Letter to the Editor

T-cell factor 1 expression in germ cell tumors withtrophoblastic differentiation

To the Editor:T-cell factor 1 (TCF-1) protein is a member of the LEF1/TCFfamily of transcription factors, which are constituents of theWnt signaling pathway, that plays an important role in embryo-nal development, adult stem cell maintenance and tumorgrowth. TCF-1 binds to the DNA through a high mobility groupand at least eight protein isoforms. The canonical Wnt oper-ates in two modes, on and off. In the off mode, the Wnt ligandis absent and cytoplasmic complex, composed of axin,adenomatous polyposis coli (APC), Casein kinase 1 (Ck1) andGlycogen Synthase Kinase (Gsk3), stimulates the destructionof β-catenin. Consequently, as β-catenin fails to enter thenucleus and activates T-cell transcription factors, the TCFsinstead bind to a group of co-repressor proteins and inhibittranscription of β-catenin dependent genes.1 In the on mode,Wnt ligand binding with membrane receptor inhibits cytoplas-mic destruction complex, which allows translocation ofβ-catenin into nucleus and binding with amino-terminal end ofTCF. As a consequence of this interaction, TCFs becometranscriptional activators which bind to Wnt response ele-ments of target genes, and increased activation of this signal-ing pathway may lead to development of cancer.2

Previous studies have indicated that the Wnt signalingpathway plays an important role in balancing cell prolifera-tion, apoptosis and differentiation during the trophoblast dif-ferentiation.3 The β-catenin-induced TCF4 protein activatesthe GCM1/syncictin signaling pathway, which leads to fusionof the human choriocarcinoma cells.4 Expression of Wntantagonist Wnt5a, found normally in human cytotrophoblastcells, is completely absent from choriocarcinoma cell lineJAR, whereas exogenous recombinant Wnt5a applied tochoriocarcinoma cells decreases their proliferation andinduces apoptosis, suggesting it acts as a tumor suppressorfor placental choriocarcinomas.5 Hypermethylation of theAPC suppressor gene has been associated with all humanchoriocarcinoma cell lines.6 Dickkopf-related protein 1(DKK1), another Wnt signaling pathway antagonist, is abun-dantly present in human cytotrophoblast cells, but it is absentfrom choriocarcinoma cells lines JAR and JEG3. When givenexogenously to cells, it reduces proliferation of both chorio-carcinoma cells lines and induces apoptosis of JAR cells.This tumor suppressor effect is believed to be accomplished

through c-Jun N-terminal kinase, without directly involvingWnt signaling pathway.7 TCF-1 stimulates the growthof human malignant hematopoietic cells independently ofβ-catenin binding, i.e. its activity is accomplished throughbinding to ATF2 [activating transcription factor 2] family ofproteins. It is thought that this alternative mechanism isresponsible for development of some hematopoietic tumors.8

Increased expression of TCF-1 protein has been reportedrecently in various human malignancies including renal cellcarcinoma and hepatocellular tumors (adenoma and carci-noma).9,10 The status of TCF-1 protein has not been analyzedin germ cell tumors of gonads including the tumors withtrophoblastic differentiation. In the present report usingimmunohistochemistry (Clone: sc-8589, Santa Cruz Biotech-nology, Santa Cruz, CA, USA, dilution 1:50) we exploredTCF-1 expression in a subset of germ cell tumors with tro-phoblastic differentiation and compared it with adjacentnormal/benign reproductive tissues (negative control) andtumor-infiltrating T-lymphocytes (positive control). TCF-1protein was scored for the intensity and percentage inthe choriocarcinoma cells. Tumor-infiltrating lymphocytesretained a strong, nuclear expression of TCF-1 protein(Fig. 1c), whereas normal and benign tissues (testis, ovary,endometrium and myometrium) were negative (Fig. 1a,c).Pure ovarian choriocarcinomas (n = 3) exhibited predomi-nantly strong TCF-1 expression (score 3+) in the range20–70% of the tumors cells (Fig. 1b). In mixed germ celltumors of the testis (n = 5), choriocarcinoma cells alsoshowed intense TCF-1 protein expression (Fig. 1d), whereasother germ cell compartments (seminoma, embryonal carci-noma, yolk sac tumor and teratoma) exhibited only weak(score 1+) and focal TCF-1 positivity (<10% of the cells)(Fig. 1c). Our preliminary data indicate that TCF-1 proteinmay be actively involved in pathogenesis of a subset of germcell tumors with trophoblastic differentiation. Further func-tional and clinical studies should validate the relevance ofTCF-1 protein in these tumors.

Ljiljana Serman,1 Tamara Nikuseva Martic1

and Semir Vranic2

1Department of Biology, School of Medicine,University of Zagreb, Zagreb, Croatia, and2Department of Pathology, Clinical Center,

University of Sarajevo, Sarajevo,Bosnia and Herzegovina

Pathology International 2014; 64: 86–87 doi:10.1111/pin.12126

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© 2014 The AuthorsPathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd

REFERENCES

1 Wallmen B, Schrempp M, Hecht A. Intrinsic properties of Tcf1and Tcf4 splice variants determine cell-type-specific Wnt/β-catenin target gene expression. Nucleic Acids Res 2012; 40:9455–69.

2 Arce L, Yokoyama NN, Waterman ML. Diversity of LEF/TCFaction in development and disease. Oncogene 2006; 25: 7492–504.

3 Knöfler M, Pollheimer J. Human placental trophoblast invasionand differentiation: A particular focus on Wnt signaling. FrontGenet 2013; 4: 190.

4 Matsuura K, Jigami T, Taniue K et al. Identification of a linkbetween Wnt/β-catenin signalling and the cell fusion pathway.Nat Commun 2011; 2: 548.

5 Peng S, Zhang J, Chen J, Wang H. Effects of Wnt5a protein onproliferation and apoptosis in JAR choriocarcinoma cells. MolMed Rep 2011; 4: 99–104.

6 Wong NC, Novakovic B, Weinrich B et al. Methylation of theadenomatous polyposis coli (APC) gene in human placenta and

hypermethylation in choriocarcinoma cells. Cancer Lett 2008;268: 56–62.

7 Peng S, Miao C, Li J, Fan X, Cao Y, Duan E. Dickkopf-1 inducedapoptosis in human placental choriocarcinoma is independentof canonical Wnt signaling. Biochem Biophys Res Commun2006; 350: 641–7.

8 Grumolato L, Liu G, Haremaki T et al. β-Catenin-independentactivation of TCF1/LEF1 in human hematopoietic tumor cellsthrough interaction with ATF2 transcription factors. PLoS Genet2013; 9: e1003603.

9 Nikuševa-Martic T, Serman L, Zeljko M et al. Expression ofsecreted frizzled-related protein 1 and 3, T-cell factor 1 andlymphoid enhancer factor 1 in clear cell renal cell carcinoma.Pathol Oncol Res 2013; 19: 545–51.

10 Yuzugullu H, Benhaj K, Ozturk N et al. Canonical Wnt signalingis antagonized by noncanonical Wnt5a in hepatocellular carci-noma cells. Mol Cancer 2009; 8: 90.

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c dFigure 1 (a–d) A case of pure ovarianchoriocarcinoma with a strong, nuclearTCF-1 protein expression in (b) malignanttrophoblastic cells while (a) normal ovarianstroma was devoid of TCF-1 expression;A case of mixed nonseminomatous tes-ticular cancer with lack of TCF-1 expres-sion in (c) embryonal carcinoma cells andbenign testicular tissue while (d) adjacentmalignant trophoblastic cells exhibitedTCF-1 positivity. (c) Note also the pres-ence of TCF-1 protein in the tumor infiltrat-ing lymphocytes (×10).

Letter to the Editor 87

© 2014 The AuthorsPathology International © 2014 Japanese Society of Pathology and Wiley Publishing Asia Pty Ltd