Antagonism between granulocytic maturation and deacetylase inhibitor-induced apoptosis in acute promyelocytic leukaemia cells.

BACKGROUND: Transcriptional repression is a key mechanism driving leukaemogenesis. In acute promyelocytic leukaemia (APL), the fusion protein promyelocytic leukaemia-retinoic acid receptor-α fusion (PML-RARα) recruits transcriptional repressors to myeloid differentiation genes. All-trans-retinoic acid (ATRA) induces the proteasomal degradation of PML-RARα and granulocytic differentiation. Histone deacetylases (HDACs) fall into four classes (I-IV) and contribute to the transcription block caused by PML-RARα. METHODS: Immunoblot, flow cytometry, and May-Grünwald-Giemsa staining were used to analyze differentiation and induction of apoptosis. RESULTS: A PML-RARα- and ATRA-dependent differentiation programme induces granulocytic maturation associated with an accumulation of the myeloid transcription factor CCAAT/enhancer binding protein (C/EBP)ɛ and of the surface protein CD11b. While this process protects APL cells from inhibitors of class I HDAC activity, inhibition of all Zinc-dependent HDACs (classes I, II, and IV) with the pan-HDACi (histone deacetylase inhibitor(s)) LBH589 induces apoptosis of immature and differentiated APL cells. LBH589 can eliminate C/EBPɛ and the mitochondrial apoptosis regulator B-cell lymphoma (BCL)-xL in immature and differentiated NB4 cells. Thus, BCL-xL and C/EBPɛ are newly identified molecular markers for the efficacy of HDACi against APL cells. CONCLUSIONS: Our results could explain the therapeutic limitations occurring with ATRA and class I HDACi combinations. Pro-apoptotic effects caused by pan-HDAC inhibition are not blunted by ATRA-induced differentiation and may provide a clinically interesting alternative.

In various tumour cell lines the peptide bradykinin B(2) receptor antagonist, Hoe 140 (Icatibant), may act as mitogenic agonist.

This study examined the mitogenic effects of bradykinin (BK, Arg-Pro-Pro-Gly-Phe-Ser-Pro-Phe-Arg), the peptide bradykinin B(2) receptor antagonist Hoe 140 (D-Arg(0)[Hyp(3)-Thi(6)-D-Tic(7)-Oic(8)]BK, and the orally active, nonpeptide B(2) receptor antagonist FR 173657 ((E)-3-(6-acetamido-3-pyridyl)-N-[N-2-4-dichloro-3-[(2-methyl-8-quino linyl) oxymethyl]phenyl]-N-methylaminocarbonyl-methyl]acrylamide) in three different human tumour cell lines: the small cell lung carcinoma (SCLC) cell line H-69, the breast carcinoma cell line EFM-192A, and the colon carcinoma cell line SW-480. In these cell lines activation of mitogen-activated protein kinase (MAPK) is involved in BK-induced stimulation of cell proliferation and may be mediated by both G(q) proteins (SW-480) and G(i) proteins (EFM-192A; H-69). In these cells BK as well as Hoe 140 increased the rate of DNA synthesis measured with the [(3)H]-thymidine uptake assay. Hoe 140 did neither antagonize nor potentiate the effect of BK. FR 173657 did not stimulate [(3)H]-thymidine incorporation but clearly antagonized the mitogenic effects of BK as well as Hoe 140. In H-69 cells, FR 173657 induced a decrease in the basal rate of DNA synthesis. In all three cell lines BK and Hoe 140 stimulated the activity of MAPK. Their effect on MAPK activity was completely abolished by FR 173657 which itself did not increase the activity of MAPK. In H-69 cells, the basal activity of MAPK was slightly inhibited by FR 173657. In the cell lines SW-480 and H-69 both BK and Hoe 140 but not FR 173657 stimulated phosphatidylinositol hydrolysis. In H-69 cells, FR 173657 decreased basal inositol phosphate formation. Our results show that in certain tumour cell lines the classical peptide B(2) receptor antagonist, Hoe 140, may act as mitogenic B(2) receptor agonist whereas the nonpeptide B(2) receptor antagonist, FR 173657, does not. In H-69 cells FR 173657 was found to exhibit properties of an inverse agonist.

In vivo effects of OK-432, inosine pranobex and its salt components on macrophage subpopulations in spleen and peritoneum of mice during the primary humoral immune response.

Subsets of macrophages (BM 8-, la- and esterase-positive subtypes) in the spleen and the peritoneum of mice were affected differently by immunomodulators during the humoral immune response. I.p. application of inosine pranobex (INPX), as well as of its salt moiety (DIPPACBA) and its dimethylaminopropanol (DIP) and acetamidobenzoic acid (PACBA) components, increased the number of nonspecific esterase-bearing cells in the peritoneum on day 3. INPX and DIPPACBA stimulated the la+ macrophage on day 3, DIPPACBA the BM 8+ macrophage only on day 1 and DIP on day 5. In spleen, DIP and PACBA had marked effects on the la+ subset in addition to a marginal effect on the BM 8+ phenotype on day 1. DIPPACBA also influenced the BM 8+ macrophage slightly on day 1. In contrast, the microbial product OK-432 stimulated BM 8+ and la+ macrophages in spleen markedly on day 1, but only marginally on days 3 and 5. However, it exerted a strong effect on both subtypes in peritoneum on days 3 and 5. OK-432 was found to be without any influence on esterase-bearing macrophages. The results show that the heterogeneity of macrophages is not only represented by subset markers, but also by their susceptibility to immunomodulators in different organs and stages of the immune response.