RS4;11 Xenograft Rat Model Service for Leukemia

The RS4;11 xenograft rat model represents a powerful translational platform for investigating KMT2A-rearranged acute lymphoblastic leukemia, faithfully recapitulating the systemic dissemination, bone marrow infiltration, and organ tropism characteristic of this high-risk hematologic malignancy. Alfa Cytology provides expertly managed RS4;11 xenograft rat studies that deliver reproducible engraftment kinetics and comprehensive pharmacological readouts, empowering your leukemia drug development program with decision-quality preclinical data from lead characterization through candidate selection.

Overview of RS4;11 Xenograft Rat Model for Leukemia

The RS4;11 cell line was originally established in 1985 by Stong and colleagues from the bone marrow aspirate of a 32-year-old female patient diagnosed with acute lymphoblastic leukemia (ALL) in first relapse, specifically the L2 morphological subtype. This cell line harbors the hallmark t(4;11)(q21;q23) chromosomal translocation, which generates the oncogenic KMT2A-AFF1 fusion transcript (also known as MLL-AF4)—the most frequent KMT2A rearrangement observed in infant and adult ALL and strongly associated with aggressive disease course and poor clinical outcomes. When introduced into immunodeficient rat hosts via intravenous inoculation, RS4;11 cells home to the bone marrow niche, proliferate within the hematopoietic microenvironment, and subsequently disseminate to peripheral blood, spleen, liver, and central nervous system—mimicking the natural progression of human systemic leukemia with remarkable fidelity.

Fig 1. HDAC7 expression in RS4;11 cells and various t(4;11) cells/primary cells (Western Blot and qPCR) (de Barrios, Oriol, et al., 2025)

The RS4;11 xenograft model has proven particularly valuable for preclinical evaluation of glucocorticoid response, given the cell line's documented sensitivity to dexamethasone both in vitro and in vivo. Its molecular profile—encompassing mutant TP53, homozygous deletion of the CDKN2A/CDKN2B locus, trisomy 8 with MYC duplication, and isochromosome 7q—mirrors the complex karyotypic landscape of high-risk human ALL. In the rat host, the larger circulating blood volume and more substantial bone marrow compartment relative to murine systems facilitate serial pharmacokinetic sampling, repeated bone marrow aspirations for minimal residual disease monitoring, and comprehensive multi-organ necropsy analyses, making this model an indispensable asset for leukemia therapeutic development.

Cell Line Information: RS4;11

The RS4;11 cell line stands as one of the most extensively characterized models of KMT2A-rearranged acute lymphoblastic leukemia, with a well-documented clinical provenance and a molecular fingerprint that closely reflects the genomic complexity of high-risk human disease. Its robust engraftment capacity in immunodeficient hosts and predictable disease kinetics have made it a cornerstone resource for leukemia preclinical research worldwide. The following table summarizes the essential characteristics of the RS4;11 cell line.

Our Services

Alfa Cytology brings deep expertise in hematologic malignancy preclinical model development, offering end-to-end RS4;11 xenograft rat model services that span study design, cell preparation, animal inoculation, longitudinal disease monitoring, and terminal multi-parameter tissue characterization. We recognize that each leukemia therapeutic program carries unique analytical demands—whether your focus centers on glucocorticoid combination strategies, targeted agents against KMT2A-rearranged disease, or novel modalities disrupting the bone marrow microenvironment—and we architect every study protocol to generate reproducible, publication-quality data that informs critical preclinical decisions.

Workflow of RS4;11 Xenograft Rat Model Construction

Establishment of a reproducible RS4;11 xenograft rat model demands meticulous attention to cell viability, inoculation technique, and post-procedural monitoring to ensure consistent engraftment and valid pharmacological readouts. The workflow described below outlines the standardized protocol employed at Alfa Cytology for generating reliable systemic leukemia xenografts in immunodeficient rat hosts, with each phase optimized to minimize procedural variability and maximize translational fidelity.

1. Cell Preparation and Quality Control: RS4;11 cells are expanded in suspension culture under standardized conditions and harvested during mid-logarithmic growth phase. Cell viability is assessed by trypan blue exclusion, with only preparations exceeding 95% viability accepted for inoculation. The cell suspension is washed twice in sterile PBS, counted, and adjusted to the target concentration—typically 3–5 × 10⁶ cells in 200–500 μL PBS—prior to inoculation.
2. Animal Selection and Acclimation: Immunodeficient nude rats (e.g., Hsd:Rh-rnu) aged 8–10 weeks are procured from accredited commercial breeders and housed for a minimum 7-day acclimation period within our AAALAC-accredited vivarium. Animals are maintained under controlled environmental conditions (12-hour light-dark cycle, 22 ± 2°C, 50–60% relative humidity) with free access to sterilized standard chow and autoclaved water. Body weights are recorded at arrival and at randomization.
3. Intravenous Cell Inoculation: Rats are briefly warmed under a heat lamp to dilate the lateral tail veins, then gently restrained. A single-cell suspension of RS4;11 cells in 200–500 μL sterile PBS is injected slowly into the lateral tail vein using a 26-gauge needle. Successful intravenous delivery is confirmed by absence of swelling or resistance during injection. Alternatively, for studies requiring bone marrow-targeted engraftment, cells may be delivered via intrafemoral or intratibial injection under brief isoflurane anesthesia. Animals are returned to their cages and monitored until fully ambulatory.
4. Disease Monitoring and Engraftment Assessment: Beginning 7–10 days post-inoculation, peripheral blood is collected via tail vein nick or saphenous vein puncture (50–100 μL) into EDTA-coated tubes. The percentage of human CD45+ leukemic cells is quantified by flow cytometry using species-specific antibodies (anti-human CD45, anti-mouse/rat CD45). Engraftment is defined as detection of ≥1% human CD45⁺ cells in peripheral blood. Body weights are recorded twice weekly, and animals are examined daily for signs of pallor, lethargy, hunched posture, or reduced mobility.
5. Treatment Initiation and Dosing: Once engraftment is confirmed and peripheral leukemic burden reaches protocol-specified thresholds—commonly 1–5% human CD45⁺ cells—animals are randomized into treatment and control cohorts using stratification by leukemic burden to ensure inter-group balance. Test articles are administered via the designated route (oral gavage, intraperitoneal, intravenous, or subcutaneous) according to the sponsor-defined dosing schedule. Vehicle controls receive equivalent volumes of formulation buffer on an identical schedule.
6. Endpoint Assessment and Necropsy: Studies are terminated upon reaching protocol-defined endpoints, which may include high peripheral leukemic burden (typically >60–80% human CD45⁺ cells), significant body weight loss (>20%), severe anemia (pallor), neurological deficits suggestive of CNS infiltration, or general morbidity. At termination, animals are humanely euthanized. Peripheral blood is collected via cardiac puncture for complete blood count, flow cytometry, and pharmacokinetic profiling. Bone marrow is flushed from femora and tibiae for engraftment quantification. Spleen, liver, brain, and lymph nodes are harvested, weighed, photographed, and allocated for downstream analyses.
7. Histopathological and Molecular Analyses: Bone marrow and spleen specimens are processed for formalin-fixed paraffin embedding (FFPE), with additional portions snap-frozen in liquid nitrogen or stabilized in RNAlater for molecular analyses. Standard evaluations include H&E staining for morphology, anti-human CD45 immunohistochemistry for leukemic cell infiltration quantification, and TUNEL or cleaved caspase-3 staining for apoptotic index. Flow cytometry panels assess lineage markers (CD19, CD10, CD34, CD38) and minimal residual disease burden. Supplementary analyses such as KMT2A-AFF1 fusion transcript quantification by RT-qPCR, glucocorticoid receptor expression profiling, and gene expression microarray are available upon request.

Fig 2. RS4;11 Xenograft Rat Model construction workflow.

Case Study-RS4;11 Xenograft Rat Model Development

In a recent preclinical engagement, Alfa Cytology established an intravenous RS4;11 xenograft cohort in nude rats to evaluate the anti-leukemic activity of a novel KMT2A-AFF1 fusion protein disruptor administered as monotherapy and in combination with standard-of-care dexamethasone. Following tail vein inoculation of 5 × 10⁶ RS4;11 cells, animals were randomized into vehicle control, single-agent, dexamethasone-only, and combination treatment arms once peripheral blood human CD45⁺ cells reached approximately 3–5%. The study incorporated twice-weekly flow cytometry monitoring of leukemic burden, serial body weight assessment, and terminal analyses encompassing bone marrow engraftment quantification, spleen histopathology, and KMT2A-AFF1 fusion transcript level determination by RT-qPCR. Pharmacokinetic blood sampling at multiple time points enabled correlation of plasma drug exposure with anti-leukemic response, generating an integrated dataset that supported the sponsor's preclinical development milestone. All procedures were conducted under IACUC-approved protocols with full veterinary oversight.

Why Choose Alfa Cytology?

Partnering with Alfa Cytology for your RS4;11 xenograft rat model program means engaging a CRO that combines specialized hematology-oncology expertise with rigorous operational standards and unwavering commitment to data quality. Our integrated service architecture streamlines every phase of your leukemia preclinical study, from cell line qualification through final report delivery.

• Dedicated hematologic malignancy model expertise with extensive experience in RS4;11 xenograft establishment, ensuring high engraftment rates and reproducible disease kinetics across study cohorts.
• In-house flow cytometry capabilities for longitudinal monitoring of human CD45⁺ leukemic burden in peripheral blood, bone marrow, and solid organs, enabling real-time assessment of therapeutic response.
• Flexible study architectures accommodating monotherapy efficacy, combination regimen evaluation, dose-escalation designs, and pharmacokinetic/pharmacodynamic integration tailored to your compound profile.
• Comprehensive molecular pathology services spanning H&E, IHC, IF, RT-qPCR for fusion transcript quantification, and gene expression profiling, all performed within our integrated analytical laboratory.
• AAALAC-accredited vivarium facilities with IACUC-approved protocols, on-site veterinary staff, and stringent animal welfare standards that meet or exceed regulatory expectations.
• Proactive project management with transparent milestone tracking, regular data updates, and rapid responsiveness to protocol amendments or emerging findings.
• Competitive timelines from study initiation to final report, supported by streamlined workflows, established relationships with certified animal vendors, and dedicated scientific teams.

Contact Us

Whether you are advancing a novel agent targeting KMT2A-rearranged leukemia, exploring glucocorticoid combination strategies, or investigating the bone marrow microenvironment in ALL, Alfa Cytology stands ready to support your preclinical program with expertly executed RS4;11 xenograft rat model services. Reach out to us today to discuss your study objectives, review our capabilities, or request a customized proposal designed to generate the high-quality data your development pipeline requires.

For research use only. Not intended for any clinical use.