Drug Responses in Plexiform Neurofibroma Type I (PNF1) Cell Lines Using High-Throughput Data and Combined Effectiveness and Potency

Simple Summary Neurofibromatosis 1 (NF1) is a genetic disorder that predisposes patients to developing nerve sheath tumors that are difficult to treat. There is currently just one drug approved for the treatment of NF1-related inoperable plexiform neurofibromas (for a limited patient population), highlighting the need for further drug discovery in this field. High-throughput screening data are used to guide drug development, but identifying and selecting promising targets can be complex. The aim of our study is to improve the value of high-throughput screening data by combining potency and effectiveness into single-value indices (S, Delta S, and Delta S mean), which are used to assess and rank drug sensitivity and drug resistance in cells exposed to potential therapeutic drugs. Our approach with S indices was applied to cell lines derived from plexiform neurofibromas of patients with NF1 gene mutations. The use of S indices provides valuable additional and independent information for discriminating among candidate compounds for follow-up pre-clinical evaluations.Abstract Background: Neurofibromatosis type 1 (NF1) is a genetic disorder characterized by heterozygous germline NF1 gene mutations that predispose patients to developing plexiform neurofibromas, which are benign but often disfiguring tumors of the peripheral nerve sheath induced by loss of heterozygosity at the NF1 locus. These can progress to malignant peripheral nerve sheath tumors (MPNSTs). There are no approved drug treatments for adults with NF1-related inoperable plexiform neurofibromas, and only one drug (selumetinib), which is an FDA-approved targeted therapy for the treatment of symptomatic pediatric plexiform neurofibromas, highlighting the need for additional drug screening and development. In high-throughput screening, the effectiveness of drugs against cell lines is often assessed by measuring in vitro potency (AC50) or the area under the curve (AUC). However, the variability of dose-response curves across drugs and cell lines and the frequency of partial effectiveness suggest that these measures alone fail to provide a full picture of overall efficacy. Methods: Using concentration-response data, we combined response effectiveness (EFF) and potency (AC50) into (a) a score characterizing the effect of a compound on a single cell line, S = log[EFF/AC50], and (b) a relative score, Delta S, characterizing the relative difference between a reference (e.g., non-tumor) and test (tumor) cell line. Delta S was applied to data from high-throughput screening (HTS) of a drug panel tested on NF1-/- tumor cells, using immortalized non-tumor NF1+/- cells as a reference. Results: We identified drugs with sensitivity, targeting expected pathways, such as MAPK-ERK and PI3K-AKT, as well as serotonin-related targets, among others. The Delta S technique used here, in tandem with a supplemental Delta S web tool, simplifies HTS analysis and may provide a springboard for further investigations into drug response in NF1-related cancers. The tool may also prove useful for drug development in a variety of other cancers.