A novel fate-mapping approach allows intratumoral profiling of hypoxic cells II

We designed a novel approach to fate-map hypoxic cells in order to determine their cellular response to physiological O2 gradients. Our system causes a change in the expressing fluorescent protein upon hypoxic exposure (DsRed -> GFP). We generated hypoxia fate-mapping tumors using MDA-MB-231 cells expressing our system. Metastatic lungs were resected 2 weeks after primary tumor removal, mechanically disrupted and digested with collagenase to obtain a cell suspension. The cell suspension was enriched using magnetic-activated cell sorting (MACS) and DsRed+ cells were isolated from GFP+ cells by fluorescence-activated cell sorting (FACS) directly into Tris Reagent (Zymo Research). Total RNA was extracted from cells using TRIzol (Invitrogen) and purified using Direct-zol RNA mini kit (Zymo Research) with DNase I treatment. After RNA purification, samples were confirmed to have a RIN value > 9.0 when measured on an Agilent Bioanalyzer. Libraries for RNA-Seq were prepared with KAPA Stranded RNA-Seq Kit. The workflow consisted of mRNA enrichment, cDNA generation, end repair to generate blunt ends, A-tailing, adaptor ligation and 12 cycles of PCR amplification. Unique adaptors were used for each sample in order to multiplex samples into several lanes. Sequencing was performed on Illumina Hiseq 3000/4000 with a 150bp pair-end run. A data quality check was done on Illumina SAV. Demultiplexing was performed with Illumina Bcl2fastq2 v 2.17 program.