INPP4B promotes PI3Kα-dependent late endosome formation and Wnt/β-catenin signaling in breast cancer

INPP4B promotes PDAC aggressiveness via PIKfyve and TRPML-1-mediated lysosomal exocytosis

Aggressive solid malignancies, including pancreatic ductal adenocarcinoma (PDAC), can exploit lysosomal exocytosis to modify the tumor microenvironment, enhance motility, and promote invasiveness. However, the molecular pathways through which lysosomal functions are co-opted in malignant cells remain poorly understood. In this study, we demonstrate that inositol polyphosphate 4-phosphatase, Type II (INPP4B) overexpression in PDAC is associated with PDAC progression. We show that INPP4B overexpression promotes peripheral dispersion and exocytosis of lysosomes resulting in increased migratory and invasive potential of PDAC cells. Mechanistically, INPP4B overexpression drives the generation of PtdIns(3,5)P2 on lysosomes in a PIKfyve-dependent manner, which directs TRPML-1 to trigger the release of calcium ions (Ca2+). Our findings offer a molecular understanding of the prognostic significance of INPP4B overexpression in PDAC through the discovery of a novel oncogenic signaling axis that orchestrates migratory and invasive properties of PDAC via the regulation of lysosomal phosphoinositide homeostasis.

Role of INPP4B in the proliferation, migration, invasion, and survival of human endometrial cancer cells

BACKGROUND

Inositol polyphosphate 4-phosphatase type II (INPP4B) has been identified as a tumor repressor in several human cancers while its role in endometrial cancer has not been investigated yet. Therefore, the current study was designed to determine whether INPP4B participates in the progression of endometrial cancer by utilizing clinical data and experimental determination.

MATERIALS AND METHODS

We first include six chemotherapy-treated patients with recurrent and metastatic endometrioid carcinoma to determine the relationship between INPP4B mutation and relative tumor burden. By using siRNA-mediated gene silencing and vector-mediated gene overexpression, we further determined the effect of manipulating INPP4B expression on the proliferation, invasion, and survival of endometrial cancer cells. Furthermore, the repressing effect of INPP4B together with its role in chemotherapy was further validated by xenograft tumor-bearing mice models. Western blot analysis was used to explore further downstream signaling modulated by INPP4B expression manipulation.

RESULTS

Two of the patients were found to have INPP4B mutations and the mutation frequency of INPP4B increased during the progression of chemotherapy resistance. Endometrial cancer cells with silenced INPP4B expression were found to have promoted tumor cell proliferation, invasion, and survival. Endometrial cancer cells overexpressing INPP4B were found to have decreased tumor cell proliferation, invasion, and survival. An in vivo study using six xenograft tumor-bearing mice in each group revealed that INPP4B overexpression could suppress tumor progression and enhance chemosensitivity. Furthermore, INPP4B overexpression was found to modulate the activation of Wnt3a signaling.

CONCLUSION

The current study suggested that INPP4B could be a suppressor in endometrial cancer progression and might be a target for endometrial cancer treatment. Also, INPP4B might serve as a predictor of chemosensitivity determination.

PIK3IP1: structure, aberration, function, and regulation in diseases

Phosphoinositide 3-kinase (PI3K) pathway, controlling diverse functions in cells, is one of the most frequently dysregulated pathways in cancer. Several negative regulators have been reported to intricately constrain the overactivation of PI3K pathway. Phosphatidylinoinosidine-3-kinase interacting protein 1 (PIK3IP1), as a unique transmembrane protein, is a newly discovered negative regulator of PI3K pathway. PIK3IP1 negatively regulates PI3K activity by directly binding to the p110 catalytic subunit of PI3K. It has been reported that PIK3IP1 is frequently low expressed in tumors and autoimmune diseases. In tumor cells and impaired cardiomyocyte, PIK3IP1 inhibits cell proliferation and survival. Consistently, the expression of PIK3IP1 is related with the condition of cancer. In addition, PIK3IP1 inhibits the inflammatory response and immune function via maintaining the quiescent state of immune cells. Thus, low expression of PIK3IP1 represents the severe condition of autoimmune diseases. PIK3IP1 is regulated by transcription factors, epigenetic factors or micro-RNAs to facilitate its normal function in different cellular contexts. This review integrates the total findings on PIK3IP1 in different disease, and summaries the structure, biological functions and regulatory mechanisms of PIK3IP1.

INPP4B suppresses HER2-induced mesenchymal transition in HER2+ breast cancer and enhances sensitivity to Lapatinib

Human epidermal growth factor receptor 2 positive (HER2+) breast cancer (BC) tends to metastasize and has a bad prognosis due to its high malignancy and rapid progression. Inositol polyphosphate 4-phosphatase isoenzymes type II (INPP4B) plays unequal roles in the development of various cancers. However, the function of INPP4B in HER2+ BC has not been elucidated. Here we found that INPP4B expression was significantly lower in HER2+ BC and positively correlated with the prognosis by bioinformatics and tissue immunofluorescence analyses. Overexpression of INPP4B inhibited cell proliferation, migration, and growth of xenografts in HER2+ BC cells. Conversely, depletion of INPP4B reversed these effects and activated the PDK1/AKT and Wnt/β-catenin signaling pathways to promote epithelial-mesenchymal transition (EMT) progression. Moreover, INPP4B overexpression blocked epidermal growth factor (EGF) -induced cell proliferation, migration and EMT progression, whereas INPP4B depletion antagonized HER2 depletion in reduction of cell proliferation and migration of HER2+ BC cells. Additionally, Lapatinib (LAP) inhibited HER2+ BC cell survival, proliferation and migration, and its effect was further enhanced by overexpression of INPP4B. In summary, our results illustrate that INPP4B suppresses HER2+ BC growth, migration and EMT, and its expression level affects patient outcome, further providing new insights into clinical practice.

Decorin impeded the advancement of thyroid papillary carcinoma by thwarting the EGFR/ FER/ SHP2 signaling-induced sustenance of early endosomes

Objective

This study explores the inhibition of papillary thyroid carcinoma proliferation by Decorin via the EGFR/SHP2/FER pathway.

Method

ology: Thirty-two pairs of papillary thyroid carcinoma tissues and adjacent normal tissues were collected for immunohistochemical analysis. Thyroid cancer cell lines with overexpressed or silenced Decorin were employed in subcutaneous tumor formation experiments in nude mice. Cell membrane proteins were extracted for Western blot and immunofluorescence analyses.

Results

Reduced Decorin expression in human papillary thyroid carcinoma was associated with inhibited formation of the EGFR/SHP2/FER complex. Immunohistochemical analysis revealed lower Decorin levels in carcinoma tissues compared to adjacent normal tissues, corroborated by decreased Decorin and PTEN levels in carcinoma as shown by Western Blot. Overexpression of Decorin in mouse models diminished tumor growth, an effect reversed by Decorin silencing and mitigated by FER inhibition. Decorin modulated Rab5-GTP and Rab7-GTP levels, impacting endosome transition and subsequent signaling pathways.

Conclusion

Decorin inhibits papillary thyroid carcinoma proliferation by disrupting the EGFR/SHP2/FER pathway and modulating endosomal transport.

Investigating the multifaceted cooperation of autophagy, PI3K/AKT signaling pathways, and INPP4B gene in de novo acute myeloid leukemia patients

BACKGROUND

Acute myeloid leukemia (AML) has been the most prevalent form of acute leukemia among adults, and it has been associated with poor survival rates over the last four decades. Understanding the processes involved in leukemogenesis, particularly autophagy and signaling pathways, can provide critical insights into their roles in disease development, risk assessment, and potential therapeutic interventions. This study investigated gene expression changes, focusing on MAP1LC3B and BECN1, related to autophagy, as well as PI3KCA and AKT1 in the PI3K-AKT pathway, and INPP4B, which regulates this signaling cascade.

METHODS

We collected blood samples from 21 AML patients and 9 healthy volunteers. Gene expression was analyzed through qPCR following RNA extraction and cDNA synthesis. Statistical analysis encompassed t-tests, ANOVA, and correlation coefficients.

RESULTS

AML patients exhibited significantly increased MAP1LC3B gene expression (****P < 0.0001; fold change = 11.9) and significantly reduced levels of INPP4B (****P < 0.0001; fold change = 0.026), AKT1 (*P < 0.05; fold change = 0.59), and PI3KCA (****P < 0.0001; fold change = 0.16) compared to healthy controls. However, BECN1 gene expression did not significantly differ between the two groups. Additionally, noteworthy correlations were observed between INPP4B and BECN1 (r = 0.57; P = 0.006) and BECN1 and PI3KCA (r = 0.61; P = 0.003) in AML patients.

CONCLUSIONS

This study highlights variations in leukemogenesis pathways, exemplified by increased MAP1LC3B expression and diminished expression of regulatory genes in specific AML cases. These findings contribute to our comprehension of the molecular mechanisms underlying AML and may inform future diagnostic and therapeutic approaches.

AS1411 binds to nucleolin via its parallel structure and disrupts the exos-miRNA-27a-mediated reciprocal activation loop between glioma and astrocytes

The interaction between glioma cells and astrocytes promotes the proliferation of gliomas. Micro-RNAs (miRNAs) carried by astrocyte exosomes (exos) may be involved in this process, but the mechanism remains unclear. The oligonucleotide AS1411, which consists of 26 bases and has a G-quadruplex structure, is an aptamer that targets nucleolin. In this study, we demonstrate exosome-miRNA-27a-mediated cross-activation between astrocytes and glioblastoma and show that AS1411 reduces astrocytes' pro-glioma activity. The enhanced affinity of AS1411 toward nucleolin is attributed to its G-quadruplex structure. After binding to nucleolin, AS1411 inhibits the entry of the NF-κB pathway transcription factor P65 into the nucleus, then downregulates the expression of miRNA-27a in astrocytes surrounding gliomas. Then, AS1411 downregulates astrocyte exosome-miRNA-27a and upregulates the expression of INPP4B, the target gene of miRNA-27a in gliomas, thereby inhibiting the PI3K/AKT pathway and inhibiting glioma proliferation. These results were verified in mouse orthotopic glioma xenografts and human glioma samples. In conclusion, the parallel structure of AS1411 allows it to bind to nucleolin and disrupt the exosome-miRNA-27a-mediated reciprocal activation loop between glioma cells and astrocytes. Our results may help in the development of a novel approach to therapeutic modulation of the glioma microenvironment.

Bulk and single-cell RNA sequencing reveal the contribution of laminin γ2 -CD44 to the immune resistance in lymphocyte-infiltrated squamous lung cancer subtype

The high heterogeneity of lung squamous cell carcinomas (LUSC) and the complex tumor microenvironment lead to non-response to immunotherapy in many patients. Therefore, characterizing the heterogeneity of the tumor microenvironment in patients with LUSC and further exploring the immune features and molecular mechanisms that lead to immune resistance will help improve the efficacy of immunotherapy in such patients. Herein, we retrospectively analyzed the RNA sequencing (RNA-seq) data of 513 LUSC samples with other multiomics and single-cell RNA-seq data and validated key features using multiplex immunohistochemistry. We divided these samples into six subtypes (CS1-CS6) based on the RNA-seq data and found that CS3 activates the immune response with a high level of lymphocyte infiltration and gathers a large number of patients with advanced-stage disease but increases the expression of exhausted markers cytotoxic T-lymphocyte associated protein 4, lymphocyte-activation gene 3, and programmed death-1. The prediction of the response to immunotherapy showed that CS3 is potentially resistant to immune checkpoint blockade therapy, and multi-omic data analysis revealed that CS3 specifically expresses immunosuppression-related proteins B cell lymphoma 2, GRB2-associated binding protein, and dual-specificity phosphatase 4 and has a high mutation ratio of the driver gene ATP binding cassette subfamily A member 13. Furthermore, single-cell RNA-seq verified lymphocyte infiltration in the CS3 subtype and revealed a positive relationship between the expression of LAMC2-CD44 and immune resistance. LAMC2 and CD44 are epithelial-mesenchymal transition-associated genes that modulate tumor proliferation, and multicolor immunofluorescence validated the negative relationship between the expression of LAMC2-CD44 and immune infiltration. Thus, we identified a lymphocyte-infiltrated subtype (CS3) in patients with LUSC that exhibited resistance to immune checkpoint blockade therapy, and the co-hyperexpression of LAMC2-CD44 contributed to immune resistance, which could potentially improve immunological efficacy by targeting this molecule pair in combination with immunotherapy.

PRL1 and PRL3 promote macropinocytosis via its lipid phosphatase activity

PRL1 and PRL3, members of the protein tyrosine phosphatase family, have been associated with cancer metastasis and poor prognosis. Despite extensive research on their protein phosphatase activity, their potential role as lipid phosphatases remains elusive. Methods: We conducted comprehensive investigations to elucidate the lipid phosphatase activity of PRL1 and PRL3 using a combination of cellular assays, biochemical analyses, and protein interactome profiling. Functional studies were performed to delineate the impact of PRL1/3 on macropinocytosis and its implications in cancer biology. Results: Our study has identified PRL1 and PRL3 as lipid phosphatases that interact with phosphoinositide (PIP) lipids, converting PI(3,4)P2 and PI(3,5)P2 into PI(3)P on the cellular membranes. These enzymatic activities of PRLs promote the formation of membrane ruffles, membrane blebbing and subsequent macropinocytosis, facilitating nutrient extraction, cell migration, and invasion, thereby contributing to tumor development. These enzymatic activities of PRLs promote the formation of membrane ruffles, membrane blebbing and subsequent macropinocytosis. Additionally, we found a correlation between PRL1/3 expression and glioma development, suggesting their involvement in glioma progression. Conclusions: Combining with the knowledge that PRLs have been identified to be involved in mTOR, EGFR and autophagy, here we concluded the physiological role of PRL1/3 in orchestrating the nutrient sensing, absorbing and recycling via regulating macropinocytosis through its lipid phosphatase activity. This mechanism could be exploited by tumor cells facing a nutrient-depleted microenvironment, highlighting the potential therapeutic significance of targeting PRL1/3-mediated macropinocytosis in cancer treatment.

Downregulation of INPP4B is Associated with Poor Prognosis in Epithelial Ovarian Carcinoma

Background

INPP4B is a tyrosine-specific phosphatase in the human body, which plays an important role in the developing process of carcinogenesis. However, The correlation between INPP4B and epithelial ovarian cancer is rarely explored. In this study, the expression of INPP4B in human epithelial ovarian carcinoma and normal ovaries was detected, to explore the correlation between INPP4B expression and clinicopathological risk factors of epithelial ovarian carcinoma and to clarify its significance in the developing process of and prognosis of epithelial ovarian carcinoma.

Methods

The expression of INPP4B in various tumors was detected by bioinformatics method, and the expression in epithelial ovarian cancer and normal control group was detected by Elisa. The immunohistochemical method was used in this experiment to analyze the expression of INPP4B in specimens of 100 cases of epithelial ovarian carcinoma and 20 cases of normal ovaries. Analysis of clinicopathological risk factors and related survival analysis was carried out on the expression of INPP4B in 100 cases of epithelial ovarian carcinoma.

Results

The results showed that the positive expressed INPP4B protein in epithelial ovarian carcinoma was significantly less, compared with that in normal ovaries (P < 0.05). The expression of INPP4B was significantly associated with many clinicopathologic factors, such as tumor differentiation (P < 0.001), FIGO stage (P < 0.001), lymph node metastasis (P < 0.001) and distant metastasis at recurrence (P=0. 009), but not with age, pathologic type of tumor, serum CA125 at recurrence and chemotherapy sensitivity.

Conclusion

In epithelial ovarian carcinoma, there is a downregulation of INPP4B expression, which may be related to poor tumor differentiation, late FIGO stage, lymph node metastasis, distant metastasis at recurrence and insensitivity to chemotherapy. Under-expression of INPP4B, lymph node metastasis, FIGO stage, and distant metastasis at recurrence are factors of poor prognostic. The under-expression level of INPP4B may be involved in the progression of epithelial ovarian carcinoma.

Inositol phosphatase INPP4B sustains ILC1s and intratumoral NK cells through an AKT-driven pathway

Innate lymphoid cells (ILCs) are a heterogeneous population of lymphocytes that coordinate early immune responses and maintain tissue homeostasis. Type 1 innate immune responses are mediated by natural killer (NK) cells and group 1 ILCs (ILC1s). Despite their shared features, NK cells and ILC1s display profound differences among various tissue microenvironments. Here, we identify the inositol polyphosphatase INPP4B as a hallmark feature of tissue-resident ILC1s and intratumoral NK cells using an scRNA-seq atlas of tissue-associated and circulating NK/ILC1s. Conditional deletion of Inpp4b in ILC1s and NK cells reveals that it is necessary for the homeostasis of tissue-resident ILC1s but not circulating NK cells at steady-state. Inpp4b-deficient cells display increased rates of apoptosis and reduced activation of the prosurvival molecule AKT. Furthermore, expression of Inpp4b by NK/ILC1s is necessary for their presence in the intratumoral environment, and lack of Inpp4b impairs antitumor immunity. These findings highlight INPP4B as a novel regulator of tissue residency and antitumor function in ILC1s and NK cells.

Predictive, preventive, and personalized medicine in breast cancer: targeting the PI3K pathway

Breast cancer (BC) is a multifaceted disease characterized by distinct molecular subtypes and varying responses to treatment. In BC, the phosphatidylinositol 3-kinase (PI3K) pathway has emerged as a crucial contributor to the development, advancement, and resistance to treatment. This review article explores the implications of the PI3K pathway in predictive, preventive, and personalized medicine for BC. It emphasizes the identification of predictive biomarkers, such as PIK3CA mutations, and the utility of molecular profiling in guiding treatment decisions. The review also discusses the potential of targeting the PI3K pathway for preventive strategies and the customization of therapy based on tumor stage, molecular subtypes, and genetic alterations. Overcoming resistance to PI3K inhibitors and exploring combination therapies are addressed as important considerations. While this field holds promise in improving patient outcomes, further research and clinical trials are needed to validate these approaches and translate them into clinical practice.

A new role for phosphoinositides in regulating mitochondrial dynamics

Phosphoinositides are a minor group of membrane-associated phospholipids that are transiently generated on the cytoplasmic leaflet of many organelle membranes and the plasma membrane. There are seven functionally distinct phosphoinositides, each derived via the reversible phosphorylation of phosphatidylinositol in various combinations on the inositol ring. Their generation and termination is tightly regulated by phosphatidylinositol-kinases and -phosphatases. These enzymes can function together in an integrated and coordinated manner, whereby the phosphoinositide product of one enzyme may subsequently serve as a substrate for another to generate a different phosphoinositide species. This regulatory mechanism not only enables the transient generation of phosphoinositides on membranes, but also more complex sequential or bidirectional conversion pathways, and phosphoinositides can also be transferred between organelles via membrane contacts. It is this capacity to fine-tune phosphoinositide signals that makes them ideal regulators of membrane organization and dynamics, through their recruitment of signalling, membrane altering and lipid transfer proteins. Research spanning several decades has provided extensive evidence that phosphoinositides are major gatekeepers of membrane organization, with roles in endocytosis, exocytosis, autophagy, lysosome dynamics, vesicular transport and secretion, cilia, inter-organelle membrane contact, endosome maturation and nuclear function. By contrast, there has been remarkably little known about the role of phosphoinositides at mitochondria - an enigmatic and major knowledge gap, with challenges in reliably detecting phosphoinositides at this site. Here we review recent significant breakthroughs in understanding the role of phosphoinositides in regulating mitochondrial dynamics and metabolic function.

Cavin1 activates the Wnt/β-catenin pathway to influence the proliferation and migration of hepatocellular carcinoma

INTRODUCTION AND OBJECTIVES

Cavin1 is a cell membrane caveolin, with controversial function in different tumors. Meanwhile, the role of Cavin1 in hepatocellular carcinoma (HCC) progression remains unclear. In this study, we attempted to elucidate the significance of Cavin1 in HCC occurrence and progression.

MATERIALS AND METHODS

Cavin1 content was examined in HCC tissues and paired adjacent normal liver tissues by qRT-PCR and IHC among 81 HCC patients. The Cavin1-mediated regulation of HCC proliferation and metastasis was assessed through in vitro and in vivo experiments. Finally, using GSEA, we found out Cavin1 could be a potential regulator of the Wnt pathway. The alterations of the Wnt pathway-related proteins were identified by Western Blot analysis.

RESULTS

Cavin1 was lower expressed in HCC, which implied poor survival outcomes in HCC patients. Phenotypic experiments revealed that Cavin1 strongly suppressed HCC proliferation and migration in vitro and in vivo. Besides, altered epithelial-mesenchymal transition (EMT)-related protein expressions were detected. Based on our GSEA analysis, Cavin1 activated the Wnt pathway, and Western Blot analysis revealed diminished β-catenin, c-Myc, and MMP9 contents upon Cavin1 overexpression.

CONCLUSIONS

Cavin1 suppresses HCC progression by modulating HCC proliferation and migration via inhibiting the Wnt/β-catenin axis activation.

Distinct mouse models of Stargardt disease display differences in pharmacological targeting of ceramides and inflammatory responses

Mutations in many visual cycle enzymes in photoreceptors and retinal pigment epithelium (RPE) cells can lead to the chronic accumulation of toxic retinoid byproducts, which poison photoreceptors and the underlying RPE if left unchecked. Without a functional ATP-binding cassette, sub-family A, member 4 (ABCA4), there is an elevation of all-trans-retinal and prolonged buildup of all-trans-retinal adducts, resulting in a retinal degenerative disease known as Stargardt-1 disease. Even in this monogenic disorder, there is significant heterogeneity in the time to onset of symptoms among patients. Using a combination of molecular techniques, we studied Abca4 knockout (simulating human noncoding disease variants) and Abca4 knock-in mice (simulating human misfolded, catalytically inactive protein variants), which serve as models for Stargardt-1 disease. We compared the two strains to ascertain whether they exhibit differential responses to agents that affect cytokine signaling and/or ceramide metabolism, as alterations in either of these pathways can exacerbate retinal degenerative phenotypes. We found different degrees of responsiveness to maraviroc, a known immunomodulatory CCR5 antagonist, and to the ceramide-lowering agent AdipoRon, an agonist of the ADIPOR1 and ADIPOR2 receptors. The two strains also display different degrees of transcriptional deviation from matched WT controls. Our phenotypic comparison of the two distinct Abca4 mutant-mouse models sheds light on potential therapeutic avenues previously unexplored in the treatment of Stargardt disease and provides a surrogate assay for assessing the effectiveness for genome editing.

Regulation of B-1 cell numbers and B cell-mediated antibody production by Inpp4b

T and B lymphocytes are crucial players in cellular and humoral immune responses. The development, activation and differentiation of T and B lymphocytes are regulated by the best characterized PI3K-PI (3,4,5) P3-AKT phosphoinositide signalling pathway. As a branch of the phosphoinositide signalling pathway, the lipid phosphatase INPP4B inhibits AKT activation through degrading the phosphoinositide signalling messenger PI (3,4) P2. However, the role of Inpp4b in T and B lymphocytes remains elusive. Here, we reported that Inpp4b was highly expressed in human and murine T- and B-1 lymphocytes. Despite its higher expression in T lymphocytes, neither T cell development and homeostasis nor in vitro T cell activation and CD4+ T cell differentiation were altered upon loss of Inpp4b. Interestingly, combined direct phenotype analysis of Inpp4b conventional knockout mice and adoptive transfer studies revealed that ablation of Inpp4b intrinsically reduced peritoneal B-1 cells rather B-2 cells. Moreover, Inpp4b deficiency led to impaired thymus independent (TI) and thymus dependent (TD) antigens-induced antibody production. Further in vitro analysis revealed that CD40-mediated B cell proliferation was impaired upon ablation of Inpp4b. Our findings reveal that Inpp4b is required in regulating B-1 cell numbers and B cell-mediated antibody production.

SEPTIN3 Promotes Progression of Triple-Negative Breast Cancer via Activating Wnt Pathway

Background

There is a lack of targeted therapies for triple-negative breast cancer (TNBC), necessitating the search for novel targets. Patients with TNBC exhibit elevated expression of neuron-specific septin-3 (SEPTIN3), leading to poor prognosis. This study aimed to investigate the modulation of SEPTIN3 expression in TNBC cells.

Methods

The relative expression levels of SEPTIN3 in TNBC tissues and cell lines were determined using Western blotting and qRT-PCR. We generated lentivirally transduced TNBC cell lines so such that SEPTIN3 was overexpressed or knocked down. Next, the effect of SEPTIN3 on the biological behavior of TNBC cells was detected using a series of functional assays, including CCK8, colony formation, scratch, and transwell assays. We monitored the tumorigenicity of SEPTIN3 overexpressed cells and performed Ki-67 immunostaining in mice. The mechanism mediated by SEPTIN3 was studied using functional enrichment analysis and Western blotting.

Results

Protein and mRNA expression levels of SEPTIN3 were observed to be increased in TNBC tissues and cell lines. SEPTIN3 knockdown reduced cell growth, invasion, and migration, whereas SEPTIN3 overexpression exerted the opposite effects. SEPTIN3 was observed to favor cell growth and tumorigenicity in vivo. In addition, SEPTIN3 promoted TNBC cell aggressiveness and proliferation via activation of the Wnt signaling pathway.

Conclusion

SEPTIN3 emerged as an oncogene that accelerates tumor progression by regulating the Wnt signaling pathway.

Phosphoinositides in New Spaces

Phosphoinositides (PIs) are phospholipids derived from phosphatidylinositol. PIs are regulated via reversible phosphorylation, which is directed by the opposing actions of PI kinases and phosphatases. PIs constitute a minor fraction of the total cellular lipid pool but play pleiotropic roles in multiple aspects of cell biology. Genetic mutations of PI regulatory enzymes have been identified in rare congenital developmental syndromes, including ciliopathies, and in numerous human diseases, such as cancer and metabolic and neurological disorders. Accordingly, PI regulatory enzymes have been targeted in the design of potential therapeutic interventions for human diseases. Recent advances place PIs as central regulators of membrane dynamics within functionally distinct subcellular compartments. This brief review focuses on the emerging role PIs play in regulating cell signaling within the primary cilium and in directing transfer of molecules at interorganelle membrane contact sites and identifies new roles for PIs in subcellular spaces.

The mechanisms of class 1A PI3K and Wnt/β-catenin coupled signaling in breast cancer

The class IA PI3K signaling pathway is activated by growth factor stimulation and regulates a signaling cascade that promotes diverse events including cell growth, proliferation, migration and metabolism. PI3K signaling is one of the most commonly hyperactivated pathways in breast cancer, leading to increased tumor growth and progression. PI3K hyperactivation occurs via a number of genetic and epigenetic mechanisms including mutation or amplification of PIK3CA, the gene encoding the p110α subunit of PI3Kα, as well as via dysregulation of the upstream growth factor receptors or downstream signaling effectors. Over the past decade, extensive efforts to develop therapeutics that suppress oncogenic PI3K signaling have been undertaken. Although FDA-approved PI3K inhibitors are now emerging, their clinical success remains limited due to adverse effects and negative feedback mechanisms which contribute to their reduced efficacy. There is an emerging body of evidence demonstrating crosstalk between the PI3K and Wnt/β-catenin pathways in breast cancer. However, PI3K exhibits opposing effects on Wnt/β-catenin signaling in distinct tumor subsets, whereby PI3K promotes Wnt/β-catenin activation in ER+ cancers, but paradoxically suppresses this pathway in ER- breast cancers. This review discusses the molecular mechanisms for PI3K-Wnt crosstalk in breast cancer, and how Wnt-targeted therapies have the potential to contribute to treatment regimens for breast cancers with PI3K dysregulation.

Deterministic early endosomal maturations emerge from a stochastic trigger-and-convert mechanism

Endosomal maturation is critical for robust and timely cargo transport to specific cellular compartments. The most prominent model of early endosomal maturation involves a phosphoinositide-driven gain or loss of specific proteins on individual endosomes, emphasising an autonomous and stochastic description. However, limitations in fast, volumetric imaging long hindered direct whole cell-level measurements of absolute numbers of maturation events. Here, we use lattice light-sheet imaging and bespoke automated analysis to track individual very early (APPL1-positive) and early (EEA1-positive) endosomes over the entire population, demonstrating that direct inter-endosomal contact drives maturation between these populations. Using fluorescence lifetime, we show that this endosomal interaction is underpinned by asymmetric binding of EEA1 to very early and early endosomes through its N- and C-termini, respectively. In combination with agent-based simulation which supports a 'trigger-and-convert' model, our findings indicate that APPL1- to EEA1-positive maturation is driven not by autonomous events but by heterotypic EEA1-mediated interactions, providing a mechanism for temporal and population-level control of maturation.

Wnt/β-catenin signaling pathway-a versatile player in apoptosis and autophagy

The Wnt/β-catenin signaling pathway is a highly conserved pathway that is involved in cell development, proliferation, differentiation, apoptosis and autophagy. Among these processes, apoptosis and autophagy occur physiologically during host defense and the maintenance of intracellular homeostasis. Mounting evidence suggests that the crosstalk between Wnt/β-catenin-regulated apoptosis and autophagy has broad functional significance in various diseases. Herein, we summarize the recent studies in understanding the role of the Wnt/β-catenin signaling pathway in apoptosis and autophagy, and draw the following conclusions: a) For apoptosis, the regulation of Wnt/β-catenin is generally positive. However, a small amount of evidence indicates the presence of a negatively regulated relationship between Wnt/β-catenin and apoptosis; b) Wnt/β-catenin influences the occurrence and development of autophagy by regulating autophagy-related factors, and these factors in turn affect Wnt/β-catenin pathway; c) Wnt/β-catenin always balances the molecular damage caused by the crosstalk between autophagy and apoptosis in a compensatory manner. Understanding the specific role of the Wnt/β-catenin signaling pathway during different stages of autophagy and apoptosis may provide new insights into the progression of related diseases regulated by the Wnt/β-catenin signaling pathway.

The FDA-Approved Drug Pyrvinium Selectively Targets ER+ Breast Cancer Cells with High INPP4B Expression

The majority of breast cancers are estrogen receptor-positive (ER⁺), and endocrine therapies that suppress ER signaling are the standard-of-care treatment for this subset. However, up to half of all ER⁺ cancers eventually relapse, highlighting a need for improved clinical therapies. The phosphoinositide phosphatase, INPP4B, is overexpressed in almost half of all ER⁺ breast cancers, and promotes Wnt/β-catenin signaling, cell proliferation and tumor growth. Here, using cell viability assays, we report that INPP4B overexpression does not affect the sensitivity of ER⁺ breast cancer cells to standard-of-care treatments including the anti-estrogen 4-hydroxytamoxifen (4-OHT) or the PI3Kα inhibitor alpelisib. Examination of four small molecule Wnt inhibitors revealed that ER⁺ breast cancer cells with INPP4B overexpression were more sensitive to the FDA-approved drug pyrvinium and a 4-OHT-pyrvinium combination treatment. Using 3D culture models, we demonstrated that pyrvinium selectively reduced the size of INPP4B-overexpressing ER⁺ breast cancer spheroids in the presence and absence of 4-OHT. These findings suggest that repurposing pyrvinium as a Wnt inhibitor may be an effective therapeutic strategy for human ER⁺ breast cancers with high INPP4B levels.

Nanomaterial-assisted CRISPR gene-engineering - A hallmark for triple-negative breast cancer therapeutics advancement

Triple-negative breast cancer (TNBC) is the most violent class of tumor and accounts for 20–24% of total breast carcinoma, in which frequently rare mutation occurs in high frequency. The poor prognosis, recurrence, and metastasis in the brain, heart, liver and lungs decline the lifespan of patients by about 21 months, emphasizing the need for advanced treatment. Recently, the adaptive immunity mechanism of archaea and bacteria, called clustered regularly interspaced short palindromic repeats (CRISPR) combined with nanotechnology, has been utilized as a potent gene manipulating tool with an extensive clinical application in cancer genomics due to its easeful usage and cost-effectiveness. However, CRISPR/Cas are arguably the efficient technology that can be made efficient via organic material-assisted approaches. Despite the efficacy of the CRISPR/Cas@nano complex, problems regarding successful delivery, biodegradability, and toxicity remain to render its medical implications. Therefore, this review is different in focus from past reviews by (i) detailing all possible genetic mechanisms of TNBC occurrence; (ii) available treatments and gene therapies for TNBC; (iii) overview of the delivery system and utilization of CRISPR-nano complex in TNBC, and (iv) recent advances and related toxicity of CRISPR-nano complex towards clinical trials for TNBC.

Aging-related features predict prognosis and immunotherapy efficacy in hepatocellular carcinoma

The aging microenvironment serves important roles in cancers. However, most studies focus on circumscribed hot spots such as immunity and metabolism. Thus, it is well ignored that the aging microenvironment contributes to the proliferation of tumor. Herein, we established three prognosis-distinctive aging microenvironment subtypes, including AME1, AME2, and AME3, based on aging-related genes and characterized them with “Immune Exclusion,” “Immune Infiltration,” and “Immune Intermediate” features separately. AME2-subtype tumors were characterized by specific activation of immune cells and were most likely to be sensitive to immunotherapy. AME1-subtype tumors were characterized by inhibition of immune cells with high proportion of Catenin Beta 1 (CTNNB1) mutation, which was more likely to be insensitive to immunotherapy. Furthermore, we found that CTNNB1 may inhibit the expression of C-C Motif Chemokine Ligand 19 (CCL19), thus restraining immune cells and attenuating the sensitivity to immunotherapy. Finally, we also established a robust aging prognostic model to predict the prognosis of patients with hepatocellular carcinoma. Overall, this research promotes a comprehensive understanding about the aging microenvironment and immunity in hepatocellular carcinoma and may provide potential therapeutic targets for immunotherapy.

Endosome maturation links PI3Kα signaling to lysosome repopulation during basal autophagy

Autophagy depends on the repopulation of lysosomes to degrade intracellular components and recycle nutrients. How cells co‐ordinate lysosome repopulation during basal autophagy, which occurs constitutively under nutrient‐rich conditions, is unknown. Here, we identify an endosome‐dependent phosphoinositide pathway that links PI3Kα signaling to lysosome repopulation during basal autophagy. We show that PI3Kα‐derived PI(3)P generated by INPP4B on late endosomes was required for basal but not starvation‐induced autophagic degradation. PI(3)P signals were maintained as late endosomes matured into endolysosomes, and served as the substrate for the 5‐kinase, PIKfyve, to generate PI(3,5)P₂. The SNX‐BAR protein, SNX2, was recruited to endolysosomes by PI(3,5)P₂ and promoted lysosome reformation. Inhibition of INPP4B/PIKfyve‐dependent lysosome reformation reduced autophagic clearance of protein aggregates during proteotoxic stress leading to increased cytotoxicity. Therefore under nutrient‐rich conditions, PI3Kα, INPP4B, and PIKfyve sequentially contribute to basal autophagic degradation and protection from proteotoxic stress via PI(3,5)P₂‐dependent lysosome reformation from endolysosomes. These findings reveal that endosome maturation couples PI3Kα signaling to lysosome reformation during basal autophagy.

Inhibition of lipid kinase PIKfyve reveals a role for phosphatase Inpp4b in the regulation of PI(3)P-mediated lysosome dynamics through VPS34 activity

Lysosome membranes contain diverse phosphoinositide (PtdIns) lipids that coordinate lysosome function and dynamics. The PtdIns repertoire on lysosomes is tightly regulated by the actions of diverse PtdIns kinases and phosphatases; however, specific roles for PtdIns in lysosomal functions and dynamics are currently unclear and require further investigation. It was previously shown that PIKfyve, a lipid kinase that synthesizes PtdIns(3,5)P₂ from PtdIns(3)P, controls lysosome "fusion-fission" cycle dynamics, autophagosome turnover, and endocytic cargo delivery. Furthermore, INPP4B, a PtdIns 4-phosphatase that hydrolyzes PtdIns(3,4)P₂ to form PtdIns(3)P, is emerging as a cancer-associated protein with roles in lysosomal biogenesis and other lysosomal functions. Here, we investigated the consequences of disrupting PIKfyve function in Inpp4b-deficient mouse embryonic fibroblasts. Through confocal fluorescence imaging, we observed the formation of massively enlarged lysosomes, accompanied by exacerbated reduction of endocytic trafficking, disrupted lysosome fusion-fission dynamics, and inhibition of autophagy. Finally, HPLC scintillation quantification of ³H-myo-inositol labelled phosphoinositides and phosphoinositide immunofluorescence staining, we observed that lysosomal PtdIns(3)P levels were significantly elevated in Inpp4b-deficient cells due to the hyperactivation of phosphatidylinositol 3-kinase catalytic subunit VPS34 enzymatic activity. In conclusion, our study identifies a novel signaling axis that maintains normal lysosomal homeostasis and dynamics, which includes the catalytic functions of Inpp4b, PIKfyve, and VPS34.

Breast Cancer Genomics: Primary and Most Common Metastases

Specific genomic alterations have been found in primary breast cancer involving driver mutations that result in tumorigenesis. Metastatic breast cancer, which is uncommon at the time of disease onset, variably impacts patients throughout the course of their disease. Both the molecular profiles and diverse genomic pathways vary in the development and progression of metastatic breast cancer. From the most common metastatic site (bone), to the rare sites such as orbital, gynecologic, or pancreatic metastases, different levels of gene expression indicate the potential involvement of numerous genes in the development and spread of breast cancer. Knowledge of these alterations can, not only help predict future disease, but also lead to advancement in breast cancer treatments. This review discusses the somatic landscape of breast primary and metastatic tumors.

Inositol Polyphosphate 4-Phosphatase Type II Is a Tumor Suppressor in Multiple Myeloma

Inositol polyphosphate-4-phosphatase type II (INPP4B) has been identified as a tumor suppressor, while little is known about its expression and function in multiple myeloma (MM). In this study, we evaluated the expression of INPP4B in 28 cases of newly diagnosed MM patients and 42 cases of extramedullary plasmacytoma (EMP) patients compared with normal plasma cells and found that low INPP4B expression was correlated with poor outcomes in MM patients. Moreover, expression of INPP4B in seven MM cell lines was all lower than that in normal plasma cells. In addition, loss of function of INPP4B promoted cell proliferation in MM cells; however, gain of function suppressed MM cells proliferation and arrested the cell cycle at G0/G1 phage. Meanwhile, knockdown of INPP4B enhanced resistance, but overexpression promoted sensitivity to bortezomib treatment in MM cells. Mechanistically, we found that INPP4B exerted its role via inhibiting the phosphorylation of Akt at lysine 473 but not threonine 308, which attenuated the activation of the PI3K/Akt/mammalian target of rapamycin (mTOR) signaling pathway. Therefore, we identified an inhibitory effect of INPP4B in MM, and our findings suggested that loss of INPP4B expression is a risk factor of aggressive MM.

A Highly Sensitive Fluorescent Akt Biosensor Reveals Lysosome-Selective Regulation of Lipid Second Messengers and Kinase Activity

The serine/threonine protein kinase Akt regulates a wide range of cellular functions via phosphorylation of various substrates distributed throughout the cell, including at the plasma membrane and endomembrane compartments. Disruption of compartmentalized Akt signaling underlies the pathology of many diseases such as cancer and diabetes. However, the specific spatial organization of Akt activity and the underlying regulatory mechanisms, particularly the mechanism controlling its activity at the lysosome, are not clearly understood. We developed a highly sensitive excitation-ratiometric Akt activity reporter (ExRai-AktAR2), enabling the capture of minute changes in Akt activity dynamics at subcellular compartments. In conjunction with super-resolution expansion microscopy, we found that growth factor stimulation leads to increased colocalization of Akt with lysosomes and accumulation of lysosomal Akt activity. We further showed that 3-phosphoinositides (3-PIs) accumulate on the lysosomal surface, in a manner dependent on dynamin-mediated endocytosis. Importantly, lysosomal 3-PIs are needed for growth-factor-induced activities of Akt and mechanistic target of rapamycin complex 1 (mTORC1) on the lysosomal surface, as targeted depletion of 3-PIs has detrimental effects. Thus, 3-PIs, a class of critical lipid second messengers that are typically found in the plasma membrane, unexpectedly accumulate on the lysosomal membrane in response to growth factor stimulation, to direct the multifaceted kinase Akt to organize lysosome-specific signaling.

A late endosome signaling hub that couples PI3Kα and WNT/β-catenin signaling in breast cancer

AKT is the central phosphoinositide 3-kinase (PI3K) signaling effector, however, PIK3CA (p110α subunit of PI3Kα)-mutant estrogen receptor-positive (ER⁺) breast cancers exhibit minimal AKT activation and the downstream signaling is poorly characterized. We discovered that a subset of PIK3CA-mutant ER⁺ breast cancers exhibit increased inositol polyphosphate 4-phosphatase type II (INPP4B) expression, which promotes late endosome formation and glycogen synthase kinase 3 beta (GSK3β) trafficking, leading to enhanced Wingless-related integration site (WNT)/catenin beta 1 (β-catenin) activation.

Targeting PI3K/AKT/mTOR Signaling Pathway in Breast Cancer

Breast cancer is the most frequently diagnosed cancer and the primary cause of cancer death in women worldwide. Although early diagnosis and cancer growth inhibition has significantly improved breast cancer survival rate over the years, there is a current need to develop more effective systemic treatments to prevent metastasis. One of the most commonly altered pathways driving breast cancer cell growth, survival, and motility is the PI3K/AKT/mTOR signaling cascade. In the past 30 years, a great surge of inhibitors targeting these key players has been developed at a rapid pace, leading to effective preclinical studies for cancer therapeutics. However, the central role of PI3K/AKT/mTOR signaling varies among diverse biological processes, suggesting the need for more specific and sophisticated strategies for their use in cancer therapy. In this review, we provide a perspective on the role of the PI3K signaling pathway and the most recently developed PI3K-targeting breast cancer therapies.

Cell Biology of Canonical Wnt Signaling

Wnt signaling has multiple functions beyond the transcriptional effects of β-catenin stabilization. We review recent investigations that uncover new cell physiological effects through the regulation of Wnt receptor endocytosis, Wnt-induced stabilization of proteins (Wnt-STOP), macropinocytosis, increase in lysosomal activity, and metabolic changes. Many of these growth-promoting effects of canonical Wnt occur within minutes and are independent of new protein synthesis. A key element is the sequestration of glycogen synthase kinase 3 (GSK3) inside multivesicular bodies and lysosomes. Twenty percent of human proteins contain consecutive GSK3 phosphorylation motifs, which in the absence of Wnt can form phosphodegrons for polyubiquitination and proteasomal degradation. Wnt signaling by either the pharmacological inhibition of GSK3 or the loss of tumor-suppressor proteins, such as adenomatous polyposis coli (APC) and Axin1, increases lysosomal acidification, anabolic metabolites, and macropinocytosis, which is normally repressed by the GSK3-Axin1-APC destruction complex. The combination of these cell physiological effects drives cell growth. Expected final online publication date for the Annual Review of Cell and Developmental Biology, Volume 37 is October 2021. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.