Retroviruses as etiologic agents of some animal and human leukemias and lymphomas and as tools for elucidating the molecular mechanism of leukemogenesis

Abstract

IT HAS LONG BEEN KNOWN that retroviruses (RNA tumor viruses, type-C viruses, oncornaviruses, leukemia viruses) can induce a variety of neoplasias (leukemias and lymphomas, sarcomas, and occasionally carcinomas) in animals, and they have been identified as the prime factor in the pathogenesis of many naturally occurring leukemias and lymphomas in several animal species. Although there are recent reviews on retroviruses, they focus chiefly on the molecular biology of viral replication and in vitro cellular transformation. In our view, several advances in retroviral oncology have merged within the past few years, resulting in a heightened appreciation of the role of retroviruses in naturally occurring leukemias and a rapid expansion in our understanding, although still fragmentary, of the mechanisms by which they transform cells. Simultaneously, the search for a possible viral etiology of some human leukemias and lymphomas has led to the isolation of a novel retrovirus, HTLV, from cultured human neoplastic T cells. Recent epidemiologic and biochemical evidence has associated HTLV with a specific type of adult T-cell leukemia and lymphoma. The purposes of this review are: (1) to summarize briefly the role of retroviruses in naturally occurring leukemias and lymphomas of animals, drawing specifically on features that are instructive in considering a viral etiology of certain human leukemias and lymphomas; (2) to describe our current concepts of the molecular mechanisms of retroviral transformation and how they may be applicable to human leukemias; and (3) to summarize the recent results dealing with the isolation of HTLV and its characterization as a possible etiologic agent of certain T-cell leukemias and lymphomas in man.