Abstract 5136: HER2 or EGFR inhibition interacts with tumor microenvironment by downregulation of PD-L1 and chemokines

Abstract

Abstract Background: Agents targeting HER2 or EGFR have been applied in several cancer types. Tumor microenvironment including tumor-infiltrating lymphocytes could be a predictive marker in HER2- or EGFR- targeted therapy, although there are some controversies. However, the effects of HER2 and EGFR inhibition on tumor microenvironment are unclear. Method: We screened HER2, EGFR, and PD-L1 expression in gastric cancer cell lines by western blot (SNU216, SNU668, SNU719, AGS, N87, YCC3, and YCC10). HER2 and EGFR was inhibited by using dual inhibitor (afatinib, lapatinib). After HER2 and EGFR inhibition, the change of PD-L1 expression was evaluated in HER2 overexpressed cell lines (SNU216, N87, SKBR3) at western blot, FACS, PCR, and qPCR. Selective blockade for down-steam molecules of HER2 and EGFR was conducted by using pictilisib (PI3K inhibitor) and trametinib (MEK inhibitor). The change of chemokines such as CXCL1, CCL2, and CCL21 was evaluated after HER2 and EGFR inhibition by PCR. In clinical data, PD-L1 expression and HER2 expression in resected gastric cancer were also evaluated by immunohistochemistry analysis. Results: EGFR-overexpressed or HER2-overexpressed gastric cancer cell lines (SNU216, SNU668, N87) showed higher protein expression of PD-L1. PD-L1 expression decreased with dose-dependent manner in afatinib- or lapatinib- treated cell lines (SNU216, N87, SKBR3). In pictilisib-treated cell lines, PD-L1 was also down-regulated. However, trametinib-treated cell lines did not show down-regulation of PD-L1. After lapatinib treatment in HER2 overexpressed cell lines, CXCL1, CCL21, and CCL2 decreased with dose-dependent manner. In 289 patients with resected gastric cancer, there was a significant association between HER2 and PD-L1 expression (p = 0.03). Conclusions: PD-L1 is associated with HER2 and EGFR expression. PD-L1 is regulated by inhibition of PI3K pathway. Therefore, HER2 or EGFR inhibition could interact with tumor microenvironment by down-regulation of expression of PD-L1 and chemokines. Citation Format: Jin Won Kim, Ji Hea Sung, Mi Hyun Kang, Ji-Won Kim, Se-Hyun Kim, Keun-Wook Lee, Hye Seung Lee, Jee Hyun Kim. HER2 or EGFR inhibition interacts with tumor microenvironment by downregulation of PD-L1 and chemokines. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 5136.