HSPG2 Antibody

What is HSPG2 and why is it important in research?

HSPG2 (Heparan Sulfate Proteoglycan 2) is a large basement membrane-specific proteoglycan with a mass of approximately 468.8 kDa and 4391 amino acid residues in humans. It is primarily localized in the extracellular matrix and is secreted by cells. HSPG2 is an integral component of basement membranes and is notably expressed in cerebrospinal fluid, fibroblasts, and urine . The protein undergoes post-translational modifications including O-glycosylation and protein cleavage. It is important in research due to its roles in tissue architecture, cell signaling, and its implications in various pathological conditions including Schwartz-Jampel syndrome and multiple cancer types .

What are the common applications for HSPG2 antibodies in scientific research?

HSPG2 antibodies are utilized across multiple experimental platforms in scientific research:

• Immunohistochemistry (IHC) - Most widely used application for tissue localization

• Western Blot (WB) - For protein detection and quantification

• Enzyme-Linked Immunosorbent Assay (ELISA) - For quantitative measurement

• Immunofluorescence (IF) - For subcellular localization studies

Over 70 citations in the scientific literature describe the use of HSPG2 antibodies across these applications . These diverse methodologies allow researchers to investigate HSPG2 expression, localization, and function in various biological contexts, particularly in cancer research and developmental biology.

What is the expected molecular weight of HSPG2 in Western blot analysis?

The expected molecular weight for HSPG2 in Western blot analysis is approximately 469 kDa . This large molecular weight reflects the protein's substantial size and complex structure. In experimental validation, researchers have observed bands at this expected size when using anti-HSPG2 antibodies. For example, Western blot analysis using the anti-HSPG2 antibody PB9277 demonstrated a specific band at approximately 469 kDa when testing human Caco-2 and A549 whole cell lysates . It's worth noting that there has been some confusion regarding the molecular weight, as evidenced by a researcher question about a discrepancy between observing a 69 kDa versus 469 kDa band, which was clarified to be 469 kDa according to UniProt database information .

What alternative names and orthologs exist for HSPG2?

HSPG2 is known by several alternative names in scientific literature:

HSPG2 orthologs have been identified across multiple species, including mouse, rat, bovine, frog, zebrafish, chimpanzee, and chicken . This conservation across species indicates the evolutionary importance of this protein and provides researchers with various model organisms for studying HSPG2 function.

How does HSPG2 expression correlate with prognosis across different cancer types?

HSPG2 demonstrates variable expression patterns across cancer types, with significant prognostic implications:

The variable expression patterns and differential prognostic significance across cancer types highlight the context-dependent roles of HSPG2 in cancer biology.

What is the relationship between HSPG2 and normal hematopoiesis in acute myeloid leukemia?

HSPG2 plays a significant role in normal hematopoiesis, particularly in the context of acute myeloid leukemia (AML):

• HSPG2 in bone marrow endothelial progenitor cells (BM EPCs) specifically supports normal hematopoiesis. Knockdown experiments targeting HSPG2 demonstrated that the hematopoiesis-support ability of BM EPCs is directly related to their HSPG2 expression level .

• Ara-C (cytarabine) intervention, a common chemotherapy agent in AML, was found to impair both HSPG2 levels and BM EPC functions, suggesting a mechanism by which chemotherapy might affect normal hematopoiesis .

• HSPG2 treatment in vitro was able to alleviate the damage caused by Ara-C, indicating a potential protective effect for normal hematopoietic function .

• Importantly, HSPG2 did not increase the leukemia cells-supporting ability of EPCs in complete remission, suggesting specificity for normal hematopoiesis rather than promoting leukemic cell growth .

• RNA-sequencing revealed that HSPG2 knockdown decreased the regulation of angiogenesis and hematopoiesis while increasing the negative regulation of cell migration in BM EPCs .

These findings suggest that HSPG2 could be explored as a potential target for protecting normal hematopoiesis during AML treatment.

How does HSPG2 interact with the tumor immune microenvironment across cancer types?

HSPG2 demonstrates significant associations with tumor immune microenvironment components across multiple cancer types:

• HSPG2 expression correlates with immune cell infiltration patterns in various cancers, as demonstrated by TIMER database analysis. These correlations include associations with cancer-associated fibroblasts, endothelial cells, and hematopoietic stem cells .

• HSPG2 expression has been linked to immune checkpoint inhibitor outcomes in melanoma and non-small-cell lung cancer, suggesting a role in modulating response to immunotherapy .

• DNA methylation status of HSPG2 correlates with its expression and immunological features in multiple cancer types, indicating epigenetic regulation may influence HSPG2's role in the tumor immune microenvironment .

• The significant correlation between HSPG2 and tumor mutational burden (TMB) and microsatellite instability (MSI) in certain cancers suggests interactions with mechanisms that influence tumor immunogenicity and potential response to immunotherapy .

These associations highlight HSPG2's complex role in modulating the tumor immune microenvironment, which may have implications for understanding treatment response and developing targeted therapies.

What is the relationship between HSPG2 and epigenetic modifications in cancer biology?

HSPG2 demonstrates important relationships with epigenetic modifications, particularly DNA methylation, in cancer:

• DNA methylation of the HSPG2 promoter differs between tumor and normal tissues in several cancer types, suggesting epigenetic dysregulation may influence HSPG2 expression in cancer .

• Analysis using the UALCAN and SMART databases revealed specific distribution patterns of methylated probes in chromosomes related to HSPG2, providing insights into the regulatory mechanisms of this gene .

• The correlation between HSPG2 methylation status and gene expression suggests that epigenetic modifications are a key regulatory mechanism controlling HSPG2 levels in different cancer contexts .

• Epigenetic changes in HSPG2 may influence downstream pathways including angiogenesis, cell migration, and immune infiltration, contributing to the varied roles of HSPG2 in different cancer types .

Understanding these epigenetic relationships provides potential avenues for therapeutic targeting and biomarker development in cancer diagnostics and prognostics.

What are the optimal conditions for Western blot detection of HSPG2?

Based on validated protocols, the following conditions are optimal for Western blot detection of HSPG2:

• Gel Preparation and Electrophoresis:

  • Use a 5-20% SDS-PAGE gradient gel to accommodate the large size of HSPG2 (469 kDa)

  • Run stacking gel at 70V and resolving gel at 90V for 2-3 hours

  • Load approximately 50μg of protein sample per lane under reducing conditions

• Protein Transfer:

  • Transfer proteins to a nitrocellulose membrane at 150mA for 50-90 minutes

  • Longer transfer times may be necessary due to the high molecular weight of HSPG2

• Blocking and Antibody Incubation:

  • Block membrane with 5% non-fat milk in TBS for 1.5 hours at room temperature

  • Incubate with anti-HSPG2 antibody (e.g., PB9277) at 0.5 μg/mL overnight at 4°C

  • Wash with TBS-0.1% Tween three times, 5 minutes each

  • Probe with goat anti-rabbit IgG-HRP secondary antibody at 1:10000 dilution for 1.5 hours at room temperature

• Detection:

  • Develop using an enhanced chemiluminescent detection kit

  • Expect to observe a specific band at approximately 469 kDa

These optimized conditions have been validated using human Caco-2 and A549 whole cell lysates and provide clear detection of HSPG2 with minimal background interference.

How can one address cross-reactivity concerns when using HSPG2 antibodies across species?

When addressing cross-reactivity concerns for HSPG2 antibodies across different species, researchers should consider:

• Sequence Homology Analysis:

  • HSPG2 orthologs exist in multiple species including mouse, rat, bovine, frog, zebrafish, chimpanzee, and chicken

  • Before testing, analyze sequence homology between the human HSPG2 epitope and the target species to predict potential cross-reactivity

• Validation Studies:

  • Perform preliminary testing with positive and negative controls from the target species

  • Consider using tissue known to express high HSPG2 levels, such as basement membranes

  • A verified customer query indicated interest in using anti-HSPG2 antibody PB9277 (validated for human tissues) on bovine tissues, with the manufacturer suggesting "a good chance of cross-reactivity"

• Pilot Experiments:

  • Conduct titration experiments with different antibody concentrations

  • Include appropriate blocking controls to distinguish specific from non-specific binding

  • Test multiple antibodies targeting different epitopes of HSPG2 if available

• Alternative Validation Methods:

  • Confirm findings using complementary approaches (e.g., IF, IHC, and WB)

  • Consider RNA-level validation (qPCR) alongside protein detection

  • For novel species applications, validate with knockdown/knockout controls if possible

• Manufacturer Resources:

  • Some manufacturers offer innovator award programs for researchers who test and validate antibodies in new species applications, as mentioned in response to a customer query about bovine cross-reactivity

Following these approaches can help ensure reliable results when extending HSPG2 antibody use across species.

What methodologies can be used to investigate HSPG2's role in hematopoiesis and bone marrow function?

Several methodologies have been successfully employed to investigate HSPG2's role in hematopoiesis and bone marrow function:

• siRNA Knockdown Approaches:

  • siRNA targeting HSPG2 in bone marrow endothelial progenitor cells (BM EPCs) has been utilized to assess functional outcomes

  • Validation of knockdown efficiency via qPCR and flow cytometry is essential

  • In one study, after screening multiple siRNA sequences, si HSPG2 2# demonstrated the highest knockdown efficacy (0.2 ± 0.01-fold, P < .0001) and was selected for subsequent experiments

• Flow Cytometry Analysis:

  • Flow cytometry quantification of HSPG2 protein levels before and after interventions

  • Assessment of BM EPC quantities through double-positive-stained cells

  • Data analysis using specialized software such as BD FACSDiva v8.0

• Pharmacological Interventions:

  • Treatment with agents like Ara-C (cytarabine) to investigate the relationship between chemical interventions and HSPG2 expression

  • Dose-response studies showed that HSPG2 mRNA expression levels in BM EPCs decreased as Ara-C concentration increased

• Transcriptomic Analysis:

  • RNA-sequencing to identify gene expression changes related to HSPG2 modulation

  • Analysis of pathways affected by HSPG2 knockdown, including regulation of angiogenesis, hematopoiesis, and cell migration

  • Validation of key differentially expressed genes by qPCR, including ECM1, ANGPT2, IL-34, DCSTAMP, VSIR, and INHBA

• In Vitro Functional Assays:

  • Assessment of hematopoiesis-support ability of BM EPCs with various HSPG2 levels

  • Evaluation of HSPG2 treatment effects on BM EPC functions impaired by chemotherapy

  • Testing of HSPG2's impact on leukemia cells-supporting ability

These methodologies provide complementary approaches to comprehensively investigate HSPG2's role in normal and pathological hematopoiesis.

How can HSPG2 antibodies be used for cancer diagnosis and prognosis assessment?

HSPG2 antibodies have demonstrated significant utility for cancer diagnosis and prognosis assessment across multiple applications:

These applications highlight HSPG2's emerging role as a valuable biomarker in cancer diagnosis and prognosis, particularly for BLCA and MESO.

What is the significance of HSPG2 in bladder cancer and mesothelioma specifically?

HSPG2 demonstrates particular significance in bladder urothelial carcinoma (BLCA) and mesothelioma (MESO) through several key aspects:

These findings collectively establish HSPG2 as a particularly valuable biomarker in BLCA and MESO, with potential applications spanning diagnosis, prognosis assessment, and therapeutic development.

How does HSPG2 expression correlate with tumor mutational burden and microsatellite instability across cancers?

The relationship between HSPG2 expression and tumor mutational burden (TMB) and microsatellite instability (MSI) reveals important insights into cancer biology and potential therapeutic implications:

• Correlation Analysis Methodology:

  • Spearman's correlation analysis was employed to examine the relationship between HSPG2 expression and both TMB and MSI across various cancer types

  • TMB is defined as the total number of base mutations per million cells in a tumor and is recognized for its ability to stimulate production of tumor-specific and highly immunogenic antibodies

  • MSI results from DNA mismatch repair (MMR) abnormalities, leading to gene duplication disorders and tumor development with prognostic implications

• Cancer-Specific Correlations:

  • The relationship between HSPG2 expression and TMB/MSI varies significantly across cancer types

  • These correlations can provide insights into the biological mechanisms through which HSPG2 may influence or be influenced by genomic instability in different tumor contexts

  • Understanding these relationships is particularly relevant for cancers where immunotherapy response is associated with TMB/MSI status

• Immunotherapy Implications:

  • TMB is considered a novel target for predicting the efficacy of tumor immunotherapy

  • The correlation between HSPG2 and TMB might help identify patients likely to benefit from immune checkpoint inhibitors

  • HSPG2's association with immune checkpoint inhibitor outcomes in melanoma and non-small-cell lung cancer further supports this connection

• Mechanistic Insights:

  • The correlations between HSPG2, TMB, and MSI suggest potential interactions between the extracellular matrix environment (where HSPG2 functions) and genomic stability mechanisms

  • These relationships may reflect either causative influences or parallel processes in tumor evolution

These correlations highlight HSPG2's potential role as a biomarker that bridges extracellular matrix biology with genomic stability features that influence immunotherapy response.

How can researchers address molecular weight discrepancies in HSPG2 Western blot results?

Researchers encountering molecular weight discrepancies in HSPG2 Western blot results should consider the following troubleshooting approaches:

• Confirm Expected Size:

  • The expected molecular weight for full-length HSPG2 is approximately 469 kDa according to UniProt database (P98160)

  • A customer question noted confusion between observing a 69 kDa versus 469 kDa band, highlighting this common issue

• Gel System Optimization:

  • Use gradient gels (5-20% SDS-PAGE) to accommodate the large size of HSPG2

  • Extend electrophoresis running time (2-3 hours) to allow proper separation of high molecular weight proteins

  • Include high molecular weight markers that cover the 400-500 kDa range

• Sample Preparation Considerations:

  • Ensure complete protein denaturation without degradation

  • Use freshly prepared samples to minimize proteolysis

  • Consider adding additional protease inhibitors if fragmentation is suspected

  • Evaluate whether observed lower MW bands represent physiological proteolytic fragments of HSPG2 or experimental artifacts

• Transfer Optimization:

  • Extend transfer time (50-90 minutes at 150mA) for large proteins

  • Consider using specialized transfer methods for high molecular weight proteins

  • Verify transfer efficiency with reversible staining of the membrane

• Antibody Selection:

  • Different antibodies may target various epitopes of HSPG2, potentially recognizing fragments or isoforms

  • Confirm antibody specificity with appropriate controls

  • Consider using antibodies validated specifically for Western blot applications

• Interpretation of Multiple Bands:

  • HSPG2 undergoes post-translational modifications and cleavage, potentially generating fragments like Endorepellin and LG3 peptide

  • Document all observed bands and consider whether they correspond to known processed forms of HSPG2

By systematically addressing these considerations, researchers can resolve molecular weight discrepancies and achieve reliable detection of HSPG2 in Western blot experiments.

What controls should be included when validating HSPG2 knockdown experiments?

When validating HSPG2 knockdown experiments, a comprehensive set of controls should be included to ensure experimental rigor and reliable interpretation:

• siRNA Control Selection:

  • Non-targeting siRNA control (siNC) with similar chemical modifications as the targeting siRNA

  • Multiple siRNA sequences targeting different regions of HSPG2 to confirm specificity of effects

  • In one study, researchers tested multiple siHSPG2 sequences and selected the most effective (sequence 2#) based on knockdown efficiency (0.2 ± 0.01-fold reduction, P < .0001)

• Knockdown Validation Controls:

  • mRNA level validation: qPCR to quantify HSPG2 transcript levels

  • Protein level validation: Flow cytometry or Western blot to confirm protein reduction

    • Flow cytometry showed significantly lower HSPG2 levels in siHSPG2 group compared to siNC group (4001.0 ± 110.1 vs. 5192.0 ± 71.9, P = .02)

  • Time course assessment: Validation at multiple time points to track the duration of knockdown effect

• Functional Readout Controls:

  • Positive controls known to affect the same pathways/processes as HSPG2

  • Dose-dependent controls if using pharmacological interventions in conjunction with knockdown

  • For example, when studying Ara-C effects alongside HSPG2 knockdown, concentration-dependent effects on HSPG2 expression should be demonstrated

• Rescue Experiments:

  • Reintroduction of HSPG2 expression to demonstrate reversal of knockdown phenotypes

  • Use of recombinant HSPG2 protein to restore function in knockdown cells

• Cell Viability and Specificity Controls:

  • Cell viability assessments to ensure knockdown effects are not due to cytotoxicity

  • Evaluation of related genes (e.g., other proteoglycans) to confirm specificity

  • Analysis of housekeeping genes to verify general cellular transcription is unaffected

• Analysis Controls:

  • Technical replicates to account for experimental variation

  • Biological replicates using different cell preparations or donor samples

  • Appropriate statistical analysis with corrections for multiple comparisons

Implementing these controls ensures that observed effects in HSPG2 knockdown experiments can be confidently attributed to the specific reduction of HSPG2 rather than off-target effects or experimental artifacts.

What are the key considerations for optimizing immunohistochemical detection of HSPG2 in different tissue types?

Optimizing immunohistochemical (IHC) detection of HSPG2 across different tissue types requires attention to several key parameters:

• Tissue Fixation and Processing:

  • Formalin fixation duration affects epitope accessibility; optimize fixation time for HSPG2 detection

  • Consider specialized fixatives for certain tissue types where HSPG2 epitopes may be sensitive to standard processing

  • Paraffin embedding versus frozen sections may yield different results for HSPG2 detection

• Antigen Retrieval Methods:

  • HSPG2 may require specific antigen retrieval conditions due to its large size and complex structure

  • Compare heat-induced epitope retrieval (HIER) using citrate buffer (pH 6.0) versus EDTA buffer (pH 9.0)

  • Optimization of retrieval duration and temperature is essential for different tissue types

• Antibody Selection and Validation:

  • Choose antibodies validated specifically for IHC applications

  • Verify antibody specificity using positive control tissues known to express HSPG2

  • The PB9277 antibody has been validated for IHC(P) in human lung cancer tissue

• Protocol Optimization by Tissue Type:

  • Different tissues may require modified protocols:

    • Vascular-rich tissues: Special blocking to reduce background

    • Basement membrane-rich tissues: Enhanced permeabilization may be necessary

    • Extracellular matrix-dense tissues: Extended incubation times may improve detection

• Detection System Selection:

  • For tissues with low HSPG2 expression, amplification systems may be necessary

  • Chromogenic versus fluorescent detection based on research requirements

  • Multiplex IHC considerations when co-localizing HSPG2 with other markers

• Negative and Positive Controls:

  • Include tissue-matched negative controls (antibody omission, isotype controls)

  • Use tissues with known HSPG2 expression patterns as positive controls

  • HSPG2 knockdown tissues as gold-standard negative controls when available

• Quantification Approaches:

  • Standardized scoring systems for HSPG2 expression intensity

  • Digital image analysis parameters for consistent quantification

  • Consideration of HSPG2's extracellular localization in scoring methods

By systematically optimizing these parameters for each tissue type, researchers can achieve reliable and consistent immunohistochemical detection of HSPG2 across diverse experimental contexts.

What are the most promising future directions for HSPG2 antibody applications in research?

The future of HSPG2 antibody applications in research appears promising across several frontiers:

• Cancer Diagnostics and Prognostics:

  • Development of standardized HSPG2-based diagnostic panels for bladder urothelial carcinoma (BLCA) and mesothelioma (MESO), where HSPG2 has shown particular significance as an independent prognostic factor

  • Integration of HSPG2 testing with other biomarkers to enhance prognostic accuracy across multiple cancer types

  • Exploration of HSPG2's relationship with tumor mutational burden (TMB) and microsatellite instability (MSI) to predict immunotherapy response

• Therapeutic Monitoring:

  • Using HSPG2 antibodies to monitor treatment responses in cancers where HSPG2 expression correlates with clinical outcomes

  • Development of companion diagnostics for therapies targeting pathways influenced by HSPG2

• Hematopoiesis Research:

  • Further investigation of HSPG2's role in normal hematopoiesis and potential protective effects during chemotherapy

  • Application of HSPG2 antibodies to monitor bone marrow endothelial progenitor cell function in hematological disorders

  • Exploration of HSPG2 as a potential therapeutic target to protect normal hematopoiesis during cancer treatment

• Technical Innovations:

  • Development of more sensitive detection methods for HSPG2 fragments and post-translationally modified forms

  • Creation of isoform-specific antibodies to distinguish between different HSPG2 variants

  • Application of HSPG2 antibodies in emerging technologies such as spatial transcriptomics and multi-omics approaches

• Therapeutic Development:

  • Use of HSPG2 antibodies in drug screening assays to identify compounds that modulate HSPG2 function

  • Exploration of HSPG2-targeting therapeutic approaches in cancers where it contributes to disease progression

  • Development of antibody-drug conjugates targeting HSPG2 in tumors with high expression

These future directions highlight HSPG2's position at the intersection of basic science, diagnostic development, and therapeutic innovation, with particularly strong potential in cancer and hematological research applications.

How can researchers integrate HSPG2 antibody data with other molecular markers for comprehensive disease profiling?

Researchers can employ several strategies to effectively integrate HSPG2 antibody data with other molecular markers for comprehensive disease profiling:

By implementing these integration strategies, researchers can develop more comprehensive disease profiles and uncover novel insights into the complex roles of HSPG2 in health and disease.

What are the best practices for publishing and reporting HSPG2 antibody-based research findings?

When publishing and reporting HSPG2 antibody-based research findings, researchers should adhere to the following best practices:

• Antibody Documentation:

  • Provide complete details about the HSPG2 antibody used, including:

    • Manufacturer, catalog number, and clone ID (for monoclonal antibodies)

    • Host species and immunogen information

    • Antibody concentration used

    • Validation status for the specific application (e.g., PB9277 antibody validated for Western blot in human samples)

• Experimental Protocol Transparency:

  • For Western blot:

    • Detail the gel percentage (e.g., 5-20% gradient), running conditions, transfer parameters, blocking reagents, and detection methods

    • Include molecular weight markers and loading controls

  • For IHC/IF:

    • Specify fixation method, antigen retrieval protocol, antibody dilution, incubation conditions, and detection system

  • For flow cytometry:

    • Document instrument settings, gating strategy, controls, and analysis software

• Controls and Validation:

  • Describe positive and negative controls used

  • For knockdown studies, document verification of HSPG2 reduction at both mRNA and protein levels

  • Demonstrate antibody specificity through appropriate control experiments

• Data Presentation:

  • Include representative images of antibody staining/detection

  • Present quantitative data with appropriate statistical analysis

  • Clearly indicate sample sizes and replication numbers

  • Use standardized units for HSPG2 quantification to enable cross-study comparisons

• Result Interpretation:

  • Discuss findings in the context of known HSPG2 biology

  • Address any discrepancies with previous literature

  • Acknowledge limitations in antibody specificity or experimental approach

  • Consider alternative interpretations of results

• Data Sharing:

  • Deposit raw data in appropriate repositories when possible

  • Provide detailed supplementary methods to enable replication

  • Consider sharing antibody validation data beyond what's included in the main manuscript

• Reporting Guidelines Compliance:

  • Follow established reporting guidelines such as ARRIVE for animal studies or REMARK for prognostic marker studies

  • For clinical studies, adhere to STARD guidelines for diagnostic accuracy studies