Molecular profiling of epigenetic landscape of cancer cells during extracellular matrix detachment.

During cancer, a major challenge faced by oncologists is the treatment of metastasis; a leading cause of cancer-related deaths around the world. Metastasis involves a highly ordered sequence of events starting with the detachment of tumor cells from the extracellular matrix (E.C.M.). In normal cells, detachment from E.C.M. triggers programmed cell death, termed anoikis. However, tumor cells dodge their way to anoikis and spread to distant sites for initiating the metastatic program. In this work, we explored the impact of E.C.M. detachment on the expression of some major oncogenic histone methyltransferases. Results showed both EZH2 expression and its enzymatic activity were significantly increased in E.C.M. detached cancer cells when compared to the attached cells. Inhibition of EZH2 results in a significant reduction in cell proliferation, spheroids size, and induction in apoptosis in E.C.M. detached cells. Furthermore, we observed a reduction in EZH2 expression levels in single cells when compared to clusters of E.C.M. detached cells. Finally, we combined the EZH2 inhibition with AMPK, known to be highly expressed in E.C.M. detached cancer cells and observed antagonistic effects between the two pathways. The observed results clearly showed that E.C.M. detached cancer cells require oncogenic EZH2 and can be targeted by EZH2 inhibitors.