Introduction: PDAC is an extremely aggressive tumor with a poor prognosis and remarkable therapeutic resistance. The dense extracellular matrix (ECM) which characterizes PDAC progression is considered a fundamental determinant of chemoresistance, with major contributions from mechanical factors. This study combined biomechanical and pharmacological approaches to evaluate the role of the cell-adhesion molecule ITGA2, a key regulator of ECM, in PDAC resistance to gemcitabine. Methods: The prognostic value of ITGA2 was analysed in publicly available databases and tissue-microarrays of two cohorts of radically resected and metastatic patients treated with gemcitabine. PANC-1 and its gemcitabine-resistant clone (PANC-1R) were analysed by RNA-sequencing and label-free proteomics. The role of ITGA2 in migration, proliferation, and apoptosis was investigated using hydrogel-coated wells, siRNA-mediated knockdown and overexpression, while collagen-embedded spheroids assessed invasion and ECM remodeling. Results: High ITGA2 expression correlated with shorter progression-free and overall survival, supporting its impact on prognosis and the lack of efficacy of gemcitabine treatment. These findings were corroborated by transcriptomic and proteomic analyses showing that ITGA2 was upregulated in the PANC-1R clone. The aggressive behavior of these cells was significantly reduced by ITGA2 silencing both in vitro and in vivo, while PANC-1 cells growing under conditions resembling PDAC stiffness acquired resistance to gemcitabine, associated to increased ITGA2 expression. Collagen-embedded spheroids of PANC-1R showed a significant matrix remodeling and spreading potential via increased expression of CXCR4 and MMP2. Additionally, overexpression of ITGA2 in MiaPaCa-2 cells triggered gemcitabine resistance and increased proliferation, both in vitro and in vivo, associated to upregulation of phospho-AKT. Conclusions: ITGA2 emerged as a new prognostic factor, highlighting the relevance of stroma mechanical properties as potential therapeutic targets to counteract gemcitabine resistance in PDAC.

Background: Pancreatic ductal adenocarcinoma acquired resistance to chemotherapy poses a major limitation to patient survival. Despite understanding some biological mechanisms of chemoresistance, much about those mechanisms remains to be uncovered. Mechanobiology, which studies the physical properties of cells, holds promise as a potential target for addressing the challenges of chemoresistance in PDAC. Therefore, we, here in an initial step, assessed the altered mechanobiology of PDAC cells with acquired chemoresistance to gemcitabine and paclitaxel. Methods: Five PDAC cell lines and six stably resistant subclones were assessed for force generation on elastic micropillar arrays. Those measurements of mechanical phenotype were complemented by single-cell motility and invasion in 3D collagen-based matrix assays. Further, the nuclear translocation of Yes-associated protein (YAP), as a measure of active mechanical status, was compared, and biomarkers of the epithelial-to-mesenchymal transition (EMT) were evaluated using RT-qPCR. Results: The PDAC cells with acquired chemoresistance exert higher traction forces than their parental/wild-type (WT) cells. In 2D, single-cell motility was altered for all the chemoresistant cells, with a cell-type specific pattern. In 3D, the spheroids of the chemoresistant PDAC cells were able to invade the matrix and remodel collagen more than their WT clones. However, YAP nuclear translocation and EMT were not significantly altered in relation to changes in other physical parameters. Conclusions: This is the first study to investigate and report on the altered mechanobiological features of PDAC cells that have acquired chemoresistance. A better understanding of mechanical features could help in identifying future targets to overcome chemoresistance in PDAC.

Background Pancreatic ductal adenocarcinoma (PDAC) acquired resistance to chemotherapy poses a major limitation to patient survival. Despite understanding of some biological mechanisms of chemoresistance, much of those mechanisms remain to be uncovered. Mechanobiology, which studies physical properties of cells, holds promise as a potential target for addressing challenges of chemoresistance in PDAC. Therefore, we here in an initial step, assessed the altered mechanobiology of PDAC cells with acquired chemoresistance to gemcitabine and paclitaxel. Methods Five PDAC cell lines and six stably-resistant subclones were assessed for force generation on elastic micropillar arrays. Those measurements of mechanical phenotype were complemented by single-cell motility and invasion in collagen matrix were investigated using 2D models and 3D extracellular matrix-mimetic, respectively. Further the nuclear translocation of Yes-associted protein (YAP), as a measure of active mechanical status, was compared, and biomarkers of the epithelial-to-mesenchymal transition (EMT) were evaluated using RT-PCR. Results PDAC cells with acquired chemoresistance exert higher traction forces than their parental/wild-type (WT) cells. In 2D, single-cell motility was altered for all chemoresistant cells, with a cell-type specific pattern. In 3D, spheroids of chemoresistant PDAC cells were able to invade the matrix, and remodel collagen more than their WT clones. However, YAP nuclear translocation and EMT were not significantly altered in relation to changes in other physical parameters. Conclusion This is the first study to investigate and report on the altered mechanobiological features for PDAC cells that have acquired chemoresistance. A better understanding of mechanical features could help in identifying future targets to overcome chemoresistance in PDAC.

Aims Chemotherapies such as gemcitabine/nab-paclitaxel are confronted with intrinsic or acquired resistance in pancreatic ductal adenocarcinoma (PDAC). We aimed to identify novel actionable mechanisms to overcome such resistance. Methods Three paclitaxel (PR) and gemcitabine resistant (GR) PDAC models were established. Transcriptomics and proteomics were used to identify conserved mechanisms of drug resistance. Genetic and pharmacological approaches were used to overcome paclitaxel resistance. Results Upregulation of ABCB1 through locus amplification was identified as a conserved feature unique to PR cells. ABCB1 was not affected in any of the GR models and no cross resistance was observed. The ABCB1 inhibitor verapamil or siRNA mediated ABCB1 depletion sensitized PR cells to paclitaxel and prevented efflux of ABCB1 substrates in all models. ABCB1 expression was detected in PDAC patients that had received gemcitabine/nab-paclitaxel treatment. A pharmacological screen identified known and novel kinase inhibitors that attenuate efflux of ABCB1 substrates and sensitize PR PDAC cells to paclitaxel. Conclusion Upregulation of ABCB1 through locus amplification represents a novel, conserved mechanism of PDAC paclitaxel resistance. ABCB1 has not been previously implicated in PR PDAC. The synthetic lethal interactions identified in this study can be further (pre)clinically explored as therapeutic strategies to overcome paclitaxel resistance in PDAC.

Phosphorylated nucleosides and their derivatives sit at the center of cellular energetics, signaling, and biosynthesis, yet they are largely invisible to routine reversed-phase metabolomics. Their phosphate groups chelate metal ions, producing severe peak tailing and chromatographic irreproducibility that consign them to the "dark metabolome." We report nucleotidomics, a workflow that recovers this phosphorylated fraction on standard reversed-phase LC-MS. Each sample is split in two; one aliquot is analyzed as-is, the other treated with a nucleoside digestion mix that strips enzyme-accessible phosphate groups, returning phosphorylated forms to their parent nucleosides. Subtracting the untreated signal from the treated one cancels the pre-existing free nucleoside pool common to both aliquots, leaving ∑P: the summed abundance of the phosphorylated forms of each nucleoside. ∑P is therefore an indirect, semi-quantitative readout — it flags phosphate-bearing pools but cannot resolve mono-, di-, and triphosphates. Seven-minute analytical cycles keep total instrument time practical despite the doubled injection count. In two gemcitabine-treated pancreatic ductal adenocarcinoma cell lines, the paired injections returned 1071 putatively annotated metabolites and 23 endogenous phosphorylated species surviving manual curation. The method recapitulated the drug's established pharmacology: extensive phosphorylation of gemcitabine, formation of the deaminated metabolite dFdU and its phosphates, and depletion of the deoxyadenosine and deoxyguanosine phosphate pools, consistent with ribonucleotide reductase inhibition. Untargeted analysis revealed deoxyinosine depletion, likely reflecting reduced deoxyadenosine pools. A high-sensitivity fragmentation protocol with extended ion accumulation (sniperMS2) yielded candidate identifications of trace species: free queuosine phosphates and endogenous 5′-methylthioinosine, to our knowledge not previously measured directly in human cells. ∑P alone gave tentative evidence for GDP-fucose phosphorylation. By rendering the nucleotide constituent of the dark metabolome accessible, nucleotidomics extends routine metabolomic workflows to the cellular nucleotidome without the need for specialized chromatography.