CITED1 Expression in Liver Development and Hepatoblastoma

Abstract

Hepatoblastoma, the most common pediatric liver cancer, consists of epithelial mixed embryonal/fetal (EMEF) and pure fetal histologic subtypes, with the latter exhibiting a more favorable prognosis. Few embryonal histology markers that yield insight into the biologic basis for this prognostic discrepancy exist. CBP/P-300 interacting transactivator 1 (CITED1), a transcriptional co-activator, is expressed in the self-renewing nephron progenitor population of the developing kidney and broadly in its malignant analog, Wilms tumor (WT). In this current study, CITED1 expression is detected in mouse embryonic liver initially on post-coitum day 10.5 (e10.5), begins to taper by e14.5, and is undetectable in e18.5 and adult livers. CITED1 expression is detected in regenerating murine hepatocytes following liver injury by partial hepatectomy and 3,5-diethoxycarbonyl-1,4-dihydrocollidine. Importantly, while CITED1 is undetectable in normal human adult livers, 36 of 41 (87.8%) hepatoblastoma specimens express CITED1, where it is enriched in EMEF specimens compared to specimens of pure fetal histology. CITED1 overexpression in Hep293TT human hepatoblastoma cells induces cellular proliferation and upregulates the Wnt inhibitors Kringle containing transmembrane protein 1 (KREMEN1) and CXXC finger protein 4 (CXXC4). CITED1 mRNA expression correlates with expression of CXXC4 and KREMEN1 in clinical hepatoblastoma specimens. These data show that CITED1 is expressed during a defined time course of liver development and is no longer expressed in the adult liver but is upregulated in regenerating hepatocytes following liver injury. Moreover, as in WT, this embryonic marker is reexpressed in hepatoblastoma and correlates with embryonal histology. These findings identify CITED1 as a novel marker of hepatic progenitor cells that is re-expressed following liver injury and in embryonic liver tumors.

β-Catenin Activation in a Novel Liver Progenitor Cell Type Is Sufficient to Cause Hepatocellular Carcinoma and Hepatoblastoma

“…GFP + cells in fetal kidney served as a control (Table 1a). In contrast to the very low frequency of GFP + cells in livers from the BAC transgenic mice, widespread endogenous CITED1 protein expression has been observed in fetal liver from wild-type mice at E11.5 – E14.5 (18). Thus, while the transgene includes 190kb from the 5′ region of the Cited1 gene, transgene expression is much more restricted than that of the endogenous locus.…”

“…Alternatively, HCCs may arise following dedifferentiation of adult hepatocytes and re-expression of fetal markers during the course of malignant transformation (2). The recent observation of CITED1 expression in regenerating hepatocytes following partial hepatectomy or DDC treatment (18) suggests that fetal markers can be re-expressed in adult hepatocytes during regeneration.…”

Kremen1 restricts Dkk activity during posterior lateral line development in zebrafish

“…Our data indicate that in the absence of Kremen1 function, Wnt signaling is prematurely downregulated in the pLLP in a non-cell-autonomous manner through an ectopic expansion of Dkk proteins. As improper Wnt signaling has been implicated in collective cancer invasion (Friedl and Gilmour, 2009), and expression of kremen1 is altered in some cancers (Dun et al, 2010;Murphy et al, 2012), our findings may provide a potential mechanism for Wnt misregulation during disease. …”

CITED1 confers stemness to Wilms tumor and enhances tumorigenic responses when enriched in the nucleus

“…We have shown previously that CITED1 repressed epithelial differentiation of cultured metanephric mesenchymes, and induced the WNT inhibitor KREMEN1 , the DKK1 receptor, in a hepatoblastoma cell line [9, 12]. Given that ectopic expression of wild-type CITED1 induced DKK1 in WiT49 cells from the above microarray, we sought to validate these observed changes and to screen for additional alterations in known effectors of the WNT signaling cascade using this experimental model.…”

“…One fundamental observation from these previous studies is that CITED1, which in the CM of the developing kidney is predominantly detected in the cytosol, becomes enriched in the nuclei of WT blastema [7, 10]. Control of CITED1 subcellular localization is currently unknown, although it is developmentally regulated, showing cytosolic predominance in nephron progenitors and hepatic primordia, but a nuclear preference in trabeculae of the developing heart [12]. Diverging further from its expression domain in the embryonic kidney, in which it is absent among the earliest nephronic structures, CITED1 can be detected rarely in primitive epithelial structures of WT but appears principally to be a marker of blastema.…”