BACKGROUND: Suppressor of Cytokine Signaling 7 (SOCS7) is a member of the SOCS family and is known to interact with Phospholipase Cγ-1 (PLCγ-1), one of the Insulin like Growth Factor - I (IGF-I) receptor downstream molecules. In the present study, we sought to examine the effect of knocking down SOCS7 gene on breast cancer cells growth and migration and to elucidate whether this has involved IGF-I — PLCγ-1 signaling using the PLCγ-1 blocker U73122.

METHODS: Suitable breast cancer cells (MCF7 and MDA-MB-231) were transfected with anti-SOCS7 ribozymal transgene, to create sublines with SOCS7 knockdown that was verified by RT-PCR. The growth and migration of the cells were evaluated in the presence or absence of IGF-I and PLCγ-1 inhibitor using in vitro growth assay and Electrical Cell Impedance Sensing (ECIS) migration assay.

RESULTS: MCF7ΔSOCS7 and MDA-MB-231ΔSOCS7 (SOCS7 knockdown) were constructed. Both sublines showed a higher rate of growth compared to control cells with and without IGF-I stimulation. U73122 treatment did not appear to change this growth outcome. Using ECIS migration assay, it was shown that knocking down SOCS7 had a significant positive effect on the migration of MCF7 and MDA-MB-231 cells, and that both IGF-I treatment and SOCS7 knockdown had a synergistic positive influence on their migration (p < 0.05). We further demonstrated that the impact of U73122 on the IGF-I migratory effect was dependent upon SOCS7 knockdown as it has significantly blocked the stimulatory effect of IGF-I on MCF7ΔSOCS7 and MDA-MB-231ΔSOCS7 migration but not that of the control cells. While SOCS7 has acted to control the IGF-I effect, it appeared to cancel the inhibitory function of U73122, indicating a specific anti - PLCγ-1 role for SOCS7 in IGF-I induced breast cancer cellular migration.

CONCLUSION: SOCS7 loss resulted in increased growth and migration of breast cancer cells and this had a synergistic effect on their response to IGF-I. This role could be related to its interaction with PLCγ-1 during the cellular migration but not the growth. It may be possible that SOCS7 acts through different mechanism to control the cellular growth.

Citation Information: Cancer Res 2012;72(24 Suppl):Abstract nr P1-04-03.