Potentiation of the malignant phenotype of the undifferentiated ARO thyroid cell line by insertion of the bcl-2 gene.
We have reported that bcl-2 is expressed in normal human thyroid epithelium and that its expression is down-regulated in undifferentiated thyroid tumors. Production of IL-6 was concomitantly down-regulated in these forms. Based on these observations, we analyzed whether insertion of bcl-2 would reverse the highly malignant phenotype of a thyroid cell line (ARO) derived from an undifferentiated carcinoma. This cell line fails to produce Bcl-2 and IL-6. By infection with a bcl-2 retroviral vector, ARO cells expressing bcl-2 (ARObcl-2) were obtained. Compared with parental cells, expression of bcl-2 was associated with enhancement of growth potential (DNA synthesis, in vitro proliferation rate, anchorage-independent growth in semi-solid media). Chemotaxis and invasive potential in Boyden chambers were also increased. bcl-2-expressing cells showed a reduced response to apoptotic stimuli (low-serum conditions or anti-neoplastic drugs). Large branched colonies were formed in Matrigel from ARObcl-2 cells but not from parental cells. Finally, ARObcl-2 cells showed a decreased latency of tumor appearance when injected into immunodeficient mice. Potentiation of the malignant phenotype of ARO cells by bcl-2 was not ascribed to altered expression of (i) cytokine/growth factors (IL-4, IL-6, IL-8, IL-10, IL-12, TGF-alpha, TGF-beta), (ii) thyroid-specific transcripts (TG, TPO, TSH-R, PIGF, PAX-8) or (iii) genes influencing tumor aggressiveness [VEGF, HMGI (Y), HMGI-C]. Our data indicate that bcl-2 potentiates the malignant phenotype of ARO cells not only by limiting the response to apoptotic stimuli but also by enhancing proliferation and tumor aggressiveness.
Basolo
F
F
Department of Oncology, University of Pisa, Italy.
Fiore
L
L
Fusco
A
A
Giannini
R
R
Albini
A
A
Merlo
G R
GR
Fontanini
G
G
Conaldi
P G
PG
Toniolo
A
A
D000818:Animals; D017209:Apoptosis; D002455:Cell Division; D002460:Cell Line; D002471:Cell Transformation, Neoplastic; D002633:Chemotaxis; D003094:Collagen; D016207:Cytokines / Q000032:analysis / Q000096:biosynthesis; D004338:Drug Combinations; D019254:Genes, bcl-2; D006801:Humans; D007797:Laminin; D051379:Mice; D016513:Mice, SCID; D009361:Neoplasm Invasiveness; D010641:Phenotype; D011509:Proteoglycans; D019253:Proto-Oncogene Proteins c-bcl-2 / Q000032:analysis / Q000235:genetics; D013961:Thyroid Gland; D013964:Thyroid Neoplasms / Q000235:genetics* / Q000276:immunology / Q000473:pathology* / Q000503:physiopathology; D014183:Transplantation, Heterologous
D016207:Cytokines; D004338:Drug Combinations; D007797:Laminin; D011509:Proteoglycans; D019253:Proto-Oncogene Proteins c-bcl-2; C059485:matrigel; D003094:Collagen