Triple-negative breast cancer (TNBC) is a subtype of breast cancer (BC) with the most aggressive phenotype and poor overall survival. Using bioinformatics tools, we identified LINC00908 encoding a 60–aa polypeptide and differentially expressed in TNBC tissues. We named this endogenously expressed polypeptide ASRPS (a small regulatory peptide of STAT3). ASRPS expression was down-regulated in TNBCs and associated with poor overall survival. We showed that LINC00908 was directly regulated by ERα, which was responsible for the differential down-regulation of LINC00908 in TNBCs. ASRPS directly bound to STAT3 through the coiled coil domain (CCD) and down-regulated STAT3 phosphorylation, which led to reduced expression of VEGF. In human endothelial cells, a mouse xenograft breast cancer model, and a mouse spontaneous BC model, ASRPS expression reduced angiogenesis. In a mouse xenograft breast cancer model, down-regulation of ASRPS promoted tumor growth, and ASRPS acted as an antitumor peptide. We presented strong evidence that LINC00908-encoded polypeptide ASRPS represented a TNBC-specific target for treatment.

IntroductionIt has been demonstrated that the interplay of adhesion molecule CD44 and its ligands can regulate cancer cell proliferation, migration and invasion, as well as tumor-associated angiogenesis and is related to breast cancer patient survival. In this two-stage, case control study, we determined whether common functional tagSNPs (single nucleotide polymorphisms) are associated with breast cancer risk and prognosis.MethodsFive tagSNPs of CD44 (rs10836347C>T, rs13347C>T, rs1425802A>G, rs11821102G>A, rs713330T>C) were selected and genotyped in 1,853 breast cancer patients and 1,992 healthy control subjects in Eastern and Southern populations. Potential function of rs13347C>T and association between this variation and breast cancer were further studied.ResultsCompared with the most common rs13347CC genotype, variant genotypes (CT and TT) increased an individual's susceptibility to breast cancer, especially in estrogen receptor (ER) negative patients (odds ratio (OR) = 1.37, 95%CI = 1.17 to 1.59 for ER positive patients; OR = 2.37, 95% CI = 2.00 to 2.80 for ER negative patients). We also found that rs13347CT+ TT genotypes predicts lower five-year survival rate (hazard ratio (HR) = 1.85, 95% CI = 1.09 to 3.15, P = 0.023), with the lowest survival probability in ER negative T allele carriers. Furthermore, our reporter assay findings, although preliminary and rather modest, showed that miR-509-3p may suppress CD44 expression more strongly in C allele carriers than T allele carriers (P < 0.01). Similarly, rs13347 variant genotypes (CT and TT) carriers were shown to have more CD44 expression than CC carriers in both immunohistochemistry (P < 0.001) and western blotting (P = 0.001) results.ConclusionThese findings suggest that CD44 rs13347C>T polymorphism may affect breast cancer development and prognosis by increasing CD44 expression.

Graphical Abstract Highlights d KCNH6 regulates insulin secretion and glucose hemostasis in humans and mice d KCNH6 dysfunction causes a phenotype from hyper-to hypoinsulinemia and diabetes d KCNH6 dysfunction increases intracellular calcium levels and hyperinsulinemia d Chronic elevation of intracellular calcium causes b cell loss and hypoinsulinemia In Brief Yang et al. show that KCNH6 plays a key role in insulin secretion and glucose hemostasis in humans and mice. Dysfunction of KCNH6 results in a hyperinsulinemia phenotype in the short term and hypoinsulinemia and diabetes in the long term. SUMMARYGlucose-stimulated insulin secretion from islet b cells is mediated by K ATP channels. However, the role of non-K ATP K + channels in insulin secretion is largely unknown. Here, we show that a non-K ATP K + channel, KCNH6, plays a key role in insulin secretion and glucose hemostasis in humans and mice. KCNH6 p.P235L heterozygous mutation co-separated with diabetes in a four-generation pedigree. Kcnh6 knockout (KO) or Kcnh6 p.P235L knockin (KI) mice had a phenotype characterized by changing from hypoglycemia with hyperinsulinemia to hyperglycemia with insulin deficiency. Islets from the young KO mice had increased intracellular calcium concentration and increased insulin secretion. However, islets from the adult KO mice not only had increased intracellular calcium levels but also had remarkable ER stress and apoptosis, associated with loss of b cell mass and decreased insulin secretion. Therefore, dysfunction of KCNH6 causes overstimulation of insulin secretion in the short term and b cell failure in the long term.

TGF-b signaling pathway plays a key role in breast cancer metastasis. Recent studies suggest that TGF-b regulates tumor progression and invasion not only via transcriptional regulation, but also via translational regulation. Using both bioinformatics and experimental tools, we identified a micropeptide CIP2A-BP encoded by LINC00665, whose translation was downregulated by TGF-b in breast cancer cell lines. Using TNBC cell lines, we showed that TGF-b-activated Smad signaling pathway induced the expression of translation inhibitory protein 4E-BP1, which inhibited eukaryote translation initiation factor elF4E, leading to reduced translation of CIP2A-BP from LINC00665. CIP2A-BP directly binds tumor oncogene CIP2A to replace PP2A's B56c subunit, thus releasing PP2A activity, which inhibits PI3K/AKT/NFjB pathway, resulting in decreased expression levels of MMP-2, MMP-9, and Snail. Downregulation of CIP2A-BP in TNBC patients was significantly associated with metastasis and poor overall survival. In the MMTV-PyMT model, either introducing CIP2A-BP gene or direct injection of CIP2A-BP micropeptide significantly reduced lung metastases and improved overall survival. In conclusion, we provide evidence that CIP2A-BP is both a prognostic marker and a novel therapeutic target for TNBC.