Serglycin Regulates Cytoskeletal‐related Proteins Associated with Cell Motility in Breast Cancer In Vitro

Abstract

Despite advances in cancer treatment, triple‐negative (ER−/PR−/HER2−) breast cancer represents a complicated subtype with no specific treatment regime. Serglycin (SRGN) is an intracellular proteoglycan which has been shown to be highly expressed in the triple‐negative MDA‐MB‐231 breast cancer cell line. In this study, we aim to decipher the molecular networks and pathways regulated by SRGN in breast cancer cells using a global gene expression analysis approach. We first analyzed the expression of SRGN in a dataset containing 1,881 breast cancer tissues from the GOBO database (http://co.bmc.lu.se/gobo/gobo.pl). For the in vitro experiments, siRNA‐mediated down‐regulation of the SRGN gene in MDA‐MB‐231 cells was performed. Transcriptomic analysis of si‐SRGN breast cancer cells was then carried out. Subsequently real time PCR for specific gene targets and expression of selected proteins by Western Blot were performed. Cell motility was determined using commercially available cell migration chambers. The Gene Set analysis from the GOBO database verified that the SRGN gene is highly expressed in basal (triple negative) breast tumors. Knockdown of the SRGN gene in MDA‐MB‐231 cells induced differential expression of 225 genes. Gene ontology analysis revealed the presence of a cluster of genes that were highly enriched in cellular processes, including cell movement. Reduced expression of SRGN was accompanied by down‐regulation of several cytoskeletal‐related genes, namely ABLIM1, LIMA1, CFL1, RAC1, RAC2 and RHOA, concomitant with decreased cell motility. Decreased expression of RAC1 and RHOA proteins were also demonstrated. The results suggest that SRGN is important in regulating actin cytoskeletal organization associated with cell migration, a crucial event during cancer metastasis.Support or Funding InformationThis work is supported by the National Medical Research Council Singapore Grant NMRC/CIRG/1370/2013.