Tp53/17p13.1 deletion detection by FISH at Chughtai Lab

Introduction to Tp53/17p13.1 Deletion Detection by FISH

The Tp53/17p13.1 deletion detection by FISH (Fluorescence In Situ Hybridization) is a highly specialized molecular cytogenetic test performed to identify the loss of the TP53 tumor suppressor gene. Located on the short arm of chromosome 17 at position 13.1 (17p13.1), the TP53 gene is widely recognized as the “guardian of the genome.” It plays a critical role in regulating the cell cycle, facilitating DNA repair, and initiating apoptosis (programmed cell death) when genetic damage is irreparable. When a deletion occurs in this specific region, cells lose a vital regulatory mechanism, allowing damaged or mutated cells to proliferate uncontrollably. This genetic aberration is a key driver in various hematological malignancies and solid tumors.

Fluorescence In Situ Hybridization (FISH) is the gold standard technology used to detect this deletion. Unlike conventional karyotyping, which requires actively dividing cells and has limited resolution, FISH utilizes fluorescently labeled DNA probes that bind specifically to complementary target sequences on the patient’s DNA. By examining these fluorescent signals under a specialized fluorescence microscope, cytogeneticists can identify the presence, absence, or structural rearrangement of the TP53 gene in both metaphase and interphase cells. This high-resolution testing is essential for accurate diagnosis, risk stratification, prognostic assessment, and therapeutic planning in modern oncology.

At Chughtai Lab, this advanced molecular investigation is conducted under strict quality control protocols. The diagnostic value of detecting a 17p13.1 deletion cannot be overstated; it is one of the most critical prognostic markers in chronic lymphocytic leukemia (CLL), multiple myeloma, acute myeloid leukemia (AML), and myelodysplastic syndromes (MDS). Identifying this deletion helps oncologists understand the aggressive nature of the disease and select targeted therapies that bypass the dysfunctional TP53 pathway, thereby optimizing patient outcomes.

Clinical Procedure: What to Expect

Patient Preparation

Appropriate patient preparation is essential to ensure sample integrity and accurate diagnostic results. Patients undergoing the Tp53/17p13.1 deletion detection by FISH at Chughtai Lab should observe the following guidelines:

• No Fasting Required: There is generally no requirement to fast before this test. Patients can consume food and liquids normally unless instructed otherwise by their referring physician.
• Clinical Documentation: It is mandatory to provide a complete clinical history, including previous hematological reports (such as Complete Blood Count and bone marrow biopsy findings), suspected diagnosis, and details of any ongoing or past chemotherapy or immunotherapy.
• Medication Review: Patients should inform their healthcare provider of all medications, supplements, and blood thinners they are currently taking. In most cases, routine medications do not need to be discontinued.
• Consent Form: Since this is a specialized genetic/molecular test, patients or their legal guardians may be required to sign an informed consent form prior to sample collection.

During the Procedure

The procedure involves the collection of an appropriate biological specimen, followed by complex laboratory processing. The step-by-step process includes:

• Specimen Collection: Depending on the clinical indication, the sample required is either peripheral blood or bone marrow aspirate. Peripheral blood is collected via standard venipuncture from a vein in the arm into a sodium heparin (green-top) tube. Bone marrow aspirate is collected by a qualified hematologist or oncologist through a specialized procedure, typically from the posterior iliac crest, and placed in a heparinized syringe or tube.
• Laboratory Processing: Once the sample arrives at the specialized cytogenetics department of Chughtai Lab, the cells are cultured, harvested, and fixed onto glass slides.
• Hybridization: The slides are treated with a mixture of two fluorescently labeled DNA probes: a locus-specific probe for the TP53 gene (labeled with one fluorophore, typically red or green) and a control probe specific to the centromere of chromosome 17 (CEP17, labeled with a contrasting fluorophore). The probes and target DNA are co-denatured and allowed to hybridize overnight.
• Analysis and Interpretation: Post-hybridization washes are performed to remove unbound probes. The slides are counterstained with DAPI (a blue fluorescent DNA stain) and analyzed under a high-power fluorescence microscope equipped with specialized filters and digital imaging software. A molecular pathologist or cytogeneticist counts the signals in a minimum of 100 to 200 interphase nuclei to determine the percentage of cells harboring the deletion.
• Safety and Comfort: Venipuncture involves minimal discomfort, similar to a standard blood test. Bone marrow aspiration, while more invasive, is performed under local anesthesia to minimize pain. The laboratory phase of the test carries no risk to the patient.

When is a Tp53/17p13.1 Deletion Detection by FISH Performed?

Chronic Lymphocytic Leukemia (CLL) Prognostication

The detection of the 17p13.1 deletion is a critical step in the initial workup of patients diagnosed with Chronic Lymphocytic Leukemia (CLL). It is performed prior to the initiation of any treatment because the presence of this deletion is associated with a highly aggressive disease course, rapid progression, and resistance to standard chemoimmunotherapy regimens (such as FCR – Fludarabine, Cyclophosphamide, and Rituximab). Identifying this deletion guides oncologists to prescribe targeted therapies like BTK inhibitors or BCL-2 inhibitors.

Multiple Myeloma Risk Stratification

In multiple myeloma, the TP53 deletion is classified as a high-risk cytogenetic abnormality. Physicians request this FISH test on bone marrow aspirate samples at the time of diagnosis to stratify patients into risk categories. Patients with a high percentage of plasma cells showing the 17p13.1 deletion often experience shorter remission periods and poorer overall survival, necessitating more intensive therapeutic strategies, including early autologous stem cell transplantation and novel triplet or quadruplet drug combinations.

Acute Myeloid Leukemia (AML) and Myelodysplastic Syndromes (MDS) Evaluation

For patients presenting with unexplained cytopenias, suspected MDS, or newly diagnosed AML, TP53 deletion testing by FISH is highly indicated. In MDS, a 17p deletion is frequently associated with complex karyotypes, rapid transformation to AML, and poor response to hypomethylating agents. In AML, it represents an adverse-risk genetic category. Detecting this mutation helps clinicians determine if the patient is a candidate for early allogeneic hematopoietic stem cell transplantation.

Selection of Targeted Therapeutic Regimens

Modern oncology relies heavily on precision medicine. Because the TP53 gene product is essential for the mechanism of action of conventional DNA-damaging chemotherapies, tumors lacking this gene do not respond to standard treatments. Detecting the deletion helps avoid futile toxicities from ineffective chemotherapy and allows patients to be immediately directed toward pathway-specific targeted therapies and clinical trials designed to bypass TP53-mediated cell death.

Monitoring Disease Progression and Treatment Response

This test is also performed periodically to monitor clonal evolution in patients with established hematological malignancies. Over time, under the selective pressure of treatment, a minor clone of cells harboring the TP53 deletion may expand, leading to disease relapse or transformation (such as Richter’s transformation in CLL). Repeating the FISH test helps clinicians detect these genetic shifts early and adjust the treatment protocol accordingly.

What Does a Tp53/17p13.1 Deletion Detection by FISH Detect?

The Tp53/17p13.1 deletion detection by FISH is designed to identify specific cytogenetic patterns and abnormalities within the target cells. The test detects and reports the following clinical and technical findings:

• Normal Diploid Pattern: The presence of two normal signals for the TP53 gene and two normal signals for the chromosome 17 centromere (CEP17) in analyzed cells, indicating no deletion.
• Heterozygous TP53 Deletion: The loss of one copy of the TP53 gene on one of the chromosome 17 homologues, represented by a pattern of one TP53 signal and two CEP17 signals.
• Homozygous TP53 Deletion: The extremely rare loss of both copies of the TP53 gene, characterized by the complete absence of TP53 signals in the presence of CEP17 signals.
• Monosomy 17: The loss of an entire chromosome 17, indicated by the presence of only one TP53 signal and one CEP17 signal per cell.
• Polysomy 17: The presence of extra copies of chromosome 17, indicated by three or more signals for both TP53 and CEP17.
• Clonal Size (Percentage of Deleted Cells): The exact proportion of analyzed nuclei that exhibit the 17p13.1 deletion, which is crucial for determining the prognostic impact.
• Clonal Heterogeneity: The coexistence of different cell populations, some with the deletion and others with normal or alternative genetic patterns.
• Isochromosome 17q: A structural abnormality where the short arm (p) is lost and replaced by an extra long arm (q), leading to TP53 deletion, detected via specific signal patterns.
• Complex Karyotypic Changes: Highly abnormal signal distributions suggesting severe genomic instability and complex chromosomal rearrangements.
• Therapeutic Resistance Markers: Genetic profiles indicating a high likelihood of resistance to alkylating agents and purine analogues.
• High-Risk Disease Profiles: Genetic confirmation of high-risk status in multiple myeloma and chronic lymphocytic leukemia.
• Clonal Evolution: The emergence of a new TP53-deleted clone in a patient previously tested negative, indicating disease progression.
• Post-Transplant Chimerism/Engraftment Status: Assessment of the disappearance of the abnormal TP53-deleted clone following successful bone marrow transplantation.

Turnaround Time and Report Access at Chughtai Lab

Due to the highly specialized nature of molecular cytogenetics, which involves cell culture, hybridization, and manual microscopic analysis by expert scientists, the turnaround time for the Tp53/17p13.1 deletion detection by FISH is typically 7 to 10 working days. Chughtai Lab is committed to delivering accurate and timely results to facilitate prompt clinical decision-making.

Patients and referring physicians can easily access reports through Chughtai Lab’s advanced digital infrastructure. Reports can be downloaded online via the official Chughtai Lab website using the patient’s case number and password. Additionally, reports are accessible through the Chughtai Lab Mobile App, available on iOS and Android platforms. For convenience, automated SMS notifications are sent to patients as soon as their verified reports are ready for download or collection from any of the numerous Chughtai Lab collection centers across Pakistan.

Tp53/17p13.1 Findings Overview

The following table outlines the common cytogenetic findings evaluated during the Tp53/17p13.1 deletion detection by FISH, comparing normal and abnormal states:

Structure / Parameter Evaluated	Normal Findings	Possible Abnormal Findings
TP53 Gene Copy Number (17p13.1)	Two intact copies (two fluorescent signals per cell)	One copy (heterozygous deletion) or zero copies (homozygous deletion)
Chromosome 17 Centromere (CEP17)	Two intact copies (two fluorescent signals per cell)	One copy (monosomy 17) or three or more copies (polysomy 17)
Signal Ratio (TP53 to CEP17)	1:1 ratio (2 TP53 signals and 2 CEP17 signals)	Decreased ratio (e.g., 1 TP53 signal and 2 CEP17 signals indicating deletion)
Percentage of Deleted Cells (Cut-off)	Below the laboratory’s established analytical cut-off (typically < 5-10%)	Elevated percentage of cells showing deletion (ranging from low-level clones to > 90%)
Genomic Stability	Uniform diploid signal pattern across all analyzed cells	Highly variable signal patterns indicating complex clonal evolution and genomic instability
Chromosome 17 Structure	Normal structural integrity of both chromosome 17 homologues	Presence of isochromosome 17q [i(17q)] or other unbalanced translocations involving 17p

Note: Diagnostic findings should always be interpreted by a qualified healthcare professional together with the patient’s symptoms, medical history, physical examination, laboratory investigations, previous imaging studies, and other relevant clinical information. Additional investigations or specialist consultation may be recommended depending on the findings.

Why Choose Chughtai Lab for Tp53/17p13.1 Deletion Detection by FISH?

• Experienced Healthcare Professionals: Our molecular pathology and cytogenetics department is staffed by highly qualified pathologists, geneticists, and technologists specializing in FISH technology.
• Patient-Focused Care: We prioritize patient comfort and convenience, offering seamless sample collection and dedicated support throughout the testing process.
• Quality Diagnostic Services: Chughtai Lab adheres to rigorous international quality control standards, ensuring the highest level of accuracy and reproducibility for genetic tests.
• Professional Reporting: Reports are detailed, comprehensive, and include clear clinical interpretations to assist oncologists in treatment planning.
• Modern Diagnostic Approach: We utilize state-of-the-art fluorescence microscopes, high-resolution digital imaging systems, and validated locus-specific probes.
• Comfortable Environment: Our collection centers across Pakistan provide a clean, safe, and professional environment for blood and bone marrow sample collection.
• Convenient Location: With an extensive network of laboratories and collection points nationwide, patients can easily access our services.
• Commitment to Accurate Diagnosis: We understand the critical nature of oncological diagnostics and are dedicated to providing precise genetic insights that impact patient lives.