title: The role of oncogenic Ras in human skin tumorigenesis depends on the clonogenic potential of the founding keratinocytes.
abstract: The role of Ras in human skin tumorigenesis induction is still ambiguous. Overexpression of oncogenic Ras causes premature senescence in cultured human cells and hyperplasia in transgenic mice. Here, we investigated whether the oncogenic insult outcome might depend on the nature of the founding keratinocyte. We demonstrate that overexpression of the constitutively active Ras-V12 induces senescence in primary human keratinocyte cultures, but that some cells escape senescence and proliferate indefinitely. Ras overexpression in transient-amplifying- or stem-cell-enriched cultures shows that p16 (encoded by CDKN2A) levels are crucial for the final result. Indeed, transient-amplifying keratinocytes expressing high levels of p16 are sensitive to Ras-V12-induced senescence, whereas cells with high proliferative potential, but that do not display p16, are resistant. The subpopulation that sustains the indefinite culture growth exhibits stem cell features. Bypass of senescence correlates with inhibition of the pRb (also known as RB1) pathway and resumption of telomerase reverse transcriptase (TERT) activity. Immortalization is also sustained by activation of the ERK1 and ERK2 (ERK1/2, also known as MAPK3 and MAPK1) and Akt pathways. Moreover, only transduced cultures originating from cultures bearing stem cells induce tumors in nude mice. Our findings demonstrate that the Ras overexpression outcome depends on the clonogenic potential of the recipient keratinocyte and that only the stem cell compartment is competent to initiate tumorigenesis.
authors.affiliation: IDI Farmaceutici, Pomezia, 00040 Rome, Italy.
authors.forename: Riccardo
authors.initials: R
authors.lastname: Maurelli
authors.affiliation: Vascular Pathology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Lavinia
authors.initials: L
authors.lastname: Tinaburri
authors.affiliation: Vascular Pathology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Fabio
authors.initials: F
authors.lastname: Gangi
authors.affiliation: Vascular Pathology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Sergio
authors.initials: S
authors.lastname: Bondanza
authors.affiliation: Vascular Pathology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Anna Lisa
authors.initials: AL
authors.lastname: Severi
authors.affiliation: Experimental Immunology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Claudia
authors.initials: C
authors.lastname: Scarponi
authors.affiliation: Experimental Immunology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Cristina
authors.initials: C
authors.lastname: Albanesi
authors.affiliation: Charles River Laboratories, Research Model and Services, 23885 Calco (LC), Italy.
authors.forename: Giuseppe
authors.initials: G
authors.lastname: Mesiti
authors.affiliation: Molecular and Cellular Biology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Liliana
authors.initials: L
authors.lastname: Guerra
authors.affiliation: Vascular Pathology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy.
authors.forename: Maurizio C
authors.initials: MC
authors.lastname: Capogrossi
authors.affiliation: Vascular Pathology Laboratory, Fondazione Luigi Maria Monti, IDI-IRCCS, Rome, Italy e.dellambra@idi.it.
authors.forename: Elena
authors.initials: E
authors.lastname: Dellambra
mesh_terms: D000818:Animals; D049109:Cell Proliferation; D002471:Cell Transformation, Neoplastic / Q000235:genetics; D016922:Cellular Senescence; D018920:Coculture Techniques; D006801:Humans; D015603:Keratinocytes / Q000201:enzymology*; D051379:Mice; D008819:Mice, Nude; D041681:NIH 3T3 Cells; D009368:Neoplasm Transplantation; D014411:Neoplastic Stem Cells / Q000502:physiology; D016283:Proto-Oncogene Proteins p21(ras) / Q000235:genetics* / Q000378:metabolism; D015398:Signal Transduction; D012878:Skin Neoplasms / Q000235:genetics* / Q000473:pathology
chemical_list: C117307:KRAS protein, human; D016283:Proto-Oncogene Proteins p21(ras)
keywords: Clonogenic potential; Primary human keratinocyte; Ras; Tumorigenesis