title: Detection of melanoma-derived cancer-testis antigen CT16 in patient sera by a novel immunoassay.
abstract: Cancer-testis antigens (CTAs) are expressed mainly in various cancer tissues and in testis or placenta. Because of their restricted expression pattern, the CTAs can be potentially used for vaccine development and diagnostic applications. CTA CT16 has been found to be expressed in lung and renal cancers as well as in melanomas. Detection of CT16 protein directly from patient serum could facilitate monitoring of tumor growth and response to therapy in CT16-positive patients. A highly sensitive time-resolved fluorescence-based immunoassay measuring CTA CT16 in serum was developed. Generally, CTAs have not been measured directly from body fluids. CT16 level was detectable in 14 of 23 (61%) patients with metastatic melanoma, whereas none of the nine healthy volunteers collected by us had measurable CT16 level. For an unknown reason, 1 of 20 commercial control serum samples gave a positive result. The Wilcoxon-Mann-Whitney exact test showed statistically significant difference when patients with metastatic melanoma were compared to our control group (p = 0.006) or to the commercial set (p < 0.001). Four melanoma patients had exceptionally high serum CT16 level. CT16 did not correlate either with S100B, a recognized marker of progressing melanoma, or with unspecific serum marker lactate dehydrogenase. Elevation of CT16 titers preceded or followed the clinical diagnosis of disease progression in four patients with metastatic melanoma. As a conclusion, our results show that CT16 protein can be measured directly from patient serum, and the developed assay has a potential for clinical use.
authors.affiliation: Department of Biochemistry and Food Chemistry, University of Turku, Turku, Finland. pekka.rappu@utu.fi
authors.forename: Pekka
authors.initials: P
authors.lastname: Rappu
authors.forename: Camilla
authors.initials: C
authors.lastname: Nylund
authors.forename: Noora
authors.initials: N
authors.lastname: Ristiniemi
authors.forename: Janne
authors.initials: J
authors.lastname: Kulpakko
authors.forename: Pia
authors.initials: P
authors.lastname: Vihinen
authors.forename: Micaela
authors.initials: M
authors.lastname: Hernberg
authors.forename: Tuomas
authors.initials: T
authors.lastname: Mirtti
authors.forename: Kalle
authors.initials: K
authors.lastname: Alanen
authors.forename: Markku
authors.initials: M
authors.lastname: Kallajoki
authors.forename: Meri-Sisko
authors.initials: MS
authors.lastname: Vuoristo
authors.forename: Seppo
authors.initials: S
authors.lastname: Pyrhönen
authors.forename: Jyrki
authors.initials: J
authors.lastname: Heino
mesh_terms: D001483:Base Sequence; D014408:Biomarkers, Tumor / Q000097:blood*; D045744:Cell Line, Tumor; D017931:DNA Primers; D006801:Humans; D007106:Immune Sera; D007118:Immunoassay / Q000379:methods*; D008545:Melanoma / Q000097:blood* / Q000473:pathology; D058950:Melanoma-Specific Antigens / Q000097:blood*; D008875:Middle Aged; D009362:Neoplasm Metastasis
chemical_list: D014408:Biomarkers, Tumor; D017931:DNA Primers; D007106:Immune Sera; D058950:Melanoma-Specific Antigens; C558361:melanoma-derived CT16 cancer testis antigen, human