Prohibitin expression is increased in phorbol ester-treated chronic leukemic B-lymphocytes

Chronic lymphocytic leukemia (CLL) is characterized by the gradual accumula tion of immature B-lymphocytes CLL B-lymphocytes mature to a plasmacytoid p henotype when treated in vitro with phorbol esters. CLL B-cell apparent mat uration is associated with altered expression of specific plasma membrane a nd mitochondrial proteins including heightened expression of a 30-kDa heat shock protein 60 (hsp60) analog. During our efforts to further characterize this hsp60 analog by mass spectrometry, Eve detected the mitochondrial pro tein prohibitin in phorbol-ester-matured CLL B-lymphocytes Prohibitin modul ates cell proliferation and inhibits cell cycle traverse in several systems , although few data are available far lymphocytes A twofold increase in pro hibitin concentration was observed in phorbol-ester-mature d compared to re sting CLL B-cells as determined by quantitative Western immunoblot analysis . A similar increase in prohibitin was observed in phorbol-ester-treated no rmal human B-lymphocyte populations. An antisense oligonucleotide complemen tary to the 5' coding region of the prohibitin gene blunted the increase in prohibitin protein in phorbol-ester-treated CLL, B-cells by 42%. These dat a suggest that increased prohibitin expression is associated with and may f acilitate B-cell maturation. (C) 2001 Academic Press.