xav939 and Melanoma

Many tumors dysregulate Wnt/β-catenin pathway to promote stem-cell-like phenotype, tumorigenesis, immunosuppression, and resistance to targeted cancer immunotherapies. Therefore, targeting this pathway is a promising therapeutic approach to suppress tumor progression and elicit robust anti-tumor immunity. In this study, using a nanoparticle formulation for XAV939 (XAV-Np), a tankyrase inhibitor that promotes β-catenin degradation, we investigated the effect of β-catenin inhibition on melanoma cell viability, migration, and tumor progression using a mouse model of conjunctival melanoma. XAV-Nps were uniform and displayed near-spherical morphology with size stability for upto 5 days. We show that XAV-Np treatment of mouse melanoma cells significantly suppresses cell viability, tumor cell migration, and tumor spheroid formation compared to control nanoparticle (Con-Np) or free XAV939-treated groups. Further, we demonstrate that XAV-Np promotes immunogenic cell death (ICD) of tumor cells with a significant extracellular release or expression of ICD molecules, including high mobility group box 1 protein (HMGB1), calreticulin (CRT), and adenosine triphosphate (ATP). Finally, we show that local intra-tumoral delivery of XAV-Nps during conjunctival melanoma progression significantly suppresses tumor size and conjunctival melanoma progression compared to Con-Nps-treated animals. Collectively, our data suggest that selective inhibition of β-catenin in tumor cells using nanoparticle-based targeted delivery represents a novel approach to suppress tumor progression through increased tumor cell ICD.

Topics: Animals; beta Catenin; Cell Line, Tumor; Immunogenic Cell Death; Melanoma; Wnt Signaling Pathway

Numerous tyrosine kinase inhibitors (TKIs) targeting c-Met are currently in clinical trials for several cancers. Their efficacy is limited due to the development of resistance. The present study aims to elucidate this mechanism of c-Met TKI resistance by investigating key mTOR and Wnt signaling proteins in melanoma cell lines resistant to SU11274, a c-Met TKI. Xenografts from RU melanoma cells treated with c-Met TKIs SU11274 and JNJ38877605 showed a 7- and 6-fold reduction in tumor size, respectively. Resistant cells displayed upregulation of phosphorylated c-Met, mTOR, p70S6Kinase, 4E-BP1, ERK, LRP6, and active β-catenin. In addition, GATA-6, a Wnt signaling regulator, was upregulated, and Axin, a negative regulator of the Wnt pathway, was downregulated in resistant cells. Modulation of these mTOR and Wnt pathway proteins was also prevented by combination treatment with SU11274, everolimus, an mTOR inhibitor, and XAV939, a Wnt inhibitor. Treatment with everolimus, resulted in 56% growth inhibition, and a triple combination of SU11274, everolimus and XAV939, resulted in 95% growth inhibition in RU cells. The V600E BRAF mutation was found to be positive only in MU cells. Combination treatment with a c-Met TKI and a BRAF inhibitor displayed a synergistic effect in reducing MU cell viability. These studies indicate activation of mTOR and Wnt signaling pathways in c-Met TKI resistant melanoma cells and suggest that concurrent targeting of c-Met, mTOR, and Wnt pathways and BRAF may improve efficacy over traditional TKI monotherapy in melanoma patients.

Topics: Animals; Antineoplastic Combined Chemotherapy Protocols; Cell Line, Tumor; Drug Resistance, Neoplasm; Everolimus; Heterocyclic Compounds, 3-Ring; Heterografts; Human Growth Hormone; Humans; Indoles; Male; Melanoma; Mice, Inbred BALB C; Mice, Nude; Mutation; Phosphorylation; Piperazines; Protein Structure, Tertiary; Proto-Oncogene Proteins c-met; Pyrazoles; Pyridazines; Signal Transduction; Sirolimus; Skin Neoplasms; Sulfonamides; TOR Serine-Threonine Kinases; Wnt Proteins

T-oligo, an 11-base oligonucleotide homologous to the 3'-telomeric overhang, is a novel, potent therapeutic modality in melanoma and multiple other tumor types. T-oligo is proposed to function in a manner similar to experimental disruption of the telomere overhang and induces DNA damage responses including apoptosis, differentiation and senescence. However, important components involved in T-oligo induced responses are not defined, particularly the role of p53, TRF1 and TRF2 in mediating the T-oligo induced responses. In MU, PM-WK, and MM-MC melanoma cells, exposure to T-oligo upregulates p53 expression and phosphorylation, resulting in cellular differentiation and activation of a caspase-mediated apoptotic cascade. However, siRNA-mediated knockdown of p53 completely blocks T-oligo induced differentiation and significantly decreases apoptosis, suggesting that p53 is an important mediator of T-oligo induced responses. In addition, we characterized the roles of telomere binding proteins, TRF1, TRF2, and tankyrase-1, in T-oligo induced damage responses. We demonstrate that tankyrase-1 activity is required for initiation of T-oligo induced damage responses including p53 phosphorylation and reduction of cellular proliferation. These results highlight TRF1, TRF2, tankyrase-1 and p53 as important elements in T-oligo mediated responses and suggest new avenues for research into T-oligo's mechanism of action.

Topics: Apoptosis; Cell Differentiation; Cell Line, Tumor; Cell Proliferation; Cellular Senescence; DNA Damage; DNA Repair; Gene Expression; Heterocyclic Compounds, 3-Ring; Humans; Melanoma; Oligonucleotides; Phosphorylation; RNA Interference; RNA, Small Interfering; Skin Neoplasms; Tankyrases; Telomere; Telomeric Repeat Binding Protein 1; Telomeric Repeat Binding Protein 2; Tumor Suppressor Protein p53; Up-Regulation