PTEN Loss Research Articles

ATP citrate lyase is an essential player in the metabolic rewiring induced by PTEN loss during T-ALL development.

Alterations inactivating the tumor suppressor gene PTEN drive the development of solid and hematological cancers, such as T-cell acute lymphoblastic leukemia (T-ALL), whereby PTEN loss defines poor-prognosis patients. We investigated the metabolic rewiring induced by PTEN loss in T-ALL, aiming at identifying novel metabolic vulnerabilities. We showed that the enzyme ATP citrate lyase (ACLY) is strictly required for the transformation of thymic immature progenitors and for the growth of human T-ALL, which remain dependent on ACLY activity even upon transformation. Whereas PTEN mutant mice all died within 17 weeks, the concomitant ACLY deletion prevented disease initiation in 70% of the animals. In these animals, ACLY promoted BCL-2 epigenetic upregulation and prevented the apoptosis of pre-malignant DP thymocytes. Transcriptomic and metabolic analysis of primary T-ALL cells next translated our findings to the human pathology, showing that PTEN-altered T-ALL cells activate ACLY and are sensitive to its genetic targeting. ACLY activation thus represents a metabolic vulnerability with therapeutic potential for high-risk T-ALL patients.

Colorectal carcinoma progression is not influenced by the pseudokinase PEAK1.

The scaffold protein PEAK1 acts downstream of integrin adhesion complexes and the epidermal growth factor receptor, orchestrating signaling events that control cell proliferation and cytoskeletal remodeling. In this study we investigated the role of PEAK1 in colorectal carcinoma (CRC) progression using various in vitro and in vivo models to replicate the stepwise pathogenesis of CRC. While we observed a cell-type specific role for PEAK1 in the proliferation and in human CRC cell lines in vitro, our in vivo experiments using different CRC mouse models driven by loss of Apc, with or without oncogenic Kras or Pten loss suggest that PEAK1 does not significantly contribute to tumor formation in vivo. However, the survival time of Peak1-/- mice in the Apcfl/+ model appeared to be slightly increased. Furthermore, PEAK1 promotes EGF-induced Caco-2 cell proliferation and regulates spheroid polarization and lumenization. Given that the Caco-2 cells harbor mutations in the tumor suppressors APC and β-CATENIN, but not in other tumor suppressors or in proto-oncogenes, we conclude that the PEAK1's impact on colon carcinogenesis is limited, potentially playing a role in the initial stage of the adenoma to carcinoma progression.

TMIC-66. A NEW MOUSE MODEL THAT COMBINES DRIVER MUTATIONS TO ACCURATELY RECAPITULATE THE DIVERSE PHENOTYPES OF HUMAN GLIOBLASTOMA

Abstract To effectively beat glioblastoma, new pre-clinical models are needed: to dissect the biology of processes like migration and therapy resistance; to understand immune suppression and immunotherapy; and to use as a model for testing in therapeutic development. We have developed a new panel of glioblastoma mouse models, which engineer well-characterised glioblastoma driver mutations into an immortalised eGFP murine astrocyte-like cell. These “GEM-CLeM” are Genetically Engineered Mouse Cell Line Models. When transplanted intra-cranially into immunocompetent mice, these lines formed tumors with the key characteristics of glioblastoma – migratory and invasive, with rapid proliferation and infiltration of suppressive immune cells. The eGFP expression allowed detection of glioblastoma cells in situ and ex vivo, and the ability to readily distinguish tumor and stromal components of the tumors. Importantly, different combinations of driver mutations led to diverse tumor phenotypes. Loss of Pten with over-expression of mutant RAS generated tumors with 100% efficiency and the same time to tumor onset as the commonly used GL261 cell line. However, unlike GL261 tumors the Pten-RASV12 tumors had a highly invasive edge and extensive migration, and were full of pro-tumorigenic macrophages and monocytes, with very few T-cells or dendritic cells. Together, this recapitulated the phenotype of human wildtype IDH1 glioblastoma. In contrast, the very common EGFRvIII mutant did not drive tumor formation in combination with Pten loss. We also modelled mutant IDH glioblastoma by combining loss of p53 with overexpression of IDH1R132H. These were slow growing, densely packed tumors with extensive microglial involvement in addition to pro-tumorigenic macrophages. This GEM-CLeM system combines the benefits of the traditional genetically engineered mouse models with accessible, rapid, reproducible tumor formation. The GEM-CLeM lines are amenable to further genetic manipulation, so cells can be customised with other mutations to ask important biological questions in the presence of an intact tumor immune microenvironment.

Mechanisms of Immune Evasion in PTEN Loss Prostate Cancer

PTEN (phosphatase and tensin homolog) is a frequently lost tumor suppressor gene in prostate cancer, leading to aggressive tumor behavior and poor clinical outcomes. PTEN loss results in aberrant activation of the PI3K/AKT/mTOR pathway, promoting oncogenesis. These alterations also lead to an immunosuppressive tumor microenvironment with altered immune cell infiltration, cytokine profiles, and immune checkpoint regulation. This review aims to provide a comprehensive overview of the mechanisms underlying PTEN loss in prostate cancer and the consequent immune alterations observed in this subtype, thus underscoring the importance of understanding PTEN-mediated immune modulation for the development of effective therapeutic interventions in prostate cancer.

Rabex-5 E3 and Rab5 GEF domains differ in their regulation of Ras, Notch, and PI3K signaling in Drosophila wing development.

Rabex-5 (also called RabGEF1), a protein originally characterized for its Rab5 GEF function, also has an A20-like E3 ubiquitin ligase domain. We and others reported that Rabex-5 E3 activity promotes Ras mono- and di-ubiquitination to inhibit Ras signaling in Drosophila and mammals. Subsequently, we reported that Rabex-5 inhibits Notch signaling in the Drosophila hematopoietic system. Here we report genetic interactions using Rabex-5 transgenes encoding domain-specific mutations that show that Rabex-5 requires an intact E3 domain to inhibit Notch signaling in the epithelial tissue of the developing wing. Surprisingly, we discovered that Rabex-5 with an impaired E3 domain but active Rab5 GEF domain suppresses Notch loss-of-function phenotypes and enhances both Notch duplication phenotypes and activated Ras phenotypes consistent with a model that the Rab5 GEF activity of Rabex-5 might positively regulate Ras and Notch. Positive and negative regulation of developmental signaling by its different catalytic domains could allow Rabex-5 to precisely coordinate developmental signaling to fine-tune patterning. Finally, we report that Rabex-5 also inhibits the overgrowth due to loss of PTEN or activation of PI3K but not activation of AKT. Inhibition of Ras, Notch, and PI3K signaling may explain why Rabex-5 is deleted in some cancers. Paradoxically, Rabex-5 is reported to be an oncogene in other cancers. We propose that Rabex-5 acts as a tumor suppressor via its E3 activity to inhibit Ras, Notch, and PI3K signaling and as an oncogene via its Rab5 GEF activity to enhance Ras and Notch signaling.

Higher risk of recurrence in early-stage breast cancer patients with increased levels of ribosomal protein S6

PI3K/AKT/mTOR pathway is implicated in breast cancer progression and recurrence. The identification of PIK3CA and AKT1 mutations and loss of PTEN serve as selection criterion for targeted therapies involving selective inhibitors. However, they do not consistently align with pathway activation, and high-cost determinations limit their routine application. PI3K-downstream epigenetic regulatory mechanisms broaden the alterations that amplify pathway activity and, consequently, sensitivity to selective inhibitors. In this retrospective observational study, conducted within a cohort of early-stage breast cancer patients, we determined phosphorylated ribosomal protein S6 (pS6) at Ser240/244 by immunohistochemistry as an indicator of PI3K pathway activation. Log-Rank test and Cox proportional hazards regression were used to analyze the clinical relevance of pS6, alone and together with clinicopathological variables, regarding recurrence-free survival. ROC curves and the area under the curves were used to evaluate the calibration and discrimination properties of uni- and multivariate models. Our results show that a high percentage of pS6 positive tumor cells was associated with an unfavorable prognosis in a cohort of 129 hormone receptor positive/HER2 negative breast cancer patients (Hazard Ratio = 5.92; Log-Rank p = 9.5e-08; median follow-up = 53 months). When assessed in combination with lymph node status, the predictive capacity was higher compared to both univariate models individually. In conclusion, pS6 could represent a novel independent marker for predicting recurrence risk in luminal breast cancer.

Malignant Peripheral Nerve Sheath Tumor of the Pancreas with Molecular Confirmation: A Case Report with Comprehensive Histopathologic and Molecular Characterization

Abstract Introduction/Objective Malignant peripheral nerve sheath tumors (MPNSTs) are rare soft tissue sarcomas arising from a peripheral nerve or exhibiting nerve sheath differentiation. They are often associated with neurofibromatosis type 1, and most often arise in the trunk, extremities, or head and neck region. In patients without neurofibromatosis type 1, sporadic de novo or radiotherapy-associated MPNSTs can pose a diagnostic challenge. MPNSTs arising from visceral organs are exceedingly rare. Here we report a case of MPNST arising in the pancreas. Methods/Case Report The patient is a 75-year-old female, MUTYH mutation carrier, with prior history of breast and bladder cancers, each treated with respective local excision and radiation therapy. Magnetic resonance imaging (MRI) performed for pancreatic cancer screening showed a 4.7 cm heterogeneous mass in the pancreatic tail suggestive of pancreatic neoplasm. Fine needle aspiration cytology was non-diagnostic. However, due to the radiologic concern for malignancy, the patient proceeded with surgical resection by distal pancreatectomy with splenectomy. Macroscopically, a 6.5 cm, tan-white, partially necrotic mass was identified in the pancreatic tail. Microscopic examination showed a spindle cell neoplasm arranged in a vague fascicular fashion with moderate nuclear pleomorphism, geographic necrosis, and frequent mitotic figures (15 per 10 high power fields). Fifteen lymph nodes were negative for metastasis. The tumor was confined to the pancreas grossly and microscopically. Immunohistochemical stains showed the neoplastic spindle cells to be positive for TLE1 (diffuse) and S100 (patchy), while negative for SOX10, CD117, DOG1, desmin, actin, MyoD1, ERG, STAT6, and ALK1. In addition, H3K27me3 showed loss of nuclear expression. Next generation sequencing (NGS) revealed gene mutations in NF1, TP53, PIK3CA, and PTEN, and copy number losses involving CDKN2A and CDKN2B. Genome-wide DNA methylation analysis was performed which revealed copy number losses of CDKN2A/B and gains of PTCH1 and MDM2. However, the Sarcoma DNA Methylation Classifier did not provide any diagnostic matches. Overall, the morphologic features, loss of H3K27me3 expression, presence of NF1 and TP53 mutations, and copy number losses in CDKN2A/B supported a diagnosis of high-grade MPNST. The patient has been followed clinically without adjuvant therapy. Results (if a Case Study enter NA) N/A Conclusion We report an extremely rare case of MPNST of the pancreas with molecular confirmation.

Comprehensive mutational profiling identifies new driver events in cutaneous leiomyosarcoma.

Cutaneous leiomyosarcoma (cLMS) is a rare soft tissue neoplasm, showing smooth muscle differentiation, that arises from the mesenchymal cells of the dermis. To-date, genetic investigation of these tumours has involved studies with small sample sizes and limited analyses that identified recurrent somatic mutations in RB1 and TP53, copy number gain of MYCOD and IGF1R, and copy number loss of PTEN. To better understand the molecular pathogenesis of cLMS, we comprehensively explored the mutational landscape of these rare tumours to identify candidate driver events. In this retrospective, multi-institutional study, we performed whole-exome sequencing and RNA sequencing on 38 cases of cLMS. TP53 and RB1 were identified as significantly mutated, thus, represent validated driver genes of cLMS. COSMIC mutational signatures SBS7a/b and DBS1 were recurrent, thus, ultraviolet light exposure may be an aetiological factor driving cLMS. Analysis of significantly recurrent somatic copy number alterations, which represent candidate driver events, found focal (<10Mb) deletions encompassing TP53 and KDM6B, and amplifications encompassing ZMYM2, MYOCD, MAP2K4 and NCOR1. A larger (24 Mb) recurrent deletion encompassing CYLD was also identified as significant. Significantly recurrent broad copy number alterations, involving at least half of a chromosome arm, included deletions of 6p/q, 10p/q, 11q, 12q, 13q and 16p/q, and amplification of 15q. Notably PTEN is located on 10q, RB1 on 13q and IGFR1 on 15q. Fusion gene analysis identified recurrent CRTC1/3::MAML2 fusions, as well as many novel fusions in individual samples. Our analysis of the largest number of cLMS cases to-date highlights the importance of large cohort sizes and the exploration beyond small targeted gene panels when performing molecular analyses, as it allowed a comprehensive exploration of the mutational landscape of these tumours and identification of novel candidate driver events. It also uniquely afforded the opportunity to compare the molecular phenotype of cLMS with LMS of other tissue types, such as uterine and soft tissue LMS. Given that molecular profiling has resulted in the development of novel targeted treatment approaches for uterine and soft tissue LMS, our study now allows the same opportunities to become available for patients with cLMS.

B-328 A Novel Pathway of Akt-Dependent PARP1 Activation Through the Nuclear Localization of EPRS1

Abstract Background Glutamyl-prolyl-tRNA synthetase (EPRS1) is the only bifunctional aminoacyl-tRNA synthetase (aaRS) and is essential for interpreting the genetic code. EPRS1, along with seven other aaRSs, forms the multi-tRNA synthetase complex (MSC). EPRS1 consists of two catalytic domains, GluRS and ProRS, connected by a linker region. Several aaRSs within the MSC, including EPRS1, can dissociate from the MSC in response to specific stimuli. This dissociation enables non-canonical activities distinct from their primary role in protein synthesis. Breast cancer cells harboring a loss-of-function mutation in phosphatase and tensin homolog (PTEN) are known to have more activity in the serine/threonine kinase Akt. Poly-(ADP)-ribose polymerase 1 (PARP1), plays a vital role in DNA damage repair (DDR). PARP1 deposits one or more ADP-Ribose moieties onto damaged DNA or other proteins in a process referred to as PARylation. We hope to connect Akt activation and PARP1 activity through the nuclear localization and noncanonical function of EPRS1. We hypothesize, that when Akt is activated, either through the loss of PTEN function or through stimuli such as heat shock or H2O2 treatment, will stimulate the nuclear localization of EPRS1 and modulate PARP1 activity. Methods To test our hypothesis, we evaluate Akt activation, EPRS1 localization, and PARP1 activity. Using pharmacological activators and inhibitors of Akt, we test if inhibitors and activators alone are sufficient to cause the nuclear localization of EPRS1. Biochemically, we isolate nuclear and cytosolic fractions used in various western blot analysis. We use a variety of assays for PARP1 activity and DDR that include immobilized histones, calculating IC50s of PARP1 inhibitors, comet assay, and confocal microscopy. To ascertain the connection between PARP1 and EPRS1 we use LC-MS/MS analysis and immunoprecipitation. Results We show, in both patient-derived and cultured breast cancer cells, elevated levels of EPRS1 not only in the cytoplasm, but also within the nucleus. We find that nuclear localization EPRS1 is facilitated by a nuclear localization sequence (NLS) located within the linker region of the protein. Breast cancer cells harboring a loss-of-function in PTEN exhibit higher levels of EPRS1 in the nucleus compared to PTEN-positive cells. In EPRS1 knockdown cells, there is diminished expression of multiple tumor-related transcription factors, DNA-damage repair, tumor cell survival, and PARP1 auto-PARylation. We demonstrate that nuclear EPRS1 binds to and shares an interactome with PARP1. Conclusions EPRS1-mediated regulation of PARP1 activity provides a new mechanistic link between PTEN loss in breast cancer cells, PARP1 activation, and cell survival and tumor growth. Targeting the non-canonical activity of EPRS1, without inhibiting canonical tRNA ligase activity, might provide a new therapeutic approach in breast and other forms of cancer, potentially supplementing existing cancer therapeutics.

PTEN Deficiency Induced by Extracellular Vesicle miRNAs from Clonorchis sinensis Potentiates Cholangiocarcinoma Development by Inhibiting Ferroptosis.

The human phosphatase and tensin homolog (PTEN) is a tumor suppressor. A slight deficiency in PTEN might cause cancer susceptibility and progression. Infection by the liver fluke Clonorchis sinensis could lead to persistent loss of PTEN in cholangiocarcinoma. However, the mechanism of PTEN loss and its malignant effect on cholangiocarcinoma have not yet been elucidated. Extracellular vesicles secreted by Clonorchis sinensis (CS-EVs) are rich in microRNAs (miRNAs) and can mediate communication between hosts and parasites. Herein, we delved into the miRNAs present in CS-EVs, specifically those that potentially target PTEN and modulate the progression of cholangiocarcinoma via ferroptosis mechanisms. CS-EVs were extracted by differential ultra-centrifugation for high-throughput sequencing of miRNA. Lentiviral vectors were used to construct stably transfected cell lines. Erastin was used to construct ferroptosis induction models. Finally, 36 miRNAs were identified from CS-EVs. Among them, csi-miR-96-5p inhibited PTEN expression according to the predictions and dual luciferase assay. The CCK-8 assay, xenograft tumor assays and transwell assay showed that csi-miR-96-5p overexpression and PTEN knockout significantly increased the proliferation and migration of cholangiocarcinoma cells and co-transfection of PTEN significantly reversed the effect. In the presence of erastin, the cell proliferation and migration ability of the negative transfection control group were significantly impaired, although they did not significantly change with transfection of csi-miR-96-5p and PTEN knockout, indicating that they obtained ferroptosis resistance. Mechanistically, csi-miR-96-5p and PTEN knockout significantly inhibited ferroptosis through a decrease in ferrous ion (Fe2+) and malondialdehyde (MDA), and an increase in glutathione reductase (GSH), Solute carrier family 7 member 11 (SLC7A11) and glutathione peroxidase 4 (GPX4). In conclusion, loss of PTEN promoted the progression of cholangiocarcinoma via the ferroptosis pathway and csi-miR-96-5p delivered by CS-EVs may mediate this process.

Prognostic Importance of PTEN, p53, and MDM2 Expressions in Endometrioid and Serous-Type Endometrial Carcinomas

Aim: Endometrial carcinomas (ECs) are neoplasms with the highest rate of change in the phosphatidylinositol 3-kinase (PI3K)/AKT/mammalian target of rapamycin (mTOR) pathway. In this study, the relationship among PTEN, MDM2, and p53 protein expression in the PI3K/AKT/mTOR pathway with clinicopathological data in endometrioid endometrial carcinomas (EECs) and serous-type endometrial carcinomas (SECs) was evaluated. Material and Method: A hundred and twenty cases of patients who underwent hysterectomy for EC between 2009 and 2021 were included in the study. Thirty cases of SEC and 90 cases of EEC were evaluated. EEC cases consist of grades 1-3 tumors, and each group includes 30 patients. p53 was examined in two groups as normal/wild type and abnormal/mutant type. PTEN and MDM2 were examined in two groups: positive and negative. The relationship among p53, PTEN, and MDM2 immunohistochemical expression status with histological grade, myometrial invasion, cervical invasion, lymphovascular invasion (LVI), metastatic lymph nodes, presence of tumor in peritoneal fluid, tumor stage, and overall and progression-free survival was evaluated. Results: Loss of PTEN was associated with EEC compared to SEC (p

A retrospective analysis suggests PTEN expression is associated with favorable clinicopathological features of breast cancer

The phosphatase and tensin homolog (PTEN) gene acts as a tumor suppressor by regulating the PI3K/AKT pathway, crucial for cell growth and survival. Mutations or loss of PTEN are common in breast cancer, leading to uncontrolled cell growth. Understanding PTEN’s role is vital for targeted therapies. 276 formalin-fixed paraffin-embedded (FFPE) breast cancer tissue blocks from 2012 to 2016 were analyzed for PTEN expression. Immunohistochemistry was performed to identify and assess tumor related clinicopathological characteristics as well as patient demographics. These were statistically matched with PTEN expression. Only 27.5% of the breast cancer tumors were PTEN-positive. PTEN expression correlated significantly with smaller tumor size, lower tumor grade, positive estrogen and progesterone receptor status, and favorable/unfavorable Ki67 status (p < 0.001). No significant association was found with vascular invasion, histologic type, age, HER2 status, staging, or lymph node involvement (p > 0.05). The study confirms PTEN's association with favorable clinicopathological features in breast cancer, supporting its role as a prognostic marker. These findings underscore the importance of PTEN in breast cancer biology and its potential as a therapeutic target. Furthermore these findings confirm the prevalence of advanced stage and aggressive breast cancer tumors in Ghana.

Abstract A060: Dysregulation of PTEN expression in a subset of Cancer Associated Fibroblasts by Tumor Secreted Factors in PDAC

Abstract Pancreatic Ductal Adenocarcinoma (PDAC) is a deadly malignancy. Cancer associated fibroblasts (CAFs) play a complex role in the PDAC tumor microenvironment (TME), with a subset contributing significantly to tumor progression. Phosphatase and tensin homolog (PTEN) is a tumor suppressor and its loss is associated with increased tumor aggressiveness. Our group previously demonstrated PTEN loss in SMA+ positive CAFS correlated with worsened outcomes in patients and in mouse PDAC models. Our group previously demonstrated the loss of PTEN in CAFS led to activation of Stat3, resulting in an immunosuppressive microenvironment (Lefler et al, 2022 PMID: 35803738). However, little is known of the signals produced by tumor cells or other cell types in the TME that trigger loss of PTEN in CAFs. This study aims to to elucidate the molecular mechanisms underlying PTEN loss in CAFs in PDAC. To address this gap, we employed single cell RNA sequencing of tumors from a mouse PDAC model and identified a (PDRGFRa+Lys6+Stat3+Pten-low) CAF subpopulation. Comparing normal pancreas epithelial cells to tumor cells in this data set, we identified the IL6 family of cytokines, (IL6; Oncostatin-M, OSM; and Leukemia Inhibitory Factor, LIF) and Transforming Growth Factor beta 1 (TGFb1) as potential ligands that regulated PTEN, while myeloid cells were a source of the IL6 family member Oncostatin M (OSM). Treatment of isolated CAFs with these factors revealed no significant difference in PTEN mRNA expression. Thus, we developed an in vitro reporter system in which a PTEN-GFP fusion protein is expressed in CAFs. Treating these CAFs with IL6, OSM and TGFb1 (but not LIF) led to a significant decrease in GFP fluorescence. Analysis of endogenous PTEN by western blot confirmed these results. We posited that expression of PTEN E3 ligases might be increased by treatment with these factors, leading to destruction of PTEN. In support of this hypothesis, the expression of E3 ligases WWP1 and WWP2 was increased by treatment with IL6 and OSM. Additionally, preliminary data has revealed that PTEN is oxidized in isolated CAFs, which causes loss of PTEN activity and potentially increased protein turnover. Current experiments are aimed at testing these potential mechanisms. To conclude, PTEN is dysregulated post-transcriptionally in CAFs. The mechanism of PTEN dysregulation could be via increased expression of E3 ligases that target PTEN and/or PTEN oxidation. Future efforts will be aimed at testing whether inhibition of these pathways can restore PTEN expression in mouse PDAC models. These pathways and interactions could be further exploited for therapeutic benefit in curbing PDAC progression. Citation Format: Ivo N. Woogeng, Lu Han, Samaneh Saberi, Cameron Bumbleburg, Joseph Beaudet, Sudarshana Sharma, Michael Ostrowski. Dysregulation of PTEN expression in a subset of Cancer Associated Fibroblasts by Tumor Secreted Factors in PDAC [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Advances in Pancreatic Cancer Research; 2024 Sep 15-18; Boston, MA. Philadelphia (PA): AACR; Cancer Res 2024;84(17 Suppl_2):Abstract nr A060.

Impact of PIK3CA gain and PTEN loss on mantle cell lymphoma biology and sensitivity to targeted therapies

AbstractBesides many other mutations in known cancer driver genes, mantle cell lymphoma (MCL) is characterized by recurrent genetic alterations of important regulators of the phosphoinositol-3-kinase (PI3K) cascade including PIK3CA gains and PTEN losses. To evaluate the biological and functional consequences of these aberrations in MCL, we have introduced transgenic expression of PIK3CA (PIK3CA UP) and performed knockout/knockdown of PTEN gene (PTEN KO/KD) in 5 MCL cell lines. The modified cell lines were tested for associated phenotypes including dependence on upstream B-cell receptor (BCR) signaling (by an additional BCR knockout). PIK3CA overexpression decreased the dependence of the tested MCL on prosurvival signaling from BCR, decreased levels of oxidative phosphorylation, and increased resistance to 2-deoxy-glucose, a glycolysis inhibitor. Unchanged protein kinase B (AKT) phosphorylation status and unchanged sensitivity to a battery of PI3K inhibitors suggested that PIK3CA gain might affect MCL cells in AKT-independent manner. PTEN KO was associated with a more distinct phenotype: AKT hyperphosphorylation and overactivation, increased resistance to multiple inhibitors (most of the tested PI3K inhibitors, Bruton tyrosine kinase inhibitor ibrutinib, and BCL2 inhibitor venetoclax), increased glycolytic rates with resistance to 2-deoxy-glucose, and significantly decreased dependence on prosurvival BCR signaling. Our results suggest that the frequent aberrations of the PI3K pathway may rewire associated signaling with lower dependence on BCR signaling, better metabolic and hypoxic adaptation, and targeted therapy resistance in MCL.

PTEN Loss Shapes Macrophage Dynamics in High-Grade Serous Ovarian Carcinoma.

High-grade serous ovarian carcinoma (HGSC) remains a disease with poor prognosis that is unresponsive to current immune checkpoint inhibitors. Although PI3K pathway alterations, such as PTEN loss, are common in HGSC, attempts to target this pathway have been unsuccessful. We hypothesized that aberrant PI3K pathway activation may alter the HGSC immune microenvironment and present a targeting opportunity. Single-cell RNA sequencing identified populations of resident macrophages specific to Pten-null omental tumors in murine models, which were confirmed by flow cytometry. These macrophages were derived from peritoneal fluid macrophages and exhibited a unique gene expression program, marked by high expression of the enzyme heme oxygenase-1 (HMOX1). Targeting resident peritoneal macrophages prevented the appearance of HMOX1hi macrophages and reduced tumor growth. In addition, direct inhibition of HMOX1 extended survival in vivo. RNA sequencing identified IL33 in Pten-null tumor cells as a likely candidate driver, leading to the appearance of HMOX1hi macrophages. Human HGSC tumors also contained HMOX1hi macrophages with a corresponding gene expression program. Moreover, the presence of these macrophages was correlated with activated tumoral PI3K/mTOR signaling and poor overall survival in patients with HGSC. In contrast, tumors with low numbers of HMOX1hi macrophages were marked by increased adaptive immune response gene expression. These data suggest targeting HMOX1hi macrophages as a potential therapeutic strategy for treating poor prognosis HGSC. Significance: Macrophages with elevated HMOX1 expression are enriched in PTEN-deficient high-grade serous ovarian carcinoma, promote tumor growth, and represent a potential therapeutic target.

Glioma lateralization: Focus on the anatomical localization and the distribution of molecular alterations (Review).

It is well known how the precise localization of glioblastoma multiforme (GBM) predicts the direction of tumor spread in the surrounding neuronal structures. The aim of the present review is to reveal the lateralization of GBM by evaluating the anatomical regions where it is frequently located as well as the main molecular alterations observed in different brain regions. According to the literature, the precise or most frequent lateralization of GBM has yet to be determined. However, it can be said that GBM is more frequently observed in the frontal lobe. Tractus and fascicles involved in GBM appear to be focused on the corticospinal tract, superior longitudinal I, II and III fascicles, arcuate fascicle long segment, frontal strait tract, and inferior fronto‑occipital fasciculus. Considering the anatomical features of GBM and its brain involvement, it is logical that the main brain regions involved are the frontal‑temporal‑parietal‑occipital lobes, respectively. Although tumor volumes are higher in the right hemisphere, it has been determined that the prognosis of patients diagnosed with cancer in the left hemisphere is worse, probably reflecting the anatomical distribution of some detrimental alterations such as TP53 mutations, PTEN loss, EGFR amplification, and MGMT promoter methylation. There are theories stating that the right hemisphere is less exposed to external influences in its development as it is responsible for the functions necessary for survival while tumors in the left hemisphere may be more aggressive. To shed light on specific anatomical and molecular features of GBM in different brain regions, the present review article is aimed at describing the main lateralization pathways as well as gene mutations or epigenetic modifications associated with the development of brain tumors.

Effect of oncolytic Newcastle disease virus harboring PTEN gene on pancreatic adenocarcinoma growth through inhibition of PI3K/mTOR signaling and promotion of apoptosis.

49 Background: Pancreatic ductal adenocarcinoma (PDAC) is a highly aggressive and intractable cancer, warranting the need for more effective therapies. Cell proliferation, progression, and severity in PDAC are highly activated owing to KRAS mutations and low PTEN expression. Methods: A recombinant Newcastle disease virus (rNDV) harboring PTEN (rNDV-PTEN) was constructed to infect PDAC cells to artificially induce PTEN expression. The cancer killing effect of the rNDV-PTEN virus was observed in an in vitro assay, and 107.0 pfu/dose(0.1 ml) of the rNDV-PTEN virus was inoculated through intravenous injection into a PANC-1 cell transplanted mouse to prove the tumor growth inhibition effect. Apoptotic signaling-related proteins were analyzed with Western blotting and qPCR assays based on the mRNA. During the treatment, biomarkers were also analyzed. Results: Factitious PTEN expression in KRAS-mutated PDAC cells following rNDV-PTEN infection lowered PI3K/AKT/mTOR signaling, induced PDAC cell death, and suppressed tumor growth. PTEN overexpression promoted apoptotic and autophagic signaling pathways in PANC-1 cells and orthotopic xenograft mice. rNDV-PTEN has substantial cancer cell-killing effects and inhibits tumor growth. rNDV-PTEN injection into animals did not elicit an immune response against rNDV and improved blood parameters, such as glucose, triglyceride, and total cholesterol levels. Conclusions: rNDV-PTEN showed a strong tumor-suppressive effect on PDAC, which was caused by an abnormally activated PI3K/AKT/mTOR signaling pathway due to KRAS mutations and PTEN loss. We also showed that rNDV-PTEN is relatively safe for use in cancer therapy. Further studies using patient-derived PDAC cells with the same genetic background, as well as more extensive animal safety tests, are required to demonstrate rNDV-PTEN as a PDAC therapeutic. However, PTEN gene-containing rNDV may be a very promising therapeutic candidate for pancreatic cancer treatment.

Assessments of prostate cancer cell functions highlight differences between a pan-PI3K/mTOR inhibitor, gedatolisib, and single-node inhibitors of the PI3K/AKT/mTOR pathway.

Metastatic castration-resistant prostate cancer (mCRPC) is characterized by loss of androgen receptor (AR) sensitivity and oncogenic activation of the PI3K/AKT/mTOR (PAM) pathway. Loss of the PI3K regulator PTEN is frequent during prostate cancer (PC) initiation, progression, and therapeutic resistance. Co-targeting the PAM/AR pathways is a promising mCRPC treatment strategy but is hampered by reciprocal negative feedback inhibition or feedback relief. Most PAM inhibitors selectively spare (or weakly inhibit) one or more key nodes of the PAM pathway, potentiating drug resistance depending on the PAM pathway mutation status of patients. We posited that gedatolisib, a uniformly potent inhibitor of all class I PI3K isoforms, as well as mTORC1 and mTORC2, would be more effective than inhibitors targeting single PAM pathway nodes in PC cells. Using a combination of functional and metabolic assays, we evaluated a panel of PC cell lines with different PTEN/PIK3CA status for their sensitivity to multi-node PAM inhibitors (PI3K/mTOR: gedatolisib, samotolisib) and single-node PAM inhibitors (PI3Kα: alpelisib; AKT: capivasertib; mTOR: everolimus). Gedatolisib induced anti-proliferative and cytotoxic effects with greater potency and efficacy relative to the other PAM inhibitors, independent of PTEN/PIK3CA status. The superior effects of gedatolisib were likely associated with more effective inhibition of critical PAM-controlled cell functions, including cell cycle, survival, protein synthesis, oxygen consumption rate, and glycolysis. Our results indicate that potent and simultaneous blockade of all class I PI3K isoforms, mTORC1, and mTORC2 could circumvent PTEN-dependent resistance. Gedatolisib, as a single agent and in combination with other therapies, reported promising preliminary efficacy and safety in various solid tumor types. Gedatolisib is currently being evaluated in a Phase 1/2 clinical trial in combination with darolutamide in patients with mCRPC previously treated with an AR inhibitor, and in a Phase 3 clinical trial in combination with palbociclib and fulvestrant in patients with HR+/HER2- advanced breast cancer.

Myeloid PTEN loss affects the therapeutic response by promoting stress granule assembly and impairing phagocytosis by macrophages in breast cancer

Breast cancer (BRCA) has become the most common type of cancer in women. Improving the therapeutic response remains a challenge. Phosphatase and tensin homologue deleted on chromosome 10 (PTEN) is a classic tumour suppressor with emerging new functions discovered in recent years, and myeloid PTEN loss has been reported to impair antitumour immunity. In this study, we revealed a novel mechanism by which myeloid PTEN potentially affects antitumour immunity in BRCA. We detected accelerated stress granule (SG) assembly under oxidative stress in PTEN-deficient bone marrow-derived macrophages (BMDMs) through the EGR1-promoted upregulation of TIAL1 transcription. PI3K/AKT/mTOR (PAM) pathway activation also promoted SG formation. ATP consumption during SG assembly in BMDMs impaired the phagocytic ability of 4T1 cells, potentially contributing to the disruption of antitumour immunity. In a BRCA neoadjuvant cohort, we observed a poorer response in myeloid PTENlow patients with G3BP1 aggregating as SGs in CD68+ cells, a finding that was consistent with the observation in our study that PTEN-deficient macrophages tended to more readily assemble SGs with impaired phagocytosis. Our results revealed the unconventional impact of SGs on BMDMs and might provide new perspectives on drug resistance and therapeutic strategies for the treatment of BRCA patients.

A Transcriptomics Analysis of the Regulation of Lens Fiber Cell Differentiation in the Absence of FGFRs and PTEN.

Adding 50% vitreous humor to the media surrounding lens explants induces fiber cell differentiation and a significant immune/inflammatory response. While Fgfr loss blocks differentiation in lens epithelial explants, this blockage is partially reversed by deleting Pten. To investigate the functions of the Fgfrs and Pten during lens fiber cell differentiation, we utilized a lens epithelial explant system and conducted RNA sequencing on vitreous humor-exposed explants lacking Fgfrs, or Pten or both Fgfrs and Pten. We found that Fgfr loss impairs both vitreous-induced differentiation and inflammation while the additional loss of Pten restores these responses. Furthermore, transcriptomic analysis suggested that PDGFR-signaling in FGFR-deficient explants is required to mediate the rescue of vitreous-induced fiber differentiation in explants lacking both Fgfrs and Pten. The blockage of β-crystallin induction in explants lacking both Fgfrs and Pten in the presence of a PDGFR inhibitor supports this hypothesis. Our findings demonstrate that a wide array of genes associated with fiber cell differentiation are downstream of FGFR-signaling and that the vitreous-induced immune responses also depend on FGFR-signaling. Our data also demonstrate that many of the vitreous-induced gene-expression changes in Fgfr-deficient explants are rescued in explants lacking both Fgfrs and Pten.