ag-490 and Melanoma

Hernandezine is isolated from an herbal medicine that selectively inhibits multidrug resistance and improves the efficacy of drugs for cancer treatment. To date, no studies on hernandezine in melanoma have been conducted. In this study, hernandezine was found to inhibit proliferation and induce apoptosis in melanoma A375 cells and B16 cells. In hernandezine-treated melanoma cells, G0/G1 cycle arrest occurred accompanied by significantly downregulated levels of phosphorylated JAK2 and STAT3. In addition, the cycle arrest could be enhanced by AG490 (JAK2 inhibitor), suggesting that the JAK2/STAT3 pathway is involved in cell cycle regulation in hernandezine-treated melanoma cells. Hernandezine-treated melanoma cells exhibited autophagy-specific structures, autophagy markers (LC3II/LC3-I), and autophagic flow over time. Moreover, 3-MA (autophagy inhibitor) significantly inhibited apoptosis, indicating that hernandezine promotes apoptosis by inducing autophagy. Combined with differential expression of P-AMPK, P-ACC (downstream targets of adenine monophosphate activated protein kinase, AMPK), and P-p70S6K (downstream targets of mammalian target of rapamycin, mTOR) and significant inhibition of apoptosis by AMPK inhibitor complex C (CC) in hernandezine-treated melanoma cells suggested that hernandezine could induce autophagy via the AMPK-mTOR pathway, thereby inducing apoptosis. This study first analyzed the effect of melanoma cells by hernandezine and provided a theory for hernandezine in the treatment of melanoma.

Topics: AMP-Activated Protein Kinases; Apoptosis; Autophagy; Benzylisoquinolines; Cell Line, Tumor; Cell Proliferation; Humans; Melanoma; Signal Transduction; TOR Serine-Threonine Kinases

Anoikis is an anchorage-independent cell death. Resistance to anoikis is one of the key features of metastatic cells. Here, we analyzed the role of STAT3 in anoikis resistance in melanoma cells leading to metastasis. When grown under anchorage-independent conditions, significant proportion of cells resisted anoikis and these resistant cells had higher rate of migration and invasion as compared to the cells grown under anchorage-dependent conditions. The anoikis resistant cells also had significantly higher expression and phosphorylation of STAT3 at Y705 than the cells that were attached to the basement membrane. STAT3 inhibitors, AG 490 and piplartine (PL) induced anoikis in a concentration-dependent manner in anoikis resistant cells. Over-expression of STAT3 or treatment with IL-6 not only increased anoikis resistance, but also protected the cancer cells from PL-induced anoikis. On the other hand, silencing STAT3 decreased the potential of cancer cells to resist anoikis and to migrate. STAT3 knock-down cells and PL treated cells did not form tumors as well as failed to metastasize in SCID-NSG mice as compared to untreated anchorage-independent cells, which formed big tumors and extensively metastasized. In summary, our results for the first time establish STAT3 as a critical player that renders anoikis resistance to melanoma cells and enhance their metastatic potential.

Topics: Animals; Anoikis; Cell Line, Tumor; Gene Knockdown Techniques; Heterografts; Humans; Male; Melanoma; Mice; Mice, SCID; Phosphorylation; Piperidones; Signal Transduction; STAT3 Transcription Factor; Transfection; Tyrphostins

Metastasis, a multistep process, is a major cause of mortality in cancer patients. Thus, it is hoped that inhibition of metastasis at any step, such as proliferation, migration, or invasion, using small-molecule inhibitors will reduce this mortality. Recent study suggests that the Janus kinase/signal transducer and activator of transcription 3 signal transduction pathway is a central pathway that regulates tumor progression and metastasis and can be blocked using tyrosine kinase inhibitors. In this study we used a synthetic tyrosine kinase inhibitor, AG490, to block the constitutive activation of the Janus kinase/signal transducer and activator of transcription 3 pathway in A549 lung carcinoma and A375 melanoma cell lines. Our results show that AG490 at subtoxic doses can effectively suppress tumor cell proliferation by limiting the expression of cyclin D1. Furthermore, AG490 is seen to induce apoptosis, inhibit cellular migration by disrupting actin organization, and suppress matrix metalloproteinase 2 activity. Taken together, these data demonstrate that AG490 can exert antimetastatic activity by inhibiting cellular proliferation, invasion, and migration.

Topics: Actins; Apoptosis; Cell Line, Tumor; Cell Movement; Cell Proliferation; Cyclin D1; Dose-Response Relationship, Drug; Enzyme Inhibitors; Humans; In Vitro Techniques; Janus Kinase 2; Lung Neoplasms; Matrix Metalloproteinase 2; Melanoma; Protein-Tyrosine Kinases; STAT3 Transcription Factor; Tyrphostins