Plitidepsin Has a Dual Effect Inhibiting Cell Cycle and Inducing Apoptosis via Rac1/c-Jun NH₂-Terminal Kinase Activation in Human Melanoma Cells

Abstract

Melanoma is the most aggressive skin cancer and a serious health problem worldwide because of its increasing incidence and the lack of satisfactory chemotherapy for late stages of the disease. The marine depsipeptide Aplidin (plitidepsin) is an antitumoral agent under phase II clinical development against several neoplasias, including melanoma. We report that plitidepsin has a dual effect on the human SK-MEL-28 and UACC-257 melanoma cell lines; at low concentrations (Յ45 nM), it inhibits the cell cycle by inducing G 1 and G 2 /M arrest, whereas at higher concentrations it induces apoptosis as assessed by poly-(ADP-ribose) polymerase cleavage and the appearance of a hypodiploid peak in flow cytometry analyses. Plitidepsin activates Rac1 GTPase and c-Jun NH 2 -terminal kinase (JNK). In addition, it induces AKT and p38 mitogen-activated protein kinase (MAPK) phosphorylation. By using inhibitors, we found that JNK and p38 MAPK activation depends on Rac1 but not on phosphatidylinositol 3-kinase (PI3K), whereas AKT activation is independent of Rac1 but requires PI3K activity. Plitidepsin cytotoxicity diminishes by Rac1 inhibition or by the blockage of JNK and p38 MAPK using 4-(4-fluorophenyl)-2-(4-methylsulfinylphenyl)-5-(4-pyridyl)1H-imidazole (SB203580), but not by PI3K inhibition using wortmannin or 2-(4-morpholinyl)-8-phenyl-4H-1-benzopyran-4-one (LY294002). It is remarkable that plitidepsin and dacarbazine, the alkylating agent most active for treating metastatic melanoma, show a synergistic antiproliferative effect that was paralleled at the level of JNK activation. These results indicate that Rac1/JNK activation is critical for cell cycle arrest and apoptosis induction by plitidepsin in melanoma cells. They also support the combined use of plitidepsin and dacarbazine in in vivo studies.Metastatic melanoma is an aggressive skin cancer whose incidence has rapidly increased over the past five decades. Although patients with early stage melanoma can be treated efficiently by surgical dissection, patients with metastatic melanoma have a very poor prognosis, with a median survival of less than 1 year (Jemal et al., 2005). Effective therapies for advanced stages of this disease have not been defined, because malignant melanoma has proven to be highly resistant to standard antineoplastic treatment. Dacarbazine (DTIC) is an alkylating agent considered the most active agent for treating metastatic melanoma, and it is the only drug approved by both the United States Food and Drug Administration and the European Agency for the Evaluation of Medicinal Products for use in this disease. However, dacarbazine has only a response rate Ͻ20%, with complete response observed in Ͻ5% of cases (Lev et al., 2003). It is clear that additional therapeutic agents are needed for advanced resistant melanoma.Aplidin (plitidepsin) is a marine antitumor agent isolated from the Mediterranean tunicate Aplidium albicans that displays a potent activity against human hematological and solid tumors cell lines. The compound has comThis work w...

Marine Sponge Cribrochalina vasculum Compounds Activate Intrinsic Apoptotic Signaling and Inhibit Growth Factor Signaling Cascades in Non–Small Cell Lung Carcinoma

“…It has been shown that Akt regulates cell cycle by controlling of cyclins and CDK inhibitors (49)(50)(51)(52). In addition, JNK is involved in cell-cycle progression and mediates G 2 -M phase cell-cycle arrest in different tumor cells (53)(54)(55)(56)(57)(58). As both, decreased phosphorylation of Akt and increased phosphorylation of JNK are evident after treatment with 1, these signaling cascades may be responsible for the observed G 2 -M arrest upon treatment.…”

Apoptotic effects of a high performance liquid chromatography (HPLC) fraction of Antrodia camphorata mycelia are mediated by down-regulation of the expressions of four tumor-related genes in human non-small cell lung carcinoma A549 cell

“…Many investigations have suggested that the expression level of RhoGDI-␣ closely modulates the JNK activity, which is strongly related to the apoptotic cell death (Muñoz-Alonso et al, 2008;Park et al, 2009). In this study we found that Fr-6 could knockdown the RhoGDI-␣ gene expression in human A549 cells and JNK inhibitor SP600125 could abrogate Fr-6-mediated JNK activation and cell death.…”

c-Jun N-Terminal Kinase Phosphorylation Is a Biomarker of Plitidepsin Activity

“…Previous studies have shown that plitidepsin induces JNK phosphorylation in a variety of cultured solid and hematological cancer cell lines [3,4,5,9,11,15]. Given the advanced clinical development of plitidepsin in multiple myeloma and leukemia, we have evaluated the effect of plitidepsin on the viability and the level of JNK phosphorylation in a panel of these different cancer cell types.…”

“…In cultured cells from solid tumors, plitidepsin induces dose-dependent cell cycle arrest or an acute apoptotic process due primarily to the sustained activation of c-Jun N -terminal kinase (JNK) as revealed by an increased level of phosphorylation [2,3]. Plitidepsin also activates other kinases such as the epidermal growth factor receptor, protein kinase C-δ and the extracellularly regulated and p38 mitogen-activated protein kinases (ERK, p38MAPK) in a cell-dependent context [4,5].…”