Protein factors that regulate the growth and differentiation of mouse myeloid leukaemia cells

We have purified and characterized several protein factors that regulate the growth and differentiation of mouse myeloid leukaemia M1 cells. The differentiation factor (D-factor) from conditioned medium (CM) of Ehrlich ascites tumour cells is a glycoprotein of Mr 40,000-50,000. Its amino acid sequence was found to be almost identical to that of leukaemia inhibitory factor (LIF) from Krebs II ascites cells. The differentiation inhibitory factor (I-factor) from the CM of variant M1 cell clones which were resistant to several differentiation inducers is a basic protein of apparent Mr 68,000. The growth inhibitory factor (GI-factor) that specifically inhibits the partially differentiated and still growing monocytic leukaemia M1 cells was isolated from the CM of a clone of M1 cells resistant to the differentiation inducers. This GI-factor is a basic protein with an Mr of 25,000. Regulation by these protein factors together with other known cytokines of growth and differentiation of M1 cells is reported.

Easy and accurate targeting of deep-seated hepatic tumors under laparoscopy with a forward-viewing convex-array transducer

BACKGROUND

It is technically difficult to puncture deep-seated hepatic tumors by conventional laparoscopic ultrasonography with a linear-array probe. We have developed a laparoscopic ultrasonography system with a convex-array probe.

METHODS

The laparoscopic system used had a fixed forward-viewing convex-array transducer, and a guide groove for puncture was added to the back of the unit. These characteristics enabled us to continuously monitor the position of the needle tip on the ultrasonographic image immediately after puncturing on the liver surface. We attempted tumor puncture in 11 patients with hepatocellular carcinoma under a new probe guidance.

RESULTS

The mean puncturing distance up to the tumors was 38.7 mm. All punctures were successful on the first pass and the tumors were treated with radiofrequency ablation.

CONCLUSION

Using this new equipment, puncturing hepatic tumors for treatment is relatively easy, irrespective of the position of the tumor.

Laparoscopic adhesiolysis for recurrent small bowel obstruction: long-term follow-up

BACKGROUND

Recurrent small bowel obstruction caused by postoperative adhesions has traditionally been treated by conventional laparotomy, but laparoscopic management of acute small bowel obstruction has been reported. The aim of this study was to assess the long-term efficacy and clinical outcome of laparoscopic adhesiolysis for recurrent small bowel obstruction.

METHODS

After conservative treatment, elective laparoscopic treatment was attempted in 17 patients hospitalized for recurrent small bowel obstruction after abdominal or pelvic surgery.

RESULTS

Postoperative adhesions were identified laparoscopically in all patients. Laparoscopic treatment was possible in 14 patients (82.4%). Conversion to laparotomy was required for 3 patients (17.6%) because of intestinal perforation (n = 1) or a convoluted mass of adherent bowel (n = 2). Long-term follow-up was possible in 16 patients. Two recurrences of small bowel obstructions were noted over a mean follow-up period of 61.7 months.

CONCLUSIONS

Laparoscopic adhesiolysis is a safe and effective treatment for recurrent small bowel obstruction. Conversion to laparotomy should be considered in patients with dense adhesions.

Central serotonergic mechanisms on head twitch response induced by benzodiazepine receptor agonists

Intraperitoneal injection of benzodiazepine receptor agonists (estazolam, zopiclone, triazolam: 0.03-0.24 mmol/kg) induces the head twitch response (HTR). The present study was undertaken to examine the possible participation of the serotonergic system in the mechanism of head twitches induced by benzodiazepine receptor agonists (BZ-RAs). The HTR induced by BZ-RAs was suppressed by pretreatment with ketanserine (1 mg/kg, i.p.), a selective 5-HT(2) receptor antagonist. Pretreatment with fluoxetine (10 mg/kg, i.p.), a 5-HT reuptake inhibitor, and 8-hydroxy-2-(di-n-propylamino)tetralin, a 5-HT(1A) receptor agonist, also suppressed the HTR induced by BZ-RAs. These results suggest that the HTR induced by BZ-RAs may be the result of an activation of postsynaptic 5-HT(2) receptors, probably due to direct action.

The role of laparoscopic US and laparoscopic US-guided aspiration biopsy in the diagnosis of multicentric hepatocellular carcinoma

BACKGROUND

Detection of small hepatocellular carcinomas has become possible with improvements in various diagnostic imaging techniques. However, intraoperative US can detect lesions not visualized by any preoperative imaging study in which case it is difficult to determine whether the lesion is a hepatocellular carcinoma.

METHODS

Nodular lesions detected by laparoscopic US in 186 patients with hepatocellular carcinoma were examined and we evaluated the diagnostic ability of laparoscopic US to detect multicentric hepatocellular carcinoma.

RESULTS

One hundred thirty-four new nodular lesions were detected by laparoscopic US in 64 (34.4%) of 186 patients. Aspiration biopsy under laparoscopic US guidance was performed on the 134 nodules, and 28 nodules in 23 (12.4%) of the 186 patients were histologically diagnosed as hepatocellular carcinoma. Of these 23 patients, 18 had been diagnosed with solitary hepatocellular carcinoma before laparoscopic US. One hundred six of the newly detected lesions were initially diagnosed as noncarcinomatous nodules, but the diagnosis of 10 of these lesions was changed to hepatocellular carcinoma during follow-up that was as long as 96 months.

CONCLUSIONS

Laparoscopic US is useful in the initial diagnosis of hepatocellular carcinoma and impacts treatment selection by more accurately defining the presence of multicentric hepatocellular carcinomas.

Prognosis of small hepatocellular carcinoma after laparoscopic ethanol injection

BACKGROUND

Most patients with hepatocellular carcinoma have underlying cirrhosis, and this impairment of liver function makes hepatectomy difficult, prompting the use of other modalities such as transcatheter arterial embolization and percutaneous ethanol injection.

METHODS

Laparoscopic ethanol injection was performed in 48 previously untreated patients with hepatocellular carcinoma smaller than 2 cm in diameter. Long-term survival was evaluated.

RESULTS

In 12 patients, hepatocellular carcinoma was not detected by trans-cutaneous ultrasonography but could be demonstrated by laparoscopic ultrasonography. Laparoscopic ethanol injection did not cause serious complications in any patient. The mean hospital stay after ethanol injection was 8.6 days (4 to 15 days). The cumulative survival rate was 86.7% at 3 years and 60.0% at 5 years. According to the Child-Pugh classification, the cumulative survival rate at 5 years was 87.9% for class A, 65.7% for class B, and 28.6% for class C.

CONCLUSIONS

The long-term prognosis for patients with small hepatocellular carcinoma treated solely by laparoscopic ethanol injection is satisfactory but still dependent on underlying liver function.

Differentiation therapy of leukemia: achievements, limitations and future prospects

Differentiation therapy in patients with acute promyelocytic leukemia (APL) using all-trans-retinoic acid (ATRA) has now been established as an effective strategy for the treatment of leukemia. However, the clinical response of patients with leukemias other than APL to differentiation inducers is limited, often with inconsistent outcome. Recently, numerous new differentiation inducers for various leukemia cells have been developed, some of which have had therapeutic effects on various leukemias in preclinical and clinical trials. Additionally, molecular control mechanisms of differentiation, and apoptosis of various leukemia cells by differentiation inducers have been studied extensively. These studies suggest that problems underlying the current discrepancy between preclinical and clinical therapeutic efficacy of leukemias can be overcome by these basic studies together with multidisciplinary studies on the therapy of leukemias in combination with differentiation therapy and other conventional therapies.

Microwave coagulation therapy on hepatomas: CT and MR appearance after therapy

Laparoscopic microwave coagulation (LMC) for hepatocellular carcinomas (HCCs) was performed on 26 HCCs in 17 patients. Contrast-enhanced CT (CECT) and MR images (T1-weighted imaging [T1WI], T2WI, gadolinium-diethylenetriamine pentaacetic acid [Gd-DTPA] T1WI) were obtained to determine changes over time. The irradiated center exhibited low to moderate intensity with surrounded high intensity (HI) on T2WI and Gd-DTPA T1WI. On T1WI, lesions showed four patterns of intensity: uniform HI (30.8%), arcuate HI (26.9%), mainly low with spot HI (30.8%), and isointensity to hypointensity (11.5%). Follow-up imaging at more than 170 days revealed isointensity to hypointensity on T1WI (96.2%) and reduced HI on T2-weighted imaging (T2WI) and Gd-DTPA T1WI. All lesions became less conspicuous and were reduced in volume. HCC shows time-related changes in signals and size after LMC. Identifying the irradiated lesion is necessary to estimate the adequacy of treatment by comparison with the pretherapeutic image.

Plasma beta-carotene, retinol, and alpha-tocopherol levels in relation to glycemic control of children with insulin-dependent diabetes mellitus

Plasma beta-carotene, alpha-tocopherol and retinol were measured in 15 female and 5 male children with insulin-dependent diabetes mellitus (IDDM), and the correlations with plasma hemoglobin A1c (HbA1c) and fructosamine were analyzed. Twelve female and 8 male children served as age-matched controls. The plasma beta-carotene and alpha-tocopherol levels of the IDDM children were significantly higher than those of the control children, but there were no differences in plasma retinol or total lipid levels. The plasma beta-carotene level, beta-carotene/retinol ratio and beta-carotene/total lipids ratio each showed significant correlations with serum HbA1c and fructosamine in all subjects studied. Similarly, the plasma alpha-tocopherol level and alpha-tocopherol/total lipids ratio were correlated with these indexes of glycemic control. These findings suggest certain mechanisms may exist to prevent lipid peroxidation and vascular complications in IDDM patients.

Enhancement of anticancer effects of radiation and conventional anticancer agents by a quinolinone derivative, vesnarinone: studies on human gastric cancer tissue xenografts in nude mice

Vesnarinone (3,4-dihydro-6-[4-(3,4-dimethoxybenzoyl)-1-piperazinyl]-2(1H)- quinolinone), a quinolinone derivative, is an orally active inotropic agent used in Japan for the treatment of chronic heart failure. Recently, it has been reported that vesnarinone induces differentiation and apoptosis in certain types of leukaemia and solid tumour cells, and exhibits antitumour effect on several tumours xenografted in nude mice. In the present study, we examined the antitumour effect of vesnarinone in combination with radiation and conventional anticancer agents in nude mice xenografted with human gastric carcinoma, a poorly-differentiated adenocarcinoma, MKN-45 cell line which has a wild-type p53 gene. Vesnarinone treatment combined with radiation resulted in a higher antitumour activity compared with a single treatment with either vesnarinone or radiation alone. Further, vesnarinone treatment together with radiation and conventional anticancer agents including 5-FU and picibanil (an immunopotentiator) produced the highest antitumour effect compared with any other treatment. Additionally, the combination treatment induced marked differentiation and apoptosis of the tumour cells and an increase in the expression of p53 gene in the treated tumour cells. The results suggest that vesnarinone, in combination with radiation and the conventional antitumour agents, may be of clinical interest for treatment of certain types of gastric tumours.

Antioxidant vitamin levels in plasma and low density lipoprotein of obese girls

To investigate the antioxidant status of obese children, we analyzed beta-carotene and alpha-tocopherol levels in plasma and low density lipoprotein (LDL). We also analyzed the fatty acid composition of LDL as a substrate for oxidative stress. The plasma beta-carotene and alpha-tocopherol levels were relatively lower in obese girls than in normal controls. However, the plasma alpha-tocopherol/lipids ratio was significantly lower in obese girls than in normal controls. Both LDL beta-carotene and LDL alpha-tocopherol levels were significantly lower in obese girls than in normal controls, although no obvious differences were observed in plasma levels. In obese girls LDL contained more polyunsaturated fatty acid (PUFA) compared with normal controls. When the peroxidizability index (PI) was calculated to estimate the susceptibility of lipids to oxidative stress, obese girls had significantly higher PI values than normal controls. Both the LDL beta-carotene/PI ratio and the LDL alpha-tocopherol/PI ratio were significantly lower in obese girls than in normal controls. These results indicate the increased susceptibility of LDL to oxidative stress in obese girls which may promote atherosclerosis later in life.

Involvement of dopaminergic neurons in mouse-killing aggression in rats

The sites associated with dopamine neurons which produce mouse-killing aggression (muricide) were examined in the rat brain. Muricide appeared in 60-80% of rats after being fed a thiamine-deficient diet for 28 days. Microinjection of dopamine (500 ng/rat) into the olfactory bulb (OB) significantly suppressed muricide, whereas injection into other brain areas failed to do so. The incidence of muricide after dopamine injection was 40% at 5 min and 20% at 15-30 min. When 6-hydroxydopamine (8 micrograms/0.5 microliter), following pretreatment with desmethylimipramine (25 mg/kg i.p.), was injected twice into the ventral tegmental area (VTA) or the olfactory bulb (OB) in nonkiller rats during thiamine-deficient feeding, the occurrence of muricide gradually increased over time. The present results suggest that degeneration of dopamine neurons projecting from the VTA to the OB may be related to mouse-killing aggression in rats.

[Relationship between learning behavior and genetic factor on immobility shown during forced swimming test]

The relationship between learning and genetic factor on immobility in mice during a forced swimming test (FST) has been studied. The duration of immobility during the FST did not change significantly after the administration of either scopolamine (2.5 mg/kg, ip) or cyclohexamine (150 mg/kg, ip), although both drugs produced impairment in the learning task. This suggests that the increase in immobility observed during the second trial of the FST may not be related to learning which could occur during the first trial. Concerning the strain difference, first, the duration of immobility in C3H mice was shorter than that in ICR, ddY, C57BL and BALB mice. Second, after receiving shock stress in a box, ICR, ddY and C57BL mice, but not C3H mice showed a marked decrease in locomotor activity when placed in the box again without shock. Also during the FST, both C57BL and ddY mice, but not C3H mice showed prolongation of immobility and reduction in swimming after shock stress. The changes in locomotor activity, and immobility and swimming during the FST caused by shock stress in ddY mice recovered to normal levels after treatment with imipramine. From these results, it is suggested that the immobility shown during the FST, which may be independent of learning and dependent on some genetic factor, is a suitable model of depression in animals.

Detection of in vivo differentiation of murine WEHI-3B D+ leukemia cells transfected with the lac-Z marker gene using two-color flow cytometry

The in vivo induction of the differentiation of murine WEHI-3B D+ myelomonocytic leukemia cells was measured by flow cytometry, simultaneously staining leukemia cells for the marker exogenous beta-galactosidase and for differentiation by the antigen Mac-1 (CD11b/CD18). The WEHI-3B D+ leukemia cells were transfected with the E. coli lac-Z gene by electroporation and subclones that constitutively expressed high levels of the lac-Z gene product beta-galactosidase were established. Flow cytometric analyses of cells in the peritoneal cavities of mice bearing leukemia cells showed that cells continued to express beta-galactosidase for at least 14 days, and they were distinguishable from host-derived cells in vivo by their expression of the transfected gene. Simultaneous determination of the beta-galactosidase activity and Mac-1 content of cells in the peritoneal cavities of mice revealed that administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF) to the mice enhanced the expression of Mac-1 antigen by beta-galactosidase-positive cells. The results demonstrate that G-CSF may have clinical potential as a therapeutic differentiating agent, and that flow cytometric analysis provides a useful in vivo system to evaluate the therapeutic potential of agents capable of inducing terminal differentiation.

Induction of Ley antigen by 5-aza-2'-deoxycytidine in association with differentiation and apoptosis in human pancreatic cancer cells

We investigated the effect of 5-aza-2'-deoxycytidine (ADC) (a specific inhibitor of DNA methylation) on differentiation, Lewisy (Ley) antigen expression, and DNA fragmentation (a biochemical marker of apoptosis) in human pancreatic cancer MIA PaCa-2 cells. ADC markedly inhibited the growth of MIA PaCa-2 cells. Flow cytometric analysis showed that ADC suppressed the cell population in the G1 phase, but enhanced it in the G2/M phase. On the other hand, several markers of cell differentiation including morphological and biochemical alterations were distinctly induced in cells treated with ADC. Morphologically, the cells were enlarged and thinner than the untreated control cells, and intracellular alkaline phosphatase (ALP) activity was markedly increased. Additionally, biochemical markers of apoptosis including DNA fragmentation and Ley antigen expression were induced in association with the appearance of morphological and biochemical markers of differentiation (ALP). These results suggest that the hypomethylation of DNA is involved in the molecular mechanism of growth inhibition, induction of apoptosis, and differentiation in human pancreatic cancer MIA PaCa-2 cells.

Induction of differentiation and enhancement of vincristine sensitivity of human erythroleukemia HEL cells by vesnarinone, a positive inotropic agent

We examined the effect of vesnarinone, an oral cardiotonic, on the growth and differentiation of human myeloid leukemia cells. Vesnarinone alone markedly induced erythroid differentiation of HEL cells. All-trans-retinoic acid also induced erythroid differentiation of the cells, and the differentiation was greatly enhanced by combined treatment with vesnarinone and retinoic acid. HEL cells are highly resistant to some anticancer drugs, including vincristine, but treatment with vesnarinone greatly increased the sensitivity of HEL cells to vincristine. Enhancement of vincristine sensitivity by vesnarinone was not as significant for other leukemia cells. Expression of P-glycoprotein in HEL cells was effectively inhibited by vesnarinone, suggesting that the restoration of vincristine sensitivity is associated with decrease of P-glycoprotein expression in HEL cells. The plasma level of vesnarinone required to induce differentiation of leukemia cells is 30 micrograms/mL, which could be achieved with oral administration. These results suggest that vesnarinone should be useful in differentiation therapy for some types of myelogenous leukemia.

Induction by 5-aza-2'-deoxycytidine, an inhibitor of DNA methylation, of Le(y) antigen, apoptosis and differentiation in human lung cancer cells

We recently developed a monoclonal antibody directed to carbohydrate antigen Le(y), BM-1/JIMRO, and found that expression of Le(y) antigen defined by BM-1/JIMRO was associated with the process of apoptosis, but not with cell proliferation or necrosis. In the present experiments, we examined with BM-1/JIMRO the effects of various differentiation inducers on the growth and expression of Le(y) antigen in human lung cancer A549 cells. We found that a specific inhibitor of methylation of DNA, 5-aza-2' deoxycytidine (ADC), could markedly induce expression of Le(y) antigen in association with induction of apoptosis and differentiation in the A549 cells. These results suggest that hypomethylation of DNA is involved in the molecular mechanisms of induction of Le(y) antigen, apoptosis and differentiation in the cells.

A new function of Nm23/NDP kinase as a differentiation inhibitory factor, which does not require it's kinase activity

We recently identified a differentiation inhibiting factor (I-factor) in mouse myeloid leukemia M1 cells as a murine homolog of nm23-H2/nucleoside diphosphate kinase (NDPK)-B gene product. We examined the I-factor activities of several authentic nm23/NDPK proteins, i.e. recombinant rat NDPK alpha and beta, recombinant mouse nm23-M1 and -M2, and recombinant human nm23-H1 and -H2 containing a mutant nm23-H2His protein lacing NDPK activity. Almost all these nm23/NDPK proteins showed I-factor activity. Moreover, to understand the active domain exhibiting I-factor activity of nm23-H2 protein lacking NDPK activity, we have investigated the I-factor activities of some truncated nm23-H2 proteins. The truncated nm23-H2 protein containing N-terminal peptide 1-60 retained the I-factor activity. These results provide the first evidence for a function of nm23/NDPK as a differentiation inhibiting factor in leukemic cells, that is independent of its NDPK activity and dependent on the presence of N-terminal peptide.

alpha-Methylated tryptamine derivatives induce a 5-HT receptor-mediated head-twitch response in mice

The two alpha-methylated tryptamine derivatives, 5- (5-FMT) and 6-fluoro-alpha-methyltryptamine (6-FMT), rapidly induced a head-twitch response (HTR) in mice. Two derivatives that lack the methyl group in their chemical structures, 5- (5-FT) and 6-fluorotryptamine (6-FT), did not induce the HTR. The induced HTR was depressed by pretreatment with cycloheptadine, p-chlorophenylalanine or fluoxetine, but was potentiated by 5,7-dihydroxytryptamine. Both 5- and 6-FMT increased brain 5-HT levels in hypothalamus, hippocampus, brainstem, striatum and cortex. 5-FMT decreased the levels of 5-hydroxyindoleacetic acid in those regions, but 6-FMT caused a significant decrease in only the hypothalamus and cortex. The two methylated derivatives inhibited mouse brain MAO-A activity more selectively than non-methylated derivatives. The results suggest that the HTR induced by 5- and 6-FMT may result from increased activity of central 5-HT neurons, probably due to increased 5-HT levels after MAO-A inhibition. This probably results in release of 5-HT with a concomitant increased interaction with postsynaptic 5-HT2 receptors. The present results also indicate the importance of the methyl group to selective MAO-A inhibition by the substrate-analogues tested, and the concomitantly induced animal behavior.

Effect of cytokines on the proliferation and differentiation of acute promyelocytic leukemia cells: possible relationship to the development of "retinoic acid syndrome"

The effect of cytokines on the proliferation and differentiation of leukemia cells from 5 patients with acute promyelocytic leukemia (APL) was examined. Interleukin-1 beta (IL-1), interleukin-3 (IL-3), granulocyte-macrophage colony-stimulating factor (GM-CSF) and granulocyte colony-stimulating factor (G-CSF) augmented uptake of 3H-thymidine into the DNA of APL cells in a dose-dependent manner in all cases. This stimulatory effect was pronounced in some, but not all, cells treated with all-trans retinoic acid (ATRA). However, nitroblue tetrazolium-reducing activity was induced in a concentration-dependent manner by ATRA in all cases. The cytokines greatly enhanced NBT reduction of APL cells treated with ATRA, and a mixture of cytokines was more effective than a single cytokine. Although GM-CSF, IL-3 and IL-1 significantly modulated the ATRA-induced morphological changes, they did not induce CD14 expression, a typical marker of monocytic differentiation. In the presence of ATRA, GM-CSF potentiated production and secretion of tumor necrosis factor-alpha (TNF) in response to lipopolysaccharide, as well as interferon-gamma which is a potent inducer of monocytic differentiation in APL cells. On the other hand, production of TNF in ATRA-treated cells was not affected by G-CSF which significantly enhanced granulocytic differentiation. The effect of cytokines on APL cell differentiation should be considered in ATRA treatment for APL patients. Potentiation of cytokine production in APL cells associated with myelomonocytic differentiation is noteworthy in the pathogenesis of "retinoic acid syndrome".

Fundamentals of chemo-differentiation therapy of myeloid leukemia

It has been shown recently that various myeloid leukemia cells can be induced by numerous compounds to differentiate terminally into non-growing mature cells. Furthermore, some of these compounds have been found to be clinically useful for the therapy of certain types of myeloid leukemia. To improve this new method of differentiation therapy of leukemia, we have studied on basic issues of such differentiation therapy including 1) development of more effective new inducers of differentiation of leukemia cells, 2) isolation and characterization of cytokines regulating growth and differentiation of leukemia cells, and 3) rationale for chemo-differentiation therapy of leukemia which is a combination chemotherapy of leukemia with differentiation inducers and cytotoxic anticancer drugs. In this article, recent results of our studies on these basic issues on differentiation therapy of leukemia are reviewed.

Flow-cytometric analysis of in vivo induction of differentiation of WEHI-3B myelomonocytic leukemia cells by recombinant granulocyte colony-stimulating factor

An animal leukemia model was developed to investigate in vivo induction of differentiation of myeloid leukemia cells. An aneuploid cell line (C15) was isolated from mouse myelomonocytic leukemia WEHI-3B D+ cells. The C15 cells contained twice as much DNA as the parental cells but retained the morphology of myelomonocytic cells and the ability to differentiate into macrophage-like cells in response to all-trans retinoic acid (ATRA) in vitro. When the C15 cells were inoculated into the peritoneal cavity of syngeneic Balb/c mice (10(6) cells/mouse), the mice died of leukemia within 19 days. The DNA content and differentiation antigen (Mac-1) of the cells in the peritoneal cavity were determined by dual-parameter flow cytometry. On day 12 after inoculation, the C15 cells were distinguishable from normal host cells in the peritoneal cavity by their different DNA content. The administration of recombinant human granulocyte colony-stimulating factor (rhG-CSF) (10 micrograms/day) to mice bearing C15 cells induced the leukemia cells to express Mac-1 antigen and to change morphologically into mature granulocytic cells. Because the C15 cells were not responsive to G-CSF in suspension culture in vitro, this result suggests that the cytokine's actions on the cells in vivo and in vitro are different. This experimental model for analyzing in vivo differentiation of leukemia cells will be useful for studying the therapeutic effects of potential differentiation-inducing agents.

Three different cDNAs encoding mouse D-factor/LIF receptor

Three cDNAs for mouse differentiation-stimulating factor (D-factor)/leukemia inhibitory factor (LIF) receptor were isolated from a cDNA library prepared from the liver of a pregnant mouse. A probe for screening was prepared by the RT-PCR method using human cDNA sequences as primers. The mouse D-factor receptor cDNA encoded 1,092 amino acids, which had a marked homology with the human counterpart and consisted of signal sequence, extracellular, transmembrane, and cytoplasmic domains. The WSXWS motif found in members of the cytokine receptor family was also present in the extracellular domain of the mouse D-factor receptor. A second form of cDNA that had a 501 bp insertion was isolated. The insertion introduced a stop codon so that the mRNA encoded the soluble receptor lacking transmembrane and intracellular domains. Because the insertion contained polyadenylation signals, two different sizes of mRNA encoding the soluble receptor were produced, depending on whether or not it utilized these signals. Transcripts utilizing these signals were 2.6-3 kb in size, and were very abundantly expressed in the liver. Transcripts that did not use these signals were longer than 5 kb and of similar size to the mRNA for the cellular receptor.

Effects of herbimycin A and its derivatives on growth and differentiation of Ph1-positive acute lymphoid leukemia cell lines

The molecular basis of the Philadelphia chromosome (Ph1) is a structurally altered c-abl (bcr/abl) gene which encodes an abnormally large protein with protein tyrosine kinase activity. Herbimycin A, an inhibitor of tyrosine kinase, preferentially inhibited the growth of Ph1-positive acute lymphoid leukemia (ALL) cell lines, as well as Ph1-positive chronic myeloid leukemia (CML) cell lines. Although noncytotoxic concentrations of herbimycin A induced erythroid differentiation of two CML-derived cell lines, K562 and KU812, in a previous study, the differentiation-inducing effect of herbimycin A on Ph1-positive ALL cell lines was less strong. Herbimycin A enhanced some differentiation-associated properties of one Ph1-positive ALL cell line, L2, but the effect of herbimycin A on the other Ph1-positive ALL cell lines was cytotoxic rather than cytostatic (differentiation-inducing). Several derivatives of herbimycin A were synthesized and their effects on the cell proliferation of Ph1-positive CML and ALL cell lines were examined. The sensitivities of the Ph1-positive cell lines to herbimycin A derivatives were different from the data on the rat kidney cell line infected with Rous sarcoma virus (v-src) derived from a previous study, suggesting bcr/abl kinase may differ in sensitivity from other tyrosine kinases. Moreover, the sensitivities of the ALL cell lines were not the same as those of the CML cell lines. These results suggest that a specific inhibitor of bcr/abl kinase could be an effective antileukemic agent against Ph1-positive CML or ALL.

Selective effect of O-alkyl lysophospholipids on the growth of a human lung giant cell carcinoma cell line

Various alkyl ether lipids were synthesized and their effects on the proliferation of human lung carcinoma cells were examined. The proliferation of Lu-65, a giant cell carcinoma cell line, was significantly decreased with 1 microgram/ml (3-tetradecyloxy-2-methoxy) propyl-2-trimethylammonioethyl phosphate, while the proliferation of Lu-99, another giant cell carcinoma cell line, was unaffected even by treatment with 5 micrograms/ml of the alkyl lysophosphocholine. Adenocarcinoma PC-9 and small cell carcinoma H-69 cells were also fairly resistant to the alkyl ether lipid. Among the alkyl ether lipids tested, 3-nonadecyloxy-2-methoxypropyl 2-trimethylammonioethyl phosphate was the most effective in inhibiting the growth of Lu-65 cells. However, the pyridinioethyl derivative had higher selectivity for the growth of Lu-65 cells than the choline derivative. The sensitivity of Lu-65 cells to the alkyl lysophospholipids was similar to that of human myeloid leukemia cells including HL-60. However, the sensitivities of Lu-65 cells to the other types of alkyl ether lipids were much lower than those of HL-60 cells. These results indicate that Lu-65 cells are selectively sensitive to alkyl lysophospholipids.

Inhibition by interleukin 4 of leukemia inhibitory factor-, interleukin 6-, and dexamethasone-induced differentiation of mouse myeloid leukemia cells: role of c-myc and junB proto-oncogenes

Interleukin 4 (IL-4) inhibited the differentiation of mouse myeloid leukemia M1 cells induced by leukemia inhibitory factor (LIF), interleukin 6, or dexamethasone and conversely enhanced the induction of M1 cell differentiation by 1 alpha,25-dihydroxyvitamin D3. IL-4 blocked LIF-induced differentiation of M1 cells when it was added to the culture medium within 10 h after LIF, but IL-4 did not block differentiation when it was added 12 h after LIF. These results indicate that IL-4 inhibited a critical intermediate step in myeloid leukemia cell differentiation. LIF markedly stimulated the expression of junB mRNA within 2 h but suppressed the expression of c-myb and c-myc after 2- and 12-h treatment, respectively. IL-4 did not significantly affect LIF-induced junB expression or suppression of c-myb expression. However, it interfered significantly with the LIF-induced suppression of c-myc gene expression. Similar results were obtained when interleukin 6 was used to induce differentiation of M1 cells. Dexamethasone and 1 alpha,25-dihydroxyvitamin D3 did not induce junB gene expression but suppressed the expression of c-myb and c-myc. IL-4 also interfered with dexamethasone-induced suppression of c-myc gene expression. On the other hand, IL-4 enhanced 1 alpha,25-dihydroxyvitamin D3-induced down-regulation of c-myc gene expression, consistent with its enhancement of differentiation. These results indicate that the change in c-myc expression induced by IL-4 in M1 cells is closely associated with the effect of IL-4 on the induction of differentiation of M1 cells.

Inhibition of granulocytic differentiation of acute promyelocytic leukemia cells in primary culture by transforming growth factor-beta

We investigated the effect of transforming growth factor-beta 1 (TGF beta) on the proliferation and differentiation of cultured acute promyelocytic leukemia (APL) cells with the chromosomal t(15;17) translocation obtained from four patients to determine the role of TGF beta on growth and differentiation of APL cells. DNA synthesis, determined by 3H-thymidine uptake, was inhibited in the presence and absence of granulocyte colony-stimulating factor (G-CSF) in a dose-dependent manner by TGF beta in APL cells obtained from three of the four cases. TGF beta and G-CSF did not significantly affect the differentiation of APL cells, but all-trans retinoic acid (RA) induced morphological and functional differentiation in all APL cells tested. G-CSF markedly enhanced RA-induced granulocytic differentiation in APL cells obtained from all four cases. In cells in which TGF beta inhibited DNA synthesis, it also inhibited RA-induced granulocytic differentiation of APL cells and, to a greater degree, granulocytic differentiation induced by RA plus G-CSF. These results suggest that TGF beta is a negative regulator of the proliferation and differentiation of APL cells. The significance of TGF beta as an endogenous regulator in differentiation therapy with RA of APL patients is discussed.

Pregnancy associated increase in mRNA for soluble D-factor/LIF receptor in mouse liver

We examined the distribution of mRNAs for differentiation-stimulating factor (D-factor)/leukemia inhibitory factor (LIF) receptor in various mouse tissues by Northern blotting. A mouse cDNA fragment encoding the D-factor receptor was prepared by the RT-PCR method using human cDNA sequences as primers. The smallest mRNA (3 kb) was present in the liver, but not detectable in other tissues examined. Larger mRNAs (5 and 10 kb) were present in the placenta and the M1 cells, and also detectable in the liver, kidney, heart, lung, brain and embryos. Expression of 3 kb mRNA in the liver increased during pregnancy, being 20 times the initial level on day 15. D-factor receptor cDNAs were isolated from a cDNA library prepared from the liver of a pregnant mouse. Most of the cDNA clones encoded a soluble receptor. A cDNA probe specific for the cellular receptor did not hybridize with 3 kb mRNA in the liver. These results suggest that 3 kb mRNA encodes a soluble D-factor receptor and that the liver is the primary site of synthesis of this soluble receptor.

Genistein exhibits preferential cytotoxicity to a leukemogenic variant but induces differentiation of a non-leukemogenic variant of the mouse monocytic leukemia Mm cell line

Mouse leukemia Mm-A and Mm-S2 cells are subclones of mouse monocytic leukemia Mm cells, Mm-A cells having much higher leukemogenicity than Mm-S2 cells. The growth-inhibitory effects of several protein kinase inhibitors on leukemogenic Mm-A and non-leukemogenic Mm-S2 cells were examined. Most inhibitors of protein serine/threonine kinases inhibited the growth of Mm-A and Mm-S2 cells similarly, but some protein tyrosine kinase inhibitors exhibited differential inhibitory effects on Mm-A and Mm-S2 cells. Genistein inhibited growth of Mm-A cells more effectively than that of Mm-S2 cells, but another inhibitor of tyrosine kinase, herbimycin A, preferentially inhibited growth of non-leukemogenic Mm-S2 cells. Genistein induced or enhanced several differentiation markers of Mm-S2 cells, such as cell spreading, immunophagocytosis, nitroblue tetrazolium (NBT) reduction and lysozyme activity in a dose-dependent manner, but herbimycin A did not. Genistein was cytotoxic to Mm-A cells rather than inducing cell differentiation. Genistein has effects on several other cellular events as well as inhibition of tyrosine kinases. However, it effectively inhibited protein tyrosine phosphorylation in Mm-A cells and its decrease of tyrosine phosphorylation was closely associated with its inhibition of cell growth. Thus, a genistein-sensitive tyrosine kinase(s) may play an important role in the growth and/or survival of leukemogenic Mm-A cells.

Induction of differentiation and growth suppression of myeloid leukemia cells by sera of patients with hematological disorders

In severe infection, the host responds to foreign agents and produces cytokines to activate lymphocytes and macrophages. Some of these cytokines can modulate growth and differentiation of myeloid leukemia cells. We examined differentiation-inducing activities in the sera from 9 patients with leukemia or lymphoma. These results indicate that some sera from infected patients, even with acute leukemia, have significant differentiation-inducing activities on both mouse and human leukemia cells, and that cytokines having differentiation-inducing activities varied for different specimens.

Differentiation of human myeloblastic leukemia ML-1 cells into macrophages by staurosporine, an inhibitor of protein kinase activities

Protein kinase activities are involved in cellular proliferation and differentiation, and inhibitors of these activities are useful for studying the mechanisms of induction of differentiation. We found that staurosporine, an inhibitor of protein kinase activities, induced morphological differentiation of human myeloblastic leukemia ML-1 cells along myelomonocytic lineage and also induced functional differentiation (increase in nitroblue tetrazolium-reducing and lysozyme activities) in the cells. Several other protein kinase inhibitors such as 1-(5-isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), sphingosine, N-(6-aminoethyl)-5-chloro-1-naphthalenesulfonamide and 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9) did not induce the differentiation of ML-1 cells. Treatment with staurosporine induced formation of granules in ML-1 cells, and the granules showed metachromasia by toluidine blue staining; however, histamine content did not increase. The "metachromatic" ML-1 cells were positive for CD14, indicating that staurosporine induced the differentiation of ML-1 cells into metachromatic monocytes/macrophages, 1 alpha,25-dihydroxyvitamin D3 (VD3) enhanced appearance of metachromatic granules in staurosporine-treated cells. These results suggest that modulation of protein phosphorylation by a staurosporine-sensitive protein kinase(s) may be associated with differentiation of ML-1 leukemia cells.

Pregnancy associated increase in differentiation-stimulating factor (D-factor)/leukemia inhibitory factor (LIF)-binding substance(s) in mouse serum

Differentiation-stimulating factor (D-factor)/leukemia inhibitory factor (LIF) is known to have multiple biological activities besides induction of differentiation of mouse myeloid leukemia M1 cells. Little is known about how its activities are regulated in vivo, but it has been suggested to play a regulatory role in the mechanisms involved in development of mice. In this study, we found that a single class of D-factor-binding substance is present in normal mouse serum and that it increases transiently in the late stage of pregnancy. It inhibits the induction of differentiation of mouse myeloid leukemic M1 cells by D-factor by blocking the binding of this factor to the cells. It is a heat-labile protein with an apparent molecular weight of 130,000-150,000. The binding of 125I-D-factor to the substance is specific since it was inhibited by excess unlabeled D-factor, but not by interleukin 6 or interferon gamma. The dissociation constant of the binding substance for mouse D-factor in normal mouse serum is 6.6-9.4 nM. In the late stage of pregnancy, the amount of the D-factor-binding substance in the serum apparently increases about 30-fold. These results suggest that the D-factor-binding substance regulates the activity of D-factor during embryonic development of mice.

Differentiation of human monoblastic leukemia U937 cells induced by inhibitors of myosin light chain kinase and prevention of differentiation by granulocyte-macrophage colony-stimulating factor

Inhibitors of protein kinase activities are useful for the study of intracellular signal transduction and some of these inhibitors are reported to induce differentiation of human leukemia cells. We examined effects of granulocyte-macrophage colony-stimulating factor (GM-CSF) in combination with several kinase inhibitors on differentiation of human leukemia U937 cells. Nitroblue tetrazolium (NBT)-reducing activity, a typical marker of myelomonocytic differentiation, of U937 cells was induced by genistein and GM-CSF enhanced this activity. GM-CSF also induced the NBT-reducing activity of the cells in combination with 2,5-dihydroxycinnamic acid methyl ester, psi-tectorigenin and staurosporine, although each of them did not induce the activity. Inhibitors of myosin light chain kinase, 1-(5-chloronaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-9) and 1-(5-iodonaphthalene-1-sulfonyl)-1H-hexahydro-1,4-diazepine hydrochloride (ML-7), induced in U937 cells NBT-reduction, and lysozyme and alpha-naphthyl acetate esterase activities. GM-CSF inhibited this differentiation and counteracted the anti-proliferation effect of the kinase inhibitors. These results suggest that some protein kinases are involved in differentiation of U937 cells and the kinases inhibited by ML-9 and ML-7 are associated with signal transduction of GM-CSF.

Effect of recombinant human D-factor on the growth of leukemic blast progenitors from acute myeloblastic leukemia patients

We studied the effects of D-factor on the growth of leukemic blast progenitors from 15 patients with acute myeloblastic leukemia and two leukemia cell lines in methylcellulose and suspension cultures. When stimulated by granulocyte colony-stimulating factor (G-CSF), granulocyte-macrophage colony-stimulating factor or interleukin-3, leukemic blast progenitors undergo terminal division with limited differentiation in methylcellulose culture, forming blast colonies. Leukemic blast progenitors can renew themselves. The self-renewal can be detected as secondary colony formation after replating primary blast colonies in fresh methylcellulose media and by the growth of clonogenic cells in suspension culture. D-Factor suppressed primary and secondary colony formation in methylcellulose culture. Furthermore, D-factor suppressed clonogenic cell recovery in suspension culture. The suppression by D-factor of the growth of leukemic blast progenitors was not significantly dependent upon the colony-stimulating factors used as growth-stimulating factors. High concentration of G-CSF did not overcome the suppressive effect of D-factor. The results indicate that D-factor is effective in suppressing not only terminal division but also self-renewal of leukemic blast progenitors.

Interleukin 4 potentiates the antiproliferative effect of 1 alpha, 25-dihydroxyvitamin D3 on mouse monocytic leukemia cells but antagonizes the antiproliferative effects of interferon alpha, beta and interleukin 6

Mouse monocytic leukemia Mm cells are a line of spontaneously differentiated cells obtained from mouse myeloblastic leukemia M1 cells. The effect of interleukin 4(IL-4) on the proliferation of Mm cells in the presence or absence of growth inhibitory substances was investigated. In semi-solid agar culture, IL-4 markedly inhibited colony formation by Mm cells, reducing the number of colonies to 50% of that in control cultures at concentration of 3 U/ml. In contrast, IL-4 did not inhibit colony formation by the parent M1 cells. In liquid culture, IL-4 alone inhibited the proliferation of Mm cells only slightly. However, a combination of IL-4 and 1 alpha,25-dihydroxyvitamin D3 (VD3), which alone did not inhibit growth significantly, markedly inhibited the growth of Mm cells. This combination also increased the lysozyme activity of Mm cells significantly. On the other hand, IL-4 suppressed the antiproliferative effects of interferon alpha, beta and IL-6, which are growth inhibitory cytokines for these Mm cells. These results indicate that IL-4 can modulate the growth of monocytic leukemia Mm cells and that its modulatory effects depend on growth inhibitory substances.

[Pharmacological studies of nutritive and tonic crude drugs on fatigue in mice]

The aim of the present study was to clarify acute anti-fatiguing effects of three crude liquid drug preparations (S1-S3), containing almost the same amounts of Ginseng Radix, Epimedii Herba and Agkistrodon Japonicae, with each differentially containing an additional 11, 13 or 15 crude drugs. After preloading forced swimming or tetrabenazine (TBZ: 50, 100 mg/kg, i.p.), each of the S1-S3 preparations applied orally (0.1 ml/10 g) significantly increased the duration times of swimming together with decreased total duration times of immobility during swimming. These effects peaked 60 min postinjection with the following decreasing order of effectiveness: S3 > S2 > S1. The same order of efficacy was also found for increased locomotor activity and decreased durations of swimming immobility after TBZ. After pretreatment with 200 mg/kg TBZ preparations S1-S3 also increased the numbers of jumping on a hot plate with greatly reduced latency. Without preloading the forced swimming, S1-S3 did not have any effect on jumping and its latency, but both S2 and S3 significantly, but more weakly, as compared to those after its preloading, decreased the immobility times. These results indicate that these crude preparations may cause tonic effects and so far tested, these effects seem to be more effective on subjects fatigued with physical and/or mental works than an normal subjects.

Prolongation by differentiation-stimulating factor/leukemia inhibitory factor of the survival time of mice implanted with mouse myeloid leukemia cells

Mouse myeloid leukemic M1 cells can be induced to differentiate into macrophages by differentiation-stimulating factor (D-factor)/leukemia inhibitory factor (LIF). We examined the effect of D-factor on the survival times of syngeneic mice implanted with two different clones (T-22 and R-4) of M1 cells. D-factor induced differentiation and suppressed DNA synthesis of sensitive T-22 cells but not resistant R-4 cells in vitro. For in vivo experiments, we used recombinant mouse D-factor (rmD-factor) produced in mammalian cells, which is glycosylated and is more stable in vitro and in vivo than unglycosylated rmD-factor produced in Escherichia coli. Treatment with rmD-factor prolonged the survival times of mice implanted with T-22 cells but not R-4 cells.

Control of growth and differentiation of Philadelphia chromosome-positive leukemia cells by tyrosine kinase inhibitors

Herbimycin A, a selective inhibitor of tyrosine kinase activity, induced differentiation of leukemia cells isolated from Philadelphia chromosome-positive chronic myelogenous leukemia patients. However, it did not induce differentiation of leukemia cells from acute myelogenous leukemia patients, although these cells could be induced to differentiate by treatment with appropriate compounds. A selective inhibitor of tyrosine kinase might be useful in chemotherapy of Philadelphia chromosome-positive leukemia.

Synthesis of active metabolite(s) from 1 alpha-hydroxyvitamin D3 by human monocytic leukemia cells

Synthesis of the biologically active metabolite(s) from 1 alpha-hydroxyvitamin D3 (1 alpha(OH)D3) was examined in various types of human leukemia cell lines. Untreated monocytoid leukemia cells (U937 and HEL/S) metabolized 1 alpha (OH)D3 to the active metabolite(s), possibly 1 alpha, 24- and/or 1 alpha, 25-dihydroxyvitamin D3, and these cells were efficiently induced to differentiate by treatment with 1 alpha (OH)D3. However, the other types of leukemia cells did not efficiently metabolize it and were not induced to differentiate by 1 alpha (OH)D3. The possible therapeutic advantage of 1 alpha (OH)D3 in the treatment of monocytic leukemia is discussed.

The role of granulocyte-macrophage colony-stimulating factor in induction of monocytic differentiation of HL-60 cells: synergistic interaction with 1 alpha, 25-dihydroxyvitamin D3 and interferon-gamma in inducing interleukin-1 beta

1 alpha, 25-Dihydroxyvitamin D3 (D3) (100 nM) and interferon-gamma (IFN-gamma) (100 U/ml) cooperatively inhibited the proliferation of HL-60 cells, and synergistically induced their monocytic differentiation. The growth-promoting effect of granulocyte-macrophage colony-stimulating factor (GM-CSF) (10 ng/ml) was inhibited appreciably by D3 and slightly by IFN-gamma. Despite the clear difference in their effects on growth of HL-60 cells, both IFN-gamma and GM-CSF in combination with D3 induced cell cycle changes, decreasing the number of cells in the S phase and increasing their percentage in the G1/0 phase. GM-CSF alone had no effect on differentiation, but enhanced differentiation induced by D3 distinctly though to a limited extent, and also enhanced monocytic differentiation, including morphological changes of HL-60 cells in the presence of D3 and IFN-gamma. GM-CSF as well as D3 and IFN-gamma induced interleukin-1 beta (IL-1 beta) production by the HL-60 cells, clearly indicating their importance in differentiation of these cells. IFN-gamma and GM-CSF had mutually potentiating effects and induced maximum IL-1 beta production in response to lipopolysaccharide (LPS) in the presence of D3. Thus despite its growth-promoting effect, GM-CSF is a potential inducer of monocytic differentiation of human myeloid leukemia cells, because in cooperation with IFN-gamma it induced monocyte-macrophage differentiation of HL-60 cells in the presence of D3.

Effects of novel uracil analogs on proliferation and differentiation of human myeloid leukemia cells

Twenty-seven novel nucleobases and nucleosides were synthesized by structural modification of uracil, and their effects on growth and differentiation of human myeloid leukemia HL-60 cells were examined. Some of the compounds inhibited the growth of HL-60 effectively. The nitroblue tetrazolium (NBT)-reducing activities of cells treated with the concentrations of these compounds for 50% inhibition of growth were compared. TI-66 (2,4-dibenzyl-6-fluoro-7,7,8,8-tetramethyl-cis-2,4-diazabicyclo-[4.2.0] octane-3,5-dione) was the most effective inducer of NBT-reducing activity and morphological differentiation of HL-60 cells into cells of the myelomonocytic lineage. TI-66 was also effective for induction of differentiation of another human myelogenous leukemia cell line, ML-1 cells, but not for differentiation of human erythroid leukemia K562 or HEL cells, or monocytic U937 cells. The effect of TI-66 in inducing differentiation of HL-60 cells was additive or more than additive in combination with retinoic acid or vitamin D3. Adenine or hypoxanthine alone induced NBT-reducing activity of the cells, and at suboptimal concentrations these compounds enhanced the effect of TI-66, but the enhanced NBT-reducing activities did not exceed the maximal activity induced by TI-66 alone. Simultaneous treatment of HL-60 cells with hypoxanthine reduced the growth inhibition by TI-66 alone. TI-66 was about 150 times more potent on a molar basis than adenine in inducing differentiation of HL-60 cells. These results suggest that nucleobase analogs such as TI-66 should be useful for differentiation therapy of some types of myelogenous leukemia.

Herbimycin A, an inhibitor of tyrosine kinase, prolongs survival of mice inoculated with myeloid leukemia C1 cells with high expression of v-abl tyrosine kinase

Herbimycin A, a benzoquinonoid ansamycin antibiotic, reduces intracellular phosphorylation by some tyrosine kinases, including v-abl. The mouse megakaryoblastic cell line C1 expresses v-abl protein at high levels. Herbimycin A at about 20 ng/ml caused 50% inhibition of growth of C1 cells but at 100 ng/ml scarcely affected the growth of another mouse leukemia cell line, M1 cells, or of normal bone marrow cells. Injection of 10(6) C1 cells into nude mice resulted in death of all the mice within 30 days. Administration of herbimycin A significantly enhanced the survival of mice inoculated with C1 cells but scarcely affected the survival of mice inoculated with M1 cells. These results suggest that herbimycin A and/or related compounds may be useful for treatment of some types of leukemia in which tyrosine kinase activity is implicated as a determinant of the oncogenic state.

Leukemia inhibitory factor/differentiation-stimulating factor (LIF/D-factor): regulation of its production and possible roles in bone metabolism

Leukemia inhibitory factor/differentiation-stimulating factor (LIF/D-factor), expression of its mRNA, and possible roles in bone metabolism were studied in murine primary and clonal osteoblast-like cells. Local bone-resorbing factors such as IL-1, TNF alpha, and LPS strongly induced expression of LIF/D-factor mRNA in both clonal MC3T3-E1 cells and primary osteoblast-like cells. Neither parathyroid hormone nor 1 alpha,25-dihydroxyvitamin D3 stimulated expression of LIF/D-factor mRNA. LIF/D-factor per se did not stimulate expression of its own mRNA. Appreciable amounts of LIF/D-factor were detected in synovial fluids from rheumatoid arthritis (RA) patients but not in those with osteoarthritis (OA). Simultaneous treatment with LIF/D-factor, IL-1, and IL-6 at the concentrations found in synovial fluids from RA patients greatly enhanced bone resorption, though these cytokines did not stimulate bone resorption when separately applied. This suggests that LIF/D-factor produced by osteoblasts is in concert with other bone-resorbing cytokines such as IL-1 and IL-6 involved in the bone resorption seen in the joints of RA patients. LIF/D-factor specifically bound to MC3T3-E1 cells with an apparent dissociation constant of 161 pM and 1,100 binding sites/cell. LIF/D-factor dose-dependently suppressed incorporation of [3H]thymidine into MC3T3-E1 cells. In addition, it potentiated the alkaline phosphatase activity induced by retinoic acid, though LIF/D-factor alone had no effect on enzyme activity. These results suggest that LIF/D-factor is involved in not only osteoclastic bone resorption but also osteoblast differentiation in conjugation with other osteotropic factors.