title: Inhibition of endogenous reverse transcriptase antagonizes human tumor growth.
abstract: Undifferentiated cells and embryos express high levels of endogenous non-telomerase reverse transcriptase (RT) of retroposon/retroviral origin. We previously found that RT inhibitors modulate cell growth and differentiation in several cell lines. We have now sought to establish whether high levels of RT activity are directly linked to cell transformation. To address this possibility, we have employed two different approaches to inhibit RT activity in melanoma and prostate carcinoma cell lines: pharmacological inhibition by two characterized RT inhibitors, nevirapine and efavirenz, and downregulation of expression of RT-encoding LINE-1 elements by RNA interference (RNAi). Both treatments reduced proliferation, induced morphological differentiation and reprogrammed gene expression. These features are reversible upon discontinuation of the anti-RT treatment, suggesting that RT contributes to an epigenetic level of control. Most importantly, inhibition of RT activity in vivo antagonized tumor growth in animal experiments. Moreover, pretreatment with RT inhibitors attenuated the tumorigenic phenotype of prostate carcinoma cells inoculated in nude mice. Based on these data, the endogenous RT can be regarded as an epigenetic regulator of cell differentiation and proliferation and may represent a novel target in cancer therapy.
authors.affiliation: Istituto Superiore di Sanità, Viale Regina Elena 299, Via del Castro Laurenziano 25, 00161 Rome, Italy.
authors.forename: Ilaria
authors.initials: I
authors.lastname: Sciamanna
authors.forename: Matteo
authors.initials: M
authors.lastname: Landriscina
authors.forename: Carmine
authors.initials: C
authors.lastname: Pittoggi
authors.forename: Michela
authors.initials: M
authors.lastname: Quirino
authors.forename: Cristina
authors.initials: C
authors.lastname: Mearelli
authors.forename: Rosanna
authors.initials: R
authors.lastname: Beraldi
authors.forename: Elisabetta
authors.initials: E
authors.lastname: Mattei
authors.forename: Annalucia
authors.initials: A
authors.lastname: Serafino
authors.forename: Alessandra
authors.initials: A
authors.lastname: Cassano
authors.forename: Paola
authors.initials: P
authors.lastname: Sinibaldi-Vallebona
authors.forename: Enrico
authors.initials: E
authors.lastname: Garaci
authors.forename: Carlo
authors.initials: C
authors.lastname: Barone
authors.forename: Corrado
authors.initials: C
authors.lastname: Spadafora
mesh_terms: D001973:Bromodeoxyuridine / Q000633:toxicity; D002453:Cell Cycle / Q000187:drug effects; D002455:Cell Division / Q000187:drug effects*; D045744:Cell Line, Tumor; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D006801:Humans; D008545:Melanoma / Q000473:pathology*; D018613:Microscopy, Confocal; D034741:RNA, Small Interfering; D012194:RNA-Directed DNA Polymerase / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D004791:Enzyme Inhibitors; D034741:RNA, Small Interfering; D012194:RNA-Directed DNA Polymerase; D001973:Bromodeoxyuridine