Kelber, J. | bioRxiv Science

bioRxiv2026

KDM6A is enzymatically active at the Golgi apparatus where it is necessary for maintenance of Golgi apparatus morphology

KDM6A and KDM6B, lysine demethylases, play a central role in regulation of transcription through their demethylation activity towards H3K27me3 and have also been shown to be dynamically regulated upon epithelial-mesenchymal transition (EMT). In particular, KDM6A has been implicated in a variety of malignancies and is frequently mutated in cancers including those in kidney, bladder, colorectal, and breast. KDM6A and KDM6B function as part of the COMPASS-like protein complex (CLC) which includes methyltransferases KMT2C/KMT2D and the regulatory WRAD-subcomplex. KDM6A total protein is known to be suppressed by TGF-{beta} in MCF10A breast cells; however, our examination of protein localization by immunofluorescence and LC-MS/MS reveals that KDM6A expression is lost in the nucleus but retained in the Golgi apparatus, independent of other CLC complex members. Importantly, KDM6A isolated from a biochemically-separated subcellular membranous fraction possesses the catalytic JmjC domain and is enzymatically active, indicating that KDM6A may have non-nuclear substrates. Further, knockdown of KDM6A and treatment with TGF-{beta} similarly alter Golgi apparatus morphology, in a cell type specific manner, suggesting context-dependent regulatory functions. These findings support a model in which KDM6A is necessary to maintain Golgi apparatus morphology and is enzymatically active outside of the nucleus.

cell biology↗

bioRxiv2020

A SNAI2-PEAK1 stromal axis drives progression and lapatinib resistance in HER2-positive breast cancer by supporting a cytokine expression profile that converges on PI3K/Akt signaling

Intercellular mechanisms by which the stromal microenvironment contributes to solid tumor progression and targeted therapy resistance remain poorly understood, presenting significant clinical hurdles. PEAK1 (Pseudopodium-Enriched Atypical Kinase One) is an actin cytoskeleton- and focal adhesion-associated pseudokinase that promotes cell state plasticity and cancer metastasis by mediating growth factor-integrin signaling crosstalk. Here, we determined that stromal PEAK1 expression predicts poor outcomes in HER2-positive breast cancers high in SNAI2 expression and enriched for MSC content. Notably, we identified that mesenchymal stem cells (MSCs) and cancer-associated fibroblasts (CAFs) express high PEAK1 protein levels and MSCs require PEAK1 to potentiate tumorigenesis, lapatinib resistance and metastasis of HER2-positive breast cancer cells. Analysis of PEAK1-dependent secreted factors from MSCs revealed a CCL4-, INHBA- and GDF5-focused network that converged on PI3K/Akt signaling. In this regard, we observed that MSC expression of PEAK1 is required for sustained Akt phosphorylation in neighboring HER2-positive breast cancer cells following lapatinib treatment. Finally, we uncovered a significant correlation between INHBA and PEAK1 expression levels in breast cancer, and that INHBA is an excellent predictor of disease relapse and decreased survival in HER2-positive tumors enriched for PEAK1 expression and MSC content. Importantly, we provide the first evidence that PEAK1 promotes tumorigenic phenotypes through a previously unrecognized SNAI2-PEAK1-INHBA-PI3K/Akt stromal to tumor cell signaling axis. These results establish a new, targetable intercellular mechanism that may be leveraged to improve targeted therapy responses and patient outcomes in breast cancer and other stroma-rich malignancies.

cancer biology↗