Additive effects of c-erbB-2, c-Ha-ras, and transforming growth factor-alpha genes on in vitro transformation of human mammary epithelial cells.
MCF-10A cells are a spontaneously immortalized untransformed human mammary epithelial cell line. We have previously shown that overexpression of a human point-mutated c-Ha-ras proto-oncogene, the rat c-neu (c-erbB-2) proto-oncogene, or the human transforming growth factor-alpha (TGF-alpha) gene in MCF-10A cells leads to in vitro transformation of such cells. To ascertain whether the introduction of two of these genes into MCF-10A human mammary epithelial cells induces a completely tumorigenic phenotype, we infected MCF-10A Ha-ras and MCF-10A TGF-alpha cells with a recombinant retroviral vector containing the human c-erbB-2 proto-oncogene and the hygromycin-resistance gene. Ten MCF-10A TGF-alpha/c-erbB-2 (MCF-10A TE) and 10 MCF-10A Ha-ras/c-erbB-2 (MCF-10A HE) hygromycin-resistant clones were randomly selected and expanded into cell lines. MCF-10A TE and MCF-10A HE clones expressed a 10-fold to 40-fold increase in p185 erbB-2 protein levels compared with parental uninfected cells. These cells exhibited a fourfold increase in their growth rate in serum-free medium and showed a strongly reduced mitogenic response to exogenous epidermal growth factor or TGF-alpha compared with MCF-10A cells. Moreover, both MCF-10A TE and MCF-10A HE clones exhibited a fivefold to 20-fold higher cloning efficiency in soft agar than MCF-10A Ha-ras, MCF-10A c-erbB-2, or MCF-10A TGF-alpha clones. However, neither MCF-10A TE nor MCF-10A HE cells were able to grow as tumors in vivo when they were injected into nude mice. These results suggest that c-Ha-ras, c-erbB-2, and TGF-alpha genes have an additive effect on the in vitro transformation of an immortalized human mammary epithelial cell line, but that additional genetic changes such as activation of other proto-oncogenes or inactivation of a tumor suppressor gene may be necessary to elicit a fully tumorigenic phenotype.
Ciardiello
F
F
Cattedra di Oncologia Medica, II Facoltà di Medicina e Chirurgia, Naples, Italy.
Gottardis
M
M
Basolo
F
F
Pepe
S
S
Normanno
N
N
Dickson
R B
RB
Bianco
A R
AR
Salomon
D S
DS
D000818:Animals; D001943:Breast Neoplasms / Q000235:genetics* / Q000473:pathology; D002455:Cell Division; D002471:Cell Transformation, Neoplastic / Q000235:genetics*; D002999:Clone Cells; D004848:Epithelium / Q000473:pathology; D066246:ErbB Receptors / Q000502:physiology; D005260:Female; D011905:Genes, ras / Q000502:physiology*; D006801:Humans; D008325:Mammary Neoplasms, Experimental / Q000235:genetics / Q000473:pathology; D051379:Mice; D008807:Mice, Inbred BALB C; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins / Q000502:physiology*; D018719:Erb-b2 Receptor Tyrosine Kinases; D016211:Transforming Growth Factor alpha / Q000502:physiology*
D066246:ErbB Receptors; D000090063:Proto-Oncogene Mas; D011518:Proto-Oncogene Proteins; D018719:Erb-b2 Receptor Tyrosine Kinases; D016211:Transforming Growth Factor alpha; C000715470:MAS1 protein, human