FAM3D is essential for colon homeostasis and host defense against inflammation associated carcinogenesis.

The physiological homeostasis of gut mucosal barrier is maintained by both genetic and environmental factors and its impairment leads to pathogenesis such as inflammatory bowel disease. A cytokine like molecule, FAM3D (mouse Fam3D), is highly expressed in mouse gastrointestinal tract. Here, we demonstrate that deficiency in Fam3D is associated with impaired integrity of colonic mucosa, increased epithelial hyper-proliferation, reduced anti-microbial peptide production and increased sensitivity to chemically induced colitis associated with high incidence of cancer. Pretreatment of Fam3D-/- mice with antibiotics significantly reduces the severity of chemically induced colitis and wild type (WT) mice co-housed with Fam3D-/- mice phenocopy Fam3D-deficiency showing increased sensitivity to colitis and skewed composition of fecal microbiota. An initial equilibrium of microbiota in cohoused WT and Fam3D-/- mice is followed by an increasing divergence of the bacterial composition after separation. These results demonstrate the essential role of Fam3D in colon homeostasis, protection against inflammation associated cancer and normal microbiota composition.

PSMP/MSMP promotes hepatic fibrosis through CCR2 and represents a novel therapeutic target.

BACKGROUND & AIMS: C-C motif chemokine receptor 2 (CCR2) has been recognized as a promising target for the treatment of liver fibrosis. PC3-secreted microprotein (PSMP)/microseminoprotein (MSMP) is a novel chemotactic cytokine and its receptor is CCR2. In the present study we investigated the expression and role of PSMP in liver fibrosis/cirrhosis. METHODS: PSMP expression was studied in patients with fibrosis/cirrhosis and in 3 murine models of liver fibrosis, including mice treated with carbon tetrachloride (CCl4), bile-duct ligation, or a 5-diethoxycarbonyl-1,4-dihydrocollidine diet. The role of PSMP was evaluated in Psmp-/- mice and after treatment with a PSMP antibody in wild-type mice. The direct effects of PSMP on macrophages and hepatic stellate cells were studied in vitro. RESULTS: In this study, we found that PSMP was highly expressed in fibrotic/cirrhotic tissues from patients with different etiologies of liver disease and in the 3 experimental mouse models of fibrosis. Damage-associated molecular pattern molecules HMGB-1 and IL-33 induced hepatocytes to produce PSMP. PSMP deficiency resulted in a marked amelioration of hepatic injury and fibrosis. In CCl4-induced hepatic injury, the infiltration of macrophages and CCR2+ monocytes into the liver was significantly decreased in Psmp-/- mice. Consistent with the decreased levels of intrahepatic macrophages, proinflammatory cytokines were significantly reduced. Moreover, adeno-associated virus-8 vectors successfully overexpressing human PSMP in Psmp-/- mouse livers could reverse the attenuation of liver injury and fibrosis induced by CCl4 in a CCR2-dependent manner. Treatment with a specific PSMP-neutralizing antibody, 3D5, prevented liver injury and fibrosis induced by CCl4 in mice. At the cellular level, PSMP directly promoted M1 polarization of macrophages and activation of LX-2 cells. CONCLUSION: PSMP enhances liver fibrosis through its receptor, CCR2. PSMP is a potentially attractive therapeutic target for the treatment of patients with liver fibrosis. LAY SUMMARY: Our present study identifies the essential role of the protein PSMP for the development and progression of liver fibrosis in humans and mice. PSMP promotes liver fibrosis through inflammatory macrophage infiltration, polarization and production of proinflammatory cytokines, as well as direct activation of hepatic stellate cells via its receptor CCR2. A PSMP antibody can significantly reduce liver fibrosis development in vivo. These findings indicate that PSMP is a potential therapeutic target and its antibody is a potential therapeutic agent for the treatment of liver fibrosis.

FAM19A1 is a new ligand for GPR1 that modulates neural stem-cell proliferation and differentiation.

FAM19A1 is a member of the family with sequence similarity 19 with unknown function. FAM19A1 mRNA expression is restricted to the CNS. Here, we report that FAM19A1 is a classic secretory protein, and expression levels correlate with brain development, increasing from embryonic d 12.5, peaking between postnatal d (P)1 and P7 and decreasing at wk 8. The adult hippocampus is a region of FAM19A1 high expression. Recombinant FAM19A1 suppressed the proliferation and self-renewal of neural stem cells (NSCs) and altered the lineage progression of NSCs with promoted neuron differentiation and suppressed astrocyte differentiation. Although GPCR 1 (GPR1) has been reported to be expressed in the CNS, its functions in the brain remain unclear. We identified GPR1 to be a functional receptor for FAM19A1. FAM19A1 interacted with GPR1 via the N-terminal domain (GPR1-ND), and its NSC modulatory functions required the Rho-associated protein kinase (ROCK) /ERK1/2 and ROCK/signal transducer and activator of transcription 3 signaling pathways. GPR1-ND that selectively bound to FAM19A1 neutralized the effects of FAM19A1 on NSC functions. Taken together, our results show, for the first time to our knowledge, that FAM19A1 is a novel regulatory factor of the proliferation and differentiation of NSCs, and identified a novel mechanism by which GPCR mediates the effects of FAM19A1 on NSC functions that may be important for brain development and neurogenesis. Additional exploration of the functions of FAM19A1 and GPR1 in the CNS may broaden the range of therapeutic options available for major brain disorders.-Zheng, C., Chen, D., Zhang, Y., Bai, Y., Huang, S., Zheng, D., Liang, W., She, S., Peng, X., Wang, P., Mo, X., Song, Q., Lv, P., Huang, J., Ye, R. D., Wang, Y. FAM19A1 is a new ligand for GPR1 that modulates neural stem-cell proliferation and differentiation.

LRRC25 plays a key role in all-trans retinoic acid-induced granulocytic differentiation as a novel potential leukocyte differentiation antigen.

Leukocyte differentiation antigens (LDAs) play important roles in the immune system, by serving as surface markers and participating in multiple biological activities, such as recognizing pathogens, mediating membrane signals, interacting with other cells or systems, and regulating cell differentiation and activation. Data mining is a powerful tool used to identify novel LDAs from whole genome. LRRC25 (leucine rich repeat-containing 25) was predicted to have a role in the function of myeloid cells by a large-scale "omics" data analysis. Further experimental validation showed that LRRC25 is highly expressed in primary myeloid cells, such as granulocytes and monocytes, and lowly/intermediately expressed in B cells, but not in T cells and almost all NK cells. It was down-regulated in multiple acute myeloid leukemia (AML) cell lines and bone marrow cells of AML patients and up-regulated after all-trans retinoic acid (ATRA)-mediated granulocytic differentiation in AML cell lines and acute promyelocytic leukemia (APL; AML-M3, FAB classification) cells. Localization analysis showed that LRRC25 is a type I transmembrane molecule. Although ectopic LRRC25 did not promote spontaneous differentiation of NB4 cells, knockdown of LRRC25 by siRNA or shRNA and knockout of LRRC25 by the CRISPR-Cas9 system attenuated ATRA-induced terminal granulocytic differentiation, and restoration of LRRC25 in knockout cells could rescue ATRA-induced granulocytic differentiation. Therefore, LRRC25, a potential leukocyte differentiation antigen, is a key regulator of ATRA-induced granulocytic differentiation.

The PSMP-CCR2 interactions trigger monocyte/macrophage-dependent colitis.

Monocytes/macrophages have been found to be an important component of colitis. However, the key chemokine that initiates the CCR2+ monocytes migration from circulation to colitis tissue remains to be undiscovered. PC3-secreted microprotein (PSMP) is a novel chemokine whose receptor is CCR2. The physiological and pathological functions of PSMP have not yet been reported. In this study, PSMP was found to be expressed in colitis and colonic tumor tissues from patients and significantly up-regulated in mouse DSS-induced colitis tissues. PSMP overexpression in the colon aggravated the DSS-induced colitis and the anti-PSMP neutralizing antibody mollified the colitis by reducing macrophage infiltration and inhibiting the expression of IL-6, TNF-α and CCL2. Furthermore, we demonstrated that lipopolysaccharide and muramyl dipeptide induced PSMP expression in the colonic epithelial cells. PSMP was up-regulated in the initial stage prior to IL-6, TNF-α and CCL2 up-regulated expression in DSS colitis and promoted the M1 macrophages to produce CCL2. PSMP chemo-attracted Ly6Chi monocytes in a CCR2 dependent manner via in situ chemotaxis and adoptive transfer assays. Our data identify PSMP as a key molecule in ulcerative colitis, which provides a novel mechanism of monocyte/macrophage migration that affects gut innate immunity and makes PSMP a potential target for controlling colitis.

Knockout of MARCH2 inhibits the growth of HCT116 colon cancer cells by inducing endoplasmic reticulum stress.

Membrane-associated RING-CH protein 2 (MARCH2), a member of the MARCH family, functions in vesicle trafficking and autophagy regulation. In this study, we established MARCH2 knockout HCT116 cell lines using CRISPR/Cas9-mediated genome editing to evaluate the role of MARCH2 in colon cancer in vitro and in vivo. Knockout of MARCH2 suppressed cell proliferation, and promoted autophagy, apoptosis and G2/M phase cell cycle arrest. These effects were associated with activation of endoplasmic reticulum (ER) stress. In addition, loss of MARCH2 sensitized HCT116 cells to the chemotherapy drugs etoposide and cisplatin. Moreover, we analyzed the clinical significance of MARCH2 in human colon carcinoma (n=100). High MARCH2 expression was significantly associated with advanced clinicopathological features and poorer overall survival in colon carcinoma. MARCH2 expression correlated negatively with expression of the unfolded protein response molecule p-PERK in colon cancer. Collectively, these data reveal a relationship between MARCH2, ER stress and colon cancer, and indicates MARCH2 may have an important role in the development and progression of colon cancer.

CMTM8 is Frequently Downregulated in Multiple Solid Tumors.

Previous studies have demonstrated that overexpression of CMTM8 inhibits cell growth and induces apoptosis in multiple types of cancer cells, whereas the downregulation of CMTM8 induces the epithelial-to-mesenchymal (EMT)-like phenotype in hepatocyte carcinoma cells, implying its important roles in tumorigenesis and tumor metastasis. No extensive studies on the expression of CMTM8 in either normal or tumorous human tissues have been reported to date. Here, using real-time quantitative polymerase chain reaction, we analyzed CMTM8 expression in multiple normal human tissue samples. Moreover, by applying high-throughput immunohistochemical staining of tissue microarrays with homemade anti-CMTM8 antibodies, we studied CMTM8 expression in carcinoma samples and adjacent normal samples of 6 types of human tissues. CMTM8 is widely expressed in many normal human tissues and is frequently downregulated or absent in multiple solid tumors (liver, lung, colon, rectum, esophagus, stomach). χ tests revealed a significant negative correlation between CMTM8 expression and tumorigenesis: liver, lung (squamous carcinoma), colon, rectum, P<0.0001; esophagus, P<0.001; stomach, P<0.01. Real-time quantitative polymerase chain reaction analysis of samples from esophageal carcinomas and the adjacent normal tissues revealed that CMTM8 mRNA levels are reduced in carcinomas compared with normal tissues, indicating that CMTM8 is potentially downregulated at the mRNA level (P<0.01). This is the first extensive study of CMTM8 expression in both normal and tumorous human tissues. Our findings strongly supported the potential role of CMTM8 as a novel tumor suppressor and may shape further functional studies on this gene.

Functional characterization of the tumor suppressor CMTM8 and its association with prognosis in bladder cancer.

Previous research revealed that CMTM8 acts as a tumor suppressor gene in variety cancers. However, the role of CMTM8 in bladder cancer has never been reported. In this study, the expression profile of CMTM8 was examined in bladder cancer tissues and bladder cancer cell lines. The effects of CMTM8 on bladder cancer cell proliferation, apoptosis, migration, and invasion were examined. Bladder tumor tissues from 84 cases were examined for CMTM8 expression by immunohistochemistry. Disease-specific survival was investigated using a Kaplan-Meier analysis, and Cox proportional hazards analysis was assessed. Our results showed that upregulation of CMTM8 in the T24 cell line could suppress T24 cells proliferation, migration and invasion and enhance the sensitivity to Epirubicin. Kaplan-Meier analysis revealed that the expression of CMTM8 was correlated with the survival time of bladder cancer patients. Altogether, our data suggested that CMTM8 is an important tumor suppressor gene in human bladder cancer and qualified as a useful prognostic indicator for patients with bladder cancer.

PHF23 (plant homeodomain finger protein 23) negatively regulates cell autophagy by promoting ubiquitination and degradation of E3 ligase LRSAM1.

Autophagy is a multistep process that involves the degradation and digestion of intracellular components by the lysosome. It has been proved that many core autophagy-related molecules participate in this event. However, new component proteins that regulate autophagy are still being discovered. At present, we report PHF23 (PHD finger protein 23) with a PHD-like zinc finger domain that can negatively regulate autophagy. Data from experiments indicated that the overexpression of PHF23 impaired autophagy, as characterized by decreased levels of LC3B-II and weakened degradation of endogenous and exogenous autophagic substrates. Conversely, knockdown of PHF23 resulted in opposite effects. Molecular mechanism studies suggested that PHF23 interacts with LRSAM1, which is an E3 ligase key for ubiquitin-dependent autophagy against invading bacteria. PHF23 promotes the ubiquitination and proteasome degradation of LRSAM1. We also show that the PHD finger of PHF23 is a functional domain needed for the interaction with LRSAM1. Altogether, our results indicate that PHF23 is a negative regulator associated in autophagy via the LRSAM1 signaling pathway. The physical and functional connection between the PHF23 and LRSAM1 needs further investigation.

CMTM1_v17 is a novel potential therapeutic target in breast cancer.

Chemokine-like factor (CKLF)-like MARVEL transmembrane domain-containing 1 (CMTM1) consists of at least 23 alternatively spliced isoforms designated CMTM1_v1-v23. In the present study, we detected CMTM1_v17 expression in multiple human normal and tumor tissues and found that CMTM1_v17 was highly expressed in testis and many tumor tissues including breast tumor. The overexpression of CMTM1_v17 in the breast cancer cell line MDA-MB-231 promoted cell proliferation and resistance to tumor necrosis factor-α (TNF-α)-induced apoptosis. Moreover, siRNA-mediated silencing of CMTM1_v17 sensitized MDA-MB-231 cells to TNF-α-induced apoptosis. We propose that CMTM1_v17 may be a novel potential target for therapy in breast cancer patients. The present study provides insight into a novel mechanism by which CMTM1_v17 enhances cellular proliferation and abrogates TNF-α-induced apoptosis. These findings also have implications for clinical practice as they highlight the potential for therapeutic targeting of CMTM1_v17 for the treatment of breast and other cancers in which CMTM1_v17 impacts cellular proliferation and survival.

PC3-secreted microprotein is a novel chemoattractant protein and functions as a high-affinity ligand for CC chemokine receptor 2.

PC3-secreted microprotein (PSMP) or microseminoprotein is a newly discovered secreted protein whose function is currently unknown. In this study, PSMP was found to possess chemotactic ability toward monocytes and lymphocytes, and its functional receptor was identified as CCR2B. PSMP was identified as a chemoattractant protein from a PBMC chemoattractant platform screen that we established. The mature secreted PSMP was able to chemoattract human peripheral blood monocytes, PBLs, and CCR2B-expressing THP-1 cells, but not peripheral blood neutrophils, even though it does not contain the classical structure of chemokines. CCR2B was identified as one receptor for PSMP-mediated chemotaxis by screening HEK293 cells that transiently expressed classical chemokine receptors; results obtained from the chemotaxis, calcium flux, receptor internalization, and radioligand-binding assays all confirmed this finding. To further identify the major function of PSMP, we analyzed its expression profile in tissues. PSMP is highly expressed in benign prostatic hyperplasia and in some prostate cancers, and can also be detected in breast tumor tissue. In response to PSMP stimulation, phosphorylated ERK levels downstream of CCR2B signaling were upregulated in the PC3 cell line. Taken together, our data collectively suggest that PSMP is a chemoattractant protein acting as a novel CCR2 ligand that may influence inflammation and cancer development.

Recombinant human PDCD5 protein enhances chemosensitivity of breast cancer in vitro and in vivo.

Resistance to paclitaxel is common for treatment of breast cancer. Programmed cell death 5 (PDCD5) accelerates apoptosis in different cell types in response to various stimuli; moreover PDCD5 has been shown to be down-regulated in many tumors. In this study, protein levels of PDCD5 were found to be up-regulated in paclitaxel-treated MDA-MB-231 breast cancer cells. MTT, CCK-8, and clonogenic assays have shown that recombinant human PDCD5 (rhPDCD5) alone could not produce an obvious growth inhibition. However, upon paclitaxel triggering apoptosis, rhPDCD5 protein potentiated chemotherapeutic drugs-induced growth arrest in MDA-MB-231, SK-BR-3, and ZR-75-1 breast cancer cells. In vivo, we use a human breast cancer xenograft model to study. We found that rhPDCD5 dramatically improves the antitumor effects of paclitaxel treatment by intraperitoneal administration. These data suggest that rhPDCD5 has the potential to use as a therapeutic agent to enhance the paclitaxel sensitivity of breast cancer cells.

[Preparation and identification of the polyclonal antibody against human VSTM1].

AIM: To prepare and characterize the polyclonal antibody against human VSTM1. METHODS: VSTM1 has two main isoforms, VSTM1-v1, a type I transmembrane protein, and VSTM1-v2, a classical secretory protein, lacking only the transmembrane domain compared with VSTM1-v1. Two recombinant prokaryotic proteins of VSTM1-v2, Trx-His-S-VSTM1-v2 and GST-VSTM1-v2, were constructed, expressed, purified, and then used for immunization of New Zealand rabbits to prepare anti-VSTM1 antibody and coupling with CNBr-activated Sepharose 4B to purify the antibody by immunoaffinity chromatography, respectively. ELISA was performed to detect the titers of the antiserums. After purification, the antibody was identified by Western blotting and immunofluorescence cytochemistry. RESULTS: The titers of the antiserums from the two immunized rabbits were both 1:10(6);. Western blotting confirmed that the purified antibody could recognize both the overexpressed and endogenous VSTM1 specifically. Immunofluorescence cytochemistry verified that the antibody could also recognize the overexpressed VSTM1-v1 on the surface of HEK293T cells. CONCLUSION: The rabbit antibody against human VSTM1 of a high titer has been obtained, which can be used for recognizing endogenous VSTM1 in immunofluorescence cytochemistry.

Simvastatin induces estrogen receptor-alpha expression in bone, restores bone loss, and decreases ERα expression and uterine wet weight in ovariectomized rats.

We previously reported that simvastatin induces estrogen receptor-alpha (ERα) in murine bone marrow stromal cells in vitro. In this study, we investigated the effect of simvastatin on ERα expression in bone and uterus in ovariectomized (OVX) rats and evaluated bone mass, bone strength, and uterine wet weight. Three-month-old Sprague-Dawley female rats received OVX or sham operation. Six weeks later, the rats were treated orally with simvastatin (5 or 10 mg/kg/day), or intraperitoneally with 17-ß-estradiol (E(2)) or a combination of simvastatin and E(2) for 6 weeks. Uterine wet weight, bone mineral density (BMD) of lumbar vertebrae, biomechanics of lumbar vertebrae, and induction of ERα expression in the bone and uterus were analyzed. The 6-week simvastatin treatment improved lumbar vertebral BMD and boosted biomechanical performance of the vertebral body compared to the OVX control, suggesting that simvastatin can treat osteoporosis caused by estrogen deficiency. More interestingly, simvastatin could increase ERα expression and synergy with estradiol in bone while antagonizing estradiol in the uterus, along with uterus atrophy and uterine wet weight decreases. In conclusion, these data suggest that simvastatin exert opposing modulatory effects on ERα expression on bone and uterus in ovariectomized rats, inducing ERα expression and synergy with estrogen to perform anabolic effects on the bones while decreasing E2 efficacy and uterine wet weight. This finding may be helpful to explain the mechanism of statin treatment in osteoporosis caused by estrogen deficiency.

[Effect of simvastatin on inducing endothelial progenitor cells homing and promoting bone defect repair].

OBJECTIVE: To investigate the effect of simvastatin on inducing endothelial progenitor cells (EPCs) homing and promoting bone defect repair, and to explore the mechanism of local implanting simvastatin in promoting bone formation. METHODS: Simvastatin (50 mg) compounded with polylactic acid (PLA, 200 mg) or only PLA (200 mg) was dissolved in acetone (1 mL) to prepare implanted materials (Simvastatin-PLA material, PLA material). EPCs were harvested from bone marrow of 2 male rabbits and cultured with M199; after identified by immunohistochemistry, the cell suspension of EPCs at the 3rd generation (2 x 10(6) cells/mL) was prepared and transplanted into 12 female rabbits through auricular veins (2 mL). After 3 days, the models of cranial defect with 15 cm diameter were made in the 12 female rabbits. And the defects were repaired with Simvastatin-PLA materials (experimental group, n=6) and PLA materials (control group, n=6), respectively. The bone repair was observed after 8 weeks of operation by gross appearance, X-ray film, and histology; gelatin-ink perfusion and HE staining were used to show the new vessels formation in the defect. Fluorescence in situ hybridization (FISH) was performed to show the EPCs homing at the defect site. RESULTS: All experimental animals of 2 groups survived to the end of the experiment. After 8 weeks in experimental group, new bone formation was observed in the bone defect by gross and histology, and an irregular, hyperdense shadow by X-ray film; no similar changes were observed in control group. FISH showed that the male EPC containing Y chromosome was found in the wall of new vessels in the defect of experimental group, while no male EPC containing Y chromosome was found in control group. The percentage of new bone formation in defect area was 91.63% +/- 4.07% in experimental group and 59.45% +/- 5.43% in control group, showing significant difference (P < 0.05). CONCLUSION: Simvastatin can promote bone defect repair, and its mechanism is probably associated with inducing EPCs homing and enhancing vasculogenesis.

[Study on local implantation of simvastatin for repairing rabbit radial critical size defects].

OBJECTIVE: To find an ideal material for repairing bone defect by local implanting simvastatin compounded with poly-lactic acid (PLA) into the radial critical size defects of rabbits, and to observe the reparative effect and type of bone formation induced by simvastatin. METHODS: Twelve 4-months-old male New Zealand white rabbits (2.3-2.8 kg) with 22 mm radial critical size defects on both sides were randomized into 4 groups (all n=3). Right side and left side of every rabbit were set as controls with each other. The left defects (experimental groups) of groups A, B, and C were implanted with cylinder-like compound scaffolds containing 50, 100, and 200 mg of simvastatin (fixed with 250 mg PLA), or auto-bone graft as group D, respectively. The right defects of groups A, B, and C were implanted with scaffolds containing only 250 mg PLA. The right defects of group D were left without any treatment. Digital X-ray images of bone defects were taken 8 and 16 weeks after operation, X-ray was scored double blind and X-ray pixel value was measured. Animals were euthanized 16 weeks postoperatively. CT was applied to analyze new bone formation volume in the defects. In addition, morphological characters of new bones were observed through micro-CT and histology. RESULTS: X-ray films showed that the bone defect of each experimental side had much cloud-like callus, and the bone stump were not clear 8 weeks after operation; and the cortex in the defect was continuous and the medullary was recanalized 16 weeks after operation. In control sides, the cortexes were discontinuous and the ends of fractures were sclerified. At 8 and 16 weeks after operation, the X-ray scores, pixel values and the CT volume percentage of new bone in experiment sides were all significantly higher than those in control sides (P < 0.05). The X-ray scores of experimental sides in groups C and D were significantly higher than those in groups A and B 8 weeks after operation (P < 0.05), and the X-ray scores of experimental sides in groups B and D were significantly higher than those in groups A and C 16 weeks after operation (P < 0.05). The X-ray pixel values of experimental sides of group B were significantly higher than those of groups A, C, and D 8 weeks after operation (P < 0.05). The new bone formation volume of experimental side of groups B and D was higher than that of groups A and C (P < 0.05), and group D was significantly higher than that of group B (P < 0.05). Micro-CT showed bone defects of experimental sides of group B had totally healed, with connected medullary cavities and continuous bone cortex, on the contrary bone defects of control sides of group B did not healed completely. Histological observation showed better bone remodeling effects of the experimental sides than control sides, with connected medullary cavities and continuous bone cortex. And the osteogenetic type was endochondral ossification. CONCLUSION: Local implantation of simvastatin can promote repairing rabbit radial critical bone defect, 100 mg is the best dose of repairing the bone defects.

[Sensitizing effect of recombinant human PDCD5 protein on chemotherapy of acute monocytic leukemia cell line U937 and its mechanism].

This study was aimed to investigate the sensitizing effect of recombinant human PDCD5 (rhPDCD5) protein on chemotherapy of U937 cell line and its mechanism. The flow cytometry was performed to assess the changes of cell apoptosis and cell cycle influenced by rhPDCD5. Hochst 33258 staining was used to observe morphology of the apoptotic cells. The activity change of caspase-3 was detected to analyse the possible mechanisms of rhPDCD5-induced apoptosis. RT-PCR was performed to observe the expression level of drug-resistant genes. The results showed that the percentage of apoptotic cells and the activity of caspase-3 remarkably increased in U937 cells treated with rhPDCD5 combined with chemotherapeutic drug; the cell cycle arrest induced by anti-tumor drug was also enhanced when combined with rhPDCD5; meanwhile, the expression levels of drug-resistant genes were down-regulated in jointly treated U937 cells. It is concluded that the chemosensitizing mechanisms of rhPDCD5 are complex. rhPDCD5 may increase the cytotoxicity of anti-tumor drugs by promoting the caspase-3-related apoptosis, influencing cell cycle, decreasing the expression of drug-resistant genes and reversing drug-resistance.

Potent antitumor activities of recombinant human PDCD5 protein in combination with chemotherapy drugs in K562 cells.

Conventional chemotherapy is still frequently used. Programmed cell death 5 (PDCD5) enhances apoptosis of various tumor cells triggered by certain stimuli and is lowly expressed in leukemic cells from chronic myelogenous leukemia patients. Here, we describe for the first time that recombinant human PDCD5 protein (rhPDCD5) in combination with chemotherapy drugs has potent antitumor effects on chronic myelogenous leukemia K562 cells in vitro and in vivo. The antitumor efficacy of rhPDCD5 protein with chemotherapy drugs, idarubicin (IDR) or cytarabine (Ara-C), was examined in K562 cells in vitro and K562 xenograft tumor models in vivo. rhPDCD5 protein markedly increased the apoptosis rates and decreased the colony-forming capability of K562 cells after the combined treatment with IDR or Ara-C. rhPDCD5 protein by intraperitoneal administration dramatically improved the antitumor effects of IDR treatment in the K562 xenograft model. The tumor sizes and cell proliferation were significantly decreased; and TUNEL positive cells were significantly increased in the combined group with rhPDCD5 protein and IDR treatment compared with single IDR treatment groups. rhPDCD5 protein, in combination with IDR, has potent antitumor effects on chronic myelogenous leukemia K562 cells and may be a novel and promising agent for the treatment of chronic myelogenous leukemia.

NSA2, a novel nucleolus protein regulates cell proliferation and cell cycle.

NSA2 (Nop seven-associated 2) was previously identified in a high throughput screen of novel human genes associated with cell proliferation, and the NSA2 protein is evolutionarily conserved across different species. In this study, we revealed that NSA2 is broadly expressed in human tissues and cultured cell lines, and located in the nucleolus of the cell. Both of the putative nuclear localization signals (NLSs) of NSA2, also overlapped with nucleolar localization signals (NoLSs), are capable of directing nucleolar accumulation. Moreover, over-expression of the NSA2 protein promoted cell growth in different cell lines and regulated the G1/S transition in the cell cycle. SiRNA silencing of the NSA2 transcript attenuated the cell growth and dramatically blocked the cell cycle in G1/S transition. Our results demonstrated that NSA2 is a nucleolar protein involved in cell proliferation and cell cycle regulation.

PDCD5 interacts with Tip60 and functions as a cooperator in acetyltransferase activity and DNA damage-induced apoptosis.

Tip60 is a histone acetyltransferase (HAT) involved in the acetyltransferase activity and the cellular response to DNA damage. Here, we show that programmed cell death 5 (PDCD5), a human apoptosis-related protein, binds to Tip60 and enhances the stability of Tip60 protein in unstressed conditions. The binding amount of PDCD5 and Tip60 is significantly increased after UV irradiation. Further, PDCD5 enhances HAT activity of Tip60 and Tip60-dependent histone acetylation in both basal and UV-induced levels. We also find that PDCD5 increases Tip60-dependent K120 acetylation of p53 and participates in the p53-dependent expression of apoptosis-related genes, such as Bax. Moreover, we demonstrate the biological significance of the PDCD5-Tip60 interaction; that is, they function in cooperation to accelerate DNA damage-induced apoptosis and knockdown of PDCD5 or Tip60 impairs their apoptosis-accelerating activity, mutually. Consistent with this, PDCD5 levels increase significantly on DNA damage in U2OS cells, as does Tip60. Together, our findings indicate that PDCD5 may play a dual role in the Tip60 pathway. Specifically, under normal growth conditions, PDCD5 contributes to maintaining a basal pool of Tip60 and its HAT activity. After DNA damage, PDCD5 functions as a Tip60 coactivator to promote apoptosis.