Elsevier

Human Pathology

Volume 44, Issue 4, April 2013, Pages 526-533
Human Pathology

Original contribution
Glypican 3 expression in tumors with loss of SMARCB1/INI1 protein expression,☆☆

https://doi.org/10.1016/j.humpath.2012.06.014Get rights and content

Summary

Glypican 3 (GPC3), a membrane-bound heparin sulfate proteoglycan, is mutated in Simpson-Golabi-Behmel syndrome, characterized by tissue overgrowth and an increased risk of embryonal malignancies such as Wilms tumor. Malignant rhabdoid tumor (MRT), originally described as a rhabdomyosarcomatoid variant of Wilms tumor, is a tumor with loss of SMARCB1/INI1 protein expression. We analyzed the frequency of GPC3 protein expression, GPC3 mRNA, and serum-soluble GPC3 levels in 71 cases of tumors with loss of SMARCB1/INI1 protein expression, including 14 MRTs, 48 epithelioid sarcomas (ES) (proximal-type, 21; distal-type, 27), 4 extraskeletal myxoid chondrosarcomas, and 5 pediatric undifferentiated soft-tissue sarcomas. We found that GPC3 overexpression of more than 10% of the labeling index was recognized in 6 (42.9%) MRTs, 1 (2.1%) proximal-type ES, and 3 (60%) pediatric undifferentiated soft-tissue sarcomas (MRT vs ES, P = .0003). All the remaining cases revealed GPC3-absent expression of less than 1% of the labeling index. The median values of GPC3 mRNA in the GPC3-absent expression group and overexpression group were 10.2 and 309, respectively, with a statistically significant difference between these 2 groups (P = .004). However, there was no statistically significant difference in the prognoses of these 2 groups of MRT (P = .99). In analyzable cases of small-number MRT and pediatric undifferentiated soft-tissue sarcoma, there is no significant correlation between GPC3 immunoreactivity and serum-soluble GPC3 level. Therefore, evaluation of GPC3 immunoexpression may be a useful diagnostic tool to distinguish ES from MRT, especially extrarenal MRT. It was suggested that MRTs with GPC3 overexpression may become a new target of GPC3 immunotherapy.

Introduction

Glypican 3 (GPC3), which is located in Xq26, is a member of the glypican family of heparin-sulfate proteoglycans. This protein is linked to the cell surface through a glycosylphosphatidylinositol anchor, and is thought to regulate cell growth and apoptosis through interactions with morphogenic or growth factors such as Wnt5a, fibroblast growth factor 2, bone morphogenic protein 7, and tissue factor pathway inhibitor [1], [2], [3]. Loss-of-function mutations in the human GPC3 gene result in Simpson-Golabi-Behmel syndrome, an X-linked condition characterized by severe malformations and pre- and postnatal overgrowth. Furthermore, these patients have a high risk of developing embryonal tumors, mostly Wilms kidney tumor and neuroblastoma [4].

Malignant rhabdoid tumor (MRT), which was originally described in 1978 as a rhabdomyosarcomatoid variant of Wilms tumor, is a rare and highly aggressive embryonal tumor in infancy or childhood [5]. SMARCB1/INI1 (INI1) immunohistochemical expression has not been detected in any MRT cases except in rare examples, and this feature has been reported to be useful for the correct diagnosis of MRT [6], [7], [8]. However, loss of INI1 protein expression has also been demonstrated in all renal medullary carcinomas, almost all epithelioid sarcomas, half of epithelioid malignant peripheral nerve sheath tumors, about half of pediatric myoepithelial carcinomas, and some extraskeletal myxoid chondrosarcomas [9], [10], [11], [12], [13].

In the present study, we analyzed the frequency of GPC3 protein expression in a large series of MRT cases and other tumors with loss of INI1 protein expression. Furthermore, we examined mRNA expressions of GPC3 in frozen samples by quantitative reverse transcriptase polymerase chain reaction (RT-PCR) and serum-soluble GPC3 protein in preoperative blood samples by enzyme-linked immunosorbent assay (ELISA).

Section snippets

Patients

Tumors with loss of INI1 protein expression in the present study were selected from among more than 15 000 cases of bone and soft-tissue tumors registered in the Department of Anatomic Pathology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, Japan, between 1955 and 2010. The primary monoclonal antibodies used in the case selection were BAF47, an antibody to the SMARCB1/INI1 gene product (clone 25; 1:250; 20-minute microwave; BD Transduction Laboratories, San Diego, CA). As a

Glypican 3 immunoreactivity

The results of the immunohistochemical analysis are summarized in Table 3. In 6 of the 14 MRTs (42.9%), 1 (2.1%) of the 48 epithelioid sarcomas and 3 of the 5 pediatric undifferentiated soft-tissue sarcomas (60%), overexpression of more than 10% of LI was recognized (Fig. 1A-D). However, all the remaining cases showed absent expression of less than 1% of LI (Fig. 1E-H). GPC3 immunoreactivity was found significantly more frequently in MRT than in epithelioid sarcoma (P = .0003) or proximal-type

Discussion

MRT is characterized by rhabdoid cells having a globoid, and hyaline or eosinophilic intracytoplasmic inclusions [8], [16]. However, the existence of rhabdoid cells is recognized in a wide variety of tumors, such as epithelioid sarcoma, synovial sarcoma, extraskeletal myxoid chondrosarcoma, leiomyosarcoma, malignant mesothelioma and desmoplastic small round-cell tumors [8]. The histological features of proximal-type epithelioid sarcoma particularly resemble those of MRT, especially extrarenal

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      Immunophenotype shows characteristically, loss of SMARCB1 (INI-1). Most tumors also express epithelial markers (keratins and EMA) and could also express CD99, synaptophysin, ERG, SALL4 and glypican-3 among others [93,94]. All these tumors are related to tumor suppressor role for the SWI/SNF (SWItch/Sucrose Non-Fermenting) complex involved in the remodeling of chromatin.

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      Other studies reported variable percentage of GPC3 immunoreactivity in rhabdomyosarcomas and malignant rhabdoid tumors [80,81]. Interestingly, in the latter malignancies, originally described as rhabdomyosarcomatoid variants of Wilms tumors, GPC3 overexpression has been suggested as a useful diagnostic tool and a candidate target for immunotherapy [82]. Immunohistochemical analyses on a multitumor array revealed also consistent GPC3 expression in liposarcomas [83].

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      That being said, several recent studies have proposed a variety of potential tools to help in this situation. For instance, Kohashi et al.119 detected glypican 3 overexpression in over 40% of MRT versus only 2% of proximal ES, and subsequently demonstrated differential microRNA expression between MRT and ES as well.120 SALL4 immunoexpression has likewise been shown to be demonstrable in two thirds of MRT but only rarely in ES.121

    • ERG and SALL4 expressions in SMARCB1/INI1-deficient tumors: A useful tool for distinguishing epithelioid sarcoma from malignant rhabdoid tumor

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    Disclosure/conflict of interest: The authors declare that there are no conflicts of interest to disclose.

    ☆☆

    This study was supported in part by a Grant-in-Aid for Scientific Research (B) (No. 21390107) and Young Scientists (B) (No.21790356) from the Japan Society for the Promotion of Science, the National Cancer Center Research and Development Fund (23-B-12), and Health and Labor Science Research Grants for Clinical Research from the Ministry of Health, Labor and Welfare, Tokyo, Japan. The English used in this manuscript was revised by KN International (http://www.kninter.com/).

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