Abstract: Splice variants are transcripts that exhibit various functions or activities and are obtained from alternative splicing of precursor mRNA.An increasing number of tumor-specific splice variants are being discovered and their roles in cancer development and progression are being investigated.In this study, the expression patterns and activities of tumor-specific splice variants were characterized.The results suggest that a variant-specific gene therapy that targets cancer cells would be more specific and would have minimal effect on healthy tissues.Using antisense oligonucleotides, mRNA that contributed to cancer cell survival and altered splicing patterns was downregulated in a clinical trial.The results provide a new appreciation for the gene therapy of cancer.Identification of novel tumor-specific splice variants and constant improvement of therapeutic strategies by modifying splicing patterns can lead to the development of more effective and safer cancer therapies.