Figure 7. Prostaglandin E₂ mediates sensitivity to T-DM1 in resistant cells.

(A) The expression of genes involved in the prostaglandin pathway is highly modified in resistant cells to T-DM1. The results shown are the expression fold changes of TR or TCR over parental cells for the indicated genes determined by RT-qPCR. (B) Sensitivity to aspirin studied by MTT assay was found to be increased in TR and TCR cells compared to S cells (^*: P<0,05; ^**: P<0,01). (C) Quantification by ELISA of PGE2 in the supernatant of each cell line shows an increased amount in TR cells compared to parental cells. (D) Wound healing assay performed on OE-19 S, TR and TCR cell lines in the absence or presence of 10 μM PGE₂. The addition of PGE₂ decreased the migration speed of the parental cell line but had no effect on the migration speed of both resistant cell lines. (E) Cell survival after exposure to 1 nM T-DM1 and 10 μM PGE₂ was studied by Annexin V/PI staining after 72h exposure. The presence of PGE₂ increases the sensitivity to T-DM1 of resistant models. (F) The increased sensitivity to T-DM1 in the presence of PGE₂ was confirmed by xCELLigence. After overnight incubation cells were exposed to 1 μM PGE₂ and/or 0,1 nM T-DM1. The normalized cell index of TR and TCR cells exposed to T-DM1 and PGE₂ is inferior to control, PGE₂ and T-DM1.A single experiment is shown, representative of 3 experiments.