Abstract 2627: Inhibition of TGFβ in colorectal cancer cells is associated with a compensatory activation of AXL and p38 MAPK signaling pathways

Abstract

According to the consensus molecular subtypes (CMS), almost 23% of human colorectal cancer (CRC) are classified in the CMS4 group, characterized by a mesenchymal signature and the activation of transforming growth factor β (TGF-β) signaling. AXL is a tyrosine kinase receptor involved in epithelial to mesenchymal transition, angiogenesis and immune modulation in CRC. We have previously demonstrated that AXL gene is amplified in approximately 5% of human CRC, and that AXL inhibition causes a significant blockade of CRC cell proliferation and migration. Here we have evaluated the role of TGF-β signaling and the potential interaction between TGF-β and AXL in human CRC cell lines. We assessed the expression and activation of TGF-β and AXL in a panel of six human CRC cell lines by western blot (WB) and real time PCR. We tested the sensitivity of HCT116 and LOVO cells to treatment with galunisertib ( LY21209761), a selective TGF-β R1 inhibitor, by MTT, cell invasion, wound healing and soft-agar colony forming assays. Further, intracellular CRC cell signaling was evaluated following galunisertib treatment by WB. TGF-β receptors 1 and 2 were expressed in all human CRC cell lines (HCT116, SW480, LOVO, LIM 1215, SW48 and CaCo2), whereas AXL expression was restricted to HCT116, SW480, LOVO cells. Treatment with galunisertib had little or no effect on cancer cell growth, whereas it partially reduced TGF-β induced cell migration, invasion and colony formation in HCT116 and LOVO cells (that co-expressed both TGF-β receptors and AXL). Interestingly, TGF-β inhibition resulted in a concomitant significant activation of AXL and p38 MAPK in both cell lines, that could represent a cancer cell adaptive mechanism of resistance to galunisertib treatment. These results suggest a potential functional cross talk between TGF-β, AXL and p38 MAPK signals in human CRC cells. In this respect, further experiments are ongoing to better understand this interaction with the aim of identifying potential novel anti-AXL and anti-TGF-β therapeutic strategies. Citation Format: Davide Ciardiello, Pietro Paolo Vitiello, Nunzia Matrone, Valentina Belli, Claudia Cardone, Luca Poliero, Carola Borrelli, Gianluca Arrichiello, Giulia Martini, Vincenza Ciaramella, Giusi Barra, Floriana Morgillo, Teresa Troiani, Davide Melisi, Fortunato Ciardiello, Erika Martinelli. Inhibition of TGFβ in colorectal cancer cells is associated with a compensatory activation of AXL and p38 MAPK signaling pathways [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2019; 2019 Mar 29-Apr 3; Atlanta, GA. Philadelphia (PA): AACR; Cancer Res 2019;79(13 Suppl):Abstract nr 2627.