Project description:Metastasis is responsible for the majority of breast cancer (BrCa) deaths; however, the underlying mechanisms remain largely elusive. Here, we report that suppression of MBD2 alternative splicing under hypoxia, which favors the production of MBD2a, facilitates BrCa metastasis. Specifically, we found that MBD2a promotes, whereas its less-known short form MBD2c suppresses metastasis. We elucidate that HIF-1 activation under hypoxia facilitates MBD2a production via repression of SRSF2-mediated alternative splicing and, as a result, the elevated MBD2a outcompetes MBD2c for binding to the promoter CpG islands to activate the expression of FZD1, thereby promoting EMT and metastasis. Strikingly, clinical data reveals significantly correlated expression pattern of MBD2a and MBD2c with the invasiveness of malignancy, indicating the opposing roles for MBD2 splicing variants in regulating human BrCa metastasis. Thus, our findings establish a novel link between MBD2 switching and tumor metastasis, and provide promising therapeutic strategy and predictive biomarkers for hypoxia-driven BrCa metastasis.
Project description:Hypoxia is a common feature of many solid tumors due to aberrant proliferation and angiogenesis that is associated with tumor progression and metastasis. Most of the well-known hypoxia effects are mediated through hypoxia-inducible factors (HIFs). Identification of the long-lasting effects of hypoxia beyond the immediate HIF-induced alterations could provide a better understanding of hypoxia-driven metastasis and potential strategies to circumvent it. Here, we uncovered a hypoxia-induced mechanism that exerts a prolonged effect to promote metastasis. In breast cancer patient-derived circulating tumor cell (CTC) lines and common breast cancer cell lines, hypoxia downregulated tumor intrinsic type I interferon (IFN) signaling and its downstream antigen presentation (AP) machinery in luminal breast cancer cells, via both HIF-dependent and HIF-independent mechanisms. Hypoxia induced durable IFN/AP suppression in certain cell types that was sustained after returning to normoxic conditions, presenting a “hypoxic memory” phenotype. Hypoxic memory of IFN/AP downregulation was established by specific hypoxic priming, and cells with hypoxic memory had an enhanced ability for tumorigenesis and metastasis. Overexpression of IRF3 enhanced IFN signaling and reduced tumor growth in normoxic, but not hypoxic, conditions. The histone deacetylase inhibitor (HDACi) entinostat upregulated IFN targets and erased the hypoxic memory. These results point to a mechanism by which hypoxia facilitates tumor progression through a long-lasting memory that provides advantages for CTCs during the metastatic cascade.
Project description:Hypoxia is a common feature of many solid tumors due to aberrant proliferation and angiogenesis that is associated with tumor progression and metastasis. Most of the well-known hypoxia effects are mediated through hypoxia-inducible factors (HIFs). Identification of the long-lasting effects of hypoxia beyond the immediate HIF-induced alterations could provide a better understanding of hypoxia-driven metastasis and potential strategies to circumvent it. Here, we uncovered a hypoxia-induced mechanism that exerts a prolonged effect to promote metastasis. In breast cancer patient-derived circulating tumor cell (CTC) lines and common breast cancer cell lines, hypoxia downregulated tumor intrinsic type I interferon (IFN) signaling and its downstream antigen presentation (AP) machinery in luminal breast cancer cells, via both HIF-dependent and HIF-independent mechanisms. Hypoxia induced durable IFN/AP suppression in certain cell types that was sustained after returning to normoxic conditions, presenting a “hypoxic memory” phenotype. Hypoxic memory of IFN/AP downregulation was established by specific hypoxic priming, and cells with hypoxic memory had an enhanced ability for tumorigenesis and metastasis. Overexpression of IRF3 enhanced IFN signaling and reduced tumor growth in normoxic, but not hypoxic, conditions. The histone deacetylase inhibitor (HDACi) entinostat upregulated IFN targets and erased the hypoxic memory. These results point to a mechanism by which hypoxia facilitates tumor progression through a long-lasting memory that provides advantages for CTCs during the metastatic cascade.
Project description:Metastatic colorectal cancer (mCRC) is the major cause of death in patients with CRC. Hypoxia is a hallmark of solid tumors that promotes cell metabolic adaptation and metastasis. However, the mechanism linking mCRC to hypoxia-regulated metabolic adaptation remains unclear. Here, we found that inorganic pyrophosphatase 2 (PPA2) suppresses mCRC progression via its phosphatase function. PPA2 is expressed at low levels in mCRC specimens and lowly expressed PPA2 mediates better responses to hypoxia to enhance CRC glycolysis and metastasis by promoting hypoxia-inducible factor-1α (HIF-1α) signaling. Mechanistically, PPA2 decreases HIF-1α stability through noncanonical ubiquitin-mediated proteasomal degradation via recruitment of E3 ligase neural precursor cell-expressed developmentally downregulated gene 4 (NEDD4), which inhibits glycolysis and metastasis-related gene expression. Furthermore, PPA2 directly interacts with NEDD4 and dephosphorylates NEDD4 at the T758 residue, leading to the increased interaction between NEDD4 and HIF-1α. Under hypoxic stress, NAD-dependent protein deacetylase sirtuin-5 (SIRT5) promotes the dissociation of PPA2 and NEDD4 by inducing PPA2 desuccinylation at the K176 residue, which ultimately contributes to the improved stability of HIF-1α under hypoxic conditions. Our findings reveal the suppressive role of PPA2 in HIF-1α-dependent mCRC, suggesting that the SIRT5-PPA2-NEDD4-HIF-1α axis can be assessed for integrated prognosis evaluation and represents a potential therapeutic target.
Project description:N6-methyladenosine (m6A) modification is the most abundant internal mRNA modification in eukaryotes. Hypoxia induces reprogramming of m6A epitranscriptome, but the detail underlying regulator mechanism remains elusive in breast cancer. Here we reported that hypoxia induced elevated m6A modification involved in tumor progression. m6A- sequencing (m6A-seq) combined with RNA sequencing (RNA-seq) identified RIPOR3 as a key target gene of m6A modification under hypoxic stress. Hypoxia-induced increased of RIPOR3 m6A levels promoted its mRNA stability and expression, thereby facilitating the progression and metastasis of breast cancer. Besides, RIPOR3 was overexpressed in breast cancer cells and breast tumor tissues, and elevation of RIPOR3 expression was associated with poor prognosis. Mechanistically, RIPOR3 bound to EGFR and the interaction was enhanced under hypoxia, promoting the activation of the EGFR downstream PI3K-AKT signaling pathway. Altogether, our studies reveal that RIPOR3 responds to hypoxic stress to promote EGFR-PI3K-AKT signal pathway, facilitating breast cancer progression and metastasis, thus presenting itself as a potential therapeutic target.
Project description:N6-methyladenosine (m6A) modification is the most abundant internal mRNA modification in eukaryotes. Hypoxia induces reprogramming of m6A epitranscriptome, but the detail underlying regulator mechanism remains elusive in breast cancer. Here we reported that hypoxia induced elevated m6A modification involved in tumor progression. m6A- sequencing (m6A-seq) combined with RNA sequencing (RNA-seq) identified RIPOR3 as a key target gene of m6A modification under hypoxic stress. Hypoxia-induced increased of RIPOR3 m6A levels promoted its mRNA stability and expression, thereby facilitating the progression and metastasis of breast cancer. Besides, RIPOR3 was overexpressed in breast cancer cells and breast tumor tissues, and elevation of RIPOR3 expression was associated with poor prognosis. Mechanistically, RIPOR3 bound to EGFR and the interaction was enhanced under hypoxia, promoting the activation of the EGFR downstream PI3K-AKT signaling pathway. Altogether, our studies reveal that RIPOR3 responds to hypoxic stress to promote EGFR-PI3K-AKT signal pathway, facilitating breast cancer progression and metastasis, thus presenting itself as a potential therapeutic target.
Project description:Coactivator associated arginine methyltransferase 1 has been reported to play paramount roles in estrogen receptor alpha (ERα)-positive breast cancer. It promotes breast cancer development and metastasis. However, little research about CARM1 has been focused on triple-negative breast cancer (TNBC). Here, we report that CARM1 promotes proliferation, epithelial-mesenchymal transition (EMT) and stemness in TNBC. CARM1 transactivates Hypoxia-inducible factor 1 subunit alpha (HIF1A) and is physically associated with it. They function together in a concerted complex to regulate downstream targets and promote the carcinogenesis and metastasis of TNBC.
Project description:Reciprocal interactions between breast cancer cells and the tumor microenvironment are important for cancer progression and metastasis. We report here that the deletion or inhibition of sphingosine kinase 2 (SphK2), which produces sphingosine-1-phosphate (S1P), markedly suppresses syngeneic breast tumor growth and lung metastasis in mice by creating a hostile microenvironment for tumor growth and invasion. SphK2 deficiency decreased S1P and concomitantly increased ceramides, including C16-ceramide, in stromal fibroblasts. Ceramide accumulation suppressed activation of cancer-associated fibroblasts (CAFs) by upregulating stromal p53, which restrained production of tumor-promoting factors to reprogram the tumor microenvironment and restrict breast cancer establishment. Ablation of p53 in SphK2-deficient fibroblasts reversed these effects, enabled CAF activation and promoted tumor growth and invasion. These data uncovered a novel role of SphK2 in regulating non-cell autonomous functions of p53 in stromal fibroblasts and their transition to tumor-promoting CAFs, paving the way for the development of a strategy to target the tumor microenvironment and enhance therapeutic efficacy.