Irrigation solutions in head and neck cancer surgery: a preclinical efficacy study.

INTRODUCTION: It is common practice to irrigate the operative site following tumor resection during major head and neck surgery. A variety of irrigation solutions are used, but there are few data on their relative efficacies in this context. METHODS: The effect of different irrigation solutions on cell survival was assessed by clonogenic survival assay in 5 head and neck squamous cell carcinoma cell lines at different time points. RESULTS: Saline had no effect on cell survival in any of the cell lines tested. Hydrogen peroxide, povidone-iodine, and a hydrogen peroxide/povidone-iodine mix caused complete cell death in all cell lines. Irrigation with distilled water caused a significant reduction in cell survival in 3 cell lines. Duration of exposure showed no effect on cell survival. CONCLUSION: These data suggest a significant difference in the cytocidal effect of commonly used irrigation solutions on head and neck cancer cells in an in vitro model.

Suppression of homologous recombination sensitizes human tumor cells to IGF-1R inhibition.

Inhibition of type 1 IGF receptor (IGF-1R) sensitizes to DNA-damaging cancer treatments, and delays repair of DNA double strand breaks (DSBs) by non-homologous end-joining and homologous recombination (HR). In a recent screen for mediators of resistance to IGF-1R inhibitor AZ12253801, we identified RAD51, required for the strand invasion step of HR. These findings prompted us to test the hypothesis that IGF-1R-inhibited cells accumulate DSBs formed at endogenous DNA lesions, and depend on residual HR for their repair. Indeed, initial experiments showed time-dependent accumulation of γH2AX foci in IGF-1R -inhibited or -depleted prostate cancer cells. We then tested effects of suppressing HR, and found that RAD51 depletion enhanced AZ12253801 sensitivity in PTEN wild-type prostate cancer cells but not in cells lacking functional PTEN. Similar sensitization was induced in prostate cancer cells by depletion of BRCA2, required for RAD51 loading onto DNA, and in BRCA2(-/-) colorectal cancer cells, compared with isogenic BRCA2(+/-) cells. We also assessed chemical HR inhibitors, finding that RAD51 inhibitor BO2 blocked RAD51 focus formation and sensitized to AZ12253801. Finally, we tested CDK1 inhibitor RO-3306, which impairs HR by inhibiting CDK1-mediated BRCA1 phosphorylation. R0-3306 suppressed RAD51 focus formation consistent with HR attenuation, and sensitized prostate cancer cells to IGF-1R inhibition, with 2.4-fold reduction in AZ12253801 GI50 and 13-fold reduction in GI80. These data suggest that responses to IGF-1R inhibition are enhanced by genetic and chemical approaches to suppress HR, defining a population of cancers (PTEN wild-type, BRCA mutant) that may be intrinsically sensitive to IGF-1R inhibitory drugs.