Article

Cells lacking the fumarase tumor suppressor are protected from apoptosis through a hypoxia-inducible factor-independent, AMPK-dependent mechanism.

Department of Oncological Sciences, University of Torino, School of Medicine, Turin, Italy.
Molecular and Cellular Biology (Impact Factor: 5.04). 05/2012; 32(15):3081-94. DOI: 10.1128/MCB.06160-11
Source: PubMed

ABSTRACT Loss-of-function mutations of the tumor suppressor gene encoding fumarase (FH) occur in individuals with hereditary leiomyomatosis and renal cell cancer syndrome (HLRCC). We found that loss of FH activity conferred protection from apoptosis in normal human renal cells and fibroblasts. In FH-defective cells, both hypoxia-inducible factor 1α (HIF-1α) and HIF-2α accumulated, but they were not required for apoptosis protection. Conversely, AMP-activated protein kinase (AMPK) was activated and required, as evidenced by the finding that FH inactivation failed to protect AMPK-null mouse embryo fibroblasts (MEFs) and AMPK-depleted human renal cells. Activated AMPK was detected in renal cysts, which occur in mice with kidney-targeted deletion of Fh1 and in kidney cancers of HLRCC patients. In Fh1-null MEFs, AMPK activation was sustained by fumarate accumulation and not by defective energy metabolism. Addition of fumarate and succinate to kidney cells led to extracellular signal-regulated kinase 1/2 (ERK1/2) and AMPK activation, probably through a receptor-mediated mechanism. These findings reveal a new mechanism of tumorigenesis due to FH loss and an unexpected pro-oncogenic role for AMPK that is important in considering AMPK reactivation as a therapeutic strategy against cancer.

0 Bookmarks
 · 
151 Views
  • [Show abstract] [Hide abstract]
    ABSTRACT: The tyrosine kinase encoded by the MET oncogene is activated by gene mutation or amplification in tumors, which in most instances maintain addiction, i.e., dependency, to MET activation. This makes MET an attractive candidate for targeted therapies. Here we show that, in 3/3 MET-addicted human gastric cancer cell lines, MET kinase inhibition resulted in a 3- to 4-fold increased expression of the antiapoptotic small heat-shock protein of 27 kDa (HSP27, HSPB1). HSP27 increase depended on the inhibition of the MEK/ERK pathway and on heat-shock factor 1 (HSF1) and hypoxia-inducible factor-1α (HIF-1α) regulation. Importantly, HSP27-silenced MET-addicted cells underwent 2- and 3-fold more apoptosis following MET inhibition in vitro and in vivo, respectively. Likewise, in human cancer cells susceptible to epidermal growth factor receptor (EGFR) inhibition, EGFR inhibitors induced HSP27 expression and were strengthened by HSP27 suppression. In control cell lines that were not affected by drugs targeting MET or EGFR, these drugs did not induce HSP27 increase. Therefore, in cancer therapies targeting the MET pathway, the induction of HSP27 might limit the efficacy of anti-MET agents. As HSP27 increase also impairs the effectiveness of EGFR inhibitors and is known to protect cells from chemotherapeutics, the induction of HSP27 by targeted agents might strongly affect the success of combination treatments.-Musiani, D., Konda, J. D., Pavan, S., Torchiaro, E., Sassi, F., Noghero, A., Erriquez, J., Perera, T., Olivero, M., Di Renzo, M. F. Heat-shock protein 27 (HSP27, HSPB1) is up-regulated by MET kinase inhibitors and confers resistance to MET-targeted therapy.
    The FASEB Journal 06/2014; 28(9). DOI:10.1096/fj.13-247924 · 5.48 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: The multifunctional AMPK-activated protein kinase (AMPK) is an evolutionarily conserved energy sensor that plays an important role in cell proliferation, growth, and survival. It remains unclear whether AMPK functions as a tumor suppressor or a contextual oncogene. This is because although on one hand active AMPK inhibits mammalian target of rapamycin (mTOR) and lipogenesis-two crucial arms of cancer growth-AMPK also ensures viability by metabolic reprogramming in cancer cells. AMPK activation by two indirect AMPK agonists AICAR and metformin (now in over 50 clinical trials on cancer) has been correlated with reduced cancer cell proliferation and viability. Surprisingly, we found that compared with normal tissue, AMPK is constitutively activated in both human and mouse gliomas. Therefore, we questioned whether the antiproliferative actions of AICAR and metformin are AMPK independent. Both AMPK agonists inhibited proliferation, but through unique AMPK-independent mechanisms and both reduced tumor growth in vivo independent of AMPK. Importantly, A769662, a direct AMPK activator, had no effect on proliferation, uncoupling high AMPK activity from inhibition of proliferation. Metformin directly inhibited mTOR by enhancing PRAS40's association with RAPTOR, whereas AICAR blocked the cell cycle through proteasomal degradation of the G2M phosphatase cdc25c. Together, our results suggest that although AICAR and metformin are potent AMPK-independent antiproliferative agents, physiological AMPK activation in glioma may be a response mechanism to metabolic stress and anticancer agents.
    Proceedings of the National Academy of Sciences 01/2014; 111(4):E435-44. DOI:10.1073/pnas.1311121111 · 9.81 Impact Factor
  • Source
    [Show abstract] [Hide abstract]
    ABSTRACT: Rare, sporadic uterine leiomyomas arise in the setting of severe metabolic aberration due to a somatic fumarate hydratase mutation. Germline mutations account for the hereditary leiomyomatosis and renal cell carcinoma syndrome, which predisposes for cutaneous and uterine leiomyomas and aggressive renal cell carcinomas. Altered fumarate hydratase leads to fumarate accumulation in affected cells with formation of S-(2-succino)-cysteine, which can be detected with the polyclonal antibody. High levels of these modified cysteine residues are found characteristically in fumarate hydratase-deficient cells but not in normal tissues or tumors unassociated with hereditary leiomyomatosis and renal cell carcinoma syndrome. We hypothesized that S-(2-succino)-cysteine-positive leiomyomas, indicating fumarate hydratase aberration, have morphologic features that differ from those without S-(2-succino)-cysteine positivity. Hematoxylin and eosin-stained slides of uterine smooth-muscle tumors were prospectively analyzed for features suggesting hereditary leiomyomatosis and renal cell carcinoma syndrome, such as prominent eosinophilic macronucleoli with perinucleolar halos, yielding nine cases. Germline genetic testing for fumarate hydratase mutations was performed in three cases. A detailed morphological analysis was undertaken, and S-(2-succino)-cysteine immunohistochemical analysis was performed with controls from a tissue microarray (leiomyomas (19), leiomyosarcomas (29), and endometrial stromal tumors (15)). Of the nine study cases, four had multiple uterine smooth muscle tumors. All cases had increased cellularity, staghorn vasculature, and fibrillary cytoplasm with pink globules. All cases had inclusion-like nucleoli with perinuclear halos (7 diffuse, 1 focal). All showed diffuse granular cytoplasmic labeling with the S-(2-succino)-cysteine antibody. Two of three tested patients had germline fumarate hydratase mutations. Only one leiomyoma from the tissue microarray controls was immunohistochemically positive, and it showed features similar to other immunohistochemically positive cases. Smooth-muscle tumors with fumarate hydratase aberration demonstrate morphological reproducibility across cases and S-(2-succino)-cysteine immuno-positivity. Although the features described are not specific for the germline fumarate hydratase mutation or the hereditary leiomyomatosis and renal cell carcinoma syndrome, their presence should suggest fumarate hydratase aberration. Identifying these cases is an important step in the diagnostic workup of patients with possible hereditary leiomyomatosis and renal cell carcinoma.Modern Pathology advance online publication, 6 December 2013; doi:10.1038/modpathol.2013.215.
    Modern Pathology 12/2013; DOI:10.1038/modpathol.2013.215 · 6.36 Impact Factor

Full-text

Download
147 Downloads
Available from
Jun 1, 2014