Clone M-3 Syngeneic Model Service for Melanoma

The Clone M-3 syngeneic model is the Jackson-era ancestor of murine melanoma research, engrafting a highly pigmented, culture-cloned derivative of the classic Cloudman S91 melanoma into syngeneic DBA/2 hosts where visible melanin production provides a built-in tumor-visualization biomarker. Alfa Cytology delivers this historic model as a complete preclinical service — authenticated multi-repository banking, subcutaneous, intradermal, or mammary-fat-pad implantation formats, checkpoint inhibitor benchmarking, and full histopathology — giving sponsors a nearly century-old lineage with modern quantitative readouts.

Overview of Clone M-3 Syngeneic Model for Melanoma

Clone M-3 descends from one of the most venerable tumors in experimental oncology: the Cloudman S91 melanoma, which arose in a male DBA/2 mouse during the Jackson Laboratory era and became a standard vehicle for studying pigment-cell transformation long before genetically engineered models existed. The line was adapted to culture from an S91 tumor carried in a (C × DBA) F₁ male mouse, and its documentation in the 1966 Science report on the animal cell culture collection makes it one of the oldest continuously available mouse melanoma lines anywhere. What sets Clone M-3 apart immediately is its appearance: it is highly pigmented, producing visible melanin, so tumor burden can in part be followed by pigmentation itself — a built-in biomarker no other major syngeneic line offers. Cytogenetically the line is hypertetraploid, and its karyotype was mapped at molecular resolution in a 2021 cytogenetic characterization. Its culture demands are distinctive too: the canonical formulations — Ham's F10 with 15% fetal bovine serum, or ATCC's F-12K with 15% horse serum — reflect its melanocyte heritage rather than the generic DMEM routines of most tumor lines.

Fig 1. Immune profiling of Clone M-3 (S91) tumors after photodynamic immune stimulation, showing markedly increased CD3+ T cell infiltration at the treated tumor site. (Pires, L., et al., 2026)

Biologically, Clone M-3 occupies an instructive position in the melanoma immunology landscape. Unlike the poorly immunogenic B16 lines, it expresses MHC class I constitutively at high levels, yet roughly 80% of its cells exhibit partial resistance to interferon-γ for MHC I and ICAM-1 induction — a documented nuance that moderates its immunogenicity and rewards careful interpretation of checkpoint data. In vivo it is brisk but tractable: 10⁶ subcutaneous cells in the high axilla of DBA/2J mice double in about four days, keeping studies to a 20–25-day window, while intradermal implantation grows measurably slower — a route-sensitivity that makes the line useful for dermal-microenvironment questions. Modern CRO practice has added the mammary-fat-pad "subQperior" geometry, which delivers nearly 100% take rates, homogeneous growth, larger volumes, a longer treatment window, and minimal ulceration. Checkpoint benchmarking is established: anti-VISTA efficacy studies and 17-marker flow-cytometric immune profiling have been run against this line, and its radiation-survival assay heritage — Yohem, Bregman, and Meyskens's melanoma-colony work in the 1980s — makes it a natural substrate for radiotherapy and radiosensitizer questions. For sponsors, Clone M-3 offers something no B16 derivative can: a pigmented, MHC-I-high, Jackson-lineage melanoma with nearly a century of experimental continuity.

Cell Line Information: Clone M-3 Syngeneic Model

Clone M-3 (ATCC CCL-53.1; Cellosaurus CVCL_4512) is the culture-adapted, melanin-producing clone of the Cloudman S91 murine melanoma, distributed by the American Type Culture Collection, ECACC, and Asian repositories. Core characteristics are compiled below.

Our Services

Engaging Alfa Cytology for the Clone M-3 syngeneic model places a near-century-old melanoma lineage under one accountable team: authenticated multi-repository banks are maintained with the line's melanocyte-specific medium formulations and split discipline, syngeneic DBA/2 hosts are sourced and acclimated, tumors are established by the subcutaneous, intradermal, or mammary-fat-pad route at the documented inocula, and treatment arms — checkpoint inhibitors, radiotherapy regimens, or pigmentation-targeting agents — run through scheduled caliper monitoring (with pigmentation scoring where informative) to terminal histopathology with immune-marker panels, all under IACUC-compliant conditions and returned as an audit-ready data package.

Workflow of Clone M-3 Syngeneic Model Construction

Clone M-3 studies turn on route selection — subcutaneous for classic kinetics, intradermal for dermal microenvironment questions, mammary fat pad for extended windows — wrapped around the line's distinctive culture stewardship. A standard program proceeds as follows.

1. Cell preparation and quality control: Clone M-3 cells are expanded at low passage in the melanocyte-heritage formulations (Ham's F10 + 15% FBS or F-12K + horse serum), confirmed mycoplasma-free, and pigmentation phenotype verified by visual inspection; suspensions are prepared fresh at 10⁶ cells per inoculum.
2. Host selection and acclimation: Male or female DBA/2 mice, typically 6–10 weeks of age, are quarantined and acclimated in a specific-pathogen-free barrier facility.
3. Implantation: subcutaneous route. 10⁶ cells in 0.1 mL sterile PBS are implanted in the high axilla; the site is compressed briefly, and pigmented tumors with ~4-day doubling kinetics become measurable within the first days of the 20–25-day study window.
4. Implantation: intradermal or mammary-fat-pad routes. For dermal-microenvironment questions, cells are implanted intradermally with expectation of delayed growth; for extended treatment windows, the mammary-fat-pad geometry delivers nearly 100% takes with homogeneous, minimally ulcerating tumors.
5. Randomization and treatment. Mice are randomized by tumor volume into arms, and test articles: checkpoint inhibitors (anti-VISTA benchmarking available), radiotherapy regimens, or pigmentation-targeting modalities — are dosed per protocol with body weight recorded.
6. Longitudinal monitoring: Tumors are measured by caliper on the protocol cadence; pigmentation intensity is scored where informative as a built-in biomarker, and clinical signs are recorded daily against predefined humane endpoints.
7. Immune profiling where specified: For immunotherapy arms, tumor-infiltrating leukocytes are characterized by flow cytometry against the 17-marker panel validated for this model, and MHC I/ICAM-1 induction assays can accompany interferon-pathway mechanism studies.
8. Endpoint analysis and reporting: At termination, primary tumors are resected and weighed; tissues undergo H&E with melanoma histology, immunohistochemistry (CD8, CD4, FoxP3, F4/80, CD31, PD-L1, MHC I panels), melanin-content assessment where relevant, and metastatic-organ screening, with all data consolidated into the final report.

Fig 2. Clone M-3 Syngeneic Model construction workflow.

Case Study-Clone M-3 Syngeneic Model

Alfa Cytology has applied the Clone M-3 syngeneic platform to preclinical programs spanning checkpoint inhibitor screening, radiotherapy and radiosensitizer evaluation, pigmentation-targeting modalities, and dermal-microenvironment mechanism studies in melanoma. In these engagements, caliper and pigmentation-scored readouts tracked primary tumor kinetics across the three implantation routes, while terminal histopathology with immune-marker panels and 17-marker flow-cytometric profiling completed the pharmacological and immunological assessment. Study parameters — implantation route, inoculum, monitoring cadence, and endpoint panels — are tailored to each program. Case materials can be shared under confidentiality agreements upon request.

Why Choose Alfa Cytology?

Clone M-3 rewards teams that honor its identity: the melanocyte-heritage culture formulations, the pigmentation biomarker, the MHC-I-high-with-IFNγ-resistance immunology, and the route-sensitivity between subcutaneous, intradermal, and mammary-fat-pad formats. Alfa Cytology fields these capabilities in-house, making the Clone M-3 syngeneic model a distinctive asset for your melanoma program.

• Near-century-old Jackson-lineage provenance, documented since the 1966 cell-culture collection report.
• Built-in pigmentation biomarker, enabling visual tumor tracking alongside caliper measurement.
• Melanocyte-heritage culture stewardship, with the F10/horse-serum formulations respected natively.
• Three validated routes — subcutaneous, intradermal, and mammary-fat-pad — each with documented kinetics.
• Distinctive immunophenotype literacy, fluent in the high MHC I / partial IFNγ-resistance literature.
• Radiation-assay heritage, from the melanoma-colony methodology of the 1980s onward.
• IACUC-compliant, documentation-rich operations delivering audit-ready records throughout the study.

Contact Us

If your melanoma program would benefit from a pigmented, Jackson-lineage syngeneic platform, contact us today to discuss Clone M-3 study design, route selection, and endpoint strategy with our scientific team. Reach out for a confidential consultation and project quotation — Alfa Cytology looks forward to advancing your next preclinical study.

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