Biomedical subjects

Xiaolong Fan

Publications and source records attributed to Xiaolong Fan.

13 recordsLinked to original sources

PubMed2006

Temporal trends of esophageal cancer during 1995-2004 in Nanao Island, an extremely high-risk area in China.

The purpose of our study was to investigate the temporal malignant tumor incidence rates among the 70,000 residents at the relatively isolated Nanao Island in South China Sea. The data on all malignant tumor cases from Nanao Cancer Registry during 1995-2004 were coded, computerized, and analyzed using the software SPSS10.0. The tumor incident cases, crude incident rate, age-standardized incidence rate, their sex distribution and temporal trend were assessed. A total of 1450 new cancer cases (990 males and 460 females) were identified. The annual average age-standardized incidence rate (ASR) of malignant tumors was 208.18/100,000. The age-standardized incidence rate of the ten leading cancers in both sexes combined per 100,000 population were 74.47 for esophageal cancer (EC), 34.81 for cardiac cancer (CC), 25.66 for liver cancer, 26.01 for lung cancer, 18.52 for stomach cancer, 4.45 for nasopharyngeal cancer, 3.91 for breast cancer, 2.53 for colon/rectum cancer, 2.45 for bladder cancer and 1.92 for pancreatic cancer. These ten types of cancers make up to 93% of all cancer cases, with EC and CC being the most prevalent and making up 52% of the total cases. The incidence rates of esophagus, liver, lung, breast, nasopharyngeal, and colon/rectum cancers showed increasing trends during the period from 1995 to 2004 in Nanao Island. Astounding the EC ASR were 72-150/100,000 among male and 26-64/100,000 among female in Nanao Island during 1995-2004. The EC incidence rate in Nanao population is among the highest across the world, which suggests that there are potential genetic and/or environmental factors affecting this particular population.

Age Distribution↗

PubMed2006

Coxsackievirus and adenovirus receptor expression in non-malignant lung tissues and clinical lung cancers.

Adenoviral vector mediated gene delivery has been applied in clinical trials and mechanistic studies to explore new treatment approaches for lung cancers. The expression of coxsackievirus adenovirus receptor (CAR), the primary receptor for the most commonly used adenovirus serotype 5 (Ad5)-based vectors, predominantly determines the permissiveness of lung cancer cells. CAR expression is also suggested to modulate tumor cell proliferation capacity. Here, we studied CAR expression in archival lung cancer specimens by using well-characterized CAR 72 antibodies. High levels of CAR expression were observed in most of the 32 cases of squamous cell carcinoma lung cancers and in all the five cases of small cell lung cancers investigated. In contrast, high levels of CAR expression were detected only in 6 of 22 adenocarcinoma lung cancers. The relative levels of CAR expression did not correlate with the pathologic grade in lung cancers, and was thus inconsistent with a role of modulating cancer cell proliferation. Of note, CAR expression was not detected in non-malignant alveolar cells. Our data suggest a preferred utility of Ad5 vector mediated gene delivery to squamous cell carcinoma lung cancers, small cell lung cancers, but not to the majority of adenocarcinoma lung cancers.

Adult↗

PubMed2006

Human short-term repopulating cells have enhanced telomerase reverse transcriptase expression.

Telomerase activity has been suggested to be critically involved in hematopoietic stem cell (HSC) self-renewal. However, it has been unclear whether human HSCs have telomerase activity and how telomerase activity is regulated within the HSC and progenitor pool. Here, we isolated living cord-blood (CB) CD34(+) cells with up-regulated human telomerase reverse transcriptase (hTERT) expression by using an hTERT-reporting adenoviral vector encoding destabilized green fluorescent protein (dGFP) driven by the hTERT promoter, and functionally characterized them in comparison with control vector-transduced CD34(+) cells expressing GFP. Following a 2-day serum-free transduction protocol, cells were sorted into a dGFP(+) and a GFP(+) fraction. Cell-cycle analysis revealed that the dGFP(+) cells had a greater proportion of cells in S/G(2)/M phase compared with the GFP(+) cells, (56% +/- 1.8% vs 35% +/- 4.3%; P < .001) and fewer cells in G(0) phase (8.1% +/- 3.0% vs 20% +/- 4.7%; P < .01) However, the colony-forming and short-term nonobese diabetic/severe combined immunodeficient (NOD/SCID) B2m(-/-) mice bone marrow-repopulating capacities were similar between the dGFP(+) and the GFP(+) cells. Interestingly, the dGFP(+) cells had a 6-fold lower repopulating capacity in NOD/SCID mice compared with the GFP(+) cells and lacked secondary NOD/SCID B2m(-/-) mice bone marrow-repopulating capacity. Thus, up-regulation of hTERT expression within the CB HSC pool is accompanied by decreased self-renewal capacity.

Animals↗

PubMed2006

Glioma stem cells: evidence and limitation.

Gliomas, in particular the high-grade anaplastic glioma and glioblastoma multiforme (GBM), are manifested by morphological, genetic and phenotypic heterogeneity. Most of the studies hitherto have been performed on bulk glioma cells, with limited understanding on the origin and the relative contribution of particular glioma cell populations to glioma growth and progression. Recent studies have demonstrated the existence of a small fraction of glioma cells endowed with features of primitive neural progenitor cells and tumor-initiating function. Such cells have been defined as glioma stem cells. However, questions remain as to whether the currently identified glioma stem cells are the cell-of-origin for glioma initiation and progression, or the results of such processes. In this review, we discuss the current evidence and limitation in identifying glioma stem cells and the potential origin of glioma stem cells in the context of post-natal neural cell regeneration and their transformation mechanisms. The implication of these findings for glioma diagnosis and treatment will also be reviewed.

Animals↗

PubMed2006

Detection of cell cycle- and differentiation stage-dependent human telomerase reverse transcriptase expression in single living cancer cells.

Elevated telomerase activity is an important molecular signature of cancer cells and primitive cells in regenerative tissues. However, isolation of single living cells with endogenous telomerase activity has not yet been possible. Here, we developed adenovirus serotype 35 tropism-based vectors encoding destabilized enhanced green fluorescence protein with a half-life of 2 h (d2EGFP) driven by the human telomerase reverse transcriptase (hTERT) promoter. As assessed in telomerase-positive or -negative cell lines, the d2EGFP expression positively correlated with hTERT transcript content and telomerase activity. In retinoic acid-induced differentiating HL-60 cells, the d2EGFP expression is diminished in the same manner as the hTERT expression. Individual cells from HeLa and HL-60 cell lines exhibited heterogeneous d2EGFP expression, which was cell cycle dependent, as the sorted d2EGFP+ HL-60 cells contained twice as many cells in S/G2/M phase of the cell cycle compared with the d2EGFP- HL-60 cells. However, both cell populations exhibited the same proliferation and regeneration capacities. Heterogeneous d2EGFP expression was also detected in xenograft glioblastoma multiforme cells with tumor formation capacity. Thus, d2EGFP expression reported cell cycle- and differentiation stage-dependent hTERT expression. Our study facilitates isolation and characterization of single living cells with telomerase activity.

Adenoviridae↗

PubMed2006

Increased expression of cyclin A1 protein is associated with all-trans retinoic acid-induced apoptosis.

Deregulated cell growth and inhibition of apoptosis are hallmarks of cancer. All-trans retinoic acid induces clinical remission in patients with acute promyelocytic leukemia by inhibiting cell growth and inducing differentiation and apoptosis of the leukemic blasts. An important role of the cell cycle regulatory protein, cyclin A1, in the development of acute myeloid leukemia has previously been demonstrated in a transgenic mouse model. We have recently shown that there was a direct interaction between cyclin A1 and a major all-trans retinoic acid receptor, RAR alpha, following all-trans retinoic acid treatment of leukemic cells. In the present study, we investigated whether cyclin A1 might be involved in all-trans retinoic acid-induced apoptosis in U-937 leukemic cells. We found that all-trans retinoic acid-induced apoptosis was associated with concomitant increase in cyclin A1 expression. However, there was no induction of cyclin A1 mRNA expression following the all-trans retinoic acid-induced apoptosis. Treatment of cells with a caspase inhibitor was not able to prevent all-trans retinoic acid-induced up-regulation of cyclin A1 expression. Interestingly, induced cyclin A1 expression in U-937 cells led to a significant increase in the proportion of apoptotic cells. Further, U-937 cells overexpressing cyclin A1 appeared to be more sensitive to all-trans retinoic acid-induced apoptosis indicating the ability of cyclin A1 to mediate all-trans retinoic acid-induced apoptosis. Induced cyclin E expression was not able to initiate cell death in U-937 cells. Our results indicate that cyclin A1 might have a role in apoptosis by mediating all-trans retinoic acid-induced apoptosis.

Apoptosis↗

PubMed2005

Cell type- and region-dependent coxsackie adenovirus receptor expression in the central nervous system.

Model systems have shown that adenoviral vector mediated transient gene expression can potentially be applied for the treatment of brain tumours, neurodegenerative diseases and brain injuries. Most studies utilized adenovirus serotype 5 (Ad5) based vectors, which as adhesion molecules require the coxsackie adenovirus receptor (CAR) as a critical determinant for cellular infection. In this report, we have systematically characterized CAR expression in the adult human central nervous system (CNS) by using immunohistochemistry. A total of 85 specimens from various CNS regions were investigated for CAR expression in a cell type-dependent context. The most marked staining positivity was found in the choroid plexus and the pituitary gland. The neocortex had scattered positive neurons, while the white matter was mainly negative. We need to consider the possible adverse effects and the possible damage caused by adenoviral gene therapy if the virus-vector also binds to normal brain cells.

Adult↗

PubMed2005

Superior neovascularization and muscle regeneration in ischemic skeletal muscles following VEGF gene transfer by rAAV1 pseudotyped vectors.

Recombinant adeno-associated virus serotype 2 (rAAV2) vector has been widely employed for gene therapy. Recent progress suggests that the new serotypes of AAV showed a better performance than did AAV2 in normal tissues. Here, we evaluate the potential role of human vascular endothelial growth factor (VEGF) gene transfer using rAAV vector pseudotyped with serotype 1 capsid proteins (rAAV1) in the treatment of muscle ischemia. In ischemic skeletal muscles, the rAAV1-LacZ vector allowed higher level, broader distribution, and long-lasting gene expression compared with the rAAV2-LacZ vector. Muscle VEGF165 production following the rAAV1-VEGF165 vector injection was 5-10 times higher than that following the rAAV2-VEGF165 vector injection. VEGF165 production mediated by the rAAV1-VEGF165 vector stimulated a large set of neovascularization with relatively mature vascular structures and enhanced muscle regeneration in the ischemic skeletal muscles. Thus, the rAAV1-VEGF165 vector mediated gene transfer may be a therapeutic approach to peripheral vascular diseases.

Adenoviridae↗

PubMed2004

Development of an adenoviral vector system with adenovirus serotype 35 tropism; efficient transient gene transfer into primary malignant hematopoietic cells.

BACKGROUND: A paucity of coxsackie adenovirus receptor (CAR) hampers the adenovirus serotype 5 (Ad5)-based vector-mediated gene transfer into malignant hematopoietic cells. Fiber-retargeted adenoviral vectors with species B tropism can potentially bypass the CAR requirement and facilitate efficient gene transfer into malignant hematopoietic cells. METHODS: For feasible generation of fiber-retargeted adenoviral vectors, we have modified the versatile AdEasy system with a chimeric fiber gene encoding the Ad5 fiber tail domain and Ad35 fiber shaft and knob domains. An Ad5-based vector encoding the green fluorescent protein (GFP) gene under the control of the PGK promoter with Ad35 fiber receptor specificity was generated (Ad5F35-GFP). The Ad5F35-GFP vector-mediated gene transfer efficiency was compared with a fiber non-modified Ad5-GFP vector, which also encodes the GFP gene under the control of the PGK promoter. RESULTS: We demonstrated that a variety of Ad5-refractory malignant myeloid and B lymphoid cell lines were highly permissive to the Ad5F35-GFP vector infection. Importantly, primary chronic myeloid leukemic (CML) cells and chronic lymphocytic leukemia (CLL) B cells were superiorly transduced by the Ad5F35-GFP vector at a multiplicity of infection (MOI) of 100 compared with the Ad5-GFP vector. CONCLUSIONS: Our study will facilitate the generation of fiber-retargeted adenoviral vectors and enable transient genetic manipulation of primary malignant hematopoietic cells.

Adenoviridae↗

PubMed2004

Functionally distinct subpopulations of cord blood CD34+ cells are transduced by adenoviral vectors with serotype 5 or 35 tropism.

Adenovirus serotype 5 (Ad5)-based vectors can be retargeted with fiber receptor specificity of serotype 35 adenovirus (Ad5F35) and thereby bypass the paucity of the coxsackie and adenovirus receptor (CAR) on hematopoietic cells by utilizing CD46 as cellular receptor. The gene transfer efficiency into NOD/SCID repopulating cells by an Ad5F35-GFP vector was investigated in comparison with its corresponding Ad5-GFP vector. Cord blood CD34+ cells were transduced following overnight culture under serum-free conditions supported by early acting cytokines. In agreement with previous findings, the Ad5F35-GFP vector showed significant superiority to the Ad5-GFP vector in gene transfer into cells with primitive immunophenotype. However, the Ad5F35-GFP vector allowed efficient gene transfer into both dividing and nondividing CD34+ cells, whereas the Ad5-GFP vector preferentially allowed gene transfer into dividing cells expressing lower levels of CD34 antigen, which correlated with high levels of CAR expression. The sorted GFP+ cells following Ad5F35-GFP transduction at relatively low multiplicity of infection consistently reconstituted the NOD/SCID mouse bone marrow with multilineage differentiation. In contrast, the GFP+ cells following Ad5-GFP transduction were nearly devoid of reconstitution capacity. Thus, Ad5F35 vectors encoding functional genes can facilitate transient genetic manipulation of human NOD/SCID repopulating cells.

Adenoviridae↗

PubMed2003

TGF-beta signaling-deficient hematopoietic stem cells have normal self-renewal and regenerative ability in vivo despite increased proliferative capacity in vitro.

Studies in vitro implicate transforming growth factor beta (TGF-beta) as a key regulator of hematopoiesis with potent inhibitory effects on progenitor and stem cell proliferation. In vivo studies have been hampered by early lethality of knock-out mice for TGF-beta isoforms and the receptors. To directly assess the role of TGF-beta signaling for hematopoiesis and hematopoietic stem cell (HSC) function in vivo, we generated a conditional knock-out model in which a disruption of the TGF-beta type I receptor (T beta RI) gene was induced in adult mice. HSCs from induced mice showed increased proliferation recruitment when cultured as single cells under low stimulatory conditions in vitro, consistent with an inhibitory role of TGF-beta in HSC proliferation. However, induced T beta RI null mice show normal in vivo hematopoiesis with normal numbers and differentiation ability of hematopoietic progenitor cells. Furthermore HSCs from T beta RI null mice exhibit a normal cell cycle distribution and do not differ in their ability long term to repopulate primary and secondary recipient mice following bone marrow transplantation. These findings challenge the classical view that TGF-beta is an essential negative regulator of hematopoietic stem cells under physiologic conditions in vivo.

Activin Receptors, Type I↗

PubMed2003

Enforced adenoviral vector-mediated expression of HOXB4 in human umbilical cord blood CD34+ cells promotes myeloid differentiation but not proliferation.

Retroviral overexpression of the transcription factor HOXB4 results in a rapid increase in proliferation of murine hematopoietic stem cells both in vivo and in vitro. Therefore, we asked whether transient overexpression of HOXB4 would increase proliferation of human primitive hematopoietic progenitors. Transient overexpression of HOXB4 was generated in umbilical cord blood (CB) CD34(+) cells by a recombinant adenovirus (AdHOXB4) expressing HOXB4 together with the enhanced green fluorescent protein (GFP). Transduced, GFP(+) cells were cultured in serum-free medium containing cytokines that primarily support the growth of primitive hematopoietic progenitors. In contrast to previous findings using retroviral overexpression of HOXB4, we did not observe any increase in proliferation of primitive progenitors or increased colony formation of clonogenic progenitors, including progenitor progeny from long-term culture-initiating cells following adenoviral vector overexpression of HOXB4 in CB CD34(+) cells. However, enforced expression of HOXB4 by the adenoviral vector significantly increased myeloid differentiation of primitive hematopoietic progenitors. Since retroviral vectors generate low and continuous levels of transgene expression in contrast to the high, transient levels generated by the adenoviral vector, our findings suggest that the high levels of HOXB4 expression generated by AdHOXB4 in human CB CD34(+) cells direct the cells toward a myeloid differentiation program rather than increased proliferation.

Adenoviridae↗

PubMed2002

Transient disruption of autocrine TGF-beta signaling leads to enhanced survival and proliferation potential in single primitive human hemopoietic progenitor cells.

Hemopoietic stem cells (HSCs) are maintained at relative quiescence by the balance between the positive and negative regulatory factors that stimulate or inhibit their proliferation. Blocking the action of negative regulatory factors may provide a new approach for inducing HSCs into proliferation. A variety of studies have suggested that TGF-beta negatively regulates cell cycle progression of HSCs. In this study, a dominant negatively acting mutant of TGF-beta type II receptor (TbetaRIIDN) was transiently expressed in HSCs by using adenoviral vector-mediated gene delivery, such that the effects of disrupting the autocrine TGF-beta signaling in HSCs can be directly examined at a single cell level. Adenoviral vectors allowing the expression of TbetaRIIDN and green fluorescence protein in the same CD34(+)CD38(-)Lin(-) cells were constructed. Overexpression of TbetaRIIDN specifically disrupted TGF-beta-mediated signaling. Autocrine TGF-beta signaling in CD34(+)CD38(-)Lin(-) cells was studied in single cell assays under serum-free conditions. Transient blockage of autocrine TGF-beta signaling in CD34(+)CD38(-)Lin(-) cells enhanced their survival. Furthermore, the overall proliferation potential and proliferation kinetics in these cells were significantly enhanced compared with the CD34(+)CD38(-)Lin(-) cells expressing green fluorescence protein alone. Therefore, we have successfully blocked the autocrine TGF-beta-negative regulatory loop of primitive hemopoietic progenitor cells.

ADP-ribosyl Cyclase↗