dehydroxymethylepoxyquinomicin and Melanoma

Constitutive activation of nuclear factor κB (NF-κB) characterizes melanoma cells. To explore the molecular mechanism of melanoma cell survival by constitutive NF-κB activation, we used the NF-κB inhibitor dehydroxymethylepoxyquinomicin (DHMEQ), which directly binds to NF-κB. DHMEQ abrogated constitutive NF-κB activity, which included RelA (p65)/p50 in melanoma cell lines G361 and HMV-II; however, the reduction of the viability was marginal. Expression of c-FLIP was not observed in the melanoma cell lines tested, and DHMEQ could not repress the expression of the Bcl-2 family proteins Bcl-2 and Bcl-xL. Concomitant treatment with DHMEQ and the inhibitor of antiapoptotic Bcl-2 family proteins, GX15-070, triggered synergistic reduction of the viability and induced apoptosis of G361 cells. These results indicate that abrogation of the NF-κB pathway alone is not sufficient to suppress the survival of melanoma cells. The NF-κB and the antiapoptotic Bcl-2 pathways cooperatively support the survival, and the dual targeting triggers synergistic reduction of the viability and induces apoptosis of melanoma cells.

Topics: Antineoplastic Combined Chemotherapy Protocols; Apoptosis; Benzamides; Cell Line, Tumor; Cell Survival; Cyclohexanones; Drug Synergism; Humans; Indoles; Melanoma; NF-kappa B; Proto-Oncogene Proteins c-bcl-2; Pyrroles; Signal Transduction; Tumor Cells, Cultured

Purpose. To examine the involvement of nuclear factor-kappa B (NFkappaB) pathways in uveal melanoma (UM) and to assess their potential as a therapeutic target for metastatic UM. Methods. Samples from primary (n = 7) and metastatic (n = 7) UM were evaluated for NFkappaB transcription factor family expression by quantitative PCR (QPCR), immunofluorescent staining, and Western blot analysis. The effect of two NFkappaB inhibitors, DHMEQ and BMS-345541, on two cell lines derived from UM liver metastases was assessed. Cell proliferation was examined by MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide] assay, methylene blue assay, and immunostaining for Ki-67. Apoptosis was assessed by immunostaining for activated caspase 3. Results. NFkappaB1, NFkappaB2, RelA, RelB, and NIK were expressed in primary UM and in its liver metastases. NFkappaB2, RelB, and NIK showed significantly higher mRNA levels in metastases from UM compared with primary tumors (3.4-fold, P = 0.03; 3.6-fold, P = 0.05; 3.5-fold, P = 0.03; respectively). NFkappaB2 protein activation was 3.9-fold higher in metastases (P = 0.03). NFkappaB inhibition reduced metastatic cell proliferation by 9.2-fold and 1.9-fold according to Ki67 staining (P = 0.04) and methylene blue assay (P = 6 x 10(-7)), respectively. Both NFkappaB inhibitors achieved dose-dependent reductions of UM cell proliferation in both cell lines (P < 0.001). NFkappaB inhibition resulted in a 6.3-fold increase of apoptosis (P = 7 x 10(-7)). Conclusions. These data indicate that the NFkappaB1 and NFkappaB2 pathways are active in both primary and metastatic UM and that these pathways regulate metastatic cell proliferation and apoptosis. The role of NFkappaB as a therapeutic target for UM should be further evaluated.

Topics: Apoptosis; Benzamides; Blotting, Western; Caspase 3; Cell Proliferation; Cyclohexanones; Fluorescent Antibody Technique, Indirect; Humans; Imidazoles; Ki-67 Antigen; Liver Neoplasms; Melanoma; NF-kappa B; Quinoxalines; Reverse Transcriptase Polymerase Chain Reaction; RNA, Messenger; Tumor Cells, Cultured; Uveal Neoplasms