Constitutive expression of lymphoma-associated NFKB-2/Lyt-10 proteins is tumorigenic in murine fibroblasts.
The NFKB-2 (Lyt-10) gene codes for an NF-kappaB-related transcription factor containing rel-polyG-ankyrin domains. Rearrangements of the NFKB-2 locus leading to the production of 3' truncated NFKB-2 proteins are recurrently found in lymphoid neoplasms, particularly cutaneous lymphomas. Such mutant NFKB-2 proteins have lost the ability to repress transcription that is typical of NFKB-2 subunit p52, and function as constitutive transcriptional activators. To verify whether the expression of abnormal NFKB-2 proteins can lead to malignant transformations in mammalian cells, we transfected human lymphoblastoid cell lines and murine fibroblasts (Balb/3T3) with expression vectors carrying the cDNAs coding for normal NFKB-2p52, Lyt-10C alpha or LB40 proteins, which are representative of the abnormal types found in lymphoma cases. The expression of both normal and mutant NFKB-2 proteins has a lethal effect on lymphoblastoid cells and a cytotoxic effect was also observed in murine fibroblasts. The fibroblast cell lines expressing Lyt-10C alpha or LB40, but not those expressing normal NFKB-2p52, were capable of forming colonies in soft agar. The analysis of individual clones revealed that cloning efficiency correlated with the expression levels of the abnormal proteins. Injection of the Lyt-10C alpha-transfected Balb cells in SCID mice led to tumor formation in all of the animals, whereas no tumors were observed in the mice injected with control or NFKB-2p52-transfected cells, thus indicating that abnormal NFKB-2 protein expression is tumorigenic in vivo. Our results show that mutant NFKB-2 proteins can lead to the transformed phenotype, and support the hypothesis that alterations in NFKB-2 genes may play a role in lymphomagenesis.
Ciana
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Istituto di Scienze Mediche, Università di Milano, Ospedale Maggiore IRCCS Milan, Italy.
Neri
A
A
Cappellini
C
C
Cavallo
F
F
Pomati
M
M
Chang
C C
CC
Maiolo
A T
AT
Lombardi
L
L
D016475:3T3 Cells / Q000166:cytology / Q000187:drug effects* / Q000502:physiology; D000818:Animals; D002471:Cell Transformation, Neoplastic / Q000187:drug effects; D005260:Female; D006801:Humans; D008223:Lymphoma / Q000235:genetics / Q000378:metabolism*; D051379:Mice; D008807:Mice, Inbred BALB C; D016513:Mice, SCID; D009154:Mutation; D016328:NF-kappa B / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D052003:NF-kappa B p52 Subunit; D009363:Neoplasm Proteins / Q000096:biosynthesis / Q000235:genetics; D011518:Proto-Oncogene Proteins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
D016328:NF-kappa B; D052003:NF-kappa B p52 Subunit; D009363:Neoplasm Proteins; D011518:Proto-Oncogene Proteins