Stable Expression of the Wild-Typep53Gene in Human Lung Cancer Cells after Retrovirus-Mediated Gene Transfer

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Abstract
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 β-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. Mutations of the p53 tumor suppressor gene are the most common yet described for human cancer. In this article, long-term stable expression of wild-type p53 is achieved in human lung cancer cells using retroviral-mediated gene transduction. Stable p53 expression is shown for 6 months, resulting in a reduction in the rate of cell proliferation. Evidence is presented for a bystander effect with transduced cells reducing the proliferation rate of nontransduced cells in a mixing experiment. The existence of bystander effects suggests that therapeutic effects may occur in vivo without transduction of all tumor cells.