Elevated levels of cyclin A1 and A (A2) mRNA in acute myeloid leukaemia are associated with increased survival

Cyclin A (A2) and cyclin A1 are members of the G2 cyclins, which are involved in the control of G2/M and G1/S transitions as well as mitosis. Human cyclin A1 was cloned as an A-type cyclin that is highly expressed in acute myeloid leukaemia (AML). The clinical significance of these cyclins in myeloid leukaemia remains to be clarified. We investigated the relative levels of these transcripts in 80 patients with de novo AML. Correlations with clinical parameters showed that the initial white blood cell count and serum lactate dehydrogenase levels were inversely associated with cyclin A (A2) mRNA levels (r = -0.276, P = 0.019) and cyclin A1 mRNA levels (r = -0.241, P = 0.042) respectively. They were independently associated with increased overall survival [P = 0.035 for cyclin A (A2) and P = 0.016 for cyclin A1]. Multivariate analysis using Cox's proportional hazard model showed that elevated cyclin A1 mRNA levels contributed significantly to the better prognosis of patients with AML. Furthermore, the analysis of survival probability showed that the group with high levels of both cyclin A (A2) and A1 survived significantly longer than the group with low expression of both these cyclins (P = 0.002). These data indicate that high expression levels of both cyclin A (A2) and A1 are associated with good prognosis in AML patients.

Down-Regulation of prostate-specific antigen expression by ligands for peroxisome proliferator-activated receptor gamma in human prostate cancer

The peroxisome proliferator-activated receptor gamma (PPARgamma) is a member of the nuclear receptor superfamily. Recent studies found that ligand-activated PPARgamma regulated differentiation and clonal growth of several types of cancer cells, including prostate cancer, suggesting that PPARgamma could be a tumor suppressor. Troglitazone was a widely used antidiabetic drug that activates PPARgamma. Recently, we reported that this agent had antiprostate cancer effects in vitro and in vivo. In this study, we administered troglitazone for over 1.5 years to an individual with occult recurrent prostate cancer. Using the prostate-specific antigen (PSA) levels as a surrogate marker of the disease, the oral administration of troglitazone (600-800 mg/day) reduced the increase velocity of PSA levels, suggesting clinical efficacy of troglitazone in prostate cancer. PSA promoter/ enhancer reporter assays showed that the PPARgamma ligands troglitazone (10(-5) M), pioglitazone (10(-5) M), or 15-deoxy-delta12,14-prostaglandin J2 (10(-5) M) down-regulated androgen-stimulated reporter gene activity in LNCaP cells, a prostate cancer cell line. The PSA promoter contains androgen receptor response elements (AREs). Reporter gene studies showed that troglitazone inhibited androgen activation of the AREs in the PSA regulatory region. Consistent with inhibition of gene expression, 2 days of incubation of LNCaP with troglitazone dramatically suppressed PSA protein expression without suppressing AR expression, suggesting that troglitazone inhibited ARE activation by a mechanism other than down-regulation of expression of the AR. Taken together, ligands of PPARgamma may be a useful therapeutic approach for the treatment of prostate cancer and may be acting, in part, by inhibiting transactivation of androgen-responsive genes.

Characterization of a novel analogue of 1alpha,25(OH)(2)-vitamin D(3) with two side chains: interaction with its nuclear receptor and cellular actions

The hormone 1alpha,25(OH)(2)-vitamin D(3) (125D) binds to its nuclear receptor (VDR) to stimulate gene transcription activity. Inversion of configuration at C-20 of the side chain to generate 20-epi-1alpha,25(OH)(2)D(3) (20E-125D) increases transcription 200-5000-fold over 125D with its 20-normal (20N) side chain. This enhancement has been attributed to the VDR ligand-binding domain (LBD) having different contact sites for 20N and 20E side chains that generate different VDR conformations. We synthesized 1alpha, 25-dihydroxy-21-(3-hydroxy-3-methylbutyl)vitamin D(3) (Gemini) with two six-carbon side chains (both 20N and 20E orientations). Energy minimization calculations indicate the Gemini side chain possesses significantly more energy minima than either 125D or 20E-125D (2346, 207, and 127 minima, respectively). We compared activities of 125D, 20E-125D, and Gemini, respectively, in several assays: binding to wild-type (100%, 147%, and 38%) and C-terminal-truncated mutant VDR; transcriptional activity (of the transfected osteopontin promoter in ROS 17/2.8 cells: ED(50) 10, 0.005, and 1.0 nM); mediation of conformational changes in VDR assessed by protease clipping (major trypsin-resistant fragment of 34, 34, and 28 kDa). For inhibition of cellular clonal growth of human leukemia (HL-60) and breast cancer (MCF7) cell lines, the ED(50)(125D)/ED(50)(Gem) was respectively 380 and 316. We conclude that while Gemini readily binds to the VDR and generates unique conformational changes, none of them is able to permit a superior gene transcription activity despite the presence of a 20E side chain.