Abstract 3673: The BMI1/Sp1/IGF1R pathway mediates pemetrexed resistance in non-small cell lung cancer cells

Abstract

Abstract Background: Lung cancer is the leading cause of cancer death in Taiwan and worldwide and non-small cell lung cancers (NSCLCs) account for more than 85% of lung cancers. Pemetrexed is approved for several steps of nonsquamous NSCLC therapy but drug resistance often occurs in long-term treatment. Cancer stem cells (CSCs) are considered as the rare subpopulation of cancer cells with the features of tumor initiation, drug resistance, and metastatic capability. The signaling pathway and potential targets contribute to the maintenance of pemetrexed-resistant cancer stem cell remain unknown. Methods: To investigate the mechanism of pemetrexed resistance in lung cancers, the pemetrexed-resistant A549 cells were established (A400). The sphere-formation assay, western blot analysis and real-time qPCR were employed to identify cancer stem cells and study their properties. Result: We first discovered that the pemetrexed-resistant A549 cells (called A400) contained more CSC activity than the parental A549 cells including the increased number of tumorspheres and the upregulation of BMI1, c-Myc, Sox2 and p-IGF1Rtyr1165/1166 expression. The treatment of PTC-209, a BMI1 inhibitor, displayed a greater inhibitory effect in cell proliferation in A400 than A549 cells and it suppressed tumorsphere formation capability of A400 cells. In addition, PTC-209 treatment downregulated the expression of IGF1R, p-IGF1Rtyr1165/1166, and Sp1, a positive regulatory transcriptional factor in IGF1R expression, in A400 cells. We also found that Sp1 was increased in A400 when compared to parental A549 cells. With the treatment of Sp1 inhibitor in A400 cells, the expression of IGF1R was suppressed without changing BMI1 level. Finally, we examined the therapeutic effect of BMI1 inhibition in vivo and resulted found that intraperitoneal administration of PTC-209 enhanced the pemetrexed efficacy in NOD/SCID mice harboring A400 xenograft tumors. Conclusion: Our data reveal that BMI1/Sp1/IGF1R pathway is upregulated in pemetrexed resistant NSCLCs and targeting BMI1 could be a therapeutic strategy in NSCLCs when pemetrexed resistance occurs. Citation Format: Wen-Ling Wang, Peng-Ju Chien, Wen-Wei Chang, Bing-Yen Wang. The BMI1/Sp1/IGF1R pathway mediates pemetrexed resistance in non-small cell lung cancer cells [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 3673.