Biology subjects

Biber, P.

Publications and source records attributed to Biber, P..

3 recordsLinked to original sources

bioRxiv2026

PSMD14 drives melanoma cell survival and MAPK inhibitor resistance through histone H2A deubiquitination

Melanoma progression and resistance to targeted therapies remain major clinical challenges, driven in part by the remarkable phenotypic plasticity of melanoma cells. Identifying molecular mechanisms that couple tumor survival to adaptative drug responses is therefore essential. Here, we identify PSMD14, a proteasome-associated deubiquitinase, as an essential regulator of melanoma plasticity, growth, survival, and therapeutic resistance with strong prognostic significance in metastatic disease. An unbiased siRNA screen targeting the human deubiquitinase family revealed PSMD14 (proteasome 26S subunit, non-ATPase 14) as a top regulator of melanoma cell proliferation. Integrative analyses of DepMap, TCGA, and patient-derived datasets revealed that PSMD14 is frequently upregulated in melanoma, enriched in metastatic lesions, and significantly associated with poor patient outcome. Functional and pharmacological studies demonstrated that genetic depletion or inhibition of PSMD14 suppresses proliferation, clonogenic and long-term growth, and viability of melanoma cells across BRAF-, NRAS-, and NF1-driven genotypes, while inducing DNA damage and apoptosis. Consistently, PSMD14 inhibition markedly reduced tumor growth in Nras and Braf syngeneic mouse models. Mechanistically, we uncover a non-proteolytic role for PSMD14 as an epigenetic regulator of chromatin state. Proteomic and biochemical analyses identified histone H2A as a direct interactor and substrate of PSMD14. PSMD14 deubiquitinates H2A at lysine 119 independently of the proteasome, antagonizing the Polycomb E3 ligase RING1B. Loss of PSMD14 allows the increment of H2AK119 ubiquitination, transcriptional repression of pro-survival genes, including MCL1 and BCL2, and apoptotic cell death, effects rescued by RING1B depletion. Importantly, we demonstrate that the PSMD14-H2A axis governs melanoma adaptation to MAPK pathway inhibition. PSMD14 expression and H2AK119 ubiquitination dynamically correlate with therapeutic response, drug-tolerant persistence, and acquired resistance. Targeting PSMD14 genetically or pharmacologically enhances the efficacy of BRAF and MEK inhibitors, suppresses the emergence of drug-tolerant persister cells, and prevents tumor relapse in vivo. Together, this findings establish PSMD14 as a chromatin-rewiring enzyme that links proteostasis to epigenetic control of melanoma plasticity and therapy resistance, highlighting PSMD14 as a promising biomarker and therapeutic target in aggressive and drug-resistant melanoma.

cancer biology↗

bioRxiv2024

USP9X is a mechanosensitive deubiquitinase that controls tumor cell invasiveness and drug response through YAP stabilization

Post-translational modification by ubiquitin is crucial for protein turnover. Deubiquitinases (DUBs) remove ubiquitin chains from target proteins to prevent their degradation by the proteasome, thus acting as gatekeepers of protein homeostasis alongside the ubiquitin-proteasome system (UPS). Tumor cells exhibit remarkable plasticity, enabling them to adapt to anticancer treatments and the conditions of the tumor microenvironment, including mechanical cues from the extracellular matrix (ECM). However, the role of DUBs in mechanotransduction remains unexplored. To identify DUBs involved in cancer cell mechanosignaling, we used melanoma cells grown on collagen matrices with varying stiffnesses and an activity-based ubiquitin probe to profile DUB activities. Our approach, combined with quantitative proteomics, revealed that ubiquitin-specific protease 9X (USP9X) is sensitive to ECM stiffness through discoidin domain receptors (DDR)/actomyosin signaling pathway. In silico analysis further indicated that the mechanosensor YAP is part of the USP9X interactome, and USP9X expression correlates with the YAP transcriptional signature in melanoma. We hypothesized that mechanical signals regulate YAP levels through USP9X DUB activity. Consistently, low collagen stiffness reduced YAP expression, and siRNA-mediated depletion or pharmacological inhibition of USP9X decreased YAP protein expression in tumor cells. Conversely, knockdown of the ubiquitin E3 ligase {beta}TrCP increased YAP protein levels. Affinity purification of polyubiquitinated proteins using Tandem Ubiquitin Binding Entities (TUBEs) showed that combined USP9X and proteasome inhibition increased YAP poly-ubiquitination, revealing that USP9X deubiquitinates YAP to prevent its proteasomal degradation. Targeting USP9X impaired stiffness-mediated responses, including YAP nuclear translocation and transcriptional activity, cell migration and invasion, and drug resistance. An experimental metastasis assay showed that stable knockdown of USP9X impaired melanoma cell lung colonization. Finally, targeting USP9X in a syngeneic BRAF-mutant melanoma model counteracted targeted therapy-induced ECM remodeling, enhanced treatment efficacy, and delayed tumor relapse. Our findings reveal a novel role of USP9X in cancer cell mechanobiology and drug resistance through stiffness-dependent stabilization of the oncoprotein YAP, proposing USP9X as a targetable "mechano-DUB" in cancer.

cancer biology↗

bioRxiv2024

Extracellular matrix stiffness determines the phenotypic behavior of dedifferentiated melanoma cells through a DDR1/2-dependent YAP mechanotransduction pathway

Extracellular matrix (ECM) stiffening, resulting from increased collagen deposition and cross-linking, is a key biophysical factor of the tumor microenvironment. Cutaneous melanoma is a deadly metastatic cancer. Its aggressiveness stems from high intratumoral heterogeneity, resulting from the plasticity of melanoma cells, which transit from a melanocytic state to dedifferentiated therapy-resistant and invasive phenotypes, characterized by mesenchymal and/or neural crest stem cell-like features. Phenotypic plasticity is regulated by stroma-derived soluble factors, but the functional impact of ECM stiffening on melanoma cell phenotypes remains ill defined. Here, we found that melanoma cell subpopulations display difference in mechanical responsiveness. Compared to melanocytic cells, mesenchymal dedifferentiated cells showed increased proliferation, migration and resistance to MAP kinase-targeted therapy when seeded on stiff collagen. By contrast, a soft ECM impaired their proliferation and migration and sensitized them to targeted therapy. In addition, extracellular mechanical signals are required to sustain melanoma cell identity and dedifferentiation features. Further analyses indicated that the mechanosensitivity nature of dedifferentiated cells relies on the expression and activation of collagen receptors DDR1 and DDR2 that control actomyosin cytoskeleton reorganization and YAP mechanotransduction pathway. Inhibiting both DDR in dedifferentiated melanoma cells abrogated their mechano-induced behavior and drug-resistant phenotype, while forcing their expression in melanocytic cells induced mechanical responsiveness and a less differentiated phenotype. Our results reveal that phenotypic reprogramming endows dedifferentiated melanoma cells with increased sensitivity and addiction to ECM stiffness. We propose that mechano-addiction mediated by DDR collagen receptors may represent a novel vulnerability for aggressive dedifferentiated cancer cells that can be exploited for therapeutic benefits.

cancer biology↗