Effects of dietary methionine supplementation from different sources on growth performance and meat quality of barrows and gilts

Methionine is indispensable for growth and meat formation in pigs. However, it is still unclear that increasing dietary sulphur-containing amino acid (SAA) levels using different methionine sources affects the growth performance and meat quality of barrows and gilts. To investigate this, 144 pigs (half barrows and half gilts) were fed the control (100% SAA, CON), DL-Methionine (125% SAA, DL-Met)-supplemented, or OH-Methionine (125% SAA, OH-Met)-supplemented diets during the 11-110 kg period. The results showed that plasma methionine levels varied among treatments during the experimental phase, with increased plasma methionine levels observed following increased SAA consumption during the 25-45 kg period. In contrast, pigs fed the DL-Met diet had lower plasma methionine levels than those fed the CON diet (95-110 kg). Additionally, gilts fed the DL-Met or OH-Met diets showed decreased drip loss in longissimus lumborum muscle (LM) compared to CON-fed gilts. OH-Met-fed gilts had higher pH45min values than those fed the CON or DL-Met diets, whereas OH-Met-fed barrows had higher L45min values than those fed the CON or DL-Met diets. Moreover, increased consumption of SAA, regardless of the methionine source, tended to decrease the shear force of the LM in pigs. In conclusion, this study indicates that increasing dietary levels of SAA (+25%) appeared to improve the meat quality of gilts by decreasing drip loss and increasing meat tenderness.

[Epidemiological characteristics of local COVID-19 epidemics and control experience in routine prevention and control phase in China]

The COVID-19 pandemic is still ongoing in the world, the risk of COVID-19 spread from other countries or in the country will exist for a long term in China. In the routine prevention and control phase, a number of local COVID-19 epidemics have occurred in China, most COVID-19 cases were sporadic ones, but a few case clusters or outbreaks were reported. Winter and spring were the seasons with high incidences of the epidemics; border and port cities had higher risk for outbreaks. Active surveillance in key populations was an effective way for the early detection of the epidemics. Through a series of comprehensive prevention and control measures, including mass nucleic acid screening, close contact tracing and isolation, classified management of areas and groups at risk, wider social distancing and strict travel management, the local COVID-19 epidemics have been quickly and effectively controlled. The experiences obtained in the control of the local epidemics would benefit the routine prevention and control of COVID-19 in China. The occurrence of a series of COVID-19 case clusters or outbreaks has revealed the weakness or deficiencies in the COVID-19 prevention and control in China, so this paper suggests some measures for the improvement of the future prevention and control of COVID-19.

[Course of disease and related epidemiological parameters of COVID-19: a prospective study based on contact tracing cohort]

Objective: To analyze the course of disease and epidemiological parameters of COVID-19 and provide evidence for making prevention and control strategies. Methods: To display the distribution of course of disease of the infectors who had close contacts with COVID-19 cases from January 1 to March 15, 2020 in Guangdong Provincial, the models of Lognormal, Weibull and gamma distribution were applied. A descriptive analysis was conducted on the basic characteristics and epidemiological parameters of course of disease. Results: In total, 515 of 11 580 close contacts were infected, with an attack rate about 4.4%, including 449 confirmed cases and 66 asymptomatic cases. Lognormal distribution was fitting best for latent period, incubation period, pre-symptomatic infection period of confirmed cases and infection period of asymptomatic cases; Gamma distribution was fitting best for infectious period and clinical symptom period of confirmed cases; Weibull distribution was fitting best for latent period of asymptomatic cases. The latent period, incubation period, pre-symptomatic infection period, infectious period and clinical symptoms period of confirmed cases were 4.50 (95%CI:3.86-5.13) days, 5.12 (95%CI:4.63-5.62) days, 0.87 (95%CI:0.67-1.07) days, 11.89 (95%CI:9.81-13.98) days and 22.00 (95%CI:21.24-22.77) days, respectively. The latent period and infectious period of asymptomatic cases were 8.88 (95%CI:6.89-10.86) days and 6.18 (95%CI:1.89-10.47) days, respectively. Conclusion: The estimated course of COVID-19 and related epidemiological parameters are similar to the existing data.

[Clinical outcomes of COVID-19 cases and influencing factors in Guangdong province]

Objective: To analyze the clinical courses and outcomes of COVID-19 cases and the influencing factors in Guangdong province and provide basis for the formulation or adjustment of medical care and epidemic control strategy for COVID-19. Methods: We collected demographic data, medical histories, clinical courses and outcomes of 1 350 COVID-19 patients reported in Guangdong as of 4 March 2020 via epidemiological investigation and process tracking. Disease severity and clinical course characteristics of the patients and influencing factors of severe illness were analyzed in our study. Results: Among 1 350 cases of COVID-19 cases in Guangdong, 72 (5.3%) and 1 049 (77.7%) were mild and ordinary cases, 164 (12.1%) were severe cases, 58 (4.3%) were critical cases and 7 (0.5%) were fatal. The median duration of illness were 23 days (P(25), P(75): 18, 31 days) and the median length of hospitalization were 20 days (P(25), P(75): 15,27 days). For severe cases, the median time of showing severe manifestations was on the 12(th) day after onset (P(25), P(75): 9(th) to 15(th) days), and the median time of severe manifestation lasted for 8 days (P(25), P(75): 4, 14 days). Among 1 066 discharged/fetal cases, 36.4% (36/99) and 1.0% (1/99) of the mild cases developed to ordinary cases and severe cases respectively after admission; and 5.2% (50/968) and 0.6% (6/968) of the ordinary cases developed to severe cases, and critical cases respectively after admission. In severe cases, 11.4% developed to critical cases (10/88). The influencing factors for severe illness or worse included male (aHR=1.87, 95%CI: 1.43-2.46), older age (aHR=1.67, 95%CI: 1.51-1.85), seeking medical care on day 2-3 after onset (aHR=1.73, 95%CI: 1.20-2.50) pre-existing diabetes (aHR=1.75, 95%CI: 1.12-2.73) and hypertension (aHR=1.49, 95%CI: 1.06-2.09). Conclusions: The course of illness and length of hospitalization of COVID-19 cases were generally long and associated with severity of disease clinical outcomes. The severe cases were mainly occurred in populations at high risk. In the epidemic period, classified management of COVID-19 cases should be promoted according to needs for control and prevention of isolation and treatment for the purpose of rational allocation of medical resources.

[Prognostic significance of NCCN-International Prognostic Index (NCCN-IPI) for patients with peripheral T-cell lymphoma treated with CHOP-based chemotherapy]

目的

明确美国国家综合癌症网络国际预后指数（NCCN-IPI）对外周T细胞淋巴瘤（PTCL）患者化疗后的预后评估价值。

方法

回顾性分析2003年1月至2013年5月接受CHOP或CHOP样方案化疗的162例初治PTCL患者的临床资料，采用国际预后指数（IPI）和NCCN-IPI进行危险分层和预后评估。

结果

①162例患者预期5年总生存（OS）和无进展生存（PFS）率分别为33%和20%，中位OS和PFS时间分别为17.0和9.2个月。②多因素分析提示美国东部肿瘤协作组体能状态评分（ECOG评分）≥2分（PFS：HR＝2.418，95%CI 1.535～3.809，P<0.001；OS：HR＝2.347，95%CI 1.435～3.839，P＝0.001）和存在特定的结外病变部位（PFS：HR＝1.800，95%CI 1.216～2.665，P＝0.003；OS：HR＝1.608，95%CI 1.054～2.454，P＝0.027）是影响患者PFS和OS的独立危险因素；ALK⁺是影响间变性大细胞淋巴瘤患者PFS（HR＝0.424，95%CI 0.184～0.975，P＝0.043）及OS（HR＝0.276，95%CI 0.087～0.877，P＝0.029）的独立预后良好因素。③NCCN-IPI低危组患者的生存率显著高于IPI低危组患者（5年OS率74%对54%，χ²＝5.041，P＝0.025；5年PFS率50%对38%，χ²＝5.295，P＝0.021），差异均有统计学意义。

结论

NCCN-IPI较IPI对低危PTCL患者具有更好的预后判断意义，可作为PTCL患者有效的预后分层工具。

[Efficacy of additional two cycles of rituximab administration for patients with diffuse large B-cell lymphoma in first remission]

Objective: To analyze the efficacy of additional two cycles of rituximab administration for Chinese patients with diffuse large B-cell lymphoma (DLBCL) in first complete remission (CR) after six cycles of standard 21-day rituximab plus cyclophosphamide, doxorubicin, vincristine and prednisone (R-CHOP21). Methods: Retrospective analysis was performed in 351 patients with DLBCL diagnosed from March 2003 to March 2012. International Prognosis Index (IPI), Revised (R)-IPI and National Comprehensive Cancer Network (NCCN)-IPI were calculated for each patient. Patients were divided into GCB and non-GCB subtype according to Han's Classification. Progression-free survival (PFS) and overall survival (OS) were analyzed using Kaplan-Meier methods. Results: 282 (80.3%) patients achieved CR and 132 (46.8%) of 282 cases received additional two rituximab therapy. The other 150 (53.2%) patients entered into observation on the intention of the patients. No significant difference was observed in baseline characteristics between the two groups. 3-year estimated PFS for additional rituximab group and observation group were 80.0% and 78.1% (P=0.334), while 3-year estimated OS were 89.7% vs. 86.1% (P=0.452). By subgroup analysis, prolonged PFS were observed in R-IPI low-risk and NCCN-IPI low-risk patients after additional two rituximab cycles. Conclusion: For patients with DLBCL in first remission after standard six cycles of R-CHOP21 regimen, additional two cycles of rituximab maintenance did not significantly improve the general prognosis, but low-risk subgroups of R-IPI and NCCN-IPI could benefit from this regimen.

[Single scrotal-incision orchidopexy without ligation of processus vaginalis for palpable undescended testis]

OBJECTIVE

To determine the feasibility and short-term effect of single scrotal-incision orchidopexy (SSIO) without ligation of the processus vaginalis (PV) in the treatment of palpable undescended testis (PUDT).

METHODS

This retrospective study included 109 cases of PUDT (125 sides) and 15 cases of impalpable undescended testis (IUDT). The former underwent SSIO without PV ligation (group A, n = 53) or standard inguinal orchidopexy with PV ligation (group B, n = 56) while the latter received laparoscopic exploration (group C). We analyzed the success rate of SSIO in the management of PUDT, postoperative complications, and incidence rates of hernia and hydrocele, and compared the relevant parameters between groups A and B.

RESULTS

The median age of the PUDT patients was 1.4 (0.6－11.0) years. Group A included 24 cases of left PUDT (2 with hydrocele), 20 cases of right PUDT (1 with hydrocele), and 9 cases of bilateral PUDT, the success rate of which was 95.1%. Group B consisted of 27 cases of left PUDT, 22 cases of right PUDT (3 with hernias), and 7 cases of bilateral PUDT. The rate of PV patency in the PUDT patients was 80.8% (101/125). Laparoscopic exploration of the 15 IUDT patients revealed 2 cases of congenital testis absence, 6 cases of testis dysplasia, all treated by surgical removal, 3 cases of staying around the inner ring, descended by inguinal orchidopexy, and the other 4 treated by laparoscopic surgery. The incisions healed well in all cases, with no testicular atrophy, inguinal hernia or hydrocele.

CONCLUSIONS

Single scrotal-incision orchidopexy without PV ligation is a safe and feasible procedure for the treatment of palpable undescended testis, which avoids the risk of inguinal hernia or hydrocele.

[Ladder step strategy for surgical repair of congenital concealed penis in children]

OBJECTIVE

To assess the feasibility of the ladder step strategy in surgical repair of congenital concealed penis in children.

METHODS

This study included 52 children with congenital concealed penis treated in the past two years by surgical repair using the ladder step strategy, which consists of five main steps: cutting the narrow ring of the foreskin, degloving the penile skin, fixing the penile skin at the base, covering the penile shaft, and reshaping the prepuce. The perioperative data of the patients were prospectively collected and statistically described.

RESULTS

Of the 52 patients, 20 needed remodeling of the frenulum and 27 received longitudinal incision in the penoscrotal junction to expose and deglove the penile shaft. The advanced scrotal flap technique was applied in 8 children to cover the penile shaft without tension, the pedicled foreskin flap technique employed in 11 to repair the penile skin defect, and excision of the webbed skin of the ventral penis performed in another 44 to remodel the penoscrotal angle. The operation time, blood loss, and postoperative hospital stay were 40－100 minutes, 5－30 ml, and 3－6 days, respectively. Wound bleeding and infection occurred in 1 and 5 cases, respectively. Follow-up examinations at 3 and 6 months after surgery showed that all the children had a satisfactory penile appearance except for some minor complications (2 cases of penile retraction, 2 cases of redundant ventral skin, and 1 case of iatrogenic penile curvature).

CONCLUSIONS

The ladder step strategy for surgical repair of congenital concealed penis in children is a simple procedure with minor injury and satisfactory appearance of the penis.

Single-nucleotide polymorphisms in dopamine receptor D1 are associated with heroin dependence but not impulsive behavior

Previous studies suggested that dopamine receptors may be associated with drug dependence and impulsive behavior. In this study, we examined whether dopamine receptor D1 (DRD1) is associated with heroin dependence and the impulsive behavior in patients with heroin dependence. The participants included 367 patients with heroin dependence and 372 healthy controls from a Chinese Han population. We examined the potential association between heroin dependence and 8 single-nucleotide polymorphisms (rs686, rs4867798, rs1799914, rs4532, rs5326, rs265981, rs10078714, rs10078866) of DRD1, and the associations between single single-nucleotide polymorphism, haplotypes, and impulsive behavior. Compared with the healthy controls, heroin dependence patients showed a significantly lower frequency of GG homozygotes of rs5326 (P = 0.027), significantly lower frequency of the G allele of rs5326 (P = 0.007, odds ratio = 0.718, 95% confidence interval = 0.565-0.913), and higher frequency of the rs265981 G allele (P = 0.0002, odds ratio = 1.711, 95% confidence interval = 1.281-2.287). Furthermore, strong linkage disequilibrium was observed in 2 blocks (D' > 0.9). However, no association was observed between haplotypes and heroin dependence in the 2 blocks. This genetic behavior correlation study showed that the 2 single-nucleotide polymorphisms, rs5326 and rs265981, were not associated with the impulsive behavior in patients with heroin dependence. These findings indicate that DRD1 gene polymorphisms are related to heroin dependence in a Chinese Han population and may be informative for future genetic or biological studies on heroin dependence.

Functional polymorphisms of the glutamate receptor N-methyl D-aspartate 2A gene are associated with heroin addiction

Heroin dependence is a debilitating psychiatric disorder with a complex inheritance mechanism. Genetic polymorphisms in functional regions of the glutamate receptor, N-methyl D-aspartate 2A (GRIN2A) gene, which encodes the 2A subunit of the N-methyl D-aspartate (NMDA) receptor, may modulate the risk of heroin addiction. We investigated the potential association between 8 single nucleotide polymorphisms (SNPs) of the GRIN2A gene (SNPs rs3219790, rs1014531, rs8044472, rs8045712, rs9933624, rs9940680, rs1420040, and rs767749) and heroin addiction using the MassARRAY system and GeneScan. A total of 405 heroin-addicted patients and 397 healthy control subjects were recruited for this study. Statistically significant differences were observed for rs3219790 in the promoter region of the GRIN2A gene. The frequency of the (GT)26 repeats in the heroin addiction group was significantly higher than that in the control group [X(2) = 5.475, P = 0.019, odds ratio (OR) = 1.367, 95% confidence interval (CI) = 1.051-1.776]. Strong linkage disequilibrium was observed in block 1 (D' > 0.9). However, significant evidence of linkage disequilibrium was not observed between the 7 SNPs in our sample population. These data suggest that GRIN2A gene polymorphisms confer susceptibility to heroin addiction and support the hypothesis that dysfunction of GRIN2A is involved in the pathophysiological process of heroin addiction.

Roles of functional NFKB1 and β-TrCP insertion/deletion polymorphisms in mRNA expression and epithelial ovarian cancer susceptibility

Epithelial ovarian cancer (EOC) is the leading cause of death among all gynecological cancers. Nuclear factor-kappa B (NF-κB) is involved in carcinogenesis and in the development of EOC. The β-transducin repeat-containing protein (β-TrCP) is a positive regulator of the NF-κB signaling pathway. Recent studies have indicated that the -94 ins/del ATTG polymorphism in the promoter region of the NFKB1 gene, and the 9N ins/del polymorphism in the 3'-untranslated region of the β-TrCP gene are associated with increased susceptibility to a variety of cancers. We examined a potential association between these two polymorphisms and EOC. Genotypes were determined for 187 patients with EOC and 221 healthy control subjects, using the MassARRAY system. We found a significant association between the -94 ins/del ATTG genotype distribution and EOC. The frequency of the -94 del ATTG allele was significantly lower in EOC patients compared to healthy controls. The NF-κB mRNA level in cancer tissue was significantly correlated with -94 ins/del ATTG genotypes. Compared to the ATTG1/ATTG1 phenotype, the NF-κB mRNA level was 2.089 and 1.257 times higher in the ATTG2 (insertion)/ATTG2 homozygote and the ATTG1 (deletion)/ATTG2 heterozygote, respectively. However, we found no evidence of association between the 9N ins/del polymorphism of the β-TrCP gene and EOC in this Chinese population. Based on these results, we suggest that the NF-κB -94 ins/del ATTG polymorphism is a risk factor for EOC susceptibility.

Uptake of liposomes by cultured cardiomyocytes

Small unilamellar liposomes (SUV) of different phospholipid/polymer composition were labeled with NBD-PC, which served as a bilayersituated fluorescence marker. Neonatal cardiomyocytes were incubated with liposomes and then the cell-associated fluorescence was measured. The factors influencing the liposome uptake by cardiomyocytes such as concentration of lipid, time of incubation, membrane fluidity of liposomes, charge lipid/polymer modification of liposomes and anoxia of cultured cardiomyocytes were investigated. The liposome uptake by cardiomyocytes increased dose-dependently and time-dependently. Liposome uptake was strongly influenced by the electrical charge and modified polymer. After 2 h incubation, the uptake of positively charged liposomes was 1.7-fold higher than that of negatively charged one and both higher than that of the neutral one. The presence of PE-PEG2000 distinctly reduced the liposome uptake and the difference between the uptake of charged and neutral liposome. Anoxia increased the uptake of liposome at the first hour (increased 20%), but after 2 h incubation the liposome uptake by hypoxia cellswas less than that of normoxia cells (decreased 18%). Mechanisms involved are also discussed.

Enhanced oral bioavailability of breviscapine after encapsulation in a liposomal formulation

This report firstly describes the pharmacokinetic study of liposomal breviscapine (LB) after oral administration in rats. The mean Cmax and AUC(0-->t) of LB were 3.3 and 3.1-fold higher than those of breviscapine solution (BS). The oral absorption of breviscapine was significantly increased after encapsulation in the liposomal formulation.

Binding of the initiation factor sigma(70) to core RNA polymerase is a multistep process

The interaction of RNA polymerase and its initiation factors is central to the process of transcription initiation. To dissect the role of this interface, we undertook the identification of the contact sites between RNA polymerase and sigma(70), the Escherichia coli initiation factor. We identified nine mutationally verified interaction sites between sigma(70) and specific domains of RNA polymerase and provide evidence that sigma(70) and RNA polymerase interact in at least a two-step process. We propose that a cycle of changes in the interface of sigma(70) with core RNA polymerase is associated with progression through the process of transcription initiation.

degS (hhoB) is an essential Escherichia coli gene whose indispensable function is to provide sigma (E) activity

DegS (HhoB), a putative serine protease related to DegP/HtrA, regulates the basal and induced activity of the essential Escherichia coli sigma factor sigma (E), which is involved in the cellular response to extracytoplasmic stress. DegS promotes the destabilization of the sigma (E)-specific anti-sigma factor RseA, thereby releasing sigma (E) to direct gene expression. We demonstrate that degS is an essential E. coli gene and show that the essential function of DegS is to provide the cell with sigma (E) activity. We also show that the putative active site of DegS is periplasmic and that DegS requires its N-terminal transmembrane domain for its sigma (E)-related function.

[Changes of ultrastructure and function of the aortic endothelium in streptozotocin-diabetic rats and effect of perindopril]

To investigate the alteration of ultrastructure and function of the aortic endothelium in streptozotocin (STZ)-diabetic rats and the effect of perindopril, male SD rats were randomly divided into normal group (NC), diabetes control group (DC), diabetes group treated with perindopril (2 mg.kg-1.d-1) which was administered after 4 weeks. At 4, 8, 16 weeks after injecting STZ, glucose, plasma endothelin-1 and angiotensin II were respectively measured, and we also observed aortic endothelial cell under the electron microscope.

RESULTS

In DC group, there were mitochondrial edema and vacuolization obviously in aortic endothelial cells at 8 weeks, and extensive endothelial cell necrosis and exfoliation were observed at 16 weeks, while pathological changes in the DP group were abated significantly. Plasma Ang II levels were increased significantly at different times in DC group, and plasma ET-1 levels were obviously increased at 8 weeks and greatly decreased at 16 weeks. In DP groups, plasma Ang II levels obviously decreased, ET-1 levels declined at 8 weeks and statistically elevated at 16 weeks.

CONCLUSION

There are changes of ultrastructure and function in aortic endothelial cell in different durations of diabetes. Plasma ET-1 level may be a marker of aortic endothelial cell injury, perindopril may have protective effect on aortic endothelial cell in diabetic rats.

In vitro studies on cellular and molecular mechanisms of arsenic trioxide (As2O3) in the treatment of acute promyelocytic leukemia: As2O3 induces NB4 cell apoptosis with downregulation of Bcl-2 expression and modulation of PML-RAR alpha/PML proteins

It has been shown recently in China that arsenic trioxide (As2O3) is a very effective treatment for acute promyelocytic leukemia (APL). APL patients resistant to all-trans retinoic acid (ATRA) and conventional chemotherapy can still respond to AS2O3. In this study, we addressed the possible cellular and molecular mechanisms of this treatment by using NB4 cells as a model. The results show that: (1) As2O3 triggers relatively specific NB4 cell apoptosis at micromolar concentration, as proved by morphology, histogramic related nuclear DNA contents, and DNA gel eletrophoresis. (2) As2O3 does not influence bax, bcl-x, c-myc, and p53 gene expression, but downregulates bcl-2 gene expression at both mRNA and protein levels. (3) As2O3 induces a significant modulation of the PML staining pattern in NB4 cells and HL-60 cells. The micropunctates characteristic of PML-RAR alpha in NB4 cells dissappear after treatment with As2O3, whereas a diffuse PML staining occurs in the perinuclear cytoplasmic region. In addition, a low percentage of untreated NB4 cells exhibits an accumulation of PML positive particles in a compartment of cytoplasm. The percentage of these cells can be significantly increased after As2O3 treatment. A similar PML staining pattern is observed in apoptotic cells. (4) ATRA pretreatment does not influence As2O3-induced apoptosis. These results suggest that induction of cell apoptosis can be one of the mechanisms of the therapeutic effect of As2O3. Moreover, this apoptosis induction occurs independently of the retinoid pathway and may be mediated, at least partly, through the modulation of bcl-2, as well as PML-RAR alpha and/ or PML proteins.

Pharmacokinetics and efficacy of low-dose all-trans retinoic acid in the treatment of acute promyelocytic leukemia

A clinical trial was conducted in order to evaluate the therapeutic effect and side-effects of low-dose ATRA in the treatment of acute promyelocytic leukemia (APL). We compared the pharmacokinetic features in normal individuals with single oral ATRA at 15 mg/m2 and 45 mg/m2, respectively. The results showed that maximal plasma concentration (Cpmax) with oral 15 mg/m2 ATRA was high enough (10(-6) M) to induce APL cell differentiation. Based on these results, 27 cases of de novo APL patients were treated with continuous oral ATRA at the dose of 15-20 mg/m2/day and 24/26 evaluable cases (92%) achieved clinical CR after 13 to 67 days of ATRA treatment. No patient experienced RAS and DIC. The Cpmax with a single dose of ATRA on day 1 of treatment and immediately at CR obtained with continuous ATRA in three cases demonstrated similar values in one patient and an approximately two-fold decrease in two patients. More importantly, compared with a relatively well-matched historic group of 20 APL patients treated with high-dose ATRA, our results suggest that low-dose ATRA is as effective as high-dose in treating APL patients and may provide advantages through decreased hyperleukocytosis and other side-effects.

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.