Oncogenesis

The insulin receptor (IR) is markedly overexpressed in both human and mouse prostate cancer, with a significant elevation in the IR-A/IR-B ratio across patient tissues, cell lines, and Hi-Myc mouse prostates. To elucidate the role of IR-B in prostate tumorigenesis, we generated a prostate-specific IR-B knockout (KO) mouse model using Pbsn-Cre-driven recombination. Prostate-restricted loss of IR-B was confirmed at the transcript level and did not affect other tissues. Crossing these mice with Hi-Myc transgenics revealed that IR-B deficiency promotes accelerated progression to invasive adenocarcinoma, characterized by enhanced cellular proliferation and atypical histopathology. Transcriptomic and metabolomic profiling of dorsolateral prostate lobes demonstrated activation of PI3K/AKT and mTOR signaling, along with upregulation of IRS1/2/4 and IGF2. Metabolite analyses indicated elevated fatty acid levels and enhanced lipolysis pathways, implicating metabolic reprogramming in tumor progression. Notably, glucose and lipid metabolism genes, including GLUT1, GLUT12, FASN, and GPR120, were upregulated, accompanied by an increased BCL2/BAX ratio, suggesting apoptosis inhibition. Functional studies further revealed opposing roles of dietary fatty acids: {omega}-3 polyunsaturated fatty acids (EPA, DHA) suppressed prostate cancer cell survival, proliferation, and PI3K/AKT signaling while promoting apoptosis, whereas {omega}-6 fatty acid (arachidonic acid) exerted pro-tumorigenic, anti-apoptotic effects. Collectively, these findings identify IR-B loss as a driver of metabolic and signaling reprogramming that accelerates prostate tumorigenesis, while highlighting {omega}-3 fatty acids as potential modulators counteracting IR-B-deficient prostate cancer progression.

Nutrient availability is a critical environmental factor that influences the metabolism and adaptability of cancer cells, including acute lymphoblastic leukaemia (ALL) cells, prone to relapse in the central nervous system (CNS). Currently available cell culture media contain supraphysiological nutrient levels and do not represent the restricted metabolic environment of CNS-ALL which resides in the leptomeninges surrounded by cerebrospinal fluid (CSF). Therefore, we formulated a novel physiological CSF-like cell culture medium (CSFmax) that recapitulates the unique metabolite composition of the CSF. Through in vitro and in vivo metabolic and functional studies, we demonstrate that ALL cells cultured in CSFmax rewire their metabolism, closely mimicking the metabolic phenotype of CNS-ALL, including their metabolic activity and redox state. Utilising CSFmax, in comparison to conventional nutrient-rich culture media, we identified an essential role for autophagy in ALL adaptation to the CNS niche. This was evident by increased autophagic activity and selective sensitisation of ALL cells to pharmacological inhibition of autophagy and genetic knockout of Unc-51 Like Autophagy Activating Kinase 1 (ULK1) or autophagy related 7 (ATG7). Importantly, using a robust preclinical in vivo model, mice xenografted with ULK1 and ATG7 deficient ALL cells exhibited reduced CNS disease burden when compared to mice xenografted with control cells. Overall, our findings provide strong evidence that physiological CSFmax is superior to current in vitro culture systems in recapitulating the metabolic signature of CNS resident ALL cells. By exploiting this system, we revealed for the first time autophagy as a targetable therapeutic vulnerability in CNS-ALL. Key PointsO_LICulturing ALL cells in bespoke CSF-like medium (CSFmax) recapitulates the metabolic adaptation of ALL cells in the CNS niche C_LIO_LIAutophagy is critical for metabolic adaptation and survival of CNS resident ALL cells C_LI

Tunneling nanotubes (TNTs) are actin-based cytoplasmic connections that can mediate intercellular transfer of various cellular cargo and have been implicated in cancer progression and chemoresistance. However, the signalling mechanisms driving their formation remain poorly understood. Given the frequent dysregulation of EGFR and c-Met signalling in non-small cell lung cancer (NSCLC), and prior evidence of TNTs in lung adenocarcinoma patient samples, we investigated the role of EGFR and c-Met receptor signalling crosstalk in TNT induction in A549 lung adenocarcinoma cells. Stimulation with EGF, HGF, or in combination induced a concentration dependent increase in the formation of TNTs. TNTs exhibited typical characteristics, including F-actin expression, non-adherence to the substratum and facilitated intercellular trafficking of lysosomes, mitochondria, and lipid vesicles. EGFR was identified as a novel component of TNTs, but had little co-localisation with the c-Met receptor. Co-stimulation with HGF and EGF did not produce consistent additive or synergistic effects on TNT formation, suggesting shared downstream signalling. Furthermore, although EGFR and c-Met inhibition blocked EGF- and HGF-induced TNTs respectively, inhibition of both receptors was required to suppress TNTs following dual HGF/EGF treatment. Interestingly, blocking the EGF receptor alongside c-Met resulted in a more potent inhibition of HGF-induced TNTs, indicating crosstalk. Furthermore, inhibition of downstream MEK and PI3K pathways reduced HGF- or EGF- induced TNT formation, but dual inhibition was required to completely block TNT formation in HGF+EGF co-stimulated cells. These findings reveal a novel convergence of EGFR and c-Met and their downstream MAPK/PI3K pathways in TNT regulation, which can have important clinical implications in combinatorial receptor and cell signalling pathway targeting in NSCLC.

Prostate cancer is the second most common malignancy among men, with androgen deprivation therapy (ADT) serving as the standard treatment due to the hormone sensitivity of prostate tumors. However, therapeutic resistance frequently develops, leading to castration-resistant prostate cancer (CRPC), an aggressive and lethal disease. A recently defined subtype, stem cell-like CRPC (CRPC-SCL), accounts for approximately 25% of CRPC cases and demonstrates poor responsiveness to ADT. CRPC-SCL is characterized by the expression of Cluster of Differentiation 44 (CD44), a glycoprotein that promotes hyaluronic acid binding and uptake. Within CRPC-SCL patient-derived xenograft (PDX) model, CD44 high (CD44hi) cells exhibit enhanced tumorigenicity and proliferative capacity. Importantly, iron metabolism emerges as a critical regulator of this population: CD44hi cells maintain elevated intracellular iron, which sustains CD44 expression and stem cell-like properties by modulating H3K9me2 modification. Leveraging this vulnerability, inhibition of the iron-regulatory factor NRF2 was shown to increase intracellular free iron and selectively induce ferroptosis in CD44hi cells. These findings highlight the therapeutic potential of targeting iron metabolism to induce ferroptosis as a novel treatment strategy for CRPC-SCL.

Chemoresistance is a major contributor to poor clinical outcomes in AML patients and can arise from interactions between AML cells and the bone marrow microenvironment (BME). How immune cells, particularly macrophages (M{varphi}s), facilitate this process requires better clarification. This study shows that M2-like M{varphi}s protect AML cells from apoptosis induced by daunorubicin (DNR) and cytarabine (Ara-C). This protection occurs via co-culture and is linked to enhanced mitochondrial transfer from M{varphi}s to AML cells. M{varphi}s interacted with AML cells via tunneling nanotube (TNT)-like structures. Furthermore, inhibition of mitochondrial transfer using cytochalasin B reduced the protective effect, indicating that mitochondria mediate this process. M{varphi}s transferred functional mitochondria to AML cells as evidenced by enhanced metabolic capacity and reduced reactive oxygen species levels in AML cells under chemotherapy stress. TH-257 (LIMK inhibitor) and metformin blocked mitochondrial transfer and M{varphi}-driven chemoprotection. Moreover, increased transcript expression levels of RhoC and cofilin correlate with inferior overall survival in AML patients. These findings suggest that M2-like M{varphi}s contribute to chemoresistance through TNT-mediated mitochondrial transfer and the LIMK-Cofilin pathway, identifying potential therapeutic targets to circumvent chemoresistance in AML.

The TGF-{beta} signaling pathway has both tumor-suppressing and metastasis-promoting effects in cancer. However, the molecular determinants governing this switch remain unclear. Here, we explored the miR-16-1-3p/MDM2/p53 axis as a critical conductor of the TGF-{beta}-Smad pathway in osteosarcoma. Although miR-16-1-3p overexpression by itself markedly reduces proliferative and clonogenic potential of U2OS cells, when paired with TGF-{beta} treatment, it significantly increases arrest cells in G1 phase and nearly extinguishing the growth capability of these cells. MiR-16-1-3p overexpression inhibited TGF-induced actin remodeling and EMT featuring, significantly decreasing vimentin levels. TGF-{beta} enhances both 2D and 3D migration, but miR-16-1-3p overexpression, alone or with TGF-{beta}, strongly counteracts its pro-migratory effects. MiR-16-1-3p restored p53 stability by targeting MDM2, redirecting TGF-{beta}-Smad signaling toward p21 activation and proliferation inhibition while attenuating its EMT-promoting capacity. Administration of TGF-{beta} together with miR-16-1-3p dramatically increases the sensitivity of wild-type U2OS cells to cisplatin, exceeding that of TGF-{beta} therapy alone by more than an order of magnitude. Administering TGF-{beta} and miR-16-1-3p together significantly reduces the tumor nodule volume and Ki67 expression, while effectively eradicates metastases in the chicken chorioallantoic membrane (CAM) in vivo model. For the first time, our research demonstrates that miR-16-1-3p shifts TGF-{beta}1 signaling from a facilitator of metastasis to a promoter of anti-growth effects through MDM2 inhibition and p53 stabilization, effectively reducing the self-renewal and invasiveness of cancer stem cells in human osteosarcoma model. This process preserves TGF-{beta}s tumor-suppressive role while limiting its associated cancer risks.

Cancer metabolism rewiring is one of the hallmarks of cancer, enabling cancer cell survival in a nutrient deprived microenvironment. Key to this is nutrient scavenging where cancer cells rely on extracellular proteins, including extracellular matrix (ECM) components, to sustain their proliferation. ECM uptake is mediated by 2{beta}1 integrin, however it is not clear how this process is controlled by nutrient availability. Here we demonstrated that amino acid starvation promoted ECM internalisation, by inducing the expression of 2 integrin. Mechanistically, starvation-driven RAS/MAPK pathway activation in cells harbouring oncogenic RAS mutations and mTOR inhibition increased 2 integrin, while the GCN2-depedent integrated stress response was not required. Functionally, elevated 2 integrin levels promoted cell adhesion and migration in nutrient starved cells. Finally, 2 integrin was found upregulated in pancreatic tumours and correlated with poor prognosis in pancreatic adenocarcinoma patients. Together, these data indicate that the nutrient- starved pancreatic cancer microenvironment synergises with KRAS mutation to drive pancreatic cancer aggressiveness.

Early achievement of deep remission improves patients outcome in chronic myeloid leukemia (CML) treatment, highlighting the need for predictive indicators before therapy initiation. This study aimed to develop a tool to predict CML treatment responses to guide optimal therapy selection. Using hierarchical clustering of complete blood count (CBC) data at diagnosis, patients were stratified into two clusters. Patients in Cluster 1 had higher BCR::ABL1IS mRNA levels at 3 and 6 months post-treatment and lower rates of major molecular response compared to cluster 2. Cluster 1 also showed increased granulocyte and immature white blood cell counts and decreased erythroid parameters. Flow cytometric analysis of bone marrow mononuclear cells revealed that cluster 1 had a significant increase in hematopoietic stem cell fractions and a higher ratio of granulocyte-macrophage progenitors to megakaryocyte-erythroid progenitors compared to cluster 2. These findings suggest that differences in bone marrow progenitor cell differentiation affect peripheral blood profiles. Artificial intelligence-driven ghost cytometry (GC) was evaluated for its ability to comprehensively capture these changes and successfully distinguished patients with poorer treatment responses, with GC scores at diagnosis strongly correlating with BCR::ABL1IS mRNA levels at 3 and 6 months post-treatment initiation. The study indicates that multivariate analysis of CBC or GC analysis may enable simple, early prediction of CML treatment efficacy, potentially contributing to effective and individualized CML therapy.

Here, we examined the consequences of biologically relevant vitamin D deficiency, a known risk factor for aggressive prostate cancer, using ex vivo and in vivo models. Phenotypic and single-cell RNA sequencing of mouse prostate organoids showed that vitamin D deficiency stunted luminal cell differentiation more than androgen deficiency, which is a known driver of prostate development. Mice fed a vitamin D-deficient diet showed significantly altered expression of androgen-responsive genes in their prostate luminal cells, as determined by single-cell RNA sequencing. MDA-PCa-2b human prostate cancer cells, when maintained for 6 months in 1,25-dihydroxyvitamin D, lost the ability to form xenografts, despite normal proliferation in vitro. RNA sequencing showed that these cells also had disruptions in androgen signaling and multiple cancer-related pathways. This study offers new insights and validation of vitamin Ds role in both benign and malignant prostate biology, underscoring its essential hormonal functions and supporting strategies for vitamin D supplementation to reduce prostate cancer risk in vulnerable populations. STATEMENT OF SIGNIFICANCEVitamin D is an essential hormone, however, the non-calcemic consequences of vitamin D deficiency remain poorly defined, despite its high prevalence in the population. This study demonstrates significant biological consequences of vitamin D deficiency on prostate cells at biologically relevant levels in multiple systems.

The equilibrium between cell death and cell division is crucial for maintaining tissue homeostasis in a multicellular organism. Apoptosis plays an essential role in preserving homeostasis and hence occurs in a coordinated manner. However, inhibition of apoptosis is one of the hallmarks of cancer. Apoptosis Inhibitor 5 (Api5), an anti-apoptotic protein, is upregulated in various cancers, including ovarian, bladder, cervical, and lung cancers. Studies have demonstrated that altered expression of Api5 leads to the transformation of non-tumorigenic breast epithelial cells. However, the mechanism regulating this process is not well-elucidated. Our study demonstrates that overexpression of Api5 increased FGF2 (Fibroblast Growth Factor 2) levels both at protein and transcript levels. We studied the mechanistic details of changes in morphology, proliferation, and polarity observed upon FGF2/FGFR1 deregulation in Api5-overexpressing cells. Deciphering the signalling mechanism underlying Api5-FGF2-mediated breast tumorigenesis revealed that the PDK1/Akt and Ras/MAPK/ERK pathways regulated multiple transformation phenotypes. PDK1/Akt enhanced proliferation and altered morphology during initial stages, whereas Ras/MAPK/ERK regulated polarity disruption, proliferation, and reduced apoptosis during later stages of morphogenesis. In conclusion, this study provides insights into the signalling mechanism regulating the transformation phenotypes associated with Api5 overexpression in a non-tumorigenic breast epithelial cell line.

Pancreatic ductal adenocarcinoma (PDAC) is the most common form of pancreatic cancer and carries the poorest prognosis among all cancers, largely because it is frequently diagnosed at metastatic stages. It is therefore critical to identify reliable markers of preinvasive stages and to decipher the network driving preinvasive lesions to invasive carcinoma. Here, we generated a zebrafish model in which KRASG12D is specifically expressed in pancreatic acinar cells, inducing acinar-to-ductal metaplasia that faithfully mirrors mammalian tumorigenesis. Single cell RNA-seq allowed us to capture transcriptional changes occurring at early stages of the disease. Cross-species comparison with mouse and human scRNAseq transcriptomes revealed a striking conservation of the genes upregulated during metaplasia, triggering common signalling pathways and regulatory programs. Notably, metaplastic cells reactivate a broad set of developmental genes expressed in multipotent pancreatic progenitors. Mapping the acinar-to-cancer trajectories revealed a set of cytoskeletal and migration-related genes specifically upregulated during the late phase of metaplasia, immediately prior to malignant transformation, likely conferring invasive potential to these cells. SCENIC analysis further identified regulatory networks that become progressively activated as cells transition toward cancer, suggesting their involvement in the acquisition of malignant traits. In conclusion, our cross-species comparison demonstrates a high degree of conservation in the molecular mechanisms driving pancreatic cancer progression from early to late stages across evolutionarily distant species, including zebrafish, mouse, and human, highlighting critical pathways that should be targeted to prevent cancer progression. To allow researchers to easily explore gene expression profiles during pancreatic cancer progression across all three species, the datasets are publicly accessible via a user-friendly web platform (https://www.zddm.page.gd/)

The non-canonical translation of specific mRNAs has been implicated in oncogenesis and cancer progression. We previously identified eukaryotic Initiation Factor 5B (eIF5B) as a key factor in Internal Ribosome Entry Site (IRES)-mediated translation of a subset of mRNAs encoding anti-apoptotic proteins. Here, we demonstrate that EIF5B is predominantly expressed in cancer cells compared to other cell types in the Oral Squamous Cell Carcinoma (OSCC) microenvironment. Higher EIF5B mRNA and protein expression are associated with poor patient outcomes. We show that eIF5B depletion in OSCC cells blunted pro-growth, pro-inflammatory, and pro-angiogenic signaling pathways and significantly increased TNF-related apoptosis-inducing ligand (TRAIL)-induced cell death. This is achieved through decreased translation of mRNAs encoding critical factors associated with OSCC pathophysiology. Importantly, the level of interaction of eIF5B with tRNAiMet was significantly higher in OSCC cells compared to non-cancerous fibroblasts. This suggests that OSCC cells (but not non-cancerous fibroblasts) rely heavily on eIF5B for translation initiation. In an in vivo flank xenograft model using nude mice, eIF5B knockdown in UMSCC-29 cells led to a significant reduction in tumor volume compared to control tumors. Also, the immunohistochemical analysis of the xenografted tumor sections demonstrated decreased staining intensity of critical factors associated with OSCC pathophysiology in eIF5B-depleted tumors relative to controls. Collectively, our data demonstrate that OSCC cells are uniquely dependent on eIF5B-tRNA interactions to sustain translation of pro-survival mRNAs. Targeting eIF5B disrupts these oncogenic programs, sensitizing OSCC cells to apoptosis and suppressing pro-angiogenic and pro-growth signaling.

Autophagy, a key lysosomal degradation pathway regulating metabolic adaptation in cancer, plays fundamental roles in both the tumor and host stromal compartments during cancer progression. An important unanswered question is whether and how autophagy in specific host stromal elements, such as endothelial cells, influences metastasis. Here, we scrutinize how the genetic loss of autophagy in endothelial cells impacts primary tumor progression and metastasis in the Polyoma Middle T (PyMT) model of luminal B breast cancer. In both autochthonous and orthotopic mammary transplant models, PyMT primary tumor growth is significantly delayed upon endothelial cell Atg12 or Atg5 genetic deletion (Atg12 or 5 ECKO), which correlates with increased tumor cell apoptosis and HIF1 activation. In contrast, PyMT-bearing Atg12 ECKO mice exhibit increased metastasis, as well as higher rates of primary tumor and lung metastatic recurrence following surgical resection of PyMT primary tumors. Experimental metastasis assays further corroborate that loss of endothelial cell autophagy in Atg12 ECKO host animals promotes PyMT metastatic colonization and outgrowth, resulting in increased lung metastases compared to controls. Similarly, in the Rat Insulin Promoter T antigen pancreatic neuroendocrine tumor (RT2-PNET) model, endothelial cell deletion of Atg12 promotes liver micro-metastases. Taken together, these results from distinct preclinical cancer models reveal that endothelial cell autophagy suppresses metastatic seeding and progression and broach that autophagy inhibition in host endothelial cells may adversely influence the efficacy of systemic autophagy-lysosomal pathway inhibition in the clinical oncology setting.

Few studies with pre-diagnostic samples have estimated associations between circulating metabolites and risk of advanced prostate cancer. We performed untargeted metabolomic profiling of pre-diagnostic blood samples from 212 advanced prostate cancer cases (stage [&ge;]T3b or lethal during follow-up) and 212 matched controls from the Health Professionals Follow-up Study. 243 metabolites were assayed using liquid chromatography-tandem mass spectrometry (Broad Institute) and met quality control standards. We used multivariable conditional logistic regression to generate odds ratios (OR) and 95% confidence intervals (95%CI) for associations between individual metabolites and risk of advanced prostate cancer, and conducted metabolite set enrichment tests to identify metabolite classes enriched in advanced prostate cancer. Subgroup analyses were conducted by body mass index (BMI) and time between blood draw and diagnosis. Levels of 16 lipid species were nominally associated with advanced prostate cancer at p<0.05, though none were statistically significant after multiple testing correction. The strongest signals were for C56:1 triacylglycerol (TAG; OR: 1.34, 95%CI: 1.07-1.67) and C38:4 diacylglycerol (DAG; OR: 1.27, 95%CI: 1.04-1.55). Enrichment analyses revealed six metabolite classes associated with advanced prostate cancer after multiple testing adjustment, the top four of which were DAGs and TAGs: DAGs overall (P=3.4E-07), unsaturated DAGs (P=5.9E-07), unsaturated TAGs (P=2.3E-06), and TAGs overall (P=2.4E-06). 43 metabolites were nominally associated with advanced prostate cancer among individuals with BMI <25 kg/m2; only three demonstrated nominal associations in individuals with BMI [&ge;]25 kg/m2. These findings suggest associations between circulating pre-diagnostic lipid levels and aggressive prostate cancer risk, particularly in lean individuals.

BackgroundTherapeutic Inducers of Natural Killer cell Killing (ThINKK) represent a novel class of immunotherapy designed to enhance the graft-versus-leukemia effect of hematopoietic stem cell transplantation in pediatric patients with high-risk or relapse leukemia. Our previous work identified high expression of TRAIL as a key signature of Natural Killer (NK) cell stimulation by ThINKK. In this study, we aim to elucidate the mechanisms underlying acute lymphoblastic leukemia (ALL) killing by ThINNK-stimulated NK cells and to identify predictive sensitivity markers of this innovative approach. MethodsWe performed NK cell cytotoxic assays using a panel of genetically diverse ALL cell lines and patients samples. Gene deletion and gene enforced expression in sensitive or resistant cell lines were performed to demonstrate the role of TRAIL-receptors expression and death receptor signaling pathway in ALL cell death induced by ThINKK-stimulated NK cells. These findings were further validated through the analysis of primary patients samples and transcriptomic profiling of a cohort of 320 ALL patients from the CHU Sainte-Justine. ResultsWe found that ALL sensitivity to ThINKK-stimulated NK cell killing was independent of their genetic background or their HLA expression. In addition, our data revealed the dual role of TRAIL: first, a strong NK cell activating receptor that induced rapid killing of ALL expressing TRAIL-R2, and second, a death-receptor ligand inducing ALL apoptosis following sustained engagement with its receptors. The transcriptomic analysis of ALL patients samples indicated that TRAIL-R2 and TRAIL-R1 are widely expressed across ALL subtypes and are not downregulated at relapse. ConclusionThese findings support the use of TRAIL receptor expression as a biomarker of sensitivity to ThINKK immunotherapy and establish a mechanistic framework to guide patient stratification and therapeutic optimization.

The formation of the premetastatic niche prepares distant tissues for tumor cell engraftment. Endothelial cells are critical mediators of premetastatic niche formation, orchestrating extravasation of circulating tumor cells and critical pro-tumor immune cells, such as neutrophils. In mouse models of breast cancer, we show that primary tumors upregulate the non-signaling chemokine receptor ACKR1 in the endothelium of the lung premetastatic niche. ACKR1-expressing venules were found to be preferential sites of neutrophil and tumor cell localization within lung tissue. A newly generated conditional ACKR1 allele was used to show that endothelial-specific removal of ACKR1 expression significantly reduces metastatic engraftment in the lung. When ACKR1 is activated by tumor-secreted factors, endothelial ACKR1 functions to promote neutrophil recruitment within the lung parenchyma. We conclude that ACKR1 is a critical component of the endothelial response to tumors at the metastatic site of the lung, leading to neutrophil recruitment and promotion of tumor cell metastasis. SUMMARYEndothelial cells play critical roles in breast cancer metastasis. ACKR1 is upregulated in the endothelium of the lung metastatic niche in response to primary mammary tumors. Endothelial ACKR1 expression was found to promote neutrophil infiltration into the metastatic niche and support breast tumor cell metastasis to the lung.

PTEN (phosphatase and tensin homologue deleted on chromosome ten) is a tumour suppressor, the function of which is impaired in many diverse cancers. It has phosphoinositide lipid phosphatase activity by which it suppresses activation of the oncogenic PI3K signalling network but in vitro also displays activity against protein substrates and is able to auto-dephosphorylate its Thr366 residue. Here we generate germline knock-in mice expressing PTEN-Y138L, a mutant enzyme which selectively lacks protein phosphatase activity and retains lipid phosphatase activity. Homozygous PtenY138L/Y138L mice die in utero before E10.5. Primary MEFs and thymocytes with only a single PtenY138L allele display normal low levels of AKT phosphorylation indicating effective regulation of PI3K signalling by endogenous PTEN-Y138L in vivo. Heterozygous Pten+/Y138L mice have reduced overall survival compared to wild type littermates and develop tumours in multiple organs. Our data imply that in addition to its lipid phosphatase activity, the protein phosphatase activity of PTEN is also required for normal embryonic development and tumour suppression.

Chemoresistance, a leading cause of treatment failure in cancer, is commonly explained by Darwinian selection of treatment-resistant cell clones. However, recurring resistant tumors invariably display complex phenotypes that contribute to increased malignancy, unlikely to have been selected for by chemotherapy. The growing awareness of (non - genetic) phenotypic plasticity led to the hypothesis that chemotherapy, while reducing tumor burden, also inflicts cell stress that induces stem-like states in cells that survive treatment. Here we examined the transcriptomes of HL-60 leukemic cancer cells that survived exposure to three commonly used drugs at submaximal doses for two to four days, and compared differentially expressed genes to those associated with prognosis in public transcriptome databases of acute myeloid leukemia cohorts. While among the genes differentially upregulated in surviving cells, some reflect the therapeutic effect of chemotherapy as they were associated with favorable outcomes in cohort data, many genes upregulated were associated with poor survival, notably genes involved in stemness, epithelial-mesenchymal transition (EMT), inflammation, drug resistance, and apoptosis evasion. These findings support the idea that treatment effectiveness is the net result of an intrinsic tradeoff: Cytocidal treatment, intended to quantitatively reduce cancer cells, also qualitatively increases the malignancy of non-killed cells, which could contribute to residual disease and relapse. This result has implications for drug screening of new therapeutics, as well as in vitro profiling of patient-derived tumor cell susceptibility to existing drugs, which only assess suppression of cancer cell growth and survival. Statement of SignificanceCells surviving chemotherapy upregulate many genes that may affect prognosis. Therefore, drug screening must embrace a more holistic assessment of the biological quality of cell response beyond the rate of cell killing.

Well- and dedifferentiated liposarcomas (WDLPS and DDLPS) are characterized by extensive copy- number alterations rather than recurrent gene-inactivating mutations, obscuring the molecular mechanisms that drive disease progression and, critically, the transition from well-differentiated to the more aggressive dedifferentiated tumor states. Despite marked differences in clinical behavior and prognosis, the regulatory events underlying adipocytic lineage destabilization in DDLPS remain poorly understood. Here, we establish an in vivo model of retroperitoneal liposarcoma in Xenopus tropicalis through early embryonic mosaic perturbation of p53 and Rb pathway components. Combined disruption reproducibly induced retroperitoneal WDLPS development, demonstrating that pathway-level deregulation of the MDM2-p53 and CDK4-Rb axes is sufficient to initiate liposarcoma development in vivo. Strikingly, additional perturbation of transcriptional co-activator ep300 in this context resulted in increased tumor dedifferentiation, yielding lesions composed of spatially coexisting well- and dedifferentiated adipocytic states. In contrast, direct targeted disruption of downstream adipogenic regulators recurrently lost in human DDLPS, including cebpa, g0s2, and dgat2, failed to induce dedifferentiation in the same genetic context in vivo. These findings indicate that dedifferentiation cannot be explained by loss of downstream adipocytic effectors alone but instead reflects destabilization of higher-order regulatory programs governing adipocytic identity. Together, these results establish an in vivo model that closely reflects the clinical situation on a pathway level and provides initial mechanistic insight into how adipocytic differentiation may become destabilized during disease progression. This framework offers a foundation for future studies leveraging higher-order and multi-omic approaches to dissect the molecular processes underlying the WDLPS-to-DDLPS transition.

BackgroundWnt/{beta}-catenin signalling is dysregulated in acute myeloid leukaemia (AML), where it lacks effective targeting strategies. Previously, we discovered that {beta}-catenin interacts with several RNA-binding proteins (RBP), indicating post-transcriptional influence which is yet to be therapeutically interrogated in AML. MethodsCo-immunoprecipitation confirmed protein interactions, and TCF/LEF reporters were used to assess Wnt signalling output in leukaemia cells. Regulatory crosstalk was assessed using immunoblotting and RT-qPCR approaches following lentiviral transduction of myeloid cell lines. Targeting of {beta}-catenin and LIN28B was tested through combinations of genetic and pharmacological inhibition in AML cells. ResultsThe most frequent RBP-binding motif amongst {beta}-catenin-bound mRNAs was the GGAG motif targeted by oncofetal miRNA-regulating RBP; LIN28B. {beta}-Catenin:LIN28B interactions were detected in lymphoid and myeloid cell lines, plus primary human CD34 fetal-liver HSCs. LIN28B positively regulated Wnt signalling output through LEF1 regulation involving a post-transcriptional let7 miRNA mechanism. Further miRNA sequencing of {beta}-catenin- and LIN28B-depleted myeloid cells revealed potential cooperative and antagonistic function in miRNA regulation. Finally, dual-targeting both {beta}-catenin and LIN28B through either genetic and/or pharmacological means preferentially reduced AML cell viability. ConclusionThe {beta}-catenin:LIN28B axis could represent a novel synthetically lethal relationship in AML which could be exploited in rare subtypes where LIN28B expression becomes reactivated.