Alterations of differentiation, clonal proliferation, cell cycle progression and bcl-2 expression in RAR alpha-altered sublines of HL-60.
All-trans retinoic acid (RA) induces granulocytic differentiation of acute promyelocytic leukemia cells both in vivo and in vitro. In the HL-60 wild-type (WT) early promyelocytic leukemia cell line, granulocytic differentiation appears to be directly mediated by the nuclear receptor RAR alpha. An HL-60 subline resistant to RA (HL-60 R) contains a point mutation which results in a truncation of 52 amino acids at the COOH end of RAR alpha. Cross-talk between differentiation, clonal inhibition of growth and apoptosis was studied using HL-60 WT, HL-60 R, and HL-60 R infected by a retroviral vector containing RAR alpha (LX) as targets, which were cultured with various retinoids, vitamin D3 analogs, HMBA, or DMSO. None of these compounds induced significant differentiation of HL-60 R and HL-60 LX, but they did induce differentiation of HL-60 WT. In contrast, retinoids inhibited the clonal proliferation of HL-60 WT, HL-60 R, and HL-60 LX. Vitamin D3 analogs including KH1060 stimulated the clonal growth of HL-60 R; but they inhibited clonal growth of HL-60 WT and LX. Levels of Bcl-2 strongly decreased in HL-60 WT and LX after treatment by retinoids, while no change in expression occurred in HL-60 R. Neither KH 1060 nor 9-cis RA induced apoptosis of HL-60 R, but these agents did induce apoptosis in HL-60 LX WT. Taken together, we showed that HL-60 R has a global defect in its ability to be induced to differentiate by a variety of pathways, not merely the retinoid pathway. Furthermore, our HL-60 models showed that inhibition of proliferation and induction of apoptosis and differentiation can be dissociated. Clinically, these results suggest that several putative differentiation agents may have anti-cancer (antiproliferative) activities, even though they do not induce differentiation of the cancer cells.
Grillier
I
I
Division of Hematology/Oncology, Cedars-Sinai Medical Center/UCLA School of Medicine, Los Angeles, CA 90048, USA.
Umiel
T
T
Elstner
E
E
Collins
S J
SJ
Koeffler
H P
HP
D000970:Antineoplastic Agents / Q000494:pharmacology*; D002453:Cell Cycle / Q000187:drug effects / Q000502:physiology; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002455:Cell Division / Q000187:drug effects / Q000502:physiology; D002999:Clone Cells; D019008:Drug Resistance, Neoplasm; D018922:HL-60 Cells / Q000378:metabolism* / Q000473:pathology*; D006801:Humans; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000096:biosynthesis*; D018168:Receptors, Retinoic Acid / Q000502:physiology*; D000072482:Retinoic Acid Receptor alpha; D012176:Retinoids / Q000494:pharmacology; D014212:Tretinoin / Q000494:pharmacology*
D000970:Antineoplastic Agents; D019253:Proto-Oncogene Proteins c-bcl-2; C000607071:RARA protein, human; D018168:Receptors, Retinoic Acid; D000072482:Retinoic Acid Receptor alpha; D012176:Retinoids; D014212:Tretinoin