Lysyl oxidase is essential for hypoxia-induced metastasis

Notch signaling mediates hypoxia-induced tumor cell migration and invasion

Tumor hypoxia is linked to increased metastatic potential, but the molecular mechanisms coupling hypoxia to metastasis are poorly understood. Here, we show that Notch signaling is required to convert the hypoxic stimulus into epithelial-mesenchymal transition (EMT), increased motility, and invasiveness. Inhibition of Notch signaling abrogated hypoxia-induced EMT and invasion, and, conversely, an activated form of Notch could substitute for hypoxia to induce these processes. Notch signaling deploys two distinct mechanisms that act in synergy to control the expression of Snail-1, a critical regulator of EMT. First, Notch directly up-regulated Snail-1 expression by recruitment of the Notch intracellular domain to the Snail-1 promoter, and second, Notch potentiated hypoxia-inducible factor 1alpha (HIF-1alpha) recruitment to the lysyl oxidase (LOX) promoter and elevated the hypoxia-induced up-regulation of LOX, which stabilizes the Snail-1 protein. In sum, these data demonstrate a complex integration of the hypoxia and Notch signaling pathways in regulation of EMT and open up perspectives for pharmacological intervention with hypoxiainduced EMT and cell invasiveness in tumors.

Regulation of hypoxia-inducible genes by ETS1 transcription factor

Hypoxia-inducible factor (HIF-1) regulates the expression of genes that facilitate tumor cell survival by making them more resistant to therapeutic intervention. Recent evidence suggests that the activation of other transcription factors, in cooperation with HIF-1 or acting alone, is involved in the upregulation of hypoxia-inducible genes. Here we report that high cell density, a condition that might mimic the physiologic situation in growing tumor and most probably representing nutritional starvation, upregulates hypoxia-inducible genes. This upregulation can occur in HIF-independent manner since hypoxia-inducible genes carbonic anhydrase 9 (CA9), lysyloxidase like 2 (LOXL2) and n-myc-down regulated 1 (NDRG1)/calcium activated protein (Cap43) can be upregulated by increased cell density under both normoxic and hypoxic conditions in both HIF-1 alpha-proficient and -deficient mouse fibroblasts. Moreover, cell density upregulates the same genes in 1HAEo- and A549 human lung epithelial cells. Searching for other transcription factors involved in the regulation of hypoxia-inducible genes by cell density, we focused our attention on ETS1. As reported previously, members of v-ets erythroblastosis virus E26 oncogene homolog (ETS) family transcription factors participate in the upregulation of hypoxia-inducible genes. Here, we provide evidence that ETS1 protein is upregulated at high cell density in both human and mouse cells. The involvement of ETS1 in the upregulation of hypoxia-inducible genes was further confirmed in a luciferase reporter assay using cotransfection of ETS1 expression vector with NDRG1/Cap43 promoter construct. The downregulation of ETS1 expression with small interfering RNA (siRNA) inhibited the upregulation of CA9 and NDRG1/Cap43 caused by increased cell density. Collectively, our data indicate the involvement of ETS1 along with HIF-1 in regulating hypoxia-inducible genes.

Cancer stem cells: implications for the progression and treatment of metastatic disease

Metastasis is the major cause of death for cancer patients with solid tumours, due mainly to the ineffectiveness of current therapies once metastases begin to form. Further insight into the biology of metastasis is therefore essential in order to gain a greater understanding of this process and ultimately to develop better cancer therapies. Metastasis is an inefficient process, such that very few cells that leave a tumour successfully form macrometastases in distant sites. This suggests that only a small subset of cells can successfully navigate the metastatic cascade and eventually re-initiate tumour growth to form life-threatening metastases. Recently, there has been growing support for the cancer stem cell (CSC) hypothesis which stipulates that primary tumours are initiated and maintained by a small subpopulation of cancer cells that possess "stem-like" characteristics. Classical properties of normal stem cells are strikingly reminiscent of the observed experimental and clinical behaviour of metastatic cancer cells, including an unlimited capacity for self renewal; the requirement for a specific 'niche' or microenvironment to grow; use of the stromal cell-derived factor 1 (SDF-1)/chemokine receptor 4 (CXCR4) axis for migration; enhanced resistance to apoptosis and an increased capacity for drug resistance. Therefore, in addition to playing a role in primary tumour formation, we believe that CSCs are also key players in the metastatic process. We will review the current evidence supporting this idea and discuss the potential implications of the CSC hypothesis with regards to experimental investigation and treatment of metastatic disease.

Recent advances in metastasis research

Advances in the early prediction, detection, and treatment of metastatic disease has improved the outlook in cancer patients in recent decades, however, metastasis remains the major cause of death in affected individuals. Metastasis occurs in a series of discreet biological steps in which a single, frequently clinically occult micrometastatic cell travels from the primary tumor to a distant location, where it lodges, grows, and ultimately results in the patient's death. Recent work has provided many new insights in the mechanisms and biology behind metastatic spread. This short review surveys some of the most important recent developments that have helped increase our understanding of the three broad phases of metastasis - the genesis of the metastatic cell through the loss of local constraints in the primary tumor microenvironment, dissemination of the cell to a distant organ while avoiding immune surveillance, and finally lodging and growth of the overt metastasis. These studies are providing mounting evidence that the interactions between tumor and normal cells and tissues are critical for disease progression - a paradigm that will provide a fertile area for future research.

Hypoxia and metabolism. Hypoxia, DNA repair and genetic instability

Areas of hypoxic tumour tissue are known to be resistant to treatment and are associated with a poor clinical prognosis. There are several reasons why this might be, including the capacity of hypoxia to drive genomic instability and alter DNA damage repair pathways. Significantly, current models fail to distinguish between the complexities of the hypoxic microenvironment and the biological effects of acute hypoxia exposures versus longer-term, chronic hypoxia exposures on the transcription and translation of proteins involved in genetic stability and cell survival. Acute and chronic hypoxia might lead to different biology within the tumour and this might have a direct effect on the design of new therapies for the treatment of hypoxic tumours.

Direct regulation of TWIST by HIF-1alpha promotes metastasis

Stabilization of the hypoxia-inducible factor-1alpha (HIF-1alpha) transcription complex, caused by intratumoural hypoxia, promotes tumour progression and metastasis, leading to treatment failure and mortality in different types of human cancers. The transcription factor TWIST is a master regulator of gastrulation and mesoderm-specification and was implicated recently as an essential mediator of cancer metastasis. Notably, HIF-1alpha- and TWIST-null mice show similarities in their phenotypes. Here, we have shown that hypoxia or overexpression of HIF-1alpha promotes epithelial-mesenchymal transition (EMT) and metastastic phenotypes. We also found that HIF-1 regulates the expression of TWIST by binding directly to the hypoxia-response element (HRE) in the TWIST proximal promoter. However, siRNA-mediated repression of TWIST in HIF-1alpha-overexpressing or hypoxic cells reversed EMT and metastastic phenotypes. Co-expression of HIF-1alpha, TWIST and Snail in primary tumours of patients with head and neck cancers correlated with metastasis and the worst prognosis. These results provide evidence of a key signalling pathway involving HIF-1alpha and TWIST that promotes metastasis in response to intratumoural hypoxia.

The role of hypoxia-inducible factors in tumorigenesis

Hypoxia-inducible factors (HIFs) are essential mediators of the cellular oxygen-signaling pathway. They are heterodimeric transcription factors consisting of an oxygen-sensitive alpha subunit (HIF-alpha) and a constitutive beta subunit (HIF-beta) that facilitate both oxygen delivery and adaptation to oxygen deprivation by regulating the expression of genes that control glucose uptake, metabolism, angiogenesis, erythropoiesis, cell proliferation, and apoptosis. In most experimental models, the HIF pathway is a positive regulator of tumor growth as its inhibition often results in tumor suppression. In clinical samples, HIF is found elevated and correlates with poor patient prognosis in a variety of cancers. In summary, HIF regulates multiple aspects of tumorigenesis, including angiogenesis, proliferation, metabolism, metastasis, differentiation, and response to radiation therapy, making it a critical regulator of the malignant phenotype.

Biology of hypoxia-inducible factor-2alpha in development and disease

The transcriptional response to hypoxia is primarily mediated by two hypoxia-inducible factors--HIF-1alpha and HIF-2alpha. While these proteins are highly homologous, increasing evidence suggests they have unique transcriptional targets and differential impact on tumor growth. Furthermore, non-transcriptional effects of the HIF-alpha subunits, including effects on the Notch and c-Myc pathways, contribute to their distinct functions. HIF-2alpha transcriptional targets include genes involved in erythropoiesis, angiogenesis, metastasis, and proliferation. Therefore, HIF-2alpha contributes significantly to both normal physiology as well as tumorigenesis. Here, we summarize the function of HIF-2alpha during development as well as its contribution to pathologic conditions, such as tumors and vascular disease.

Biology of HIF-1alpha

The increase in body size of humans and other vertebrates requires a physiological infrastructure to provide adequate delivery of oxygen to tissues and cells to maintain oxygen homeostasis. The heart, lungs and the vasculature are all part of a highly regulated system that ensures the distribution of the precise amount of oxygen needed throughout the mammalian organism. Given its fundamental impact on physiology and pathology, it is no surprise that the response of cells to a lack of oxygen, termed hypoxia, has been the focus of many research groups worldwide for many decades now. The transcriptional complex hypoxia-inducible factor has emerged as a key regulator of the molecular hypoxic response, mediating a wide range of physiological and cellular mechanisms necessary to adapt to reduced oxygen.

Hypoxia promotes fibrogenesis in vivo via HIF-1 stimulation of epithelial-to-mesenchymal transition

Hypoxia has been proposed as an important microenvironmental factor in the development of tissue fibrosis; however, the underlying mechanisms are not well defined. To examine the role of hypoxia-inducible factor-1 (HIF-1), a key mediator of cellular adaptation to hypoxia, in the development of fibrosis in mice, we inactivated Hif-1alpha in primary renal epithelial cells and in proximal tubules of kidneys subjected to unilateral ureteral obstruction (UUO) using Cre-loxP-mediated gene targeting. We found that Hif-1alpha enhanced epithelial-to-mesenchymal transition (EMT) in vitro and induced epithelial cell migration through upregulation of lysyl oxidase genes. Genetic ablation of epithelial Hif-1alpha inhibited the development of tubulointerstitial fibrosis in UUO kidneys, which was associated with decreased interstitial collagen deposition, decreased inflammatory cell infiltration, and a reduction in the number of fibroblast-specific protein-1-expressing (FSP-1-expressing) interstitial cells. Furthermore, we demonstrate that increased renal HIF-1alpha expression is associated with tubulointerstitial injury in patients with chronic kidney disease. Thus, we provide clinical and genetic evidence that activation of HIF-1 signaling in renal epithelial cells is associated with the development of chronic renal disease and may promote fibrogenesis by increasing expression of extracellular matrix-modifying factors and lysyl oxidase genes and by facilitating EMT.

Hypoxia-inducible factor signaling in the development of tissue fibrosis

Capillary rarefaction is a hallmark of fibrotic diseases and results in reduced blood perfusion and oxygen delivery. In the kidney, tubulointerstitial fibrosis, which leads to the destruction of renal tissue and the irreversible loss of kidney function, is associated with hypoxia and the activation of Hypoxia-Inducible-Factor (HIF) signaling. HIF-1 and HIF-2 are basic-helix-loop-helix transcription factors that allow cells to survive in a low oxygen environment by regulating energy metabolism, vascular remodeling, erythropoiesis, cellular proliferation and apoptosis. Recent studies suggest that HIF activation promotes epithelial to mesenchymal transition (EMT) and renal fibrogenesis. These findings raise the possibility that the spectrum of HIF activated biological responses to hypoxic stress may differ under conditions of acute and chronic hypoxia. Here we discuss the role of HIF signaling in the pathogenesis and progression of chronic kidney disease.

Graded hypoxia modulates the invasive potential of HT1080 fibrosarcoma and MDA MB231 carcinoma cells

Spatial and temporal oxygen heterogeneity exists in most solid tumour microenvironments due to an inadequate vascular network supplying a dense population of tumour cells. An imbalance between oxygen supply and demand leads to hypoxia within a significant proportion of a tumour, which has been correlated to the likelihood of metastatic dissemination in both rodent tumour models and human patients. Experimentally, it has been demonstrated that near-anoxic in vitro exposure results in transiently increased metastatic potential in some tumour cell lines. The purpose of this study was to examine the effect of graded low oxygen conditions on the invasive phenotype of human tumour cells using an in vitro model of basement membrane invasion, in which we measured oxygen availability directly at the invasion surface of the transwell chamber. Our results show a relationship between culture vessel geometry and time to achieve hypoxia which may affect the interpretation of low oxygen experiments. We exposed the human tumour cell lines, HT1080 and MDA MB231, to graded normobaric oxygen (5% O(2)-0.2% O(2)) either during or prior to in vitro basement membrane invasion to simulate conditions of intravasation and extravasation. A secondary aim was to investigate the potential regulation of matrix metalloproteinase activity by oxygen availability. We identified significant reductions in invasive ability under low oxygen conditions for the HT1080 cell line and an increase in invasion at intermediate oxygen conditions for the MDA MB231 cell line. There were differences in the absolute activity of the individual matrix metalloproteinases, MMP-2, -9, -14, between the two cell lines, however there were no significant changes following exposure to hypoxic conditions. This study demonstrates cell line specific effects of graded oxygen levels on invasive potential and suggests that intermediate levels of low oxygen may increase metastatic dissemination.

Evaluating distant metastases in breast cancer: from biology to outcomes

There is an urgent need to understand distant metastases in breast cancer as they are the most lethal form of recurrence and a major cause of mortality in patients. Some predictors for distant metastases, including nodal status, tumor grade, and hormonal status, are useful in identifying patients at increased risk for distant metastases. Adjuvant endocrine therapy has been the treatment of choice for postmenopausal women with hormone-sensitive breast cancer, and some therapies have shown significant reductions in the risk of distant metastases. Skeletal metastases in breast cancer are treated with bisphosphonates with a certain level of success. With more new agents undergoing clinical trials, a thorough review of the specific and long-term safety of these agents is essential, as is a better understanding of the deterioration in the quality of life and cost concerns of patients who develop distant metastases. Gene-expression profiling is a new entrant in the field of distant metastases diagnosis, which is largely successful in defining gene signatures that predict the development of distant metastases. This review will discuss the biology and the impact of distant metastases on outcomes for patients with breast cancer; it also encompasses the current status, emerging focus, and future perspectives in treatment of skeletal metastases in patients with breast cancer.

Mechanisms operative in the antitumor activity of temozolomide in glioblastoma multiforme

PURPOSE

Glioblastoma multiforme (GBM) is the most frequent and incurable brain tumor in adults. Although temozolomide (TMZ) does not cure GBM, it has demonstrated anti-GBM activity and has improved survival (8-14 months) and quality of life. We studied the mechanisms by which TMZ affects 2 human GBM cell lines; U251-MG and U87-MG, aiming to unravel the drug-activated cascades to enable the development of combination therapies that will improve the efficacy of TMZ.

MATERIALS AND METHODS

The 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyltetrazolium assay was used to assess cell viability. Modulation of gene expression by TMZ therapy was assayed by gene profiling and verified by quantitative real-time polymerase chain reaction. Protein levels influenced by the treatment were studied by Western blots and immunocytochemistry.

RESULTS

Increasing concentrations of TMZ decreased cell viability in a concentration-dependent manner. The expression of 1,886 genes was altered >2-fold after TMZ treatment. We focused on the 81 genes similarly altered by TMZ treatment in both cell lines to neutralize tissue-specific characteristics. Fourteen target genes of hypoxia-inducible factor (HIF-1), were found to be up-regulated after TMZ treatment including vascular endothelial growth factor (VEGF). HIF-1alpha expression was constant at the mRNA level; however, its post-treatment protein levels increased compared with those of untreated control cells.

DISCUSSION

The genetic analyses suggest that treatment with TMZ activates stress mechanisms in GBM cells that include the angiogenesis-inducing proteins HIF-1alpha and VEGF. We propose that treatment with TMZ be supplemented with either an antibody to VEGF or down-regulators of HIF-1alpha to improve clinical results of TMZ in the treatment of GBM.

Prolyl 4-hydroxylases, key enzymes in the synthesis of collagens and regulation of the response to hypoxia, and their roles as treatment targets

Prolyl 4-hydroxylases (P4Hs) have central roles in the synthesis of collagens and the regulation of oxygen homeostasis. The 4-hydroxyproline residues generated by the endoplasmic reticulum (ER) luminal collagen P4Hs (C-P4Hs) are essential for the stability of the collagen triple helix. Vertebrate C-P4Hs are alpha2beta2 tetramers with three isoenzymes differing in their catalytic alpha subunits. Another P4H family, the HIF-P4Hs, hydroxylates specific prolines in the alpha subunit of the hypoxia-inducible transcription factor (HIF), a master regulator of hypoxia-inducible genes, and controls its stability in an oxygen-dependent manner. The HIF-P4Hs are cytoplasmic and nuclear enzymes, likewise with three isoenzymes in vertebrates. A third vertebrate P4H type is an ER transmembrane protein that can act on HIF-alpha but not on collagens. All P4Hs require Fe2+, 2-oxoglutarate, O2, and ascorbate. C-P4Hs are regarded as attractive targets for pharmacological inhibition to control excessive collagen accumulation in fibrotic diseases and severe scarring, while HIF-P4H inhibitors are believed to have beneficial effects in the treatment of diseases such as myocardial infarction, stroke, peripheral vascular disease, diabetes, and severe anemias. Studies with P4H inhibitors in various animal models of fibrosis, anemia, and ischemia and ongoing clinical trials with HIF-P4H inhibitors support this hypothesis by demonstrating efficacy in many applications.

Hypoxia inducible factor-1 independent pathways in tumor angiogenesis

Among the factors that can stimulate angiogenesis, vascular endothelial growth factor has emerged as one of the most important, and inhibition of vascular endothelial growth factor has recently shown efficacy in the treatment of advanced colorectal cancer. Hypoxia develops within solid tumors and is one of the most potent stimuli of vascular endothelial growth factor expression. This effect is mediated primarily by hypoxia inducible factor-1 (HIF-1), often considered a master regulator of angiogenesis in hypoxia. Consequently, inhibition of HIF-1 has been proposed as a strategy to block tumor angiogenesis therapeutically. However, accumulating evidence indicates that HIF-independent pathways can also control angiogenesis. This review highlights some of the key signaling pathways independent of HIF-1 that can stimulate angiogenesis in hypoxia. Understanding the full spectrum of molecular pathways that control tumor angiogenesis is critical for the optimal design of targeted therapies.

Strategic plans to promote head and neck cancer translational research within the radiation therapy oncology group: a report from the translational research program

Head and neck cancer is the fifth most common cancer in the United States, with an overall survival rate of approximately 40-50%. In an effort to improve patient outcomes, research efforts designed to maximize benefit and reduce toxicities of therapy are in progress. Basic research in cancer biology has accelerated this endeavor and provided preclinical data and technology to support clinically relevant advances in early detection, prognostic and predictive biomarkers. Recent completion of the Human Genome Project has promoted the rapid development of novel "omics" technologies that allow more broad based study from a systems biology perspective. However, clinically relevant application of resultant gene signatures to clinical trials within cooperative groups has advanced slowly. In light of the large numbers of variables intrinsic to biomarker studies, validation of preliminary data for clinical implementation presents a significant challenge and may only be realized with large trials that involve significant patient numbers. The Radiation Therapy Oncology Group (RTOG) Head and Neck Cancer Translational Research Program recognizes this problem and brings together three unique features to facilitate this research: (1) availability of large numbers of clinical specimens from homogeneously treated patients through multi-institutional clinical trials; (2) a team of physicians, scientists, and staff focused on patient-oriented head-and-neck cancer research with the common goal of improving cancer care; and (3) a funding mechanism through the RTOG Seed Grant Program. In this position paper we outline strategic plans to further promote translational research within the framework of the RTOG.

Hypoxia and cancer

A major feature of solid tumours is hypoxia, decreased availability of oxygen, which increases patient treatment resistance and favours tumour progression. How hypoxic conditions are generated in tumour tissues and how cells respond to hypoxia are essential questions in understanding tumour progression and metastasis. Massive tumour-cell proliferation distances cells from the vasculature, leading to a deficiency in the local environment of blood carrying oxygen and nutrients. Such hypoxic conditions induce a molecular response, in both normal and neoplastic cells, that drives the activation of a key transcription factor; the hypoxia-inducible factor. This transcription factor regulates a large panel of genes that are exploited by tumour cells for survival, resistance to treatment and escape from a nutrient-deprived environment. Although now recognized as a major contributor to cancer progression and to treatment failure, the precise role of hypoxia signalling in cancer and in prognosis still needs to be further defined. It is hoped that a better understanding of the mechanisms implicated will lead to alternative and more efficient therapeutic approaches.

Association of expression aberrances and genetic polymorphisms of lysyl oxidase with areca-associated oral tumorigenesis

PURPOSE

Areca nut use is the major cause of oral squamous cell carcinoma (OSCC) in Southern Asians. Areca nut contains a high level of free copper ions. Lysyl oxidase (LOX) is a copper-activated enzyme critical for extracellular matrix organization. Contradictory evidence has been put forward to suggest that LOX may be either an oncogenic or a suppressive element. This study investigated the oncogenic significance of LOX in areca-associated OSCC.

EXPERIMENTAL DESIGN

The expression assays and polymorphism analysis were done to know the clinicopathologic implications of LOX status in OSCC. Knockdown and overexpression experiments were conducted to know the phenotypic effects of LOX on OSCC cells.

RESULTS

Up-regulation of LOX mRNA and LOX protein expression in OSCCs relative to adjacent oral mucosa was found. Precancerous lesions had the highest LOX mRNA expression. Areca nut extract up-regulated LOX expression in oral epithelial cells. Knockdown of LOX induced cellular migration and invasion, but it reduced the anchorage-independent growth and xenographic tumorigenesis of OSCC cells. The reduction of migration and invasion by LOX overexpression was partially rescued by blockage of LOX activity. The Arg158Gln polymorphism was associated with earlier clinical stage of OSCC. Wild-type LOX overexpression induced anchorage-independent growth in OSCC cells, but this was not for LOXArg158Gln overexpression.

CONCLUSION

LOX exerts oncogenic roles in areca-associated OSCC. This potential could be affected by the existence of LOX propeptide domain or genetic polymorphism.

Mechanistic and prognostic significance of aberrant methylation in the molecular pathogenesis of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, accounting for an estimated 600,000 deaths annually. Aberrant methylation, consisting of DNA hypomethylation and/or promoter gene CpG hypermethylation, is implicated in the development of a variety of solid tumors, including HCC. We analyzed the global levels of DNA methylation as well as the methylation status of 105 putative tumor suppressor genes and found that the extent of genome-wide hypomethylation and CpG hypermethylation correlates with biological features and clinical outcome of HCC patients. We identified activation of Ras and downstream Ras effectors (ERK, AKT, and RAL) due to epigenetic silencing of inhibitors of the Ras pathway in all HCC. Further, selective inactivation of SPRY1 and -2, DAB2, and SOCS4 and -5 genes and inhibitors of angiogenesis (BNIP3, BNIP3L, IGFBP3, and EGLN2) was associated with poor prognosis. Importantly, several epigenetically silenced putative tumor suppressor genes found in HCC were also inactivated in the nontumorous liver. Our results assign both therapeutic and chemopreventive significance to methylation patterns in human HCC and open the possibility of using molecular targets, including those identified in this study, to effectively inhibit HCC development and progression.

Mechanistic and prognostic significance of aberrant methylation in the molecular pathogenesis of human hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is the fifth most common cancer worldwide, accounting for an estimated 600,000 deaths annually. Aberrant methylation, consisting of DNA hypomethylation and/or promoter gene CpG hypermethylation, is implicated in the development of a variety of solid tumors, including HCC. We analyzed the global levels of DNA methylation as well as the methylation status of 105 putative tumor suppressor genes and found that the extent of genome-wide hypomethylation and CpG hypermethylation correlates with biological features and clinical outcome of HCC patients. We identified activation of Ras and downstream Ras effectors (ERK, AKT, and RAL) due to epigenetic silencing of inhibitors of the Ras pathway in all HCC. Further, selective inactivation of SPRY1 and -2, DAB2, and SOCS4 and -5 genes and inhibitors of angiogenesis (BNIP3, BNIP3L, IGFBP3, and EGLN2) was associated with poor prognosis. Importantly, several epigenetically silenced putative tumor suppressor genes found in HCC were also inactivated in the nontumorous liver. Our results assign both therapeutic and chemopreventive significance to methylation patterns in human HCC and open the possibility of using molecular targets, including those identified in this study, to effectively inhibit HCC development and progression.

Expression and prognostic significance of a panel of tissue hypoxia markers in head-and-neck squamous cell carcinomas

PURPOSE

To investigate the expression pattern of hypoxia-induced proteins identified as being involved in malignant progression of head-and-neck squamous cell carcinoma (HNSCC) and to determine their relationship to tumor pO(2) and prognosis.

METHODS AND MATERIALS

We performed immunohistochemical staining of hypoxia-induced proteins (carbonic anhydrase IX [CA IX], BNIP3L, connective tissue growth factor, osteopontin, ephrin A1, hypoxia inducible gene-2, dihydrofolate reductase, galectin-1, IkappaB kinase beta, and lysyl oxidase) on tumor tissue arrays of 101 HNSCC patients with pretreatment pO(2) measurements. Analysis of variance and Fisher's exact tests were used to evaluate the relationship between marker expression, tumor pO(2), and CA IX staining. Cox proportional hazard model and log-rank tests were used to determine the relationship between markers and prognosis.

RESULTS

Osteopontin expression correlated with tumor pO(2) (Eppendorf measurements) (p = 0.04). However, there was a strong correlation between lysyl oxidase, ephrin A1, and galectin-1 and CA IX staining. These markers also predicted for cancer-specific survival and overall survival on univariate analysis. A hypoxia score of 0-5 was assigned to each patient, on the basis of the presence of strong staining for these markers, whereby a higher score signifies increased marker expression. On multivariate analysis, increasing hypoxia score was an independent prognostic factor for cancer-specific survival (p = 0.015) and was borderline significant for overall survival (p = 0.057) when adjusted for other independent predictors of outcomes (hemoglobin and age).

CONCLUSIONS

We identified a panel of hypoxia-related tissue markers that correlates with treatment outcomes in HNSCC. Validation of these markers will be needed to determine their utility in identifying patients for hypoxia-targeted therapy.

Hypoxia enhances metastatic efficiency in HT1080 fibrosarcoma cells by increasing cell survival in lungs, not cell adhesion and invasion

This study examined possible mechanisms for hypoxia-increased metastasis in a green fluorescent protein-labeled human fibrosarcoma cell line (HT1080). The efficiency of the lung arrest of tumor cells, which can be dependent on the adhesive potential of the tumor cells, was assessed by measuring the level of integrin alpha3beta1 protein and by adhesion assays, whereas the extravasation potential was examined by an invasion assay. These properties were not changed by exposure to hypoxia, indicating that lung arrest and extravasation are unlikely to play a major role in the effect of hypoxia on metastasis in this model. The main effect of hypoxic exposure was found to be increased survival after lung arrest as determined by clonogenic assay of tumor cells recovered from mouse lungs after i.v. injection. Concomitantly, apoptosis was identified as responsible for the death of lung-arrested cells, suggesting the involvement of an altered apoptotic response following hypoxic exposure of these cells. Consistent with this finding, we found that the effect of hypoxia on both increased metastasis and survival of arrested cells was inhibited by treatment with farnesylthiosalicylic acid. However, this effect was not due to down-regulation of hypoxia-inducible factor-1alpha, a mechanism of action of this drug reported by previous studies. Further detailed studies of the mechanisms of action of the drug are needed.

Hypoxia-inducible factors and cancer

Decreased oxygen availability is a common feature during embryonic development as well of malignant tumours. Hypoxia regulates many transcription factors, and one of the most studied is the hypoxia-inducible factor (HIF). As a consequence of HIF stabilisation, the cell constitutively upregulates the hypoxic programme resulting in the expression of genes responsible for global changes in cell proliferation, angiogenesis, metastasis, invasion, de-differentiation and energy metabolism. Of the three known alpha subunits of HIF transcription factors, HIF-1alpha and HIF-2alpha have been the most studied. Their differential expression and function have been widely discussed, however no clear picture has been drawn on how these two transcription factors differently regulate common and unique target genes. Their role as oncogenes has also been suggested in several studies. In this review we provide an overview of the current knowledge on some of the most important aspects of HIFalpha regulation, its role in tumour angiogenesis and energetic metabolism. We also give an overview of how the modulation of HIF regulating pathways is a potential therapeutic target that may have benefits in the treatment of cancer.

Hypoxic radiosensitization: adored and ignored

Since observations from the beginning of the last century, it has become well established that solid tumors may contain oxygen-deficient hypoxic areas and that cells in such areas may cause tumors to become radioresistant. Identifying hypoxic cells in human tumors has improved by the help of new imaging and physiologic techniques, and a substantial amount of data indicates the presence of hypoxia in many types of human tumors, although with a considerable heterogeneity among individual tumors. Controlled clinical trials during the last 40 years have indicated that this source of radiation resistance can be eliminated or modified by normobaric or hyperbaric oxygen or by the use of nitroimidazoles as hypoxic radiation sensitizers. More recently, attention has been given to hypoxic cytotoxins, a group of drugs that selectively or preferably destroys cells in a hypoxic environment. An updated systematic review identified 10,108 patients in 86 randomized trials designed to modify tumor hypoxia in patients treated with curative attempted primary radiation therapy alone. Overall modification of tumor hypoxia significantly improved the effect of radiotherapy, with an odds ratio of 0.77 (95% CI, 0.71 to 0.86) for the outcome of locoregional control and with an associated significant overall survival benefit (odds ratio = 0.87; 95% CI, 0.80 to 0.95). No significant influence was found on the incidence of distant metastases or on the risk of radiation-related complications. Ample data exist to support a high level of evidence for the benefit of hypoxic modification. However, hypoxic modification still has no impact on general clinical practice.

Review: implications of in vitro research on the effect of radiotherapy and chemotherapy under hypoxic conditions

As it is now well established that human solid tumors frequently contain a substantial fraction of cells that are hypoxic, more and more in vitro research is focusing on the impact of hypoxia on the outcome of radiotherapy and chemotherapy. Indeed, the efficacy of irradiation and many cytotoxic drugs relies on an adequate oxygen supply. Consequently, hypoxic regions in solid tumors often contain viable cells that are intrinsically more resistant to treatment with radiotherapy or chemotherapy. Moreover, efforts have been made to exploit hypoxia as a potential difference between malignant and normal tissues.Nowadays, a body of evidence indicates that oxygen deficiency clearly influences some major intracellular pathways such as those involved in cell proliferation, cell cycle progression, apoptosis, cell adhesion, and others. Obviously, when investigating the effects of radiotherapy or chemotherapy or both combined under hypoxic conditions, it is essential to consider the influences of hypoxia itself on the cell. In this review, we first focus on the effects of hypoxia per se on some critical biological pathways. Next, we sketch an overview of preclinical and clinical research on radiotherapy, chemotherapy, and chemoradiation under hypoxic conditions.

Evaluation of HIF-1 inhibitors as anticancer agents

Hypoxia-inducible factor 1 (HIF-1) regulates the transcription of many genes involved in key aspects of cancer biology, including immortalization, maintenance of stem cell pools, cellular dedifferentiation, genetic instability, vascularization, metabolic reprogramming, autocrine growth factor signaling, invasion/metastasis, and treatment failure. In animal models, HIF-1 overexpression is associated with increased tumor growth, vascularization, and metastasis, whereas HIF-1 loss-of-function has the opposite effect, thus validating HIF-1 as a target. In further support of this conclusion, immunohistochemical detection of HIF-1alpha overexpression in biopsy sections is a prognostic factor in many cancers. A growing number of novel anticancer agents have been shown to inhibit HIF-1 through a variety of molecular mechanisms. Determining which combination of drugs to administer to any given patient remains a major obstacle to improving cancer treatment outcomes.

Targeting hypoxia cell signaling for cancer therapy

Hypoxia, a decrease in oxygen levels, is a hallmark of solid tumors. Hypoxic cells are more resistant to killing by ionizing radiation and chemotherapy, are more invasive and metastatic, resistant to apoptosis, and genetically unstable. Over the last two decades, the discovery of Hypoxia Inducible Factors, a family of transcription factors crucially involved in the response of mammalian cells to oxygen deprivation, has led to the identification of a molecular target associated with hypoxia suitable for the development of cancer therapeutics. These features of solid tumors may offer a unique opportunity for selective therapeutic approaches. A number of strategies targeting hypoxia and/or Hypoxia Inducible Factors (HIF) have been developed over the last several years and will be described. The exponentially growing interest in therapeutic strategies targeting hypoxia/HIF will undoubtedly generate more active compounds for preclinical and clinical development. A rational development plan aimed to validate target inhibition in preclinical models and early clinical trials is essential for a rapid translation of these agents to the treatment of human cancers.

Hypoxia, gene expression, and metastasis

Hypoxia poses many problems to the treatment of cancer. Hypoxic tumors are more resistant to chemotherapy and radiation. In addition, hypoxia induces a number of genes responsible for increased invasion, aggressiveness, and metastasis of tumors. The augmented metastatic potential due to hypoxia-mediated gene expression is discussed in this section. Particular attention is given to recent studies of specific genes involved in the key steps of metastasis, including extracellular matrix interactions, migration, and proliferation.

Metastasis and stem cell pathways

Recent studies have described a small population of self-renewing and multipotent cells within tumors termed "cancer stem cells." These cells share many traits with somatic and embryonic stem cells and are thought to be responsible for driving tumor progression in a growing list of neoplastic diseases. Cells within solid tumors encounter hypoxia due to poor vascular function. Both long-standing and emerging data describe hypoxic effects on somatic and embryonic stem cells, and it is likely that hypoxia also has profound effects on cancer stem cells. These effects include the activation of pathways that induce the dedifferentiation of cancer cells, the maintenance of stem cell identity, and increased metastatic potential. Hypoxia may contribute to tumor progression by specifically impacting these pathways in cancer stem cells.

Microenvironmental influences in melanoma progression

An often overlooked facet of tumor biology research is the involvement of the surrounding tumor microenvironment. Increasing evidence is being presented to support a major role for stromal components in all stages of tumorigenesis including initiation, progression, and metastasis. Melanoma serves as a model for studying cellular and stromal interactions within the tumor microenvironment due to the array of cell types localized to these lesions. Here, we discuss the both the molecular mechanisms, as well as the extracellular and contextual input that contribute to melanoma progression. Special emphasis is given to the assorted cell types and their interactions with the extracellular matrix and adjacent cells. Melanoma progression also initiates development of intralesional hypoxic regions; the relative significance of hypoxia in disease is also addressed. Lastly, a number of laboratories are currently developing innovative strategies to study melanoma within a microenvironmental platform. These promising model systems and their potential for closing current gaps in knowledge of disease are reviewed. The development of such models holds translational value that cannot be achieved with most current systems.

Effects of hypoxia on heterotypic macrophage interactions

The role of macrophages in modulating the systemic response to hypoxia and oxidative stress is emerging from basic biological processes, such as the regulation of red blood cell production, and from analysis of tumor progression, as a key factor determining whether cells survive, proliferate or differentiate under micro-environmental pressures. Our recent work identified a novel role for macrophages in promoting expansion of erythroid progenitors in vitro while confirming previous data that macrophages are not required for red cell enucleation. This work emerged from analyses of hypoxia and cell death in the Rb null fetal liver where we demonstrated that defects in erythropoietic islands were due to deterioration in the fetal liver microenvironment that disrupted heterotypic interactions of macrophages with erythroblasts and not to intrinsic defects in Rb null macrophages. The significance of these findings for the effect of hypoxia on macrophage interactions and activity during tumor progression is also discussed.

Hypoxia and hepatocellular carcinoma: The therapeutic target for hepatocellular carcinoma

Hypoxia enhances proliferation, angiogenesis, metastasis, chemoresistance, and radioresistance of hepatocellular carcinoma (HCC); suppresses differentiation and apoptosis of HCC; and consequently leads to resistance of transarterial embolization (with or without chemotherapy). Because transarterial embolization contributes to angiogenesis via inducing hypoxia, therapy combined with transarterial embolization and antiangiogenic therapy provides a new strategy for the treatment of HCC. Unfortunately, hypoxia leads to the escape of HCC cells from transarterial embolization and antiangiogenic therapy. Thus combined therapy that induces and targets hypoxia may be of benefit to HCC patients. Because angiogenesis plays an important role in recurrence of HCC after resection, antiangiogenic therapy is beneficial to HCC patients following surgical resection of the tumor.

Lysyl oxidase (LOX) down-regulation by TNFalpha: a new mechanism underlying TNFalpha-induced endothelial dysfunction

OBJECTIVE

TNFalpha is a pro-inflammatory cytokine that induces endothelial dysfunction and promotes atherosclerosis progression. Down-regulation of lysyl oxidase (LOX), a key enzyme in extracellular matrix maturation, by pro-atherogenic risk factors such as LDL and homocysteine, is associated with an impairment of endothelial barrier function. Our hypothesis is that the inflammatory cytokine TNFalpha could also modulate LOX expression/function in endothelial cells.

METHODS

The study was carried out in human umbilical vein endothelial cells (HUVEC), porcine aortic endothelial cells (PAEC) and bovine aortic endothelial cells (BAEC). LOX mRNA levels were analysed by real-time PCR and LOX activity was assessed by a high sensitive fluorescent assay. Promoter activity was determined by transient transfection using a luciferase reporter system.

RESULTS

TNFalpha decreases LOX mRNA levels in endothelial cells in a dose- and time-dependent manner. The effect of TNFalpha was observed at low concentrations (0.1-1 ng/mL) and was maximal at 2.5 ng/mL (after 21 h). In transfection assays, TNFalpha reduced LOX transcriptional activity to a similar extent than LOX mRNA. Furthermore, TNFalpha decreases endothelial LOX enzymatic activity. By using both TNF receptor (TNFR) agonist and blocking antibodies we determined the involvement of TNFR2 on LOX down-regulation. Moreover, while TNFR-associated factor-2 (TRAF-2) did not mediate signalling events leading to LOX inhibition, PKC inhibitors counteracted the TNFalpha-induced decrease of LOX mRNA levels. Finally, TNFalpha administration significantly reduced vascular LOX expression in rat aorta.

CONCLUSIONS

Endothelial dysfunction induced by TNFalpha is associated with a decrease of LOX expression/activity. Thus, LOX seems to be involved in the impairment of endothelial function triggered by different pathological conditions.

Anticancer therapeutics: A surge of new developments increasingly target tumor and stroma

The Annual Meeting of the American Association for Cancer Research (AACR) brings together research in fundamental biology, translational science, drug development and clinical testing of emerging anticancer therapies. Among the highlights of the 2007 Annual Meeting were major research themes on drug action, drug resistance and new drug development. Instead of striving for a comprehensive overview, we showcase several trends, concepts and research areas that exemplify the complexity of drug resistance and its reversal as we currently understand it. Many of the studies discussed here deal with the interaction of tumor cells with their stromal microenvironment; structural proteins as well as cellular components, fibroblasts as well as inflammatory cells. Target identification, target validation and dealing with the challenge of resistance are recurring themes. Specific classes of molecules discussed are the taxanes, tyrosine kinase inhibitors, anti-angiogenic, anti-stromal and anti-metastatic agents. In the latter three categories, targets reviewed are delta-like ligand 4 (DLL4), integrins, nodal, galectins, lysyl oxidases and thrombospondins, several of which belong to the p53-tumor suppressor repertoire of secreted proteins. Finally, developments in other inhibitor classes such as PI3K/Akt and Rho GTPase inhibitors and thoughts on possible novel combination therapies are briefly summarized. The report also includes relevant publications to July 2007.

The potential role of intrinsic hypoxia markers as prognostic variables in cancer

Tumor hypoxia is related to tumor progression and therapy resistance, which leads to poor patient outcome. It has been suggested that measuring the hypoxic status of a tumor helps to predict patient outcome and to select more targeted treatment. However, current methods using needle electrodes or exogenous markers have limitations due to their invasiveness or necessity for preinjection. Recent studies showed that hypoxia-regulated genes could be alternatively used as endogenous hypoxia markers. This is a review of 15 hypoxia-regulated genes, including hypoxia-inducible factor-1 and its targets, and their correlation with tumor hypoxia and patient outcome from 213 studies. Though most of the studies showed significance of these genes in predicting prognosis, there was no definitive prognostic and hypoxia marker. In conclusion, this review suggests the need for further studies with standardized methods to examine gene expression, as well as the use of multiple gene expressions.

Mammary epithelial cell: influence of extracellular matrix composition and organization during development and tumorigenesis

Stromal-epithelial interactions regulate mammary gland development and are critical for the maintenance of tissue homeostasis. The extracellular matrix, which is a proteinaceous component of the stroma, regulates mammary epithelial growth, survival, migration and differentiation through a repertoire of transmembrane receptors, of which integrins are the best characterized. Integrins modulate cell fate by reciprocally transducing biochemical and biophysical cues between the cell and the extracellular matrix, facilitating processes such as embryonic branching morphogenesis and lactation in the mammary gland. During breast development and cancer progression, the extracellular matrix is dynamically altered such that its composition, turnover, processing and orientation change dramatically. These modifications influence mammary epithelial cell shape, and modulate growth factor and hormonal responses to regulate processes including branching morphogenesis and alveolar differentiation. Malignant transformation of the breast is also associated with significant matrix remodeling and a progressive stiffening of the stroma that can enhance mammary epithelial cell growth, perturb breast tissue organization, and promote cell invasion and survival. In this review, we discuss the role of stromal-epithelial interactions in normal and malignant mammary epithelial cell behavior. We specifically focus on how dynamic modulation of the biochemical and biophysical properties of the extracellular matrix elicit a dialogue with the mammary epithelium through transmembrane integrin receptors to influence tissue morphogenesis, homeostasis and malignant transformation.

Delta9-Tetrahydrocannabinol inhibits epithelial growth factor-induced lung cancer cell migration in vitro as well as its growth and metastasis in vivo

Delta(9)-Tetrahydrocannabinol (THC) is the primary cannabinoid of marijuana and has been shown to either potentiate or inhibit tumor growth, depending on the type of cancer and its pathogenesis. Little is known about the activity of cannabinoids like THC on epidermal growth factor receptor-overexpressing lung cancers, which are often highly aggressive and resistant to chemotherapy. In this study, we characterized the effects of THC on the EGF-induced growth and metastasis of human non-small cell lung cancer using the cell lines A549 and SW-1573 as in vitro models. We found that these cells express the cannabinoid receptors CB(1) and CB(2), known targets for THC action, and that THC inhibited EGF-induced growth, chemotaxis and chemoinvasion. Moreover, signaling studies indicated that THC may act by inhibiting the EGF-induced phosphorylation of ERK1/2, JNK1/2 and AKT. THC also induced the phosphorylation of focal adhesion kinase at tyrosine 397. Additionally, in in vivo studies in severe combined immunodeficient mice, there was significant inhibition of the subcutaneous tumor growth and lung metastasis of A549 cells in THC-treated animals as compared to vehicle-treated controls. Tumor samples from THC-treated animals revealed antiproliferative and antiangiogenic effects of THC. Our study suggests that cannabinoids like THC should be explored as novel therapeutic molecules in controlling the growth and metastasis of certain lung cancers.

Identification of differentially secreted biomarkers using LC-MS/MS in isogenic cell lines representing a progression of breast cancer

Proteins secreted (the secretome) from cancer cells are potentially useful as biomarkers of the disease. Using LC-MS/MS, the secreted proteomes from a series of isogenic breast cancer cell lines varying in aggressiveness were analyzed by mass spectrometry: nontumorigenic MCF10A, premalignant/tumorigenic MCF10AT, tumorigenic/locally invasive MCF10 DCIS.com, and tumorigenic/metastatic MCF 10CA cl. D. Proteomes were obtained from conditioned serum-free media, partially fractionated using a small reverse phase C2 column, and digested with trypsin for analysis by LC-MS/MS, using a method previously shown to give highly enriched secreted proteomes (Mbeunkui et al. J. Proteome Res. 2006, 5, 899-906). The search files produced from five analyses (three separate preparations) were combined for database searching (Mascot) which produced a list of over 250 proteins from each cell line. The aim was to discover highly secreted proteins which changed significantly in abundance corresponding with aggressiveness. The most apparent changes were observed for alpha-1-antichymotrypsin and galectin-3-binding protein which were highly secreted proteins from MCF10 DCIS.com and MCF10CA cl. D, yet undetected in the MCF10A and MCF10AT cell lines. Other proteins showing increasing abundance in the more aggressive cell lines included alpha-1-antitrypsin, cathepsin D, and lysyl oxidase. The S100 proteins, often associated with metastasis, showed variable changes in abundance. While the cytosolic proteins were low (e.g., actin and tubulin), there was significant secretion of proteins often associated with the cytoplasm. These proteins were all predicted as products of nonclassical secretion (SecretomeP, Center for Biological Sequence Analysis). The LC-MS/MS results were verified for five selected proteins by western blot analysis, and the relevance of other significant proteins is discussed. Comparisons with two other aggressive breast cancer cell lines are included. The protein with consistent association with aggressiveness in all lines, and in unrelated cancer cells, was the galectin-3-binding protein which has been associated with breast, prostate, and colon cancer earlier, supporting the approach and findings. This analysis of an isogenic series of cell lines suggests the potential usefulness of the secretome for identifying prospective markers for the early detection and aggressiveness/progression of cancer.

Hypoxia and podocyte-specific Vhlh deletion confer risk of glomerular disease

Hypoxia is a potent regulator of a multitude of cellular processes, including metabolism and cell survival. The transcriptional response to oxygen deprivation is mainly mediated by hypoxia-inducible factors (HIFs), which are targeted for proteasomal degradation by the von Hippel-Lindau tumor suppressor protein (pVHL) under normoxia. Podocytes, as part of the glomerular filtration barrier, are prone to hypoxic injury during diseases affecting the glomerulus. VHL and HIF1 were functional in mature murine podocytes in vivo and in vitro, with HIF1 protein stabilization and target gene transcription under both hypoxia and VHL deficiency. Podocyte-specific Vhlh gene loss, mimicking podocyte hypoxia, in young mice of mixed background led to glomerulomegaly and occasional glomerulosclerosis, despite preserved glomerular development. In parallel, hypoxia effects on podocytes in cell culture included increased susceptibility to apoptosis, associated with nuclear translocation of apoptosis-inducing factor (AIF). Similarly, Vhlh gene inactivation in podocytes in vitro resulted in a significant survival disadvantage, particularly in conjunction with additional proapoptotic stimuli. Evaluation of the global transcriptional response to hypoxia in podocytes by microarray analysis revealed a typical upregulation of HIF target genes as well as the induction of genes relevant for stress response, cell-cell, and cell-extracellular matrix interaction. While the lack of a prominent phenotype in young mice with VHL-deficient podocytes is consistent with the absence of specific glomerular manifestations in human VHL disease, a low-oxygen environment of podocytes may contribute to the progression of glomerular disease by altering cellular metabolism and survival.

Identification of novel epigenetically modified genes in human melanoma via promoter methylation gene profiling

The inactivation of tumor-related genes through the aberrant methylation of promoter CpG islands is thought to contribute to tumor initiation and progression. We therefore investigated promoter methylation events involved in cutaneous melanoma by screening 30 genes of interest for evidence of promoter hypermethylation, examining 20 melanoma cell lines and 40 freshly procured melanoma samples. Utilizing quantitative methylation-specific PCR, we identified five genes (SOCS1, SOCS2, RAR-beta 2, TNFSF10C, and TNFSF10D) with hypermethylation frequencies ranging from 50% to 80% in melanoma cell lines as well as freshly procured tissue samples. Eighteen genes (LOX, RASSF1A, WFDC1, TM, APC, TFPI2, TNFSF10A, CDKN2A, MGMT, TIMP3, ASC, TPM1, IRF8, CIITA-PIV, CDH1, SYK, HOXB13, and DAPK1) were methylated at lower frequencies (2-30%). Two genes (CDKN1B and PTEN), previously reported as methylated in melanoma, and five other genes (RECK, IRF7, PAWR, TNFSF10B, and Rb) were not methylated in the samples screened here. Daughter melanoma cell lines showed identical methylation patterns when compared with original samples from which they were derived, as did synchronous metastatic lesions from the same patient. We identified four genes (TNFSF10C, TNFSF10D, LOX, and TPM1) that have never before been identified as hypermethylated in melanoma, with an overall methylation frequency of 60, 80, 50, and 10%, respectively, hypothesizing that these genes may play an important role in melanoma progression.

Hypoxia-inducible factor-1 facilitates cervical cancer progression in human papillomavirus type 16 transgenic mice

Advanced cervical cancer remains a vexing clinical challenge despite screening programs. Many of these cancers are hypoxic, and expression of the alpha subunit of the major regulator of the hypoxic cellular response, the transcription factor hypoxia-inducible factor-1 (HIF-1), is correlated with poor prognosis. Here, we tested a functional role for HIF-1alpha in pathogenesis of cervical cancer in estrogen-treated transgenic mice. Double-transgenic (DTG) mice developed locally invasive cervical cancers 70 times larger than K14-HPV16 mice. In vivo bromodeoxyuridine incorporation was elevated in DTG cancers without a significant increase in apoptosis. HIF-1alpha gain of function did not up-regulate canonical HIF-1 targets in premalignant DTG cervices, in contrast to elevation of these targets in K14-HIF-1alpha transgenic cervices. The DTG transcriptional signature included up-regulation of mRNAs encoding cytokines and chemokines, immune signaling molecules, extracellular proteases, and cell motility factors, as well as reduced expression of cell adhesion and epithelial differentiation genes. Importantly, a set of gene markers derived from the DTG transcriptome predicted cervical cancer progression in patients. This study suggests a novel paradigm for HIF-1 function evident in multistage carcinogenesis as opposed to established malignancies, including interaction with viral oncogenes to induce multiple genomic networks in premalignancy that fosters the development of advanced cervical cancer.

Selective upregulation and amplification of the lysyl oxidase like-4 (LOXL4) gene in head and neck squamous cell carcinoma

Members of the lysyl oxidase family (LOX) are copper and lysyl-tyrosine quinone cofactor-containing amine oxidases that are important for the assembly and maintenance of components of the extracellular matrix. Our previous results demonstrated that a novel member, LOXL4, is overexpressed in head and neck squamous cell carcinoma (HNSCC) compared to normal squamous epithelium. Results of the current study showed overexpression of the LOXL4 transcript in 74% (46 of 62) of invasive HNSCC tumours and 90% of both primary and metastatic HNSCC cell lines. Significant correlation was found between LOXL4 expression and local lymph node metastases versus primary tumour types (p<0.01) and higher tumour stages (p<0.01). Immunocytochemistry demonstrated cellular overexpression of the LOXL4 protein that correlated with the increased mRNA transcription in HNSCC cells. HNSCC cell lines displayed in significant subset of nuclei increased copies of the LOX4 gene locus on chromosome 10q24, demonstrated by fluorescence in situ hybridization (FISH). Extensive metaphase cytogenetic analysis was performed on UTSCC19A cells, identifying an isochromosome i(10)(q10). Taken together, these results highlight LOXL4 expression as a distinctive trait and suggest a functional role for LOXL4 in the molecular pathogenesis of invasive head and neck carcinomas.

Transcriptomic signatures in breast cancer

High throughput DNA microarray technology has been broadly applied to the study of breast cancer to classify molecular subtypes, to predict outcome, survival, response to treatment, and for the identification of novel therapeutic targets. Although results are promising, this technology will not have a full impact on routine clinical practice until there is further standardization of techniques and optimal clinical trial design. Due to substantial disease heterogeneity and the number of genes being analyzed, collaborative, multi-institutional studies are required to accrue enough patients for sufficient statistical power. Newer bioinformatic approaches are being developed to assist with the analysis of this important data.

Snail, Zeb and bHLH factors in tumour progression: an alliance against the epithelial phenotype?

The molecular mechanisms that underlie tumour progression are still poorly understood, but recently our knowledge of particular aspects of some of these processes has increased. Specifically, the identification of Snail, ZEB and some basic helix-loop-helix (bHLH) factors as inducers of epithelial-mesenchymal transition (EMT) and potent repressors of E-cadherin expression has opened new avenues of research with potential clinical implications.