Yoshitsugu Miki

Interleukin-6 (IL-6) functions as an in vitro autocrine growth factor in renal cell carcinomas.

Interleukin‐6 (IL‐6) was found to be a growth factor of renal cell carcinomas. Furthermore, renal cell carcinomas freshly isolated from the patients expressed mRNA of IL‐6 and secreted biologically active IL‐6 under the culture conditions where the tumor cells could grow, but they did not produce IL‐6 nor proliferate in the absence of fetal calf serum. The production of IL‐6 by the tumor cells was also demonstrated by immunostaining of the IL‐6‐producing cells utilizing anti‐IL‐6 antiserum. Moreover, anti‐IL‐6 antiserum specifically inhibited the in vitro tumor growth. All data indicated that IL‐6 functions as an in vitro autocrine growth factor of renal cell carcinomas.

B Cell Growth and Differentiation Factors and Mechanism of B Cell Activation

B cells, one of the best understood eukariotic cells, originate from pluripotent hematopoietic stem cells and differentiate into immunoglobulin {Ig)-secreting cells through multistep developmental stages, such as pre-pre-B cells, pre-B cells, immature B cells, mature B cells, activated B cells and Ig-secreting cells. An understanding of the stimuli which cause the activation, proliferation and differentiation of B cells is critical to the delineation of the normal regulation of the immune responses as well as proliferation and differentiation of eukariotic cells. Since the discovery of T-B collaboration in the antibody response, extensive studies on the regulatory molecules involved in B cell activation have been done. More than a decade ago, Dutton and his colleagues (1971) suggested the involvement of soluble helper factors in the T cell-dependent activation of B cells into Ig-secreting cells. Since then, hundreds of factors, antigen specific or nonspecific, have been reported and those results have supported the notion that helper or suppressor function of T cells in B cell activation can be replaced by the soluble products released from T cells. Kishimoto and Ishizaka (1975) and Kishimoto and his colleagues (1975) have shown Ig-induction in rabbit B cells by anti-Ig and T cell-derived helper factors, suggesting that 2 signals, crosslinkage of Ig-receptors and helper factors, could induce activation of B cells into Igproducing cells. This finding was confirmed by several investigators in murine or human B cells (Parker etal. 1979, Isakson etal. 1981, Yoshizaki et al. 1982)and also supported the notion that helper function of T cells was mediated by T cellderived helper factors.

Functional and possible physical association of scavenger receptor with cytoplasmic tyrosine kinase Lyn in monocytic THP-1-derived macrophages

Acetyl LDL (modified low‐density lipoprotein), which is thought to be taken up through scavenger receptor A (SR‐A), rapidly induced the appearance of phosphotyrosine proteins in monocytic THP‐1‐derived macrophages in vitro. The two alternative forms of Lyn (p53 and p56) were found to be tyrosine‐phosphorylated within 30 s after the stimulation with acetyl LDL. The catalytic activity of Lyn measured by an in vitro kinase assay had also increased in acetyl LDL‐stimulated THP‐1‐derived macrophages. Furthermore, Lyn could be co‐immunoprecipitated with SR‐A from the cell lysate. These observations suggest a functional and possible physical association of SR‐A with Lyn in THP‐1‐derived macrophages, and also imply a possible involvement of Lyn in SR‐A signal transduction.

Reduction of atherosclerosis despite hypercholesterolemia in lyn‐deficient mice fed a high‐fat diet

Oxidation and other modifications of serum low‐density lipoprotein (LDL) are associated with the development of atherosclerosis, and a scavenger receptor and CD40 signalling are also known to play important roles in the process. We previously showed that the Src family protein‐tyrosine kinase Lyn is physically and/or functionally associated with macrophage type‐I and type‐II class‐A scavenger receptors (MSR‐A) and CD40.

Expression of scavenger receptors on renal cell carcinoma cells in vitro.

Messenger RNAs and proteins of scavenger receptor thought to be macrophage specific protein were expressed in renal cell carcinoma (RCC) cells in vitro. Acetyl LDL was taken up into RCC cells and promoted the production of interleukin-6 (IL-6), an in vitro autocrine growth factor to proliferate the cells. These results suggested that RCC cells might have a scavenger pathway which has not yet been demonstrated except for macrophages.

Suicide process of renal cell carcinoma cells encountering mumps virus

Renal cell carcinoma cells produced the substance(s) which killed them (suicide factor(s)) after co‐culture with mumps virus. The suicide factor(s) were heat‐sensitive and were degraded with trypsin. Furthermore, actinomycin D inhibited the production of the substance(s) by cancer cells. Considering these facts, the substance(s) were thought to be protein(s) derived from de novo synthesis in cancer cells. It was demonstrated that renal cell carcinoma cells proliferated with the autocrine loop of interleukin‐6 (IL‐6). Mumps virus almost completely inhibited the IL‐6 production in several hours. Because of these two facts, the suicide process might be initiated in renal cell carcinoma cells after encountering mumps virus, i.e. inhibition or the autocrine growth loop of IL‐6 followed by the induction of an autocrine killing loop of unknown substance(s).

ACTIVATION OF HUMAN MONOCLONAL B CELLS WITH ANTI-Ig AND T CELL-DERIVED HELPER FACTOR(S) AND BIOCHEMICAL ANALYSIS OF THE TRANSMEMBRANE SIGNALING IN B CELLS

ABSTRACT Ig production was induced in human leukemic B cells or a transformed B cell line (CESS) by anti-Ig or T cell-derived helper factor(s). It was shown that three signals, i.e., crosslinkage of Ig receptors by anti-Ig, B cell growth factor (BCGF) and T cell replacing factor (TRF), were required for the activation of leukemic B cells into Ig-producing cells. Establishment of human T hybridomas secreting monoclonal immunoregulatory molecules showed that BCGF or TRF was different from the factor required for the proliferation of T cells (IL-2). Injection of the cytoplasm from TRF-stimulated CESS cells into non-stimulated cells induced IgG production, suggesting TRF-induced generation of the cytoplasmic sub-stnace responsible for the signal transmission. The binding of TRF with TRF acceptors induced methylation of membrane phospholipids followed by the activation of serine esterase. TRF-activated serine esterase was shown to be involved in the generation of the cytoplasmic factor(s) which were responsible for the signal transmission from membrane to nuclei.

T Cell Replacing Factor (TRF)-Induced IgG Production in a Human B Cell Line and the Mechanism of Transmembrane Signaling through TRF-Acceptors

Binding of a given antigen with surface immunoglobulins (sIg) initiates a complex series of activation processes of B lymphocytes into immunoglobulin (Ig)-producing cells under the influence of helper T cells. In spite of intensive investigations of the triggering and regulation of immunocompetent cells, the subcellular biochemical mechanisms operative in those phenomena remain poorly understood. One of the central problems in analyzing such events is an extensive diversity of the cell types in the immune system as well as a complexity of interactions between them. The diversity is reflected not only in the large repertoire of antigenic specificities expressed by lymphocytes, but also in the many subsets of lymphocytes with distinct functions. In such situations, tumors derived from cells of the immune system of established cell lines have been used as models of clones of immune cells which can be subjected to biochemical and molecular analysisl1–5. If those neoplastic cells or cell lines can be affected by external signals and activated into different states of differentiation, they especially prove useful for the molecular analysis of signaling and activation of lymphocytes.

Regulation of human B lymphocytes differentiation: Characterization of B cell stimulatory factors

B lymphocytes originate from pluripotent hematopoietic stem cells and differentiate into antibody producing cells through several distinct differentiation stages. Commitment of the antigen specificity in each B cell clone occurs at the stage of pre B cells by two step DNA rearrangements including V, D and J segments, i.e. from DJ joining to the functional VDJ formation (1). Following the rearrangement of heavy chain genes, light chain gene rearrangements occur (2) and 7S IgM molecules are expressed as antigen receptors on the surface of mature B cells. A given antigen selects a B cell clone with a matched receptor and activates this clone into antibody producing cells under the influence of helper T cells.