The effect of Nannochloropsis oceanica feed inclusion on rabbit muscle proteome.

Nannochloropsis oceanica is a microalga, highly concentrated in protein and EPA (eicosapentaenoic acid). It has a recalcitrant cell wall that decreases nutrient digestibility. The objective of this study is to evaluate the effect of Nannochloropsis oceanica feed inclusion on the muscle proteome of fattening rabbits. Twenty rabbits were housed in individual cages for 5 weeks and were fed a control diet (n = 10) and one with 4.45% inclusion of microalga, replacing whole soybean meal (n = 10). After slaughter, samples of gastrocnemius muscle were taken for label-free proteomic analysis. A total of 1497 proteins were identified, 46 with differential abundance. Control rabbits had high abundance of proteins related to protein metabolism, suggesting higher muscle protein turnover. They also had higher abundance of structural proteins, suggesting a less tender meat by comparison with algae-fed rabbits. These had high abundance of proteins related to amino acid catabolism (Phe, Tyr) and synthesis (Gln). In addition, they had high abundance of proteins related to protein breakdown, overall suggesting that more tender meat may result from algae feeding. BIOLOGICAL SIGNIFICANCE: Microalgae are interesting feedstuffs particularly from a sustainability point of view. Their use in farm animal diets could simultaneously enhance the nutritional value and quality of meat. However, the biochemical pathways behind such improvement remain uncharacterized, namely in the rabbit species. By using a proteomics approach, this study will enlighten such biochemical pathways and relate them with productive performance parameters. In addition, results reflect some anti-nutritional properties of the recalcitrant cell wall over amino acid digestibility and consequently, its availability for protein synthesis.

Pathobiological implications of the d16HER2 splice variant for stemness and aggressiveness of HER2-positive breast cancer.

We have previously shown that the d16HER2 splice variant is linked to HER2-positive breast cancer (BC) tumorigenesis, progression and response to Trastuzumab. However, the mechanisms by which d16HER2 contributes to HER2-driven aggressiveness and targeted therapy susceptibility remain uncertain. Here, we report that the d16HER2-positive mammary tumor cell lines MI6 and MI7, derived from spontaneous lesions of d16HER2 transgenic (tg) mice and resembling the aggressive features of primary lesions, are enriched in the expression of Wnt, Notch and epithelial-mesenchymal transition pathways related genes compared with full-length wild-type (WT) HER2-positive cells (WTHER2_1 and WTHER2_2) derived from spontaneous tumors arising in WTHER2 tg mice. MI6 cells exhibited increased resistance to anoikis and significantly higher mammosphere-forming efficiency (MFE) and self-renewal capability than the WTHER2-positive counterpart. Furthermore, d16HER2-positive tumor cells expressed a higher fraction of CD29High/CD24+/SCA1Low cells and displayed greater in vivo tumor engraftment in serial dilution conditions than WTHER2_1 cells. Accordingly, NOTCH inhibitors impaired mammosphere formation only in MI6 cells. A comparative analysis of stemness-related features driven by d16HER2 and WTHER2 in ad hoc engineered human BC cells (MCF7 and T47D) revealed a higher MFE and aldehyde dehydrogenase-positive staining in d16HER2- vs WTHER2-infected cells, sustaining consistent BC-initiating cell enrichment in the human setting. Moreover, marked CD44 expression was found in MCF7_d16 and T47D_d16 cells vs their WTHER2 and Mock counterparts. Clinically, BC cases from two distinct HER2-positive cohorts characterized by high levels of expression of the activated-d16HER2 metagene were significantly enriched in the Notch family and signal transducer genes vs those with low levels of the metagene.

CD49d prevails over the novel recurrent mutations as independent prognosticator of overall survival in chronic lymphocytic leukemia.

CD49d, the alpha-chain of the integrin heterodimer α4ß1, was identified among the strongest predictors of overall survival (OS) in chronic lymphocytic leukemia (CLL), along with IGHV mutational status and deletion of the 17p chromosome involving TP53. In addition to TP53, the clinical relevance of NOTCH1, SF3B1 and BIRC3 gene mutations has been recently emphasized. By analyzing a cohort of 778 unselected CLL patients, we assessed the clinical relevance of CD49d as an OS predictor in subgroups defined by mutation/deletion of the TP53, NOTCH1, SF3B1 and BIRC3 genes. In this context, CD49d emerged as an independent predictor of OS in multivariate Cox analysis (Hazard ratio =1.88, P<0.0001). Consistently, high CD49d expression identified CLL subsets with inferior OS in the context of each category of a previously reported hierarchical risk stratification model. Moreover, by evaluating the relative importance of biological prognosticators by random survival forests, CD49d was selected among the top-ranked OS predictor (variable importance =0.0410), along with IGHV mutational status and TP53 abnormalities. These results confirmed CD49d as an independent negative OS prognosticator in CLL also in comprehensive models comprising the novel recurrent mutations. In this context, TP53 disruption and NOTCH1 mutations retained prognostic relevance, in keeping with their roles in CLL cell immuno-chemoresistance.

Human responses against HER-2-positive cancer cells in human immune system-engrafted mice.

BACKGROUND: Human immune system (HIS)-engrafted mice are new tools to investigate human immune responses. Here, we used HIS mice to study human immune responses against human HER-2-positive cancer cells and their ability to control tumour growth and metastasis. METHODS: BALB/c Rag2(-/-), Il2rg(-/-) mice were engrafted with CD34(+) or CD133(+) human cord blood hematopoietic stem cells (HSC) and vaccinated with human HER-2-positive cancer cells SK-OV-3 combined to human IL-12. RESULTS: Both CD34(+) or CD133(+) human HSC gave long-term engraftment and differentiation, both in peripheral blood and in lymphoid organs, and production of human antibodies. Vaccinated mice produced specific anti-HER-2 human IgG. An s.c. SK-OV-3 challenge was significantly inhibited (but not abolished) in both vaccinated and non-vaccinated HIS mice. Tumours were heavily infiltrated with human and murine cells, mice showed NK cells and production of human interferon-γ, that could contribute to tumour growth inhibition. Vaccinated HIS mice showed significantly inhibited lung metastases when compared with non-vaccinated HIS mice and to non-HIS mice, along with higher levels of tumour-infiltrating human dendritic cells. CONCLUSION: Anti-HER-2 responses were elicited through an adjuvanted allogeneic cancer cell vaccine in HIS mice. Human immune responses elicited in HIS mice effectively inhibited lung metastases.

Tear proteomics in evaporative dry eye disease.

PURPOSE: To analyze tear protein variations in patients suffering from dry eye symptoms in the presence of tear film instability but without epithelial defects. METHODS: Five microlitres of non-stimulated tears from 60 patients, suffering from evaporative dry eye (EDE) with a break-up time (BUT) <10 s, and from 30 healthy subjects as control (no symptoms, BUT >10 s) were collected. Tear proteins were separated by mono and bi-dimensional SDS-PAGE electrophoresis and characterized by immunoblotting and enzymatic digestion. Digested peptides were analyzed by liquid chromatography coupled to electrospray ionization quadrupole-time of flight mass spectrometry followed by comparative data analysis into Swiss-Prot human protein database using Mascot. Statistical analysis were performed by applying a t-test for independent data and a Mann-Whitney test for unpaired data (P<0.05). RESULTS: In EDE patients vscontrols, a significant decrease in levels of lactoferrin (data in %+/-SD): 20.15+/-2.64 vs 24.56+/-3.46 (P=0.001), lipocalin-1: 14.98+/-2.70 vs 17.73+/-2.96 (P=0.0001), and lipophilin A-C: 2.89+/-1.06 vs 3.63+/-1.37 (P=0.006) was revealed, while a significant increase was observed for serum albumin: 9.45+/-1.87 vs 3.46+/-1.87 (P=0.0001). No changes for lysozyme and zinc alpha-2 glycoprotein (P=0.07 and 0.7, respectively) were shown. Proteomic analysis showed a downregulation of lipophilin A and C and lipocalin-1 in patients, which is suggested to be associated with post-translational modifications. CONCLUSIONS: Data show that tear protein changes anticipate the onset of more extensive clinical signs in early stage dry eye disease.

A multi-DNA preventive vaccine for p53/Neu-driven cancer syndrome.

The highly aggressive cancer syndrome of female mice carrying a p53 knockout allele and a rat HER-2/neu (Neu) transgene (BALB-p53Neu) can be prevented by a cell vaccine presenting three components: Neu, interleukin (IL)-12 production, and allogeneic major histocompatibility complex (MHC) alleles (Triplex cell vaccine). Here we tested a second-generation Triplex DNA-based vaccine (Tri-DNA), consisting of the combination of three gene components (a transmembrane-extracellular domain fragment of the Neu gene, IL-12 genes, and the H-2D(q) allogeneic MHC gene), carried by separate plasmids. The Tri-DNA vaccine was at least as effective as the Triplex cell vaccine for cancer immunoprevention, giving a similar delay in the onset of mammary cancer and complete protection from salivary cancer. Both vaccines induced anti-Neu antibodies of the murine IgG2a isotype at similar levels. The Tri-DNA vaccine gave more restricted immunostimulation, consisting of a fully helper T cell type 1 (Th1)-polarized response, with effective production of interferon (IFN)-gamma in response to the vaccine but no spontaneous production, and no induction of anti-Neu IgG3 antibodies. On the other hand, the Triplex cell vaccine induced both Th1 and Th2 cytokines, a strong increase in spontaneous IFN-gamma production, and high levels of IgG3 antibodies recognizing Neu-positive syngeneic cells. In conclusion, the Tri-DNA vaccine is as effective as Triplex cell vaccine, exploiting a more restricted immune stimulation.

CD99 isoforms dictate opposite functions in tumour malignancy and metastases by activating or repressing c-Src kinase activity.

CD99 gene encodes two distinct proteins, produced by alternative splicing of CD99 gene transcript. Full-length CD99 isoform (CD99wt) is formed by an extracellular domain, followed by a transmembrane domain and a 36 amino-acid intracytoplasmic domain, which is partially deleted in the truncated, short form (CD99sh). A differential expression of these two CD99 molecules can lead to distinct functional outcomes in lymphocytes. To investigate the functional effects of CD99 molecules on malignancy, forced overexpression of the two CD99 isoforms was induced in osteosarcoma and prostate cancer cells. The two isoforms exhibited opposite functions: the major form dramatically inhibits anchorage-independent growth, anoikis resistance, migration and metastasis, whereas the CD99sh remarkably favours the phenomena. A mechanistic analysis of CD99-transfected osteosarcoma cells points to involvement of c-Src family kinase activity in regulating CD99 functions in malignancy. Ser168 residue of CD99 plays a pivotal role in the reversion of the malignant phenotype. Our findings highlight the involvement of CD99 in crucial processes of cancer malignancy, serving as a curtain raiser for this, so far neglected molecule. In addition, a dualistic role for the two CD99 isoforms was shown in agreement with what was observed for other cell adhesion molecules.

New target antigens for cancer immunoprevention.

Prevention of cancer through the activation of the immune system has been explored in recent years in preclinical systems thanks to the availability of several new transgenic mouse models that closely mimic the natural history of human tumors. The most thoroughly investigated model of cancer immunoprevention is the mammary carcinoma of HER-2/neu transgenic mouse. In this system it has clearly been shown that the activation of immune defences in healthy individuals can effectively prevent the subsequent onset of highly aggressive mammary carcinomas. A complete prevention was obtained using a combination of three signals (the so called "triplex" vaccine) that included the specific antigen (p185, the product of HER-2/neu) and nonspecific signals like allogeneic histocompatibility antigens and interleukin 12. The analysis of protective immune responses in models of cancer immunoprevention revealed some unexpected features, in particular the central role of antibodies in immunoprevention, at variance with conventional immuno-therapy which is firmly based on cytotoxic T cells. In the HER-2/neu system anti-p185 antibodies, in addition to immunological functions leading to tumor cell lysis, inhibit p185 dimerization and induce its internalization, resulting in the inhibition of mitogenic signaling. Most current tumor antigens appear to be unsuitable targets for cancer immunoprevention. An ideal antigen should have a crucial pathogenetic role in tumor growth to avoid the selection of antigen loss variants. Downregulation of major histocompatibility complex (MHC) expression during tumor progression frequently limits antigen recognition by MHC-restricted T cells. Thus an ideal antigen for cancer immunoprevention should be recognized both by T cells and by antibodies. Antibody binding to cell surface oncogenic determinants, in addition to complement- and cell-mediated tumor cell lysis, can block mitogenic signaling and induce internalization, resulting in tumor growth arrest. A search for new tumor antigens should be conducted among molecules that are directly involved in neoplastic transformation and are recognizable by the immune response also in MHC loss variants. Novel tumor antigens fulfilling both conditions will be crucial for the development of cancer immunoprevention and will provide new targets also for cancer immunotherapy.

Enhanced inhibition of tumour growth and metastasis, and induction of antitumour immunity by IL-2-IgG2b fusion protein.

Cytokine-immunoglobulin (Ig)-fusion proteins have attracted increasing interest as antitumour agents. Here, we have investigated the antimetastatic and antitumour responses elicited in vivo by mammary adenocarcinoma cells (TS/A) engineered to secrete interleukin (IL)-2-IgG fusion proteins. TS/A cells were transfected with DNA coding for IL-2-IgG2b, IgG2b or IL-2, and injected subcutaneously into syngeneic mice. Animals injected with TS/A-IL-2 or TS/A-IL-2-IgG2b both efficiently rejected tumours, whereas treatment with parental cells or TS/A-IgG2b was lethal. Interestingly, only mice vaccinated with IL-2-IgG2b fusion protein-secreting cells showed a long-lasting protective immunity against a later challenge with parental tumour cells. Moreover, the metastatic potential of TS/A-IL-2-IgG2b-transfected cells was dramatically decreased compared with TS/A-IL-2-cells, with a virtual absence of lung metastases after intravenous injection. Adenocarcinomas secreting IL-2-IgG2b exhibited a more prominent, early and persistent infiltration of CD4+, CD8+ and natural killer (NK) cells than TS/A-IL-2 cells. Therefore, upon transfection into adenocarcinoma cells, the IgG2b part of IL-2 fusion protein exerts intriguing added antitumour properties over IL-2 alone, thus contributing to a long-lasting tumour immunity, probably by the recruitment of specific immune effector cells. These findings suggest a promising new oncotherapeutic strategy for poorly immunogenic tumours: vaccination with tumour cells engineered to secrete IL-2-IgG2b fusion protein.

Combined allogeneic tumor cell vaccination and systemic interleukin 12 prevents mammary carcinogenesis in HER-2/neu transgenic mice.

Transgenic Balb/c mice expressing the transforming rat HER-2/neu oncogene develop early and multifocal mammary carcinomas. Within the first 5 months of life the tissue-specific expression of HER-2/neu causes a progression in all their 10 mammary glands from atypical hyperplasia to invasive carcinoma. It was previously observed that chronic administration of interleukin (IL)-12 increased tumor latency, but every mouse eventually succumbed to multiple carcinomas. A significant improvement in tumor prevention was sought by administering allogeneic mammary carcinoma cells expressing HER-2/neu combined with systemic IL-12. This treatment reduced tumor incidence by 90% and more than doubled mouse lifetime. For the maximum prevention p185(neu) antigen must be expressed by allogeneic cells. IL-12 treatment strongly increased the cell vaccine efficacy. The mammary glands of mice receiving the combined treatment displayed a markedly reduced epithelial cell proliferation, angiogenesis, and HER-2/neu expression, while the few hyperplastic foci were heavily infiltrated by granulocytes, macrophages, and CD8(+) lymphocytes. Specific anti-HER-2/neu antibodies were produced and a nonpolarized activation of CD4(+) and CD8(+) cells secreting IL-4 and interferon (IFN)-gamma were evident. A central role for IFN-gamma in the preventive effect was proven by the lack of efficacy of vaccination in IFN-gamma gene knockout HER-2/neu transgenic Balb/c mice. A possible requirement for IFN-gamma is related to its effect on antibody production, in particular on IgG2a and IgG2b subclasses, that were not induced in IFN-gamma knockout HER-2/neu mice. In conclusion, our data show that an allogeneic HER-2/neu-expressing cell vaccine combined with IL-12 systemic treatment can prevent the onset of genetically determined tumors.

Identification of new genes related to the myogenic differentiation arrest of human rhabdomyosarcoma cells.

Rhabdomyosarcoma is a soft tissue tumor committed to the myogenic lineage but arrested prior to terminal differentiation. To identify new genes implicated in the block in myogenic differentiation of rhabdomyosarcoma cells and those responsible for their proceeding along the myogenic pathway we used cDNA microarrays to compare gene expression profiles of two clones of the human embryonal rhabdomyosarcoma cell line RD with different myogenic potentials: RD/12, which is unable to differentiate, and RD/18, which shows elements able to terminally differentiate, as defined by the expression of myosin heavy chain (up to 50% of the population) and the formation of multinucleated myotube-like structures. We identified 80 genes differentially expressed by the two clones. Differentiating RD/18 cells overexpressed the myogenic transcription factor myogenin along with known myogenic markers; myogenin transfection into undifferentiated RD/12 cells was able to revert the phenotype giving rise to 94% of clones displaying a differentiated morphology. RD/18 cells also expressed several genes not known to be expressed in rhabdomyosarcoma or muscle cells, such as pigment-epithelium derived factor and endothelin-3. Poorly differentiated RD/12 cells, along with genes related to mesenchymal lineage or early myogenic commitment, also expressed genes not previously known to be related to the differentiation block of human rhabdomyosarcoma, such as monocyte chemotactic protein-1, connective tissue growth factor and insulin-like growth factor binding protein-5. Differential expression of these genes in a time course of differentiation suggested their potential roles as either new myogenic markers or repressors of differentiation. These results identify a cluster of new genes related to the aberrant myogenic differentiation program of human rhabdomyosarcoma cells.

An anti-apoptotic role for NGF receptors in human rhabdomyosarcoma.

The expression and biological function of Nerve Growth Factor (NGF) receptors was studied in a panel of rhabdomyosarcoma cell lines derived from embryonal and alveolar histotype. All the cell lines expressed both the high affinity receptor TrkA and the low affinity receptor p75(NTR). Treatment with exogenous NGF did not considerably alter rhabdomyosarcoma cell growth or differentiation, but significantly inhibited spontaneous apoptosis as well as apoptosis, and induced by serum starvation or apoptosis induced by treatment with cycloheximide (CHX). Rhabdomyosarcoma cell lines expressed NGF and other neurotrophins and trace amounts of NGF protein were found in the supernatants of rhabdomyosarcoma cell cultures. Blocking the putative autocrine loop with an anti-NGF antibody resulted in an increase in apoptosis compared with control cultures. These data suggest that the simultaneous presence of both high and low affinity NGF receptors engaged by endogenous or exogenous NGF might contribute to the escape from apoptosis exhibited by the rhabdomyosarcoma cells.

Prevention of spontaneous neu-expressing mammary tumor development in mice transgenic for rat proto-neu by DNA vaccination.

The HER-2/neu proto-oncogene is overexpressed in 20-30% of human breast cancers and is associated with high recurrence risk. The oncogenic potential of HER-2/neu, together with its elevated expression in tumors, cell surface localization, and immunogenicity in some patients, make this oncoprotein an ideal target for immunotherapeutic approaches. To test the efficacy of immune-based strategies in eliciting an antitumor response, we used the N#202 transgenic mouse model engineered to overexpress the rat neu proto-oncogene under the control of the mouse mammary tumor virus promoter; females of this line develop spontaneous focal mammary tumors by 6 months of age. Transgenic mice immunized intramuscularly with a HER-2 cDNA ligated into the VR1012 (VICAL) expression vector under the control of the cytomegalovirus promoter developed significantly fewer spontaneous tumors as compared with mice injected with the empty vector (P < 0.0001) or not injected (P = 0.0006). However, this protection was observed only when immunization was started in 3-month-old but not in 6-month-old mice. These data suggest that the xenogeneic HER-2 DNA sequence can break immune tolerance to rat neu in transgenic N#202 mice and induce protective immunity that impairs the neu oncogene-driven progression of mammary carcinogenesis. The preventive effect achieved by our immunological approach appeared not to be based on anti-neu specific B and T cell immune attacks but was more possibly based on different mechanisms including aspecific and inflammatory immunological responses.

Inhibition of insulin-like growth factor I receptor increases the antitumor activity of doxorubicin and vincristine against Ewing's sarcoma cells.

Innovative treatment modalities are needed for Ewing's sarcoma (ES), a neoplasm with a disappointingly low survival rate despite the use of aggressive multimodal therapeutic approaches. We and others (D. Yee et al., J. Clin. Investig., 86: 1806-1814, 1990; K. Scotlandi et al., Cancer Res., 56: 4570-4574, 1996) have previously shown the existence and the pathogenetic relevance of an autocrine loop, mediated by the insulin-like growth factor-I receptor (IGF-IR), which is crucial for survival and proliferation of ES cells in vitro. Moreover, we reported that the IGF-IR-blocking monoclonal antibody (MAb), alphaIR3, as well as suramin, a drug that can interfere with growth factor by binding to the receptors, inhibited both the tumorigenic and the metastatic ability of ES cells in athymic mice. In this study, we analyzed whether agents that can block the IGF-IR-mediated loop are of value in association with conventional cytotoxic drugs for the design of more effective therapeutic regimens. Both alphaIR3 MAb and suramin treatment significantly increased the antitumor in vitro effects of doxorubicin and vincristine, two drugs with a leader action on ES. These findings were obtained by both simultaneous and sequential treatments. Analysis of the proliferation rate and of apoptosis revealed that alphaIR3 MAb and suramin significantly enhanced the G(1)-phase rate induced by doxorubicin, without substantially affecting doxorubicin-G(2)-M-blockage of cell cycle, and significantly increased the induction of apoptosis, which confirmed that the specific blockage of IGF-IR deprives ES cells of an important tool for the prevention of drug-induced apoptosis. Moreover, combination treatments of doxorubicin plus alphaIR3 MAb significantly increase the doxorubicin-induced impairment of the ability of ES cells to form colonies in soft agar. In conclusion, we showed that, in ES, the blockage of IGF-IR by a neutralizing MAb or by suramin may greatly potentiate the antitumor activity of conventional chemotherapeutic drugs.

Therapy of lung metastases through combined vaccination with carcinoma cells engineered to release IL-13 and IFN-gamma.

TS/A spontaneous mouse mammary adenocarcinoma cells were engineered to release interferon-gamma (IFN-gamma), a Th1 cytokine (TS/A-IFNgamma) and interleukin-13 (IL-13), a Th2 cytokine (TS/A-IL13). Mice bearing lung micrometastases induced by parental TS/A cells received repeated subcutaneous vaccinations with TS/A-IFN-gamma admixed with TS/A-IL13 engineered cells. This combined treatment cured up to 75% of mice, whereas vaccinations with either TS/A-IFNgamma or TS/A-IL13 alone cured only 20-40% of mice. Combined TS/A-IL13 and TS/A-IFNgamma therapeutic vaccinations elicited a reactive infiltrate of CD4+ and CD8+ lymphocytes in lung metastases and an increased production of IFN-gamma in the spleen and lung, suggesting a shift of the immune response toward the Th1 type. The type of infiltrating cells along with the lack of efficacy in T cell-deficient mice point to a major role of T cells. In conclusion, no antagonism but a synergistic and effective definitive cure stems from the combined vaccination with tumor cells engineered to release a Th1 and a Th2 cytokine.

Prevention by delay: nonspecific immunity elicited by IL-12 hinders Her-2/neu mammary carcinogenesis in transgenic mice.

As a natural consequence of the expression of the activated transforming rat Her-2/neu oncogene all mammary glands of female transgenic BALB/c (BALB-neuT) mice develop atypical epithelial hyperplasia which progresses to invasive carcinoma. A lobular carcinoma is palpable in all mammary glands of 33-week-old BALB-neuT mice. This progression is markedly delayed by systemic administration of IL-12. In a series of studies the best administration schedule, the lowest dose and the most effective administration time have been defined. The cellular and molecular mechanisms resulting in the delay of carcinogenesis have been established. By means of a series of downstream mediators IL-12 inhibits the angiogenic burst that goes along with the passage from preneoplastic to neoplastic and invasive lesions; it also recruits lymphoid cells in the mammary pad and activates their cytotoxicity towards neoplastic cells and newly formed vessels; and furthermore, it induces lymphoid cells to trigger antiangiogenic activities in neoplastic epithelial cells. Effective, low-dose and non-toxic IL-12 treatments may thus be envisaged as a possible option in the management of preneoplastic mammary lesions and in mammary cancer prevention.

The metastatic ability of Ewing's sarcoma cells is modulated by stem cell factor and by its receptor c-kit.

Ewing's sarcoma is a primitive highly malignant tumor of bone and soft tissues usually metastasizing to bone, bone marrow, and lung. Growth factor receptors and their ligands may be involved in its growth and dissemination. We analyzed the expression of c-kit and its ligand stem cell factor (SCF) in a panel of six Ewing's sarcoma cell lines. All cell lines exhibited substantial levels of surface c-kit expression, and five of six displayed transmembrane SCF on the cell surface. Expression of c-kit was down-modulated in all lines by exposure to exogenous SCF. The SCF treatment was able to confer to cells a growth advantage in vitro, due both to an increase in cell proliferation and to a reduction in the apoptotic rate. When used in the lower compartment of a migration chamber, SCF acted as a strong chemoattractant for Ewing's sarcoma cells. The pretreatment of cells with SCF reduced their chemotactic response to SCF. In athymic nude mice, Ewing's sarcoma cells injected intravenously metastasized to the lung and to a variety of extrapulmonary sites, including bone and bone marrow. Metastatic sites resembled those observed in Ewing's sarcoma patients and corresponded to SCF-rich microenvironments. The in vitro pretreatment of cells with SCF strongly reduced the metastatic ability of Ewing's sarcoma cells, both to the lung and to extrapulmonary sites. This could be dependent on the down-modulation of c-kit expression observed in SCF-pretreated cells, leading to a reduced sensitivity to the chemotactic and proliferative actions of SCF. Our results indicate that the response to SCF mediated by c-kit may be involved in growth, migration, and metastatic ability of Ewing's sarcoma cells.

Concomitant amplification and expression of PAX7-FKHR and MYCN in a human rhabdomyosarcoma cell line carrying a cryptic t(1;13)(p36;q14).

Alveolar rhabdomyosarcoma (ARMS) is associated with the specific chromosomal translocation (2;13)(q35;q14) or its rarer variant t(1;13)(p36;q14), which produces the fusion gene PAX7-FKHR. Here we describe the human cell line RC2, derived from an ARMS, which harbors a cryptic t(1;13)(p36;q14) and concomitantly shows amplification of the PAX7-FKHR fusion gene and of the MYCN oncogene. The t(1;13) and MYCN oncogene were studied by standard cytogenetic analysis and molecular techniques. The reverse transcriptase polymerase chain reaction demonstrated the expression of PAX7-FKHR mRNA in RC2 cells, although karyotype analysis failed to demonstrate a t(1;13)(p36;q14) chromosomal translocation or a derivative 13 chromosome. Double minute chromosomes were detected in all the metaphases studied. Fluorescence in situ hybridization analysis revealed multiple copies of the PAX7-FKHR fusion gene localized exclusively on a subset of double minutes, whereas multiple copies of MYCN were identified on other double minute chromosomes. Southern-blot analysis demonstrated that RC2 cells contain approximately 20 copies of the MYCN oncogene. So far no continuous RMS cell line carrying the t(1;13)(p36;q14) has been described, and PAX7-FKHR and MYCN amplifications have always been reported to occur separately in rhabdomyosarcoma (RMS). The availability of an ARMS cell line that harbors the t(1;13)(p36;q14) constitutes a useful tool for further understanding the role of the PAX7-FKHR fusion gene in RMS oncogenesis and may improve knowledge of the possible relation between PAX7-FKHR and MYCN amplification.