Inactivation of wild-type p53 by a dominant negative mutant renders MCF-7 cells resistant to tubulin-binding agent cytotoxicity.

The present study was performed to gain insight into the role of p53 on the cytotoxicity of tubulin-binding agents (TBA) on cancer cells. Drug sensitivity, cell cycle distribution and drug-induced apoptosis were compared in 2 lines derived from the mammary adenocarcinoma MCF-7: the MN-1 cell line containing wild-type p53 (wt-p53) and the MDD2 line, containing a dominant negative variant of the p53 protein (mut-p53). The MDD2 cell line was significantly more resistant to the cytotoxic effects of vinblastine and paclitaxel than the MN1 cell line. MN1 cells, but not MDD2 cells, displayed wt-p53 protein accumulation as well as p21/WAF1 and cyclin G1 induction after exposure to TBA. Both cell lines arrested at G(2)/M after drug treatment. However exposure of MN1 cells to TBA resulted in a stronger variation in mitochondrial membrane potential, associated with cleavage of PARP, and more apoptosis, as measured by annexin V expression. After exposure to vinblastine, Raf 1 kinase activity was reduced in MDD2 cells but not in MN1 cells. Addition of flavopiridol to vinblastine- and paclitaxel-treated cells reversed the MDD2-resistant phenotype by inducing G(1)cell cycle arrest and inhibiting endoreduplication. We conclude that the p53 status of cancer cells influences their sensitivity to TBA cytotoxicity. This effect is likely to involve differences in the apoptotic cascade.

Identification and cloning of an 85-kDa protein homologous to RING3 that is upregulated in proliferating endothelial cells.

A central event in angiogenesis is proliferation of blood vessels, which plays a major role in the progression of a number of inflammatory and neoplastic diseases. It is responsible for the switch of endothelial cells from an antiangiogenic to an angiogenic phenotype. To identify novel activated/proliferating-related proteins in human endothelial cells, a subtractive immunization approach was used to elicit a host antibody response against human dermal microvascular endothelial cells (HDMECs) stimulated with a potent angiogenic cytokine such as VPF/VEGF165. In this study, a new mAb, LY9, which is highly specific to VPF/VEGF165-activated HDMECs, was isolated. Stimulation of HDMECs by VPF/VEGF165 or basic fibroblast growth factor (bFGF) resulted in a dose-dependent and time-dependent increase in the binding of LY9. On Western-blot analysis, LY9 identified an 85-kDa protein (p85) in the lysates of several endothelial cells derived from microvascular or large vessel sources, the expression of which is dramatically increased by VPF/VEGF165. The mAb also identified p85 in primary cell cultures of human foreskin keratinocytes but failed to recognize human fibroblasts (MRC5) and a number of different human tumor cell lines, including MG63 osteosarcoma and MCF7 breast carcinoma cells. Immunological screening of a human keratinocyte lambdagt11 cDNA expression library with LY9 identified a partial cDNA clone of 750 bp. DNA sequencing of this clone and predicted amino acids showed more than 93% homology to RING3 kinase, a member of a newly described family of bromodomain-containing proteins that transactivates in the nucleus the promoters of a number of the E2F family of transcription factors. This molecule may represent a new signaling target activated by VPF/VEGF165 and bFGF that allows endothelial cells to enter the proliferative phase of the angiogenic process.

Leukemia inhibitory factor antagonizes gonadotropin induced-testosterone synthesis in cultured porcine leydig cells: sites of action.

In the present report, the action of leukemia inhibitory factor (LIF) on testicular steroid hormone formation was studied. For this purpose, the direct effects of LIF were evaluated on basal and human (h)CG-stimulated testosterone synthesis by cultured, purified Leydig cells isolated from porcine testes. LIF reduced (more than 60%) hCG-stimulated testosterone synthesis. This inhibitory effect was exerted in a dose- and time-dependent manner. The maximal and half-maximal effects were obtained with, respectively, 10 ng/ml (0.5 nM ) and 2.5 ng/ml (0.125 nM ) of LIF after a 48-h treatment of the Leydig cells. Such an effect of the cytokine was not a cytotoxic effect, because it was reversible and Leydig cells recovered most of their steroidogenic activity after the removal of LIF. Considering the sites of action of LIF in inhibiting gonadotropin-stimulated testosterone formation, it was shown that LIF significantly (P < 0.002) reduced, in a comparable range (about 60% decrease), testosterone synthesis stimulated with LH/hCG or with pharmacological agents that enhance cAMP levels (cholera toxin, forskolin, and PG E2), and testosterone synthesis stimulated with 8-bromo-cAMP. Such an observation indicates that the antigonadotropic action of the cytokine is exerted in a predominant manner at a step (or steps) located beyond cAMP formation. Furthermore, incubation of Leydig cells with 22R-hydroxycholesterol (5 microg/ml, 2 h), a cholesterol substrate derivative that does not need an assisted process to be delivered to the inner mitochondrial membrane, reversed most of the inhibitory effect of LIF on the steroid hormone formation. Such results indicate that LIF acts by reducing cholesterol substrate availability in the mitochondria. Consequently, LIF action was tested on steroidogenic acute regulatory protein and PBR (peripheral benzodiazepine receptor) shown to be potentially involved in such a cholesterol transfer. LIF reduced, in a dose- and time-dependent manner, LH/hCG-induced steroidogenic acute regulatory protein messenger RNA levels. The maximal inhibitory effect was obtained with 6.6 ng/ml of LIF after 48 h of treatment. In contrast, LIF had no effect on PBR messenger RNA expression or PBR binding. This inhibitory effect of LIF on Leydig cell steroidogenesis is probably exerted via an auto/paracrine action of the cytokine. Indeed, by immunohistochemistry, LIF and LIF receptor proteins were identified in Leydig and Sertoli cells but not in other testicular cell types, except for LIF receptor in spermatogonia. Furthermore, the presence of LIF and its receptor in Leydig cells at the neonatal and adult periods suggests that the inhibitory effect of LIF on androgen formation reported here probably occurs in both the fetal and the adult Leydig cell populations during testicular development.

A new Mr 55,000 surface protein implicated in melanoma progression: association with a metastatic phenotype.

Emergence of the invasive phenotype is a key event in the progression of human melanoma from benign proliferative lesions to malignant lesions. Recently we successfully selected in vivo from a poorly metastatic M4Beu. human melanoma cell line two variants (7GP and T1P26) that generate a higher frequency of spontaneous metastases to the lungs into immune-suppressed neonatal rats. Both cell lines showed no significant differences in the integrin profile of the subunits analyzed except for beta3, which was reduced to a background level in metastatic variants. To investigate how these variant sublines of human melanomas manage to sustain growth in the absence of alpha(v)beta3, a subtractive immunization approach was used to elicit host antibody response against cell surface proteins expressed on metastatic variants. In this study, a new monoclonal antibody (MoAb), LY1, that is highly specific for the 7GP and T1P26 variants, was isolated. LY1 identifies a membrane protein of Mr 55,000 on melanoma variants with epitopes that were resistant to sugar-cleaving enzymes. Immunostaining cells from variants by LY1 showed that staining is distributed to the cell periphery with high labeling intensity at the cell-to-cell contact points. This MoAb significantly inhibited invasion of metastatic variants through a reconstituted basement membrane (Matrigel) in vitro. Moreover, tumor growth of melanoma variants was dramatically affected in vivo with this MoAb. In vitro studies indicate that the LY1 MoAb does not inhibit chemotactic migration of the metastatic variants, the adhesion of tumor cells to vitronectin, collagen IV, fibronectin, and laminin, or cell proliferation. Expression of this antigen is high in human striated muscle, heart, spleen, brain, and lung and absent in kidney, liver, and pancreas. Using 59 fixed, paraffin-embedded archival tissues of human melanomas and nevi, LY1-reactive cells were not observed in melanocytes, nevi, or radial growth phase primary melanomas. In sharp contrast, LY1 selectively stained melanocytes derived from the vertical growth phase of many primary melanomas and metastatic melanomas. These results provide evidence that the Mr 55,000 protein expressed by selected variants with increased metastatic properties in vivo plays a functionally important role in determining metastasis. This molecule may represent a new metastatic risk marker in human melanoma and may be of biological importance in the identification of fatal metastatic subpopulations that have acquired competence for metastasis production.

Developmental and hormonal regulation of the expression of oligodendrocyte-specific protein/claudin 11 in mouse testis.

The proliferation and differentiation of testicular progenitor stem cells into highly specialized germ cells (spermatozoa) are largely controlled by the hormonally (FSH and testosterone) regulated adjacent supporting Sertoli cells. However, the factors involved in this control remain largely unknown. In the present study, the technique of differential display PCR was used to identify target transcripts to FSH action in cultured murine Sertoli cells. Among these target transcripts, we identified the oligodendrocyte-specific protein (OSP), also known as claudin 11, which had recently been shown to play a key role in the formation of the hematotesticular barrier. Our data show that the testicular expression of OSP is dependent upon male gonad development and systemic and local signaling molecules. Indeed, OSP is expressed early in fetal development in Sertoli cells, immediately after the peak of SRY (sex-determining region, Y gene) expression, but just before that of the anti-Mullerian hormone. Postnatally, OSP expression starts to increase from day 3 to reach a plateau between days 6 and 16 postnatally. In the prepubertal and adult testes, an apparent decline in OSP messenger RNA (mRNA) levels was found, probably because of the increasing number of germ cells (which do not express OSP). Among the signaling molecules that control testicular OSP expression, we have identified FSH and tumor necrosis factor-alpha (TNFalpha). Indeed, using a model of purified cultured mouse Sertoli cells, we demonstrate that FSH inhibits, in a dose (ED50 = 4 ng/ml)- and time (maximal effect after 24 h)-dependent manner, the levels of OSP mRNA. Such an inhibitory effect was mimicked by 8-bromo-cAMP, suggesting that FSH may use the cAMP/protein kinase A pathway to inhibit OSP mRNA levels. TNFalpha was also shown to inhibit OSP expression in cultured Sertoli cells. The maximal effect was observed after 48 h of TNFalpha treatment with an ED50 of 4.5 ng/ml. Together, our results indicate that OSP expression 1) starts during fetal life at a critical period, probably under SRY control and during testicular formation; and 2) is regulated by hormones (FSH) and cytokines (TNFalpha) in the adult testis, suggesting a critical role for these molecules in the (re)modeling process of the hematotesticular barrier during spermatogenesis.

A novel SMAD4 gene mutation in seminoma germ cell tumors.

Transforming growth factor (TGF)-beta is known as an antiproliferative factor in the majority of mammalian cells, including stem germ cells. Lack of TGF-beta-induced growth inhibition has been associated with disruptions of TGF-beta receptors and SMADs. In the present study, we performed a mutational analysis of the TGF-beta signaling system, including TGF-beta receptor type I and type II and SMADs (SMAD1-SMAD7), in 20 seminoma germ cell tumors. Using reverse transcription-PCR, single-strand conformational polymorphism, and sequencing analysis, the COOH-terminal domain of SMAD4 was found to be mutated: a single thymine was inserted between nt 1521 and 1522 in 2 of 20 tumors analyzed. This addition of a thymine creates a frameshift and a new stop signal at codon 492, which leads to premature termination of the encoded protein. Such a mutation potentially abrogates signaling from TGF-beta as well as the other TGF-beta family members, including activin and bone morphogenetic protein, which all use the SMAD pathway. Immunohistological analysis confirmed the loss of expression of SMAD4 protein in the seminoma tissues with the insertional mutation. To our knowledge, this is the first description of a novel SMAD4 insertional mutation in seminoma testicular germ cell tumors. This mutational inactivation of SMAD4/COOH-terminal domain may cause TGF-beta unresponsiveness. It could thus provide a basis for understanding the potential role of the TGF-beta system in germ cell tumorigenesis.

[Sarcoma of the pulmonary artery]. / Sarcomes de l'artére pulmonaire.

Two cases of pulmonary artery angiosarcomas are reported. Pulmonary artery tumor was diagnosed during exploratory thoracotomy in the first case. It was suspected on magnetic resonance imaging and confirmed by surgery in the second case. The therapeutic was a right pneumonectomy for the first patient and a tumor resection followed by chemotherapy and radiotherapy on cerebral metastases for the second patient. Both our patients died, 13 and 44 months after surgery. On the basis of histological and immunohistochemical findings both tumors were angiosarcomas. Ultrastructural examination in the second case revealed an endothelial differentiation. The review of 142 previously reported cases of pulmonary artery sarcomas and these ultrastructural findings suggest that pulmonary artery sarcomas may have multiple origins; leiomyosarcomas deriving from arterial smooth muscle; angiosarcomas deriving from the endothelium and undifferentiated sarcomas or "myointimal sarcomas" deriving from myointimal cells.

Cellular distribution of transforming growth factor betas 1, 2, and 3 and their types I and II receptors during postnatal development and spermatogenesis in the boar testis.

Transforming growth factor betas (TGF betas) 1, 2, and 3 and their types I and II receptors (TGF betas RI and RII) were immunolocalized 1) during testicular development from the perinatal to the adult period and 2) in maturing germ cell populations at successive seminiferous epithelium stages. In the perinatal testis, TGF beta isoforms and receptors were both preponderant in Leydig cells and in spermatogonia. At prepuberty, their expression appeared in Sertoli cells, while germ cells showed specific TGF beta1 and TGF betaRI staining in the spermatocytes. In the adult testis, TGF beta ligands exhibited a preferential tubular distribution. TGF beta1 was mainly detected in young spermatocytes, TGF beta2 in Sertoli cells, and TGF beta3 in Sertoli and premeiotic germ cells. Although the two receptors were systematically observed together in various cells, our data indicate a predominance of one in comparison with the other depending on the cell type. TGF betaRI was predominant in meiotic and differentiated germ cells and TGF betaRII in somatic cells. Finally, in the adult testis, TGF betas 1, 3, and RI showed a germ-cell pattern that depended upon the stage of the seminiferous epithelium cycle. Specifically, staining for the ligands was predominant before meiosis, and TGF betaRI was present particularly during meiosis and spermiogenesis. Together, the temporal and spatial distribution of the TGF beta system components suggests that these signaling molecules may play a crucial role during specific steps of testicular development and during different waves of seminiferous epithelium maturation leading to spermatogenesis.

Cellular distribution of EGF, TGFalpha and their receptor during postnatal development and spermatogenesis of the boar testis.

The epidermal growth factor (EGF), the transforming growth factor alpha (TGFalpha) and the epidermal growth factor receptor (EGFr) have been immunolocalized, (i) during the testicular postnatal development (i.e. at the perinatal, prepubertal and adult periods), and (ii) during the seminiferous epithelium cycle in the different germ cell types. While TGFalpha was essentially observed in somatic cells, specifically in perinatal Leydig cells and in mature Sertoli cells, EGF was localized both in germ cells and in somatic cells with a preferential tubular expression. Furthermore, identification of EGFr in different testicular cell types indicates that during postnatal development and spermatogenesis, testicular cells are potentially responsive to EGF in that they express EGFr. Indeed, in the course of the gonadal development, the EGFr distribution was evidenced both in somatic and germ cells with a specific germ cell pattern depending upon the seminiferous epithelium cycle. A predominant EGFr staining was evidenced during the meiotic process and the spermiogenesis. Together, the present data are in favor of the involvement of the TGFalpha/EGF system in the local control of testicular cells during development and particularly of its potential direct implication in crucial steps of spermatogenesis such as meiosis and spermiogenesis.

Tumor induction by v-Jun homodimers in chickens.

To study the contribution of v-Jun homodimers to oncogenesis, we constructed artificial v-Jun derivatives in which the natural dimerization domain of v-Jun was replaced by an heterologous homodimerization domain from either the viral EB1 or the yeast GCN4 transcription factor. The resulting v-Jun chimeric proteins, called v-Juneb1 and v-Jungcn4, which can no longer dimerize with Jun or Fos, should only form homodimers in the cell. Helper-independent retroviruses expressing v-Jun, v-Juneb1 and v-Jungcn4 were generated. All three viruses transformed primary cultures of chick embryo cells with the same high efficiency and promoted local tumor growth after subcutaneous injection of infected cells in young animals. In contrast, after intravenous injection of viral suspensions into chick embryos, only the chimeric proteins produced internal tumors that were lethal. These tumors were leiomyosarcomas located within the liver and along the digestive tract. Thus, in vivo, v-Juneb1 and v-Jungcn4 are more potent oncoproteins than v-Jun. These data demonstrate that when forced to accumulate, v-Jun homodimers can induce tumors efficiently. They also show that the oncogenic potential of v-Jun can be regulated through the properties of its dimerization domain.

Thrombospondin modulates melanoma--platelet interactions and melanoma tumour cell growth in vivo.

In this study we have investigated the role of thrombospondin (TSP) as a possible ligand playing a key role in human M3Da. melanoma cell interaction with platelets and in tumour growth. TSP is secreted (80 +/- 6 ng TSP 10(-6) cells) and bound to the surface of M3Da. cells via receptors different from CD36, as shown by biosynthetic labelling and immunofluorescence studies. The levels of TSP binding to M3Da. cells evaluated by binding studies, using an anti-TSP monoclonal antibody (MAb) (LYP8), shows 367,000 +/- 58,000 (mean +/- s.d.) LYP8 binding sites per cell with a dissociation constant (Kd) of 67 nM. TSP binding to M3Da. cells shows 400,000 +/- 50,000 TSP binding sites per cell with a Kd of 10 nM. The capacity of anti-TSP MAb (LYP8) to inhibit M3Da.-platelet interactions was followed on an aggregometer and evaluated by electron microscopy studies. The biological role of TSP binding to M3Da. cells was investigated by implanting subcutaneously the M3Da. cell line in nude mice and following the size and time of in vivo tumour growth. Reducing the availability or the functional level of TSP by using an anti-TSP MAb (LYP8) resulted in a significant decrease in platelet aggregates interacting with M3Da. melanoma cells. Using an enzyme-linked immunosorbent assay, purified alpha nu beta 3 was shown to bind TSP. Moreover, LYP8-coated M3Da. cells showed a reduced capacity to form tumours in vivo. M3Da. cells were observed to attach and spread on human platelet TSP-coated plastic wells. This attachment by M3Da. cells was inhibited in a similar way by LYP8 and an anti-alpha nu beta 3 MAb (LYP18). The results obtained in this study show that TSP secreted and bound to the surface of a human melanoma cell line (M3Da.) acts as a link between aggregated platelets and the M3Da. cell surface. Moreover, these results shows that TSP can modulate tumour growth in vivo. Reagents such as MAbs directed against TSP and peptides derived from TSP could not only be used as a new therapeutic approach in the control of tumour metastasis of melanoma, but may also contribute to elucidation of the role of TSP in cancer biology.

[A new biomaterial in surgery of ptosis with frontalis suspension: wide pore PTFE]. / Un nouveau biomatériau dans la chirurgie du ptosis avec suspension au muscle frontal: le PTFE à larges pores.

BACKGROUND: In brow suspension, there is agreement that fresh tissue (autogenous fascia lata or temporalis fascia) provides the best results in terms of low complications and duration of the effect. Yet, the morbidity of fresh tissue harvesting is not negligible. Many alternative materials have disadvantages in terms of duration of the procedure and side effects. METHODS: We have used a new material: wide porous expanded polytetrafluoroethylene (eP.T.F.E.). This material is an inert vitreous teflon alloplast with a high biocompatibility. It is close to Gore-Tex, but differs from it by a higher porosity (over 90%) and wider diameter of its pores (over 50 mus). We performed a series of 60 brow suspension from February 1992 to March 1994, using this new material. RESULTS: We did not encounter any significant complications due to the material and in circumstance, we did not deplore any migration, infection or extrusion of the ePTFE. The biocompatibility seems to be increased, as it has been demonstrated by light and electron microscopy of the implanted material who revealed that fibrovascular ingrowth was significantly achieve two months after surgery. CONCLUSION: The first results of this series are very encouraging. They can favourably be compared with the results of other series using different types of materials available in brow suspension. Though our longest follow-up is 30 months, further study is necessary to evaluate the long term results and eventual long term side effects of ePTFE, which avoid harvesting fresh tissues, thus reducing the brow suspension procedure's morbidity.

Human melanoma cell lines differ in their capacity to release ADP and aggregate platelets.

In this study we have investigated, using three different human melanoma cell lines (M1Do., M3Da., M4Be.). the varying capacity of melanoma cells to induce platelet aggregation in the presence or absence of inhibitors of ADP or thrombin. The expression levels of different integrins (alpha v, beta 3, alpha v beta 3, alpha IIb, alpha v beta 3) were evaluated by immunoprecipitation, binding and flow cytometry studies. The level of ADP in supernatants of melanoma cells were quantified by ADP bioassay and HPLC. Platelets were irreversibly aggregated by M3Da, as shown by electron microscopy, in contrast to M1Do, which induced a slow reversible aggregation. M4Be. did not induce platelet aggregation. In both cases, with M3Da. or M1Do., apyrase but not PPACK inhibited platelet induced aggregation. An anti-alpha v beta 3 monoclonal antibody (LYP18) or polyclonal antibody inhibited platelet aggregation. A similar number of LYP18 molecules bound to the surface of M1Do., M3Da. and M4Be. cell lines. Biological HPLC assays of ADP present in the supernatant of tumour cell lines showed the highest concentration of ADP to be secreted by M3Da., followed by M1Do., and none detected for M4Be. These results show that differences in in vitro aggregating potential of the three human melanoma cell lines are not related to low integrin expression levels but to their ability to generate ADP. Generation of ADP by human melanoma cells may act as important modulator of melanoma-platelet interactions.

Hepatocarcinoma-specific mutant p53-249ser induces mitotic activity but has no effect on transforming growth factor beta 1-mediated apoptosis.

Mutations affecting the p53 gene abrogate its tumor suppressor activity. It is, however, unclear whether such mutations can generate mutant p53 proteins with an intrinsic transforming ability. More importantly, the mechanism(s) by which they exert such activity is unknown. We report here that p53-deficient hepatoma cells (Hep3B) transfected with mutant p53-249ser (codon 249 Arg-->Ser) acquire a new phenotype with an increased in vitro survival and mitotic activity. However, such a phenotypic change is not sufficient to cause a major shift in the poor tumorigenic potential of these cells. This is apparently due to transforming growth factor beta 1-mediated apoptotic death of Hep3B cells which is not affected by the expression of p53-249ser.

Desmoplastic small round cell tumors of the abdomen.

BACKGROUND: Desmoplastic small round cell tumors (DSRCT) have been only recently identified. METHODS: The authors report DSRCT in two pediatric patients (an 8-year-old boy and 12-year-old boy). In both patients, the initial diagnosis was rhabdomyosarcoma. The resistance to standard chemotherapy and radiation therapy prompted the authors to review the initial biopsy specimens and perform complementary immunophenotypic characterization. RESULTS: These analyses revealed that the tumor cells were strongly positive for keratin epithelial marker antigen, desmin, vimentin, neurospecific enolase, and S100 protein, corresponding to pleomorphic differentiation, characteristic of DSRCT: CONCLUSIONS: The authors suggest that extensive immunohistologic characterization be performed in all cases of small round cell tumors of the abdomen so that the diagnosis of DSRCT is not overlooked. These rare tumors are refractory to chemotherapy, and initial aggressive surgery is warranted.

[Giant cell fibroblastoma. Apropos of 2 cases]. / Le fibroblastome à cellules gèantes. A propos de deux observations.

Two cases of giant cell fibroblastoma (GCF) are reported. One presented as cervical tumor in a 11 year old child and the second localized in axillar region of 14 year old boy. Histologically both showed a typical distinctive appearance of this entity when focal fusocellular cells arranged in a storiform pattern was also constated in one. The immunohistochemical and ultrastructural study ruled out a vascular origin. The clinical and pathological findings suggest that CGF represent a juvenile form of dermatofibrosarcoma protuberans.

Alteration of the inner surface of venous catheters by antineoplastic drugs.

Septic complications and thrombosis are frequent causes of long-term venous catheter implantation failure and tend to occur more frequently in oncology than in patients using catheters for hyperalimentation only. The purpose of this in vitro study was to study extensively the inner surface behaviour and the possible changes in their mechanical properties of various silicone and polyurethane catheters after exposure to a flow of the most common antineoplastic drugs. Silicone catheters appeared to be the best choice for cytostatic drug infusions because of their chemical stability, but the addition of an opacifier imposes a protective inner and outer layer to improve their surface properties for biocompatibility.

Expression of integrin receptors on 45 clinical neuroblastoma specimens.

Immunohistological expression of integrins has been analyzed on 45 neuroblastoma specimens representative of the different clinical and histological forms of the tumor. None of the specimens expressed the alpha 5 chain of the integrins. The beta 1 chain was expressed on all specimens, the alpha 1 chain on 44 specimens and the alpha 3 chain on 42; the 4 specimens which lacked alpha 1 or alpha 3 were stage-4 neuroblastomas. The alpha 2 chain was expressed on 18 specimens, and the alpha 6 chain on 17; 15 reacted with both. Their reactivity was related to the maturation of the tumor rather than the stage of the disease: they were expressed on low-grade, well-differentiated specimens; stage 3-4 neuroblastoma specimens analyzed at diagnosis were negative, but usually expressed both chains when analyzed after in vivo differentiation by chemotherapy. alpha v reacted with 18 specimens and beta 3 with 12, without strict relation with the stage of the disease and/or its degree of differentiation; 9 well-differentiated specimens expressed the beta 4 chain; only 4 well-differentiated specimens expressed the alpha 4 chain. The 4 specimens which lacked alpha 1-beta 1 or alpha 3-beta 1 expression had n-myc amplification, whereas those which expressed either alpha 4, beta 4, beta 3 or alpha v had no amplification. Furthermore, the expression of the 3 heterodimers alpha 4-beta 1, alpha v-beta 3 and alpha 6-beta 4 was essentially observed on primary tumors which developed in the mediastinum. The expression of alpha 2-beta 1 and alpha 6-beta 1 was observed on both n-myc-positive and -negative specimens. beta 1 and alpha 3 were diffusely expressed on all counterparts of these tumors, from undifferentiated neuroblasts to ganglion and Schwann cells. The alpha 1 chain reacted with undifferentiated and intermediate neuroblasts as well as with Schwann cells, but ganglion cells were negative. alpha 2 and alpha 6 chains were negative on undifferentiated neuroblasts, variably expressed on intermediate neuroblasts, and restricted to Schwann cells in ganglioneuroma. The expression of alpha 4 and beta 4 was restricted to Schwann cells. alpha v and beta 3 occasionally reacted with undifferentiated and intermediate neuroblasts; alpha v was strongly positive on Schwann cells but negative on ganglion cells, whereas beta 3 was positive on both neuronal and non-neuronal populations.