Childhood-Onset Lupus Nephritis in the Childhood Arthritis and Rheumatology Research Alliance Registry: Short-Term Kidney Status and Variation in Care

OBJECTIVE

The goal was to characterize short-term kidney status and describe variation in early care utilization in a multicenter cohort of patients with childhood-onset systemic lupus erythematosus (cSLE) and nephritis.

METHODS

We analyzed previously collected prospective data from North American patients with cSLE with kidney biopsy-proven nephritis enrolled in the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry from March 2017 through December 2019. We determined the proportion of patients with abnormal kidney status at the most recent registry visit and applied generalized linear mixed models to identify associated factors. We also calculated frequency of medication use, both during induction and ever recorded.

RESULTS

We identified 222 patients with kidney biopsy-proven nephritis, with 64% class III/IV nephritis on initial biopsy. At the most recent registry visit at median (interquartile range) of 17 (8-29) months from initial kidney biopsy, 58 of 106 patients (55%) with available data had abnormal kidney status. This finding was associated with male sex (odds ratio [OR] 3.88, 95% confidence interval [95% CI] 1.21-12.46) and age at cSLE diagnosis (OR 1.23, 95% CI 1.01-1.49). Patients with class IV nephritis were more likely than class III to receive cyclophosphamide and rituximab during induction. There was substantial variation in mycophenolate, cyclophosphamide, and rituximab ever use patterns across rheumatology centers.

CONCLUSION

In this cohort with predominately class III/IV nephritis, male sex and older age at cSLE diagnosis were associated with abnormal short-term kidney status. We also observed substantial variation in contemporary medication use for pediatric lupus nephritis between pediatric rheumatology centers. Additional studies are needed to better understand the impact of this variation on long-term kidney outcomes.

CXCR2 expression during melanoma tumorigenesis controls transcriptional programs that facilitate tumor growth

BACKGROUND

Though the CXCR2 chemokine receptor is known to play a key role in cancer growth and response to therapy, a direct link between expression of CXCR2 in tumor progenitor cells during induction of tumorigenesis has not been established.

METHODS

To characterize the role of CXCR2 during melanoma tumorigenesis, we generated tamoxifen-inducible tyrosinase-promoter driven BrafV600E/Pten-/-/Cxcr2-/- and NRasQ61R/INK4a-/-/Cxcr2-/- melanoma models. In addition, the effects of a CXCR1/CXCR2 antagonist, SX-682, on melanoma tumorigenesis were evaluated in BrafV600E/Pten-/- and NRasQ61R/INK4a-/- mice and in melanoma cell lines. Potential mechanisms by which Cxcr2 affects melanoma tumorigenesis in these murine models were explored using RNAseq, mMCP-counter, ChIPseq, and qRT-PCR; flow cytometry, and reverse phosphoprotein analysis (RPPA).

RESULTS

Genetic loss of Cxcr2 or pharmacological inhibition of CXCR1/CXCR2 during melanoma tumor induction resulted in key changes in gene expression that reduced tumor incidence/growth and increased anti-tumor immunity. Interestingly, after Cxcr2 ablation, Tfcp2l1, a key tumor suppressive transcription factor, was the only gene significantly induced with a log2 fold-change greater than 2 in these three different melanoma models.

CONCLUSIONS

Here, we provide novel mechanistic insight revealing how loss of Cxcr2 expression/activity in melanoma tumor progenitor cells results in reduced tumor burden and creation of an anti-tumor immune microenvironment. This mechanism entails an increase in expression of the tumor suppressive transcription factor, Tfcp2l1, along with alteration in the expression of genes involved in growth regulation, tumor suppression, stemness, differentiation, and immune modulation. These gene expression changes are coincident with reduction in the activation of key growth regulatory pathways, including AKT and mTOR.

CXCR2 expression during melanoma tumorigenesis controls transcriptional programs that facilitate tumor growth

Background

Though the CXCR2 chemokine receptor is known to play a key role in cancer growth and response to therapy, a direct link between expression of CXCR2 in tumor progenitor cells during induction of tumorigenesis has not been established.

Methods

To characterize the role of CXCR2 during melanoma tumorigenesis, we generated tamoxifen-inducible tyrosinase-promoter driven Braf ^V600E /Pten ^-/- /Cxcr2 ^-/- and NRas ^Q61R /INK4a ^-/- /Cxcr2 ^-/- melanoma models. In addition, the effects of a CXCR1/CXCR2 antagonist, SX-682, on melanoma tumorigenesis were evaluated in Braf ^V600E /Pten ^-/- and NRas ^Q61R /INK4a ^-/- mice and in melanoma cell lines. Potential mechanisms by which Cxcr2 affects melanoma tumorigenesis in these murine models were explored using RNAseq, mMCP-counter, ChIPseq, and qRT-PCR; flow cytometry, and reverse phosphoprotein analysis (RPPA).

Results

Genetic loss of Cxcr2 or pharmacological inhibition of CXCR1/CXCR2 during melanoma tumor induction resulted in key changes in gene expression that reduced tumor incidence/growth and increased anti-tumor immunity. Interestingly, after Cxcr2 ablation, Tfcp2l1 , a key tumor suppressive transcription factor, was the only gene significantly induced with a log ₂ fold-change greater than 2 in these three different melanoma models.

Conclusions

Here, we provide novel mechanistic insight revealing how loss of Cxcr2 expression/activity in melanoma tumor progenitor cells results in reduced tumor burden and creation of an anti-tumor immune microenvironment. This mechanism entails an increase in expression of the tumor suppressive transcription factor, Tfcp2l1, along with alteration in the expression of genes involved in growth regulation, tumor suppression, stemness, differentiation, and immune modulation. These gene expression changes are coincident with reduction in the activation of key growth regulatory pathways, including AKT and mTOR.

Intraarticular steroids as DMARD-sparing agents for juvenile idiopathic arthritis flares: Analysis of the Childhood Arthritis and Rheumatology Research Alliance Registry

BACKGROUND

Children with juvenile idiopathic arthritis (JIA) who achieve a drug free remission often experience a flare of their disease requiring either intraarticular steroids (IAS) or systemic treatment with disease modifying anti-rheumatic drugs (DMARDs). IAS offer an opportunity to recapture disease control and avoid exposure to side effects from systemic immunosuppression. We examined a cohort of patients treated with IAS after drug free remission and report the probability of restarting systemic treatment within 12 months.

METHODS

We analyzed a cohort of patients from the Childhood Arthritis and Rheumatology Research Alliance (CARRA) Registry who received IAS for a flare after a period of drug free remission. Historical factors and clinical characteristics and of the patients including data obtained at the time of treatment were analyzed.

RESULTS

We identified 46 patients who met the inclusion criteria. Of those with follow up data available 49% had restarted systemic treatment 6 months after IAS injection and 70% had restarted systemic treatment at 12 months. The proportion of patients with prior use of a biologic DMARD was the only factor that differed between patients who restarted systemic treatment those who did not, both at 6 months (79% vs 35%, p < 0.01) and 12 months (81% vs 33%, p < 0.05).

CONCLUSION

While IAS are an option for all patients who flare after drug free remission, it may not prevent the need to restart systemic treatment. Prior use of a biologic DMARD may predict lack of success for IAS. Those who previously received methotrexate only, on the other hand, are excellent candidates for IAS.

Social determinants of health influence disease activity and functional disability in Polyarticular Juvenile Idiopathic Arthritis

BACKGROUND

Social determinants of health (SDH) greatly influence outcomes during the first year of treatment in rheumatoid arthritis, a disease similar to polyarticular juvenile idiopathic arthritis (pJIA). We investigated the correlation of community poverty level and other SDH with the persistence of moderate to severe disease activity and functional disability over the first year of treatment in pJIA patients enrolled in the Childhood Arthritis and Rheumatology Research Alliance Registry.

METHODS

In this cohort study, unadjusted and adjusted generalized linear mixed effects models analyzed the effect of community poverty and other SDH on disease activity, using the clinical Juvenile Arthritis Disease Activity Score-10, and disability, using the Child Health Assessment Questionnaire, measured at baseline, 6, and 12 months.

RESULTS

One thousand six hundred eighty-four patients were identified. High community poverty (≥20% living below the federal poverty level) was associated with increased odds of functional disability (OR 1.82, 95% CI 1.28-2.60) but was not statistically significant after adjustment (aOR 1.23, 95% CI 0.81-1.86) and was not associated with increased disease activity. Non-white race/ethnicity was associated with higher disease activity (aOR 2.48, 95% CI: 1.41-4.36). Lower self-reported household income was associated with higher disease activity and persistent functional disability. Public insurance (aOR 1.56, 95% CI 1.06-2.29) and low family education (aOR 1.89, 95% CI 1.14-3.12) was associated with persistent functional disability.

CONCLUSION

High community poverty level was associated with persistent functional disability in unadjusted analysis but not with persistent moderate to high disease activity. Race/ethnicity and other SDH were associated with persistent disease activity and functional disability.

C-49 Externalizing Behavior Differences Between FASD and ACC: 11-13 Year Olds

Objective

Investigate the externalizing behaviors of rule breaking and aggression among children ages 11-13 years with partial (pACC), full Agenesis of the Corpus Collosum (ACC) or Fetal Alcohol Spectrum Disorders (FASD) in order to broaden our understanding of the behaviors found in pre- and young adolescents with these diagnoses.

Method

This sample was taken from two data sets; one with individuals with ACC, the other individuals with FASD. The data for both ACC and FASD studies were gathered using mailing lists. Packets included informed consent, the Child Behavior Checklist (CBCL), the FAS BeST with additional developmental questions, and a demographic questionnaire. Of the 511 ACC packets returned, 47 were analyzed. Of the nearly 50 FASD packets returned, 7 were analyzed (n = 54).

Results

A multivariate analysis of variance (MANOVA) of the 54 participant’s external behaviors of rule breaking and aggression were analyzed. Participants with diagnoses of FASD present with higher rates of externalizing behaviors than those with pACC and ACC. Aggressive behaviors have a small effect size (n2 = .151) and rule breaking behaviors present with a large effect size (n2 = .441).

Conclusions

Treatment plans for those with FAS and ACC differ greatly from the commonly provided misdiagnoses of Autism, Attention Deficit/Hyperactivity Disorder (ADHD), Oppositional Defiant Disorder and Conduct Disorder, which can leave clients with FAS and ACC misunderstood and improperly treated. By examining the common and differing external behavioral traits of FAS and ACC, clinicians can have stronger evidence when considering differential diagnoses and treatment plans.

Modification of properties of yttria stabilized zirconia epitaxial thin films by excimer laser annealing

This study focuses on the ultrafast improvement of surface wettability, electrical, and room temperature magnetic characteristics of cubic zirconia single crystalline thin films after laser annealing. The point defects generated by the laser treatment are envisaged to play a critical role in altering the above properties. Yttria stabilized zirconia (YSZ) thin films were epitaxially grown on Si(100) substrates by pulsed laser deposition technique and subsequently annealed by a KrF excimer laser beam (τ = 25 ns) using low-energy laser pulses. An atomically sharp interface, parallel to the film free surface, between laser annealed layer and the pristine region was observed. The single crystalline nature of thin films was preserved following the laser treatment. The laser-solid interaction with YSZ led to the introduction of point defects, i.e., oxygen vacancies, resulting in a strained structure which, in turn, resulted in the formation of a tetragonal-like zirconia. With the increase of number of laser pulses the laser treated films got highly disordered due to the high concentration of the point defects, while maintaining their crystalline nature. Although the surface of the pristine sample showed weak hydrophilic characteristics (contact angle ∼ 73°), the laser annealed samples exhibited significantly improved hydrophilic characteristics. It was found that there is an optimum number of laser pulses where the maximum hydrophilicity (contact angle ∼ 22°) is obtained. The carrier concentration in the sample with the highest hydrophilicity was determined to be higher by about 5 orders of magnitude compared to the pristine sample. This sample possessed the lowest electrical resistivity. The laser annealed YSZ epilayers showed a superior room-temperature ferromagnetic behavior, compared to the pristine samples. A 2-fold enhancement in the magnetization of the samples was observed following the laser treatment which is a clear demonstration of the key role of defects and their transient distribution throughout the lattice. All these observations were correlated with the formation of point defects due to the photon interaction with YSZ and absorption of energy of the KrF laser photons to produce defects.

Engineered three-dimensional microfluidic device for interrogating cell-cell interactions in the tumor microenvironment

Stromal cells in the tumor microenvironment play a key role in the metastatic properties of a tumor. It is recognized that cancer-associated fibroblasts (CAFs) and endothelial cells secrete factors capable of influencing tumor cell migration into the blood or lymphatic vessels. We developed a microfluidic device that can be used to image the interactions between stromal cells and tumor cell spheroids in a three dimensional (3D) microenvironment while enabling external control of interstitial flow at an interface, which supports endothelial cells. The apparatus couples a 200-μm channel with a semicircular well to mimic the interface of a blood vessel with the stroma, and the design allows for visualization of the interactions of interstitial flow, endothelial cells, leukocytes, and fibroblasts with the tumor cells. We observed that normal tissue-associated fibroblasts (NAFs) contribute to the "single file" pattern of migration of tumor cells from the spheroid in the 3D microenvironment. In contrast, CAFs induce a rapid dispersion of tumor cells out of the spheroid with migration into the 3D matrix. Moreover, treatment of tumor spheroid cultures with the chemokine CXCL12 mimics the effect of the CAFs, resulting in similar patterns of dispersal of the tumor cells from the spheroid. Conversely, addition of CXCL12 to co-cultures of NAFs with tumor spheroids did not mimic the effects observed with CAF co-cultures, suggesting that NAFs produce factors that stabilize the tumor spheroids to reduce their migration in response to CXCL12.

Abstract P1-05-01: Chemokine-mediated nuclear translocation and novel nuclear role for LIM and SH3 Protein-1(LASP-1) in breast cancer

Background: LASP-1 (LIM and SH3 protein-1) mediates cell migration, proliferation and survival in several breast cancer cell lines. LASP-1 is a scaffold protein that plays a critical role in cytoskeletal organization and cell motility. Silencing of LASP-1 in breast cancer cells inhibits cell migration and proliferation by 40%. We discovered that LASP-1 associates with chemokine receptors that are involved in migration of tumor cells or leukocytes in the tumor microenvironment or to the metastatic sites. LASP-1 directly binds to the chemokine receptors CXCR1, CXCR2, CXCR3 and CXCR4, suggesting that LASP-1 is a general mediator of CXC chemokine mediated migration and possibly cell survival. This established LASP-1 as a key component of the “CXC chemokine receptor chemosynapse”. This is highly significant as chemokine receptors CXCR2, CXCR4 and CXCR3 play a paramount role in primary and metastatic breast cancer. CXCR1 is involved in self-renewal of breast cancer stem cells that contribute to metastasis and drug resistance. The increase in expression level of LASP-1 with an increasing invasiveness of the tumor cells implicates a role for LASP-1 in tumor progression and lymph node metastases. Nuclear localization of LASP-1 (44% of LASP-1 positive specimens) was observed in tissue sections of aggressive and invasive breast cancer that positively correlated with poor survival rate. This is suggestive of a key role for nuclear LASP-1 in breast cancer progression.

Methodology/Results: We investigated the chemokine-mediated nuclear translocation of LASP-1 in breast cancer and endothelial cell lines. Initially, cell surface expression of CXCR4 was profiled in breast cancer cell lines by FACS analysis. Medium to high CXCR4 expressers were stimulated with CXCL12 and the subcellular status of LASP-1 was examined by confocal microscopy. LASP-1 accumulated in the nucleus of the CXCL12-stimulated cells. Surprisingly, in MDA-MB-231 cells that were isolated from the mouse bone metastatic lesions had LASP-1 in the nucleus even in the absence of any stimulation by CXCL12. Additionally, the nuclear translocation of LASP-1 was observed in EGF- or heregulin-stimulated cells. Ligand activated CXCR2 in human endothelial cell line was also able to drive the nuclear accumulation of LASP-1.

In order ascertain the role played by nuclear LASP-1 it was stably knocked down (KD). The control silenced (NS) and LASP-1 KD cells were grown in 3D-matrigel. Morphology of the 3D-clusters and the profile of the secreted cytokines were assessed by light microscopy and cytokine antibody microarray respectively along with additional biochemical methods and gene expression analysis by oligo microarray.

Conclusions/Significance: We demonstrate here for the first time that LASP-1 translocates to the nucleus through activation of i) GPCRs -chemokine receptors CXCR2, CXCR4 and ii) Receptor tyrosine kinases - EGF receptor and HER2. Shuttling of LASP1 to the nucleus through the activation of a variety of receptors present in the tumor cells, macrophages, neutrophils and endothelial cells of the tumor microenvironment is of high significance. Silencing of LASP-1 in breast cancer cells revealed an altered profile of the 3D-clusters and the secreted cytokines.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-05-01.

A flat inclined modular photobioreactor for outdoor mass cultivation of photoautotrophs

A flat inclined modular photobioreactor (FIMP) for mass cultivation of photoautotrophic microorganisms is described. It consists of flat glass reactors connected in cascade facing the sun with the proper tilt angles to assure maximal exposure to direct beam radiation. The optimal cell density in reference to the length of the reactor light path was evaluated, and the effect of the tilt angle on utilization of both direct beam as well as diffuse sunlight was quantitatively assessed. The mixing mode and extent were also optimized in reference to productivity of biomass. The FIMP proved very successful in supporting continuous cultures of the tested species of photoautotrophs, addressing the major criteria involved in design optimization of photobioreactors: Made of fully transparent glass, inclined toward the sun and endowed with a high surface-to-volume ratio, it combines an optimal light path with a vigorous agitation system. The maximal exposure to the culture to solar irradiance as well as the substantial control of temperature facilitate, under these conditions, a particularly high, extremely light-limited optimal cell density. The integrated effects of these growth conditions resulted in record volumetric and areal output rates of Monodus subterraneus, Anabana siamensis, and Spirulina platensis. (c) 1996 John Wiley & Sons, Inc.

Photic Volume in Photobioreactors Supporting Ultrahigh Population Densities of the Photoautotroph Spirulina platensis

Characterization of the photic zone and light penetration depth in cultures with ultrahigh cell densities represents a major issue in mass cultures of phytoautotrophic microorganisms grown in enclosed photobioreactors. In a study of the effect of underwater optical properties on the penetration depth of photosynthetically active radiation, the inherent optical properties of algal suspensions, i.e., absorption and scattering coefficients, as well as their apparent optical properties, i.e., the reflectance and the vertical attenuation coefficient of downwelling irradiance, were determined by using high-spectral-resolution radiometric measurements. The vertical attenuation coefficient was used to estimate quantitatively the depth of light penetration into a reactor containing an ultrahigh cell density (chlorophyll concentration, up to 300,000 mg m(sup-3)). For such a high cell density, the photic volume in the reactor was found to be extremely small; nevertheless, it differed between the blue and red light (less than 0.06 mm) and the green light (about 0.5 mm). This suggests a singular role for green light under the unique circumstances existing in ultrahigh-cell-density cultures of photoautotrophs.

WBC changes as a pharmacodynamic marker of outcome in metastatic renal cell carcinoma (mRCC) patients (Pts) receiving sunitinib

5043

Background: Sunitinib is a VEGF, PDGF, c-Kit and FLT-3 inhibitor with significant anti-tumor activity in mRCC. Myelosuppression is a common side effect observed in mRCC pts treated with sunitinib. Thus, the association of myelosuppression with clinical outcome was investigated. Methods: All mRCC pts receiving sunitinib at The Cleveland Clinic Taussig Cancer Center with available data were investigated. White blood cell (WBC) and differential counts at baseline and day 28 of cycle 1 were collected. Peripheral blood mononuclear cell (PBMC) T helper 1 (Th1), T helper 2 (Th2) and T regulatory cell (Treg) numbers at baseline and day 28 of C1 were determined using flow cytometry. Hematologic parameters were analyzed as continuous variables and also dichotomized using a recursive partitioning algorithm. Fisher’s exact test was used to analyze categorical data, the log rank test was used to assess time to progression (TTP) and Spearman’s rank correlation was used to summarize associations between hematologic and immune parameters. Results: Sixty-seven pts were studied (75% male, median age 59 yrs). Objective responses (OR) included 2 complete and 35 partial responses (overall response rate 55%), with a median (m) TTP of 12.4 months. There was a significant reduction (end of C1 vs. baseline) in the absolute neutrophil count (ANC) (m decrease of 46.4%; p <0.001) and absolute monocyte count (m decrease of 41.3%; p<0.001), but not absolute lymphocyte count (m 6.6% decrease; p=0.5). A decrease in the ANC of =2.5K/uL compared to <2.5 K/uL was associated with improved OR (64% vs. 36%; p= .07) and TTP (m 20.6 months vs. 8 months; p=.003). Patients demonstrating a maximum lymphocyte count =1.2 K/uL at anytime during treatment compared to patients with a maximum lymphocyte count <1.2 K/uL also had a greater OR (64% vs. 25%, p=.02) and TTP (m 17.6 months vs. 4.2 months, p=.03). Changes in Treg number and Th1 and Th2 response bias of PBMC did not correlate with ANC/ lymphocyte changes or clinical outcome. Conclusions: Treatment with sunitinib produces significant neutropenia with minimal effects on total lymphocyte numbers. Changes in ANC and maximum lymphocyte count could represent a pharmacodynamic marker of clinical outcome for mRCC patients treated with sunitinib.

No significant financial relationships to disclose.

Differential regulation of CXC ligand 1 transcription in melanoma cell lines by poly(ADP-ribose) polymerase-1

The continuous production of the CXC ligand 1 (CXCL1) chemokine by melanoma cells is a major effector of tumor growth. We have previously shown that the constitutive expression of this chemokine is dependent upon transcription factors nuclear factor-kappa B (NF-kappaB), stimulating protein-1 (SP1), high-mobility group-I/Y (HMGI/Y), CAAT displacement protein (CDP) and poly(ADP-ribose) polymerase-1 (PARP-1). In this study, we demonstrate for the first time the mechanism of transcriptional regulation of CXCL1 through PARP-1 in melanoma cells. In its inactive state, PARP-1 binds to the CXCL1 promoter in a sequence-specific manner and prevents binding of NF-kappaB (p65/p50) to its element. However, activation of the PARP-1 enzymatic activity enhances CXCL1 expression, owing to the loss of PARP-1 binding to the CXCL1 promoter, accompanied by enhanced binding of p65 to the promoter. The delineation of the role of NF-kappaB-interacting factors in the putative CXCL1 enhanceosome will provide key information in developing strategies to block constitutive expression of this and other chemokines in cancer and to develop targeted therapy.

T regulatory cells (Treg) in patients with metastatic renal cell carcinoma (mRCC) decrease during sunitinib treatment: Correlations with clinical responses and T helper 1/T helper 2 (Th1/Th2) bias

2526

Background: High numbers of regulatory T cells (Treg) and high expression of forkhead box transcription factor (FoxP3) in Treg are associated with decreased survival in various malignancies, likely via immunosuppression. Studies demonstrate Th1 suppression (IFN-γ) and Th2 (Il-4) promotion in metastatic renal cell carcinoma (mRCC) patients (pts). The aim of the present study was to determine the profile of Th1, Th2, and Treg at baseline and after 28 days of therapy with the multi-targeted tyrosine kinase inhibitor, sunitinib malate (SU11248). Further, correlation of changes in these parameters and tumor shrinkage (TS) was examined. Methods: Blood was obtained from cytokine-refractory, clear cell mRCC pts on day 1 (pre-treatment) and after 28 days of sunitinib 50mg daily. T cell cytokine expression (IL-4, IFN-γ), percentage in peripheral blood mononuclear cells of CD3+/CD4+/CD25hi+/FoxP3+ cells, and percentage of Treg that were FoxP3+ were evaluated using flow cytometry. Tumor measurements were performed after 2 cycles of therapy. Correlations between immune parameters and TS were assessed with Spearman rank correlations. Results: Ten pts were evaluable for Th1/Th2 responses; 9 for Treg. At baseline 7/10 had Th2 bias and 3/10 had Th1 bias. On day 28, pts maintained Th1 bias (n=3), switched to Th1 bias (n=3), or had decrease in magnitude of Th2 response (n=4). Additionally, a median 74.5% decrease occurred after 28 days of sunitinib in the percentage of CD3/CD4/CD25hi+/FoxP3+ in peripheral blood mononuclear cells, with a median 68.0% decrease of FoxP3+ Treg (CD3/CD4/CD25hi+) cells. Decrease in number of Treg correlated with relative change in Th1 response and Th2 bias (p<.05 for all correlations). All pts had TS including 2 pts with partial response. Degree of TS correlated with relative change in Th1 response (p=.03), and Th2 bias (p=.06), as well as the relative change in FoxP3+ Treg (p=.06). Conclusions: Our results suggest that sunitinib promotes an immunostimulatory Th1 bias and reduces Treg. This immunostimulatory mechanism may contribute to the anti-tumor effect in mRCC. Further studies are on-going.

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Sustainable, high-yielding outdoor mass cultures of Chaetoceros muelleri var. subsalsum and Isochrysis galbana in vertical plate reactors

Continuous cultures of Chaetoceros muelleri and Isochrysis galbana were grown outdoors in flat plate-glass reactors in which light-path length (LPL) varied from 5 to 30 cm. High daily productivity (13 to 16 g cell mass per square meter of irradiated reactor surface) for long periods of time was obtained in reactors in which the optical path as well as cell density were optimized. 'Twenty centimeters was the optimal LPL, yielding the highest areal productivity of cell mass (g m(-2)d(-1)), eicosapentaenoic acid, and docosahexaenoic acid, which was identical with that previously found for polysaccharide production of Porphyridium and not far from the optimal LPL affecting maximal productivity in Nannochloropsis species. Relating the energy impinging on a given reactor surface area to the appropriate number of cells showed that the most efficient light dose per cell, obtained with the 20-cm LPL reactor, was approximately 2.5 times lower than the light dose available per cell in the 5-cm LPL reactor, in which a significant decline in areal cell density accompanied the lowest areal output of cell mass. The most effective harvesting regimen was in the range of 10% to 15% of culture volume harvested daily and replaced with fresh growth medium, resulting in a sustainable culture density of 24 x 10(6) and 28 x 10(6) cells/ml of C. muelleri and I. galbana, respectively.

Induction of melanoma in murine macrophage inflammatory protein 2 transgenic mice heterozygous for inhibitor of kinase/alternate reading frame

The molecular and genetic events that contribute to the genesis and progression of cutaneous malignant melanoma are poorly understood, attributable in large part to the different genetic alterations accompanying tumorigenesis. Inhibitor of kinase 4a (INK4a) is often inactivated in families with hereditary melanoma. Loss of INK4a/alternate reading frame (ARF) in mice is associated with increased incidence of other tumors such as lymphoma and fibrosarcoma. However, the incidence of melanoma in INK4a/ARF-deficient mice is very low. Our previous studies have revealed that the CXC chemokine, CXCL1, is overexpressed in human malignant melanoma cells and is linked to transformation of immortalized murine melanocytes. To study the direct role of CXCL1 on the genesis of primary melanoma lesions, transgenic mouse lines were established that express the murine homologue of CXCL1, murine macrophage inflammatory protein 2 (MIP-2), under the transcriptional control of the tyrosinase promoter/enhancer (Tyr-MIP-2) in the mice that were deficient or not deficient for INK4a/ARF. Strong MIP-2 immunoreactivity was associated with pigmented melanocytes in the hyperproliferative hair follicles in the Tyr-MIP-2 transgenic mice, and the level of MIP-2 expression was similar in both INK4a/ARF heterozygous or wild-type mice. After treatment of mice with 7,12-dimethylbenz(a)anthracene, cutaneous melanomas formed in 12% (17/145) of the Tyr-MIP-2 transgene-positive mice, whereas only 2% (3/146) of the Tyr-MIP-2 transgene-negative mice developed melanoma. When melanocytes cultured from MIP-2 transgenic mice null for INK4a/ARF were transplanted into nude mice, melanoma formation occurred in 83% (10/12) of the cases with a latency period of 3 months. However, no melanoma lesions arose in nude mice injected with INK4a/ARF -/- melanocytes, which did not express the MIP-2 transgene. Our results demonstrate that constitutive expression of MIP-2 in INK4a/ARF-deficient melanocytes facilitates formation of malignant melanoma.

Constitutive IkappaB kinase activity correlates with nuclear factor-kappaB activation in human melanoma cells

Constitutive IKK activity associated with increased IkappaBalpha phosphorylation and degradation contribute to the high level of endogenous nuclear factor-kappaB (NF-kappaB) activation in Hs294T melanoma cells as compared with RPE cells (R. L. Shattuck-Brandt and A. Richmond, Cancer Res., 57: 3032-3039, 1997; M. N. Devalaraja et al., Cancer Res., 59: 1372-1377, 1999). To determine whether this endogenous NF-kappaB activation was characteristic of melanoma, we examined the level of constitutive activation of NF-kappaB in a number of melanoma cell lines. We demonstrate here that eight melanoma cell lines exhibit increased IkappaB kinase (IKK) activity, enhanced phosphorylation of IkappaBalpha and p65, and enhanced nuclear localization of p65/p50 in comparison to normal human epidermal melanocytes. The chemokines, CXC ligand 1 (CXCL1) and CXCL8, but not CXCL5, are highly expressed in most of the melanoma cell lines, suggesting that the constitutive production of chemokines is highly correlated to endogenous NF-kappaB activity. Our failure to observe a direct relationship between the fold activation of IKK, CXCL1, or CXCL8 mRNA levels and secretion of these chemokines into the culture medium suggest that regulation of chemokine expression also occurs at the posttranscription level of mRNA stability and/or translational control. Moreover, recombinant CXCL1 can directly induce IKK activity in normal human epidermal melanocytes in a concentration-dependent manner after up-modulation of CXCL1 protein expression, whereas inhibition of IKKbeta activity results in down-modulation of CXCL1 protein expression. Finally, CXCL1 antibody blocks IKK activity and inhibits the proliferation of melanoma cells to further support the concept that the constitutive activation of NF-kappaB and autocrine effects of CXCL1 play an important role in the pathogenesis of melanoma.

The role of CDP in the negative regulation of CXCL1 gene expression

The CXC chemokine, melanoma growth stimulatory activity/growth-regulated protein, CXCL1 is an important modulator of inflammation, wound healing, angiogenesis, and tumorigenesis. Transcription of CXCL1 is regulated through several cis-acting elements including Sp1, NF-kappa B, and an element that lies immediately upstream of the NF-kappa B element, the immediate upstream region (IUR). A transcription element data base search indicated that the IUR element contains a binding site for the transcriptional repressor, human CUT homeodomain protein/CCAAT displacement protein (CDP). It is shown here that in electrophoretic mobility shift assays, complexes obtained with the IUR oligonucleotide probe are supershifted by anti-CDP antibodies and that a CDP polypeptide containing a high affinity DNA binding domain binds to the sequence GGGATCGATC in the IUR element. In Southwestern blot analyses, oligonucleotides containing the wild-type IUR sequence, but not a mutant oligonucleotide with substitutions in the GGGATCGATC sequence, bind a 170--180-kDa protein. Furthermore, overexpression of the CDP protein blocks CXCL1 promoter activity in reporter gene assays, whereas overexpression of an antisense CDP construct leads to a significant increase in CXCL1 promoter activity. Mutations in the IUR element, which map in the putative CDP-binding site, inhibit the binding of CDP to the IUR element and favor increased transcription from the CXCL1 promoter. Based on these results, we propose that transcriptional regulation of the CXCL1 gene is mediated in part by CDP, which could play an important role in inflammatory processes and tumorigenesis.

A role for poly(ADP-ribose) polymerase in the transcriptional regulation of the melanoma growth stimulatory activity (CXCL1) gene expression

The melanoma growth stimulatory activity/growth-regulated protein, CXCL1, is constitutively expressed at high levels during inflammation and progression of melanocytes into malignant melanoma. It has been shown previously that CXCL1 overexpression in melanoma cells is due to increased transcription as well as stability of the CXCL1 message. The transcription of CXCL1 is regulated through several cis-acting elements including Sp1, NF-kappaB, HMGI(Y), and the immediate upstream region (IUR) element (nucleotides -94 to -78), which lies immediately upstream to the nuclear factor kappaB (NF-kappaB) element. Previously, it has been shown that the IUR is necessary for basal and cytokine-induced transcription of the CXCL1 gene. UV cross-linking and Southwestern blot analyses indicate that the IUR oligonucleotide probe selectively binds a 115-kDa protein. In this study, the IUR element has been further characterized. We show here that proximity of the IUR element to the adjacent NF-kappaB element is critical to its function as a positive regulatory element. Using binding site oligonucleotide affinity chromatography, we have selectively purified the 115-kDa IUR-F. Mass spectrometry/mass spectrometry/matrix-assisted laser desorption ionization/time of flight spectroscopy and amino acid analysis as well as microcapillary reverse phase chromatography electrospray ionization tandem mass spectrometry identified this protein as the 114-kDa poly(ADP-ribose) polymerase (PARP1). Furthermore, 3-aminobenzamide, an inhibitor of PARP-specific ADP-ribosylation, inhibits CXCL1 promoter activity and reduces levels of CXCL1 mRNA. The data point to the possibility that PARP may be a coactivator of CXCL1 transcription.

Optimization of a flat plate glass reactor for mass production of Nannochloropsis sp. outdoors

The relationships between areal (g m(-2) per day) and volumetric (g l(-1) per day) productivity of Nannochloropsis sp. as affected by the light-path (ranging from 1.3 to 17.0 cm) of a vertical flat plate glass photobioreactor were elucidated. In general, the shorter the length of the light-path (LP), the smaller the areal volume and the higher the volumetric productivity. The areal productivity in relation to the light-path, in contrast, yielded an optimum curve, the highest areal productivity was obtained in a 10 cm LP reactor, which is regarded, therefore, optimal for mass production of Nannochloropsis. An attempt was made to identify criteria by which to assess the efficiency of a photobioreactor in utilizing strong incident energy. Two basic factors which relate to reactor efficiency and its cost-effectiveness have been defined as (a) the total illuminated surface required to produce a set quantity of product and (b) culture volume required to produce that quantity. As a general guide line, the lower these values are, the more efficient and cost-effective the reactor would be. An interesting feature of this analysis rests with the fact that an open raceways is as effective in productivity per illuminated area as a flat-plate reactor with an optimal light path, both cultivation systems requiring ca. 85 m(2) of illuminated surface to produce 1 kg dry cell mass of Nannochloropsis sp. per day. The difference in light utilization efficiency between the two very different production systems involves three aspects - first, the open raceway requires ca. 6 times greater volume than the 10 cm flat plate reactor to produce the same quantity of cell-mass. Second, the total ground area (i.e. including the ground area between reactors) for the vertical flat plate reactor is less than one half of that occupied by an open raceway, indicating the former is more efficient, photosynthetically, compared with the latter. Finally, the harvested cell density is close to one order of magnitude higher in the flat plate reactor, which carries economic significance. The advantage of vertical lamination of photoautotrophic cells provided by vertical plate reactors, is thereby clearly seen. The optimal population density (i.e. which results in the highest areal productivity) in the 10 cm plate reactor was obtained by a daily harvest of 10% of culture volume, yielding an annual average of ca. 12.1 g dry wt. m(-2) per day (on the basis of the overall illuminated reactor surfaces, i.e. front and back) or 240 mg l(-1) per day.

Identification of a motif in the carboxyl terminus of CXCR2 that is involved in adaptin 2 binding and receptor internalization

Agonist treatment of cells expressing the chemokine receptor, CXCR2, induces receptor phosphorylation and internalization through a dynamin-dependent mechanism. In the present study, we demonstrate that a carboxyl terminus-truncated mutant of CXCR2 (331T), which no longer undergoes agonist-induced phosphorylation, continues to undergo ligand-induced internalization in HEK293 cells. This mutant receptor exhibits reduced association with beta-arrestin 1 but continues to exhibit association with adaptin 2 alpha and beta subunits. Replacing Leu320-321 and/or Ile323-Leu324 with Ala (LL320,321AA, IL323,324AA, and LLIL320,321,323,324AAAA) in wild-type CXCR2 or 331T causes little change in ligand binding and signaling through Ca(2+) mobilization but greatly impairs the agonist-induced receptor sequestration and ligand-mediated chemotaxis. The LL320,321AA, IL323,324AA, and LLIL320,321,323,324AAAA mutants of CXCR2 exhibit normal binding to beta-arrestin 1 but exhibit decreased binding to adaptin 2alpha and beta. These data demonstrate a role for the LLKIL motif in the carboxyl terminus of CXCR2 in receptor internalization and cell chemotaxis and imply a role for adaptin 2 in the endocytosis of CXCR2.

The CXC chemokine receptor 2, CXCR2, is the putative receptor for ELR+ CXC chemokine-induced angiogenic activity

We have previously shown that members of the ELR(+) CXC chemokine family, including IL-8; growth-related oncogenes alpha, beta, and gamma; granulocyte chemotactic protein 2; and epithelial neutrophil-activating protein-78, can mediate angiogenesis in the absence of preceding inflammation. To date, the receptor on endothelial cells responsible for chemotaxis and neovascularization mediated by these ELR(+) CXC chemokines has not been determined. Because all ELR(+) CXC chemokines bind to CXC chemokine receptor 2 (CXCR2), we hypothesized that CXCR2 is the putative receptor for ELR(+) CXC chemokine-mediated angiogenesis. To test this postulate, we first determined whether cultured human microvascular endothelial cells expressed CXCR2. CXCR2 was detected in human microvascular endothelial cells at the protein level by both Western blot analysis and immunohistochemistry using polyclonal Abs specific for human CXCR2. To determine whether CXCR2 played a functional role in angiogenesis, we determined whether this receptor was involved in endothelial cell chemotaxis. We found that microvascular endothelial cell chemotaxis in response to ELR(+) CXC chemokines was inhibited by anti-CXCR2 Abs. In addition, endothelial cell chemotaxis in response to ELR(+) CXC chemokines was sensitive to pertussis toxin, suggesting a role for G protein-linked receptor mechanisms in this biological response. The importance of CXCR2 in mediating ELR(+) CXC chemokine-induced angiogenesis in vivo was also demonstrated by the lack of angiogenic activity induced by ELR(+) CXC chemokines in the presence of neutralizing Abs to CXCR2 in the rat corneal micropocket assay, or in the corneas of CXCR2(-/-) mice. We thus conclude that CXCR2 is the receptor responsible for ELR(+) CXC chemokine-mediated angiogenesis.

MGSA/GRO-mediated melanocyte transformation involves induction of Ras expression

The MGSA/GRO protein is endogenously expressed in almost 70% of the melanoma cell lines and tumors, but not in normal melanocytes. We have previously demonstrated that over-expression of human MGSA/GROalpha, beta or gamma in immortalized murine melanocytes (melan-a cells) enables these cells to form tumors in SCID and nude mice. To examine the possibility that the MGSA/GRO effect on melanocyte transformation requires expression of other genes, differential display was performed. One of the mRNA's identified in the screen as overexpressed in MGSA/GRO transformed melan-a clones was the newly described M-Ras or R-Ras3 gene, a member of the Ras gene superfamily. Over-expression of MGSA/GRO upregulates M-Ras expression at both the mRNA and protein levels, and this induction requires an intact glutamine-leucine-arginine (ELR)-motif in the MGSA/GRO protein. Western blot examination of Ras expression revealed that K- and N-Ras proteins are also elevated in MGSA/GRO-expressing melan-a clones, leading to an overall increase in the amount of activated Ras. MGSA/GRO-expressing melan-a clones exhibited enhanced AP-1 activity. The effects of MGSA/GRO on AP-1 activation could be mimicked by over-expression of wild-type M-Ras or a constitutively activated M-Ras mutant in control melan-a cells as monitored by an AP-1-luciferase reporter, while expression of a dominant negative M-Ras blocked AP-1-luciferase activity in MGSA/GRO-transformed melan-a clones. In the in vitro transformation assay, over-expression of M-Ras mimicked the effects of MGSA/GRO by inducing cellular transformation in control melan-a cells, while over-expression of dominant negative M-Ras in MGSA/GROalpha-expressing melan-a-6 cells blocked transformation. These data suggest that MGSA/GRO-mediated transformation requires Ras activation in melanocytes.

Optical properties of Nannochloropsis sp and their application to remote estimation of cell mass

The absorption and scattering coefficients and reflectance spectra of ultra-high density Nannochloropsis occulata cultures were investigated in detail to identify the optical properties of the cultures and devise algorithms for remote estimation of dry cell mass in ultra-high cell density cultures. High-spectral resolution measurements of apparent absorption and attenuation as well as reflectance from 400 to 900 nm were carried out in relation to the dry weight, cell count, and pigment concentration in outdoor cultures. Indices calculated as (R(NIR) - R(red))/(R(NIR) + R(red)) and R(NIR)/R(red), in which R(NIR) is reflectance in the range from 750 to 800 nm and R(red) is reflectance in the range 670-680 nm, were used for remote assessment of dry cell mass. Remote estimation in the range 1 to 8 g/L was accomplished with an error of less than 0.66 g/L. A different index, i.e., (R(NIR) - R(red)) was employed for estimation of cell-chlorophyll concentration. This is the first report of in vivo specific absorption coefficient of chlorophyll-a and specific scattering coefficient per dry algal weight of Nannochloropsis sp., providing a basis for remote monitoring of dense phytoplankton masses.

Cytokines revisited at Hilton head

The Seventh International Cytokine Society Meeting, held in December 1999 at Hilton Head, provided once more an ideal setting for an intense discussion and remodeling of concepts regarding the biology and molecular biology of cytokines and chemokines. Approximately 400 scientists gathered at the beach-side resort, forgoing the beauty of the ocean to listen to their colleagues in the field, in a program ably organized by Jan Vilcek, Scott Durum, Bruce Beutler and Ann Richmond. Here, we attempt to cover some of the highlights on gene regulation, T helper cell differentiation, signal transduction, receptor trafficking, chemokines, apoptosis, disease models, and new cytokines.

Childhood diabetes: dietary aspects

Insulin-dependent diabetes mellitus in children requires a delicate balance between injected insulin and food intake, taking into account physical activity and growth.

Molecular cloning and characterization of a mouse gene with homology to the Duffy-antigen receptor for chemokines

The Duffy antigen receptor for chemokines (DARC) is a receptor for both CXC and CC chemokines. We have cloned a mouse gene with a predicted amino acid sequence homology of approximately 63% to human DARC and localized this gene to mouse chromosome 1 between the Xmv41 and D1Mit166 loci. We further demonstrated that, like the human gene, the mouse gene exhibits a single intron of 462 bp which interrupts the open reading frame between the codons for the seventh and eighth amino acid residues. Northern blot analyses revealed that putative mDARC mRNA is highly expressed in adult mouse spleen and skeletal muscle and in whole embryos between embryonic days 8.5 to 12. Northern blot analysis of hemangiosarcomas which develop spontaneously in the spleen of the Eker rat reveal expression of mRNAs which hybridize with both DARC and CXCR2 probes, suggesting a potential role of these receptors in the angiogenesis associated with tumor formation.

Role of clathrin-mediated endocytosis in CXCR2 sequestration, resensitization, and signal transduction

CXCR2 is a seven-transmembrane receptor that transduces intracellular signals in response to the chemokines interleukin-8, melanoma growth-stimulatory activity/growth-regulatory protein, and other ELR motif-containing CXC chemokines by coupling to heterotrimeric GTP-binding proteins. In this study, we explored the mechanism responsible for ligand-induced CXCR2 endocytosis. Here, we demonstrate that dynamin, a component of clathrin-mediated endocytosis, is essential for CXCR2 endocytosis and resensitization. In HEK293 cells, dynamin I K44A, a dominant-negative mutant of dynamin that inhibits the clathrin-mediated endocytosis, blocks the ligand-stimulated CXCR2 sequestration. Furthermore, co-expression of dynamin I K44A significantly delays dephosphorylation of CXCR2 after ligand stimulation, suggesting that clathrin-mediated endocytosis plays an important role in receptor dephosphorylation and resensitization. In addition, ligand-mediated receptor down-regulation is attenuated when receptor internalization is inhibited by dynamin I K44A. Interestingly, inhibition of receptor endocytosis by dynamin I K44A does not affect the CXCR2-mediated stimulation of mitogen-activated protein kinase. Most significantly, our data indicate that the ligand-stimulated receptor endocytosis is required for CXCR2-mediated chemotaxis in HEK293 cells. Taken together, our findings suggest that clathrin-mediated CXCR2 internalization is crucial for receptor endocytosis, resensitization, and chemotaxis.

Multiple chemotactic factors: fine control or redundancy?

Recruitment of leukocytes either during development or to the site of injury is crucial. The molecular regulation of cell trafficking is complex but well orchestrated by the temporal and spatial expression of a multitude of chemokines (chemoattractant cytokines) and chemokine receptors. The chemokines, classified primarily into four classes (CC, C, CXC and CX3C) bind either to specific or shared receptors and often exhibit intra-class redundancy. At the cellular level, the biological activity of chemokines is finely controlled by varied receptor display, binding affinity and/or varied signal-transducing mechanisms. Perturbation in these finely regulated processes leads to acute or chronic inflammatory conditions, developmental abnormalities and tumorigenesis/angiogenesis.

Elevated constitutive IkappaB kinase activity and IkappaB-alpha phosphorylation in Hs294T melanoma cells lead to increased basal MGSA/GRO-alpha transcription

The basal transcription of the CXC chemokine, melanocyte growth stimulatory activity (MGSA)/growth-regulated protein (GRO)-alpha, is up-regulated in Hs294T melanoma cells compared with the normal retinal pigment epithelial (RPE) cells. Previous studies characterized a cytokine-inducible, functional nuclear factor (NF)-kappaB consensus element in the immediate 5' regulatory region of the MGSA/GRO-alpha gene at -78 bp. Although the cytokine-inducible mechanisms for transcription of this gene are fairly well delineated, the mechanisms involved in its basal up-regulation of transcription in Hs294T melanoma cells are poorly understood. Recently, we demonstrated an increased rate of IkappaB-alpha degradation in Hs294T cells, which leads to an increased nuclear localization of NF-kappaB (R. L. Shattuck-Brandt and A. Richmond. Cancer Res., 57: 3032-3039, 1997). Here we demonstrate that Hs294T melanoma cells have elevated basal IkappaB kinase (IKK) activity relative to RPE cells, causing an increased constitutive IkappaB-alpha phosphorylation and degradation. We also show here that the resultant elevated nuclear NF-kappaB (p50/p65) in these cells is responsible for the increased basal transcription of MGSA/GRO-alpha. Pretreatment of Hs294T or RPE cells with proteasome inhibitors MG115 or MG132 captures the slower migrating, constitutively phosphorylated form of IkappaB-alpha in Hs294T melanoma cells, but not in RPE cells. In addition, a phospho-specific antibody that specifically recognizes the inhibitory form of IkappaB that is phosphorylated at Ser-32 reacted with IkappaB-alpha in Hs294T cell, but not in unstimulated RPE cells. Although the basal level of protein expression of IKK-alpha or IKK-beta are the same in both Hs294T and RPE cells, immunoprecipitation with IKK-alpha antibody combined with activity assay reveal a constitutively active IKK complex in Hs294T melanoma cells. Cotransfection of a 350-bp MGSA/GRO-alpha promoter-luciferase reporter construct with either the dominant negative IKK-alpha or the repressors of NF-kappaB, the IkappaB-alpha wild type or mutants lacking the inducible phosphorylation sites, demonstrates that the increased basal MGSA/GRO-alpha transcription in the Hs294T cells is due to the enhanced nuclear activation of NF-kappaB.

Thirty-eight-year evaluation of a surgical technique to protect the external branch of the superior laryngeal nerve during thyroidectomy

The purpose of this study is to evaluate a surgical technique for the preservation of the function of the external branch of the superior laryngeal nerve (EBSLN) during total thyroid lobectomy and total thyroidectomy. Permanent injury to this nerve can be a disaster, especially in singers and professional speakers who depend on control of pitch, and a clear and forceful voice. Voice changes may be either obvious or subtle. For better voice analysis, a detailed questionnaire is necessary. Thus, the evaluation in this study is based on laryngoscopy of 934 nerves in 675 patients and detailed subjective voice evaluation of 66 patients during the last 2 years of the study. There are 2 surgical principles. First, the EBSLN is not routinely exposed; the distal 1.5 to 2.0 cm (critical area) of the superior thyroid vessels are carefully dissected, exposed, and ligated, preferably independently. Careful observation ensures that the EBSLN is not included in the ligature. Second, the ultimate evaluation of the surgical technique is the effect of voice changes on the patient's lifestyle. Laryngoscopy of 934 nerves found bowing, temporary in 4 patients and permanent in 1 patient (limited follow-up). Of the 66 patients with voice evaluations, 14 had changes: 9 had temporary changes, while 5 had permanent changes. In these 14 patients, voice changes had no effect on lifestyle in 13, and the effects were indeterminate in 1 (unavailable for follow-up). The estimated deleterious effect of voice changes on lifestyle is no greater than 1.5% of the 66 patient responders.

Proteolytic cleavage and activation of pro-macrophage-stimulating protein and upregulation of its receptor in tissue injury

Macrophage stimulating protein (MSP) exists in blood as inactive pro-MSP. Cleavage yields active MSP, the ligand for a membrane receptor (RON) that is expressed on keratinocytes as well as macrophages. Because both cells have roles in tissue injury, we looked for active MSP and expressed RON in wounds. Concentration of pro-MSP + MSP in wound exudates was in the range for optimal activity. Western blot showed that MSP comprised about half the total, in contrast to less than 10% of the total in blood plasma. The presence of MSP was attributed to an exudate pro-MSP convertase that had an inhibitor profile consistent with a trypsin-like serine protease. Exudate evoked morphologic changes in macrophages in vitro like that of MSP. Removal of this activity by an anti-MSP column shows that exudate stimulation of macrophages is due to MSP. RON was infrequently detected in normal skin. RON protein was markedly upregulated in burn wound epidermis and accessory structures, in proliferating cells or differentiated cells, or both. RON was also detected on macrophages and capillaries. Tissue injury leads to cleavage of pro-MSP to MSP, which has potential to act on keratinocytes, macrophages, and capillaries, all components of the wound healing response.

Identification and characterization of an MGSA/GRO pseudogene

Three linked genes for the CXC-chemokine melanoma growth stimulatory activity/growth related protein (MGSA/GRO) have been previously characterized and mapped to chromosome 4q12-q13. We have isolated and characterized a pseudogene, MGSA/GRO delta, which is 83% similar to the MGSA/GRO alpha gene in the region spanning the 5' UTR, first and second exons, and the first intron. The 5' upstream sequence for the MGSA/GRO delta gene, which is also very similar to the MGSA/GRO alpha, beta, gamma genes, contains a conserved NF-kappa B motif, a TATA box, and a transcription initiation site. However, the sequence becomes markedly divergent after the second exon and hybridization studies indicate that sequences similar to the third and forth exons of other MGSA/GRO genes are not present in this gene. Additional sequence differences include alteration of the MGSA/GRO delta translation initiation codon and a one base insertion resulting in an apparent frame shift and early termination within exon 2. Multiple mutations such as these are characteristic of pseudogenes.

Interruption of G protein-coupling in CXCR2 does not alter ligand binding, but eliminates ligand-activation of GTPgamma35S binding, calcium mobilization, and chemotaxis

CXCR2 is a seven-transmembrane receptor that transduces intracellular signals in response to the chemokines IL-8, MGSA/GRO, and other ELR motif-containing CXC chemokines by coupling to heterotrimeric GTP-binding proteins. In this study, we have mutated two putative G protein-coupling regions of CXCR2 and characterized the effects of these mutations on ligand-activated signal transductions: aspartic acid 89 in the second transmembrane domain and the HRAMR sequence (BBXXB motif, found in the third intracellular loop where B indicates a basic amino acid and X represents any amino acid). The Asp89 was replaced by either asparagine (D89N) or glutamic acid (D89E). For the BBXXB motif, the first two basic amino acids were mutated to two neutral isoleucines (HR-II), or alternatively, two isoleucines were inserted between alanine and methionine (II-insert). When expressed in human embryonic kidney 293 cells, the D89E mutant was localized intracellularly with no detectable cell surface expression. In contrast, D89N, HR-II, and II-insert mutants displayed cell surface expression, with Kd values and expression levels similar to that of the wild-type transfectant. The ability of the mutants to transduce signal was assessed by ligand-stimulated GTPgamma35S binding, mobilization of intracellular free Ca2+, and chemotaxis assays. Both D89N and HR-II mutants signaled similarly to a wild-type receptor in all three assays. However, the II-insert mutant exhibited a loss of ligand-stimulated GTPgamma35S binding, calcium mobilization, and chemotaxis. Unexpectedly, this receptor underwent ligand-induced sequestration comparable to wild-type CXCR2. These data indicate that Asp89 and the basic amino acids in the third intracellular domain do not play essential roles in ligand-induced signal transduction through CXCR2. However, proper secondary structure and orientation of the third intracellular loop of CXCR2 are essential for ligand-mediated signal transduction but not for receptor sequestration.

Enhanced tumor-forming capacity for immortalized melanocytes expressing melanoma growth stimulatory activity/growth-regulated cytokine beta and gamma proteins

Three human MGSA/GRO genes encode 3 highly related chemokines, MGSA/GRO alpha, -beta and -gamma. All 3 MGSA/GRO proteins bind to the same receptors, but with differing affinities, and stimulate a number of biological responses including chemotaxis, angiogenesis, and growth regulation. We have previously demonstrated that MGSA/GRO alpha can be isolated from culture medium conditioned by malignant melanoma cells and that continuous secretion of MGSA/GRO alpha contributes to the transformation of immortalized murine melanocytes. The present study was designed to determine whether MGSA/GRO beta or -gamma have similar effects on melanocyte tumorigenicity. Stable Melan-a clones expressing either human MGSA/GRO beta or -gamma exhibited enhanced ability to form large colonies in soft agar and tumors in nude mice. The clones expressing the MGSA/GRO beta or -gamma transgene formed tumors within 2 months after injection; the tumors were highly pigmented and expressed immunoreactive MGSA/GRO beta or -gamma protein. Furthermore, when conditioned medium from Melan-a clones expressing MGSA/GRO alpha, -beta or -gamma transgenes were examined for the ability to induce angiogenesis in the rat cornea, strong angiogenic responses were observed. This angiogenic response was blocked by antibodies to the respective MGSA/GRO protein, but not by normal rabbit serum. By contrast, angiogenic responses were observed in only 2 of 12 corneal implants (17%) containing medium conditioned by Melan-a clones expressing the neomycin resistance marker alone.

Mechanism and biological significance of constitutive expression of MGSA/GRO chemokines in malignant melanoma tumor progression

By reverse transcriptase-polymerase chain reaction, enzyme-linked immunosorbent assay, and immunohistochemistry, MGSA-alpha, -beta, -gamma, and CXCR2 mRNA expression and proteins are detected in 7 out of 10 human melanoma lesions. The biological consequence of constitutive expression of the MGSA/GRO chemokine in immortalized melanocytes was tested in SCID and nude mouse models. Continuous expression of MGSA/GRO-alpha, -beta, or -gamma in immortalized melan-a mouse melanocytes results in nearly 100% tumor formation for each of the clones tested, whereas clones expressing only the neomycin resistance vector form tumors <10% of the time. Moreover, antibodies to the MGSA/GRO proteins slow or inhibit the formation of tumors in the SCID mouse model and block the angiogenic response to conditioned medium from the tumor-producing clones. Transcription of the MGSA/GRO chemokines is regulated by an enhancesome-like complex comprised of the nuclear factor-kappaB (NF-kappaB), HMG(I)Y, IUR, and Sp1 elements. In Hs294T melanoma cells the half life of the IKB protein is shortened in comparison to normal retinal epithelial cells, facilitating the endogenous nuclear localization of NF-kappaB. We propose that this endogenous nuclear NF-kappaB, working in concert with the 115-kDa IUR-binding factor, promotes constitutive expression of MGSA/GRO genes.