Biomedical subjects

Raymond E Meyn

Publications and source records attributed to Raymond E Meyn.

22 records · Page 2Linked to original sources

PubMed2003

Adenovirus-mediated wild-type p53 radiosensitizes human tumor cells by suppressing DNA repair capacity.

Functional inactivation of the p53 gene and robust DNA repair capacity may be among the salient causes of radioresistance in tumor cells. We expressed the wild-type (wt) p53 gene in a p53-mutant human epidermoid carcinoma cell line, A431, using an adenoviral vector [adenovirus-p53 (Ad-p53), INGN 201], examined its radiosensitivity, and correlated p53 status and radiosensitivity with cellular repair functions. Using clonogenic survival assays and the terminal deoxynucleotidyl transferase-mediated nick end labeling assay for apoptosis, we demonstrated that preirradiation treatment with Ad-p53 significantly increased the radiosensitivity of A431 cells over controls. Induction of p53 expression using a construct where p53 expression was under the control of an inducible promoter also significantly increased radiosensitivity of H1299 lung tumor cells, which are otherwise null for p53. These results did not correlate with radiation-induced apoptosis but did correlate with functional impairment of DNA repair and suppressed expression of several repair-related genes, such as Ku70, DNA-dependent protein kinase, ataxia telangiectasia mutated, and X-ray-sensitive complementation group 4. Normal human fibroblast MRC-9 cells showed no impairment in the repair capability due to Ad-p53 despite the suppression of some repair genes. Expression of Ku70, which is known to mediate diverse cellular functions, correlated with the differential effects of p53 on radiosensitivity in the normal and tumor cells.

Adenoviridae↗

PubMed2002

Inhibition of human lung cancer growth following adenovirus-mediated mda-7 gene expression in vivo.

Overexpression of the melanoma differentiation associated gene-7 (mda-7) in vitro results in suppression of lung cancer cell proliferation. However, the ability of MDA-7 to suppress lung cancer in vivo has not been previously demonstrated. In this study, we investigated the possibility of inducing overexpression of the mda-7 gene in human non-small cell lung carcinoma cells in vivo and its effects on tumor growth. Adenovirus-mediated overexpression of MDA-7 in p53-wild-type A549 and p53-null H1299 subcutaneous tumors resulted in significant tumor growth inhibition through induction of apoptosis. In addition, decreased CD31/PECAM expression and upregulation of APO2/TRAIL were observed in tumors expressing MDA-7. In vivo studies correlated well with in vitro inhibition of lung tumor cell proliferation and endothelial cell differentiation mediated by Ad-mda7. These data demonstrate that Ad-mda7 functions as a multi-modality anti-cancer agent, possessing both, pro-apoptotic and anti-angiogenic properties. We demonstrate for the first time the potential therapeutic effects of Ad-mda7 in human lung cancer.

Adenoviridae↗

PubMed2002

Adenovirus-mediated mda-7 gene expression radiosensitizes non-small cell lung cancer cells via TP53-independent mechanisms.

We examined the ability of adenoviral-mediated expression of the melanoma differentiation associated gene-7 (Ad-mda-7), to radiosensitize non-small cell lung cancer (NSCLC) cell lines (A549 (wt-TP53/wt-RB1) and H1299 (del-TP53/wt-RB1)), and normal human lung fibroblast (NHLF) lines (CCD-16 and MRC-9). Results of clonogenic assays indicated that Ad-mda7 enhanced the radiosensitivity of the NSCLC cells independent of their TP53 gene status. On the other hand, the NHLF cell lines seemed to be relatively resistant to the cytotoxic effects of Ad-mda7 and were not radiosensitized compared with the NSCLC cells. We further examined the basis for this difference in the ability of Ad-mda7 to radiosensitize NSCLC cells compared with normal cells. Radiation-induced apoptosis was restored in the NSCLC lines, but not in the normal lines. Western blot analysis revealed that Ad-mda7 enhances radiosensitivity independently of any ability to upregulate the expression of Fas or Bax in NSCLC cells. Further analysis indicated that phosphorylated c-Jun expression was increased by Ad-mda7 in both A549 and H1299 cells, but not in CCD-16 cells. These results support the use of gene replacement with Ad-mda7 in combination with radiotherapy for the treatment of NSCLC.

Adenoviridae↗

PubMedDate not supplied

A recombinant adenovirus expressing wild-type Bax induces apoptosis in prostate cancer cells independently of their Bcl-2 status and androgen sensitivity.

Using a binary co-transfection strategy of Ad/GT Bax and Ad/PGK-GV16, we have succeeded in inducing overexpression of Bax protein in three prostate cell lines (androgen-insensitive DU145 and PC3, and androgen-sensitive LNCaP). The expression of Bax protein by this system was sufficient to induce all three prostate lines to undergo apoptosis. The fact that DU145 cells which have a p53 mutation and are deficient in Bax, responded to this treatment, suggests that this effect is independent of these pathways. Initiation of the cleavage of Caspase-3 (CPP32/Yama/apopain) and PARP (poly (ADP-ribose) polymerase) by the introduction of Bax were confirmed by western blot analysis. Bcl-2 expression is relevant in the progression of prostate cancer and contributes to an androgen, apoptotic-resistant phenotype in the advanced stages. We examined stable Bcl-2 overexpressing DU145, PC3 and LNCaP cell lines as models of advanced prostate cancer. The adenoviral co-transfection system induced Bax protein expression and apoptosis even in these Bcl-2 transfected cell lines. Taken together, our results suggest that this Bax expression system might represent a useful gene therapy strategy when applied to the treatment of prostate cancer and its efficacy would be independent of the Bcl-2 status and androgen sensitivity of these cancers.

Adenoviridae↗