Biology subjects

Schwarzmueller, L.

Publications and source records attributed to Schwarzmueller, L..

4 recordsLinked to original sources

bioRxiv2025

GLYATL1 is associated with metabolic and epigenetic changes and with endocrine resistance in luminal breast cancer

Estrogen receptor alpha (ER)-positive luminal breast cancer is commonly treated with aromatase inhibitors (AI) to block estrogen signaling; however, resistance frequently develops, limiting therapy success. We observed that GLYATL1 (Glycine-N-Acyltransferase Like 1) expression is upregulated in AI-resistant breast cancer cell models and in patients undergoing AI therapy, correlating with poorer survival. Here we demonstrate that GLYATL1 promotes resistance to estrogen deprivation by elevating succinate levels and altering epigenetic histone marks associated with active transcription. Knockdown or knockout of GLYATL1 reverses these effects and reduces proliferation under estrogen-deprived conditions. Notably, GLYATL1 expression is positively regulated by estrogen receptor alpha signaling independently of estrogen. These findings reveal GLYATL1 as a metabolic and epigenetic mediator of endocrine therapy resistance, suggesting it as a potential target to overcome AI resistance in luminal breast cancer.

cancer biology↗

bioRxiv2025

PAK1 activation drives divergent resistance mechanisms to aromatase inhibition and Tamoxifen in a luminal A breast cancer model

Breast cancer is the most frequent malignancy and the second leading cause of cancer-related mortality in women worldwide, and is a heterogeneous disease regarding driver mechanisms, therapies, and outcome. Estrogen receptor-positive (ER+) tumors are treated with endocrine therapies such as Tamoxifen or aromatase inhibitors (AI), aimed at disrupting tumor-promoting estrogen signaling. While these therapies are initially effective, resident tumor cells can develop resistance, leading to relapse. The p21-activated kinase 1 (PAK1) is a key regulator of multiple oncogenic signaling pathways and has been implicated in resistance to Tamoxifen. However, it remains unclear, whether PAK1 also affects the response to other endocrine therapies. Using global phosphoproteomic profiling of endocrine resistant cell line models, we observed elevated PAK1 activity in cells resistant to Tamoxifen and to estrogen deprivation, respectively, with further increases following EGF stimulation. Pharmacological inhibition of PAK1 effectively reduced cell proliferation in both resistance models, however, with distinct effects on PAK1 downstream substrates and pathways. In the Tamoxifen resistance context, PAK1 reduces apoptosis via inhibition of the pro-apoptotic protein BAD, whereas in the AI resistance model PAK1 rather triggers proliferation via RAF1. Our findings position PAK1 as a common mediator of resistance to different endocrine therapies and offer insights into the distinct signaling networks that are involved. In summary, our results suggest that targeting PAK1 may present a novel therapeutic strategy to overcome endocrine therapy resistance in ER+ breast cancer, potentially enhancing the efficacy of both Tamoxifen and AI treatments.

cancer biology↗

bioRxiv2019

Cell-to-cell variability in JAK2/STAT5 pathway components and cytoplasmic volumes define survival threshold in erythroid progenitor cells

Survival or apoptosis is a binary decision in individual cells. Yet, at the cell population level, a graded increase in survival of CFU-E cells is observed upon stimulation with Erythropoietin (Epo). To identify components of JAK2/STAT5 signal transduction that contribute to the graded population response, a cell population-level model calibrated with experimental data was extended to study the behavior in single cells. The single-cell model showed that the high cell-to-cell variability in nuclear phosphorylated STAT5 is caused by variability in the amount of EpoR:JAK2 complexes and of SHP1 as well as the extent of nuclear import due to the large variance in the cytoplasmic volume of CFU-E cells. 24 to 118 pSTAT5 molecules in the nucleus for 120 min are sufficient to ensure cell survival. Thus, variability in membrane-associated processes are responsible to convert a switch-like behavior at the single-cell level to a graded population level response. HighlightsO_LIMathematical modeling enables integration of heterogeneous data C_LIO_LISingle-cell modeling captures binary decision process C_LIO_LIMultiple sources of cell-to-cell variability in erythroid progenitor cells C_LIO_LIMinimal amount of active STAT5 sufficient for survival of erythroid progenitor cells C_LI

systems biology↗

bioRxiv2017

An antisense RNA capable of modulating the expression of the tumour suppressor microRNA-34a

The microRNA-34a is a well-studied tumor suppressor microRNA (miRNA) and a direct downstream target of TP53 with roles in several pathways associated with oncogenesis, such as proliferation, cellular growth, and differentiation. Due to its broad tumor suppressive activity, it is not surprising that miR34a expression is altered in a wide variety of solid tumors and hematological malignancies. However, the mechanisms by which miR34a is regulated in these cancers is largely unknown. In this study, we find that a long non-coding RNA transcribed antisense to the miR34a host gene, is critical for miR34a expression and mediation of its cellular functions in multiple types of human cancer. We name this long non-coding RNA lncTAM34a, and characterize its ability to facilitate miR34a expression under different types of cellular stress in both TP53 deficient and wild type settings.

cancer biology↗