Adenoviral-mediated mda-7 expression suppresses DNA repair capacity and radiosensitizes non-small-cell lung cancer cells.
The melanoma differentiation-associated gene-7 (mda-7) was identified by virtue of its enhanced expression in human melanoma cells induced into terminal differentiation. Enforced expression of mda-7 in human cancer cell lines of diverse origins results in the suppression of growth and induction of apoptosis. We have shown that adenoviral-mediated mda-7 (Ad-mda7) radiosensitizes non-small-cell lung cancer (NSCLC) cells by enhancing the apoptotic pathway. To identify the mechanism of this radiosensitization, we examined the level of proteins involved in the nonhomologous end-joining (NHEJ) pathway of DNA double-strand break (DSB) repair. Western blot analysis indicated that the expression of NHEJ pathway components Ku70, XRCC4, and DNA ligase IV was downregulated in NSCLC cells--A549 with Ad-mda7 treatment. No such change was observed in normal human CCD16 fibroblasts previously shown not to be radiosensitized by Ad-mda7. The biological significance of these changes of expression of proteins critical for repair of radiation-induced DSBs was confirmed via the analysis of DSB rejoining kinetics using pulsed field gel electrophoresis and assessment of host cell reactivation capacity following Ad-mda7 treatment. Based on these results, we hypothesize that Ad-mda7 sensitizes NSCLC cells to ionizing radiation by suppressing the activity of NHEJ, a pathway essential for repair of radiation-induced DSBs.
Department of Experimental Radiation Oncology, The University of Texas MD Anderson Cancer Center, Houston, TX 77030, USA.
Takashi
T
Nishikawa
Anupama
A
Munshi
Michael D
MD
Story
Sheikh
S
Ismail
Craig
C
Stevens
Sunil
S
Chada
Raymond E
RE
Meyn
D000256:Adenoviridae / Q000235:genetics*; D002289:Carcinoma, Non-Small-Cell Lung; D002460:Cell Line; D045744:Cell Line, Tumor; D004260:DNA Repair / Q000235:genetics*; D016147:Genes, Tumor Suppressor; D005910:Glioma; D006801:Humans; D007378:Interleukins / Q000235:genetics / Q000378:metabolism* / Q000528:radiation effects; D008168:Lung; D008175:Lung Neoplasms; D011839:Radiation, Ionizing; D011838:Radiation-Sensitizing Agents; D011994:Recombinant Proteins / Q000378:metabolism / Q000528:radiation effects; D014162:Transfection; D000099180:Interleukin-24
D007378:Interleukins; D011838:Radiation-Sensitizing Agents; D011994:Recombinant Proteins; D000099180:Interleukin-24