Browsing by Subject "C-MYC"

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  • Utz, Begüm; Turpin, Rita; Lampe, Johanna; Pouwels, Jeroen; Klefström, Juha (2020)
    Breast cancer is the most common form of cancer in women. Despite significant therapeutic advances in recent years, breast cancer also still causes the greatest number of cancer-related deaths in women, the vast majority of which (>90%) are caused by metastases. However, very few mouse mammary cancer models exist that faithfully recapitulate the multistep metastatic process in human patients. Here we assessed the suitability of a syngrafting protocol for a Myc-driven mammary tumor model (WAP-Myc) to study autochthonous metastasis. A moderate but robust spontaneous lung metastasis rate of around 25% was attained. In addition, increased T cell infiltration was observed in metastatic tumors compared to donor and syngrafted primary tumors. Thus, the WAP-Myc syngrafting protocol is a suitable tool to study the mechanisms of metastasis in MYC-driven breast cancer.
  • Laine, Anni; Nagelli, Srikar G.; Farrington, Caroline; Butt, Umar; Cvrljevic, Anna N.; Vainonen, Julia P.; Feringa, Femke M.; Gronroos, Tove J.; Gautam, Prson; Khan, Sofia; Sihto, Harri; Qiao, Xi; Pavic, Karolina; Connolly, Denise C.; Kronqvist, Pauliina; Elo, Laura L.; Maurer, Jochen; Wennerberg, Krister; Medema, Rene H.; Joensuu, Heikki; Peuhu, Emilia; de Visser, Karin; Narla, Goutham; Westermarck, Jukka (2021)
    Basal-like breast cancers (BLBC) are characterized by defects in homologous recombination (HR), deficient mitotic checkpoint, and high-proliferation activity. Here, we discover CIP2A as a candidate driver of BLBC. CIP2A was essential for DNA damage-induced initiation of mouse BLBC-like mammary tumors and for survival of HR-defective BLBC cells. CIP2A was dispensable for normal mammary gland development and for unperturbed mitosis, but selectively essential for mitotic progression of DNA damaged cells. A direct interaction between CIP2A and a DNA repair scaffold protein TopBP1 was identified, and CIP2A inhibition resulted in enhanced DNA damage-induced TopBP1 and RAD51 recruitment to chromatin in mammary epithelial cells. In addition to its role in tumor initiation, and survival of BRCA-deficient cells, CIP2A also drove proliferative MYC and E2F1 signaling in basal-like triple-negative breast cancer (BL-TNBC) cells. Clinically, high CIP2A expression was associated with poor patient prognosis in BL-TNBCs but not in other breast cancer subtypes. Small-molecule reactivators of PP2A (SMAP) inhibited CIP2A transcription, phenocopied the CIP2A-deficient DNA damage response (DDR), and inhibited growth of patient-derived BLBC xenograft. In summary, these results demonstrate that CIP2A directly interacts with TopBP1 and coordinates DNAdamage-induced mitotic checkpoint and proliferation, thereby driving BLBC initiation and progression. SMAPs could serve as a surrogate therapeutic strategy to inhibit the oncogenic activity of CIP2A in BLBCs. Significance: These results identify CIP2A as a nongenetic driver and therapeutic target in basal-like breast cancer that regulates DNA damage-induced G2-M checkpoint and proliferative signaling.
  • Heino, Sarika; Fang, Shentong; Lähde, Marianne; Högström, Jenny; Nassiri, Sina; Campbell, Andrew; Flanagan, Dustin; Raven, Alexander; Hodder, Michael; Nasreddin, Nadia; Xue, Hai-Hui; Delorenzi, Mauro; Leedham, Simon; Petrova, Tatiana; Sansom, Owen; Alitalo, Kari (2021)
    Somatic mutations in APC or CTNNB1 genes lead to aberrant Wnt signaling and colorectal cancer (CRC) initiation and progression via-catenin-T cell factor/lymphoid enhancer binding factor TCF/LEF transcription factors. We found that Lef1 was expressed exclusively in Apc-mutant, Wnt ligand-independent tumors, but not in ligand-dependent, serrated tumors. To analyze Lef1 function in tumor development, we conditionally deleted Lef1 in intestinal stem cells of Apc(fl/fl) mice or broadly from the entire intestinal epithelium of Apc(fl/fl) or Apc(Min/+) mice. Loss of Lef1 markedly increased tumor initiation and tumor cell proliferation, reduced the expression of several Wnt antagonists, and increased Myc proto-oncogene expression and formation of ectopic crypts in Apc-mutant adenomas. Our results uncover a previously unknown negative feedback mechanism in CRC, in which ectopic Lef1 expression suppresses intestinal tumorigenesis by restricting adenoma cell dedifferentiation to a crypt-progenitor phenotype and by reducing the formation of cancer stem cell niches.
  • Tomasovic, Ana; Kurrle, Nina; Wempe, Frank; De-Zolt, Siike; Scheibe, Susan; Koli, Katri; Serchinger, Martin; Schnuetgen, Frank; Sueruen, Duran; Sterner-Kock, Anja; Weissmann, Norbert; von Meichner, Harald (2017)
    Latent transforming growth factor beta binding protein 4 (LTBP4) belongs to the fibrillin/LTBP family of proteins and plays an important role as a structural component of extracellular matrix (ECM) and local regulator of TGF beta signaling. We have previously reported that Ltbp4S knock out mice (Ltbp4S-/-) develop centrilobular emphysema reminiscent of late stage COPD, which could be partially rescued by inactivating the antioxidant protein Sestrin 2 (Sesn2). More recent studies showed that Sesn2 knock out mice upregulate Pdgfr beta-controlled alveolar maintenance programs that protect against cigarette smoke induced pulmonary emphysema. Based on this, we hypothesized that the emphysema of Ltbp4S-/- mice is primarily caused by defective Pdgfr beta signaling. Here we show that LTBP4 induces Pdgfr beta signaling by inhibiting the antioxidant Nr12/Keap1 pathway in a TGF beta-dependent manner. Overall, our data identified Ltbp4 as a major player in lung remodeling and injury repair. (C) 2016 The Authors. Published by Elsevier B.V.
  • Dave, Kashyap; Sur, Inderpreet; Yan, Jian; Zhang, Jilin; Kaasinen, Eevi; Zhong, Fan; Blaas, Leander; Li, Xiaoze; Kharazi, Shabnam; Gustafsson, Charlotte; De Paep, Ayla; Mansson, Robert; Taipale, Jussi (2017)
    The gene desert upstream of the MYC oncogene on chromosome 8q24 contains susceptibility loci for several major forms of human cancer. The region shows high conservation between human and mouse and contains multiple MYC enhancers that are activated in tumor cells. However, the role of this region in normal development has not been addressed. Here we show that a 538 kb deletion of the entire MYC upstream super-enhancer region in mice results in 50% to 80% decrease in Myc expression in multiple tissues. The mice are viable and show no overt phenotype. However, they are resistant to tumorigenesis, and most normal cells isolated from them grow slowly in culture. These results reveal that only cells whose MYC activity is increased by serum or oncogenic driver mutations depend on the 8q24 super-enhancer region, and indicate that targeting the activity of this element is a promising strategy of cancer chemoprevention and therapy.
  • Rodriguez, Alfredo; Zhang, Kaiyang; Färkkilä, Anniina; Filiatrault, Jessica; Yang, Chunyu; Velazquez, Martha; Furutani, Elissa; Goldman, Devorah C.; Garcia de Teresa, Benilde; Garza-Mayen, Gilda; McQueen, Kelsey; Sambel, Larissa A.; Molina, Bertha; Torres, Leda; Gonzalez, Marisol; Vadillo, Eduardo; Pelayo, Rosana; Fleming, William H.; Grompe, Markus; Shimamura, Akiko; Hautaniemi, Sampsa; Greenberger, Joel; Frias, Sara; Parmar, Kalindi; D'Andrea, Alan D. (2021)
    Bone marrow failure (BMF) in Fanconi anemia (FA) patients results from dysfunctional hematopoietic stem and progenitor cells (HSPCs). To identify determinants of BMF, we performed single-cell transcriptome profiling of primary HSPCs from FA patients. In addition to overexpression of p53 and TGF-beta pathway genes, we identified high levels of MYC expression. We correspondingly observed coexistence of distinct HSPC subpopulations expressing high levels of TP53 or MYC in FA bone marrow (BM). Inhibiting MYC expression with the BET bromodomain inhibitor (+)-JQ1 reduced the clonogenic potential of FA patient HSPCs but rescued physiological and genotoxic stress in HSPCs from FA mice, showing that MYC promotes proliferation while increasing DNA damage. MYC-high HSPCs showed significant downregulation of cell adhesion genes, consistent with enhanced egress of FA HSPCs from bone marrow to peripheral blood. We speculate that MYC overexpression impairs HSPC function in FA patients and contributes to exhaustion in FA bone marrow.
  • Haikala, Heidi M.; Klefstrom, Juha; Eilers, Martin; Wiese, Katrin E. (2016)
    Apoptosis caused by deregulated MYC expression is a prototype example of intrinsic tumor suppression. However, it is still unclear how supraphysiological MYC expression levels engage specific sets of target genes to promote apoptosis. Recently, we demonstrated that repression of SRF target genes by MYC/MIZ1 complexes limits AKT-dependent survival signaling and contributes to apoptosis induction. Here we report that supraphysiological levels of MYC repress gene sets that include markers of basal-like breast cancer cells, but not luminal cancer cells, in a MIZ1-dependent manner. Furthermore, repressed genes are part of a conserved gene signature characterizing the basal subpopulation of both murine and human mammary gland. These repressed genes play a role in epithelium and mammary gland development and overlap with genes mediating cell adhesion and extracellular matrix organization. Strikingly, acute activation of oncogenic MYC in basal mammary epithelial cells is sufficient to induce luminal cell identity markers. We propose that supraphysiological MYC expression impacts on mammary epithelial cell identity by repressing lineage-specific target genes. Such abrupt cell identity switch could interfere with adhesion-dependent survival signaling and thus promote apoptosis in pre-malignant epithelial tissue.
  • Aakko, Sofia; Straume, Anne Hege; Birkeland, Einar Elvbakken; Chen, Ping; Qiao, Xi; Lonning, Per Eystein; Kallio, Marko J. (2019)
    Taxanes are chemotherapeutic agents used in the treatment of solid tumors, particularly of breast, ovarian, and lung origin. However, patients show divergent therapy responses, and the molecular determinants of taxane sensitivity have remained elusive. Especially the signaling pathways that promote death of the taxane-treated cells are poorly characterized. Here we describe a novel part of a signaling route in which c-Myc enhances paclitaxel sensitivity through upregulation of miR-203b-3p and miR-203a-3p; two clustered antiapoptosis protein BcI-xL controlling microRNAs. In vitro, the miR-203b-3p decreases the expression of BcI-xL by direct targeting of the gene's mRNA 3'UTR. Notably, overexpression of the miR-203b-3p changed the fate of paclitaxel-treated breast and ovarian cancer cells from mitotic slippage to cell death. In breast tumors, high expression of the miR-203b-3p and MYC was associated with better therapy response and patient survival. Interestingly, in the breast tumors, MYC expression correlated negatively with BCL2L1 expression but positively with miR-203b-3p and miR-203a-3p. Finally, silencing of MYC suppressed the transcription of both miRNAs in breast tumor cells. Pending further validation, these results may assist in patient stratification for taxane therapy.
  • Haikala, Heidi M.; Anttila, Johanna M.; Marques, Elsa; Raatikainen, Tiina; Ilander, Mette; Hakanen, Henna; Ala-Hongisto, Hanna; Savelius, Mariel; Balboa, Diego; Von Eyss, Bjoern; Eskelinen, Vilja; Munne, Pauliina; Nieminen, Anni I.; Otonkoski, Timo; Schüler, Julia; Laajala, Teemu D.; Aittokallio, Tero; Sihto, Harri; Mattson, Johanna; Heikkilä, Päivi; Leidenius, Marjut; Joensuu, Heikki; Mustjoki, Satu; Kovanen, Panu; Eilers, Martin; Leverson, Joel D.; Klefström, Juha (2019)
    Elevated MYC expression sensitizes tumor cells to apoptosis but the therapeutic potential of this mechanism remains unclear. We find, in a model of MYC-driven breast cancer, that pharmacological activation of AMPK strongly synergizes with BCL-2/BCL-X-L inhibitors to activate apoptosis. We demonstrate the translational potential of an AMPK and BCL-2/BCL-X-L co-targeting strategy in ex vivo and in vivo models of MYC-high breast cancer. Metformin combined with navitoclax or venetoclax efficiently inhibited tumor growth, conferred survival benefits and induced tumor infiltration by immune cells. However, withdrawal of the drugs allowed tumor re-growth with presentation of PD-1+/CD8+ T cell infiltrates, suggesting immune escape. A two-step treatment regimen, beginning with neoadjuvant metformin+venetoclax to induce apoptosis and followed by adjuvant metformin+venetoclax+anti-PD-1 treatment to overcome immune escape, led to durable antitumor responses even after drug withdrawal. We demonstrate that pharmacological reactivation of MYC-dependent apoptosis is a powerful antitumor strategy involving both tumor cell depletion and immunosurveillance.
  • Myant, Kevin; Qiao, Xi; Halonen, Tuuli; Come, Christophe; Laine, Anni; Janghorban, Mahnaz; Partanen, Johanna I.; Cassidy, John; Ogg, Erinn-Lee; Cammareri, Patrizia; Laitera, Tiina; Okkeri, Juha; Klefstrom, Juha; Sears, Rosalie C.; Sansom, Owen J.; Westermarck, Jukka (2015)
    An understanding of the mechanisms determining MYC's transcriptional and proliferation-promoting activities in vivo could facilitate approaches for MYC targeting. However, post-translational mechanisms that control MYC function in vivo are poorly understood. Here, we demonstrate that MYC phosphorylation at serine 62 enhances MYC accumulation on Lamin A/C-associated nuclear structures and that the protein phosphatase 2A (PP2A) inhibitor protein CIP2A is required for this process. CIP2A is also critical for serum-induced MYC phosphorylation and for MYC-elicited proliferation induction in vitro. Complementary transgenic approaches and an intestinal regeneration model further demonstrated the in vivo importance of CIP2A and serine 62 phosphorylation for MYC activity upon DNA damage. However, targeting of CIP2A did not influence the normal function of intestinal crypt cells. These data underline the importance of nuclear organization in the regulation of MYC phosphorylation, leading to an in vivo demonstration of a strategy for inhibiting MYC activity without detrimental physiological effects.
  • Demyanenko, Svetlana; Sharifulina, Svetlana (2021)
    Histone deacetylase (HDAC) and histone acetyltransferase (HAT) regulate transcription and the most important functions of cells by acetylating/deacetylating histones and non-histone proteins. These proteins are involved in cell survival and death, replication, DNA repair, the cell cycle, and cell responses to stress and aging. HDAC/HAT balance in cells affects gene expression and cell signaling. There are very few studies on the effects of stroke on non-histone protein acetylation/deacetylation in brain cells. HDAC inhibitors have been shown to be effective in protecting the brain from ischemic damage. However, the role of different HDAC isoforms in the survival and death of brain cells after stroke is still controversial. HAT/HDAC activity depends on the acetylation site and the acetylation/deacetylation of the main proteins (c-Myc, E2F1, p53, ERK1/2, Akt) considered in this review, that are involved in the regulation of cell fate decisions. Our review aims to analyze the possible role of the acetylation/deacetylation of transcription factors and signaling proteins involved in the regulation of survival and death in cerebral ischemia.