IL-6 Inhibition With MEDI5117 Decreases The Fraction of Head and Neck Cancer Stem Cells and Prevents Tumor Recurrence

Head and neck squamous cell carcinomas (HNSCC) exhibit a small population of uniquely tumorigenic cancer stem cells (CSC) endowed with self-renewal and multipotency. We have recently shown that IL-6 enhances the survival and tumorigenic potential of head and neck cancer stem cells (i.e. ALDH(high)CD44(high) cells). Here, we characterized the effect of therapeutic inhibition of IL-6 with a novel humanized anti-IL-6 antibody (MEDI5117) using three low-passage patient-derived xenograft (PDX) models of HNSCC. We observed that single agent MEDI5117 inhibited the growth of PDX-SCC-M1 tumors (P < .05). This PDX model was generated from a previously untreated HNSCC. In contrast, MEDI5117 was not effective at reducing overall tumor volume for PDX models representing resistant disease (PDX-SCC-M0, PDX-SCC-M11). Low dose MEDI5117 (3 mg/kg) consistently decreased the fraction of cancer stem cells in PDX models of HNSCC when compared to IgG-treated controls, as follows: PDX-SCC-M0 (P < .001), PDX-SCC-M1 (P < .001), PDX-SCC-M11 (P = .04). Interestingly, high dose MEDI5117 (30 mg/kg) decreased the CSC fraction in the PDX-SCC-M11 model (P = .002), but not in PDX-SCC-M0 and PDX-SCC-M1. MEDI5117 mediated a dose-dependent decrease in the number of orospheres generated by ALDH(high)CD44(high) cells cultured in ultra-low attachment plates (P < .05), supporting an inhibitory effect on head and neck cancer stem cells. Notably, single agent MEDI5117 reduced the overall recurrence rate of PDX-SCC-M0, a PDX generated from the local recurrence of human HNSCC. Collectively, these data demonstrate that therapeutic inhibition of IL-6 with low-dose MEDI5117 decreases the fraction of cancer stem cells, and that adjuvant MEDI5117 inhibits recurrence in preclinical models of HNSCC.

Simvastatin inhibits the expression of inflammatory cytokines and cell adhesion molecules induced by LPS in human dental pulp cells

AIM

To investigate the effect of simvastatin on lipopolysaccharide (LPS)-stimulated inflammatory cytokines, cell adhesion molecules and nuclear factor-κB (NF-κB) transcription factors in human dental pulp cells (HDPCs).

METHODOLOGY

The effect of LPS and simvastatin on human dental pulp cell (HDPCs) viability was measured using a 3-[4, 5-dimethylthiazol-2-yl]-2, 5 diphenyltetrazolium bromide (MTT) assay. The expression of inflammatory cytokines and cell adhesion molecules was evaluated by reverse-transcription polymerase chain reaction (RT-PCR), enzyme-linked immunosorbent assay (ELISA) and Western blot analysis. NF-κB transcription factors were evaluated by Western blot analysis. Statistical analysis was performed with analysis of variance (anova).

RESULTS

The viability of cells exposed to different concentrations of E. coli LPS, P. gingivalis LPS and simvastatin was not significantly different compared with that of control cells (P > 0.05). LPS significantly increased interleukin (IL)-1β (P < 0.05) and IL-6 mRNA expression (P < 0.05) and vascular cell adhesion molecule-1 (VCAM-1) (P < 0.05) and intercellular adhesion molecule-1 (ICAM-1) protein expression (P < 0.05) in HDPCs. Treatment with simvastatin significantly attenuated LPS-stimulated production of IL-1β, IL-6, VCAM-1 and ICAM-1 (P < 0.05). Treatment with simvastatin decreased LPS-induced expression of p65 and phosphorylation of IκB and also significantly decreased the phosphorylation of p65 and IκB in the cytoplasm and the level of p65 in the nucleus (P < 0.05).

CONCLUSIONS

Simvastatin has a suppressing effect on LPS-induced inflammatory cytokine, cell adhesion molecules and NF-κB transcription factors in HDPCs. Therefore, simvastatin might be a useful candidate as a pulp-capping agent in vital pulp therapy.

Wnt/β-Catenin Signaling Determines the Vasculogenic Fate of Postnatal Mesenchymal Stem Cells

Vasculogenesis is the process of de novo blood vessel formation observed primarily during embryonic development. Emerging evidence suggest that postnatal mesenchymal stem cells are capable of recapitulating vasculogenesis when these cells are engaged in tissue regeneration. However, the mechanisms underlining the vasculogenic differentiation of mesenchymal stem cells remain unclear. Here, we used stem cells from human permanent teeth (dental pulp stem cells [DPSC]) or deciduous teeth (stem cells from human exfoliated deciduous teeth [SHED]) as models of postnatal primary human mesenchymal stem cells to understand mechanisms regulating their vasculogenic fate. GFP-tagged mesenchymal stem cells seeded in human tooth slice/scaffolds and transplanted into immunodeficient mice differentiate into human blood vessels that anastomize with the mouse vasculature. In vitro, vascular endothelial growth factor (VEGF) induced the vasculogenic differentiation of DPSC and SHED via potent activation of Wnt/β-catenin signaling. Further, activation of Wnt signaling is sufficient to induce the vasculogenic differentiation of postnatal mesenchymal stem cells, while Wnt inhibition blocked this process. Notably, β-catenin-silenced DPSC no longer differentiate into endothelial cells in vitro, and showed impaired vasculogenesis in vivo. Collectively, these data demonstrate that VEGF signaling through the canonical Wnt/β-catenin pathway defines the vasculogenic fate of postnatal mesenchymal stem cells. Stem Cells 2016;34:1576-1587.

Targeting MDM2 for Treatment of Adenoid Cystic Carcinoma

PURPOSE

There are no effective treatment options for patients with advanced adenoid cystic carcinoma (ACC). Here, we evaluated the effect of a new small molecule inhibitor of the MDM2-p53 interaction (MI-773) in preclinical models of ACC.

EXPERIMENTAL DESIGN

To evaluate the anti-tumor effect of MI-773, we administered it to mice harboring three different patient-derived xenograft (PDX) models of ACC expressing functional p53. The effect of MI-773 on MDM2, p53, phospho-p53, and p21 was examined by Western blots in 5 low passage primary human ACC cell lines and in MI-773-treated PDX tumors.

RESULTS

Single-agent MI-773 caused tumor regression in the 3 PDX models of ACC studied here. For example, we observed a tumor growth inhibition index of 127% in UM-PDX-HACC-5 tumors that was associated with an increase in the fraction of apoptotic cells (P = 0.015). The number of p53-positive cells was increased in MI-773-treated PDX tumors (P < 0.001), with a correspondent shift in p53 localization from the nucleus to the cytoplasm. Western blots demonstrated that MI-773 potently induced expression of p53 and its downstream targets p21, MDM2, and induced phosphorylation of p53 (serine 392) in low passage primary human ACC cells. Notably, MI-773 induced a dose-dependent increase in the fraction of apoptotic ACC cells and in the fraction of cells in the G1 phase of cell cycle (P < 0.05).

CONCLUSIONS

Collectively, these data demonstrate that therapeutic inhibition of the MDM2-p53 interaction with MI-773 activates downstream effectors of apoptosis and causes robust tumor regression in preclinical models of ACC. Clin Cancer Res; 22(14); 3550-9. ©2016 AACR.

The Perivascular Niche and Self-Renewal of Stem Cells

Postnatal stem cells are typically found in niches that provide signaling cues to maintain their self-renewal and multipotency. While stem cell populations may serve distinct purposes within their tissue of origin, understanding the conserved biology of stem cells and their respective niches provides insights to the behavior of these cells during homeostasis and tissue repair. Here, we discuss perivascular niches of two distinct stem cell populations (i.e., hematopoietic stem cells, mesenchymal stem cells) and explore mechanisms that sustain these stem cells postnatally. We highlight work that demonstrates the impact of cellular crosstalk to stem cell self-renewal and maintenance of functional perivascular niches. We also discuss the importance of the crosstalk within the perivascular niche to the biology of stem cells, and describe the regenerative potential of perivascular cells. We postulate that signaling events that establish and/or stabilize the perivascular niche, particularly through the modulation of self-renewing factors, are key to the long-term success of regenerated tissues.

Anti-tumor effect of inhibition of IL-6 signaling in mucoepidermoid carcinoma

Mucoepidermoid carcinoma (MEC) is the most frequent malignant salivary gland cancer. Response to chemoradiotherapy is modest, and therefore radical surgery remains the standard-of-care. Emerging evidence suggests that Interleukin (IL)-6 signaling correlates with the survival of cancer stem cells and resistance to therapy. Here, we investigated whether inhibition of IL-6 receptor (IL-6R) signaling with tocilizumab (humanized anti-human IL-6R antibody) sensitizes MEC to chemotherapy using human mucoepidermoid carcinoma cell lines (UM-HMC) and correspondent xenograft models. In vitro, we observed that tocilizumab inhibited STAT3 phosphorylation but had no measurable effect in MEC cell viability (UM-HMC-1,-3A,-3B). In contrast, the anti-tumor effect of single agent tocilizumab on MEC xenografts was comparable to paclitaxel or cisplatin. Combination of tocilizumab with cisplatin or paclitaxel enhanced the inhibitory effect of chemotherapy on xenograft growth (P < 0.05), time to failure (P < 0.01), decreased vascular endothelial growth factor (VEGF) expression and tumor microvessel density (P < 0.05) without added systemic toxicities. Notably, tocilizumab decreased the fraction of MEC cancer stem cells (ALDH(high)CD44(high)) in vitro, and prevented paclitaxel-induced increase in the fraction of cancer stem cells in vivo (P < 0.05). Collectively, these findings demonstrate that tocilizumab enhances the anti-tumor effect of conventional chemotherapy in preclinical models of mucoepidermoid carcinoma, and suggest that patients might benefit from combination therapy with an inhibitor of IL-6R signaling and chemotherapeutic agent such as paclitaxel.

Endothelial interleukin-6 defines the tumorigenic potential of primary human cancer stem cells

Head and neck squamous cell carcinomas (HNSCC) contain a small subpopulation of stem cells endowed with unique capacity to generate tumors. These cancer stem cells (CSC) are localized in perivascular niches and rely on crosstalk with endothelial cells for survival and self-renewal, but the mechanisms involved are unknown. Here, we report that stromal interleukin (IL)-6 defines the tumorigenic capacity of CSC sorted from primary human HNSCC and transplanted into mice. In search for the cellular source of Interleukin-6 (IL-6), we observed a direct correlation between IL-6 levels in tumor-associated endothelial cells and the tumorigenicity of CSC. In vitro, endothelial cell-IL-6 enhanced orosphere formation, p-STAT3 activation, survival, and self-renewal of human CSC. Notably, a humanized anti-IL-6R antibody (tocilizumab) inhibited primary human CSC-mediated tumor initiation. Collectively, these data demonstrate that endothelial cell-secreted IL-6 defines the tumorigenic potential of CSC, and suggest that HNSCC patients might benefit from therapeutic inhibition of IL-6/IL-6R signaling.

The dental pulp stem cell niche based on aldehyde dehydrogenase 1 expression

AIM

To detect cells expressing the stem cell marker ALDH1 (aldehyde dehydrogenase1) in the pulp of human permanent teeth and to investigate the expression of ALDH1 in isolated dental pulp cells.

METHODOLOGY

Pulp tissue was collected and processed for immunohistochemistry to detect ALDH1-, STRO-1- and CD90-positive cells. In addition, cells were isolated and analysed by flow cytometry for ALDH1 activity and for the cell surface markers CD44, CD73, CD90, STRO-1 and CD45. Cells were also examined for multidifferentiation capacity. Within these cells, an ALDH1(+) cell subpopulation was selected and evaluated for multidifferentiation capacity.

RESULTS

The immunohistochemistry analyses showed that ALDH1-, CD90- and STRO-1-positive cells were located mainly in the perivascular areas and nerve fibres of dental pulps. Cells on the fifth passage had high expression for CD44, CD73 and CD90, whereas moderate labelling was observed for STRO-1 and ALDH1 in flow cytometry analysis. On the same passages, cells were able to differentiate into osteogenic, adipogenic and chondrogenic lineages. The ALDH1(+) cell subpopulation also demonstrated multilineage differentiation ability.

CONCLUSIONS

Dental pulp stem cells reside in the vicinity of blood vessels and nerve fibres, indicating the possible existence of more than one stem cell niche in dental pulps. Furthermore, ALDH1 was expressed by isolated dental pulp cells, which had mesenchymal stem cell characteristics. Thus, it can be suggested that ALDH1 may be used as a DPSC marker.

Stem cell-based pulp tissue engineering: variables enrolled in translation from the bench to the bedside, a systematic review of literature

Stem cell-based therapy (SC-BT) is emerging as an alternative for endodontic therapies. The interaction between stem cells and scaffolds plays a crucial role in the generation of a 'friendly cell' microenvironment. The aim of this systematic review was to explore techniques applied to regenerate the pulp-dentine complex tissue using SC-BT. An electronic search into the SciVerse Scopus (SS), ISI Web Science (IWS) and Entrez PubMed (EP) using specific keywords was performed. Specific inclusion and exclusion criteria were predetermined. The search yielded papers, out of which full-text papers were included in the final analyses. Data extraction pooled the results in four main topics: (a) influence of the chemical properties of the scaffolds over cell behaviour; (b) influence of the physical characteristics of scaffolds over cell behaviour; (c) strategies applied to improve the stem cell/scaffold interface; and (d) influence of cue microenvironment on stem cell differentiation towards odontoblast-like cells and pulp-like tissue formation. The relationship between the scaffolds, the environment and the growth factors released from dentine are critical for de novo pulp tissue regeneration. The preconditioning of dentine walls with ethylenediaminetetraacetic acid (EDTA) was imperative for successful pulp-dentine complex regeneration. An analyses of the grouped results revealed that pulp regeneration was an attainable goal.

BH3-mimetic small molecule inhibits the growth and recurrence of adenoid cystic carcinoma

OBJECTIVES

To evaluate the anti-tumor effect of BM-1197, a new potent and highly specific small molecule inhibitor of Bcl-2/Bcl-xL, in preclinical models of human adenoid cystic carcinoma (ACC).

METHODS

Low passage primary human adenoid cystic carcinoma cells (UM-HACC-2A,-2B,-5,-6) and patient-derived xenograft (PDX) models (UM-PDX-HACC) were developed from surgical specimens obtained from 4 patients. The effect of BM-1197 on cell viability and cell cycle were evaluated in vitro using this panel of low passage ACC cells. The effect of BM-1197 on tumor growth, recurrence and tumor cell apoptosis in vivo was evaluated with the PDX model of ACC (UM-PDX-HACC-5).

RESULTS

Exposure of low passage primary human ACC cells to BM-1197 mediated an IC50 of 0.92-2.82 μM. This correlated with an increase in the fraction of apoptotic cells (p<0.0001) and an increase in caspase-3 activity (p<0.0001), but no noticeable differences in cell cycle (p>0.05). In vivo, BM-1197 inhibited tumor growth (p=0.0256) and induced tumor cell apoptosis (p=0.0165) without causing significant systemic toxicities, as determined by mouse weight over time. Surprisingly, weekly BM-1197 decreased the incidence of tumor recurrence (p=0.0297), as determined by Kaplan-Meier analysis.

CONCLUSION

These data demonstrated that single agent BM-1197 induces apoptosis and inhibits tumor growth in preclinical models of adenoid cystic carcinoma. Notably, single agent BM-1197 inhibited tumor recurrence, which is considered a major clinical challenge in the clinical management of adenoid cystic carcinoma. Collectively, these results suggest that patients with adenoid cystic carcinoma might benefit from therapy with a BH3-mimetic small molecule.

Effects of ciprofloxacin-containing antimicrobial scaffolds on dental pulp stem cell viability-In vitro studies

OBJECTIVE

A combination of antibiotics, including but not limited to metronidazole (MET) and ciprofloxacin (CIP), has been indicated to eradicate bacteria in necrotic immature permanent teeth prior to regenerative procedures. It has been shown clinically that antibiotic pastes may lead to substantial stem cell death. The aim of this study was to synthesise scaffolds containing various concentrations of CIP to enhance cell viability while preserving antimicrobial properties.

DESIGN

Polydioxanone (PDS)-based electrospun scaffolds were processed with decreasing CIP concentrations (25-1 wt.%) and morphologically evaluated using scanning electron microscopy (SEM). Cytotoxicity assays were performed to determine whether the amount of CIP released from the scaffolds would lead to human dental pulp stem cell (hDPSC) toxicity. Similarly, WST-1 assays were performed to evaluate the impact of CIP release on hDPSC proliferation. Pure PDS scaffolds and saturated double antibiotic solution MET/CIP (DAP) served as both positive and negative controls, respectively. Antibacterial efficacy against E. faecalis (Ef) was tested.

RESULTS

A significant decrease in hDPSC' viability at concentrations 5-25 wt.% was observed. However, concentrations below 5wt.% did not impair cell viability. Data from the WST-1 assays indicated no detrimental impact on cell proliferation for scaffolds containing 2.5 wt.% CIP or less. Significant antimicrobial properties were seen for CIP-scaffolds at lower concentrations (i.e., 1 and 2.5 wt.%).

CONCLUSION

The obtained data demonstrated that a reduced concentration of CIP incorporated into PDS-based scaffolds maintains its antimicrobial properties while enhancing viability and proliferation of dental pulp stem cells.

Dental pulp stem cell responses to novel antibiotic-containing scaffolds for regenerative endodontics

AIM

To evaluate both the drug-release profile and the effects on human dental pulp stem cells' (hDPSC) proliferation and viability of novel bi-mix antibiotic-containing scaffolds intended for use as a drug delivery system for root canal disinfection prior to regenerative endodontics.

METHODOLOGY

Polydioxanone (PDS)-based fibrous scaffolds containing both metronidazole (MET) and ciprofloxacin (CIP) at selected ratios were synthesized via electrospinning. Fibre diameter was evaluated based on scanning electron microscopy (SEM) images. Pure PDS scaffolds and a saturated CIP/MET solution (i.e. 50 mg of each antibiotic in 1 mL) (hereafter referred to as DAP) served as both negative (nontoxic) and positive (toxic) controls, respectively. High-performance liquid chromatography (HPLC) was performed to investigate the amount of drug(s) released from the scaffolds. WST-1(®) proliferation assay was used to evaluate the effect of the scaffolds on cell proliferation. LIVE/DEAD(®) assay was used to qualitatively assess cell viability. Data obtained from drug release and proliferation assays were statistically analysed at the 5% significance level.

RESULTS

A burst release of CIP and MET was noted within the first 24 h, followed by a sustained maintenance of the drug(s) concentration for 14 days. A concentration-dependent trend was noticed upon hDPSCs' exposure to all CIP-containing scaffolds, where increasing the CIP concentration resulted in reduced cell proliferation (P < 0.05) and viability. In groups exposed to pure MET or pure PDS scaffolds, no changes in proliferation were observed.

CONCLUSIONS

Synthesized antibiotic-containing scaffolds had significantly lower effects on hDPSCs proliferation when compared to the saturated CIP/MET solution (DAP).

The effectiveness of propolis on gingivitis: a randomized controlled trial

BACKGROUND

A randomized, double-blind, controlled clinical trial was conducted to evaluate the effectiveness of a propolis rinse on induced gingivitis by using the co-twin study design.

METHODS

Twenty-one twin pairs (n=42) were enrolled in a gingivitis study with oral hygiene promotion (14 days) and gingivitis induction (21 days). During the gingivitis induction phase, one member of the twin pair was randomly assigned to a 2% typified propolis rinse, and the other was assigned a color-matched 0.05% sodium fluoride plus 0.05% cetylpyridinium chloride rinse (positive control). Patients rinsed twice daily with 20 mL for 30 seconds for 21 days. Gingivitis was measured on days -14 (baseline), 0 (after hygiene phase), and 21 (after no-hygiene phase) by using the Papillary Bleeding Score (PBS) and by standard digital imaging of the gum tissues (G-parameter).

RESULTS

The 38 persons who completed the study (age 13-22 years) were well balanced according to PBS at baseline and G-parameter after the initial hygiene phase. After 21 days without oral hygiene, the propolis rinse and positive control rinse groups did not differ significantly for average PBS measurements or G-parameter.

CONCLUSIONS

Use of a 2% typified propolis rinse was equivalent to a positive control rinse during a 21-day no-hygiene period.

Tissue-engineering-based strategies for regenerative endodontics

Stemming from in vitro and in vivo pre-clinical and human models, tissue-engineering-based strategies continue to demonstrate great potential for the regeneration of the pulp-dentin complex, particularly in necrotic, immature permanent teeth. Nanofibrous scaffolds, which closely resemble the native extracellular matrix, have been successfully synthesized by various techniques, including but not limited to electrospinning. A common goal in scaffold synthesis has been the notion of promoting cell guidance through the careful design and use of a collection of biochemical and physical cues capable of governing and stimulating specific events at the cellular and tissue levels. The latest advances in processing technologies allow for the fabrication of scaffolds where selected bioactive molecules can be delivered locally, thus increasing the possibilities for clinical success. Though electrospun scaffolds have not yet been tested in vivo in either human or animal pulpless models in immature permanent teeth, recent studies have highlighted their regenerative potential both from an in vitro and in vivo (i.e., subcutaneous model) standpoint. Possible applications for these bioactive scaffolds continue to evolve, with significant prospects related to the regeneration of both dentin and pulp tissue and, more recently, to root canal disinfection. Nonetheless, no single implantable scaffold can consistently guide the coordinated growth and development of the multiple tissue types involved in the functional regeneration of the pulp-dentin complex. The purpose of this review is to provide a comprehensive perspective on the latest discoveries related to the use of scaffolds and/or stem cells in regenerative endodontics. The authors focused this review on bioactive nanofibrous scaffolds, injectable scaffolds and stem cells, and pre-clinical findings using stem-cell-based strategies. These topics are discussed in detail in an attempt to provide future direction and to shed light on their potential translation to clinical settings.

Fluorapatite-modified scaffold on dental pulp stem cell mineralization

In previous studies, fluorapatite (FA) crystal-coated surfaces have been shown to stimulate the differentiation and mineralization of human dental pulp stem cells (DPSCs) in two-dimensional cell culture. However, whether the FA surface can recapitulate these properties in three-dimensional culture is still unknown. This study examined the differences in behavior of human DPSCs cultured on electrospun polycaprolactone (PCL) NanoECM nanofibers with or without the FA crystals. Under near-physiologic conditions, the FA crystals were synthesized on the PCL nanofiber scaffolds. The FA crystals were evenly distributed on the scaffolds. DPSCs were cultured on the PCL+FA or the PCL scaffolds for up to 28 days. Scanning electron microscope images showed that DPSCs attached well to both scaffolds after the initial seeding. However, it appeared that more multicellular aggregates formed on the PCL+FA scaffolds. After 14 days, the cell proliferation on the PCL+FA was slower than that on the PCL-only scaffolds. Interestingly, even without any induction of mineralization, from day 7, the upregulation of several pro-osteogenic molecules (dmp1, dspp, runx2, ocn, spp1, col1a1) was detected in cells seeded on the PCL+FA scaffolds. A significant increase in alkaline phosphatase activity was also seen on FA-coated scaffolds compared with the PCL-only scaffolds at days 14 and 21. At the protein level, osteocalcin expression was induced only in the DPSCs on the PCL+FA surfaces at day 21 and then significantly enhanced at day 28. A similar pattern was observed in those specimens stained with Alizarin red and Von Kossa after 21 and 28 days. These data suggest that the incorporation of FA crystals within the three-dimensional PCL nanofiber scaffolds provided a favorable extracellular matrix microenvironment for the growth, differentiation, and mineralization of human DPSCs. This FA-modified PCL nanofiber scaffold shows promising potential for future bone, dental, and orthopedic regenerative applications.

Glucose-regulated protein 78 (Grp78) confers chemoresistance to tumor endothelial cells under acidic stress

OBJECTIVES

This study was designed to investigate the activation of the unfolded protein response (UPR) in tumor associated endothelial cells (TECs) and its association with chemoresistance during acidic pH stress.

MATERIALS AND METHODS

Endothelial cells from human oral squamous cell carcinomas (OSCC) were excised by laser capture microdissection (LCM) followed by analysis of UPR markers (Grp78, ATF4 and CHOP) using quantitative PCR. Grp78 expression was also determined by immunostaining. Acidic stress was induced in primary human dermal microvascular endothelial cells (HDMECs) by treatment with conditioned medium (CM) from tumor cells grown under hypoxic conditions or by adjusting medium pH to 6.4 or 7.0 using lactic acid or hydrochloric acid (HCl). HDMEC resistance to the anti-angiogenic drug Sunitinib was assessed with SRB assay.

RESULTS

UPR markers, Grp78, ATF4 and CHOP were significantly upregulated in TECs from OSCC compared to HDMECs. HDMECs cultured in acidic CM (pH 6.0-6.4) showed increased expression of the UPR markers. However, severe acidosis led to marked cell death in HDMECs. Alternatively, HDMECs were able to adapt when exposed to chronic acidosis at pH 7.0 for 7 days, with concomittant increase in Grp78 expression. Chronic acidosis also confers drug resistance to HDMECs against Sunitinib. Knockdown of Grp78 using shRNA resensitizes HDMECs to drug treatment.

CONCLUSIONS

UPR induction in ECs under acidic pH conditions is related to chemoresistance and may contribute to therapeutic failures in response to chemotherapy. Targeting Grp78, the key component of the UPR pathway, may provide a promising approach to overcome ECs resistance in cancer therapy.

Endothelial cell-secreted EGF induces epithelial to mesenchymal transition and endows head and neck cancer cells with stem-like phenotype

Emerging evidence suggests that endothelial cell-secreted factors contribute to the pathobiology of squamous cell carcinoma (SCC) by enhancing invasive migration and resistance to anoikis. Here, we report that SCC cells within the perivascular niche have undergone epithelial to mesenchymal transition (EMT) in a primary human SCC of a patient that developed distant metastases. Endothelial cell-secreted EGF induced EMT of human SCC cells in vitro and also induced acquisition of a stem-like phenotype. In vivo, tumor xenografts vascularized with EGF-silenced endothelial cells exhibited a smaller fraction of cancer stem-like cells (ALDH(+)CD44(+)) and were less invasive than tumors vascularized with control endothelial cells. Collectively, these results demonstrated that endothelial cell-EGF induces EMT and acquisition of stem-like properties by head and neck tumor cells. On this basis, we suggest that vascular endothelial cells contribute to tumor dissemination by secreting factors that endow carcinoma cells with enhanced motility and stemness.

Transcriptional factor ATF6 is involved in odontoblastic differentiation

ATF6 is an endoplasmic reticulum (ER) membrane-bound transcription factor that regulates various cellular functions. The purpose of this study was to investigate the role of ATF6 in odontoblast differentiation. Rat tooth germs were isolated, changes in gene expression were evaluated over time, and localization of ATF6 was determined by immunohistochemistry. Human dental pulp cells (HDPCs) were cultured with 50 µg/mL ascorbic acid and 5 mmol/L β-glycerophosphate or 100 ng/mL bone morphogenetic protein 2 to induce differentiation. Translocation of ATF6 was observed by immunofluorescence and confocal microscopy. Overexpression of ATF6 was performed with an adenoviral vector. Matrix mineralization was evaluated by alizarin red staining. Immunoreactivity to anti-ATF6 was observed in the odontoblastic layer of the molar tooth germ, and expressions of ATF6, dentin sialophosphoprotein (DSPP) and dentin matrix protein 1 (DMP1) increased gradually during tooth germ development. When HDPCs were cultured in differentiation media, ATF6, DSPP, and DMP1 expression increased with the expression of unfolded protein response (UPR) markers, BiP and CHOP. Immunofluorescence results showed that ATF6 protein moved from cytoplasm to nucleus when cells were exposed to differentiation media. Notably, overexpression of ATF6 increased DSPP and DMP1 expression, alkaline phosphatase (ALP) activity, and matrix mineralization in HDPC cultures. Inhibition of ATF6 decreased ALP activity and mineralization. These results suggest that ER membrane-bound transcriptional factor ATF6 may be involved in odontoblastic differentiation.

Endothelial cell-derived interleukin-6 regulates tumor growth

BACKGROUND

Endothelial cells play a complex role in the pathobiology of cancer. This role is not limited to the making of blood vessels to allow for influx of oxygen and nutrients required for the high metabolic demands of tumor cells. Indeed, it has been recently shown that tumor-associated endothelial cells secrete molecules that enhance tumor cell survival and cancer stem cell self-renewal. The hypothesis underlying this work is that specific disruption of endothelial cell-initiated signaling inhibits tumor growth.

METHODS

Conditioned medium from primary human dermal microvascular endothelial cells (HDMEC) stably transduced with silencing RNA for IL-6 (or controls) was used to evaluate the role of endothelial-derived IL-6 on the activation of key signaling pathways in tumor cells. In addition, these endothelial cells were co-transplanted with tumor cells into immunodefficient mice to determine the impact of endothelial cell-derived IL-6 on tumor growth and angiogenesis.

RESULTS

We observed that tumor cells adjacent to blood vessels show strong phosphorylation of STAT3, a key mediator of tumor progression. In search for a possible mechanism for the activation of the STAT3 signaling pathway, we observed that silencing interleukin (IL)-6 in tumor-associated endothelial cells inhibited STAT3 phosphorylation in tumor cells. Notably, tumors vascularized with IL-6-silenced endothelial cells showed lower intratumoral microvessel density, lower tumor cell proliferation, and slower growth than tumors vascularized with control endothelial cells.

CONCLUSIONS

Collectively, these results demonstrate that IL-6 secreted by endothelial cells enhance tumor growth, and suggest that cancer patients might benefit from targeted approaches that block signaling events initiated by endothelial cells.

Spatial distribution of cancer stem cells in head and neck squamous cell carcinomas

BACKGROUND

CD44 and aldehyde dehydrogenase 1 (ALDH1) are considered putative markers of highly tumorigenic cells (i.e., cancer stem-like cells) in head and neck squamous cell carcinomas. This small subset of cells is believed to be the primary responsible for tumor initiation and progression. The objectives of this study were (i) to evaluate the patterns of CD44 and ALDH1 expression in the tumor center and in the invasive front, as well as in adjacent non-tumor epithelium, and (ii) to correlate these findings with clinical parameters.

MATERIALS AND METHODS

The sample comprised 44 patients with primary head and neck squamous cell carcinomas. Hematoxylin and eosin (HE) staining was used for histopathological tumor grading and for morphological analysis of adjacent non-tumor epithelium. Semiquantitative analysis was performed in histological sections immunostained for CD44 and ALDH1.

RESULTS

ALDH1 immunostaining in the invasive front showed positive association with tumor size, regional metastasis, tumor histopathological grading, and disease progression. Moreover, expression of this marker in both tumor invasive front and adjacent non-tumor epithelium was related with more aggressive tumors. CD44 immunostaining was heterogeneous in all areas evaluated and did not show association with clinical data.

CONCLUSION

Collectively, these data suggest that ALDH1 immunostaining in the invasive front and in adjacent non-tumor epithelium may help identify tumors with a more aggressive behavior, potentially contributing to improving treatment customization and the monitoring of patients with head and neck cancer.

White mineral trioxide aggregate induces migration and proliferation of stem cells from the apical papilla

INTRODUCTION

Regenerative endodontic protocols recommend white mineral trioxide aggregate (WMTA) as a capping material because of its osteoinductive properties. Stem cells from the apical papilla (SCAP) are presumed to be involved in this regenerative process, but the effects of WMTA on SCAP are largely unknown. Our hypothesis was that WMTA induces proliferation and migration of SCAP.

METHODS

Here we used an unsorted population of SCAP (passages 3-5) characterized by high CD24, CD146, and Stro-1 expression. The effect of WMTA on SCAP migration was assessed by using transwells, and its effect on proliferation was determined by the WST-1 assay. Fetal bovine serum (FBS) and calcium chloride-enriched medium were used as positive controls.

RESULTS

The SCAP analyzed here showed a low percentage of STRO-1+ and CD24+ cells. Both set and unset WMTA significantly increased the short-term migration of SCAP after 6 hours (P < .05), whereas calcium chloride-enriched medium did after 24 hours of exposure. Set WMTA significantly increased proliferation on days 1-5, whereas calcium-enriched medium showed a significant increase on day 7, with a significant reduction on proliferation afterwards. SCAP migration and proliferation were significantly and steadily induced by the presence of 2% and 10% FBS.

CONCLUSIONS

Collectively, these data demonstrate that WMTA induced an early short-term migration and proliferation of a mixed population of stem cells from apical papilla as compared with a later and longer-term induction by calcium chloride or FBS.

Oncogenic somatic events in tissue-specific stem cells: a role in cancer recurrence?

Tissue-specific stem cells (TSSCs) are a very unique cell type, with critical and well-defined roles for the homeostasis of high turnover tissues (such as the blood and the skin). Emerging evidence suggests that TSSCs are implicated in malignancies, with several theories being proposed and tested, including many attempts to identify the cells of origin and studies deigned to understand how TSSCs participate in age-related increase in cancer risk. A currently unexplored possibility in this respect is the plausible theory that an oncogenic event that arises at a TSSC would promote tissue replenishment by cells containing these mutations, with progressive propagation of such mutated TSSCs in the niche. Therefore, the effect of a somatic oncogenic event in a single TSSC may have more important implications than previously anticipated, resulting in sustained and progressively higher cancer risk. This model could have important implications for tumor recurrence, since in some cases the underlying cause might be the development of a new tumor originated from daughter cells of the TSSC that suffered the first oncogenic hit, rather than proliferation of residual cancer cells. In this review, we present and discuss approaches for testing the proposed theory of tumorigenesis and cancer risk, as well as practical implications for biomedical research and clinical practice.

Characterization of tumorigenic cell lines from the recurrence and lymph node metastasis of a human salivary mucoepidermoid carcinoma

The long-term outcome of patients with mucoepidermoid carcinoma is poor. Limited availability of cell lines and lack of xenograft models is considered a major barrier to improved mechanistic understanding of this disease and development of effective therapies.

OBJECTIVE

To generate and characterize human mucoepidermoid carcinoma cell lines and xenograft models suitable for mechanistic and translational studies.

METHODS

Five human mucoepidermoid carcinoma specimens were available for generation of cell lines. Cell line tumorigenic potential was assessed by transplantation and serial in vivo passaging in immunodeficient mice, and cell line authenticity verified by short tandem repeat (STR) profiling.

RESULTS

A unique pair of mucoepidermoid carcinoma cell lines was established from a local recurrence (UM-HMC-3A) and from the metastatic lymph node (UM-HMC-3B) of the same patient, 4 years after surgical removal of the primary tumor. These cell lines retained epithelial-like morphology through 100 passages in vitro, contain the Crtc1-Maml2 fusion oncogene (characteristic of mucoepidermoid carcinomas), and express the prototypic target of this fusion (NR4A2). Both cell lines generated xenograft tumors when transplanted into immunodeficient mice. Notably, the xenografts exhibited histological features and Periodic Acid Schiff (PAS) staining patterns that closely resembled those found in human tumors. STR profiling confirmed the origin and authenticity of these cell lines.

CONCLUSION

These data demonstrate the generation and characterization of a pair of tumorigenic salivary mucoepidermoid carcinoma cell lines representative of recurrence and lymph node metastasis. Such models are useful for mechanistic and translational studies that might contribute to the discovery of new therapies for mucoepidermoid carcinoma.

Fluorapatite enhances mineralization of mesenchymal/endothelial cocultures

In addition to the widely used mesenchymal stem cells (MSCs), endothelial cells appear to be a favorable cell source for hard tissue regeneration. Previously, fluorapatite was shown to stimulate and enhance mineralization of MSCs. This study aims to investigate the growth of endothelial cells on synthesized ordered fluorapatite surfaces and their effect on the mineralization of adipose-derived stem cells (ASCs) through coculture. Endothelial cells were grown on fluorapatite surfaces and characterized by cell counting, flow cytometry, scanning electron microscopy, and enzyme-linked immunosorbent assay (ELISA). Cells were then cocultured with ASCs and stained for alkaline phosphatase and mineral formation. Fibroblast growth factor (FGF) pathway perturbation and basic FGF (bFGF) treatment of the ASCs were also conducted to observe their effects on differentiation and mineralization of these cells. Fluorapatite surfaces showed good biocompatibility in supporting endothelial cells. Without a mineralization supplement, coculture with endothelial cells induced osteogenic differentiation of ASCs, which was further enhanced by the fluorapatite surfaces. This suggested a combined stimulating effect of endothelial cells and fluorapatite surfaces on the enhanced mineralization of ASCs. Greater amounts of bFGF release by endothelial cells alone or cocultures with ASCs stimulated by fluorapatite surfaces, together with FGF pathway perturbation and bFGF treatment results, suggested that the FGF signaling pathway may function in this process.

Dental pulp tissue engineering in full-length human root canals

The clinical translation of stem-cell-based dental pulp regeneration will require the use of injectable scaffolds. Here, we tested the hypothesis that stem cells from exfoliated deciduous teeth (SHED) can generate a functional dental pulp when injected into full-length root canals. SHED survived and began to express putative markers of odontoblastic differentiation after 7 days when mixed with Puramatrix™ (peptide hydrogel), or after 14 days when mixed with recombinant human Collagen (rhCollagen) type I, and injected into the root canals of human premolars in vitro. Roots of human premolars injected with scaffolds (Puramatrix™ or rhCollagen) containing SHED were implanted subcutaneously into immunodeficient mice (CB-17 SCID). We observed pulp-like tissues with odontoblasts capable of generating new tubular dentin throughout the root canals. Notably, the pulp tissue engineered with SHED injected with either Puramatrix™ or rhCollagen type I presented similar cellularity and vascularization when compared with control human dental pulps. Analysis of these data, collectively, demonstrates that SHED injected into full-length human root canals differentiate into functional odontoblasts, and suggests that such a strategy might facilitate the completion of root formation in necrotic immature permanent teeth.

CT perfusion can predict overexpression of CXCL8 (interleukin-8) in head and neck squamous cell carcinoma

BACKGROUND AND PURPOSE

Increased angiogenesis in head and neck squamous cell carcinoma correlates to more aggressive tumors with increased morbidity. Because both elevated blood flow and high serum CXCL8 levels are correlated with increased angiogenesis, our objective was to see if elevated blood flow measured with CT perfusion correlated with CXCL8 levels, thereby helping to identify candidates for targeted therapies that inhibit the Bcl-2 proangiogenic pathway associated with CXCL8.

MATERIALS AND METHODS

Seven patients with locally recurrent or metastatic head and neck squamous cell carcinoma were enrolled in the trial. These patients underwent CT perfusion and the following parameters were measured: blood volume, blood flow, capillary permeability, and MTT; relative values were calculated by dividing by normal-appearing muscle. Serum was drawn for CXCL8 enzyme-linked immunosorbent assay analysis in these patients.

RESULTS

There was a significant positive correlation between the CXCL8 levels and relative blood flow (r = 0.94; P = .01). No correlation was found between CXCL8 and relative blood volume, relative capillary permeability, or relative MTT.

CONCLUSIONS

Relative blood flow may be useful as a surrogate marker for elevated CXCL8 in patients with head and neck squamous cell cancer. Patients with elevated relative blood flow may benefit from treatment targeting the Bcl-2 proangiogenic pathways.

Salivary gland cancer stem cells

Emerging evidence suggests the existence of a tumorigenic population of cancer cells that demonstrate stem cell-like properties such as self-renewal and multipotency. These cells, termed cancer stem cells (CSC), are able to both initiate and maintain tumor formation and progression. Studies have shown that CSC are resistant to traditional chemotherapy treatments preventing complete eradication of the tumor cell population. Following treatment, CSC are able to re-initiate tumor growth leading to patient relapse. Salivary gland cancers are relatively rare but constitute a highly significant public health issue due to the lack of effective treatments. In particular, patients with mucoepidermoid carcinoma or adenoid cystic carcinoma, the two most common salivary malignancies, have low long-term survival rates due to the lack of response to current therapies. Considering the role of CSC in resistance to therapy in other tumor types, it is possible that this unique sub-population of cells is involved in resistance of salivary gland tumors to treatment. Characterization of CSC can lead to better understanding of the pathobiology of salivary gland malignancies as well as to the development of more effective therapies. Here, we make a brief overview of the state-of-the-science in salivary gland cancer, and discuss possible implications of the cancer stem cell hypothesis to the treatment of salivary gland malignancies.

Synergistic combination of small molecule inhibitor and RNA interference against antiapoptotic Bcl-2 protein in head and neck cancer cells

B-cell lymphoma 2 (Bcl-2) is an antiapoptotic protein that is overexpressed in head and neck squamous cell carcinomas, which has been implicated in development of radio- and chemoresistance. Small molecule inhibitors such as AT-101 (a BH3-mimetic drug) have been developed to inhibit the antiapoptotic activity of Bcl-2 proteins, which proved effective in restoring radio- and chemo-sensitivity in head and neck cancer cells. However, high doses of AT-101 are associated with gastrointestinal, hepatic, and fertility side effects, which prompted the search for other Bcl-2 inhibitors. Short interfering RNA (siRNA) proved to inhibit antiapoptotic Bcl-2 protein expression and trigger cancer cell death. However, transforming siRNA molecules into a viable therapy remains a challenge due to the lack of efficient and biocompatible carriers. We report the development of degradable star-shaped polymers that proved to condense anti-Bcl-2 siRNA into "smart" pH-sensitive and membrane-destabilizing particles that shuttle their cargo past the endosomal membrane and into the cytoplasm of head and neck cancer cells. Results show that "smart" anti-Bcl-2 particles reduced the mRNA and protein levels of antiapoptotic Bcl-2 protein in UM-SCC-17B cancer cells by 50-60% and 65-75%, respectively. Results also show that combining "smart" anti-Bcl-2 particles with the IC25 of AT-101 (inhibitory concentration responsible for killing 25% of the cells) synergistically inhibits cancer cell proliferation and increases cell apoptosis, which reduce the survival of UM-SCC-17B cancer cells compared to treatment with AT-101 alone. Results indicate the therapeutic benefit of combining siRNA-mediated knockdown of antiapoptotic Bcl-2 protein expression with low doses of AT-101 for inhibiting the growth of head and neck cancer cells.

Immunoprofiling of oral squamous cell carcinomas reveals high p63 and survivin expression

BACKGROUND

Cancer is a multifactorial disease composed of cells that show somatic mutations and epigenetic changes. The aim of this study was to investigate the expression of proteins involved in the development and maintenance of epithelia, cell cycle regulation, and apoptosis in human oral squamous cell carcinoma (OSCC) tissue samples.

METHODS

A tissue microarray containing 65 primary human OSCC specimens was immunolabeled for bcl-2, survivin, epidermal growth factor receptor (EGFR), p21, p53, p63, and cleaved caspase-3.

RESULTS

Samples were scored for percentage of positively stained tumor cells and staining intensity. A total immunostaining score was also calculated, using the product of percentage and intensity scores. All specimens showed high scores, > 75%, for p63 and survivin, and 75.4% of the specimens also presented high EGFR expression. All cases showed p53-positive cells. p21 showed a diffuse staining pattern. The percentage of cells positive for cleaved caspase-3 and bcl-2 was low.

CONCLUSIONS

The high frequency of tumor cells expressing p63 and survivin highlights the role of these proteins in the malignant transformation of oral epithelium. Collectively, our results suggest that p63 and survivin may constitute attractive targets for cancer therapy in patients with OSCC.

Inhibition of histone deacetylase impacts cancer stem cells and induces epithelial-mesenchyme transition of head and neck cancer

The genome is organized and packed into the nucleus through interactions with core histone proteins. Emerging evidence suggests that tumors are highly responsive to epigenetic alterations that induce chromatin-based events and dynamically influence tumor behavior. We examined chromatin organization in head and neck squamous cell carcinoma (HNSCC) using acetylation levels of histone 3 as a marker of chromatin compaction. Compared to control oral keratinocytes, we found that HNSCC cells are hypoacetylated and that microenvironmental cues (e.g., microvasculature endothelial cells) induce tumor acetylation. Furthermore, we found that chemical inhibition of histone deacetylases (HDAC) reduces the number of cancer stem cells (CSC) and inhibits clonogenic sphere formation. Paradoxically, inhibition of HDAC also induced epithelial-mesenchymal transition (EMT) in HNSCC cells, accumulation of BMI-1, an oncogene associated with tumor aggressiveness, and expression of the vimentin mesenchymal marker. Importantly, we observed co-expression of vimentin and acetylated histone 3 at the invasion front of human HNSCC tumor tissues. Collectively, these findings suggest that environmental cues, such as endothelial cell-secreted factors, modulate tumor plasticity by limiting the population of CSC and inducing EMT. Therefore, inhibition of HDAC may constitute a novel strategy to disrupt the population of CSC in head and neck tumors to create a homogeneous population of cancer cells with biologically defined signatures and predictable behavior.

Endothelial differentiation of SHED requires MEK1/ERK signaling

The discovery that dental pulp stem cells are capable of differentiating into endothelial cells raises the exciting possibility that these cells can be a single source of odontoblasts and vascular networks in dental tissue engineering. The purpose of this study was to begin to define signaling pathways that regulate endothelial differentiation of SHED. Stem cells from exfoliated deciduous teeth (SHED) exposed to endothelial growth medium (EGM-2MV) supplemented with vascular endothelial growth factor (VEGF) differentiated into VEGFR2-positive and CD31-positive endothelial cells in vitro. In vivo, VEGFR1-silenced SHED seeded in tooth slice/ scaffolds and transplanted into immunodeficient mice showed a reduction in human CD31-positive blood vessels as compared with controls (p = 0.02). Exposure of SHED to EGM2-MV supplemented with VEGF induced potent activation of ERK and Akt signaling, while it inhibited phosphorylation of STAT3. Notably, genetic (MEK1 silencing) or chemical (U0126) inhibition of ERK signaling restored constitutive STAT3 phosphorylation and inhibited the differentiation of SHED into endothelial cells. Collectively, analysis of these data unveiled the VEGF/MEK1/ERK signaling pathway as a key regulator of the endothelial differentiation of dental pulp stem cells.

The unfolded protein response induces the angiogenic switch in human tumor cells through the PERK/ATF4 pathway

Neovascularization is a limiting factor in tumor growth and progression. It is well known that changes in the tumor microenvironment, such as hypoxia and glucose deprivation (GD), can induce VEGF production. However, the mechanism linking GD to tumor growth and angiogenesis is unclear. We hypothesize that GD induces the angiogenic switch in tumors through activation of the unfolded protein response (UPR). We report that UPR activation in human tumors results in elevated expression of proangiogenic mediators and a concomitant decrease in angiogenesis inhibitors. cDNA microarray results showed that GD-induced UPR activation promoted upregulation of a number of proangiogenic mediators (VEGF, FGF-2, IL-6, etc.) and downregulation of several angiogenic inhibitors (THBS1, CXCL14, and CXCL10). In vitro studies revealed that partially blocking UPR signaling by silencing protein kinase RNA-like ER kinase (PERK) or activating transcription factor 4 (ATF4) significantly reduced the production of angiogenesis mediators induced by GD. However, suppressing the alpha subunit of hypoxia-inducible factors had no effect on this process. Chromatin immunoprecipitation (ChIP) confirmed binding of ATF4 to a regulatory site in the VEGF gene. In vivo results confirmed that knockdown of PERK in tumor cells slows down tumor growth and decreases tumor blood vessel density. Collectively, these results show that the PERK/ATF4 arm of UPR mediates the angiogenic switch and is a potential target for antiangiogenic cancer therapy.

Perivascular stem cell niche in head and neck cancer

Cancers may contain a small sub-population of uniquely tumorigenic cells that exhibit self-renewal and multipotency, i.e. cancer stem cells (CSCs). These cells reside in invasive fronts in close proximity to blood vessels in many tumors, including head and neck squamous cell carcinomas (HNSCCs). Recent evidence suggests that CSC resist chemotherapy and "drive" local recurrence and metastatic spread. Notably, endothelial cell-initiated signaling is critical for the survival and self-renewal of CSC and may play a role in resistance to therapy. Therefore, patients with head and neck cancer might benefit from therapies that target the CSC directly or their supportive perivascular niche.

Orosphere assay: a method for propagation of head and neck cancer stem cells

BACKGROUND

Recent evidence suggests that head and neck squamous cell carcinomas (HNSCCs) harbor a small subpopulation of highly tumorigenic cells, designated cancer stem cells. A limiting factor in cancer stem cell research is the intrinsic difficulty of expanding cells in an undifferentiated state in vitro.

METHODS

Here, we describe the development of the orosphere assay, a method for the study of putative head and neck cancer stem cells. An orosphere is defined as a nonadherent colony of cells sorted from primary HNSCCs or from HNSCC cell lines and cultured in 3-dimensional soft agar or ultralow attachment plates. Aldehyde dehydrogenase activity and CD44 expression were used here as stem cell markers.

RESULTS

This assay allowed for the propagation of head and neck cancer cells that retained stemness and self-renewal.

CONCLUSION

The orosphere assay is well suited for studies designed to understand the pathobiology of head and neck cancer stem cells.

RAIN-Droplet: a novel 3D in vitro angiogenesis model

Angiogenesis is fundamentally required for the initialization, development and metastatic spread of cancer. A rapidly expanding number of new experimental, chemical modulators of endothelial cell function have been described for the therapeutic inhibition of angiogenesis in cancer. Despite this expansion, there has been very limited parallel growth of in vitro angiogenesis models or experimental tools. Here we present the Responsive Angiogenic Implanted Network (RAIN)-Droplet model and novel angiogenesis assay using an endothelial cell culture model of microvascular endothelial cells encapsulated in a spontaneously self-assembling, toroidal hydrogel droplet uniquely yielding discrete, pre-formed, angiogenic networks that may be embedded in 3D matrices. On embedding, radial growth of capillary-like sprouts and cell invasion was observed. The sprouts formed not only as outgrowths from endothelial cells on the surface of the droplets, but also, uniquely, from the pre-formed network structures within the droplet. We demonstrate proof of principle for the utility of the model showing significant inhibition of sprout formation (P<0.001) in the presence of bevacizumab, an anti-angiogenic antibody. Using the RAIN-Droplet assay, we also demonstrate a novel dose-dependent pro-angiogenic function for the characteristically anti-angiogenic multi-kinase inhibitor sorafenib. Exposure of endothelial cells in 3D culture to low, non-lethal doses (<1 μM) of sorafenib after initiation of sprouting resulted in the formation of significantly (P<0.05) more endothelial sprouts compared with controls over a 48-h period. Higher doses of sorafenib (5 μM) resulted in a significant (P<0.05) reduction of sprouting over the same time period. The RAIN-Droplet model is a highly versatile and simply constructed 3D focal sprouting approach well suited for the study of vascular morphogenesis and for preclinical testing of drugs. Furthermore, the RAIN-Droplet model has facilitated the discovery of a novel pro-angiogenic capacity for sorafenib, which may impact the clinical application and dosing regimen of that drug.

In vitro differentiation and mineralization of dental pulp stem cells on enamel-like fluorapatite surfaces

Our previous studies have shown good biocompatibility of fluorapatite (FA) crystal surfaces in providing a favorable environment for functional cell-matrix interactions of human dental pulp stem cells (DPSCs) and also in supporting their long-term growth. The aim of the current study was to further investigate whether this enamel-like surface can support the differentiation and mineralization of DPSCs, and, therefore, act as a potential model for studying the enamel/dentin interface and, perhaps, dentine/pulp regeneration in tooth tissue engineering. The human pathway-focused osteogenesis polymerase chain reaction (PCR) array demonstrated that the expression of osteogenesis-related genes of human DPSCs was increased on FA surfaces compared with that on etched stainless steel (SSE). Consistent with the PCR array, FA promoted mineralization compared with the SSE surface with or without the addition of a mineralization promoting supplement (MS). This was confirmed by alkaline phosphatase (ALP) staining, Alizarin red staining, and tetracycline staining for mineral formation. In conclusion, FA crystal surfaces, especially ordered (OR) FA surfaces, which mimicked the physical architecture of enamel, provided a favorable extracellular matrix microenvironment for the cells. This resulted in the differentiation of human DPSCs and mineralized tissue formation, and, thus, demonstrated that it may be a promising biomimetic model for dentin-pulp tissue engineering.

The stimulation of adipose-derived stem cell differentiation and mineralization by ordered rod-like fluorapatite coatings

In this study, the effect of ordered rod-like FA coatings of metal discs on adipose-derived stem cell (ASC)'s growth, differentiation and mineralization was studied in vitro; and their mineral inductive effects in vivo. After 3 and 7 days, the cell number on the metal surfaces was significantly higher than those on the ordered and disordered FA surfaces. However, after 4 weeks much greater amounts of mineral formation was induced on the two FA surfaces with and even without osteogenesis induction. The osteogenic profiles showed the up regulation of a set of pro-osteogenic transcripts and bone mineralization phenotypic markers when the ASCs were grown on FA surfaces compared to metal surfaces at 7 and 21 days. In addition to BMP and TGFβ signaling pathways, EGF and FGF pathways also appeared to be involved in ASC differentiation and mineralization. In vivo studies showed accelerated and enhanced mineralized tissue formation integrated within ordered FA coatings. After 5 weeks, over 80% of the ordered FA coating was integrated with a mineralized tissue layer covering the implants. Both the intrinsic properties of the FA crystals and the topography of the FA coating appeared to dominate the cell differentiation and mineralization process.

Odontoblast RNA stability in different temperature-based protocols for tooth storage

AIM

To evaluate the effect of four tooth storage temperature-based methods on quality of RNA obtained from cells retrieved from human dental pulps and human pre-dentine.

METHODOLOGY

RNA was isolated from dental pulp tissue and from cells retrieved by scraping the pre-dentine of freshly extracted human third molars (n = 15) using TRIzol(®) reagent. Teeth were randomly assigned to the following temperature conditions: immediate RNA isolation after tooth extraction, liquid nitrogen (24 h), -80 °C (24 h), 20 °C (24 h) and 4 °C (6 h). RNA integrity was checked by the density of 28S and 18S ribosomal RNA. RT-PCR was used to analyse the expression of odontoblast makers (DSPP, DMP1 and MEPE) and the housekeeping gene GAPDH.

RESULTS

All experimental conditions evaluated preserved RNA integrity. The three odontoblastic markers were amplified from the pulp tissue and from the cells associated with pre-dentine.

CONCLUSION

The four storage options allowed RNA isolation for RT-PCR analysis. These findings may facilitate the use of clinically derived human dental pulp and odontoblasts for endodontic research.

Metronomic dosing of BH3 mimetic small molecule yields robust antiangiogenic and antitumor effects

Bcl-2 is an antiapoptotic protein that has also been found to function as a proangiogenic signaling molecule. Improvements in antiangiogenic therapy can be engendered by metronomic dosing. Thus, we hypothesized that BH3-mimetic drugs that antagonize Bcl-2 family proteins may exert a greater efficacy when dosed metronomically. To examine this hypothesis, we employed AT101, an orally available and well-tolerated BH3-mimetic drug that has been established as effective. In a mouse xenograft model of human squamous cell carcinomas (SCC) that includes a humanized vasculature, we explored the effects of docetaxel in combination with either daily (metronomic) or weekly (bolus) doses of AT101. In addition, we explored the effect of single or combination therapy on angiogenesis and survival of endothelial or SCC cells in vitro. Metronomic AT101 therapy increased mouse survival, decreased tumor mitotic index, and decreased tumor microvessel density, compared with bolus therapy. Therapeutic potentiation was achieved by similar overall drug exposure and without altering systemic toxicities. Combinations of AT101 and docetaxel produced additive toxicity in both endothelial and SCC tumor cells. Notably, subapoptotic concentrations of AT101 potently inhibited the angiogenic potential of endothelial cells. Taken together, our findings unveil the efficacious benefits that can be achieved by metronomic delivery of BH3-mimetic drugs, in particular suggesting that SCC patients with might benefit from low-dose continuous administration of these drugs.

Regenerative endodontics in light of the stem cell paradigm

Stem cells play a critical role in development and in tissue regeneration. The dental pulp contains a small sub-population of stem cells that are involved in the response of the pulp to caries progression. Specifically, stem cells replace odontoblasts that have undergone cell death as a consequence of the cariogenic challenge. Stem cells also secrete factors that have the potential to enhance pulp vascularisation and provide the oxygen and nutrients required for the dentinogenic response that is typically observed in teeth with deep caries. However, the same angiogenic factors that are required for dentine regeneration may ultimately contribute to the demise of the pulp by enhancing vascular permeability and interstitial pressure. Recent studies focused on the biology of dental pulp stem cells revealed that the multipotency and angiogenic capacity of these cells could be exploited therapeutically in dental pulp tissue engineering. Collectively, these findings suggest new treatment paradigms in the field of endodontics. The goal of this review is to discuss the potential impact of dental pulp stem cells to regenerative endodontics.

The biology of head and neck cancer stem cells

Emerging evidence indicates that a small population of cancer cells is highly tumorigenic, endowed with self-renewal, and has the ability to differentiate into cells that constitute the bulk of tumors. These cells are considered the "drivers" of the tumorigenic process in some tumor types, and have been named cancer stem cells. Epithelial-mesenchymal transition (EMT) appears to be involved in the process leading to the acquisition of stemness by epithelial tumor cells. Through this process, cells acquire an invasive phenotype that may contribute to tumor recurrence and metastasis. Cancer stem cells have been identified in human head and neck squamous cell carcinomas (HNSCC) using markers such as CD133 and CD44 expression, and aldehyde dehydrogenase (ALDH) activity. The head and neck cancer stem cells reside primarily in perivascular niches in the invasive front where endothelial-cell initiated events contribute to their survival and function. In this review, we discuss the state-of-the-knowledge on the pathobiology of cancer stem cells, with a focus on the impact of these cells to head and neck tumor progression.

Tooth slice/scaffold model of dental pulp tissue engineering

Multipotency is a defining characteristic of post-natal stem cells. The human dental pulp contains a small subpopulation of stem cells that exhibit multipotency, as demonstrated by their ability to differentiate into odontoblasts, neural cells, and vascular endothelial cells. These discoveries highlight the fundamental role of stem cells in the biology of the dental pulp and suggest that these cells are uniquely suited for dental pulp tissue-engineering purposes. The availability of experimental approaches specifically designed for studies of the differentiation potential of dental pulp stem cells has played an important role in these discoveries. The objective of this review is to describe the development and characterization of the Tooth Slice/Scaffold Model of Dental Pulp Tissue Engineering. In addition, we discuss the multipotency of dental pulp stem cells, focusing on the differentiation of these cells into functional odontoblasts and into vascular endothelial cells.

Endothelial derived factors inhibit anoikis of head and neck cancer stem cells

Recent evidence demonstrated that cancer stem cells reside in close proximity to blood vessels in human head and neck squamous cell carcinomas (HNSCC). These findings suggest the existence of a supporting perivascular niche for cancer stem cells. The purpose of this study was to evaluate the effect of endothelial cell-secreted factors on the behavior of head and neck cancer stem-like cells (HNCSC). HNCSC were identified by sorting UM-SCC-22A (cell line derived from a primary squamous cell carcinoma of the oropharynx) and UM-SCC-22B (derived from the metastatic lymph node of the same patient) for CD44 expression and ALDH (aldehyde dehydrogenase) activity. HNCSC (ALDH+CD44+) and control (ALDH-CD44-) cells were cultured in ultra-low attachment plates in presence of conditioned medium from primary human endothelial cells. ALDH+CD44+ generated more orospheres than control cells when cultured in suspension. The growth factor milieu secreted by endothelial cells protected HNCSC against anoikis. Mechanistic studies revealed that endothelial cell-secreted vascular endothelial growth factor (VEGF) induces proliferation of HNCSC derived from primary UM-SCC-22A, but not from the metastatic UM-SCC-22B. Likewise, blockade of VEGF abrogated endothelial cell-induced Akt phosphorylation in HNCSC derived from UM-SCC-22A while it had a modest effect in Akt phosphorylation in HNCSC from UM-SCC-22B. This study revealed that endothelial cells initiate a crosstalk that protect head and neck cancer stem cells against anoikis, and suggest that therapeutic interference with this crosstalk might be beneficial for patients with head and neck cancer.

Endothelial cell Bcl-2 and lymph node metastasis in patients with oral squamous cell carcinoma

BACKGROUND

Loco-regional spread of disease causes high morbidity and is associated with the poor prognosis of malignant oral tumors. Better understanding of mechanisms underlying the establishment of lymph node metastasis is necessary for the development of more effective therapies for patients with oral cancer. The aims of this work were to evaluate a possible correlation between endothelial cell Bcl-2 and lymph node metastasis in patients with oral squamous cell carcinoma (OSCC), and to study signaling pathways that regulate Bcl-2 expression in lymphatic endothelial cells.

METHODS

Endothelial cells were selectively retrieved from paraffin-embedded tissue sections of primary human OSCC from patients with or without lymph node metastasis by laser capture microdissection. RT-PCR was used to evaluate Bcl-2 expression in tumor-associated endothelial cells and in tumor cells. In vitro, mechanistic studies were performed to examine the effect of vascular endothelial growth factor (VEGF)-C on the expression of Bcl-2 in primary human lymphatic endothelial cells.

RESULTS

We observed that Bcl-2 expression is upregulated in the endothelial cells of human oral tumors with lymph node metastasis as compared to endothelial cells from stage-matched tumors without metastasis. VEGF-C induced Bcl-2 expression in lymphatic endothelial cells via VEGFR-3 and PI3k/Akt signaling. Notably, OSCC cells express VEGF-C and induce Bcl-2 in lymphatic endothelial cells.

CONCLUSIONS

Collectively, this work unveiled a mechanism for the induction of Bcl-2 in lymphatic endothelial cells and suggested that endothelial cell Bcl-2 contributes to lymph node metastasis in patients with oral squamous cell carcinoma.

TGF-β1 regulates the invasive and metastatic potential of mucoepidermoid carcinoma cells

BACKGROUND

Patients with mucoepidermoid carcinoma exhibit poor long-term prognosis because of the lack of therapeutic strategies that effectively block tumor progression. We have previously characterized the Ms cells as a highly metastatic mucoepidermoid carcinoma cell line that expresses high levels of transforming growth factor β1 (TGF-β1). Here, we studied the effect of suppressing TGF-β1 by RNA silencing on the invasive and metastatic potential of mucoepidermoid carcinoma.

METHODS

Cell motility, substratum adhesion, and transmembrane invasion were estimated by migration, matrigel adhesion, and matrigel invasion assay. Matrix metalloproteinase (MMP)-2 and MMP-9 activity were determined using gelatin gel zymography. Balb/c nu/nu nude mice lung metastatic model was used to test the metastatic ability of the Ms cells. Lung metastatic tumors were experimentally induced by mice tail vein inoculation of cancer cells.

RESULTS

TGF-β1 silencing inhibits cell motility, substratum adhesion, and transmembrane invasion. In vivo, a significant decrease in lung metastasis was observed when mice received tail vein injections of TGF-β1-silenced mucoepidermoid carcinoma cells, as compared to controls.

CONCLUSION

These results unveil a critical role for TGF-β1 in the progression of mucoepidermoid carcinomas and suggest that patients with this malignancy may benefit from therapeutic inhibition of the effectors of the TGF-β1 pathway.