Translating whole exome sequencing (WES) for prospective clinical use may impact the care of cancer patients; however, multiple innovations are necessary for clinical implementation. These include: (1) rapid and robust WES from formalin-fixed paraffin embedded (FFPE) tumor tissue, (2) analytical output similar to data from frozen samples, and (3) clinical interpretation of WES data for prospective use. In this study, we describe a prospective clinical WES platform for archival FFPE tumor samples. The platform employs computational methods for effective clinical analysis and interpretation of WES data. When applied retrospectively to 511 exomes, the interpretative framework revealed a "long tail" of somatic alterations in clinically important genes. Prospective application of this approach identified clinically relevant alterations in 15/16 patients. Overall, this methodology may inform the widespread implementation of precision cancer medicine.
While the combination of endocrine therapy and CDK4/CDK6 inhibitors has been shown to be effective in the metastatic ER+ breast cancer setting, to test whether it is effective in an earlier stage neoadjuvant setting, the FELINE trial (NCT02712723) was established to test the efficacy of letrozole and ribociclib in a ER-positive, HER2-negative patients in a randomized, placebo-controlled, multicenter trial. Patients were randomized to one of three arms: those in Arm A received letrozole and placebo, Arm B letrozole and intermittent ribociclib, and Arm C letrozole and continuous ribociclib. Samples were collected at screening (Day 0), Cycle 1 (Day 14), and end of trial (Day 180). Samples from 24 patients, where cancer cells were present at Day 0 and one additional time point, were subjected to whole-exome sequencing profiling.
Mitochondrial genomes are separated from the nuclear genome for most of the cell cycle by the nuclear double membrane, intervening cytoplasm and the mitochondrial double membrane. Despite these physical barriers we show that somatically acquired mitochondrial-nuclear genome fusion sequences are present in cancer cells. Most occur in conjunction with intranuclear genomic rearrangements and the features of the fusion fragments indicate that non-homologous end joining and/or replication-dependent DNA double strand break repair are the dominant mechanism involved. This study includes 12 pairs of whole-genome sequences (tumour and paired-normal), which present somatic mitochondrial DNA integrations in tumour genomes. Reference: Young Seok Ju et al., Frequent somatic transfer of mitochondrial DNA into the nuclear genome of human cancer cells, Genome Research (2015).
