Biomedical subjects

Dong Yu

Publications and source records attributed to Dong Yu.

46 records · Page 3Linked to original sources

PubMed2002

Insulin-like growth factor I receptor is expressed at normal levels in Nijmegen breakage syndrome cells.

Nijmegen breakage syndrome (NBS) is an autosomal recessive disorder sharing a pleiotropic phenotype with ataxia-telangiectasia (A-T), including increased radiosensitivity and cancer disposition. Insulin-like growth factor I receptor (IGF-IR) expression is reportedly decreased in A-T cells, which is thought to contribute to its increased radiosensitivity. In this study, we investigated whether the same mechanism underlies the radiosensitivity of NBS cells. GM7166VA7 cells lacking NBS1 protein displayed a phenotype of increased radiosensitivity, while the introduction of NBS1 cDNA conferred radioresistance comparable to normal cells. IGF-IR expression levels were essentially the same among normal, NBS, and NBS1-complemented NBS cells. There was no significant difference between NBS and NBS1-complemented cells in activation of major downstream pathways of IGF-IR upon IGF-I stimulation, including phosphatidylinositol-3(') kinase (PI3-K) and mitogen-activated protein kinase (MAPK). Collectively, IGF-IR-related events are unlikely to be disrupted in NBS cells, and therefore, defects in IGF-IR signaling do not explain the increased radiosensitivity of NBS cells.

Cell Line, Transformed↗

PubMed2002

Immunostimulatory properties of phosphorothioate CpG DNA containing both 3'-5'- and 2'-5'-internucleotide linkages.

Synthetic oligodeoxyribonucleotides containing CpG-dinucleotides (CpG DNA) in specific sequence contexts activate the vertebrate immune system. We have examined the effect of 3'-deoxy-2'-5'-ribonucleoside (3'-deoxynucleoside) incorporation into CpG DNA on the immunostimulatory activity. Incorporation of 3'-deoxynucleosides results in the formation of 2'-5'-internucleotide linkages in an otherwise 3'-5'-linked CpG DNA. In studies, both in vitro and in vivo, CpG DNA containing unnatural 3'-deoxynucleoside either within the CpG-dinucleotide or adjacent to the CpG-dinucleotide failed to induce immunostimulatory activity, suggesting that the modification was not recognized by the receptors. Incorporation of the same modification distal to the CpG-dinucleotide in the 5'-flanking sequence potentiated the immunostimulatory activity of the CpG DNA. The same modification when incorporated in the 3'-flanking sequence had an insignificant effect on immunostimulatory activity of CpG DNA. Interestingly, substitution of a 3'-deoxynucleoside in the 5'-flanking sequence distal to the CpG-dinucleotide resulted in increased IL-6 and IL-10 secretion with similar levels of IL-12 compared with parent CpG DNA. The incorporation of the same modification in the 3'-flanking sequence resulted in lower IL-6 and IL-10 secretion with similar levels of IL-12 compared with parent CpG DNA. These results suggest that site-specific incorporation of 3'-deoxynucleotides in CpG DNA modulates immunostimulatory properties.

Animals↗

PubMed2002

Construction of a self-excisable bacterial artificial chromosome containing the human cytomegalovirus genome and mutagenesis of the diploid TRL/IRL13 gene.

The full-length genome of human cytomegalovirus strain AD169 was cloned as an infectious bacterial artificial chromosome (BAC) plasmid, pAD/Cre. The BAC vector, flanked by LoxP sites, was inserted immediately after the Us28 open reading frame without deletion of any viral sequences. The BAC vector contained the Cre recombinase-encoding gene disrupted by an intron under control of the simian virus 40 early promoter. When pAD/Cre was transfected into primary human foreskin fibroblast cells, Cre was expressed and mediated site-specific recombination between the two LoxP sites, excising the BAC DNA backbone. This gave rise to progeny virus that was wild type with the exception of an inserted 34-bp LoxP site. We performed site-directed mutagenesis on pAD/Cre to generate a series of viruses in which the TRL/IRL13 diploid genes were disrupted and subsequently repaired. The mutants reach the same titer as the wild-type virus, indicating that the TRL/IRL13 open reading frames are not required for virus growth in cell culture. The sequence of the TRL13 open reading frame in the low-passage Toledo strain of human cytomegalovirus is quite different from the corresponding region in the AD169 strain. One of multiple changes is a frameshift mutation. As a consequence, strain Toledo encodes a putative TRL13 protein whose C-terminal domain is larger (extending through the TRL14 coding region) and encodes in a reading frame different from that of strain AD169. We speculate that the strain AD169 coding region has drifted during passage in the laboratory. We propose that TRL13 has been truncated in strain AD169 and that the partially overlapping TRL14 open reading frame is not functional. This view is consistent with the presence of both TRL13 and -14 on all mRNAs that we have mapped from this region, an organization that would include the much longer strain Toledo TRL13 open reading frame on the mRNAs.

Amino Acid Sequence↗

PubMed2002

Antisense anti-MDM2 mixed-backbone oligonucleotides enhance therapeutic efficacy of topoisomerase I inhibitor irinotecan in nude mice bearing human cancer xenografts: In vivo activity and mechanisms.

Antisense oligonucleotides have been investigated as anticancer agents administered alone or in combination with conventional chemotherapeutics. In the present study, we demonstrated synergistic effects between anti-MDM2 antisense oligonucleotides and the clinically used anticancer agent irinotecan, using nude mouse models of human colon cancers (LS174T and DLD-1). Surprisingly, a 5-base mismatch oligonucleotide also showed similar effects. To elucidate the underlying mechanisms, in vitro and in vivo pharmacokinetic and pharmacodynamic studies were performed. In LS174T cells, the antisense oligonucleotide, but not the mismatch oligonucleotide, specifically inhibited MDM2 expression, resulting in a significant increase in irinotecan-associated p53 activation and p21 induction. In DLD-1 cells, the antisense oligonucleotide specifically inhibited MDM2 expression, resulting in a significant increase in irinotecan-associated p21 induction although mutant p53 levels remained unchanged. Both oligonucleotides increased tissue uptake of irinotecan and the conversion of irinotecan to its active metabolite SN-38. These results suggest that oligonucleotides have a role in irinotecan metabolism and action, providing a basis for future development of antisense oligonucleotides as a sensitizer for irinotecan-based therapy.

Animals↗

PubMed2002

Towards optimal design of second-generation immunomodulatory oligonucleotides.

The goal of using of oligodeoxyribonucleotides containing CpG dinucleotides (CpG DNA) as immunomodulatory agents has been realized in recent years. Therapeutic applications of CpG DNA as monotherapies and as adjuvants in combination with vaccines, antibodies, antigens and allergens for a number of disease indications are rapidly expanding, and the safety and efficacy of several first-generation CpG DNA agents are being evaluated in human clinical trials. The biological effects of CpG DNA have been known for two decades; however, only recently has a specific receptor(s) that recognizes CpG DNA and activates immune cascade been identified. A number of sequence and structural characteristics of CpG DNA and chemical modifications that influence immunostimulatory activity have been identified. In this article we summarize the recent progress in understanding the structural and chemical characteristics of CpG DNA that are significant for molecular recognition. In addition, we describe the design of second-generation CpG DNA agents, and clinical applications of first-generation agents.

Adjuvants, Immunologic↗

PubMed2002

GEM 231, a second-generation antisense agent complementary to protein kinase A RIalpha subunit, potentiates antitumor activity of irinotecan in human colon, pancreas, prostate and lung cancer xenografts.

GEM 231, a second-generation antisense oligonucleotide targeted against the RIalpha subunit of protein kinase A (PKA) was co-administered with the chemotherapeutic agent irinotecan, a topoisomerase-I inhibitor, to study the antitumor efficacy of the combination in nude mice bearing various human tumor xenografts. The combination treatment of GEM 231 and irinotecan produced enhanced and prolonged tumor-growth inhibition, compared with irinotecan monotherapy, against human colon (HCT-116), pancreas (Panc-1), prostate (PC3) and lung (SKMES) tumors in mice. The extent of tumor-growth inhibition, however, varied among the different tumor models studied. The tumor-growth inhibition depended on the dose of GEM 231 co-administered with irinotecan. The combination of GEM 231 (20 mg/kg, i.p., 5 days on 2 days off x 7) and irinotecan (50 mg/kg, i.v., qwk x 3) produced significantly longer tumor-growth delay than did irinotecan administered alone. Importantly, the co-administration of irinotecan and GEM 231 did not result in higher toxicity compared with monotherapies in the several tumor models tested. These results suggest that the use of irinotecan in combination with GEM 231 may increase the therapeutic index of irinotecan in cancer patients.

Animals↗

PubMed2002

Antisense oligonucleotide targeted to RIalpha subunit of cAMP-dependent protein kinase (GEM231) enhances therapeutic effectiveness of cancer chemotherapeutic agent irinotecan in nude mice bearing human cancer xenografts: in vivo synergistic activity, pharmacokinetics and host toxicity.

The RIalpha-subunit of cAMP-dependent protein kinase (PKA) is overexpressed in various human cancers and PKA has been suggested to be a potential target for cancer therapy. We have shown an antisense oligonucleotide with advanced chemistry (mixed-backbone oligonucleotide) targeted to PKA RIalpha-subunit (GEM231) to have anti-tumor activity in vitro and in vivo. In the present study, we demonstrated synergistic effects between the anti-PKA antisense oligonucleotide and the clinically used anticancer agent irinotecan, using nude mouse models of human cancers of colon (LS174T and DLD-1), breast (MCF-7), prostate (DU-145 and PC-3) and lung (H1299). To elucidate the underlying mechanisms, in vivo pharmacokinetics of irinotecan was determined following pre-treatment of oligo GEM 231 in CD-1 mice and nude mice bearing LS174T xenografts. GEM 231 increased tissue uptake of irinotecan. However, no significant change in host toxicity was observed following combination treatment of irinotecan and GEM231 compared with irinotecan alone. These results suggest that GEM231 have a role in irinotecan metabolism and its antitumor activity, providing a basis for future development of this oligonucleotide as a chemosensitizer for irinotecan-based therapy.

Animals↗

PubMed2002

Anti-tumor efficacy of a novel antisense anti-MDM2 mixed-backbone oligonucleotide in human colon cancer models: p53-dependent and p53-independent mechanisms.

BACKGROUND: The MDM2 oncogene is amplified or overexpressed in many human cancers and MDM2 levels are associated with poor prognosis. MDM2 not only serves as a negative regulator of p53 but also has p53-independent activities. This study investigates the functions of the MDM2 oncogene in colon cancer growth and the potential value of MDM2 as a drug target for cancer therapy, by inhibiting MDM2 expression with an antisense anti-human-MDM2 oligonucleotide. MATERIALS AND METHODS: The selected antisense mixed-backbone oligonucleotide was evaluated for its in vitro and in vivo antitumor activity in human colon cancer models: LS174T cell line containing wild-type p53 and DLD-1 cell line containing mutant p53. The levels of MDM2, p53 and p21 proteins were quantified by Western blot analysis. RESULTS: In vitro antitumor activity was found in both cell lines, resulting from specific inhibition of MDM2 expression. In vivo antitumor activity of the oligonucleotide occurred in a dose-dependent manner in both models and synergistically or additive therapeutic effects of MDM2 inhibition and the cancer chemotherapeutic agents 10-hydroxycamptothecin and 5-fluorouracil were also observed. CONCLUSIONS: These results suggest that MDM2 have a role in tumor growth through both p53-dependent and p53- independent mechanisms. We speculate that MDM2 inhibitors have a broad spectrum of antitumor activities in human cancers regardless of p53 status. This study should provide a basis for future development of anti-MDM2 antisense oligonucleotides as cancer therapeutic agents used alone or in combination with conventional chemotherapeutics.

Animals↗

PubMedDate not supplied

Intraoral one-stage curved osteotomy for the prominent mandibular angle: a clinical study of 407 cases.

BACKGROUND: Many Oriental people have a square face with a prominent mandibular angle. This article presents a good osteotomy method for the prominent mandibular angle (PMA). METHODS: Two modifications of the conventional procedures have been made. The first is a one-stage curved osteotomy for the mandibular angle. The second is nonresection of the masseter muscle. The surgical procedure has been performed using an intraoral approach with a direct field of vision. RESULTS: From October 1996 to December 2002, a total of 407 patients with PMA underwent surgery using this method with satisfactory results. The PMA osteotomy procedure was performed for only 248 patients. In addition, 29 patients received concurrent zygomatic reduction osteotomy, 38 patients underwent concurrent genioplasty, 41 patients had concurrent chin augmentation with excised PMA bone fragment, 2 patients received concurrent submental liposuction, and 39 patients underwent concurrent buccal fat pad resection. CONCLUSION: The described method is a very simple procedure with fewer complications for the surgical treatment of PMA.

Adolescent↗

PubMedDate not supplied

Conjugation of ligands at the 5'-end of CpG DNA affects immunostimulatory activity.

Bacterial DNA and synthetic oligonucleotides containing unmethylated CpG dinucleotides (CpG DNA) activate the vertebrate immune system and promote Th1-like immune responses. Several CpG DNAs are currently being tested in clinical trials as either alone or in combination with vaccines, antibodies, and allergens separately or as conjugates for a number of disease indications including cancers, allergies, and asthma. In this paper, we show that conjugation of an oligonucleotide and a CpG DNA through their 5'-ends (5'-5'-linked DNA) significantly reduces the immunostimulatory activity of the CpG DNA. In addition, we found that the reduction in immunostimulatory activity of 5'-5'-linked CpG DNA depends on the size of the oligonucleotide conjugated to CpG DNA. Conjugation of a smaller group or molecule, such as a phosphorothioate group, at the 5'-end of CpG DNA has an insignificant effect on immunostimulatory activity. However, conjugation of a mononucleotide, tetra- or longer oligonucleotide or a fluorescein molecule to the 5'-end of a CpG DNA (5'-5'-linked DNA) significantly suppresses the immunostimulatory activity of CpG DNA. Surprisingly, conjugation of an oligonucleotide or a ligand through the 3'-end of CpG DNA (3'-3'-linked DNA) has an insignificant effect on immunostimulatory activity. Studies of cellular uptake and activation of transcription factor NF-kappaB in J774 cells using fluorescein-conjugated CpG DNAs suggest that the differences in the immune stimulation of 5'- and 3'-end-conjugated CpG DNAs is not as a result of differences in their cellular uptake properties. These results suggest that for optimal immunostimulatory activity, ligands should not be attached at the 5'-end of the CpG DNA.

3' Flanking Region↗