Author Correction: Loss of Phd2 cooperates with BRAFV600E to drive melanomagenesis.

The original version of this Article contained an error in the spelling of the author Brett L. Ecker, which was incorrectly given as Brett Ecker. This has now been corrected in both the PDF and HTML versions of the Article.

Loss of Phd2 cooperates with BRAFV600E to drive melanomagenesis.

Prolyl hydroxylase domain protein 2 (PHD2) is a well-known master oxygen sensor. However, the role of PHD2 in tumor initiation remains controversial. We find that during the transition of human nevi to melanoma, the expression of PHD2 protein is significantly decreased and lower expression PHD2 in melanoma is associated with worse clinical outcome. Knockdown of PHD2 leads to elevated Akt phosphorylation in human melanocytes. Mice with conditional melanocyte-specific expression of Phd2lox/lox (Tyr::CreER;Phd2lox/lox) fail to develop pigmented lesions. However, deletion of Phd2 in combination with expression of BRafV600E in melanocytes (Tyr::CreER;Phd2lox/lox;BRafCA) leads to the development of melanoma with 100% penetrance and frequent lymph node metastasis. Analysis of tumor tissues using reverse phase protein arrays demonstrates that Phd2 deletion activates the AKT-mTOR-S6 signaling axis in the recovered tumors. These data indicate that PHD2 is capable of suppressing tumor initiation largely mediated through inhibiting of the Akt-mTOR signaling pathway in the melanocyte lineage.

Anticancer activity of ß-Elemene and its synthetic analogs in human malignant brain tumor cells.

Malignant brain tumors are aggressive in both children and adults. Despite recent improvements in diagnostic techniques, therapeutic approaches remain disappointing and unsuccessful. There is an urgent need for promising anticancer agents to improve overall survival of patients with brain cancer. ß-Elemene has been shown to have antiproliferative effects on many types of carcinomas. In this study, we compared the cytotoxic efficacy of ß-elemene and its synthetic analogs in the brain tumor cell lines A172, CCF-STTG1, and U-87MG. ß-Elemene exhibited cytotoxicity towards the tumor lines, effectively suppressing tumor cell survival. The inhibitory effect of ß-elemene was mediated by the induction of apoptosis, as demonstrated by three assays. The annexin V assay showed that ß-elemene increased the percentage of early- and late-apoptotic cells. Apoptotic nuclei were detected in cancer cells in situ by the terminal deoxynucleotidyltransferase-mediated deoxy-UTP-fluorescein nick end labeling (TUNEL) staining, and the number of TUNEL-positive cells was significantly increased at 24-72 h following drug treatment of the cell lines. Cell death enzyme-linked immunosorbent assay (ELISA) gave similar results. Furthermore, ß-elemene increased caspase-3/7/10 activity, up-regulated protein expression of BAX, and down-regulated the one of BCL-2, BCL-XL, and of X-linked inhibitor of apoptosis (XIAP) in the cells, suggesting that apoptotic signaling pathways are involved in the responses triggered by ß-elemene. Compared with ß-elemene, only three of the 10 synthetic ß-elemene analogs studied here, exerted comparable cytotoxic efficacy towards the three brain tumor lines: the analogs Lr-1 and Lr-2 had the same antitumor efficacy, while Lr-3 was less potent than ß-elemene. Thus, some synthetic analogs of ß-elemene may inhibit brain cancer cell growth and proliferation, and the synthetic analogs Lr-1 and Lr-2 may have great potential as alternatives to ß-elemene for anticancer therapy. Overall, this study provides, to our knowledge, the first evidence showing that synthetic analogs of ß-elemene hold promise for patients with brain tumors.

Enhancement of cisplatin-induced apoptosis by ß-elemene in resistant human ovarian cancer cells.

ß-Elemene is a new anticancer compound extracted from the Chinese medicinal herb Rhizoma zedoariae. We have shown previously that ß-elemene increases cisplatin cytotoxicity and enhances cisplatin sensitivity via blocking cell cycle progression at G2/M phase in resistant ovarian tumor cells. In the current study, we asked whether ß-elemene-augmented cisplatin activity in ovarian carcinoma cells is mediated through the induction of apoptosis. Here, we show that ß-elemene triggered apoptotic cell death in chemoresistant human ovarian cancer A2780/CP and MCAS cells in a dose- and time-dependent fashion, as assessed by six different apoptosis assays. Intriguingly, ß-elemene was a stronger inducer of apoptosis than cisplatin in this model system, and a synergistic effect on induction of cell death was observed when the tumor cells were treated with both agents. Furthermore, ß-elemene plus cisplatin exposure significantly disrupted the mitochondrial transmembrane potential (ΔΨ (m)) and increased the release of cytochrome c from mitochondria into the cytoplasm. The combination treatment with both compounds also induced increases in caspase-3/8/9 activities and caspase-9 cleavage, enhanced protein expression of Bax and phosphorylation of Bcl-2 at Ser-70, and reduced the protein levels of Bcl-2 and Bcl-X(L) in the platinum-resistant ovarian cancer cells. Taken together, these data indicate that ß-elemene sensitizes chemoresistant ovarian carcinoma cells to cisplatin-induced apoptosis and that the augmented effect of ß-elemene on cisplatin cytotoxicity and sensitivity in resistant ovarian tumor cells is mediated through a mitochondria- and caspase-dependent cell death pathway.

ß-Elemene enhances susceptibility to cisplatin in resistant ovarian carcinoma cells via downregulation of ERCC-1 and XIAP and inactivation of JNK.

ß-Elemene is a promising new plant-derived drug with broad-spectrum anticancer activity. It also increases cisplatin cytotoxicity and enhances cisplatin sensitivity in resistant human carcinoma cells. However, little is known about the mechanism of its action. To explore the potential therapeutic application of ß-elemene as a drug-resistance modulator, this study investigated the underlying mechanism of ß-elemene activity in cisplatin-resistant ovarian cancer cells. ß-Elemene enhanced cisplatin sensitivity to a much greater extent in chemoresistant A2780/CP70 and MCAS human ovarian carcinoma cells compared to the chemosensitive parental cell line A2780. The dose-modifying factors for cisplatin were between 35 and 60 for A2780/CP70 cells and between 1.6 and 2.5 for A2780 cells. In the cisplatin-resistant ovarian carcinoma cells, ß-elemene abrogated cisplatin­induced expression of excision repair cross-complementation group­1 (ERCC-1), a marker gene in the nucleotide excision repair pathway that repairs cisplatin-caused DNA damage. In addition, ß-elemene not only reduced the level of X-linked inhibitor of apoptosis protein (XIAP), but also downregulated cisplatin-mediated XIAP expression in chemoresistant cells. Furthermore, ß-elemene blocked the cisplatin-stimulated increase in the level of phosphorylated c-Jun NH2-terminal kinase (JNK) in these cells. These novel findings suggest that the ß-elemene enhancement of cisplatin sensitivity in human chemoresistant ovarian cancer cells is mediated at least in part through the impairment of DNA repair activity and the activation of apoptotic signaling pathways, thereby making resistant ovarian cancer cells susceptible to cisplatin-induced cell death.

ß-elemene effectively suppresses the growth and survival of both platinum-sensitive and -resistant ovarian tumor cells.

The development of cisplatin drug resistance remains a chief concern in ovarian cancer chemotherapy. ß-Elemene is a natural plant product with broad-spectrum antitumor activity towards many types of carcinomas. This study aimed to define the biological and therapeutic significance of ß-elemene in chemoresistant ovarian cancer. In the present study, ß-elemene significantly inhibited cell growth and proliferation of both the cisplatin-sensitive human ovarian cancer cell line A2780 and its cisplatin-resistant counterpart A2780/CP. ß-Elemene also suppressed the growth of several other chemosensitive and chemoresistant ovarian cancer cell lines, including ES-2, MCAS, OVCAR-3, and SKOV-3, with the half maximal inhibitory concentration (IC(50)) values ranging from 54 to 78 µg/ml. In contrast, the IC(50) values of ß-elemene for the human ovarian epithelial cell lines IOSE-386 and IOSE-397 were 110 and 114 µg/ml, respectively, which are almost two-fold those for the ovarian cancer cell lines. Cell cycle analysis demonstrated that ß-elemene induced a persistent block of cell cycle progression at the G(2)/M phase in A2780 and A2780/CP cells. This was mediated by alterations in cyclin and cyclin-dependent kinase expression, including the down-regulation of CDC2, cyclin A, and cyclin B1, and the up-regulation of p21(WAF1/CIP1) and p53 proteins. Moreover, ß-elemene triggered apoptosis and irreversible cell death in both sensitive and resistant ovarian cancer cells via the activation of caspase-3, -8 and 9; the loss of mitochondrial membrane potential (δΨm); the release of cytochrome c into the cytosol; and changes in the expression of BCL-2 family proteins. All of these molecular changes were associated with ß-elemene-induced growth inhibition and cell death of ovarian cancer cells. Our results demonstrate that ß-elemene has antitumor activity against both platinum-sensitive and resistant ovarian cancer cells, and thus has the potential for development as a chemotherapeutic agent for cisplatin-resistant ovarian cancer.