In:
Journal of Clinical Oncology, American Society of Clinical Oncology (ASCO), Vol. 30, No. 15_suppl ( 2012-05-20), p. 8526-8526
Abstract:
8526 Background: Brain metastases are a major contributor to mortality in stage IV melanoma patients. In melanoma, the RAF-MEK-ERK (MAPK) and PI3K-AKT-mTOR (AKT) signaling pathways play a major role in tumor progression and therapy resistance. On the basis of significant improvement in overall survival, the BRAF inhibitor vemurafenib recently gained FDA approval for the treatment of patients with metastatic BRAFV600E mutated melanoma. However, ongoing clinical studies suggest short-lived responses to BRAF inhibitors in melanoma brain metastases. Methods: We observed in several melanoma patients that chemotherapeutics or BRAF inhibitors yielded a significant regression of extracerebral metastases while brain metastases progressed or newly occurred. We therefore aimed at identifying factors that may contribute to treatment resistance of brain metastases. Results: Immunohistochemistry of matched brain and extracerebral melanoma metastases demonstrated an identical pattern of ERK, p-ERK and AKT staining but a different pattern of p-AKT and PTEN staining with hyperactivation of AKT and loss of PTEN expression in brain metastases. Mutation analysis revealed no difference in BRAF, NRAS or KIT mutation status in matched brain and extracerebral metastases. By contrast, in monolayer culture expression of ERK, p-ERK, AKT, p-AKT and PTEN was identical in cell lines derived from brain and extracerebral metastases. Furthermore, melanoma cells stimulated by astrocyte-conditioned medium showed hyperactivation of AKT compared to melanoma cells stimulated by fibroblast-conditioned medium. When inhibiting the MAPK and AKT signaling pathways at different levels in cells freshly isolated from melanoma brain metastases, growth inhibition and apoptosis induction was most pronounced with novel PI3K inhibitors such as BKM120 and BEZ235. Conclusions: These data suggest that 1) hyperactivation of the AKT survival pathway is brain environment-induced and relevant for the survival of melanoma cells in the brain parenchyma and that 2) inhibition of AKT signaling may be a suitable strategy to enhance and/or prolong the antitumor effect of chemotherapeutics or BRAF inhibitors in melanoma brain metastases.
Type of Medium:
Online Resource
ISSN:
0732-183X
,
1527-7755
DOI:
10.1200/jco.2012.30.15_suppl.8526
Language:
English
Publisher:
American Society of Clinical Oncology (ASCO)
Publication Date:
2012
detail.hit.zdb_id:
2005181-5
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