Role of epidermal growth factor receptor and STAT-3 activation in autonomous proliferation of SUM-102PT human breast cancer cells.
This report describes the isolation and characterization of a new human breast cancer cell line, SUM-102PT, obtained from a minimally invasive human breast carcinoma. SUM-102PT cells have a near diploid karyotype, and early-passage cells had minor chromosomal abnormalities including a 5, 12 and a 6, 16 reciprocal translocation. The cells were isolated and have been continually cultured in three defined media, one of which contains exogenous epidermal growth factor (EGF). SUM-102PT cells have also been carried in an EGF-free medium supplemented with progesterone. All SUM-102PT cells require EGF receptor (EGFR) activation for continuous growth, because incubation of the cells with EGFR-neutralizing antibodies or with EGFR kinase inhibitors blocks growth of these cells. Southern analysis indicates that the EGFR gene is not amplified in these cells; however, these cells express high levels of EGFR mRNA. Thus, SUM-102PT is representative of a class of human breast cancers characterized by high level EGFR expression in the absence of gene amplification. SUM-102PT cells cultured in EGF-free, progesterone-containing medium express high levels of constitutively active EGFR. Conditioned medium from SUM-102PT cells contains an EGF-like mitogen that binds to a heparin-agarose affinity matrix with high affinity. Northern analysis for various EGF family members indicates that SUM-102PT cells synthesize heparin binding (HB)-EGF mRNA. HB-EGF protein is detectable on the surface of these cells by immunohistochemistry, and SUM-102PT cells are killed by diphtheria toxin, which acts by binding to HB-EGF. Furthermore, HB-EGF antibodies partially neutralize the mitogenic activity of the conditioned medium. Thus, EGFR activation in SUM-102PT cells is mediated, at least in part, by autocrine/juxtacrine stimulation by HB-EGF. SUM-102PT cells also express constitutively active STAT-3 homodimers. Constitutively tyrosine-phosphorylated STAT-3 homodimers were also detected in another breast cancer cell line, MDA468, which has an EGFR amplification and also has constitutive EGFR activity. Thus, SUM-102PT is a new human breast cancer cell line that expresses activated EGFR as a result of an autocrine/juxtacrine interaction with HB-EGF which, in turn, results in activation of STAT-3.
Sartor
C I
CI
Department of Radiation Oncology, University of Michigan Medical School, Ann Arbor 48109-0582, USA.
Dziubinski
M L
ML
Yu
C L
CL
Jove
R
R
Ethier
S P
SP
D000230:Adenocarcinoma / Q000473:pathology* / Q000503:physiopathology; D001943:Breast Neoplasms / Q000473:pathology* / Q000503:physiopathology; D002455:Cell Division / Q000187:drug effects; D004268:DNA-Binding Proteins / Q000502:physiology*; D004815:Epidermal Growth Factor / Q000502:physiology*; D066246:ErbB Receptors / Q000502:physiology*; D005260:Female; D006801:Humans; D008875:Middle Aged; D019000:Phosphotyrosine / Q000378:metabolism; D012334:RNA, Neoplasm / Q000235:genetics; D020794:Receptor Protein-Tyrosine Kinases / Q000502:physiology*; D011960:Receptors, Estrogen / Q000032:analysis; D050796:STAT3 Transcription Factor; D015398:Signal Transduction; D015534:Trans-Activators / Q000502:physiology*; D014407:Tumor Cells, Cultured
D004268:DNA-Binding Proteins; D012334:RNA, Neoplasm; D011960:Receptors, Estrogen; D050796:STAT3 Transcription Factor; C494086:STAT3 protein, human; D015534:Trans-Activators; D019000:Phosphotyrosine; D004815:Epidermal Growth Factor; D066246:ErbB Receptors; D020794:Receptor Protein-Tyrosine Kinases