Anaplastic lymphoma kinase protein expression, genetic abnormalities, and phosphorylation in soft tissue tumors: Phosphorylation is associated with recurrent metastasis

Gene and protein abnormalities of anaplastic lymphoma kinase (ALK) play an important role in the pathogenesis of various cancers and serve as important therapeutic targets. We investigated ALK protein expression, phosphorylation, and genetic aberrations using fluorescence in situ hybridization (FISH) in 81 soft tissue tumor samples: inflammatory myofibroblastic tumor, n=1; alveolar soft part sarcoma, n=2; leiomyosarcoma, n=10; well-differentiated liposarcoma, n=7; pleomorphic liposarcoma, n=2; extraskeletal osteosarcoma, n=1; epithelioid sarcoma, n=1; synovial sarcoma, n=4; malignant peripheral nerve sheath tumor, n=4; undifferentiated pleomorphic sarcoma, n=19; rhabdomyosarcoma, n=6; myxofibrosarcoma, n=8; myxoid liposarcoma, n=11; fibrosarcoma, n=4; and desmoid-type fibromatosis, n=1. ALK protein expression, gene signal gain (without translocation), and phosphorylation were observed in 33/81 (40.7%), 55/81 (67.9%), and 30/81 (37.0%) tumor samples, respectively. ALK protein expression was statistically associated with phosphorylation, but not with gene signal gain. ALK phosphorylation-positive cases showed a statistically worse metastasis-free survival compared with phosphorylation-negative cases (P=0.0215). Particularly, metastasis of myxoid liposarcoma was associated with ALK phosphorylation (P=0.0019), but not with ALK protein expression or gene signal gain. However, the prognosis had no association with ALK protein expression, gene signal gain, or phosphorylation. ALK protein expression and phosphorylation play an important role in tumor biology and provide potential therapeutic targets for soft tissue tumors. Future research should focus on the oncogenic role and the efficacy of potential inhibitors of ALK.