title: CD44 alternative splicing and hnRNP A1 expression are associated with the metastasis of breast cancer.
abstract: CD44 is a transmembrane receptor for hyaluronic acid. CD44 pre-mRNA contains 19 exons, 9 of which are alternatively spliced. Among the CD44 spliced variants, the v4-7 variant, one of the v6 exon-containing isoforms that contains variable exon 4, 5, 6 and 7, confers metastatic potential to non-metastatic cells. Splicing of CD44 and the function of CD44 isoforms are different in breast cancer cells. hnRNP A1 is a ubiquitously expressed protein with an inhibitory function in pre-mRNA splicing. We showed that CD44v6 isoform, which includes all of the v6-containing mRNA isoforms, had the highest expression level in non-metatatic breast cancer cells (MCF7) when compared to the level in metastatic breast cancer cells (MDA-MB-231) and normal breast cells (MCF10A). Furthermore we showed that hnRNP A1 knockdown regulated splicing of CD44 differently in breast cancer cells. We showed here that CD44 isoform expression is completely different in MDA-MB-231 cells than that in MCF7 and MCF10A cells, whereas MCF7 and MCF10A cells had a similar expression pattern of CD44 isoforms. RT-PCR analysis of CD44v6 showed that MCF7 and MCF10A cells predominantly expressed the c5v6v7v8v9v10c6 isoform. However, in addition to this isoform, MDA-MB-231 cells also expressed the c5v6v8v9v10c6 and c5v6c6 isoforms. We also found that knockdown of hnRNP A1 significantly reduced the expression of c5v6v7v8v9v10c6 and c5v6v8v9v10c6, and promoted the expression of c5v6c6. hnRNP A1 knockdown significantly induced cell death. In addition, hnRNP A1 knockdown induced a decrease in cell invasion in the MDA-MB-231 cells. Our results indicate that the knockdown of hnRNP A1 has a specific function on the splicing of CD44 in breast cancer cells.
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Tiing Jen
authors.initials: TJ
authors.lastname: Loh
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Heegyum
authors.initials: H
authors.lastname: Moon
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Sunghee
authors.initials: S
authors.lastname: Cho
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Hana
authors.initials: H
authors.lastname: Jang
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Yong Chao
authors.initials: YC
authors.lastname: Liu
authors.affiliation: Department of Endocrinology, Yanji Hospital, Jilin, P.R. China.
authors.forename: Hongmei
authors.initials: H
authors.lastname: Tai
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Da-Woon
authors.initials: DW
authors.lastname: Jung
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Darren R
authors.initials: DR
authors.lastname: Williams
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Republic of Korea.
authors.forename: Hey-Ran
authors.initials: HR
authors.lastname: Kim
authors.affiliation: Department of Laboratory Medicine, Chonnam National University Medical School and Chonnam National University Hwasun Hospital, Hwasun, Republic of Korea.
authors.forename: Myung-Geun
authors.initials: MG
authors.lastname: Shin
authors.affiliation: Hormel Institute, University of Minnesota, Austin, MN, USA.
authors.forename: D Joshua
authors.initials: DJ
authors.lastname: Liao
authors.affiliation: Jiangsu Key Laboratory of Neuroregeneration, Nantong University, Nantong, Jiangsu, P.R. China.
authors.forename: Jianhua
authors.initials: J
authors.lastname: Zhou
authors.affiliation: Key Laboratory for Molecular Enzymology and Engineering, The Ministry of Education, College of Life Sciences, Jilin University, Changchun, Jilin, P.R. China.
authors.forename: Wei
authors.initials: W
authors.lastname: Shi
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Xuexiu
authors.initials: X
authors.lastname: Zheng
authors.affiliation: School of Life Sciences, Gwangju Institute of Science and Technology, Gwangju, Republic of Korea.
authors.forename: Haihong
authors.initials: H
authors.lastname: Shen
mesh_terms: D017398:Alternative Splicing; D001943:Breast Neoplasms / Q000235:genetics* / Q000378:metabolism / Q000473:pathology*; D045744:Cell Line, Tumor; D002465:Cell Movement / Q000235:genetics; D049109:Cell Proliferation / Q000235:genetics; D002470:Cell Survival / Q000235:genetics; D005260:Female; D005455:Fluorescent Antibody Technique; D015972:Gene Expression Regulation, Neoplastic / Q000502:physiology; D055785:Gene Knockdown Techniques; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B / Q000096:biosynthesis*; D006801:Humans; D018960:Hyaluronan Receptors / Q000096:biosynthesis / Q000235:genetics*; D015151:Immunoblotting; D009361:Neoplasm Invasiveness / Q000235:genetics* / Q000473:pathology; D020033:Protein Isoforms; D034741:RNA, Small Interfering; D020133:Reverse Transcriptase Polymerase Chain Reaction; D014162:Transfection
chemical_list: C497483:CD44 protein, human; D000076245:Heterogeneous Nuclear Ribonucleoprotein A1; D034481:Heterogeneous-Nuclear Ribonucleoprotein Group A-B; D018960:Hyaluronan Receptors; D020033:Protein Isoforms; D034741:RNA, Small Interfering