The hypoxia-inducible transcription factors (HIFs) directly and indirectly mediate cellular adaptation to reduced oxygen tensions. Recent studies have shown that the histone demethylase genes JMJD1A, JMJD2B, and JARID1B are HIF targets, suggesting that HIFs indirectly influence gene expression at the level of histone methylation under hypoxia. In this study, we identify a subset of hypoxia-inducible genes that are dependent on JMJD1A in both renal cell and colon carcinoma cell lines. JMJD1A regulates the expression of adrenomedullin (ADM) and growth and differentiation factor 15 (GDF15) under hypoxia by decreasing promoter histone methylation. In addition, we demonstrate that loss of JMJD1A is sufficient to reduce tumor growth in vivo, demonstrating that histone demethylation plays a significant role in modulating growth within the tumor microenvironment. Thus, hypoxic regulation of JMJD1A acts as a signal amplifier to facilitate hypoxic gene expression, ultimately enhancing tumor growth.Cellular hypoxia occurs when the demands of growth and metabolism of a tissue surpass the vascular oxygen supply. In response to hypoxia, cells undergo specific alterations in gene expression patterns geared to promote cell survival and maintain homeostasis. This response not only is important in normal development but also is a critical part in the progression of cancers (7). Hypoxia has been implicated in activating the metabolic shift to anaerobic glycolysis, promoting the epithelial-to-mesenchymal transition (EMT), inducing the secretion of proangiogenic factors, and remodeling the extracellular matrix. Although several transcription programs are activated in response to hypoxia, the hypoxia-inducible factors (HIFs) regulate a critical repertoire of genes, making them central regulators of the cellular response to hypoxia (10, 34).The HIFs are heterodimeric transcription factors consisting of an oxygen-sensitive alpha subunit (HIF-1␣, HIF-2␣, or HIF-3␣) and a constitutively expressed HIF-1␤ subunit (also known as the arylhydrocarbon nuclear translocator [ARNT]). Under conditions where oxygen concentration is not limiting, HIF-␣ subunits are hydroxylated by prolyl-hydroxylases, targeting them for ubiquitin-mediated degradation by the von Hippel-Lindau tumor suppressor (VHL) (18,19). Under hypoxic conditions, HIF-␣ protein is stabilized, translocates to the nucleus, dimerizes with ARNT, and binds hypoxia-responsive elements (HREs) in the regulatory regions of target genes (51). HIF-1␣ and HIF-2␣ will bind the same sequences in cells but do not have completely overlapping abilities to regulate genes (5, 17, 44). Under certain conditions, HIF-3␣ functions as a dominant negative, antagonizing the activity of HIF-1 and HIF-2 (32).Several hundred genes are induced in response to hypoxia, and a great deal of research has been focused on identifying direct HIF target genes (34). The massive transcriptional reorganization mediated by hypoxia and HIFs suggests that changes in histone modification would create epigenetic reinforcement o...

Dysregulation of the von Hippel-Lindau/hypoxia-inducible transcription factor (HIF) signaling pathway promotes clear cell renal cell carcinoma (ccRCC) progression and metastasis. The protein kinase GAS6/AXL signaling pathway has recently been implicated as an essential mediator of metastasis and receptor tyrosine kinase crosstalk in cancer. Here we establish a molecular link between HIF stabilization and induction of AXL receptor expression in metastatic ccRCC. We found that HIF-1 and HIF-2 directly activate the expression of AXL by binding to the hypoxia-response element in the AXL proximal promoter. Importantly, genetic and therapeutic inactivation of AXL signaling in metastatic ccRCC cells reversed the invasive and metastatic phenotype in vivo. Furthermore, we define a pathway by which GAS6/AXL signaling uses lateral activation of the met proto-oncogene (MET) through SRC proto-oncogene nonreceptor tyrosine kinase to maximize cellular invasion. Clinically, AXL expression in primary tumors of ccRCC patients correlates with aggressive tumor behavior and patient lethality. These findings provide an alternative model for SRC and MET activation by growth arrest-specific 6 in ccRCC and identify AXL as a therapeutic target driving the aggressive phenotype in renal clear cell carcinoma.targeted therapy | kidney cancer | VHL | hepatocellular carcinoma K idney cancer is a leading cause of cancer-related deaths in the United States. Metastasis to distant organs including the lung, bone, liver, and brain is the primary cause of death in kidney cancer patients, as only 12% of patients with metastatic kidney cancer will survive past 5 y, in comparison with 92% of patients with a localized disease (1). Because kidney cancer is chemo-and radiation-resistant, targeted therapies are needed for the prevention and management of metastatic kidney cancer.The von Hippel-Lindau (VHL)-hypoxia-inducible transcription factor (HIF) pathway is a critical regulator of clear cell renal cell carcinoma (ccRCC) tumor initiation and metastasis. VHL is a classic tumor suppressor controlling tumor initiation in ∼90% of ccRCC tumors (2, 3). VHL is the substrate recognition component of an E3 ubiquitin ligase complex containing the elongins B and C (4, 5), Cullin-2 (6), and Rbx1 (7) that targets the hydroxylated, oxygen-sensitive α-subunits of HIFs (HIF-1, -2, and -3) for ubiquitination and degradation by the 26S proteasome (8, 9). Thus, the primary function ascribed to VHL is the regulation of HIF protein stability. In VHL-deficient tumors, HIF transcriptional activity is constitutively active and contributes to both ccRCC tumor initiation and metastasis (8-11). Although many downstream HIF targets controlling ccRCC tumor initiation have been defined, key targets involved in ccRCC metastasis remain to be identified.AXL, a member of the TAM family of receptor tyrosine kinases (RTKs), has recently been described as an essential mediator of cancer metastasis. Additionally, AXL has been reported to mediate RTK crosstalk and resistance to targeted kina...

The receptor tyrosine kinase AXL is thought to play a role in metastasis, but the therapeutic efficacy of an AXL targeting agent remains largely untested in metastatic disease. In this study, we defined AXL as a therapeutic target for metastatic ovarian cancer. AXL is primarily expressed in metastases and advanced stage human ovarian tumors but not in normal ovarian epithelium. Genetic inhibition of AXL in human metastatic ovarian tumor cells is sufficient to prevent the initiation of metastatic disease in vivo. Mechanistically, inhibition of AXL signaling in animals with metastatic disease results in decreased invasion and MMP activity. Most importantly, soluble human AXL receptors that imposed a specific blockade of the GAS6/AXL pathway had a profound inhibitory effect on progression of established metastatic ovarian cancer without normal tissue toxicity. These results offer the first genetic validation of GAS6/AXL targeting as an effective strategy for inhibition of metastatic tumor progression in vivo. Furthermore, this study defines soluble AXL receptor therapy as a therapeutic candidate agent treating metastatic ovarian cancer, where current therapies are ineffective.