Fax +41 61 306 12 34 E-Mail karger@karger.ch www.karger.com Research Article Tumor Biol 2005;26:227–235 DOI: 10.1159/000087377 Identiﬁcation of New Splice Variants and Differential Expression of the Human Kallikrein 10 Gene, a Candidate Cancer Biomarker George M. Yousef a Nicole M.A. White a Iacovos P. Michael b, c Jane Chan-Kyung Cho c John Desmond Robb a Lisa Kurlender b, c Saba Khan b Eleftherios P. Diamandis b, c a Discipline of Laboratory Medicine, Memorial University, St. John’s, b Department of Pathology and Laboratory Medicine, Mount Sinai Hospital, and c Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Canada matches with the sequence of KLK10 , while the rest of the mRNA matches with a portion of the polycystic kid- ney disease gene, found on chromosome 15. This variant could not be experimentally veriﬁed in either normal or cancerous tissues. There are 39 reported single nucleo- tide polymorphisms (SNPs) for the gene, in which three result in amino acid substitutions. SAGE analysis shows a clear upregulation of KLK10 in ovarian, pancreatic, co- lon, and gastric cancers. The gene is, however, down- regulated in breast and prostate cancers. A three-fold decrease in expression levels was noted in actinic kera- tosis, compared to normal skin from the same patient. The differential regulation of KLK10 in ovarian and pros- tate cancers was experimentally veriﬁed by RT-PCR anal- ysis. In addition, a signiﬁcant number of clones were isolated from carcinomas of the head and neck. Fewer clones were found in carcinomas of the skin, brain and prostate. Orthologues were identiﬁed in three other spe- cies, with the highest degree of homology observed with the mouse and rat orthologues (42% in each). In conclu- sion new splice variants of the KLK10 gene were identi- ﬁed. These in silico analyses show a differential expres- sion of the gene in various malignancies and provide the basis for directing experimental efforts to investigate the possible role of the gene as a cancer biomarker. Copyright © 2005 S. Karger AG, Basel Key Words Serine proteases  KLK10  NES1  Breast cancer  Ovarian cancer  Tumor markers  Kallikreins  Serial Analysis of Gene Expression  Cancer Genome Anatomy Project  Splice variants Abstract The human kallikrein gene 10 (KLK10 ) is a member of the kallikrein gene family on chromosome 19q13.4. This gene was identiﬁed by its downregulation in breast can- cer, and preliminary evidence suggests that it may act as a tumor suppressor. A computer-based analysis was performed on EST and SAGE clones from the Cancer Genome Anatomy Project and other databases. Experi- mental veriﬁcation of differential expression of KLK10 in cancer was performed by PCR using gene-speciﬁc prim- ers. The mRNA and EST analysis allowed the construc- tion of the longest transcript of the gene and character- ization of a 5 extension of the reported mRNA. In addition, seven new splice variants of KLK10 were identiﬁed. One of these variants, named KLK10 splice variant 3 (KLK10- SV3) which starts with a novel ﬁrst exon, was experimen- tally veriﬁed. This variant is predicted to encode for the same protein as the ‘classical’ KLK10 mRNA, since the ﬁrst exon is untranslated. One variant mRNA partially Received: March 23, 2005 Accepted after revision: April 12, 2005 Published online: August 9, 2005 Dr. E.P. Diamandis Mount Sinai Hospital, Department of Pathology and Laboratory Medicine 600 University Avenue Toronto, Ontario M5G 1X5 (Canada) Tel. +1 416 586 8443, Fax +1 416 586 8628, E-Mail ediamandis@mtsinai.on.ca © 2005 S. Karger AG, Basel 1010–4283/05/0265–0227$22.00/0 Accessible online at: www.karger.com/tbi