Human MCF7 cells engineered to overexpress MYF6 vs. Control cells containing empty vector constructs [Rec1]

Background: Proliferation is an important hallmark of cancer development and progression. Tumor growth rate significantly influences the course of the disease, and patients with tumors that have a high proliferation rate have an increased risk (10-20%) of metastasis and death. The genomic region encoding the transcription factor MYF6 is often altered in breast cancer, and alterations in MYF6 methylation have been linked to several different cancer types. However, the functional role of MYF6 in cancer remain unknown. Here, we have dissected the functional role of MYF6 in ER+ breast cancer. Methods: We analyzed cancer cell growth, proliferation, apoptosis, in vivo tumor formation, EMT phenotype and BCSC propagation in MCF7 and T47D ER+ breast cancer models with inducuble MYF6 overexpression or MYF6 knockdown. Additionally, we performed detailed molecular profiling and network analysis, and Western blot validation of identified targets. Results: We show that MYF6 suppresses PI3K/Akt/mTOR and Wnt pathway signaling, two important pathways of cell proliferation, and suppression was accompanied by reduced cell growth in vitro and in vivo, and G0/G1 phase cell cycle arrest. MYF6 also induced an EMT phenotype and forced the cells into a cancer stem cell-like state, leading to resistance to -irradiation. Network analysis of molecular profiling data revealed that MYF6 activates hypoxia signaling and HIF1A was identified as a downstream target and an upstream regulator of MYF6. Conclusion: Our results suggest both a tumor-suppressive and oncogenic role of MYF6 in ER+ breast cancer, and we theorize that, subject to the presence or absence of yet unidentified cellular factors, MYF6 can switch from a growth-inhibiting tumor suppressor to an oncogene state, associated with cancer stem cells and treatment resistance. Transcriptional profiling of human ER+ MCF7 breast cancer cells modified by stable site-specific insertion of MYF6. Gene expression was induced for 48 h with Doxycycline and gene expression compared to control cell lines. Two MCF7-MYF6 cell lines were generated (MYF6 Rec1 and MYF6 Rec2). The goal was to determine the effects of MYF6 gene transfection on global gene expression and molecular phenotypes in ER+ breast cancer. Two-condition experiment, with dye-swaps: MCF7-MYF6 Rec1 vs. MCF7-Ctrl cells. Biological replicates: 4 Ctrl replicates and 4 MYF6 Rec1 replicates.