EO771 Syngeneic Model Service for Breast Cancer

The EO771 syngeneic model of breast cancer engrafts a luminal B–like murine mammary adenocarcinoma into immunocompetent C57BL/6 hosts, pairing endocrine-therapy relevance with access to the richest transgenic mouse toolkit in preclinical research. Alfa Cytology delivers the complete EO771 workflow—low-passage cell banking, mammary fat-pad implantation, burden-balanced randomization, scheduled dosing and metastasis-inclusive endpoint analysis—giving sponsors decision-ready preclinical datasets shaped to their program, strictly within a preclinical scope.

Overview of EO771 Syngeneic Model for Breast Cancer

The EO771 story stretches back to 1948, when a spontaneous mammary carcinoma arising in a C57BL/6 mouse was first described—making this one of the oldest tumor models in continuous use—before the line was isolated in the early 1950s and, decades later, formally adapted for anticancer drug testing. It is now distributed by ATCC as CRL-3461 and has become the default C57BL/6 syngeneic breast cancer line. A landmark 2020 characterization assigned it a luminal B–like phenotype—estrogen receptor α negative, estrogen receptor β positive, progesterone receptor positive and ErbB2 positive—and showed the cells respond in vitro to anti-estrogens including tamoxifen, 4-hydroxy-tamoxifen, endoxifen and fulvestrant, a response profile that distinguishes EO771 sharply from the triple-negative-like 4T1 model. The same literature urges caution: the subtype assignment is not universally accepted, and the ATCC itself flags the cells as genetically unstable in continuous culture, so disciplined low-passage handling is essential.

Fig 1. Mechanistic schematic of the EO771 luminal B phenotype: estrogens activate nuclear ERβ→ERE target genes; tamoxifen blocks ERβ signaling while activating p38/JNK apoptosis and MMP3 upregulation. (Le Naour, Augustin, et al., 2020)

In vivo, EO771 grows more deliberately than its BALB/c counterpart, which widens treatment windows and suits combination and mechanistic designs. Standard practice implants one million cells into the mammary fat pad, where the tumor takes reliably and progresses with spontaneous spread to lung and, in reported designs, peritoneum and brain; because the host is C57BL/6—the strain around which the world’s knockout, knock-in and T-cell-receptor transgenic collections are built—the model supports mechanistic immuno-oncology experiments impossible on other backgrounds, from myeloid-depletion crosses to antigen-specific T-cell tracking. Luciferase-labeled derivatives (for example, a CMV-Luc-GFP dual reporter) add whole-body bioluminescence tracking. Trade-offs to weigh are the debated subtype classification, the drift risk that demands fresh, authenticated stocks, and kinetics slow enough to require planning, but within those boundaries EO771 offers a uniquely versatile, endocrine-relevant venue for preclinical breast cancer research in a fully immunocompetent host.

Cell Line Information: EO771

Key characteristics of EO771 and its commonly used derivatives are summarized below.

Our Services

With in vivo oncology specialists overseeing each stage and pathology, bioluminescence imaging and immune-profiling capabilities in-house, Alfa Cytology molds every EO771 engagement around the sponsor’s hypothesis—controlling passage number, calibrating implant dose and site, and pairing dosing cadence with endpoint panels so the model’s endocrine sensitivity and immunocompetent setting yield clean, decision-grade preclinical data.

Workflow of EO771 Syngeneic Model Construction

Construction of the EO771 syngeneic model is an implantation workflow whose quality rests on fresh low-passage cells, healthy C57BL/6 recipients, standardized fat-pad technique and a disciplined measurement cadence. A standard engagement proceeds as follows:

1. Source and qualify cells: EO771 or EO771-luc stocks are cleared by mycoplasma PCR and identity verification, with a strict low-passage policy to counter the line’s genetic instability; luciferase expression is titrated in vitro with D-luciferin before expansion.
2. Prepare recipients: female C57BL/6 mice (typically 6–8 weeks old; transgenic C57BL/6 lines where mechanistic readouts are required) complete acclimation and health screening and are individually marked before implantation.
3. Prepare the inoculum: log-phase cells are harvested, washed, counted and resuspended in a PBS–Matrigel mixture (commonly 20 µL total per fat pad).
4. Implant: 1 × 10⁶ cells are introduced into the #2 or #4 mammary fat pad through a small dissected pocket, with consistent site selection so caliper geometry stays reproducible; flank implantation is offered as a simpler alternative.
5. Randomize: when tumors reach palpability, animals are assigned to groups balanced by tumor volume and body weight.
6. Dose and follow: test articles (including endocrine agents where relevant) are administered on schedule; tumors are measured with calipers two to three times weekly (volume typically π/6 × length × width × height), with bioluminescence substituted or added for luciferase cohorts; body weight and clinical status are logged in parallel.
7. Terminate and analyze: tumors are resected and weighed; lungs, peritoneum and brain are inspected for metastasis; tissues then enter histopathology (with subtype-marker IHC for ERβ, PR and ErbB2), immunohistochemistry, flow-cytometric immune profiling and molecular analysis.

Fig 2. EO771 Syngeneic Model construction workflow.

Case Study-EO771 Syngeneic Model Development

Alfa Cytology maintains an active preclinical case-study file on the EO771 platform: establishment-phase optimization of implant dose and site under a low-passage cell policy, in vivo growth tracking by caliper or bioluminescence, endocrine- and immunotherapy-based intervention studies, and systematic metastasis evaluation across lung, peritoneum and brain with matched subtype-marker and immune profiling. Representative growth curves, imaging series and endpoint summaries can be shared upon request and will be updated as new programs conclude.

Why Choose Alfa Cytology?

EO771 rewards careful husbandry and flexible design more than raw speed, and those are exactly the habits Alfa Cytology brings:

• Low-passage, authenticated EO771 banking with scheduled STR re-verification to contain genetic drift.
• Reliable mammary fat-pad implantation with Matrigel-optimized take rates and consistent caliper geometry.
• A C57BL/6 setting compatible with knockout, knock-in and TCR-transgenic hosts for mechanistic immuno-oncology.
• An endocrine-therapy angle rare among syngeneic breast models, with ERβ/PR/ErbB2-marker IHC at endpoint.
• Dual-modality monitoring that pairs quantitative bioluminescence with caliper-based volume tracking.
• Slower kinetics converted into an advantage — wider, more forgiving treatment windows for combination designs.
• One accountable project contact with milestone-by-milestone visibility.
• A strictly preclinical scope—every study is planned, executed and reported as non-clinical research.

Contact Us

Interested in the EO771 syngeneic breast cancer model for your next preclinical program? Reach out to us with your agent, timeline and endpoint wish-list, and the Alfa Cytology team will respond with a customized plan covering model setup, dosing strategy and analysis workflow—contact us today and move your program forward with confidence.

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