The cellular retinoic acid binding protein II is a positive regulator of retinoic acid signaling in breast cancer cells

The role of the cellular retinoic acid binding protein type II (CRABPII) in the retinoic acid (RA) signaling pathway is poorly understood. Northern blot analysis of 12 breast cell lines showed that CRABPII mRNA content correlated with growth inhibition by RA, suggesting that this binding protein enhances cellular response to RA. Ectopic CRABPII expression supported dose-dependent growth inhibition by RA in SC115-resistant but not MDA-MB-231-resistant cells, indicating that CRABPII is sufficient to rescue RA antiproliferation in a permissive background. In both cell lines, ectopic binding protein enhanced gene activation by RA. Thus, induction of tissue transglutaminase by all-trans-RA and, surprisingly, 9-cis-RA was enhanced 5-fold over and above the level of induction in control cells (SC115), and activation of a RA response element reporter was enhanced 3-fold (MDA-MB-231). A 5-fold enhancement of RA induction of RA receptor beta expression as a result of ectopic binding protein expression was also demonstrated (SC115). These findings indicate that CRABPII is a positive regulator of RA signaling in breast cells.

Use of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia (APL): I. As2O3 exerts dose-dependent dual effects on APL cells

Recent clinical studies in China showed that As2O3 is an effective and relatively safe drug in the treatment of acute promyelocytic leukemia (APL). We found previously that As2O3 can trigger apoptosis of APL cell line NB4 cells, which is associated with downregulation of bcl-2 gene expression and modulation of PML-RAR alpha chimeric protein. To further understand the mechanisms of this alternative therapy for APL, we investigated in this report the effects of a wide range of concentrations of As2O2 on cultured primary APL cells, all-trans retinoic acid (ATRA)-susceptible (NB4 cells) and ATRA-resistant (MR2 subclone) APL cell lines. The results indicated that As2O3 had dose-dependent dual effects on APL cells: inducing preferentially apoptosis at relatively high concentrations (0.5 to 2 micromol/L) and inducing partial differentiation at low concentrations (0.1 to 0.5 micromol/L). The rapid modulation and degradation of PML-RAR alpha proteins, which was induced by As2O3 at 0.1 to 2 micromol/L, could contribute to these two effects. Bone marrow and peripheral blood examination showed that myelocyte-like cells, probably as a result of partial in vivo differentiation, and degenerative cells increased after 2 to 3 weeks of continuous in vivo As2O3 treatment when leukemic promyelocytes decreased. In conclusion, combination of induction of apoptosis and partial differention could be the main cellular mechanisms of As2O3 in the treatment of APL, and PML-RAR alpha could play an important role in determining the specific effects of As2O3 on APL cells.

Angioscopic assessment of coronary lesions underlying thrombus

This study examines the characteristics of coronary lesions in which thrombus is found as assessed by angioscopy before percutaneous transluminal coronary angioplasty in patients with various coronary syndromes. Our findings demonstrate that the plaque underlying intracoronary thrombus is usually yellow and/or disrupted, and support in vitro observations that lipid-rich plaques are highly thrombogenic and that disruption of these plaques is associated with in situ thrombosis.

Management of asymptomatic rising PSA after prostatectomy or radiation therapy

Controversy exists over the optimal management of patients with an asymptomatic rising prostate-specific antigen (PSA) following definitive therapy for clinically localized prostate adenocarcinoma. Post-prostatectomy patients whose residual disease is felt to be confined to the area immediately adjacent to the prostatic bed may benefit from external-beam radiation therapy. Systemic recurrence may be managed with either watchful waiting or treated with hormone deprivation. Post-radiation therapy patients felt to have local disease progression may undergo salvage radical prostatectomy (if disease is clinically confined to the prostate gland) or cryotherapy (although this is still considered "experimental"). Patients who are not candidates for salvage therapy can be managed with watchful waiting or hormone deprivation. For patients in whom definitive therapy has failed, treatment should be individualized according to pathologic stage (if post-prostatectomy), rate of PSA progression, surgical candidacy status (if post-radiation therapy), and attitudes and expectations of the physician and patient.

Body Shape Questionnaire: studies of validity and reliability

OBJECTIVE

The Body Shape Questionnaire (BSQ) is a useful measure of weight and shape concern. The purpose of this study is to contribute new psychometric information on the BSQ in order to assist clinicians and researchers who intend to use this measure.

METHOD

This paper reports average scores on American samples of clinical subjects referred for body image problems, obese persons seeking weight reduction, and nonclinical samples of college students and adults.

RESULTS AND DISCUSSION

The BSQ demonstrated good test-retest reliability, concurrent validity with other measures of body image, and criterion validity for clinical status.

Human breast carcinoma slice cultures retain retinoic acid sensitivity

We have shown earlier that surgical human breast cancer tissue can be maintained in culture as in culture as intact tissue slices (organ culture). Because tumor organ culture ostensibly preserves the interacting network of tumor cells, stromal fibroblasts, endothelial cells and extracellular matrix, it represents a rather complex culture system. Such a system may be especially useful in preclinical trials, where the objective is to make extrapolations to the even more complex in vivo situation. A classical therapeutic target in breast cancer is the estrogen receptor, and we showed earlier that human breast cancer slices retain expression of this receptor in culture. Retinoic acid, the active form of vitamin A, is also an important (negative) growth regulator in breast cancer. In the present communication, we used in situ hybridization to monitor the expression of retinoic acid receptors in tumor slices cultured for 4 days. We show that both members of the all-trans retinoic acid and 9-cis retinoic acid receptor family (RAR and RXR, respectively) are expressed. Moreover, RNase protection analysis showed that expression of the cellular retinoic acid-binding protein type II gene, a known retinoic acid target gene, is upregulated by treatment with 1 microM all-trans retinoic acid for 2 days. These findings attest to the feasibility of using tumor organ cultures as a preclinical model for the evaluation of synthetic vitamin A derivatives (retinoids).

Defective expression of cellular retinol binding protein type I and retinoic acid receptors alpha2, beta2, and gamma2 in human breast cancer cells

Because the retinoic acid (RA) signaling pathway regulates cell proliferation and differentiation, inactivation of genes integral to the pathway represents a potential mechanism of carcinogenesis. We have studied in human breast cancer cells (T47D, MCF-7, ZR75-1, MDA-MB-231, and BT20) the expression of a subset of retinoid signaling genes that are themselves transcriptionally up-regulated by RA, the cellular retinol binding protein type I (CRBPI) and the RA receptors (RARs) alpha2, beta2, and gamma2. We find that constitutive expression of these genes is low or undetectable, and that expression levels are seldom responsive to 24 h treatment with 1 microM all-trans or 9-cis RA (Northern blot analysis). This is in contrast to breast fibroblasts, which show RA-dependent expression of all four genes under the same conditions. Moreover, normal human breast epithelial cells express CRBPI and RARbeta2 at the mRNA level, suggesting that loss of expression of these genes is tied to malignant transformation. RARbeta2, but not CRBPI, was also expressed in RA-treated MTSV1-7 cells, an immortalized but nontumorigenic luminal epithelial cell line. Lack of CRBPI and RARbeta2 expression in cancer cells was not due to general impairment of RA signaling, as shown by RA activation of a RARE3-tk-CAT reporter in a subclone of MDA-MB-231 cells that did not express either CRBPI or RARbeta2. These results suggest that at least two independent defects in the expression of proteins that function in retinoid signaling may be involved in breast carcinogenesis.

Angioscopic predictors of early adverse outcome after coronary angioplasty in patients with unstable angina and non-Q-wave myocardial infarction

BACKGROUND

Clinical and angiographic criteria have a limited ability to predict adverse outcome in patients with unstable angina who are undergoing percutaneous transluminal coronary angioplasty (PTCA). We investigated whether the use of angioscopy can improve prediction of early adverse outcome after PTCA.

METHODS AND RESULTS

Angioscopic characterization of the culprit lesion was performed before PTCA in 32 patients with unstable angina and 10 with non-Q-wave infarction. Seven patients (17%) had an adverse outcome (myocardial infarction, repeat PTCA, or need for coronary artery bypass graft surgery) within 24 hours after PTCA. Six of 18 patients with a yellow culprit lesion had an adverse outcome compared with 1 of 24 in whom the culprit lesion was white (P = .03). Six of 20 patients with plaque disruption suffered an adverse outcome compared with 1 of 22 with nondisrupted plaques (P = .04). Six of 17 patients with intraluminal thrombus had an adverse outcome, whereas only 1 of 25 patients without thrombus suffered an adverse outcome (P = .01). Yellow color, disruption, and thrombus at the culprit lesion site were associated with an eightfold increase in risk of adverse outcome after PTCA. The prediction of PTCA outcome based on characteristics of the plaque that were identifiable by angioscopy was superior to that estimated by the use of angiographic variables.

CONCLUSIONS

In patients with unstable angina and non-Q-wave infarction, angioscopic features of disruption, yellow color, or thrombus at the culprit lesion site can identify patients at high risk of early adverse outcome after PTCA. Angioscopy was superior to angiography for prediction of PTCA outcome.

RIG-E, a human homolog of the murine Ly-6 family, is induced by retinoic acid during the differentiation of acute promyelocytic leukemia cell

In vivo all-trans-retinoic acid (ATRA), a differentiation inducer, is capable of causing clinical remission in about 90% of patients with acute promyelocytic leukemia (APL). The molecular basis for the differentiation of APL cells after treatment with ATRA remains obscure and may involve genes other than the known retinoid nuclear transcription factors. We report here the ATRA-induced gene expression in a cell line (NB4) derived from a patient with APL. By differential display-PCR, we isolated and characterized a novel gene (RIG-E) whose expression is up-regulated by ATRA. The gene is 4.0 kb long, consisting of four exons and three introns, and is localized on human chromosome region 8q24. The deduced amino acid sequence predicts a cell surface protein containing 20 amino acids at the N-terminal end corresponding to a signal peptide and an extracellular sequence containing 111 amino acids. The RIG-E coded protein shares some homology with CD59 and with a number of growth factor receptors. It shares high sequence homology with the murine LY-6 multigene family, whose members are small cysteine-rich proteins differentially expressed in several hematopoietic cell lines and appear to function in signal transduction. It seems that so far RIG-E is the closest human homolog of the LY-6 family. Expression of RIG-E is not restricted to myeloid differentiation, because it is also present in thymocytes and in a number of other tissues at different levels.

Upregulation of cytokeratins 8 and 18 in human breast cancer T47D cells is retinoid-specific and retinoic acid receptor-dependent

The mamary gland is chiefly composed of luminal epithelial cells expressing cytokeratins (K) 8, 18 and 19, and basal/myoepithelial cells expressing cytokeratins 5 and 14. Human breast cancer T47D cells have a luminal phenotype and are growth-inhibited by retinoids, a class of compounds known to regulate cytokeratin expression. To extend our knowledge of retinoid action in breast cancer, we have studied the retinoid regulation of cytokeratin expression in the T47D model. We found that retinoid inhibition of T47D cell growth was accompanied by increases in K8, K18 and K19 mRNA steady-state levels (Northern blot analysis). The effect on K8 was studied in greater detail. This effect was seen with as low as 1 nM all-trans retinoic acid (tRA) and was maximal (up to 7 fold over control) with 1 microM tRA (the highest dose tested). Time-course studies revealed a detectable effect at 1 h and a maximal effect at 8-24 h. Non-retinoidal growth inhibitors (tamoxifen, BrcAMP and genistein) did not modulate K8 expression, demonstrating that the effect of tRA was specific, K8 mRNA upregulation was blocked by actinomycin D and cycloheximide, suggesting, in accordance with other studies, that tRA exerted a transcriptional effect that was secondary to de novo protein synthesis. Five retinoids known to activate retinoic acid receptor (RAR) and/or retinoid X receptor (RXR) - tRA; 9-cis-retinoic acid, 9cRA; 13-cis RA, 13cRA; retinyl acetate; and N-(4-hydroxyphenyl) retinamide 4HPR - inhibited T47D cell growth and increased K8 expression, whereas an arotinoid (Ro-40-8757) that is not a RAR activator caused growth inhibition but did not upregulate K8. Activation of RAR alpha contributed to K8 upregulation, since this effect was partially blocked by the RAR alpha-selective antagonist Ro-41-5253. Analogous results were obtained throughout when blots were reprobed with K18 cDNA. Western blot and immunocytochemistry experiments demonstrated that protein levels of K8 and K18 increased by 2 days of treatment with 1 microM tRA. These results show that retinoids enhance the expression of cognate cytokeratin markers of luminal differentiation in T47D breast cancer cells.

Amino-terminal protein-protein interaction motif (POZ-domain) is responsible for activities of the promyelocytic leukemia zinc finger-retinoic acid receptor-alpha fusion protein

Promyelocytic leukemia zinc finger-retinoic acid receptor a (PLZF-RARalpha), a fusion receptor generated as a result of a variant t(11;17) chromosomal translocation that occurs in a small subset of acute promyelocytic leukemia (APL) patients, has been shown to display a dominant-negative effect against the wild-type RARalpha/retinoid X receptor alpha (RXRalpha). We now show that its N-terminal region (called the POZ-domain), which mediates protein-protein interaction as well as specific nuclear localization of the wild-type PLZF and chimeric PLZF-RARalpha proteins, is primarily responsible for this activity. To further investigate the mechanisms of PLZF-RARalpha action, we have also studied its ligand-receptor, protein-protein, and protein-DNA interaction properties and compared them with those of the promyelocytic leukemia gene (PML)-RARalpha, which is expressed in the majority of APLs as a result of t(15;17) translocation. PLZF-RARalpha and PML-RARalpha have essentially the same ligand-binding affinities and can bind in vitro to retinoic acid response elements (RAREs) as homodimers or heterodimers with RXRalpha. PLZF-RARalpha homodimerization and heterodimerization with RXRalpha were primarily mediated by the POZ-domain and RARalpha sequence, respectively. Despite having identical RARalpha sequences, PLZF-RARalpha and PML-RARalpha homodimers recognized with different affinities distinct RAREs. Furthermore, PLZF-RARalpha could heterodimerize in vitro with the wild-type PLZF, suggesting that it may play a role in leukemogenesis by antagonizing actions of not only the retinoid receptors but also the wild-type PLZF and possibly other POZ-domain-containing regulators. These different protein-protein interactions and the target gene specificities of PLZF-RARalpha and PML-RARalpha may underlie, at least in part, the apparent resistance of APL with t(11;17) to differentiation effects of all-trans-retinoic acid.

Establishment of a human acute promyelocytic leukemia-ascites model in SCID mice

Acute promyelocytic leukemia (APL) is an interesting model for cancer research because of the presence of the specific PML-RARalpha fusion gene associated with the clinical response to retinoic acid differentiation therapy. To better understand and improve differentiation induction with retinoic acid, we have established a human APL-ascites model in SCID mice using the NB4 human APL cell line. NB4 (1 x 10(6) cells) were transplanted into the peritoneum (IP) of SCID mice for 1 month. NB4 ascites cells (A-NB4) appeared, which were then engrafted in SCID mice periodically for 18 passages at an interval of 3 to 4 weeks with a 100% success rate of tumor induction. The mean survival times of SCID mice transplanted with 1 x 10(6) A-NB4 cells was 21.6 +/- 2.3 days. Analysis of the biologic characteristics of ninth passage NB4 ascitic cells was performed and they were found to have the morphologic, immunologic, cytogenetic, and molecular features of cultured NB4 cells. Furthermore, A-NB4 cells were capable of differentiating when treated with all-trans retinoic acid (ATRA), as manifested by enhanced NBT reduction and CD11b expression. In vivo treatment with ATRA in SCID mice for 4 days also increased NBT reduction by A-NB4 cells. ATRA treatment significantly prolonged survival time in the group after transplantation (28.1 +/- 6.8 to 29.1 +/- 8.4 days) compared with the control (P < .001). Furthermore, treatment with adriamycin, an effective chemotherapeutic drug in APL, had a strong growth suppressive effect on A-NB4 cells. These results demonstrate that this SCID-APL (NB4 ascites cells) model is a useful preclinical system for evaluating new or known drugs in the treatment of APL.

Reduced and altered DNA-binding and transcriptional properties of the PLZF-retinoic acid receptor-alpha chimera generated in t(11;17)-associated acute promyelocytic leukemia

Acute promyelocytic leukemia (APL) associated with chromosomal rearrangement t(11;17) is a distinct syndrome which, unlike typical t(15;17) APL, fails to respond to all-trans retinoic acid (ATRA) therapy. In t(11;17) the PLZF gene, encoding a Krüppel-like zinc finger protein, is fused to the retinoic acid receptor-alpha (RAR alpha) gene, yielding two classes of chimeric proteins. PLZF protein was found in the nucleus in a punctate speckled pattern that differed from the nuclear body expression pattern of the PML protein affected in t(15;17) APL. The reciprocal PLZF-RAR alpha and RAR alpha-PLZF fusion proteins were localized to the nucleus both in the presence and absence of ATRA. PLZF-RAR alpha, in combination with the retinoid X receptor (RXR) bound to a retinoic acid-responsive element (RARE) less efficiently than RAR alpha and formed multimeric DNA-protein complexes. PLZF-RAR alpha stimulated ATRA-dependent transcription of RARE-containing reporter genes with diminished activity compared to wild-type RAR alpha. In addition, PLZF-RAR alpha antagonized the function of coexpressed wild-type RAR alpha, an effect relieved by over-expression of RXR. Leukemogenesis in t(11;17) APL may be related to interference with ATRA-mediated differentiation due to sequestration of RXR by the PLZF-RAR alpha chimera. However, disruption of the function of the myeloid-specific PLZF protein may also play an important role.

Leukemia translocation gene, PLZF, is expressed with a speckled nuclear pattern in early hematopoietic progenitors

The PLZF gene was discovered by studying a rearrangement of the RAR alpha locus in a patient with acute promyelocytic leukemia and a t(11;17) chromosomal translocation. To understand further the potential role(s) of the PLZF gene product in hematopoiesis, we have examined its expression levels in a variety of murine tissues and in established cell lines that are representative of various stages of myeloid and lymphoid development. We show that murine PLZF(mPLZF) is expressed at the highest levels in undifferentiated, multipotential hematopoietic progenitor cells and that its expression declines as cells become more mature and committed to various hematopoietic lineages. Data obtained with established cell lines are corroborated by results showing the lack of human PLZF protein expression in mature peripheral blood mononuclear cells and high PLZF levels in the nuclei of CD34+ human bone marrow progenitor cells. Interestingly, unlike many transcription factors, PLZF protein in these cells possesses distinct punctate nuclear distribution, suggesting its compartmentalization in the nucleus. Taken together, our data suggest a role for PLZF protein in early hematopoiesis and the requirement of downregulation of its expression for proper differentiation of most hematopoietic lineages.

Cell cycle gene expression and E2F transcription factor complexes in human melanoma cells induced to terminally differentiate

Defects in cellular differentiation are a common occurrence in human cancers. The combination of recombinant human fibroblast interferon (IFN-beta) and the antileukemic compound mezerein (MEZ) results in an irreversible loss of proliferative capacity and terminal cell differentiation in H0-1 human melanoma cells. In contrast, either agent alone induces reversible growth arrest and/or specific components of the differentiation process without inducing terminal differentiation. The current study investigates changes in cell cycle, cell cycle gene expression and E2F transcription factor complex formation during the processes of reversible and irreversible (terminal) differentiation. Induction of both terminal differentiation and reversible differentiation (MEZ treatment) results in a temporal decrease in DNA synthesis and the percentage of cells in S phase and a decrease in the expression of cell cycle and growth regulated genes, including cdc2, cyclin A, cyclin B, histone H1, histone H4, nm23-H1, p53 and c-myc. Persistent gene expression changes occur in terminally differentiated cells, but not in reversibly differentiated cells. H0-1 cells contain several E2F binding activities, including uncomplexed E2F, an E2F-p107-cyclin A-cdk2 kinase complex and an Rb-E2F complex. Induction of growth arrest by MEZ results in a slow migrating gelshift band that contains E2F associated with the pRb2/p130 protein. There is also a loss of the Rb-E2F complex. Induction of terminal differentiation after treatment with IFN-beta + MEZ generates a second pRb2/p130-E2F complex that migrates considerably faster than the pRb2/p130-E2F complex resulting from growth arrest. The slower migrating complex may contribute to growth arrest, whereas the faster migrating complex may play a role in terminal differentiation. Our results demonstrate that terminal cell differentiation involves a co-ordinate and continuous suppression of a number of cell cycle and growth related genes and results in the development of a novel E2F transcription factor complex not apparent in growth arrested and reversibly differentiated human melanoma cells.

Structural requirements for differentiation-induction and growth-inhibition of mouse erythroleukemia cells by isoflavones

Isoflavones are natural plant phytoestrogens which have been shown to have anticancer proliferation, differentiation and chemopreventive effects. In order to determine structure-function requirements, we compared the effects of several isoflavone derivatives and one flavone on mouse erythroleukemia (MEL) cell growth and differentiation. All chemicals tested are closely related in structure to genistein (4',5,7-trihydroxyisoflavone), a known differentiation inducer and tyrosine protein kinase inhibitor. Genistein, daidzein (4',7-dihydroxyisoflavone) and genistin (7-glucoside of genistein) induced differentiation of MEL cells based on benzidine staining. Biochanin A (5,7-dihydroxy-4'-metho-xyisoflavone) and apigenin (4',5,7-trihydroxyflavone) had no differentiation inducing effect. The potency of these chemicals on cell growth inhibition was apigenin > genistein > genistin > biochanin A > daidzein. These results suggest that the isoflavone structure and 4'-hydroxyl group are essential for the differentiation induction effect, whereas trihydroxyl derivatives are good growth inhibitors. Daidzein is a potent differentiation inducer with the least cytotoxic effect.

Expression of the zinc-finger gene PLZF at rhombomere boundaries in the vertebrate hindbrain

To investigate the potential biological role(s) of the PLZF gene, discovered as a fusion with the RARA locus in a patient with acute promyelocytic leukemia harboring a t(11;17) chromosomal translocation, we have isolated its murine homologue (mPLZF) and studied its patterns of developmental expression. The levels of mPLZF mRNAs increased perinatally in the liver, heart, and kidney, but with the exception of the heart, they were either absent or very low in the adult tissues. In situ analysis of mPLZF expression in mouse embryos between 7.0 and 10.5 days of development revealed that mPLZF mRNAs and proteins were coexpressed in spatially restricted and temporally dynamic patterns in the central nervous system. In the hindbrain region, a segmental pattern of expression correlated with the development of the rhombomeres. From 9.0 days of development, starting first in rhombomeres 3 and 5, there was an ordered down-regulation of expression in the center of each rhombomere, so that 1 day later elevated levels of mPLZF mRNAs and proteins were restricted to cells surrounding the rhombomeric boundaries. The chicken homologue of the PLZF gene, which we have also cloned, demonstrated a similar segmental pattern of expression in the hindbrain. To date, PLZF represents the only example of a transcription factor with elevated expression at rhombomeric boundaries. The high degree of evolutionary conservation between the patterns of PLZF expression during mammalian and avian central nervous system development suggests that it has an important functional role in the regionalization of the vertebrate hindbrain, potentially regulating boundary cell interactions.

Tuberculosis in the HIV-infected patient

After decades of decline, tuberculosis has emerged as a global health challenge. In the setting of HIV immunocompromise, TB occurs frequently, early, and often atypically. New infections can take an accelerated course. The usual tests for diagnosing Mycobacterium tuberculosis infection are less sensitive when CD4+ counts are low. Increased prevalence of treatment failure, drug-resistant strains, and nosocomial transmission of multidrug-resistant TB are discussed as are new diagnostic tests that will accelerate the time to diagnosis and allow better epidemiologic tracking. Early recognition, isolation, appropriate therapy, and environmental controls that will protect staff and patients from the risk of exposure are also described.

Effect of retinoic acid isomers on proliferation, differentiation and PML relocalization in the APL cell line NB4

Retinoic acids exert a wide physiological role in development and differentiation. Retinoic acids have also been used in the treatment of human cancers, particularly in acute promyelocytic leukemia (APL). A structure-function relationship of the RA isomers in terms of clinical effect has been observed since all-trans retinoic acid (ATRA) induces a high complete remission rate while 13-cis retinoic acid (13-cis RA) shows much poorer effect. In this study, we examined the effect of RA isomers, including ATRA, 13-cis RA and 9-cis RA, on the proliferation and differentiation of NB4 cells. A number of parameters such as cell growth curve, dynamics of cell cycle, expression of clusters of differentiation and reduction of nitro blue tetrazolium (NBT) as well as immunofluorescence staining of PML were used to evaluate the effects of three isomers at two concentrations (10(-8) M and 10(-7) M). It has been shown that during the first 48 h of RA treatment, the APL cell differentiation was coupled with the cell proliferation. Although similar effects of proliferation inhibition and differentiation induction were observed among the three isomers at 10(-7) M, significant differences appeared at a concentration of 10(-8) M, 9-cis RA showed a higher activity than that of ATRA, while ATRA showed better results than 13-cis RA. Our results provide further evidence that 9-cis RA could be a promising molecule in differentiation induction of malignant cells.

Retinoic acid is required for and potentiates differentiation of acute promyelocytic leukemia cells by nonretinoid agents

Patients with acute promyelocytic leukemia (APL) associated with the t(15;17) translocation and fusion of the promyelocytic leukemia (PML) and retinoic acid receptor-alpha (RAR-alpha) genes achieve complete remission but not cure with all-trans retinoic acid (RA), NB4, a cell line derived from a patient with t(15;17) APL that undergoes granulocytic differentiation when treated with pharmacologic doses of RA, was used as a model for differentiation therapy of APL. We found that NB4 cells are resistant to differentiation by nonretinoid inducers such as hexamethylene bisacetamide (HMBA), butyrates, vitamin D3, or hypoxanthine, all of which can induce differentiation in the commonly used HL60 leukemia cell line. Preexposure of NB4 cells to low concentrations of RA for a period as short as 30 minutes abolished resistance to nonretinoids and potentiated differentiation. Sequential RA and HMBA treatment yielded maximal differentiation by 3 days of drug exposure, whereas the effect of RA alone peaked after 6 days and yielded a smaller percentage of differentiated cells. RA also reversed NB4 cell resistance to butyrates and allowed for synergistic differentiation by these agents. Pretreatment with HMBA before exposure to RA failed to stimulate differentiation. Sequential RA/HMBA treatment also markedly increased the extent of differentiation of primary cultures of bone marrow and peripheral blood mononuclear cells from three APL patients. In one case RA/HMBA treatment overcame resistance to RA in vitro. Together, these results suggest that intermittent low doses of RA followed by either HMBA or butyrates may be a useful combination in the treatment of APL. This clinical strategy may help prevent or overcome RA resistance in APL.

Effect of autonomic nervous system dysfunction on the circadian pattern of myocardial ischemia in diabetes mellitus

OBJECTIVES

The aim of this study was to determine the prevalence and characteristics of ambulatory myocardial ischemia in patients with diabetes mellitus and to delineate the relation between the presence and severity of autonomic nervous system dysfunction and the incidence and time of onset of myocardial ischemia.

BACKGROUND

Conflicting data exist with regard to the circadian pattern of myocardial infarction and other cardiovascular events, such as ambulatory ischemia, in diabetes.

METHODS

We performed ambulatory electrocardiographic monitoring in 60 patients with diabetes and coronary artery disease. Autonomic nervous system testing was performed in a subgroup of 25 patients with myocardial ischemia after discontinuation of all antianginal medications.

RESULTS

Thirty-eight of 60 patients had evidence of ambulatory ischemia; 91% of all ischemic episodes were asymptomatic. The 25 patients with ambulatory ischemia who underwent autonomic nervous system testing had a peak incidence of ischemia between 6 AM and noon (46 of 133 ischemic episodes, p < 0.007), compared with the other three 6-h periods. Fifteen of the 25 patients had no or mild autonomic nervous system dysfunction and demonstrated a similar peak incidence of ischemia between 6 AM and noon (p = 0.0009). However, the 10 patients with moderate to severe autonomic nervous system dysfunction did not experience a morning peak of ischemia, and the number of ischemic episodes was distributed evenly throughout the day (p = 0.4).

CONCLUSIONS

Silent ischemia is highly prevalent among patients with diabetes and coronary artery disease. Time of onset of ischemia in diabetic patients follows a circadian distribution, with a peak incidence in the morning hours. However, patients with significant autonomic nervous system dysfunction did not demonstrate such a peak, suggesting that alterations in sympathovagal balance may have an effect on the circadian pattern of cardiovascular events.

Induction of cell migration by pro-urokinase binding to its receptor: possible mechanism for signal transduction in human epithelial cells

A human epithelial cell line, WISH, and a mouse cell line, LB6-uPAR, transfected with the human urokinase receptor (uPAR), both expressed high affinity uPAR but undetectable levels of urokinase (uPA). In two independent assays, binding of exogenous pro-uPA produced an up to threefold enhancement of migration. The migration was time and concentration dependent and did not involve extracellular proteolysis. This biologic response suggested that uPAR can trigger an intracellular signal. Since this receptor is a glycosyl-phosphatidylinositol-linked protein, we postulated that it must do so by interacting with other proteins, among which, by analogy to other systems, would be a kinase. To test this hypothesis, we carried out a solid phase capture of uPAR from WISH cell lysates using either antibodies against uPAR or pro-uPA adsorbed to plastic wells, followed by in vitro phosphorylation of the immobilized proteins. SDS-PAGE and autoradiography revealed two phosphorylated protein bands of 47 and 55 kD. Both proteins were phosphorylated on serine residues. Partial sequence of the two proteins showed a 100% homology to cytokeratin 18 (CK18) and 8 (CK8), respectively. A similar pattern of phosphorylation was obtained with lysates from A459 cells, a lung carcinoma, but not HL60, LB6-uPAR or HEp3 cell lysates, suggesting that the identified multiprotein uPAR-complex may be specific for simple epithelia. Moreover, immunocapture with antibody to another glycosyl-phosphatidylinositol-linked protein, CD55, which is highly expressed in WISH cells, was ineffective. The kinase was tentatively identified as protein kinase C, because it was inhibited by an analogue of staurosporine more specific for PKC and not by a PKA or tyrosine kinase inhibitors. The kinase was tentatively identified as PKC epsilon because of its resistance to PMA down-modulation, independence of Ca2+ for activity, and reaction with a specific anti-PKC epsilon antibody in Western blots. Cell fractionation into cytosolic and particulate fractions revealed that all four proteins, the kinase, uPAR, CK18, and CK8, were present in the particulate fraction. In vivo, CK8, and to a lesser degree CK18, were found to be phosphorylated on serine residues. Occupation of uPAR elicited a time-dependent increase in the phosphorylation intensity of CK8, a cell shape change and a redistribution of the cytokeratin filaments. These results strongly suggest that uPAR serves not only as an anchor for uPA but participates in a signal transduction pathway resulting in a pronounced biological response.

Myelodysplastic syndrome transforming to acute promyelocytic-like leukemia with trisomy and rearrangement of chromosome 11

Variants of the t(15;17)(q22;q12-q21) chromosomal rearrangement associated with acute promyelocytic leukemia (APL) have been previously described and they frequently involve either chromosome 15 and/or 17. Previously we reported a rare variant t(11;17). We now describe two patients with myelodysplastic syndrome (MDS) that transformed to APL-like leukemia. Both had trisomy 11 at the diagnosis of APL-like leukemia. Following treatment for APL, patient 1 reverted to MDS and showed a normal karyotype. When leukemia recurred, his bone marrow karyotype was 47,XY,t(4;11), +11,der(22)t(1;22). Both patients were treated with all-trans retinoic acid (ATRA) for APL for 5 weeks, but failed to respond. The karyotype of patient 1 after ATRA treatment was 46,XY,t(4;11); the trisomy 11 had been lost and the bone marrow was replaced with immature myeloblasts without promyelocytes. In patient 2, the karyotype remained the same as at diagnosis, i.e., 47,X,-Y,dir ins(4;7),del(5), +6,del(7), +8, + 11,-18. Molecular analysis by reverse transcriptase PCR analysis showed the presence of wild type retinoic acid receptor alpha (RARA) and the absence of the PML-RARA chimeric gene associated with t(15;17). Additional analysis of PLZF, a new zinc finger gene associated with t(11;17), also showed the absence of this hybrid gene. These data support the concept that APL is a heterogeneous disorder and that variants with chromosome 11 rearrangement exist that do not respond to ATRA.

PLZF-RAR alpha fusion proteins generated from the variant t(11;17)(q23;q21) translocation in acute promyelocytic leukemia inhibit ligand-dependent transactivation of wild-type retinoic acid receptors

Recently, we described a recurrent variant translocation, t(11;17)(q23;q21), in acute promyelocytic leukemia (APL) which juxtaposes PLZF, a gene encoding a zinc finger protein, to RARA, encoding retinoic acid receptor alpha (RAR alpha). We have now cloned cDNAs encoding PLZF-RAR alpha chimeric proteins and studied their transactivating activities. In transient-expression assays, both the PLZF(A)-RAR alpha and PLZF(B)-RAR alpha fusion proteins like the PML-RAR alpha protein resulting from the well-known t(15;17) translocation in APL, antagonized endogenous and transfected wild-type RAR alpha in the presence of retinoic acid. Cotransfection assays showed that a significant repression of RAR alpha transactivation activity was obtained even with a very low PLZF-RAR alpha-expressing plasmid concentration. A "dominant negative" effect was observed when PLZF-RAR alpha fusion proteins were cotransfected with vectors expressing RAR alpha and retinoid X receptor alpha (RXR alpha). These abnormal transactivation properties observed in retinoic acid-sensitive myeloid cells strongly implicate the PLZF-RAR alpha fusion proteins in the molecular pathogenesis of APL.