DDX20 interlinking with SNRPE endows MYC-driven triple-negative breast cancer therapeutic vulnerability in a splicing-independent manner

Abstract

Abstract Background: Aberrant splicing is a hallmark of cancer. For MYC-driven cancers, such as triple-negative breast cancer, hypersensitivity to spliceosome-targeted therapy is a novel anticancer strategy since it also triggers antitumorimmunity. Of the approximately 200 known spliceosomal genes, core spliceosomes are essential for cancer cell survival, yet the underlying mechanisms remain elusive. Methods: First, SNPRE representing the core spliceosomal Sm gene was screened using a multiomics database analysis approach. Then, we investigated the effect of SNRPE on the growth of TNBC cells in vitro and in vivo. We identified DDX20 from the interacting partners of SNPRE as a potential molecule involved in spliceosome vulnerability using coimmunoprecipitationtechniques. The mechanism of the SNRPE-DDX20 axis in tumor spliceosome therapeutic vulnerability was determined by various techniques,including RNA-seq, chromatin immunoprecipitation and other technologies. Results: In our research, SNRPE was upregulated in TNBC and predicted poor prognosis. Downregulation of SNRPE attenuated the vitality of TNBC in vivo and in vitro. We hypothesized and confirmed DDX20 as an important factor in core spliceosome therapeutic vulnerability. In DDX20-knockout TNBC cells, cell survival is no longer dependent onintracellular splicing activity orSNPRE expression. In DDX20/SNRPE double-downregulated cells, growth ability was restored due to MTOR reactivation via a splicing-independent pathway. In SNRPE-knockdown TNBC cells, ETV3 and its corepressor DDX20 function together to block MTOR expression to induce growth suppression. Once SNRPE expression was high, ETV3 bound to the C-terminus of DDX20 was replaced by SNRPE-containing components, whilethe binding affinity of released ETV3 to MTOR was reduced, and eventually, MTOR was expressed sufficiently to promote proliferation. Conclusions: Our results reveal that DDX20 is an adaptor in the crosstalk between RNA splicing (SnRNP components such as SNRPE) and the MTOR pathway in MYC-driven TNBC. Patients with high DDX20 expression are likely suitable for treatment with spliceosome modulators, leading to double killing effects by cell arrest and antitumorimmunity. Targeting DDX20 may serve as a therapeutic target for MYC-driven cancers.