Proto-oncogene expression in bovine peripheral blood leukemic lymphocytes during their spontaneous proliferation, differentiation and apoptosis in vitro

The expression of various proto-oncogenes in primary culture of lymphocytes from peripheral blood of bovine with chronic lymphocytic leukemia (CLL) was studied. Cellular proto-oncogenes encode proteins that propagate growth, differentiation or apoptosis signals from cell membrane to nucleus. The proliferation and differentiation of normal eukaryotic cells are precisely controlled. Tumor cells usually are characterized both by the continuous growth signal and by the block of cell differentiation. We have previously reported that along with spontaneous proliferation, bovine CLL lymphocytes continuously differentiate and enter apoptosis in vitro. CLL cells with an autocrine growth mechanism and at the same time undergoing spontaneous differentiation and apoptosis in vitro provide a new model system to investigate the possible involvement of various proto-oncogenes in the regulation of cellular proliferation, differentiation and apoptosis. Northern blot analysis revealed simultaneous expression of a number of proto-oncogenes in CLL cells. Transcripts of c-fos, c-myc, c-myb, A-raf, c-raf1, hck, IL-2 receptor alpha-chain (IL-2R alpha) were found in lymphocytes at the peak of their proliferative activity in culture. Kinetics studies demonstrated that CLL cells constitutively express transcripts of so-called immediate response nuclear proto-oncogenes c-myc, c-fos as well as cytoplasmic proto-oncogenes hck and c-raf1, i.e., genes coding for tyrosine and serine-threonine protein kinases, respectively. Expression level did not change significantly during all stages of CLL cells in culture. The results show that continuous expression of c-myc mRNA does not prevent CLL cell differentiation and may be associated with apoptotic cell death.

Cell surface phenotypic changes induced in H9 T cells chronically infected with HTLV type I or HIV type 1 or coinfected with the two viruses

To investigate whether HTLV-I infection, HIV-I infection, or HIV-I infection of HTLV-I-infected cells affect the expression of cellular surface molecules, an HTLV-I-infected T cell line derived from the H9 T cell line was established (H36). H9 cells uninfected or infected with HTLV-I were then infected with HIV-1. We have compared the density of different surface markers on these three infected H9 T cell lines. These markers consist of T cell-specific antigens (CD2, CD3, CD4, and CD8), activated T cell antigens (CD25 and CD71), major histocompatibility complex (MHC) antigens (class I and II), and adhesion molecules (LFA-1 and ICAM-1). The experiments reported in this article show that chronic HTLV-I infection, HIV-1 infection, and HIV-1 infection of HTLV-I-infected T cells modulate the expression of several immunologically important cell surface antigens. The nature and the extent of T lymphoid cell phenotypic modulation depend on the infecting virus. Furthermore, HTLV-I and HIV-1 interact with each other in the phenotypic modulation of coinfected cells.