Hepatocyte growth factor enhances CXCR4 expression favoring breast cancer cell invasiveness

The Effect of Hypoxia on the Expression of CXC Chemokines and CXC Chemokine Receptors-A Review of Literature

Hypoxia is an integral component of the tumor microenvironment. Either as chronic or cycling hypoxia, it exerts a similar effect on cancer processes by activating hypoxia-inducible factor-1 (HIF-1) and nuclear factor (NF-κB), with cycling hypoxia showing a stronger proinflammatory influence. One of the systems affected by hypoxia is the CXC chemokine system. This paper reviews all available information on hypoxia-induced changes in the expression of all CXC chemokines (CXCL1, CXCL2, CXCL3, CXCL4, CXCL5, CXCL6, CXCL7, CXCL8 (IL-8), CXCL9, CXCL10, CXCL11, CXCL12 (SDF-1), CXCL13, CXCL14, CXCL15, CXCL16, CXCL17) as well as CXC chemokine receptors—CXCR1, CXCR2, CXCR3, CXCR4, CXCR5, CXCR6, CXCR7 and CXCR8. First, we present basic information on the effect of these chemoattractant cytokines on cancer processes. We then discuss the effect of hypoxia-induced changes on CXC chemokine expression on the angiogenesis, lymphangiogenesis and recruitment of various cells to the tumor niche, including myeloid-derived suppressor cells (MDSCs), tumor-associated macrophages (TAMs), tumor-associated neutrophils (TANs), regulatory T cells (T_regs) and tumor-infiltrating lymphocytes (TILs). Finally, the review summarizes data on the use of drugs targeting the CXC chemokine system in cancer therapies.

Functions of chemokines in the perineural invasion of tumors (Review)

The perineural invasion (PNI) of malignant tumors is a form of tumor progression in which cancer cells encroach along nerves. PNI hinders curative resection. Residual tumor cells in or around nerves can bring about local recurrence, infiltration and metastasis. This behavior is usually associated with a poor clinical prognosis. Therefore, it is necessary to investigate novel ligand-receptor crosstalk between nerves and tumor cells that promote the process of PNI. Chemokines are regarded as one of pivotal factors involved in the process of PNI. The present review collates information provided by previous studies with regard to the role of chemokines in PNI. The study presents a definition of PNI in cancer, generalizes the biological characteristics and the expression of chemokines and their receptors in cancer types associated with PNI, and discusses the underlying molecular mechanisms of chemokines, the reciprocal interactions between chemokines and other factors in PNI, and the interconnectivity of the microenvironment and chemokines. The aim of the review is to thoroughly illustrate the molecular cues of chemokines in cancer with PNI and to identify novel antitumor targets.

Stromal-derived factor-1α/CXCL12-CXCR4 chemotactic pathway promotes perineural invasion in pancreatic cancer

Perineural invasion (PNI) is considered as an alternative route for the metastatic spread of pancreatic cancer cells; however, the molecular changes leading to PNI are still poorly understood. In this study, we show that the CXCL12/CXCR4 axis plays a pivotal role in the neurotropism of pancreatic cancer cells to local peripheral nerves. Immunohistochemical staining results revealed that CXCR4 elevation correlated with PNI in 78 pancreatic cancer samples. Both in vitro and in vivo PNI models were applied to investigate the function of the CXCL12/CXCR4 signaling in PNI progression and pathogenesis. The results showed that the activation of the CXCL12/CXCR4 axis significantly increased pancreatic cancer cells invasion and promoted the outgrowth of the dorsal root ganglia. CXCL12 derived from the peripheral nerves stimulated the invasion and chemotactic migration of CXCR4-positive cancer cells in a paracrine manner, eventually leading to PNI. In vivo analyses revealed that the abrogation of the activated signaling inhibited tumor growth and invasion of the sciatic nerve toward the spinal cord. These data indicate that the CXCL12/CXCR4 axis may be a novel therapeutic target to prevent the perineural dissemination of pancreatic cancer.

Pim kinases in hematological malignancies: where are we now and where are we going?

The proviral insertion in murine (PIM) lymphoma proteins are a serine/threonine kinase family composed of three isoformes: Pim-1, Pim-2 and Pim-3. They play a critical role in the control of cell proliferation, survival, homing and migration. Recently, overexpression of Pim kinases has been reported in human tumors, mainly in hematologic malignancies. In vitro and in vivo studies have confirmed their oncogenic potential. Indeed, PIM kinases have shown to be involved in tumorgenesis, to enhance tumor growth and to induce chemo-resistance, which is why they have become an attractive therapeutic target for cancer therapy. Novel molecules inhibiting Pim kinases have been evaluated in preclinical studies, demonstrating to be effective and with a favorable toxicity profile. Given the promising results, some of these compounds are currently under investigation in clinical trials. Herein, we provide an overview of the biological activity of PIM-kinases, their role in hematologic malignancies and future therapeutic opportunities.

Induction of chemokine receptor CXCR4 expression by transforming growth factor-β1 in human basal cell carcinoma cells

BACKGROUND

Higher CXCR4 expression enhances basal cell carcinoma (BCC) invasion and angiogenesis. The underlying mechanism of increased CXCR4 expression in invasive BCC is still not well understood.

OBJECTIVE

To investigate the mechanisms involved in the regulation of CXCR4 expression in invasive BCC.

METHODS

We used qRT-PCR, RT-PCR, Western blot, and flow cytometric analyses to examine different CXCR4 levels among the clinical samples, co-cultured BCC cells and BCC cells treated with recombinant transforming growth factor-β1 (TGF-β1) and connective tissue growth factor (CTGF). Immunohistochemical studies were used to demonstrate the correlation between TGF-β1 and CXCR4 expressions. The signal transduction pathway and transcriptional regulation were confirmed by treatments with chemical inhibitors, neutralizing antibodies, or short interfering RNAs, as well as luciferase reporter activity.

RESULTS

Invasive BCC has higher TGF-β1 and CTGF levels compared to non-invasive BCC. Non-contact dermal fibroblasts co-culture with human BCC cells also increases the expression of CXCR4 in BCC cells. Treatment with recombinant human TGF-β1, but not CTGF, enhanced the CXCR4 levels in time- and dose-dependent manners. The protein level and surface expression of CXCR4 in human BCC cells was increased by TGF-β1 treatment. TGF-β1 was intensely expressed in the surrounding fibroblasts of invasive BCC and was positively correlated with the CXCR4 expression of BCC cells. The transcriptional regulation of CXCR4 by TGF-β1 is mediated by its binding to the TGF-β receptor II and phosphorylation of the extracellular signal-related kinase 1/2 (ERK1/2)-ETS-1 pathway.

CONCLUSION

TGF-β1 induces upregulation of CXCR4 in human BCC cells by phosphorylation of ERK1/2-ETS-1 pathway.

Modulation of hepatocyte growth factor secretion in human female reproductive tract stromal fibroblasts by poly (I:C) and estradiol

PROBLEM

Hepatocyte Growth Factor (HGF) secretion facilitates epithelial cell growth and development in the female reproductive tract (FRT) and may contribute to pathological conditions such as cancer and endometriosis. We hypothesized that estradiol and poly (I:C), a synthetic RNA mimic, may have a regulatory effect on HGF secretion by stromal fibroblasts from FRT tissues.

METHOD OF STUDY

Following hysterectomies, normal tissue from the uterus, endocervix, and ectocervix were dispersed into stromal cell fractions by enzymatic digestion and differential filtering. Stromal fibroblasts were cultured and treated with estradiol and/or poly (I:C), and conditioned media were analyzed for HGF via enzyme-linked immunosorbent assay.

RESULTS

Treating uterine fibroblasts with estradiol or poly (I:C) significantly increased HGF secretion. When uterine fibroblasts were co-treated with estradiol and poly (I:C), the effect on HGF secretion was additive. In contrast, stromal fibroblasts from endo- and ecto-cervix were unresponsive to estradiol, but were stimulated to secrete HGF by poly (I:C).

CONCLUSION

HGF secretion is uniquely regulated in the uterus, but not in ecto- and endo-cervix, by estradiol. Moreover, potential viral pathogens further induce HGF. These findings have potential applications in understanding both hormonal regulation of normal tissue as well as the role of HGF in tumorogenesis, endometriosis, and human immunodeficiency virus infection.

Comparative role of acetylation along c-SRC/ETS1 signaling pathway in bone metastatic and invasive mammary cell phenotypes

Metastatic cells switch between different modes of migration through supramolecular plasticity mechanism(s) still largely unknown. The aim of the present paper was to clarify some molecular aspects of the epigenetic control of migration of 1833-bone metastatic cells compared to MDA-MB231-parental mammary carcinoma cells. Active c-Src overexpression enhanced 1833-cell spontaneous migration and CXCR4-mediated chemoinvasion toward CXCL12 ligand. Only in metastatic cells, in fact, c-Src seemed to stabilize nuclear CXCR4-protein receptor possibly due to tyrosine phosphorylation, by impairing protein-degradative smear and causing instead an electrophoretic-mobility shift; the cytosolic steady-state level of CXCR4 was enhanced, and the protein appeared also phosphorylated. These findings suggested the triggering of unique signaling pathways in metastasis for homing of breast-cancer cells to congenial environment of specific organs. Microenvironmental stimuli activating c-Src might influence Ets1 binding to CXCR4 promoter and consequent transactivation, as well as CXCR4 post-translational regulatory mechanisms such as phosphorylation. Enhancement of Ets1 activity and CXCR4 induction by c-Src overexpression were prevented by histone deacetylase (HDAC) blockade. In contrast, HDAC inhibition with trichostatin A increased cytosolic phosphorylated CXCR4 expression in MDA-MB231 cells, but Ets1 involvement was practically unneeded. c-Src might be suggested as a bio-marker predicting metastasis sensitivity patterns to HDAC inhibitors. Rationally designed and individualized therapy may become possible as more is learned about the target molecules of HDAC's inhibitory agents and their roles, as undertaken for CXCR4 that is likely to be crucial for homing, angiogenesis and survival in a c-Src-dependent manner in bone-metastatic mammary cells.

HGF upregulates CXCR4 expression in gliomas via NF-kappaB: implications for glioma cell migration

Invasion is a hallmark of malignant gliomas and is the main reason for therapeutic failure and recurrence of the tumor. CXCR4 is a key chemokine receptor implicated in glioma cell migration whose expression is regulated by hypoxia. Here, we report that hepatocyte growth factor (HGF) upregulated CXCR4 protein expression in glioma cells. HGF pre-treatment increased migration of U87MG and LN229 glioma cells towards the CXCR4 ligand, stromal cell-derived factor-1alpha (SDF-1alpha). AMD3100, a CXCR4 inhibitor, inhibited the increased migration of HGF pre-treated LN229 glioma cells towards SDF-1alpha. Following exposure to HGF and hypoxia, both cell lines showed nuclear translocation of NF-kappaB (p65). The HGF- and hypoxia-induced nuclear translocation of NF-kappaB (p65) involved phosphorylation and degradation of IkappaB-alpha. Knock-down of NF-kappaB expression inhibited the induction of CXCR4 expression in response to HGF, but not to hypoxia. However, knock-down of NF-kappaB expression inhibited the induction of CXCR4 expression in response to hypoxia in the presence of HGF. NF-kappaB mediated migration towards SDF-1alpha in response to HGF. Knock-down of NF-kappaB expression resulted in decreased migration of HGF pre-treated glioma cells towards SDF-1alpha. Therefore, HGF upregulates CXCR4 expression via NF-kappaB and leads to enhanced migration. To our knowledge, this is the first report to show that a crosstalk mediated by NF-kappaB exists between the SDF-1alpha/CXCR4 and HGF/c-Met axes relevant to glioma cell migration. These findings imply that effective inhibition of glioma invasion should be directed against several ligand/receptor signaling pathways.

Regulation of expression of stromal-derived factor-1 receptors: CXCR4 and CXCR7 in human rhabdomyosarcomas

Rhabdomyosarcomas (RMS) express CXCR4 and CXCR7 receptors that bind prometastatic alpha-chemokine stromal-derived factor-1 (SDF-1). In this report, we analyzed the activity of both promoters in a model of less metastatic human embryonal-RMS cell line (RD) and more metastatic alveolar-like RMS (RD cells transduced with paired box gene 3/forkhead homologue; PAX3-FKHR fusion gene). First, CXCR4 is barely detectable in RD and becomes upregulated in RD/PAX3-FKHR cells. In contrast, CXCR7 highly expressed in RD becomes downregulated in RD/PAX3-FKHR cells. Next, promoter deletion and mutation studies revealed that whereas (a) expression of CXCR4 in RD and RD/PAX3-FKHR cells required nuclear respiratory factor-1 (NRF-1) binding site and (b) was additionally upregulated by direct interaction of NRF-1 with PAX3-FKHR, CXCR7 promoter activity required a proximal nuclear factor-kappaB-binding motif. The requirement of these factors for CXCR4 and CXCR7 promoter activities was additionally supported after blocking NRF-1 and nuclear factor-kappaB. Furthermore, CXCR4 expression in PAX3-FKHR(+) RMS cells seems to be enhanced because of the interaction of PAX3-FKHR and NRF-1 proteins in the proximal part of the promoter that prevents access of the negative regulator of transcription YY1 to its binding site. Finally, although hypoxia enhances CXCR4 and CXCR7 promoter activity and receptor expression in RD cells, it inhibits CXCR7 expression in RD/PAX3-FKHR cells. In conclusion, SDF-1 binding receptors CXCR4 and CXCR7 are differently regulated in RMS cells. The upregulation of CXCR4 and downregulation of CXCR7 expression by PAX3-FKHR or hypoxia may give SDF-1 an advantage to better engage the CXCR4 receptor, thus increasing RMS motility.

PAUF functions in the metastasis of human pancreatic cancer cells and upregulates CXCR4 expression

Pancreatic cancer is characterized by early metastatic spread, but the process of tumor cell dissemination is largely unknown. In this study we show that the soluble protein pancreatic adenocarcinoma upregulated factor (PAUF) has an important role in the metastasis and progression of the disease. Variations in the level of PAUF, either by overexpression or knockdown, resulted in altered migration, invasion and proliferation capacity of pancreatic cancer cells. Moreover, depletion of PAUF in metastatic cells dramatically abrogated the spread of the cells to distant organs in an orthotopic xenograft mouse model. PAUF elicited the activation of the extracellular signal-regulated kinase (ERK), c-Jun N-terminal kinase (JNK) and AKT intracellular signaling cascades and consequently their downstream transcription factors in an autocrine manner. Genome-wide expression analysis revealed that C-X-C chemokine receptor type 4 (CXCR4) expression was induced by PAUF overexpression but was repressed by PAUF knockdown. The PAUF-mediated increase in cancer cell motility was attenuated by the CXCR4 inhibitor, AMD3100, or by anti-CXCR4 antibody. Furthermore, immunohistochemical analysis of pancreatic tumor tissues clearly showed a significant positive correlation between PAUF and CXCR4 expression. Collectively, these findings indicate that PAUF enhances the metastatic potential of pancreatic cancer cells, at least in part, by upregulating CXCR4 expression.

NF-kappaB activation, dependent on acetylation/deacetylation, contributes to HIF-1 activity and migration of bone metastatic breast carcinoma cells

Here, we show that NF-kappaB-HIF-1 interaction contributed to breast cancer metastatic capacity by means of an incomplete epithelial/mesenchymal transition and influencing migration, as shown in 1833 (human) and 4T1 (mouse) metastatic cells after different stimuli. The 1833 and the transforming growth factor-beta1-exposed 4T1 cells showed both epithelial (E-cadherins) and mesenchymal (N-cadherins and vimentin) markers, and common mechanisms contributed to the retention of certain epithelial characteristics and the control of migration. The complex NF-kappaB-HIF-1 reciprocal regulation and the enhanced c-Jun expression played a functional role in exacerbating the invasiveness of 1833 cells after p50/p65 transfection and of 4T1 cells exposed to transforming growth factor-beta1. Twist expression seemed to exert a permissive role also regulating epithelial/mesenchymal transition markers. After c-Src wild-type (Srcwt) transfection, c-Src-signal transducer overexpression in 1833 cells increased HIF-1 transactivating activity and invasiveness, and changed E-cadherin/N-cadherin ratio versus mesenchymal phenotype. The transcription factor pattern and the motile phenotype of metastatic 1833 cells were influenced by p65-lysine acetylation and HDAC-dependent epigenetic mechanisms, which positively regulated basal NF-kappaB and HIF-1 activities. However, HDAC3 acted as a corepressor of NF-kappaB activity in parental MDA-MB231 cells, thus explaining many differences from the derived 1833 clone, including reduced HIF-1alpha and c-Jun expression. Invasiveness was differently affected by HDAC knockdown in 1833 and MDA-MB231 cells. We suggest that acetylation/deacetylation are critical in establishing the bone-metastatic gene signature of 1833 cells by regulating the activity of NF-kappaB and HIF-1, and further clarify the epigenetic control of transcription factor network in the motile phenotype of 1833 cells.

Prognostic significance of CXCL12 expression in patients with colorectal carcinoma

The present study investigated the protein expression level of CXCL12 in colorectal cancer and aimed to elucidate its association with prognosis. CXCL12 positivity in 50% or more of tumor cells was defined as high expression and that in less than 50% of the tumor cells as low expression. CXCL12+ tumor budding at the invasive front was divided into 2 grades: high with 10 or more budding foci per x200 field of view and low grade with fewer than 10 budding foci. Patients with high expression (72.7%) and high grade CXCL12+ tumor budding (43.0%) had significantly shorter survival than patients with low expression (P = .014) and low grade (P = .003), respectively. Patients with a combination of high expression and high grade had the worst outcome (P < .001). Our study demonstrated that CXCL12 expression in colorectal cancer cells and at sites of budding were significant prognostic factors. Furthermore, together with lymph node metastasis, a combination of both expression patterns was a more powerful independent prognostic factor.

Estrogen-related cancer microenvironment of breast carcinoma

Stromal cells establish the microenvironment based on interaction with tumor cells, which is essential for cancer growth, invasion and metastasis. Fibroblasts are the primary component of stroma, and carcinoma-associated fibroblasts (CAFs) demonstrate tumor-promoting activities compared with normal counterparts. In breast cancers, stromal fibroblasts adjacent to the tumor express aromatase, a key enzyme in the synthesis of estrogen, resulting in in situ estrogen production, and aromatase is a primary target of endocrine therapy. Thus, stromal fibroblasts demonstrate multiple functions in the genesis and progression of breast cancers. In this paper, we discuss the importance of tumor-stromal crosstalk in breast cancers, and describe our system to predict the efficacy of endocrine therapy and to analyze estrogen signals in individual breast cancers.

Blockade of SDF-1/CXCR4 signalling inhibits pancreatic cancer progression in vitro via inactivation of canonical Wnt pathway

Extra-pancreatic metastasis is a difficult problem for surgical intervention in pancreatic cancer. CXC chemokine receptor 4 (CXCR4) was considered to have an important role in this process. We hypothesized it may contribute to the pancreatic cancer progression through influencing canonical Wnt pathway. The purpose of this study was to examine the functional role of CXCR4 in the progression of pancreatic cancers and explore the possible mechanism. To this end, the relation between CXCR4 and clinical characteristics was analysed. shRNA against CXCR4 was applied to disrupt the SDF-1/CXCR4 signal transduction pathways in pancreatic cancer cell lines. Our results showed that overall survival in the case of patients positive for CXCR4 expression was significantly lower than that in the case of patients negative for CXCR4 expression. Notably, in vitro studies we observed that the abrogation of CXCR4 could obviously influence the pancreatic cancer cell phenotype including cell proliferation, colony formation, cell invasion and also inhibit the TOPflash activity. In addition, Wnt target genes and mesenchymal markers such as Vimentin and Slug were also inhibited in CXCR4 knockdown cells. Collectively, these data reported here demonstrate CXCR4 could modulate the canonical Wnt pathway and perhaps be a promising therapeutic target for pancreatic cancer progression.

Inhibitory effect of HGF on invasiveness of aggressive MDA-MB231 breast carcinoma cells, and role of HDACs

Hepatocyte growth factor (HGF), through Met receptor binding, fulfils numerous functions in invasive tumour growth (survival/proliferation, motility, apoptosis), but epigenetic control of gene expression in this process is poorly understood. In HGF-treated breast cancer cells we studied (a) the chemoinvasion towards CXCL12 (ligand of the chemokine-receptor CXCR4) and (b) the mechanistic basis, that is, the transduction pathways that regulate CXCR4-mediated invasion, and the role played by histone deacetylases (HDACs) after blockade with trichostatin A (TSA). In highly invasive and metastatic MDA-MB231 cells HGF had a dual inhibitory effect, reducing spontaneous migration and specific chemoinvasion towards CXCL12, the latter by decreasing CXCR4 transactivation and protein level. After HGF the levels of phosphorylated (therefore active) c-Src and Akt persistently increased, indicating a role of these signal transducers in the HGF-dependent cellular and molecular effects. c-Src wild-type expression vector (Srcwt) increased active c-Src and mimicked the HGF-dependent inhibition of CXCR4 transactivation. Our findings indicate that HDACs participated in the HGF-inhibitory effects. In fact, blockade of HDACs hindered the HGF- and Srcwt-dependent reductions of CXCR4 transactivation and invasiveness, while inhibition of endogenous c-Src was additive with HGF, further reducing specific chemoinvasion. In conclusion, in MDA-MB231 cells HDAC blockade with TSA partly counteracted the HGF-dependent effects through molecular events that included enhancement of the expression of the genes for invasiveness Met and CXCR4 (depending on serum conditions), reduction of endogenous phospho-c-Src/c-Src and phosphoAkt/Akt ratios and triggering of apoptosis. The potential therapeutic use of TSA should take into account the variable aggressiveness of breast carcinoma cells and microenvironment signals such as HGF at the secondary growth site of the tumour. It was interesting that HGF reduced motility and CXCR4 functionality only of MDA-MB231 cells, and not of low-invasive MCF-7 cells, suggesting a mechanism implicated in metastatic cell homing.

Retention of human bone marrow-derived cells in murine lungs following bleomycin-induced lung injury

We studied the capacity of adult human bone marrow-derived cells (BMDC) to incorporate into distal lung of immunodeficient mice following lung injury. Immunodeficient NOD/SCID and NOD/SCID/beta(2) microglobulin (beta(2)M)(null) mice were administered bleomycin (bleo) or saline intranasally. One, 2, 3 and 4 days after bleo or saline, human BMDC labeled with CellTracker Green CMFDA (5-chloromethylfluorescein diacetate) were infused intravenously. Retention of CMFDA(+) cells was maximal when delivered 4 days after bleo treatment. Seven days after bleo, <0.005% of enzymatically dispersed lung cells from NOD/SCID mice were CMFDA(+), which increased 10- to 100-fold in NOD/SCID/beta(2)M(null) mice. Preincubation of BMDC with Diprotin A, a reversible inhibitor of CD26 peptidase activity that enhances the stromal-derived factor-1 (SDF-1/CXCL12)/CXCR4 axis, resulted in a 30% increase in the percentage of CMFDA(+) cells retained in the lung. These data indicate that human BMDC can be identified in lungs of mice following injury, albeit at low levels, and this may be modestly enhanced by manipulation of the SDF-1/CXCR4 axis. Given the overall low number of human cells detected, methods to increase homing and retention of adult BMDC, and consideration of other stem cell populations, will likely be required to facilitate engraftment in the treatment of lung injury.

Hypoxia enhances CXCR4 expression favoring microglia migration via HIF-1alpha activation

Migration toward pathological area is the first critical step in microglia engagement during the central nervous system (CNS) injury, although the molecular mechanisms underlying microglia mobilization have not been fully understood. Here, we report that hypoxia promotes stromal cell-derived factor-1alpha (SDF-1alpha) induced microglia migration by inducing the CXC chemokine receptor 4 (CXCR4) expression. Exposure to hypoxia significantly enhanced CXCR4 expression levels in N9 microglia cell. Then, cell migration induced by SDF-1, a CXCR4-specific ligand, was observed accelerated. Blockade of hypoxia inducible factor-1alpha (HIF-1alpha) activation by inhibitors of phosphoinositide-3-kinase (PI3K)/Akt signaling pathway abrogated both of hypoxia-induced CXCR4 up-regulation and cell-migration acceleration. These results point to a crucial role of Hypoxia-HIF-1alpha-CXCR4 pathway during microglia migration.

Involvement of hypoxia-inducing factor-1alpha-dependent plasminogen activator inhibitor-1 up-regulation in Cyr61/CCN1-induced gastric cancer cell invasion

Cysteine-rich 61 (Cyr61/CCN1), one of the members of CCN family, has been implicated in the progression of human malignancies. Previously, our studies have demonstrated that Cyr61/CCN1 has a role in promoting gastric cancer cell invasion, but the mechanism is not clear yet. Here, we found that hypoxia-inducing factor-1alpha (HIF-1alpha) protein, but not mRNA, expression was significantly elevated in gastric cancer cells overexpressing Cyr61. Supportively, a profound reduction of endogenous HIF-1alpha protein was noted in one highly invasive cell line, TSGH, when transfected with antisense Cyr61. By comparison, the induction kinetics of HIF-1alpha protein by recombinant Cyr61 (rCyr61) was distinct from that of insulin-like growth factor-1 and CoCl(2) treatment, both well known for induction of HIF-1alpha. Using cycloheximide and MG132, we demonstrated that the Cyr61-mediated HIF-1alpha up-regulation was through de novo protein synthesis, rather than increased protein stability. rCyr61 could also activate the PI3K/AKT/mTOR and ERK1/2 signaling pathways, both of which were essential for HIF-1alpha protein accumulation. Blockage of HIF-1alpha activity in Cyr61-expressing cells by transfecting with a dominant negative (DN)-HIF-1alpha strongly inhibited their invasion ability, suggesting that elevation in HIF-1alpha protein is vital for Cyr61-mediated gastric cancer cell invasion. In addition, several HIF-1alpha-regulated invasiveness genes were examined, and we found that only plasminogen activator inhibitor-1 (PAI-1) showed a significant increase in mRNA and protein levels in cells overexpressing Cyr61. Treatment with PAI-1-specific antisense oligonucleotides or function-neutralizing antibodies abolished the invasion ability of the Cyr61-overexpressing cells. Transfection with dominant negative-HIF-1alpha to block HIF-1alpha activity also effectively reduced the elevated PAI-1 level. In conclusion, our data provide a detailed mechanism by which Cyr61 promoted gastric cancer cell invasive ability via an HIF-1alpha-dependent up-regulation of PAI-1.

Microenvironmental regulation of estrogen signals in breast cancer

In breast cancers, estrogen activates estrogen receptor (ER) through genomic and nongenomic pathways, which leads to nuclear and extranuclear processes that promote the proliferation of breast cancer cells. Growth factor receptor signaling pathways also activate ER via phosphorylation through the signal crosstalks between estrogen and growth factors. The intratumoral levels of estrogen and growth factors, therefore, profoundly influence ER activity, which are regulated by the tumor-stromal interactions in the microenvironment. In postmenopausal breast cancers, tumor cells activate stromal fibroblasts to express aromatase, a key enzyme in estrogen biosynthesis, resulting in intratumoral estrogen production. At present, aromatase inhibitors are used as a first-line endocrine therapy for breast cancers. We developed a comprehensive system to evaluate the ER-activating ability of stromal fibroblasts for individual patients, and found that it varied among individual cases. This system might be useful for predicting the individual response to endocrine therapy and analyzing the tumor microenvironment. In addition to estrogen production, tumor-associated fibroblasts lead to the progression of breast cancer via different pathways. A study to differentiate the microenvironmental regulation of estrogen-dependent and -independent breast cancer growth would also be useful to improve hormone therapy for breast cancer.

Organ selectivity in metastasis: regulation by chemokines and their receptors

Cancer metastasis results from a non-random process, in which organ selectivity by the tumor cells is largely determined by factors that are expressed at the remote organs that eventually turn into preferred sites of metastasis formation. These factors support the consecutive steps required for metastasis formation, including tumor cell adhesion to microvessel walls, extravasation into target tissue and migration. Of the different components that regulate organ selectivity, instrumental roles were recently attributed to chemokines and their receptors. The present review presents the rationale standing behind the first studies looking at the potential involvement of chemokine-related components in organ selectivity. Based on these studies and many others that followed, the current paradigm is that chemokines that are expressed at specific organs determine to large extent organ specificity by promoting tumor cell adhesion to microvessel walls, by facilitating processes of extravasation into the target tissue and by inducing tumor cell migration. Moreover, chemokines can possibly support additional steps that are required for "successful" establishment of metastases, such as tumor cell proliferation and survival. The review focuses on the CXCL12-CXCR4 pair as the role model in our current understanding of chemokine involvement in organ selectivity. This review also describes the prominent roles played by CCR7 and its corresponding chemokine ligands (CCL21, CCL19) in lymph node metastasis, and of the CCR10-CCL27 axis in melanoma skin survival and metastasis. Overall, the present discussion describes chemokines as important constituents of the tumor microenvironment at metastatic sites, dictating directionality of chemokine receptor-expressing tumor cells, facilitating their adhesion and extravasation, and eventually contributing to organ selectivity.

c-Src/Histone Deacetylase 3 Interaction Is Crucial for Hepatocyte Growth Factor–Dependent Decrease of CXCR4 Expression in Highly Invasive Breast Tumor Cells

Hepatocyte growth factor (HGF), a cytokine of tumor microenvironment, exerts opposite effects on CXCR4 expression in MCF-7 (low invasive) and MDA-MB231 (highly invasive) breast carcinoma cells, and here, we show that completely different molecular mechanisms downstream of c-Src activation were involved. As experimental models, we used cells transfected with two CXCR4 promoter constructs and treated with HGF or cotransfected with c-Src wild-type (Srcwt) expression vector; phospho-c-Src formation was enhanced in both cell lines. In MCF-7 cells, consistent with activations of CXCR4Luc constructs after HGF treatment and Srcwt expression, Ets1 and nuclear factor-kappaB (NF-kappaB) transcription factors were activated. In contrast, in MDA-MB231 cells, CXCR4Luc construct, Ets1 and NF-kappaB activities decreased. The divergence point seemed to be downstream of HGF/c-Src and consisted in the interaction between c-Src and the substrate histone deacetylase 3 (HDAC3). Only in MDA-MB231 cells, HDAC3 level was enhanced in membranes and nuclei 30 min after HGF and colocalized/coimmunoprecipitated with phospho-c-Src and phosphotyrosine. Thus, the CXCR4 induction by HGF in MCF-7 cells required NF-kappaB and Ets1 activations, downstream of phosphoinositide-3-kinase/Akt, whereas in HGF-treated MDA-MB231 cells, HDAC3 activation via c-Src probably caused a reduction of transcription factor activities, such as that of NF-kappaB. These results indicate possible roles of HGF in invasive growth of breast carcinomas. By enhancing CXCR4 in low invasive tumor cells, HGF probably favors their homing to secondary sites, whereas by suppressing CXCR4 in highly invasive cells, HGF might participate to retain them in the metastatic sites.

Effects of simulated altitude (normobaric hypoxia) on cardiorespiratory parameters and circulating endothelial precursors in healthy subjects

BACKGROUND

Circulating Endothelial Precursors (PB-EPCs) are involved in the maintenance of the endothelial compartment being promptly mobilized after injuries of the vascular endothelium, but the effects of a brief normobaric hypoxia on PB-EPCs in healthy subjects are scarcely studied.

METHODS

Clinical and molecular parameters were investigated in healthy subjects (n = 8) in basal conditions (T0) and after 1 h of normobaric hypoxia (T1), with Inspiratory Fraction of Oxygen set at 11.2% simulating 4850 mt of altitude. Blood samples were obtained at T0 and T1, as well as 7 days after hypoxia (T2).

RESULTS

In all studied subjects we observed a prompt and significant increase in PB-EPCs, with a return to basal value at T2. The induction of hypoxia was confirmed by Alveolar Oxygen Partial Pressure (PAO2) and Spot Oxygen Saturation decreases. Heart rate increased, but arterial pressure and respiratory response were unaffected. The change in PB-EPCs percent from T0 to T1 was inversely related to PAO2 at T1. Rapid (T1) increases in serum levels of hepatocyte growth factor and erythropoietin, as well as in cellular PB-EPCs-expression of Hypoxia Inducible Factor-1alpha were observed.

CONCLUSION

In conclusion, the endothelial compartment seems quite responsive to standardized brief hypoxia, possibly important for PB-EPCs activation and recruitment.

Dynamic stromal-epithelial interactions during progression of MCF10DCIS.com xenografts

MCF10DCIS.com cells form comedo type ductal carcinoma in situ in immune-deficient mice before forming invasive ductal carcinoma. As the lesions mature, both stromal and epithelial cells undergo phenotypic changes detected by immunohistochemistry. Myofibroblasts are present before the formation of carcinoma in situ and after development of invasive carcinoma. MCF10DCIS. com lesions develop a myoepithelial layer prior to exhibiting a basement membrane surrounding the ductal mass. TGFbeta1 is initially expressed by the epithelial cells but is expressed by stroma in invasive carcinoma. Stromal derived factor-1 is detected in epithelial cells in early carcinoma in situ but is produced in stromal cells in invasive carcinoma. The receptor CXCR4 is expressed by epithelial cells in the xenografts at all times, as is the hepatocyte growth factor receptor c-met. MCF10DCIS.com xenografts illustrate the dynamic interplay of epithelium and stroma in the development of carcinoma in situ and subsequent invasive carcinoma. Although the phenotype of the epithelial cells may be dependent upon the stroma, the malignant epithelium induces the development of the stroma necessary for progression to the invasive stage. (c) 2007 Wiley-Liss, Inc.

Tumor immunoediting and immunosculpting pathways to cancer progression

Recent studies have suggested that a natural function of the immune system is to respond and destroy aberrant, dysfunctional cells by a process called immunosurveillance. These studies also suggest that the tumors that arise despite immunosurveillance have been immunosculpted by the immune system. The purported abilities of tumors to induce immune tolerance and suppression, the increased pathogenic behavior of the tumor cells following exposure to immune effectors and the loss of immunogenicity (i.e. immunoediting) often observed in advanced stage tumors could be the result of immunosculpting. In some cases, these immunosculpting features may be permanent and irreversible. However, in other cases, reversible epigenetic mechanisms may underlie the immune resistant tumor phenotype. Regardless, these immune-induced alterations could contribute to cancer pathogenesis. Understanding the mechanisms by which tumors evade immunity will be important for disease prevention and therapeutics.

Profiles of chemokine receptors in melanocytic lesions: de novo expression of CXCR6 in melanoma

Selective expression of certain chemokine receptors by melanoma cells and the presence of their ligands in tissues might govern organ site-specific metastasis. Because the expression profile of chemokine receptors in tissues of melanocytic origin is unknown, we performed a comprehensive study on melanocytic tissue samples investigating the expression of 18 chemokine receptors at the mRNA level by real-time polymerase chain reaction, using a semiquantitative approach, and of 3 chemokine receptors (CXCR6, CCR9, and XCR1) at the protein level. We report on the de novo expression of CXCR6 in primary melanomas and melanoma metastases, but absence in melanoma cell lines and congenital nevi. CXCR4 and CCR1 were the only 2 chemokine receptors that were consistently expressed in melanocytes, melanoma cell lines, primary, and metastatic melanoma; CCR1 expression increased significantly over progression. CCR9 and XCR1 transcripts were found in melanocytic lesions, and expression was confirmed by immunohistochemistry. Transcripts for CCR10 were not found in any of the lesions, but in some melanoma cell lines. Expression of CCR7 was observed in primary melanomas and some metastases. CCR5 was exclusively expressed in primary melanomas and some cutaneous metastases. Results revealed a restricted and differential pattern of chemokine receptor expression in melanoma tissue, which varies substantially from the expression profile of melanoma cell lines and warrants functional studies on some receptors.

Hypoxia-inducible factor 1 and VEGF upregulate CXCR4 in glioblastoma: implications for angiogenesis and glioma cell invasion

Hypoxia and hypoxia-inducible factor-1 (HIF-1) play a critical role in glioblastoma multiforme (GBMs). CXCR4 is involved in angiogenesis and is upregulated by HIF-1alpha. CXCR4 is a chemokine receptor for stromal cell-derived factor-1 (SDF-1)alpha, also known as CXCL12. We hypothesized that CXCR4 would be upregulated by hypoxia in GBMs. First, we investigated the expression of HIF-1alpha and CXCR4 in GBMs. CXCR4 was consistently found colocalized with HIF-1alpha expression in pseudopalisading glioma cells around areas of necrosis. In addition, angiogenic tumor vessels were strongly positive for CXCR4. Next, we tested the in vitro effect of hypoxia and vascular endothelial growth factor (VEGF) on the expression of CXCR4 in glioma cell lines and in human brain microvascular endothelial cells (HBMECs). Exposure to hypoxia induced significant expression of CXCR4 and HIF-1alpha in glioma cells, whereas treatment with exogenous VEGF increased CXCR4 expression in HBMECs. We also transfected U87MG glioma cells with an HIF-1alpha construct and observed that CXCR4 was upregulated in these cells even in normoxic conditions. We then used a lentivirus-mediated shRNA expression vector directed against HIF-1alpha. When exposed to hypoxia, infected cells failed to show HIF-1alpha and CXCR4 upregulation. We performed migration assays under normoxic and hypoxic conditions in the presence or absence of AMD3100, a CXCR4 inhibitor. There was a significant increase in the migration of U87MG and LN308 glioma cells in hypoxic conditions, which was inhibited in the presence of AMD3100. These studies demonstrate the critical role played by hypoxia and CXCR4 in glioma cell migration. Based on these studies, we suggest that hypoxia regulates CXCR4 in GBMs at two levels. First, through HIF-1alpha in the pseudopalisading tumor cells themselves and, secondly, by the VEGF-stimulated angiogenic response in HBMECs. We believe this knowledge may lead to a potentially important two-pronged therapy against GBM progression using chemotherapy targeting CXCR4.

Negative regulation of chemokine receptor CXCR4 by tumor suppressor p53 in breast cancer cells: implications of p53 mutation or isoform expression on breast cancer cell invasion

Chemokine receptor CXCR4 and its ligand CXCL12 are suggested to be involved in migration, invasion and metastasis of breast cancer cells. Mutation of the tumor suppressor gene p53 in breast cancer is associated with metastasis and aggressive clinical phenotype. In this report, we demonstrate that wild type but not the dominant-negative mutant (V143A) or cancer-specific mutants (R175H or R280K) of p53 repress CXCR4 expression. Recently described cancer-specific p53 isoform, Delta133p53, also failed to repress CXCR4 promoter activity. Short-interfering RNA-mediated depletion of p53 increased endogenous CXCR4 expression in MCF-7 breast cancer cells that contain wild-type p53. Basal CXCR4 promoter activity in HCT116 colon carcinoma cells deleted of p53 [HCT116(p53KO)] was 10-fold higher compared to that in parental HCT116 cells with functional wild-type p53. Deletion analysis of CXCR4 promoter identified a seven-base pair p53-repressor element homologous to cyclic AMP/AP-1 response (CRE/AP-1) element. Electrophoretic mobility shift and chromatin immunoprecipitation assays revealed binding of ATF-1 and cJun to the CRE/AP-1 element. The p53 rescue drug PRIMA-1 reduced CXCR4 mRNA and cell surface expression in MDA-MB-231 cells, which express R280K mutant p53. CP-31398, another p53 rescue drug, similarly reduced cell surface levels of CXCR4. PRIMA-1-mediated decrease in CXCR4 expression correlated with reduced invasion of MDA-MB-231 cells through matrigel. These results suggest a mechanism for elevated CXCR4 expression and metastasis of breast cancers with p53 mutations or isoform expression. We propose that p53 rescue drugs either alone or in combination with chemotherapeutic drugs may be effective in reducing CXCR4-mediated metastasis.

New signals from the invasive front

Approximately 90% of all cancer deaths arise from the metastatic spread of primary tumours. Of all the processes involved in carcinogenesis, local invasion and the formation of metastases are clinically the most relevant, but they are the least well understood at the molecular level. Revealing their mechanisms is one of the main challenges for exploratory and applied cancer research. Recent experimental progress has identified a number of molecular pathways and cellular mechanisms that underlie the multistage process of metastasis formation: these include tumour invasion, tumour-cell dissemination through the bloodstream or the lymphatic system, colonization of distant organs and, finally, fatal outgrowth of metastases.

Metastasis-associated protein 1 enhances stability of hypoxia-inducible factor-1alpha protein by recruiting histone deacetylase 1

The expression of metastasis-associated protein 1 (MTA1) correlates well with tumor metastases; however, the associated molecular mechanism is not fully understood. Here, we explored the possibility of cross-talk between MTA1 and hypoxia-inducible factor-1alpha (HIF-1alpha), a key regulator of angiogenic factors. We observed that the expression of MTA1 was strongly induced under hypoxia in breast cancer cell lines such as MCF-7 and MDA-MB-231. When MTA1 was overexpressed, the transcriptional activity and stability of HIF-1alpha protein were enhanced. MTA1 and HIF-1alpha are physically associated in vivo and they were localized completely in the nucleus when coexpressed. MTA1 induced the deacetylation of HIF-1alpha by increasing the expression of histone deacetylase 1 (HDAC1). MTA1 counteracted to the action of acetyltransferase, ARD1, and it did not stabilize the HIF-1alpha mutant that lacks the acetylation site, K532R. These results indicate that acetylation is the major target of MTA1/HDAC1 function. Collectively, our data provide evidence of a positive cross-talk between HIF-1alpha and MTA1, which is mediated by HDAC1 recruitment, and indicate a close connection between MTA1-associated metastasis and HIF-1-induced tumor angiogenesis.