Abstract
Heat shock protein 90 (HSP90) stabilizing oncoproteins has been an attractive target in cancer therapy. 17-N-Allylamino-17-demethoxygeldanamycin (17-AAG), an HSP90 inhibitor, was tested in phase II/III clinical trials, but due to lack of efficacy, clinical evaluation of 17-AAG has achieved limited success, which led to resistance to 17-AAG. However, the mechanism of 17-AAG resistance has not clearly been identified. Here, we identified LGALS3BP (Lectin, galactoside-binding soluble 3 binding protein), a secretory glycoprotein, as a 17-AAG resistance factor. In the clinical reports, it was suggested that LGALS3BP was associated with low survival rate, development of cancer progression, and enhancement of metastasis in human cancers. As we confirmed that the LGALS3BP level was increased in 17-AAG-resistant cells (H1299_17R) compared with that of the parental cell line (H1299_17P), knockdown of LGALS3BP expression increased sensitivity to 17-AAG in H1299_17R cells. Overexpression of LGALS3BP also augmented PI3K/Akt and ERK signaling pathways. Furthermore, we determined that the PI3K/Akt signaling pathway was involved in LGALS3BP-mediated 17-AAG resistance in vitro and in vivo, demonstrating that LGALS3BP mediates the resistance against 17-AAG through PI3K/Akt activation rather than ERK activation. These findings suggest that LGALS3BP would be a target to overcome resistance to 17-AAG in lung cancer. For example, the combination of 17-AAG and PI3K/Akt inhibitor would effectively suppress acquired resistance to 17-AAG. In conclusion, targeting of LGALS3BP-mediated-specific survival signaling pathway in resistant cells may provide a novel therapeutic model for the cancer therapy. Mol Cancer Ther; 16(7); 1355-65. ©2017 AACR.