Cyclooxygenase-2 (COX-2) is frequently overexpressed in human cancers and contributes to the malignant phenotype. Our data indicate unphosphorylated signal transducers and activators of transcription 6 (STAT6) may transcriptionally upregulate COX-2 expression and protect against apoptosis in NSCLC cells. In A427 and H2122, NSCLC cell lines that constitutively express COX-2, only unphosphorylated STAT6 was detectable by western blot, thus, all of the following STAT6-dependent effects are attributed to the unphosphorylated protein.In both cell lines, small-interfering RNA-mediated knockdown of STAT6 or stable expression of dominant-negative STAT6 decreased COX-2 expression. In contrast, transfection with a phosphorylation-deficient mutant STAT6 increased COX-2 levels. Immunofluorescent staining revealed the presence of STAT6 in H2122 nuclei, suggesting a direct role in gene regulation for the unphosphorylated protein. Consistent with this hypothesis, unphosphorylated STAT6 increased luciferase expression from a COX-2 promoter reporter construct. STAT6 coimmunoprecipitated with the transcriptional co-activator, p300, and chromatin immunoprecipitation assays demonstrated that these proteins bind a consensus STAT6 binding site located within the COX-2 promoter. STAT6 DNA-binding specificity was confirmed by electrophoretic mobility shift assay. As COX-2 over-expression has been clearly linked to apoptosis resistance and other hallmarks of malignancy, these findings suggest a novel role of unphosphorylated STAT6 in the pathogenesis of nonsmall cell lung cancer.

While external ionizing radiation has been used for treating non-small cell lung cancer (NSCLC), improved efficacy of this modality would be an important advance. Ectopic expression of the sodium iodide symporter (NIS) and thyroperoxidase (TPO) genes in NSCLC cells facilitated concentration of iodide in NSCLC cells, which markedly induced apoptosis in vitro and in vivo. Preincubation of the NIS/TPO-modified NSCLC cells in iodide followed by ionizing radiation generates bystander tumoricidal effects and potently enhances tumor cell killing. This iodide-induced bystander effect is associated with enhanced gap junction intercellular communication (GJIC) activity and increased connexin-43 (Cx43) expression. Thus, iodide may serve as an enhancer to markedly improve the efficacy of radiation therapy in combined therapeutic modalities.