Blockade of phospholipid scramblase 1 with its N-terminal domain antibody reduces tumorigenesis of colorectal carcinomas in vitro and in vivo

Chung-Wei Fan,Ya-Shan Chen,Chun-Yu Chen,Chia-Rui Shen,Yeh-Pin Chou,Wei-Shan Wei,Kuei-Tien Chen,Yung-Bin Kuo,Err-Cheng Chan

doi:10.1186/1479-5876-10-254

Abstract

BackgroundMembrane-bound phospholipid scramblase 1 (PLSCR1) is involved in both lipid trafficking and cell signaling. Previously, we showed that PLSCR1 is overexpressed in many colorectal carcinomas (CRCs). In the present study, we investigated the tumorigenic role of PLSCR1 in CRC and suggest that it is a potential therapeutic target.MethodsTo identify PLSCR1 as a therapeutic target, we studied the tumorigenic properties of CRC cell lines treated with a monoclonal antibody (NP1) against the N-terminus of PLSCR1 in vitro and in vivo. We also investigated cell cycle status and epidermal growth factor receptor–related pathways and downstream effectors of PLSCR1 after blocking its function with NP1.ResultsTreating CRC cells with NP1 in vitro and in vivo decreased cell proliferation, anchorage-independent growth, migration, and invasion. Adding NP1 to the CRC cell line HT29 caused arrest at G1/S. Treating HT29 cells with NP1 significantly decreased the expression of cyclin D1 and phosphorylation levels of Src, the adaptor protein Shc, and Erks. The reduced level of cyclin D1 led to an increase in the activated form of the tumor suppressor retinoblastoma protein via dephosphorylation. These actions led to attenuation of tumorigenesis.ConclusionsTherefore, PLSCR1 may serve as a potential therapeutic target for CRC.

Highlights

We identified several differentially expressed proteins in colorectal carcinoma (CRC) cells using gelassisted digestion and label-free mass spectrophotometry [1]
Elevated expression of phospholipid scramblase 1 (PLSCR1) in CRC cell lines and various human cancer cells Western blotting with NP1 was performed on lysates from various cell lines including eight CRC lines (CoLo205, HCT116, SW620, LoVo, HCT15, SW480, WiDr, HT29), HepG2 cells, and one Treatment with NP1 reduces tumorigenic properties of CRC cells in vitro and in vivo To inhibit PLSCR1 function, we used NP1 to treat CRC cell lines, and proliferation was compared with that of cells treated with isotype-control IgG
Colonies formed by untreated HT29 cells were much larger than those formed by NP1-treated cells, suggesting a substantial potential for NP1 to inhibit the ability of HT29 colony formation (Figure 3A)

Summary

Introduction

We identified several differentially expressed proteins in colorectal carcinoma (CRC) cells using gelassisted digestion and label-free mass spectrophotometry [1]. We demonstrated a novel target, phospholipid scramblase (PLSCR1), which is overexpressed in most CRC tissues. PLSCR1 seems to function as a signal transduction molecule. The effects of PLSCR1 on cell proliferation and maturation may be related to altered expression of cellular inositol triphosphate receptors [6]. PLSCR1 has been reported to be a substrate for protein kinase Cδ, thereby elevating phosphatidylserine exposure in cells undergoing apoptosis [9]. PLSCR1 is a substrate of a tyrosine kinase associated with the IgE receptor [10], c-Abl tyrosine kinases [11], and c-Src [12], implying a possible role for PLSCR1 in one or more intracellular signaling pathways that regulate cell proliferation or apoptosis. We showed that PLSCR1 is overexpressed in many colorectal carcinomas (CRCs). We investigated the tumorigenic role of PLSCR1 in CRC and suggest that it is a potential therapeutic target

Methods

Results

Conclusion