LncRNA ZNF649-AS1 promotes trastuzumab resistance and TAM-dependent PD-L1 expression in breast cancer by regulating EXOC7 alternative splicing.

ABSTRACT

BACKGROUND: Trastuzumab resistance is a serious clinical problem in the treatment of HER2-positive breast cancer (BC). The lncRNA ZNF649-AS1 was previously found to promote HER2-positive BC trastuzumab resistance. The study aims to explore the molecular mechanism of ZNF649-AS1 in HER2-positive BC trastuzumab resistance. METHODS: Tumor tissue and peripheral blood samples were collected from 20 HER2-positive BC patients with trastuzumab-resistant and non-resistant, respectively. Trastuzumab-resistant BC cell lines SKBR-3-TR and BT474-TR were established. RIP was employed to confirm the binding of ZNF649-AS1, PRPF8 and exocyst complex component 7 (EXOC7). RNA expression of EXOC7-L (Full length of EXOC7) and EXOC7-S (Spliceosome of EXOC7) were detected using agarose gel electrophoresis. Expressions of macrophage markers CD68+ CD206+ were measured by flow cytometry. RESULTS: ZNF649-AS1 expression was upregulated in HER2-positive BC trastuzumab resistance. ZNF649-AS1 downregulation inhibited trastuzumab resistance in HER2-positive BC. ZNF649-AS1 regulated EXOC7 alternative splicing by binding with PRPF8. EXOC7-S knockdown suppressed trastuzumab resistance and TAM-dependent PD-L1 expression in HER2-positive BC. EXOC7-S overexpression abolished the effects of ZNF649-AS1 knockdown on trastuzumab resistance and TAM-dependent PD-L1 expression in HER2-positive BC. CONCLUSION: ZNF649-AS1 promoted trastuzumab resistance and TAM-dependent PD-L1 expression in HER2-positive BC via promoting alternative splicing of EXOC7 by PRPF8.