XXXX originates from retrovirus @entity281 of proliferating type 2 pneumocytes during pulmonary post-natal development or tissue repair.

@entity1 @entity32 @entity742 @entity5 @entity2 @entity420 @entity651 @entity281 @entity105 @entity204 @entity13900 @entity2220
@entity13900 ) is a unique oncogenic virus with distinctive biological properties. @entity13900 is the only virus causing a naturally occurring @entity2 ( @entity420 , OPA) and possessing a major structural protein that functions as a dominant oncoprotein. @entity2 is the major cause of @entity204 among @entity5 @entity1 . OPA can be an extremely useful animal model in order to identify the cells originating @entity2220 and to study the early events of @entity105 . In this study, we demonstrated that @entity2220 in @entity742 originates from @entity281 and transformation of proliferating type 2 pneumocytes (termed here lung alveolar proliferating cells, LAPCs). We excluded that OPA originates from a bronchioalveolar stem cell, or from mature post-mitotic type 2 pneumocytes or from either proliferating or non-proliferating Clara cells. We show that young animals possess abundant LAPCs and are highly susceptible to @entity13900 @entity281 and transformation. On the contrary, healthy adult @entity742 , which are normally resistant to experimental OPA induction, exhibit a relatively low number of LAPCs and are resistant to @entity13900 @entity281 of the respiratory epithelium. Importantly, induction of @entity651 increased dramatically the number of LAPCs in adult @entity742 and rendered these animals fully susceptible to @entity13900 @entity281 and transformation. Furthermore, we show that @entity13900 preferentially infects actively dividing cell in vitro. Overall, our study provides unique insights into pulmonary biology and @entity105 and suggests that @entity13900 and its host have reached an evolutionary equilibrium in which productive @entity281 (and transformation) can occur only in cells that are scarce for most of the lifespan of the @entity742 . Our data also indicate that, at least in this model, @entity32 can predispose to @entity281 and @entity5 .
