Excess PLAC8 promotes an unconventional ERK2-dependent EMT in colon cancer
Cunxi Li, … , Lila Solnica-Krezel, Robert J. Coffey
Cunxi Li, … , Lila Solnica-Krezel, Robert J. Coffey
Published April 1, 2014
Citation Information: J Clin Invest. 2014;124(5):2172-2187. https://doi.org/10.1172/JCI71103.
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Research Article Oncology

Excess PLAC8 promotes an unconventional ERK2-dependent EMT in colon cancer

Abstract

The epithelial-to-mesenchymal transition (EMT) transcriptional program is characterized by repression of E-cadherin (CDH1) and induction of N-cadherin (CDH2), and mesenchymal genes like vimentin (VIM). Placenta-specific 8 (PLAC8) has been implicated in colon cancer; however, how PLAC8 contributes to disease is unknown, and endogenous PLAC8 protein has not been studied. We analyzed zebrafish and human tissues and found that endogenous PLAC8 localizes to the apical domain of differentiated intestinal epithelium. Colon cancer cells with elevated PLAC8 levels exhibited EMT features, including increased expression of VIM and zinc finger E-box binding homeobox 1 (ZEB1), aberrant cell motility, and increased invasiveness. In contrast to classical EMT, PLAC8 overexpression reduced cell surface CDH1 and upregulated P-cadherin (CDH3) without affecting CDH2 expression. PLAC8-induced EMT was linked to increased phosphorylated ERK2 (p-ERK2), and ERK2 knockdown restored cell surface CDH1 and suppressed CDH3, VIM, and ZEB1 upregulation. In vitro, PLAC8 directly bound and inactivated the ERK2 phosphatase DUSP6, thereby increasing p-ERK2. In a murine xenograft model, knockdown of endogenous PLAC8 in colon cancer cells resulted in smaller tumors, reduced local invasion, and decreased p-ERK2. Using MultiOmyx, a multiplex immunofluorescence-based methodology, we observed coexpression of cytosolic PLAC8, CDH3, and VIM at the leading edge of a human colorectal tumor, supporting a role for PLAC8 in cancer invasion in vivo.

Authors

Cunxi Li, Haiting Ma, Yang Wang, Zheng Cao, Ramona Graves-Deal, Anne E. Powell, Alina Starchenko, Gregory D. Ayers, Mary Kay Washington, Vidya Kamath, Keyur Desai, Michael J. Gerdes, Lila Solnica-Krezel, Robert J. Coffey

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Figure 10

Expression of PLAC8, CDH1, CDH3, CK, and VIM in a medullary CRC.

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Expression of PLAC8, CDH1, CDH3, CK, and VIM in a medullary CRC. (A) Com...
(A) Composite view of PLAC8 (white), CDH1 (red), CDH3 (green), CK (magenta), and VIM (blue) expression. (B) Transition from CDH1- to CDH3-expressing cells from boxed region in A (dotted line). (C) Cells within the CDH3+ (gray) region have cytosolic PLAC8 expression (false-colored, blue). (D) Expression of CK (false-colored, red), VIM (false-colored, green) and cytosolic PLAC8 expression (false-colored, blue) within the CDH3+ (gray) cells. Cells with cytosolic PLAC8 expression and coexpression of CK and VIM are boxed and enlarged in C and D. (E–I) Single-marker expression of panels composited in A. Scale bars in the insets of C and D: 25 μm; other scale bars: 75 μm.