Abstract 108: Insulin-like growth factor binding protein 4 exerts differential effects on breast cancer cell proliferation based on the expression status of pregnancy-associated plasma protein A

Abstract

Abstract Insulin-Like Growth Factor Binding Protein 4 (IGFBP-4) is one of six binding proteins involved in sequestering insulin-like growth factors 1 and 2 (IGFs). IGFBP-4 expression is induced by estrogen receptor α (ERα), and its classical function is to prevent activation of IGF-1 receptor (IGF-1R) by sequestration of IGF-1. However, the aggressive triple-negative breast cancer cell line MDA-MB-231 shows high expression of IGFBP-4 along with its protease, pregnancy-associated plasma protein A (PAPP-A). Further, inhibition of IGFBP-4 in MDA-MB-231 cells is sufficient to reduce migration. To better understand the function of IGFBP-4 as a pro-cancer or anti-cancer protein, its anti-proliferative effects in ERα positive cells must be reconciled with its pro-migratory effects in triple negative cells. The role of IGFBP-4 in proliferation across four breast cancer cell lines representing ERα positive and triple negative subtypes was investigated. Stable transfection with IGFBP-4 expression construct in the MCF-7 and T-47D cell lines, which have silenced the PAPP-A gene, shows a reduction in proliferation. Further, MCF-7 parental cells cultured in conditioned media containing IGFBP-4 also show reduced proliferation, suggesting that the anti-proliferative effect of IGFBP-4 is associated with the absence of PAPP-A. Stable IGFBP-4 transfection of triple-negative MDA-MB-468 cell line, which has low extracellular IGFBP-4 when compared to MDA-MB-231 but does express PAPP-A, was sufficient to increase proliferation. Taken together, these results support the conclusion that proliferative effects of IGFBP-4 are dependent upon the expression status of PAPP-A. Citation Format: Keenan L. Flynn, Kevin D. Houston. Insulin-like growth factor binding protein 4 exerts differential effects on breast cancer cell proliferation based on the expression status of pregnancy-associated plasma protein A [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2022; 2022 Apr 8-13. Philadelphia (PA): AACR; Cancer Res 2022;82(12_Suppl):Abstract nr 108.