INHIBITION OF HUMAN ONCOGENE EXPRESSION BY INTERFERON

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The enzyme lysyl oxidase functions as a suppressor of the phenotypic expression of the ras oncogene. NIH 3T3 mouse cells transformed by LTR-c-H-ras expressed very low levels of lysyl oxidase; expression was restored after interferon beta-mediated reversion. Revertants were retransformed by a lysyl oxidase antisense expression construct; the original transformed cells were reverted after transfection with a lysyl oxidase sense expression construct. Lysyl oxidase transcriptional regulatory sequences will be defined to investigate how the gene is switched off during ras transformation, and how reversion with interferon leads to the restoration of expression. Since demethylation of revertants caused retransformation and loss of lysyl oxidase expression, the control region may require methylation for activity. Positive and/or negative regulatory proteins that bind to the transcriptional regulatory control sequences, perhaps induced by either interferon or ras, will be identified and studied. The possible coordinate regulation of lysyl oxidase, collagen structural genes, and enzymes involved in collagen synthesis following ras transformation and reversion will be investigated. Lysyl oxidase expression in cell lines transformed by oncogenes other than ras will also be studied to reveal any similarities in method of action or interrelationships among ras and other oncogenes. If a relationship exists between lysyl oxidase activity and normal cell growth and behavior, understanding the regulatory mechanisms of this gene may provide opportunities for therapy: drugs that modify lysyl oxidase expression can be identified, and possibly in the future, gene replacement therapy could be considered. Cell lines of human cancers that arise from cells that produce collagen or elastin and lysyl oxidase will be examined for alterations in lysyl oxidase message expression and enzyme activity as well as collagen or elastin levels. If lysyl oxidase gene expression is decreased in any of these human cancers, expression experiments employing the human lysyl oxidase gene will be performed to attempt reversion. Lysyl oxidase has also been localized to some types of epithelia cells. Tumors arising from these tissues will be examined for any changes in lysyl oxidase expression. Normal tissue and cell lines derived from tumors of tissues that show a high incidence of mutation in the ras oncogene will also be examined to determine if there is a correlation between lysyl oxidase expression and transformation similar to that seen in the mouse fibroblast system. The relationship between immature collagen and elastin in cell matrix and possible changes in the binding/activity of growth-promoting or -controlling factors will also be studied.