Recent molecularly targeted approach gains advance in breast cancer treatment. However, the estimated 5-year survival rate has not met the desired expectation for improvement, especially for patients with triple-negative breast cancer (TNBC). Here we report that the lncRNA PVT1 promotes KLF5/beta-catenin signaling to drive TNBC tumorigenesis. PVT1 is upregulated in clinical TNBC tumors. Using genetic approaches targeting PVT1 in TNBC cells, we found that PVT1 depletion inhibited cell proliferation, colony formation, and orthotopic xenograft tumor growth. Mechanistically, PVT1 binds with KLF5 and increases its stability via BAP1, which upregulates beta-catenin signaling, resulting in enhanced TNBC tumorigenesis. PVT1, KLF5, and beta-catenin were also revealed to be co-expressed in clinical TNBC samples. Our findings uncover a new singaling pathway to mediate TNBC, and provide PVT1 as a new target for improving treatment of TNBC.

Lysine acetyltransferase KAT6A is a chromatin regulator that contributes to histone modification and cancer, but the basis of its actions are not well understood. Here we identify a KAT6A signaling pathway that facilitates glioblastoma (GBM) where it is upregulated. KAT6A expression was associated with GBM patient survival. KAT6A silencing suppressed cell proliferation, cell migration, colony formation and tumor development in an orthotopic mouse xenograft model system. Mechanistic investigations demonstrated that KAT6A acetylates lysine 23 of histone H3 (H3K23), which recruits the nuclear receptor binding protein TRIM24 to activate PIK3CA transcription, thereby enhancing PI3K/AKT signaling and tumorigenesis. Overexpressing activated AKT or PIK3CA rescued the growth inhibition due to KAT6A silencing. Conversely, the pan-PI3K inhibitor LY294002 abrogated the growth-promoting effect of KAT6A. Overexpression of KAT6A or TRIM24, but not KAT6A acetyltransferase activity- deficient mutants or TRIM24 mutants lacking H3K23ac binding sites promoted PIK3CA expression, AKT phosphorylation and cell proliferation. Taken together, our results define an essential role of KAT6A in glioma formation, rationalizing its candidacy as a therapeutic target for GBM treatment.

Despite the development of adjuvant therapies, glioblastoma (GBM) patients remain incurable, thus justifying the urgent need of new therapies. CDK5 plays a critical role in GBM and is a potential target for GBM. However, the mechanism by which CDK5 promotes GBM tumorigenicity remains largely unknown. Here, we identify TRIM59 as a substrate of CDK5. EGFR-activated CDK5 directly binds to and phosphorylates TRIM59, a ubiquitin ligase at serine 308, which recruits PIN1 for cis–trans isomerization of TRIM59, leading to TRIM59 binding to importin α5 and nuclear translocation. Nuclear TRIM59 induces ubiquitination and degradation of the tumor suppressive histone variant macroH2A1, leading to enhanced STAT3 signaling activation and tumorigenicity. These findings are confirmed by inhibition of CDK5-activated TRIM59 activity that results in suppression of intracranial tumor growth. Correlative expressions of the components of this pathway are clinically prognostic. Our findings suggest targeting CDK5/TRIM59 signaling axis as a putative strategy for treating GBM.