It is intended to provide a disease marker reflecting a cancerous disease; a method of detecting a cancerous disease by using the disease marker; a method of screening a drug efficacious in ameliorating the disease; and a CTL inducing agent. Namely, a polynucleotide having at least 15 consecutive bases in the base sequence of ASK gene, CKS1 gene, MELK gene, STK12 gene, TTK gene or GPR87 gene and/or a polynucleotide complementary thereto are used as a disease marker for cancerous diseases. ASK, CKS1, MELK, STK12, TKK or GPR87 or a peptide originating therein is used as a CTL inducing agent.