Abstract
Recently immunoglobulins (Igs) have been found to be expressed by cells other than B lymphocytes, including various human carcinoma cells. Sarcomas are derived from mesenchyme, and the knowledge about the occurrence of Ig production in sarcoma cells is very limited. Here we investigated the phenomenon of immunoglobulin G (IgG) expression and its molecular basis in 3 sarcoma cell lines. The mRNA transcripts of IgG heavy chain and kappa light chain were detected by RT-PCR. In addition, the expression of IgG proteins was confirmed by Western blot and immunofluorescence. Immuno-electron microscopy localized IgG to the cell membrane and rough endoplasmic reticulum. The essential enzymes required for gene rearrangement and class switch recombination, and IgG germ-line transcripts were also identified in these sarcoma cells. Chromatin immunoprecipitation results demonstrated histone H3 acetylation of both the recombination activating gene and Ig heavy chain regulatory elements. Collectively, these results confirmed IgG expression in sarcoma cells, the mechanism of which is very similar to that regulating IgG expression in B lymphocytes.
Highlights
Until recently it was believed that immunoglobulins (Igs) were the characteristic products of only B lymphocytes and plasma cells
Both immunoglobulin G (IgG) heavy chain and kappa light chain were expressed in sarcoma cell lines To exclude contamination with B lymphocytes in the sarcoma cell lines, RT-PCR with CD19 primers was performed
In this study we investigated IgG locus events in the mesenchyme derived sarcoma cell lines A673, U-2 OS and HT1080
Summary
Until recently it was believed that immunoglobulins (Igs) were the characteristic products of only B lymphocytes and plasma cells. In the past couple of years several research groups have reported that Igs can be produced by non-lymphoid lineage cells [1], including human epithelial cancer cells [2,3], human umbilical endothelial cells [4], human and mouse neurons [5,6], testicular spermatogenic cells and epididymal epithelial cells [7], and lactating mammary gland epithelial cells [8]. Our group has found that IgG protein was present in a wide variety of sarcoma tissues with IgG protein expression correlating well with proliferation markers and tumor grades [9]. Whether IgG was produced by these sarcoma tumor cells and the molecular basis for IgG expression in soft tissue sarcomas have not been investigated
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