Biomedical subjects

F Giancotti

Publications and source records attributed to F Giancotti.

At least 19 recordsLinked to original sources

PubMed1998

Alpha3beta1-integrin as a critical mediator of the hepatic differentiation response to the extracellular matrix.

The extracellular matrix (ECM) promotes the differentiation of many cell types, and ECM remodeling in the liver has been implicated in embryonic development, tissue injury, and oncogenesis. Integrins are heterodimeric ECM receptors that play critical roles in transducing the composition of the ECM in the cell environment. We previously showed that mouse H2.35 cells, a conditionally transformed, liver-derived cell line, assume a more differentiated hepatocyte morphology and enhanced liver-specific gene expression when the cells are cultured on gelatinous ECM substrata. Here we show that H2. 35 cells express relatively high levels of alpha3beta1-integrins, similar to that previously shown for immature hepatocytes, transformed hepatocytes, and biliary cells. However, the cell morphological responses that depend on alpha3beta1-integrin have not been defined. We found that transfecting H2.35 cells with antisense RNA construct directed to alpha3-subunit messenger RNA perturbs the initial cell attachment to laminin and collagen, and strongly inhibits cell morphological, proliferative, and gene expression responses to a collagen gel substratum. In situ hybridization to mouse embryo tissues demonstrates the presence of alpha3-subunit messenger RNAs in newly formed hepatocytes. We suggest that alpha3beta1-integrins are important for immature and transformed hepatocytes to respond morphologically to the extracellular matrix.

Animals↗

PubMed1998

EBV-associated primary lymphomas in salivary glands of HIV-infected patients.

The lymph nodes within and around salivary glands are commonly involved in inflammatory processes, but rarely the site of primary lymphomas. We observed six cases of primary salivary gland lymphoma in HIV-infected patients and studied them in parallel with three cases of primary salivary gland lymphoma unrelated to HIV and three cases of HIV-related salivary gland lymphadenopathies in order to characterize this new entity. We found that all salivary gland lymphomas in HIV-infected patients were of high histologic grade while salivary gland lymphomas unrelated to HIV were predominantly of low grade MALT type. All lymphomas in both categories expressed the B-cell phenotype. Just as HIV-unrelated lymphomas frequently arise on the background of chronic inflammatory lymphoid processes, lesions characteristic of HIV-lymphadenopathy were still present in some lymphomas of HIV-infected patients. EBV RNA transcripts (EBER) were demonstrated in three, and latent membrane protein (LMP) in two of the six HIV-related and in none of the three HIV-unrelated lymphomas. The three EBER-positive lymphomas were of the histologic types known to express the virus in most cases. The presence of HIV in the form of the core protein p24 and envelope glycoprotein gp41 on the dendritic reticular cells of germinal centers was ascertained in the cases of HIV-related lymphadenopathies but also in the coexistent lymphadenopathies of lymphomas. The practical importance of diagnosing the salivary lymphadenopathies and lymphomas associated with the HIV-infection resides in avoiding their misdiagnosis and surgical removal as tumors of salivary glands.

Adult↗

PubMed1997

EBV-associated anorectal lymphomas in patients with acquired immune deficiency syndrome.

Primary lymphomas of the gastrointestinal tract represent 9% of all non-Hodgkin lymphomas, and of these only 3% arise in the rectum or anus. In contrast to their rare occurrence in the general population, the incidence of anorectal lymphomas in patients with acquired immune deficiency syndrome (AIDS), particularly homosexual patients, may be as high as 26% as reported in our own series of AIDS-associated lymphomas. To determine the characteristics of this entity, we studied 15 cases of primary anorectal lymphoma in AIDS patients and compared them with four cases of anorectal lymphoma unrelated to AIDS. The cases in our study were also compared with the reports of rectal lymphoma in the medical literature over the past 30 years. In the present series, the AIDS patients were all male with a median age of 34 years, human immunodeficiency virus (HIV)-positive, with homosexuality as the main risk factor. The four non-AIDS patients included a woman and had a median age of 66.5 years. Histologically, the anorectal lymphomas in AIDS patients were all high grade, predominantly immunoblastic, and polymorphous. In the non-AIDS patients, only two of four lymphomas were high grade, including one Burkitt type. All tumors were of B-cell phenotype. In the AIDS-associated anorectal lymphomas, the presence of Epstein-Barr virus (EBV) in a latent form was demonstrated by an abundance of Epstein-Barr-encoded RNA (EBER) in 14 of 15 cases and latent membrane protein (LMP) in four cases. All anorectal lymphomas unrelated to AIDS were negative for EBV. The unusual anorectal location of AIDS-associated lymphomas is explainable by the high incidence of preceding traumatic lesions and chronic infections in the area. As a result, EBV-carrying B cells may be attracted to the field providing the cell population that, under the conditions of immune deficiency, is able to give rise to high-grade lymphomas.

Acquired Immunodeficiency Syndrome↗

PubMed1996

Transfection of beta 4 integrin subunit into a neoplastic keratinocyte line fails to restore terminal differentiation capacity or influence proliferation.

Loss of expression of specific integrins is a feature of poorly differentiated oral squamous cell carcinomas (SCCs) and cell lines derived from them. In order to test whether there is a direct link between reduced alpha 6 beta 4 integrin expression and abnormal keratinocyte growth and differentiation we 'repaired' an SCC line. H376, by transfection of the beta 4 integrin subunit. We analysed five independent beta 4 transfectant clones and compared them with four empty vector control clones and with the parental cell line. Elevated cell surface expression of alpha 6 beta 4 was not correlated with changes in anchorage dependent or independent growth and was not sufficient to induce expression of the terminal differentiation marker, involucrin. Introduction of the beta 4 integrin subunit did not have a major effect on cell adhesion to laminin 1 or 5 and did not result in formation of stable anchoring contacts. We conclude that loss of alpha 6 beta 4 is not directly responsible for the abnormal behaviour of the H376 cell line.

Antigens, CD↗

PubMed1994

Reactivity of lung tumors with lung-derived and non-lung-derived monoclonal antibodies.

The reactivity of 74 lung-derived monoclonal antibodies (MAbs) provided by the Third International Workshop on Lung Tumor Antigens and of 41 non-lung-derived commercially available MAbs against sections of 15 lung tumors of various histologic types was investigated by immunohistochemistry. Three MAbs with specificity for human neural-cell adhesion molecule (H-NCAM) and 3 MAbs with specificity for small-cell lung carcinoma (SCLC) were able to distinguish between neuro-endocrine (NE) and non-NE tumors. Fifteen MAbs stained non-small-cell carcinomas (NSCLC) but not SCLC. Neuron-specific enolase (NSE) stained all NE tumors but also some of the non-NE tumors. Two MAbs showed specificity for mesotheliomas. Carcino-embryonic MAb strongly stained all SCLC and NSCLC. Among MAbs with lymphoid-cell specificities, Leu 7 (CD57) stained SCLC, but not NSCLC. LN2 (CD45R), LN3 (HLA-DR), Leu 22 (CD43) and BLA 36 reacted with NSCLC and were non-reactive with SCLC. Some of the lung-derived MAbs showed immune staining of lymphoma and melanoma.

Antibodies, Monoclonal↗

PubMed1993

Axonal regulation of Schwann cell integrin expression suggests a role for alpha 6 beta 4 in myelination.

Ensheathment and myelination of axons by Schwann cells in the peripheral nervous system requires contact with a basal lamina. The molecular mechanism(s) by which the basal lamina promotes myelination is not known but is likely to reflect the activity of integrins expressed by Schwann cells. To initiate studies on the role of integrins during myelination, we characterized the expression of two integrin subunits, beta 1 and beta 4, in an in vitro myelination system and compared their expression to that of the glial adhesion molecule, the myelin-associated glycoprotein (MAG). In the absence of neurons, Schwann cells express significant levels of beta 1 but virtually no beta 4 or MAG. When Schwann cells are cocultured with dorsal root ganglia neurons under conditions promoting myelination, expression of beta 4 and MAG increased dramatically in myelinating cells, whereas beta 1 levels remained essentially unchanged. (In general agreement with these findings, during peripheral nerve development in vivo, beta 4 levels also increase during the period of myelination in sharp contrast to beta 1 levels which show a striking decrease.) In cocultures of neurons and Schwann cells, beta 4 and MAG appear to colocalize in nascent myelin sheaths but have distinct distributions in mature sheaths, with beta 4 concentrated in the outer plasma membrane of the Schwann cell and MAG localized to the inner (periaxonal) membrane. Surprisingly, beta 4 is also present at high levels with MAG in Schmidt-Lanterman incisures. Immunoprecipitation studies demonstrated that primary Schwann cells express beta 1 in association with the alpha 1 and alpha 6 subunits, while myelinating Schwann cells express alpha 6 beta 4 and possibly alpha 1 beta 1. beta 4 is also downregulated during Wallerian degeneration in vitro, indicating that its expression requires continuous Schwann cell contact with the axon. These results indicate that axonal contact induces the expression of beta 4 during Schwann cell myelination and suggest that alpha 6 beta 4 is an important mediator of the interactions of myelinating Schwann cells with the basal lamina.

Animals↗

PubMed1993

[Mechano-electric feedback and ventricular arrhythmias in heart failure. The possible role of permanent cardiac stimulation in preventing ventricular tachycardia].

Left ventricular dysfunction has been identified as the strongest independent predictor of sudden death in patients with ventricular tachyarrhythmias. It has been suggested that some of these arrhythmias might be due to myocardial stretch which may alter cellular electrophysiological properties. In heart failure (HF) the abnormal mechanics of contraction may directly initiate an arrhythmia by mechano-electric feedback (MEF), defined as changes in mechanical state that precede and alter transmembrane potential. So far, the significance of MEF and its role in clinical arrhythmogenesis have received minimal attention. We report data of 3 patients, aged from 60 to 64 years (mean age 62 +/- 2), affected by HF from 28.3 +/- 3.5 months and ventricular arrhythmias recorded by Holter: premature contractions, couplets, nonsustained ventricular tachycardia (VT). Sinus rhythm was present in 2 patients, atrial fibrillation in the last one. Many VT episodes started after an abrupt spontaneous increase in ventricular cycle length or following an ectopic beat. A permanent VVI pacemaker (MEDTRONIC Legend) was implanted in each patient and programmed at different rate from 50 to 80 b/min. During the upper rates, 70 and 80 b/min, VT episodes decreased from 292 +/- 181 to 161 +/- 95 and 97 +/- 63 (p < 0.05), respectively. In fact, the permanent pacemaker could prevent the lengthening of ventricular cycle and the myocardial fibers stretch due to the increase in ventricular volume. In conclusion, in patients with HF and ventricular arrhythmias a pacemaker may be useful in preventing VT episodes and, probably, sudden death.

Analysis of Variance↗

PubMed1990

Nerve growth factor induces increased expression of a laminin-binding integrin in rat pheochromocytoma PC12 cells.

Rat pheochromocytoma PC12 cells exposed to nerve growth factor differentiate as sympathetic neurons and extend neurites on laminin and to a much lesser extent on fibronectin. Analysis of laminin fragments indicated that neurite outgrowth occurs mainly on fragment P1, corresponding to the center of the cross, and only poorly on fragment E8, a long arm structure that is active with other neuronal cells. Integrin antibodies prevented adhesion and neurite sprouting of these cells on laminin, fragment P1, and fibronectin. By affinity chromatography we isolated an integrin-type receptor for laminin consisting of two subunits with molecular massess of 180 and 135 kDa. The latter is recognized by an antiserum to integrin beta 1 subunit. The bound laminin receptor could be displaced by EDTA, but not by Arg-Gly-Asp or Tyr-Ile-Gly-Ser-Arg peptides. Affinity chromatography on laminin fragments showed that the 180/135 kDa receptor binds to P1. The expression of the 180-kDa alpha subunit of the laminin receptor at the cell surface was increased 10-fold after NGF treatment. The effect of NGF is specific since the amount of a 150-kDa fibronectin-binding integrin alpha subunit remained unchanged. Moreover, the increased expression of the 180/135 kDa receptor at the cell surface corresponded to a selective increase in cell adhesion to laminin and to fragment P1. The 180/135-kDa complex is thus an integrin-type receptor for laminin whose expression and binding specificity correlates with the capacity of NGF-induced PC12 cells to extend neurites on laminin.

Adrenal Gland Neoplasms↗

PubMed1989

Cloning of cDNA for a novel mouse membrane glycoprotein (gp42): shared identity to histocompatibility antigens, immunoglobulins and neural-cell adhesion molecules.

A full-length clone encoding a murine membrane glycoprotein, gp42, was selected from a mouse fibroblast cDNA expression library by screening with a polyclonal antiserum. The deduced amino acid (aa) sequence indicates that gp42 is a transmembrane protein of 273 aa with a large N-terminal portion exposed outside the cell and a short cytoplasmic domain. Computer assisted analysis shows that gp42 is distinct from previously characterized proteins, but shares a number of structural features with the class II histocompatibility antigens. The sizes of the extracellular domains of gp42 and of class II histocompatibility antigens are similar, the position of four cysteines and the location of several aa residues are conserved. Some of these conserved residues are also present in immunoglobulins (Ig) and in the neural-cell adhesion molecule, thus indicating that gp42 is a new member of the Ig superfamily.

Amino Acid Sequence↗

PubMed1989

Interaction of fibronectin with cultured human endothelial cells: characterization of the specific receptor.

In this study we provide a characterization of the fibronectin (FN) binding to endothelial cells (EC), and we identify the FN binding site on these cells. 125I-FN binding to EC in suspension was time dependent and reached a plateau at 4 h. Cold FN inhibited this interaction in a concentration-dependent way, but vitronectin, fibrinogen, and IgG were poorly effective. About 80% of the total FN associated to EC at the equilibrium was specifically bound; of this, 60% was reversibly bound, while 20% appeared to be internalized. The FN binding was saturable and an apparent dissociation constant of about 0.23 x 10(-6) mol/L and a maximal number of binding sites of about 9.8 x 10(5) was estimated from binding isotherms. Autoradiography data showed that EC-associated 125I-FN was all in high mol wt form that did not enter the gel. We then characterize the FN receptor (FNR) in EC. An antiserum to the FNR isolated from human placenta inhibited FN binding to EC by 89%, and using the immunoblotting technique, it recognized two bands in the EC detergent extract of mol wt 125/160 Kd. This antiserum also recognized the EC membrane protein complex eluted from the FN affinity column by an arg-gly-asp (RGD) peptide. When this complex was included into liposomes, it poorly bound to FN. However, the binding was strikingly increased by addition of Mn in the buffer and was specific for FN in respect to other substrata. These data define the FN binding site in EC and indicate that it is functionally and structurally related to that isolated from human placenta.

Antigens, Surface↗

PubMed1989

Inhibition of experimental metastasis of murine fibrosarcoma cells by oligopeptide analogues to the fibronectin cell-binding site.

We have analyzed the effect of the synthetic oligopeptides Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) and Gly-Arg-Gly-Glu-Ser-Pro (GRGESP), analogues to the fibronectin cell-binding sequence, on the formation of experimental lung metastasis. SR-BALB were injected alone or in conjunction with GRGDSP or GRGESP in the tail vein of BALB/c mice. Co-injection with GRGESP reduced by approximately 70% the number of metastatic colonies per mouse. However, co-injection with the closely related peptide GRGDSP, containing the conservative substitution Glu/Asp, did not affect metastatic behavior. GRGESP peptide anti-metastatic activity was not due to a toxic effect on tumor cells or on mice. In vitro adhesion assays testing for a possible effect of the peptide on cell-matrix interactions indicated that the GRGESP peptide did not affect cell adhesion to the matrix proteins tested.

Animals↗

PubMed1987