(1) To identify and (2) validate genes that are up-regulated in ovarian cance r, and (3) to investigate whether the activity of a candidate gene, creatine kin ase B (CKB) is elevated in preoperative sera from ovarian cancer patients compar ed to patients with benign pelvic masses and normal controls. MICROMAX cDNA micr oarray system and RNA derived from pooled ovarian cancer cell lines and normal o vary surface epithelial cells (HOSE) were used to identify differentially expres sed genes. Using RNA from both cell lines and from tissue obtained through laser capture microdissection (LCM), we performed quantitative PCR in order to valida te up-regulation of one of these genes, creatine kinase B (CKB). Using a commer cially available enzyme assay, CKB activity was measured in pre-op-erative ser um samples obtained from 45 ovarian cancer patients, 49 patients with a benign p elvic mass, as well as 37 normal controls. Statistical analysis was preformed us ing an unpaired Students t test. Microarray technology revealed that CKB gene expression had a cancer to HOSE ratio of 18. RNA levels of CKB, measured by real -time PCR, were elevated a mean (and standard error) of 36-fold (8.4) in cance r cell lines compared with HOSEcells and 22.75-fold (10.45) in microdissected o varian cancer epithelial cells compared with normal ovarian epithelial cells. In serum, the mean (±standard error) of CKB enzyme activity in cancer cases was 24.7 U/L units (±5.1) compared to 9.6 U/L (±1.6) for benign mass cas es (P = 0.0088) and to 8.5 U/L (1.7) for normal controls (P = 0.0096). Microarra y technology offers a method to identify tumor biomarkers with potential clinica l usefulness. Our data indicated that CKB gene expression is up-regulated in ov arian cancer cells in vitro and in vivo and that CKB enzyme activity is signific antly elevated in sera from ovarian cancer patients, including those with stage I disease. These findings suggest a potential role for CKB as a marker for early diagnosis. (1) To identify and (2) validate genes that are up-regulated in ovarian cancers, and (3) to investigate whether the activity of a candidate gene, creatine kin ase B (CKB) is elevated in preoperative sera from ovarian cancer patients compar ed to patients with benign pelvic masses and normal controls. MICROMAX cDNA micr oarray system and RNA derived from pooled ovarian cancer cell lines and normal o vary surface epithelial cells (HOSE) were used to identify differentially expres sed genes. Using RNA from both cell lines and from tissue obtained through laser capture microdissection (LCM), we performed quantitative PCR in order to validate te up-regulation of one of these genes, creatine kinase B (CKB). Using a commer cially available enzyme assay, CKB activity was Measured in pre-op-erative seru m samples obtained from 45 ovarian cancer patients, 49 patients with a benign p elvic mass, as well as 37 normal controls. Statistical analysis was preformed us ing an unpaired Student’s test. Microarray technology revealed that CKB gene expression had a cancer to HOSE ratio of 18. RNA levels of CKB, measured by real-time PCR, were elevated a mean (and standard error) of 36-fold (8.4) in cancerous r with serum HOSE cells and 22.75-fold (10.45) in microdissected o varian cancer epithelial cells compared with normal ovarian epithelial cells. In serum, the mean (± standard error) of CKB enzyme activity in cancer cases was 24.7 U / L units compared to 9.6 U / L (± 1.6) for benign mass cas es (P = 0.0088) and to 8.5 U / L (1.7) for normal controls (P = 0.0096). Microarra y technology offers a method to identify tumor biomarkers with potential clinical usefulness. Our data indicates that CKB gene expression is up-regulated in ov arian cancer cells in vitro and in vivo and in vivo and that CKB enzyme activity is significantly aly elevated in sera from ovarian cancer patients, including those with stage I disease. These findings suggest a potential role for CKB as a marker for early diagnosis.