Sensitivity to the MEK inhibitor E6201 in melanoma cells is associated with mutant BRAF and wildtype PTEN statusReportar como inadecuado

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Molecular Cancer

, 11:75

First Online: 05 October 2012Received: 05 March 2012Accepted: 02 October 2012


BackgroundMelanoma is the most lethal form of skin cancer, but recent advances in molecularly targeted agents against the Ras-Raf-MAPK pathway demonstrate promise as effective therapies. Despite these advances, resistance remains an issue, as illustrated recently by the clinical experience with vemurafenib. Such acquired resistance appears to be the result of parallel pathway activation, such as PI3K, to overcome single-agent inhibition. In this report, we describe the cytotoxicity and anti-tumour activity of the novel MEK inhibitor, E6201, in a broad panel of melanoma cell lines n = 31 of known mutational profile in vitro and in vivo. We further test the effectiveness of combining E6201 with an inhibitor of PI3K LY294002 in overcoming resistance in these cell lines.

ResultsThe majority of melanoma cell lines were either sensitive IC50 < 500 nM, 24-31 or hypersensitive IC50 < 100 nM, 18-31 to E6201. This sensitivity correlated with wildtype PTEN and mutant BRAF status, whereas mutant RAS and PI3K pathway activation were associated with resistance. Although MEK inhibitors predominantly exert a cytostatic effect, E6201 elicited a potent cytocidal effect on most of the sensitive lines studied, as evidenced by Annexin positivity and cell death ELISA. Conversely, E6201 did not induce cell death in the two resistant melanoma cell lines tested. E6201 inhibited xenograft tumour growth in all four melanoma cell lines studied to varying degrees, but a more pronounced anti-tumour effect was observed for cell lines that previously demonstrated a cytocidal response in vitro. In vitro combination studies of E6201 and LY294002 showed synergism in all six melanoma cell lines tested, as defined by a mean combination index < 1.

ConclusionsOur data demonstrate that E6201 elicits a predominantly cytocidal effect in vitro and in vivo in melanoma cells of diverse mutational background. Resistance to E6201 was associated with disruption of PTEN and activation of downstream PI3K signalling. In keeping with these data we demonstrate that co-inhibition of MAPK and PI3K is effective in overcoming resistance inherent in melanoma.

KeywordsMelanoma BRAF PTEN MEK inhibition E6201 PI3K MAPK AbbreviationsAktProtein kinase B

CICombination index

DMSODimethyl sulfoxide

ELISAEnzyme-linked immunosorbent assay

ERKExtracellular signal-regulated kinase

IGF-1RInsulin-like growth factor 1 receptor

MAPKMitogen-activated protein kinase

MEKMitogen-activated protein kinase-extracellular signal-regulated kinase kinase

mTORMammalian target of rapamycin

PI3KPhosphoinositide 3-kinase

PTENPhosphatase and tensin homolog

RasRat sarcoma

SRBSulforhodamine B.

Electronic supplementary materialThe online version of this article doi:10.1186-1476-4598-11-75 contains supplementary material, which is available to authorized users.

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Autor: Sara A Byron - David C Loch - Candice L Wellens - Andreas Wortmann - Jiayi Wu - John Wang - Kenichi Nomoto - Pamela M 


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