Effects of norcantharidin, a protein phosphatase type-2A inhibitor, on the growth of normal and malignant haemopoietic cells.
Cantharidin is a natural toxin that inhibits protein phosphatase type 2A (PP2A) and has antitumour effects in man. We have studied the synthetic analogue, norcantharidin (NCTD), which has less nephrotoxic and phlogogenic side-effects, investigating the effects on the normal haemopoietic system and leukaemia cell growth. Daily intraperitoneal (i.p.) injection of NCTD induced dose and circadian time-dependent transient leucocytosis in normal mice, but did not accelerate bone marrow (BM) regeneration, or have haemopoietic offe-effects following chronic administration. NCTD stimulated the cell cycle progression of granulocyte-macrophage colony-forming cells (GM-CFC), stimulated DNA synthesis and increased the frequency of mitotic cells in short-term human BM cultures. NCTD also stimulated the production of interleukin (IL)-1 beta, colony stimulating activity (CSA) and tumour necrosis factor (TNF)-alpha. Continuous in vitro NCTD treatment, however, inhibited both DNA synthesis and GM-CFC growth. Fluorescence-activated cell sorting (FACS) analysis of DNA profiles and cytological studies in HL-60, K-562 or MRC5V2 (fibroblast) cells indicated that low doses of NCTD accelerated the G1/S phase transition, while higher doses or prolonged incubations inhibited the cell cycle at the G2/M phases or during the formation of postmitotic daughter cells. Electron microscopy revealed that NCTD impaired the neogenesis of chromatin material and nuclear membrane during the M/G1 phase transition in K-562 cells. The biphasic effect of NCTD may be due to inhibition of PP2A activity, which regulates the cell cycle, both at the restriction point and at the G2 and M phases. Our data provide new insight into the cellular and molecular actions of NCTD, and partly explain its therapeutical effects in cancer patients.
Liu
X H
XH
Institut du Cancer et d'Immunogénétique, Hôpital Paul Brousse, Villejuif, France.
Blazsek
I
I
Comisso
M
M
Legras
S
S
Marion
S
S
Quittet
P
P
Anjo
A
A
Wang
G S
GS
Misset
J L
JL
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D001853:Bone Marrow / Q000187:drug effects / Q000473:pathology*; D001643:Bridged Bicyclo Compounds / Q000494:pharmacology*; D019086:Bridged Bicyclo Compounds, Heterocyclic; D002455:Cell Division / Q000187:drug effects; D004354:Drug Screening Assays, Antitumor; D006412:Hematopoietic Stem Cells / Q000187:drug effects; D006801:Humans; D007938:Leukemia / Q000473:pathology; D007958:Leukocyte Count; D007962:Leukocytes / Q000187:drug effects / Q000648:ultrastructure; D007964:Leukocytosis / Q000139:chemically induced; D008297:Male; D051379:Mice; D008808:Mice, Inbred CBA; D008811:Mice, Inbred DBA; D014407:Tumor Cells, Cultured
D000970:Antineoplastic Agents; D001643:Bridged Bicyclo Compounds; D019086:Bridged Bicyclo Compounds, Heterocyclic; C069741:norcantharidin