Abstract 3256: Glypican-3 (GPC3) inhibits the metastasis development in a murine breast cancer model through the activation of p38MAPK signaling pathway
Authors: Tascon Rocio S. , Castillo Lilian , Bal de Kier Joffé Elisa , Peters María G. 
Published: August 2015

Abstract
GPC3 reexpression into the murine mammary adenocarcinoma LM3 cells (GPC3 negative) induced an inhibition of the metastatic ability in vivo, while in vitro caused a reversion of the epithelial to mesenchymal transition (EMT), suggesting its role as a metastasis suppressor. Although GPC3 signaling mechanism is unknown, we found that LM3-GPC3 cells exhibit an inhibition of Akt and canonical Wnt pathways, while non-canonical Wnt (PCP) and p38 pathways are activated.
In relation to cell parameters, GPC3 reexpression caused a significant increase in the apoptosis induced by nutrient depletion. Moreover, when LM3-GPC3 starved cells were treated with the p38 inhibitor SB203580, we observed a decrease in the apoptosis, suggesting that p38 activation is responsible of the increase in the susceptibility to apoptotic death detected in LM3-GPC3 cells.
The aim of this work was to analyze if the effects of GPC3 on in vivo cell behavior are due to p38 activation. Our assays showed that p38 inhibition had no effect on s.c. primary tumor growth but modulated spontaneous metastasis. Thus, about 60% of animals treated with SB203580 developed lung spontaneous metastases while no LM3-GPC3 tumor-bearing mice did so. We decided to confirm whether the activation of p38 is necessary for the inhibitory effect of GPC3 on metastasis development through an experimental metastasis assay. LM3-GPC3 #1 and #2, and LM3-vector #1 and #2 cells were inoculated i.v. into female BALB/c mice. Simultaneously, the p38 inhibitor SB203580 or the vehicle DMSO, were injected i.p. into mice. Our results confirmed that mice inoculated with LM3-GPC3 cells show a lower number of lung nodules than animals inoculated with LM3-vector cells. On the other hand, when mice injected with LM3-GPC3 cells were treated with SB203580, they showed a significantly higher number of lung nodules, similar to those found in animals inoculated with control cells (Lung nodules Md [Rg]: 31 [10-52] LM3-vector #1; 27 [22-30]] LM3-vector #2; 11 [0-17] LM3-GPC3 #1 +DMSO; 13 [2-19] LM3-GPC3 #2 +DMSO; 20 [11-64] LM3-GPC3 #1 +SB203589; 35 [17-57] LM3-GPC3 #2 +SB203589; U-Mann Whitney test p&lt;0.0001). So, the p38 inhibitor SB203580 was able to revert the inhibitory action of GPC3 on metastasis development.
In sum, we have confirmed that GPC3 acts as metastasis suppressor in this murine breast cancer model. We also demonstrated that GPC3 would be able to inhibit metastatic development through p38 signaling pathway activation.
Citation Format: Rocio S. Tascon, Lilian Castillo, Elisa Bal de Kier Joffé, María G. Peters. Glypican-3 (GPC3) inhibits the metastasis development in a murine breast cancer model through the activation of p38MAPK signaling pathway. [abstract]. In: Proceedings of the 106th Annual Meeting of the American Association for Cancer Research; 2015 Apr 18-22; Philadelphia, PA. Philadelphia (PA): AACR; Cancer Res 2015;75(15 Suppl):Abstract nr 3256. doi:10.1158/1538-7445.AM2015-3256