| Abstract: |
Activating mutations of BRAF occur in ∼7% of all human tumors and in the majority of melanomas. These tumors are very sensitive to pharmacologic inhibition of mitogen-activated protein kinase/extracellular signal-regulated kinase kinase (MEK), which causes loss of D-cyclin expression, hypophosphorylation of Rb, and G1 arrest. Growth arrest is followed by differentiation or senescence and, in a subset of BRAF mutant tumors, by apoptosis. The former effects result in so-called "stable disease" and, in patients with cancer, can be difficult to distinguish from indolent tumor growth. The profound G1 arrest induced by MEK inhibition in BRAF mutant tumors is associated with a marked decline in thymidine uptake and is therefore potentially detectable in vivo by noninvasive 3′-deoxy- 3′-[18F]fluorothymidine ([18F]FLT) positron emission tomography (PET) imaging. In SKMEL-28 tumor xenografts, MEK inhibition completely inhibited tumor growth and induced differentiation with only modest tumor regression. MEK inhibition also resulted in a rapid decline in the [ 18F]FLT signal in V600E BRAF mutant SKMEL-28 xenografts but not in BRAF wild-type BT-474 xenografts. The data suggest that [18F]FLT PET can effectively image induction of G1 arrest by MEK inhibitors in mutant BRAF tumors and may be a useful noninvasive method for assessing the early biological response to this class of drugs. ©2007 American Association for Cancer Research. |
| Keywords: |
controlled study; unclassified drug; genetics; nonhuman; positron emission tomography; radiopharmaceuticals; mouse; animal; metabolism; animals; mice; animal tissue; melanoma; enzyme inhibition; mitogen activated protein kinase kinase 1; animal experiment; animal model; cell differentiation; tumor regression; tumor xenograft; drug effect; drug resistance; drug screening; drug resistance, neoplasm; tumor cells, cultured; xenograft model antitumor assays; physiology; cancer inhibition; blotting, western; drug antagonism; diagnostic agent; cell culture; nude mouse; mice, nude; western blotting; positron-emission tomography; radiopharmaceutical agent; drug derivative; scintiscanning; cell cycle arrest; b raf kinase; mitogen activated protein kinase kinase; cell cycle g1 phase; map kinase kinase 1; g1 phase; proto-oncogene proteins b-raf; braf protein, mouse; n (2,3 dihydroxypropoxy) 3,4 difluoro 2 (2 fluoro 4 iodoanilino)benzamide; benzamide derivative; benzamides; dideoxynucleosides; diphenylamine; 3' deoxy 3' fluorothymidine f 18; 2',3' dideoxynucleoside derivative; map2k1 protein, mouse
|
