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Volume 6 (2002), Issue 3, Pages 89-96

Differential Expression of IRS-1 and IRS-2 in Uterine Leiomyosarcomas with Distinct Oncogenic Phenotypes: Lack of Correlation with Downstream Signaling Events

1Divisione di Oncologia Sperimentale 2, Centro di Riferimento Oncologico-IRCCS, Aviano 33081, Italy
2Dipartimento di Scienze e Tecnologie Biomediche and MATI Excellence Center, Università di Udine, Udine 35100, Italy
3Dipartimento di Medicina Sperimentale e Patologia, Università La Sapienza, Roma, Italy

Copyright © 2002 Hindawi Publishing Corporation. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


Purpose: Insulin receptor substrates (IRSs) are essential for insulin-induced mitogenic effects on several cell types but they also are involved in cell transformation.We investigated whether the differential constitutive expression and potential distinct downstream signaling events of IRS-1 and IRS-2 might be related to discrete tumourigenic phenotypes of three human uterine leiomyosarcoma cell lines, one of which was specifically isolated for the present study.

Methods and results: SK-UT-1B egressed effectively from a gellyfied Matrigel matrix and grew as did DMR cells in an anchorage-independent manner in agar and induced rapidly growing tumours in nude mice. On the contrary, SK-LMS-1 cells did not emigrate from Matrigel, neither grew in agar nor were they tumourigenic. IRS-2 was highly expressed in the more malignant cell lines, whereas IRS-1 was present only in SK-LMS-1 cells. However, upon insulin stimulation both IRS- 1 and IRS-2 were tyrosine phosphorylated with a similar kinetic in the respective cell lines; furthermore, after 1 min of insulin stimulation PI3-kinase associated with IRSs and after 2 min Shc was phosphorylated and associated with Grb2 with minor differences detectable among the various cell lines in the duration of phosphorylation and/or in their association irrespective of whether IRS-1 or IRS-2 were expressed.

Discussion: Our findings tend to exclude that the malignancy displayed by uterine leiomyosarcomas might be directly linked to the activation of distinct IRS-1- or IRS-2-dependent pathways.