Combination Tetrathiomolybdate and Radiation Therapy in a Mouse Model of Head and Neck Squamous Cell Carcinoma

Abstract

To assess the effect of combining tetrathiomolybdate therapy and radiation treatment (RT) on tumor growth in the mouse head and neck squamous cell carcinoma (HNSCC) model. Design: One million HNSCC cells were injected subcutaneously into the flanks of C3H/HeJ mice and the tumors grown to an average of 301 mm 3 (day 0). Mice were randomized into 4 groups: (a) no therapy, (b) tetrathiomolybdate alone, (c) RT alone, or (d) tetrathiomolybdateϩRT. Data from 3 experiments with these 4 groups were analyzed. A gaussian mixed model was fit to the initialized logarithm of the tumor size counts between days 7 and 16 (linear component), and growth rates were compared. Assays using 3-(4,5-dimethylthiazol-2yl)-2,5 diphenyltetrazolium bromide (MTT) were conducted on HNSCC cells in culture with varying doses of tetrathiomolybdate. Interventions: Treated mice were given tetrathiomolybdate in their water and observed for clinical evidence of toxic effects associated with copper depletion as measured by ceruloplasmin assay. When tumor sizes reached an average of 535 mm 3 , mice receiving RT were given a single fraction of 750 rad (7.5 Gy), a dose determined in previous experiments to slow but not cure tumor growth, permitting an examination of interaction of radiation with tetrathiomolybdate. Results: Data from 3 separate experiments were analyzed. There were a total of 37 mice in the untreated group, 32 mice in the tetrathiomolybdate alone group, 38 mice in the RT alone group, and 46 mice in the tetrathiomolybdateϩRT group. Ceruloplasmin assays showed that we had obtained adequate copper reduction throughout the experiments to inhibit angiogenesis with minimal toxic effects. The tetrathiomolybdateϩRT combined therapy group of mice showed a statistically significant decrease in tumor growth compared with both the tetrathiomolybdate alone (P=.001) and RT alone groups (PϽ.001). Conclusion: The combination of the anti-angiogenic copper chelating agent tetrathiomolybdate with RT improved local control of HNSCC in an isogenic mouse model compared with either therapy alone.

A New Generation of Ultrasmall Nanoparticles Inducing Sensitization to Irradiation and Copper Depletion to Overcome Radioresistant and Invasive Cancers

“…Few studies have evaluated the effect of copper chelation associated with radiation therapy. In 2006, Khan et al showed that the combination of TM and radiotherapy improved local control of HNSCC in an isogenic mouse model [18]. Despite these promising results, there are currently no nanoparticles combining copper chelation and radiosensitization in their effect.…”

Targeting copper in cancer therapy: ‘Copper That Cancer’

“…There is compelling evidence that copper chelation alone is insufficient to kill malignant cells, necessitating its use in combination with other agents to be an effective therapeutic option. [180][181][182] Supporting this approach, TM and doxorubicin together are more potent at delaying SUM149 breast carcinoma xenograft growth and at inducing apoptosis, than either treatment administered alone. 182 Similarly, treating mice bearing head and neck squamous cell carcinoma 180 or lung cancer 181 with TM in combination with radiation therapy improves tumor growth inhibition.…”

“…[180][181][182] Supporting this approach, TM and doxorubicin together are more potent at delaying SUM149 breast carcinoma xenograft growth and at inducing apoptosis, than either treatment administered alone. 182 Similarly, treating mice bearing head and neck squamous cell carcinoma 180 or lung cancer 181 with TM in combination with radiation therapy improves tumor growth inhibition. The use of standard antiangiogenic therapies in combination with radiation therapy has also shown promise in clinical trials (reviewed in ref.…”

Copper and Copper Complexes in Tumor Therapy

“…However, in vitro studies did not reveal any impact on cell proliferation. Furthermore, TM was found to enhance the effectiveness of radiotherapy in treating HNSCC, resulting in a more potent tumor suppressive effect compared to radiotherapy alone [30] …”