Abstract
Purpose :
Metastatic uveal melanoma (UM) has very poor prognosis and a median survival of less than 12 months. UM currently does not have any approved therapy. We aimed at identifying and validating new therapeutic targets for developing single/combination therapy approaches for patients with metastatic UM. We tested a small molecule inhibitor (NT157) of Insulin Receptor Substrates1/2 (IRS-1/2) in the IGF-1/IGF-1R signaling pathway, in UM, and validated its efficacy in vitro and in vivo.
Methods :
We determined expression of IRS-1 in 20 primary and 5 metastatic UM tumors by IHC staining and in a panel of UM cells by western blot. Cell proliferation and migration assays were done in UM cells with/without the IRS-1 inhibitor, NT157, to determine the effect of this inhibitor on UM cell growth and migration. Levels of IGF-1R pathway effectors and apoptosis markers were determined with/without NT157 treatment by western blots. Effect of IRS-1 inhibition on primary UM tumors in a chicken chorioallantoic membrane (CAM) model for UM were assessed by tumor size measurement with/without NT157 treatment. Effect on liver and lung metastasis was determined by comparisons of human Alu PCR of liver and lung tissue from NT157 treated/untreated chicken embryos. RPPA analysis post NT157 treatment was done to determine possible combination therapy partners with IRS-1 inhibition.
Results :
IRS-1 was expressed in all primary and metastatic UM tumors and UM cells tested. IRS-1 inhibition blocked UM cell survival in varying degrees in 7 UM cell lines tested and blocked cell migration. NT157 treatment blocked IGF-1R, Erk1/2 and Akt activation and increased cleaved PARP in sensitive UM cells. In the chicken CAM model, IRS-1 inhibition significantly reduced tumor growth in tumors grown from NT157-sensitive UM cells. RPPA analysis of UM cells post NT157 treatment significantly upregulated/downregulated levels of multiple effectors of cellular signaling pathways.
Conclusions :
IRS-1 is expressed in primary and metastatic UM tumors and UM cells. Inhibition of IRS-1 in UM cells resulted in reduced cell survival and migration in varying degrees. IGF-1/IGF-1R pathway signaling was blocked and apoptosis induced upon IRS-1 inhibition in vitro. UM tumor growth from NT157-sensitive UM cells in a chicken CAM model were significantly reduced in tumors treated with NT157. Overall our data shows that IRS-1 may be targeted in UM to develop possible therapeutic strategies.
This is a 2020 ARVO Annual Meeting abstract.