Intracellular CD24 disrupts the ARF-NPM interaction and enables mutational and viral oncogene-mediated p53 inactivation

SIRT7 promotes lung cancer progression by destabilizing the tumor suppressor ARF

Sirtuin 7 (SIRT7) is a member of the mammalian family of nicotinamide adenine dinucleotide (NAD+)-dependent histone/protein deacetylases, known as sirtuins. It acts as a potent oncogene in numerous malignancies, but the molecular mechanisms employed by SIRT7 to sustain lung cancer progression remain largely uncharacterized. We demonstrate that SIRT7 exerts oncogenic functions in lung cancer cells by destabilizing the tumor suppressor alternative reading frame (ARF). SIRT7 directly interacts with ARF and prevents binding of ARF to nucleophosmin, thereby promoting proteasomal-dependent degradation of ARF. We show that SIRT7-mediated degradation of ARF increases expression of protumorigenic genes and stimulates proliferation of non-small-cell lung cancer (NSCLC) cells both in vitro and in vivo in a mouse xenograft model. Bioinformatics analysis of transcriptome data from human lung adenocarcinomas revealed a correlation between SIRT7 expression and increased activity of genes normally repressed by ARF. We propose that disruption of SIRT7-ARF signaling stabilizes ARF and thus attenuates cancer cell proliferation, offering a strategy to mitigate NSCLC progression.

LncRNA IL21-AS1 facilitates tumour progression by enhancing CD24-induced phagocytosis inhibition and tumorigenesis in ovarian cancer

CD24 is overexpressed in various tumours and considered a regulator of cell migration, invasion, and proliferation. Recent studies have found that CD24 on ovarian cancer (OC) and triple-negative breast cancer cells interacts with the inhibitory receptor sialic-acid-binding Ig-like lectin 10 (Siglec-10) on tumour-associated macrophages (TAMs) to inhibit phagocytosis by macrophages. Because of its multiple roles in regulating the immune response and tumorigenesis, CD24 is a very promising therapeutic target. However, the regulatory mechanism of CD24 in OC remains unclear. Here, we found that the long noncoding RNA (lncRNA) IL21-AS1, which was upregulated in OC, inhibited macrophage-mediated phagocytosis and promoted OC cell proliferation and apoptosis inhibition. More importantly, after IL21-AS1 knockdown, a significant survival advantage was observed in mice engrafted with tumours. Mechanistically, we identified IL21-AS1 as a hypoxia-induced lncRNA. Moreover, IL21-AS1 increased HIF1α-induced CD24 expression under hypoxic conditions. In parallel, we found that IL21-AS1 acted as a competing endogenous RNA (ceRNA) for miR-561-5p to regulate CD24 expression. Finally, IL21-AS1 increased CD24 expression in OC and facilitated OC progression. Our findings provide a molecular basis for the regulation of CD24, thus highlighting a potential strategy for targeted treatment of OC.

CD24 induced cellular quiescence-like state and chemoresistance in ovarian cancer cells via miR-130a/301a-dependent CDK19 downregulation

Cancer stem-like cell (CSC) is thought to be responsible for ovarian cancer recurrence. CD24 serves as a CSC marker for ovarian cancer and regulates the expression of miRNAs, which are regulators of CSC phenotypes. Therefore, CD24-regulated miRNAs may play roles in manifesting the CSC phenotypes in ovarian cancer cells. Our miRNA transcriptome analysis showed that 94 miRNAs were up or down-regulated in a CD24-high clone from an ovarian cancer patient compared to a CD24-low one. The CD24-dependent expression trend of the top 7 upregulated miRNAs (miR-199a-3p, 34c, 199a-5p, 130a, 301a, 214, 34b*) was confirmed in other 8 clones (4 clones for each group). CD24 overexpression upregulated the expression of miR-199a-3p, 34c, 199a-5p, 130a, 301a, 214, and 34b* in TOV112D (CD24-low) cells compared to the control, while CD24 knockdown downregulated the expression of miR-199a-3p, 199a-5p, 130a, 301a, and 34b* in OV90 (CD24-high) cells. miR-130a and 301a targeted CDK19, which induced a cellular quiescence-like state (increased G0/G1 phase cell population, decreased cell proliferation, decreased colony formation, and decreased RNA synthesis) and resistance to platinum-based chemotherapeutic agents. CD24 regulated the expression of miR-130a and 301a via STAT4 and YY1 phosphorylation mediated by Src and FAK. miR-130a and 301a were positively correlated in expression with CD24 in ovarian cancer patient tissues and negatively correlated with CDK19. Our results showed that CD24 expression may induce a cellular quiescence-like state and resistance to platinum-based chemotherapeutic agents in ovarian cancer via miR-130a and 301a upregulation. CD24-miR-130a/301a-CDK19 signaling axis could be a prognostic marker for or a potential therapeutic target against ovarian cancer recurrence.

Targeting CD24/Siglec-10 signal pathway for cancer immunotherapy: recent advances and future directions

The small, heavily glycosylated protein CD24 is primarily expressed by many immune cells and is highly expressed mostly in cancer cells. As one of the most crucial biomarkers of cancers, CD24 is frequently highly expressed in solid tumors, while tumor-associated macrophages express Siglec-10 at high levels, Siglec-10 and CD24 can interact on innate immune cells to lessen inflammatory responses to a variety of disorders. Inhibiting inflammation brought on by SHP-1 and/or SHP-2 phosphatases as well as cell phagocytosis by macrophages, the binding of CD24 to Siglec-10 can prevent toll-like receptor-mediated inflammation. Targeted immunotherapy with immune checkpoint inhibitors (ICI) has lately gained popularity as one of the best ways to treat different tumors. CD24 is a prominent innate immune checkpoint that may be a useful target for cancer immunotherapy. In recent years, numerous CD24/Siglec-10-related research studies have made tremendous progress. This study discusses the characteristics and workings of CD24/Siglec-10-targeted immunotherapy and offers a summary of current advances in CD24/Siglec-10-related immunotherapy research for cancer. We then suggested potential directions for CD24-targeted immunotherapy, basing our speculation mostly on the results of recent preclinical and clinical trials.

Targeting CD24 in Cancer Immunotherapy

Immunotherapy is a hot area in cancer treatment, and one of the keys to this therapy is the identification of the right tumour-associated or tumour-specific antigen. Cluster of differentiation 24 (CD24) is an emerging tumour-associated antigen that is commonly and highly expressed in various tumours. In addition, CD24 is associated with several cancer-related signalling pathways and closely interacts with other molecules and immune cells to influence tumour progression. Monoclonal antibodies, antibody-drug conjugates (ADCs), chimeric antigen receptor (CAR) T-cell therapy, and CAR-NK cell therapy are currently available for the treatment of CD24. In this review, we summarise the existing therapeutic approaches and possible future directions targeting CD24.

CD24 targeting with NK-CAR immunotherapy in testis, prostate, renal and (luminal-type) bladder cancer and identification of direct CD24 interaction partners

Alternative therapeutic options targeting urologic malignancies, such as germ cell tumours, as well as urothelial, renal and prostate carcinomas, are still urgently needed. The membrane protein CD24 represents a promising immunotherapeutical approach. The present study aimed to decipher the molecular function of CD24 in vitro and evaluate the cytotoxic capacity of a third-generation natural killer (NK) cell chimeric antigen receptor (CAR) against CD24 in urologic tumour cell lines. Up to 20 urologic tumour cell lines and several non-malignant control cells were included. XTT viability assays and annexin V/propidium iodide flow cytometry analyses were performed to measure cell viability and apoptosis rates, respectively. Co-immunoprecipitation followed by mass spectrometry analyses identified direct interaction partners of CD24. Luciferase reporter assays were used to functionally validate transactivation of CD24 expression by SOX2. N- and O-glycosylation of CD24 were evaluated by enzymatic digestion and mass spectrometry. The study demonstrates that SOX2 transactivates CD24 expression in embryonal carcinoma cells. In cells of different urological origins, CD24 interacted with proteins involved in cell adhesion, ATP binding, phosphoprotein binding and post-translational modifications, such as histone acetylation and ubiquitination. Treatment of urological tumour cells with NK-CD24-CAR cells resulted in a decreased cell viability and apoptosis induction specifically in CD24+ tumour cells. Limitations of the study include the in vitro setting, which still has to be confirmed in vivo. In conclusion, we show that CD24 is a promising novel target for immune therapeutic approaches targeting urologic malignancies.

CD24-Fc suppression of immune related adverse events in a therapeutic cancer vaccine model of murine neuroblastoma

Introduction

The combination of Myc-suppressed whole tumor cells with checkpoint inhibitors targeting CTLA-4 and PD-L1 generates a potent therapeutic cancer vaccine in a mouse neuroblastoma model. As immunotherapies translate from pre-clinical to clinical trials, the potential immune-related adverse events (irAEs) associated with induction of potent immunity must be addressed. The CD24-Siglec 10/G interaction is an innate checkpoint that abrogates inflammatory responses to molecules released by damaged cells, but its role in cancer immunology is not well defined. We investigate irAEs of an effective whole cell neuroblastoma vaccine and subsequently the effect of CD24-Fc, a CD24 and Fc fusion protein, on both the vaccine efficacy and induced irAEs in a mouse neuroblastoma model.

Methods

To test whether the whole tumor cell vaccination leads to autoimmune responses in other organ systems we harvested lung, heart, kidney and colon from naïve mice (n=3), unvaccinated tumor only mice (n=3), and vaccinated mice with CD24 Fc (n=12) or human IgG-Fc control (n=12) after tumor inoculation and vaccination therapy at day 30. The Immune cell infiltrates and immunogenic pathway signatures in different organ systems were investigated using NanoString Autoimmune Profiling arrays. Nanostring RNA transcript results were validated with immunohistochemistry staining.

Results

The whole tumor cell vaccine combined with immune checkpoint therapy triggers occult organ specific immune cell infiltrates, primarily in cardiac tissue and to a lesser extent in the renal and lung tissue, but not in the colon. CD24-Fc administration with vaccination partially impedes anti-tumor immunity but delaying CD24-Fc administration after initial vaccination reverses this effect. CD24-Fc treatment also ameliorates the autoimmune response induced by effective tumor vaccination in the heart.

Discussion

This study illustrates that the combination of Myc suppressed whole tumor cell vaccination with checkpoint inhibitors is an effective therapy, but occult immune infiltrates are induced in several organ systems in a mouse neuroblastoma model. The systemic administration of CD24-Fc suppresses autoimmune tissue responses, but appropriate timing of administration is critical for maintaining efficacy of the therapeutic vaccine.

CD24-Siglec interactions in inflammatory diseases

CD24 is a small glycosylphosphatidylinositol (GPI)-anchored glycoprotein with broad expression in multiple cell types. Due to differential glycosylation, cell surface CD24 have been shown to interact with various receptors to mediate multiple physiological functions. Nearly 15 years ago, CD24 was shown to interact with Siglec G/10 to selectively inhibit inflammatory response to tissue injuries. Subsequent studies demonstrate that sialylated CD24 (SialoCD24) is a major endogenous ligand for CD33-family of Siglecs to protect the host against inflammatory and autoimmune diseases, metabolic disorders and most notably respiratory distress in COVID-19. The discoveries on CD24-Siglec interactions propelled active translational research to treat graft-vs-host diseases, cancer, COVID-19 and metabolic disorders. This mini-review provides a succinct summary on biological significance of CD24-Siglec pathway in regulation of inflammatory diseases with emphasis on clinical translation.

Emerging phagocytosis checkpoints in cancer immunotherapy

Cancer immunotherapy, mainly including immune checkpoints-targeted therapy and the adoptive transfer of engineered immune cells, has revolutionized the oncology landscape as it utilizes patients' own immune systems in combating the cancer cells. Cancer cells escape immune surveillance by hijacking the corresponding inhibitory pathways via overexpressing checkpoint genes. Phagocytosis checkpoints, such as CD47, CD24, MHC-I, PD-L1, STC-1 and GD2, have emerged as essential checkpoints for cancer immunotherapy by functioning as "don't eat me" signals or interacting with "eat me" signals to suppress immune responses. Phagocytosis checkpoints link innate immunity and adaptive immunity in cancer immunotherapy. Genetic ablation of these phagocytosis checkpoints, as well as blockade of their signaling pathways, robustly augments phagocytosis and reduces tumor size. Among all phagocytosis checkpoints, CD47 is the most thoroughly studied and has emerged as a rising star among targets for cancer treatment. CD47-targeting antibodies and inhibitors have been investigated in various preclinical and clinical trials. However, anemia and thrombocytopenia appear to be formidable challenges since CD47 is ubiquitously expressed on erythrocytes. Here, we review the reported phagocytosis checkpoints by discussing their mechanisms and functions in cancer immunotherapy, highlight clinical progress in targeting these checkpoints and discuss challenges and potential solutions to smooth the way for combination immunotherapeutic strategies that involve both innate and adaptive immune responses.

TUBB4A interacts with MYH9 to protect the nucleus during cell migration and promotes prostate cancer via GSK3β/β-catenin signalling

Human tubulin beta class IVa (TUBB4A) is a member of the β-tubulin family. In most normal tissues, expression of TUBB4A is little to none, but it is highly expressed in human prostate cancer. Here we show that high expression levels of TUBB4A are associated with aggressive prostate cancers and poor patient survival, especially for African-American men. Additionally, in prostate cancer cells, TUBB4A knockout (KO) reduces cell growth and migration but induces DNA damage through increased γH2AX and 53BP1. Furthermore, during constricted cell migration, TUBB4A interacts with MYH9 to protect the nucleus, but either TUBB4A KO or MYH9 knockdown leads to severe DNA damage and reduces the NF-κB signaling response. Also, TUBB4A KO retards tumor growth and metastasis. Functional analysis reveals that TUBB4A/GSK3β binds to the N-terminal of MYH9, and that TUBB4A KO reduces MYH9-mediated GSK3β ubiquitination and degradation, leading to decreased activation of β-catenin signaling and its relevant epithelial-mesenchymal transition. Likewise, prostate-specific deletion of Tubb4a reduces spontaneous tumor growth and metastasis via inhibition of NF-κB, cyclin D1, and c-MYC signaling activation. Our results suggest an oncogenic role of TUBB4A and provide a potentially actionable therapeutic target for prostate cancers with TUBB4A overexpression.

The β-tubulin family protein TUBB4A is highly expressed in cancer but it’s molecular role is unclear. Here, the authors show that TUBB4A is required to protect the nucleus from genomic instability during migration and that it’s over expression promotes cancer progression.

Odontogenic MSC Heterogeneity: Challenges and Opportunities for Regenerative Medicine

Cellular heterogeneity refers to the genetic and phenotypic differences among cells, which reflect their various fate choices, including viability, proliferation, self-renewal probability, and differentiation into different lineages. In recent years, research on the heterogeneity of mesenchymal stem cells has made some progress. Odontogenic mesenchymal stem cells share the characteristics of mesenchymal stem cells, namely, good accessibility, low immunogenicity and high stemness. In addition, they also exhibit the characteristics of vasculogenesis and neurogenesis, making them attractive for tissue engineering and regenerative medicine. However, the usage of mesenchymal stem cell subgroups differs in different diseases. Furthermore, because of the heterogeneity of odontogenic mesenchymal stem cells, their application in tissue regeneration and disease management is restricted. Findings related to the heterogeneity of odontogenic mesenchymal stem cells urgently need to be summarized, thus, we reviewed studies on odontogenic mesenchymal stem cells and their specific subpopulations, in order to provide indications for further research on the stem cell regenerative therapy.

The microRNA-3622 family at the 8p21 locus exerts oncogenic effects by regulating the p53-downstream gene network in prostate cancer progression

For human prostate cancer, the chromosome 8p21 locus, which contains NKX3.1 and the microRNA (miR)-3622 family (miR-3622a/b), is a frequently deleted region. Thus, miR-3622 is proposed as a suppressor for prostate cancer, but its role remains debatable. In the present study, we found that expression of miR-3622a was lower, whereas expression of miR-3622b-3p was higher in human prostate cancer tissues than in normal prostate tissues. miR-3622a-3p inhibited cell migration and invasion of human prostate cancer cells, whereas miR-3622b-3p facilitated cell proliferation, migration, and invasion. To address the opposing roles of miR-3622 family members in various human prostate cancer cell lines, we knocked out (KO) endogenous miR-3622, including both miR-3622a/b. Our results showed that miR-3622 KO reduced cell proliferation, migration, and invasion in vitro and tumor growth and metastasis in vivo. Functional analyses revealed that miR-3622 regulated the p53-downstream gene network, including AIFM2, c-MYC, and p21, to control apoptosis and the cell cycle. Furthermore, using CRISPR interference, miRNA/mRNA immunoprecipitation assays, and dual-luciferase assays, we established that AIFM2, a direct target of miR-3622b-3p, is responsible for miR-3622 KO-induced apoptosis. We identified an miR-3622-AIFM2 axis that contributes to oncogenic function during tumor progression. In addition, miR-3622 KO inhibited the epithelial-mesenchymal transition involved in prostate cancer metastasis via upregulation of vimentin. The results show that miR-3622b-3p is upregulated in human prostate cancers and has an oncogenic function in tumor progression and metastasis via repression of p53 signaling, especially through an miR-3622-AIFM2 axis. In contrast, for human prostate cancer, deletion of the miR-3622 locus at 8p21 reduced the oncogenic effects on tumor progression and metastasis.

It’s Getting Complicated—A Fresh Look at p53-MDM2-ARF Triangle in Tumorigenesis and Cancer Therapy

Anti-tumorigenic mechanisms mediated by the tumor suppressor p53, upon oncogenic stresses, are our bodies’ greatest weapons to battle against cancer onset and development. Consequently, factors that possess significant p53-regulating activities have been subjects of serious interest from the cancer research community. Among them, MDM2 and ARF are considered the most influential p53 regulators due to their abilities to inhibit and activate p53 functions, respectively. MDM2 inhibits p53 by promoting ubiquitination and proteasome-mediated degradation of p53, while ARF activates p53 by physically interacting with MDM2 to block its access to p53. This conventional understanding of p53-MDM2-ARF functional triangle have guided the direction of p53 research, as well as the development of p53-based therapeutic strategies for the last 30 years. Our increasing knowledge of this triangle during this time, especially through identification of p53-independent functions of MDM2 and ARF, have uncovered many under-appreciated molecular mechanisms connecting these three proteins. Through recognizing both antagonizing and synergizing relationships among them, our consideration for harnessing these relationships to develop effective cancer therapies needs an update accordingly. In this review, we will re-visit the conventional wisdom regarding p53-MDM2-ARF tumor-regulating mechanisms, highlight impactful studies contributing to the modern look of their relationships, and summarize ongoing efforts to target this pathway for effective cancer treatments. A refreshed appreciation of p53-MDM2-ARF network can bring innovative approaches to develop new generations of genetically-informed and clinically-effective cancer therapies.

ZBTB28 inhibits breast cancer by activating IFNAR and dual blocking CD24 and CD47 to enhance macrophages phagocytosis

Breast cancer is the leading cause of cancer death in female. Until now, advanced breast cancer is still lack effective treatment strategies and reliable prognostic markers. In the present article, we introduced the physiologic and pathologic functions and regulation mechanisms of ZBTB28, a tumor suppressor gene, in breast cancer. ZBTB28 is frequently silenced in breast cancer due to promoter CpG methylation, and its expression is positively correlated with breast cancer patient survival. The antineoplastic effect of ZBTB28 in breast cancer was elucidated through a series of in vitro and in vivo measurements, including cell proliferation, apoptosis, cell cycle, epithelial mesenchymal transition (EMT), and growth of xenografts. Furthermore, ZBTB28 can directly regulate IFNAR to activate interferon-stimulated genes and potentiate macrophage activation. Ectopic ZBTB28 expression in breast cancer cells was sufficient to downregulate CD24 and CD47 to promote phagocytosis of macrophages, demonstrating that ZBTB28 was beneficial for the combination treatment of anti-CD24 and anti-CD47. Collectively, our results reveal a mode of action of ZBTB28 as a tumor suppressor gene and suggest that ZBTB28 is an important regulator of macrophage phagocytosis in breast cancer, holding promise for the development of novel therapy strategies for breast cancer patients.

CRISPR interference and activation of the microRNA-3662-HBP1 axis control progression of triple-negative breast cancer

MicroRNA-3662 (miR-3662) is minimally expressed in normal human tissues but is highly expressed in all types of cancers, including breast cancer. As determined with The Cancer Genome Atlas dataset, miR-3662 expression is higher in triple-negative breast cancers (TNBCs) and African American breast cancers than in other breast cancer types. However, the functional role of miR-3662 remains a topic of debate. Here, we found that inhibition or knockout of endogenous, mature miR-3662 in TNBC cells suppresses proliferation and migration in vitro and tumor growth and metastasis in vivo. Functional analysis revealed that, for TNBC cells, knockout of miR-3662 reduces the activation of Wnt/β-catenin signaling. Furthermore, using CRISPR-mediated miR-3662 activation and repression, dual-luciferase assays, and miRNA/mRNA immunoprecipitation assays, we established that HMG-box transcription factor 1 (HBP-1), a Wnt/β-catenin signaling inhibitor, is a target of miR-3662 and is most likely responsible for miR-3662-mediated TNBC cell proliferation. Our results suggest that miR-3662 has an oncogenic function in tumor progression and metastasis via an miR-3662-HBP1 axis, regulating the Wnt /β-catenin signaling pathway in TNBC cells. Since miR-3662 expression occurs a tumor-specific manner, it is a promising biomarker and therapeutic target for patients who have TNBCs with dysregulation of miR-3662, especially African Americans.

CD24, A Review of its Role in Tumor Diagnosis, Progression and Therapy

CD24, is a mucin-like GPI-anchored molecules. By immunohistochemistry, it is widely detected in many solid tumors, such as breast cancers, genital system cancers, digestive system cancers, neural system cancers and so on. The functional roles of CD24 are either fulfilled by combination with ligands or participate in signal transduction, which mediate the initiation and progression of neoplasms. However, the character of CD24 remains to be intriguing because there are still opposite voices about the impact of CD24 on tumors. In preclinical studies, CD24 target therapies, including monoclonal antibodies, target silencing by RNA interference and immunotherapy, have shown us brighten futures on the anti-tumor application. Nevertheless, evidences based on clinical studies are urgently needed. Here, with expectancy to spark new ideas, we summarize the relevant studies about CD24 from a tumor perspective.

Metastatic Pediatric Sclerosing Epithelioid Fibrosarcoma

Sclerosing epithelioid fibrosarcoma (SEF) is a rare and aggressive soft-tissue sarcoma thought to originate in fibroblasts of the tissues comprising tendons, ligaments, and muscles. Minimally responsive to conventional cytotoxic chemotherapies, >50% of SEF patients experience local recurrence and/or metastatic disease. SEF is most commonly discovered in middle-aged and elderly adults, but also rarely in children. A common gene fusion occurring between the EWSR1 and CREB3L1 genes has been observed in 80%–90% of SEF cases. We describe here the youngest SEF patient reported to date (a 3-yr-old Caucasian male) who presented with numerous bony and lung metastases. Additionally, we perform a comprehensive literature review of all SEF-related articles published since the disease was first characterized. Finally, we describe the generation of an SEF primary cell line, the first such culture to be reported. The patient described here experienced persistent disease progression despite aggressive treatment including multiple resections, radiotherapy, and numerous chemotherapies and targeted therapeutics. Untreated and locally recurrent tumor and metastatic tissue were sequenced by whole-genome, whole-exome, and deep-transcriptome next-generation sequencing with comparison to a patient-matched normal blood sample. Consistent across all sequencing analyses was the disease-defining EWSR1–CREB3L1 fusion as a single feature consensus. We provide an analysis of our genomic findings and discuss potential therapeutic strategies for SEF.

Glycosylation Modulates Plasma Membrane Trafficking of CD24 in Breast Cancer Cells

In breast cancer, expression of Cluster of Differentiation 24 (CD24), a small GPI-anchored glycoprotein at the cell periphery, is associated with metastasis and immune escape, while its absence is associated with tumor-initiating capacity. Since the mechanism of CD24 sorting is unknown, we investigated the role of glycosylation in the subcellular localization of CD24. Expression and localization of wild type N36- and/or N52-mutated CD24 were analyzed using immunofluorescence in luminal (MCF-7) and basal B (MDA-MB-231 and Hs578T) breast cancer cells lines, as well as HEK293T cells. Endogenous and exogenously expressed wild type and mutated CD24 were found localized at the plasma membrane and the cytoplasm, but not the nucleoplasm. The cell lines showed different kinetics for the sorting of CD24 through the secretory/endocytic pathway. N-glycosylation, especially at N52, and its processing in the Golgi were critical for the sorting and expression of CD24 at the plasma membrane of HEK293T and basal B type cells, but not of MCF-7 cells. In conclusion, our study highlights the contribution of N-glycosylation for the subcellular localization of CD24. Aberrant N-glycosylation at N52 of CD24 could account for the lack of CD24 expression at the cell surface of basal B breast cancer cells.

Nucleophosmin/B23 promotes endometrial cancer cell escape from macrophage phagocytosis by increasing CD24 expression

Despite recent therapeutic breakthroughs, advanced and/or recurrent endometrial cancer still poses a significant health burden globally. While immunotherapy can theoretically lead to durable responses, the benefits to patients remain limited. In an effort to identify novel immunotherapeutic targets, we specifically focused on the potential role of nucleophosmin (NPM, also known as B23) - a nucleolar phosphoprotein involved in tumorigenesis - in cancer immune evasion. Expression profiling with oligonucleotide microarrays was conducted to identify differentially expressed genes in NPM/B23-silenced endometrial cancer cells. CD24 - a heat-stable antigen commonly overexpressed in solid tumors and a target for cancer immunotherapy - was identified as one of the key NPM/B23-regulated molecules. We found that NPM/B23 was capable of inducing CD24 expression, with the Sp1 binding site in the CD24 promoter being essential for NPM/B23-mediated transcriptional activation. Interestingly, NPM/B23 silencing in endometrial cancer cells enhanced phagocytic removal by macrophages through a decreased exposure of CD24 on the cell surface. Conversely, restoration of CD24 expression in NPM/B23-silenced endometrial cancer cells inhibited macrophage-mediated phagocytosis. These results indicate that NPM/B23-driven CD24 overexpression enables endometrial cancer cells to evade from phagocytosis. We further suggest that CD24 may serve as a novel target for endometrial cancer immunotherapy. KEY MESSAGES: NPM/B23 induced CD24 expression in endometrial tumorigenesis. Sp1 binding site in the CD24 promoter is essential for the activation. NPM/B23 silencing enhanced phagocytosis by macrophages through decrease of CD24 on cancer cells. Restoration of CD24 expression in NPM/B23-silenced cancer cells inhibited macrophage-mediated phagocytosis.

A Comparative in Silico Analysis of CD24's Prognostic Value in Human and Canine Prostate Cancer

CD24 is a cell surface molecule anchored by glycosyl-phosphatidyl-inositol and expressed by different human cancers, including prostate cancer (PC). Some studies have demonstrated that CD24 expression is associated with poor patient outcome; however, few studies have investigated CD24 expression in spontaneous animal models of human PC, such as canine PC. This study aimed to evaluate the expression of CD24 in human PC using the in silico analysis of the data obtained from The Cancer Genome Atlas (TCGA) and comparing it with the previously published prostatic canine transcriptome data. In addition, CD24 expression was confirmed by immunohistochemistry in an independent cohort of canine prostatic samples and its prognostic significance assessed. The systematic review identified 10 publications fitting with the inclusion criteria of this study. Of the 10 manuscripts, 5 demonstrated a direct correlation between CD24 overexpression and patient prognoses. CD24 expression was also associated with PSA relapse (2/5) and tumor progression (1/5). However, the in silico analysis did not validate CD24 as a prognostic factor of human PC. Regarding canine PC, 10 out of 30 normal prostates and 27 out of 40 PC samples were positive for CD24. As in humans, there was no association with overall survival. Overall, our results demonstrated a significant CD24 overexpression in human and canine prostate cancer, although its prognostic value may be questionable. However, tumors overexpressing CD24 may be a reliable model for new target therapies and dogs could be used of a unique preclinical model for these studies.

Quiescence, Stemness and Adipogenic Differentiation Capacity in Human DLK1-/CD34+/CD24+ Adipose Stem/Progenitor Cells

We explore the status of quiescence, stemness and adipogenic differentiation capacity in adipose stem/progenitor cells (ASCs) ex vivo, immediately after isolation from human subcutaneous white adipose tissue, by sorting the stromal vascular fraction into cell-surface DLK1⁺/CD34⁻, DLK1⁺/CD34^dim and DLK1⁻/CD34⁺ cells. We demonstrate that DLK1⁻/CD34⁺ cells, the only population exhibiting proliferative and adipogenic capacity, express ex vivo the bonafide quiescence markers p21^Cip1, p27^Kip1 and p57^Kip2 but neither proliferation markers nor the senescence marker p16^Ink4a. The pluripotency markers NANOG, SOX2 and OCT4 are barely detectable in ex vivo ASCs while the somatic stemness factors, c-MYC and KLF4 and the early adipogenic factor C/EBPβ are highly expressed. Further sorting of ASCs into DLK1⁻/CD34⁺/CD24⁻ and DLK1⁻/CD34⁺/CD24⁺ fractions shows that KLF4 and c-MYC are higher expressed in DLK1⁻/CD34⁺/CD24⁺ cells correlating with higher colony formation capacity and considerably lower adipogenic activity. Proliferation capacity is similar in both populations. Next, we show that ASCs routinely isolated by plastic-adherence are DLK1⁻/CD34⁺/CD24⁺. Intriguingly, CD24 knock-down in these cells reduces proliferation and adipogenesis. In conclusion, DLK1⁻/CD34⁺ ASCs in human sWAT exist in a quiescent state, express high levels of somatic stemness factors and the early adipogenic transcription factor C/EBPβ but senescence and pluripotency markers are barely detectable. Moreover, our data indicate that CD24 is necessary for adequate ASC proliferation and adipogenesis and that stemness is higher and adipogenic capacity lower in DLK1⁻/CD34⁺/CD24⁺ relative to DLK1⁻/CD34⁺/CD24⁻ subpopulations.

DNA Promoter Methylation and ERG Regulate the Expression of CD24 in Prostate Cancer

CD24 is overexpressed in many human cancers and is a driver of tumor progression. Herein, molecular mechanisms leading to up-regulation of CD24 in prostate cancer were studied. DNA methylation of the CD24 gene promoter at four loci using quantitative methylation-specific PCR was evaluated. Expression of CD24 in tumor tissues was studied by immunohistochemistry. To corroborate the results in vitro, ERG-inducible LNCaP TMPRSS2:ERG (T2E) cells and luciferase promoter assays were used. DNA methylation of the CD24 promoter was significantly higher in tumors than in benign tissue and was associated with biochemical recurrence-free survival, tumor grade, and stage. CD24 mRNA and protein expression were significantly higher in T2E-positive, ERG-overexpressing, and/or PTEN-deficient cases. Higher levels of CD24 protein expression conferred shorter biochemical recurrence-free survival, and these observations were confirmed using The Cancer Genome Atlas prostate adenocarcinoma data. In silico analysis of the CD24 promoter revealed an ERG binding site in between the DNA methylation sites. ERG overexpression led to a strong induction of CD24 mRNA and protein expression. Luciferase promoter assays using the wild-type and mutated ERG binding site within the CD24 promoter showed ERG-dependent activation. Collectively, our results suggest that promoter DNA methylation of the CD24 gene and T2E fusion status are factors involved in the up-regulation of CD24 in patients with prostate cancer.

The Emerging Role of CD24 in Cancer Theranostics-A Novel Target for Fluorescence Image-Guided Surgery in Ovarian Cancer and Beyond

Complete cytoreductive surgery is the cornerstone of the treatment of epithelial ovarian cancer (EOC). The application of fluorescence image-guided surgery (FIGS) allows for the increased intraoperative visualization and delineation of malignant lesions by using fluorescently labeled targeting biomarkers, thereby improving intraoperative guidance. CD24, a small glycophosphatidylinositol-anchored cell surface receptor, is overexpressed in approximately 70% of solid cancers, and has been proposed as a prognostic and therapeutic tumor-specific biomarker for EOC. Recently, preclinical studies have demonstrated the benefit of CD24-targeted contrast agents for non-invasive fluorescence imaging, as well as improved tumor resection by employing CD24-targeted FIGS in orthotopic patient-derived xenograft models of EOC. The successful detection of miniscule metastases denotes CD24 as a promising biomarker for the application of fluorescence-guided surgery in EOC patients. The aim of this review is to present the clinical and preclinically evaluated biomarkers for ovarian cancer FIGS, highlight the strengths of CD24, and propose a future bimodal approach combining CD24-targeted fluorescence imaging with radionuclide detection and targeted therapy.

The neural stem-cell marker CD24 is specifically upregulated in IDH-mutant glioma

BACKGROUND

Malignant gliomas have disproportionally high morbidity and mortality. Heterozygous mutations in the isocitrate dehydrogenase 1 (IDH1) gene are most common in glioma, resulting in predominantly arginine to histidine substitution at codon 132. Because IDH1R132H requires a wild-type allele to produce (D)-2-hydroxyglutarate for epigenetic reprogramming, loss of IDH1R132H heterozygosity is associated with glioma progression in an IDH1-wildtype-like phenotype. Although previous studies have reported that transgenic IDH1R132H induces the expression of nestin-a neural stem-cell marker, the underlying mechanism remains unclear. Furthermore, this finding seems at odds with better outcome of IDH1R132H glioma because of a negative association of nestin with overall survival.

METHODS

Gene expression was compared between IDH1R132H-hemizygous and IDH1R132H-heterozygous glioma cells under adherent and spheroid growth conditions. The results were validated for (D)-2-hydroxyglutarate responsiveness by pharmacologic agents, associations with DNA methylation by bioinformatic analysis, and associations with overall survival. Bisulfite DNA sequencing, chromatin immunoprecipitation, and pharmacological approach were used.

FINDINGS

Neural stem-cell marker genes, including CD44, NES, and PROM1, are generally downregulated in IDH-mutant gliomas and IDH1R132H-heterozygous spheroid growth compared respectively with IDH-wildtype gliomas and IDH1R132H-hemizygous spheroid growth, in agreement with their negative associations with patient outcome. In contrast, CD24 is specifically upregulated and apparently associated with better survival. CD24 and NES expression respond differentially to alteration of (D)-2-hydroxyglutarate levels. CD24 upregulation is associated with histone and DNA demethylation as opposed to hypermethylation in the downregulated genes.

INTERPRETATION

The better outcome of IDH-mutant glioma is orchestrated exquisitely through epigenetic reprogramming that directs bidirectional expression of neural stem-cell marker genes.

Novel insights into the function of CD24: A driving force in cancer

CD24 is a highly glycosylated protein with a small protein core that is linked to the plasma membrane via a glycosyl-phosphatidylinositol anchor. CD24 is primarily expressed by immune cells but is often overexpressed in human tumors. In cancer, CD24 is a regulator of cell migration, invasion and proliferation. Its expression is associated with poor prognosis and it is used as cancer stemness marker. Recently, CD24 on tumor cells was identified as a phagocytic inhibitor ("do not eat me" signal) having a suppressive role in tumor immunity via binding to Siglec-10 on macrophages. This finding is reminiscent of the demonstration that soluble CD24-Fc can dampen the immune system in autoimmune disease. In the present review, we summarize recent progress on the role of the CD24-Siglec-10 binding axis at the interface between tumor cells and the immune system, and the role of CD24 genetic polymorphisms in cancer. We describe the specific function of cytoplasmic CD24 and discuss the presence of CD24 on tumor-released extracellular vesicles. Finally, we evaluate the potential of CD24-based immunotherapy.

Fibrinogen Alpha Chain Knockout Promotes Tumor Growth and Metastasis through Integrin-AKT Signaling Pathway in Lung Cancer

Fibrinogen is an extracellular matrix protein composed of three polypeptide chains with fibrinogen alpha (FGA), beta (FGB) and gamma (FGG). Although fibrinogen and its related fragments are involved in tumor angiogenesis and metastasis, their functional roles are incompatible. A recent genome-scale screening reveals that loss of FGA affects the acceleration of tumor growth and metastasis of lung cancer, but the mechanism remains elusive. We used CRISPR/Cas9 genome editing to knockout (KO) FGA in human lung adenocarcinoma (LUAD) cell lines A549 and H1299. By colony formation, transwell migration and matrix invasion assays, FGA KO increased cell proliferation, migration, and invasion but decreased the expressions of epithelial-mesenchymal transition marker E-cadherin and cytokeratin 5/8 in A549 and H1299 cells. However, administration of FGA inhibited cell proliferation and migration but induced apoptosis in A549 cells. Of note, FGA KO cells indirectly cocultured by transwells with FGA wild-type cells increased FGA in the culture medium, leading to decreased migration of FGA KO cells. Furthermore, our functional analysis identified a direct interaction of FGA with integrin α5 as well as FGA-integrin signaling that regulated the AKT-mTOR signaling pathway in A549 cells. In addition, we validated that FGA KO increased tumor growth and metastasis through activation of AKT signaling in an A549 xenograft model. IMPLICATIONS: These findings demonstrate that that loss of FGA facilities tumor growth and metastasis through the integrin-AKT signaling pathway in lung cancer.

A CD24-p53 axis contributes to African American prostate cancer disparities

BACKGROUND

Using a functional analysis of prostate cancer cells, we found a CD24-dependent inactivation of mutant p53, but the clinical significance of this observation remained uncertain. Here, we validated these results with samples of human prostate cancer and explored the role of a CD24-p53 axis in racial disparities of prostate cancer.

METHODS

Samples of formalin-fixed, paraffin-embedded prostate cancer from 141 European Americans (EAs) and 147 African Americans (AAs) in two independent sample cohorts were assessed for protein expression of CD24, mutant p53, mouse double minute 2 human homolog (MDM2), and cyclin dependent kinase inhibitor 2A (ARF) using immunohistochemical analyses. All samples were analyzed for TP53^R175H and TP53^R273H .

RESULTS

CD24, mutant p53, MDM2, and ARF proteins were expressed in 55%, 24%, 39%, and 68% of prostate cancer samples, respectively. CD24 and mutant p53 were present more frequently in late-stage and metastatic prostate cancer. The presence of CD24 was associated with a greater than fourfold risk of metastasis, which included lymph node and distant metastases. H score analysis showed positive correlations of CD24 expression with mutant p53 (r = .308, P < .001) and MDM2 (r = .227, P = .004). There was a negative correlation for CD24 with ARF (r = -.280, P < .001). A racial disparity was evident for CD24 (AAs/EAs: 64% vs 47%; P = .004) but not for mutant p53 (AA/EA: 28% vs 21%; P = .152). In 32 CD24⁺ /mutant p53⁺ cases, a TP53^R273H mutation was found in five cases, but no TP53^R175H mutation was found.

CONCLUSION

The CD24-p53 axis may contribute to aggressive and metastatic prostate cancers, especially those of AAs. This observation enhances understanding of the pathogenesis of prostate cancer and its associated racial disparities.

CD24: a marker of granulosa cell subpopulation and a mediator of ovulation

Granulosa cells (GCs) play a critical role in driving the formation of ovarian follicles and building the cumulus-oocyte complex surrounding the ovum. We are particularly interested in assessing oocyte quality by examining the detailed gene expression profiles of human cumulus single cells. Using single-cell RNAseq techniques, we extensively investigated the single-cell transcriptomes of the cumulus GC populations from two women with normal ovarian function. This allowed us to elucidate the endogenous heterogeneity of GCs by uncovering the hidden GC subpopulation. The subsequent validation results suggest that CD24(+) GCs are essential for triggering ovulation. Treatment with human chorionic gonadotropin (hCG) significantly increases the expression of CD24 in GCs. CD24 in cultured human GCs is associated with hCG-induced upregulation of prostaglandin synthase (ARK1C1, PTGS2, PTGES, and PLA2G4A) and prostaglandin transporter (SLCO2A1 and ABCC4) expression, through supporting the EGFR-ERK1/2 pathway. In addition, it was observed that the fraction of CD24(+) cumulus GCs decreases in PCOS patients compared to that of controls. Altogether, the results support the finding that CD24 is an important mediator of ovulation and that it may also be used for therapeutic target of ovulatory disorders.

Reduced DAXX Expression Is Associated with Reduced CD24 Expression in Colorectal Cancer

The presence of an activating mutation of the Wnt/β-catenin signaling pathway is found in ~90% of colorectal cancer (CRC) cases. Death domain-associated protein (DAXX), a nuclear protein, interacts with β-catenin in CRC cells. We investigated DAXX expression in 106 matched sample pairs of CRC and adjacent normal tissue by Western blotting. This study evaluated DAXX expression and its clinical implications in CRC. The results revealed that DAXX expression was significantly lower in the patients with the positive serum carcinoembryonic antigen (CEA) screening results compared to the patients with negative CEA screening levels (p < 0.001). It has been reported that CD24 is a Wnt target in CRC cells. Here, we further revealed that DAXX expression was significantly correlated with CD24 expression (rho = 0.360, p < 0.001) in 106 patients. Consistent with this, in the CEA-positive subgroup, of which the carcinomas expressed DAXX at low levels, they were significantly correlated with CD24 expression (rho = 0.461, p < 0.005). Therefore, reduced DAXX expression is associated with reduced CD24 expression in CRC. Notably, in the Hct116 cells, DAXX knockdown using short-hairpin RNA against DAXX (shDAXX) not only caused significant cell proliferation, but also promoted metastasis. The DAXX-knockdown cells also demonstrated significantly decreased CD24 expression, however the intracellular localization of CD24 did not change. Thus, DAXX might be considered as a potential regulator of CD24 or β-catenin expression, which might be correlated with proliferative and metastatic potential of CRC.

Amplification of the CD24 Gene Is an Independent Predictor for Poor Prognosis of Breast Cancer

CD24 is a glycosyl-phosphatidyl-inositol linked glycoprotein expressed in a broad range of cell types including cancer cells. Although it is overexpressed in nearly 70% of human cancers, copy number variation of the CD24 locus has not been reported for any cancer. Here, we analyzed the genomics, transcriptomics, and clinical data of 1082 breast cancer (BRCA) samples and other cancer samples from the clinically annotated genomic database, The Cancer Genome Atlas (TCGA). The GISTIC2 method was applied to stratify the CD24 copy number, and Cox regression was performed to compare hazard ratio (HR) of CD24 overexpression, amplification and other traditional prognosis features for overall survival (OS). Our data demonstrated that CD24 amplification strongly correlated with its mRNA overexpression as well as TP53 mutant, cancer proliferation and metastasis features. In particular, CD24 amplification was enriched in basal-like subtype samples and associated with poor clinical outcome. Surprisingly, based on the univariate Cox regression analysis, CD24 overexpression (HR = 1.62, P = 0.010) and copy number amplification (HR = 1.79, P = 0.022) was more relevant to OS than TP53 mutant, mutation counts, diagnosis age, and BRCA subtypes. And based on multivariate survival analysis, CD24 amplification remained the most significant and independent predictor for worse OS (HR = 1.88, P = 0.015).

MicroRNA-1205, encoded on chromosome 8q24, targets EGLN3 to induce cell growth and contributes to risk of castration-resistant prostate cancer

The chromosome 8q24.21 locus, which contains the proto-oncogene c-MYC, long non-coding RNA PVT1, and microRNAs (miRs), is the most commonly amplified region in human prostate cancer. A long-range interaction of genetic variants with c-MYC or long non-coding PVT1 at this locus contributes to the genetic risk of prostate cancer. At this locus is a cluster of genes for six miRs (miR-1204, −1205, −1206, −1207–3p, −1207–5p, and −1208), but their functional role remains elusive. Here, the copy numbers and expressions of miRs-1204~1208 were investigated using quantitative PCR for prostate cancer cell lines and primary tumors. The data revealed that copy numbers and expression of miR-1205 were increased in both castration-resistant prostate cancer cell lines and in primary tumors. In castration-resistant prostate cancer specimens, the copy number at the miR-1205 locus correlated with expression of miR-1205. Furthermore, functional analysis with an miR-1205 mimic, an miR-1205 inhibitor, and CRISPR/Cas9 knockout revealed that, in human prostate cancer cells, miR-1205 promoted cell proliferation and cell cycle progression and inhibited hydrogen peroxide-induced apoptosis. In these cells, miR-1205 downregulated expression of the Egl-9 family hypoxia inducible factor 3 (EGLN3) gene and targeted a site in its 3’-untranslated region to downregulate its transcriptional activity. Thus, by targeting EGLN3, miR-1205 has an oncogenic role and may contribute to the genetic risk of castration-resistant prostate cancer.

Dysregulation of p53-RBM25-mediated circAMOTL1L biogenesis contributes to prostate cancer progression through the circAMOTL1L-miR-193a-5p-Pcdha pathway

p53, circRNAs and miRNAs are important components of the regulatory network that activates the EMT program in cancer metastasis. In prostate cancer (PCa), however, it has not been investigated whether and how p53 regulates EMT by circRNAs and miRNAs. Here we show that a Amotl1-derived circRNA, termed circAMOTL1L, is downregulated in human PCa, and that decreased circAMOTL1L facilitates PCa cell migration and invasion through downregulating E-cadherin and upregulating vimentin, thus leading to EMT and PCa progression. Mechanistically, we demonstrate that circAMOTL1L serves as a sponge for binding miR-193a-5p in PCa cells, relieving miR-193a-5p repression of Pcdha gene cluster (a subset of the cadherin superfamily members). Accordingly, dysregulation of the circAMOTL1L-miR-193a-5p-Pcdha8 regulatory pathway mediated by circAMOTL1L downregulation contributes to PCa growth in vivo. Further, we show that RBM25 binds directly to circAMOTL1L and induces its biogenesis, whereas p53 regulates EMT via direct activation of RBM25 gene. These findings have linked p53/RBM25-mediated circAMOTL1L-miR-193a-5p-Pcdha regulatory axis to EMT in metastatic progression of PCa. Targeting this newly identified regulatory axis provides a potential therapeutic strategy for aggressive PCa.

A comprehensive bioinformatics analysis on multiple Gene Expression Omnibus datasets of nonalcoholic fatty liver disease and nonalcoholic steatohepatitis

Fatty liver disease is one of the leading causes of chronic damage in western countries. Approximately 25% of adults in the United States have fatty livers in the absence of excessive alcohol consumption, a condition termed nonalcoholic fatty liver disease (NAFLD). Little is known about the prevalence and genetic background of NAFLD or the factors that determine its development. In this study, we used the Gene-Cloud of Biotechnology Information bioinformatics platform to carry out a comprehensive bioinformatics analysis identifying differentially expressed genes (DEGs), key biological processes and intersecting pathways. We imported 3 Gene Expression Omnibus datasets (GSE31803, GSE49541, and GSE63067). Then, we assessed the expression of the DEGs in clinical samples. We found that CD24 was the only gene co-expressed in all 3 datasets. "Glycolysis/gluconeogenesis", "p53 signaling pathway" and "glycine, serine and threonine metabolism" were 3 common pathways related to the fatty liver process. In NAFLD tissues, CD24, COL1A1, LUM, THBS2 and EPHA3 were upregulated, and PZP was downregulated. CD24 is a core gene among these DEGs and have not yet been studied of its impact on NAFLD. Co-expressed genes, common biological processes and intersecting pathways identified in the study might play an important role in NAFLD progression. Further studies are needed to elucidate the mechanism of these potential genes and pathways in NAFLD.

CD24-p53 axis suppresses diethylnitrosamine-induced hepatocellular carcinogenesis by sustaining intrahepatic macrophages

It is generally assumed that inflammation following diethylnitrosamine (DEN) treatment promotes development of hepatocellular carcinoma (HCC) through the activity of intrahepatic macrophages. However, the tumor-promoting function of macrophages in the model has not been confirmed by either macrophage depletion or selective gene depletion in macrophages. Here we show that targeted mutation of Cd24 dramatically increased HCC burden while reducing intrahepatic macrophages and DEN-induced hepatocyte apoptosis. Depletion of macrophages also increased HCC burden and reduced hepatocyte apoptosis, thus establishing macrophages as an innate effector recognizing DEN-induced damaged hepatocytes. Mechanistically, Cd24 deficiency increased the levels of p53 in macrophages, resulting in their depletion in Cd24^-/- mice following DEN treatment. These data demonstrate that the Cd24-p53 axis maintains intrahepatic macrophages, which can remove hepatocytes with DNA damage. Our data establish a critical role for macrophages in suppressing HCC development and call for an appraisal of the current dogma that intrahepatic macrophages promote HCC development.

Molecular determinants of prostate cancer metastasis

Metastatic cancer remains largely incurable and fatal. The general course of cancer, from the initiation of primary tumor formation and progression to metastasis, is a multistep process wherein tumor cells at each step must display specific phenotypic features. Distinctive capabilities required for primary tumor initiation and growth form the foundation, and sometimes may remain critical, for subsequent metastases. These phenotypic features must remain easily malleable during the acquisition of additional capabilities unique and essential to the metastatic process such as dissemination to distant tissues wherein tumor cells interact with foreign microenvironments. Thus, the metastatic phenotype is a culmination of multiple genetic and epigenetic alterations and subsequent selection for favorable traits under the pressure of ever-changing tumor microenvironments. Although our understanding of the molecular programs that drive cancer metastasis are incomplete, increasing evidence suggests that successful metastatic colonization relies on the dissemination of cancer stem cells (CSCs) with tumor-regenerating capacity and adaptive programs for survival in distant organs. In the past 2-3 years, a myriad of novel molecular regulators and determinants of prostate cancer metastasis have been reported, and in this Perspective, we comprehensively review this body of literature and summarize recent findings regarding cell autonomous molecular mechanisms critical for prostate cancer metastasis.

Nuclear CD24 Drives Tumor Growth and Is Predictive of Poor Patient Prognosis

Elevated tumor expression of the cell surface GPI-linked CD24 protein signals poor patient prognosis in many tumor types. However, some cancer cells selected to be negative for surface CD24 (surCD24-) still retain aggressive phenotypes in vitro and in vivo Here, we resolve this apparent paradox with the discovery of biologically active, nuclear CD24 (nucCD24) and finding that its levels are unchanged in surCD24- cells. Using the complementary techniques of biochemical cellular fractionation and immunofluorescence, we demonstrate a signal for CD24 in the nucleus in cells from various histologic types of cancer. Nuclear-specific expression of CD24 (NLS-CD24) increased anchorage-independent growth in vitro and tumor formation in vivo Immunohistochemistry of patient tumor samples revealed the presence of nucCD24, whose signal intensity correlated positively with the presence of metastatic disease. Analysis of gene expression between cells expressing CD24 and NLS-CD24 revealed a unique nucCD24 transcriptional signature. The median score derived from this signature was able to stratify overall survival in four patient datasets from bladder cancer and five patient datasets from colorectal cancer. Patients with high scores (more nucCD24-like) had reduced survival. These findings define a novel and functionally important intracellular location of CD24; they explain why surCD24- cells can remain aggressive, and they highlight the need to consider nucCD24 in both fundamental research and therapeutic development. Cancer Res; 77(18); 4858-67. ©2017 AACR.

Siglec-G represses DAMP-mediated effects on T cells

The role of negative regulators or suppressors of the damage-associated molecular pattern-mediated (DAMP-mediated) stimulation of innate immune responses is being increasingly appreciated. However, the presence and function of suppressors of DAMP-mediated effects on T cells, and whether they can be targeted to mitigate T cell-dependent immunopathology remain unknown. Sialic acid-binding immunoglobulin-like lectin G (Siglec-G) is a negative regulator of DAMP-mediated responses in innate immune cells, but its T cell-autonomous role is unknown. Utilizing loss-of-function-based (genetic knockout) and gain-of-function-based (agonist) approaches, we demonstrate that in the presence of certain DAMPs, Siglec-G suppressed in vitro and in vivo T cell responses. We also demonstrate that its T cell-autonomous role is critical for modulating the severity of the T cell-mediated immunopathology, graft-versus-host disease (GVHD). Enhancing the Siglec-G signaling in donor T cells with its agonist, a CD24Fc fusion protein, ameliorated GVHD while preserving sufficient graft-versus-tumor (GVT) effects in vivo. Collectively, these data demonstrate that Siglec-G is a potentially novel negative regulator of T cell responses, which can be targeted to mitigate GVHD.

The CD24 surface antigen in neural development and disease

A cell's surface molecular signature enables its reciprocal interactions with the associated microenvironments in development, tissue homeostasis and pathological processes. The CD24 surface antigen (heat-stable antigen, nectadrin; small cell lung cancer antigen cluster-4) represents a prime example of a neural surface molecule that has long been known, but whose diverse molecular functions in intercellular communication we have only begun to unravel. Here, we briefly summarize the molecular fundamentals of CD24 structure and provide a comprehensive review of CD24 expression and functional studies in mammalian neural developmental systems and disease models (rodent, human). Striving for an integrated view of the intracellular signaling processes involved, we discuss the most pertinent routes of CD24-mediated signaling pathways and functional networks in neurobiology (neural migration, neurite extension, neurogenesis) and pathology (tumorigenesis, multiple sclerosis).

A redox mechanism underlying nucleolar stress sensing by nucleophosmin

The nucleolus has been recently described as a stress sensor. The nucleoplasmic translocation of nucleolar protein nucleophosmin (NPM1) is a hallmark of nucleolar stress; however, the causes of this translocation and its connection to p53 activation are unclear. Using single live-cell imaging and the redox biosensors, we demonstrate that nucleolar oxidation is a general response to various cellular stresses. During nucleolar oxidation, NPM1 undergoes S-glutathionylation on cysteine 275, which triggers the dissociation of NPM1 from nucleolar nucleic acids. The C275S mutant NPM1, unable to be glutathionylated, remains in the nucleolus under nucleolar stress. Compared with wild-type NPM1 that can disrupt the p53–HDM2 interaction, the C275S mutant greatly compromises the activation of p53, highlighting that nucleoplasmic translocation of NPM1 is a prerequisite for stress-induced activation of p53. This study elucidates a redox mechanism for the nucleolar stress sensing and may help the development of therapeutic strategies.

Nucleoplasmic translocation of NPM1 is integral to nucleolar stress sensing. Here, the authors show that nucleolar oxidation is a general cellular stress response, and that oxidation-related glutathionylation of NPM1 triggers its translocation and facilitates p53 activation.

CD24 is a genetic modifier for risk and progression of prostate cancer

CD24 plays an oncogenic role in the onset and progression of various human cancers, including prostate cancer. In the present study, we identified two linkage disequilibrium blocks with four recombination hotspot motifs in human CD24 locus. To elucidate whether genetic variants of CD24 are associated with susceptibility to prostate cancer and its disease status, we conducted a case-control association study with two P170 C/T and P-534 A/C polymorphisms of CD24 in 590 patients with prostate cancer and 590 healthy controls. A significant increased risk of prostate cancer was found in men with the P170^T/T genotype over the P170^C/C genotype (odd ratio = 1.74, 95% confidence interval = 1.16-2.63, P = 0.008), and in men with the P-534^C/C genotype over the P-534^A/A genotype (odd ratio = 1.47, 95% CI = 1.18-2.26, P = 0.003). Cochran-Armitage trend analysis showed that the P170^T allele was significantly correlated with an increased risk of prostate cancer progression (P = 0.029, trend between genotypes and stages) and this observation was also validated in an independent sample cohort. Next, we found that tumors with P170^T or P-534^C alleles had more twofold increased protein expressions of CD24 as compared to those with P170^C or P-534^A alleles, respectively. Likewise, tumors with a combination of P170^T/T and P-534^C/C genotypes were associated with a high mRNA level of CD24. Our data suggest a significant association of CD24 genetic variants with prostate cancer onset and progression, which provides new insight into molecular genetics of prostate cancer; however, these findings need to be validated in multiple independent cohorts. © 2016 Wiley Periodicals, Inc.

Co-Expression of Cancer Stem Cell Markers Corresponds to a Pro-Tumorigenic Expression Profile in Pancreatic Adenocarcinoma

Pancreatic ductal adenocarcinoma (PDAC) remains one of the most lethal malignancies. Its dismal prognosis is often attributed to the presence of cancer stem cells (CSCs) that have been identified in PDAC using various markers. However, the co-expression of all of these markers has not yet been evaluated. Furthermore, studies that compare the expression levels of CSC markers in PDAC tumor samples and in cell lines derived directly from those tumors are lacking. Here, we analyzed the expression of putative CSC markers—CD24, CD44, epithelial cell adhesion molecule (EpCAM), CD133, and nestin—by immunofluorescence, flow cytometry and quantitative PCR in 3 PDAC-derived cell lines and by immunohistochemistry in 3 corresponding tumor samples. We showed high expression of the examined CSC markers among all of the cell lines and tumor samples, with the exception of CD24 and CD44, which were enriched under in vitro conditions compared with tumor tissues. The proportions of cells positive for the remaining markers were comparable to those detected in the corresponding tumors. Co-expression analysis using flow cytometry revealed that CD24⁺/CD44⁺/EpCAM⁺/CD133⁺ cells represented a significant population of the cells (range, 43 to 72%) among the cell lines. The highest proportion of CD24⁺/CD44⁺/EpCAM⁺/CD133⁺ cells was detected in the cell line derived from the tumor of a patient with the shortest survival. Using gene expression profiling, we further identified the specific pro-tumorigenic expression profile of this cell line compared with the profiles of the other two cell lines. Together, CD24⁺/CD44⁺/EpCAM⁺/CD133⁺ cells are present in PDAC cell lines derived from primary tumors, and their increased proportion corresponds with a pro-tumorigenic gene expression profile.

GON4L Drives Cancer Growth through a YY1-Androgen Receptor-CD24 Axis

In principle, the inhibition of candidate gain-of-function genes defined through genomic analyses of large patient cohorts offers an attractive therapeutic strategy. In this study, we focused on changes in expression of CD24, a well-validated clinical biomarker of poor prognosis and a driver of tumor growth and metastasis, as a benchmark to assess functional relevance. Through this approach, we identified GON4L as a regulator of CD24 from screening a pooled shRNA library of 176 candidate gain-of-function genes. GON4L depletion reduced CD24 expression in human bladder cancer cells and blocked cell proliferation in vitro and tumor xenograft growth in vivo Mechanistically, GON4L interacted with transcription factor YY1, promoting its association with the androgen receptor to drive CD24 expression and cell growth. In clinical bladder cancer specimens, expression of GON4L, YY1, and CD24 was elevated compared with normal bladder urothelium. This pathway is biologically relevant in other cancer types as well, where CD24 and the androgen receptor are clinically prognostic, given that silencing of GON4L and YY1 suppressed CD24 expression and growth of human lung, prostate, and breast cancer cells. Overall, our results define GON4L as a novel driver of cancer growth, offering new biomarker and therapeutic opportunities. Cancer Res; 76(17); 5175-85. ©2016 AACR.

CD24 cell surface expression in Mvt1 mammary cancer cells serves as a biomarker for sensitivity to anti-IGF1R therapy

Background

The pro-tumorigenic effects of the insulin-like growth factor receptor (IGF1R) are well described. IGF1R promotes cancer cell survival and proliferation and prevents apoptosis, and, additionally it was shown that IGF1R levels are significantly elevated in most common human malignancies including breast cancer. However, results from phase 3 clinical trials in unselected patients demonstrated lack of efficacy for anti-IGF1R therapy. These findings suggest that predictive biomarkers are greatly warranted in order to identify patients that will benefit from anti-IGF1R therapeutic strategies.

Methods

Using the delivery of shRNA vectors into the Mvt1 cell line, we tested the role of the IGF1R in the development of mammary tumors. Based on CD24 cell surface expression, control and IGF1R-knockdown (IGF1R-KD) cells were FACS sorted into CD24⁻ and CD24⁺ subsets and further characterized in vitro. The tumorigenic capacity of each was determined following orthotopic inoculation into the mammary fat pad of female mice. Tumor cells were FACS characterized upon sacrifice to determine IGF1R effect on the plasticity of this cell’s phenotype. Metastatic capacity of the cells was assessed using the tail vein assay.

Results

In this study we demonstrate that downregulation of the IGF1R specifically in cancer cells expressing CD24 on the cell surface membrane affect both their morphology (from mesenchymal-like into epithelial-like morphology) and phenotype in vitro. Moreover, we demonstrate that IGF1R-KD abolished both CD24⁺ cells capacity to form mammary tumors and lung metastatic lesions. We found in both cells and tumors a marked upregulation in CTFG and a significant reduction of SLP1 expression in the CD24⁺/IGF1R-KD; tumor-suppressor and tumor-promoting genes respectively.

Moreover, we demonstrate here that the IGF1R is essential for the maintenance of stem/progenitor-like cancer cells and we further demonstrate that IGF1R-KD induces in vivo differentiation of the CD24⁺ cells toward the CD24^- phenotype. This further supports the antitumorigenic effects of IGF1R-KD, as we recently published that these differentiated cells demonstrate significantly lower tumorigenic capacity compared with their CD24⁺ counterparts.

Conclusions

Taken together these findings suggest that CD24 cell surface expression may serve as a valuable biomarker in order to identify mammary tumors that will positively respond to targeted IGF1R therapies.

Electronic supplementary material

The online version of this article (doi:10.1186/s13058-016-0711-7) contains supplementary material, which is available to authorized users.

CD24 Is Not Required for Tumor Initiation and Growth in Murine Breast and Prostate Cancer Models

CD24 is a small, heavily glycosylated, GPI-linked membrane protein, whose expression has been associated with the tumorigenesis and progression of several types of cancer. Here, we studied the expression of CD24 in tumors of MMTV-PyMT, Apc^1572/T+ and TRAMP genetic mouse models that spontaneously develop mammary or prostate carcinoma, respectively. We found that CD24 is expressed during tumor development in all three models. In MMTV-PyMT and Apc^1572T/+ breast tumors, CD24 was strongly but heterogeneously expressed during early tumorigenesis, but decreased in more advanced stages, and accordingly was increased in poorly differentiated lesions compared with well differentiated lesions. In prostate tumors developing in TRAMP mice, CD24 expression was strong within hyperplastic lesions in comparison with non-hyperplastic regions, and heterogeneous CD24 expression was maintained in advanced prostate carcinomas. To investigate whether CD24 plays a functional role in tumorigenesis in these models, we crossed CD24 deficient mice with MMTV-PyMT, Apc^1572T/+ and TRAMP mice, and assessed the influence of CD24 deficiency on tumor onset and tumor burden. We found that mice negative or positive for CD24 did not significantly differ in terms of tumor initiation and burden in the genetic tumor models tested, with the exception of Apc^1572T/+ mice, in which lack of CD24 reduced the mammary tumor burden slightly but significantly. Together, our data suggest that while CD24 is distinctively expressed during the early development of murine mammary and prostate tumors, it is not essential for the formation of tumors developing in MMTV-PyMT, Apc^1572T/+ and TRAMP mice.

CD24 genetic variants contribute to overall survival in patients with gastric cancer

AIM

To investigate the role of single nucleotide polymorphisms (SNPs) in CD24 gene in susceptibility and overall survival of gastric cancer (GC).

METHODS

We genotyped 3 tagging SNPs of CD24-P-534 in the promoter region, P170 in the coding region of exon 2 and P1527 in the 3' untranslated region - using polymerase chain reaction-restriction fragment length polymorphism in specimens from 679 histologically-confirmed GC cases, 111 gastric atrophy (GA) cases and 976 tumor-free controls. Serum immunoglobulin G antibodies to Helicobacter pylori (H. pylori) of all subjects were detected by enzyme-linked immunosorbent assay. CD24 expression was evaluated by immunohistochemistry in 131 GC specimens. Correlations between SNPs and risk of GC or GA were shown by P values and odd ratios (ORs) with 95% confidence intervals (95%CI) compared with the most common genotype of each SNP using the unconditional logistic regression model after adjusting for age, sex and H. pylori infection. Survival within each SNP group was plotted by Kaplan-Meier method and compared by log-rank test (recessive model). Hazard ratios with 95%CIs were computed by Cox regression model after adjusting for age, sex, histological type, tumor differentiation, clinical stage and post-operational chemotherapy.

RESULTS

All of the three loci were in Hardy-Weinberg equilibrium in the control group. Median follow-up time for the 600 GC patients included in the survival analysis was 36.2 mo (range, 2.1-66.7 mo; 95%CI: 34.3-36.5 mo). Patients with the P-534 A/A genotype had significantly shorter survival (HR = 1.38, 95%CI: 1.01-1.88, P = 0.042) than did the C/C or C/A genotype carriers after adjusting for age, sex, histological type, tumor differentiation, clinical stage and post-operational chemotherapy. This trend was more evident in patients who lived longer than 2.5 years (HR = 7.55, 95%CI: 2.16-26.32, P = 0.001). The P170 T/T genotype was associated with a shorter lifespan than the non-T/T genotypes, but not significantly so. None of the three genetic variants was found to be associated with risk of GC (including tumor stage, grade and distant metastasis) or with risk of gastric atrophy. Furthermore, no difference of CD24 expression was found among the genotypes.

CONCLUSION

The P-534 site in CD24 gene affects the overall survival of gastric cancer and may serve as a prognostic marker for gastric cancer.

Silencing of CD24 Enhances the PRIMA-1-Induced Restoration of Mutant p53 in Prostate Cancer Cells

PURPOSE

In prostate cancer cells, there is CD24-dependent inactivation of mutant p53, but the mechanism and its significance remain largely unknown. Here, we validated this observation and explored the therapeutic potential of targeting CD24 in TP53 mutant prostate cancer cells.

EXPERIMENTAL DESIGN

Overall, 553 prostate cancers (522 formalin-fixed paraffin-embedded and 31 frozen tissues) were assessed for protein or mRNA expression of CD24 and TP53 The effects of CD24 on p53-dependent transcriptional regulation, cancer cell growth, the cell cycle, apoptosis, and mutant p53 restoration were also determined.

RESULTS

As determined with three sample cohorts, CD24 and p53 were not expressed in prostate epithelial cells but in prostate cancer cells in 48% of cases for CD24 and 16% of cases for p53 (mutant form). Expressions of CD24 and mutant p53 were more frequently observed in late-stage and metastatic prostate tumors. Mutant p53 accompanied with CD24 was expressed in most cases (91.6%, 76/83). Silencing of CD24 increased the transcriptional activity of p53 target genes, such as CDKNA1, VDR, and TP53INP1, leading to suppression of p53-dependent cell growth, cell-cycle arrest, and apoptosis in most TP53-mutant prostate cancer cells. Silencing of CD24 enhanced restoration of PRIMA-1-induced mutant p53 in endogenous TP53(P223L/V274F) DU145 cells and in PC3 cells transfected with TP53(R273H) CONCLUSIONS: In human prostate cancers, there is CD24-dependent inactivation of mutant p53. The coexpression of CD24 and p53 may help identify aggressive cancers. Targeting CD24 provides a strategy to enhance mutant p53-restoring therapies, especially in patients with TP53(R273H) prostate cancer. Clin Cancer Res; 22(10); 2545-54. ©2015 AACR.

CD24 tracks divergent pluripotent states in mouse and human cells

Reprogramming is a dynamic process that can result in multiple pluripotent cell types emerging from divergent paths. Cell surface protein expression is a particularly desirable tool to categorize reprogramming and pluripotency as it enables robust quantification and enrichment of live cells. Here we use cell surface proteomics to interrogate mouse cell reprogramming dynamics and discover CD24 as a marker that tracks the emergence of reprogramming-responsive cells, while enabling the analysis and enrichment of transgene-dependent (F-class) and -independent (traditional) induced pluripotent stem cells (iPSCs) at later stages. Furthermore, CD24 can be used to delineate epiblast stem cells (EpiSCs) from embryonic stem cells (ESCs) in mouse pluripotent culture. Importantly, regulated CD24 expression is conserved in human pluripotent stem cells (PSCs), tracking the conversion of human ESCs to more naive-like PSC states. Thus, CD24 is a conserved marker for tracking divergent states in both reprogramming and standard pluripotent culture.

Characterizing the cellular stages that lead to induced reprogramming is of much interest and cell surface markers could offer unique advantages for this. Here the authors use surface proteomics and discover CD24 as a marker that tracks reprogramming-responsive cells and enables the analysis and enrichment of transgene-dependent and -independent induced pluriopotent stem cells.

Regulation of NEIL1 protein abundance by RAD9 is important for efficient base excision repair

RAD9 participates in DNA damage-induced cell cycle checkpoints and DNA repair. As a member of the RAD9-HUS1-RAD1 (9-1-1) complex, it can sense DNA damage and recruit ATR to damage sites. RAD9 binding can enhance activities of members of different DNA repair pathways, including NEIL1 DNA glycosylase, which initiates base excision repair (BER) by removing damaged DNA bases. Moreover, RAD9 can act independently of 9-1-1 as a gene-specific transcription factor. Herein, we show that mouse Rad9^−/− relative to Rad9^+/+ embryonic stem (ES) cells have reduced levels of Neil1 protein. Also, human prostate cancer cells, DU145 and PC-3, knocked down for RAD9 demonstrate reduced NEIL1 abundance relative to controls. We found that Rad9 is required for Neil1 protein stability in mouse ES cells, whereas it regulates NEIL1 transcription in the human cells. RAD9 depletion enhances sensitivity to UV, gamma rays and menadione, but ectopic expression of RAD9 or NEIL1 restores resistance. Glycosylase/apurinic lyase activity was reduced in Rad9^−/− mouse ES and RAD9 knocked-down human prostate cancer whole cell extracts, relative to controls. Neil1 or Rad9 addition restored this incision activity. Thus, we demonstrate that RAD9 regulates BER by controlling NEIL1 protein levels, albeit by different mechanisms in human prostate cancer versus mouse ES cells.