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Selected Publication:

Type of publication: Doctoral Thesis
Type of document:

Year: 2010

Authors: Peter, Barbara

Title: Role of KIT and Plk-1 as potential therapeutic targets in canine and human neoplastic mast cells.

Other title: Die Bedeutung von KIT und Plk-1 als potentielle Drug Targets in kaninen und humanen neoplastischen Mastzellen

Source: Dissertation, Vet. Med. Univ. Wien, pp. 109.


Authors Vetmeduni Vienna:

Peter Barbara

Advisor(s):
Thalhammer Johann

Reviewer(s):
Saalm├╝ller Armin
Thalhammer Johann

Vetmed Research Units:
University Clinic for Small Animals, Clinical Unit of Internal Medicine Small Animals


Graduation date: 03.03.11


Abstract:
Advanced human and canine mast cell neoplasms are characterized by uncontrolled growth of neoplastic mast cells and drug resistance. The tyrosine kinase receptor KIT is often mutated and activated and thus contributes to malignant growth of mast cells. However, apart from KIT, other KIT-independent pathways are also be involved in neoplastic mast cell proliferation. Therefore, current research is seeking new targets in neoplastic mast cells and exploring the effects of various targeted drugs. In the first manuscript we determined the effects of the multikinase inhibitor INNO-406 (bafetinib) on primary neoplastic canine and human mast cells, the canine mastocytoma cell line C2, the human mast cell leukemia cell line HMC-1.1 bearing the KIT mutant V560G, and HMC-1.2 cells harbouring KIT V560G and KIT D816V. INNO-406 was found to inhibit proliferation in HMC-1.1 cells (IC50: 30-40 nM), but not in HMC-1.2 cells or primary neoplastic cells in patients with KIT D816V-positive systemic mastocytosis. In canines, growth-inhibitory effects of INNO-406 were seen in C2 cells (IC50: 50-100 nM) exhibiting a KIT exon 11 internal tandem-duplication and in primary neoplastic MC harbouring wild type exon 11, whereas no effects were seen in neoplastic mast cells exhibiting a polymorphism at amino acid 581 in exon 11. INNO-406 was found to block KIT phosphorylation in HMC-1.1 cells and C2 cells, but not in HMC-1.2 cells, whereas Lyn-phosphorylation was blocked by INNO-406 in all types of mast cells. In conclusion the major target of INNO-406 in neoplastic mast cells appears to be KIT. Drug responses may depend on the presence and type of KIT mutation: in human mast cells, the KIT D816V mutant introduces resistance, and in canine mastocytomas, an exon 11 polymorphism may be indicative of resistance against INNO-406. In the second manuscript the effects of the polo-like-kinase (Plk-1) inhibitor BI 2536 on growth and viability of neoplastic mast cells were studied. Plk-1 is a serine/threonine kinase that plays an essential role in mitosis in mesenchymal cells and is overexpressed in various tumor entities. Plk-1 has recently been introduced as a new drug target in myeloid leukemias and solid tumors. In this study, we analyzed the expression and function of Plk-1 in human and canine neoplastic mast cells. As determined by immunostaining, primary human neoplastic mast cells as well as the mast cell leukemia cell line HMC-1 and the canine mastocytoma cell line C2 were found to display phosphorylated Plk-1. In addition, human neoplastic MC expressed Plk-1 mRNA. A Plk-1-specific siRNA induced apoptosis in HMC-1 cells whereas no effect was seen with a control siRNA. The Plk-1-targeting drug BI 2536 was found to inhibit proliferation in HMC-1 cells in a dose-dependent manner. BI 2536 also produced growth inhibition in primary human and canine neoplastic mast cells and in the canine mastocytoma cell line C2. The growth-inhibitory effects of BI 2536 on neoplastic mast cells were found to be associated with a mitotic arrest and with consecutive apoptosis. Finally, BI 2536 was found to synergize with the KIT-targeting kinase inhibitor midostaurin (PKC412) in producing growth inhibition in neoplastic mast cells. In control experiments, BI 2536 did not induce apoptosis in normal cultured human mast cells. Together, our data show that Plk-1 is a potential therapeutic target in neoplastic mast cells. Targeting of Plk-1 may be an attractive pharmacologic concept in advanced human systemic mastocytosis and aggressive mast cell tumors in dogs.

Keywords:
KIT / Plk-1 / mast cells / targeted therapy / Tyrosine Kinase Inhibitor / INNO-406 / BI 2536


Publication(s) resulting from University thesis:

Peter, B; Gleixner, KV; Cerny-Reiterer, S; Herrmann, H; Winter, V; Hadzijusufovic, E; Ferenc, V; Schuch, K; Mirkina, I; Horny, HP; Pickl, WF; M├╝llauer, L; Willmann, M; Valent, P (2011): Polo-like kinase-1 as a novel target in neoplastic mast cells: demonstration of growth-inhibitory effects of small interfering RNA and the Polo-like kinase-1 targeting drug BI 2536. Haematologica. 2011; 96(5):672-680
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Peter, B; Hadzijusufovic, E; Blatt, K; Gleixner, KV; Pickl, WF; Thaiwong, T; Yuzbasiyan-Gurkan, V; Willmann, M; Valent, P (2010): KIT polymorphisms and mutations determine responses of neoplastic mast cells to bafetinib (INNO-406). Exp Hematol. 2010; 38(9):782-791

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