A splice shifting oligonucleotide consisting of linked nucleosides comprising (i) 10 to 25 linked nucleosides having a nucleobase sequence comprising up to 12 contiguous nucleobases complementary to a target region of equal length of a nucleic acid sequence harbouring a splicing regulatory sequence of 6-12 nucleotides comprised in the sequences selected from the list consisting of SEQ ID NO: 76 ( HRAS Exon 2 + flanking sequences), a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 76, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 76, SEQ ID NO: 77 ( KRAS Exon 2 + flanking sequences), and a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 77, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 77, SEQ ID NO: 78 ( NRAS Exon 2 + flanking sequences), a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 78, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 78, and wherein the oligonucleotide does not comprise a stretch of more than 5 consecutive unmodified RNA nucleosides, and (ii) a fragment capable of binding a splicing inhibitory protein consisting of 10 to 30 linked nucleosides having a nucleobase sequence which is not complementary to a region of equal length of a nucleic acid sequence selected from the list consisting of SEQ ID NO: 76 ( HRAS Exon 2 + flanking sequences), SEQ ID NO: 78 ( NRAS Exon 2 + flanking sequences), and SEQ ID NO: 77 ( KRAS Exon 2 + flanking sequences), and (iii) optionally a delivery vehicle, such as an aptamer. (i) 10 to 25 linked nucleosides having a nucleobase sequence comprising up to 12 contiguous nucleobases complementary to a target region of equal length of a nucleic acid sequence harbouring a splicing regulatory sequence of 6-12 nucleotides comprised in the sequences selected from the list consisting of SEQ ID NO: 76 ( HRAS Exon 2 + flanking sequences), a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 76, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 76, SEQ ID NO: 77 ( KRAS Exon 2 + flanking sequences), and a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 77, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 77, SEQ ID NO: 78 ( NRAS Exon 2 + flanking sequences), a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 78, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 78, and wherein the oligonucleotide does not comprise a stretch of more than 5 consecutive unmodified RNA nucleosides, and SEQ ID NO: 76 ( HRAS Exon 2 + flanking sequences), a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 76, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 76, SEQ ID NO: 77 ( KRAS Exon 2 + flanking sequences), and a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 77, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 77, SEQ ID NO: 78 ( NRAS Exon 2 + flanking sequences), a nucleic acid sequence having at least 80% sequence identity to SEQ ID NO: 78, a nucleic acid sequence having 1 or 2 substitutions when compared to SEQ ID NO 78, and wherein the oligonucleotide does not comprise a stretch of more than 5 consecutive unmodified RNA nucleosides, and (ii) a fragment capable of binding a splicing inhibitory protein consisting of 10 to 30 linked nucleosides having a nucleobase sequence which is not complementary to a region of equal length of a nucleic acid sequence selected from the list consisting of SEQ ID NO: 76 ( HRAS Exon 2 + flanking sequences), SEQ ID NO: 78 ( NRAS Exon 2 + flanking sequences), and SEQ ID NO: 77 ( KRAS Exon 2 + flanking sequences), and SEQ ID NO: 76 ( HRAS Exon 2 + flanking sequences), SEQ ID NO: 78 ( NRAS Exon 2 + flanking sequences), and SEQ ID NO: 77 ( KRAS Exon 2 + flanking sequences), (iii) optionally a delivery vehicle, such as an aptamer.