Glutathione S-transferase enzyme expression in hematopoietic cell lines implies a differential protective role for T1 and A1 isoenzymes in erythroid and for M1 in lymphoid lineages

Background and Objectives. Glutathione S-transferases (GSTs) are phase II m etabolizing enzymes which catalyze the conjugation of glutathione (GSH) to electrophilic substrates and possess seleniumindependent glutathione peroxi dase activity. The GST enzyme family includes the cytosolic Isoforms GST-al pha (GSTA), mu (GSTM), pi (GSTP), theta (GSTT) and sigma (GSTS). GSTT1, P1 and M1 are polymorphic and altered polymorphic frequency of genes encoding these proteins has been suggested as a potential risk factor for the develo pment of hematopoietic malignancies. Overexpression of GSTs has also been i mplicated in chemotherapeutic drug resistance. This study was undertaken to elucidate the potential functional relevance of these genetic polymorphism s in hematopoiesis. Design and Methods. GST genotype of 14 hematopoletic ce ll lines was determined by poly-merase-chain-reaction (PCR), Gene expressio n of GSTs in cell lines was detected by real-time quantitative reverse tran scriptase-polymerase chain reaction (RT-PCR) on TaqMan 7700 and by semi-qua ntitative RT-PCR. Cytosolic GST protein expression was detected by Western blot. GST conjugation activity was assayed using 1-chloro-2,4-dinitrobenzen e (CDNB) as substrate. Results. GSTP1 expression was higher than other GSTs in 13/14 cell lines and paralleled CDNB conjugation activity. GSTP1 and GS TM1 predominated In lymphoid lines whilst T1 expression was relatively grea test in erythroid lines but was absent in 7/12 non-null lines, GSTT2 was ex pressed in only 3/14 lines. The 3 cell lines which expressed GSTA1 were all erythroid, interpretation and Conclusions. Glutathione S-transferases show ed differential lineage expression in hematopoietic cell lines. This implie s a greater cyto-protective role for GSTT1 and GSTA1 in erythroid cells aci d GSTM1 in lymphoid cells. We postulate that inherited gene deletion of GST T1 and M1 may produce increased genotoxic susceptibility for erythroid and lymphoid cells respectively, following exposure to xenobiotics that are sub strates for these enzymes. (C) 2000, Ferrata Storti Foundation.