon, Moretti, Luigi, Lu, Bo
• Format: Article
• Language: English
• Subjects: Analysis; Angiogenesis; Animal models; Animals; Apoptosis; Apoptosis - drug effects; Autophagy; Base Sequence; BAX protein; Biochemistry; Cancer; Cancer therapies; Cancer treatment; Caspase; Caspase Inhibitors; Caspase-3; Cell death; Cell Line, Tumor; Cell survival; Clinical trials; Cysteine Proteinase Inhibitors - pharmacology; Cytotoxicity; Delay; DNA nucleotidylexotransferase; Drug dosages; Edema; Embryo fibroblasts; Embryos; Fibroblasts; Growth; Growth factors; Health aspects; Humans; Immune system; In vitro methods and tests; In vivo methods and tests; Inhibition; Inhibitors; Ionizing radiation; Ligands; Lung cancer; Lung diseases; Lung Neoplasms - blood supply; Lung Neoplasms - pathology; Lung Neoplasms - radiotherapy; Medical research; Mice; Mice, Knockout; Mortality; Oncology; Oncology/Lung Cancer; Oxadiazoles - pharmacology; Penicillin; Phagocytosis; Pneumonia; Proteins; Pulmonary fibrosis; Pyrazines - pharmacology; Radiation; Radiation effects; Radiation Tolerance; Radioresistance; Radiosensitivity; Radiotherapy; Respiratory distress syndrome; RNA, Small Interfering; Rodents; Staining; Therapy; Transplantation, Heterologous; Tumors; Von Willebrand factor
• ISSN: 1932-6203; 1932-6203
• DOI: 10.1371/journal.pone.0002275

Lung cancer remains the leading cause of cancer death worldwide. Radioresistance of lung cancer cells results in unacceptable rate of loco-regional failure. Although radiation is known to induce apoptosis, our recent study showed that knockdown of pro-apoptotic proteins Bak and Bax resulted in an increase in autophagic cell death and lung cancer radiosensitivity in vitro. To further explore the potential of apoptosis inhibition as a way to sensitize lung cancer for therapy, we tested M867, a novel chemical and reversible caspase-3 inhibitor, in combination with ionizing radiation in vivo and in vitro. M867 reduced clonogenic survival in H460 lung cancer cells (DER = 1.27, p = 0.007) compared to the vehicle-treated treated cells. We found that administration of M867 with ionizing radiation in an in vivo mouse hind limb lung cancer model was well tolerated, and produced a significant tumor growth delay compared to radiation alone. A dramatic decrease in tumor vasculature was observed with M867 and radiation using von Willebrand factor staining. In addition, Ki67 index showed >5-fold reduction of tumor proliferation in the combination therapy group, despite the reduced levels of apoptosis observed with terminal deoxynucleotidyl transferase-mediated dUTP nick end labeling staining. Radiosensitizing effect of M867 through inhibiting caspases was validated using caspase-3/-7 double-knockout (DKO) mouse embryonic fibroblasts (MEF) cell model. Consistent with our previous study, autophagy contributed to the mechanism of increased cell death, following inhibition of apoptosis. In addition, matrigel assay showed a decrease in in vitro endothelial tubule formation during the M867/radiation combination treatment. M867 enhances the cytotoxic effects of radiation on lung cancer and its vasculature both in vitro and in vivo. M867 has the potential to prolong tumor growth delay by inhibiting tumor proliferation. Clinical trials are needed to determine the potential of this combination therapy in patients with locally advanced lung cancer.