qHTS for Inhibitors of Mutant Isocitrate Dehydrogenase 1 (IDH1): U87 Cytotoxicity Assay for Probe SAR
Malignant glioblastomas (WHO grade IV), including primary and secondary glioblastomas, are among the most lethal with a median survival of one year, and unfortunately they are also the most prevalent type of brain tumors . By and large the standard of care of gliomas remains the use of the oral alkylating agent temozolomide and radiotherapy following surgical tumor resection . There is an urgent unmet medical need for novel therapeutics for gliomas. ..more
BioActive Compounds: 2
Malignant glioblastomas (WHO grade IV), including primary and secondary glioblastomas, are among the most lethal with a median survival of one year, and unfortunately they are also the most prevalent type of brain tumors . By and large the standard of care of gliomas remains the use of the oral alkylating agent temozolomide and radiotherapy following surgical tumor resection . There is an urgent unmet medical need for novel therapeutics for gliomas.
IDH mutations occur in up to 70% of grade II-IV secondary glioblastomas, and IDH1 R132H is the most prevalent mutation . Interestingly, IDH mutations are also present in ~10% of AML (acute myeloid leukemia) patients . Wild-type (WT) IDH1 catalyzes the conversion of isocitrate to -ketoglutarate with the concomitant reduction of NADP+ to NADPH. In contrast, IDH1 R132H catalyzes the conversion of alpha-ketoglutarate to 2-hydroxyglutarate (2-HG) with the concomitant oxidation of NADPH to NADP+ . Recently, a second significant advancement for the field was the finding that IDH is an oncogene, and that its metabolic product 2-HG may contribute to the pathogenesis of IDH-mutated cancers. Indeed, unbiased metabolite profiling of a U87MG stable cell line engineered to express IDH1 R132H mutant protein demonstrated that mutated IDH1 confers a gain-of-function to produce the onco-metabolite 2-HG, and in effect classifying IDH1 as an oncogene . These studies demonstrated the power of utilizing 2-HG as a biomarker for IDH-mutated cancers, as well as adding to the wealth of data linking the metabolite 2-HG to cancer. Although this link to cancer is tantalizing, the direct evidence of how 2-HG drives pathogenesis of gliomas and AML remains a subject of further research.
The goal of this cell assay is to identify whether the small-molecule inhibitors of IDH1 R132H are cytotoxic in U87MG-IDH1 R132H cells. Compounds were screened as concentration-titration series that ranged from 50 microM to 14 nM.
NIH Molecular Libraries Probe Production Network [MLPCN]
NIH Chemical Genomics Center [NCGC]
MLSCN Grant: R03 DA032129
PI Name: Dr. Lenny Dang
Cells were dispensed into 96-well black solid bottom plates at 2500 cells/well (RPMI medium with 10% FBS). The plates were incubated overnight at 37 oC and 5% CO2. The media was aspirated off and fresh media (RPMI and 10% FBS) with compounds in 7-point dose response was added. The plates were incubated for 48 hours at 37 oC and 5% CO2. From each well 100 microL was removed and used for LC-MS analysis to quantitate the amount of 2-HG product. The remaining cells/media were incubated for 24 additional hours at which point 100 uL of Cell Titer Glo (Promega) was added. The plates were shaken for 10 minutes and then incubated at room temperature for 20 minutes. The luminescence was read on the ViewLux in end-point mode (0.5 sec).
Concentration-response curves were fitted to the signals arising from the resulting selective ion monitoring. The concentration-response curves were then classified based on curve quality (r2), response magnitude and degree of measured activity, and compounds were subsequently categorized based on their curve class. Inactive compounds showed no effect on cytotoxicity as read out by luminescence relative to the DMSO control.
Keywords: Isocitrate dehydrogenase, IDH1, IDH1 R132H, 2-HG, 2-hydroxyglutarate, AML, glioma, MLSMR, MLPCN, NIH Roadmap, qHTS, NCGC
1. Compounds are first classified as having full titration curves, partial modulation, partial curve (weaker actives), single point activity (at highest concentration only), or inactive. See data field "Curve Description". For this assay, toxic compounds are ranked higher than compounds that showed apparent activation.
2. For all inactive compounds, PUBCHEM_ACTIVITY_SCORE is 0. For all active compounds, a score range was given for each curve class type given above. Active compounds have PUBCHEM_ACTIVITY_SCORE between 40 and 100. Inconclusive compounds have PUBCHEM_ACTIVITY_SCORE between 1 and 39. Fit_LogAC50 was used for determining relative score and was scaled to each curve class' score range.
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4. Mardis ER, Ding L, Dooling DJ, Larson DE, McLellan MD, Chen K, Koboldt DC, Fulton RS, Delehaunty KD, McGrath SD et al: Recurring mutations found by sequencing an acute myeloid leukemia genome. N Engl J Med 2009, 361(11):1058-1066.
5. Dang L, White DW, Gross S, Bennett BD, Bittinger MA, Driggers EM, Fantin VR, Jang HG, Jin S, Keenan MC et al: Cancer-associated IDH1 mutations produce 2-hydroxyglutarate. Nature 2009, 462(7274):739-744.
Categorized Comment - additional comments and annotations
* Activity Concentration. ** Test Concentration.
Data Table (Concise)