Adaptive anoikis resistance promotes ovarian cancer metastasis
Anoikis resistance or evasion of cell death triggered by cell detachment is a hallmark of cancer that is concurrent with cell survival and metastasis. Phenotypes of anoikis resistant cancer cells have been extensively investigated, however, how exposure to suspension stress may lead to acquisition of a anoikis resistance phenotype has not been previously described in detail.  Here we show using a spectrum of ovarian cancer cells, that cycles of suspension stress followed by attached growth, leads to adaptation and acquisition of resistance to cell death in suspension . Comparing the stepwise transcriptomic changes as cells acquire resistance, we find strong transcriptional reprogramming in the population with a majority of differentially expressed genes being downregulated during progressive acquisition of anoikis resistance. Adapted anoikis resistant cells display an enhanced dependency on oxidative phosphorylation and are capable of evasion from T cell-mediated immune surveillance. We find that such acquired anoikis resistance is not genetic. However, transcriptional reprogramming is essential to this process as acquisition of such adaptive anoikis resistance invitro and invivo are both exquisitely sensitive to specific inhibition of transcriptional reprogramming. Our data demonstrate that recovery from the verge of anoikis leads to adaptation that promotes metastasis in ovarian cancer, but can be therapeutically prevented by specific inhibitors to transcriptional reprogramming. Overall design: To assess the effects of exposure to cycles of  matrix detachment stress, cells were grown in attached conditions and subject to a 24 hr period of suspension cultures followd by expansion in attached cultures. Tis cycle was repeated for 7-8 rounds. P0 refers to the parental cell line and P1 refers to cells from suspension cultures. RNA seq was performed from RNA collected from the cells ( three independent biological trplcaites) over time alternating between suspension stress and expansion in attached cultures.  For WES, DNA was collected at baseline, at mid point and after cells had adapted to the suspension stress and was conducted on DNA collected from two biologiccal trials