Receptor tyrosine kinase pathway analysis sheds light on similarities between clear‐cell sarcoma and metastatic melanoma

Abstract

To highlight possible similarities and differences in receptor tyrosine kinase (RTK) and downstream signalling activation profiles between clear-cell sarcomas (CCS) and metastatic melanomas (MM), frozen, and paired-matched fixed samples of six CCS with EWSR1 rearrangement (EWSR1+), five CCS without EWSR1 rearrangement (EWSR1-), and seven MM were investigated by means of biochemical, immunohistochemical, FISH, molecular analyses, and immunofluorescence confocal microscopy. Fixed samples of a further 10 CCS and 14 MM were investigated by means of sequencing for BRAF, NRAS, and KRAS mutations and FISH analyses for the gain of chromosomes 22 and 8. RTK analysis of all CCS/MM samples showed activation of short-form (sf) recepteur d'origine nantais (RON) RTK and of PDGFRB, MET, and HER3. Analysis of downstream signaling revealed consistent phosphorylation patterns of PI3K/AKT, RSK, and the mTOR targets S6 and 4EBP1. Analysis of frozen and fixed material from 21 CCS and 21 MM showed the presence of the V600E BRAF mutation in 2/12 EWSR1+ and 3/9 EWSR1- CCS and 9/21 MM and demonstrated a significant (P < 0.001) correlation between the gain of chromosomes 22 and 8 and EWSR1- CCS. Our results show that BRAF mutation can also be present in CCS and support the proposed aberration of chromosomes 22 and 8 as a possibly useful nonrandom hallmark of EWSR1- CCS. Besides, they broaden the spectrum of the similarities of RTK pathway activation between CCS and MM, thus suggesting that new drugs found to be active in melanoma and RON inhibitors could have a role in CCS treatment. © 2011 Wiley Periodicals, Inc.

BRAF-mutated clear cell sarcoma is sensitive to vemurafenib treatment

“…Therefore, reliable differential diagnosis between CCS and melanoma is virtually impossible, especially when restricted to standard morphological tools. Furthermore, existing molecular assays also have limitations, given that some CCSs do not contain EWSR1 translocations, while others have EWSR1 gene fusions combined with either BRAF or NRAS mutation [48][49][50]53]. For the time being, the discrimination between clear cell sarcoma and melanoma is predominantly an academic interest.…”

“…For the time being, the discrimination between clear cell sarcoma and melanoma is predominantly an academic interest. If we consider that BRAF mutations have been repeatedly detected in patients with the clinical diagnosis of clear cell sarcoma [48][49][50], and the BRAF-mutated CCSs may be sensitive to targeted treatment, this would suffice to justify routine BRAF testing in all patients diagnosed with or suspected for metastatic CCS.…”

“…The available literature describes only a few cases of clear cell sarcoma harboring BRAF mutation. Interestingly, some BRAF-mutated CCS specimens are characterized by the presence of concurrent EWSR/ATF1 translocation [48][49][50]. Here we report a patient with BRAF-mutated clear cell sarcoma, which demonstrated complete clinical response to vemurafenib.…”

“…Tumor tissue was found to be negative for EWSR1/ATF1 or EWSR1/CREB1 translocations. While looking for potentially actionable genetic lesions, we considered evidence for occurrence of BRAF mutations in CCSs [48][49][50] and subjected the tumor DNA to BRAF analysis; this test revealed a common substitution of valine to glutamic acid in the codon 600. The disease relapse was detected 2 months after surgery, and included malignant lesions at postoperative scar and distant metastases in the 7th left rib (2.2×0.9×0.7 cm).…”

Melan-A/MART-1 immunity in a EWS-ATF1 translocated clear cell sarcoma patient treated with sunitinib: a case report

“…Importantly, a proportion of CCS cases lack specific translocation and thus, clinical presentation as well as fluorescence in situ hybridization (FISH) analysis and reverse transcription polymerase chain reaction (RT-PCR) for the specific translocation are crucial to distinguish the two entities. Receptor tyrosine kinase expression/activation [8] and gene expression analysis [9] indicate that MITF drives the same down-stream pathways in CCS and in melanoma, and that PDGFRβ and c-Met are expressed by CCS [10,11]. Moreover, BRAF activating mutations have been occasionally detected in both EWS-ATF1 positive and negative CCS [8,12,13].…”