Biomedical subjects

D W Cai

Publications and source records attributed to D W Cai.

8 recordsLinked to original sources

PubMed1996

[Recombinant virus-mediated transfer of the wild-type p53 gene is a potent therapeutic strategy for human cancer].

Tumor suppressor p53 gene, which is most commonly mutated in human cancers, plays an important role in the control of cell cycle and the induction of apoptosis (programmed cell death). Transfection of the wild-type p53 gene into tumor cells induced either growth suppression or apoptosis. We have examined the effect of the recombinant retroviral or adenoviral vector expressing the wild-type p53 gene on the tumor cell proliferation as well as on the sensitivity of infected-tumor cells to various anticancer agents. The possible application of recombinant virus-mediated direct in vivo transfer of the wild-type p53 gene to human cancer therapy will be discussed.

Adenoviridae↗

PubMed1995

Tumorigenesis and cell evolution.

All kinds of hypotheses have been proposed to explain the mechanism of tumorigenesis. Up until now, we have not had any generally acknowledged model that helps us understand the process. In this paper, I propose a dynamic model of how tumor cells escape the supervision of the immune system; I also examine the possibility that tumorigenesis is a two-stage process. Finally, I suggest that our understanding of the molecular level of tumorigenesis be reappraised.

Biological Evolution↗

PubMed1995

Suppression of lung cancer cell growth by ribozyme-mediated modification of p53 pre-mRNA.

An anti-p53 ribozyme (catalytic RNA) designed to cleave the p53 pre-messenger RNA (mRNA) can efficiently reduce the level of endogenous mutant p53 mRNA. Retrovirus-mediated transduction of a hammerhead ribozyme (Rz5a) designed to cleave unspliced p53 RNA at codon 187 near the boundary of intron 5 and exon 6 reduced the level of mutant p53 RNA and protein in the human H226Br lung cancer cell line, which contains a homozygous p53 mutation at codon 254. The catalytic cleavage of the p53 pre-mRNA but not the p53 mRNA by the ribozyme was shown in vitro. The cleavage of the p53 pre-mRNA by this ribozyme was specific because a mutation in its catalytic domain (Rz5m) abolished the cleavage activity in vitro. Expression of the Rz5a ribozyme significantly suppressed the growth of the H226Br cells in culture. However, another ribozyme (Rz7a) targeted at codon 264 of the p53 gene near the boundary of intron 7 and exon 8 showed in vitro cleavage of the pre-mRNA but did not suppress cell growth. The site of modification in the p53 pre-mRNA may determine the degree of ribozyme-mediated growth suppression in this cell line. Our findings that p53 pre-mRNA can be modified by a specific ribozyme in vivo suggest a possible role for these agents in gene therapy strategies for cancer.

Base Sequence↗

PubMed1994

Therapeutic effect of a retroviral wild-type p53 expression vector in an orthotopic lung cancer model.

BACKGROUND: Mutations in the p53 tumor suppressor gene (also known as TP53) are common in human lung cancers. The wild-type form of p53 is dominant over the mutant; thus, restoration of wild-type p53 function in lung cancer cells may suppress their growth as tumors. PURPOSE: We investigated the therapeutic efficacy of direct administration of a retroviral wild-type p53 (wt-p53) expression vector (LNp53B) in an orthotopic human lung cancer model in nu/nu mice. METHODS: Proliferation of H226Br cells was determined by cell counting after infection with LNp53B in vitro. Irradiated (350 cGy) female BALB/c nu/nu mice were inoculated intratracheally with 2 x 10(6) H226Br cells (whose p53 gene has a homozygous mutation at codon 254) and treated beginning 3 days later with an intratracheal instillation of LNp53B retroviral supernatant for 3 days. RESULTS: Infection with LNp53B inhibited proliferation of H226Br cells in vitro. Thirty days after tumor cell inoculation, 62%-80% of the control mice showed macroscopic tumors of the right main stem bronchus. LNp53B suppressed H226Br tumor formation in 62%-100% of mice, and the effect was abrogated by dilution of the retroviral supernatant with inactive vector. CONCLUSIONS: Direct administration of a retroviral vector expressing wt-p53 may inhibit local growth in vivo of human lung cancer cells with abnormal p53 expression. IMPLICATIONS: Development of gene-replacement treatment strategies based on the type of mutations found in target cancers is warranted and may lead to the development of new adjunctive therapies and gene-specific prevention strategies for lung cancer.

Animals↗

PubMed1994

Retroviral-mediated transduction of p53 gene increases TGF-beta expression in a human glioblastoma cell line.

Transforming growth factor-beta (TGF-beta) has been implicated as a potent growth regulator; the degree of responses to it, whether positive or negative, generally correlates with the stage of cell differentiation in various cell types. We examined the effect of the p53 gene, which participates in the control of cell-cycle progression, on the expression of human TGF-beta. The human glioblastoma cell line SNB-19, which expresses the latent form of TGF-beta, was transfected with a retroviral vector containing wild-type p53 (wt-p53) or p53 with a mutation (mut-p53) at codon 273. Stable G418-resistant SNB-19 clones were isolated. The growth kinetics of wt-p53 transfectants were suppressed compared with those of parental cells, vector transfectants, or mut-p53 transfectants, as assayed by growth-curve measurements and 3H-thymidine incorporation; however, RNA dot blot and Western blot analyses demonstrated that wt-p53 and mut-p53 transfectants expressed higher amounts of TGF-beta 1 and TGF-beta 2 mRNA and intracellular TGF-beta isoform proteins, respectively, than parental cells. By means of the biological assay for active TGF-beta (Mv1Lu cell-growth-inhibition assay), we observed that both transfectants produced active TGF-beta, whereas the parental cells produced only the latent form. These results suggest that, while only the wt-p53 gene inhibits tumor-cell progression, both wt-p53 and codon 273-mutated p53 can cause increased TGF-beta expression.

Base Sequence↗

PubMed1994

[c-myc gene and p53 protein expression in human primary liver carcinoma].

Photobiotin-labelled c-myc gene probe was used to study primary liver carcinoma (PHC) by in situ hybridization on the paraffin sections as well as immunohistochemistry staining for p53 protein expression in 42 cases from high liver cancer incidence regions. The results are as follows: c-myc gene and p53 protein expression were both located in the nuclei. The positive incidences of overexpression of both c-myc gene and p53 protein in PHC were 76% and 55% respectively. The distribution and strength of the overexpression of c-myc gene and p53 protein in PHC are related to the degree of cell differentiation and the overexpression in the liver tissue surrounding the carcinoma is lower than that detected in the PHC tissue.

Carcinoma, Hepatocellular↗

PubMed1993

A retroviral wild-type p53 expression vector penetrates human lung cancer spheroids and inhibits growth by inducing apoptosis.

Multicellular tumor spheroids approximate the three-dimensional configuration of primary and metastatic tumors. The effects of retrovirus-mediated transduction of wild-type p53 (wt-p53) were studied on multicellular tumor spheroids of human non-small cell lung cancer cell lines H322a, the p53 gene of which is homozygously mutated at codon 248, and WT226b, which has endogenous wt-p53. The growth of WT226b spheroids was not affected by exogenous wt-p53 transduction; the growth of H322a spheroids, however, was significantly inhibited by the addition of wt-p53 virus stocks. Transduction of cells by the wt-p53 retroviral vector and penetration of multiple cell layers in H322a spheroids was demonstrated by in situ polymerase chain reaction/hybridization with the neomycin-resistant neo probe. Apoptotic changes indicating programmed cell death were observed in H322a spheroids treated with the wt-p53 virus. These results suggest that retroviral vectors can penetrate into multiple cell layers of three-dimensional tumor masses and induce potentially therapeutic effects.

Apoptosis↗

PubMed1993

Stable expression of the wild-type p53 gene in human lung cancer cells after retrovirus-mediated gene transfer.

A retroviral vector-mediated system was established to allow efficient transduction of the wild-type p53 gene into human lung cancer cell lines H358a (deleted p53) and H322a (mutant p53). LNSX/p53 constructs incorporating p53 cDNA driven by a beta-actin promoter mediated stable integration of p53. p53 mRNA and protein were detected in these cell lines 6 months after transduction by Northern and Western blot analyses. Restoration of the wild-type p53 gene suppressed growth in the two transduced cell lines but had no effect in another transduced tumor cell line, H460a, which has an endogenous wild-type p53 gene. A high transduction efficiency was obtained in cell lines H460a, H322a, and H358a after five cycles of transduction in vitro. Mixing experiments showed that transduced cells could reduce the growth rate of nontransduced cells; this reduction may have been mediated by factors shed into the supernatant of the transduced cell cultures.

Base Sequence↗