Head And Neck Squamous Cell Carcinoma Tumor Cells Research Articles

Modulation of endothelial cell network formation in vitro by molecular signaling of head and neck squamous cell carcinoma (HNSCC) exposed to cetuximab

Overexpression of EGFR plays a key-role in head and neck squamous cell carcinoma (HNSCC) and justifies the extensive use of cetuximab, a monoclonal anti-EGFR antibody, as well as EGFR-tyrosine kinase inhibitors (EGFR-TKI), which have been reported to inhibit tumor cell growth and the secretion of pro-angiogenic factors by tumor cells, such as VEGF and IL-8. Moreover, vessel normalization in tumors, suggesting a more complex mediation of endothelial cell growth control has also been observed in vivo.The present study was designed to investigate the angiogenic consequences of exposure of HNSCC tumor cell lines to cetuximab and intercellular signaling between tumor and endothelial cells by secretion of pro- and anti-angiogenic mediators in the conditioned media (CM).The results achieved showed that cetuximab decreased the secretion of VEGF by HNSCC cells and that exposure of human umbilical vein endothelial cells (HUVEC) to CM from HNSCC cells exposed to cetuximab induced an increase in endothelial cell network formation. Angiogenesis proteome profiling showed that cetuximab induced a complex alteration of the secretion of pro- and anti-angiogenic factors by HNSCC cells without enabling to identify a unique molecular marker.Expression of endothelial membrane receptors (VEGFR-2, EGFR, PECAM-1 and Notch-4) was investigated and only EGFR expression was found influenced when HUVEC were exposed to CM from cetuximab-exposed HNSCC cells.These results showed that the decrease in the secretion of pro-angiogenic agents like VEGF by HNSCC cells exposed to cetuximab could not be sufficient to justify its anti-angiogenic activity in vitro.

Identification of HN-1-Peptide Target in Head and Neck Squamous Cell Carcinoma Cells

The HN-1 module was previously reported to ensure efficient targeting of head and neck squamous cell carcinoma (HNSCC). Aim of this work was to indentify the target of HN-1. Targeting of HN-1 peptide was compared in normal epithelial cells (BEAS-2B) and in HNSCC tumor cells (SCC-25 and Detroit 562). Experimental, cell culture, cell polarity, and adhesion conditions were tested; structure models of peptides were created. Indeed, HN-1 was able to target HNSCC tumor cells in the previously published conditions. The targeting efficiency of immortalized normal epithelial cells was significantly lower. Nevertheless, in other experimental conditions the binding was less efficient and not specific. A scrambled sequence of HN-1, with altered order of amino acids showed even better targeting efficiency than HN-1. HN-1 was only uptaken in adherent cells, not in suspension. In conclusion, HN-1-peptide-targeting is not based on sequence specificity, but more on electrostatic interactions with the cell surface of the tumor cells.

Abstract 4752: Cortactin and coronin 1B cooperate to promote tumor cell invasion in head and neck squamous cell carcinoma

Abstract Amplification of chromosome 11q13 in head and neck squamous cell carcinoma (HNSCC) is a common occurrence associated with poor patient prognosis. Within the core amplified region is the gene that encodes cortactin (CTTN), a filamentous (F)- actin binding protein and Src kinase substrate that stabilizes Arp2/3-F-actin branchpoints in dynamic cortical F-actin structures. CTTN amplification results in increased lymph node metastases and decreased survival rates in HNSCC patients. CTTN amplification in HNSCC cell lines enhances tumor cell motility and invasion. Chromosomal regions of varying length flanking the core 11q13 amplicon are often amplified in HNSCC, and contain several genes with the potential to cooperate with CTTN in regulating actin dynamics. One of these genes within the 11q13 region outside of the core amplicon is CORO1B (coronin 1B), an actin-binding protein that antagonizes cortactin function by promoting the breakdown of cortactin-stabilized Arp2/3-F-actin branches, resulting in impaired cell motility. Here we show that coronin 1B is a potential mediator of HNSCC invasion. CORO1B amplification and overexpression occurs in a subset of HNSCC patients with CTTN amplification. Coronin 1B localizes with cortactin within HNSCC invadopodia, ventral membranous protrusions responsible for degrading extracellular matrix to facilitate loco-regional invasion and extracapsular spread. RNAi-mediated coronin 1B knockdown decreases the number of invadopodia per cell, enhances cell spreading and reduces extracellular matrix degradation. These results collectively point to a potential role for coronin 1B in regulating HNSCC tumor cell invasion through modulating cortactin activity and invadopodia function. Our data also support a potential diagnostic function for CORO1B amplification in denoting a previously unidentified HNSCC subset that may display increased invasiveness in cases containing 11q13 amplification. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 4752. doi:10.1158/1538-7445.AM2011-4752

Glucose, not glutamine, is the dominant energy source required for proliferation and survival of head and neck squamous carcinoma cells

Tumor metabolism is an essential contributor to disease progression and response to treatment. An understanding of the metabolic phenotype of head and neck squamous cell carcinoma (HNSCC) will allow the development of appropriate antimetabolic strategies for this tumor type. A panel of 15 HNSCC cell lines was assayed for glucose and glutamine dependence and sensitivity to metabolic inhibitors. In addition, broad-spectrum metabolomic analysis using mass spectrometry/liquid chromatography was combined with individual measurements of reducing potential, adenosine triphosphate, and lactate production to characterize cellular metabolic phenotypes. HNSCC energy and reducing potential levels closely mirrored extracellular glucose concentrations. Glucose starvation induced cell death despite the activation of secondary energetic pathways. Conversely, glutamine was not required for HNSCC survival and did not serve as a significant source of energy. 2-deoxyglucose (2-DG) and its fluorinated derivative decreased glycolytic and Krebs cycle activity, cellular energy, and reducing potential and inhibited HNSCC cell proliferation. 2-DG effects were potentiated by the addition of metformin, but not by inhibitors of the pentose phosphate pathway or glutaminolysis. Despite dependence on glucose catabolism, the authors identified a subset of cell lines with relative resistance to starvation. Exploration of 1 such cell line (HN30) suggested that the presence of wild-type p53 can partially protect tumor cells from glucose starvation. HNSCC tumor cells are dependent on glucose, not glutamine, for energy production and survival, providing a rationale for treatment strategies that target glucose catabolism. However, antimetabolic strategies may need to be tailored to the tumor background, more specifically, p53 status.

Extraribosomal function of metallopanstimulin‐1: reducing paxillin in head and neck squamous cell carcinoma and inhibiting tumor growth

Metallopanstimulin-1 (MPS-1) is a multifunctional ribosomal protein RPS27 that contains a zinc finger domain of the C(4) type. MPS-1 has been found to be increased in the sera of a number of different cancers, including head and neck squamous cell carcinoma (HNSCC). However, little is known about the effect of a high-level MPS-1 in regulating cancer cell behavior. In this study, we overexpressed MPS-1 protein in the HNSCC cell line UMSCC-1. We found MPS-1 distributes not only in the cytosol, but also in the nuclei. In addition, MPS-1 is secreted into the culture medium. In vitro and in vivo experiments show that growth of UMSCC-1 cells transfected with MPS-1 is dramatically inhibited. Moreover, we also found that with overexpressing MPS-1, UMSCC-1 cells were arrested on G0/G1 phase, cell proliferation rate was reduced, and tumor angiogenesis was impaired. Further gene array analysis, immunohistochemistry staining and Western blotting reveal that MPS-1 reduces paxillin mRNA and protein levels in UMSCC-1 cells both in vitro and in vivo. Together, these data indicate that when MPS-1 is overexpressed, it has an extraribosomal function as a strong inhibitor of HNSCC tumor cell growth, which may be exerted by reduced paxillin gene expression.

A Systematic Assessment of Radiation Dose Enhancement by 5-Aza-2′-Deoxycytidine and Histone Deacetylase Inhibitors in Head-and-Neck Squamous Cell Carcinoma

Investigations of epigenetic drugs have shown that radiotherapy can be successfully combined with histone deacetylase inhibitors (HDAC-Is) for the treatment of head-and-neck squamous cell carcinoma (HNSCC). Whether the reversal of epigenetic silencing by demethylating agents with or without HDAC-Is can also act as radiosensitizing remains unclear. This study therefore aimed to investigate whether 5-aza-2'-deoxycytidine (DAC) alone or in combination with the HDAC-Is trichostatin A, LBH589, or MGCD0103 could radiosensitize HNSCC tumor cell lines. Histone acetylation status and expression of epigenetically silenced genes at the DNA, RNA, and protein levels were assessed as measures of drug effectiveness in six HNSCC cell lines. Based on their colony-forming capacity, colony assays were performed in four of six cell lines to evaluate the radiosensitizing potential of DAC with or without HDAC-Is. Additional assays of cell survival, apoptosis, cell proliferation, and DNA damage were performed. Radiosensitization was observed in two HNSCC cell lines treated with noncytotoxic doses of DAC with or without HDAC-Is before irradiation. The radiosensitizing doses induced histone hyperacetylation and reversal of gene silencing to variable extents and increased radiation-induced cell-cycle arrest. A role for low-dose DAC with or without HDAC-Is as radiosensitizers in HNSCC seems promising and is supportive of future clinical use, especially for combinations of DAC with LBH589 or MGCD0103, although the mechanisms by which they work will require further study.

Association Between Hypermethylated Tumor and Paired Surgical Margins in Head and Neck Squamous Cell Carcinomas

Surgical margin status is reported to be a relevant prognostic factor in head and neck squamous cell carcinoma (HNSCC), associated with a high risk of local recurrence. This study examines whether gene-promoter hypermethylation could be detected in HNSCC surgical margins with no histologic evidence of malignancy, and if so, whether it reflects epigenetic events of primary tumors. Promoter methylation status of MGMT, p16, and DAP-K genes was evaluated by methylation-specific PCR in 20 primary HNSCC tumors. Histopathologically negative surgical margins of hypermethylated tumors were collected, and their methylation status compared with the primary tumor status. Promoter hypermethylation in at least one of the three tested genes was detected in 65% (13 of 20) of tumors. MGMT was hypermethylated in 50% (10 of 20), DAP-K in 45% (9 of 20), and p16 in 20% (4 of 20) of tumors. Methylation status was analyzed in 35 margins from 11 of 13 patients showing promoter hypermethylation in the tumor tissue. Identical methylation events were seen for at least one gene in primary tumor and surgical margins in 9 of 11 cases (82%). Association was found for gene-specific hypermethylation status in tumors and paired surgical margins, and gene-specific concordance was 63% for MGMT (kappa = 0.24), 90% for DAP-K (kappa = 0.74), and 90% for p16 (kappa = 0.79). Our results support the hypothesis that detection of gene promoter hypermethylation in HNSCC tumor cells-free surgical margins may be a helpful biomarker to identify molecularly altered fields in areas adjacent to the tumor.

Use of fluorescent labeled anti–epidermal growth factor receptor antibody to image head and neck squamous cell carcinoma xenografts

Physicians and surgeons rely on subtle tissue changes to detect the extent of tumors and the presence of residual disease in the clinical setting. The development of a cancer-specific fluorescent contrast agent has the potential to provide real-time tumor imaging in the clinic or operating room. Because epidermal growth factor receptor (EGFR) is highly overexpressed on the surface of head and neck squamous cell carcinoma (HNSCC), we sought to determine if fluorescently labeled anti-EGFR antibody could be used to image HNSCC xenografts in vivo. Cetuximab or control isotype-matched IgG1 was conjugated with the Cy5.5 fluorochrome and systemically injected into mice bearing human split thickness skin grafts, tumor cell line xenografts, transplanted human tumor xenografts, or mouse mesothelioma tumors. Xenografts were imaged by time-domain fluorescence imaging or fluorescence stereomicroscopy. Both imaging modalities detected specific uptake of cetuximab-Cy5.5 in HNSCC xenografts with significantly higher fluorescence levels relative to control IgG1-Cy5.5. Tumor xenograft fluorescence was higher compared with background (before injection), human split thickness skin grafts, or mouse mesothelioma tumors at 24, 48, and 72 h. Fluorescence was detected in multiple HNSCC tumor cell lines with variable EGFR expression levels. Mock resections of flank tumors using fluorescence stereomicroscopy showed that small (2 mm) specimens could be detected in the surgical wound bed. These results show the feasibility of using fluorescently labeled anti-EGFR antibody to detect human tumors in the surgical setting.

The Influence of Hyaluronan-CD44 Interaction on Topoisomerase II Activity and Etoposide Cytotoxicity in Head and Neck Cancer

To investigate the downstream molecular targets of hyaluronan (HA)-CD44 and phospholipase C (PLC)-mediated calcium ion (Ca(2+)) signaling in head and neck squamous cell carcinoma (HNSCC). Hyaluronan is a ligand for the CD44 receptor, which interacts with multiple signaling pathways to influence cellular behavior. We recently determined that HA-CD44 interaction promotes PLC-mediated Ca(2+) signaling and cisplatin resistance in HNSCC. Proliferation of HNSCC tumor cells and topoisomerase (Topo) II enzymatic activity, including DNA-cleavable complex formation and DNA decatenation, were analyzed in the presence or absence of HA, the Topo II poison etoposide (VP-16), and various inhibitors of PLC and Ca(2+)-calmodulin kinase II (CaMKII) signaling. Treatment with HA promoted Topo II phosphorylation, suggesting that HA can modulate Topo II activity. Topoisomerase II-mediated DNA cleavable complex formation was increased by VP-16, and this increase was significantly enhanced by noncytotoxic doses of the PLC inhibitor U73122 and the CaMKII inhibitor KN-62, implicating PLC and CaMKII in Topo II regulation. However, the drug- and inhibitor-mediated increase in DNA cleavable complex formation was reduced with HA pretreatment. Inhibitors of PLC and CaMKII also enhanced VP-16 inhibition of Topo II-mediated DNA decatenation. Treatment with HA reduced VP-16 cytotoxic activity. On the other hand, U73122 and KN-62 enhanced VP-16 cytotoxic activity and reduced the ability of HA to promote VP-16 resistance. Our results suggest that HA, PLC, and CaMKII are upstream regulators of Topo II-mediated DNA metabolism in HNSCC and that this signaling pathway could be a promising target for the development of novel therapies against HNSCC.

Cross-talk between G Protein–Coupled Receptor and Epidermal Growth Factor Receptor Signaling Pathways Contributes to Growth and Invasion of Head and Neck Squamous Cell Carcinoma

G protein-coupled receptors (GPCR) and the epidermal growth factor receptor (EGFR) are often both overexpressed and contribute to the growth of cancers by activating autocrine pathways. GPCR ligands have been reported to trigger EGFR signaling via receptor cross-talk in cancer cells. Here, we show that GPCR ligands prostaglandin E2 (PGE2) and bradykinin (BK) activate EGFR signaling. Inhibition of EGFR using several strategies, including small-molecule inhibitors and an EGFR-specific antibody, resulted in partial attenuation of signaling downstream of EGFR. PGE2 and BK triggered EGFR signaling by increasing selective autocrine release of transforming growth factor-alpha (TGF-alpha). Inhibition of tumor necrosis factor-alpha-converting enzyme abrogated BK- or PGE2-mediated activation of EGFR signaling. Both PGE2 and BK stimulated head and neck squamous cell carcinoma (HNSCC) invasion via EGFR. Treatment of HNSCC cells with the BK antagonist CU201 resulted in growth inhibition. The combination of CU201 with the EGFR small-molecule inhibitor erlotinib resulted in additive inhibitory effects on HNSCC cell growth in vitro. Inhibition of the PGE2 synthesis pathway with sulindac induced HNSCC cytotoxicity at high doses (EC(50), 620 micromol/L). However, combined inhibition of both EGFR with the tyrosine kinase inhibitor erlotinib and GPCR with sulindac at low doses of 6 and 310 micromol/L, respectively, resulted in synergistic killing of HNSCC tumor cells. Combined blockade of both EGFR and GPCRs may be a rational strategy to treat cancers, including HNSCC that shows cross-talk between GPCR and EGFR signaling pathways.

EphB4 provides survival advantage to squamous cell carcinoma of the head and neck

The receptor tyrosine kinase EphB4 and its ligand EphrinB2 play critical roles in blood vessel maturation, and are frequently overexpressed in a wide variety of cancers. We studied the aberrant expression and biological role of EphB4 in head and neck squamous cell carcinoma (HNSCC). We tested the effect of EphB4-specific siRNA and antisense oligonucleotides (AS-ODN) on cell growth, migration and invasion, and the effect of EphB4 AS-ODN on tumor growth in vivo. All HNSCC tumor samples express EphB4 and levels of expression correlate directly with higher stage and lymph node metastasis. Six of 7 (86%) HNSCC cell lines express EphB4, which is induced either by EGFR activation or by EPHB4 gene amplification. EphrinB2 was expressed in 65% tumors and 5 of 7 (71%) cell lines. EphB4 provides survival advantage to tumor cells in that EphB4 siRNA and AS-ODN significantly inhibit tumor cell viability, induce apoptosis, activate caspase-8, and sensitize cells to TRAIL-induced cell death. Furthermore, EphB4-specific AS-ODN significantly inhibits the growth of HNSCC tumor xenografts in vivo. Expression of EphB4 in HNSCC tumor cells confers survival and invasive properties, and thereby provides a strong rationale for targeting EphB4 as novel therapy for HNSCC.

Fibroblast-derived MT1-MMP promotes tumor progression in vitro and in vivo

BackgroundIdentification of fibroblast derived factors in tumor progression has the potential to provide novel molecular targets for modulating tumor cell growth and metastasis. Multiple matrix metalloproteases (MMPs) are expressed by both mesenchymal and epithelial cells within head and neck squamous cell carcinomas (HNSCCs), but the relative importance of these enzymes and the cell source is the subject of controversy.MethodsThe invasive potential of HNSCC tumor cells were assessed in vitro atop type I collagen gels in coculture with wild-type (WT), MMP-2 null, MMP-9 null or MT1-MMP null fibroblasts. A floor of mouth mouse model of HNSCC was used to assess in vivo growth after co-injection of FaDu tumor cells with MMP null fibroblasts.ResultsHere we report changes in tumor phenotype when FaDu HNSCCs cells are cocultured with WT, MMP-2 null, MMP-9 null or MT1-MMP null fibroblasts in vitro and in vivo. WT, MMP-2 null and MMP-9 null fibroblasts, but not MT1-MMP null fibroblasts, spontaneously invaded into type I collagen gels. WT fibroblasts stimulated FaDu tumor cell invasion in coculture. This invasive phenotype was unaffected by combination with MMP-9 null fibroblasts, reduced with MMP-2 null fibroblasts (50%) and abrogated in MT1-MMP null fibroblasts. Co-injection of FaDu tumor cells with fibroblasts in an orthotopic oral cavity SCID mouse model demonstrated a reduction of tumor volume using MMP-9 and MMP-2 null fibroblasts (48% and 49%, respectively) compared to WT fibroblasts. Consistent with in vitro studies, MT1-MMP null fibroblasts when co-injected with FaDu cells resulted in a 90% reduction in tumor volume compared to FaDu cells injected with WT fibroblasts.ConclusionThese data suggest a role for fibroblast-derived MMP-2 and MT1-MMP in HNSCC tumor invasion in vitro and tumor growth in vivo.

Heparanase Expression at the Invasion Front of Human Head and Neck Cancers and Correlation with Poor Prognosis

Head and neck squamous cell carcinomas (HNSCC) are characterized by a poor prognosis due to aggressive, recurrent tumor growth. Expression of the extracellular matrix-degrading enzyme heparanase was associated with poorer prognosis in several cancers. We analyzed the presence of heparanase in HNSCC tissues and tumor cells and its potential prognostic significance. We analyzed the expression of the active form of heparanase in HNSCC tissues in corresponding tumor cell cultures and after xenotransplantation of tumor cell cultures into NOD/Scid mice by immunohistochemistry, Western blot analysis, and reverse transcription-PCR in altogether 25 patients and did a comparison with clinicopathologic data of the patients. Heparanase expression in situ was detected in all tumor biopsies in the tumor stroma and in tumor cells from 13 of 19 primary tumors and 9 of 12 lymph node metastases. Heparanase was localized in disseminated tumor cells, in tumor cell clusters invading adjacent stromal tissues, and in tumor cells at the tumor invasion front. Lymph node metastases expressed higher levels of heparanase compared with corresponding primary tumors. In contrast to a heterogeneous expression pattern in tumor tissues, all corresponding HNSCC tumor cell cultures showed a rather homogeneous heparanase expression on the mRNA and protein levels. Comparison of heparanase expression in situ and in corresponding tumor cell cultures in vitro or after xenotransplantation into NOD/Scid mice revealed that heparanase expression was regulated in vivo. Lack of heparanase in tumor cells from primary tumors or lymph node metastases was correlated with prolonged disease-free survival and overall survival. Heparanase expression seems to be involved in the invasiveness and aggressiveness of HNSCC.

Expression of vascular endothelial growth factor receptors on tumor cells in head and neck squamous cell carcinoma.

Angiogenesis is essential for the growth of solid tumors, including head and neck squamous cell carcinoma (HNSCC). Angiogenesis is regulated by angiogenic factors such as vascular endothelial growth factor (VEGF) and VEGF receptors (VEGFRs) 1, 2, and 3 known to be located on vascular endothelial cells (VECs). We hypothesize that VEGFRs are also expressed on HNSCC tumor cells in vitro and in vivo and likely control tumor function in vivo. Immunohistochemical analysis for VEGFR-1 (n = 13), VEGFR-2 (n = 21), and VEGFR-3 (n = 16) was performed on human HNSCC tumor samples. Specimens were analyzed for receptor expression and staining intensity. A cultured oral SCC cell line (SCC-25) and a pharyngeal SCC cell line (FADU) were also studied for receptor expression. The HNSCC tumor cells expressed VEGFR-1, VEGFR-2, and VEGFR-3 in all specimens evaluated. Staining for all 3 receptors was also found on tumor-associated macrophages and fibroblasts, except that VEGFR-2 was not present on fibroblasts. Staining intensity for VEGFR-1 and VEGFR-2 was significantly higher in tumor cells and macrophages than in VECs stained for the same receptor. Both cultured HNSCC cell lines demonstrated expression of all 3 receptors. This represents the first report of all 3 VEGFRs being expressed by HNSCC cells. These findings indicate that VEGF may be an autocrine regulator of tumor cell activity in addition to its known angiogenic effects on VECs. The presence of VEGFRs on tumor-associated macrophages and fibroblasts contributes to the complexity of the VEGF/VEGFR system in human cancer.

The ARF-p16 gene locus in carcinogenesis and therapy of head and neck squamous cell carcinoma.

We have identified families with a high incidence of tumors including head and neck squamous cell carcinoma (HNSCC). The occurrence of melanoma in these kindreds suggested that the ARF-p16 gene may be involved in carcinogenesis. We wished to determine the gene defect associated with the familial predisposition to HNSCC and to determine whether restoration of the gene may have therapeutic benefit. Translational molecular research. Molecular techniques were used to identify mutations of the ARF-p16 gene from the affected families and to test the activity of p16 and ARF mutants. In additional, HNSCC tumor tissue was analyzed to determine whether the wild-type p16 allele was lost or maintained. ARF-expressing adenoviruses were created, and their effect on HNSCC cell lines and normal head and neck epithelial cells was determined. Mutation of the ARF-p16 gene was found in two families with predisposition to develop HNSCC. Independent mutations detected in the germline DNA of both families inactivated p16, but not ARF, and the inactive mutant p16 allele segregated with disease within both families. The wild-type p16 allele was lost in HNSCC tumor tissue from both families. The efficacy of ARF in treatment of HNSCC was found to depend on retention of p53 activity within HNSCC tumor cells. Remarkably, ARF expression was found to kill cells, depending on loss of retinoblastoma activity. Because loss of retinoblastoma activity is nearly universal in tumors, ARF killed tumor cells that retained p53, but ARF spared normal cells. Our results support the recognition of a new clinical entity of familial head and neck cancer. We have shown that this syndrome is associated with inactivating mutations of the p16 gene that these mutations segregate with disease in two described families. Loss of the wild-type p16 allele in HNSCC tissue from both families strongly supports the role of the mutant p16 in carcinogenesis. We have also investigated the therapeutic utility of the alternate reading frame product of the p16 gene, ARF. The finding that ARF kills cells depending on loss of retinoblastoma activity and retention of p53 suggests that ARF may be effective in treatment of roughly 50% of head and neck cancers while sparing normal cells. Recognition of p16 mutations as an etiological factor in familial HNSCC provides an accessible tool for diagnosis of this syndrome. Clinical acceptance of familial head and neck cancer will ensure that patients are appropriately diagnosed and managed.

Retinoic acid modulates the ability of macrophages to participate in the induction of the angiogenic phenotype in head and neck squamous cell carcinoma.

Angiogenesis, an essential step in the development of neoplasia, is a complex process that involves the interaction of tumor cells with stromal cells. Tumor-associated macrophages (TAMs) can participate in the induction of angiogenesis and are of prognostic value in some neoplasms. Specimens from head and neck squamous cell carcinomas (HNSCC) often contain large numbers of TAMs. In addition, experimental evidence has demonstrated that HNSCC tumor cells can attract and activate macrophages to participate in the expression of the angiogenic phenotype. These findings suggest that antiangiogenic therapies for HNSCC must include strategies that will block the recruitment of macrophages into the tumor microenvironment. We investigated the ability of retinoic acid (RA) to modulate the ability of tumor cells to recruit and activate monocytes for participation in tumor angiogenesis. Owing to a decrease in the secretion of MCP-1 and transforming growth factor-beta 1 (TGF-beta 1), tumor cells treated with RA were unable to induce peripheral blood monocyte (PBM) chemotaxis. Also, as a result of the decrease in TGF-beta 1 secretion, RA-treated tumor cells were unable to activate macrophages for secretion of vascular endothelial growth factor (VEGF) and interleukin-8 (IL-8). In addition to its affects on tumor cells, RA also directly altered the ability of monocytes to participate in the tumor angiogenesis process. PBM exposed to RA were unable to migrate toward inducers of PBM such as MCP-1 and TGF-beta 1. Finally, RA decreased the ability of tumor-activated macrophages to secrete IL-8 and VEGF. These data demonstrate alternative mechanisms by which RA may modulate angiogenesis in the tumor microenvironment. In addition, it underscores the necessity to develop antiangiogenic treatment protocols that can block each of the ways in which new blood vessel growth is induced in tumor microenvironments.