Epithelial mechenchymal transition (EMT) has recently been linked to stem cell phenotype1, 2. However, the molecular mechanism involving regulation of EMT and stemness remains elusive. Here, using genomic approaches, we discovered that tumor suppressor p53 plays a role in regulating both EMT and EMT-associated stem cell properties through transcriptional activation of miR-200c. p53 transactivates miR-200c through direct binding to the miR-200c promoter. Loss of p53 in mammary epithelial cells leads to decreased expression of miR-200c and activates EMT program, accompanied by increased mammary stem cell population. Re-expressing miR-200c suppresses genes that mediate EMT and stemness properties3, 4 and thereby reverts mesenchymal and stem cell-like phenotype caused by loss of p53 to differentiated epithelial cell phenotype. Furthermore, loss of p53 negatively correlates with miR-200c level but positively with increased expression of EMT and stemness markers as well as high tumor grade in a cohort of breast tumors. Together, this study elucidates a role of p53 in regulating EMT-MET (mechenchymal epithelial transition) and stemness or differentiation plasticity and reveals a potential therapeutic implication to suppress EMT associated-cancer stem cells through activation of p53-miR-200c pathway.

Summary It has been proposed that an aggressive secondary cancer stem cell population arises from a primary cancer stem cell population through acquisition of additional genetic mutations and drives cancer progression. Overexpression of Polycomb protein EZH2, essential in stem cell self-renewal, has been linked to breast cancer progression. However, critical mechanism linking increased EZH2 expression to BTIC (breast tumor initiating cell) regulation and cancer progression remains unclear. Here, we identify a mechanism in which EZH2 expression-mediated downregulation of DNA damage repair leads to accumulation of recurrent RAF1 gene amplification in BTICs, which activates p-ERK-β-catenin signaling to promote BTIC expansion. We further reveal that AZD6244, a clinical trial drug that inhibits RAF1-ERK signaling, could prevent breast cancer progression by eliminating BTICs.

Accumulated evidence shows that EZH2 is deregulated in a wide range of cancer types, and it has a crucial role in stem cell maintenance and tumour development. Therefore, blocking EZH2 expression or activity may represent a promising strategy for anticancer treatment. In this review, we address the current understanding of the mechanisms underlying EZH2 regulation alongside the function of EZH2 gene targets that are involved in cancer progression. Finally, we will describe cancer therapies that target EZH2 or its downstream cascades, which could potentially reverse the oncogenic and stemness properties of the tumour cells to suppress cancer progression and recurrence.

Cancer stem cells, which share many common properties and regulatory machineries with normal stem cells, have recently been proposed to be responsible for tumorigenesis and to contribute to cancer resistance 1 . The main challenges in cancer biology are to identify cancer stem cells and to define the molecular events required for transforming normal cells to cancer stem cells. Here we show that Pten deletion in mouse haematopoietic stem cells leads to a myeloproliferative disorder, followed by acute T-lymphoblastic leukaemia (T-ALL). Self-renewable leukaemia stem cells (LSCs) are enriched in the c-Kit mid CD3 + Lin − compartment, where unphosphorylated β-catenin is significantly increased. Conditional ablation of one allele of the β-catenin gene substantially decreases the incidence and delays the occurrence of T-ALL caused by Pten loss, indicating that activation of the β-catenin pathway may contribute to the formation or expansion of the LSC population. Moreover, a recurring chromosomal translocation, T(14;15), results in aberrant overexpression of the c-myc oncogene in c-Kit mid CD3 + Lin − LSCs and CD3 + leukaemic blasts,

We demonstrate that PTEN loss causes reduced NKX3.1 expression in both murine and human prostate cancers. Restoration of Nkx3.1 expression in vivo in Pten null epithelium leads to decreased cell proliferation, increased cell death, and prevention of tumor initiation. Whereas androgen receptor (AR) positively regulates NKX3.1 expression, NKX3.1 negatively modulates AR transcription and consequently the AR-associated signaling events. Consistent with its tumor suppressor functions, NKX3.1 engages cell cycle and cell death machinery via association with HDAC1, leading to increased p53 acetylation and half-life through MDM2-dependent mechanisms. Importantly, overexpression of Nkx3.1 has little effect on Pten wild-type epithelium, suggesting that PTEN plays a predominant role in PTEN-NKX3.1 interplay. Manipulating NKX3.1 expression may serve as a therapeutic strategy for treating PTEN-deficient prostate cancers.