Abstract PR17: Single-cell analysis reveals an adaptive, slowly-dividing, de-differentiated, drug-resistant cell state selectively inhibitable by drug combinations

In this study, we monitor the responses of BRAFV600E melanoma cells to RAF/MEK inhibitors at the single-cell level in real time using time-lapse live-cell imaging, and then analyze the resulting cell states using transcriptional, biochemical and phenotypic profiling. We found that exposure of tumor cells to RAF/MEK inhibitors elicits heterogeneous and time-variable responses in which some cells die, some arrest and a fraction of slowly-cycling cells adapts to drug, adopting a reversible drug-resistance phenotype characterized by up-regulation of markers of neural crest, a melanocyte precursor, including NGFR (the low affinity nerve growth factor receptor, also known as p75NTR or CD271). The slowly-cycling NFGRHigh state induced by RAF/MEK inhibitors is only transiently stable: after 1-2 weeks of outgrowth in drug-free medium, such cells reset to their initial state as measured by the restoration of RAF/MEK inhibitor sensitivity, accelerated rate of cell division and reduced expression of NGFR. Transcriptional and biochemical profiling of cell lines and human tumors implicates a role for the c-Jun/ECM/FAK/Src cascade in driving the de-differentiated (NGFRHigh) resistance program. We identify multiple drugs targeting this cascade as well as BET bromodomain inhibitors that block the slowly-cycling NGFRHigh state in cell lines and in a BRAFV600E melanoma xenograft model and increase sensitivity to RAF/MEK inhibitors. Our study reveals directly how drug adaptation happens in indiv...
Source: Molecular Cancer Therapeutics - Category: Cancer & Oncology Authors: Tags: Resistance against Drug Combinations: Oral Presentations - Proffered Abstracts Source Type: research