Transcriptional up-regulation of FoxM1 in response to hypoxia is mediated by HIF-1

Combining Bevacizumab with Radiation or Chemoradiation for Solid Tumors: A Review of the Scientific Rationale, and Clinical Trials

Radiation therapy or the combination of radiation and chemotherapy is an important component in the local control of many tumor types including glioblastoma, rectal cancer, and pancreatic cancer. The addition of anti-angiogenic agents to chemotherapy is now standard treatment for a variety of metastatic cancers including colorectal cancer and non-squamous cell lung cancer. Anti-angiogenic agents can increase the efficacy of radiation or chemoradiation for primary tumors through mechanisms such as vascular normalization and augmentation of endothelial cell injury. The most commonly used anti-angiogenic drug, bevacizumab, is a humanized monoclonal antibody that binds and neutralizes vascular endothelial growth factor A (VEGF-A). Dozens of preclinical studies nearly uniformly demonstrate that inhibition of VEGF-A or its receptors potentiates the effects of radiation therapy against solid tumors, and this potentiation is generally independent of the type or schedule of radiation and timing of VEGF-A inhibitor delivery. There are now several clinical trials combining bevacizumab with radiation or chemoradiation for the local control of various primary, recurrent, and metastatic tumors, and many of these early trials show encouraging results. Some added toxicities occur with the delivery of bevacizumab but common toxicities such as hypertension and proteinuria are generally easily managed while severe toxicities are rare. In the future, bevacizumab and other anti-angiogenic agents may become common additions to radiation and chemoradiation regimens for tumors that are difficult to locally control.

Overcoming evasive resistance from vascular endothelial growth factor a inhibition in sarcomas by genetic or pharmacologic targeting of hypoxia-inducible factor 1α

Increased levels of hypoxia and hypoxia-inducible factor 1α (HIF-1α) in human sarcomas correlate with tumor progression and radiation resistance. Prolonged antiangiogenic therapy of tumors not only delays tumor growth but may also increase hypoxia and HIF-1α activity. In our recent clinical trial, treatment with the vascular endothelial growth factor A (VEGF-A) antibody, bevacizumab, followed by a combination of bevacizumab and radiation led to near complete necrosis in nearly half of sarcomas. Gene Set Enrichment Analysis of microarrays from pretreatment biopsies found that the Gene Ontology category “Response to hypoxia” was upregulated in poor responders and that the hierarchical clustering based on 140 hypoxia-responsive genes reliably separated poor responders from good responders. The most commonly used chemotherapeutic drug for sarcomas, doxorubicin (Dox), was recently found to block HIF-1α binding to DNA at low metronomic doses. In four sarcoma cell lines, HIF-1α shRNA or Dox at low concentrations blocked HIF-1α induction of VEGF-A by 84–97% and carbonic anhydrase 9 by 83–93%. HT1080 sarcoma xenografts had increased hypoxia and/or HIF-1α activity with increasing tumor size and with anti-VEGF receptor antibody (DC101) treatment. Combining DC101 with HIF-1α shRNA or metronomic Dox had a synergistic effect in suppressing growth of HT1080 xenografts, at least in part via induction of tumor endothelial cell apoptosis. In conclusion, sarcomas respond to increased hypoxia by expressing HIF-1α target genes that may promote resistance to antiangiogenic and other therapies. HIF-1α inhibition blocks this evasive resistance and augments destruction of the tumor vasculature.

Hypoxia-induced pulmonary arterial smooth muscle cell proliferation is controlled by forkhead box M1

Pulmonary arterial hypertension (PAH) is a devastating disease, and no effective treatments are available. Hypoxia-induced pulmonary artery remodeling, including smooth muscle cell proliferation, contributes to PAH, but the exact mechanisms underlying this abnormal process are largely undefined. The forkhead box M1 (FoxM1) transcription factor regulates cancer cell growth by modulating gene expression critical for cell cycle progression. Here, we report for the first time, to the best of our knowledge, a novel function of FoxM1 in the hypoxia-stimulated proliferation of human pulmonary artery smooth muscle cells (HPASMCs). Exposure to hypoxia caused a marked up-regulation of FoxM1 gene expression, mainly at the transcription level, and this induction correlated with HPASMC cell proliferation. The knockdown of FoxM1 inhibited the hypoxia-stimulated proliferation of HPASMCs. We found that the knockdown of HIF-2α, but not HIF-1α, diminished FoxM1 induction in response to hypoxia. However, the knockdown of FoxM1 did not alter expression levels of HIF-2α or HIF-1α, suggesting that HIF-2α is an upstream regulator of FoxM1. Furthermore, the knockdown of FoxM1 prevented the hypoxia-induced expression of aurora A kinase and cyclin D1. Collectively, our results suggest that hypoxia induces FoxM1 gene expression in an HIF-2α-dependent pathway, thereby promoting HPASMC proliferation.

Increased expression of FoxM1 transcription factor in respiratory epithelium inhibits lung sacculation and causes Clara cell hyperplasia

Foxm1 is a member of the Forkhead Box (Fox) family of transcription factors. Foxm1 (previously called Foxm1b, HFH-11B, Trident, Win, or MPP2) is expressed in multiple cell types and plays important roles in cellular proliferation, differentiation and tumorigenesis. Genetic deletion of Foxm1 from mouse respiratory epithelium during initial stages of lung development inhibits lung maturation and causes respiratory failure after birth. However, the role of Foxm1 during postnatal lung morphogenesis remains unknown. In the present study, Foxm1 expression was detected in epithelial cells of conducting and peripheral airways and changing dynamically with lung maturation. To discern the biological role of Foxm1 in the prenatal and postnatal lung, a novel transgenic mouse line that expresses a constitutively active form of FoxM1 (FoxM1 N-terminal deletion mutant or FoxM1-ΔN) under the control of lung epithelial-specific SPC promoter was produced. Expression of the FoxM1-ΔN transgene during embryogenesis caused epithelial hyperplasia, inhibited lung sacculation and expression of the type II epithelial marker, pro-SPC. Expression of FoxM1-ΔN mutant during the postnatal period did not influence alveologenesis but caused focal airway hyperplasia and increased proliferation of Clara cells. Likewise, expression of FoxM1-ΔN mutant in conducting airways with Scgb1a1 promoter was sufficient to induce Clara cell hyperplasia. Furthermore, FoxM1-ΔN cooperated with activated K-Ras to induce lung tumor growth in vivo. Increased activity of Foxm1 altered lung sacculation, induced proliferation in the respiratory epithelium and accelerated lung tumor growth, indicating that precise regulation of Foxm1 is critical for normal lung morphogenesis and development of lung cancer.

HIF-1alpha partners with FoxA2, a neuroendocrine-specific transcription factor, to promote tumorigenesis

In this issue of Cancer Cell, Qi et al. report a novel mechanism by which HIF-1alpha synergizes with a tissue-specific transcription factor, FoxA2, to promote a transcriptional program that supports prostate tumor formation and progression.

Advances in understanding the relationship between hepatic hypoxia-inducible factor-1 alpha and hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is characterized by hypoxia due to robust cell proliferation. Hypoxia can promote tumor cell proliferation, metastasis and neovasculogenesis, inhibit differentiation and apoptosis, and decrease chemosensitivity and radiosensitivity. Hypoxia-inducible factor-1α (HIF-1α) is a key mediator of physiological and pathological hypoxia response and controls the transcription of numerous genes that are of pivotal importance for angiogenesis and cellular metabolism. Therefore, HIF-1α is closely related with the proliferation, metastasis and apoptosis of HCC cells. Recently, HIF-1α-based gene therapy has become a novel adjunctive strategy for the management of HCC. This review focuses on the relationship between HIF-1α and the progression and therapy of HCC.

Forkhead box M1 transcription factor: a novel target for cancer therapy

FoxM1 signaling has been reported to be associated with carcinogenesis. Therefore, the FoxM1 may represent a novel therapeutic target, and thus the development of agents that will target FoxM1 is likely to have significant therapeutic impact on human cancer. This review describes the mechanisms of signal transduction associated with FoxM1 and provides emerging evidence in support of its role in the carcinogenesis. Further, we summarize data on several FoxM1 inhibitors especially "chemopreventive agents" and these agents could be useful for targeted inactivation of FoxM1, which indeed could become a novel approach for the prevention and/or treatment of human cancer.

Pro-proliferative FoxM1 is a target of p53-mediated repression

The p53 tumor suppressor protein acts as a transcription factor to modulate cellular responses to a wide variety of stresses. In this study we show that p53 is required for the downregulation of FoxM1, an essential transcription factor that regulates many G2/M-specific genes and is overexpressed in a multitude of solid tumors. After DNA damage, p53 facilitates the repression of FoxM1 mRNA, which is accompanied by a decrease in FoxM1 protein levels. In cells with reduced p53 expression, FoxM1 is upregulated after DNA damage. Nutlin, a small-molecule activator of p53, suppresses FoxM1 levels in two cell lines in which DNA damage facilitates only mild repression. Mechanistically, p53-mediated inhibition of FoxM1 is partially p21 and retinoblastoma (Rb) family dependent, although in some cases p21-independent repression of FoxM1 was also observed. The importance of FoxM1 to cell fate was indicated by the observation that G2/M arrest follows FoxM1 ablation. Finally, our results indicate a potential contribution of p53-mediated repression of FoxM1 for maintenance of a stable G2 arrest.