The novel marker, DOG1, is expressed ubiquitously in gastrointestinal stromal tumors irrespective of KIT or PDGFRA mutation status

Abstract

We recently characterized gene expression patterns in gastrointestinal stromal tumors (GISTs) using cDNA microarrays, and found that the gene FLJ10261 (DOG1, discovered on GIST-1), encoding a hypothetical protein, was specifically expressed in GISTs. The immunoreactivity of a rabbit antiserum to synthetic DOG1 peptides was assessed on two soft tissue tumor microarrays. The tissue microarrays included 587 soft tissue tumors, with 149 GISTs, including 127 GIST cases for which the KIT and PDGFRA mutation status was known. Immunoreactivity for DOG1 was found in 136 of 139 (97.8%) of scorable GISTs. All seven GIST cases with a PDGFRA mutation were DOG1-positive, while most of these failed to react for KIT. The immunohistochemical findings were confirmed with in situ hybridization probes for DOG1, KIT, and PDGFRA. Other neoplasms in the differential diagnosis of GIST, including desmoid fibromatosis (0 of 17) and Schwannoma (0 of 3), were immunonegative for DOG1. Only 4 of 438 non-GIST cases were immunoreactive for DOG1. DOG1, a protein of unknown function, is expressed strongly on the cell surface of GISTs and is rarely expressed in other soft tissue tumors. Reactivity for DOG1 may aid in the diagnosis of GISTs, including PDGFRA mutants that fail to express KIT antigen, and lead to appropriate treatment with imatinib mesylate, an inhibitor of the KIT tyrosine kinase.

Figure 1

Gene array measurement of KIT and DOG1 mRNA expression in 30 soft tissue tumors. Red indicates a relatively high level of expression whereas green denotes a low level of expression. Gene array data for STTs 524, 629, 417, 418, 219, 111, 656, 94, 335, 794, 1148, 850, 616, 710, 523, 526, 740, 607, and 1220 have been previously reported.

Figure 2

Hierarchical clustering of CD117 (KIT) immunohistochemistry, CD117 in situ hybridization, PDGFRA in situ hybridization, DOG1 immunohistochemistry, and DOG1 in situ hybridization. The results for GISTs on the two TMAs have been combined. Antisera or hybridization probes are in columns, tumors in rows. Bright red denotes strong reactivity, whereas dark red and green indicate low and absent reactivity, respectively. White means missing data.

Figure 3

Staining results on GISTs for CD117 (KIT) immunohistochemistry, CD117 in situ hybridization, PDGFRA in situ hybridization, DOG1 immunohistochemistry, and DOG1 in situ hybridization in graphic form (see also Table 1).

Figure 4

Immunohistochemical staining with anti-DOG1 serum (S284) and KIT on two GISTs [TMA 822 (A) and 3688 (B)] and a synovial sarcoma [TMA 856 (C)].

Figure 5

In situ hybridization of a GIST and leiomyosarcoma with anti-sense probes to DOG1 and KIT on a GIST and a leiomyosarcoma (LMS). The corresponding negative control sense probes are included in the inset in the top right corner of the GIST sample.

Figure 6

In situ hybridization of KIT, DOG1, and PDGFRA with GISTs. A: GIST with mutation in KIT shows positive in situ hybridization for KIT and DOG1 but not PDGFRA. B: GIST with mutation in PDGFRA shows positive in situ hybridization for DOG1 and PDGFRA but not for KIT. C: Negative control leiomyosarcoma.