Deletion of CD44 promotes adipogenesis by regulating PPARγ and cell cycle-related pathways

CD44, a cell surface adhesion receptor and stem cell biomarker, is recently implicated in chronic metabolic diseases. Ablation of CD44 ameliorates adipose tissue inflammation and insulin resistance in obesity. Here, we investigated cell type-specific CD44 expression in human and mouse adipose tissue and further studied how CD44 in preadipocytes regulates adipocyte function. Using Crispr Cas9-mdediated gene deletion and lentivirus-mediated gene re-expression, we discovered that deletion of CD44 promotes adipocyte differentiation and adipogenesis, whereas re-expression of CD44 abolishes this effect and decreases insulin responsiveness and adiponectin secretion in 3T3-L1 cells. Mechanistically, CD44 does so via suppressing Pparg expression. Using quantitative proteomics analysis, we further discovered that cell cycle-regulated pathways were mostly decreased by deletion of CD44. Indeed, re-expression of CD44 moderately restored expression of proteins involved in all phases of the cell cycle. These data were further supported by increased preadipocyte proliferation rates in CD44-deficient cells and re-expression of CD44 diminished this effect. Our data suggest that CD44 plays a crucial role in regulating adipogenesis and adipocyte function possibly through regulating PPARγ and cell cycle-related pathways. This study provides evidence for the first time that CD44 expressed in preadipocytes plays key roles in regulating adipocyte function outside immune cells where CD44 is primarily expressed. Therefore, targeting CD44 in (pre)adipocytes may provide therapeutic potential to treat obesity-associated metabolic complications.

HMMR triggers immune evasion of hepatocellular carcinoma by inactivation of phagocyte killing

Hepatocellular carcinoma (HCC) acquires an immunosuppressive microenvironment, leading to unbeneficial therapeutic outcomes. Hyaluronan-mediated motility receptor (HMMR) plays a crucial role in tumor progression. Here, we found that aberrant expression of HMMR could be a predictive biomarker for the immune suppressive microenvironment of HCC, but the mechanism remains unclear. We established an HMMR-/- liver cancer mouse model to elucidate the HMMR-mediated mechanism of the dysregulated "don't eat me" signal. HMMR knockout inhibited liver cancer growth and induced phagocytosis. HMMRhigh liver cancer cells escaped from phagocytosis via sustaining CD47 signaling. Patients with HMMRhighCD47high expression showed a worse prognosis than those with HMMRlowCD47low expression. HMMR formed a complex with FAK/SRC in the cytoplasm to activate NF-κB signaling, which could be independent of membrane interaction with CD44. Notably, targeting HMMR could enhance anti-PD-1 treatment efficiency by recruiting CD8+ T cells. Overall, our data revealed a regulatory mechanism of the "don't eat me" signal and knockdown of HMMR for enhancing anti-PD-1 treatment.

Resting and activated bovine neutrophils and eosinophils differ in their responses to adrenergic agonists

Polymorphonuclear cells (PMN) provide a rapid response to infection and tissue damage and stress can modify these critical innate immune defences. The study of adrenergic receptor (AR) expression and function in bovine PMNs is limited but both neutrophils and eosinophils express numerous AR genes but differ significantly in their expression of individual AR genes. A flow cytometric technique was developed to differentiate between bovine neutrophils and eosinophils so both neutrophil and eosinophil responses to adrenergic agonists could be analysed. Neutrophils and eosinophils displayed significantly different changes in CD11b, L-selectin, and CD44 expression when activated by bovine serum opsonized zymosan and recombinant bovine interferon gamma. The responses of activated and resting neutrophils and eosinophils were then compared following stimulation with endogenous adrenergic agonists, epinephrine (E) norepinephrine (NE), and synthetic agonists targeting α1-, α2-, or β-ARs. Both resting and activated neutrophils and eosinophils displayed differences in iROS, CD44, and L-selectin expression following stimulation with E and NE. Resting neutrophils displayed pro-inflammatory responses to both E and NE, while resting eosinophils displayed a pro-inflammatory response to only NE. No single synthetic adrenergic agonist fully recapitulated responses observed with either E or NE and responses to adrenergic agonists were dose-dependent. In conclusion, bovine eosinophils and neutrophils responded to multiple adrenergic agonists by altering expression of proteins involved in immune surveillance and pro-inflammatory responses. Significant differences in neutrophil and eosinophil responses to adrenergic agonists are consistent with their differences in AR gene expression. This highlights the importance of analysing separately these two PMN subpopulations when investigating the effects of either endogenous or synthetic AR agonists.

All-trans retinoic acid pretreatment of mesenchymal stem cells enhances the therapeutic effect on acute kidney injury

A promising new therapy option for acute kidney injury (AKI) is mesenchymal stem cells (MSCs). However, there are several limitations to the use of MSCs, such as low rates of survival, limited homing capacity, and unclear differentiation. In search of better therapeutic strategies, we explored all-trans retinoic acid (ATRA) pretreatment of MSCs to observe whether it could improve the therapeutic efficacy of AKI. We established a renal ischemia/reperfusion injury model and treated mice with ATRA-pretreated MSCs via tail vein injection. We found that AKI mice treated with ATRA-MSCs significantly improved renal function compared with DMSO-MSCs treatment. RNA sequencing screened that hyaluronic acid (HA) production from MSCs promoted by ATRA. Further validation by chromatin immunoprecipitation experiments verified that retinoic acid receptor RARα/RXRγ was a potential transcription factor for hyaluronic acid synthase 2. Additionally, an in vitro hypoxia/reoxygenation model was established using human proximal tubular epithelial cells (HK-2). After co-culturing HK-2 cells with ATRA-pretreated MSCs, we observed that HA binds to cluster determinant 44 (CD44) and activates the PI3K/AKT pathway, which enhances the anti-inflammatory, anti-apoptotic, and proliferative repair effects of MSCs in AKI. Inhibition of the HA/CD44 axis effectively reverses the renal repair effect of ATRA-pretreated MSCs. Taken together, our study suggests that ATRA pretreatment promotes HA production by MSCs and activates the PI3K/AKT pathway in renal tubular epithelial cells, thereby enhancing the efficacy of MSCs against AKI.

Tumor necrosis factor-inducible gene 6 protein and its derived peptide ameliorate liver fibrosis by repressing CD44 activation in mice with alcohol-related liver disease

BACKGROUND

Alcohol-related liver disease (ALD) is a major health concern worldwide, but effective therapeutics for ALD are still lacking. Tumor necrosis factor-inducible gene 6 protein (TSG-6), a cytokine released from mesenchymal stem cells, was shown to reduce liver fibrosis and promote successful liver repair in mice with chronically damaged livers. However, the effect of TSG-6 and the mechanism underlying its activity in ALD remain poorly understood.

METHODS

To investigate its function in ALD mice with fibrosis, male mice chronically fed an ethanol (EtOH)-containing diet for 9 weeks were treated with TSG-6 (EtOH + TSG-6) or PBS (EtOH + Veh) for an additional 3 weeks.

RESULTS

Severe hepatic injury in EtOH-treated mice was markedly decreased in TSG-6-treated mice fed EtOH. The EtOH + TSG-6 group had less fibrosis than the EtOH + Veh group. Activation of cluster of differentiation 44 (CD44) was reported to promote HSC activation. CD44 and nuclear CD44 intracellular domain (ICD), a CD44 activator which were upregulated in activated HSCs and ALD mice were significantly downregulated in TSG-6-exposed mice fed EtOH. TSG-6 interacted directly with the catalytic site of MMP14, a proteolytic enzyme that cleaves CD44, inhibited CD44 cleavage to CD44ICD, and reduced HSC activation and liver fibrosis in ALD mice. In addition, a novel peptide designed to include a region that binds to the catalytic site of MMP14 suppressed CD44 activation and attenuated alcohol-induced liver injury, including fibrosis, in mice.

CONCLUSIONS

These results demonstrate that TSG-6 attenuates alcohol-induced liver damage and fibrosis by blocking CD44 cleavage to CD44ICD and suggest that TSG-6 and TSG-6-mimicking peptide could be used as therapeutics for ALD with fibrosis.

A Galectin-9-Driven CD11chigh Decidual Macrophage Subset Suppresses Uterine Vascular Remodeling in Preeclampsia

BACKGROUND

Preeclampsia is a serious disease of pregnancy that lacks early diagnosis methods or effective treatment, except delivery. Dysregulated uterine immune cells and spiral arteries are implicated in preeclampsia, but the mechanistic link remains unclear.

METHODS

Single-cell RNA sequencing and spatial transcriptomics were used to identify immune cell subsets associated with preeclampsia. Cell-based studies and animal models including conditional knockout mice and a new preeclampsia mouse model induced by recombinant mouse galectin-9 were applied to validate the pathogenic role of a CD11chigh subpopulation of decidual macrophages (dMφ) and to determine its underlying regulatory mechanisms in preeclampsia. A retrospective preeclampsia cohort study was performed to determine the value of circulating galectin-9 in predicting preeclampsia.

RESULTS

We discovered a distinct CD11chigh dMφ subset that inhibits spiral artery remodeling in preeclampsia. The proinflammatory CD11chigh dMφ exhibits perivascular enrichment in the decidua from patients with preeclampsia. We also showed that trophoblast-derived galectin-9 activates CD11chigh dMφ by means of CD44 binding to suppress spiral artery remodeling. In 3 independent preeclampsia mouse models, placental and plasma galectin-9 levels were elevated. Galectin-9 administration in mice induces preeclampsia-like phenotypes with increased CD11chigh dMφ and defective spiral arteries, whereas galectin-9 blockade or macrophage-specific CD44 deletion prevents such phenotypes. In pregnant women, increased circulating galectin-9 levels in the first trimester and at 16 to 20 gestational weeks can predict subsequent preeclampsia onset.

CONCLUSIONS

These findings highlight a key role of a distinct perivascular inflammatory CD11chigh dMφ subpopulation in the pathogenesis of preeclampsia. CD11chigh dMφ activated by increased galectin-9 from trophoblasts suppresses uterine spiral artery remodeling, contributing to preeclampsia. Increased circulating galectin-9 may be a biomarker for preeclampsia prediction and intervention.

Extracellular matrix marker LAMC2 targets ZEB1 to promote TNBC malignancy via up-regulating CD44/STAT3 signaling pathway

BACKGROUND

Triple negative breast cancer (TNBC) is a heterogeneous and aggressive disease characterized by a high risk of mortality and poor prognosis. It has been reported that Laminin γ2 (LAMC2) is highly expressed in a variety of tumors, and its high expression is correlated with cancer development and progression. However, the function and mechanism by which LAMC2 influences TNBC remain unclear.

METHODS

Kaplan-Meier survival analysis and Immunohistochemical (IHC) staining were used to examine the expression level of LAMC2 in TNBC. Subsequently, cell viability assay, wound healing and transwell assay were performed to detect the function of LAMC2 in cell proliferation and migration. A xenograft mouse model was used to assess tumorigenic function of LAMC2 in vivo. Luciferase reporter assay and western blot were performed to unravel the underlying mechanism.

RESULTS

In this study, we found that higher expression of LAMC2 significantly correlated with poor survival in the TNBC cohort. Functional characterization showed that LAMC2 promoted cell proliferation and migration capacity of TNBC cell lines via up-regulating CD44. Moreover, LAMC2 exerted oncogenic roles in TNBC through modulating the expression of epithelial-mesenchymal transition (EMT) markers. Luciferase reporter assay verified that LAMC2 targeted ZEB1 to promote its transcription. Interestingly, LAMC2 regulated cell migration in TNBC via STAT3 signaling pathway.

CONCLUSION

LAMC2 targeted ZEB1 via activating CD44/STAT3 signaling pathway to promote TNBC proliferation and migration, suggesting that LAMC2 could be a potential therapeutic target in TNBC patients.

A Predictive Noninvasive Single-Nucleotide Variation-Based Biomarker Signature for Resectable Pancreatic Cancer: Protocol for a Prospective Validation Study

BACKGROUND

Single-nucleotide variations (SNVs; formerly SNPs) are inherited genetic variants that can be easily determined in routine clinical practice using a simple blood or saliva test. SNVs have potential to serve as noninvasive biomarkers for predicting cancer-specific patient outcomes after resection of pancreatic ductal adenocarcinoma (PDAC). Two recent analyses led to the identification and validation of three SNVs in the CD44 and CHI3L2 genes (rs187115, rs353630, and rs684559), which can be used as predictive biomarkers to help select patients most likely to benefit from pancreatic resection. These variants were associated with an over 2-fold increased risk for tumor-related death in three independent PDAC study cohorts from Europe and the United States, including The Cancer Genome Atlas cohorts (reaching a P value of 1×10-8). However, these analyses were limited by the inherent biases of a retrospective study design, such as selection and publication biases, thereby limiting the clinical use of these promising biomarkers in guiding PDAC therapy.

OBJECTIVE

To overcome the limitations of previous retrospectively designed studies and translate the findings into clinical practice, we aim to validate the association of the identified SNVs with survival in a controlled setting using a prospective cohort of patients with PDAC following pancreatic resection.

METHODS

All patients with PDAC who will undergo pancreatic resection at three participating hospitals in Switzerland and fulfill the inclusion criteria will be included in the study consecutively. The SNV genotypes will be determined using standard genotyping techniques from patient blood samples. For each genotyped locus, log-rank and Cox multivariate regression tests will be performed, accounting for the relevant covariates American Joint Committee on Cancer stage and resection status. Clinical follow-up data will be collected for at least 3 years. Sample size calculation resulted in a required sample of 150 patients to sufficiently power the analysis.

RESULTS

The follow-up data collection started in August 2019 and the estimated end of data collection will be in May 2027. The study is still recruiting participants and 142 patients have been recruited as of November 2023. The DNA extraction and genotyping of the SNVs will be performed after inclusion of the last patient. Since no SNV genotypes have been determined, no data analysis has been performed to date. The results are expected to be published in 2027.

CONCLUSIONS

This is the first prospective study of the CD44 and CHI3L2 SNV-based biomarker signature in PDAC. A prospective validation of this signature would enable its clinical use as a noninvasive predictive biomarker of survival after pancreatic resection that is readily available at the time of diagnosis and can assist in guiding PDAC therapy. The results of this study may help to individualize treatment decisions and potentially improve patient outcomes.

INTERNATIONAL REGISTERED REPORT IDENTIFIER (IRRID)

DERR1-10.2196/54042.

circCDK13-loaded small extracellular vesicles accelerate healing in preclinical diabetic wound models

Chronic wounds are a major complication in patients with diabetes. Here, we identify a therapeutic circRNA and load it into small extracellular vesicles (sEVs) to treat diabetic wounds in preclinical models. We show that circCDK13 can stimulate the proliferation and migration of human dermal fibroblasts and human epidermal keratinocytes by interacting with insulin-like growth factor 2 mRNA binding protein 3 in an N6-Methyladenosine-dependent manner to enhance CD44 and c-MYC expression. We engineered sEVs that overexpress circCDK13 and show that local subcutaneous injection into male db/db diabetic mouse wounds and wounds of streptozotocin-induced type I male diabetic rats could accelerate wound healing and skin appendage regeneration. Our study demonstrates that the delivery of circCDK13 in sEVs may present an option for diabetic wound treatment.

Expression of CD44, PCNA and E-cadherin in pterygium tissues

PURPOSE

Pterygium is a common ocular surface disease defined by fibrovascular conjunctival growth extending onto the cornea. However, its pathogenesis remains unclear. This study aimed to determine the role of CD44, proliferating cell nuclear antigen (PCNA), and E-cadherin in pterygium formation and recurrence.

METHODS

Sixty patients with pterygium participated in the study, and we collected conjunctival samples from 30 patients to form a control group. CD44, PCNA, and E-cadherin expressions in surgically excised pterygium were compared with tissue samples from the control group.

RESULTS

We observed that the percentages of CD44 and PCNA were statistically higher in the primary pterygium group and recurrent pterygium group than in the control group (P < 0.001 and P < 0.001, respectively). Conversely, E-cadherin values were statistically higher in the control group than in the primary and recurrent pterygium groups (P = 0.013 and P < 0.001, respectively).

CONCLUSION

Cell proliferation and cell adhesion factors may play important roles in the pathogenesis of pterygium.

SPP1 represents a therapeutic target that promotes the progression of oesophageal squamous cell carcinoma by driving M2 macrophage infiltration

BACKGROUND

Tumour-associated macrophages (TAMs) are an important component of the tumour microenvironment (TME). However, the crosstalk between oesophageal squamous cell carcinoma (ESCC) cells and TAMs remains largely unexplored.

METHODS

Clinical samples and the TCGA database were used to evaluate the relevance of SPP1 and TAM infiltration in ESCC. Mouse models were constructed to investigate the roles of macrophages educated by SPP1 in ESCC. Macrophage phenotypes were determined using qRT‒PCR and immunohistochemical staining. RNA sequencing was performed to elucidate the mechanism.

RESULTS

Increasing expression of SPP1 correlated with M2-like TAM accumulation in ESCC, and they both predicted poor prognosis in the ESCC cohort. Knockdown of SPP1 significantly inhibited the infiltration of M2 TAMs in xenograft tumours. In vivo mouse model experiments showed that SPP1-mediated education of macrophages plays an essential role in the progression of ESCC. Mechanistically, SPP1 recruited macrophages and promoted M2 polarisation via CD44/PI3K/AKT signalling activation and then induced VEGFA and IL6 secretion to sustain ESCC progression. Finally, blockade of SPP1 with RNA aptamer significantly inhibited tumour growth and M2 TAM infiltration in xenograft mouse models.

CONCLUSIONS

This study highlights SPP1-mediated crosstalk between ESCC cells and TAMs in ESCC. SPP1 could serve as a potential target in ESCC therapy.

CRISPR/Cas9-mediated silencing of CD44: unveiling the role of hyaluronic acid-mediated interactions in cancer drug resistance

A comprehensive overview of CD44 (CD44 Molecule (Indian Blood Group)), a cell surface glycoprotein, and its interaction with hyaluronic acid (HA) in drug resistance mechanisms across various types of cancer is provided, where CRISPR/Cas9 gene editing was utilized to silence CD44 expression and examine its impact on cancer cell behavior, migration, invasion, proliferation, and drug sensitivity. The significance of the HA-CD44 axis in tumor microenvironment (TME) delivery and its implications in specific cancer types, the influence of CD44 variants and the KHDRBS3 (KH RNA Binding Domain Containing, Signal Transduction Associated 3) gene on cancer progression and drug resistance, and the potential of targeting HA-mediated pathways using CRISPR/Cas9 gene editing technology to overcome drug resistance in cancer were also highlighted.

Extracellular Matrix Remodeling in Atopic Dermatitis Harnesses the Onset of an Asthmatic Phenotype and Is a Potential Contributor to the Atopic March

The development of atopic dermatitis in infancy, and subsequent allergies, such as asthma in later childhood, is known as the atopic march. The mechanism is largely unknown, however the course of disease indicates an inter-epithelial crosstalk, through the onset of inflammation in the skin and progression to other mucosal epithelia. In this study, we investigated if and how skin-lung epithelial crosstalk contributes to the development of the atopic march. First, we emulated inter-epithelial crosstalk through indirect coculture of bioengineered atopic-like skin disease models and three-dimensional bronchial epithelial models triggering an asthma-like phenotype in the latter. A subsequent secretome analysis identified thrombospondin-1, CD44, complement factor C3, fibronectin, and syndecan-4 as potentially relevant skin-derived mediators. Because these mediators are extracellular matrix-related proteins, we then studied the involvement of the extracellular matrix, unveiling distinct proteomic, transcriptomic, and ultrastructural differences in atopic samples. The latter indicated extracellular matrix remodeling triggering the release of the above-mentioned mediators. In vivo mouse data showed that exposure to these mediators dysregulated activated circadian clock genes which are increasingly discussed in the context of atopic diseases and asthma development. Our data point toward the existence of a skin-lung axis that could contribute to the atopic march driven by skin extracellular matrix remodeling.

CD44 Expression in Clear Cell Renal Cell Carcinoma (ccRCC) Correlates with Tumor Grade and Patient Survival and Is Affected by Gene Methylation

Clear cell RCC (ccRCC) represents the most common type of kidney cancer, with surgery being the only potential curative treatment. Almost one-third of ccRCC patients relapse either locally or as cases of distant metastases. Several biomarkers have been employed in order to separate ccRCC patients with better prognosis or to predict treatment outcomes, with limited results. CD44 is a membrane glycoprotein with multiple roles in normal development but also cancer. Recently, the CD44 standard isoform has been implicated in tumor progression and the metastasis cascade through microenvironment interactions. Here, through CD44 immunohistochemical staining of ccRCC patient samples and TCGA data analysis, we sought to elucidate the expression patterns (mRNA and protein) of CD44 in clear cell RCC and correlate its expression with clinicopathological parameters. We were able to show that CD44 expression presents a positive association with tumor grade and overall survival, predicting a worse patient outcome in ccRCC. In addition, our data indicate that the CD44 mRNA upregulation can be attributed to reduced gene methylation, implicating epigenetic gene regulation in ccRCC development and progression.

Dynamics of CD44+ bovine nucleus pulposus cells with inflammation

Intervertebral Disc (IVD) degeneration has been associated with a chronic inflammatory response, but knowledge on the contribution of distinct IVD cells, namely CD44, to the progression of IVD degeneration remains elusive. Here, bovine nucleus pulposus (NP) CD44 cells were sorted and compared by gene expression and proteomics with the negative counterpart. NP cells were then stimulated with IL-1b (10 ng/ml) and dynamics of CD44 gene and protein expression was analyzed upon pro-inflammatory treatment. The results emphasize that CD44 has a multidimensional functional role in IVD metabolism, ECM synthesis and production of neuropermissive factors. CD44 widespread expression in NP was partially associated with CD14 and CD45, resulting in the identification of distinct cell subsets. In conclusion, this study points out CD44 and CD44-based cell subsets as relevant targets in the modulation of the IVD pro-inflammatory/degenerative cascade.

Hyaluronic Acid Prevents Fusion of Brain Tumor-Derived Spheroids and Selectively Alters Their Gene Expression Profile

Hyaluronic acid (HA), a major glycosaminoglycan of the brain extracellular matrix, modulates cell behaviors through binding its receptor, Cd44. In this study, we assessed the influence of HA on high-grade brain tumors in vitro. The model comprised cell cultures derived from six rodent carcinogen-induced brain tumors, forming 3D spheroids prone to spontaneous fusion. Supplementation of the standard culture medium with 0.25% HA significantly inhibited the fusion rates, preserving the shape and size uniformity of spheroids. The 3D cultures were assigned to two groups; a Cd44lo group had a tenfold decreased relative expression of Cd44 than another (Cd44hi) group. In addition, these two groups differed by expression levels of Sox2 transcription factor; the correlation analysis revealed a tight negative association for Cd44 and Sox2. Transcriptomic responses of spheroids to HA exposure also depended on Cd44 expression levels, from subtle in Cd44lo to more pronounced and specific in Cd44hi, involving cell cycle progression, PI3K/AKT/mTOR pathway activation, and multidrug resistance genes. The potential HA-induced increase in brain tumor 3D models' resistance to anticancer drug therapy should be taken into account when designing preclinical studies using HA scaffold-based models. The property of HA to prevent the fusion of brain-derived spheroids can be employed in CNS regenerative medicine and experimental oncology to ensure the production of uniform, controllably fusing neurospheres when creating more accurate in vitro brain models.

Coupled scRNA-seq and Bulk-seq reveal the role of HMMR in hepatocellular carcinoma

Background

Hyaluronan-mediated motility receptor (HMMR) is overexpressed in multiple carcinomas and influences the development and treatment of several cancers. However, its role in hepatocellular carcinoma (HCC) remains unclear.

Methods

The "limma" and "GSVA" packages in R were used to perform differential expression analysis and to assess the activity of signalling pathways, respectively. InferCNV was used to infer copy number variation (CNV) for each hepatocyte and "CellChat" was used to analyse intercellular communication networks. Recursive partitioning analysis (RPA) was used to re-stage HCC patients. The IC50 values of various drugs were evaluated using the "pRRophetic" package. In addition, quantitative reverse transcription polymerase chain reaction (qRT-PCR) was performed to confirm HMMR expression in an HCC tissue microarray. Flow cytometry (FCM) and cloning, Edu and wound healing assays were used to explore the capacity of HMMR to regulate HCC tumour.

Results

Multiple cohort studies and qRT-PCR demonstrated that HMMR was overexpressed in HCC tissue compared with normal tissue. In addition, HMMR had excellent diagnostic performance. HMMR knockdown inhibited the proliferation and migration of HCC cells in vitro. Moreover, high HMMR expression was associated with "G2M checkpoint" and "E2F targets" in bulk RNA and scRNA-seq, and FCM confirmed that HMMR could regulate the cell cycle. In addition, HMMR was involved in the regulation of the tumour immune microenvironment via immune cell infiltration and intercellular interactions. Furthermore, HMMR was positively associated with genomic heterogeneity with patients with high HMMR expression potentially benefitting more from immunotherapy. Moreover, HMMR was associated with poor prognosis in patients with HCC and the re-staging by recursive partitioning analysis (RPA) gave a good prognosis prediction value and could guide chemotherapy and targeted therapy.

Conclusion

The results of the present study show that HMMR could play a role in the diagnosis, prognosis, and treatments of patients with HCC based on bulk RNA-seq and scRAN-seq analyses and is a promising molecular marker for HCC.

Anchoring of hyaluronan glycocalyx to CD44 reduces sensitivity of HER2-positive gastric cancer cells to trastuzumab

Trastuzumab is widely used in human epidermal growth factor receptor 2 (HER2)-positive gastric cancer (GC) therapy, but ubiquitous resistance limits its clinical application. In this study, we first showed that CD44 antigen is a significant predictor of overall survival for patients with HER2-positive GC. Next, we found that CD44 could be co-immunoprecipitated and co-localized with HER2 on the membrane of GC cells. By analyzing the interaction between CD44 and HER2, we identified that CD44 could upregulate HER2 protein by inhibiting its proteasome degradation. Notably, the overexpression of CD44 could decrease the sensitivity of HER2-positive GC cells to trastuzumab. Further mechanistic study showed that CD44 upregulation could induce its ligand, hyaluronan (HA), to deposit on the cancer cell surface, resulting in covering up the binding sites of trastuzumab to HER2. Removing the HA glycocalyx restored sensitivity of the cells to trastuzumab. Collectively, our findings suggested a role for CD44 in regulating trastuzumab sensitivity and provided novel insights into HER2-targeted therapy.

Blocking EGR1/TGF-β1 and CD44s/STAT3 Crosstalk Inhibits Peritoneal Metastasis of Gastric Cancer

Peritoneal metastasis (PM) continues to limit the clinical efficacy of gastric cancer (GC). Early growth response 1 (EGR1) plays an important role in tumor cell proliferation, angiogenesis and invasion. However, the role of EGR1 derived from the tumor microenvironment in reshaping the phenotypes of GC cells and its specific molecular mechanisms in increasing the potential for PM are still unclear. In this study, we reported that EGR1 was significantly up-regulated in mesothelial cells from GC peritoneal metastases, leading to enhanced epithelial-mesenchymal transformation (EMT) and stemness phenotypes of GC cells under co-culture conditions. These phenotypes were achieved through the transcription and secretion of TGF-β1 by EGR1 in mesothelial cells, which could regulate the expression and internalization of CD44s. After being internalized into the cytoplasm, CD44s interacted with STAT3 to promote STAT3 phosphorylation and activation, and induced EMT and stemness gene transcription, thus positively regulating the metastasis of GC cells. Moreover, TGF-β1 secretion in the PM microenvironment was significantly increased compared with the matched primary tumor. The blocking effect of SHR-1701 on TGF-β1 was verified by inhibiting peritoneal metastases in xenografts. Collectively, the interplay of EGR1/TGF-β1/CD44s/STAT3 signaling between mesothelial cells and GC cells induces EMT and stemness phenotypes, offering potential as a therapeutic target for PM of GC.

High prevalence of CD44 and its ligand low molecular weight hyaluronan in plasma of HNSCC patients: clinical significance

BACKGROUND

This study aims to evaluate the role of cancer stem cell marker, CD44, and its ligand HA as potential molecular biomarker for early detection of HNSCC.

METHODS AND RESULTS

The expression profile (mRNA/Protein) of CD44 variants were analysed in primary HNSCC lesions and plasma of the patients. Then, prevalence of HA variants was analysed in plasma of the patients. The mRNA expression of CD44 variants, CD44S and CD44v3, were significantly high in both early (stage I/II) and late (stage III/IV) invasive lesions, with predominant expression of CD44v3 in the late-stage lesions. In plasma of HNSCC patients, increased levels of SolCD44, CD44-ICD and unique 62 KD CD44 variants with respect to standard CD44S were seen, in comparison to their prevalence in plasma of normal individuals. The abundance of CD44-ICD and 62 KD variants were significantly high in plasma of late stage HNSCC patients. Interestingly, significantly high level of low molecular weight HA(LMW HA) with respect to high molecular weight HA(HMW HA) was seen in plasma of HNSCC patients irrespective of clinical stages. On the contrary, high HMW HA level in plasma of normal individuals was seen. The high level of LMW HA in plasma of HNSCC patients might be due to combinatorial effect of increased mRNA expression of HA synthesizing enzyme HAS1/2/3 and HA degrading enzyme HYAL1/2, as seen in the primary HNSCC samples.

CONCLUSION

Thus, our data revealed the importance of specific CD44 and HA variants in plasma of HNSCC patients during its development as potential non-invasive molecular biomarker of the disease.

Expression of CD44 is regulated by ELF3 in 5-FU treated colorectal cancer cells

The development of chemoresistance in colorectal cancer (CRC) cells was usually thought to be inevitable as a result of continuing exposure to chemotherapeutic drugs. The existence of cancer stem cells (CSCs) within CRC tissues was recently suggested to play importance roles for this process. In this study, in order to mimic a dose schedule used in clinic (continuous infusion), low dose of fluorouracil (IC10 of 5-FU) was used to treat CRC cells. Our results showed that the expression of CD44, including some other CSCs markers were all increased after 5-FU treatment. The stemness properties of survived CRC cells were also observed to be enhanced. RNA-seq analysis revealed that ELF3, one of the members of ETS (E26 transformation-specific) transcription activator family, was increased along with CD44 after 5-FU treatment of CRC cells. Results from dual-luciferase reporter assay revealed that the transcription of CD44 could be activated by ELF3 in CRC cells. The induced CD44 expression in 5-FU treated CRC cells could also be decreased after the expression of ELF3 was inhibited. Moreover, it could be observed that the expression of ELF3 is significantly higher in CD44+ CRC cells. Taken together, our results suggested that CD44 expression might be regulated by ELF3 and could be induced after 5-FU treatment of CRC cells. Inhibition of ELF3 might be a promising treatment method when it was used in combination with chemotherapeutics to overcome chemoresistance formation during CRC treatment in clinic.

Spontaneous metastasis xenograft models link CD44 isoform 4 to angiogenesis, hypoxia, EMT and mitochondria-related pathways in colorectal cancer

Hematogenous metastasis limits the survival of colorectal cancer (CRC) patients. Here, we illuminated the roles of CD44 isoforms in this process. Isoforms 3 and 4 were predominantly expressed in CRC patients. CD44 isoform 4 indicated poor outcome and correlated with epithelial-mesenchymal transition (EMT) and decreased oxidative phosphorylation (OxPhos) in patients; opposite associations were found for isoform 3. Pan-CD44 knockdown (kd) independently impaired primary tumor formation and abrogated distant metastasis in CRC xenografts. The xenograft tumors mainly expressed the clinically relevant CD44 isoforms 3 and 4. Both isoforms were enhanced in the paranecrotic, hypoxic tumor regions but were generally absent in lung metastases. Upon CD44 kd, tumor angiogenesis was increased in the paranecrotic areas, accompanied by reduced hypoxia-inducible factor-1α and CEACAM5 but increased E-cadherin expression. Mitochondrial genes and proteins were induced upon pan-CD44 kd, as were OxPhos genes. Hypoxia increased VEGF release from tumor spheres, particularly upon CD44 kd. Genes affected upon CD44 kd in xenografts specifically overlapped concordantly with genes correlating with CD44 isoform 4 (but not isoform 3) in patients, validating the clinical relevance of the used model and highlighting the metastasis-promoting role of CD44 isoform 4.

CD44s and CD44v8-10 isoforms confer acquired resistance to osimertinib by activating the ErbB3/STAT3 signaling pathway

AIMS

Although epidermal growth factor receptor (EGFR)-mutant lung cancers respond well to osimertinib, acquired resistance to osimertinib eventually develops through EGFR-dependent and EGFR-independent resistance mechanisms. CD44 splicing variants are widely expressed in lung cancer tissues. However, it remains unclear whether specific splicing variants are involved in acquired resistance to osimertinib.

MAIN METHODS

The real-time PCR was performed to measure the expression levels of total CD44 and specific CD44 splicing variants (CD44s or CD44v). Gene knockdown and restoration were performed to investigate the effects of CD44 splicing variants on osimertinib sensitivity. Activation of the signaling pathway was evaluated using receptor-tyrosine-kinase phosphorylation membrane arrays, co-immunoprecipitation, and western blotting.

KEY FINDINGS

Clinical analysis demonstrated that the expression level of total CD44 increased in primary cancer cells from lung adenocarcinomas patients after the development of acquired resistance to osimertinib. Furthermore, osimertinib-resistant cells showed elevated levels of either the CD44s variant or CD44v variants. Manipulations of CD44s or CD44v8-10 were performed to investigate their effects on treatment sensitivity to osimertinib. Knockdown of CD44 increased osimertinib-induced cell death in osimertinib-resistant cells. However, restoration of CD44s or CD44v8-10 in CD44-knockdown H1975/AZD-sgCD44 cells induced osimertinib resistance. Mechanically, we showed that ErbB3 interacted with CD44 and was transactivated by CD44, that consequently triggered activation of the ErbB3/STAT3 signaling pathway and led to CD44s- or CD44v8-10-mediated osimertinib resistance.

SIGNIFICANCE

CD44 is a co-receptor for ErbB3 and triggers activation of the ErbB3 signaling axis, leading to acquired resistance to osimertinib. CD44/ErbB3 signaling may represent a therapeutic target for overcoming osimertinib resistance.

The v8-10 variant isoform of CD44 is selectively expressed in the normal human colonic stem cell niche and frequently is overexpressed in colon carcinomas during tumor development

CD44 protein and its variant isoforms are expressed in cancer stem cells (CSCs), and various CD44 isoforms can have different functional roles in cells. Our goal was to investigate how different CD44 isoforms contribute to the emergence of stem cell (SC) overpopulation that drives colorectal cancer (CRC) development. Specific CD44 variant isoforms are selectively expressed in normal colonic SCs and become overexpressed in CRCs during tumor development. We created a unique panel of anti-CD44 rabbit genomic antibodies to 16 specific epitopes that span the entire length of the CD44 molecule. Our panel was used to comprehensively investigate the expression of different CD44 isoforms in matched pairs (n = 10) of malignant colonic tissue and adjacent normal mucosa, using two (IHC & IF) immunostaining approaches. We found that: i) CD44v8-10 is selectively expressed in the normal human colonic SC niche; ii) CD44v8-10 is co-expressed with the SC markers ALDH1 and LGR5 in normal and malignant colon tissues; iii) colon carcinoma tissues frequently (80%) stain for CD44v8-10 while staining for CD44v6 was less frequent (40%). Given that CD44v8-10 expression is restricted to cells in the normal human colonic SC niche and CD44v8-10 expression progressively increases during CRC development, CD44v8-10 expression likely contributes to the SC overpopulation that drives the development and growth of colon cancers. Since the CD44 variant v8-10 epitope is located on CD44's extracellular region, it offers great promise for targeted anti-CSC treatment approaches.

Cell aggregation activates small GTPase Rac1 and induces CD44 cleavage by maintaining lipid raft integrity

Lipid rafts are highly ordered membrane domains that are enriched in cholesterol and glycosphingolipids and serve as major platforms for signal transduction. Cell detachment from the extracellular matrix (ECM) triggers lipid raft disruption and anoikis, which is a barrier for cancer cells to metastasize. Compared to single circulating tumor cells (CTCs), our recent studies have demonstrated that CD44-mediatd cell aggregation enhances the stemness, survival and metastatic ability of aggregated cells. Here, we investigated whether and how lipid rafts are involved in CD44-mediated cell aggregation. We found that cell detachment, which mimics the condition when tumor cells detach from the ECM to metastasize, induced lipid raft disruption in single cells, but lipid raft integrity was maintained in aggregated cells. We further found that lipid raft integrity in aggregated cells was required for Rac1 activation to prevent anoikis. In addition, CD44 and γ-secretase coexisted at lipid rafts in aggregated cells, which promoted CD44 cleavage and generated CD44 intracellular domain (CD44 ICD) to enhance stemness of aggregated cells. Consequently, lipid raft disruption inhibited Rac1 activation, CD44 ICD generation, and metastasis. Our findings reveal two new pathways regulated by CD44-mediated cell aggregation via maintaining lipid raft integrity. These findings also suggest that targeting cell aggregation-mediated pathways could be a novel therapeutic strategy to prevent CTC cluster-initiated metastasis.