Blocking ubiquitination of hnRNPA1 maintains the self-renewal of breast cancer stem cells via mutually exclusive splicing of PKM pre-mRNA

PKM serves as a rate-limiting enzyme in glycolysis, which produces two isoforms depending on the inclusion of either exon 9 (PKM1) or exon 10 (PKM2). The M2 pyruvate kinase (PKM2) isoform is commonly upregulated in various cancers, where it plays a pivotal role in regulating Warburg effect. Breast cancer stem cells (BCSCs) exhibit enhanced glycolysis, which is crucial for their self-renewal. However, the specific role of PKM2 in BCSCs remains largely unexplored. Here, we report that PKM2 expression is upregulated in BCSCs. Meanwhile, we identify that LINC00887 is significantly upregulated in BRCA through a genome-wide LNCRNA microarray. Moreover, we recognize that hnRNPA1 interacts with PKM pre-mRNA and regulates its mutually exclusive splicing. Furthermore, we demonstrate that LINC00887 maintains the self-renewal of BCSCs by promoting PKM2 splicing and reprogramming glucose metabolism. Mechanistically, LINC00887 upregulates PKM2 expression by binding hnRNPA1, thereby concealing its ubiquitination site, which blocks its ubiquitination and maintains its stability. Consistently, overexpression of hnRNPA1 almost completely rescues/reverses the inhibitory effects of LINC00887 KD in BRCA.Collectively, our study characterizes the LINC00887/hnRNPA1/PKM1/2 axis in BRCA and reveals the essential role of LINC00887 in BCSCs self-renewal/maintenance through promoting hnRNPA1-mediated PKM2 splicing, highlighting the therapeutic potential of targeting cancer metabolism.