Adult T-cell leukemia-lymphoma

Abstract

Adult T-cell leukemia-lymphoma (ATL) is a distinct malignancy of CD4+/CD25+/CCR4+/FoxP3+ or- Treg/TH2 cells etiologically associated with human T-cell lymphotropic virus type I (HTLV-1). However, expression of the virus including Tax oncoprotein appears just after in vitro culture, integration sites of the provirus into host genome is random, and chromosomal/genetic abnormality is complex. Therefore, ATL is a single HTLV-1 disease entity with diverse molecular features. Also, the clinical features and prognosis are diverse leading to subtype classification into acute, lymphoma, chronic, and smoldering types defined by organ involvement and LDH and calcium values. It has been estimated that worldwide between 15 and 20 million individuals are infected with HTLV-1. Recently, it was estimated that approximately 1.1 million HTLV-1-infected individuals reside in Japan, and the annual incidence of ATL to be approximately 1,000. HTLV-1 infection early in life, presumably from breast-feeding, is crucial for the development of ATL. The age-specific occurrence of ATL and complex genome abnormalities accumulated in disease progression suggested a multistep carcinogenesis model.