Biomedical subjects

Bo Lu

Publications and source records attributed to Bo Lu.

13 recordsLinked to original sources

PubMed2005

Enhanced radiation damage of tumor vasculature by mTOR inhibitors.

It is known that radiation activates the phosphoinositol-3 kinase (PI3K)/Akt pathway and that inhibition of PI3K or Akt sensitizes tumor vasculature to radiotherapy. Mammalian target of rapamycin (mTOR) is a downstream target of Akt, and we hypothesized that irradiation activates mTOR signaling in both glioma and endothelial cells (ECs) and that radiosensitization results from inhibiting mTOR signaling. mTOR inhibitors, rapamycin and RAD001 (everolimus) were found to radiosensitize vascular ECs, but failed to sensitize glioma cells as determined by clonogenic assay. Therefore, we investigated the anti-angiogenic effects of mTOR inhibitors. Increased phospho-mTOR protein was detected in irradiated human umbilical vein endothelial cells (HUVEC), but not in GL261 glioma cells. Phospho-S6, a biomarker for mTOR signaling, was also found to be induced following irradiation in HUVEC and this effect was inhibited by PI3K or mTOR inhibitors. Significant increase in cleaved caspase 3 was detected when Rad001 was combined with radiation. Endothelial tube formation was significantly diminished following treatment with rapamycin and 3 Gy of radiation. Histological sections of GL261 tumors from mice showed a greatly reduced vascular density when treated with RAD001 and radiation. Power Weighted Doppler of glioma xenografts in mice showed a significant reduction in vasculature and blood flow compared with mice treated with 3 Gy or RAD001 alone. We conclude that irradiation activates mTOR signaling in vascular endothelium and that rapamycin and RAD001 increased apoptosis of ECs in response to radiation. To the authors' best knowledge this is the first study which demonstrates that mTOR inhibitors may be a way to target the vasculature by radiosensitizing the vascular endothelium resulting in better tumor control as seen in experiments demonstrating increased tumor growth delay in mice treated with rapamycin with radiation compared with mice treat with either treatment alone. We conclude that mTOR inhibitors have increased efficacy as antiangiogenics when combined with radiation.

Angiogenesis Inhibitors↗

PubMed2005

Nuclear survivin predicts recurrence and poor survival in patients with resected nonsmall cell lung carcinoma.

BACKGROUND: Survivin, which is a member of the inhibitor of apoptosis protein gene family, regulates both programmed cell death and mitosis. It has been shown that survivin expression and its subcellular localization both have prognostic value for patients with malignant disease. In this study, the authors investigated whether nuclear or cytoplasmic staining of survivin was a prognostic marker for patients with lung carcinoma. METHODS: Paraffin-embedded tissue blocks from 144 patients with Stage I and II resected nonsmall cell lung carcinoma (NSCLC) were obtained for immunohistochemical staining. Three specimens from each patient were prepared and stained with a survivin-specific antibody. Nuclear and cytoplasmic staining was graded from 1 to 3 based on intensity. RESULTS: Patients who had nuclear staining for survivin had a significantly increased risk of disease recurrence (hazard ratio, 2.95; P = 0.0046) and death (hazard ratio, 2.74; P = 0.0086). CONCLUSIONS: The nuclear presence of survivin may be an independent biomarker for disease recurrence and overall survival in patients with resected Stage I and II NSCLC.

Adult↗

PubMed2005

Epidermal growth factor receptor gene polymorphisms predict pelvic recurrence in patients with rectal cancer treated with chemoradiation.

An association between epidermal growth factor receptor (EGFR) signaling pathway and response of cancer cells to ionizing radiation has been reported. Recently, a polymorphic variant in the EGFR gene that leads to an arginine-to-lysine substitution in the extracellular domain at codon 497 within subdomain IV of EGFR has been identified. The variant EGFR (HER-1 497K) may lead to attenuation in ligand binding, growth stimulation, tyrosine kinase activation, and induction of proto-oncogenes myc, fos, and jun. A (CA)(n) repeat polymorphism in intron 1 of the EGFR gene that alters EGFR expression in vitro and in vivo has also been described. In the current pilot study, we assessed both polymorphisms in 59 patients with locally advanced rectal cancer treated with adjuvant or neoadjuvant chemoradiation therapy using PCR-RFLP and a 5'-end [gamma-(33)P]ATP-labeled PCR protocol. We tested whether either polymorphism alone or in combination can be associated with local recurrence in the setting of chemoradiation treatment. We found that patients with HER-1 497 Arg/Arg genotype or lower number of CA repeats (both alleles <20) tended to have a higher risk of local recurrence (P = 0.24 and 0.31, respectively). Combined analysis showed the highest risk for local recurrence was seen in patients who possessed both a HER-1 497 Arg allele and <20 CA repeats (P = 0.05, log-rank test). Our data suggest that the HER-1 R497K and EGFR intron 1 (CA)(n) repeat polymorphisms may be potential indicators of radiosensitivity in patients with rectal cancer treated with chemoradiation.

Adult↗

PubMed2005

Endostatin polymorphism 4349G/A(D104N) is not associated with aggressiveness of disease in prostate [corrected] cancer.

Endostatin is an important inhibitory molecule which mediates the sequential steps involved in angiogenesis. Lower level or impaired function of endostatin is associated with a higher risk of developing malignant solid tumors and with a worse prognosis of the disease. The endostatin N104 polymorphism might be associated with an impaired ability to inhibit angiogenesis. We analyzed the tissues from 98 Caucasian prostate cancer patients for the presence of D104N polymorphism. The frequencies of homozygous 4349G/G(104D/D), and heterozygous 4349G/A(104D/N) were 83.67%(82/98) and 16.33%(16/98), respectively; no individuals were homozygous 4349A/A(104N/N). With the Fisher's exact test we found the genotype of D104N was not significantly related to age, tumor grade, PSA and clinical stage (P > 0.05). There was no difference in relapse free survival(RFS) or overall survival(OS) between patients with 104D/N and those with 104D/D (P = 0.8283, 0.3713 respectively). We concluded that endostatin polymorphism was not associated with the aggressiveness of prostate cancer in Caucasian patients.

Aged↗

PubMed2004

The Use of Antisense Oligonucleotides in Evaluating Survivin as a Therapeutic Target for Radiation Sensitization in Lung Cancer.

Elucidating the mechanism of over and under expression of proteins is critical in developing a better understanding of cancer. Multiple techniques are used to examine differential expression of proteins in cells and assess changes in protein expression in response to therapies such as radiation. Reduced expression can be caused by protein inactivation, mRNA instability, or reduced transcription. The following protocol was used to determine the mechanism for the reduced expression of an antiapoptotic factor, survivin, in normal tissues in response to radiation and the defect in cancer cells that prevents this reduction. We also examined ways to overcome survivin over expression in cancer cells in order to sensitize them to radiation. We will focus on the use of antisense oligonucleotides, cell cycle analysis, and luciferase reporter genes.

Journal Article↗

PubMed2004

XIAP and survivin as therapeutic targets for radiation sensitization in preclinical models of lung cancer.

Survivin and XIAP are members of inhibitors of apoptosis (IAPs) family. They are upregulated in various malignancies. Inactivation of these molecules has resulted in chemosensitization. The purpose of this study was to determine whether inhibition of survivin, XIAP, or both enhances radiotherapy in a lung cancer model. Transient transfection of H460 cells with antisense oligonucleotides (ASOs) against either molecule has specifically reduced their expression, by Western analysis. Results from 3-(4,5-methylthiazol-2-yl)-2,5-diphenyl-tetrazolium bromide and clonogenic assays suggest that inhibition of survivin or XIAP greatly decreased cell survival following irradiation. A significantly increased number of apoptotic cells were detected when H460 cells were treated with either antisurvivin, anti-XIAP or both ASOs (P=0.03, 0.0003 and 0.01, respectively) plus irradiation. H460 xenografts that were treated with ASOs plus radiotherapy demonstrated growth delay beyond 15 days. Growth delay in the groups of combined treatment was greater than that in other groups. However, treatment with ASOs alone did not affect tumor growth delay in mice, but decreased the survival of H460 cells in culture. Antisense treatment did not cause any mortality or weight loss during the 32 days of study. These data suggest that inhibition of survivin or XIAP radiosensitizes H460 lung cancer cells by upregulating apoptosis and downregulating cell survival. Combination of radiotherapy and inhibition of survivin and XIAP through the antisense approach results in improved tumor control by radiotherapy in a mouse model of lung cancer.

Animals↗

PubMed2004

Survivin as a therapeutic target for radiation sensitization in lung cancer.

Expression of survivin is elevated in most malignancies, especially in radiation-resistant cell lines. In this study, we investigated how radiation affects survivin expression in primary endothelial cells as well as in malignant cell lines. We found that 3 Gy significantly reduced survivin protein level in human umbilical vein endothelial cells (HUVECs) but not in tumor cell lines. Flow cytometry studies suggest that the down-regulation of survivin is independent of cell cycle. In addition, survivin mRNA level was also down-regulatable by irradiation. However, it was abrogated by actinomycin D-mediated inhibition of gene transcription. Luciferase reporter gene assays suggest that irradiation suppressed the survivin promoter. p53 overexpression reduced survivin expression, but overexpression of a p53 mutant failed to abolish the radiation-induced down-regulation in HUVECs. Alteration of p53 status in Val138 lung cancer cell line also failed to restore the radiation-inducible down-regulation. Overexpression of survivin in 293 cells prevented apoptosis induced by irradiation and increased cell viability after irradiation. The inhibition of survivin using antisense oligonucleotides caused a significant decrease in cell viability of irradiated H460 lung cancer cells. These data suggest that radiation transcriptionally down-regulates survivin in HUVECs. This regulatory mechanism is defective in malignancies and is not mediated by p53. Survivin overexpression may lead to resistance to radiotherapy by inhibiting apoptosis and enhancing cell viability. The inhibition of survivin results in sensitization of H460 lung cancer cells to radiation. These studies suggest that survivin may be a target for cancer therapy.

DNA Damage↗

PubMed2004

Broad spectrum receptor tyrosine kinase inhibitor, SU6668, sensitizes radiation via targeting survival pathway of vascular endothelium.

PURPOSE: Recent studies have demonstrated radiosensitization by inhibiting receptor tyrosine kinases (RTKs). Irradiation activates RTKs and their downstream prosurvival molecule, Akt. In this study, we investigated the mechanism by which SU6668, an inhibitor of RTKs involved in angiogenic pathways, enhances effects of irradiation. METHODS AND MATERIALS: Western blots were used to determine Akt phosphorylation. Clonogenic assays were performed to determine endothelial survival after combination of SU6668 and irradiation. This combination therapy was also tested in mouse models with Lewis lung carcinoma or glioblastoma multiforme (GL261) for inhibition of tumor growth and tumor vasculature by examining tumor volume, tumor vascular window, and blood flow. RESULTS: We found that SU6668 inhibited the Akt activation inducible by irradiation. Clonogenic survival of endothelial cells was decreased after the combined therapy compared with radiotherapy alone. In vivo studies demonstrated reduction of tumor vasculature and blood flow. In addition, 21 Gy in 7 fractions given concurrently with SU6668 resulted in tumor growth delay compared to either treatment alone. CONCLUSION: These data suggest that the combination therapy was more effective in destroying tumor vasculature than either treatment alone. SU6668 augments tumor-suppressive effects of radiotherapy in Lewis lung carcinoma and GL261 xenographs, possibly through reducing the survival of tumor endothelium.

Animals↗

PubMed2004

Optimal multivariate matching before randomization.

Although blocking or pairing before randomization is a basic principle of experimental design, the principle is almost invariably applied to at most one or two blocking variables. Here, we discuss the use of optimal multivariate matching prior to randomization to improve covariate balance for many variables at the same time, presenting an algorithm and a case-study of its performance. The method is useful when all subjects, or large groups of subjects, are randomized at the same time. Optimal matching divides a single group of 2n subjects into n pairs to minimize covariate differences within pairs-the so-called nonbipartite matching problem-then one subject in each pair is picked at random for treatment, the other being assigned to control. Using the baseline covariate data for 132 patients from an actual, unmatched, randomized experiment, we construct 66 pairs matching for 14 covariates. We then create 10000 unmatched and 10000 matched randomized experiments by repeatedly randomizing the 132 patients, and compare the covariate balance with and without matching. By every measure, every one of the 14 covariates was substantially better balanced when randomization was performed within matched pairs. Even after covariance adjustment for chance imbalances in the 14 covariates, matched randomizations provided more accurate estimates than unmatched randomizations, the increase in accuracy being equivalent to, on average, a 7% increase in sample size. In randomization tests of no treatment effect, matched randomizations using the signed rank test had substantially higher power than unmatched randomizations using the rank sum test, even when only 2 of 14 covariates were relevant to a simulated response. Unmatched randomizations experienced rare disasters which were consistently avoided by matched randomizations.

Adult↗

PubMed2004

Radiation-guided drug delivery systems.

A primary limiting factor for cancer treatment is normal tissue toxicity. Targeted cancer treatment can potentially maximize cancer cure and minimize normal tissue toxicity. Physical energy can be used to activate inert oncologic drugs. X-rays have an advantage over other forms of physical energy because tissue penetration and precise localization can be achieved. Radiation can be used to control drug delivery through radiation-inducible gene therapy. Radiation-guided drug delivery systems involve the targeting of immunoconjugates to radiation-inducible neoantigens induced by irradiation of neoplasms. Magnetic fields can compliment these technologies by drawing magnetic particles containing oncologic drugs toward an externally applied magnetic field. The field of targeted drug delivery by use of external radiation fields will ultimately bring new delivery systems into clinical trials. This review highlights radiation-guided cancer drug delivery systems, at preclinical and clinical stages of development, to tumors and tumor blood vessels.

Animals↗

PubMed2004

Receptor tyrosine kinase inhibitors as anti-angiogenic agents.

Receptor tyrosine kinases (RTKs) and their ligands have been implicated in angiogenesis and current data suggest that they are potential cancer therapeutic targets. Split-kinase domain RTKs, including receptors for vascular endothelial growth factor receptor, platelet-derived growth factor and fibroblast growth factor, have important roles in tumor angiogenesis. RTK inhibitors targeting tumor microvasculature have shown promising results in preclinical studies, and use of these compounds as single agents, or in combination with other cytotoxic therapies, including radiation, is an area of active clinical investigation. Preclinical and clinical data from representative anti-angiogenic RTK inhibitors will be discussed in this review.

Angiogenesis Inhibitors↗

PubMed2004

[Biomechanical study of medical hard tissue adhesive bonding butterfly fracture fragment in middle part of fresh human tibia].

A medical hard tissue adhesive, octyl-a-cyanoacrylate, was tested in 6 fresh human tibiae. A 90 degrees butter-fly fracture fragment was made in the middle part of tibia by bandsaw. The compressive stress, torsional stress and angular deflection were assessed before and after osteoectomy respectively. After adhesive bonding, the compressive stress, torsional stress and angular deflection were tested again. The butterfly fracture fagment decreased the bending strength, torsion strength, yielding strength of tibia bone. In torsion test, the torque of tibia before osteoectomy is greater than bonded tibia, the bonded tibia is greater than that of the unbonded tibia. In compression test, before adhesive bonding broken, the compressive curve slope of tibia before osteoectomy is greater than that of bonded tibia, the bonded tibia is greater than that of the unbonded tibia. In angular deflection test before adhesive bonding of broken,the curve slope of tibia before osteoectomy is not different from that of bonded tibia (P>0.05), the slope the bonded tibia is greater than the slope of unbonded tibia(P<0.05). The elastic modulus, rigidity coefficient and moment of area inertia show no statistical difference between the bonded tibia and intact tibia. The used of medical hard tissue adhesive to bond the fracture fragment could improve the bending strength, torsion strength, yielding strength of tibia bone. In operation, it can reduce the soft tissue injury when the fracture fragment is being fixed, and this will benefit bone healing.

Biomechanical Phenomena↗

PubMed2003

[Reconstruction of large genomic segment coding for human immunoglobulin kappa chain by meiotic homologous recombination of yeast artificial chromosome].

Meiotic homologous recombination between overlapping yeast artificial chromosome (YAC) can be used to reconstruct larger genomic segment in vivo. We have screened CEPH and Olson human genomic YAC libraries and obtained two YAC clones containing the large genomic segments coding for partial human Ig kappa. In order to reconstruct whole gene cluster of human Ig kappa, two yeast cells containing the different YAC described over were mated and induced to undergo meiotic division and sporulation. Analyzing the results of PCR and Southern blotting, we obtained a clone containing a single recombinant YAC with 400 kb in length, which spans almost the entire gene cluster of human Ig kappa, including 32 V kappa, 5 J kappa, constant domain genes. Besides, we have improved and simplified the traditional method of meiotic recombination between overlapping YACs, and the results indicate the feasibility of this method to reconstruct any larger intact genomic segments.

Chromosomes, Artificial, Yeast↗