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Biomedical subjects

P A Marks

Publications and source records attributed to P A Marks.

At least 19 recordsLinked to original sources
PubMed1992

A rise and fall in 1,2-diacylglycerol content signal hexamethylene bisacetamide-induced erythropoiesis.

Previous studies have suggested a role for protein kinase C (PKC) during induction of murine erythroleukemia cell (MELC) differentiation by hexamethylene bisacetamide (HMBA) (Melloni, E., Pontremoli, S., Viotti, P. L., Patrone, M., Marks, P. A., and Rifkind, R. A. (1989) J. Biol. Chem. 264, 18414-18418). The present studies assess the effect of HMBA on the content of 1,2-diacylglycerol (DG), the physiologic activator of PKC, in MELC variants. Exposure of parental Sc9 cells to HMBA induced a rapid rise and fall in DG content. The DG level increased within seconds from 225 pmol.10(6) cells-1 to a maximum of 305 pmol.10(6) cells-1 at 5 min. Thereafter, DG content fell reaching control levels at 30 min and 46% of control at 4 h. Similar DG elevations were detected in HMBA-resistant, phorbol ester-resistant, and vincristine-resistant MELC lines. Early DG elevation was followed by the characteristic rapid fall in both the phorbol ester-resistant and vincristine-resistant lines, both of which differentiate rapidly in response to HMBA. In contrast, in an HMBA-resistant MELC the DG level failed to fall for at least 10 h. Selection of HMBA-resistant cells for vincristine resistance restores both HMBA sensitivity and the rapid fall in DG content. Addition of a synthetic DG, 1-oleyl-2-acetyl glycerol (OAG), along with HMBA and every 2 h for the next 48 h blocked differentiation, as measured by accumulation of benzidine-reactive cells or by the commitment assay in methyl-cellulose. However, if addition of OAG was delayed for just a few minutes, until endogenous DG levels began to fall, differentiation was no longer inhibited. Rapid elevation of DG content is the earliest reported event during HMBA action and a subsequent fall in the DG content appears to be a critical step in the process of commitment to terminal differentiation.

Acetamides↗
PubMed1992

Hexamethylene bisacetamide in myelodysplastic syndrome and acute myelogenous leukemia: a phase II clinical trial with a differentiation-inducing agent.

Hexamethylene bisacetamide (HMBA) is a potent inducer of differentiation of a number of transformed cell lines in vitro. We report results of a phase II clinical trial in 41 patients with myelodysplastic syndrome (MDS) or acute myelogenous leukemia (AML) to whom HMBA was administered by continuous infusion for 10 days and repeated after an interval of 18 to 75 days. HMBA induced a complete remission (CR) in three patients and a partial remission (PR) in six patients. The median duration of CR was 6.8 months (range 1.3 to 16 months) and 3.7 months for PR (range 1 to 7 months). No significant difference was observed between responders and nonresponders with respect to the mean HMBA plasma levels, which were 0.86 +/- 0.04 mmol/L and 0.87 +/- 0.12 mmol/L, respectively. In certain patients morphologic and chromosome analyses provided evidence that HMBA induced differentiation of transformed hematopoietic precursors. The most prominent toxicity was thrombocytopenia, generally reversible on cessation of administration of HMBA.

Acetamides↗
PubMed1992

Cloning of a D-type cyclin from murine erythroleukemia cells.

We report the complete coding sequence of a cDNA, designated CYL2, derived from a murine erythroleukemia cell library. CYL2 is considered to encode a D-type cyclin because (i) there is cross hybridization with CYL1 (a murine homolog of human cyclin D1) and the encoded protein has 64% amino acid sequence identity with CYL1 and (ii) murine erythroleukemia cell-derived CYL2 contains an amino acid sequence identical to that previously reported for the C-terminal portion of a partially sequenced CYL2. Transcripts of murine erythroleukemia cell CYL2 undergo alternative polyadenylylation like that of human cyclin D1. A major 6.5-kilobase CYL2 transcript changes its expression during the cell cycle with a broad peak through G1 and S phases and a decrease in G2/M phases. The present findings suggest that CYL2 plays a role in the G1 to S phase progression.

Amino Acid Sequence↗
PubMed1992

Protein kinase C isozymes epsilon and alpha in murine erythroleukemia cells.

Protein kinase C (PKC) has a role in signal transduction during hexamethylene bisacetamide (HMBA)-induced differentiation of murine erythroleukemia cells (MELC). Separation of MELC PKC isozymes by hydroxylapatite chromatography yields a major peak (III) and a minor peak (II) of PKC activity, previously reported to contain the PKC alpha and beta isozymes, respectively. In the present study, we confirm that peak III activity is PKC alpha but show that peak II contains PKC epsilon and little or no PKC beta. Immunoblot analysis with isozyme-specific anti-alpha and anti-epsilon PKC antibodies detected PKC alpha in peak III and PKC epsilon in peak II. Peak III activity was markedly enhanced (up to 20-fold) by phosphatidylserine, diolein, and Ca2+, whereas addition of these cofactors to the reaction mixture stimulated peak II activity only 2- to 4-fold. RNase protection analysis of MELC RNA showed that PKC alpha and PKC epsilon RNAs were in a ratio of approximately 2:1, but PKC beta RNA was barely detectable. Taken together, these data indicate that MELC contain PKC alpha and PKC epsilon but little or no PKC beta.

Animals↗
PubMed1992

Embryonic differentiation of sexual dimorphism in vasotocin and mesotocin levels in chickens.

Chicken embryos of both sexes were injected on the tenth day of incubation with either estradiol benzoate (EB), aromatase inhibitor [1,4,6-androstatrien-3, 17-dione (ATD)], antiestrogen [tamoxifen (TAM)], antiandrogen [flutamide (FLU)], or the oil vehicle as control (C). At adulthood, at the age of 26 weeks, 10 chickens of each sex were killed and the amounts of immunoreactive arginine vasotocin (AVT) and mesotocin (MT) in the anterior hypothalamus (AHA), posterior hypothalamus (PHA), neurohypophysis (NHP), and pineal gland (PNL) were determined. Control hens had significantly more AVT in PNL and less MT in AHA and NHP than the corresponding roosters. This sexual dimorphism was affected by the embryonic treatments; TAM increased AVT in AHA of cockerels but not of hens. In both sexes, TAM and FLU increased AVT content in NYP. In males, but not in females, ATD also increased AVT content in the NHP. TAM and FLU administration to the female embryo reduced PNL AVT to the amount present in normal males. None of the treatments effected AHA MT in hens, while in cockerels TAM increased it. In females, TAM and FLU significantly increased NHP MT to the level of C males. In roosters, ATD, TAM, and FLU increased NHP MT further. In hens, but not roosters, FLU reduced MT in PNL. These results indicate that embryonic differentiation of the MT and AVT systems is affected by gonadal steroids in chickens.

Animals↗
PubMed1992

Changes in p34cdc2 kinase activity and cyclin A during induced differentiation of murine erythroleukemia cells.

Hexamethylene bisacetamide (HMBA)-induced murine erythroleukemia (MELC) differentiation is characterized by a prolongation of the initial G1 which follows passage through S phase in the presence of inducer. Commitment to terminal cell division is first detected in a portion of the cell population during this prolonged G1. HMBA-induced commitment is stochastic. This study has examined changes in two known cell cycle regulators, p34cdc2 and cyclin A, in cycle-synchronized MELC in the absence and presence of HMBA. Histone H1 kinase activity of p34cdc2, and the levels of CDC2Mm mRNA, 1.8-kilobase mRNA of cyclin A, and cyclin A protein changed during cell cycle progression in MELC, and all of them were suppressed during G1. The suppression of the H1 kinase activity and cyclin A expression continued through the prolonged G1 in MELC cultured with HMBA, whereas p34cdc2 protein level did not vary through the cell cycle in MELC cultured without or with inducer. Phosphorylation of p34cdc2 in uninduced MELC gradually increased as cells progressed from G1 to S. In induced MELC, an increase in phosphorylation of p34cdc2 occurred during the prolonged G1, and prior to the exit of the bulk of the cells from G1 to S. These results suggest that in HMBA-induced MELC, p34cdc2 phosphorylation per se is not a limiting factor in determining G1 to S progression. The persistent suppression of cyclin A expression and histone H1 kinase activity may play a role in HMBA-induced commitment to terminal differentiation.

Acetamides↗
PubMed1992

Expression and phosphorylation of the retinoblastoma protein during induced differentiation of murine erythroleukemia cells.

Phosphorylation and dephosphorylation of the retinoblastoma protein, pRB, play a role in the control of cell cycle progression and expression of differentiation in eukaryotic cells. The regulation of pRB level and phosphorylation state was investigated during the induction of differentiation of murine erythroleukemia cells (MELC) by the chemical agent hexamethylene bisacetamide (HMBA). In MELC, there is a critical time in G1 or early S phase when HMBA must be present in order to induce differentiation. This is followed by prolongation of the subsequent G1 phase, resumption of progression through the cell cycle for several generations, and then cell cycle arrest in G1-G0. Associated with HMBA-induced prolongation of G1, there is an increase in the amount of the underphosphorylated form of pRB. A variant cell line (DS19/VCR-C) with accelerated kinetics of HMBA-mediated differentiation shows a more marked increase in underphosphorylated pRB. In culture with HMBA, as MELC resume progression through the cell cycle, pRB is present in the phosphorylated form. The total amount of pRB increases approximately 3-fold over the succeeding cell divisions prior to terminal arrest in G1. This increase in pRB is inhibited by dexamethasone, which also blocks HMBA-induced MELC differentiation. During this period, RB mRNA also increases approximately 3- to 5-fold, which reflects an increase in the rate of transcription, with no change in mRNA stability. The state of phosphorylation and amount of pRB appear to be involved in the control of HMBA-induced terminal cell division of MELC.

Acetamides↗
PubMed1991

Potent cytodifferentiating agents related to hexamethylenebisacetamide.

Bishydroxamic acids are effective inducers of differentiation in murine erythroleukemia cells. Flexible analogs of suberic acid bisdimethylamide are approximately 100 times as active as the parent compound or hexamethylenebisacetamide. They also induce differentiation of human promyelocytic leukemia cells (HL-60) and a subclone of human colon carcinoma cells (HT-29-U4). Some rigid bishydroxamic acids with benzene rings in the spacers are even more active toward murine erythroleukemia cells but show curious biological differences. In contrast to the flexible molecules, those with benzene spacers show poor activity toward HL-60 cells; they also have different geometric requirements, and they are not additive with hexamethylenebisacetamide in their effect. It is likely that rigid bishydroxamic acids, with a benzene ring spacer, induce differentiation by a different mechanism in spite of their chemical resemblance to the flexible bisamide and bishydroxamic acid inducers.

Acetamides↗
PubMed1991

Characteristics of erythroleukemia cells selected for vincristine resistance that have accelerated inducer-mediated differentiation.

The induction of murine erythroleukemia cells (MELC; DS19/Sc9) to terminal differentiation by hexamethylenebisacetamide (HMBA) is characterized by a latent period of 10-12 hr before onset of commitment to terminal-cell division and increased transcription of globin genes. MELC variants, derived from this parental cell line, selected for resistance to vincristine (VC), can be induced to differentiate with little or no latent period. This study shows that accelerated HMBA-induced commitment is characteristic of MELC with a low level (2- to 5-fold) of VC resistance in four independently derived cell lines. Both resistance to VC and accelerated differentiation are stable phenotypes for at least 50 passages (approximately 5 months) in the absence of VC. Low-level VC-resistant MELC do not display increased levels of P-glycoprotein or mdr1, mdr2, and mdr3 mRNAs, nor do they exhibit cross-resistance to colchicine or doxorubicin. These cells do show (i) increased level of protein kinase C activity, (ii) reduced accumulation of [3H]VC, and (iii) restoration of VC sensitivity in the presence of verapamil. MELC selected for higher levels of VC resistance (approximately 500-fold) do express high levels of P-glycoprotein and the mdr3 gene. During HMBA-induced differentiation, DS19/Sc9 decrease [3H]VC accumulation, but P-glycoprotein content does not change. A VC-transport-associated protein, also critical for the process of induced differentiation, may be constitutively present in VC-resistant MELC, accounting for their enhanced sensitivity to inducer. This protein accumulates by exposure of VC-sensitive cells to HMBA, contributing to their differentiation and decreased level of VC accumulation.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Relationship between globin mRNA accumulation and commitment to terminal cell differentiation in inducer sensitive and resistant erythroleukemia variants.

The relationship between the kinetics of commitment to terminal cell differentiation and the rates of accumulation of globin mRNA has been examined during the induction of erythroid differentiation by polar/apolar chemical inducers in murine erythroleukemia cells (MELC), under conditions of more and less rapid commitment. Two differentiation inducers and three MELC variants have been studied. Hexamethylene bisacetamide (HMBA) initiates more rapid commitment than does dimethylsulfoxide (Me2SO). MELC variant DR10 is resistant to induction by Me2SO and responds sluggishly to HMBA, in comparison with the DS19-Sc9 variant. V3.17, an MELC variant resistant to low concentrations of vincristine, shows increased sensitivity to the inducers and an accelerated rate of commitment to terminal differentiation compared with DS19-Sc9. It is demonstrated that commitment and the actual expression of differentiation, as measured by the accumulation of alpha-, beta maj-, and beta min-globin mRNA, are temporally coordinated functions during induced differentiation of a transformed cell line by exposure to polar/apolar agents.

Acetamides↗
PubMed1990

Introduction of the beta isozyme of protein kinase C accelerates induced differentiation of murine erythroleukemia cells.

Induction of differentiation in murine erythroleukemia cells (MELCs) involves a protein kinase C (PKC)-mediated step. Vincristine-resistant cells respond more rapidly to hybrid polar/apolar inducers than the parental cells. These vincristine-resistant MELCs contain elevated levels of the beta isozyme of PKC (PKC-beta). Exogenous homologous murine PKC-beta, incorporated into permeabilized MELCs, accelerates induced differentiation. Neither rat PKC-beta, nor mouse PKC-alpha, nor rat PKC-alpha, incorporated into permeabilized MELCs, is effective in altering the kinetics of induced differentiation. This provides direct evidence for a rate-limiting role for this PKC isozyme during N,N'-hexamethylenebisacetamide-mediated induced differentiation of a transformed cell.

Acetamides↗
PubMed1990

Conversion of differentiation inducer resistance to differentiation inducer sensitivity in erythroleukemia cells.

Hexamethylene bisacetamide (HMBA) is a potent inducer of differentiation of murine erythroleukemia cells (MELC). Commitment, the irreversible initiation of the program of terminal-cell differentiation, is first detected in HMBA-sensitive DS19-SC9 MELC in culture after 10 to 12 h of exposure to HMBA. Vincristine (VC)-resistant MELC derived from the DS19-SC9 MELC line display increased sensitivity to HMBA and become committed with little or no latent period. In the present study, we showed that the MELC line R1, which is resistant to HMBA-mediated differentiation, became sensitive to inducer if selected for a low level of VC resistance (less than 10 ng of VC per ml). Four independently derived VC-resistant cell lines from HMBA-resistant R1 cells, designated R1[VCR]a to R1[VCR]d, acquired sensitivity to HMBA and the accelerated kinetics of commitment that are characteristic of VC-resistant MELC derived from the parental DS19-SC9 cells. The calcium channel blocker verapamil suppresses the VC resistance of R1[VCR] cells but does not alter the accelerated response to HMBA. In R1[VCR] cells there was no detectable increase in the level of the 140-kilodalton P-glycoprotein. Transient inhibition of protein synthesis during the latent period delays inducer-mediated commitment of VC-sensitive DS19-SC9 MELC but does not alter the accelerated commitment kinetics of R1[VCR]a cells. Previously, we have reported evidence that protein kinase C beta (PKC beta) plays a role in HMBA-induced MELC differentiation and that compared with DS19-SC9 cells, R1 cells have a relatively low level and R1[VCR]a cells have a high level of PKC beta. These findings suggest that (i) acquisition of VC resistance overcomes the block acquired by R1 cells to HMBA-mediated differentiation; (ii) the accelerated kinetics of HMBA-induced commitment of VC-resistant MELC is not dependent on the verapamil-sensitive transport channel that is responsible, at least in part, for resistance to VC; (iii) in VC-resistant MELC, there is constitutive expression or accumulation of a protein required for HMBA-induced differentiation; and (iv) an elevated level of PKC beta activity may play a role in the altered response of R1[VCR] and other VC-resistant MELC to HMBA.

ATP Binding Cassette Transporter, Subfamily B, Mem↗
PubMed1990

Approaches to more effective induction of cytodifferentiation of transformed cells and potential for cancer treatment.

Conceptually, the use of cytodifferentiation agents to suppress oncogenicity may prove most effective in long-term continuous treatment of patients whose tumors display some inherent expression of differentiated characteristics. This is the case in many pre-malignant lesions. The difficulty in evaluating the therapeutic role for HMBA is often times in separating in vivo cytotoxic from cytodifferentiation effects. Only with further studies will it be determined whether these and other cytodifferentiation agents are therapeutically useful and whether study of the mechanism faction of these agents provides additional understanding of the processes of cellular transformation and differentiation with which they interact.

Acetamides↗
PubMed1990

Clinical use of differentiating agents in cancer therapy.

Conceptually, the use of cytodifferentiation agents to suppress oncogenicity may prove most effective in long-term continuous treatment of patients whose tumors display some inherent expression of differentiated characteristics. This is the case in many pre-malignant lesions. The difficulty in evaluating the therapeutic role for HMBA, the retinoids, and cytosine arabinoside is oftentimes in separating in vivo cytotoxic from cytodifferentiation effects. Only with further studies will it be determined whether these and other cytodifferentiation agents are therapeutically useful and whether they can provide additional understanding of the processes of cellular transformation and differentiation with which they interact.

Acetamides↗