Persistent growth of BALB/C mouse plasmacytoma and human myeloma cell lines in the presence of phorbol myristate acetate is associated with continued expression of Lap18 (stathmin).
Lap18 is a highly conserved cytosolic protein that is expressed in dividing cells. Data from a number of studies show that a range of cell lines and mitogen-stimulated normal cells cultured in PMA phosphorylate and subsequently down-regulate Lap18. This has been found to be associated with growth arrest, although it is not clear that these events are causally related. In the present study we confirm that the HL60 promyelocytic leukemia and K562 erythroleukemia cell lines, when cultured with PMA, behave in this manner. This was not the case for any of five mouse plasmacytoma cell lines and six lines derived from patients with multiple myeloma or plasma cell leukemia. All of these lines contain Lap18, although the level of this protein in the mouse but not the human plasmacytoma cell-line cells is relatively low. All the neoplastic plasma cell-line cells phosphorylate Lap18 on culture with PMA, but this does not induce growth arrest nor result in down-regulation of Lap18 expression. Further experiments are required to test whether there is a mechanistic relationship between the continued growth of plasmacytoma cell lines and their failure to down-regulate Lap18 on culture in PMA.
Jones
N A
NA
Department of Immunology, University of Birmingham Medical School, Edgbaston, U.K.
Rowlands
D C
DC
Johnson
W E
WE
MacLennan
I C
IC
Brown
G
G
D000818:Animals; D002455:Cell Division / Q000187:drug effects; D015536:Down-Regulation / Q000187:drug effects; D006801:Humans; D015473:Leukemia, Promyelocytic, Acute / Q000378:metabolism / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D008868:Microtubule Proteins; D009101:Multiple Myeloma / Q000378:metabolism* / Q000473:pathology*; D010750:Phosphoproteins / Q000096:biosynthesis / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D010954:Plasmacytoma / Q000378:metabolism* / Q000473:pathology*; D050777:Stathmin; D013755:Tetradecanoylphorbol Acetate / Q000494:pharmacology*; D014407:Tumor Cells, Cultured / Q000187:drug effects
D008868:Microtubule Proteins; D010750:Phosphoproteins; C493995:STMN1 protein, human; D050777:Stathmin; C493994:Stmn1 protein, mouse; D013755:Tetradecanoylphorbol Acetate