Adenovirus-Mediated Gene Expression Radiosensitizes Non-Small Cell Lung Cancer Cells via -Independent Mechanisms

Abstract

We examined the ability of adenoviral-mediated expression of the melanoma differentiation associated gene-7 (Ad-mda-7), to radiosensitize non-small cell lung cancer (NSCLC) cell lines (A549 (wt-TP53/wt-RB1) and H1299 (del-TP53/wt-RB1)), and normal human lung fibroblast (NHLF) lines (CCD-16 and MRC-9). Results of clonogenic assays indicated that Ad-mda7 enhanced the radiosensitivity of the NSCLC cells independent of their TP53 gene status. On the other hand, the NHLF cell lines seemed to be relatively resistant to the cytotoxic effects of Ad-mda7 and were not radiosensitized compared with the NSCLC cells. We further examined the basis for this difference in the ability of Ad-mda7 to radiosensitize NSCLC cells compared with normal cells. Radiation-induced apoptosis was restored in the NSCLC lines, but not in the normal lines. Western blot analysis revealed that Ad-mda7 enhances radiosensitivity independently of any ability to upregulate the expression of Fas or Bax in NSCLC cells. Further analysis indicated that phosphorylated c-Jun expression was increased by Ad-mda7 in both A549 and H1299 cells, but not in CCD-16 cells. These results support the use of gene replacement with Ad-mda7 in combination with radiotherapy for the treatment of NSCLC.

Induction of reactive oxygen species renders mutant and wild-type K-ras pancreatic carcinoma cells susceptible to Ad.mda-7-induced apoptosis

“…In glioma and lung carcinomas, radiosensitization of cells by Ad.mda-7, which was ROS-dependent, required activation of the JNK1/2 pathway (Kawabe et al, 2002;Sarkar et al, 2002b;Yacoub et al, 2003c). In pancreatic adenocarcinoma cells, in a cell type dependent manner, the induction of cell death by ROS generating agents correlated with the modulation of discrete cassettes of multiple signaling pathways in different pancreatic tumor cells.…”

“…In these contexts, the synergy observed between the ROS-inducers and mda-7/IL-24 culminating in apoptosis in pancreatic cancer cells may proceed by inducing parallel downstream changes that normally lead to mitochondrial-mediated cell death when mda-7/ IL-24 is administered to permissive cancer cells or when the ROS-inducers are used at high concentrations. In addition, in a broad spectrum of permissive human tumor cells, ARS and ionizing radiation also enhance Ad.mda-7 and GST-MDA-7 lethality (Kawabe et al, 2002;Su et al, 2003;Yacoub et al, 2003aYacoub et al, -c, 2004Sauane et al, 2004), indicating that ROS generation can synergize with extant MDA-7 protein to enhance cell death in carcinoma cells.…”

“…Studies by several laboratories have demonstrated that Ad.mda-7 lethality is promoted by enhanced p38 MAPK signaling, and in some cells, by ERK1/2 signaling (Kawabe et al, 2002;Yacoub et al, 2003c). In glioma and lung carcinomas, radiosensitization of cells by Ad.mda-7, which was ROS-dependent, required activation of the JNK1/2 pathway (Kawabe et al, 2002;Sarkar et al, 2002b;Yacoub et al, 2003c).…”

“…Blots were probed with a random-primed [ 32 P]mda-7 cDNA probe and exposed for autoradiography. After the blots were stripped they were reprobed with a random-primed [ 32 P]gapdh cDNA probe activation of diverse signaling pathways, including ERK1/2, p38 and/or the JNK1/2/3, in a cell-typedependent manner (Kawabe et al, 2002;Sarkar et al, 2002b;Su et al, 2003;Yacoub et al, 2003aYacoub et al, , b, 2004Sauane et al, 2004). It has also been argued that Ad.mda-7 in specific situations can suppress AKT activity, which correlates with cell killing (Mhashilkar et al, 2003).…”

Ionizing radiation enhances therapeutic activity of mda-7/IL-24: overcoming radiation- and mda-7/IL-24-resistance in prostate cancer cells overexpressing the antiapoptotic proteins bcl-xL or bcl-2

“…Based on several factors including organ accessibility, the capacity to monitor disease progression during early stages using prostate specific antigen (PSA) and the lack of survival benefit of the prostate gland, viral-based gene therapies provide a practical treatment option for this disease (Mabjeesh et al, 2002). However, to realize the promise of gene therapy, identifying a gene therapeutic that does not harm normal cells, can kill not only infected tumor cells, but also has the capacity to induce a potent 'bystander antitumor effect' and to additionally radiosensitize cancer cells would represent an ideal weapon to combat this prevalent male disease and cancer in general (Su et al, 2001Kawabe et al, 2002;Yacoub et al, 2003c;Chada et al, 2004;Fisher, 2005;Sarkar et al, 2005). Recent studies indicate that the novel cytokine mda-7/IL-24, which displays the above mentioned antitumor properties, would appear to represent the perfect gene to utilize for the therapy of localized and disseminated prostate tumors (Fisher et al, 2003;Fisher, 2005;Gupta et al, 2005;Lebedeva et al, 2005;Sarkar et al, 2005).…”