2 ml medium treatment with oligo 35 resulted in dramatic changes in cell morphology at all doses formation of large clusters of calls was inhibited with respect to the controls as oligo concentration increased cells became less clumpy and more elongated increasing numbers of floating calls appeared many of which were alive as revealed by viability counts upon treatment with 15 u03bcm oligo calls became dramatically elongated and no clumps of calls could be seen see pictures a high proportion of calls were floating however viability was found to be over 50 suggesting that many of the floating calls are still alive in vivo inhibition of dna methyl transferase expression and tumorigenesis can be achieved by administration of the antisense oligonucleotides of the present invention to mammals for example administration into a mouse can be by slow infusion pump at a rate of about 0 5 3 0 nmoles hr about 0 15 1 0 mg of an oligonucleotide 20 mer per kg of body weight alternatively intravenous injection of about 1 5 mg of the oligonucleotide per kg body weight can be made into the tail vein after about 10 to 21 days the tumors can be excised and analyzed for dna methyl transferase expression as well as by observing the weight and morphology of the tumors tumors and dna methyl transferase levels of mice treated with a control oligonucleotide can be compared from the foregoing it will be appreciated that although specific embodiments of the invention have been described herein for purposes of illustration various modifications may be made without deviating from the spirit and scope of the invention.