Increased secretory leukocyte protease inhibitor (SLPI) production by highly metastatic mouse breast cancer cells.

Kevin T. Sayers,Thomas J. Sayers,Alan D. Brooks,Oleg Chertov,Michael P. Bachmann

doi:10.1371/journal.pone.0104223

Abstract

The precise molecular mechanisms enabling cancer cells to metastasize from the primary tumor to different tissue locations are still largely unknown. Secretion of some proteins by metastatic cells could facilitate metastasis formation. The comparison of secreted proteins from cancer cells with different metastatic capabilities in vivo might provide insight into proteins involved in the metastatic process. Comparison of the secreted proteins from the mouse breast cancer cell line 4T1 and its highly metastatic 4T1.2 clone revealed a prominent differentially secreted protein which was identified as SLPI (secretory leukocyte protease inhibitor). Western blotting indicated higher levels of the protein in both conditioned media and whole cell lysates of 4T1.2 cells. Additionally higher levels of SLPI were also observed in 4T1.2 breast tumors in vivo following immunohistochemical staining. A comparison of SLPI mRNA levels by gene profiling using microarrays and RT-PCR did not detect major differences in SLPI gene expression between the 4T1 and 4T1.2 cells indicating that SLPI secretion is regulated at the protein level. Our results demonstrate that secretion of SLPI is drastically increased in highly metastatic cells, suggesting a possible role for SLPI in enhancing the metastatic behavior of breast cancer cell line 4T1.

Highlights

Secreted proteins have been shown to play an important role in the tumor metastasis of numerous cancers including breast [1], ovarian [2], lung [3], and a number of others
Tumor secreted proteins are involved in a number of biological processes including changes to the extracellular matrix [4] [5], angiogenesis [6], migration of cancer cells [7], and more recently a potential involvement in epithelial to mesenchymal transition (EMT) of cancer cells [8]
Most protein bands observed from Conditioned media (CM) of 4T1 and 4T1.2 cells were identical and of similar intensity, but one standout protein band was predominantly present in 0.1 M eluate of 4T1.2 cell supernatant (Fig.1 and Fig.2A)

Summary

Introduction

Secreted proteins have been shown to play an important role in the tumor metastasis of numerous cancers including breast [1], ovarian [2], lung [3], and a number of others. The secretion of certain proteins has been shown to be related to the aggressiveness of cancer cell growth and the ability of the cancer cells to metastasize. Tumor secreted proteins are involved in a number of biological processes including changes to the extracellular matrix [4] [5], angiogenesis [6], migration of cancer cells [7], and more recently a potential involvement in epithelial to mesenchymal transition (EMT) of cancer cells [8]. The mouse breast cancer cell line 4T1 has been used to model human breast cancer since it demonstrates a similar disease progression to that seen in humans [9]. Differences in secreted proteins between these two cell lines might be indicative of proteins that could be involved in the metastatic processes

Methods

Results

Conclusion