1
|
Abstract
Cancer development is a multistep process, driven by a series of genetic and environmental alterations, that endows cells with a set of hallmark traits required for tumorigenesis. It is broadly accepted that growth signal autonomy, the first hallmark of malignancies, can be acquired through multiple genetic mutations that activate an array of complex, cancer-specific growth circuits [Hanahan D, Weinberg RA (2000) The hallmarks of cancer. Cell 100:57-70; Vogelstein B, Kinzler KW (2004) Cancer genes and the pathways they control. Nat Med 10:789-799]. The superfluous nature of these pathways is thought to severely limit therapeutic approaches targeting tumor proliferation, and it has been suggested that this strategy be abandoned in favor of inhibiting more systemic hallmarks, including angiogenesis (Ellis LM, Hicklin DJ (2008) VEGF-targeted therapy: Mechanisms of anti-tumor activity. Nat Rev Cancer 8:579-591; Stommel JM, et al. (2007) Coactivation of receptor tyrosine kinases affects the response of tumor cells to targeted therapies. Science 318:287-290; Kerbel R, Folkman J (2002) Clinical translation of angiogenesis inhibitors. Nat Rev Cancer 2:727-739; Kaiser J (2008) Cancer genetics: A detailed genetic portrait of the deadliest human cancers. Science 321:1280-1281]. Here, we report the unexpected observation that genetically diverse cancers converge at a common and obligatory growth axis instigated by HIF-2alpha, an element of the oxygen-sensing machinery. Inhibition of HIF-2alpha prevents the in vivo growth and tumorigenesis of highly aggressive glioblastoma, colorectal, and non-small-cell lung carcinomas and the in vitro autonomous proliferation of several others, regardless of their mutational status and tissue of origin. The concomitant deactivation of select receptor tyrosine kinases, including the EGFR and IGF1R, as well as downstream ERK/Akt signaling, suggests that HIF-2alpha exerts its proliferative effects by endorsing these major pathways. Consistently, silencing these receptors phenocopies the loss of HIF-2alpha oncogenic activity, abrogating the serum-independent growth of human cancer cells in culture. Based on these data, we propose an alternative to the predominant view that cancers exploit independent autonomous growth pathways and reveal HIF-2alpha as a potentially universal culprit in promoting the persistent proliferation of neoplastic cells.
Collapse
|
2
|
Aberrant epithelial morphology and persistent epidermal growth factor receptor signaling in a mouse model of renal carcinoma. Proc Natl Acad Sci U S A 2009; 106:9767-72. [PMID: 19487675 DOI: 10.1073/pnas.0902031106] [Citation(s) in RCA: 46] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
The epidermal growth factor receptor (EGFR) has frequently been implicated in hyperproliferative diseases of renal tubule epithelia. We have shown that the NF2 tumor suppressor Merlin inhibits EGFR internalization and signaling in a cell contact-dependent manner. Interestingly, despite the paucity of recurring mutations in human renal cell carcinoma (RCC), homozygous mutation of the NF2 gene is found in approximately 2% of RCC patient samples in the Sanger COSMIC database. To examine the roles of Merlin and EGFR in kidney tumorigenesis, we generated mice with a targeted deletion of Nf2 in the proximal convoluted epithelium using a Villin-Cre transgene. All of these mice developed intratubular neoplasia by 3 months, which progressed to invasive carcinoma by 6-10 months. Kidneys from these mice demonstrated marked hyperproliferation and a concomitant increase in label-retaining putative progenitor cells. Early lumen-filling lesions in this model exhibited hyperactivation of EGFR signaling, altered solubility of adherens junctions components, and loss of epithelial polarity. Renal cortical epithelial cells derived from either early or late lesions were dependent on EGF for in vitro proliferation and were arrested by pharmacologic inhibition of EGFR or re-expression of Nf2. These cells formed malignant tumors upon s.c. injection into immunocompromised mice before in vitro passage. Treatment of Vil-Cre;Nf2(lox/lox) mice with the EGFR inhibitor erlotinib halted the proliferation of tumor cells. These studies give added credence to the role of EGFR signaling and perhaps Nf2 deficiency in RCC and describe a rare and valuable mouse model for exploring the molecular basis of this disease.
Collapse
|
3
|
Bommi-Reddy A, Almeciga I, Sawyer J, Geisen C, Li W, Harlow E, Kaelin WG, Grueneberg DA. Kinase requirements in human cells: III. Altered kinase requirements in VHL-/- cancer cells detected in a pilot synthetic lethal screen. Proc Natl Acad Sci U S A 2008; 105:16484-9. [PMID: 18948595 PMCID: PMC2575446 DOI: 10.1073/pnas.0806574105] [Citation(s) in RCA: 113] [Impact Index Per Article: 7.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2008] [Indexed: 11/18/2022] Open
Abstract
Clear cell renal carcinomas are the most common form of kidney cancer and frequently are linked to biallelic inactivation of the von Hippel-Lindau (VHL) tumor suppressor gene. The VHL gene product, pVHL, has multiple functions including directing the polyubiquitylation of the HIF transcription factor. We screened 100 shRNA vectors, directed against 88 kinases, for their ability to inhibit the viability of VHL-/- renal carcinoma cells preferentially compared with isogenic cells in which pVHL function was restored. shRNAs for "hits" identified in the primary screen were interrogated in secondary screens that included shRNA titration studies. Multiple shRNAs against CDK6, MET, and MAP2K1 (also known as MEK1) preferentially inhibited the viability of 786-O and RCC4 VHL-/- cells compared with their wild-type pVHL-reconstituted counterparts. The sensitivity of pVHL-proficient cells to these shRNAs was not restored upon HIF activation, suggesting that loss of an hypoxia-inducible factor (HIF)-independent pVHL function formed the basis for selectivity. A small-molecule Cdk4/6 inhibitor displayed enhanced activity against VHL-/- renal carcinoma cells, suggesting that in some cases hits from shRNA screens such as described here might translate into therapeutic targets.
Collapse
Affiliation(s)
- Archana Bommi-Reddy
- *Department of Medical Oncology, The Dana–Farber Cancer Institute and Harvard Medical School, Boston, MA 02115
| | - Ingrid Almeciga
- *Department of Medical Oncology, The Dana–Farber Cancer Institute and Harvard Medical School, Boston, MA 02115
| | - Jacqueline Sawyer
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115; and
| | - Christoph Geisen
- *Department of Medical Oncology, The Dana–Farber Cancer Institute and Harvard Medical School, Boston, MA 02115
- The Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Wenliang Li
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115; and
| | - Ed Harlow
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115; and
| | - William G. Kaelin
- *Department of Medical Oncology, The Dana–Farber Cancer Institute and Harvard Medical School, Boston, MA 02115
- The Howard Hughes Medical Institute, Chevy Chase, MD 20815
| | - Dorre A. Grueneberg
- Department of Biological Chemistry and Molecular Pharmacology, Harvard Medical School, Boston, MA 02115; and
| |
Collapse
|
4
|
Franovic A, Gunaratnam L, Smith K, Robert I, Patten D, Lee S. Translational up-regulation of the EGFR by tumor hypoxia provides a nonmutational explanation for its overexpression in human cancer. Proc Natl Acad Sci U S A 2007; 104:13092-7. [PMID: 17670948 PMCID: PMC1941796 DOI: 10.1073/pnas.0702387104] [Citation(s) in RCA: 212] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Overexpression of the EGF receptor (EGFR) is a recurrent theme in human cancer and is thought to cause aggressive phenotypes and resistance to standard therapy. There has, thus, been a concerted effort in identifying EGFR gene mutations to explain misregulation of EGFR expression as well as differential sensitivity to anti-EGFR drugs. However, such genetic alterations have proven to be rare occurrences in most types of cancer, suggesting the existence of a more general physiological trigger for aberrant EGFR expression. Here, we provide evidence that overexpression of wild-type EGFR can be induced by the hypoxic microenvironment and activation of hypoxia-inducible factor 2-alpha (HIF2alpha) in the core of solid tumors. Our data suggest that hypoxia/HIF2alpha activation represents a common mechanism for EGFR overexpression by increasing EGFR mRNA translation, thereby diminishing the necessity for gene mutations. This allows for the accumulation of elevated EGFR levels, increasing its availability for the autocrine signaling required for tumor cell growth autonomy. Taken together, our findings provide a nonmutational explanation for EGFR overexpression in human tumors and highlight a role for HIF2alpha activation in the regulation of EGFR protein synthesis.
Collapse
Affiliation(s)
- Aleksandra Franovic
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8M5
| | - Lakshman Gunaratnam
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8M5
| | - Karlene Smith
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8M5
| | - Isabelle Robert
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8M5
| | - David Patten
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8M5
| | - Stephen Lee
- Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, Ottawa, ON, Canada K1H 8M5
- *To whom correspondence should be addressed at:
Department of Cellular and Molecular Medicine, Faculty of Medicine, University of Ottawa, 451 Smyth Road, Ottawa, ON, Canada K1H 8M5. E-mail:
| |
Collapse
|
5
|
Abstract
Germ line VHL tumor suppressor gene loss-of-function mutations cause von Hippel-Lindau disease, which is associated with an increased risk of central nervous system hemangioblastomas, clear cell renal carcinomas, and pheochromocytomas. Somatic VHL mutations are also common in sporadic clear cell renal carcinomas. The VHL gene product, pVHL, is part of a ubiquitin ligase complex that targets the alpha-subunits of the heterodimeric transcription factor hypoxia-inducible factor (HIF) for polyubiquitylation, and hence, proteasomal degradation, when oxygen is available. pVHL-defective clear cell renal carcinomas overproduce a variety of mRNAs that are under the control of HIF, including the mRNAs that encode vascular endothelial growth factor, platelet-derived growth factor B, and transforming growth factor alpha. In preclinical models, down-regulation of HIF-alpha, especially HIF-2alpha, is both necessary and sufficient for renal tumor suppression by pVHL. These observations are probably relevant to the demonstrated clinical activity of vascular endothelial growth factor antagonists in clear cell renal carcinoma and form a foundation for the testing of additional agents that inhibit HIF, or HIF-responsive gene products, in this disease.
Collapse
Affiliation(s)
- William G Kaelin
- Howard Hughes Medical Institute, Dana-Farber Cancer Institute and Brigham and Women's Hospital, Harvard Medical School, Boston, MA 02115, USA.
| |
Collapse
|
6
|
An J, Fisher M, Rettig MB. VHL expression in renal cell carcinoma sensitizes to bortezomib (PS-341) through an NF-kappaB-dependent mechanism. Oncogene 2005; 24:1563-70. [PMID: 15608669 DOI: 10.1038/sj.onc.1208348] [Citation(s) in RCA: 50] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In renal cell carcinomas (RCC), NF-kappaB blockade is required for maximal bortezomib-induced apoptosis, and expression of the von Hippel-Lindau (VHL) tumor suppressor protein downregulates NF-kappaB. Thus, we hypothesized that expression of wild-type (wt) VHL sensitizes RCC cells to bortezomib by reducing constitutive NF-kappaB activity. Using isogenic paired cell lines with and without expression of wtVHL, we have confirmed that VHL expression reduces constitutive NF-kappaB activity. Moreover, VHL expression confers markedly heightened sensitivity to the growth inhibitory effects of bortezomib in vitro. The bortezomib IC50 values were greater than two logs lower in the VHL-expressing cell lines compared to the VHL-deficient counterparts. By manipulating the level of constitutive NF-kappaB activity in an isogenic pair of RCC cell lines independently of VHL expression, we were able to demonstrate that the VHL sensitization effect is due to downregulation of NF-kappaB activity. These findings offer the enticing possibility of using VHL status as a molecular marker to identify RCC patients who may be sensitive to bortezomib. In particular, RCC patients who have non-clear-cell histologies as well as approximately 25% of clear-cell RCCs manifest expression of wtVHL and represent a subpopulation of patients that is apt to respond to bortezomib.
Collapse
Affiliation(s)
- Jiabin An
- VA Greater Los Angeles Healthcare System, Los Angeles, CA 90073, USA
| | | | | |
Collapse
|
7
|
Baba M, Hirai S, Yamada-Okabe H, Hamada K, Tabuchi H, Kobayashi K, Kondo K, Yoshida M, Yamashita A, Kishida T, Nakaigawa N, Nagashima Y, Kubota Y, Yao M, Ohno S. Loss of von Hippel-Lindau protein causes cell density dependent deregulation of CyclinD1 expression through hypoxia-inducible factor. Oncogene 2003; 22:2728-38. [PMID: 12743597 DOI: 10.1038/sj.onc.1206373] [Citation(s) in RCA: 79] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
Loss of the von Hippel-Lindau gene (VHL) expression ca-uses deregulation of contact inhibition of cell growth, which might be one of the bases of the tumor suppressor function of VHL. Here we show that this function of the VHL gene product (pVHL) depends on cell autonomous events. To identify the target gene of pVHL, which is directly involved in the contact inhibition, we compared the gene expression profile between VHL-deficient renal carcinoma 786-O cells and those infected with an adenovirus vector encoding VHL. In addition to known pVHL-regulated genes, such as vascular endothelial growth factor and carbonic anhydrase, we found cyclinD1 as a new target of pVHL at a high cell density. In VHL-expressing cells (VHL (+) cells), the cyclinD1 mRNA expression level diminishes at a high cell density, while it remains at a relatively high level in VHL-deficient cells (VHL (-) cells). The cyclinD1 expression level was also abnormally high in VHL (-) cells at a high cell density. Consequently, the phosporylation level of the retinoblastoma (Rb) protein remained high in these cells, whereas there was no phosporylated Rb in VHL (+) cells under the contact inhibition. The abnormal expression of cyclinD1 at a high cell density was observed even in VHL (+) cells under the hypoxic state. Moreover, ectopic expression of a HIF mutant resistant to pVHL-mediated proteolysis causes the abnormal cyclinD1 expression in VHL (+) cells. Taken together, these observations indicate that VHL is required for the downregulation of cyclinD1 at a high cell density through HIF.
Collapse
Affiliation(s)
- Masaya Baba
- Department of Molecular Biology, Yokohama City University School of Medicine, 3-9, Fuko-ura, Kanazawaka-ku, Yokohama 236-0004, Japan
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|