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Updated: Sep 14, 2025
Testing Cancer Immunotherapeutics in a Humanized Mouse Model Bearing Human Tumors
Published on: December 16, 2022
Impact of the PD-1/PD-L1 inhibitor SCL-1 on MDA-MB231 tumor growth in a humanized MHC-double knockout NOG mouse model
Tomoatsu Ikeya1, Tadashi Ashizawa1, Akari Kanematsu2
1Immunotherapy Division, Shizuoka Cancer Center Research Institute, 1007 Shimonagakubo, Nagaizumi-Cho, Sunto-Gun, Shizuoka, 411-8777, Japan.
Abstract:
Although triple-negative breast cancers are still challenging to treat, the development of novel neoadjuvant chemotherapy combined with immune checkpoint antibodies is promising. Our group developed the small compound-based anti-PD-1/PD-L1 inhibitor SCL-1 and reported its potent anti-tumor effects on various syngeneic mouse tumors. We herein investigated the efficacy of SCL-1 using an in vivo humanized NOG mouse system. We established a humanized mouse system using double major histocompatibility complex-knockout NOG mice transplanted with MDA-MB231 breast cancer cells and HLA-matched human PBMCs. Tumor-infiltrating lymphocytes (TILs) were analyzed using flow cytometry and real-time PCR. An RNA-sequencing analysis (RNA-seq) of SCL-1-treated MDA-MB231 tumors was performed to identify differentially expressed genes. Orally administered SCL-1 exerted potent anti-tumor effects with > 50% reduction in tumor sizes, which were dependent on PD-L1 expression and T-cell infiltration. Its effects were significantly stronger than those of nivolumab or atezolizumab. A TIL analysis revealed effector CD8+ T cells expressing cytotoxic markers and exhausted markers as well as increases in NK cells and B cells. RNA-seq showed the up-regulated expression of tumor-specific long non-coding (lnc) RNAs in SCL-1-treated tumor tissues, some of which exhibited high HLA-binding activity. SCL-1 exerted strong tumor growth inhibitory effects that were mediated by effector T-cell induction inside tumors and the up-regulated expression of lncRNAs as neoantigens leading to CTL activation. The up-regulated expression of lncRNAs in SCL-1-treated MDA-MB231 tumors is a novel result and may be one of the mechanisms responsible for the anti-tumor efficacy of SCL-1.
Insights
The novel small compound SCL-1 shows potent anti-tumor effects against triple-negative breast cancer in a humanized mouse model. This immune checkpoint inhibitor enhances T-cell activity and up-regulates long non-coding RNAs, outperforming existing therapies.
Area of Science:
- Immunology
- Oncology
- Pharmacology
Background:
- Triple-negative breast cancer (TNBC) remains challenging to treat, highlighting the need for novel therapeutic strategies.
- Neoadjuvant chemotherapy combined with immune checkpoint inhibitors shows promise for TNBC treatment.
- Small compound-based inhibitors targeting PD-1/PD-L1 pathways represent a potential therapeutic avenue.
Purpose of the Study:
- To investigate the efficacy of the novel small compound-based anti-PD-1/PD-L1 inhibitor, SCL-1, in a humanized NOG mouse model of TNBC.
- To elucidate the mechanisms underlying SCL-1's anti-tumor effects, including its impact on tumor-infiltrating lymphocytes (TILs) and gene expression.
Main Methods:
- Establishment of a humanized mouse model using double major histocompatibility complex-knockout NOG mice, MDA-MB231 breast cancer cells, and HLA-matched human peripheral blood mononuclear cells (PBMCs).
- Administration of SCL-1 orally and assessment of anti-tumor effects, including tumor size reduction.
- Analysis of TILs via flow cytometry and real-time PCR.
- RNA-sequencing (RNA-seq) analysis of SCL-1-treated tumors to identify differentially expressed genes.
Main Results:
- Orally administered SCL-1 demonstrated potent anti-tumor effects, reducing tumor sizes by over 50%, dependent on PD-L1 expression and T-cell infiltration.
- SCL-1's efficacy was significantly superior to that of nivolumab and atezolizumab.
- TIL analysis revealed an increase in effector CD8+ T cells with cytotoxic and exhausted markers, alongside elevated NK and B cell populations.
- RNA-seq identified up-regulated expression of tumor-specific long non-coding RNAs (lncRNAs) in SCL-1-treated tumors, some with high HLA-binding activity.
Conclusions:
- SCL-1 exerts strong tumor growth inhibitory effects in a humanized TNBC model, mediated by effector T-cell induction and increased T-cell infiltration.
- Up-regulation of lncRNAs, potentially acting as neoantigens, contributes to SCL-1's anti-tumor efficacy by activating cytotoxic T lymphocytes (CTLs).
- The novel finding of up-regulated lncRNAs in SCL-1-treated tumors suggests a new mechanism for its potent anti-cancer activity.
