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Her-2/neu-triggered intracellular tyrosine kinase activation: in vivo relevance of ligand-independent activation mechanisms and impact upon the efficacy of trastuzumab-based treatment.

Hudelist G, Köstler WJ, Attems J, Czerwenka K, Müller R, Manavi M, Steger GG, Kubista E, Zielinski CC, Singer CF - Br. J. Cancer (2003)

Bottom Line: Serum ECD levels were significantly higher in 15 (24%) patients with tumours exhibiting activated Her-2/neu as compared to those without detectable Her-2/neu phosphorylation (median 148.2 vs 28.5 ng ml(-1), P=0.010).Whereas response rate only showed a trend to be higher in patients with Her-2/neu-phosphorylated breast cancer (47 vs 34%, P=0.197), both uni- and multivariate analyses revealed that the median progression-free survival under trastuzumab-based treatment was significantly longer in patients with Her-2/neu-phosphorylated breast cancer-11.7 (95% CI 5.2-18.3) months-when compared to the progression-free survival of 4.5 (95% CI 3.4-5.6) months observed in patients with tumours lacking phosphorylated Her-2/neu (P=0.001).Proteolytic cleavage of the ECD represents a biologically relevant ligand-independent mechanism of Her-2/neu activation in vivo.

View Article: PubMed Central - PubMed

Affiliation: Clinical Division of Special Gynaecology, Department of Obstetrics and Gynaecology, University Hospital, Vienna, Austria.

ABSTRACT
Proteolytic cleavage of the Her-2/neu extracellular domain (ECD) has been shown to initiate receptor phosphorylation representing Her-2/neu activation in vitro. The present investigation was performed to evaluate the clinical relevance of ECD cleavage for Her-2/neu activation and the consequences of active intracellular Her-2/neu signalling reflected by tyrosine kinase phosphorylation in patients treated with the anti-Her-2/neu antibody trastuzumab. Sera from 62 patients receiving trastuzumab-based treatment for Her-2/neu overexpressing metastatic breast cancer were assessed for pretreatment ECD levels using an enzyme-linked immunosorbent assay. In parallel, Her-2/neu activation status of tumour specimens was assessed by immunohistochemistry using a Her-2/neu phosphorylation state specific antibody (PN2A) and correlated with the patients' ECD levels and clinical course of disease. Serum ECD levels were significantly higher in 15 (24%) patients with tumours exhibiting activated Her-2/neu as compared to those without detectable Her-2/neu phosphorylation (median 148.2 vs 28.5 ng ml(-1), P=0.010). Whereas response rate only showed a trend to be higher in patients with Her-2/neu-phosphorylated breast cancer (47 vs 34%, P=0.197), both uni- and multivariate analyses revealed that the median progression-free survival under trastuzumab-based treatment was significantly longer in patients with Her-2/neu-phosphorylated breast cancer-11.7 (95% CI 5.2-18.3) months-when compared to the progression-free survival of 4.5 (95% CI 3.4-5.6) months observed in patients with tumours lacking phosphorylated Her-2/neu (P=0.001). Proteolytic cleavage of the ECD represents a biologically relevant ligand-independent mechanism of Her-2/neu activation in vivo. The influence of Her-2/neu activation status upon the outcome of trastuzumab-based therapies merits further investigation in larger prospective trials.

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Western blot analysis demonstrating the phosphorylation state specifity of the PN2A antibody. Specifity of (A) anti-Her-2/neu (p185) antibody and (B) anti-phospho (tyr1248) Her-2/neu antibody (PN2A) is shown by Western blot analysis of whole-cell lysates. SKBR3 cells were treated without (lanes A1 and B8) and with 100 ng ml−1 EGF for 2 (lanes A3 and B6), 4 (lanes A4 and B5), 8 (lanes A5 and B4), 10 (lanes A6 and B3), 30 (lanes A7 and B2) and 60 (lanes A8 and B1) min (kDa, molecular weight in kilodalton, molecular weight markers at 250, 98 and 64 kDa).
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fig2: Western blot analysis demonstrating the phosphorylation state specifity of the PN2A antibody. Specifity of (A) anti-Her-2/neu (p185) antibody and (B) anti-phospho (tyr1248) Her-2/neu antibody (PN2A) is shown by Western blot analysis of whole-cell lysates. SKBR3 cells were treated without (lanes A1 and B8) and with 100 ng ml−1 EGF for 2 (lanes A3 and B6), 4 (lanes A4 and B5), 8 (lanes A5 and B4), 10 (lanes A6 and B3), 30 (lanes A7 and B2) and 60 (lanes A8 and B1) min (kDa, molecular weight in kilodalton, molecular weight markers at 250, 98 and 64 kDa).

Mentions: Figure 2Figure 2


Her-2/neu-triggered intracellular tyrosine kinase activation: in vivo relevance of ligand-independent activation mechanisms and impact upon the efficacy of trastuzumab-based treatment.

Hudelist G, Köstler WJ, Attems J, Czerwenka K, Müller R, Manavi M, Steger GG, Kubista E, Zielinski CC, Singer CF - Br. J. Cancer (2003)

Western blot analysis demonstrating the phosphorylation state specifity of the PN2A antibody. Specifity of (A) anti-Her-2/neu (p185) antibody and (B) anti-phospho (tyr1248) Her-2/neu antibody (PN2A) is shown by Western blot analysis of whole-cell lysates. SKBR3 cells were treated without (lanes A1 and B8) and with 100 ng ml−1 EGF for 2 (lanes A3 and B6), 4 (lanes A4 and B5), 8 (lanes A5 and B4), 10 (lanes A6 and B3), 30 (lanes A7 and B2) and 60 (lanes A8 and B1) min (kDa, molecular weight in kilodalton, molecular weight markers at 250, 98 and 64 kDa).
© Copyright Policy
Related In: Results  -  Collection

Show All Figures
getmorefigures.php?uid=PMC2376939&req=5

fig2: Western blot analysis demonstrating the phosphorylation state specifity of the PN2A antibody. Specifity of (A) anti-Her-2/neu (p185) antibody and (B) anti-phospho (tyr1248) Her-2/neu antibody (PN2A) is shown by Western blot analysis of whole-cell lysates. SKBR3 cells were treated without (lanes A1 and B8) and with 100 ng ml−1 EGF for 2 (lanes A3 and B6), 4 (lanes A4 and B5), 8 (lanes A5 and B4), 10 (lanes A6 and B3), 30 (lanes A7 and B2) and 60 (lanes A8 and B1) min (kDa, molecular weight in kilodalton, molecular weight markers at 250, 98 and 64 kDa).
Mentions: Figure 2Figure 2

Bottom Line: Serum ECD levels were significantly higher in 15 (24%) patients with tumours exhibiting activated Her-2/neu as compared to those without detectable Her-2/neu phosphorylation (median 148.2 vs 28.5 ng ml(-1), P=0.010).Whereas response rate only showed a trend to be higher in patients with Her-2/neu-phosphorylated breast cancer (47 vs 34%, P=0.197), both uni- and multivariate analyses revealed that the median progression-free survival under trastuzumab-based treatment was significantly longer in patients with Her-2/neu-phosphorylated breast cancer-11.7 (95% CI 5.2-18.3) months-when compared to the progression-free survival of 4.5 (95% CI 3.4-5.6) months observed in patients with tumours lacking phosphorylated Her-2/neu (P=0.001).Proteolytic cleavage of the ECD represents a biologically relevant ligand-independent mechanism of Her-2/neu activation in vivo.

View Article: PubMed Central - PubMed

Affiliation: Clinical Division of Special Gynaecology, Department of Obstetrics and Gynaecology, University Hospital, Vienna, Austria.

ABSTRACT
Proteolytic cleavage of the Her-2/neu extracellular domain (ECD) has been shown to initiate receptor phosphorylation representing Her-2/neu activation in vitro. The present investigation was performed to evaluate the clinical relevance of ECD cleavage for Her-2/neu activation and the consequences of active intracellular Her-2/neu signalling reflected by tyrosine kinase phosphorylation in patients treated with the anti-Her-2/neu antibody trastuzumab. Sera from 62 patients receiving trastuzumab-based treatment for Her-2/neu overexpressing metastatic breast cancer were assessed for pretreatment ECD levels using an enzyme-linked immunosorbent assay. In parallel, Her-2/neu activation status of tumour specimens was assessed by immunohistochemistry using a Her-2/neu phosphorylation state specific antibody (PN2A) and correlated with the patients' ECD levels and clinical course of disease. Serum ECD levels were significantly higher in 15 (24%) patients with tumours exhibiting activated Her-2/neu as compared to those without detectable Her-2/neu phosphorylation (median 148.2 vs 28.5 ng ml(-1), P=0.010). Whereas response rate only showed a trend to be higher in patients with Her-2/neu-phosphorylated breast cancer (47 vs 34%, P=0.197), both uni- and multivariate analyses revealed that the median progression-free survival under trastuzumab-based treatment was significantly longer in patients with Her-2/neu-phosphorylated breast cancer-11.7 (95% CI 5.2-18.3) months-when compared to the progression-free survival of 4.5 (95% CI 3.4-5.6) months observed in patients with tumours lacking phosphorylated Her-2/neu (P=0.001). Proteolytic cleavage of the ECD represents a biologically relevant ligand-independent mechanism of Her-2/neu activation in vivo. The influence of Her-2/neu activation status upon the outcome of trastuzumab-based therapies merits further investigation in larger prospective trials.

Show MeSH
Related in: MedlinePlus