The HIV-1 Tat protein is a potent chemoattractant for monocytes. We observed that Tat shows conserved amino acids corresponding to critical sequences of the chemokines, a family of molecules known for their potent ability to attract monocytes. Synthetic Tat

A new anti-p58 monoclonal antibody (mAb), termed CH-L, has been used to characterize a minor subset of T lymphocytes co-expressing p58 and CD3 molecules. In two-color immunofluorescence analysis, CH-L+CD3+ cells represented 0.5 to 6% of the peripheral blood lymphocytes (in 20 healthy donors). Clonal analysis showed that most CD3+CH-L+ T cell clones expressed the CD8+4- T cell receptor (TcR) alpha/beta+ phenotype, while only a few were CD8-4+ TcR alpha/beta, CD8-4- TcR alpha/beta+ or CD8-4- TcR gamma/delta+. Western blot analysis indicated that the CH-L mAb identifies the same 56-58-kDa diffuse band in both T and natural killer cell (NK) clones. A minority of T cell clones also expressed other NK-related markers such as CD16, CD56 and CD94 and two clones also reacted with the anti-p58 mAb EB6. Interestingly, most clones displayed cytolytic activity in an anti-CD3 mAb-triggered redirected killing assay against the Fc gamma receptor+ P815 target cells and NK-like activity against K562 and Raji cells. In contrast, the IGROV-1 ovarian carcinoma cell line was resistant to cytolysis by all of these clones. Since p58 molecules have previously been shown to exert regulatory functions on NK-mediated lysis, we investigated whether anti-p58 mAb could also influence cytotoxicity mediated by CD3+p58+ T lymphocytes. Lysis of P815 target cells, triggered by anti-CD3 mAb, could be inhibited by anti-p58 mAb in 8 out of 12 cytolytic clones tested, while 4 clones were not inhibited. In addition, anti-p58 mAb enhanced the cytolytic activity of 3 clones against IGROV-1 and of 4 other clones against Raji target cells. Taken together, these data indicate that p58+ T cells express heterogeneous phenotypes and different forms of TcR and, in most instances, display cytolytic functions. Perhaps more importantly, the p58 molecule appears to modulate the cytolytic activity triggered via the CD3/TcR complex.

Interleukin (IL)-15 is a four-helix bundle cytokine sharing several biological properties with IL-2. By reverse transcriptase-polymerase chain reaction analysis, human cancer cell lines of different histotypes are shown to express two IL-15 amplification products: a 524-bp band corresponding to the IL-15 mRNA found in macrophages, and another of 643 bp corresponding to an alternatively spliced mRNA including a 119-bp alternative exon. IL-15 was undetectable in the supernatant of tumor cell lines expressing either one or both of the mRNA isoforms as evaluated by a bioassay or by ELISA, indicating that IL-15 is not secreted. However, IL-15 could be detected intracellularly in some tumor cells by confocal microscopy analysis. Since the pre-proteins encoded by the two mRNA isoforms differ in the signal peptide sequence, we have analyzed the characteristics of these signal peptides and their possible role in controlling secretion. The two IL-15 cDNA isoforms, expressed in COS-7 cells, induced very low levels of IL-15 secretion. However, substitution of the sequence encoding natural signal peptide(s) with the one from IgV kappa chain in the IL-15 cDNA results in a significantly higher secretion of biologically active IL-15 (15-30-fold) upon cDNA transfection. A poor efficiency of natural signal peptides may represent one of the mechanisms involved in the control of IL-15 secretion.

The pathogenesis and progression of breast cancer involve complex interactions between hormones and polypeptide growth factors such as insulin-like growth factor-I (IGF-I). IGF-I has been found in stromal fibroblasts derived from malignant and benign breast tissue and it is a mitogen for several breast cancer cell lines. It circulates bound to specific high-affinity binding proteins, which could act as either positive or negative modulators of tumorigenesis. This study has been addressed to characterize IGF-I and its binding proteins in the serum of 85 unselected patients with early breast cancer. The IGF-I concentration was assessed by radioimmunoassay of 69 out of 85 samples before and after dissociation of the IGF-I and IGF-binding protein (IGF-BP) complex whereas IGF-BP of all 85 sera were analyzed by Western ligand blotting; estradiol and progesterone were measured by radioimmunoassay in native serum samples. In our study no differences in IGF-I serum levels between pre- and post-menopausal patients were observed. Patients with higher estradiol and progesterone serum levels did not present different IGF-I concentrations compared to patients with lower serum levels. Furthermore, IGF-I median values were not found to depend on estrogen receptor (ER) status. A heterogeneous quali-quantitative molecular pattern of binding proteins was detected: IGF-BP3 and IGF-BP1 were the most and the least expressed respectively. No correlations between ER status, or parameters related to the hormonal status, and IGF-I or binding proteins expression were observed. No significant differences in IGF-I concentration and IGF-BP expression were observed between cancer patients and a control group matched for age and menopausal status. Finally, preliminary collection of 20 sera derived from patients with late breast cancer was analyzed for IGF-I and its binding proteins content.

We have analysed the expression of interleukin-2 receptor (IL-2R) on a panel of small-cell lung cancer (SCLC) cell lines. None of the 11 SCLC cell lines studied expressed detectable surface IL-2R alpha or beta chains by indirect immunofluorescence. Reverse transcriptase-polymerase chain reaction (RT-PCR) analyses indicated that only one out of 11 cell lines expressed detectable IL-2R beta mRNA while two expressed a weak positivity for IL-2R gamma. Five SCLC cell lines were transfected with the plasmid vector RSV.5 neo containing IL-2 cDNA coding sequence. Stable transfectants secreted biologically active IL-2 (ranging from 25 to 100 U ml-1 in the culture supernatant). IL-2 transfection did not produce significant modifications in the expression of surface molecules such as IL-2R alpha and beta chains, intercellular adhesion molecule-1 (ICAM-1), CD44, HLA class I and II or in IL-2R beta or gamma mRNA. More importantly, IL-2-transfected N592 and NCI H69 cell lines completely lost their tumorigenic potential in nude mice after subcutaneous injection, whereas experimental controls transfected with RSV.5 neo vector only, displayed an in vivo growth pattern identical to that of untransfected cells. In addition, in the N592 model, IL-2-producing N592 inhibited the growth of wild-type N592 injected at the same site, while injection of parental cells on the opposite side did not significantly affect the growth of wild-type tumour cells. Histopathological analysis of the rejection process of IL-2-transfected cells demonstrated the presence of MAC-1+, MAC-3+ macrophages and of RB68C5+ granulocytes, whereas T cells were undetectable and NK cells were scarcely represented. In addition, a reduction of the tumour blood vessels was observed. The possible relevance of these data for the development of vaccination strategies using cytokine-engineered tumour cells in SCLC is discussed. Images Figure 2 Figure 4 Figure 5