title: 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.forename: Cunxi
authors.initials: C
authors.lastname: Li
authors.forename: Haiting
authors.initials: H
authors.lastname: Ma
authors.forename: Yang
authors.initials: Y
authors.lastname: Wang
authors.forename: Zheng
authors.initials: Z
authors.lastname: Cao
authors.forename: Ramona
authors.initials: R
authors.lastname: Graves-Deal
authors.forename: Anne E
authors.initials: AE
authors.lastname: Powell
authors.forename: Alina
authors.initials: A
authors.lastname: Starchenko
authors.forename: Gregory D
authors.initials: GD
authors.lastname: Ayers
authors.forename: Mary Kay
authors.initials: MK
authors.lastname: Washington
authors.forename: Vidya
authors.initials: V
authors.lastname: Kamath
authors.forename: Keyur
authors.initials: K
authors.lastname: Desai
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Gerdes
authors.forename: Lila
authors.initials: L
authors.lastname: Solnica-Krezel
authors.forename: Robert J
authors.initials: RJ
authors.lastname: Coffey
mesh_terms: D000818:Animals; D015703:Antigens, CD; D015820:Cadherins / Q000096:biosynthesis / Q000235:genetics; D045744:Cell Line, Tumor; D003110:Colonic Neoplasms / Q000235:genetics / Q000378:metabolism* / Q000473:pathology; D054642:Dual Specificity Phosphatase 6; D058750:Epithelial-Mesenchymal Transition; D057809:HEK293 Cells; D006801:Humans; D007413:Intestinal Mucosa / Q000378:metabolism* / Q000473:pathology; D051379:Mice; D019950:Mitogen-Activated Protein Kinase 1 / Q000235:genetics / Q000378:metabolism*; D009361:Neoplasm Invasiveness; D009363:Neoplasm Proteins / Q000235:genetics / Q000378:metabolism*; D011506:Proteins / Q000235:genetics / Q000378:metabolism*; D014746:Vimentin / Q000096:biosynthesis / Q000235:genetics; D015027:Zebrafish / Q000235:genetics / Q000378:metabolism*; D029961:Zebrafish Proteins / Q000235:genetics / Q000378:metabolism*
chemical_list: D015703:Antigens, CD; C513384:CDH1 protein, human; C512197:CDH3 protein, human; D015820:Cadherins; D009363:Neoplasm Proteins; C506004:PLAC8 protein, human; D011506:Proteins; D014746:Vimentin; D029961:Zebrafish Proteins; C535150:MAPK1 protein, human; D019950:Mitogen-Activated Protein Kinase 1; C517035:DUSP6 protein, human; D054642:Dual Specificity Phosphatase 6