Molecular disruption of the MRN(95) complex induces radiation sensitivity in head and neck cancer
Bert W O'Malley1, Daqing Li, James Carney
1Department of Otolaryngology--Head and Neck Cancer, University of Maryland School of Medicine, Baltimore, USA. bomalley@smail.umaryland.edu
Objectives/Hypothesis:
The goal of the project was to develop a novel treatment strategy for head and neck cancer that induces radiation sensitivity. We hypothesized that the normal cellular DNA repair response in head and neck squamous cell carcinoma after radiation therapy can be blocked by a dominant negative disruption of the functioning MRN(95) protein complex. To test this hypothesis, we have developed a novel molecular therapy that inhibits the MRN(95) complex in tumor cells. Disruption the MRN(95) complex and thus DNA repair should result in enhanced tumor killing after classic external-beam radiation therapy.
Study Design:
Experiments with human head and neck squamous cell carcinoma cell lines in vitro were performed.
Methods:
Recombinant adenovirus vectors carrying the genes for enhancing radiation were generated. Human head and neck squamous cell carcinoma cells were treated with recombinant adenovirus vectors carrying the mutated p95 gene (p95-300), which contains the C-terminus 300 amino acids of the Nbs1(p95) protein. Tumor cells were also treated with adenovirus vector carrying full-length p95 protein or DL312 control virus; then all cell lines were subjected to 2 Gy irradiation. Cell growth curves were determined through colorimetric tetrazolium salt assay.
Results:
Both the Ad-p95-300 and Ad-p94-his (full-length wild-type gene) demonstrated significant antitumor effect alone and in combination with radiation therapy compared with control samples. Cell cycle analysis demonstrated a shift toward the G2/M phase of the cell cycle. Analysis of telomerase activity demonstrated a significant decrease in telomerase activity after molecular therapy alone, and a greater decrease when combined with radiation therapy.
Conclusion:
Adenovirus-mediated mutant or full-length p95 molecular therapy demonstrated efficacy for the treatment of head and neck squamous cell carcinoma in vitro. This novel molecular therapy strategy induced significant radiation sensitization, induced a relative G2/M arrest, and decreased telomerase activity, all of which enhance the benefit of radiation therapy.
Insights
This study developed a novel molecular therapy to enhance head and neck cancer treatment. By disrupting the MRN(95) complex, the therapy increased radiation sensitivity and tumor cell killing in vitro.
Area of Science:
- Oncology
- Molecular Biology
- Radiation Therapy
Background:
- Head and neck squamous cell carcinoma (HNSCC) exhibits cellular DNA repair mechanisms that can limit treatment efficacy.
- Targeting these repair pathways presents a strategy to enhance the effectiveness of radiation therapy.
Purpose of the Study:
- To develop and evaluate a novel molecular therapy to induce radiation sensitivity in HNSCC.
- To test the hypothesis that disrupting the MRN(95) protein complex enhances tumor cell killing post-radiation.
Main Methods:
- Human HNSCC cell lines were treated with recombinant adenovirus vectors carrying mutated (p95-300) or full-length p95 genes.
- Cells were subjected to 2 Gy irradiation, and cell growth was assessed.
- Cell cycle and telomerase activity were analyzed.
Main Results:
- Both mutant and full-length p95 therapies showed antitumor effects alone and with radiation.
- A shift towards the G2/M phase of the cell cycle was observed.
- Significant decreases in telomerase activity were noted, especially when combined with radiation.
Conclusions:
- Adenovirus-mediated p95 molecular therapy is effective against HNSCC in vitro.
- This approach significantly sensitizes tumors to radiation, induces G2/M arrest, and reduces telomerase activity, improving radiation therapy outcomes.
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