VEGFR-TKI 저항성을 가지는 전이성 투명세포 콩팥세포암종에서 mTOR 경로의 활성화를 통한 PD-L1의 발현

Abstract

Background: Sunitinib is one of tyrosine kinase inhibitors (TKI) targeting vascular endothelial growth factor (VEGF) - vascular endothelial growth factor receptor (VEGFR) signaling pathways and widely used as a first-line therapy for metastatic clear cell renal cell carcinoma (mCCRCC). However, most patients eventually develop resistance to the drug. Methods: To define the resistance mechanism regard to upregulation of PD-L1 expression, 10 pairs of TKI-sensitive pre- and TKI-resistant post-treatment mCCRCC tissues were compared for gene expression profile and relating signaling pathway. A separate cohort of 109 cases of mCCRCC treated with VEGFR-TKI was validated by immunohistochemistry and analyzed for progression-free survival (PFS). A sunitinib-resistant renal cancer cell line (769-P/suR) was established after long-term treatment with sunitinib of sensitive 769-P (769-P/suS), then used for in vitro experiments such as MTT assay, qRT-PCR, western blotting, colony-forming assay, scratch test, Matrigel invasion assay, and drug sensitivity test. Results: PD-L1 expression was increased in post-treatment tissues compared to pre-treatment tissues in 3 cases among 10 paired CCRCC cases. Pathway analysis showed that the PD-L1 expression was related to the mTOR signaling pathway. These results were validated in separated cohort PD-L1 expression was associated with activation of mTOR pathway in VEGFR-TKI resistant CCRCC and poor PFS in VEGFR-TKI non-responder group. The resistance to sunitinib was confirmed in 769-P/suR, which showed aggressive tumoral behavior such as higher proliferative activity and migration and invasion capacity compared to 769-P/suS. The 769-P/suR showed higher expression of not only PD-L1 but also p-Akt, p-mTOR, and pS6 kinase than 769-P/suS. Blockage of mTOR signaling with mTOR inhibitors in 769-P/suR suppressed PD-L1 expression and reduced the aggressive tumoral behavior. Conclusions: PD-L1 expression was increased via mTOR pathway at a proportion of VEGFR-TKI resistant CCRCC.