Post-translational Modifications of PML in Regulating the Functions of Nuclear Bodies --Review / 中国实验血液学杂志

Abstract　　The promyelocytic leukemia (PML) gene encoded PML protein as a tumor suppressor protein, plays important roles in the occurrence and development of various cancers including acute promyelocytic leukemia. Recent studies have indicated that there are a variety of post-translational modifications of the PML protein, such as SUMOylation, ubiquitination, phosphorylation, and acetylation in cells. These modifications of the PML protein can directly affect the formation of PML nuclear bodies (PML-NBs), repair DNA damage, and modulate cell apoptosis. Furthermore, the abnormal modifications of PML not only result in the occurrence of hematopoietic tumors, but also are closely related to the drug-resistance of cancer. Therefore, investigating the post-translational modifications of PML is significant to uncover the mechanism of formation and functions of PML-NBs, thus contributing to the prevention and treatment of related hematopoietic tumors. In this review, the characteristics of the post-translational modifications of PML protein and the relationship between these modifications and functions of PML-NBs are summarized so as to provide the potential targets for the treatment of related cancers.

BRD4 interacts with PML/RARα in acute promyelocytic leukemia / 医学前沿

Bromodomain-containing 4 (BRD4) has been considered as an important requirement for disease maintenance and an attractive therapeutic target for cancer therapy. This protein can be targeted by JQ1, a selective small-molecule inhibitor. However, few studies have investigated whether BRD4 influenced acute promyelocytic leukemia (APL), and whether BRD4 had interaction with promyelocytic leukemia-retinoic acid receptor α (PML/RARα) fusion protein to some extent. Results from cell viability assay, cell cycle analysis, and Annexin-V/PI analysis indicated that JQ1 inhibited the growth of NB4 cells, an APL-derived cell line, and induced NB4 cell cycle arrest at G1 and apoptosis. Then, we used co-immunoprecipitation (co-IP) assay and immunoblot to demonstrate the endogenous interaction of BRD4 and PML/RARα in NB4 cells. Moreover, downregulation of PML/RARα at the mRNA and protein levels was observed upon JQ1 treatment. Furthermore, results from the RT-qPCR, ChIP-qPCR, and re-ChIP-qPCR assays showed that BRD4 and PML/RARα co-existed on the same regulatory regions of their target genes. Hence, we showed a new discovery of the interaction of BRD4 and PML/RARα, as well as the decline of PML/RARα expression, under JQ1 treatment.

Involvement of PML proteins in treatment of acute promyelocytic leukemia with arsenic trioxide / 浙江大学学报·医学版

Promyelocytic leukemia (PML) protein, a tumor suppressor, plays an important role in patients with acute promyelocytic leukemia (APL) receiving arsenic trioxide (AsO) therapy. APL is a M3 subtype of acute myeloid leukemia (AML), which is characterized by expression of PML-RARα (P/R) fusion protein, leading to the oncogenesis. AsO is currently used as the first-line drug for patients with APL, and the mechanism may be:AsO directly binds to PML part of P/R protein and induces multimerization of related proteins, which further recruits different functional proteins to reform PML nuclear bodies (PML-NBs), and finally it degraded by SUMOylation and ubiquitination proteasomal pathway. Gene mutations may lead to relapse and drug resistance after AsO treatment. In this review, we discuss the structure and function of PML proteins; the pathogenesis of APL induced by P/R fusion protein; the involvement of PML protein in treatment of APL patient with AsO; and explain how PML protein mutations could cause resistance to AsO therapy.

Effects of single heat stress treatment on spermatogenic cells in mice / 中华男科学杂志

<p><b>OBJECTIVE</b>To investigate the effects of single heat stress treatment on spermatogenic cells in mice.</p><p><b>METHODS</b>We randomly divided 36 C57 male mice into a control and a heat stress treatment group and submerged the lower part of the torso in water at 25 °C and 43 °C, respectively, both for 15 minutes. At 1, 7, and 14 days after treatment, we obtained the testicular organ indexes, observed the changes in testicular morphology by HE staining, and determined the location and expression levels of the promyelocytic leukemia zinc finger (PLZF) and synaptonemal comlex protein-3 (SCP-3) in the testis tissue by immunohistochemistry and Western blot.</p><p><b>RESULTS</b>The testicular organ index was significantly lower in the heat stress treatment than in the control group (P < 0.05). Compared with the controls, the heat shock-treated mice showed loosely arranged spermatogenic cells scattered in the seminiferous tubules at 1 day after heat stress treatment, atrophied, loosely arranged and obviously reduced number of spermatogenic cells at 7 days, and relatively closely arranged seminiferous tubules and increased number and layers of spermatogenic cells at 14 days. The number of SCP-3 labelled spermatocytes obviously decreased in the heat stress-treated animals at 1 and 7 days and began to increase at 14 days. The PLZF protein expression was significantly reduced in the heat stress treatment group at 1 day as compared with that in the control (0.19 ± 0.12 vs 0.64 ± 0.03, P < 0.01), but elevated to 0.77 ± 0.02 at 7 and 14 days, even remarkably higher than in the control animals (P < 0.01).</p><p><b>CONCLUSION</b>Heat stress treatment can induce short-term dyszoospermia in mice, which can be recovered with the prolonged time after treatment.</p>

Research progress in cytoplasmic PML gene functions / 中国实验血液学杂志

The promyelocytic leukemia (PML) was originally identified and named as acute promyelocytic leukaemia (APL) . The PML, encoded by PML gene, locates in the nuclear body (NB) and shuttles in the cell nucleus-cytoplasm, so that PML completes many regulation functions. There are many research on the function of nuclear PML, but in recent years the foreign data indicate that cytoplasmic PML gene plays an important role in hematologic malignancies and solid tumors. In this article, the biological functions of PML gene in cytoplasm are reviewed.

Progress of study on PML in cancer stem cell of hematologic malignancies / 中国实验血液学杂志

The promyelocytic leukemia protein (PML), encoded by PML gene, plays a tumor suppressor in acute promyelocytic leukemia and other hematologic malignancies. Recent evidence indicates that PML involves in regulating multiple cell biological function, regulates self-renewal and maintains stable function in stem cell/cancer stem cell of multiple tissues, leading to drug resistance of cancer. This review summarizes the latest research advances about the relationship and therapeutic options between PML and cancer stem cell of hematologic neoplasms, aiming to propose a new avenue for blood cancer treatment.

Effect of topical application of a recombinant adenovirus carrying promyelocytic leukemia gene in a psoriasis-like mouse model / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the effects of topical treatment with adenovirus-mediated promyelocytic leukemia gene (PML) gene in a psoriasis-like mouse model.</p><p><b>METHODS</b>The effect of adenovirus-mediated PML gene on the granular layer of mouse tail scale epidermis and epithelial mitosis were observed on longitudinal histological sections prepared from the tail skin and vaginal epithelium of the mice.</p><p><b>RESULTS</b>Adenovirus-mediated PML gene significantly inhibited mitosis of mouse vaginal epithelial cells and promoted the formation of granular layer in mouse tail scale epidermis.</p><p><b>CONCLUSION</b>The therapeutic effect of PML gene in the psoriasis-like mouse model may be associated with increased granular cells and suppressed epidemic cell proliferation.</p>

Expression of promyelocytic leukaemia protein in Bowen's disease, skin squamous cell carcinoma and basal cell carcinoma / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the expression of promyelocytic leukaemia (PML) protein of PML protein in Bowen's disease (BD), skin squamous cell carcinoma (SCC) and basal cell carcinoma (BCC) and explore the role of PML in the pathogenesis of these diseases.</p><p><b>METHODS</b>PML protein in normal skin tissues and lesions of Bowen's disease, SCC and BCC were detected with immunohistochemistry.</p><p><b>RESULTS</b>Normal skin tissues did not express PML protein. In BCC, PML showed rather low expressions in the skin lesions (8.69% in cell nuclei and 4.35% in cytoplasm). The lesions in BD and SCC (grade I and II) showed obvious overexpression of PML protein in the cell nuclei and cytoplasm, and its expression in the cell nuclei of these lesions was significantly higher than that in grade III-IV SCC.</p><p><b>CONCLUSION</b>PML protein may play an important role in the early stage of SCC, and its overexpression may contribute to the carcinogenesis and metastasis of SCC.</p>

E2FBP1 antagonizes the p16(INK4A)-Rb tumor suppressor machinery for growth suppression and cellular senescence by regulating promyelocytic leukemia protein stability / 国际口腔科学杂志·英文版

Cellular senescence is an irreversible cell cycle arrest triggered by the activation of oncogenes or mitogenic signaling as well as the enforced expression of tumor suppressors such as p53, p16(INK4A) and promyelocytic leukemia protein (PML) in normal cells. E2F-binding protein 1 (E2FBP1), a transcription regulator for E2F, induces PML reduction and suppresses the formation of PML-nuclear bodies, whereas the down-regulation of E2FBP1 provokes the PML-dependent premature senescence in human normal fibroblasts. Here we report that the depletion of E2FBP1 induces the accumulation of PML through the Ras-dependent activation of MAP kinase signaling. The cellular levels of p16(INK4A) and p53 are elevated during premature senescence induced by depletion of E2FBP1, and the depletion of p16(INK4A), but not p53 rescued senescent cells from growth arrest. Therefore, the premature senescence induced by E2FBP1 depletion is achieved through the p16(INK4A)-Rb pathway. Similar to human normal fibroblasts, the growth inhibition induced by E2FBP1 depletion is also observed in human tumor cells with intact p16(INK4A) and Rb. These results suggest that E2FBP1 functions as a critical antagonist to the p16(INK4A)-Rb tumor suppressor machinery by regulating PML stability.

Clinical and laboratory features of patients with CD34(+) acute promyelocytic leukemia / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To explore the expression of CD34 in patients with acute promyelocytic leukemia (APL) and investigate the clinical and laboratory features of CD34(+) APL patients.</p><p><b>METHODS</b>262 APL patients diagnosed by chromosome analysis and/or fusion gene examination in the last five years were retrospectively analyzed in this study. To survey the expression of CD34 in those patients, all the cases were divided into two groups (CD34(+) APL vs. CD34(-) APL). The clinical features including age, gender, abnormal values of the peripheral hemogram before treatment, the complete remission (CR) rate and the incidence of DIC and laboratory data such as the results of morphology, immunology, cytogenetics and molecular biology (MICM) between those two groups were compared.</p><p><b>RESULTS</b>Of the 262 APL patients, 38 (14.5%) cases were positive for CD34 expression. There were no statistically significant differences between CD34(+) APL and CD34(-) APL groups in gender and age (P > 0.05). Before treatment, the median level of WBC in CD34(+) APL was 25.92 x 10(9)/L, which was significantly higher than that of CD34(-) APL (5.3 x 10(9)/L, P < 0.05). CD34(+) APL by morphology classification were mostly of the subtypes M3b and M3v (65.8%), while these subtypes in CD34(-) APL (40.3%) were significantly less (P < 0.01). There were no statistically significant differences between the two groups compared in respect of complete remission (CR) rate and the incidence of DIC (P > 0.05). The expression level of CD34 in APL had correlation to the expression level of CD2, CD7 and CD117; the latter three phenotypes in CD34(+) APL were significantly higher than those in CD34(-) APL (P < 0.01). No significant difference was found between those two groups by chromosome analysis, but there was more PML-RAR-alpha transcript short form in CD34(+) APL than that in CD34(-) APL (P < 0.05).</p><p><b>CONCLUSION</b>CD34(+) acute promyelocytic leukemia is a unique subtype of APL with different biological characteristics.</p>

Expression of PML in carcinogenesis of laryngocarcinoma and nasopharyngeal carcinoma / 临床耳鼻咽喉头颈外科杂志

OBJECTIVE@#To explore the significance of PML expression in carcinogenesis of laryngocarcinoma and nasopharyngeal carcinoma.@*METHOD@#The PML expression in 56 laryngocarcinoma tissues and 34 nasopharyngeal carcinoma tissues were examined by immunohistochemistry. Moreover, the relationship between the PML expression, with the pathologic grade,T stage and lymph node metastasis was analyzed.@*RESULT@#The PML expression decreased with the ascending of pathological tumor grade (P < 0.05) and with the increasing of T grade of tumor (P < 0.05). The expression of PML in nasopharyngeal carcinoma was lower than that in carcinoma of larynx (P < 0.05). However, either in laryngocarcinoma or in nasopharyngeal carcinoma, there was no statistical difference on PML expression between with and without lymph node metastasis in laryngo carcinoma tissues and nasopharyngeal carcinoma tissues.@*CONCLUSION@#The close relationship between PML expression and the malignant parameters such as pathological grade and T grade of laryngocarcinoma and nasopharyngeal carcinoma, indicated that PML may play a role in cancer repression but not in cancer metastasis.

Inhibition of promyelocytic leukemia gene by tazarotene in hyperproliferative epidermis of psoriasis / 南方医科大学学报

<p><b>OBJECTIVE</b>To investigate the mechanism of tazarotene against active psoriasis vulgaris.</p><p><b>METHODS</b>A randomized, controlled trial was conducted in 43 patients with active psoriasis vulgaris, who were divided into tazarotene and control groups. Promyelocytic leukemia (PML) mRNA in active psoriatic lesions before and 14 days after tazarotene treatment was detected by in situ hybridization.</p><p><b>RESULTS</b>PML mRNA expression was detected not only in the basal layer (86.96%), but also in the suprabasal layers of the epidermis in the manner of focal expression (78.26%). After tazarotene treatment, virtually no PML mRNA expression could be detected in the psoriatic lesions (8.69% in the basal layer and 4.35% in the suprabasal layers). PML mRNA expression in the control group underwent no obvious changes during the observation.</p><p><b>CONCLUSIONS</b>Tazarotene may inhibit abnormal proliferation of keratinocytes through down-regulating PML gene expression in active psoriatic epidermis.</p>

Transcriptional repression of hDaxx enhanced by adenovirus 12 E1B 55-kDa oncoprotein interacting with hDaxx / 中华医学杂志(英文版)

<p><b>BACKGROUND</b>Daxx has been identified as a nuclear protein that involves in apoptosis and transcriptional repression. Daxx co-localizes with the promyelocytic leukemia (PML) protein and regulates transcription. Human Daxx (hDaxx) is a protein that functions as a transcriptional regulation through its interaction with some DNA-associated proteins. The aim of this study was to explore the transcriptional regulatory effect of hDaxx interacting with adenovirus (Ad) 12 E1B (Ad12E1B) 55-kDa oncoprotein.</p><p><b>METHODS</b>The co-localization of hDaxx-Ad12E1B or hDaxx-PML protein in the nucleus was observed under a confocal microscope. Interaction of hDaxx and Ad12E1B was analyzed by yeast two-hybrid assay. Direct binding of hDaxx and Ad12E1B was analyzed using coimmunoprecipitation and Western blot in vivo and in vitro. The activity of a luciferase reporter gene, which was regulated by an hDaxx modulated thymidine kinase (TK) promoter, was detected in an automat luminometer.</p><p><b>RESULTS</b>Ad12E1B, which co-localized with hDaxx in the nuclei of G401-CC3 cells, disrupted the co-localization of hDaxx and PML in the PML oncogenic domains (PODs). hDaxx bound directly to Ad12E1B in vivo and in vitro. hDaxx interacted with Ad12E1B along its full length. Ad12E1B enhanced transcriptional repression activity of hDaxx.</p><p><b>CONCLUSION</b>Ad12E1B disrupts the co-localization of hDaxx with PML in PODs and enhances transcriptional repression activity of hDaxx.</p>

Overexpression of the promyelocytic leukemia gene suppresses growth of human bladder cancer cells by inducing G1 cell cycle arrest and apoptosis / 中华医学杂志(英文版)

<p><b>OBJECTIVES</b>To examine the anti-oncogenic effects of promyelocytic leukemia (PML) on bladder cancer and to explore its molecular mechanisms of growth suppression.</p><p><b>METHODS</b>Wild-type PML was transfected into bladder cancer cells (5637 cell) and expressed in a replication-deficient adenovirus-mediated gene delivery system and introduced into human bladder cancer cells (5637 cell) in vitro and in vivo. The effect and mechanisms of the PML gene in cell growth, clonogenicity, and tumorigenicity of bladder cancer cells were studied using in vitro and in vivo growth assays, soft agar colony-forming assay, cell cycle analysis, apoptosis assay and in vivo tumorigenicity assay.</p><p><b>RESULTS</b>Overexpression of PML in 5637 cells significantly reduced their growth rate and clonogenicity on soft agar. PML suppressed bladder cancer cell growth by inducing G1 cell cycle arrest and apoptosis. Adenovirus-mediated PML (Ad-PML) significantly suppressed the tumorigenicity and growth of bladder cancer cells. Intratumoral injection of Ad-PML into tumors induced by 5637 cells dramatically suppressed their growth.</p><p><b>CONCLUSIONS</b>The results indicated that overexpression of PML protein may promote efficient growth inhibition of human bladder cancer cells by inducing G1 cell cycle arrest and apoptosis, and adenovirus-mediated PML (Ad-PML) expression efficiently suppresses human bladder cancer growth.</p>

Mechanism of arsenic trioxide-induced apoptosis in hepatic blastoma cells HepG2 / 中华肿瘤杂志

<p><b>OBJECTIVE</b>To investigate the mechanism of arsenic trioxide (As(2)O(3)) induced apoptosis in hepatic blastoma cells HepG2 and its effects on cell nuclear matrix related protein promyelocytic leukaemia (PML).</p><p><b>METHODS</b>HepG2 cells were cultured in MEM medium and treated with different concentrations of As(2)O(3) for either 24 h or 96 h. In situ terminal deoxynucleotidyl transferase (TdT) labeling (TUNEL) and DNA ladder were applied to detect apoptosis. Confocal microscopy and western blot were performed to observe the expression of PML.</p><p><b>RESULTS</b>TUNEL positive apoptotic cells and DNA ladder could be detected in As(2)O(3) treated groups. The expression of PML decreased in HepG2 cells with 2 micro mol/L As(2)O(3), and micropunctates characteristic of PML protein in HepG2 cell nuclei almost disappeared after the treatment of 5 micro mol/L As(2)O(3).</p><p><b>CONCLUSION</b>As(2)O(3) induces HepG2 tumor cell apoptosis in a time- and concentration-dependent manner. As(2)O(3) may degradate the PML protein in HepG2 cell nuclei. The decreased expression of PML is closely correlated with apoptosis. Nuclear matrix associated protein PML could be the target of As(2)O(3) therapy.</p>

Nuclear matrix associated protein PML: an arsenic trioxide apoptosis therapeutic target protein in HepG2 cells / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate arsenic trioxide (As(2)O(3))-induced apoptosis and the effects on cell nuclear matrix related protein promyelocytic leukaemia (PML).</p><p><b>METHODS</b>HepG2 cells were cultured in MEM medium and treated with 0.5, 2, 5 and 10 micro mol/L As(2)O(3) for either 24 h or 96 h at each concentration. In situ terminal deoxynucleotidyl transferase (TdT) labeling (TUNEL) and DNA ladders were used to detect apoptosis. Confocal microscopy and Western blotting were used to observe the expression of PML.</p><p><b>RESULTS</b>The growth rates of HepG2 cells were slower in the As(2)O(3) treated than the untreated control group. DNA ladder and TUNEL positive apoptotic cells could be detected in As(2)O(3) treated groups. The expression of PML decreased in HepG2 cells with 2 micro mol/L As(2)O(3) treatment. Confocal images demonstrated that the expression of PML protein in HepG2 cell nuclei decreased after treatment with 2 micro mol/L As(2)O(3), and micropunctates characteristic of PML protein in HepG2 cell nuclei disappeared after treatment with 5 micro mol/L As(2)O(3).</p><p><b>CONCLUSIONS</b>Our results show that arsenic trioxide can significantly inhibit the growth of HepG2 cells in vitro. As(2)O(3) induces apoptosis in HepG2 tumor cells in a time and concentration dependent manner. As(2)O(3) may degrade the PML protein in HepG2 cell nuclei. The decreased expression of PML in As(2)O(3) treated tumor cells is most likely to be caused by apoptosis. Nuclear matrix associated protein PML could be the target of As(2)O(3) therapy.</p>

Effects of red orpiment on cell morphology and expression of PML mRNA and protein in NB4 and HL-60 cells / 中华医学杂志(英文版)

<p><b>OBJECTIVE</b>To investigate the effects of red orpiment on cell morphology, expression of promyelocytic leukemia (PML) mRNA and its protein localization in NB4 and HL-60 cell lines.</p><p><b>METHODS</b>Cell morphology was assayed by Wright's staining and fluorescence staining, while PML mRNA expression was determined by RT-PCR. PML protein localization by evaluated by immunofluorescence staining.</p><p><b>RESULTS</b>The typical apoptosis was found in NB4 and HL-60 cells after treatment with red orpiment. The fusion protein was no longer observed in NB4 cells, PML protein was relocated, and then degraded. In HL-60 cells, PML protein underwent a similar progress. The expression of promyelocytic leukemia (PML) mRNA was not changed in the treated cells.</p><p><b>CONCLUSION</b>Red orpiment inhibits the proliferation of leukemia cells by inducing them to undergo apoptosis.</p>

Change of PML/PML-RARalpha protein during treatment with tetraarsenic tetrasulfide (As4S4) in patients with acute promyelocytic leukemia / 中国实验血液学杂志

In order to explored the change of PML/PML-RARalpha protein during tetraarsenic tetrasulfide (As4S4) treatment, acute promyelocytic leukemia (APL) cells from a group of newly diagnosed APL patients were examined by indirect immunofluorescence staining with anit-PML monoclonal antibody. The results showed that all samples typically presented many microspeckle signals throughout the nucleus before treatment. The redistribution occurred as early as on the second day after As4S4 treatment, which revealed loss of microspeckles with the presentation of a few large speckles. Anti-PML staining also emerged in the perinuclear cytoplasm. At last, microspeckles and large speckles all disappeared. When the therapy was combining all-trans-retinoic acid (ATRA) with As4S4, similar results were obtained. However, APL cells from patients treated with ATRA alone performed totally different appearance, presenting microspeckles and large speckles at the same time, followed with entirely large speckles. The conclusion is that As4S4 makes redistribution of PML/PML-RARalpha protein in leukemic cells from APL patients during the treatment, which is quite different from that during the treatment of ATRA.

Study of the effects of quercetin on PML gene and protein expression and localization in leukemia cells / 中华血液学杂志

<p><b>OBJECTIVE</b>To investigate PML gene and protein expression and localization in leukemia cell lines.</p><p><b>METHODS</b>Cell morphology was assayed by Wright and fluorescence stain, PML mRNA expression by RT-PCR, and PML protein localization by immunofluorescence.</p><p><b>RESULTS</b>(1) Differentiation was observed by morphology in NB4 and HL-60 cells after treatment with all-trans retinoic acid (ATRA) while K562 cells did not show. Apoptosis was found in each cell line after treatment with quercetin. (2) After treatment with ATRA, the fusion protein disappeared and PML protein resumed in NB4 cells, while in HL-60 and K562 cells there was no difference from control cells. After treatment with quercetin, the fusion protein disappeared in NB4 cells, then degraded, and so did in HL-60 cells and K562 cells. (3) The expression of PML mRNA had no change in all the three cell lines after treatment with ATRA or quercetin.</p><p><b>CONCLUSION</b>PML plays a role of differentiation and apoptosis induction in leukemia cells at the translational level. PML in POD plays a role of apoptosis induction and growth control of leukemia cells.</p>