Vinculin-ALK Oncoprotein in a Pediatric Renal Medullary Carcinoma: Rapid Identification by Proteomic Methods.
Adrian Marino-Enriquez, Wen-Bin Ou, Christopher B Weldon, Jonathan A Fletcher, Antonio R Perez-Atayde. Brigham and Women's Hospital, Boston, MA; Harvard Medical School, Boston, MA; Children's Hospital Boston, MA
Background: Renal Medullary Carcinoma (RMC) is an aggressive malignancy that affects young black individuals with sickle cell trait. Little is known about RMC pathogenesis, there are no effective drug treatments, and average overall survival is <4 months. ALK is a druggable receptor tyrosine kinase, which is activated oncogenically in subsets of inflammatory myofibroblastic tumor, neuroblastoma, atypical large cell lymphoma and lung adenocarcinoma. Proteomic approaches have not been used previously to identify novel fusion oncogenes.
Design: Cytogenetic analysis of a pediatric RMC revealed a novel t(2;10) translocation involving the ALK gene region. A mass-spectrometry based proteomic strategy was used to rapidly characterize the putative ALK fusion partner.
Results: The patient was a 6 year-old black boy with sickle cell trait presenting with a 4.6 cm mass centered in the renal medulla. Histopathologically, the tumor consisted of sheets of polygonal to spindle shaped cells with large vesicular nuclei, clear coarse chromatin and abundant eosinophilic cytoplasm with frequent intracytoplasmic lumens, which ultrastructurally were lined by well-formed microvilli. Focal stromal desmoplasia and a diffuse lymphoplasmacytic infiltrate were present, as well as prominent vascular invasion of the renal sinus. Tumor cells were immunoreactive for cytokeratins and EMA. INI-1 nuclear expression was retained. The abnormal karyoptype was: 46,XY,t(2;10)(p23;q22),add(14)(p11), with involvement of the ALK gene region at 2p23. Dual-color FISH demonstrated ALK rearrangement, and strong ALK expression was shown by immunohistochemistry. ALK immunoprecipitation, coupled with phosphotyrosine immunoblotting, identified a strongly activated and aberrantly sized (160kDa) ALK protein. Mass spectrometry revealed this to be a vinculin-ALK fusion protein, in which the N-terminal aspect of vinculin was fused to the ALK kinase domain. These studies also demonstrated a potential mechanism of oncogenic ALK activation, mediated by vinculin interactions with talins.
Conclusions: We present a pediatric RMC harboring a novel ALK rearrangement. This study broadens the spectrum of ALK-related tumors and ALK fusion partners, provides insight into RMC pathogenesis, and establishes a biological rationale for targeted kinase-inhibitor therapeutics in this highly lethal disease.
Monday, February 28, 2011 11:45 AM
Platform Session: Section H 2, Monday Morning