Alteration of PDGFRß-Akt-mTOR pathway signaling in fibrosarcomatous transformation of dermatofibrosarcoma protuberans.

Dermatofibrosarcoma protuberans (DFSP) is a cutaneous mesenchymal tumor of intermediate malignancy and fibroblastic/myofibroblastic differentiation. Fibrosarcomatous (FS) component is a high-grade component of DFSP. The detailed oncogenic difference between DFSP and FS components is not clear. We thus investigated the Akt-mTOR pathway in both components. We used 65 tumor samples obtained from 65 patients. The phosphorylation of Akt-mTOR pathway proteins (Akt, mTOR, 4EBP1, and S6RP) and PDGFRα/ß was assessed by immunohistochemical staining, the results of which were confirmed by Western blotting. The immunohistochemical results were as follows: in ordinary DFSP components, p-PDGFRα-positive tumors were 41.9% (18/43 cases), p-PDGFRß 55.8% (24/43 cases), p-Akt 51.2% (22/43 cases), p-mTOR 39.5% (17/43 cases), p-4EBP1 46.5% (20/43 cases), and p-S6RP 41.8% (18/43 cases); in DFSP components of FS-DFSP, 52.6% (10/19 cases), 47.4% (9/19 cases), 52.6% (10/19 cases), 36.8% (7/19 cases), 52.6% (10/19 cases), and 52.6% (10/19 cases); and in FS components, 45.5% (10/22 cases), 36.4% (8/22 cases), 72.7% (16/22 cases), 54.5% (12/22 cases), 72.7% (16/22 cases), and 68.2% (15/22 cases), respectively. There were significant positive correlations of the phosphorylation of most of the Akt-mTOR pathway proteins (p-Akt, p-mTOR, p-4EBP1, and p-S6RP) with each other (P < .05). Phospho-PDGFRß was well correlated with the phosphorylation of Akt-mTOR pathway proteins in DFSP components of ordinary and FS-DFSPs, but these correlations were weaker in FS components. This study suggested the association of activation of Akt-mTOR pathway proteins and PDGFR with the progression of DFSP to FS. The Akt-mTOR pathway is thus a potential therapeutic target in imatinib-resistant DFSP/FS.

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

ERG is immunoexpressed in vascular endothelial tumors, blastic extramedullary myeloid tumors, and tumors with ERG-involved translocation, such as prostate carcinoma or Ewing sarcoma. Recently, ERG immunoexpression was reported in an epithelioid sarcoma, which is a SMARCB1/INI1-deficient tumor, although epithelioid sarcoma is not associated with chromosomal translocations involving ERG and is categorized as a tumor with uncertain differentiation. SALL4 is essential for a proliferation and stabilization of embryonic stem cells. It was reported that SALL4 expression may aid in distinguishing epithelioid sarcoma from malignant rhabdoid tumor. We analyzed the frequency of ERG and SALL4 expressions in 80 SMARCB1/INI1-deficient tumors, including 45 epithelioid sarcomas (conventional-type, 24; proximal-type, 20), 17 malignant rhabdoid tumors, 5 atypical teratoid/rhabdoid tumors, 6 undifferentiated/unclassified sarcomas, 5 myoepithelial tumors, and 4 extraskeletal myxoid chondrosarcomas. We found that ERG expression was present in 18 of the epithelioid sarcomas (41%), including 13 conventional-type (54%) and 5 proximal-type (25%), whereas all 17 of the malignant rhabdoid tumors exhibited negative immunoreactivity. One atypical teratoid/rhabdoid tumor (20%), 1 myoepithelial carcinoma (20%), 1 undifferentiated/unclassified sarcoma (17%), and no extraskeletal myxoid chondrosarcomas (0%) also showed ERG expression. SALL4 expression was recognized in 5 epithelioid sarcomas (11%), 12 malignant rhabdoid tumors (71%), 2 atypical teradoid/rhabdoid tumors (40%), 4 undifferentiated/unclassified sarcomas (67%), 1 myoepithelial tumor (20%), and none of the extraskeletal myxoid chondrosarcomas (0%). Therefore, the evaluation of ERG and SALL4 immunoexpressions may be a useful diagnostic tool to distinguish epithelioid sarcoma, especially proximal type, from malignant rhabdoid tumor.

Cancer-testis antigens PRAME and NY-ESO-1 correlate with tumour grade and poor prognosis in myxoid liposarcoma.

Myxoid liposarcoma is the second most common liposarcoma. Although myxoid liposarcoma is relatively chemosensitive and thus a good candidate for chemotherapy, cases with relapsed or metastatic disease still have poor outcome. Here, we performed a gene microarray analysis to compare the gene expression profiles in six clinical myxoid liposarcoma samples and three normal adipose tissue samples, and to identify molecular biomarkers that would be useful as diagnostic markers or treatment targets in myxoid liposarcoma. This showed that the cancer-testis antigen PRAME was up-regulated in myxoid liposarcoma. We then performed immunohistochemical, western blotting and real-time polymerase chain reaction analyses to quantify the expression of PRAME and another cancer-testis antigen, NY-ESO-1, in clinical samples of myxoid liposarcoma (n = 93), dedifferentiated (n = 46), well-differentiated (n = 32) and pleomorphic liposarcomas (n = 14). Immunohistochemically, positivity for PRAME and NY-ESO-1 was observed in 84/93 (90%) and 83/93 (89%) of the myxoid liposarcomas, and in 20/46 (43%) and 3/46 (7%) of the dedifferentiated, 3/32 (9%) and 1/32 (3%) of the well-differentiated and 7/14 (50%) and 3/21 (21%) of the pleomorphic liposarcomas, respectively. High immunohistochemical expression of PRAME and/or NY-ESO-1 was significantly correlated with tumour diameter, the existence of tumour necrosis, a round-cell component of >5%, higher histological grade and advanced clinical stage. High PRAME and NY-ESO-1 expression correlated significantly with poor prognosis in a univariate analysis. The myxoid liposarcomas showed significantly higher protein and mRNA expression levels of PRAME and NY-ESO-1 (CTAG1B) than the other liposarcomas. In conclusion, PRAME and NY-ESO-1 (CTAG1B) were expressed in the vast majority of myxoid liposarcomas, and their high-level expression correlated with tumour grade and poor prognosis. Our results support the potential use of PRAME and NY-ESO-1 as ancillary parameters for differential diagnosis and as prognostic biomarkers, and indicate that the development of immunotherapy against these cancer-testis antigens in myxoid liposarcoma would be warranted.

Differential microRNA expression profiles between malignant rhabdoid tumor and epithelioid sarcoma: miR193a-5p is suggested to downregulate SMARCB1 mRNA expression.

Malignant rhabdoid tumor and epithelioid sarcoma are classified as tumors of uncertain differentiation. However, it is controversial whether these tumors are distinct entities because they share similar histological and immunohistochemical features such as the existence of rhabdoid cells or complete loss of SMARCB1 protein expression. MicroRNAs are small non-coding RNAs, and it is suggested that knowledge of microRNA expression profiles in cancer may have substantial value for diagnostics. We first analyzed microRNA expression profiles in 13 frozen materials (five malignant rhabdoid tumors, two proximal type epithelioid sarcomas, and six conventional type epithelioid sarcomas) and subsequently examined the specific microRNA expressions in 29 paraffin-embedded materials (8 malignant rhabdoid tumors, 13 proximal type epithelioid sarcomas, and 8 conventional type epithelioid sarcomas) and 13 previously described frozen materials by quantitative RT-PCR. According to the unsupervised hierarchical clustering of microRNA, proximal type epithelioid sarcoma and conventional type epithelioid sarcoma were classified into the same category, whereas malignant rhabdoid tumor was a distinct category from both types of epithelioid sarcoma. In addition, when malignant rhabdoid tumor with SMARCB1 gene alterations and proximal type and conventional type epithelioid sarcoma with no SMARCB1 gene alterations were compared, 56 microRNAs were isolated as being significantly different (ANOVA, P<0.05). Among them, quantitative RT-PCR using frozen and paraffin-embedded materials demonstrated that expression levels of miR193a-5p (P=0.002), which has been suggested to downregulate SMARCB1 mRNA expression, showed statistically different expression levels between malignant rhabdoid tumor and epithelioid sarcoma with no SMARCB1 gene alterations. These results suggest that epithelioid sarcoma, especially proximal type epithelioid sarcoma, and malignant rhabdoid tumor are distinct tumors with respect to the microRNA expression profiles and that miR193a-5p may have an important role in the inhibition of SMARCB1 mRNA expression.