Renal Cell Carcinoma with Novel VCL-ALK Fusion: New Representative of ALK-Associated Tumor Spectrum.
Larisa Debelenko, Susana Raimondi, Najat Daw, Bangalore Shivakumar, Marilu Nelson, Dali Huang, Julia Bridge. St. Jude Children's Hospital, Memphis, TN; Nebraska Medical Center, Omaha
Background: Renal cell carcinoma (RCC) represents a model for contemporary classification of solid tumors; however, unclassifiable cases exist and are not rare in children and young adults. The anaplastic lymphoma kinase (ALK) gene has recently been implicated in subsets of pulmonary, esophageal, breast, and colon cancer strengthening the importance of molecular classification of carcinomas across different organ sites, especially considering the evolving therapies with ALK inhibitors.
Design: We studied 6 pediatric RCCs from the files of our institutions; conventional cytogenetic analyses were performed in 2 cases and all 6 cases were subjected to fluorescent in situ hybridization (FISH) with the Vysis LSI ALK break apart rearrangement probe (Abbott Molecular) and immunohistochmistriy (IHC) with the ALK/p80 monoclonal antibody (ThermoFisher Scientific). Rapid amplification of cDNA ends (RACE) was performed in 1 ALK-positive case using the 5'RACE system from Invitrogen. Western blot analysis was performed using standard protocols and ALK/p80 and hVIN-1 (Sigma-Aldrich) antibodies. Appropriate controls were run for each experiment.
Results: Two pediatric RCCs exhibited structural karyotypic abnormalities involving the ALK locus on chromosomal band 2p23. FISH studies were positive for an ALK rearrangement in one case with unusual histology and subsequent 5'RACE analysis of this tumor revealed that the 3' portion of the ALK transcript encoding for the kinase domain was fused in frame to the 5' portion of vinculin (VCL). The new fusion gene is predicted to have an open reading frame of 4122 bp encoding for a 1374-aa oncoprotein; its expression in the tumor was shown by immunoblotting and IHC with anti-VCL and anti-ALK antibodies; IHC demonstrated cytoplasmic and subplasmalemmal localization of the oncoprotein determined by its N-terminal VCL portion. FISH with a custom-designed VCL-ALK dual-fusion probe set confirmed the presence of the fusion in neoplastic cells. The 5 remaining RCCs did not show ALK rearrangement by FISH or ALK expression by IHC.
Conclusions: The data identify the kidney as a new organ site for ALK-associated carcinomas and VCL as a novel ALK fusion partner. The results should prompt further studies to advance the molecular classification of RCCs and help to select patients who would benefit from appropriate targeted therapies.
Category: Genitourinary (including renal tumors)
Wednesday, March 2, 2011 9:30 AM
Poster Session V # 101, Wednesday Morning