Phospho-TOP2A (S1106) Antibody

What is TOP2A and what role does it play in cellular processes?

TOP2A (Topoisomerase II alpha) is a 174 kDa nuclear enzyme that functions as a key decatenating enzyme, altering DNA topology by binding to double-stranded DNA molecules, generating breaks in one strand, passing the intact strand through, and religating the broken strand . This enzymatic activity is essential during DNA replication, transcription, and chromosome segregation during mitosis.

TOP2A expression is predominantly cell cycle-dependent, with highest levels during G2/M phases, serving as a sensitive and specific marker of late S-, G2-, and M-phases in transformed and developmentally regulated normal cells . Research demonstrates that dysregulation of TOP2A is associated with various cancers, including ovarian, breast, and lung cancer, making it an important biomarker and potential therapeutic target in oncology research .

Why is phosphorylation of TOP2A at S1106 significant?

Phosphorylation of TOP2A at serine 1106 (S1106) represents a critical post-translational modification that regulates TOP2A function in normal and pathological conditions. According to multiple studies, phosphorylation of TOP2A-specific sites, including S1106, occurs in a cell cycle-dependent manner and directly regulates sensitivity to TOP2A-targeted drugs .

The significance of S1106 phosphorylation is particularly evident in cancer research, where higher expressions of S1106 phosphorylated TOP2A proteins have been observed in primary tumors compared to normal control tissues . This suggests that S1106 phosphorylated TOP2A plays an important role in tumorigenesis and potentially in mechanisms of drug resistance.

Understanding S1106 phosphorylation is crucial for designing new therapeutic strategies for cancers resistant to TOP2A-targeted drugs. This phosphorylation site serves as a potential biomarker for cancer progression and treatment response across multiple cancer types, including breast cancer, renal cell carcinoma, lung adenocarcinoma, ovarian cancer, and uterine corpus endometrial carcinoma .

How does Phospho-TOP2A (S1106) expression differ between normal and cancer tissues?

Analysis of the CPTAC (Clinical Proteomic Tumor Analysis Consortium) dataset reveals significantly higher expressions of both total and S1106 phosphorylated TOP2A proteins in primary tumors compared to normal control tissues across multiple cancer types . This differential expression has been documented in:

• Breast cancer

• Clear cell renal cell carcinoma (RCC)

• Lung adenocarcinoma (LUAD)

• Ovarian cancer

• Uterine corpus endometrial carcinoma (UCEC)

• Colon cancer

In ovarian cancer specifically, TOP2A expression is significantly elevated in tumor tissues, with Kaplan-Meier analyses suggesting that higher TOP2A expression levels correlate with worse prognosis . The relationship between TOP2A expression and clinical parameters is demonstrated in the following table:

This table demonstrates significant associations between TOP2A expression and both FIGO stage (p=0.048) and histology grade (p=0.000), highlighting its clinical relevance .

What are the optimal protocols for using Phospho-TOP2A (S1106) Antibody in Western blotting?

For optimal Western blotting results with Phospho-TOP2A (S1106) Antibody, researchers should follow these evidence-based recommendations:

Sample Preparation:

• Extract proteins using lysis buffers containing phosphatase inhibitors to preserve phosphorylation status

• Quantify protein concentration and prepare 10-20 μg of total protein per lane

• Include positive controls (e.g., HeLa cell lysates) and negative controls (phosphatase-treated samples)

Gel Electrophoresis and Transfer:

• Use 8% SDS-PAGE gels due to the large size of TOP2A (174 kDa)

• Perform wet transfer at low voltage overnight at 4°C to ensure complete transfer of high molecular weight proteins

Antibody Incubation:

• Block membrane with 5% BSA in TBST for 1-2 hours at room temperature

• Incubate with Phospho-TOP2A (S1106) antibody at 1:500 dilution (optimal range: 1:500-1:2000) overnight at 4°C

• Wash thoroughly with TBST (3-4 washes)

• Incubate with appropriate HRP-conjugated secondary antibody (e.g., goat anti-rabbit HRP at 1:2000 dilution)

Detection and Validation:

• Develop using enhanced chemiluminescence reagents

• Expected band size for Phospho-TOP2A (S1106) is 174 kDa

• For specificity validation, compare with alkaline phosphatase (AP) treated lysates

Published data confirms this approach yields clean Western blots with minimal background and high specificity for the S1106 phosphorylated form of TOP2A .

What controls should be included when validating Phospho-TOP2A (S1106) Antibody specificity?

Rigorous validation of Phospho-TOP2A (S1106) Antibody specificity requires several critical controls:

Essential Negative Controls:

• Phosphatase Treatment: Treat cell lysates with alkaline phosphatase (AP) before Western blotting to eliminate phospho-specific signals while preserving total TOP2A detection. This approach was successfully demonstrated in published studies using HeLa cell lysates .

• TOP2A Knockdown: Samples with TOP2A knockdown through shRNA should show significantly reduced signal intensity. In published protocols, shRNA constructs introduced into SKOV3 and HEYA8 cells have effectively reduced TOP2A expression, providing reliable negative controls .

• Peptide Competition Assay: Pre-incubating the antibody with excess phosphorylated peptide containing the S1106 site should abolish specific staining.

Positive Controls:

• Mitotic Cell Enrichment: Since TOP2A phosphorylation is cell cycle-dependent, enriching for mitotic cells enhances phospho-TOP2A signal.

• Validated Cell Lines: HeLa cells have been confirmed for Phospho-TOP2A (S1106) detection and serve as reliable positive controls in Western blotting applications .

Application-Specific Controls:

• For Immunohistochemistry: Include known positive tissue sections (e.g., colonic adenocarcinoma has shown reliable staining at 1:100 dilution) .

• For Immunofluorescence: Include cells treated with relevant kinase inhibitors as biological negative controls.

• For Quantitative Analysis: Implement technical replicates and standardize to housekeeping proteins (e.g., β-actin) .

These validation approaches ensure that findings related to Phospho-TOP2A (S1106) detection are both specific and reliable, forming a solid foundation for further research.

How should sample preparation differ when detecting Phospho-TOP2A (S1106) in various tissue types?

Sample preparation protocols must be optimized based on tissue type to effectively detect Phospho-TOP2A (S1106):

Fresh Frozen Tissues:

• Rapidly freeze tissue samples in liquid nitrogen immediately after collection

• Homogenize in cold RIPA buffer supplemented with phosphatase inhibitors (e.g., sodium fluoride, sodium orthovanadate, and phosphatase inhibitor cocktails)

• Maintain cold chain throughout processing to prevent phosphatase activity

• Centrifuge at 14,000 × g for 15 minutes at 4°C and collect supernatant

• Determine protein concentration using Bradford or BCA assay

FFPE Tissue Samples:

• For immunohistochemistry applications, perform heat-mediated antigen retrieval before staining protocol

• Citrate buffer (pH 6.0) has been validated for effective epitope exposure

• Extend antigen retrieval time (15-20 minutes) due to the large size of TOP2A protein

• Block endogenous phosphatase activity thoroughly before antibody application

Cell Lines:

• Different cancer cell lines show variable baseline phosphorylation levels

• Ovarian cancer cell lines (SKOV3, HEYA8) have been validated for Phospho-TOP2A studies

• HeLa cells serve as excellent positive controls for S1106 phosphorylation

• Harvest cells at 70-80% confluence for optimal detection

• Consider cell cycle synchronization to enrich for phosphorylated populations

Clinical Samples:

• For patient-derived tissues, minimize cold ischemia time to preserve phosphorylation status

• Document clinical parameters including treatment history that may affect phosphorylation

• Include adjacent normal tissue whenever possible for internal comparison

• Consider parallel analysis of total TOP2A to normalize phosphorylation levels

These tissue-specific considerations ensure optimal detection of Phospho-TOP2A (S1106) across different experimental systems.

How does phosphorylation at S1106 compare with other TOP2A phosphorylation sites?

TOP2A undergoes phosphorylation at multiple sites, each with potentially distinct functional consequences. Comparing S1106 phosphorylation with other sites reveals important differences:

Major Phosphorylation Sites and Their Functions:

• S1106: Cell cycle-dependent phosphorylation that regulates sensitivity to TOP2A-targeted drugs; elevated in multiple cancer types

• S1213: Associated with DNA damage response mechanisms and detectable with specific phospho-antibodies

• S1374/S1377: Often co-phosphorylated sites related to mitotic regulation

• S1351/S1354: Frequently phosphorylated together; implicated in protein-protein interactions

• S1247, S1393, S1525: Additional phosphorylation sites with less characterized functions

• T1343/S1351/S1354: Multiple phosphorylation cluster affecting protein conformation

Relative Significance in Cancer:
Analysis of the CPTAC dataset indicates that S1106 phosphorylated TOP2A protein shows consistent elevation across multiple cancer types, including ovarian, breast, and lung cancers . S1106 phosphorylation appears particularly important in tumorigenesis and drug resistance compared to some other phosphorylation sites.

Methodological Considerations:
Different phospho-specific antibodies show varying sensitivities and specificities. For instance, Phospho-TOP2A (S1106) antibodies typically produce clear bands at 174 kDa in Western blot applications, while other phospho-antibodies may require different optimization protocols .

While all these phosphorylation sites contribute to TOP2A regulation, S1106 phosphorylation appears particularly significant in cancer contexts and drug response mechanisms, making antibodies against this modification especially valuable for oncology research.

How can Phospho-TOP2A (S1106) Antibody be used in studying drug resistance mechanisms?

Phospho-TOP2A (S1106) Antibody represents a valuable tool for investigating drug resistance mechanisms, particularly for anti-cancer therapies:

Experimental Approaches:

• Drug Response Profiling: Monitor changes in S1106 phosphorylation levels before and after treatment with TOP2A inhibitors or other chemotherapeutics. Research has established that phosphorylation at this site regulates sensitivity to TOP2A-targeted drugs .

• Resistant vs. Sensitive Cell Comparison: Compare phosphorylation patterns between drug-sensitive and drug-resistant cell lines to identify differential regulation.

• Mechanistic Studies: Combine with AKT/mTOR pathway inhibitors to investigate signaling crosstalk, as rescue experiments have shown that AKT activation (with SC79) can restore proliferation in TOP2A-knockdown cells .

Research Findings:
In ovarian cancer models, TOP2A knockdown resulted in G1 phase arrest (40.2±0.37% to 48.38±1.52% in SKOV3 cells; 53.90±1.17% to 81.42±1.04% in HEYA8 cells) and apoptotic death (4.09±1.48% to 7.69±1.43% in SKOV3 cells; 1.74±0.30% to 3.11±0.46% in HEYA8 cells) . AKT/mTOR pathway activation through SC79 treatment reduced the frequency of cells in G1 phase and restored proliferation, demonstrating a functional connection between TOP2A and AKT/mTOR signaling .

In breast cancer, elevated TOP2A O-GlcNAcylation has been shown to promote malignant progression and resistance to adriamycin (Adm) . Investigation of phosphorylation status alongside other post-translational modifications provides insights into complex resistance mechanisms.

These findings suggest that Phospho-TOP2A (S1106) antibodies can be instrumental in developing more effective treatment strategies and potentially overcoming drug resistance by revealing phosphorylation-dependent mechanisms that modulate TOP2A function.

What is the relationship between TOP2A phosphorylation and histone modifications?

Recent research has uncovered fascinating connections between TOP2A phosphorylation and histone modifications that regulate chromosome dynamics during cell division:

H2A Phosphorylation and TOP2A Recruitment:
A groundbreaking study has demonstrated that histone H2A Thr-120 phosphorylation (H2ApT120), a modification generated by the mitotic kinase Bub1, is necessary and sufficient for the centromeric localization of TOP2A during mitosis . This phosphorylation enhances histone H2A binding to TOP2A in vitro, with phosphorylated H2A (GST-H2ApS120) showing significantly stronger interaction with MBP-TOP2A (429-1,531)-10xHis compared to non-phosphorylated H2A .

Functional Significance:
The H2ApT120-mediated recruitment of TOP2A to centromeres is critical for sister chromatid disjunction. Preventing this recruitment leads to increased frequency of anaphase ultra-fine bridges (UFBs) containing catenated DNA . Importantly, tethering TOP2A to centromeres bypasses the requirement for H2ApT120 in suppressing these anaphase UFBs, confirming the functional relationship between histone phosphorylation and TOP2A activity .

Structural Requirements:
The C-gate and extreme C-terminal region of TOP2A are important for H2ApT120-dependent localization at centromeres. These findings suggest that specific domains of TOP2A interact with phosphorylated histones to regulate its chromatin association and enzymatic activity during mitosis .

Research Implications:
This relationship between histone modifications and TOP2A phosphorylation represents a fundamental mechanism for safeguarding genomic stability during mitosis. Researchers investigating TOP2A phosphorylation should consider the chromatin context, particularly histone phosphorylation status, when designing experiments to study TOP2A function in both normal and cancer cells.

How does TOP2A phosphorylation relate to cancer prognosis and treatment response?

TOP2A phosphorylation status, particularly at S1106, has significant implications for cancer prognosis and treatment response across multiple cancer types:

Prognostic Value:
Clinical data demonstrate that TOP2A expression and phosphorylation patterns correlate with cancer outcomes. In ovarian cancer:

Mechanistic Basis for Prognostic Value:

• In vitro studies show that TOP2A knockdown reduces proliferation of ovarian cancer cells (SKOV3 and HEYA8)

• TOP2A silencing induces G1 phase cell cycle arrest and apoptosis, suggesting its critical role in cancer cell survival

• Phosphorylation modulates these activities, with sites like S1106 playing key regulatory roles

Treatment Response Prediction:

• Phosphorylation of TOP2A-specific sites, including S1106, regulates sensitivity to TOP2A-targeted drugs

• In breast cancer, altered TOP2A regulation (including O-GlcNAcylation alongside phosphorylation) contributes to adriamycin resistance

• Monitoring phosphorylation status may help predict response to chemotherapy regimens

Pathway Interactions:

• AKT/mTOR pathway activation rescues proliferation in TOP2A-knockdown cells

• AKT activation increases C-myc, CyclinD1, and CDK4 protein levels in TOP2A knockdown cells, suggesting a molecular mechanism for TOP2A's impact on cell cycle regulation

• These findings indicate that combined targeting of TOP2A and AKT/mTOR signaling might be effective against certain cancers

These findings collectively suggest that analyzing TOP2A phosphorylation status, particularly at S1106, could improve cancer prognostication and treatment selection, potentially guiding the development of more effective therapeutic strategies.

How can multiplexing approaches be used to study TOP2A phosphorylation in relation to other signaling pathways?

Advanced multiplexing technologies offer powerful approaches for investigating TOP2A phosphorylation within broader signaling networks:

Multiplex Western Blotting and Protein Arrays:

• Use fluorescent secondary antibodies with distinct emission spectra to detect multiple phosphorylated proteins simultaneously

• Implement Reverse Phase Protein Array (RPPA) to quantify Phospho-TOP2A (S1106) alongside hundreds of other proteins across multiple samples

• These approaches have revealed associations between TOP2A phosphorylation and AKT/mTOR pathway activation in ovarian cancer cells

Multiplex Immunofluorescence/Immunohistochemistry:

• Apply multispectral imaging systems to visualize multiple phosphorylated proteins in tissue sections

• Analyze co-localization of Phospho-TOP2A (S1106) with other proteins at subcellular resolution

• Implement tyramide signal amplification (TSA) for enhanced sensitivity with phospho-specific antibodies

Mass Spectrometry-Based Approaches:

• Nano-LC systems coupled to Orbitrap Fusion Tribrid spectrometers have successfully identified O-GlcNAcylation sites on TOP2A

• Similar approaches can identify and quantify multiple phosphorylation sites simultaneously

• Data analysis workflows incorporating PEAKS, MaxQuant, or similar software enable systematic phosphoproteome mapping

Practical Implementation Example:
Research on TOP2A in ovarian cancer demonstrated that rescue experiments with AKT activator SC79 (4 μg/mL) activated AKT/mTOR pathway signaling, as evidenced by higher p-AKT and p-mTOR levels detected through Western blotting . This approach revealed that AKT/mTOR pathway activation in TOP2A-knockdown cells:

• Enhanced cell proliferation in CCK-8 assays

• Reduced the frequency of cells in G1 phase (from 61.7±1.2% to 43.66±1.64% in SKOV3 cells)

• Increased protein levels of C-myc, CyclinD1, and CDK4

By implementing these multiplexing strategies, researchers can gain comprehensive insights into how TOP2A phosphorylation integrates with broader cellular signaling networks, potentially revealing novel therapeutic targets and biomarkers.

What role does TOP2A phosphorylation play in neurodevelopmental disorders?

Emerging research suggests intriguing connections between TOP2A function and neurodevelopmental processes:

Autism Spectrum Disorder (ASD) Connections:

• TOP2A has been identified as a member of a core autism risk gene network consisting of 234 genes through whole-exome sequencing data analysis

• Studies in animal models have demonstrated that TOP2A promotes the development of social behavior

Experimental Evidence from Model Systems:

• TOP2A-selective inhibitor sodium salicylate (100 μM) induces social deficits in zebrafish models

• Heterozygous can4 mutant (can4+/-) exhibits social deficits compared to wild-type fish

• TOP2A morpholino knockdown (Top2a-MO) induces social deficits that can be rescued by human TOP2A mRNA (250 ng/μl)

Molecular Mechanisms:

• TOP2A may interact with chromatin regulators including Polycomb Repressive Complex 2 (PRC2)

• These interactions could affect neurodevelopmental gene expression programs

• The phosphorylation status of TOP2A, including at sites like S1106, might modulate these interactions, though this specific connection requires further investigation

Research Implications:
This emerging area presents opportunities to investigate whether TOP2A phosphorylation states differ in neurodevelopmental contexts compared to cancer biology. Researchers could apply Phospho-TOP2A (S1106) Antibody in neuronal models to determine if this phosphorylation site has significance in neurodevelopment and neurological disorders.

How does TOP2A phosphorylation regulate its enzymatic activity in different cellular contexts?

The regulation of TOP2A enzymatic activity through phosphorylation represents a complex and highly context-dependent process:

Molecular Mechanisms of Regulation:

• Phosphorylation at specific sites, including S1106, modulates TOP2A's DNA binding affinity and catalytic activity

• Different phosphorylation patterns may create distinct functional states of TOP2A adapted to specific cellular contexts

• Research in ovarian cancer cells has demonstrated that TOP2A regulates cell proliferation through AKT/mTOR pathway activity

Cell Cycle-Dependent Regulation:

• TOP2A undergoes multiple phosphorylation events during the cell cycle, with highest activity typically observed during G2/M phases

• Phosphorylation at S1106 occurs in a cell cycle-dependent manner, correlating with periods of high TOP2A activity

• This dynamic regulation ensures proper chromosome condensation and segregation during mitosis

Impact on Chromosome Dynamics:

• Phosphorylated TOP2A shows altered efficiency in resolving DNA topological problems

• H2A Thr-120 phosphorylation recruits TOP2A to centromeres during mitosis, where it decatenates sister DNAs

• This recruitment is essential for preventing anaphase ultra-fine bridges (UFBs) containing catenated DNA

Context-Specific Functions:

• In cancer cells, TOP2A knockdown results in G1 phase arrest and apoptotic death, processes potentially regulated by phosphorylation status

• In neural development, TOP2A has been implicated in social behavior regulation through interactions with chromatin regulators

• The functional significance of specific phosphorylation sites may vary across these different contexts

Technical Considerations for Research:

• Investigating these context-dependent functions requires careful selection of experimental models

• Phospho-specific antibodies, including those targeting S1106, provide valuable tools for dissecting these regulatory mechanisms

• Combining genetic approaches (knockdown/rescue) with pharmacological interventions offers comprehensive insights into TOP2A regulation

These findings highlight the multifaceted role of TOP2A phosphorylation in regulating its enzymatic activity across diverse cellular contexts, from cancer biology to neurodevelopment.